CENTRIC RELATION.pptx

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1. GOOD MORNING No one can go back and make a brand new start… But anyone can start now and make a brand new end… 1

2. CENTRIC JAW RELATION 2

3. 3   CONTENTS Introduction Definition of Centric relation Chronology of change of definition of centric relation Anatomy of Temporo mandibular joint as it pertains to centric relation Significance of Centric  relation Centric relation and Centric Occlusion Methods of recording centric relation Conclusion

4. 4 One of the objectives of Prosthodontics is to restore missing dental and oral structures in such a way that there is a harmonious relationship among teeth , bones, joints and muscles . One of the most controversial aspects of this complex relationship has been referred to as centric  jaw relation. INTRODUCTION

5. 5 It is the relationship of the mandible to the maxilla in a horizontal plane . It can also be described as the relationship of the mandible to the maxilla in the antero -posterior direction . CENTRIC JAW RELATION

6. 6 The maxillo mandibular relation in which the condyle articulate with the thinnest avascular portion of their respective disks with the complex in the anterior- superior positions against the shapes of the articular eminencia . 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. GPT (5) /(8) -1987

7. 7 GPT 9 Centric relation is defined as a maxillomandibular relationship independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences; in this position the mandible is restricted to a purely in this position the mandible is restricted to a purely rotary movement; from this unstrained, physiologic, maxillomandibular relationship, the patient can make vertical, lateral or protrusive movements; it is a clinically useful, repeatable reference position.

8. 6 Chronology of the changing definitions 1920- Mc Collum - Rearmost position 1952-Granger-uppermost,rearmost 1969-Stuart-RUM position 1977-American equilibration society –Antero- superior position 8

9. 7 1978- Celenza Condyle disk assembly- superiorly and anteriorly against posterior slope of eminence. According to GPT 4 – The jaw relation when the condyle are in the most posterior unstrained position in the glenoid fossae at any given degree of jaw separation from which lateral movement can be made.   9

10. 10 “The relationship of the mandible to the maxilla / when properly aligned condyle-disk assemblies / are in most superior position / against the eminentiae / irrespective of the vertical dimension or tooth position.” According to DAWSON  

11. 11 SIGNIFICANCE OF CENTRIC RELATION

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13. The Muscle Theory DRAWBACKS OF THE THEORY : • No anatomic explanation for posterior hinge movement • No explanation for acuteness of needle point tracing • If lateral pterygoid responsible: elliptical tracings 13

14. The Ligament theory( byFeerein ) • Binds the elements of the articulation • Lateral radiographic views • ‘Suspended’ or ‘Floating’ condyle • Anatomic arrangement- not well suited to halt retrusive movement 14

15. The Osteofiber theory • Posselt • Fibrous stop - buffer • “Retroarticular cushion” • retrusive terminal stop 15

16. The Meniscus theory (By Saizer ) 16

17. 17 CENTRIC OCCLUSION (CO) Def . - “ The occlusion of opposing teeth when the mandible is in centric relation.This may or may not coincide with the maximal intercuspal position.” ( GPT 8 th ed.) MAXIMUM INTERCUSPAL POSITION - complete intercuspation of the opposing teeth independent of the condylar position.

18. 18 H armony Between Centric Relation And Centric Occlusion : “ Centric” is an adjective and must be used with either relation or occlusion to be specific and meaningful. Centric relation is a bone-to-bone relationship whereas centric occlusion is a relationship of upper and lower teeth to each other .

19. 19 In many people, CO of the natural teeth does not coincide CR of the jaws . In natural dentition CO is usually located0.5 to 1 mm anterior to CR . Natural tooth interferences in CR  initiated impulses and responses that direct the mandible into CO .

20. 20 Deflective occlusal contacts in CR cause movement of the denture bases and displacement of the supporting tissues or direct the mandible away from the relation . Therefore , CR must be recorded for edentulous patients to enable CO to be established in harmony with it .

21. 21 CR is not harmony with CO For opposing teeth to meet evenly as in CO, the mandible must be moved away from CR

22. 22 Posselt and Glickman – reported that maximal intercuspal relation of the teeth is anterior to terminal hinge postion in 90% of analyzed individuals with full complement of teeth.   Posselt (JPD 1971/25/12) - centric occlusion placed the mandible an average of 1.2 mm anterior to its position in centric relation.   Beyron (DCNA1971, 15, 4) – only 10 % of the individuals the centric relation and centric occlusion coincide. Centric occlusion occurs anterior to centric relation at varying but short distance.

23. 23 CR in harmony with CO This can usually be achieved with centric relation and centric occlusion coinciding. In some patients a broader area of stable contacts near centric relation is necessary ,which is called “freedom of centric” or “long centric”

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25. 25 queries Why long centric not given in posteriors??

26. 26 Long centric is really just a “short protrusive.” —Frank Celenza

27. 27 According to Dawson, “ it is freedom to close the mandible either into centric relation or slightly anterior to it without varying the vertical dimension at the anterior teeth .” LONG CENTRIC

28. 28 1. Long centric involves primarily the anterior teeth.

