Trauma From Occlusion.pptx

Trauma From Occlusion

1. Trauma From Occlusion DR.SWAPNA EDIGA By-DR.SWAPNA.E

2. Contents Introduction Definition & Terms Classification Stages of tissue response to increased occlusal forces Role of occlusion in pathogenesis of Periodontal disease Human studies & Clinical trials Animal experiments TFO & Plaque Associated Periodontal Disease Diagnosis Treatment Conclusion References

3. Introduction To function occlusal harmony- masticatory apparatus- teeth & supporting tissues, TMJ & associated neuromuscular skeletal structures must operate in an integrated & dynamic manner Loss of integrated function & homeostasis in response to functional demand may lead to exacerbation of existing periodontal condition. Angle defined occlusion as the normal relation of the occlusal inclined planes of the teeth when the jaws are closed

4. Definitions- Trauma from Occlusion A condition where injury results to the supporting structures of the teeth by the act of bringing the jaws into closed position- ( Stillman 1917 ) When the occlusal forces exceed the adaptive capacity of the periodontal tissues, tissue injury results. The resultant injury is termed as trauma from occlusion. ( Orban and Glickman 1928,1933 )

5. Damage in the periodontium caused by stress on the teeth produced directly or indirectly by teeth of opposing jaw” ( WHO 1978) “An injury to the attachment apparatus as a result of excessive occlusal forces” (Glossary of Periodontic terms AAP 2001)

6. Traumatogenic Occlusion Any occlusion ( e.g malocclusion) that produces forces that cause an injury to the attachment apparatus. Other terms : Traumatic occlusion Occlusal disharmony Functional imbalance Occlusal dystrophy

7. Occlusion Traumatism The overall process by which a traumatogenic occlusion produces injury in the periodontal attachment apparatus.

8. Traumatizing Occlusion may act on individual tooth/groups of teeth In premature contact relationship In conjunction with parafunction - clenching, bruxism In conjunction with loss of migration of premolars & molar teeth with gradually developing spread of anterior of teeth of maxilla

9. Adaptive capacity of Periodontium to occlusal forces Varies in different persons & in same person at different times Influenced by

10. Physiologically normal occlusal forces in chewing and swallowing : Positive stimulus in maintaining the periodontium and the Alveolar bone in a healthy and functional condition. Impact forces : mainly high & short duration  periodontium can sustain high forces for short period Exceeding the viscoelastic buffer capacities of PDL results  in loss of tooth and bone. Continuous forces :Very low forces ( eg , orthodontic forces), continuous in one direction  displacing tooth by remodeling alveolus. Jiggling forces : Intermittent forces in 2 directions (premature contacts eg , crowns, fillings) result in widening of the alveolus and increased mobility. TYPES OF OCCLUSAL FORCES

11. Forces too high (above the adaptation level), aseptic necrosis of the PDL ( hyalinisation ) root resorption occur resulting in shorter roots.`

12. Jiggling forces different and opposite directions. Therotically same events occurs. However, they are not clearly seperated . Histologically : Aposition & resorption on either sides of PDL  widening of PDL space ( observed on radiographs) This phenomenon the increased mobility without pocket formation, migration and tipping. Hypermobility as long as the forces are exerted on the tooth not adaptation. not a sign of an ongoing process but result of a previous jiggling force.

13. Jiggling forces

14. Reasons of deflective occlusal forces. Patterns of mastication, Loss of teeth, Loss of periodontal support, Dental caries, Faulty restorations Flawed orthodontics, Defective occlusal adjustment, Occlusal habits, Inadequate form and position of the teeth.

15. EFFECTS OF OCCLUSAL DISHARMONY

16. Terminologies Occlusal trauma can be divided into 3 general categories: Occlusal Trauma: An injury to the attachment apparatus as a result of excessive occlusal force . Occlusal trauma is the tissue injury, and not the occlusal force.

17. Traumatogenic Occlusion: Any occlusion that produces forces that cause an injury to the attachment apparatus. Occlusal Traumatism: The overall process by which a traumatogenic occlusion produces injury in the periodontal attachment apparatus.

