Teeth arrangement

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Information about Teeth arrangement

Published on March 5, 2016

Author: RohanBhoil

Source: slideshare.net

1. Selection and Arrangement of Teeth for Complete Dentures By: Dr. Rohan Bhoil

2. Contents • Introduction • Review of literature • Selection of anterior teeth • Selection of Posterior teeth • Arrangement of teeth • Conclusion

3. Introduction • After casts are mounted & occlusal scheme determined. • Maintenance of vertical dimension. • Anterior teeth – primarily aesthetics. • Posterior teeth – for mastication. • Harmony.

4. Why selection and arrangement deserve special attention ?

5. • Absence of periodontium. • Single unit on an unyielding base. • Necessity of bilateral balance. • Consequences of malocclusion. • Bearing of non vertical forces. • First molar & second premolar area. • Proprioception. • Incising with natural teeth.

6. Review of Literature • Berry’s Biometric Ratio Method [1906] – Inverted CI resembles face form – Tooth size 1/16 face width & 1/20 face length • Clap’s Tabular Dimension Table Method [1910] – Tooth size based on six anterior teeth – Enabled to specify mold • Cigrande [1913] – Outline form of fingernail - Outline form of Central incisor.

7. • Pound E. (1951) - dentures should be designed according to the principle of nature. • French A. (1951) - teeth should be arranged according to the face form, arch form, width of mouth and ridge relation. • Frush & Fisher (1955 – 59) - Sex, Personality and Age of the patient.

8. • Martone A. L. (1964) - loss of the teeth & their supporting structures produce radical changes in facial appearances. • Curtis T. & Shaw E. (1987) - the esthetic results require more than the size, color, position and arrangement of complete denture teeth. • Golden proportion - by Levin

9. • Preston (1993)

10. • Ward (2000) - Recurring Esthetic Dental (RED) proportion based on the different heights of the maxillary anterior teeth. • However in a study: To evaluate the validity of Recurring Esthetic Dental proportion in natural dentition, J Conserv Dent. 2011 Jul- Sep; 14(3): 314–317., authors Shetty etal, found that RED proportion was not seen in natural dentition.

11. Methods Used to Select Artificial Anterior Teeth for the Edentulous Patient: A Historical Overview – Selten etal, Int J Prosthodont 1999:12:51 Concluded that to date, no universally reliable method of determining tooth form has been found. The Williams classification (1914) is the most universally accepted method of determining anterior tooth form.

12. Assessment of Dental Appearance Following Changes in Incisor Angulation Wolfart etal, Int J Prosthodont 2004;17:150–154. • They evaluated the assessment of attractiveness of standardized changes in incisor angulation of different tooth arrangements and found that tooth arrangements showing central incisors with ideal axes are more attractive, than angulation of one or both central incisors. And slight changes in the angulation of one or both lateral incisors do not influence attractiveness negatively.

13. • Varjao etal, in their study on Intercommissural width as a guide for selection of anterior maxillary teeth ( Int J Prosthodont, 2005; 18;513-515) – Found that a weak correlation exists between the corners of mouth and distal of canines and hence use of corners of mouth for selection of artificial teeth is generally inaccurate.

14. • Jaffar Abduo, in a systematic review (Int J Prosthodont 2013;26;26-33) on occlusal schemes for complete dentures has concluded that primarily as per patient acceptance, posterior tooth arrangement in conventional bilateral balanced occlusion and lingualized bilaterally balanced occlusion, are preferable to flat teeth arranged in monoplane occlusion.

15. 15 Anterior tooth selection • Size • Form • Shade • Material

16. Size of Anterior Teeth • Size of Face & Head – Bizygomatic width / 3.3 – maxillary anteriors – Bizygomatic width / 16 - maxillary central – Length of face / 16 – maxillary central – 10:1 ratio of cranial circumference to upper anterior teeth.

17. Anatomical Landmarks • Mark corners of mouth on wax occlusal rims. • Extension of parallel lines from lateral surface of ala of nose onto maxillary occlusal rim. • A line perpendicular to midline of palate through distal border of incisive papilla.

18. Maxillomandibular Relations -Mandibular anteriors : class II & III arches. Contour of residual ridges - teeth placed to follow contour and size selected according to this position. Vertical distance between ridges. Lips – selection of length of maxillary anteriors.

19. High Lip Line • Highest point of upper lip when smiling • Cervical necks lie at or above this line • If shorter teeth are selected, esthetics compromised

20. • Nose – Distance between tips of canine is same as width of base of nose • Philtrum – Width of upper centrals, approximates the width of philtrum

21. Pre – Extraction Records • Facial Photographs • Diagnostic Casts • Radiographs • Teeth of Close Relatives • Extracted teeth.

