Hobos Dentistry Prevention and Philosophy

Hobos Philosophy
Dentistry

1. Full Mouth Rehabilitation – Hobo’s Philosophy Dr. Divya Mehra

2. Contents Introduction Terminologies Definition – Full Mouth Rehabilitation Indications for Full Mouth Rehabilitation Analysis of Occlusion Disocclusion Necessity For Disocclusion Classification of Occlusal Rehabilitation Twin Table Twin Stage Conclusion References 2

3. Introduction – Dr. Sumiya Hobo Dr. Hobo was one of the pioneers of modern dentistry in Japan A graduate of Nihon University School of Dentistry in 1961. He attended graduate school at the Indiana University School of Dentistry, specializing in Fixed Prosthodontics. In 1972, he returned to Japan to open his International Dental Academy in Tokyo as well as one of the outstanding Laboratory Technician Schools in the World. 3

4. Dr. Hobo along with Peter K. Thomas introduced the concept of Gnathology to Japan He authored the text “Fundamentals of Fixed Prostheses” for Quintessence as well as the “Encyclopedia of Occlusion,” He retired from active teaching several years ago and passed away at the age of 69 4

5. Introduction The goal of dentistry is to increase the life span of the functioning dentition In striving to achieve its goal, dentistry uses its knowledge, skill and all the resources at its command in both maintenance work and rehabilitation The phrase full-mouth rehabilitation means different things to different people. 5

6. The aim is to provide an orderly pattern of occlusal contact and articulation that will optimize oral function, occlusal stability and esthetics. Planning and executing the restorative rehabilitation of a decimated occlusion is probably one of the most intellectually and technically demanding tasks facing a restorative dentist. 6 Introduction

7. A better understanding of the scientific principles underlying our techniques will inevitably improve those techniques, since it focuses attention on the goal and thus provides a criterion for evaluating our procedures 7 Introduction

8. Terminologies Condylar Guidance : Mandibular guidance generated by the condyle and the articular disc traversing the contours of the glenoid fossa Anterior Guidance : Incisal Guidance + Canine Guidance Incisal Guidance - During Protrusive movement Canine Guidance - During Lateral Guidance Incisal Guidance : The influence of the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements

9. Terminologies Bennet Angle: The angle formed between the sagittal plane and the average path of the advancing condyle as viewed in the horizontal plane during lateral mandibular movements Immediate mandibular lateral translation: The translatory portion of the lateral movement in which the non – working side of the condyle moves essentially straight and medially as it leaves the centric relation position Laterotrusion : Condylar movemnt on the working side in the horizontal plane

10. Full Mouth Rehabilitation - Definition Full mouth rehabilitation entails the performance of all the procedures necessary to produce healthy, esthetic, well functioning, and self maintaining masticatory mechanism. 10

11. INDICATIONS Full Mouth Rehabilitation The restoration of multiple teeth, which are missing, worn, broken-down or decayed. To replace improperly designed and executed crown and bridge work . Treatment of temporomandibular disorders may also be considered an indication for rehabilitation, but great caution is advisable in such cases. 11

12. Goal .. The following goals should be achieved when planning for an occlusal rehabilitation: Static coordinated occlusal contact of the maximum number of teeth when the condyle is in comfortable, reproducible position. An anterior guidance that is in harmony with function in lateral eccentric position on the working side. Disclusion by the anterior guidance of all posterior teeth in eccentric movements. Axial loading of teeth in centric relation, interproximation , and function.

13. Regardless of the clinical reason, the decision to carry out any treatment should be based upon achieving Oral Health, Function, Esthetics And Comfort, and treatment should be planned around these rather than the technical possibilities. 13

14. Analysis of the Occlusion The First step is :

15. Analysis of Occlusion When undertaking relatively small amounts of restorative treatment, for example : up to 2 or 3 units of crown and bridge work, it is often acceptable, and advisable to adopt a confirmative approach - that is to construct the restoration to conform to the patient's existing intercuspal position INTERCUSPAL POSITION 15

16. Analysis of Occlusion The alternative strategy is to re-organize the occlusion by establishing a new occlusal scheme around a stable condylar position. The decision to re-organize a patient's occlusion may be made on the grounds that : Either the existing IP is unacceptable and needs to be changed, or Where a very large amount of treatment is to be undertaken and the operator has the opportunity to optimize patient's occlusion. The condylar position usually chosen is termed 'centric relation' (CR). 16

