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Stability in complete denture

  1. 1. Stability In Complete Dentures 11th December 2017 Presented By- Rohit Ashok Mistry JR- 1 Department Of Prosthodontics, Crown & Bridge Guided By- Dr. Surekha Godbole Dr. Anjali Borle Dr. Seema Sathe Dr. Mithilesh Dhamande Dr. Sweta Pisulkar
  2. 2. Learning Objectives Of the Seminar Sr. No Core Area Domain Significance 1 Definition, Review of Literature, Factors Affecting Stability. Cognitive Must Know 2 Neutral Zone Concept Cognitive and psychomotor Must Know 3 Applied aspects in complete denture stability Cognitive and psychomotor Must Know 4 Complete denture stability in some abnormal cases Cognitive and psychomotor Must Know 5 Evidence based studies supporting clinical practice Cognitive Must Know 6 How to check stability in complete dentures Cognitive and psychomotor Must Know
  3. 3. Content • Introduction • Significance of Stability • Review of Literature • Factors Affecting Stability 1. The relationship of the denture base to the underlying tissues.(impression surface) 2. The relationship of the external surface and border to the surrounding orofacial musculature.(cameo) 3. The relationship of the opposing occlusal surfaces. • Neutral Zone • Complete Denture Stability in some abnormal cases. • Evidence Based findings • Checking of Stability in Complete Dentures • Summary • References
  4. 4. Stability Support Retention Introduction
  5. 5. Retention •Psychologic Comfort Support •Longetivity Success Of Prosthesis Stability •Physiologic Comfort Certain Biological, Mechanical and Physical Properties Provide T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983 ACCORDING TO JACOBSON
  6. 6. Definitions • Stability is the resistance to horizontal and rotational forces. This property prevents lateral or anteroposterior shunting of the denture base (According to Jacobson and Krol) • The resistance of a denture to movement on its tissue foundation, especially to lateral (horizontal) forces as opposed to vertical displacement. (According to GPT- 9)
  7. 7. • Stability has been cited as the most significant property in providing for the physiologic comfort of the patient. • Denture instability adversely affects support and retention and results in deleterious forces on the edentulous ridges during function. • A denture that shifts easily in response to laterally applied forces can cause a disruption in the border seal or prevent the denture base from correctly relating to the supporting tissues. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983 Significance of Stabillity
  8. 8. Review Of Literature • Fish in (1933)- demonstrated that the lingual and the buccal flange should me moulded in conformation of the surrounding musculature and provided with a clear picture about the shape of mandibular denture which favours stability. • Lundquist D.O (1959) - The muscles on the working side of unilateral chewers contract more vigorously than those on the balancing side in normal opening and closing movements. The electromyographic recordings showed that the buccinator muscle has significant role in maintaining the stability of the denture and supports the theory of the action of the buccinator muscle as described by Fish.
  9. 9. Review of Literature (Cont) • Shanahan T. E J (1962)- Dynamic impressions reproduce naturally extended borders that provide for the function of the muscle attachments and for the movements of the soft tissues under the dentures during mastication, swallowing, speech, etc in contract to static impressions. • Brill (1967)- stated that the 3 important factors essential for stability in complete denture are maximum coverage of the denture bearing area, good peripheral seal, equalization of pressure. • Jooste CH, Thomas CJ. (1992) - The retro mylohyoid extension has a stabilizing effect on complete mandibular dentures.
