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Horizontal Jaw Relation

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Horizontal Jaw Relation

The human mandible can be related to the maxilla in several positions in the horizontal plane. Among these centric relation is a significant position, because of its usefulness in relating the dentulous and edentulous mandible to maxilla, where the teeth , muscles and temporomandibular joint function in harmony. It is a position of occluso-articular harmony.

The human mandible can be related to the maxilla in several positions in the horizontal plane. Among these centric relation is a significant position, because of its usefulness in relating the dentulous and edentulous mandible to maxilla, where the teeth , muscles and temporomandibular joint function in harmony. It is a position of occluso-articular harmony.

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Horizontal Jaw Relation

  1. 1. HORIZONTAL JAW RELATION PRESENTED BY: Dr. Anshul Sahu MDS 1ST Year
  2. 2. CONTENTS:  Introduction  Centric Jaw Relation  Definitions  Chronological changes of definitions of centric relation  Review of literature  Features of Centric Jaw Relation  Criteria for Centric Relation  TMJ Socket Design  Role of Musculature  Centric relation in loading position  Complication in recording Centric Relation  Errors in Centric Relation  Factors Influencing Centric Relation Records
  3. 3.  Centric relation and centric occlusion  Recording Centric Jaw Relation  Eccentric Jaw Relation  Summary  Conclusion  References
  4. 4. INTRODUCTION The principles of good occlusion apply to both dentulous & edentulous patients. The problem is, however, that there is no accordance on the definition of good occlusion. It also is most probable that the requirements of the occlusion for complete denture differ from those of a natural dentition. For stability of complete dentures to be maintained, the opposing teeth must meet evenly on both sides of the dental arch when the teeth contact anywhere within the normal functional range of mandibular movement .
  5. 5. The human mandible can be related to the maxilla in several positions in the horizontal plane. Among these centric relation is a significant position, because of its usefulness in relating the dentulous and edentulous mandible to maxilla, where the teeth , muscles and temporomandibular joint function in harmony. It is a position of occluso-articular harmony.
  6. 6. JAW RELATION Any spartial relationship of the mandible to the maxilla. (GPT 8) Jaw relation is recorded to measure the extensibility and movements permissible by the patients Temporomandibular joint. 3 DIFFERENT TYPES: Orientation jaw relation Vertical jaw relation Horizontal jaw relation
  7. 7.  Horizontal jaw relation is the maxillomandibular relation in a horizontal plane.  Described as relationship of mandible to maxilla in the anteroposterior direction.  2 TYPES: 1) Centric Jaw Relation 2) Eccentric Jaw Relation: - Protrusive relation - Lateral relation: Left lateral; Right Lateral  The basic horizontal relationship is centric relation. It is a reference relationship that must be recognized in any prosthodontic treatment. Other horizontal relationships are deviations occurring from centric relation, they are collectively referred as eccentric relation
  8. 8. CENTRIC JAW RELATION
  9. 9. Definition: The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterior-superior position against the slopes of the articular eminences. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superior and anteriorly. It is restricted to a purely rotary movement about the transverse horizontal axis” (GPT8)
  10. 10. According to GPT 1: The most retruded relation of mandible to maxilla when the condyles are in the most posterior unstrained position in the glenoid fossae from which lateral movement can be made at any given degree of jaw separation. According to GPT 3: The most retruded physiologic relation of the mandible to the maxilla to and from which the individual can make lateral movements. It is a condition that can exist at various degree of jaw separation . It occurs around the terminal hinge axis. According to GPT 4: The jaw relation when the condyles are in the most posterior, unstrained position in the glenoid fossa at any given degree of jaw separation from which the lateral movements can be made.
  11. 11. According to GPT 5: The maxillomandibular relationship in which the condyle articulate with the thinnest avascular portion of their respective disks with the complex in the anterior – superior position against the shapes of the articular eminences. Boucher defines as: The most posterior relation of the lower to the upper jaw from which lateral movements can be made at a given vertical dimension. It is the maxilla to the mandible relation in which the condyles and disks are thought to be in the midmost, uppermost position.
  12. 12. According to Ramsford: A clinically determined position of the mandible placing both condyles into their anterior uppermost position . This can be determined in patient without pain or derangement in the TMJ. According to Lang: The relation of the mandible to the maxilla when the condyles are in the upper most and the rearmost position in the glenoid fossae . The position may not be recorded in the presence of dysfunction of the masticatory system.
