MAXILLO-MANDIBULAR RELATIONS IN PROSTHODONTICS

MAXILLOMANDIBULAR RELATIONS IN COMPLETE DENTURE PROSTHODONTICS

1. STAFF INCHARGE: DR. HOMBESH M.N. SIR. PROFESSOR, DEPT. OF PROSTHODONTICS AND CROWN AND BRIDGE, COLLEGE OF DENTAL SCIENCES, DAVANGERE . PRESENTER: DR. KRUTIKA CHIKORDE. 2 nd YEAR POSTGRADUATE DEPT. OF PROSTHODONTICS, AND CROWN AND BRIDGE COLLEGE OF DENTAL SCIENCES, DAVANGERE . MAXILLO-MANDIBULAR RELATIONSHIP PART-3

2. VERTICAL JAW RELATION VERTICAL DIMENSION AT OCCLUSION AND VERTICAL DIMENSION AT REST INCREASE OR DECREASE IN VERTICAL DIMENSION???

3. CONTENTS- INTRODUCTION CHRONOLOGY OF DEFINITIONS CENTRIC RELATION SIGNIFICANCE OF CENTRIC RELATION CRITERIA FOR CENTRIC RELATION ROLE OF MASTICATORY MUSCLES ROLE OF GLENOID FOSSA FACTORS INFLUENCING THE CENTRIC RELATION RECORD GOALS OF CENTRIC RELATION CENTRIC RELATION AND CENTRIC OCCLUSION TYPES OF CENTRIC RELATION CENTRIC RELATIONS-

4. DIFFICULTY IN RECORDING CENTRIC GUIDANCE TO ATTAIN CENTRIC VERIFYING CENTRIC RELATION RECORDING CENTRIC RELATION COMPLICATIONS IN RECORDING CENTRIC JAW RELATION PROTRUSIVE RELATION RIGHT AND LEFT LATERAL MAXILLO MANDIBULAR JAW RELATIONS SUMMARY CONCLUSION REFERENCES ECCENTRIC RELATIONS-

5. INTRODUCTION- CR is the beginning of occlusion, and all treatment modalities are based on it. There is no doubt that CR is a joint position and, therefore, requires knowledge and involvement of the temporomandibular joint (TMJ) in every CR study. The concept of CR emerged due to the search for a reproducible mandibular position that would enable the prosthodontic rehabilitation. Research in the field of CR has been controversial for more than 100 years. No where else in dentistry can one see so much debate and opposing ideas among scientists and clinicians. This challenge is still ongoing and, periodically, a clinician presents a method to record CR ‘correctly’ or redefine this mandibular position.

6. CHRONOLOGY OF CENTRIC RELATION-

7. DEFINITIONS- 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’. 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’.

8. Robinson [1951] - stated that the mandible ‘can be retruded beyond what we should consider centric into a strained retruded position’. Granger [1952] – “Upmost, rearmost position”. A second component namely a most superior position was considered necessary for bracing since the condyle was unstable when it was only in the most posterior position. 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. 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’.

9. 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 maxillomandibular relation that can be statically repeated’. GPT-2 [1960] - defined the CR as ‘the most posterior relation of the mandible to the maxilla at the established vertical relation’. 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 condyles in the glenoid fossa’. Boucher [1964] stated - ‘CR is the most posterior relation of the mandible to maxillae at the established vertical relation’.

10. Goldman and Cohen [1968] - defined CR as ‘the most posterior relation of the mandible to maxilla from which lateral movements can be made’. 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. 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. 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.

11. 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. 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’. 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. 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’.

12. 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. Authors of the latest GPT-8th edition (2005) - continued giving following seven acceptable definitions- 1. The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterio – superior position against the slopes 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. 2. The most retruded physiologic relation of the mandible to the maxillae to 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 (GPT-3).

13. 3. The most retruded relation of the mandible to the maxillae when the condyles are in the most posterior unstrained position in the glenoid fossae from which lateral movement can be made at any given degree of jaw separation (GPT-1). 4. The most posterior relation of the lower to the upper jaw from which lateral movements can be made at a given vertical dimension (Boucher). 5. A maxilla to mandible relationship in which the condyles and disks are thought to be in the midmost, uppermost position. The position has been difficult to define anatomically but is determined clinically by assessing when the jaw can hinge on a fixed terminal axis (up to 25 mm). It is a clinically determined relationship of the mandible to the maxilla when the condyle disk assemblies are positioned in their most superior position in the mandibular fossae and against the distal slope of the articular eminence (Ash).

14. 6. The relation of the mandible to the maxillae when the condyles are in the uppermost and rearmost position in the glenoid fossae. This position may not be able to be recorded in the presence of dysfunction of the masticatory system. 7. A clinically determined position of the mandible placing both condyles into their anterior uppermost position. This can be determined in patients without pain or derangement in the TMJ ( Ramsfjord ). GPT-9 (2017) - 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 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.

15. SIGNIFICANCE OF CENTRIC RELATION- More definite than Vertical dimension. 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. Pure rotations take place. Bone to bone relation Independent of position of tooth. Constant for an individual. Reproducible, repeatable and recordable. Acts as a reference point.

