Neutral zone/ orthodontic seminars

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Neutral zone/ orthodontic seminars

  1. 1. NEUTRAL ZONENEUTRAL ZONE INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. INTRODUCTIONINTRODUCTION  The goal of dentistry is for patientsThe goal of dentistry is for patients to keep all of their teeth throughoutto keep all of their teeth throughout their lives in health and comfort. Iftheir lives in health and comfort. If the teeth are lost despite all effortsthe teeth are lost despite all efforts to save them, a restoration shouldto save them, a restoration should be made in such a manner as tobe made in such a manner as to function efficiently and comfortablyfunction efficiently and comfortably in harmony with the muscles of thein harmony with the muscles of the stomatognathic system and thestomatognathic system and the temporomandibular jointstemporomandibular jointswww.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3.  The stable position of the teeth representsThe stable position of the teeth represents equilibrium of all the forces acting on them. Ifequilibrium of all the forces acting on them. If that position of equilibrium namely thethat position of equilibrium namely the neutral zone, is not found, the resultingneutral zone, is not found, the resulting dentition will not last long and will not bedentition will not last long and will not be esthetically pleasing and the patients use ofesthetically pleasing and the patients use of www.indiandentalacademy.comwww.indiandentalacademy.com
  4. 4. www.indiandentalacademy.comwww.indiandentalacademy.com
  5. 5.  functional efficiency, maximumfunctional efficiency, maximum length of use and pleasing estheticslength of use and pleasing esthetics will not have been met.will not have been met.  To understand the stable positionTo understand the stable position of teeth, the concept of neutral zoneof teeth, the concept of neutral zone is important.is important. www.indiandentalacademy.comwww.indiandentalacademy.com
  6. 6.  Neutral ZoneNeutral Zone is defined as that areais defined as that area in the mouth where, during function,in the mouth where, during function, the forces of the tongue pressingthe forces of the tongue pressing outward are neutralised by the forcesoutward are neutralised by the forces of the cheeks and lips pressingof the cheeks and lips pressing inwards.inwards. www.indiandentalacademy.comwww.indiandentalacademy.com
  7. 7. FORM AND FUNCTION:FORM AND FUNCTION:  In orthodontics and prosthodonticsIn orthodontics and prosthodontics the basic principles of treatment arethe basic principles of treatment are identical. They revolve around theidentical. They revolve around the relationship between form andrelationship between form and function..function.. www.indiandentalacademy.comwww.indiandentalacademy.com
  8. 8.  Function determines form. AbnormalFunction determines form. Abnormal functions such as deviate swallowingfunctions such as deviate swallowing pattern, mouth breathing and thumbpattern, mouth breathing and thumb sucking, will modify or dictate thesucking, will modify or dictate the form of the dental archesform of the dental arches www.indiandentalacademy.comwww.indiandentalacademy.com
  9. 9.  It is equally true that alteration ofIt is equally true that alteration of the form of a growing individual willthe form of a growing individual will alter function. If the alteration ofalter function. If the alteration of form is an improvement, there willform is an improvement, there will be a concomitant improvement inbe a concomitant improvement in function. Ideally, both the functionfunction. Ideally, both the function and form should be correctedand form should be corrected together for optimal results, and thistogether for optimal results, and this correction should take place beforecorrection should take place before growth has ceased.growth has ceased.www.indiandentalacademy.comwww.indiandentalacademy.com
  10. 10.  Prosthodontic treatment in completeProsthodontic treatment in complete dentures is also influenced by thedentures is also influenced by the concept that form follows function.concept that form follows function. Complete dentures that are constructedComplete dentures that are constructed by concepts that do not take intoby concepts that do not take into consideration the unique functioning ofconsideration the unique functioning of the individual patients musculature arethe individual patients musculature are over looking this basic law of physiology.over looking this basic law of physiology. www.indiandentalacademy.comwww.indiandentalacademy.com
  11. 11.  If form is dictated by function, thenIf form is dictated by function, then in complete denture construction,in complete denture construction, the operator must shape and formthe operator must shape and form dentures to be in harmony withdentures to be in harmony with functionfunction www.indiandentalacademy.comwww.indiandentalacademy.com
  12. 12.  In all areas of dentistry, the ultimateIn all areas of dentistry, the ultimate problem in maintaining the health of theproblem in maintaining the health of the stomatognathic system throughout life isstomatognathic system throughout life is one of harmonious pressure distribution.one of harmonious pressure distribution. The primary function of this system is theThe primary function of this system is the application, distribution and dissipation ofapplication, distribution and dissipation of the pressure of the bite and of thethe pressure of the bite and of the muscles of the lips, cheeks andmuscles of the lips, cheeks and tongue.tongue.www.indiandentalacademy.comwww.indiandentalacademy.com
  13. 13.  To put it more simply, the primaryTo put it more simply, the primary function of the stomatognathic system isfunction of the stomatognathic system is mastication.mastication.  The prosthodontist who is unaware ofThe prosthodontist who is unaware of the effect of muscle function will be facedthe effect of muscle function will be faced with cases of prosthodontic relapsewith cases of prosthodontic relapse unstable dentures.‑unstable dentures.‑ www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. THE NEUTRAL ZONE ANDTHE NEUTRAL ZONE AND DENTURE SPACEDENTURE SPACE  In completely edentulous patients thereIn completely edentulous patients there exists within the oral cavity a void thatexists within the oral cavity a void that may be called the potential denturemay be called the potential denture space. The denture space is bounded byspace. The denture space is bounded by the maxilla and soft palate above, by thethe maxilla and soft palate above, by the mandible and floor of the mouth below,mandible and floor of the mouth below, www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15.  by the tongue, medially or internally,by the tongue, medially or internally, and by the muscles and tissues ofand by the muscles and tissues of the lips and cheeks laterally orthe lips and cheeks laterally or externally. Within the denture spaceexternally. Within the denture space there is an area that has beenthere is an area that has been termed the neutral zone.termed the neutral zone. www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16. www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17.  Weath (1970) has demonstrated thatWeath (1970) has demonstrated that there is a difference in the shape ofthere is a difference in the shape of the denture space and resultant archthe denture space and resultant arch form at rest as compared to theform at rest as compared to the denture space and arch formdenture space and arch form established by function.established by function. www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. FACTORS AFFECTINGFACTORS AFFECTING THE NEUTRAL ZONETHE NEUTRAL ZONE www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. Muscles and the neutral zone:Muscles and the neutral zone:  Dentures should occupy a position inDentures should occupy a position in the mouth where all the forcesthe mouth where all the forces during function are neutralized.during function are neutralized. Otherwise, denture stability will beOtherwise, denture stability will be decreased proportionately todecreased proportionately to thethe difference in the amount of thedifference in the amount of the opposing forces.opposing forces.  Neutral zone in complete dentures isNeutral zone in complete dentures is in fact the zone previously occupiedin fact the zone previously occupied by the natural teeth.by the natural teeth.www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20. MUSCLES OF THE CHEEKMUSCLES OF THE CHEEK  The outer limits of the neutral zone areThe outer limits of the neutral zone are determined by the perioral musculature.determined by the perioral musculature.  BUCCINATORBUCCINATOR  The main determinant of length, strengthThe main determinant of length, strength and position of the perioral musculature is theand position of the perioral musculature is the buccinator muscle. The buccinator is a thin, flatbuccinator muscle. The buccinator is a thin, flat muscle composed of three bands.muscle composed of three bands.www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21.  The combined width of the threeThe combined width of the three bands covers the entire outer surfacebands covers the entire outer surface of the dento alveolar structures, thatof the dento alveolar structures, that is the teeth, alveolar process andis the teeth, alveolar process and gingival tissues.gingival tissues. The upper and lower bands areThe upper and lower bands are continuous from side to sidecontinuous from side to side without decussation. The middlewithout decussation. The middle band fibers decussate and joint intoband fibers decussate and joint into the fibers of the orbicularis oristhe fibers of the orbicularis oris.. www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22.  Because the muscle fibers form aBecause the muscle fibers form a continuous band, the size of the archcontinuous band, the size of the arch is limited by the length of theis limited by the length of the muscles when they are contractedmuscles when they are contracted repetitiously. Regardless of therepetitiously. Regardless of the reason for variations in muscle tonusreason for variations in muscle tonus in different patients, the strength ofin different patients, the strength of the contractile force, at the length ofthe contractile force, at the length of the muscle during contraction, forcesthe muscle during contraction, forces can inviolate outer limit for arch size.can inviolate outer limit for arch size. www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23.  The effects of neutral zoneThe effects of neutral zone confinement on the dentoalveolarconfinement on the dentoalveolar structures can also play a critical rolestructures can also play a critical role as a determinant of facial profile. Aas a determinant of facial profile. A restrictive perioral musculature mayrestrictive perioral musculature may prevent the dentoalveolar archesprevent the dentoalveolar arches from expanding to a normalfrom expanding to a normal alignment with the skeletal base.alignment with the skeletal base. www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24.  The commonThe common practice ofpractice of centralization, or lingualization ofcentralization, or lingualization of occlusion, prevents the buccinatorocclusion, prevents the buccinator from performing its proper function infrom performing its proper function in two ways. First, lingualization oftwo ways. First, lingualization of occlusion creates a space between theocclusion creates a space between the cheek and the teeth and the externalcheek and the teeth and the external surface of the denture, where foodsurface of the denture, where food tends to accumulate and it becomestends to accumulate and it becomes more difficult for the cheek to placemore difficult for the cheek to place the food back onto the occlusalthe food back onto the occlusal surfaces of the teeth.surfaces of the teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25.  Secondly, the space resulting fromSecondly, the space resulting from lingualization prevents the buccinatorlingualization prevents the buccinator from neutralizing the lateral forces offrom neutralizing the lateral forces of the tongue during function.the tongue during function. www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26.  MASSETER:MASSETER:  The masseter muscle has noThe masseter muscle has no influence on the neutral zone. It onlyinfluence on the neutral zone. It only affects the distobuccal border of theaffects the distobuccal border of the denture.denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  27. 27. www.indiandentalacademy.comwww.indiandentalacademy.com
