Centric jaw relation

DR. PRAJAKTA GIR

1. CENTRIC JAW RELATION PRESENTED BY – Dr. PRAJAKTA BALI GIR MDS 2 ND YEAR PG Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 1

2. CONTENT INTRODUCTION TERMINOLOGIES MUSCLES INVOLVED IN CENTRIC RELATION THEORIES OF CENTRIC RELATION RELATING CENTRIC RELATION TO CENTRIC OCCLUSION RELATING CENTRIC RELATION TO HINGE AXIS RELATING CENTRIC AND VERTICAL RELATIONS Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 2

3. CONTENT RECORDING CENTRIC RELATION : CONFLICTING CONCEPTS AND OBJECTIVES IN RECORDING CENTRIC RELATION COMPLICATIONS IN RECORDING CENTRIC RELATION RETRUDING THE MANDIBLE IN CENTRIC RELATION METHODS OF RECORDING CENTRIC RELATION SIGNIFICANCE OF CENTRIC RELATION CONCLUSION REVIEW OF LITERATURE REFERENCES Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 3

4. INTRODUCTION Following the orientation of maxilla and determination of vertical dimension, the final relation to be recorded is the horizontal relation. Horizontal jaw relation is the relation that is established antero-posteriorly and medio-laterally. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 4

5. INTRODUCTION IT IS CLASSIFIED AS: 1 . Centric relation. 2. Eccentric relation. A. Protrusive relation. B. Lateral relation. I. Right lateral relation. II. Left lateral relation Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 5

6. CENTRIC RELATION Theoretically CR is being discussed under the heading of jaw relations. Jaw relations are the relationships of the mandible with the maxilla. In this context too much importance was given to the position of the head of the condyles in the glenoid fossa which ultimately resulted in a lot of confusion. This confusion was due to the invisibility of the most unique, enigmatic temporomandibular joint. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 6 Palaskar , J.N., Murali, R. & Bansal, S. Centric Relation Definition: A Historical and Contemporary Prosthodontic Perspective. J Indian Prosthodont Soc

7. CENTRIC RELATION For almost the last six decades we assumed CR to be the most retruded position of the heads of the condyles in the glenoid fossae. Recently we could come to a conclusion that it is not the most retruded position of the heads of the condyles but rather the most anterior and superior position . The acceptance of one definition is necessary to improve communication at all levels of dentistry. Definition of CR has created more controversy than any other dental subjects, several factors contributed to this confusion. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 7 Palaskar , J.N., Murali, R. & Bansal, S. Centric Relation Definition: A Historical and Contemporary Prosthodontic Perspective. J Indian Prosthodont Soc

8. CENTRIC RELATION This article is a review of all the definitions given till date and it has been organized as follows : CR from 1929 to 1970, in 1970–1980, and through 1980–2010 Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 8 Palaskar , J.N., Murali, R. & Bansal, S. Centric Relation Definition: A Historical and Contemporary Prosthodontic Perspective. J Indian Prosthodont Soc

9. CENTRIC RELATION FROM 1929 TO 1970’S Hanau [1929] defined CR as ‘the position of the mandible in which the condylar heads are resting upon the menisci in the sockets of the glenoid fossa, regardless of the opening of the jaws’. Goodfriend [1933] considered the ‘centricity of the condyles in centric relation to be an abnormal position’. Niswonger [1934] described CR as a position where the patient can ‘clench the back teeth’ Schuyler [1935] defined CR as ‘upper lingual cusps are resting in the central fossae of the opposing lower bicuspids and molars’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 9

10. CENTRIC RELATION FROM 1929 TO 1970’S Thompson [1946] stated that ‘some believed that, in CR, the condyles are in the most retruded position in the fossae, while others maintained they are not’. Robinson [1951] stated that the mandible ‘can be retruded beyond what we should consider centric into a strained retruded position’. McCollum and Stuart [1955] proposed a definition for CR in which the condyles are in a ‘rearmost, uppermost and midmost (RUM) position in the glenoid fossae’ Moyers [1956] defined CR as ‘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’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 10

11. CENTRIC RELATION FROM 1929 TO 1970’S Stallard [1959] defined CR of the mandible as ‘the rearmost, midmost, untranslated hinged position. It is a strained relation as are all border relations. It is the only maxillamandibular relation that can be statically repeated’ Avant [1960] declared the ‘seven definitions of CR’ that appeared in GPT-2 [1960] , as ‘regrettable’ and stated that CR is a bone-to-bone (mandible to maxilla) relation, whereas centric occlusion is a tooth-to-tooth (mandibular teeth to maxillary teeth) relation. McCollum [1960] defined CR position as ‘the most retruded position of the idle condyles in the glenoid fossa’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 11

12. CENTRIC RELATION FROM 1929 TO 1970’S Boucher [1964] stated ‘CR is the most posterior relation of the mandible to maxillae at the established vertical relation’ . Graber [1966] thought that CR was an ‘unstrained, neutral position of the mandible and is deviating neither to the right nor to the left and is neither protruded nor retruded ’ . Glickman [1966] stated that CR was ‘the most retruded position to which the mandible can be carried by the patient’s musculature’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 12