16. Functional movements like chewing and swallowing are performed in this position because it is the most unstrained position. The muscles that act on the temporomandibular joint are arranged in such a way that it is easy to move the mandible to the centric position from where all movements can be made. The casts should be mounted in centric relation because it is the point from which all the movements can be made or simulated in the articulator. It is helpful in adjusting condylar guidance in an articulator to produce balanced occlusion. It is a definite entity, so it is used as a reference point in establishing centric occlusion.

17. In case of edentulous patients centric relation act as proprioceptive centre to guide occlusal movements. It is the only jaw position that permits an interference free occlusion. Centric relation is the ideal arch to arch relationship and an optimum functional position of jaws for the health, comfort and function of TMJ and musculature. Recording of an accurate centric relation is critical for the most cost effective, time effective and trouble free prosthetic dentistry.

18. CRITERIA FOR CENTRIC RELATION- The 2 most important criteria for Centric Relation are:- The complete release of the inferior lateral pterygoid muscle Proper alignment of the disc on the condyle.

19. ROLE OF MUSCULATURE- The elevator muscles are all present distal to the teeth, between the teeth and condyles. Action of these elevator muscles pulls the condylar disk assemblies against the eminence and slides them upwardly. The superficial masseter pulls the condyles against the posterior slope and up. The deep fibers of the masseter muscles pull the condyles up.

20. The internal pterygoid muscles pull the condyles up from the lingual side of the mandible. The temporalis muscles attach to the coronoid process between the teeth and the TMJs and pull the condyle up.

21. The inferior belly of the lateral pterygoid is passive during jaw closure unless activated by occlusal interferences to hold the jaw forward. Mahan et al. say that the inferior belly of the lateral pterygoid is almost always completely inactive during clenching in the retrusive position. Inactivity of the inferior belly of the lateral pterygoid muscle releases the condyles to move up.

22. SIGNIFICANCE OF GLENOID FOSSA- If maximal intercuspation requires the condyles to displace distally, the medial pole of the condyle must move downward from its apex of force position in the concave fossa. When it moves up and forward to the centric relation, the posterior tooth becomes the pivot point.

23. FACTORS INFLUENCING CENTRIC RELATION RECORDS- The resiliency of the supporting tissues Fit of the denture bases Residual alveolar arch Saliva Tongue The health and co-operation of the patient The posture of the patient The Temporo-mandibular joint and its associated neuromuscular mechanisms The skill of the dentist The technique used and the recording devices used

24. GOAL OF CENTRIC RELATION- 1. The disk is properly aligned on both condyles. 2. The condyle-disk assemblies are at the highest point possible against the posterior slopes of the eminentiae . 3. The medial pole of each condyle-disk assembly is braced by bone. 4. The inferior lateral pterygoid muscles have released contraction and are passive. 5. The TMJs can accept firm compressive loading with no sign of tenderness or tension.

25. CENTRIC RELATION AND CENTRIC OCCLUSION- Centric occlusion (GPT 8) - the occlusion of opposing teeth when the mandible is in centric relation. The understanding of centric relation is complicated by failure to distinguish between centric relation and centric occlusion. Centric occlusion is a tooth-to-tooth position whereas centric relation is bone-to-bone relation. Both may or may not be identical to each other. In persons with natural teeth, both centric relation and centric occlusion exist. After the removal of teeth, centric occlusion is lost ,while centric relation remains and serves as a reliable guide to develop centric occlusion in artificial dentures .

26. TYPES OF CENTRIC- 1. Point centric or the Gnathological centric occlusion ( Lucia, Granger ) CR=CO=MIP 2. Long centric/Freedom from centric/Area centric: CO may or may not coincide with the CR Freedom is given to close the mandible either into CR or slightly anterior to it in CO with a smooth gliding, without effecting any change in vertical dimension of occlusion. Panky , Mann -------- Long centric Beyron --------------- Area centric Ramfjord ------------- Play in centric

27. ADAPTED CENTRIC- A TMJ that is structurally deformed with a misaligned or displaced disk cannot be described as in centric relation because it does not fulfill the critical requirement of a properly aligned disk. However, some structurally deformed temporomandibular joints (TMJs) may function comfortably even though they do not fulfill the requirements for centric relation. A wide range of intracapsular structural disorders from partial to complete disk derangements with or without reduction may adapt to a conformation that permits the joints to comfortably accept maximal compressive loading by the elevator muscles. Adapted centric posture is the manageably stable relationship of the mandible to the maxilla that is achieved when deformed TMJs have adapted to a degree that they can comfortably accept firm loading when completely seated at the most superior position against the eminentiae .

28. CONCEPTS AND OBJECTIVES IN RECORDING CENTRIC RELATION- 1) Minimal closing pressure:- Objective: To make teeth touch uniformly & simultaneously at first contact, so that tissues supporting the base will not be displaced. 2) Heavy closing pressure:- Objective: To produce the same displacement of the soft tissues as would exist when heavy closing pressures are applied on the denture, which results in even distribution of forces on the ridge.

