Orientation jaw relation

Orientation jaw relation

1. Orientation Jaw Relation And Face Bow Transfer B. Ravi Dept of Prosthodontics

2. C ontents Introduction Jaw Relations Orientation J aw Relation Hinge Axis Clinical use of the Terminal Hinge Axis Controversies Review of Literature Location Of Hinge Axis

3. C ontents Facebow History of Facebow Parts of Facebow Types of Facebow Anterior and Posterior Reference Point Facebow Transfer Conclusion References

4. Introduction The missing teeth are restored by the CD,FPD,RPD to restore function & esthetics. It is essential to develop proper occlusion for maintaining health of supporting structures, orofacial musculature, and TMJ .

5. Introduction So there is a need for accurately locating the hinge axis, recording and transferring the same on to the articulator, to enable the accurate reproduction of occlusal relationship on an articulator. This is achieved by Facebow which records the position of jaws in relation to the condylar mechanism & aids in transferring the same relation onto the articulator.

6. Jaw Relations Definition: Jaw relations are defined as any one of the many relations of the mandible to the maxillae (Boucher -3) Maxillomandibular relationship is defined as any spatial relationship of the maxillae to the mandible; any one of the infinite relationships of the mandible to the maxilla. (GPT)

7. Jaw Relations These relations may be of orientation, vertical and horizontal relations. They are grouped as such because the relationship of the mandible to the maxillae is in the three dimensions of space i.e., sagittal , vertical and horizontal planes. (Gunnar E Carlson) 

8. Jaw Relations Classifications Jaw relations are classified into three groups to make them more easily understood: They are 1) Orientation jaw relations 2) Vertical jaw relations 3) Horizontal jaw relations

9. Orientation jaw relation The orientation jaw relations are those that orient the mandible to the cranium in such a way that, When the mandible is kept in its most posterior position, it can rotate in the sagittal plane around an imaginary transvers axis passing through or near the condyles .

10. Hinge axis The hinge axis is defined as an imaginary line passing through the two mandibular condyles & around which the mandible may rotate without translatory movement. (GPT)

11. Gray recognized that mandible moves by rotations , forward & lateral movements of the condyle in the glenoid fossa . Balkwell of England in 1824 called attention to the sliding action Bonwill assumed that forward motion of joint was on a straight line in forward direction. After 40 yrs Walker proved that the motion was forward & downward. History of the Hinge Axis

12. History of the Hinge Axis Bennett of England unaware of Balkwell` s proposals showed that condyles in all individuals make a side shift motion to a greater or lesser extent in the lateral movements called as Bennett movement.

13. History of the Hinge Axis Snow in 1899 recognized the importance of hinge axis & he constructed a face bow . Camplon in 1905 concluded that the dental casts should be mounted onto the articulator in such away that the rotational axis of articulator coincides with opening axis of mandible. In 1921 Dr. B.B. McCollum, along with Dr . Robert Harlan located the first actual kinematic axis.

14. Terminal Hinge Axis When the condyles are in the most superior position in the articular fossae and the mouth is purely rotated open , the axis around which movement occurs is called as Terminal hinge axis. Maximum range of terminal hinge rotation- about 12˚ Inter incisal opening: 18-25 mm

15. Terminal Hinge Axis The terminal hinge po s ition is significant because it is learnable, repeatable , and recordable position that coincides with the position of centric relation

16. Clinical Use Of The Terminal Hinge Axis The location of the transverse hinge axis serves only to orientate the maxilla and to record the static starting point for functional mandibular movements. It does not record centric relation or condylar movements. Allows the transfer of the opening axis of jaws to the articulator so that occlusion would be on the same arc of closure as in the patients mouth

17. Clinical Use Of The Terminal Hinge Axis The hinge axis recording is required to check the accuracy of two centric records . Helps in proper positioning of the casts in relation to intercondylar shaft. Vertical dimension of occlusion can be altered on the articulator

18. Hinge axis Controversies There has been a considerable debate about whether: A hinge axis exists H inge axis can be accurately located There is only one hinge axis It is clinically useful to locate the axis An arbitrary point can be satisfactorily substituted for a kinematic axis

19. Hinge axis Controversies Sloane stated that The hinge axis is not a theoretical assumption, but definitely demonstrable biomechanical factor. Sicher stated that The terminal hinge position is the most retruded position of the mandible, the centric position .  