17. The decision should be made after a detailed and careful examination of the occlusion, preferably with the use of accurate study casts mounted in a semi adjustable articulator in the retruded arc of closure. 17 Analysis of Occlusion

18. When do we Need to Reorganize Occlusion ? Reorganization may be considered when the existing intercuspal position is considered unsatisfactory for any of the following reasons: Repeated fracture or failure of teeth or restorations : Bruxism Lack of interocclusal space for restoration Unacceptable Function Unacceptable esthetics 18

19. When do we Need to Reorganize Occlusion ? Repeated fracture or failure of teeth or restorations : Clinical experience suggests that persistently failing restorations ( for example crown and bridge debonding ) are very commonly attributed to unfavorable occlusal loading which may be improved by reorganization. 19

20. Bruxism : An optimally constructed occlusion will better be able to deal with the forces generated in parafunction . 20 When do we Need to Reorganize Occlusion ?

21. Lack of interocclusal space for restoration : Re- organising the occlusion to eliminate a large horizontal component of slide between CR and IP can create a valuable interocclusal space for the restoration of worn anterior teeth. 21 When do we Need to Reorganize Occlusion ?

22. Unacceptable Function : Poor tooth to tooth contact with tilting and supraeruption of teeth may create problems with masticatory function, particularly when large number of teeth have been lost. 22 When do we Need to Reorganize Occlusion ?

23. Unacceptable esthetics : Alteration in the clinical crown height may necessitate improving esthetics. This may be made possible by constructing the restorations to a reorganised occlusion, possibly at an increased vertical dimension. 23 When do we Need to Reorganize Occlusion ?

24. So Many Indications …. 24

25. Functional Analysis of Occlusion It includes : The determination of the proper vertical height by utilizing the physiologic rest position of the mandible as a guide, and noting the existing functional freeway space. 25

26. An examination and study of the path of closure from rest position to the physical contact position of the teeth , noting whether condyle displacement occurs. 26 Functional Analysis of Occlusion

27. The effects of the occlusal pattern upon the periodontal structures. A study of the temporomandibular joint positions relative to the occlusal pattern by means of roentgenographic evaluation. 27 Functional Analysis of Occlusion

28. Check for Disocclusion DISOCCLUSION It is the separation of opposing teeth during eccentric movement of the mandible – GPT 8. 28

29. Necessity for Disocclusion Molar disocclusion during eccentric movements is effective in eliminating harmful lateral occlusal forces. Mechanically, the maxillary and mandibular teeth should be in contact during eccentric movements for optimal chewing efficiency. Maximal shear force is observed with a fully balanced occlusion 29

30. However, the condyle must follow one orbit precisely during eccentric movements for optimal function in a fully balanced occlusion. If the condyle deviates slightly, it directly influences the relation between the teeth, resulting in occlusal prematurities and deflective occlusal contacts 30 Necessity for Disocclusion

31. When the mandible is protruded, the only teeth in contact should be the anterior teeth. This is so because when the mandible is protruded the condyles are no longer braced. Since the amount of flexing of the mandible depends on varying degrees of contraction of the closing musculature, there is no way to harmonize the posterior teeth to all the different degrees of muscle force. 31 Necessity for Disocclusion

32. The anterior teeth, being farthest from the fulcrum and not nearly so subject to the flexing, and are in the best position to carry the load. Protrusive stresses on posterior teeth are further compounded by the fact that such forces are usually directed toward inclines of the upper cusps as the wider part or the lower arch moves forward into the narrower part of the upper arch. 32 Necessity for Disocclusion

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34. How Much Is Good Enough !! AMOUNT Disocclusion

35. AMOUNT of Disocclusion There is minimal literature available regarding the proper amount of disocclusion . Shooshan (1960) and Scot (1964) stated that during lateral, movement, the molars should disocclude more than 0.5 mm between maxillary and mandibular posterior teeth on the nonworking side. 35

36. Thomas (1967) stated when maxillary and mandibular cuspid has tip to tip relation during lateral movement; the molars should disocclude 1.0 mm. 36 AMOUNT of Disocclusion