29. 29 2. Long centric refers to freedom from centric, not freedom in centric. Contact in centric relation Postural closure Clearance for long centric

30. 30 ANATOMY OF TMJ AS IT PERTAINS TO CENTRIC RELATION.

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32. 32 The two most importat criteria for centric relation are : The complete release of the inferior lateral pterygoid muscles, and 2.Proper alignment of the disk on the condyle . During jaw closure with intact temporomandibular joints (TMJs), the condyle-disk assemblies are pulled up the eminentiae by a triad of strong elevator muscles.

33. 33 ROLE OF MUSCULATURE The triad of strong elevator muscles; MASSETER, MEDIAL PTERYGOID, TEMPORALIS

34. 34 TMJ SOCKET DESIGN

35. 35 ADAPTED CENTRIC POSTURE In a deformed temporomandibular joint (TMJ), the type and degree of adaptation must be determined before addressing the relationship between the occlusion and the TMJs .

36. 36 ADAPTED CENTRIC POSTURE It Is the manageable stable relationship of the mandible to the maxilla that is achieved when the deformed TMJ have adapted to the degree that they can comfortably accept firm loading when completely seated at the most superior position against the eminentia .

37. 37 Intracapsular disorders that can evolve into an adapted centric posture include : Lateral pole disk derangements 2. Complete disk derangement with formation of a pseudo-disk 3.Complete disk displacement with perforation 4.Other partial disk derangements and clicking TMJs Load testing produces no sign of tension or tenderness in either TMJ.

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39. 39 RATIONALE FOR LOAD TESTING OF TMJs In centric relation, all forces are directed through vascular, non innervated structures.

40. 40 PROPER LOAD TESTING MUST BE DONE IN INCREMENTS Gentle moderate firm

41. 41 RESPONSE TO LOAD TESTING IF THE CONDYLES ARE NOT COMPLETELY SEATED (MUSCLE BRACED) RESPONSE TO LOAD TESTING IF THE DISK IS MISALIGNED RESPONSE TO LOAD TESTING IF THERE IS INTRACAPSULAR PATHOLOGY OR INJURY

42. 42 RECORDING OF CENTRIC RELATION There are two aspects : 1.Assisting the patient to retrude the mandible 2.Recording . 

43. Methods for assisting the patient to retrude the mandible 1. Instruct the patient by saying , "Let your jaw relax, pull it back, and close slowly and easily on your back teeth .“ 2. Instruct the patient by saying, "Get the feeling of pushing your upper jaw out and closing your back teeth together." 3. Instruct the patient to protrude and retrude the mandible repeatedly while he holds his fingers lightly against his chin. Prosthodontic treatment for edentulous patient . Boucher’s, ninth edition 43

44. 4. Instruct the patient to turn the tongue backward toward the posterior border of the upper denture. 5. Instruct the patient to tap the occlusion rims or back teeth together repeatedly. It is believed that the center of muscle pull will gradually work the mandible back. Bissasu M. Use of the tongue for recording centric relation for edentulous patients. J Prosthet Dent 1999;82:369-70. 44

45. 6 . Tilt the patient's head back while the various exercises just listed are carried out. This will place tension on the inframandibular muscles and tend to pull the mandible to a retruded position. 7. Having the patient swallow. Swallowing may bring the mandible to a retruded position and may be an aid in retruding the mandible to CR. 45

46. 46 Methods to guide mandible in CR Chin point guidance-GUICHET(1970) Thumb and forefinger –position the condyle in RUM position. Bimanual method-Peter D awson(1974 ), Guides the mandible in anterosuperior position . Leaf gauge principle(Anterior Deprogrammer)- Long,Wiliamson (1980) guides the mandible to obtain maximum superior anterior braced position of condyles against the disk. 

47. 47 Chin point guidance-GUICHET(1970)

48. 48 Bimanual method-Peter Dawson(1974)

49. 49 Anterior deprogrammer Provides anterior stop to eliminate tooth contacts thereby eliminating proprioceptive influence from teeth. This allows the condyles to seat in centric relation without the influence of engram Types: 1.Pankey jig 2 . Anterior jig – Lucia 3.Leaf gauge - Long

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51. Classification by Different Authors : 1. By Boucher Static methods — interocclusal record with/with out central bearing devices and tracing devices. b. Functional methods — chew-in technique a) Needles technique b) House technique c) Patterson technique 51

52. 2. By Heartwell 1. Functional methods (chew-in) a) Needles House method b) Patterson method 2. Graphic Method a) Intraoral devices b) Extraoral devices 3. Physiological or tactile or inter occlusal check record method 52

53. Static method Involves guiding the mandible in CR with the maxillae then making a record of the relationship of the two occlusion rims to each other. Advantage - minimal displacement of the recording bases. Record made with wax or plaster 53

54. Functional method Involves functional activity or movement of the mandible at the time the record is made. Disadvantage - causes lateral and anteroposterior displacement of the recording bases. Needleshouse M eyer’s P atterson 54

55. 41 Needle-House Method 55

56. 43 Patterson Method 56

57. Meyer’s technique: - used soft wax occlusal rims. -tinfoil was placed over the wax and lubricated. -patient performed functional movements to produce a wax path -plaster index was made 57