  28. 28.  MUSCLES OF THE LIPSMUSCLES OF THE LIPS  Orbicularis orisOrbicularis oris : To a great extent: To a great extent forms the lips. In function, as informs the lips. In function, as in chewing, smiling and swallowing, itchewing, smiling and swallowing, it exerts force against the teeth andexerts force against the teeth and denture flanges, which isdenture flanges, which is counteracted by the tongue.counteracted by the tongue. www.indiandentalacademy.comwww.indiandentalacademy.com
  29. 29.  Canine muscleCanine muscle : This together with: This together with other muscles, pulls the lower lip upother muscles, pulls the lower lip up and in sucking and swallowing helpsand in sucking and swallowing helps to pull the lips forward, thus exertingto pull the lips forward, thus exerting forces on the teeth and labialforces on the teeth and labial denture flange.denture flange. www.indiandentalacademy.comwww.indiandentalacademy.com
  30. 30.  The greater zygomatic muscleThe greater zygomatic muscle pulls the angle of the, mouth upwardpulls the angle of the, mouth upward and backward.and backward.  The risorius muscle retracts theThe risorius muscle retracts the corner of the mouth.corner of the mouth.  The mentalis muscle turns theThe mentalis muscle turns the lower lip outward and in contractinglower lip outward and in contracting makes the lower labial vestibulemakes the lower labial vestibule shallow.shallow. www.indiandentalacademy.comwww.indiandentalacademy.com
  31. 31.  The triangular muscle contractsThe triangular muscle contracts during sucking to exert pressure onduring sucking to exert pressure on the teeth and the denture flanges.the teeth and the denture flanges. www.indiandentalacademy.comwww.indiandentalacademy.com
  32. 32.  The ModiolusThe Modiolus : Because of the: Because of the strength and variability of movement ofstrength and variability of movement of the area, the modiolus is extremelythe area, the modiolus is extremely important in relation to the stability ofimportant in relation to the stability of the lower denture. Unless the teeth andthe lower denture. Unless the teeth and external surface of the denture areexternal surface of the denture are properly positioned and contoured byproperly positioned and contoured by narrowing in the premolar area, thenarrowing in the premolar area, the modiolus may constantly unseat themodiolus may constantly unseat the lower denture.lower denture.www.indiandentalacademy.comwww.indiandentalacademy.com
  33. 33. www.indiandentalacademy.comwww.indiandentalacademy.com
  34. 34.  MUSCLES OF THE TONGUEMUSCLES OF THE TONGUE  The tongue is composed ofThe tongue is composed of intrinsic muscles that lie within theintrinsic muscles that lie within the tongue itself and extrinsic musclestongue itself and extrinsic muscles that insert into the tongue.that insert into the tongue.  The function of the extrinsicThe function of the extrinsic muscles the styloglossus,muscles the styloglossus, palatoglossus, hyoglossus, andpalatoglossus, hyoglossus, and genioglossus is to move the tongue‑genioglossus is to move the tongue‑ into various positionsinto various positions www.indiandentalacademy.comwww.indiandentalacademy.com
  35. 35.  . The tongue is capable of many. The tongue is capable of many varied shapes and positions duringvaried shapes and positions during speech, mastication, and swallowingspeech, mastication, and swallowing and in all of these functions is inand in all of these functions is in constant contact with the lingualconstant contact with the lingual surface of the teeth, the lingualsurface of the teeth, the lingual flange of the lower denture and theflange of the lower denture and the palatal surface of the upper denture.palatal surface of the upper denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  36. 36.  Because of this contact, the tongueBecause of this contact, the tongue is a dominant factor in establishingis a dominant factor in establishing the neutral zone and therefore in thethe neutral zone and therefore in the stability or .lack of stability of thestability or .lack of stability of the lower denture.lower denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  37. 37.  The common practice ofThe common practice of lingualization is probably one of thelingualization is probably one of the greatest influencing factors in lowergreatest influencing factors in lower denture instability, because itdenture instability, because it violates the neutral zone andviolates the neutral zone and encroaches on the tongue space.encroaches on the tongue space. www.indiandentalacademy.comwww.indiandentalacademy.com
  38. 38. www.indiandentalacademy.comwww.indiandentalacademy.com
  39. 39. DENTURE SURFACESDENTURE SURFACES  The dental profession has alwaysThe dental profession has always been concerned with equalizing thebeen concerned with equalizing the vertical forces that are delivered byvertical forces that are delivered by the occlusal surfaces of the teeth andthe occlusal surfaces of the teeth and that are counteracted by the vaultthat are counteracted by the vault and the ridges. It has ignored theand the ridges. It has ignored the importance of the horizontal forcesimportance of the horizontal forces exerted on the polished or externalexerted on the polished or external surface of the denturesurface of the denture www.indiandentalacademy.comwww.indiandentalacademy.com
  40. 40.  Thus the dental profession has beenThus the dental profession has been concerned mainly with two surfaces ‑concerned mainly with two surfaces ‑ the occlusal and the impressionthe occlusal and the impression surfaces.surfaces.  Sir Wilfred Fish in 1948 describedSir Wilfred Fish in 1948 described a denture as having three surfaces,a denture as having three surfaces, with each surface playing anwith each surface playing an independent and important role inindependent and important role in the overall fit, stability and comfortthe overall fit, stability and comfort of the denture.of the denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  41. 41.  The first surface, the impressionThe first surface, the impression surface, is that part of the denture insurface, is that part of the denture in contact with the tissues and oncontact with the tissues and on which the denture rests andwhich the denture rests and determines retention of the denture,determines retention of the denture,  The second surface, the occlusalThe second surface, the occlusal surface is that area in contact withsurface is that area in contact with the teeth, either natural or artificial,the teeth, either natural or artificial, of the opposite jaw.of the opposite jaw. www.indiandentalacademy.comwww.indiandentalacademy.com
  42. 42.  The stability of the denture when theThe stability of the denture when the teeth are in contact is determined byteeth are in contact is determined by the fit of the impression surfacethe fit of the impression surface against the tissues and the fit of theagainst the tissues and the fit of the occlusal surfaces against each other.occlusal surfaces against each other. www.indiandentalacademy.comwww.indiandentalacademy.com
  43. 43.  The third surface, the polished orThe third surface, the polished or external surface as termed by Fish,external surface as termed by Fish, is all the rest of the denture that isis all the rest of the denture that is not part of the other two surfaces. Itnot part of the other two surfaces. It is mostly denture base material, butis mostly denture base material, but it consists also of those surfaces ofit consists also of those surfaces of the teeth that are not contacting orthe teeth that are not contacting or articulating surfaces.articulating surfaces. www.indiandentalacademy.comwww.indiandentalacademy.com
  44. 44.  The buccal and lingual surfaces ofThe buccal and lingual surfaces of the posterior teeth and the labial andthe posterior teeth and the labial and lingual surfaces of the lower anteriorlingual surfaces of the lower anterior teeth are not part of the occlusalteeth are not part of the occlusal surface but are part of the polishedsurface but are part of the polished surface of the denture. The uppersurface of the denture. The upper anterior teeth actually belong to twoanterior teeth actually belong to two surfaces, both the occlusal and thesurfaces, both the occlusal and the polished surfaces.polished surfaces. www.indiandentalacademy.comwww.indiandentalacademy.com
  45. 45.  When the teeth are in contact, theWhen the teeth are in contact, the lingual surfaces of the upper anteriorlingual surfaces of the upper anterior teeth are part of the occlusal surface.teeth are part of the occlusal surface. When the teeth are apart, as inWhen the teeth are apart, as in speaking as at rest, these surfacesspeaking as at rest, these surfaces are part of the polished surface.are part of the polished surface. www.indiandentalacademy.comwww.indiandentalacademy.com
  46. 46.  The external surface is in contactThe external surface is in contact with, the cheeks, lips and tongue.with, the cheeks, lips and tongue. One can visualize that, based on aOne can visualize that, based on a square unit of area; the externalsquare unit of area; the external surface is as large as or larger thansurface is as large as or larger than the impression and occlusal surfacesthe impression and occlusal surfaces combined, depending on thecombined, depending on the anatomic structures.anatomic structures. www.indiandentalacademy.comwww.indiandentalacademy.com
  47. 47. INFLUENCE OF FORCES ONINFLUENCE OF FORCES ON DENTURE SURFACESDENTURE SURFACES  The more the ridge loss, the less theThe more the ridge loss, the less the area of the denture base and the lessarea of the denture base and the less the influence the impression surfacethe influence the impression surface area will have on the stability andarea will have on the stability and retention of the denture.retention of the denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  48. 48.  As the surface area of the impressionAs the surface area of the impression surface decreases and the externalsurface decreases and the external surface area increases, thesurface area increases, the development and contour of thedevelopment and contour of the external surface becomes moreexternal surface becomes more critical.critical. www.indiandentalacademy.comwww.indiandentalacademy.com
  49. 49.  In other words, where more of theIn other words, where more of the ridge has been lost, the more theridge has been lost, the more the denture stability and retention isdenture stability and retention is dependent on the external surfacedependent on the external surface than on the impression surface.than on the impression surface. Many unstable lower dentures areMany unstable lower dentures are caused by the external surface notcaused by the external surface not being properly formed and the teethbeing properly formed and the teeth not positioned in the neutral zone.not positioned in the neutral zone. www.indiandentalacademy.comwww.indiandentalacademy.com