13. CENTRIC RELATION FROM 1929 TO 1970’S Goldman and Cohen [1968] defined CR as ‘the most posterior relation of the mandible to maxilla from which lateral movements can be made’ Debate on the definition of CR escalated. Posterior border closure, relaxed closure, bracing position, hinge position, ligamentous position, retruded contact position, terminal hinge position added confusion to term CR. Schweitzer [1969] gave ‘almost 40 definitions of CR Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 13

14. CENTRIC RELATION FROM 1970 TO 1980’S Dawson [1973] defined CR as ‘the most superior position the condyle can assume in the glenoid fossa and it is not unstrained’ . Smith [1975] considered CR to be ‘the most retruded position of the mandible’ and concluded that the gothic arch tracing provides the most retruded and most repeatable position and thus was the most precise method. Williamson et al. [1977] stated that the hinge axis and CR are the same ; adding that this axis occurs when the mandible is in CR and a pure rotational movement of the mandible is produced in the sagittal plane Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 14

15. CENTRIC RELATION FROM 1970 TO 1980’S Lucia [1979] stated that ‘the mandible is in CR when the centers of vertical and lateral motion are in the terminal hinge position’ . Myers et al. [1980] defined CR as ‘the most posterior unstrained relation of the mandible to the maxilla at a given degree of jaw separation’. They stated that the more posterior the condyles, the more acceptable the position Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 15

16. CENTRIC RELATION FROM 1980 TO 2010 Gilbe [1983] defined CR as ‘the most superior position of the mandibular condyles with the central bearing area of the disc in contact with the articular surface of the condyle and the articular eminence. This position may not always be possible to attain due to anterior dislocation of the disc . Dawson in 1985 stated that ‘CR is achieved when the properly aligned condyle-disk assemblies are in the most superior position against the eminentia irrespective of tooth position or vertical dimension’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 16

17. CENTRIC RELATION FROM 1980 TO 2010 American College of Prosthodontist [1994] defined CR as ‘the spatial relationship between the maxilla and mandible where the condyles relate to the articular eminence in a ventro -cranial position with the pars intermedia of the disc’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 17

18. GPT DEFINITIONS GPT-1 [1956] defined CR as ‘the most retruded relation of the mandible to the maxilla when the condyles are in the most posterior unstrained position in the glenoid fossa from which lateral movements can be made, at any given degrees of jaw separation’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 18

19. GPT DEFINITIONS GPT-2 [1960] defined the CR as ‘the most posterior relation of the mandible to the maxilla at the established vertical relation’, GPT-3 [1968] defined CR as ‘the most retruded physiologic relation of the mandible to the maxilla and from which the individual can make lateral movements’. It is a condition that can exist at various degrees of jaw separation. It occurs around the terminal hinge axis . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 19

20. GPT DEFINITIONS GPT-4 [1977] defined CR as ‘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 lateral movements can be made’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 20

21. GPT DEFINITIONS GPT-5 and 6 [1987, 1994] defined the CR as ‘the relation of the mandible to the maxilla when the condyles are in their most posterior position in the glenoid fossa from which unstrained lateral movements can be made at occluding vertical dimension normal for the individual’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 21

22. GPT DEFINITIONS GPT-7 [1999] defined centric relation as ‘a maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterosuperior position against the shapes of the articular eminences. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superiorly and anteriorly and restricted to a purely rotary movement about a transverse horizontal axis’ Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 22

23. GPT DEFINITIONS GPT – 8 the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior– superior position against the shapes of the articular eminencies. 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 Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 23

24. Meaning and Controversies in definitions of GPT 4(static morphological definition) and GPT5(Functional definition) The two definitions taken from glossary of prosthodontic terms (GPT-4 and GPT-5) appear to contradict each other. The earlier definition mentions of a most posterior position of condyles in glenoid fossa while the latter definition speaks of an anterior superior position of condyle against the slopes of the articular eminence. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 24

25. Meaning and Controversies in definitions of GPT 4(static morphological definition) and GPT5(Functional definition) But surprisingly, the discrepancy between the two positions is only approximately 0.2 mm. Theoretically, the difference is only on the emphasis of the condylar position. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 25

26. Maximal intercuspal position (MIP): The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position, is also called maximal intercuspation. Centric occlusion (CO): The occlusion of opposing teeth when the mandible is in CR. This may or may not coincide with the MIP. CR is a bone-to-bone relation, while MIP and CO are tooth-to-tooth relation. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 26

27. MUSCLES INVOLVED IN CENTRIC RELATION Centric relation is not resting or postural position of the mandible. Contraction of muscles is necessary to move and fix the mandible in this position. The anatomic attachments of the posterior and middle parts of the temporal and suprahyoid muscles together with EMG studies show that these muscles move and fix the mandible in its most retruded relation to maxilla. Temporal , masseter and medial pterygoid muscles elevate the mandible. The lateral pterygoid muscle shows little activity when mandible is in centric relation. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 27

28. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 28

29. THEORIES OF CENTRIC RELATION Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 29 Saizer P. Centric relation and condylar movement: anatomic mechanism. J Prosthet Dent 1971;26(6):581-91.