29. DIFFICULTY IN RECORDING CENTRIC RELATION-

30. BIOLOGICAL CAUSES- Lack of co-ordination between groups of opposing muscles when the patient is requested to close the mouth in the retruded position. Habitual eccentric jaw relation. PHYSIOLOGICAL CAUSES- Inability of the patient to follow the dentist’s instructions is one of the major psychophysiological factors, which produce difficulty in retruding the mandible. This is overcome by instituting stretch relax exercises, training the patient to open and close his mouth, etc. Central bearing devices can also be used to retrude the mandible in these patients.

31. MECHANICAL CAUSES- Poorly fitting base plates produce difficulty in retruding the mandible. The base plates should be checked using a mouth mirror for proper adaptation. Minimal pressure should be exerted during the registration, to avoid displacement of soft tissue as much possible. If minimal pressure is exerted at the time of this registration, the jaw relation will be recorded with minimal tissue displacement and the denture will have a uniform occlusal contact when the teeth first touch.

32. METHODS FOR ASSISTING THE PATIENT TO RETRUDE THE MANDIBLE- Let your jaw relax, pull it back and close slowly and easily on your back teeth. Get the feeling of pushing your upper jaw out and close your back teeth together. Instruct the patient to protrude and retrude the mandible repeatedly while the patient holds the fingers lightly against the chin. (Swenson) Instruct the patient to turn the tongue back ward toward the posterior border of the upper denture. Instruct the patient to tap the occlusion rims or back teeth repeatedly. Tilt the patients head back while the various exercises just listed are carried out. Palpate the temporal and masseter muscles to relax them.

33. METHODS FOR ASSISTING THE PATIENT TO RETRUDE THE MANDIBLE (FENN)- Instruction to patient (Chew not bite) Tongue Retrusion Relaxation Swallowing Fatigue (Protrude & Retrude ) Head Position (Bend head backwards) Temporalis muscle check

34. ATTAINING CENTRIC RELATION- OPERATOR GUIDED: Chin point guidance (Guichet – 1970) 3 finger chin point guidance (Peter Thomas – 1980) Bilateral manipulation OTHER AIDS USED: Directly fabricated Anterior deprogramming device Pankey Jig Best bite appliance Lucia jig NTI device Leaf gauge

35. CHIN POINT GUIDANCE- Positions the condyle in the RUM position. The patient is seated upright and relaxed with the clinician positioned in front. A softened two-layer wax wafer (1.4 mm thick) is gently pushed against the cusps of the maxillary teeth with just enough force to make slight cuspal indentations. The wafer is removed, chilled and re-seated in order to check fit and stability.

36. A registration medium is applied to the mandibular surface of the wax wafer and the patient's mandible is guided into a hinge closure by the thumb and index finger of the operator. The mandible is then manually manoeuvred a few times about the hinge axis. After several smooth movements the hinge closure is completed until the mandibular teeth just indent the registration material. The risk with this method is the ease with which the condyles can be over- retruded .

37. 3 – FINGER POINT CHIN GUIDANCE- A tripod is created at the chin-point and lower border of the mandible on both sides by the thumb, index and third finger. Gentle guidance along all three digits is required in a mid-sagittal plane. This encourages anterio -superior placement of the condyles but care is required as it is easy to deflect the mandible to one side. Not recommended for edentulous subjects because the operator's hand position can lead to displacement of the lower denture base.

38. BILATERAL MANIPULATION- Step one: Recline the patient all the way back. Point the chin up. A supine patient is more relaxed and in a better position for the operator to work while seated. Pointing the chin up makes it easier to position the fingers on the mandible and prevents the tendency of some patients to protrude the jaw.

39. Step two: Stabilize the head. Lower the patient’s head enough so you can cradle it between your rib cage and forearm. Some dentists find it more comfortable to position the top of the patient’s head in the center of their abdomen. This has some disadvantages in that there is a tendency to pull back on the mandible. Whatever method is used, it is essential that the head be stabilized in a firm grip so it will not move when the mandible is being manipulated. Failure to do this is a common mistake.

40. Step three: After the head is stabilized, lift the patient’s chin again to slightly stretch the neck. Be sure you are comfortably seated, with the patient low enough to allow you to work with your forearm approximately parallel to the floor.

41. Step four: Gently position the four fingers of each hand on the lower border of the mandible. The little finger should be slightly behind the angle of the mandible. Position the pads of your fingers so they align with the bone, as if you were going to lift the head. Keep all four fingers tightly together.

42. Step five: Bring the thumbs together to form a ‘C’ with each hand. The thumbs should fit in the notch above the symphysis. No pressure should be applied at this time. All movements should be made gently.

43. Step six: With a very gentle touch, manipulate the jaw so it slowly hinges open and closed. As it hinges, the mandible will usually slip up into centric relation automatically if no pressure is applied. Any pressure applied before the condyles are completely seated will be resisted by the lateral pterygoid muscles. (Stretch – reflex reaction) The whole purpose of this step is to deactivate the muscles. They often describe this procedure as “romancing the mandible.” When hinging the jaw in this position, it is not necessary to open wide. An arc of one or two millimeters is acceptable. When arcing, do not let the teeth touch.

44. Step seven: After the mandible feels like it is hinging freely and the condyles seem to be fully seated up in their fossae. Most experienced clinicians will assume that the mandible is in centric relation. No matter how solidly the condyles seat and how freely the mandible hinges, we cannot tell by touch alone that the condyles are in centric relation. Centric relation must be verified by load testing.

