Occlusion / orthodontic continuing education


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Occlusion / orthodontic continuing education

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Contents  Introduction  TMJ & human jaw function  Musculature  Centric relation  Mandibular movements  Types of occlusion  Occlusal interferences  Pathogenic occlusion  Occlusal treatment  Conclusion www.indiandentalacademy.com
  3. 3. Organisation of occlusion  Collective arrangemaent of the teeth in function is quite important & has been subjected to a great deal of analysis discussion over the years.  There are 3 recognized concepts that describes the manner in which teeth should & should not contact in various functional & excursive positions of the mandible. www.indiandentalacademy.com
  4. 4. They are : 1. Bilateral balanced occlusion 2. Unilateral balanced occlusion / Group function 3. Mutually protected occlusion/Canine guidance www.indiandentalacademy.com
  5. 5. Bilaterally balanced occlusion  It dictates that maximum number of teeth should contact in all excursive movements of the mandible.  It is important for complete denture fabrication, in which contact on non working side is important to prevent tipping of the denture. www.indiandentalacademy.com
  6. 6.  This concept was applied to natural teeth in complete occlusal rehabilitation.  Attempt was made to reduce the load on individual teeth by sharing the stress among as many teeth as possible.  But it was very difficult to achieve. As a result of multiple teeth contact during various excursions, there was excessive frictional wear of teeth. www.indiandentalacademy.com
  7. 7.  There was increased rate of periodontal break down.  There was neuromuscular disturbances. However it was often relieved when posterior contacts on mediotrusive sides were eliminated in attempt to eliminate unfavorable loading.  So the concept of unilateral balance was evolved. www.indiandentalacademy.com
  8. 8. Unilateral balance occlusion  Also known as Group function.  It is widely accepted & used method of teeth arrangement in fixed restorative dentistry today.  It was originated by Schuyler, who observed the destruction of tooth contact on non working side. www.indiandentalacademy.com
  9. 9.  He concluded that as much as cross arch balance is not necessary in natural teeth, it is best to eliminate all tooth contact in non working side.  So in unilateral balanced occlusion, all teeth in working side should be in contact during lateral excursions.  Teeth on non working side are contoured to be free of contact. www.indiandentalacademy.com
  10. 10.  Group function of teeth on working side destributes the occlusal load.  Absence of contact on non working side prevents those teeth from being subjected to destructive, obliquely directed forces found in non working interferences.  It also saves the centric holding cusps, ie. Mandibular buccal cusps & maxillary lingual cusps from excessive wear. www.indiandentalacademy.com
  11. 11.  In this occlusal arrangement load is distributed among periodontal support of all posterior teeth on working side.  It can be advantageous if periodontal support of canine is compermised. www.indiandentalacademy.com
  12. 12.  The functionally generated path technique, described by Meyer, is used for producing restorations in unilateral balanced occlusion.  It has been adapted by Mann & Pankey for use in complete mouth occlusal rehabilitation. www.indiandentalacademy.com
  13. 13.  Allowing some freedom of movement in antero posterior direction is advantageous.  This concept is known as long centric, by Schuyler.  It is important for posterior teeth to be in harmonious gliding contact when the mandible translates from centric relation forward to make anterior teeth contact. www.indiandentalacademy.com
  14. 14.  Some authors advocates long centric because centric relation rarely coincides with maximum intercuspation in healthy natural dentition.  long centric ranges from 0.5 to 1.5 mm.  This theory says that condyle can translate horizontally in fossae over a trajectory before beginning to move downward. www.indiandentalacademy.com
  15. 15. Mutually protected occlusion  Also known as Canine protected occlusion or Organic occlusion.  Originated by D’ Amico, Stuart, Stallard,& Lucia, members of gnathological society. www.indiandentalacademy.com
  16. 16.  They observed that in many mouths with healthy periodontium & minimum wear, the teeth were arranged so that overlap of anterior teeth prevented the posterior teeth from making any contact on either working or non working sides during mandibular excursions.  This separation oclusion was termed as Disocclusion. www.indiandentalacademy.com
  17. 17.  According to this concept, anterior teeth bear all the load & posterior teeth are disoccluded in any excursive position of mandible.  Desired result is absence of frictional wear. www.indiandentalacademy.com