  10. 10. Review of Literature (Cont) • Ohkubo C, Hosoi T. (1999) The results of this study indicated that the use of a metal base to increase the weight of the mandibular denture may not affect its retention or stability. • Sho Hasegawa (2003): Suggested that denture adhesive contributes to reducing denture movement and so improves chewing function. • T P Hyde (2014)There was significant evidence that dentures made from silicone impressions were rated as more stable and more efficient than dentures made from alginate impressions after adjustment
  11. 11. Factors Contributing to Stability 1. The relationship of the denture base to the underlying tissues. 2. The relationship of the external surface and border to the surrounding orofacial musculature. 3. The relationship of the opposing occlusal surfaces. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  12. 12. Relationship Of Denture Base to Underlying Tissue. Mandibular lingual Flange. Residual Ridge Anatomy. Denture Base Adaptation. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 2, JPD Jan 1983
  13. 13. A. Denture Base Adaptation • Maximum coverage • Contacting of the flanges with the ridge slopes is a critical factor contributing to stability (Friedman) • Provide maximum contact between the tissue and denture base • Good Border Seal • Denture borders limited by movable tissue • Close adaptation of denture base • Optimal denture stability requires that those tissues that provides resistance to horizontal forces • “Maximum usage of all bony foundations where the tissues are firmly and closely attached to the bone” (Boucher) • “Stability is obtained by incorporating the surfaces of the maxillary and mandibular ridges, which are at right angle to the occlusal plane”(Boucher). T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 2, JPD Jan 1983
  14. 14. B. Mandibular lingual flange • Most desirable feature of mandibular lingual flange is that it is perpendicular to the occlusal plane • The extension of the lingual flange is dictated by the attachment of the mylohyoid muscle • The musculature of the floor of the mouth also influences the degree of intimate contact allowed. • The mucosa should be resilient and thick enough to tolerate stress T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 2, JPD Jan 1983
  15. 15. • Shanahan(1962) has Stated that the Lingual Flange of the Denture can be extended in three areas that are: • The sub lingual crescent space • The sublingual fossa area • The retro mylohyoid fossa • The base of the tongue must be utilized to stabilize the denture in the retro mylohyoid region. Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962
  16. 16. The direction of the muscle fibres in the posterior region is more vertical and so the flanges can be extended more inferiorly The direction of the muscle fibres in the anterior region is more horizontal and so the flanges are more superiorly placed The inclination of is more medial as during contraction the muscle is pulled medially The dotted lines represent the activated mylohyoid muscle T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 2, JPD Jan 1983
  17. 17. C. Residual Ridge Anatomy • The development of stability is limited by the anatomic variations • Residual Ridge height • Residual Ridge conformation • Arch Form • Palatal Form T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 2, JPD Jan 1983
  18. 18. FACTORS GOOD Stability POOR Stability Height More height Less height Conformation Large, square and broad Small, narrow and tapered Arch Form Square and Tapered Ovoid Shape of Palatal Vault Steep palatal vault Shallow palatal vault T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  19. 19. Clinical tip regarding alveoplasty at the time of extraction • The alveoplasty should be limited only to sharp spicules, severe undercuts, insufficient inter-arch distance. • Small rounded irregularities must not be removed. • The ridge must not be made smooth and even. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  20. 20. “It is not so widely understood that the actual shape of the whole of the buccal and labial and lingual surface can wreck the stability of a denture as completely as a bad impression or a wrong bite.” -Fish(1933) W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933 II. Relationship of the External Surface and Periphery to Surrounding Orofacial Musculature.