37. Hobo and Takayama (1985, 93) experimentally measured the amount of disocclusion using various methods and they concluded that the amount of disocclusion found, with various techniques was : 37 AMOUNT of Disocclusion

38. Factors Influencing Disocclusion 38

39. The Condylar Path

40. The Condylar Path The Condylar path is described by GPT as : Path traveled by the mandibular condyle in the temporomandibular joint during various mandibular movements. McCollum and Stuart described the condylar path as a fixed entity in an adult. 40

41. Buffer space However recent studies show when repetitive lateral movements were compared with the respective condylar paths, no movement traced the same line. The deviation in the condylar path during eccentric movements was attributed to the shock-absorbing nature of the articular disk. This study refers to this deviation in condylar path as a "buffer space" 41

42. Eg : Accurately Machined Gears Immobile when the gears are too close and tight A little spacing is needed to allow the gears to function smoothly Buffer spacing is essential for the condyle and the disc to function smoothly Buffer space

43. The average buffer spaces are 0.2 mm in centric relation, 0.3 mm in laterotrusion , and 0.8 mm along the protrusive and nonworking sagittal condylar path. Molar disclusion should be greater than the buffer space to avoid occlusal interferences during eccentric movements. When the average amount of disclusion is compared with buffer space, the amounts closely match. 43 Buffer space

44. The amount of disclusion should be slightly more than the buffer space to prevent deflective occlusal contacts providing separation between the opposing posterior dentition, so that when the condyle is displaced during articular disk compression, harmful occlusal forces can be controlled. 44 Buffer space

45. The difference between Eccentric and Returning Condylar Paths . In a study done by Hobo and Takayama , it was found that there was a difference between the between eccentric and returning condylar paths It was seen that the returning condylar path always passed above the eccentric path graphically, when the lines were drawn there was a difference of 13° with the protrusive path and 23° with lateral movement. The possible reasoning behind this deviation is that these paths are created by physiologic difference in the opening and the closing muscles utilized. 45

46. Why did we have to know This ?? In dentistry, the condylar path has been considered the standard reference for occlusion. However, the above results showed the condylar path was not fixed but was changeable. 50

47. Influence of the Condylar Path on Disocclusion When condyle moved 3mm – the amount of disocclusion is 1mm. So, the influence of the condylar path on disocclusion is – During protrusive movement – 0.02mm / degree During lateral movement : 0.015 mm / degree – non-working side 0.002 mm / degree - on the working side. 51

48. Influence of the Condylar Path on Disocclusion Now, also there is deviation in the condylar paths caused by the difference between the eccentric and returning paths. This difference is 13 degrees for protrusive and 23 degrees during lateral movement. So, this makes a total disocclusion , under the influence of the condylar path to be During protrusive - 0.26mm. During lateral - Working side- -0.05mm. Non – working side – 0.35 mm. Based on this, it was concluded that although the deviation of the condylar path is large, its influence on the amount disocclusion is small. 52

49. So, Condylar Path Cannot be the Sole Guiding Factor in order to Establish Good Occlusion.

50. The Anterior Guidance

51. The Anterior Guidance Early gnathological concepts focussed primarily on the condylar path They believed that the anterior guidance had no influence on the condylar path And that both were independent factors. 55

52. The Anterior Guidance To verify – Studies were conducted to record the condylar path under 2 test conditions: With tooth contact Without tooth contact – using a clutch Conclusion : Condylar path was affected by the anterior guidance More on the working side condyle, min on the non-working condyle. 56

53. Hence : Condylar Guidance and Incisal Guidance were DEPENDENT and not Independent factors 57 The Anterior Guidance

54. During No – Tooth contact : The working condyle showed a tendency to move straight laterally along the transverse horizontal axis – LATEROTRUSION On an Average – in healthy TMJs, condylar guidance is in accordance with anterior guidance 58 The Anterior Guidance

55. This Straight Axis on which the condyle travelled was called as the “Neutral Line” Hobo and Takayama conducted a study with tooth contact during lateral movement 59 The Anterior Guidance

56. The study concluded that the working condyle deviated inferiorly- below the neutral axis when the actual incisal path is steeper – DETRUSION The working condyle deviate superiorly – above the neutral axis when the actual incisal path was flatter – SURTRUSION 60