  18. 18.  Position of maximum intercuspation coincides with optimal condylar position of mandible.  All posterior teeth are in contact with forces being directed along long axis.  Anterior teeth either very lightly or out of contact slightly. www.indiandentalacademy.com
  19. 19.  As a result of anterior teeth protecting the posterior teeth in mandibular excursions & posterior teeth protecting the anterior teeth at intercuspal position, so it is called as mutually protected occlusion.  It is most widely accepted, easily fabricated & greater tolerance by the patients. www.indiandentalacademy.com
  20. 20.  It is necessary to have anterior teeth periodontally healthy.  In absence of canine or anterior bone loss, mouth should be restored to group function. www.indiandentalacademy.com
  21. 21.  It also depends on orthodontic relationship of opposing arches.  In class 2 or 3 malocclusion, mandible can not be guided by anterior teeth.  Also in cross bite cases, where maxillary &mandibular cusps interfere during working side excursions. www.indiandentalacademy.com
  22. 22. Features of Mutually protected occlusion are : 1. Uniform contact of all teeth around the arch when mandibular condylar processes are in their most superior position. 2. Stable posterior tooth contacts with vertically directed resultant forces. 3. Centric relation coinciding with maximum intercuspation. www.indiandentalacademy.com
  23. 23. 4. No contact of posterior teeth in lateral or protrusive movements. 5. Anterior tooth contacts harmonizing with functional jaw movements. www.indiandentalacademy.com
  24. 24. Criteria to achieve Mutually protected occlusion : 1. Full complement of teeth exists 2. Supporting tissues are healthy 3. No reverse articulation or cross bite 4. Occlusion is Angle’s class 1. www.indiandentalacademy.com
  25. 25.  It looks illogical to load single rooted anterior teeth to multi rooted posterior teeth during chewing.  But canine & incisors have distinct mechanical advantages over posterior teeth.  Effectiveness of forces exerted by muscles of mastication is less when loading contact occurs farther anteriorly. www.indiandentalacademy.com
  26. 26.  Mandible is a lever of class 3 type, which is the least efficient of lever system.  Farther the initial tooth to tooth contact occurs, less effective is the force exerted by musculature & smaller the load to which teeth are subjected is. www.indiandentalacademy.com
  27. 27. Effects of anatomic determinants  Condylar guidance & anterior guidance have strong influence on occlusal morphology of teeth being restored.  It is a relationship of numerous factors like immediate lateral translation, condylar inclination, disc flexibility, cusp height, cusp location, groove direction etc. www.indiandentalacademy.com
  28. 28. Molar disocclusion  On repeated lateral movements, there wont be same path due disc flexibilty.  This deviation is 0.2 mm in centric relation, 0.3 mm in working, & 0.8 mm in protrusive and non working movements. www.indiandentalacademy.com
  29. 29.  To avoid occlusal interferences & non axially directed forces on molars during eccentric movements, molar disocclusion must be equal to or more than these deviations.  It is advised to have 0.5 mm in working, 1 mm in non working & 1.1 mm separation from mesio buccal cusp tips of first molar. www.indiandentalacademy.com
  30. 30. Condylar guidance  Mainly protrusive condylar guidance & mandibular lateral translation.  Protrusive condylar path can be steep or shallow.  It has average angle of 30.4 degree from horizontal reference plane. www.indiandentalacademy.com
  31. 31.  If protrusive condylar path is steep, cusp height must be longer & vice versa. www.indiandentalacademy.com
  32. 32.  If immediate lateral translation is great, then cusp height must be shorter & vice versa. www.indiandentalacademy.com
  33. 33.  Grooves & ridges are affected by condylar path mainly lateral translation.  Nearer the tooth is to working side condyle antero posteriorly, smaller the angle between working & non working paths and vice versa. www.indiandentalacademy.com
  34. 34. Anterior guidance  The track of incisal edges of mandibular to maxillary anterior teeth from maximum intercuspation to edge to edge occlusion is called as protrusive incisal path.  Angle formed between protrusive incisal path & horizontal reference plane is called as protrusive incisal path inclination. www.indiandentalacademy.com
  35. 35.  It ranges from 50 to 70 degree.  In healthy occlusion, anterior guidance is 5 to 10 degree steeper than condylar path in sagittal plane.  Therefore when mandible moves protrusively, anterior anterior teeth guide mandible downward to create disocclusion in posterior teeth. www.indiandentalacademy.com