  13. 13. The Glossary Of Occlusal Terms, International Academy Of Gnathology 1979: The relation of mandible to maxilla when condyle are in their rearmost, uppermost, midmost position in the glenoid fossa Centric relation can exist over a range of jaw opening and is not violated until the condyle leave their posterior positions in the glenoid fossae, the unstrained hinge position of the mandible . According to Moyers: Centric relation is the position of the mandible as determined by the neuromuscular reflex first learned for controlling the mandibular position when the primary teeth were in occlusion.
  14. 14. According to Dawson: CR is the relationship of the maxilla to the mandible when the properly aligned condyle disc assembly are in the most superior position against the eminentiae irrespective of vertical dimension or tooth position. At the most superior position, the condyle disc assemblies are braced medially, thus CR is also the midmost position. A properly aligned condyle disk assembly in CR can resist max loading by the elevator muscles with no sign of discomfort.
  15. 15. CHRONOLOGICAL CHANGES OF DEFINITIONS OF CENTRIC RELATION Mc Collum(1920): Rearmost condylar position. He showed that the condyle had a pure rotational movement when the operator guided the mandible in the most retruded position in the glenoid fossa . He was the first to name this position as centric relation Granger (1952): Upmost, rearmost position . A second component namely a most superior position was considered necessary for bracing since the condyle was unstable when it was only in the most posterior position
  16. 16. Stuart (1969): Rearmost ,uppermost, midmost condylar position-(RUM) position A medial component was added for a stable condylar position (three – dimensional position ). It was considered a physiological condylar position harmonious with centric occlusion . RUM position was later accepted by the International Academy of Gnathology. American Equilibrium Society (1977): It challenged RUM position as it was considered to give pressure on the retrodiscal tissue at bilaminar zone and proposed the most anterior and upper most position of condyle opposite the slope of articular eminentia.
  17. 17. Celenza (1978): Stated that condyle disk assembly braced superiorly and anteriorly against the posterior slope of articular eminence . American equilibration society (1987): They revised their previous definition and believed that the condyle articulate with the thinnest avascular portion of the disc in the anterior ,most superior position of the dorsal slope of eminence.
  18. 18. REVIEW OF LITERATURE Physiologic Jaw Relations And Occlusion Of Complete Dentures. Shanahan JPD;1955;5;319-324  He stated the constant function of swallowing saliva is the basis for establishing the mandibular positions and occlusion.  In swallowing saliva, the mandible rises to its habitual closing terminal, then, as the saliva is swallowed mandible is forced backwards into the pharynx by the tongue, thus retruded to its physiological centric relation.
  19. 19. The hinge axis and its practical application in the determination of centric relation. Cohen ;jpd;1960;10;248  The center of meniscus is devoid of blood vessels and nerves and is pressure bearing. Due to this fact every joint has a degree of tolerance which permit the condyle to be out of its ideal position in final closure of mandible .  Morphologic point of view, there are three types of glenoid fossae:
  20. 20.  Type 1 – The anterior slope of the fossa is very light and, although the condyle may not be seated as far back as it can go in final closure, there will not be a great lateral component of force on the teeth or a pressure on the border of the meniscus. However, the ideal position of the condyle in final closure is that in which it is completely seated in the gleonoid fossa. This type of joint has the greatest degree of tolerance.  Type 2 – this is most commonly encountered. This joint has little tolerance  Type 3 - found occasionally . It has a very steep anterior wall and has no tolerance . This type of joint causes the most trouble since any slight eccentricity of the maxillomandibular relationship causes a pressure on the borders of the meniscus. If the condyle is not seated in the fossa in final closure, it can result in a strong lateral strain on the teeth
  21. 21. Anatomy of TMJ as it pertains to CR. Boucher JPD; 1962;12;464  The external pterygoid muscle supports the mandibular condyle on the articular eminence.  Muscles limit the functional posterior border movements of the mandible.  He stated that centric relation is controlled by neuromuscular reflex which does not necessarily always function in the same anteroposterior position  The terminal hinge position and the apex of the needle point tracings of the retruded mandible may be desirable positions from which to start the construction of dentures because they are reference positions, but this does not imply that it may be the ideal functional position of the mandible for all patients.