  21. 21. Certain group of muscle can facilitate stability of the complete denture in two ways The action of certain muscle groups must be permitted to occur without interference by the denture base. Recognize the normal functioning of some muscles and utilize their function to enhance stability. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  22. 22. A. Influence of Orofacial Musculature • The basic geometric design of the denture bases should be triangular T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  23. 23. To direct seating action on the mandibular denture There is contraction of muscles such as orbicularis oris(lips) and buccinator(cheeks) during functional movement (speech, deglutition, mastication). The buccal and the labial flange of the maxillary and the mandibular denture must be concave to permit positive seating by cheeks and lips. The proper contouring of the denture flanges permits the horizontally directed forces that occur during contraction of these muscles to be transmitted as vertical seating forces T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  24. 24. B. Tongue When one is examining a patient for tongue position, it is well not to mention the word tongue. -Corwin Wright Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  25. 25. Tongue Positions A Normal Tongue Position has the following Characteristics: (1)It completely fills the floor of the mouth. (2) The lateral borders rest over the ridge which would normally represent the occlusal surfaces of the teeth. (3) The tip or apex of the tongue rests on or is just to the lingual side of the lower anterior ridge. The Retracted Tongue Position has the following Characteristics: (1)The tongue is pulled back into the mouth and the floor of the mouth is exposed. (2) The lateral borders are either inside or posterior to the ridge. (3) The tip of the apex of the tongue sometimes lies in the posterior part of the floor of the mouth or may be withdrawn into the body of the tongue. Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  26. 26. Why the Normal Tongue position? • The high level of the floor of the mouth accommodates for those functions of the tongue which require it to be more than moderately extended. • The low level of the floor of the mouth accommodates for the movements of the tip of the tongue as it moves to the floor of the mouth, such as when it retrieves food. • The normal level of the floor of the mouth, along with the corresponding position of the lateral throat form, serves to satisfy the tongue for practically all of its functions. • The normal tongue position places the floor of the mouth and the lateral throat forms in their normal positions. The floor of the mouth at its normal level appears to be approximately even with the internal oblique lines on the body of the mandible. Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30 Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962
  27. 27. Tongue exercise No. 1. The tongue is thrust out and in rapidly. Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  28. 28. Tongue exercise No. 2. The tongue is swung rapidly from side to side. Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  29. 29. Tongue exercise No. 3. Thrusting the tongue out to its most extended position And pulling it back quickly Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  30. 30. Tongue exercise No. 4. Raising the tongue to its highest position through articulation of ‘eeyuh’ Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30
  31. 31. • Modiolus mo-dı΄a-las the area near the corner of the mouth where eight muscles converge; it functionally separates the labial vestibule from the buccal vestibule (GPT 9) • The 8 muscles are 1. Orbicularis Oris 2. Buccinator 3. Zygomaticus 4. Canninus 5. Triangularis 6. Levator anguli oris 7. Rizorius 8. Platysma C. Importance of Modiolus and Associated Musculature M. cruciati modioli W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1993
  32. 32. W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933
  33. 33. 1. The outline of the denture base is closer to the ridge in these area The flanges are fashioned this way to escape the action of the muscles in these regions 2. The outline of the denture base is away from the ridge in these areas A wider flange is advised in the buccal region owing to the presence of buccal pouch. W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933
  34. 34. • Transverse section of stable denture in the premolar region. • The lower denture is very narrow at this point to escape the modioli W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933
  35. 35. • Transverse section of stable denture in the first molar region. • Each side of each denture is roughly triangular in shape • The buccal flange extends under the buccinator in order that the muscles may rest on the inclined planes and hold the denture down W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933
  36. 36. Neutral Zone • The central thesis of the neutral-zone approach to complete dentures is to locate that area in the edentulous mouth where the teeth should be positioned so that the forces exerted by muscles will tend to stabilize the denture rather than unseat it. • The theory used to develop the denture base contours is based on the belief that the muscles should functionally mould not only the borders of the denture but also the entire polished surface. • The polished surface contours and the position of the teeth are to be determined Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913
  37. 37. A cross section of molar area B lateral view of incisor area. Denture space Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913
  38. 38. Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913
  39. 39. Influence of lips on denture stability A, Cross section of mouth in relaxed state. No unfavorable forces are external surfaces by the lips and cheeks. B, As the mouth opens, the denture comes under the influence of horizontal forces from the lips. C, With the mouth wide open, maximum horizontal forces are exerted on the labial and buccal external surfaces of the teeth and flanges. The distance AB when the mouth is open (below) is less than the distance AB when the mouth is at rest (above). C Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913