18. TYPES

19. ACUTE TRAUMA Acute TFO develops from An abrupt occlusal impact  biting on a hard object. Restorations, prosthetic appliances that interfere with or alter the direction of occlusal force Clinical features Tooth pain, sensitivity to percussion, and increased tooth mobility. Outcome – Injury heals and the symptoms subside if the force is dissipated 1) shift in the position of the tooth or 2) wearing away or correction of the restoration. Injury may worsen and develops into necrosis accompanied by periodontal abscess formation, or Persist as a symptom-free chronic condition Result in cemental tears.

20. CHRONIC TRAUMA More common and is of greater clinical significance Develops from- Gradual changes in occlusion produced by 1) Tooth wear, 2) Drifting , 3) Extrusion , 4) With parafunctional habits such as bruxism and clenching, rather than as a sequel of acute TFO.

21. PRIMARY TFO When TFO is the result of alterations in occlusal forces Insertion of a “high filling” Insertion of a prosthetic replacement that creates excessive forces on abutment and antagonist teeth. Orthodontic movement of teeth into functionally unacceptable positions. Drifting movement or extension of teeth into spaces created by unreplaced missing teeth, OR Changes produced Do not alter the level of connective tissue attachment and do not initiate pocket formation. Probably because the supracrestal gingival fibers are not affected and therefore prevent apical migration of the junctional epithelium.

22. SECONDARY TFO Occurs when the adaptive capacity of the tissues to withstand occlusal forces is impaired by bone loss resulting from marginal inflammation. This reduces the periodontal attachment area and alters the leverage on the remaining tissues. The periodontium becomes more vulnerable to injury and previously well-tolerated occlusal forces become traumatic.

23. Stages of Tissue response to increased occlusal forces 3 stages: Stage I: injury Stage II: repair Stage III: adaptive remodeling of periodontium

24. Stage I: Injury- increase in areas of resorption, decrease in bone formation

25. Slightly excessive pressure: PDL widening, bone resorption. Slightly excessive tension: elongation of PDL fibers, Apposition of alveolar bone Severe pressure: pressure forces root to bone-undermining resorption: necrosis of PDL & bone. Severe tension:PDL widening, thrombosis,hemorrhage , PDL tearing,bone resorption.

26. Increased pressure areas: blood vessels numerous & reduced in size. Areas of increased tension: enlarged blood vessels( Zaki 1963). Greater pressure: compression of PDL fibers, areas of hyalinization( Rygh 1974). injury to fibroblasts & connective tissue –necrosis of ligament. Vascular changes:-within 30 mins -impairment & stasis of blood flow, 2-3 hours blood vessels packed with erythrocytes fragment , 1- 7 days disintegration of blood vessels & release contents into surrounding tissue. Increased resorption of alveolar bone & tooth surface occur. Histoligicaly

27. Stage II : Repair-decreased resorption, increased bone formation Damaged cells are removed & new CT cells & fibers , bone , Cementum are formed in an attempt to restore injured periodontium Buttressing bone formation: Central: occurs within jaw. Endosteal cells deposit new bone, restore the bony trabeculae, reduces the size of marrow spaces. Peripheral: on bone surface.On facial & lingual bony plates.Lipping - Shelf like thickening of alveolar margin

28. Stage III: Adaptive remodeling of periodontium: resorption & formation return to normal If repair process does not keep pace with destruction caused by occlusion, periodontium is remodeled in an effort to create structural relationship Thickened PDL- funnel shaped at crest, angular defects in bone with no pocket formation. Tooth is loose. Increased vascularization

29. Role of occlusion in pathogenesis of Periodontal Disease Over 100 years occlusal trauma is associated with PD 1901 Karolyi : Association excessive occlusal forces & Periodontal destruction 1917-1926:Stillman- excessive occlusal force was primary cause of PD End of 1930: Excessive occlusal forces were a causative factor for PD & Occlusal discrepancies should be prophylactically treated to prevent PD 1933- Orban & Weinman , 1941- Weinmann - effect of excessive occlusal forces on periodontium and Concluded -: no relationship & cause was gingival inflammation 1950’s- 1960’s( Stahl 1962,Weinmann 1954,Ramjford 1971,) animal research- rats ,monkeys, dogs- effect of occlusal forces on periodontium: results : no relation