  22. 22. What is centric relation. George .Hughes jpd;1964;14;1066  The correct centric relation is essential in complete denture construction.  Prosthodontists disagree as to what constitutes centric relation and how it is best registered.  The present accepted definition of centric relation is based upon the relationships of the mandibular condyles to the glenoid fossae under normal or ideal conditions.  The Gothic arch tracing is the best visual device for ascertaining the horizontal relationships of mandibular positions and two dimensional movements.
  23. 23. A critique of research of the posterior limit of the mandibular position. Douglas Allen Atwood , JPD ;1968;20 ;21  Two concepts of centric relation has been discussed , i.e , anatomic and pathophysiologic theory .  Anatomic concept – centric jaw relation is the most posterior position ( a border position established by ligament )  Pathophysiologic concept – centric relation is the most posterior unstrained jaw relation ( a relation which usually is not a border position and is established by muscle action )  He states the posterior limit of the mandibular position at the vertical dimension of occlusion is usually established by structures anterior and lateral to the condyles rather than posterior to them. Both the temporomandibular ligaments and the lateral pterygoid muscles are anatomically structured to perform this function.
  24. 24. Diurnal variance of centric relation position. Shafagh ;1975;JPD;34;574  He studied diurnal variance of recording maxillomandibular relationships .  He found that records obtained in the morning showed the most antero inferior position of condyle and those made at night showed the most posterior superior position  If most retruded and superior position of condyles is desired , the evening seems to be a better time for making centric relation record .
  25. 25. Discussion Of “The Anatomy Of The Temporomandibular Joint As It Pertains To Centric Relation. Jamieson ;1962;JPD;12;473  The article supports the theory that the retrusive movement of the mandible in the glenoid fossae is limited by the external pterygoid muscles and not by the mandibular ligaments. It is generally agreed that the sphenomandibular and stylomandibular ligaments do not limit the retrusive movement of the mandible but rather assists in the limitation of the lateral and protrusive movements.
  26. 26. FEATURES OF CENTRIC JAW RELATION  It is learnable, repeatable, and recordable position which remains constant throughout life.  It is a reference position from which the mandible can move to any eccentric position and return back involuntarily.  It is the start point for developing occlusion.  Functional movements like chewing and swallowing are performed in this position, because it is the most unstrained position.  It is a reliable jaw relation, because it is bone to bone relation.  In case of dentulous patients proprioceptive impulses are obtained from PDL.  In case of edentulous patients centric relation act as proprioceptive centre to guide occlusal movements.
  27. 27.  It is the only jaw position that permits an interference free occlusion  Centric relation is the ideal arch to arch relationship and an optimum functional position of jaws for the health, comfort and function of TMJ and musculature.  Recording of an accurate centric relation is critical for the most cost effective, time effective and trouble free prosthetic dentistry.
  28. 28. CRITERIA FOR CENTRIC RELATION The 2 most important criteria for Centric Relation are:  The complete release of the inferior lateral pterygoid muscle  Proper alignment of the disc on the condyle. During jaw closure, with intact TMJ, the condyle-disc assemblies are pulled up by a triad of strong elevator muscles.
  29. 29. TMJ SOCKET DESIGN  The bony socket referred to as the glenoid fossa is the structure that is effective in stopping the upward movement of the condyle-disc assembly.  The fossa is triangular shaped with the apex towards the midline to accept the pure rotational axis of the medial poles of the condyles.  The wide part of the fossa accommodates the movement of the lateral pole during rotation.  The term centric means centered. The medial poles of the condyles are centered in the middle of the medial third of the fossa.
  30. 30.  When the condyles are fully seated, the front of the condyles (with the disc interposed) contacts against the posterior slope of the eminence.  The upward movement is stopped by the contact of the medial pole of the condyle with the heavily buttressed bone up in the medial third of the fossa.  At this point, the condyle disc assembly cannot move higher, but it can rotate in that position, even under strong muscle loading.
  31. 31. ROLE OF MUSCULATURE  The elevator muscles are all present distal to the teeth, between the teeth and condyles.  Action of these elevator muscles pulls the condylar disk assemblies against the eminence and slides them upwardly.  The inferior belly of the lateral pterygoid is passive during jaw closure unless activated by occlusal interferences to hold the jaw forward.  Mahan et al. say that the inferior belly of the lateral pterygoid is almost always completely inactive during clenching in the retrusive position.