22. Form of Anterior Teeth • Pre-extraction records • Form and Contour of Face

23. Leon William’s Classification • Square • Square – Tapering • Tapering • Ovoid

24. Dentogenic Concept • Frush & Fisher (1957), Dynesthetics • Sex factor – Feminine : softness – Masculine : boldness & hardness • Personality factor – Vigorous type, medium type & delicate type • Age factor – Incisal edge, erosion, diastema, stippling of interdental papilla.

25. Shade selection for Anterior Teeth

26. Shade Selection • Along side of nose – basic hue, value & chroma. • Under lips – only incisal edge exposed – effect of colour with mouth relaxed. • Under lips – only cervical end covered – smile. • Use of Squint test.

27. 28 Posterior tooth selection • Size • Form • Shade

28. Size of Posterior Teeth • Buccolingual Width – Sufficient to act as a table to hold food. – Less than width of natural teeth. – Not to encroach on tongue space and buccal corridor. – Limits forces directed to ridge.

29. • Mesiodistal Width – Edentulous space available. – Placed as far as possible posteriorly. – Not over beginning of ascending area of ramus and retromolar pad.

30. • Occlusogingival Height – Determined by available inter ridge space, occlusal plane and height of anterior teeth. – Teeth with largest possible vertical length that can be used without grinding are preferred for aesthetics.

31. Form of Posterior Teeth • Anatomic Teeth – Cusp teeth. – Simulate occlusal surface. – Varying degrees of inclinations (10°, 20°, 30°, 40°) – Standard is 33° – Cusp incline < 33°, is termed semi-anatomic teeth. – Advantages. – Disadvantages. 10 ° 20 ° 30 °

32. Non- Anatomic Teeth • Cuspless, Monoplane or Zero degree teeth. • Offer less resistance to horizontal forces – Bruxism – Poor residual ridges – Uncoordinated muscular movements – Mal relationship of jaws –class II & III Disadvantages Shearing efficiency Poor aesthetics Lateral & protrusive balance not possible.

33. 34 Shade Of Posterior Teeth • Harmonize with the shade of the anterior teeth. • Bulk influences the shade of teeth – select a slightly lighter shade for the premolars

34. Selection of Tooth Material • Resin – Composite Resin – Acrylic Resin • Monolithic • Cross – linked • IPN linked • Porcelain – When aesthetics are paramount – Adequate interarch space is available.

35. Resin & Porcelain Teeth • Wear potential • Grinding & adjusting • Bonding to denture base • Abrasion of opposing dentition • Colour stability • Impact sound • Rebasing • Impact resistance.

36. Posterior Tooth Forms – Historical Development • Anatomic teeth – Trubyte teeth (1914) by Gysi – Channel tooth (1927) by Sears – Metal insert in resin (1942) by Vincent – Crossblades (1961) by Sosin

37. • Non-anatomic teeth – Inverted cusp tooth (1929) by Hall- sharp concenteric ridges around cup like depressions. – True-kusp (1929) by Meyerson – buccal lingual ridges with sluiceways between them. – Chopping block (1934) by Nelson – Non-lock (1939) by Swenson – Vitallium Occlusal (1946) by Hardy

38. Teeth Arrangement • Anatomical landmarks • Ridge relation • Balanced occlusion • Neutral zone

39. Anatomical landmarks • Residual ridge – Position in relation to ridge due to resorptive pattern. • Arch form – Square, tapering & ovoid arch forms

40. • Retromolar pad – Too low a occlusal plane causes tongue biting and too high a occlusal plane can cause instability and strain.

41. • Parotid Duct – Maxillary first molar • Rugae – Labial surface of canine 10.5mm • Incisive papilla – Midline – Central incisor – Perpendicular line

42. Teeth Arrangement for Class I Ridge Relation • Wax rim contours aid selection and setting: – Occlusal vertical dimension – Angulation of facial rims affects lip support – Overjet • Place reference marks on the occlusion rims to aid in tooth selection and placement.

43. 44 Orientation Of Occlusal Plane Occlusal plane Upper rim • Anteriorly - parallel to inter pupillary line • Posteriorly - parallel to Camper's line Lower rim • Anteriorly – lower lip • Posteriorly - Half to two/third retromolar pad.