45. DIRECTLY FABRICATED ANTERIOR DEPROGRAMMING DEVICE- Fabricated directly, by molding autocuring acrylic resin to engage the incisal edges of the upper incisors. During the doughy stage, the mandible is manipulated to centric relation, or as close to it as can be achieved. The jaw is then closed so the lower incisors indent the soft acrylic, but closure is stopped short of posterior contact. After curing is completed, the tooth contact surface is ground to a smooth flat surface that permits full horizontal movement of the mandible. If the TMJs are intact and the lateral pterygoid muscles are completely released and passive; the patient can squeeze firmly to hold the condyles in centric relation as a fast-setting bite material is injected between the posterior teeth.

46. PANKEY JIG- Was designed many years ago by Dr. Keith Thornton. It is cost-effective and easy to use. It is fixated on the upper central incisors with autocure acrylic or any hard-setting material. The lower incisors slide freely against a flat surface to give unimpeded freedom for condylar movement to centric relation.

47. BEST BITE APPLIANCE- The Best-bite appliance works exactly the same way as the Pankey jig. A kit is available with an injection material for stabilizing the appliance.

48. LUCIA JIG- The Lucia jig also works the same as other anterior stops. Lucia was one of the first to employ an anterior stop. His original design was slanted to direct the condyles distally based on early misconceptions about centric relation being “most retruded.” The jig was first modified by Dr. Peter Neff to permit upward condylar movement without the distalizing effect.

49. NTI (NOCICEPTIVE TRIGEMINAL INHIBITION)- An appliance for treating migraine headaches and other facial pain problems. In reality, it is nothing more and nothing less than any of the other anterior bite stop devices. It works exactly like the other methods which are described.

50. LEAF GAUGE- Introduced by Dr. Hart; device consists of layers of flexible mylar that can be adjusted to varying thicknesses. The principle is to separate the posterior teeth by placing the gauge between the anterior teeth. It can be used as a deprogramming device for release of lateral pterygoid bracing. The material is smooth and slick, so it allows the mandible to move horizontally as the condyles seat up. After centric relation has been confirmed, layers of the gauge can be removed until the first tooth interference contacts.

51. NOTE- All of the above methods have value if used with an understanding of the goal of complete upward seating of the condyles. All methods require use of an accurate material for recording the bite relationship at the posterior teeth as the anterior stop prevents posterior occlusal contact. The ideal way to use any anterior stop is to combine its use as a muscle deprogrammer with bilateral load testing after you think centric relation has been achieved. After centric relation has been verified, have the patient clench to hold the condyles in the fully seated position while the bite recording material is placed and set.

52. VERIFYING CENTRIC RELATION- Load testing of the TMJ is an essential step in the determination and verification of centric relation or adapted centric posture. If the TMJs are in centric relation, all forces go through avascular non-innervated structures and the inferior lateral pterygoid muscles have completely released their contraction. There is no discomfort in the TMJs when loaded in this relationship, and there is no discomfort in the masticatory musculature from loading. If the condyle-disk assemblies are completely seated up to the most superior position in the fossae, all upward movement is stopped by bone.

53. At this point, the inferior lateral pterygoid muscles release all contraction. Even firm upward loading cannot stretch the muscles to cause a response because the condyles cannot move higher. This is CENTRIC RELATION. PROPER LOAD TESTING MUST BE DONE IN INCREMENTS- The first increment of load testing is always done with gentle compression. The loading process is not done to force the condyles into centric relation. Load testing is done to verify that the condyles are completely seated after the operator has gently manipulated the mandible to a freely hinging position that is suspected of being in centric relation.

54. If the condyle is not completely seated to centric relation it will be held down and forward by muscle. Load testing will then produce tension and tenderness. COMMON MISTAKES: 1. Applying Too Much Pressure Too Soon- There is a tendency of some dentists to feel that they must overpower any resistant muscles and force the condyles into centric relation. This is the opposite of what is necessary. Too much force suddenly applied elicits a stretch reflex response in the lateral pterygoid muscle, which then attempts to protect the joint by tightly contracting to hold the condyle forward.

55. 2. Not Applying Enough Upward Loading Force at the final increment- If the patient has no response to lighter compressive force, the upward force through the TMJs must be increased until the loading force is very firm. After each increment of force is increased, the patient must be asked, “Do you feel any sign of tenderness or tension in either joint?” There will be many patients whose jaw hinges freely and seems to be at a definite centric relation stopping point. Their response to load testing is negative until very firm loading force is applied, at which point they report tension or tightness (only if asked).