20. Hinge axis Controversies   The proponents of Gnathology Stated that there is one transverse hinge axis & it can be accurately located. The proponents of transographics claims that Transograph is the only instrument that can duplicate it. Others claim that Better to use articulator like Hanau , that utilizes a Face-bow mounting & an average of several readings for excursive movements.

21. Four Main Schools Of Thought Group 1 ---Absolute location of hinge axis. There is a definite transverse axis & should be located accurately. The proponents of this group claims that: with the aid of the face bow it is possible to relate the maxillary cast to the transverse axis of the articulator in the same relationship as the maxillae are related to the anatomic mandibular axis through the condyles

22. Four Main Schools Of Thought Group 1: The critics of this theory claim that most of the articulators are designed on the assumption that the transverse hinge axis is an imaginary line connecting a point in the centre of one condyle with a point in the centre of the opposite condyle . However, this optimum conditions do not exist in the mandibular apparatus, which is asymmetrical in shape and size. The condyloid processes are joined at the symphysis with no connection between the condyles . And also the condyles do not lie in a common plane of orientation

23. Four Main Schools Of Thought Group 2 ---Arbitrary location of hinge axis. Believe that arbitrary location of hinge axis is reliable, even though accurate location is valuable. The critics of this group claim that group II fails to recognize that if the hinge axis of the articulator does not coincide with the hinge axis of the patient the path of closure will not be the same.

24. Four Main Schools Of Thought   • Group 3 --Non believers in transverse hinge axis location. It is impossible to locate hinge axis with accuracy. More theoretical than practical . The critics of this group claim that the main motion is pure rotation plus slight translatory movements, the composite of which adds up to a common centre of rotation. Since this performance is repeatable, it becomes a reliable point of orientation .

25. Four Main Schools Of Thought   Group 4 -- Split axis rotation. Believe that the condyles rotate independent of each other . As the mandible is not bilaterally symmetrical and the terminal hinge position mark on one side of the face is usually a little higher than it is on the other, there cannot be a common axis . There must be two axis parallel to each other with both axes at right angle to the opening and closing movements of the mandible. The condyles are irregular and hence to not have a single point of rotation.

26. Location of hinge axis ARBITRARY METHOD OF LOCATING HINGE AXIS The arbitrary method is an accepted technique for locating the mandibular hinge axis. Although many studies have compared various arbitrary hinge axis points with kinematic location, there is no consensus as to which arbitrary point most closely and consistently lies on or near the kinematic axis .

27. Location of hinge axis KINEMATIC METHOD OF LOCATING HINGE AXIS Posselt stated that maximum separation of incisal edges in hinge motion to vary from 15 to 20mm or 10 to 13 degree opening & closing arc available for hinge axis location. In terminal hinge position the mouth opening is 12.5mm . Kurth & Feinstein located the hinge axis within 2mm of area for 10 degree arc of opening. Borgh & posselt located within 1mm of area for 15 degree & 1.5mm for 10 degree of opening arc.

28. Variables affecting hinge axis location Patient variables affecting the THA locations Condyle Asymmetry Inability to locate a true hinge axis Myospasm or joint pathosis Emotional conditions of patient

29. Variables affecting hinge axis location Factors of the recording system affecting Transvers Hinge Axis Right angle, non-right angle system of the bow Length of stylus arms and sharpness of styli

30. Review of the literature Study conducted by L. E. Kurth & I. K. Feinstein in 1951. With the aid of an articulator & working model, they demonstrated that more than one point may serve as hinge axis. So they concluded that infinite no.of points exist which may serve as hinge points. It is unlikely to locate the hinge axis accurately 

31. Review of the literature study conducted by Robert G Schollhorn in 1957 , He recorded the arbitrary center & true hinge axis in 70 dental students. He concluded that arbitrary axis of rotation which is 13mm anterior to the posterior margin of the tragus on tragal canthus line lies close to an average determined axis. In 95% of subjects Kinematic center lies within 5mm radius , which is considered to be within normal limits. So determining kinematic center is not necessary. 

32. Review of the literature Study was conducted by Richard l . Christiansen in the year 1959. He mounted the maxillary casts arbitrarily with face bow records & studied the errors in occlusion. He concluded that it is advantageous to simulate on the articulator, the anatomic relationships of residual ridges to the condyles for more harmoniously occluding complete dentures.