  40. 40. Influence of Lips Over the Lower Denture in increased ridge resorption • Ridge height is insufficient, so horizontal forces are poorly counteracted. • Alveolar ridge resorb the ridge crest falls below the origin of mentalis. • The muscle attachment folds over the ridge and comes to rest on the superior surface of the crest • This results in posterior positioning of the neutral zone and posterior positioning of the anterior teeth than that of its natural position Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913
  41. 41. III. Relationship of Opposing Occlusal Surfaces • Harmony developed between the opposing occlusal surface also contributes to stability • The denture must be free of interferences within the functional range of movement of the patient. • During functional or parafunctional movements the occlusal surface must not prematurely strike. • These unwanted forces result in lateral and torquing forces that adversely affect the stability. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  42. 42. Factors in relationship of Opposing Occlusal Surfaces A. Occlusion as factor in stability B. Tooth position & Occlusal plane C. Ridge Relation T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  43. 43. A. Occlusion as factor in Stability • To minimize dislodging forces the occlusion must be balanced throughout the functional range of movement of the patient. • The bilateral balanced occlusion is important during activities such as swallowing saliva, closing to reseat the denture, and the bruxing of the teeth. • Patients with balanced occlusion do not upset the normal static, stable and retentive position of the dentures. • Lingualized occlusion provide both limited range excursive balance and a directing of forces the lingual side of the lower ridge during working side contacts. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  44. 44. • Horizontal forces can be minimized when the patient learns to place food bilaterally • Frechette in 1961 demonstrated even force distribution regardless of tooth position in the patient who chewed bilaterally, he also concluded that bilateral chewing contributed more to the chewing than balanced occlusion. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  45. 45. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  46. 46. B. Tooth position & occlusal plane • Anterior and posterior teeth should be arranged as close as possible to the position once occupied by the natural teeth(with slight modifications to accommodate resorptive changes) • Mandibular occlusal plane that is too high can lead to reduced stability • Lateral tilting forces are magnified as the plane is raised • Mandibular denture needs to be controlled by the musculature , raised plane will hamper the tongue to reach over the occlusal plane Stensen's duct, retromolar pads, should be used to determine an acceptable occlusal plane T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  47. 47. C. Ridge Relationship • Prognathic and retrognathic patients show offset ridge relation. • If the teeth are arranged in normal position on these offset ridges adversely affect stability. • Weinberg recognizes the need to set teeth in crossbite when the ridges are in severe crossbite relation. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  48. 48. In Class III ridge relation • In class III cases the lower arch is anterior to upper arch • Sufficient mandibular occlusion must be developed so that the contact to the maxillary is more than half that of distance between the incisive papilla and the hamular notch. • This prevents the tipping of the maxillary denture anterio-posteriorly. T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
  49. 49. Complete denture stability in abnormal cases • Xerostomia reduces an ability to form suitable seal, which further affects the retention and stability of dentures the treatment options include incorporation of salivary reservoir in complete dentures and remediation with artificial salivary substitutes. • Patients who have retracted tongue position, a bleb of was 2-3 mm in dimension is placed on the lingual surface of the mandibular lower teeth and the patient is trained to place to tongue in relation to this bleb to attain normal tongue position. J. F. McCord, Identification of complete denture problems: a summary, BRITISH DENTAL JOURNAL, VOLUME 189, NO. 3, AUGUST 12 2000 K Rajeshwari, Evaluation of Resting Tongue Position in Recently Extracted and Long Term Completely Edentulous Patients: A Prospective Interventional Study,Journal of Clinical and Diagnostic Research. 2017 Apr, Vol-11(4): ZC61-ZC63
  50. 50. Evidence based Practise studies 1. There is a very insignificant difference between dentures fabricated with neutral zone technique compared to conventional technique. (treatment effect size < 0·2) ( Geerts, 2017). 2. Silicone is a better impression material than alginate in fabrication of complete denture, with respect to patient satisfaction, stability, post insertion adjustments.(T.P. Hyde,2014) 3. Use of a denture adhesive can improve resistance to bite force related dislodgement in patients who wear a maxillary complete denture.(Psillakis, 2004) 4. A pilot study conducted comparing Lingualized occlusion and bilateral balanced occlusion showed that lingualized occlusion is better accepted by patients and proved to have greater stability and masticatory performance (Kimoto et al 2006) 1. Geerts, Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health-related quality of lifeJ Oral Rehabil. 2017 2. T.P. Hyde, H.L. Craddock, J.C. Gray, S.H. Pavitt, C. Hulme, M. Godfrey, C. Fernandez, N. Navarro-Coy, S. Dillon, J. Wright, S. Brown, G. Dukanovic, P.A. Brunton, A Randomised Controlled Trial of complete denture impression materials, In Journal of Dentistry, Volume 42, Issue 8, 2014 3. Psillakis, J. J., Wright, R. F., Grbic, J. T. and Lamster, I. B. (2004), In Practice Evaluation of a Denture Adhesive Using a Gnathometer. Journal of Prosthodontics 4. Kimoto, S, Gunji, A, Yamakawa, A, Ajiro, H, Kanno, K, Shinomiya, M, Kawai, Y, Kawara, M, & Kobayashi, K 2006, 'Prospective Clinical Trial Comparing Lingualized Occlusion to Bilateral Balanced Occlusion in Complete Dentures: A Pilot Study', International Journal of Prosthodontics, vol. 19, no. 1, pp. 103-109. .