30. Glickman & co workers 1960 1960 Glickman & co workers : animal models & human Autopsy material : dogs & monkeys high restorations : no association Rhesus monkeys & Human autopsy models: phenomenon :- “ Altered pathway of destruction ” when occlusal forces were present. Altered pathway of destruction : change in orientation of periodontal & gingival fibers which occurred in presence of excessive gingival inflammation to extend along PDL This pathway caused vertical bony defects

31. Glickman & co workers conclusion Excessive forces in presence of plaque associated inflammation caused a change in the alignment of periodontal ligament ,allowing a altered pathway of inflammation/ destruction resulting in vertical bony defects Process was termed “ Co destructive effect”

32. Zone of irritation : marginal & interdental gingiva. gingival inflammation cannot be induced by TFO but is result of irritation from microbial plaque. First involvement of alveolar bone & later PDL. Progression : an even (horizontal)bone destruction Zone of co-destruction : PDL, Cementum, Alveolar bone. Coronally demarcated by trans- septal (interdental) & dento -alveolar collagen fiber bundles.the tissue in this zone becomes a lesion of TFO Fiber bundles which separate zone of co destruction affect from 2 directions: Inflammatory lesion maintained by plaque in zone of irritation Trauma induced changes in zone of co-destruction Glickmans Concept (1965,1967) Periodontal structures divided into 2 zones

33. Waerhaug(1979) concept “ Plaque front ”- was always in close approximation to epithelial attachment level & always followed morphology of bony defect. Also found excesssive occlusal forces bore no relationship to underlying bony defect & that vertical bony defects were found equally around traumatized & non traumatized teeth Conclusion: bone loss was always associated with down growth of plaque & there was no relationship between excessive occlusal forces & vertical bone loss.

34. 2 extensive studies- Polson & Lindhe ( 1970) Polson (1982)& co workers Lindhe (1982)& co workers squirrel monkeys- mesiodistal compression forces comparable to orthodontic forces beagle dogs, buccolingual forces using a high occlusal contact and a finger spring Effect of plaque & excessive occlusal forces in animal models Results: similar results Conclusion: excessive occlusal forces in absence of plaque cause loss of bone density & mobility of affected tooth but no evidence was found that occlusal force alone could cause attachment loss Conclude: excessive force alone does not cause loss of attachment, with plaque it causes.

35. Human studies & clinical trials World workshop in Periodontics “prospective studies on effect of occlusal forces on progression of Periodontics are not ethically acceptable in humans” Gher 1996 Human studies are limited to retrospective & observational research. Rosling et al 1976 Advanced PD, multiple vertical defects, mobile teeth subjected to antimicrobial therapy Infrabony pocket at Hyper mobile teeth exhibited same degree of healing as firm teeth Fleszar et al 1980 Tooth mobility on healing following periodontal therapy Pockets of clinically mobile teeth do not respond well to those of firm teeth exhibiting same degree of disease severity. Philstrom et al 1986 TFO & periodontitis Teeth with increase mobility had deeper pockets, attachment loss, bone loss compared to teeth without.

36. Clinical trials Wang & Ramjford 1994-molars with furcation involvement & mobility have greater probing depths compared to molars that are clinically immobile. Ramjford & Burgett 1992: patients who received occlusal adjustment as part of their periodontal treatment had greater attachment gain than patients who did not. These studies suggest that occlusal adjustment should be performed where indicated as part of periodontal treatment

37. Mc Guire & Nunn 1996: mobility & para functional habits that are not treated with biteguard are associated with increased attachment loss, worsening prognosis & tooth loss. Cortelleni & Tonetti 2001- mobile teeth treated with regenerative surgery did not respond compared to non mobile teeth. Harrel & Nunn 2001: occlusal discrepancies appeared to be a significant risk factor that contribute to more rapid periodontal destruction & that treatment of occlusal discrepancies seemed to slow periodontal destruction.