  32. 32. CENTRIC RELATION IN A LOADING POSITION Depending on the loading of temporomandibular joint:  Passive centric : seen during passive closure of jaw in centric relation or as projected in the articulator.  Power centric : a dynamic centric observed during mastication and deglutition.  It has been reported that compressive forces acting on the joint are relatively high and the surface of joint can withstand this load .  It is estimated that joint forces are more than 2.7 times that of forces on the occlusal table.
  33. 33.  During mastication and deglutition , loading progresses and the condyles are seated against the avascular aneural central zone of the disc by contraction of the superior head of external pterygoid muscle, the middle and anterior fibers of temporalis muscle  Hobo describes a buffer space of safety present between condyle and fossa which prevent the transmission of heavy load transferred to the condyle during function . It helps to minimise the direct force on the disc and protect it from anterior displacement and perforation .
  34. 34. COMPLICATIONS IN RECORDING CENTRIC RELATION  The structure of TMJs are such that one joint can be displaced downward by uneven pressure when records are made and yet the condyles be in their most retruded position. This situation cannot occur on the articulator and thus a deflective occlusal contact may be the source of instability,soreness and resorption despite the correctness of the other relations.  Realeff effect by Hanau: according to it, there is uneven resiliency in the soft tissues.This resiliency is present in both the mucosa and the TMJs,thus undue pressure in securing the relation must be avoided lest excessive displacement of soft tissues occur  Even though a balanced and equilized registration has been made it often is lost due to: Cast mounting procedures Processing of denture
  35. 35. ERRORS IN CENTRIC RELATION  When centric relation is not coinciding with centric relation of the patient due to:  Incorrect horizontal relation of the mandible to the maxilla  Incorrect equalization of vertical contact. Errors may be positional errors, technical errors.
  36. 36. POSITIONAL ERRORS:  Failure of the operator in his registration of the correct horizontal relationship.  Failure of the operator to record equalized vertical contact  Application of excessive closure pressure by the patient at the time of recording  Changes in the supporting area
  37. 37. TECHNICAL ERRORS:  ill fitting occlusion rims: if record bases are not stable  Indiscriminate opening and closing of the occluding device or articulator; an articulator in reality is a jig which maintains a record of position. Even if the casts are mounted correctly, the amount which we can arbitrarily vary the vertical distance between the casts is limited.  Too frequently the lab technician opens and closes the vertical distance of the articulator for the convenience in tooth arrangement. this results in the establishment of the centric occlusion which is not coinciding with centric relation.  The slight shifting teeth which occurs between the stage of final arrangement in wax and the transfer to a permanent base material.  A movement by the tooth or several teeth either horizontally, or vertically, introduces an error.
  38. 38. Symptoms Which Result From Errors In Recording Centric Relation  Loss of retention  Irritation on the crest of lower ridge in the area of premature contact.  One tooth or several teeth on one side seem long to the patient or seem to strike first.  Premature contact may be anteriorly or posteriorly.
  39. 39. ANTERIOR ERROR - when the centric occlusion established in the arrangement of teeth is anterior to the centric relation. POSTERIOR ERRORS - when centric occlusion established is posterior to the centric relation of the patient.
  40. 40. FACTORS INFLUENCING CENTRIC RELATION RECORDS  The resiliency of the supporting tissues  Fit of the denture bases  Residual alveolar arch  Saliva  Tongue  The health and cooperation of the patient  The posture of the patient  The temporomandibular joint and its associated neuromuscular mechanisms  The skill of the dentist  The technique used and the recording devices used
  41. 41. CENTRIC RELATION AND CENTRIC OCCLUSION  Centric occlusion (GPT 8)- the occlusion of opposing teeth when the mandible is in centric relation .  The understanding of centric relation is complicated by failure to distinguish between centric relation and centric occlusion .  Centric occlusion is a tooth-to-tooth position whereas centric relation is bone to bone relation  Both may or may not be identical to each other  In persons with natural teeth, both centric relation and centric occlusion exist. After the removal of teeth, centric occlusion is lost ,while centric relation remains and serves as a reliable guide to develop centric occlusion in artificial dentures .