  51. 51. Checking stability of the denture :
  52. 52. Summary • The relationship of denture base to surface tissue is an important factor in maintaining stability. • The action of the orofacial muscles are to be considered to decide the shape of denture flanges. • The extension of denture flanges is dictated by the movable tissue which further helps in attaining stability • Relationship of occlusal surfaces should be utilized to gain maximum stability. • Neutral zone is an important phenomenon, it is essential to recognize the importance of neutral zone in teeth arrangement and polished surface which gives stability.
  53. 53. Conclusion “Technique itself is merely the practical application of principles, and if the principles are unsound, the most elaborate and painstaking technique certainly is doomed to failure.” -Bohannan
  54. 54. References• T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD jan 1983. • Victor e. Beresin, frank J. Schiesser, the neutral zone in complete dentures, in the journal of prosthetic dentistry, volume 36, issue 4, 1976, 356- 367, ISSN 0022-3913 • W.E fish using muscles to stabilize the full lower denture J am dent assoc10:2163,1933 • Corwin R. Wright,evaluation of the factors necessary to develop stability in mandibular, J prosthet dent 1966;16:414-30 • Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962 • Essentials of complete denture prosthodontics, sheldon winkler 2nd ed. • Boucher's prosthodontic treatment for edentulous patients 9th ed 1985. • The glossary of prosthodontic terms, journal of prosthetic dentistry , volume 117 , issue 5 , e1 - e105 • T.P. Hyde, H.L. Craddock, J.C. Gray, S.H. Pavitt, C. Hulme, M. Godfrey, C. Fernandez, N. Navarro-Coy, S. Dillon, J. Wright, S. Brown, G. Dukanovic, P.A. Brunton, A Randomised Controlled Trial of complete denture impression materials, In Journal of Dentistry, Volume 42, Issue 8, 2014 • Geerts, Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health-related quality of life. J Oral Rehabil. 2017 Sep;44(9):702-708. doi: 10.1111/joor.12533. Epub 2017 Jul 2 • Kimoto, S, Gunji, A, Yamakawa, A, Ajiro, H, Kanno, K, Shinomiya, M, Kawai, Y, Kawara, M, & Kobayashi, K 2006, 'Prospective Clinical Trial Comparing Lingualized Occlusion to Bilateral Balanced Occlusion in Complete Dentures: A Pilot Study', International Journal of Prosthodontics, vol. 19, no. 1, pp. 103-109. • J F. McCord, Identification of complete denture problems: a summary, BRITISH DENTAL JOURNAL, VOLUME 189, NO. 3, AUGUST 12 2000 • K Rajeshwari, Evaluation of Resting Tongue Position in Recently Extracted and Long Term Completely Edentulous Patients: A Prospective Interventional Study,Journal of Clinical and Diagnostic Research. 2017 Apr, Vol-11(4): ZC61-ZC63
  55. 55. Thankyou!

Editor's Notes

  • Retention-Complete denture retention is the resistance to displacement of denture base away from the ridge
    Stability- it is the resistance to horizontal and rotational forces preventing lateral or anterio-posterior shunting of denture base
    Support- denture support is the resistance to vertical movement of the denture base towards the ridge.