  50. 50.  The forces on the external surfaceThe forces on the external surface are constantly changing inare constantly changing in magnitude and direction duringmagnitude and direction during swallowing, speaking andswallowing, speaking and mastication. It is only when themastication. It is only when the mouth is completely at rest, that themouth is completely at rest, that the forces are constant.forces are constant. www.indiandentalacademy.comwww.indiandentalacademy.com
  51. 51.  If a person's teeth were in contact allIf a person's teeth were in contact all the time, the external surface wouldthe time, the external surface would be relatively unimportant in denturebe relatively unimportant in denture stability. Conversely if a personstability. Conversely if a person never brought his teeth into contact,never brought his teeth into contact, the occlusal surface would bethe occlusal surface would be relatively unimportant and therelatively unimportant and the stability would be dependent on, thestability would be dependent on, the forces on the external surface asforces on the external surface as transmitted to the impressiontransmitted to the impression surface.surface. www.indiandentalacademy.comwww.indiandentalacademy.com
  52. 52.  The only time teeth are in contact is,The only time teeth are in contact is, during mastication and swallowing.during mastication and swallowing. This means that the patient will onlyThis means that the patient will only make tooth contact during normalmake tooth contact during normal function. But the lips, cheeks andfunction. But the lips, cheeks and tongue are constantly in function.tongue are constantly in function. This stresses the significance of theThis stresses the significance of the horizontal forces exerted by the lips,horizontal forces exerted by the lips, cheeks and tongue.cheeks and tongue. www.indiandentalacademy.comwww.indiandentalacademy.com
  53. 53.  In order to construct dentures thatIn order to construct dentures that function properly not only in chewingfunction properly not only in chewing but also in speaking and swallowing,but also in speaking and swallowing, we must develop the fit and contourwe must develop the fit and contour of the external surface of dentureof the external surface of denture just as accurately and meticulouslyjust as accurately and meticulously as the fit and contour of theas the fit and contour of the impression surface and the occlusalimpression surface and the occlusal surface.surface. www.indiandentalacademy.comwww.indiandentalacademy.com
  54. 54.  The lower posterior teeth areThe lower posterior teeth are drastically affected by the position ofdrastically affected by the position of the tongue. If the lower posteriorthe tongue. If the lower posterior teeth are lingualized excessively,teeth are lingualized excessively, normal tongue function willnormal tongue function will immediately unseat the denture. Theimmediately unseat the denture. The tongue cannot and should not betongue cannot and should not be restricted by the position of therestricted by the position of the posterior teeth.posterior teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  55. 55. MUSCLE INFLUENCE ON THEMUSCLE INFLUENCE ON THE DEVELOPMENTDEVELOPMENT OF THE DENTAL ARCHESOF THE DENTAL ARCHES  Teeth erupt into the mouth underTeeth erupt into the mouth under the influence of muscularthe influence of muscular environment. This environmentenvironment. This environment which is created by the, forceswhich is created by the, forces between the tongue, cheeks and lipsbetween the tongue, cheeks and lips has a definite influence on thehas a definite influence on the position of the erupting teeth, theposition of the erupting teeth, the resultant arch form and occlusion.resultant arch form and occlusion.www.indiandentalacademy.comwww.indiandentalacademy.com
  56. 56.  However, the muscular forces aloneHowever, the muscular forces alone do not always determine thedo not always determine the developing dental arch form. There isdeveloping dental arch form. There is genetic factor which cannot begenetic factor which cannot be overlooked. This internal factor,overlooked. This internal factor, along with the local environmentalalong with the local environmental forces, combines their influencesforces, combines their influences uniquely to determine the final archuniquely to determine the final arch form and tooth position.form and tooth position. www.indiandentalacademy.comwww.indiandentalacademy.com
  57. 57.  It would stand to reason that whenIt would stand to reason that when the teeth are erupting into the mouththe teeth are erupting into the mouth during childhood and adolescence (2during childhood and adolescence (2 - 14 year group) the muscular- 14 year group) the muscular activity and habits that develop willactivity and habits that develop will continue through life.continue through life. www.indiandentalacademy.comwww.indiandentalacademy.com
  58. 58.  Even after the teeth are lost, theEven after the teeth are lost, the forces created by these habits andforces created by these habits and actions still persist and will have aactions still persist and will have a great influence on any complete orgreat influence on any complete or extensive partial removableextensive partial removable prosthesis that is placed into theprosthesis that is placed into the mouth.mouth. www.indiandentalacademy.comwww.indiandentalacademy.com
  59. 59.  It is therefore extremely importantIt is therefore extremely important that the teeth be placed in that partthat the teeth be placed in that part of the mouth and with an arch formof the mouth and with an arch form that falls within the area formed bythat falls within the area formed by muscular forces.muscular forces. www.indiandentalacademy.comwww.indiandentalacademy.com
  60. 60.  Our objective is to utilise theOur objective is to utilise the information on denture space andinformation on denture space and muscle function so as to, position themuscle function so as to, position the teeth and the external surfaces ofteeth and the external surfaces of the denture that the force thethe denture that the force the musculature exerts, instead ofmusculature exerts, instead of having a negative influence, willhaving a negative influence, will favourably affect the dentures andfavourably affect the dentures and tend to seat or stabilize thetend to seat or stabilize the dentures.dentures. www.indiandentalacademy.comwww.indiandentalacademy.com
  61. 61.  This can be accomplished throughThis can be accomplished through awareness of the neutral zone andawareness of the neutral zone and by positioning the teeth andby positioning the teeth and developing external surfaces of thedeveloping external surfaces of the denture so that all the forces exerteddenture so that all the forces exerted are neutralized and the denture is inare neutralized and the denture is in a state of equilibrium.a state of equilibrium. www.indiandentalacademy.comwww.indiandentalacademy.com
  62. 62. DIRECTION OF FORCESDIRECTION OF FORCES  For the muscular forces to be of aFor the muscular forces to be of a stabilizing nature, the dentures muststabilizing nature, the dentures must be so constructed that they willbe so constructed that they will receive these forces at the properreceive these forces at the proper angle. Dr. Fish (1948) described theangle. Dr. Fish (1948) described the cross section of stable dentures incross section of stable dentures in the molar area to be triangular inthe molar area to be triangular in shape, with the tooth being the apexshape, with the tooth being the apex and the denture periphery the baseand the denture periphery the base of a triangle.of a triangle.www.indiandentalacademy.comwww.indiandentalacademy.com
  63. 63.  A force exerted on an inclined planeA force exerted on an inclined plane may be broken down into twomay be broken down into two components. One component acts incomponents. One component acts in the direction parallel to thethe direction parallel to the inclinedinclined plane. The other component, calledplane. The other component, called normal force, acts perpendicularly tonormal force, acts perpendicularly to the inclined plane. If the inclinedthe inclined plane. If the inclined planes of the external surface areplanes of the external surface are properly fashioned and the forces areproperly fashioned and the forces are of equal magnitude, the resultantof equal magnitude, the resultant normal force will be in a seatingnormal force will be in a seating directiondirection www.indiandentalacademy.comwww.indiandentalacademy.com
  64. 64.  By the same token, if the denturesBy the same token, if the dentures are triangular but not properlyare triangular but not properly located within the neutral zone, thelocated within the neutral zone, the lateral force will be unequal and notlateral force will be unequal and not provide the equilibrium necessary forprovide the equilibrium necessary for a stable denture. This willa stable denture. This will resultresult either in the dislodgement of theeither in the dislodgement of the denture or unequal pressure on thedenture or unequal pressure on the ridge.ridge. www.indiandentalacademy.comwww.indiandentalacademy.com
  65. 65. NEUTRALIZATION OF FORCESNEUTRALIZATION OF FORCES  The theory of the neutralization ofThe theory of the neutralization of forces that stabilize dentures and theforces that stabilize dentures and the rationale involved was one of therationale involved was one of the major contributions made bymajor contributions made by Dr.Russel Tench and his co worker,Dr.Russel Tench and his co worker, Dr.A.A.Cavalcarti.Dr.A.A.Cavalcarti. www.indiandentalacademy.comwww.indiandentalacademy.com
  66. 66.  lips, cheeks and tongue in thelips, cheeks and tongue in the passive and functioning state exertpassive and functioning state exert forces on the natural teeth. In theforces on the natural teeth. In the natural dentition, arch integrity andnatural dentition, arch integrity and tooth position are maintained whentooth position are maintained when all the forces generated by theall the forces generated by the musculature are neutralized.musculature are neutralized. www.indiandentalacademy.comwww.indiandentalacademy.com
  67. 67.  Any changes in the forces generatedAny changes in the forces generated by the musculature because ofby the musculature because of increased size, altered muscleincreased size, altered muscle function, or abnormal habit patternsfunction, or abnormal habit patterns will upset the equilibrium and resultwill upset the equilibrium and result in alteration of tooth position andin alteration of tooth position and arch form.arch form. www.indiandentalacademy.comwww.indiandentalacademy.com
  68. 68.  If we accept the assumption that theIf we accept the assumption that the teeth are positioned and maintainedteeth are positioned and maintained in a neutral state by all the forcesin a neutral state by all the forces exerted against them by theexerted against them by the musculature, it seems reasonablemusculature, it seems reasonable that when the dentures are made,that when the dentures are made, the artificial teeth should be placedthe artificial teeth should be placed in the same relative position to thein the same relative position to the musculature as the natural teeth.musculature as the natural teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  69. 69.  . The term "relative position" rather. The term "relative position" rather than exact position" is used becausethan exact position" is used because age, tonus, ridge resorption andage, tonus, ridge resorption and other factors may modify or alter theother factors may modify or alter the denture space and neutral zone sodenture space and neutral zone so that the artificial teeth, should notthat the artificial teeth, should not necessarily be in the exact samenecessarily be in the exact same position as the natural teeth.position as the natural teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  70. 70.  If the teeth are placed too farIf the teeth are placed too far lingually in the molar region, theylingually in the molar region, they will encroach on the tongue space.will encroach on the tongue space. Dr.Mayskens estimates that if theDr.Mayskens estimates that if the sizes of the mandibular teeth are toosizes of the mandibular teeth are too large or if the posterior teeth are setlarge or if the posterior teeth are set 1 mm lingually, the tongue is1 mm lingually, the tongue is deprived of approximately 1000deprived of approximately 1000 cubic mm of functional space. Thiscubic mm of functional space. This can force the tongue into ancan force the tongue into an abnormal retracted position.abnormal retracted position. www.indiandentalacademy.comwww.indiandentalacademy.com