  42. 42. RECORDING OF CENTRIC RELATION  Assisting the patient to retrude the mandible  Recording the centric relation  Verifying the record
  43. 43. METHODS TO RETRUDE THE MANDIBLE WHILE RECORDING CR RELAXATION OF JAW:  Simplest, easiest and most efficient way of causing a retrusion of mandible in centric relation is by verbal instructions to patients .  Instruct the patient by saying “Let your lower jaw relax, pull it back, and close on your back teeth”. PUSHING UPPER JAW:  In this method the patient is instructed to “Get the feeling of pushing your upper jaw out and close your back teeth together .”  By getting the feeling of pushing the upper jaw forward, they automatically pull the lower jaw backward . Once this is achieved, it is easy for them to repeat the desired motion .
  44. 44. STRETCH AND RELAX MOVEMENTS:  Patient is instructed to protrude and retrude the mandible. Dentist can aid by a slight pressure on the point of the chin  This protruding and retruding of mandible is done repeatedly until the finger on the point of the chin can feel the mandible strike its retruded position with a jar.  The operator soon develops such a sense of touch that he can feel this slight jar when the condyles hit the correct position in the joint.
  45. 45. RETRUSION OF TONGUE  Patient is instruction to keep the tip of tongue in contact with the posterior border of the maxillary record base and then patient is asked to close until the rims come into contact  Useful in securing a tentative relation but not definite enough for a final relation.  Disadvantage : likehood of displacing the mandibular record base by the action of tongue
  46. 46. RAPID TAPPING OF THE OCCLUSAL RIMS:  Gentle tapping of occlusal rims rapidly and repeatedly retrudes the mandible  Disadvantage: Difficult to record and patient can easily tap in a slightly protrusive or lateral position
  47. 47. HEAD POSITION:  Tilting the head backwards results in retrusion of the mandible because this will place tension on the inframandibular muscles and tend to pull the mandible to a retruded position  Disadvantage: Insertion and removal of occlusal rims from mouth a very difficult SWALLOWING:  Swallowing usually brings the mandible to a retruded position .  Unreliable – since person can swallow when mandible is not completely retruded but 1-2mm anterior to maxilla .
  48. 48. TEMPORALIS MUSCLE CHECK :  The temporalis muscle show reduced function when the mandible is in a protruded position . So its contraction can be felt when the mandible is in or near retruded position by placing finger tips on each side of the head.  However it can be used only as a slight indication of proximity to a CR. GENERALIZED RELAXATION OF THE PATIENT :  Total relaxation of the patient on the chair automatically brings mandible to retruded position  It is however difficult to attain
  49. 49. DIFFICULTIES IN RETRUDING  Biological problem  Psychologial problem  Mechanical problem
  50. 50. Biological Problem:  Lack of muscle co-ordination  Lack of synchronization between the protruding and retruding muscles due to “HABITUAL” eccentric jaw positions adopted by the patient to accommodate malocclusion  This may due :  Denture wearers with marked attrition of posterior teeth, as sliding movements occur due to flat occlusal surfaces. This leads to involuntary forward movement of the mandible.
  51. 51.  Also when a patient remains edentulous for a long time, the meniscus and other tissues surrounding the condyle within the capsular ligament gradually fill in the space created by a continually protruded mandible.  This condition prevents the immediate placement of the mandible into its most retruded position.  The following may help:-  Muscle exercises prior to recording centric relation are another physiologically sound device for causing a temporary forgetting of the eccentric pattern.  Drugs, e.g., Mephenesin  patient relaxation  jiggling the chin
  52. 52. Psychological Problem:  It involves patient and dentist  The more the dentist tries to overcome the apparent inability of the patient to retrude the mandible, the more confused the patient may become and the less likely he is to respond to the directions provided by dentist .  The dentist must be prepared to spend adequate time securing the CR record
  53. 53. Mechanical Problems:  Poorly fitting baseplates- it is essential that the record base on which the centric relation are made fit perfectly and not interfere with each other .  Minimal pressure should be exerted during the registration , to avoid displacement of the soft tissue as much as possible .
  54. 54. RECORDING THE CENTRIC RELATION There two basic concepts:  Minimum pressure technique  Heavy pressure technique MINIMUM PRESSURE TECHNIQUE:  The record should be made with minimal closing pressures so the tissue supporting the bases will not be displaced while the record is being made.  The objective of this concept is for the opposing teeth to touch uniformly and simultaneously at their first contact
  55. 55. HEAVY CLOSING PRESSURE:  This states that the records should be made under heavy closing pressure so that tissues under the recording bases will be displaced while the record is being made .  The objective of this concept is to produce the same displacement of the soft tissue as would exist when heavy closing pressure were applied on the denture .