56. RECORDING CENTRIC RELATION- Once the patient is trained to close the jaw into centric and the same is verified by load testing; then we can get on with the recording of the centric relation. FOR DENTATE PATIENTS (DAWSON): Wax bite records Anterior stop techniques Power Bite For large edentulous areas FOR EDENTULOUS PATIENTS (HEARTWELL): 1. Functional methods (chew-in)- a) Needles House method b) Patterson method c) Meyer’s method 2. Graphic Method- a) Intraoral devices b) Extraoral devices 3. Physiological- a) Interocclusal check record b) Pressure Method c) Static Method

57. WAX BITE RECORDS- Torch used to soften bite registration wax Shine produced by even heating Placing on to the maxillary arch and closing into centric RECORDING CENTRIC RELATION – DENTATE PATIENTS

58. Wax trimmed back to buccal cusps Wax record with tooth indentations Stored carefully in water WAX BITE RECORDS-

59. ANTERIOR STOP TECHNIQUES- A firm-setting bite paste is injected between the posterior teeth while the patient maintains firm compression against the anterior stop. Bite paste allowed to set With an anterior deprogramming device in place, centric relation is verified by load testing, and the patient is instructed to clench to maintain the loaded joint position. No posterior teeth should be allowed to contact during bite registration.

60. ANTERIOR STOP TECHNIQUES- Wax bite allowed to harden The wax bite record can be taken in combination with an anterior deprogramming device The wax bite record can be cut out at the front. Bilateral manipulation should be used to seat the joints and verify centric relation as if the anterior jig were not in place.

61. LARGE EDENTULOUS AREAS- Silicone putty adapted to opposing ridge and closed into centric. A premade wax base can be adapted on a cast of the opposing arch. Retention can be added for future attachment of silicone putty.

62. RECORDING CENTRIC RELATION – EDENTULOUS PATIENTS (PHYSIOLOGICAL) TACTILE/INTEROCCLUSAL CHECK METHOD- Once the patient has been trained to close the jaw in centric relation; a tentative jaw relation is done with occlusal rims. This tentative jaw relation is mounted and artificial teeth are set on them. Now, the trial dentures are ready for inter-occlusal check records. Trial dentures inserted into the patient and contact between teeth avoided by placing cotton rolls. Aluwax then loaded onto the occlusal surface of lower teeth.

63. Patient asked to slowly retrude and close jaw until tooth contact occurs; wax left to cool. Aluwax trimmed off from the buccal aspect of mandibular teeth to expose the cusps teeth. If the tentative record and the check record are same, then both the condylar elements will meet at the centric stops. If anyone of the condylar elements do not contact the centric stop; then the tentative recording is inaccurate. TACTILE/INTEROCCLUSAL CHECK METHOD-

64. STATIC METHOD- Once the patient is trained to close the jaws in centric relation; the denture bases with occlusal rims are indexed or sealed in the position. This is done routinely by the Nick and Notch method or the stapler pin method.

65. Trough made on mandibular occlusal rim (3mm wax removed) Nick and notch made on the maxillary occlusal rim Nick made anterior to the notch STATIC METHOD-

66. STATIC METHOD- Trough loaded with ALUWAX (height of 4.5mm) Excess wax removed carefully using wax carver

67. PRESSURE METHOD- After establishing vertical dimension, the upper occlusal rim is inserted into patient’s mouth. The height of the lower rim is fabricated to be of excess height. The lower rim is placed in a water bath to soften. Placed in the patient’s mouth and the patient is asked to close on soft wax. After the patient closes to the predertermined VDO, both rims are removed together cooled and articulated.

68. FACTORS TAKEN TO CONSIDERATION- In a functional method, a tentative centric relation and vertical dimension are measured for determining an accurate centric relation. The occlusal rims for these methods are reduced in excess than that required for the tentative vertical dimension. The exact vertical dimension at occlusion is determined only when the patient closes on the occlusal rims and their attachments. RECORDING CENTRIC RELATION – EDENTULOUS PATIENTS (FUNCTIONAL)

69. FACTORS TAKEN TO CONSIDERATION- The record bases should be very stable while recording centric jaw relation. If the record base gets displaced, the mandible will tend to move into an eccentric position. Lack of equalized pressure exerted on the record base can result in inaccuracies in recording centric jaw relation. A good neuromuscular coordination is required from the patient.

70. NEEDLES HOUSE METHOD- Involves the fabrication of occlusal rims made from impression compound. Four metal beads or styli are embedded into the premolar and molar areas of the maxillary occlusal rim The occlusal rims are inserted into the patient’s mouth The patient is asked to close on the occlusal rims and make protrusive, retrusive, right and left lateral movements of the mandible.

71. NEEDLES HOUSE METHOD- When the patient moves his mandible, the metal styli on the maxillary occlusal rim will create a marking on the mandibular occlusal rim. When all the movements are made, a diamond-shaped marking pattern rather than a line is formed on the mandibular occlusal rim . The posterior most point of this diamond pattern indicates the centric jaw relation.

72. PATTERSON’S METHOD- Uses wax occlusal rims. A trench is made in the mandibular rim, and mixture of half plaster and half carborundum paste is placed in the trench.

73. PATTERSON’S METHOD- Occlusal rims are inserted and the patient is asked to make functional movements These movements will produce compensating curves on the plaster carborundum mix. When the plaster and carborundum are reduced to the pre-determined VDO, patients are instructed to retrude the mandible and occlusion rims joined.