44. Ideal Arrangement Of Teeth • Anterior teeth

45. 48 Central Incisor • Long axis – parallel to the long axis of the patient face. • The midline of the dental arch – the centre of face • Labial contour – blend with the contour of face. • Rotation on long axis – varies depending on arch form

46. 49 Maxillary lateral incisor • Set at angle of 50 to the perpendicular • Incisal edge is about 1 mm short of the horizontal plane • Labial surface is inside at the cervical end • Distal half of rotated slight lingually

47. 50 Canine • Cervical end is more prominent labially • Canine is the turning point of arch – mesial half is harmony with ant teeth – distal half harmony with post teeth (PM) • Tip of cusp is in contact with the occlusal plane

48. The lower anterior teeth

49. 54 Central Incisor • Long axis – Parallel to vertical viewed from front • Slopes labially when viewed from side • Incisal edge 1-2mm above the horizontal plane

50. 55 Lateral Incisor • Long axis – parallel to the vertical viewed from front. • Slope labially

51. 56 Canine • Long axis - slightly lean towards midline when viewed from front – slightly lingually when viewed from side • Cusp is slightly above 0.2 mm above the horizontal plane

52. • Canine key of occlusion – The distal incline of the lower canine should align with the mesial incline of the upper canine. 57

53. Limits To Placing Anterior Teeth • The medio lateral and antero posterior position of maxillary ant teeth – limited by phonetics and esthetics

54. Phonetics • Long teeth F sounds like V • S sounds – two tongue positions – Palate – Lower anterior teeth

55. Upper posterior teeth arrangement

56. 62 First Premolar • long axis – parallel to vertical axis when view from labial side. • Palatal cusp is 0.2 mm sort of its buccal cusp from horizontal plane. Due consideration is given in esthetics in female

57. 63 2nd Premolar • Both buccal and palatal cusps touches the occlusal plane

58. 64 The First Molar • Long axis – Long axis slopes bucally when viewed distally from side. • Mesiolingual cusp

59. • Molar key of occlusion – The mesiobuccal cusp of the maxillary permanent molars should coincide with the mesiobuccal groove of the mandibular permanent molar 65

60. 66 2nd molar • More inclined than 1st molar • Cusps above horizontal plane

61. Maxillary teeth set, checked on a flat plane

62. Lower Posterior Teeth

63. 69 First Premolar Long axis – parallel to the vertical axis • lingual cusp is below the horizontal plane • buccal cusp about 02 mm above occlusal plane

64. 70 Second Premolar • Long axis –parallel to vertical axis • Both cusp are about 02 mm above the horizontal plane

65. 71 The First Molar • Long axis – leans lingually when viewed from the front – mesially when viewed from the side • All the cusps are at higher level above the horizontal plane than those of second premolar

66. 72 2nd molar • More inclined than 1st molar • Cusps above horizontal plane

67. Teeth arrangement checked in patients mouth

68. Setup for class II & III cases

69. Set up in class II jaw relations • In this setting, the flattened lingual cusp of upper premolars occludes with the flattened buccal cusp of lower premolars and a large buccal horizontal overlap occurs in the bicuspid area. • Upper molars are set with their lingual cusp in the modified central cusp of the lower teeth. • Posteriors should have a centric occlusion with stable non-deflective stops.

70. Setup in Class III relation • If ridges are edge to edge, then anterior teeth are also placed edge to edge. • In cases of extreme protrusion, – negative or reverse horizontal overlap is used, – a larger lower tooth mold can be used, – Interchange of upper and lower teeth – First premolar may be eliminated from upper arch – Transverse ridges of upper posteriors are grinded away to eliminate mesiodistal interlocking.

71. Balanced Occlusion • After centric balance is achieved, teeth arrangement is modified to achieve eccentric balance. • At least a semi-adjustable articulator is required. • For lateral balance, buccal cusps of posterior teeth should contact on working side and on non-working side, contact should occur between mandibular buccal & maxillary palatal cusps.

72. • To develop balanced occlusion in Protrusion – With the anterior teeth edge to edge, contacts should simultaneously be established in the posterior teeth. – Factors affecting balance • Condylar inclination cannot be altered. • Incisal guidance can be manipulated limitedly. • Cuspal inclination is determined by selection of teeth. • So mainly, the anterio-posterior Curve of Spee influences protrusive balance. • Thus, steeper the condylar inclination, steeper should be the compensating curve with low cuspal inclination, to achieve protrusive balance, while maintaining the centric contact.

73. Setup in neutral zone technique • Neutral zone is recorded. • Impression is indexed. • Teeth arrangement is guided by index. • Posterior teeth may require to be trimmed lingually so that they fit into index space. • Polished surfaces of denture are also contoured to replicate record.

74. 81 Characterization • Subtle chips ,stains make teeth look more natural • Highest quality of art is to conceal art

75. Conclusion • Selection and Arrangement of teeth is an art based upon biomechanical factors, governing the ultimate success of dentures.

76. References • Zarb - Bolender : Prosthodontic treatment for edentulous patients. Twelfth edition, 2004. • Sharry J.J. : Complete denture prosthodontics, 1968. • Rahn and Heartwell : Textbook of complete denture, 4th edition, 1993. • Boucher. C.O: Prosthodontic treatment for edentulous patients. Tenth edition • Dental Clinics of North America : Esthetic Dentistry, April 1989

77. Thank you !!!

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