  56. 56. METHODS OF RECORDING CENTRIC JAW RELATION 1. Physiological method: -Tactile or interocclusal check record method -Pressure less method -Pressure method 2. Functional method: -Needles house method -Patterson method 3. Graphic method: -Intra oral method -Extra oral method 4. Radiographic method
  57. 57. PHYSIOLOGIC METHOD  Based on: -Proprioceptive impulse of patient -Kinethetic sense of mandibular movement -Visual acuity and sense of touch of patient  Types: a. Tactile or interocclusal check record method b. Pressure less method c. Pressure method
  58. 58. Tactile Or Interocclusal Check Record Method:  Tentative jaw relation is recorded.  Ask the patient to retrude the mandible.  Casts are articulated based on this tentative record a) Recording tentative jaw relation:  Maxillary occlusal rim inserted to patients mouth.  Vertical dimension at rest is established. mandibular occlusal rim inserted and reduced accordingly.  Tentative centric relation recorded using tentative jaw relations. Artificial teeth are arranged.
  59. 59. b) Making the inter occlusal check record:  Upper and lower trial dentures are inserted into the mouth. keep a piece of cotton to prevent contact of opposing members.  Aluwax is added on the occlusal surface of teeth of mandibular occlusal rim  Patient asked to retrude mandible and close on the wax till tooth contact occurs.  Trial dentures removed and allowed to cool.
  60. 60. Static Or Pressure less Method: Nick Notch Method:  Patient asked to retrude mandible in position.  Upto 3mm of wax removed from mandibular occlusal rimfrom the premolar region till the distal end  1 or 2 notches are cut on the corresponding area of maxillary occlusal rim.  One nick is cut anterior to the notch, a V shaped valley  Nick: prevent lateral movement  Notch: anteroposterior movement
  61. 61.  Nick and notch are lubricated with petroleum.  Prepared occlusal rim are inserted into patient’s mouth and taught to close his mandible in maximum retruded position.  Aluwax is placed on the trough created in mandibular rim.  Mandibular occlusal rim is cooled and inserted into patients mouth and closed in centric relation.
  62. 62. Stapler Pin Method:
  63. 63. Pressure Method:  Establish vertical dimension.  Upper occlusal rim inserted. Lower occlusal rim is fabricated by softening in water bath.  Insert it into patients mouth.  Patient asked to close mouth in centric relation on soft wax in predetermined vertical dimension and then articulated.
  64. 64. FUNCTIONAL METHOD  These methods utilize the functional movements of the jaws to record the centric relation. The patient is asked to do the movements in protrusion, retrusion and right lateral and left lateral.  Types: -Needles House Method -Patterson method
  65. 65. Needles House Method:  Fabrication of occlusal rim made from impression compound  Four metal beads or styli are embedded into premolar and molar areas of maxillary occlusal rim.  Occlusal rim inserted into patients mouth and asked to close occlusal rim and make protrusive, retrussive, right and left movement of mandible.  When movements are made “diamond shaped marking pattern rather than a line is formed on the mandibular occlusal rim.
  66. 66. Patterson Method:  Occlusal rim made of modelling wax.  In trench or trough is made along the length of mandibular occlusal rim.  A1:1 mixture of pumice and dental plaster is loaded into the trench.  Perform mandibular movement till predetermined vertical dimension.  Movement generates compensative curves in plaster.
  67. 67. GRAPHIC METHOD  These methods are called so because they use graphs or tracing to record the centric relation.  The general concept of this technique is that a pen-like pointer is attached to one occlusal rim and a recording plate is placed on the other rim, the plate coated with carbon or wax on which the needle point can make the tracing, when the mandible moves in horizontal plane, the pointer draws characteristic patterns on the recording plate.  The graphic methods are either intraoral or extraoral depending upon the placement of the recording device. The extraoral is preferable to the intraoral tracing, because the extraoral is more accurate, more visible, and larger in comparing with the intraoral tracing.
  68. 68.  Types:  Arrow point/Gothic arch tracing (Intraoral/extraoral – depending on placement of device)  Pantograph  Arrow point tracing is a graphic record measured across single plane  Pantogaph is measured three dimensionally.