57. Why did we have to know This ?? The anterior guidance influences the condylar path, which infers the condylar path is influenced by the patient's occlusion. Therefore, if patient has poor occlusion, his condylar path is affected by malocclusion. If such a condylar path is measured precisely, reproduced on an articulator, and used as a reference for the fabrication of a restoration, the occlusion of the restoration can be adversely affected by the poor condylar path The condylar path on an articulator should not be a copy of the condylar path in the patient. To avoid a vicious cycle, set the condylar paths on an articulator to produce a "good" occlusion. 61

58. Influence of the Incisal Path on Disocclusion The influence of the incisal path on disocclusion is : During protrusive – 0.038 / degree During eccentric movement : 0.042 mm / degree - on non-working side. 0.039 mm / degree - on the working side. 62

59. Now, also there is deviation in the incisal path on protrusive and lateral movements. This difference is 10 degrees for both So, this makes a total disooclusion , under the influence of the incisal path to be – During protrusive - 0.38 mm. During lateral - Working side - 0.38 mm. Non – working side – 0.42 mm. Based on this, it was concluded that although the influence of incisal path on disocclusion was larger than the condylar path influence but it still could not be used as the sole guiding factor for occlusion. 63 Influence of the Incisal Path on Disocclusion

60. Cusp Shape Factor

61. Cusp Shape Factor / Cuspal Angulation Cusp Angle is "The angle made by the average slope of a cusp with the cusp plane measured mesiodistally or buccolingually " The Cusp Plane means : “the plane determined by the two buccal cusp tips and the highest lingual cusp of a molar”. The angle formed by the average cusp slope and the horizontal reference plane is called the Effective Cusp Angle 65

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63. The effective cusp angle during protrusive movement is referred to as the Sagittal Protrusive Effective Cusp Angle . The effective cusp angle during lateral movement on the working and nonworking side are referred to as the Frontal Lateral Effective Cusp Angle On The Working And Nonworking Side 67 Cuspal Angulation

64. For posterior disocclusion to occur – the slopes of the molar cusp must be parallel to condylar path and the Anterior guidance must be steeper than the condylar path If the posterior cusps are kept parallel to the anterior guidance – there will not be posterior disocclusion – even if the anterior guidance is steeper. 68 Cuspal Angulation

65. Cusp Shape Factor The shape of the cusp has great influence on the disocclusion of the posterior teeth If a balanced occlusion is to be achieved – it is necessary to make the cusp with a straight edge – Greater cuspal inclination If disocclusion is to be achieved – make cusps with a convex semicircular shape of the slope – Cuspal Inclination decreases

66. Influence of the Cusp Angle on Disocclusion The studies proved that the cusp angle did not show any deviations as they were seen in the case of the incisal and the condylar path. Amount of decrease in disocclusion During protrusive – 0.46 mm / degree increase During lateral : Working side - 0.041mm / degree increase. Non – working side – 0.46 mm / degree increase. All the above calculations proved that the influence of cusp angle is 40% - 44% of the total influence which is far greater than condylar path but comparable to incisal path. 70

67. Influence on disocclusion Influence 71

68. Since the influence of the cusp angle is more reliable than the other factors it was concluded that the new reference for occlusion should be the cusp angle of newly erupted permanent teeth not the condylar or incisal path 72 Influence on disocclusion

69. How disocclusion is achieved ??? Using protrusive movement as an example the reasons which necessitate disocclusion can be understood : 73

70. Scenario I When The sagittal condylar path inclination is 40 degrees, The cusp angle is parallel to the condylar path, and also The incisal path equal to the condylar path. Mandible only translates and does not rotate. Since the mandibular and maxillary molars slide in contact in eccentric movement, there is No Disocclusion . 74

71. Cusp angle = Condylar path = Incisal path 75

72. S cenario II When The sagital condylar path inclination is 40 degrees, The cusp angle is parallel to the condylar path, but The incisal path is steeper than the condylar path. Mandible translates and ROTATES. Maxillary and mandibular molars DISOCCLUDE. referred as “Anterior Guide Component” 76

73. Condylar path = Cusp angle Incisal path 77

74. Scenario III When The sagittal inclination of the condyle is 40 degrees, The condyle and the incisal path are parallel, however The cusp angle is shallower than the condylar path. Mandible only translates. Since the cusp angle is shallower, the maxillary and mandibular molars DISOCCLUDE Referred as “Cusp Shape Component” 78