30. THE MUSCLE THEORY Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 30 DEFENCE REFLEX CONTRACTION OF LATERAL PTERYGOID MUSCLE HALTS THE JAW centric relation is always the same at any vertical level, nor does it explain the most posterior mandibular position. no anatomic explanation is provided for the posterior hinge movement, nor for the acuteness of the “needle-point” tracing.

31. THE LIGAMENT THEORY Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 31 LIGAMENTS WHEN BECOME TENSE THEY DETERMINE THE LIMITS OF RETRUSIVE MOVEMENTS Ligaments bind the elements of the articulations, limit their possibilities of movement, and are also capable of determining terminal border positions. When the condyle is seen in lateral radiographic views in centric relation, it appears to be “suspended” or “floating.” the anatomic arrangement of the temporomandibular ligaments is not well suited to halt the retrusive condylar movement. ligamentous retrusive terminal stop provides no satisfactory location for the hinge axis. does not explain satisfactorily the lateral border movements,

32. THE OSTEOFIBER THEORY Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 32 retrusive terminal stop formed by the soft tissues of the posterior part of the roof of the glenoid fossa. this fibrous stop acts as a buffer. these tissues to be loose, fibrous, and functionally differentiated. He named this structure the “retroarticular cushion.”

33. THE MENISCUS THEORY Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 33 When the disc is in its postural position, or close to it, the upper synovial cavity continues down and backward, within the retroarticular fibrous tissues Discs with their retromeniscal fibrous tissues--stop the retrusive condylar movements

34. RELATING CENTRIC RELATION TO CENTRIC OCCLUSION C entric relation must be accurately recorded so that centric occlusion can be made to coincide with it. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 34 In the natural dentition CO is usually located anterior to CR, the average distance being 0.5 to 1 mm. If natural tooth has interferences in CR it initiate impulses and responses that direct the mandible away from deflective occlusal contacts into CO. Impulses created by closure of the teeth into CO establish memory patterns that permit the mandible to return to this position, usually without tooth interferences

35. RELATING CENTRIC RELATION TO CENTRIC OCCLUSION Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 35 The edentulous patient cannot control mandibular movements or avoid deflective occlusal contacts in CR in the same manner as the dentulous patient. Deflective occlusal contacts in CR cause movement of denture bases and displacement of the supporting tissues or direct the mandible away from this relation

36. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 36

37. RELATING CENTRIC RELATION TO HINGE AXIS Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 37 The upper cast can be accurately oriented to the opening axis of the articulator by the location of the physiologic transverse hinge axis and a facebow transfer. Opening and closing the jaws with mandible in its most retruded position to maxilla ( terminal hinge axis ) is the method used to locate transverse hinge axis. They occur without translation. Centric relation is the most retruded relation of mandible to maxilla at a particular vertical relation along pathway of terminal hinge movement. So the lower cast automatically gets oriented to opening axis of articulator with accurate centric relation recorded.

38. RELATING CENTRIC AND VERTICAL RELATIONS Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 38 There is a most retruded relation of mandible to maxilla for each vertical relation, and there is a change in the horizontal relationship of mandible to maxilla with each change in vertical relation Thus when the centric relation record is made at or very close to the desired vertical relation of occlusion, little or no vertical change will be required on the articulator and the likelihood of the errors will be reduced.

39. SIGNIFICANCE OF CENTRIC RELATION More definite than VD Most comfortable position(home of the mandible) Optimum position for health comfort and functioning of TMJ Movements of mandible start from here and end up here. physiologically acceptable position for mastication of food. Most posterior border position Acts as a reference point. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 39

40. SIGNIFICANCE OF CENTRIC RELATION Pure rotations take place. Bone to bone relation Independent of position of tooth. Constant for an individual. Reproducible, repeatable and recordable. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 40

41. FACTORS INFLUENCING CENTRIC RELATION RECORDS Resiliency of supporting tissues Fit of denture bases – Stability - Retention The TMJ and its associated neuromuscular mechanism The character of the pressure applied in making the recording. The technique used in making the recording and the associated recording devices used. Maxillo-mandibula r relationship . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 41 Yurkstas AA, Kapur KK. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent 2005;93:305-10 .

42. FACTORS INFLUENCING CENTRIC RELATION RECORDS The skill of the dentist. The health and co-operation of the patient. Posture of the patient. Character or size of the residual alveolar arch. Amount and character of saliva. Size and position of the tongue. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 42 Yurkstas AA, Kapur KK. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent 2005;93:305-10 .

43. FACTORS INFLUENCING CENTRIC RELATION RECORDS Psychic or emotional tension. Protective reflex action caused by faulty occlusal contacts. Materials and equipment used for record making. The use of articulators that do not accurately adjust to all inter occlusal check records. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 43 Yurkstas AA, Kapur KK. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent 2005;93:305-10 .