  71. 71.  In summary, the neutral zoneIn summary, the neutral zone philosophy is based on the conceptphilosophy is based on the concept that for each individual patient therethat for each individual patient there exists within the denture space aexists within the denture space a specific area where the function ofspecific area where the function of the musculature will not unseat thethe musculature will not unseat the denture, and at the same time wheredenture, and at the same time where the forces generated by the tonguethe forces generated by the tongue are neutralized by the forcesare neutralized by the forces generated by the lips and cheeksgenerated by the lips and cheeks Furthermore, denture stability is asFurthermore, denture stability is as much or more influenced by toothmuch or more influenced by tooth position and flange contour as byposition and flange contour as by any other factors.any other factors. www.indiandentalacademy.comwww.indiandentalacademy.com
  72. 72.  In other words, we should not beIn other words, we should not be 'dogmatic and insist that the tooth'dogmatic and insist that the tooth should always be placed over theshould always be placed over the crest of the ridge, or lingual to thecrest of the ridge, or lingual to the ridge or buccal to the ridge.ridge or buccal to the ridge. Placement of the teeth should bePlacement of the teeth should be detected by the musculature and willdetected by the musculature and will vary for different patients.vary for different patients. www.indiandentalacademy.comwww.indiandentalacademy.com
  73. 73. DETERMINATION OF THEDETERMINATION OF THE NEUTRAL ZONENEUTRAL ZONE DIAGNOSIS AND TREATMENTDIAGNOSIS AND TREATMENT PLANNINGPLANNING  Success in complete dentureSuccess in complete denture prosthetics is frequently dependentprosthetics is frequently dependent on what is done prior to theon what is done prior to the construction of the dentures as muchconstruction of the dentures as much as or more than on the skill andas or more than on the skill and meticulous care utilized in the actualmeticulous care utilized in the actual construction of dentures.construction of dentures. www.indiandentalacademy.comwww.indiandentalacademy.com
  74. 74.  Examination, diagnosis, andExamination, diagnosis, and treatment planning for completetreatment planning for complete dentures should be as meticulousdentures should be as meticulous and detailed as for any other branchand detailed as for any other branch of dentistry.of dentistry.  After a proper examination andAfter a proper examination and preparation of diagnostic casts we gopreparation of diagnostic casts we go in for the treatment proper.in for the treatment proper. www.indiandentalacademy.comwww.indiandentalacademy.com
  75. 75. Reversed Sequence inReversed Sequence in Denture ConstructionDenture Construction www.indiandentalacademy.comwww.indiandentalacademy.com
  76. 76.  First, the bases are very carefullyFirst, the bases are very carefully adjusted in the mouth to be sureadjusted in the mouth to be sure that they are not overextended andthat they are not overextended and that they, are stable during mouththat they, are stable during mouth opening, swallowing and speaking.opening, swallowing and speaking. www.indiandentalacademy.comwww.indiandentalacademy.com
  77. 77.  Then modelling compound instead ofThen modelling compound instead of wax, is used to fabricate occlusionwax, is used to fabricate occlusion rims. These rims which are mouldedrims. These rims which are moulded by muscle function, locate theby muscle function, locate the patients neutral zone,.patients neutral zone,. www.indiandentalacademy.comwww.indiandentalacademy.com
  78. 78.  After tentative vertical dimensionAfter tentative vertical dimension and centric relation are `established,and centric relation are `established, the final impressions are made withthe final impressions are made with a closed mouth procedure. Onlya closed mouth procedure. Only then, when the final impression isthen, when the final impression is completed, are the verticalcompleted, are the vertical dimension and centric relationdimension and centric relation refined and finalized.refined and finalized. www.indiandentalacademy.comwww.indiandentalacademy.com
  79. 79. DIAGNOSING THE LOWERDIAGNOSING THE LOWER DENTURE PROBLEMDENTURE PROBLEM  The premise behind the rationale isThe premise behind the rationale is that, in our thinking and procedures,that, in our thinking and procedures, we should separate the denture basewe should separate the denture base from that which rests on the denturefrom that which rests on the denture base - the body of the denture. Withbase - the body of the denture. With the neutral zone approach, thethe neutral zone approach, the impression surface is called the baseimpression surface is called the base and the polished surface is called theand the polished surface is called the 'body' of the denture.'body' of the denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  80. 80.  Once the operator begins to think inOnce the operator begins to think in terms of first creating a stable, baseterms of first creating a stable, base and then placing on that base, teethand then placing on that base, teeth and flange contours that will notand flange contours that will not unseat the denture base, theunseat the denture base, the problem and its solution becomeproblem and its solution become apparent and comparatively simpleapparent and comparatively simple to solve.to solve. www.indiandentalacademy.comwww.indiandentalacademy.com
  81. 81. EFFECT OF VERTICAL ANDEFFECT OF VERTICAL AND HORIZONTAL FORCESHORIZONTAL FORCES www.indiandentalacademy.comwww.indiandentalacademy.com
  82. 82.  The borders of the dentureThe borders of the denture  The body of the denture consists ofThe body of the denture consists of the external or polished surface andthe external or polished surface and the labial, buccal and lingual surfacesthe labial, buccal and lingual surfaces of the teethof the teeth The occlusal surfaces and incisal edgesThe occlusal surfaces and incisal edges of the tooth on a dentureof the tooth on a denture www.indiandentalacademy.comwww.indiandentalacademy.com
  83. 83. IDENTIFYING CAUSES OFIDENTIFYING CAUSES OF INSTABILITYINSTABILITY www.indiandentalacademy.comwww.indiandentalacademy.com
  84. 84.  First, an acrylic base is constructed,First, an acrylic base is constructed, www.indiandentalacademy.comwww.indiandentalacademy.com
  85. 85.  If we now place on this stable baseIf we now place on this stable base the body of the denture,the body of the denture, www.indiandentalacademy.comwww.indiandentalacademy.com
  86. 86.  We now have an upper and lowerWe now have an upper and lower base and body. If we instruct the‑base and body. If we instruct the‑ patient to bring the jaws togetherpatient to bring the jaws together and the denture bases are dislodged,and the denture bases are dislodged, it can only be caused by theit can only be caused by the occlusion and the occlusion should beocclusion and the occlusion should be corrected.corrected. www.indiandentalacademy.comwww.indiandentalacademy.com
  87. 87. www.indiandentalacademy.comwww.indiandentalacademy.com
  88. 88. CLINICAL AND LABORATORYCLINICAL AND LABORATORY PROCEDURESPROCEDURES www.indiandentalacademy.comwww.indiandentalacademy.com
  89. 89. www.indiandentalacademy.comwww.indiandentalacademy.com
  90. 90. PRIMARY IMPRESSIONS ANDPRIMARY IMPRESSIONS AND CONSTRUCTION OF ACRYLICCONSTRUCTION OF ACRYLIC TRAYSTRAYS www.indiandentalacademy.comwww.indiandentalacademy.com
  91. 91. SELECTION OF STOCK TRAYS www.indiandentalacademy.comwww.indiandentalacademy.com
  92. 92. SHAPING THE TRAYS www.indiandentalacademy.comwww.indiandentalacademy.com
  93. 93. www.indiandentalacademy.comwww.indiandentalacademy.com
  94. 94. www.indiandentalacademy.comwww.indiandentalacademy.com
  95. 95. Fingers in crisscross position & close the lips around the fingers, seal off the air, & draw in as if sucking through a straw & then swallow www.indiandentalacademy.comwww.indiandentalacademy.com
  96. 96. www.indiandentalacademy.comwww.indiandentalacademy.com
  97. 97. The patient is instructed to seal off the air by closing the lips around the operator’s finger & to suck & swallow vigorously . www.indiandentalacademy.comwww.indiandentalacademy.com
  98. 98. www.indiandentalacademy.comwww.indiandentalacademy.com
  99. 99. www.indiandentalacademy.comwww.indiandentalacademy.com
  100. 100. CONSTRUCTION OF THECONSTRUCTION OF THE ACRYLIC BASEACRYLIC BASE www.indiandentalacademy.comwww.indiandentalacademy.com
  101. 101. www.indiandentalacademy.comwww.indiandentalacademy.com
  102. 102. www.indiandentalacademy.comwww.indiandentalacademy.com
  103. 103. CREATING STABLE BASESCREATING STABLE BASES www.indiandentalacademy.comwww.indiandentalacademy.com
  104. 104.  Stability of base is tested by 2Stability of base is tested by 2 methodsmethods  1 base in patient’s mouth &1 base in patient’s mouth & operator’s fingers are placed onoperator’s fingers are placed on bicuspid area to firmly seat the basebicuspid area to firmly seat the base If squishing sound is heard as the baseIf squishing sound is heard as the base is seated or eases up or pops upis seated or eases up or pops up www.indiandentalacademy.comwww.indiandentalacademy.com
  105. 105.  2 ask the patient to open wide, purse2 ask the patient to open wide, purse the lips as in sucking, wet the lips &the lips as in sucking, wet the lips & speak normally if any unstabilityspeak normally if any unstability observed by the operator or theobserved by the operator or the patient himselfpatient himself www.indiandentalacademy.comwww.indiandentalacademy.com
  106. 106.  Methods for locating areas ofMethods for locating areas of overextension of the baseoverextension of the base  visual observation or eyeballingvisual observation or eyeballing  use of disclosing materialuse of disclosing material www.indiandentalacademy.comwww.indiandentalacademy.com
  107. 107. visual observation or eyeballingvisual observation or eyeballing www.indiandentalacademy.comwww.indiandentalacademy.com
  108. 108. www.indiandentalacademy.comwww.indiandentalacademy.com
  109. 109. www.indiandentalacademy.comwww.indiandentalacademy.com
  110. 110. use of disclosing materialuse of disclosing material www.indiandentalacademy.comwww.indiandentalacademy.com
  111. 111.  Mandibular- 6 sectionsMandibular- 6 sections 1 labial or buccal1 labial or buccal open widely several times, thenopen widely several times, then purse the lips as in sucking, & thenpurse the lips as in sucking, & then swallow vigorously base is removedswallow vigorously base is removed and examined.and examined. at least 1-2mm thickness ofat least 1-2mm thickness of disclosing wax, smooth & roundeddisclosing wax, smooth & rounded should be seen.should be seen. www.indiandentalacademy.comwww.indiandentalacademy.com