74. MEYER’S TECHNIQUE: Used soft wax occlusal rims to establish a generated path. Tinfoil was placed over the wax and lubricated. Patient performed functional movements to produce a wax path. Plaster index was made of the wax path and the teeth were set to the plaster index. SHANAHAN’S TECHNIQUE: Placed cones of soft wax on the mandibular rim and had the patient swallow several times During swallowing the tongue forced the mandible into CR.

75. GRAPHIC METHOD- The first known “needle point tracing” was done by Hesse in 1897. The technique was improved and popularized by Gysi around 1910. Phillips recognized that any lateral movements of the jaw would cause interference of the rims which could result in a distorted record. He developed the “ central bearing device ” which supposedly produced equalisation of pressure.

76. FACTORS TAKEN TO CONSIDERATION- Stability of the denture base. Resistance offered by the occlusal rims against occlusal forces. Difficulty in placing the central-bearing device in protruded and retruded jaws. Presence of flabby tissue and its effect on the denture base. Height of the residual alveolar ridge influencing the stability of the record base. Interference from the tongue. Efficiency of the recording devices during physiological mandibular movements.

77. FACTORS TAKEN TO CONSIDERATION- Obtaining a pointed apex in the tracing pattern. (All tracing patterns will have an apex which is a single point from where all patterns appear to arise from). Lack of coordinated movement. This can cause double tracing. The graphic tracing should harmonize with the centric relation, centric occlusion, bone to bone relation and tooth-to-tooth contact.

78. The characteristic pattern created on the recording plate is called a central arrow-point tracing. It is defined as, 'The pattern obtained on the horizontal plate used with a central bearing tracing device"—GPT. Central bearing device consist of Central bearing point/stylus pen-like pointer is attached to one occlusal rim and Central bearing plate placed on the other rim. These parts are called central bearing because they act at the center of the arch and evenly distribute forces across the supporting structures. COMPONENTS OF ARROW POINT TRACING-

79. When the mandible moves the pointer draws characteristic patterns. It is a one-dimensional graphic tracing made using gothic arch tracers. It is usually recorded in the horizontal plane. The apex of the arrow point tracing gives the centric relation. The apex of the arrow head should be sharp else the tracing is incorrect. COMPONENTS OF ARROW POINT TRACING-

80. COMPONENTS OF ARROW POINT TRACING- CENTRAL BEARING DEVICE: “A device that provides a central point of bearing or support between the maxillary and mandibular dental arches. It consists of a contacting point attached to one dental arch and a plate attached to the opposing dental arch. The plate provides the surface on which the bearing point rests or moves and on which the tracing of the mandibular movement is recorded. It may be used to distribute the occlusal forces evenly during jaw relation and/or for the correction of disharmonious occlusal contacts.” (GPT-9)

81. COMPONENTS OF ARROW POINT TRACING- CENTRAL BEARING POINT: “The contact point of the central bearing device”. (GPT). It is a triangular plate of metal with extensions provided to attach itself to the occlusal rim. In the centre of the triangle a metal pointer is present. The pointer can be adjusted in height. It is usually attached to the mandibular occlusal rim but can also be attached to the maxillary rim . Since it is placed across the tongue space of the mandibular occlusal rim; it cannot be used in patients who can not retract the tongue sufficiently and those who have macroglossia.

82. COMPONENTS OF ARROW POINT TRACING- CENTRAL BEARING PLATE: It is also a triangular piece of metal with extensions at the three corners provided to attach the plate to the occlusal rim. It is usually attached to the maxillary occlusal rim. A mixture of denatured spirit and precipitated chalk is coated on this plate. The spirit dries to leave a fine layer of precipitated chalk. The tracing is marked on this layer of precipitated chalk.

83. TYPES OF ARROW POINT TRACING- INTRA – ORAL TRACING EXTRA – ORAL TRACING

84. DIFFERENCE BETWEEN EXTRAORAL AND INTRAORAL TRACERS- EXTRAORAL TRACERS- Have both intraoral and extraoral component. Extraoral component – tracing plate and stylus. Intraoral component – central bearing point. It can also be attached to facebow. Less accurate as the tracer is away from TMJ (centre of rotation). Arrow point is larger in size and faces anteriorly. Tracing plate – mandible. Tracing pin – maxilla. Easy to visualize and guide the patient during tracing. INTRAORAL TRACERS- Comprises only an intraoral component. No extraoral component. Intraoral component – contains both central bearing device and tracing device. More accurate as the tracer is more close to TMJ (centre of rotation) Arrow point is smaller in size and faces posteriorly. Tracing plate – maxilla. Tracing pin - mandible. Since the tracing is intraoral it is difficult to visualize and guide the patient during tracing.

85. INDICATIONS- Well healed broad edentulous ridges. Adequate inter arch space. In patients with habitual centric; the use of the graphic method eliminates all occlusal contacts on the occlusal rims, thus breaking the neuromuscular reflex and allows the patient to record his true centric. CONTRAINDICATIONS- Severely resorbed ridges. Excessively flabby ridges. Difficult to place in the presence of large tongue. Decreased arch space. In patient with temporo-mandibular joint arthropathy. In patient with abnormal jaw relations.

86. ADVANTAGES- DISADVANTAGES- 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. 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.