33. Review of the literature Study conducted by T. D Foster in 1959. He stated that permanent study casts would be of more value if they are mounted in correct relationship to the FH plane particularly in facial deformity involving the jaws.. 

34. Review of the literature Study was conducted by Arne Lauritzen & George H. Bodner in 1961. They marked true hinge axis & arbitrary hinge axis by 3 methods . They concluded that in 67% of cases the true hinge axis was 5 to 13mm away from the arbitrarily located hinge axis points

35. Review of the literature Study was conducted by Vincent R. Trappazzan , Jhon B.Lazzari in 1961. They conducted the study on 14 subjects. They concluded that in 57.2% of the subjects, more than one hinge axis point was located on either one or both sides. In 42.8% of the subjects showed single hinge axis point on left & right side of the face

36. Review of the literature   Study was conducted by Lauritzen & Wolford in 1961. An experimental instrument was designed to determine how accurately the centers of 15, 10 , 5 degree arc of movement could be located consistently. The result indicated that 10 degree range of movement is sufficient for hinge axis location . The attainable accuracy by an experienced operator in locating the the center of 10 degree arc is within 0.2mm.

37. Review of the literature Study was conducted by Arthur F. Aull in 1963. He concluded that the horizontal axis is a hypothetical line. Terminal hinge position is most posterior position. Arbitrary location fails to satisfy the requirements. Do not support the split axis theory. No evidence found to believe that there is more than one hinge location.

38. Review of the literature Study was conducted by Vincent R. Trapazzan &John B. Lazzari in 1967. They concluded that the patient should be relaxed & two operators are required for location. Because of the presence of multiple hinge axis points, increasing or decreasing of the vertical dimension on the articulator needs new interocclusal record.

39. Review of the literature Study was conducted by Edwin R. Thorp , Dale E. Smith, & Jack I. Nicholls in 1978 . They compared 3 arbitrarily located axis to the true hinge axis locations. they concluded 57% of the arbitrary locations were within 6mm of the true hinge axis. The results revealed very small difference in accuracy between hinge axis face bow, Hanau –132 SM face bow& Whip mix face bow.

40. Review of the literature Study was conducted by Keki R. Kotwal in 1979. He made the casts of the dental arches of the skull & made interocclusal records, mounted the casts with & without face bow on to the Whip Mix articulator . He concluded that face bow transfer allows more accurate arc of closure on the articulator when the inter occlusal records are removed.

41. Review of the literature Study was conducted by F.M. WALKER in 1980. He concluded that arbitrary hinge axis location does not exist. Arbitrary axis locations recommended in the literature will create 6mm or more error. The true axis located inferior to tragus canthus line

42. Review of the literature Study was conducted by Mahmoud Khanics Abdel razek in1981 He located the arbitrary hinge axis by 5 methods in 120 dentulous patients & compared with true hinge axis location . He concluded that none of the methods was ideal, Dawson`s palpatory method is acceptable .

43. Review of the literature Study was conducted by Jhon H. Pitchford in 1991. He concluded that a compromised esthetic result can be produced by an anterior Reference point not in harmony with design of articulator. Minor variation of the face bow , position of orbitale pointer & indicator will allow an average value transfer of the esthetic reference position to an articulator

44. Review of the literature Study was conducted by William W. Nagy, Thomas J. Smithly & Carl G. Wirth in 2002 . More than 96% of the pre-determined points were within 2mm of the kinematic axis , 67% were within 1mm no significant difference between right & left side. They concluded that predetermined axis point was well within 5mm clinical norms for estimated location of transverse horizontal mandibular axis for the population studied.

45. Review of the literature   Study was conducted by Virgillo Ferrario , Chairello Sforza, Graziano Serrao & Johannes H. Schmitz in 2002 They assessed reliability of the postural face bow by comparing the values with those obtained by computerized non invasive instrument. They concluded that postural face bow reliably reproduced the spatial orientation of the occlusal plane relative to the true horizontal plane.

46. Face-bow Several things must be considered when transferring the mouth records of an edentulous patient to the articulator: the articulator, the face-bow , the tracing instrument for recording jaw relations, and the health of the gnathologic system .