38. Animal Experiments Orthodontic type trauma Muhlemann 1961, Waerhaug 1966, karring 1982 Teeth exposed to unilateral forces of magnitude, frequency/duration that they are unable to withstand Certain well defined reactions develop in PDL leading to bone resorption .

39. Orthodontic type trauma

40. Jiggling type trauma Healthy periodontium with normal height Supralaveolar CT was not influenced by occlusal forces: reason: tissue compartment is bordered by hard tissue only on one side- gingiva was non inflamed at start of experiment remained non inflamed & not aggravated by jiggling forces.

41. Healthy periodontium Reduced height Within certain limits a healthy periodontium with reduced height has capacity similar to periodontium of normal height to adapt to altered functional demands

42. Reduced height Within certain limits a healthy periodontium with reduced height has capacity similar to periodontium of normal height to adapt to altered functional demands

43. Plaque associated Periodontal disease Occlusal forces which allow adaptive alterations to develop in the pressure/tension zone of PDL will not aggravate a plaque associated PD

44. Lindhe & Svanberg 1974 If magnitude & direction of occlusal forces are not adapted by tissues-injury in Co-destruction is permanent. Angular bone loss continues Progressive mobility Plaque associated lesion in area of irritation & inflammatory lesion in area of co- destruction merged, the epithelium proliferated in an apical direction & PD aggravated.

45. Effects of insufficient occlusal forces May also be injurious Insufficient stimulation causes thinning of PDL Atrophy of fibers Osteoporosis of alveolar bone Reduction in bone height Hypo function causes: Open bite relationship Absence of functional antagonists Unilateral chewing habits

46. Reversibility of traumatic lesions

47. Effects of excessive occlusal forces on pulp

48. Diagnosis

49. SIGNS

50. Radiographic features Widening PDL space, thickening of lamina dura in lateral aspect of root, in apical regions & bifurcation areas. Vertical rather than horizontal destruction of interdental septum Radiolucency & condensation of alveolar bone. Root resorption

51. Detection of occlusal trauma clinically Analysis of patients occlusal relationship- Angle’s classification. The relationship between cusps is the most important factor in transmittal of occlusal forces to the periodontal structures. Initial contact between teeth is detected by gentle manipulating patient's mandible into retruded position Retruded position: both right & left condyles are firmly placed in fossa of TMJ Patient is asked to close until patient feels first contact between teeth. Centric relation : initial contact in retruded position. Patient is asked to continue to close the jaws together until maximum contact between the teeth is achieved. Centric occlusion : jaw position of maximum tooth contact

52. The distance that patient moves between retruded initial contact & point of maximum tooth contact- slide between positions of centric relation & centric occlusion(CR/CO slide).

53. Treatment Occlusal adjustment Management of parafunctional habits Temporary, provisional or long term stabilization of mobile teeth with appliances Orthodontic tooth movement Occlusal reconstruction Extraction of selected teeth

54. Occlusal adjustment (Selective Grinding) Non reversible. Reshaping of occlusal surfaces to create harmonious contact relationships between the upper and lower teeth. Thorough occlusal analysis must be embarked: Clinical assessment of occlusion:- comprehensive assessment of teeth Interarch relationships, jaws & associated muscles TMJ & their movements, examination of articulate study casts: semi adjustable articulator with models mounted in retruded position

55. Occlusal adjustment Indications Contraindications To reduce traumatic forces to teeth To reduce damage from parafunctional habits To reshape teeth: reduce soft tissue injury To reduce food impaction Occlusal adjustment without pre-treatment study & patient education Signs & symptoms of occlusal trauma Microbial induced inflammatory PD treatment. Bruxism Rx based on patient history without evidence of damage, pathosis /pain When patients emotion precludes satisfactory result. Treatment for severe extrusion, mobility/ malposition teeth that would not respond to occlusal adjustment alone.