87. PROCEDURE FOR INTRA ORAL TRACING- The record bases attached to the central- bearing point and the central-bearing plate (coated with chalk) are inserted into the patient's mouth. The central bearing point is adjusted such that it contacts the central-bearing plate at a predetermined vertical dimension . When the patient closes his mouth, the central bearing point contacts the metal plate. The patient is asked to make anteroposterior and lateral movements. While making these movements, the central-bearing point will draw the tracing pattern on the central-bearing plate.

88. PROCEDURE FOR INTRA ORAL TRACING- After completing the movements, the tracing is removed and examined. The tracing should resemble an arrow point with a sharp apex. If the apex is blunt, the record is discarded and the procedure is freshly repeated.

89. FACTORS OF IMPORTANCE- Displacement of the record bases may result from pressure if the central points are off centered. If the central bearing device is not used, rims offer resistance to horizontal movements. Tracing not acceptable until a pointed apex is obtained. Vertical dimension has to be maintained. Equalizes the pressure by distributing the forces throughout the supporting tissues. Allows the mandibular movement to be dictated by the condyles.

90. ARCH TRACING EVALUATION (GERBER)- TYPICAL FLAT ASYMMETRICAL ROUND APEX MINIATURE DOUBLE ARROW DORSALLY EXTENDED ATYPICAL/ INTERRUPTED

91. ARCH TRACING EVALUATION (GERBER)- TYPICAL: Has a well defined apex Symmetrical left and right lateral component Gothic arch angle 120 degree Indicative of a- Healthy TMJ Smooth condylar path Bilateral balanced muscle guidance.

92. ARCH TRACING EVALUATION (GERBER)- FLAT: It is similar to typical arrow point except that it has a more obtuse left and right lateral tracings. This type of arrow point signifies a marked lateral movement of condyle in the fossa. Gothic arch angle is greater than 120 degree.

93. ARCH TRACING EVALUATION (GERBER)- ASSYMETRICAL: The left and right tracing meet at an arrow point but either of the lateral tracing is shorter. It indicates a distinct inhibition of the forward movement in the right/left joint.

94. ARCH TRACING EVALUATION (GERBER)- ABSENT APEX OR ROUNDED: Instead of a sharp arrow point, the tracing is rather round. It shows a weak retrusive movement. Tracing should be repeated till a definite arrow point is obtained. Patient training is necessary.

95. ARCH TRACING EVALUATION (GERBER)- MINIATURE: This is similar to a typical arrow point but the extent of tracing is limited. It is mostly due to – Restricted mandibular movement. Interferences in the record bases. Ill fitting denture record bases mostly seen in patient with prolonged period of edentulousness since they develop an inhibition in condylar movements.

96. ARCH TRACING EVALUATION (GERBER)- DOUBLE ARROW: Indicative of habitual and retruded centric relation. Also seen when altering the vertical dimension during registration. This can be easily corrected by training the patient further until a single arrow is obtained.

97. ARCH TRACING EVALUATION (GERBER)- DORSALLY EXTENDED: The protrusive path extends beyond the apex of gothic arch. This signifies a forced strained retrusive movement of the lower jaw either by the patient (Active) or by the operator (Passive). It is also sometimes an artifact caused by the forward displacement of upper occlusal rim or backward displacement of lower occlusal rim while removing them from mouth.

98. ARCH TRACING EVALUATION (GERBER)- ATYPICAL: Break or loss of continuity of lateral incisal path of gothic arch. This happens due to posterior interference at the heels of occlusal rims during lateral movements. Check for posterior clearance before recording. The protrusive component does not meet at the apex instead it meets on either one of the lateral path. Usually seen in patient who have been using complete dentures with faulty centric relation.

99. ARCH TRACING EVALUATION (GERBER)- INTERRUPTED: Break or loss of continuity in the arrow point. Protrusive component does not meet at apex on one of the lateral path. This may happen in dentulous because of a faulty muscular pattern due to parafunctional habits like bruxism. It is also seen in very old edentulous patients, who are using complete dentures with incorrect centric relation.

100. PANTOGRAPHIC TRACING- It is defined as, "A graphic record of mandibular movement in three planes as registered by the styli on the recording tables of a pantograph; tracings of mandibular movement recorded on plates in the horizontal and sagittal planes“. -GPT

101. It is a three-dimensional graphic tracer. It is the most accurate method available to record centric jaw relation. Even eccentric jaw relation can be recorded using these instruments, very sophisticated and are generally not used in the fabrication of complete dentures. This is because complete dentures have a realeff factor that aids to compensate for the minor fabrication errors. These tracers are generally used for full-mouth rehabilitation of dentulous patients. PANTOGRAPHIC TRACING - A graphic record of mandibular movement usually recorded in the horizontal and sagittal planes as registered by styli on the recording tables of a pantograph or by means of electronic sensors. (GPT -9)

102. The instrument used to do a pantographic tracing is called a pantographic tracer. A pantographic tracer is defined as, "An instrument used to graphically record one or more planes paths of the mandibular movement and to provide information for the programming of the articulator“. -GPT. It resembles a complicated face-bow. The surface over which the tracing is done is called a flag. A stylus (tracing pointer) is present for each flag. The styli draw tracing patterns on the flags).