  36. 36.  Lingual surface of maxillary anterior teeth has both concave & convex surface, cingulam.  Mandibular incisal edge should contact maxillary lingual surfaces at transition from concavity to convexity in centric relation position. www.indiandentalacademy.com
  37. 37.  Anterior guidance affects the occlusal morphology of posterior teeth.  Greater the vertical overlap of anterior teeth, longer is posterior cusp height.  Greater the horizontal overlap of anterior teeth, shorter is posterior cusp height. www.indiandentalacademy.com
  38. 38.  By increasing anterior guidance to compensate for inadequate condylar guidance, it possible to increase cusp height.  If protrusive condylar inclination is shallow, requiring short posterior cusps, cusps may be lengthened by making the anterior guidance steeper. www.indiandentalacademy.com
  39. 39.  Increasing anterior guidance will permit the lengthening of cusps that would otherwise have to be shorter in presence of pronounced immediate lateral translation. www.indiandentalacademy.com
  40. 40. Patient adaptability  Most of the patients are able to adapt small occlusal deficiencies without exhibiting acute symptoms. lowered threshold : Patients with low pain threshold do not present much difficulty in diagnosis. But it should not be confused with hypochondria which is poor adaptability to occlusal discrepancies. www.indiandentalacademy.com
  41. 41. raised threshold : Individuals who have adapted to existing mal occlusion may be comfortable with their dentition, although numbers of signs are evident. However occlusal treatments are advised to prevent further problems. www.indiandentalacademy.com
  42. 42. Pathogenic occlusion  It is defined as an occlusal relationship capable of producing pathologic changing in stomatognathic system.  There is disharmony between teeth &TMJ to present the symptoms. www.indiandentalacademy.com
  43. 43. Signs & symptoms :  Diagnosis is difficult because of combinations of symptoms. Following symptoms can help to confirm the diagnosis – 1. Teeth 2. Periodontium 3. Musculature 4. TMJ 5. MPDS www.indiandentalacademy.com
  44. 44. Teeth  Hyper mobility - due to premature contact inCR  Open contacts – due to tooth migration, unstable occlusion  Abnormal wear – due to parafunctional activities www.indiandentalacademy.com
  45. 45. Periodontium  Widened periodontal ligament space – due to premature occlusal contact  Advanced periodontal disease – bone loss, rapid tooth migration due to occlusal descrepancies www.indiandentalacademy.com
  46. 46. Musculature  Acute or chronic muscular pain – due to bruxism  Trismus - due to no relaxation of elevator muscle www.indiandentalacademy.com
  47. 47. TMJ  Pain, clicking or popping – due to muscular origin, or internal derangement of joint.  Unilateral clicking with midline deviation – due to displaced disc. www.indiandentalacademy.com
  48. 48. MPDS  Diffuse unilateral pain in preauricular area with muscle tenderness, clicking, popping noise in contralateral Tmj joint.  Due to bruxism or clenching with chronic muscle fatigue leading to muscle spasm & altered mandibular movement.  Tooth movement may occur & malocclusion becomes apparent when muscle spasm is releived. www.indiandentalacademy.com
  49. 49.  Or malocclusion of teeth displaces the condyle, & feeedback from dentition is altered that results in muscle spasm. www.indiandentalacademy.com
  50. 50. Occlusal treatment  Any signs & symptoms that correlates occlusal interferences, then occlusal treatment should be considered.  It can be done by tooth movement by orthodontics, elimination of deflective contacts through selective reshaping of occlusal surface of teeth, or restoration & replacement of missing teeth that result in more favorable distribution of occlusal force. www.indiandentalacademy.com
  51. 51. Objectives of occlusal treatmaent 1. To direct occlusal forces along long axis of teeth. 2. To attain simultaneous contact of all teeth in CR. 3. To eliminate any occlusal contact on inclined planes to enhance positional stabilty of teeth. www.indiandentalacademy.com
  52. 52. 4. To have centric relation coincides with maximum intercuspation position. 5. To arrive at occlusal scheme selected for patient. i.e unilateratl or mutually protected occlusion. www.indiandentalacademy.com
  53. 53.  These objectives can be accomplished with removable occlusal device, fabricated from clear acrylic resin that overlies the occlusal surfaces of one arch.  Definitive occlusal treatment involves accurate manipulation of the mandible, particularly in centric relation. www.indiandentalacademy.com
  54. 54.  Because patient may resist such manipulation as a result of protective muscular reflexes, deprogramming device can be used, also called as occlusal device. www.indiandentalacademy.com