  • Fish gave that the buccinator can be divided into three parts th superior group th emiddle group and the inferior group,
    The superior group responsible for seating the upper denture the middle group responsible for pushing the food bolus in and the inferior contribute to the stability of lower denture
  • Jooste ch tested in six individuals by means of cineradiography and placement of a metal marker in the mandible and dentures during chewing exercises, with and without the relevant denture extension. Analysis of tracings of the movements of the markers revealed that statistically significant differences existed between first and second chewing experiences. Movement in a horizontal plane around a vertical axis, however, was common to all dentures during all chewing. It is concluded that the retromylohyoid extension has a stabilizing effect on complete mandibular dentures.
    Ohkubo used a 20 gm and 60 gm denture
  • The perpendicularity helps it to counteract the horizontal forces that are acting in the direction parallel to plane
  • Anteriorly the sublingual sace is recorded by action of genioglossus
    The sublingual fossa area-The mylohyoid muscle extends down from the mylohyoid
    ridge, close to the lingual surface of the body of the mandible, when the muscle is
    relaxed. In swallowing, the muscle raises with the tongue and brings the floor of
    the mouth upward to a higher level. Frequently, this muscle shows signs of flabbiness,
    and it is possible to extend the lingual flange of the denture vertically in the.
    The retromylohyoid area is recorded by asking the patient to touch his or her tongue to th echeeks, this action imitates the action of placing the foor over the occlusal table.
  • Extension dictated not by attachment but by direction of the fibre, as we can see the attachment posteriorly is much more superior as compared to anteriorly.still the lingual flanges are much more deep posteriorly. This is due to the direction of the muscles during its activation. inclination is also dictated by action as the more inferior we go more medially the muscle tends to run.
  • The arch forms as square, tapered and ovoid was given by chuck in 1932
  • Some important yet easily overlooked determinants of both denture stability and retention involves the relationship of th epolished surface of the denture base to the surrounding musculature of the orofacial capsule. Action of the musculature on the denture base generally results in lateral and vertical dislodging forces
  • The maxillary buccal flanges must incline laterally and superiorly
    The mandibular buccal flanges must incline laterally and inferiorly
    The the mandibular lingual flanges must incline medially and inferiorly

  • Wright classified tongue position as : Class 1 – Tongue lies in the floor of mouth with the tip forward and slightly below the incisal edges of mandibular anterior teeth. It has the most favourable prognosis as adequate border seal can be achieved because floor of the mouth will be high enough to cover the lingual flange.
    Class 2 – The tip is in a normal position but the tongue is broadened and flattened. Its not a favourable position.
    Class 3 – The tongue is retracted and depressed into the floor of the mouth with the tip curled upward, downward or assimilated into the body of tongue. Its very unfavourable position as an adequate border seal can’t be achieved.
  • The floor of the mouth
    is at the high level when the tongue reaches into either
    cheek or up to the roof of the mouth (Fig. 10), while
    it is at the low level when the tongue drops below the
    level of the occlusal surfaces of the mandibular teeth
    (Fig. 11). An example of the low level would be when
    the tip of the tongue reaches down to retrieve food that
    has fallen off the teeth during the function of chewing.
    The normal position which is somewhere between
    the high and low level, can be determined accurately
    only by having the patient place the tongue in a normal
    position (Fig. 12).
  • Exercise No. 1.—Thrusting the tongue out and in, in
    rapid succession. This causes an alternating action of the
    posterior and anterior fibers of the genioglossus muscles
  • Exercise No. 2.—Swinging the tongue sideways with
    great rapidity. The tongue should be out beyond the
    lower lip about one-half inch (Fig. 21). This causes an
    alternating activation of the styloglossus muscles while
    the tongue is held in its narrowed high position by the
    transversus muscles.
  • Exercise No. 3.—Thrusting the tongue out to its most
    extended position and pulling it back quickly On extension, this action is produced by the posterior
    fibers of the genioglossus muscles, and, on retraction,
    it is the action of the anterior fibers of the genioglossus
    with assistance from the styloglossus and hyoglossus
    muscles.