44. RECORDING CENTRIC RELATION Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 44

45. CONFLICTING CONCEPTS AND OBJECTIVES IN RECORDING CENTRIC RELATION MINIMAL CLOSING PRESSURE Tissues supporting the base will not be displaced objective: to make opposing denture teeth touch uniformly & simultaneously at first contact HEAVY CLOSING PRESSURE Tissues under the base will displace objective: to produce the same displacement of the soft tissues that occur when patient masticates Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 45

46. 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. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 46

47. COMPLICATIONS IN RECORDING CENTRIC RELATION 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 . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 47

48. COMPLICATIONS IN RECORDING CENTRIC RELATION Even though a balanced and equilized registration has been made it often is lost due to: Cast mounting procedures Processing of denture Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 48

49. RETRUDING THE MANDIBLE IN CENTRIC RELATION BIOLOGIC Lack of coordination between muscles. Habitual eccentric jaw positions Senility or neuro-muscular disorder PSYCHOLOGIC Inability to follow the dentist instructions MECHANICAL Poorly fitting base plate Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 49

50. METHODS PASSIVE METHODS : The mandible is retruded by the patients themselves, following the dentist’s instructions without any physical participation by the dentist. The patient is instructed to Relax, pull the jaw back and close on the back teeth. Get the feeling of pushing the upper jaw out and close on back teeth. Touch the posterior part of the upper denture with tongue and close till the rims contact. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 50

51. METHODS 4. Swallow and close. 5. Tap the occlusal rims together repeatedly and rapidly. 6. Tilt the head back while performing the above exercises. 7. Protrude and retrude the mandible repeatedly holding his/her fingers lightly against the chin. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 51

52. METHODS ACTIVE METHODS : The patient is guided to retrude the mandible with physical assistance from the dentist. The dentist places his thumb and forefinger on the patient’s chin to exert a mild but firm posterior force while patient closes on the rims. This will prevent the patient from moving the jaw anteriorly Dentist palpates the temporal and masseter muscles to relax them. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 52

53. METHODS Dawson’s bimanual palpation – the dentist stands behind the patient and places all four fingers of both hands on the lower border of the mandible on either side. The thumbs are placed over the symphysis such that they contact in the midline. The patient is instructed to open the mouth and then close slowly . As the patient closes, dentist applies an upwards lifting force with the fingers on the inferior border and simultaneously applies a downward force with the thumbs . This guides the patient to close in CR. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 53

54. METHODS OF RECORDING CENTRIC RELATION Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 54 Bansal, e t al, Critical evaluation of methods to record centric jaw relation, The Journol of lndion Prosthodontic Society ; July 2OO9 ,Vol 9: lssue 3

55. METHODS OF RECORDING CENTRIC RELATION BY BOUCHER Static methods — interocclusal record with/with out central bearing devices and tracing devices Functional methods — chew-in technique Needles technique House technique Patterson technique Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 55

56. 2 . BY HEARTWELL : Functional methods (chew-in) Needles House method Patterson method 2. Graphic Method Intraoral devices Extraoral devices 3. Physiological or tactile or inter occlusal check record method Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 56

57. 1. Functional : a. Patterson Technique b. Needles-House Technique c. Meyer’s Technique d. Shanahan’s Technique 2. Static or pressureless method : 3. Graphic : a. intra-oral b. extra-oral 4. Direct checkbite interocclusal recordings 5. Cephalometrics Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 57

58. KINGERY classified techniques for recording centric relation as: Direct Graphic Functional Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 58

59. According to smith in 1941 , moylar 1955 , & kapur in 1957 following are the methods for recording the centric relation:- Direct recording Interocclusal-check record method Pressure-less method Pressure method Graphic recording Functional recording Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 59

60. 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 DISADVANTAGES: • Inaccuracy can result from lack of equalized pressure. • Difficult to verify the accuracy of the record. • Not as accurate as graphic method. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 60

61. 1. WAX OCCLUSAL RIMS One of the most commonly used methods to record CR. The wax occlusal rims are contoured and the vertical dimension of occlusion is established ensuring even contact of the maxillary and mandibular rims anteriorly and posteriorly. The patient is trained to retrude the mandible. The various ‘guidelines’ are marked and the patient is asked to close in centric and hold the position. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 61

62. The rims are joined or sealed in this position and then removed from the mouth and articulated. The following methods can be used to seal the rims: HEAT: A hot wax knife can be used to melt and flow the wax at the junction of the rims. Care must be taken to avoid heating the lips and cheeks by adequately protecting and retracting them. The knife should not be hot enough to cause the wax to run Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 62

63. PINNING: The occlusal rims can also be sealed together using pins. Slightly warm metal staples can be used to join the sides of the rims Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 63

64. THE ABOVE METHODS OF SEALING ARE NOT RECOMMENDED DUE TO: Chances of burning and injuring lips and cheek. No equalization of pressure. Difficult to prevent movement of rims while sealing. NICK AND NOTCH METHOD: This is the recommended method for sealing the rims as there is less resistance to closure and the movement during sealing is tackled. After the rims are evened, V-shaped notches are then placed in the molar region of the maxillary occlusal rim to prevent anteroposterior movement. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 64