  55. 55. Occlusal device therapy  Also called as occlusal splint, oclusal appliance or orthotics.  It is particularly helpful in determining whether a proposed change occlusal scheme can be tolerated by patient. www.indiandentalacademy.com
  56. 56.  It is made in acrylic overlay, that allows testing of the scheme, with slight increase in vertical dimension.  If patient responds favorably to occlusal device, then restorative treatment will be positive.  So it is important diagnostic procedure before initiation of treatment. www.indiandentalacademy.com
  57. 57.  It can be made for either maxillary or mandibular teeth.  It can be made by direct or indirect technique. www.indiandentalacademy.com
  58. 58. Direct technique ( auto polymerised ) Can be done in 1 appointment.  Uses mouth as articulator, introducing errors.  Vaccum formed matrix is thin & flexible, require more coverage for stablity.  Chipping & breaking, need for chair side repair. www.indiandentalacademy.com
  59. 59.  Stains, odors, & excess wear because of porosity of acrylic.  Device can be duplicated in heat cure acrylic resin for greater durability. www.indiandentalacademy.com
  60. 60. Procedure :  Adapt a sheet ( 1 mm thickness ) of clear thermoplastc resin to diagnostic cast. Excessive undercuts should have been blocked out.  Trim the excess resin so all facial soft tissue is exposed.  On lingual surface of maxillary device, matrix should cover anterior third of hard palate for rigidity. www.indiandentalacademy.com
  61. 61.  Try the matrix for fit & stability.  Add small amount of self cure acrylic in incisal region & guide mandible in CR by bimaual manipulation technique so that shallow indentation will come in acrylic resin. www.indiandentalacademy.com
  62. 62.  Add more resin to incisors & canine region, ask patient to do retrusive, protrusive and lateral closure in soft resin.  Allow resin to polymerize. www.indiandentalacademy.com
  63. 63.  With help of marking ribbons, adjust resin to give smooth, even contacts during protrusive & lateral excursions as well as definite occlusal stop for each incisors in CR. www.indiandentalacademy.com
  64. 64.  Ask patient to wear the device overnight before the acquired protective muscle patterns are overcome.  If posterior tooth eruption to be avoided, patient must be seen again in 24 to 48 hours. www.indiandentalacademy.com
  65. 65.  Place pencil marks in depressions made by opposing functional cusps.  Remove excess resin with bur or wheel & leave those pencil marks. All other contacts must be eliminated.  Smoothen and polish the device. www.indiandentalacademy.com
  66. 66. Indirect technique  More esthetic  Less chance of breakage, warping or wear  More precise occlusal contacts with articulator  Less chair time at delivery www.indiandentalacademy.com
  67. 67.  Better adaptation to teeth & soft tissues.  Less coverage needed for stability.  Use of ball clasps for retention. www.indiandentalacademy.com
  68. 68. Indirect technique With self cure acrylic resin  Mount diagnostic casts accurately.  Be sure that device is made at same vertical dimension as centric relation recorded.  Fit articulator with incisal guide table flat. www.indiandentalacademy.com
  69. 69.  Lower the incisal guide pin until there is 1 mm of clearance between posterior teeth.  Check the clearance of 1 mm during protrusive movements.  Raise the platform wings of incisal guidance table in all lateral excursions, for 1 mm of clearance. www.indiandentalacademy.com
  70. 70.  Block out the undercuts with wax.  Form wire clasps to engage facial undercuts, seal the casts with separating medium.  Fabricate device with self cure acrylic.When resin is still soft, close the articulator.There will be depression formed by each functional cusps. www.indiandentalacademy.com
  71. 71.  Close articulator in protrusive & lateral excursions. Add or remove acrylic until it is in constant contact with anterior teeth when incisal guide pin contacts the guide table.  After it polymerize, refine the occlusion on articulator. www.indiandentalacademy.com
  72. 72.  There should be even contact for each functional cusp in CR.  A stop should exist for each anterior tooth in CR.  Protrusive contacts on incisors should be smooth & even.  There should smooth & even lateral contact on laterotrusive canines. www.indiandentalacademy.com
  73. 73. Indirect tehnique with self cure resin ( alternative technique )  Obtain accurate casts & interocclusal record.  Articulate the casts in CR.  Adjust the articulator pin until 2 mm of interocclusal clearance results. www.indiandentalacademy.com
  74. 74.  Wire clasps & 2 sheets of base plate wax are adapted on maxillary casts.  Develop anterior ramp & establish evenly destributed occlusal contact with mandibular teeth.  Wax sprues are added to posterior side of waxed device. www.indiandentalacademy.com