  112. 112. www.indiandentalacademy.comwww.indiandentalacademy.com
  113. 113. www.indiandentalacademy.comwww.indiandentalacademy.com
  114. 114. www.indiandentalacademy.comwww.indiandentalacademy.com
  115. 115.  2 lingual2 lingual swallow vigorously several times,swallow vigorously several times, wet the lips with the tongue & andwet the lips with the tongue & and count from 1 to 10count from 1 to 10 www.indiandentalacademy.comwww.indiandentalacademy.com
  116. 116. www.indiandentalacademy.comwww.indiandentalacademy.com
  117. 117.  Retromylohyoid fossaRetromylohyoid fossa lingual to retromolarpad andlingual to retromolarpad and posterior to mylohyoid ridge-posterior to mylohyoid ridge- undercut areaundercut area www.indiandentalacademy.comwww.indiandentalacademy.com
  118. 118. www.indiandentalacademy.comwww.indiandentalacademy.com
  119. 119.  Maxillary- 4 sections (excluding posteriorMaxillary- 4 sections (excluding posterior border)border) frequently under extended area infrequently under extended area in maxillary base is around the tuberosity inmaxillary base is around the tuberosity in the buccal space area.the buccal space area. functional movements –opening wide,functional movements –opening wide, pursing the lips as in sucking, bringing thepursing the lips as in sucking, bringing the upper lip down, swallowing & moving theupper lip down, swallowing & moving the upper jaw from side to side (thickness ofupper jaw from side to side (thickness of flange over tuberosity to be sure that theflange over tuberosity to be sure that the coronoid process of the mandible doesnotcoronoid process of the mandible doesnot dislodge the upperbase.dislodge the upperbase. www.indiandentalacademy.comwww.indiandentalacademy.com
  120. 120. www.indiandentalacademy.comwww.indiandentalacademy.com
  121. 121. Locating the posterior borderLocating the posterior border  Posterior border should terminate atPosterior border should terminate at the flexion line between the movablethe flexion line between the movable & nonmovable tissue of the palate.& nonmovable tissue of the palate. vibrating line/blowdown linevibrating line/blowdown line 3 marks should be made after drying3 marks should be made after drying one on each hamular notch & third inone on each hamular notch & third in the midline at flexion line.the midline at flexion line. www.indiandentalacademy.comwww.indiandentalacademy.com
  122. 122. www.indiandentalacademy.comwww.indiandentalacademy.com
  123. 123. www.indiandentalacademy.comwww.indiandentalacademy.com
  124. 124. LOCATING THE NEUTRAL ZONELOCATING THE NEUTRAL ZONE AND PLANE OF OCCLUSIONAND PLANE OF OCCLUSION  Materials:Materials:  Locating the neutral zone for theLocating the neutral zone for the lower denture is one of the mostlower denture is one of the most important factors in achievingimportant factors in achieving stability of the lower denture. Tostability of the lower denture. To locate the neutral zone and form thelocate the neutral zone and form the body of the denture, if is necessarybody of the denture, if is necessary to use materials that can be mouldedto use materials that can be moulded by the horizontal forces of theby the horizontal forces of the tongue, lips and cheeks.tongue, lips and cheeks.www.indiandentalacademy.comwww.indiandentalacademy.com
  125. 125.  Buchman, Gelb, Lott and Levin, andBuchman, Gelb, Lott and Levin, and Russell have described the use ofRussell have described the use of waxes in locating the neutral zone.waxes in locating the neutral zone.  Kline of France has advocated theKline of France has advocated the use of self curing acrylic to form ause of self curing acrylic to form a 'piezograph', which is his term for'piezograph', which is his term for the registration of the neutral zone.the registration of the neutral zone.  Health of England has, forHealth of England has, for experimental purposes used a gelexperimental purposes used a gel that is a polymer of dimethylthat is a polymer of dimethyl silocane filled with 17% calciumsilocane filled with 17% calcium silicate.silicate. www.indiandentalacademy.comwww.indiandentalacademy.com
  126. 126.  TenchTench has suggested the use ofhas suggested the use of modelling compound, whichmodelling compound, which hashas worked well. Korr's low fusing grayworked well. Korr's low fusing gray and green compound is best suitedand green compound is best suited for this purpose. It permits thefor this purpose. It permits the patient to mold the compound intopatient to mold the compound into the neutral zone with the leastthe neutral zone with the least amount of time and effort.amount of time and effort. www.indiandentalacademy.comwww.indiandentalacademy.com
  127. 127. LOCATING THE NEUTRAL ZONELOCATING THE NEUTRAL ZONE FOR THE LOWER ARCHFOR THE LOWER ARCH www.indiandentalacademy.comwww.indiandentalacademy.com
  128. 128. www.indiandentalacademy.comwww.indiandentalacademy.com
  129. 129. www.indiandentalacademy.comwww.indiandentalacademy.com
  130. 130. ESTABLISHING THE 0CCLUSALESTABLISHING THE 0CCLUSAL PLANEPLANE  In the natural dentition, the lowerIn the natural dentition, the lower occlusal plane runs from the incisalocclusal plane runs from the incisal edges of the lower anterior teethedges of the lower anterior teeth through the tips of the cusps of thethrough the tips of the cusps of the posterior teeth to a pointposterior teeth to a point approximately two thirds of theapproximately two thirds of the height of the retromolar padheight of the retromolar pad www.indiandentalacademy.comwww.indiandentalacademy.com
  131. 131.  To locate the occlusal plane, placeTo locate the occlusal plane, place the rim back into the mouth and usethe rim back into the mouth and use a sharp pointed pencil to mark thea sharp pointed pencil to mark the commisures of the lip and the heightcommisures of the lip and the height of the lower lip at rest. These threeof the lower lip at rest. These three points are connected by a line that ispoints are connected by a line that is continued on each side to a pointcontinued on each side to a point one half to two thirds the height ofone half to two thirds the height of the retromolar pad. The excessthe retromolar pad. The excess compound is trimmed to this line.compound is trimmed to this line. www.indiandentalacademy.comwww.indiandentalacademy.com
  132. 132. www.indiandentalacademy.comwww.indiandentalacademy.com
  133. 133. www.indiandentalacademy.comwww.indiandentalacademy.com
  134. 134. www.indiandentalacademy.comwww.indiandentalacademy.com
  135. 135.  To further check the correctness ofTo further check the correctness of the height of the occlusal plane,the height of the occlusal plane, observe its relationship to the lateralobserve its relationship to the lateral borders of the tongue. With theborders of the tongue. With the tongue at rest, the height of thetongue at rest, the height of the occlusal plane should be 1 2 mm‑occlusal plane should be 1 2 mm‑ below the greatest convexity of thebelow the greatest convexity of the lateral borders of the tongue. Iflateral borders of the tongue. If necessary, the compound rim cannecessary, the compound rim can be, modified by reduction orbe, modified by reduction or addition.addition. www.indiandentalacademy.comwww.indiandentalacademy.com
  136. 136. www.indiandentalacademy.comwww.indiandentalacademy.com
  137. 137. TESTING THE STABILITY OFTESTING THE STABILITY OF THE LOWER OCCLUSION RIMTHE LOWER OCCLUSION RIM  The lower occlusion rims is placedThe lower occlusion rims is placed back into the patient’s mouth andback into the patient’s mouth and checked for stability by having thechecked for stability by having the patient open wide, wet the lips withpatient open wide, wet the lips with the tongue, count from 1 to 100, andthe tongue, count from 1 to 100, and say exaggerated "oh" "ahs" andsay exaggerated "oh" "ahs" and "ees"."ees". www.indiandentalacademy.comwww.indiandentalacademy.com
  138. 138.  The next procedure is to test theThe next procedure is to test the outer edge of the rim with the tip ofouter edge of the rim with the tip of the index finger in the bicuspid andthe index finger in the bicuspid and incisor regions. If pressure on theincisor regions. If pressure on the outer edges causes the opposite sideouter edges causes the opposite side of the rim to lift up, then the rimof the rim to lift up, then the rim must be narrowed from the labial ormust be narrowed from the labial or buccal to where the vertical pressurebuccal to where the vertical pressure will not cause the rim to tilt.will not cause the rim to tilt. www.indiandentalacademy.comwww.indiandentalacademy.com
  139. 139.  This will occur where there has beenThis will occur where there has been extensive ridge resorption and whereextensive ridge resorption and where the residual ridge is narrowthe residual ridge is narrow buccolingually and labio-lingually. Ifbuccolingually and labio-lingually. If this is not corrected and the teeththis is not corrected and the teeth placed at this position, then theplaced at this position, then the vertical forces as in mastication willvertical forces as in mastication will tilt the denture.tilt the denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  140. 140.  The final test is to have the patientThe final test is to have the patient speak, swallow, wet the lips andspeak, swallow, wet the lips and open wide without the rim moving oropen wide without the rim moving or being dislodged. We have thereforebeing dislodged. We have therefore created a tray or base that is notcreated a tray or base that is not dislodged by muscle function anddislodged by muscle function and have placed on it a body that is alsohave placed on it a body that is also not displaced by muscle function.not displaced by muscle function. www.indiandentalacademy.comwww.indiandentalacademy.com
  141. 141. LOCATING THE NEUTRAL ZONELOCATING THE NEUTRAL ZONE FOR THE UPPER ARCHFOR THE UPPER ARCH  The tray is firmly seated, and withThe tray is firmly seated, and with the operator's fingers out of thethe operator's fingers out of the mouth, the patient is instructed tomouth, the patient is instructed to suck and swallow.suck and swallow. www.indiandentalacademy.comwww.indiandentalacademy.com
  142. 142.  A line is scribed about 2 mm belowA line is scribed about 2 mm below the upper lip at rest and thethe upper lip at rest and the compound is trimmed to this line.compound is trimmed to this line. The excess in the posterior is cutThe excess in the posterior is cut away parallel to the ridge. The upperaway parallel to the ridge. The upper rim is now tentatively completed andrim is now tentatively completed and will be further modified whenwill be further modified when determining vertical dimension anddetermining vertical dimension and registering centric relation.registering centric relation. www.indiandentalacademy.comwww.indiandentalacademy.com
  143. 143. www.indiandentalacademy.comwww.indiandentalacademy.com
  144. 144. VERTICAL DIMENSION:VERTICAL DIMENSION: www.indiandentalacademy.comwww.indiandentalacademy.com
  145. 145. www.indiandentalacademy.comwww.indiandentalacademy.com
  146. 146. www.indiandentalacademy.comwww.indiandentalacademy.com
  147. 147. FINAL IMPRESSIONSFINAL IMPRESSIONS  The advantage with the use of a closedThe advantage with the use of a closed mouth technique are:mouth technique are: A more accurate functional molding ofA more accurate functional molding of the borders can be obtained, especially inthe borders can be obtained, especially in the lower arch.the lower arch. By having the patient to close gentlyBy having the patient to close gently and swallow, there is more evenand swallow, there is more even distribution of pressure and impressiondistribution of pressure and impression material with less likelihood of excessivematerial with less likelihood of excessive pressure in one area or another.pressure in one area or another. www.indiandentalacademy.comwww.indiandentalacademy.com