65. A nick is cut anterior to the notch in the premolar regions, not extending throughout the width of the occlusal rim, to prevent the lateral movement. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 65

66. A trough is created in the posterior regions of the mandibular occlusal rims The patient is trained to retrude and close at CR position. Soft wax, zinc oxide eugenol impression paste, quick setting plaster and elastomeric bite materials may be used . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 66

67. The recording material is loaded in the trough created on the mandibular rim. Occlusal rims are inserted in the patient’s mouth and the patient is instructed to retrude and close. Contact should be observed in the maxillary and mandibular rims anteriorly. Once the intervening recording material sets, the rims get sealed and are removed together Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 67

68. 2. INTER-OCCLUAL CHECK RECORS As the name suggests, these records are used to verify the centric jaw relation at the time of try-in or denture insertion. They are also used to check the occlusion of teeth in existing dentures. These are also called ‘physiologic’ methods as the patient’s proprioception and tactile sense is essential in the making of an accurate record. The same recording mediums used for static registrations can also be used for this procedure Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 68

69. After the occlusal rims have been articulated with a static record, the artificial teeth are arranged and a trial denture is fabricated. At the time of try-in (or denture insertion) if the dentist feels the need to verify the CR, then this procedure is adopted. Patient is asked to rehearse retruding the mandible. The maxillary trial denture is inserted in the patient’s mouth. The recording medium like aluwax is loaded onto the occlusal surface of the teeth in the mandibular occlusal rim Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 69

70. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 70

71. The patient is asked to slowly retrude the mandible and close on the wax till the tooth contact occurs . They should not bite through the material. The recording material is allowed to set and the trial dentures are removed with the recording material. The maxillary trial denture is removed from the record and placed on the mounted maxillary cast in the articulator. The mandibular trial denture with the record is now returned to the mandibular cast on the articulator. The horizontal condylar guide locks in the articulator are released. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 71

72. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 72

73. The maxillary teeth are now seated over the record. If the previous recording of CR is the same as the check record, then both the condylar elements of the articulator will contact the centric stops, i.e. the articulated casts need not move to fit into the check records. If anyone or both of the condylar elements of the articulator does not contact the centric stops, it indicates that one of the records is inaccurate. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 73

74. INDICATIONS: It may be advisable to make interocclusal check records to verify the CR in the following conditions: Abnormally related jaws Displaceable, flabby tissues Large tongue Uncontrolled mandibular movements Factors affecting the success of interocclusal records : Uniform consistency of the recording material Accurate vertical jaw relation records Stability and fit of the record base Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 74

75. 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 Includes the various chew-in techniques : Needlehouse Patterson Meyers Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 75

76. HISTORICAL DEVELOPMENT Greene – Used plaster and pumice mixture. Needles – Mounted three studs on maxillary rims. Patterson – Used corborandum and plaster mixture. Meyer – Used soft wax occlusal rims, tin foil placed and functional movements done. Boose – Used Gnathodynomometer . Shanahan – Cones of soft wax. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 76

77. In 1905 Christenson used 'impression wax' for bite records. One early method was to have the patient close in a retruded position and attach the rims together for mounting on an articulator usually with staples or by sealing the rims with a hot instrument. Schuylor (1932) said that modeling compound was preferable to wax for occlusal records because it can be softened more evenly, cools slower and doesn't distort as much as wax. Boos (1959) felt that it was important to avoid torsion when recording Centric relation. Wax or compound, which required application of force, could displace the mandible . Thus a material such as plaster or ZnO Eugenol paste was more accurate . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 77

78. Hanau was one of the first individuals to be concerned about equailization of pressure when recording the bite. He coined the term " Realef f ' which is formed by the beginning letters of the words 'resilient and like effects‘ Payne (1955) and Hickey (1964) stated a preference for plaster because less material had to be placed in the patient's mouth for the record. In 1910 Green invented his 'PRESSOMETER' in an early attempt to equalize the pressure of recording centric relation . It consisted of celluloid strips placed between the maxillary and mandibular occlusion rims on the right and left sides. If the pressure were unequal, the rims would "hold" one strip while the other could be removed. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 78

79. In 1954 Brown recommended repeated closure into softened wax rims. Wright(1939) described the four factors he believed affected accuracy of records: resiliency of tissue saliva film fit of bases pressure applied. He concluded that the best technique was to record the occlusal record at zero pressure Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 79

80. Kingery (1952) discussed 2 fundamental principles that contribute to the success of direct recording method: The dentist's ability to recognize the Centric relation position Understanding that the recording medium directly influences the pressure developed in the recording and the subsequent equilibration of the recording . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 80

81. 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. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 81 Shanahan TEJ. Physiologic jaw relations and occlusion of complete dentures. J Prosthet Dent 2004;91(3):203-05.