  75. 75.  Laboratory silicone is adapted over wax up.  After wax is boiled off, reposition the clasps & lute them with sticky wax.  Apply separating media. Self cure is filled in the mold cavity between cast & repositioned silicone. www.indiandentalacademy.com
  76. 76. After polymerization, reattach casts to articulator & adjust occlusal contacts until mutually protected articulation is achieved. www.indiandentalacademy.com
  77. 77. Indirect technique ( heat cure )  Articulate the casts in CR. Notch the bases of cast for remounting.  Create desired device in wax, obtaining centric stops & anterior guidance. www.indiandentalacademy.com
  78. 78.  Separate the casts & flask it in conventional manner.  Process in heat cure clear acrylic.  Rearticulate & adjust the occclusion. www.indiandentalacademy.com
  79. 79.  Patient is asked to wear the device for 24 hours a day, removing it only for oral hygiene. Check it weekly, biweekly for modifications. www.indiandentalacademy.com
  80. 80. Occlusal interferences  Interferences are undesirable occlusal contacts that may produce mandibular deviation during closure to maximum intercuspation or may hinder smooth passage to & from the intercuspal position. www.indiandentalacademy.com
  81. 81. Types : 1. Centric 2. Working 3. Non working 4. Protrusive www.indiandentalacademy.com
  82. 82. Centric interference :  It is a premature contact that occurs when mandible closes with the condyles in their optimum position in the glenoid fossa.  It causes deflection of mandible in posterior, anterior or lateral direction. www.indiandentalacademy.com
  83. 83. Elimination of interference : 1. Find any interference that cause condylar process to displace anteriorly,( protrusive interference). It is mesial incline of maxillary & distal incline of mandibular teeth. 2. Continue adjustment until all teeth contact evenly ( except incisors ). If excursive movements are guided by canines, then stop when bilateral canine to canine contact is restablished. www.indiandentalacademy.com
  84. 84.  In lateral displacing prematurity, adjust buccal facing inclines of maxillary & lingual facing inclines of mandibular teeth. Premature contact can be on laterotrusive or mesiotrusive side of mandible.  In laterotrusive side, adjust buccal inclines of maxillary lingual cusps & lingual inclines of mandibular buccal cusps until there is contact on cusp tips. www.indiandentalacademy.com
  85. 85.  If it is in mesiotrusive side, adjust buccal inclines of mandibular buccal cusps & lingual inclines of maxillary lingual cusps until there is contact on cusp tips.  It is verified with Mylar shim stocks in forceps. www.indiandentalacademy.com
  86. 86. Working interference :  It occur when there is contact between maxillary & mandibular posterior teeth on the same side of the arches as the direction in which mandible is moved.  If that contact is heavy enough to disocclude anterior teeth, it is interference.  Between maxillary lingual facing cusp inclines & mandibular buccal facing cusp inclines. www.indiandentalacademy.com
  87. 87. Non working interferences :  It is occlusal contact between maxillary & mandibular teeth on the side of arches opposite the direction in which mandible has moved in lateral excursion.  It is of destructive nature, can damage the masticatoty apparatus.  Between maxillary buccal facing cusp inclines & mandibular lingual facing cusp inclines. www.indiandentalacademy.com
  88. 88. Protrusive interferences :  It is a premature contact occurring between mesial aspect of mandibular posterior & distal aspect of maxillary posteriors.  Proximity of teeth to muscles & oblique vectors of forces make contacts between opposing destructive as well as interfere to incise properly. www.indiandentalacademy.com
  89. 89. Elimination of lateral & protrusive interferences : 1. Use red & blue marking to distinguish centric and eccentric contacts. 2. Goal is to eliminate contacts between all posterior teeth during protrusive movements & to eliminate any interference on non working side as well as on working side. www.indiandentalacademy.com
  90. 90. 3 No centric contacts to be removed. 4. Lateral & protrusive contacts are eliminated by creating a groove that permits escape of the functional cusps during eccentric movements. www.indiandentalacademy.com
  91. 91. Diagnostic occlusal adjustments  2 stets of articulators are required.  1 act as reference & other is used to remove the tooth structure.  Occlusal surfaces are painted with poster paint.  Pin setting is recorded before removing enamel.  Each step is recorded carefully. www.indiandentalacademy.com
  92. 92. Objectives of selective occlusal reshaping :  Redistribute forces parallel to long axis of teeth by eliminating contacts on inclined plane & creating cusp fossa occlusion.  To eliminate deflective occlusal contacts, centric relation coincides with maximum intercuspation. www.indiandentalacademy.com