75. Condylar path = Incisal path Cusp angle 79

76. Scenario IV When The sagittal inclination of the condyle is 40 degrees, The incisal path is steeper than the condylar path, and The cusp angle is shallower than the condylar path. Mandible translates and rotates. Disocclusion is wider and is seen in healthy individuals. 80

77. Cusp angle < Condylar path < Incisal path 81

78. Classification of Occlusal Rehabilitation 82

79. Occlusal Rehabilitation There are four types of occlusal rehabilitation and situations, and each requires a different type of treatment 83

80. Type I The curve of Spee (occlusal curvature of the posterior teeth) and the incisal guidance are acceptable as presented by the patient, but The Posterior Teeth Need Rehabilitation. 84

81. Type II The curve of Spee is irregular , but the incisal guidance is acceptable. 85

82. Type III The curve of Spee and the incisal guidance are both unacceptable. 86

83. The curve of Spee and the incisal guidance are not acceptable, and The Upper and Lower Anterior Teeth Need Rehabilitation. The restoration of upper posterior teeth with the use of the functionally generated path technique 87

84. Hobo’s Twin Table Technique 88

85. Concept Hobo’s Twin Table Technique Anterior guidance is crucial in human occlusion because it influences molar disclusion that controls horizontal forces. Molar disclusion is determined by : A Cusp Shape Factor Angle of hinge rotation. 89

86. Angle of Hinge Rotation

87. Angle of Hinge Rotation Posterior disocclusion occurs when anterior guidance is steeper than the condylar path. Mandible TRANSLATES and ROTATES.

88. Angle of Hinge Rotation This rotation of the condyle compensates for the difference in the steepness of the anterior and the condylar path This is referred to as the Angle Of Hinge Rotation

89. Contribution to Disocclusion Angle of Hinge Rotation Posterior disocclusion during : Protrusion : 0.2 mm Lateral Movement Working/Non-working sides – 0.5 mm

90. Degree Of Disocclusion Measured Value Angle of hinge Rotation Cusp Shape factor (mm) Protrusive 1.1 0.2 0.9 Working 0.5 0.5 Non-Working 1.0 0.5 0.5 94

91. This new technique develops anterior guidance to create a predetermined, harmonious disclusion with the condylar path. One incisal table is used to incorporate a cusp-shape factor and the other is used for the angle of hinge rotation. This method does not require special equipment and is an uncomplicated procedure suitable for daily practice. 95 Concept Hobo’s Twin Table Technique

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93. Selection of the Articulator Two Types : Semi - adjustable Fully – adjustable Semi-adjustable creates only a straight condylar path Fully-adjustable develops a curvature Because a condylar path with a curve is more accurate and reflects a reliable anterior guidance, Fully-adjustable is preferred.

94. Selection of the Articulator These articulators duplicate the working condylar path in different ways : Semi-adjustable – Only develops a straight outward path - Sagittal deviation cannot be adjusted Fully-adjustable – reproduces the sagittal deviation

95. Selection of the Articulator In Hobo’s Twin Table Technique – the working condyle is set on the articulator tom move directly outward on the transverse horizontal axis. Hence – a Semi-adjustable Arcon Articulator With A Box-Shaped Fossa Element Is Sufficient

96. Recap Twin –Table Technique

97. Study Casts are made PROCEDURE 101

98. 102 Face Bow Transfer and IOR made PROCEDURE

99. Study Casts with Removable Anterior Segment 103 Anterior segment removed to eliminate the effects of existing anterior guidance

100. Eccentric Movements 104 Articulator is moved through eccentric movements to eliminate interferences that impede an even, gliding motion. This procedure results in a cusp-shape factor that harmonizes with the condylar path.