82. INDICATIONS : Supporting tissues are excessively displaceable Large awkward tongues Uncontrollable/ abnormal mandibular movements Check occlusion of teeth in existing dentures. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 82

83. Needle–House method: Occlusal rims are fabricated from impression compound . Four metal balls or styli are embedded in the canine and molar areas of the maxillary occlusal rim. The occlusal rims are inserted and the patient is asked to perform various functional and excursive movements of the mandible with the styli contacting the lower rim. The vertical height is reduced as the styli cuts through the lower rim and the patient is stopped at the appropriate vertical dimension. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 83

84. The styli makes three-dimensional diamond-shaped tracings , which can be transferred to a suitable articulator to duplicate the movements. The most anterior point of the marking denotes CR and can be used to mount on any articulator Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 84

85. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 85

86. PATTERSON method: Wax occlusal rims are fabricated. A trench or trough is made in the mandibular occlusal rim which is filled with equal mixture of carborundum paste and plaster . The occlusal rims are inserted and the functional mandibular movements will produce compensating curves in the plaster lower rim. As the vertical height reaches the appropriate level, the patient is asked to retrude his jaw and the occlusal rims are joined together with metal staples. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 86

87. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 87

88. MEYER’S method: 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 Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 88

89. GRAPHIC METHODS 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. Hesse (1897)– First to make a Needle point tracing. Gysi (1910)– Improved needle point tracing . Phillips (1927)– He developed a plate for the maxillar occlusal rims and a tripoded ball bearing mounted on a jackscrew for the mandibular occlusal rim. He called this as the " Central Bearing Point ". Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 89

90. WHAT DOES THE TRACING REPRESENTS ? 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. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 90

91. CONCEPT: The concept consists of attaching a stylus (a writing device with a pointed end) to one occlusal rim and a plate to the other rim. The stylus traces or marks the path in the plate as the mandible performs excursive movements from the centric position. The tracing is typically in the shape of a ‘gothic arch’ or ‘arrow head’ if the patient is trained to move the mandible from centric to protrusive, right and left lateral positions. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 91

92. COMPONENTS: The tracing can be made intraorally or extraorally . The extraoral tracing device consists of a central bearing device and a tracing device . The central bearing device consists of a central bearing point and a central bearing plate. The tracing device consists of a stylus and a recording plate. The stylus or stud and central bearing plate attached to the maxillary occlusal rim, while the central bearing point and recording plates are attached to the mandibular rim. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 92

93. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 93

94. COMPONENTS: In the intraoral tracer , the central bearing device also performs the function of a tracing device. So there is only one set of device Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 94

95. Central bearing device is a very important aspect of the device. It should be placed in the geometric centre of the maxillary and mandibular arches to serve the following functions: ▪ Maintains vertical dimension. ▪ Equalizes the pressure by distributing the forces throughout the supporting tissues. ▪ Allows mandibular movement to be dictated by the condyles. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 95

96. ADVANTAGES Documented to be the most accurate method of recording CR. Allows equalization of pressure on the supporting tissues. Easily verifiable. Can also be used to record eccentric relations. DISADVANTAGES May be difficult to locate the centre of the arches which is very important for central bearing function and accuracy of tracing. More time consuming. Training patient in making mandibular movements is strenuous. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 96

97. INDICATIONS Broad edentulous sides. Adequate interarch space. In patients with habitual centric, the use of the graphic method eliminates all occlusal contacts on the rims, thus breaking the neuromuscular reflex and allows the patient to record his true centric. CONTRAINDICATIONS Severely resorbed ridges and excessively flabby ridges as they lead to instability of denture bases. Decreased interarch space – difficult to place central bearing device without raising the vertical dimension. TMJ arthropathy. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 97

98. PROCEDURE FOR EXTRAORAL TRACING: The maxillary cast is mounted on the articulator with a facebow transfer. The mandibular cast is oriented to the maxillary cast at the established vertical dimension with a static CR record. The condylar elements of the articulator are secured against the centric stops. The central bearing and tracing devices are mounted on the respective rims Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 98

99. The patient is seated with head upright, in a comfortable position on the dental chair. The record bases with the attached devices are inserted in the patient’s mouth. They are checked for stability, contact during mandibular movements and interference Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 99

100. The stylus is retracted and patient is trained to make various excursive movements passively and actively (if needed). Patient is instructed to move the jaw forwards, right and left from centric position. The Ney Excursion Guide has been used as an aid in training the patient but patient responds better to specific locations than numbers Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 100

101. When the patient is well trained in making the movements, the recording plate is coated with a thin coating of lacquer, precipitated chalk or dark coloured wax. The coating material should not provide any resistance to movement and produce a clearly visible tracing . The stylus is made to contact the recording plate and the patient is instructed to make the specific movements. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 101

102. When an acceptable tracing is made with a single sharp apex, a centric record is obtained. The rims and tracing are prepared to receive the centric record Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 102

103. The patient is instructed to retrude the mandible such that the stylus contacts the apex of the tracing. Quick setting plaster is injected between the rims and allowed to harden thus, the centric record is obtained. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 103

104. The rims are remounted on the articulator with the new record Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 104

105. DEVICES: a. Hight tracer Sears tracer Phillips tracer Chandra tracer Stansbery tracing device Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 105

106. PROCEDURE FOR INTRAORAL TRACING: The procedure with intraoral tracer is similar, but as the tracing is not visible while being made, a thin plastic disc with a central hole is fixed on the recording plate such that the hole is placed on the apex of the tracing. The patient closes with the tip of the stylus in the hole and this ensures that the patient closes in centric and maintains the position while the record is being made. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 106

107. DEVICES : a. Coble tracer Swissdent ball bearing bite tracer Micro tracer Functiograph Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 107

108. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 108

109. Evaluation of Gothic Arch Tracings : Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 109 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 .