  93. 93.  To improve worn occlusal harmony, enhance cuspal shape, narrow occlusal table, proper developmental & supplemental grooves.  To correct marginal ridge discrepancies & extrusions so that oral hygiene will be easier.  To correct tooth malalignment through selective reshaping. www.indiandentalacademy.com
  94. 94. Clinical occlusal adjustments Contraindications of definitive occlusal adjustments :  Bruxers, habits cant be controlled.  Diagnostic correction shows excess tooth grinding.  Angle’s Class 2 & 3 relationship.  Maxillary lingual cusps contacting mandibular buccal cusps. www.indiandentalacademy.com
  95. 95.  Open anterior occlusal relationships.  Excessive wear.  Before orthodontic or orthognathic treatment.  Before occlusal appliance therapy.  Patients withTMJ pain.  Patients with jaw movements cant be manipulated easily. www.indiandentalacademy.com
  96. 96. Optimum occlusion  In placement of restorations, dentists must produce an occlusion that is nearly optimum as oral conditions of the patient.  It requires minimum adaptation by the patient. www.indiandentalacademy.com
  97. 97. Okeson’s criteria for optimum occlusion : 1. In closure, condyles are in most superoanterior position against the discs on posterior slopes eminence of glenoid fossae. Posterior teeth are in solid & even contacts, anterior teeth are in slightly lighter contact. 2. Occlusal forces are in long axes of the teeth. www.indiandentalacademy.com
  98. 98. 1. In lateral excursions, working side contacts disocclude or separate the non working side instantly. 2. In protrusive excursions, anterior tooth contacts will disocclude the posterior teeth. 3. In upright posture, posterior teeth contact more heavily than do anterior teeth. www.indiandentalacademy.com
  99. 99. Restoring lower anteriors  While restorative correction of any occlusal problem, always lower anterior should be completed first.  First consideration is to determine the correct location of incisal edges, based on most stable centric contact with upper anterior & mounted models. www.indiandentalacademy.com
  100. 100.  It is ideal if lower anterior contact in centric relation at correct vertical dimension on cingulum of upper anterior teeth.  Whenever possible, incisal edges should follow a horizontal alignment with the centre bowed up slightly.  Flat or reverse curve alignment gives a harsh appearance, not attractive. www.indiandentalacademy.com
  101. 101.  When alveolar ridge slants off a normal horizontal line, incisal edges should should still be aligned evenly along the horizontal plane. www.indiandentalacademy.com
  102. 102.  Wear on incisal edges produce sharp line angles.  Restoring the edges with rounded contour reduce the wear, but looks artificial.  Slight rounding the line angle & giving slight concavity in centre of edge looks natural without creating wear problem.  Sometimes too steep anterior guidance can be flattened by shortening the lower anterior & restoring lingual surfaces of upper teeth. www.indiandentalacademy.com
  103. 103. Restoring upper anteriors  Correct lip support : teeth not in harmony with lip are not only unstable but also uncomfortable & unesthetic.  Precise incisal edge position : it establishes correct length of each tooth & plays dominant role in esthetics and determinant of optimum function. www.indiandentalacademy.com
  104. 104.  Labial contour : some are flat, some convex, square or fan shaped, depending on patient’ smile.  Lingual contour : it is last step to prepare, based on centric relation to incisal edge position.  Phonetics : incisal edge of upper teeth should lightly touch vermillion border of lower lip during F,V sounds. www.indiandentalacademy.com
  105. 105.  Anterior guidance angles : in sufficient overjet, lengthen the upper anterior & compensate with concave lingual contour so flat guidance angle can be maintained.  In minimum overjet, don’t lengthen upper anterior without steepening anterior guidance angle. www.indiandentalacademy.com
  106. 106. Determining the type of posterior occlusal morphology There are 3 basic steps : 1. Selection of type of centric holding contacts 2. Determining type & distribution of contact in lateral excursions 3. Selection of most practical method of providing stability of occlusal form. www.indiandentalacademy.com
  107. 107. Types of centric holding contacts :  There are 3 basic ways by which centric contact is established : 1. Surface to surface contact 2. Tripod contact 3. Cusp tip to fossa contact www.indiandentalacademy.com
  108. 108. Variations of posterior contact in lateral excusions :  Whenever lower teeth move towards tongue, it should not contact.  While teeth on working side are disoccluding the teeth on non functioning side, they must also act as cuter, grinder, holders. www.indiandentalacademy.com