  148. 148.  TECHNIQUE :TECHNIQUE :  With the procedure to beWith the procedure to be described, two impression pastes ofdescribed, two impression pastes of contrasting colors are used. This iscontrasting colors are used. This is called a color coded impression‑called a color coded impression‑ procedure, the purpose of which is toprocedure, the purpose of which is to locate areas of tissue displacement.locate areas of tissue displacement. The impression trays and the twoThe impression trays and the two zinc oxide eugenol paste should be ofzinc oxide eugenol paste should be of three different colors.three different colors. www.indiandentalacademy.comwww.indiandentalacademy.com
  149. 149. LOWER SECONDARYLOWER SECONDARY IMPRESSION:IMPRESSION:  The material is mixed and placedThe material is mixed and placed evenly over the lower tray and theevenly over the lower tray and the tray is placed carefully in the mouth.tray is placed carefully in the mouth. Slight pressure is applied with theSlight pressure is applied with the forefingers in the bicuspid area untilforefingers in the bicuspid area until the paste is seen to exude from thethe paste is seen to exude from the tray around the peripheries.tray around the peripheries. www.indiandentalacademy.comwww.indiandentalacademy.com
  150. 150.  The upper rim, which has been lubricated,The upper rim, which has been lubricated, is placed into the mouth, and the patientis placed into the mouth, and the patient is guided into a hinge closure andis guided into a hinge closure and instructed not to exert any pressure afterinstructed not to exert any pressure after light contact is made. After the initiallight contact is made. After the initial contact, the patient is directed to swallowcontact, the patient is directed to swallow and remain closed. In about 30 seconds,and remain closed. In about 30 seconds, the patient is asked to open and wet thethe patient is asked to open and wet the corners of the mouth with the tongue,corners of the mouth with the tongue, purse the lips, such in as drawing throughpurse the lips, such in as drawing through a straw and then close and swallow again.a straw and then close and swallow again. At no time should excessive pressure beAt no time should excessive pressure be applied.applied. www.indiandentalacademy.comwww.indiandentalacademy.com
  151. 151.  When material has set, the lower rimWhen material has set, the lower rim and tray are removed from theand tray are removed from the mouth and inspected. If there aremouth and inspected. If there are areas of the tray showing throughareas of the tray showing through the impression material, it indicatesthe impression material, it indicates areas of excessive pressure that willareas of excessive pressure that will cause tissue displacement. Thesecause tissue displacement. These areas are relieved to a minimumareas are relieved to a minimum depth of 0.5 mm.depth of 0.5 mm. www.indiandentalacademy.comwww.indiandentalacademy.com
  152. 152.  The impression material covering theThe impression material covering the peripheris is cut away with a sharpperipheris is cut away with a sharp knife to prevent excessive pressureknife to prevent excessive pressure that will cause tissue displacement.that will cause tissue displacement. These areas are relieved to aThese areas are relieved to a minimum depth of 0.5 mm. Theminimum depth of 0.5 mm. The impression material covering theimpression material covering the peripheris is cut away with a sharpperipheris is cut away with a sharp knife to prevent excessive build up ofknife to prevent excessive build up of the borders, which would result inthe borders, which would result in overextension when theoverextension when the corrective impression is made.‑corrective impression is made.‑ www.indiandentalacademy.comwww.indiandentalacademy.com
  153. 153.  The tray is now ready for a secondThe tray is now ready for a second impression. The material of choice isimpression. The material of choice is Krex, which is white soft thin, freeKrex, which is white soft thin, free flowing and of a contrasting color toflowing and of a contrasting color to the zinc oxide eugenol used. Thethe zinc oxide eugenol used. The Krex is mixed evenly and spreadKrex is mixed evenly and spread over the entire tray and borders andover the entire tray and borders and the procedure as mentioned before isthe procedure as mentioned before is repeated. After it is set the tray isrepeated. After it is set the tray is removed and the impression isremoved and the impression is checked for defects.checked for defects. www.indiandentalacademy.comwww.indiandentalacademy.com
  154. 154. www.indiandentalacademy.comwww.indiandentalacademy.com
  155. 155. Upper impression:Upper impression:  Prior to the making of the upperPrior to the making of the upper impression, several holes are drilledimpression, several holes are drilled in the ruage area. The zinc oxidein the ruage area. The zinc oxide impression paste is mixed and placedimpression paste is mixed and placed over the trayover the tray and borders. The trayand borders. The tray is carried into the mouth andis carried into the mouth and centered over the ridges.centered over the ridges. www.indiandentalacademy.comwww.indiandentalacademy.com
  156. 156.  The anterior part of the tray isThe anterior part of the tray is seated with a light pressure toseated with a light pressure to position it properly. With the foreposition it properly. With the fore finger applying pressure in the molarfinger applying pressure in the molar area, the posterior part is seatedarea, the posterior part is seated until the material starts to flow outuntil the material starts to flow out from the posterior border.from the posterior border. www.indiandentalacademy.comwww.indiandentalacademy.com
  157. 157.  The completed lower impression isThe completed lower impression is inserted into the mouth and theinserted into the mouth and the patient is guided into a hingepatient is guided into a hinge closure, avoiding excessive pressure.closure, avoiding excessive pressure. The patient is instructed to swallowThe patient is instructed to swallow and remain closed. In 30 secondsand remain closed. In 30 seconds the patient is directed to open thethe patient is directed to open the mouth, move the jaw from side tomouth, move the jaw from side to side, purse the lips as in sucking,side, purse the lips as in sucking, bring the upper lip down hard, and‑bring the upper lip down hard, and‑ then swallows and close withoutthen swallows and close without pressure‑pressure‑ www.indiandentalacademy.comwww.indiandentalacademy.com
  158. 158.  . When the material has set the tray. When the material has set the tray is removed and the impression isis removed and the impression is inspected for pressure areas.inspected for pressure areas.  If pressure areas are present,If pressure areas are present, Krex is used for correctiveKrex is used for corrective impression and the above procedureimpression and the above procedure is carried out to get a correctedis carried out to get a corrected impression.impression. www.indiandentalacademy.comwww.indiandentalacademy.com
  159. 159. www.indiandentalacademy.comwww.indiandentalacademy.com
  160. 160. www.indiandentalacademy.comwww.indiandentalacademy.com
  161. 161. Centric relationCentric relation  The centric relation is recorded withThe centric relation is recorded with the same completed final impressionthe same completed final impression trays and compound rims.trays and compound rims.  After the vertical relation isAfter the vertical relation is rechecked and corrected for anyrechecked and corrected for any changes occuring after the finalchanges occuring after the final impression making the centricimpression making the centric relation is recorded by the check biterelation is recorded by the check bite procedure or the nick and notchprocedure or the nick and notch method.method. www.indiandentalacademy.comwww.indiandentalacademy.com
  162. 162.  After the centric relation is recordedAfter the centric relation is recorded a facebow recording is made. Aftera facebow recording is made. After this the facebow assemblage, upperthis the facebow assemblage, upper and lower final impressions, andand lower final impressions, and occlusion rims are now ready to beocclusion rims are now ready to be sent to the laboratory.sent to the laboratory. www.indiandentalacademy.comwww.indiandentalacademy.com
  163. 163. www.indiandentalacademy.comwww.indiandentalacademy.com
  164. 164. www.indiandentalacademy.comwww.indiandentalacademy.com
  165. 165. www.indiandentalacademy.comwww.indiandentalacademy.com
  166. 166. www.indiandentalacademy.comwww.indiandentalacademy.com
  167. 167. LABORATORY PROCEDURESLABORATORY PROCEDURES www.indiandentalacademy.comwww.indiandentalacademy.com
  168. 168. www.indiandentalacademy.comwww.indiandentalacademy.com
  169. 169. www.indiandentalacademy.comwww.indiandentalacademy.com
  170. 170. www.indiandentalacademy.comwww.indiandentalacademy.com
  171. 171. FABRICATION OF TONGUE, LIPFABRICATION OF TONGUE, LIP AND CHEEK MATRICESAND CHEEK MATRICES www.indiandentalacademy.comwww.indiandentalacademy.com
  172. 172. www.indiandentalacademy.comwww.indiandentalacademy.com
  173. 173. www.indiandentalacademy.comwww.indiandentalacademy.com
  174. 174. www.indiandentalacademy.comwww.indiandentalacademy.com
  175. 175. SELECTION ANDSELECTION AND ARRANGEMENT OF ANTERIORARRANGEMENT OF ANTERIOR TEETHTEETH  The neutral zone developed by eachThe neutral zone developed by each individual patient is usually not­ aindividual patient is usually not­ a narrow restricted area and thereforenarrow restricted area and therefore permits some latitude for positioningpermits some latitude for positioning of the anterior teeth to obtainof the anterior teeth to obtain adequate lip support for optimumadequate lip support for optimum facial appearance.facial appearance. www.indiandentalacademy.comwww.indiandentalacademy.com
  176. 176.  This is especially true, with theThis is especially true, with the upper neutral zone, since it is notupper neutral zone, since it is not nearly as critical for denture stabilitynearly as critical for denture stability as is the lower neutral zone.as is the lower neutral zone.  After the shade, shape, size andAfter the shade, shape, size and tooth material are selected thetooth material are selected the arrangement of the anterior teetharrangement of the anterior teeth are done.are done. www.indiandentalacademy.comwww.indiandentalacademy.com
  177. 177. www.indiandentalacademy.comwww.indiandentalacademy.com
  178. 178. SELECTION AND POSITIONINGSELECTION AND POSITIONING OF POSTERIOR TEETHOF POSTERIOR TEETH  With the neutral zone concept, eitherWith the neutral zone concept, either anatomic or non anatomic forms cananatomic or non anatomic forms can be used. The neutral zone onlybe used. The neutral zone only indicates the labiolingual orindicates the labiolingual or buccolingual position of the teeth.buccolingual position of the teeth. The occlusal forms of the teeth to beThe occlusal forms of the teeth to be used are essentially the operator'sused are essentially the operator's choice.choice. www.indiandentalacademy.comwww.indiandentalacademy.com
  179. 179.  After selection of the proper size,After selection of the proper size, occlusal morphology and material ofocclusal morphology and material of the posterior teeth to be used, we gothe posterior teeth to be used, we go in for the positioning or arrangementin for the positioning or arrangement of teeth. The following is a step byof teeth. The following is a step by step sequence for arrangement ofstep sequence for arrangement of anterior and posterior teethanterior and posterior teeth  The lower anterior teeth are set toThe lower anterior teeth are set to the height of the labial matrix and tothe height of the labial matrix and to the labial limit of the neutral zone.the labial limit of the neutral zone. www.indiandentalacademy.comwww.indiandentalacademy.com