103. COMPLICATIONS IN RECORDING CENTRIC RELATION- The structure of TMJs are such that one joint can be displaced downward by uneven pressure when records are made and yet the condyles be in their most retruded position. This situation cannot occur on the articulator and thus a deflective occlusal contact may be the source of instability, soreness and resorption despite the correctness of the other relations. Realeff effect by Hanau: According to it, there is uneven resiliency in the soft tissues. This resiliency is present in both the mucosa and the TMJ’s, thus undue pressure in securing the relation must be avoided lest excessive displacement of soft tissues occur. Even though a balanced and equalized registration has been made it often is lost due to: Cast mounting procedures,Processing of denture.

104. ECCENTRIC JAW RELATION- Eccentric jaw relation-Any jaw relation other than centric jaw relation. -(GPT) The eccentric relation that are recorded and used in complete denture construction are protrusive and right and left lateral. Purpose of making eccentric is to adjust the horizontal and lateral condylar inclination so that articulator jaw member perform eccentric movement equivalent, but not identical, to the relative movement of mandible to maxillae. These adjustments permit the condylar elements to travel to and from the centric and eccentric positions and make it possible to arrange the teeth for complete dentures in balanced occlusion.

105. Protrusive and lateral maxillo-mandibular relations record made by Functional Graphic (one plane) Tactile Methods PROTRUSIVE RELATION- It is the relation of the mandible to the maxilla when the mandible is thrust forward. If the motion in every part of the mandible as it is thrust forward has simultaneously the same velocity and direction, the motion could be correctly termed translatory.

106. The movement in the joint is downward and forward. The condyles disk assemblies are guided downward by the articular eminences of the glenoid fossae. The angle of slide varies from patient to patient and from side to side. In the same patient, the muscles responsible for a straight protrusive movement are the inferior pterygoid muscles acting simultaneously. Protrusive relation is a bone-to bone relation, which can be recorded.

107. RIGHT AND LEFT LATERAL MAXILLOMANDIBULAR RELATIONS- It is relations of the mandible to the maxillae when the mandible is moved either to the right or to the left side. The movement of the mandible is the result of the contraction of contralateral inferior pterygoid muscle. When the external pterygoid of one side contracts, the corresponding side of the mandible is pulled forward and inward, while the other side remains comparatively fixed. More harmony will exist between the mandibular movements and cuspal inclines.

108. The purpose in making eccentric record is to adjust the horizontal and lateral condylar inclinations so that the articulators jaw members performs eccentric movements equivalent to the relative movement of the mandible to maxillae. 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 to accommodate for the difference in the vertical jaw separation between the balancing and the working sides. Hanau formula- L=H/8+12. where, L=Lateral condylar inclinations H=Horizontal condylar inclination in degrees as established by protrusive relation record.

109. WAX CHECK BITES: Taken at lateral positions and it is desireable to have more than one record at each position. PLASTER/STONE POSITIONAL RECORDS: Records are taken at lateral extremes of the intra oral or extra oral tracings.

110. SUMMARY To summarize-Centric relation is a reproducible, recordable, position, and a physiologically acceptable position for deglutition. The accurate determination, recording & transfer of jaw relation records from the edentulous patient to the articulator is essential for the restoration of function, facial appearance and the maintenance of patient health. Therefore it is emphasized that irrespective of the method used, subsequent clinical checking and rechecking must be done throughout the entire denture construction phases. The skill of the dentist & the co-operation of the patient being most important factor.

111. CONCLUSION It is obvious that the skill of the prosthodontist and the cooperation of the patient are probably the most important factors in securing an accurate centric relation records. Any dentist who is willing to spend the time and energy to master the technique of recording and verifying precise centric relation will benefit in untold ways. There is no procedure in dentistry that produces so many benefits to both the patient and the dentist as the routine accurate recording of centric relation as it affects the health, comfort and function of the muscles and the TMJ.

112. REFRENCES Bouchers Prosthodontic treatment for edentulous patients-9 th edition. Essentials of complete denture prosthodontics - Sheldon winkler-2 nd edition. Prosthodontic treatment for edentulous patients - Zarb Bolender-12 th edition. Textbook of complete dentures – Rahn and Heartwell-5 th edition. Complete denture prosthodontics - Sharry JJ–3 rd edition. Dawson PE.- Evaluation, diagnosis and treatment of occlusal problems-2nd edition. TEXTBOOKS:-

113. Yukstas AA. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent. 2005 Nov;14(6):305-10. Nandini V V et al. Comparative evaluation of hight tracer, Chandra tracer, intraoral tracer, functiograph and check bite:A clinical study;J Ind Prost Soc. 2005;5(1):26-32. M. Thakur, V. Jain, H. Parkash, P. Kumar. A Comparative Evaluation of Static and Functional Methods for Recording Centric Relation and Condylar Guidance: A Clinical Study. J Indian Prosthodont Soc July-Sept 2012;12(3):175–181. Abbad NB, Srivastava R, Choukse V, Sharma V. Validity and reliability of intraoral conventional tracer and intraoral digital tracer in different positions for recording horizontal jaw relation in edentulous patients. J Indian Prosthodont Soc 2019;19:159-65. SCIENTIFIC JOURNALS:-