56. Cautions Adjustment should be done for a definite reason —not prophylactically . -tooth structure is irreplaceable. b. Adjustment should not be done in the presence of TMJ and/or muscle problems c. Adjustment should not be completed at one sitting, particularly if major adjustment is needed—give patient a chance to adapt. d. Adjustment should not create unfavorable positive occlusal consciousness on the part of the patient, e. Occlusal adjustment therapy alone may not be the only mode of occlusal therapy needed—it may need to be used in conjunction with orthodontic, prosthetic, op­erative, or other modes of therapy.

57. Faulty Occlusal Adjustment Trauma from occlusion, Oral discomfort, Hypertonicity Pain in the masticatory muscles, Bruxism, Headache. Common complaints after faulty occlusal grinding Soreness of the teeth, Food impaction, Decreased masticatory effectiveness, Temporomandibular pain Drifting of the teeth. Hypermobility of the teeth and even root resorptio n

58. Equilibrating mobile teeth In a patient with mobile teeth, it may be necessary to temporarily stabilise those teeth before equilibration is possible. If a tooth is mobile, it is very difficult if not impossible to effectively modify its shape with the aim of reducing the occlusal forces acting upon it (equilibration).

59. Whether the inflammatory periodontitis has been treated successfully. If there is an inflammatory periodontal process this should be treated initially. Subsequently when the periodontal condition is stable, occlusal therapy may be necessary for some patients and could involve either occlusal equilibration or splinting. The radiographic appearance of the periodontal support. occlusal equilibration is indicated will depend upon:

60. Occlusal equilibration is considered an effective form of therapy for teeth with increased mobility which has developed together with an increase in the width of the periodontal ligament (PDL). Reducing the occlusal interference on a tooth with normal bone support will normalize the width and height of the PDL. Eliminating any occlusal interferences for a tooth which has a reduced bone height as a result of periodontal disease will result in bone formation and remodelling of the alveolus only to the pre-trauma level

61. It is generally accepted that occlusal adjustment directed solely at establishing an ideal conceptualized pattern is contraindicated. Rather, it should only be performed when the objective is to facilitate treatment or intercept actively destructive forces. When occlusal therapy is planned as part of periodontal treatment, it is usually deferred until initial therapy aimed at minimizing inflammation throughout the periodontium has been completed. This is based upon the fact that inflammation alone can contribute significantly to a tooth’s mobility.

62. Splinting

63. Contra-indications This means that if periodontal treatment results in a stable periodontal condition which is comfortable, splinting is not needed.

64. OCCLUSAL PARAFUNCTION: BRUXISM Bruxism : clenching or grinding of the teeth when the individual is not chewing or swallowing – Ramfjord and Ash - 1966

65. Presence of tooth wear in patients is not necessarily the cause for signs and symptoms of TM disorders. Data from Rugh indicate that 83% of a group of bruxers , performed bilateral muscle contraction, whereas 17% performed unilateral contractions. Nocturnal bruxism & Daytime (diurnal) bruxism.   Most people are not aware of a bruxism habit until it is brought to their attention. When active tooth gnashing occurs, the enamel rods are fractured and become highly reflective to light. Thus shiny, bright facets

66. Sleep studies have shown that bruxism can occur in any stage of sleep but is most common in stage II. Satoh and Harada observed that bruxism tended to occur during the transition from a deeper stage of sleep to a lighter stage of sleep. Emerging evidence suggests that bruxism occurring during rapid eye movement (REM) sleep may be the most damaging. Bruxism should not be considered a brain dysfunction, but rather central nervous system instability. Rugh estimates – 5% of individuals brux to a pathologic event.

67. Bruxism occurs equally as often in children as in adults. Olkinuora divided bruxers into two categories: It is a multifactorial psychosomatic phenomenon , with individual displaying “ aggressive, controlling, precise, energetic personality on one hand ( non-stress B .) and anxious, tense types on the other (stress bruxists ) There is little evidence to suggest that bruxist have personality derangement or are mentally ill.