101. Cusp Shape Factor Incorporated 105 Areas where the tooth does not contact with the opposing occlusal surface – wax is added until it contacts evenly. The missing teeth or tooth structure spaces are replaced with wax Once the maxillary and mandibular casts interdigitate evenly during eccentric movement, it means the cusp is now parallel to the condylar path. The cusp shape factor has been harmoniously incorporated

102. Incisal Table without Disocclusion 106

103. 107 Incisal Table without Disocclusion If anterior guidance is organized according to this table – fully balanced occlusion will result

104. Incisal Table with Disocclusion

105. 109 Incisal Table with Disocclusion

106. Incisal Table with Disocclusion

107. Incisal Table with Disocclusion

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112. Tooth Preparation

113. Impressions made

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123. Advantages Can be used for a variety of prosthetic procedures Full mouth rehab Posterior quadrant restorations Anterior restorations Relatively uncomplicated Does not require any special equipment Final prosthesis results in a restoration with predictable posterior disclusion and anterior guidance in harmony with condylar path Hobo’s Twin Table Technique

124. Hobo’s Twin STAGE Technique 129

125. Although condylar path has been regarded as the main determinant for occlusion, it has been found to show deviations. Also, it has minimal influence on disocclusion Incisal Path – Less deviation than condylar path Influences disocclusion (at the 2 nd molar) – Twice as much as that of condylar path during protrusive 3 times on the Non-working side 4 times on the Working side (Lateral Movement) Hobo’s Twin STAGE Technique 130

126. Influence on disocclusion Influence 131

127. Cusp Angle – Independent from both condylar path and incisal path. Since there are minimal variations in cusp morphology of permanent teeth immediately after eruption, and If the value of the cusp angle at the time of eruption is used as a reference for occlusion, making a restoration following this guide should be ideal for the patient Standard Value of Cusp Angle 132

128. To establish a new reference for occlusion , it is necessary to define a standard value for cusp angle To obtain this – The measured amount of disocclusion was the only reliable data available. Using this data – standard cusp angle values were calculated 133 Standard Value of Cusp Angle

129. Therefore the Calculated Standard Cusp Angle is : 134 Standard Value of Cusp Angle

130. 135

131. These adjustment values are effective only when the Axis Plane is used as reference and requires a facebow transfer. When a different horizontal reference plane is used, a new computation is necessary to obtain different adjustment values. 136

132. Twin Stage Procedure In the Twin-Stage procedure, a standard cusp angle is created on a restoration . The incisal path (anterior guidance) for obtaining the standard amount of disclusion is then computed based on the mathematical model of mandibular movement. Thus, by using the standard cusp angle as the main determinant, it is possible to establish the standard amount of disclusion. The anterior guidance created in this manner may control the condylar path, since the condylar path is influenced by the anterior guidance.

133. Basic Concept Hobo’s Twin Stage Technique To create a standard cusp angle on the restoration, on articulator is mandatory The adjustment value of the articulator used to create the standard cusp angle was called "Condition 1." The adjustment value used to create anterior guidance was called "Condition 2." These articulator adjustment values were determined by computation. 138

134. Basic Concept Hobo’s Twin Stage Technique In order to provide disocclusion , the cusp angle should be shallower than the condylar path. To eliminate the effect of the anterior teeth while waxing up the posterior to create shallower cuspal angles – removable anterior segment is fabricated The cast with a removable anterior segment is fabricated. First, reproduce the occlusal morphology of posterior teeth without the anterior segment and produce a cusp angle coincident with the standard values of effective cusp angle (referred to as "Condition 1 " ) 139

135. Basic Concept Hobo’s Twin Stage Technique Secondly, Reproduce anterior morphology with the anterior segment and provide anterior guidance which produces a standard amount of disocclusion (referred to as " Condition 2" ) This is named the "twin-stage procedure." 140

136. Adjusting Values on the Articulator The standard value of sagittal protrusive effective cusp angle is 25° To obtain this cusp angle – Various combinations of Condylar path angulation and anterior guide table are possible 141

137. Adjusting Values on the Articulator The SIMPLEST combination is – adjust Sagittal condylar path - 25° Anterior guide table - 25° Wax the occlusal morphology to produce a balanced articulation. This will result in a cusp angle of 25 ° 142

138. Adjusting Values on the Articulator Other combinations : Sagittal condylar path - 10° (too shallow) Anterior guide table - 30° (too steep) OR Sagittal condylar path - 40° (too steep) Anterior guide table - 20° (too shallow) A 25 ° cusp angle can be obtained at the 1 st molar 143