  180. 180. www.indiandentalacademy.comwww.indiandentalacademy.com
  181. 181.  The upper anterior teeth are setThe upper anterior teeth are set against the labial limits of the upperagainst the labial limits of the upper matrix.matrix.  The lower posterior teeth are setThe lower posterior teeth are set against the tongue matrix and‑against the tongue matrix and‑ against the template occlusally.against the template occlusally.  The upper posterior teeth are set, toThe upper posterior teeth are set, to the buccal limits of the neutral zone.the buccal limits of the neutral zone. www.indiandentalacademy.comwww.indiandentalacademy.com
  182. 182. www.indiandentalacademy.comwww.indiandentalacademy.com
  183. 183.  The matrices are removed, and theThe matrices are removed, and the upper bow of the articulator is closedupper bow of the articulator is closed in order to evaluate the relationshipin order to evaluate the relationship of the upper and lower posteriorof the upper and lower posterior teeth.teeth.  The upper posterior teeth will haveThe upper posterior teeth will have to be rearranged to assure maximumto be rearranged to assure maximum contact with the lower posteriorcontact with the lower posterior teeth.teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  184. 184. www.indiandentalacademy.comwww.indiandentalacademy.com
  185. 185.  The upper and lower posterior teethThe upper and lower posterior teeth are checked for the buccal andare checked for the buccal and lingual relationship to each other.lingual relationship to each other.  In order to avoid an edge to edgeIn order to avoid an edge to edge relationship which might lead torelationship which might lead to check biting, the lower posteriorcheck biting, the lower posterior teeth may be moved buccally withinteeth may be moved buccally within the neutral zone, resulting in athe neutral zone, resulting in a cross bite relationship.‑cross bite relationship.‑ www.indiandentalacademy.comwww.indiandentalacademy.com
  186. 186. THE TRIAL DENTURETHE TRIAL DENTURE  The purpose of the trial denture is toThe purpose of the trial denture is to check thecheck the following.following.  Stability and retention of the basesStability and retention of the bases  Vertical dimensionVertical dimension  PhoneticsPhonetics  Centric relationCentric relation  EstheticsEsthetics www.indiandentalacademy.comwww.indiandentalacademy.com
  187. 187. www.indiandentalacademy.comwww.indiandentalacademy.com
  188. 188. www.indiandentalacademy.comwww.indiandentalacademy.com
  189. 189. www.indiandentalacademy.comwww.indiandentalacademy.com
  190. 190. www.indiandentalacademy.comwww.indiandentalacademy.com
  191. 191. PREPARATION OF THE TRIALPREPARATION OF THE TRIAL DENTURE FOR INVESTINGDENTURE FOR INVESTING  The laboratory procedures forThe laboratory procedures for investing, packing and processing ofinvesting, packing and processing of dentures when using the neutraldentures when using the neutral zone technique is generally the samezone technique is generally the same as for conventional dentures.as for conventional dentures. However, because of the materialsHowever, because of the materials used for the external impressions, itused for the external impressions, it is necessary to be especially carefulis necessary to be especially careful in some of the procedures.in some of the procedures. www.indiandentalacademy.comwww.indiandentalacademy.com
  192. 192.  Great care must be taken to be sureGreat care must be taken to be sure that none of the external impressionthat none of the external impression material has flowed under the basesmaterial has flowed under the bases of the trial denture.of the trial denture.  When zinc oxide eugenol paste hasWhen zinc oxide eugenol paste has been used for the externalbeen used for the external impression, the flasks should not beimpression, the flasks should not be allowed to remain in the boil out tank‑allowed to remain in the boil out tank‑ for more than 5 minutes, becausefor more than 5 minutes, because the zinc oxide eugenol paste willthe zinc oxide eugenol paste will liquefy and attack the stone,liquefy and attack the stone, resulting in a bleached appearance toresulting in a bleached appearance to the processed acrylic.the processed acrylic. www.indiandentalacademy.comwww.indiandentalacademy.com
  193. 193.  After processing the dentures areAfter processing the dentures are remount on the articulator. Occlusalremount on the articulator. Occlusal discrepancies are checked for withdiscrepancies are checked for with the template and carbon paper. Theythe template and carbon paper. They are corrected, the dentures areare corrected, the dentures are finished, polished and insertion isfinished, polished and insertion is done.done. www.indiandentalacademy.comwww.indiandentalacademy.com
  194. 194.  A clinical remounting is done and theA clinical remounting is done and the dentures are inserted and checkeddentures are inserted and checked for any discrepancies. The patient isfor any discrepancies. The patient is given post insertion instructionsgiven post insertion instructions which are similar to that ofwhich are similar to that of conventional complete dentures.conventional complete dentures. www.indiandentalacademy.comwww.indiandentalacademy.com
  195. 195. CONCLUSIONCONCLUSION  In summary, the neutral zoneIn summary, the neutral zone philosophy is based on the concept‑philosophy is based on the concept‑ that for each individual patient therethat for each individual patient there exists within, the denture space, aexists within, the denture space, a specific area where the function ofspecific area where the function of the musculature will not unseat thethe musculature will not unseat the denture, and at the same time wheredenture, and at the same time where the forces generated by the tonguethe forces generated by the tongue are neutralized by the forcesare neutralized by the forces generated by the lips arid cheeks.generated by the lips arid cheeks. www.indiandentalacademy.comwww.indiandentalacademy.com
  196. 196.  Furthermore, denture stability is asFurthermore, denture stability is as much or more influenced by toothmuch or more influenced by tooth position and flange contour as to anyposition and flange contour as to any other factor.other factor.  In other words, we should not beIn other words, we should not be dogmatic and insist that the teethdogmatic and insist that the teeth should always be placed over theshould always be placed over the crest of the ridge,or lingual to thecrest of the ridge,or lingual to the ridge or buccal to the ridge!ridge or buccal to the ridge! Placement of the teeth should bePlacement of the teeth should be dictated by the musculature and willdictated by the musculature and will vary forvary for different patients.different patients. www.indiandentalacademy.comwww.indiandentalacademy.com
  197. 197. REFERENCESREFERENCES  Beresin VE, Schiesser FJ.Beresin VE, Schiesser FJ. The neutralThe neutral zone in complete dentureszone in complete dentures.. J ProsthetJ Prosthet Dent. 1976 Oct;36(4):356­67.Dent. 1976 Oct;36(4):356­67. Neutral zone approach for dentureNeutral zone approach for denture fabrication for a partial glossectomyfabrication for a partial glossectomy patient: a clinical report.patient: a clinical report. :: J Prosthet Dent.J Prosthet Dent. 2000 Oct;84(4):390­32000 Oct;84(4):390­3  Bocage M, Lehrhaupt J.Bocage M, Lehrhaupt J. Lingual flangeLingual flange design in complete denturesdesign in complete dentures. :. : J ProsthetJ Prosthet Dent. 1977 May;37(5):499­506Dent. 1977 May;37(5):499­506 www.indiandentalacademy.comwww.indiandentalacademy.com
  198. 198.  Walsh JF, Walsh T.Walsh JF, Walsh T. Muscle­formedMuscle­formed complete mandibular denturescomplete mandibular dentures. :. : JJ Prosthet Dent. 1976 Mar;35(3):254­8.Prosthet Dent. 1976 Mar;35(3):254­8.  Orstavik JS, Floystrand F.Orstavik JS, Floystrand F. Retention ofRetention of complete maxillary dentures related tocomplete maxillary dentures related to soft tissue function . Acta Odontol Scand.soft tissue function . Acta Odontol Scand. 1984 Oct;42(5):313­20.1984 Oct;42(5):313­20.  Niedermeier W, Hofmann M.Niedermeier W, Hofmann M. The effectThe effect of the arrangement of the artificial sets ofof the arrangement of the artificial sets of teeth on the physical stability of totalteeth on the physical stability of total prothesesprotheses .. Dtsch Zahnarztl Z. 1979Dtsch Zahnarztl Z. 1979 Aug;34(8):616­8.Aug;34(8):616­8. www.indiandentalacademy.comwww.indiandentalacademy.com
  199. 199.  Demirel F, Oktemer M.Demirel F, Oktemer M. The relationsThe relations between alveolar ridge and the teethbetween alveolar ridge and the teeth located in neutral zone.located in neutral zone. :: J Marmara UnivJ Marmara Univ Dent Fac. 1996 Sep;2(2­3):562­6.Dent Fac. 1996 Sep;2(2­3):562­6.  Suenaga K, Sato T, Nishigawa G,Suenaga K, Sato T, Nishigawa G, Minagi SMinagi S. Relationship between size of. Relationship between size of denture foundation area and resorption ofdenture foundation area and resorption of alveolar ridge in the edentulousalveolar ridge in the edentulous mandible.mandible. :: J Oral Rehabil. 1997J Oral Rehabil. 1997 Apr;24(4):315­9.Apr;24(4):315­9.  www.indiandentalacademy.comwww.indiandentalacademy.com
  200. 200.  Khamis M, Razek A, Abdalla F.Khamis M, Razek A, Abdalla F. Two­dimensional study of the neutralTwo­dimensional study of the neutral zone at different occlusal verticalzone at different occlusal vertical heightsheights.. J Prosthet Dent. 1981J Prosthet Dent. 1981 Nov;46(5):484­9.Nov;46(5):484­9.  Alfano SG, Leupold RJ.Alfano SG, Leupold RJ. Using theUsing the neutral zone to obtainneutral zone to obtain maxillomandibular relationshipmaxillomandibular relationship records for complete denturerecords for complete denture patientspatients. :. : J Prosthet Dent. 2001J Prosthet Dent. 2001 Jun;85(6):621­3.Jun;85(6):621­3. www.indiandentalacademy.comwww.indiandentalacademy.com
  201. 201. www.indiandentalacademy.comwww.indiandentalacademy.com
  202. 202. REVIEW OF LITERATUREREVIEW OF LITERATURE  Beresin VE, Schiesser FJBeresin VE, Schiesser FJ. In 1976. In 1976 concluded that the neutral­zoneconcluded that the neutral­zone philosophy is based upon the conceptphilosophy is based upon the concept that for each individual patient therethat for each individual patient there exists within the denture space aexists within the denture space a specific area where the function ofspecific area where the function of the musculature will not unseat thethe musculature will not unseat the denture and where forces generateddenture and where forces generated by the tongue are neutralized by theby the tongue are neutralized by the forces generated by the lips andforces generated by the lips and cheeks.cheeks. www.indiandentalacademy.comwww.indiandentalacademy.com
  203. 203.  Walsh JF, Walsh T.Walsh JF, Walsh T. in 1976in 1976 presented a method whereby apresented a method whereby a patient's musculature is used topatient's musculature is used to indicate the position of the teeth andindicate the position of the teeth and to develop the shape and thicknessto develop the shape and thickness of the denture base. Of 30 patientsof the denture base. Of 30 patients tested, 28 experienced improvedtested, 28 experienced improved stability of their lower dentures.stability of their lower dentures. www.indiandentalacademy.comwww.indiandentalacademy.com