  • Raising the tongue to its highest position well forward in the mouth through the articulation
    of ‘‘eeyuh’’ . To get the full benefit of this exercise the ‘‘ee’’ should be spoken on as high a pitch as
    possible before saying the ‘‘yuh.’’ This produces an action
    of the styloglossus, stylohyoid, stylopharynegeus,
    the levators and palatopharyngi, the tensors and the
    palatoglossi, the posterior fibers of the genioglossus as
    well as the intrinsic muscles of the tongue shaping the
    ‘‘ee’’ vowel.
  • Depressor anguli oris (triangularis)
  • When the origin and insertion all the associated muscles is observed it is found that none of these muscles have more than one bony attachment. The buccinator takes origin from a curved line which is present above the molar teeth in the maxilla and runs down from a ligament along the pterygoid process to the lower molar teeth. Further they run anteriorly and decussate with the fibres of orbicularis oris. If only we conseider the action of these 2 muscles they ought to pull the face on one side.but it is not true. As there are other muscle (the x shaped aarrangement) which are arranged in such a way that it stabilizes this union at a fixed point ie Modiolus…if we say OH then the modiolus is pulled in front,while when we say ee it is fixed backward.
  • The labial flange from one buccal frenum to the other
    buccal frenum (Fig. 14) is most accurately trimmed by
    eye. The muscles of the lower lip are not conducive to
    the so-called ‘‘muscle-trimming’’ (border molding)
    method, because of the fact that the muscle fibers are
    parallel to the oral orifice. An example of the inability
    of this muscle to trim accurately is demonstrated when
    food drops into the labial fold. To remove this food by
    muscular action is extremely difficult, and the normal
    procedure for the patient is to reach into the fold with
    the tongue and sweep the food to the corner of the
    mouth where there are muscles at right angles to the
    opening. Here the food is easily retrieved and placed
    on either the teeth or the tongue
  • The concept of neutral zone stems from the idea that the denture consists of 3 major surfaces (acc to Fish) the impression surface, the occlusal surface, and the external/intaglio surface.
  • Lammie GA. Aging changes in the complete lower denture. J Prosthet
    Dent 1956;6:450-64.
  • The functional range of movement refers to the position through which the lower jaw moves horizontally during normal speech, swallowing, and mastication
  • Balanced Occlusion/ balanced articulation is the bilateral, simultaneous occlusal contact of the anterior and posterior teeth in excursive movements (According To GPT-9)
  • Lingualized occlusion is advantageous when esthetics is priority and nonantomic tooth are indicated in resorbed ridge cases
  • A primary question has always arisen that wethe the teeth must be placed on the ridge or far off the ridge….a general answer to this question is place the anterior teeth as closely in relation to the ridge as their natural position.
    Fish states that in the upper jaw there is no exception to the rule of replacing the natural teeth by setting the artificial ones in exactly the same relation to the body of maxilla .
    The neutral zone in th eupper arch is not very narrow hence there is a latitude for positioning the upper anteriors, plus the upper neutral zone is not as critical in maintaining the denture stability as the lower neutral zone.
  • Xerostomia can be caused due to factors like medication(antiepileptics, anti-anxiety, decongestant), irradiation, salivary gland pathologies etc
    Salivapowder(salivamax,nutrisal)
    Saliva solution (caphosol)
    Colgate prevident 5000 toothpaste for xerostomia patients.

    Retracted tongue position: The patients were instructed to feel the bleb of acrylic resin with tip of tongue and train themselves to keep the tongue in normal position for a period of eight months

    In patients with hyper salivation, anticholinergic drugs, botulinum toxin A, tongue acupuncture therapy are advised
  • Neutral zone technique is a RCT of 35 patients age 47-85 years of age
    Impression material wala is a RCT of 85 patients all edentulous patients above 18 years of age in this the final impression was recorded using alginate and silicone..in case of alginate the border moulding was done with green stick and in case of silicone the border moulding was done by medium body silicone
    Denture adhesive study is a 194 patients study
    Lo vs bbo 28 patirnts between 62-80 years of age
  • Place the denture in patients mouth and ask the patient to do functional movements like swallowing if the denture lifts and then settles back with a swishing sound, it is not stable.
    Ask the patient to say ohh, ah, eee the modiolus is checked by this method to check for interference.
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