47. Face-bow Definition:- The face-bow is a caliper-like instrument used to orient the maxillary cast on the articulator so that it has the same relationship to the opening axis that the maxilla has to the opening axis of the jaws. ( winkler )

48. Face-bow Definition :- The face-bow is a caliper like device that is used to record the relationship of jaws to the TMJ or the opening axis of jaws and to orient the casts in this same relationship to the opening axis of the articulator (Boucher)

49. Face-bow Definition :- Face bow is a caliper like device used to record the relationship of maxilla to the temporomandibularjoint .( Heartwell )

50. Face-bow Definition :- Caliper like instrument used to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer this relationship to an articulator; it orients the dental cast in the same relationship to the opening axis of the articulator. ( GPT-9)

51. Face-bow History of face-bow  In 1860 Bonwill concluded that the distance from the center of the condyles to the median incisal point of the lower teeth is 10 cm . 10 cm .

52. Face-bow History of face-bow   In 1866 Balkwell demonstrated an apparatus to measure the angle formed by the occlusal plane of lower teeth & the plane passing through the condyles & incisal plane of lower teeth.

53. Face-bow History of face-bow In 1880 Hayes constructed an apparatus called Caliper with median incisal point localized in relation to the two condyles .

54. Face-bow History of face-bow   In 1890 Walker invented Clinometer used to obtain the relative position of the lower cast in relation to the condylar mechanism

55. Face-bow History of face-bow In 1894 George K Bagby fabricated a device that determined the distance from the midline of the anterior occlusal rims to one of the condyles

56. Face-bow History of face-bow   At about a turn of a century Gysi developed an instrument similar to the face-bow primarily to records paths of the condyles and also used to transfer maxillary cast to articulator

57. Face-bow History of face-bow  1899 About the same time Snow introduced the snow face-bow. Majority of the face-bows used today are modifications of snow face-bow

58. Face-bow Principle of Face Bow Use The axis of opening of the articulator should be similar to the patient’s mandibular arc of movement when the prosthesis is fabricated with the help of articulators.  The mandibular cast is oriented to the maxillary cast, which in turn is oriented in the articulator. To accomplish this act of orientation, the face bow is used

59. Face-bow Classification There are two types of facebows : • Kinematic face bow which locates the true hinge axis • Arbitrary face bow, which locates the arbitrary hinge axis. These are of two types fascia type and earpiece type

60. Face-bow Classification  • Facebows that can be utilized with Hanau articulator Facia Ear piece Twirlbow Spring bow Kinematic • Facebows that can be utilized with Whipmix articulator Quick mount Ear piece Kinematic • Facebows that can be utilized with Denar articulator Facia Ear piece Slidematic and Kinematic

61. Face-bow Arbitraryn Type of Facebow Definition: A device used to relate the maxillary cast to the condylar elements of an articulator using average anatomic landmarks to estimate the position of the transverse horizontal axis on the face (GPT8). Also called ‘average axis facebow ’. It is the most commonly used face-bow in complete denture construction.

62. Face-bow Arbitraryn Type of Facebow This method generally locates the rods within 5 mm of the true hinge axis of the jaws. As this is an arbitrary hinge axis, errors in jaw relation may produce occlusal discrepancies . which should be corrected by minor occlusal adjustments during insertion..

63. Face-bow Arbitraryn Type of Facebow Ear piece type of face bow – This type of Face bow uses the external auditory meatus as an arbitrary reference point which is aligned with ear pieces.

64. Face-bow Arbitraryn Type of Facebow Facia type of face bow – the centre of condylar rotation is arbitrarily marked as 13 mm anterior to the middle of the tragus of the ear, on a line drawn from the outer canthus of the eye to the middle of the tragus of the ear – canthotragal line

65. Face-bow The kinematic- A facebow with adjustable caliper ends used to locate the transverse horizontal axis of the mandible (GPT8) kinematic- This face-bow is generally used for the fabrication of fixed partial denture and full-mouth rehabilitation. It is generally not used for complete denture fabrication because it requires a long and complex procedure to record the orientation jaw relation

66. Face-bow The kinematic- The kinematic is used to locate the true terminal hinge axis and transfer this record to the articulator when mounting the maxillary cast. It usually requires a fully adjustable articulator.

67. Face-bow The kinematic face bow allows for the precise determination of the patient's hinge axis (terminal hinge axis).