  204. 204.  Bocage M, Lehrhaupt J.Bocage M, Lehrhaupt J. in 1977in 1977 concluded that the lingual designconcluded that the lingual design advocated for complete lower denturesadvocated for complete lower dentures involves no changes in current conceptsinvolves no changes in current concepts regarding minimum­pressure, functionalregarding minimum­pressure, functional impression techniques. The sublingualimpression techniques. The sublingual horizontal extension suggested is placed inhorizontal extension suggested is placed in a biologically acceptable fashion bya biologically acceptable fashion by increasing the area of the denture, whichincreasing the area of the denture, which enhances retention and stability.enhances retention and stability. www.indiandentalacademy.comwww.indiandentalacademy.com
  205. 205.  Niedermeier W, Hofmann M.Niedermeier W, Hofmann M. inin 1979 demonstrated the effect of1979 demonstrated the effect of masticatory forces within and outsidemasticatory forces within and outside the stable stress­bearing areas of thethe stable stress­bearing areas of the complete upper denture on thecomplete upper denture on the pressure gradient and the flow ofpressure gradient and the flow of saliva into the space under thesaliva into the space under the prosthesis and showed thatprosthesis and showed that masticatory stress within the stablemasticatory stress within the stable area led to aarea led to a www.indiandentalacademy.comwww.indiandentalacademy.com
  206. 206.  continual increase in pressure in the spacecontinual increase in pressure in the space under the prosthesis. Masticatory forceunder the prosthesis. Masticatory force outside the stable area led to a decreaseoutside the stable area led to a decrease in pressure and an equalization ofin pressure and an equalization of pressure in this space as well aspressure in this space as well as dislocation and tilting of the completedislocation and tilting of the complete denture. Due to masticatory force outsidedenture. Due to masticatory force outside the stable area, the shape of the ridgethe stable area, the shape of the ridge influences the stability of the completeinfluences the stability of the complete denture.denture. www.indiandentalacademy.comwww.indiandentalacademy.com
  207. 207.  Khamis M, Razek A, Abdalla F.Khamis M, Razek A, Abdalla F. inin 1981 developed a new technique to1981 developed a new technique to locate the neutral zone. The neutrallocate the neutral zone. The neutral zone was studied on two groups ofzone was studied on two groups of patients with prominent or flatpatients with prominent or flat residual alveolar ridges. The neutralresidual alveolar ridges. The neutral zone was determined for eachzone was determined for each patient at three vertical heights. Itpatient at three vertical heights. It was studied both vertically andwas studied both vertically and horizontallyhorizontally www.indiandentalacademy.comwww.indiandentalacademy.com
  208. 208.  The width of the neutral zone wasThe width of the neutral zone was measured at different regions with thesemeasured at different regions with these conclusions: 1. The width of the neutralconclusions: 1. The width of the neutral zone is minimum at the level of thezone is minimum at the level of the occlusal plane and increases gradually asocclusal plane and increases gradually as it goes up and down. 2. The width of theit goes up and down. 2. The width of the neutral zone is also minimum at theneutral zone is also minimum at the posterior (molar) region and increasesposterior (molar) region and increases gradually toward the anterior.gradually toward the anterior. www.indiandentalacademy.comwww.indiandentalacademy.com
  209. 209.  3. There is no significant difference3. There is no significant difference in the width of the neutral zone inin the width of the neutral zone in patients with prominent or flatpatients with prominent or flat alveolar ridges. 4. The width of thealveolar ridges. 4. The width of the neutral zone increases as the verticalneutral zone increases as the vertical dimension of occlusion increases anddimension of occlusion increases and decreases as the vertical dimensiondecreases as the vertical dimension of occlusion decreases.of occlusion decreases. www.indiandentalacademy.comwww.indiandentalacademy.com
  210. 210.  Orstavik JS, Floystrand F.Orstavik JS, Floystrand F. in 1984in 1984 investigated the influence of freeinvestigated the influence of free tongue, lip, and cheek function ontongue, lip, and cheek function on the retention of complete maxillarythe retention of complete maxillary dentures. Test dentures weredentures. Test dentures were designed with full palatal coveragedesigned with full palatal coverage and functionally determined filling inand functionally determined filling in of the vestibular sulcus.of the vestibular sulcus. www.indiandentalacademy.comwww.indiandentalacademy.com
  211. 211.  The front teeth were arrangedThe front teeth were arranged primarily to meet cosmeticprimarily to meet cosmetic demands­­that is, anterior to the topdemands­­that is, anterior to the top of the residual alveolar ridge.of the residual alveolar ridge. Retention was measured asRetention was measured as resistance to dislodgement­resistance to dislodgement­ provoking loads applied vertically toprovoking loads applied vertically to the incisive edge of the centralthe incisive edge of the central incisors, using a miniature bite forceincisors, using a miniature bite force recorder.recorder. www.indiandentalacademy.comwww.indiandentalacademy.com
  212. 212.  All the participants were able to load theirAll the participants were able to load their front teeth with 35 N or more without lossfront teeth with 35 N or more without loss of retention. None of them experiencedof retention. None of them experienced denture dislodgement provided thedenture dislodgement provided the tongue, lips, and cheeks wee allowed totongue, lips, and cheeks wee allowed to act freely. If the peripheral soft tissuesact freely. If the peripheral soft tissues were separated from the vestibularwere separated from the vestibular denture flange, no obvious effect ondenture flange, no obvious effect on denture retention could be detected.denture retention could be detected. Physically preventing the tongue fromPhysically preventing the tongue from pressing against the posterior part of thepressing against the posterior part of the denture reduced the retentiondenture reduced the retention significantly.significantly. www.indiandentalacademy.comwww.indiandentalacademy.com
  213. 213.  Measurements of anterior loadsMeasurements of anterior loads tolerated after stepwise reductions oftolerated after stepwise reductions of the denture extension indicated thatthe denture extension indicated that the tongue acted primarily bythe tongue acted primarily by pressure against the tuber regions.pressure against the tuber regions. Tongue pressure against the centralTongue pressure against the central parts of the palate and lip or cheekparts of the palate and lip or cheek pressure against the vestibularpressure against the vestibular flange seemed to be of lessflange seemed to be of less importance.importance. www.indiandentalacademy.comwww.indiandentalacademy.com
  214. 214.  Demirel F, Oktemer M.Demirel F, Oktemer M. in 1996 definedin 1996 defined the neutral zone as the area where thethe neutral zone as the area where the forces of the tongue pressing outward areforces of the tongue pressing outward are neutralized by the forces of the cheeksneutralized by the forces of the cheeks and lips pressing inward. In this studyand lips pressing inward. In this study records of neutral zones of 30 edentulousrecords of neutral zones of 30 edentulous patients were used to establish thepatients were used to establish the relation between teeth arrangementrelation between teeth arrangement according to neutral zone principles andaccording to neutral zone principles and teeth arrangement according to crest ofteeth arrangement according to crest of ridge.ridge. www.indiandentalacademy.comwww.indiandentalacademy.com
  215. 215.  These 30 patients were classifiedThese 30 patients were classified according to their ages, edentulousaccording to their ages, edentulous periods and denture experience. Theperiods and denture experience. The results have shown that the lower molarsresults have shown that the lower molars were positioned a little bit closer to lingualwere positioned a little bit closer to lingual with respect to crest of ridge; premolarswith respect to crest of ridge; premolars were positioned either close to crest ofwere positioned either close to crest of ridge or they were coincided on it. In theridge or they were coincided on it. In the anterior zone, the teeth were inanterior zone, the teeth were in accordance with known principles ofaccordance with known principles of positioned of anatomic landmarks.positioned of anatomic landmarks. www.indiandentalacademy.comwww.indiandentalacademy.com
  216. 216.  Suenaga K, Sato T, Nishigawa G,Suenaga K, Sato T, Nishigawa G, Minagi S.Minagi S. in 1997 investigated thein 1997 investigated the relationship between the size of therelationship between the size of the denture foundation area and thedenture foundation area and the resorption of the alveolar ridge. Theresorption of the alveolar ridge. The denture foundation area wasdenture foundation area was recorded using a modellingrecorded using a modelling compound impression technique withcompound impression technique with border moulding.border moulding. www.indiandentalacademy.comwww.indiandentalacademy.com
  217. 217.  Both sides of each edentulousBoth sides of each edentulous mandible were examined separately,mandible were examined separately, making a total of 110 experimentalmaking a total of 110 experimental sides in the study. On a stone castsides in the study. On a stone cast made from each impression, the sizemade from each impression, the size of of the superficial dentureof of the superficial denture foundation area and of the projectedfoundation area and of the projected denture foundation area on thedenture foundation area on the tentative plane of occlusion of eachtentative plane of occlusion of each anatomical zone were measured.anatomical zone were measured. www.indiandentalacademy.comwww.indiandentalacademy.com
  218. 218.  The vertical height of the alveolar ridge atThe vertical height of the alveolar ridge at the lateral incisor and first molar regionthe lateral incisor and first molar region was also evaluated. The size of thewas also evaluated. The size of the superficial denture foundation area in thesuperficial denture foundation area in the antero­lingual and postero­lingual zonesantero­lingual and postero­lingual zones showed no significant correlation with theshowed no significant correlation with the degree of alveolar ridge resorption. Thedegree of alveolar ridge resorption. The size of the projected denture foundationsize of the projected denture foundation area on the tentative plane of occlusion inarea on the tentative plane of occlusion in the anterior section showed negativethe anterior section showed negative significant correlation with the degree ofsignificant correlation with the degree of alveolar ridge resorption.alveolar ridge resorption. www.indiandentalacademy.comwww.indiandentalacademy.com
  219. 219.  Alfano SG, Leupold RJ.Alfano SG, Leupold RJ. In 2001In 2001 presented a technique for obtainingpresented a technique for obtaining maxillomandibular registration formaxillomandibular registration for complete denture patients.. Thecomplete denture patients.. The maxillary rim is formed with the usemaxillary rim is formed with the use of conventional techniques. Theof conventional techniques. The mandibular rim is made frommandibular rim is made from modeling plastic impressionmodeling plastic impression compound on a record base formedcompound on a record base formed by the patient into the neutral zone.by the patient into the neutral zone. www.indiandentalacademy.comwww.indiandentalacademy.com

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