110. Evaluation of Gothic Arch Tracings : Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 110 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.

111. Evaluation of Gothic Arch Tracings : Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 111 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

112. PANTOGRAPHIC TRACING: Pantograph: An instrument used to graphically record in, one or more planes, paths of mandibular movement and to provide information for the programming of an articulator (GPT8). Pantographic tracing ( pantogram ): A graphic record of mandibular movement usually recorded in the horizontal, sagittal and frontal planes as registered by styli on the recording tables of a pantograph or by means of electronic sensors (GPT8). Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 112

113. PANTOGRAPHIC TRACING: The pantograph is a device that records the movement in all three planes. The tracing is called a pantographic tracing or pantogram . To put it simply, it will consist of styli and recording plates placed in all three planes and the various jaw movements from centric position traced in all the planes . The recordings are transferred to a fully adjustable articulator, which is capable of accepting and reproducing these movements. This can also be used to record eccentric relations. Records are very accurate but procedure is complex Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 113

114. CEPHALOMETRICS: Use of cephalometrics to record CR was described by Pyott and Schaeffer. The proper CR and vertical dimension of occlusion were determined by cephalometric radiographs. This method, however, was somewhat impractical and never gained widespread usage. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 114

115. ECCENTRIC RECORDS DEFINITION: Any relationship of the mandible to the maxilla other than CR (GPT8). The relation recorded by moving the mandible forward is called protrusive relation record. The relation recorded by moving the mandible mesio - laterally is called lateral relation record . Eccentric relation depends on the shape of the mandibular fossae . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 115

116. ECCENTRIC RECORDS Functional method- Needles-House and patterson technique. Graphic method. Tactile or Direct check methods. Pantography Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 116

117. GRAPHIC METHOD : A distance of 5-6 mm is measured from the apex and is marked. Instruct the patient to protrude until the stylus rests on the marked point. Inject the plaster between the occlusal rims and allow it to set. Remove the occlusal rims from the mouth and transfer this relation to the articulator. the eccentric jaw relation is made with a protrusive distance of 5-6 mm because it is believed that with a shorter distance, the condyle would not move down its path and the distance is sufficient to be recorded on the articulator . Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 117

118. TACTILE OR DIRECT CHECK RECORD METHOD : This is the most common method to make a protrusive relation record using soft wax. The preferred time to make the eccentric jaw relation records is after the teeth have been arranged for try in. LATERAL RECORDS : more harmony will exist between the mandibular movements and cuspal inclines. The most common methods of lateral relation record are. 1 .Graphic method. Check bites of wax. Positional records of stone/plaster. 4.pantography. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 118

119. GRAPHIC METHOD : Requires 2 records -one on left side -one on right side Articulator is adjusted as record is made Additional layers of wax are placed on balancing side Hanau formula- L=H/8+12 WAX CHECK BITES: taken at lateral positions and it is desire able to have more than one record at each position. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 119

120. PLASTER/STONE POSITIONAL RECORDS : records are taken at lateral extremes of the intra oral or extra oral tracings Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 120

121. SUMMARY Centric relation is a most Reproducible Reliable Repeatable Recordable Reference position. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 121

122. de Moraes Melo Neto CL, da Silva EV, de Sousa Ervolino IC, Dos Santos DM, de Magalhães Bertoz AP, Goiato MC. Comparison of different methods for obtaining centric relation: a systematic review . General Dentistry. 2020 Jan 1;69(1):31-6. The objective of this study was to compare techniques of different methods of obtaining centric relation to verify which technique generates the greatest reproducibility of the centric relation. The PubMed/MEDLINE, Cochrane Library, SciELO , Scopus, and Web of Science databases were searched for articles published up to May 15, 2018. The search terms were combinations of "dental centric relation" with each of the following terms (individually): "reproducibility of findings"; "jaw relation record"; "chin point"; "gothic arch"; "bimanual manipulation"; "swallowing"; and "jig." Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 122

123. The inclusion criteria included clinical studies in English that had to compare at least 2 techniques representing different methods for obtaining centric relation (based on the reproducibility of the centric relation) in individuals without temporomandibular dysfunction; and studies performed in individuals with complete or nearly complete dentition or complete edentulism . Methods (techniques) included in this study were guided methods (chin point guidance and bimanual manipulation); graphic methods (intraoral and extraoral gothic arch tracing); and physiologic methods (swallowing and tongue retrusion along the palate). A total of 1638 articles were identified. After the inclusion and exclusion criteria were applied, 7 articles were included in this review.  Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 123