68. Face-bow 43 Hanau Spring Bow It is the most commonly used face-bow • Arbitrary earpiece type, arbitrary facia type and kinematic face-bows are also available from hanau • Reference points- posterior - Porion , the superior border of external auditory meatus anterior -Infra orbital notch • Plane of reference-Frankfort horizontal plane

69. Face-bow 43 Hanau Twirl Bow • It is an earpiece type of facebow It is not commonly used for CD construction • Allows the maxillary arch to be transferred to the articulator without physically attaching the face-bow to the articulator • Relates the maxillary arch to FH plane • A horizontal orbital pointer is attached to the right temple arm

70. Face-bow 43 Whip mix face bow • Ear piece type of face bow • It has a built in hinge axis locator. • Automatically locates the hinge axis when the ear pieces are placed in the external auditory meatus • Has a nasion relator assembly with aplastic nose piece

71. Face-bow 43 Quick Mount Facebow • It is an earpiece type of facebow • Used with whipmix articulator • Reference points- posterior : external auditory meatus anterior : nasion • Plane of reference-axis-orbital plane

72. Face-bow 43 Quick Mount Facebow • Made up of specially contoured ear pieces on the condylar ends of the bow • Consists of a scale that can measure intercondylar distance • Parts- Bow with plastic ear pieces Crossbar Facebow toggle assembly Nasion relator assembly with plastic nose piece

73. Face-bow 43 Slidematic Facebow • Type of ear piece facebow • Used with denar articulator • Reference points - posterior: external auditory meatus anterior: 43mm above incisal edge of right central incisor in dentulous patient or 43mm above the lower border of upper lip in edentulous patient • Reference plane : anterior reference point is selected so that occlusal plane will be positioned in the middle of articulator

74. Face-bow 43 Dentatus (1944, Sweden ) DENTATUS • It is a shaft type instrument. • The condylar element attached to the upper member & the condylar path is strraight . • The intercondylar distance is fixed. • The articulator received a hinge axis face-bow. • The features are similar to Hanau mode Accept static protrusive interocclusal records / registrations + Accepts a face-bow transfer –

75. Newer advancements Today there are more advanced techniques that make use of ultrasonic arcs, connected to computers with graphical representations and parameter calculations for programming the articulator.

76. Face-bow Parts of face-bow

77. Face-bow Parts of face-bow records the plane of the cranium U-shaped metal frame

78. Face-bow Parts of face-bow Ear piece type of facebow Facia type of facebow

79. Face-bow Parts of face-bow Orbital pointer with clamp

80. Face-bow Parts of face-bow Bite fork 3mm

81. Face-bow Parts of face-bow bite fork for dentulous patients

82. Face-bow Parts of face-bow 1 3 2 Locking device

83. Orbitale (B) Located by Hanau facebow with help of orbital pointer . Orbitale minus 7 mm. (C) This plane represents Frankfort plane. Nasion minus 23mm (A) Used with quick mount facebow (Whip mix ) Anterior Reference Point

84. Ala of nose (D) This plane represents campers plane 43 mm superior from lower border of upper lip / above incisal edges of right central incisors (Denar reference plane locator – Denar facebow uses this reference point ) Incisal edge plus articulator midpoint to articulator axis: Horizontal plane distance 6. Anterior Reference Point

85. Orbitale Orbitale is the lowest point of the infraorbital rim of skull which can be palpated on the patient through the overlying tissues and the skin. One orbitale and the two posterior points that determine the horizontal axis of rotation will define the axis – orbital plane.

86. Orbital Minus 7mm The Frankfort horizontal plane passes through both the poria and one orbital point. Because porion is a skeletal landmark, Sicher ’ recommended to use the midpoint of the upper border of the external auditory meatus as the posterior cranial landmark on a patient 7

87. Orbital Minus 7mm Gonzalez’ pointed out that this posterior tissue landmark on the average lies 7 mm superior to the horizontal axis. The recommended compensation for this discrepancy is to mark the anterior point of reference 7 mm below orbitale on the patient or to position the orbital pointer 7 mm above the orbital indicator of the articulator 7

88.  According to Sicher , another skull landmark, the Nasion can be approximately located in the head as the deepest part of the midline depression just below the level of eyebrows. The Nasion guide, or positioner , of the Quick-mount face- bow, which is designed to be used with the Whip-Mix articulator, fits into this depression. Nasion Minus 23mm

89. Crossbar is located 23 mm below the mid point of Nasion positioner . When the facebow is positioned anteriorly by nasion guide, the crossbar will be in approximate region of orbitale . So, crossbar is the actual anterior reference point locator Hence it also employs an approximate axis- orbitale plane. Nasion Minus 23mm

90. Alae Of the Nose In most of the conventional complete denture techniques it is imperative to make tentative or the actual occlusal plane parallel with the horizontal plane. This relationship can be achieved as a line from the ala of the nose to the center of the auditory meatus that describes Camper’s line .