68. Portable electromyographic recording devices indicate.. 0verall,it may be concluded that emotional stress acts together with other factors to produce bruxism. There is little support for the popular belief that occlusal mal-relationships or interferences may precipitate bruxism.

69. TREATMENT OF BRUXISM 1. Behavioural modality – explanation and arousal of the patients awareness of the habit. If pain and stiffness are associated, physical therapy. Anti-anxiety drugs.. Ware – 1982 – advocated use of antidepressants as a means of inhibiting the REM sleep. 2. Night guard appliance (max stabilization splint). Aim is to protect the tooth surface and to dissipate forces. More practical for treating nocturnal bruxism..

70. Splints are more significant in the management of the destructive effects of bruxism. Patient instructed to wear the splint during sleep. Should be adjusted again in 2-3 weeks.. Should be observed for bruxofacets . If present should be burnished away. Balancing should be completed before patient dismissal 3. Coronoplasty – recently placed dental restorations or other occlusal treatments. Occlusal adjustment, reconstruction, or orthodontic treatment are contraindicated as a means of controlling bruxism.

71. SELECTIVE GRINDING

72. TERMINOLOGY Intercuspal position (ICP): Synonyms : centric occlusion (CO), habitual occlusion, acquired centric, habitual centric, maximum intercuspation . Median occlusal position (MOP): a dynamic contact position of the teeth that may be obtained on command by a snap jaw closure foll moderate jaw opening Retruded position (RP): Any position of the mandible on the terminal hinge path. Synonyms : centric relation (CR), Terminal hinge position. Retruded contact position (RCP): The end point of terminal hinge closure Synonym: centric relation contact (CRC).

73. Laterotrusion : Synonym: working movement. Mediotrusion : Synonyms : non-working side movement, balancing movement. Laterotrusive side: Synonyms : working side, functional side. Mediotrusive side: Synonyms: nonworking side, balancing side, nonfunctional side, idling side. According to Ramfjord , “ centric occlusion is a tooth to tooth and jaw to jaw relationship, in which the teeth are in ideal intercuspation and all components of masticatory system – the TMJ, the neuromuscular elements and occlusal surfaces are in harmonious relationship.”

74. Centric Relation The most orthopedically stable joint position is when the condyles are in their most superoanterior position in the articular fossae, resting against the posterior slopes of the articular with the discs propoerly interposed . All elevator muscles activated … no occlusal influences Musculoskeletal stable position

75. PATIENT COUNSELING PROPER DIAGNOSIS Point out loose teeth Relate wear problems Study the occlusal relationship Demonstrate on the mounted casts Tell the patient to expect further adjustments. Never start coronoplasty unless both the dentist and the patient are committed to complete it.

76. TIMING IN RELATION TO SURGERY

77. PRELIMINARY GRINDING First step in treatment Done when the patient complains of pain or discomfort or when normal function is prevented by excessive mobility. Spot grinding

78. DEFINITIVE GRINDING Progressive tooth mobility. Radiographic signs of trauma. Performed after eliminating the inflammation in periodontal tissues.

79. CHECK GRINDING Performed as a final measure. Usually a month after surgery, the mouth is checked for trauma that may have resulted from a slight shifting of the teeth.

80. FOR LOCATING CR:

81. STEPS IN OCCLUSAL ADJUSTMENT I. Initial grinding II. Harmonization in terminal hinge occlusion, III. Harmonization in protrusive position and movement, IV. Harmonization in lateral occlusal position and lateral excursion, V. Reestablishment of physiologic occlusal anatomy and careful polishing of all ground surfaces .

82. INITIAL GRINDING

83. ABNORMAL WEAR The occlusal table is made smaller Occlusal forces will become centered over the tooth and will tend to be transmitted along the long axis of the tooth This step is indicated only when such narrowing would neither disturb vertical dimension (by removing cusp tips that contact in centric) nor induce cheek biting.

84. EXTRUSION Unesthetic appearance May be the premature tooth in many movements. The plane of occlusion is disturbed

85. ESTHETICS When individual anterior teeth are disproportionately longer than the same teeth on the other side of the mouth, they may be ground to a more symmetric & regular form.