  109. 109. It is decided by selecting one of the following working side occlusion : 1. Group function 2. Partial group function 3. Posterior disocclusion www.indiandentalacademy.com
  110. 110. Selecting occlusal form for stability : There are 4 basic types to choose form in normal arch relationship : Type 1 : lower buccal cusps contact upper fossa.There are no other centric contacts.Working side excursive function is limited to lingual inclines of upper buccal cusps. www.indiandentalacademy.com
  111. 111. Type 2 : centric contacts on tips of lower buccal cusps & upper lingual cusps. Working side excursive function is limited to lingual inclines of upper buccal cusps. www.indiandentalacademy.com
  112. 112. Type 3 : centric contact on tips of lower buccal cusps & upper lingual cusps. Working excursion contact is limited to the lingual incline of upper buccal cusps & buccal incline of lower lingual cusps. www.indiandentalacademy.com
  113. 113. Type 4 : tripod contact There are 2 types : 1. Contacts on sides of cusps & walls of fossa 2. Centric contact on brims of fossa& top of wide cusp tips with no contact in eccentric excursions. www.indiandentalacademy.com
  114. 114. Restoring lower posteriors  It is advised to restore lower posterior first than upper.  Posterior teeth in lower arch is accurately restored with cusp tip to fossa contact with following basics : 1. Correct height & placement of buccal cusps 2. Correct height & placement of lingual cusps 3. Correct placement of fossa 4. Correct incline of fossa wall 5. Accurate ridge & groove direction www.indiandentalacademy.com
  115. 115. placement of lower buccal cusps : Buccal cusp placement for bucco lingual stability : the lower buccal cusp must be positioned such that its contacts directs the stress through the long axis of both upper & lower teeth. The main force vector should be as parallel as possible to long axis of both upper & lower tooth. www.indiandentalacademy.com
  116. 116. Mesiodistal placement of lower buccal cusps : for attaining mesi distal stability  Cusp tip should be centered in correctly designed upper fossa , than on incline or flat surface contact.  It will direct the force through long axis & eliminate possibility of plunger cusp for food impaction.  There will not be tendency for cusp tips to migrate out of fossae. www.indiandentalacademy.com
  117. 117. Locating lower buccal cusps for non interfering excursions :  While locating cusp tip placement, path of egress from centric relation should be considered.  Egress towards buccal is equally non interfering on each of contacts.  However if centric stop is placed on distal, egress towards lingual is interfered by upper lingual cusp.  If lower buccal cusp tip is placed in upper mesial fossa, it moves out on excursion towards lingual. www.indiandentalacademy.com
  118. 118.  Path of any lower cusp can be determined in mouth or articulator by visualizing the path as being at right angles to imaginary line from rotating condyle to the cusp in question.  Path depicted on opposing side from rotating condyle shows balancing excursions, while on same side shows working excursions. www.indiandentalacademy.com
  119. 119. Contouring cusp tips :  In correctly contoured cusp tip to fossae contact, the cusp tip contacts in centric relation & through any purely horizontal movements.  If lateral excursion contacts is desired, side of the cusp takes over & cusp tip is disoccluded.This minimizes wear on centric holding contacts. www.indiandentalacademy.com
  120. 120.  Wide cusp tips produce neither better function nor better stabilty.  Properly contoured small cusp tip fits into base of saucer shaped fossa that helps to stabilize it.  Small cusp tip permit good anatomy, require less force & produce less stress. www.indiandentalacademy.com
  121. 121. Contouring the lower fossa :  Inner incline of upper canine dictates the incline limitations of lower posterior inclines facing it.  Lower working side incline can not be steeper than lateral anterior guidance incline of cuspid. It should be made flatter because it is not necessary for lower incline to contact in function. www.indiandentalacademy.com
  122. 122.  Balancing incline should never be allowed to contact in function.  So it should also be flatter than lateral guidance of cuspid.  If angle is steeper than lateral anterior guidance, upper lingual cusp will be locked into lower fossa & back teeth will clash stressfully in lateral excursions. www.indiandentalacademy.com
  123. 123. Contouring ridges & grooves :  Its action is to crush, tear & shred food against upper inclines.  Extreme preciseness is not required because in cusp tip to fossa relationship only the base of lower fossa contact the upper lingual cusp.  Walls of fossa never contacts & grooves are opened up to avoid contact. www.indiandentalacademy.com