91. Advantages of anterior reference point Determines which plane in the head will become the plane of reference. Determines the level at which the casts are mounted To establish a base line for comparative studies between patient. Can visualize anterior teeth & occlusion in the articulator in the same frame of reference.

92. 26 Posterior reference points Bergstrom’s point -. About 10 mm anterior to the center of the spherical insert for the external auditory meatus and 7 mm below the Frankfort horizontal plane. Bergstrom point is found to be the most frequently closest to the hinge axis, and Beyron point is the next most accurate posterior point of reference FH

93. 26 Posterior reference points Beyron’s point - A point 13mm anterior to the posterior margin of tragus of the ear on a line from centre of the tragus to the outer canthus of eye. FH

94. 26 Posterior reference points Gysi point - Gysi placed it 11–13 mm anterior to the upper third of the tragus of the ear on a line extending from the upper margin of the external auditory meatus to the outer canthus of the eye.

95. 26 Posterior reference points Lundeens point- 13mm anterior of tragus on line joining base of tragus to outer canthus of eye.  

96. 26 Posterior reference points Simpson’s point About 11 mm anterior to the superior border of tragus on Camper’s line

97. 26 Posterior reference points Denar’ s – 12 mm anteriror to posterior border of tragus and 5 mm inferior to line from EOM and outer canthus

98. Face-bow record Accurate mounting - three points Criteria for selection of points Ease of location Convenience Reproducibility

99. Taking a face bow record

100. Taking a face bow record

101. Taking a face bow record

102. Taking a face bow record

103. Taking a face bow record

104. Mounting Articulator Direct Method Indirect Method

105. Direct mounting

106. Direct mounting

107. Direct mounting

108. Indirect mounting After the direct transfer had been completed, the spring-bow was unscrewed from the transfer assembly. The mounting platform was secured on the lower member by the cast support. The transfer assembly was secured onto the mounting platform, and the cast support was raised to support the bitefork index following which the maxillary cast was mounted.

109. Indirect mounting The mandibular casts were then mounted using maximum intercuspation Alu wax record for both direct and indirect transfers. A single protrusive record for each subject was made in Alu wax to program the directly and indirectly transferred casts.

110. 54 Advantages of using face bow “ Lazzari ” It aids in securing the antero-posterior cast position with relation to condyles of the mandible. It acts as an aid in the vertical positioning of the cast on the articulator. It assists in correctly transferring the inclination of the occlusal plane to the articulator .

111. 40 Errors in face bow recording Movement of the skin Unstable edentulous ridges Angle of opening is small – 10º--12º Inter-observer error

112. A definite cusp fossa or cusp tip to tip incline relation is desired. When interocclusal check records are used for verification of jaw positions. When the occlusal vertical dimension is subjected to change, and alterations of tooth occlusal surfaces are necessary to accommodate the change. To diagnose existing occlusion in patients mouth Indications for use of face-bow

113. 55 Situations where face bow is not required Monoplane teeth are arranged in balance occlusion and mandible in most retruded position at acceptable VD No intended change in VDO the articulators developed not to receive facebow transfer

114. Concepts &Review of literature

115. Concepts &Review of literature Stansberry (1928) was dubious about the value of facebow and adjustable articulators . He thought that since an opening movement about the hinge axis took the teeth out of contact the use of these instruments was ineffective except for the arrangement of the teeth in centric occlusion.