58. Physiologic technique  Shanahan (1955)  cones of soft wax placed on the mandibular occlusal rim  patient was asked to swallow repeatedly.  He believed that during swallowing, the tongue forced the mandible into Centric relation position .  The cones of soft were then moved and Centric relation was recorded using this method . Shanahan TEJ. Physiologic jaw relations and occlusion of complete dentures. J Prosthet Dent 2004;91(3):203-05. 58

59. STATIC OR PRESSURELESS METHOD Nick and Notch method : 59

60. DIRECT INTEROCCLUSAL RECORDS  Physiologic method or static method.  1756 Phillip Pfaff first described 60

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62. 62 Anterior deprogrammer Provides anterior stop to eliminate tooth contacts thereby eliminating proprioceptive influence from teeth. This allows the condyles to seat in centric relation without the influence of engram Types: 1.Pankey jig 2 . Anterior jig – Lucia 3.Leaf gauge - Long 62

63. 63 Leaf gauge A device called a leaf gauge consists of a number of leaves of plastic and can be used to locate the mandible in centric relation . 0.010 inch thick , 0.5 inch wide , and 2 inches long . Long JH. Locating centric relation with a leaf gauge. Journal of Prosthetic Dentistry. 1973 Jun 1;29(6):608-10. 63

64. 64 Lucia jig The Lucia Jig is a technique that allows clinicians to obtain an accurate bite registration by stabilizing the mandible in a harmonious position. . 64

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67. 67 NTI (Nociceptive Trigeminal Inhibition) An anterior bite stop . Indicated for the prevention and treatment of bruxism, temporomandibular disorders (TMDs), tension-type headaches, and migraine . Clark GT, Minakuchi H: Oral appliances. TMDs An Evidence-Based Approach to Diagnosis and Treatment. Edited by: Laskin DM, Greene CS, Hylander WL. 2006, Chicago: Quintessence, 377-390. 67

68. GRAPHIC RECORDINGS The earliest graphic recordings were based on studies of mandibular movements by Balkwill in 1866 . The intersection of the arcs produced by the right and left condyles formed the apex of what is known as GOTHIC ARCH TRACING. 68 67

69. Historical development  Hesse (1897)- First to make a Needle point tracing.  Gysi (1910)- Improved needle point tracing . Phillips (1927)- He developed a plate for the maxillary occlusal rims and a tripoded ball bearing mounted on a jackscrew for the mandibular occlusal rim. He called this as the " Central Bearing Point ". 69 68

70. What does the tracing represent? Border movements of the mandible in the horizontal plane and its apex is the most retruded position (relaxed position) of the mandible. Advantage of reproducibility - can verify the centric relation. 70 69

71. Classification of Graphic recordings 1. Intraoral tracings 2. Extraoral tracings 71 70

72. Intraoral tracing assembly 72 71

73. Intraoral tracing 73 73

74. Types of tracers Intraoral Tracing Devices: TYPES OF TRACERS Eg: a. Coble tracer b . Swissdent ball bearing bite tracer c. Micro tracer d. Functiograph 74 74

75. Extra oral Tracings 75 75

76. 2. Extraoral Tracing Devices: Eg: a. Hight tracer b. Sears tracer c. Phillips tracer d. Chandra tracer e. Stansbery tracing device 76 76

77. Hight tracer 77 77

78. Extraoral tracing ( Hight tracing device) 78 78

79. Extraoral tracing 79 79

80. Evaluation of Gothic Arch Tracings: 80 80

81. Classical, pointed form The symmetry indicates an undisturbed movement sequence in the joints and uniform muscle guidance. Classical flat form Indicates distinct flat lateral movements of the condyles in the fossa. 81 Babita Yeshwante , et al A Path way to the Centric – Gothic Arch. Int J of Allied Med Sci and Clin Res 2015;3(3):308-312. 81

82. Weak Gothic arch tracing Indicates a lax and negligent performance of the movements . The registration must be repeated: Stronger movements must be demanded from the patient. Asymmetrical form The tracing indicates a distinct inhibition of the forward component of the lateral movement in the right joint. 82 82

83. Miniature Gothic arch tracing This tracing points restricted mandibular movements. •Due to badly fitting and pain-causing record bases or •Long standing edentulous state with inhibited movement in the joints. Vertical line protrudes beyond the arrow point forcible retraction or pushing of the mandible or tracing obtained with protruded mandible 83 83

84. 84 Double Arrow Point seen when vertical dimension is altered during registration. Interrupted Gothic Arch This happens due to posterior interference at the heels of occlusal rims during lateral movements . Atypical Form Protrusive component does not meet at apex 84

85. 85 Intra oral v/s extra oral graphic recording methods The intra-oral tracings cannot be observed during tracing ; however , extra-oral tracings are visible while the tracing is being made. the intraoral tracings are very small, it is difficult to find a true apex. 85

86. 86 Boucher prefers the extra oral device. Boucher also recommended that centric relation should be made with minimal pressure to prevent displacement of the tissues. 86

87. 87 Solomon claimed that in intraoral method the errors are likely to be less because the tracing is situated closer to the centers of movements in the temporomandibular joint 87