124. None of the reviewed studies evaluated edentulous individuals. Two articles compared physiologic methods with guided methods; one concluded that the swallowing technique generates greater variability than guided methods, and the other concluded that there was no difference between the swallowing technique and chin point guidance. Of 5 articles comparing intraoral gothic arch tracing with guided methods, 2 showed similar results between different methods, 2 showed superior results for gothic arch tracing, and 1 showed superior results for the guided methods. Based on the guided methods and swallowing technique, it is not possible to conclude which technique can generate the greatest reproducibility of the centric relation. It is possible to suggest that in most cases intraoral gothic arch tracing is superior or equivalent when compared to guided methods. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 124

125. Jonathan P. Wien, Gary R. Goldstein , Mark Andrawis , Mijin Choi, and Jennifer W. Priebe , (2018) Defining centric relation , jpd . The purpose of this study was to identify those aspects or attributes within the existing definitions of CR in which there was agreement or disagreement among the members of the AP . After pretesting and institutional review board approval, a second survey of the AP membership was performed using both email and postal mail survey methods of contact. The CR Attributes Survey separated and stratified the previous definitions of CR into 5 domains: spatial relationship, condylar position, articular disks, mandibular movement, and recording. Each domain attribute was evaluated by agree-uncertain-disagree assessments. Also recorded were demographics, perception of scientific evidence, and open comments. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 125

126. Of the total 146 fellows, 100 completed the survey for an overall response rate of 68.5%. The query completion rate ranged from 96% to 98%. The CR Attributes Survey revealed those components within each domain in which there was strong agreement, disagreement, or uncertainty. The survey assessment of those queries with a moderate to strong agreement were that CR is a “spatial relationship” that is (1) a clinically determined relationship of the mandible to the maxilla, (2) a repeatable position, (3) is independent of tooth contact, and (4) is a physiologic position. Relative to “disks,” the condyles articulate with the thinnest avascular intermediate zone of their respective disks; however, there is a lack of sufficient evidence to determine the position of the disks and the condyles. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 126

127. Relative to “mandibular movement,” CR is (1) a starting point for vertical, lateral, or protrusive movements, (2) is where the individual can make to and from lateral movements, and (3) is restricted to pure rotary movement about a transverse horizontal axis. Relative to “recording CR” (1) it can be determined in patients without pain or derangement of the temporomandibular joints (TMJs), (2) but may not be recordable in the presence of dysfunction of the masticatory system, or (3) due to the neuromuscular influence or proprioception from the dentition, (4) is a clinical useful repeatable reference position for mounting casts, or (5) for developing a functional treatment occlusion, (6) at an established vertical dimension, and (7) may vary slightly by recording method. Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 127

128. The CR Attributes Survey revealed a majority agreement or consensus for various CR attributes that should be considered for defining the term ‘centric relation.’ In contrast, those CR attributes with a plurality agreement, disagreement, or uncertainty outcomes should be considered for exclusion. The evaluated weakness of these latter attributes indicates the need for further research and reassessment. (J Prosthet Dent 2017; Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 128

129. REFERENCES Charles M . Heartwell JR. and rahn a. o:syllabus of complete dentures.fourth edition. John sharry , complete denture prosthodontics. Winklers , essentials of complete denture prosthodontics Carl . O. boucher :prosthodontic treatment for edentulous patients,10 edition. Ernest.r . granger:centric relation,j.p.d 1952:2 160-169 Kingery.r.h:problems associated with centric relation;j.p.d1952;2;307.. Shanahan T E. Physiologic jaw relations and occlusion of complete dentures. J Prosthet Dent 1955; 5: 319-322 Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 129 Bansal, e t al, Critical evaluation of methods to record centric jaw relation, The Journol of lndion Prosthodontic Society ; July 2OO9 ,Vol 9: lssue 3

130. REFERENCES Prosthodontic treatment foe edentulous patients- zarb-bolender 12 th edn . The Academy of Prosthodontics. Glossary of prosthodontic terms. J Prosthet Dent 1999; 81: 48-106. The Academy of Prosthodontics. Glossary of prosthodontic terms. J Prosthet Dent 1994; 71: 40-116. The Academy of Prosthodontics. Glossary of prosthodontic terms. J Prosthet Dent 2005; 94: 10-85. Saizer P. Centric relation and condylar movement: anatomic mechanism. J Prosthet Dent 1971;26(6):581-91. Palaskar , J.N., Murali, R. & Bansal, S. Centric Relation Definition: A Historical and Contemporary Prosthodontic Perspective. J Indian Prosthodont Soc Yurkstas AA, Kapur KK. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent 2005;93:305-10. Centric relation records-Historical review Department of Prosthodontics, Crown & Bridge and Oral Implantology, DDCH, Udaipur 130 Bansal, e t al, Critical evaluation of methods to record centric jaw relation, The Journol of lndion Prosthodontic Society ; July 2OO9 ,Vol 9: lssue 3