139. Adjusting Values on the Articulator 144 Articulator Adjustment To Achieve The Standard Cusp Angle

140. Whats Recommended ???? If the adjustment values of the condylar path and the incisal guide table are not kept the same – a 25- degree cusp angle will be obtained only at the 1 st molar When both kept the same - 25- degree cusp angle created on each cusp of posterior teeth Hence , recommended !! This is the adjustment value for the articulator to achieve Condition 1 145

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142. Adjusting for Generating Disocclusion After waxing the cusp angle to standard value , the anterior guidance should be established to produce the standard disocclusion Again, infinite combinations of condylar path and incisal guide table are possible. Recommended combination : Condylar path – 40° Incisal Guide table - 45 ° 147

143. Adjusting for Generating Disocclusion This combination will result in a Standard amount of disocclusionon molars A physiological Anterior Guidance This is the articulator adjustment for Condition 2 148

144. Adjusting for Generating Disocclusion Other Combinations :

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146. Fabrication of Each Occlusal Scheme Since the standard cusp angles were used as the main determinant of occlusion, the measurement of the Condylar path was not necessary, and the tooth contact condition during eccentric movements was controlled precisely by every selected occlusal scheme. 151

147. Fabrication of Each Occlusal Scheme To reproduce the amount of disclusion for each occlusion scheme, different adjustment values of an articulator were required . The different occlusal schemes include : Mutually Protected Group Function Balanced occlusion 152

148. Fabrication of Each Occlusal Scheme Mutually Protected Occlusal Scheme : Most suitable for natural dentition 153 Condylar path inclination Bennett Angle Anterior guide table sagittal Inclination LateraL Wing Condition 1 25 15 25 10 Condition 2 40 15 45 20

149. Fabrication of Each Occlusal Scheme Group Function Occlusal Scheme : Indicated when canine guidance is absent as a result of the loss of a canine. To create group function, articulator adjustment values for "Condition 2" must be modified. In group function, the amount of disclusion on the working side during lateral movement must be zero. This can be achieved by changing the lateral wing angle of the anterior guide table tor Condition 2 from 20 to 0 degrees. The amount of disclusion on the nonworking side becomes 0.5 mm 154

150. Fabrication of Each Occlusal Scheme Group Function Occlusal Scheme : To create group function, articulator adjustment values for "Condition 2" must be modified. The amount of disclusion on the working side during lateral movement must be zero. 155 Condylar path inclination Bennett Angle Anterior guide table sagittal Inclination Lateral Wing Condition 1 25 15 25 10 Condition 2 40 15 45

151. Fabrication of Each Occlusal Scheme Balanced Occlusion : Recommended for complete dentures. To create this articulation Condition 1 should be used to produce both the cusp angle and anterior guidance. 156 Condylar path inclination Bennett Angle Anterior guide table sagittal Inclination Lateral Wing Condition 1 25 15 25 10 Condition 2 25 15 25 10

152. Physiological Discrepancy 157 The sagittal condylar path distributes + 14 degrees (SD) from the mean value (40 degrees).

153. If the sagittal condylar path of the patient is steeper than the articulator adjustment value (40 degrees), this difference is harmless because the amount of disclusion increases. On the contrary, if the condylar path in the patient is shallower than 40 degrees , the amount of disclusion decreases to some extent. The sagittal condylar path distributes + 14 degrees (SD) from the mean value (40 degrees). 158 Physiological Discrepancy

154. Within this limit, the lowest value of an eccentric condylar path (26 degrees) is almost equal to the mean of the returning condylar path , so the discrepancy must be harmless. However, when the returning condylar path is much shallower than its mean, cuspal interferences MAY occur 159 Physiological Discrepancy

155. When the condylar path of a patient is 16 degrees , there is no disocclusion , and maxillary and mandibular cusps slide in contact evenly. Accordingly, when the condylar path becomes shallower than 16 degrees , cuspal interferences WILL occur. 160 Physiological Discrepancy

156. Facebow transfer Step-wise procedure 161

157. Mock Up 163

158. Tooth Preparation 164

159. 165 Mounting of master casts with removable anterior segment

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161. Establish the Cusp Angle – Condition 1 167

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163. Wax up the anterior teeth – Condition 2 169

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165. Metal Try in 171

166. Ceramic Build-up 172

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168. Completed Ceramic Build-up 174

169. Finished Restoration 175

170. Twin Stage vs Twin Table The Twin-Stage Procedure was developed as the advanced version of the Twin-Table Technique. The Twin-Table Technique has several disadvantages compared to the Twin-Stage Procedure.