  124. 124. Placement of lower lingual cusps :  Lower lingual cusp is non functional as far as contact ic concerned. However still it should act as gripper & grinder of food.  Cusp tips should be rounded & smooth to hold the tongue out of the way, but should be located over root within long axis.  Distance between lower buccal & lingual cusp tip is same as upper cusp tips. www.indiandentalacademy.com
  125. 125.  Distance between buccal & lingual cusp tip should not be greater than half of total buccolingual width of tooth at its widest part.  Lower lingual cusp height is about 1 mm shorter than buccal cusp tip. It is further lower in first premolar. www.indiandentalacademy.com
  126. 126. Procedure for locating buccal & lingual cusp tips : 1. Draw line on central grooves of upper posterior. 2. Try to select fossae for cusp tip placement & mark it. 3. Buccal cusp tip is placed where each line intersect. 4. Drill a hole at each cusp tip location by bur. www.indiandentalacademy.com
  127. 127. 5. Insert 3 mm long 14 gauge wax sprue into hole & close the articulator. 6. Flow red inlay wax around occlusal part of die to engage sprue wax. 7. Articulator is opened & wax is added around die and crown is build up. www.indiandentalacademy.com
  128. 128. 8. Broadrick occlusal plane analyzer is used to determine height of buccal & lingual cusp based on curve of wilson and curve of spee. 9. Then dark cusp tips are never touched. 10. Buccal anatomy is carved. Crest of contour is at gingival & middle third junction. www.indiandentalacademy.com
  129. 129. 1. Lingual cusp tips are located by measuring the upper cusp teeth with double pointed caliper. 2. Then lingual contour is carved. Crest of contour is at middle third. www.indiandentalacademy.com
  130. 130. Procedure to make fossa contour guide : 1. Anterior guide table is flattened to zero degree. 2. Special fossa contour pin is inserted in place of incisal pin. 3. Softented wax is placed on flat guide table & upper model is moved in left and right excursions, but not go in protrusion.Take guidance with upper cuspid. www.indiandentalacademy.com
  131. 131. 4.When lateral guidance pathways are cut sharp into the wax, pin is raised, & applied separating media. 5. Same guidance is duplicated in self cure acrylic. www.indiandentalacademy.com
  132. 132. There are 3 basic rules for using fossa contour guide : 1. Always hold the handle perpendicular. 2. Never destroy the predetermined cusp tip. 3. Locate fossa in proper relation to cusp tips. www.indiandentalacademy.com
  133. 133. Restoring upper posteriors  There should be sufficient thickness of metal & porcelain in all excursions.  Generally it is checked in CR only.  If anterior guidance is not finalized & lower posteriors are not in final form, it is not possible to determine clearance for upper posteriors. www.indiandentalacademy.com
  134. 134.  Dentist has to decide whether upper inclines has to be in group function, partial group function or total disocclusion in excursive movements.  Accordingly inclines are contoured& angulated.  Supplemental grooves are cut into inclines to increase gripping ability of tooth surface.  Grooves are carved smaller than cusp tips. www.indiandentalacademy.com
  135. 135.  If we select to provide Group function on working side, length of the contact stroke should be progressively shorter from anterior teeth back.  Molar contact is only maintained for a fraction of its inclined surface, while cuspid contact is maintained all the way to incisal edge. www.indiandentalacademy.com
  136. 136.  If molar contact is maintained for entire incline, protection from guidance is lost.  Stress exerted against the molar is severe because of its torque effect near condylar fulcrum. www.indiandentalacademy.com
  137. 137.  Upper occlusal inclines should be contoured to disclude in a manner that allows the anterior teeth to maintain contact the longest.  Second molar should contact in a working side excursion for no more than half its incline length. www.indiandentalacademy.com
  138. 138.  Occlusion on restoration is often ruined by errors of cementation.  Unless some space is given for cement, the most meticulously made crowns will be high after cementation. www.indiandentalacademy.com
  139. 139. Conclusion The perfection of skills required to provide sophisticated treatment of complex occlusal problems may take years to acquire. However, the minimum expectation of the competent practitioner is the ability to diagnose & treat simple occlusal disharmonies, should be able to produce restorations that will avoid creation of iatrogenic occlusal disease. www.indiandentalacademy.com
  140. 140. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com