86. UNEVEN MARGINAL RIDGES Marginal ridges maybe unequal in height; may not meet at the contact area Correct them by grinding or restorative dentistry

87. PLUNGER CUSP The elongated distobuccal cusp of the maxillary molar wedges the lower molars and forces them apart. Food impaction occurs during mastication Shortening & rounding without taking the tooth out of CO

88. ROTATED,MALPOSED OR TILTED TEETH Esthetics a problem Careful grinding to improve the crown form

89. WEAR FACETS AND ABRADED TEETH Teeth subject to masticatory and parafunctional activity tend to wear. Abraded teeth need more force in mastication so it need to be reduced

90. SHARP EDGES Can cause irritation to the tongue and cheek . Sharp edges of restorations protruding beyond the enamel surface. Undermining or chipping of enamel exposing sharp edges .

91. ANTERIOR OPEN BITE Never grind posterior teeth to bring teeth in contact.

92. Predicting the outcome of selective grinding It is appropriate only when alteration of the tooth is minimal so that all the correction can be made within the enamel structure. Exposure of dentin poses problem ( increased sensitivity, caries susceptibility, and wear) and thus shouldn’t be left untreated The “rule of thirds” is helpful in predicting the success of a selective grinding procedure.

93. RULE OF THIRD (Burch J.G. 1980) This rule has been developed to aid in determining the appropriate treatment. The inner inclines of the posterior centric cusps are divided into thirds.

94. When the mandible is in CR position- if the opposing centric cusp tip contacts on the third closest to the central fossa- Selective Grinding

95. When the mandible is in CR position- if the opposing centric cusp tip contacts on the middle third – Crowns and FPDs

96. When the mandible is in CR position- if the opposing centric cusp tip contacts on the third closest to the opposing centric cusp tip- Orthodontics

97. Anterioposterior Direction of the slide

98. Developing an acceptable centric relation contact position

99. Achieving the centric contact relation With light pressure, encourage small hinge movements. Exert more pressure as the jaw falls downwards and backwards to the retruded position, try to seek ligamentous resistance of the TMJs. If not try again. Talk in low tones, using repetitive phrases – “just let it go”

100. In CR, a mesial incline of the maxillary tooth contacts a distal incline (arrow) of the mandibular tooth the contact closest to the cusp tip is located on the mandibular tooth. This incline is elimainated allowing only the cusp tip to contact during the next closure this mandibular cusp tip contacts mesial inclines(arrow) of the maxillary cusp. This incline is reshaped into a flat surface (i.e. hollow grinding) On the next closure the mandibular cusp tip can be seen to contact the maxillary flat surface and the treatment goals for this pair of contact is achieved Mesial view

101. A. the mandibular buccal cusp prematurely contacts, preventing the contact of the maxillary lingual cusp. B. no contact during the laterotrusive movements (large arrows) C. no contact during mediotrusive movement (large arrows) D. the fossa area opposing the mandibular buccal cusp is reduced E. this reduction allows contact of the maxillary lingual cusp tip. In case there is a contact during the laterotrusive and mediotrusive contacts  the mandibular buccal cusp is shortened.

102. Static occlusion Static occlusion is described as occlusion which occurs in intercuspal position. It is an occlusion in centric relation with maximum intercuspation .

103. Dynamic Occlusion Dynamic occlusion refers to the occlusal contacts that are made when the mandible is moving relative to maxilla. The mandible is moved due to muscles of mastication and the pathway along which it moves is determined not only by muscles of mastication but by two other guiding systems .

104. Posterior guidance system is provided by the temperomandibular joint. Anterior guidance system by teeth. Canine guidance Group function

105. Ideal Occlusion In ideal static occlusion , occlusion occurs in centric relation and there is provision for free centric movements.

106. In protrusive movement there is contact in canines and disclusion in the remaining posterior teeth(Canine Guidance)

107. In lateral movement there are multiple contacts on working side i.e. premolars and molars, and disclusion on the non working side ( group function ).