171. Twin Stage vs Twin Table The Twin-Table technique – Disadvantages The cusp angle was fabricated parallel to the measured condylar path, and the cusp angle became too steep. To obtain a standard amount of disocclusion with such a steep cusp angle, the incisal path had to be set at an angle that was extremely steep . This made the patient uncomfortable. In addition an anterior guide table of an articulator was fabricated by means of resin moulding. It was technique sensitive

172. Twin Stage vs Twin Table The Twin-Stage procedure – Advantages Measurement of the condylar path not necessary, complicated instruments such as the pantograph and fully adjustable articulator become unnecessary. The guideline for optimum occlusion is shown clearly by the adjustment values of an articulator (conditions 1 and 2), it is possible to diagnose eccentric occlusal relations of the patient precisely and simply.

173. Twin Stage vs Twin Table The procedure can be indicated for almost every phase of restorative and prosthodontic work including the Single Crown, FPD, Implants, Complete-mouth Reconstructions, and Complete Dentures.

174. Presently, the twin-stage procedure is Contraindicated in the following cases : 180 Twin Stage vs Twin Table

175. Variation Between The Two Techniques Twin table technique Twin stage technique Patients condylar inclination is recorded and followed Fixed condylar guidance of 40 degree is followed. Molar disclusion is determined by a cusp shape factor and an angle of hinge rotation Molar disclusion is determined by a standard cusp angle and the anterior guidance Develops anterior guidance to create a predetermined, harmonious disclusion with the condylar path. Standard cusp angle is used as the main determinant of to establish the standard amount of disclusion. The anterior guidance created in this manner helps control the condylar path, since the condylar path is influenced by anterior guidance. 181

176. One incisal table is used to incorporate a cusp-shape factor and the other is used for the angle of hinge rotation. Condition 1 gives a standard cusp angle and condition 2 helps give anterior guidance for predetermined disclusion The anterior guidance and the patients condylar inclination are in harmony The anterior guidance and the patients condylar inclination may or may not be in harmony The amount of disclusion determined in the articulator and that seen in patients mouth are same. The amount of disclusion doesn’t change in patient’s Mouth The amount of disclusion changes (increase or decreases) in patient’s mouth as in this technique a fixed value of 40° as the condylar inclination is followed. So as the condylar inclination varies the amount of disclusion also varies from the predetermined value 182

177. Inter – occlusal bite records are required for the programming of the articulator to patient’s condylar inclination No such records are required as the condylar inclination is pre determined to 40 Generally followed only for full mouth rehabilitation in dentate patients (fixed prosthesis) Can be followed for both dentate (fixed prosthesis) and edentulous patients (complete dentures) 183

178. Conclusion Occlusal rehabilitation is a radical and serious procedure. It should not be undertaken merely because the occlusal relationship existing does not conform to preconceived concepts of the normal or ideal. In the presence of functional adequacy conservative treatment is indicated. 184

179. Patients who have had full mouth rehabilitation commonly say that their mouth feel “stronger”. The masticatory muscles have obviously not been strengthened by the therapy. What has happened is that the patient can exert greater force with comfort and without anticipation of pain than they could before and that therefore they do exert a greater force. 185 Conclusion

180. The individual patient’s reaction bears witness to these benefits and should inspire us, in terms of human satisfaction as well as of scientific progress, to strive continuously for improvement in the techniques of full mouth rehabilitation. 186 Conclusion

181. References.. Sumaiya Hobo, Hisao Takayama : Oral Rehabilitation Clinical Determnation of Occlusion. Twin table technique for occlusal rehabiliation : Part I – Mechanism Of Anterior Guidance J Prosthet Dent 1991;66:299-303. Twin table technique for occlusal rehabiliation : Part II– Clinical Procedure J Prosthet Dent 1991;66:471-7. 187

182. Biologic laws governing functions of muscles that move mandible. Part – I. J Prosthet Dent. 1977; 37:648-56. A practical approach to full mouth rehabilitation. J Prosthet Dent. 1987;57:261. Formula for adjusting the horizontal condylar path of the semi adjustable articulator with interocclusal records. Part – I. J Prosthet Dent. 1986;55:422-6.

183. 189 Thank You…