  69. 69. Arrow Point/Gothic Arch Tracing: TYPES: 1) INTRA ORAL TRACING POINT:  Central bearing device is located intra orally.  Tracer is placed within the mouth.  Central bearing point & plate is inserted into patients mouth.  Central bearing point is adjusted such that it contact the central bearing plate at predetermined vertical dimension.  Ask to make anteroposterior and lateral movements.  Central bearing point will draw the tracing pattern on central bearing plate  Tracing should resemble an arrow point with a sharp apex.
  70. 70. 2) EXTRA ORAL POINT TRACER:  Concept similar to intra oral tracer.  Additionally have an attachment that project outside mouth.  Record bases attached to recording devices inserted in patients mouth.  Central bearing point is retracted to conduct training exercises.  Recording plate which projects extra orally is coated with precipitated chalk and denatured alcohol.  Patient asked to perform all movements.  Examine for sharp apex.
  71. 71. EXTRA AND INTRA ORAL TRACING EXTRAORAL TRACING:  Larger than intraoral  Apex is more discernible  It is visible while tracing is being done, so easier to guide the patient  Patient can be guided properly  Tracing point is sharper than the intra oral one.  Tracing plate is mounted on the mandibular rim  Error can be more as - tracing is situated outside the mouth further away from the centers of mandibular movement. -presence of extra oral tracer prevent the lips from meeting each other and remain passive
  72. 72. TYPES OF EXTRA ORAL TRACERS  Hight tracers(with or without central bearing point)  Stransbery tracers
  73. 73.  Sears trivet (is a central bearing point tracer with two registration pins)
  74. 74.  Phillips tracer (multiple tracers)  Multiple tracers add little to the accuracy of the tracing but do add something to the understanding of the mandibular movement.
  75. 75. TYPES OF INTRAORAL ARROW TRACERS  Ballard  Masserman
  76. 76.  Coble tracer  Micro tracer
  77. 77. Pantographic Tracing:  A graphic record of mandibular movements in three planes as registered by styli on recordable tables of a pantograph tracing of mandibular movement recorded on plates in horizontal and sagittal planes.  Make the rim contact at desired vertical relationship.  Strips of celluloid paper are placed between the rim and pulled out. Patient is asked to close and restrain the celluloid from slipping away, mandible goes to centric relation.  Softened wax is placed on mandibular occlusal rim and patient is asked to bite in centric relation.
  78. 78. ECCENTRIC RELATION
  79. 79.  An eccentric relation is any relationship of the mandible to the maxillae other than centric relation.  The purpose in making an eccentric relation record is to adjust the horizontal and lateral condylar inclinations so that the articulator jaw members perform eccentric movements equivalent.  This permits to arrange the teeth in balanced occlusion  Eccentric positions: protrusive, retrusive, right lateral and left lateral. Methods to Record:  Functional or chew in  Graphic  Tactile or direct check record.
  80. 80.  LATERAL RELATION RECORD: Hanau recorded a formula to arrive at an acceptable lateral inclination L=H/8+12 Where L= lateral condylar guidance, H= horizontal condylar guidance  Eccentric maxillomandibular relation records is performed at the same setting, same sitting and with the same equipment used for centric relation
  81. 81. SUMMARY  Centric relation is a most reproducible , reliable, repeatable , recordable, and reference position  CENTRIC RELATION IS DEFINED AS THE maxillomandibular relation in which the condyles articulate with the thinnest avascular portion of their respective articular disks with the complex in an anterio superior position against the slopes of articular eminences.  Eccentric relations are any other positions other than centric relation-p  Centric relation should coincide with centric occlusion otherwise will affect the stability of the dentures.  It can be recorded by various methods: Direct recording Graphic recording Functional recording Cephalometric recording
  82. 82. CONCLUSION  Any dentist who is willing to spend the time and energy to master the technique of recording and verifying precisely correct horizontal jaw relation will benefit in untold ways. There is no procedure in dentistry that can produce as many tangible benefits to both the doctor and the patient as the routine correct recoding of horizontal jaw relation, verified for accuracy as it affects the health , comfort, function of the muscles, and Temporomandibular joint.
  83. 83. REFERENCES  Zarb GA,Bolender CL,Carlsson GE Boucher’s prosthodontic treatment for edentulous patients 11th edition  Dawson PE Evaluation,diagnosis and treatment of occlusal problems 2nd edition  Sharry JJ Complete denture prosthodontics 3rd edition  Heartwell CM,Rahn AO Syllabus of complete dentures 4th edition  Winkler’s Essentials of complete denture prosthodontics 2nd edition
  84. 84. THANK YOU

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