116. Mclean (1937) stated that the hinge portion of the joint is the great equalizer for disharmonies between the gnathodynamic factors of occlusion . When occlusion is synthesized on articulator without accurate hinge axis orientation , there may be minor cuspal conflicts, which must be removed by selective spot grinding. Concepts &Review of literature

117. Kurth LE, Feinstein IK (1951) with aid of articulator and working model , demonstrated that more than one point may serve as a hinge axis and concluded that an infinite number of points exist which may serve as hinge points. Concepts &Review of literature

118. Craddock and Symmons (1952) considered that the accurate determination of the hinge axis was only of academic interest since it would never be found to be more than a few millimeters distance form the assumed center in the condyle it self . Concepts &Review of literature

119. Sloane ( 1952) stated “ the mandibular axis is not a theoretical assumption, but a definite demonstrable biomechanical fact. It is an axis upon which the mandible rotates in an opening and closing function when comfortably, not forcibly retruded. Concepts &Review of literature

120. Bandrup-Morgsen (1953) , discussed the theory and history of face bows . He quoted the work of Beyron who had demonstrated that the axis of movement of the mandible did not always pass through the centers of the condyles . They concluded that complicated forms of registration were rarely necessary for practical work. Concepts &Review of literature

121. Lazarri (1955) gave application of Hanau model ”c” facebow. Concepts &Review of literature

122. Sicher (1956) stated “the hinge position or terminal hinge position is that position of the mandible from which or in which pure hinge movement of a variable wide range is possible” Concepts &Review of literature

123. Robert.G.Schallhorn (1957), (studying the arbitrary center and kinematic center of the mandibular condyle for face bow mountings . He concluded that using the arbitrary axis for face bow mountings on a semiadjustable articulator is justified . He said that, in over 95% of the subjects the kinematic center lies within a radius of 5 mm from the arbitrary center. Concepts &Review of literature

124. Brekke (1959) in reference to a single intercondylar transverse axis stated “unfortunately this optimum condition does not prevail in mandibular apparatus, which is symmetric in shape and size, and has its condyloid process joined at the symphysis, with no connection directly at the condyles. The assumption of a single intercondylar transverse axis is, therefore open to serious question”. Concepts &Review of literature

125. Christiansen RL (1959) studied the rationale of facebow in maxillary cast mounting and concluded that it is advantageous to simulate on the articulator the anatomic relationship of the residual ridges to the condyles for more harmoniously occluding complete dentures. Concepts &Review of literature

126. Weinberg ( 1961 ) evaluated the facebow mounting and stated that a deviations from the hinge axis of 5mm will result in an anteroposterior displacement error of 0.2 mm at the second molar. Concepts &Review of literature

127. Lucia VO (1964 ) described the technique for recording centric relation with help of anterior programming device. Concepts &Review of literature

128. Teteruck and Lundeen (1966) ,evaluated the accuracy of the earpiece face bow and concluded that only 33% of the conventional axis locations were within 6 mm of true hinge axis as 56.4% located by ear face- bow . They also recommended the use of earpiece bow for its accuracy, speed of handling, and simplicity of orienting the maxillary cast. Concepts &Review of literature

129. Trapazazano, Lazzari (1967) concluded that, since multiple condylar hinge axis points were located, the high degree of infallibility attributed to hinge axis points may be seriously questioned. Concepts &Review of literature

130. Thorp, Smith , and Nicholis (1978), evaluated the use of face bow in complete denture occlusion . Their study revealed very small differences between a hinge axis face bow Hanau 132-sm face bow, and whip mix ear- bow. Concepts &Review of literature

131. Neol D.Wilkie (1979) analyzed and discussed five commonly used anterior points of reference for a face bow transfer . He said that not utilizing a third point of reference may result in an unnatural appearance in the final prosthesis and even damage to the supporting tissue . He suggests the use of the axis–oribitale plane because of the ease of making and locating orbitale and therefore the concept is easy to teach and understand. Concepts &Review of literature

132. Concepts &Review of literature Stade E et al(1982) (38) evaluated esthetic consideration in the use of facebow .

133. Concepts &Review of literature Palik J.F et al(1985) (39) concluded in his study on the accuracy of earpiece facebow that regardless of any arbitrary position chosen, a minimum error of 5mm from the axis can be expected

134. Conclusion Failure to use the facebow leads to error in occlusion. Hinge axis forms a major component of every masticatory movement of the mandible and therefore cannot be disregarded that hinge axis should be accurately captured and transferred to the articulator, so that it becomes a fine representative of the patient and biologically acceptable restoration is possible. Thus, the use of facebow should form a integral part of one prosthodontic treatment.

135. References Boucher's Prosthodontic treatment for edentulous patient 10th edition. Essentials of complete Denture Prosthodontics by Sheldon Winkler-2nd edition. Syllabus of complete dentures by Charles M. Heartwell 4th edition 5th edition. RangaRajan text book of prosthodontics Deepak Nallaswami text book of prosthodontics