2. THIS - is what we want to prevent

3. Charles H. Tweed As we learn more about growth and its potentials, more about the influences of function on the developing denture, and more about the normal mesiodistal position of the denture in its relation to basal jawbones and head structures, we will acquire a better understanding of when and how to intervene in the guidance of growth so that Nature may better approximate her growth plan for the individual patient.

4. Charles H. Tweed In other words, knowledge will gradually replace harsh mechanics, and in the not-too-distant future the vast majority of orthodontic treatment will be carried out during the mixed-dentition period of growth and development and prior to the difficult age of adolescence.

5. Lower incisor crowding

6. GUIDANCE OF DENTAL ERUPTION by Yuehua Liu DDS, PhD, M.Orth.RCS(Edin) DDS, PhD, M.Orth.RCS(Edin)

7. Development of the human dentition

8. History of guidance of eruption - Earliest description of ‘ serial extraction ’ in the dental literature was by Robert Bunon in 1743 - The prescribed sequence was c-d-4 - Kjellgren introduced the term “ serial extraction ” in 1929 - Hotz called it ‘ guidance of eruption ’ - The big question is: “ to commit or to omit ? ”

9. Decide to ‘ omit ’ or ‘ commit ’

10. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

11. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

12. Transitional development of dentition

14. Early permanent dentition development is usually complete by 12 years of age

15. Transitional dentition- 6 to 12 years of age

16. Transitional incisor liability: 4-6 mm in the mandible; and 6-8 mm in the maxilla ( Moorrees & Chadha 1965 )

17. How does Nature cope with the “ incisor liability ” ?

19. Transitional development of dentition Nature ’ s way to overcome ‘ incisor liability ’ : (a) primate spaces and inter-dental spaces (a) primate spaces and inter-dental spaces (b) labial positioning (b) labial positioning (c) inter-canine width increase (c) inter-canine width increase (d) leeway spaces (d) leeway spaces

20. Transitional development of dentition Nature ’ s way to overcome ‘ incisor liability ’ : (a) primate spaces and inter-dental spaces (a) primate spaces and inter-dental spaces (b) labial positioning (b) labial positioning (c) inter-canine width increase (c) inter-canine width increase (d) leeway spaces (d) leeway spaces

21. Transitional development of dentition Nature ’ s way to overcome ‘ incisor liability ’ : (a) primate spaces and inter-dental spaces (a) primate spaces and inter-dental spaces (b) labial positioning (b) labial positioning (c) inter-canine width increase (c) inter-canine width increase (d) leeway spaces (d) leeway spaces

22. Transitional development of dentition Nature ’ s way to overcome ‘ incisor liability ’ : (a) primate spaces and inter-dental spaces (a) primate spaces and inter-dental spaces (b) labial positioning (b) labial positioning (c) inter-canine width increase (c) inter-canine width increase (d) leeway spaces (d) leeway spaces

23. Inter-canine width increase from “ secondary spacing ”

24. Inter-canine width increases to 9 years of age ( Moorrees & Reed 1965 )

25. Transitional development of dentition Nature ’ s way to overcome ‘ incisor liability ’ : (a) primate spaces and inter-dental spaces (a) primate spaces and inter-dental spaces (b) labial positioning (b) labial positioning (c) inter-canine width increase (c) inter-canine width increase (d) leeway spaces (d) leeway spaces

27. deciduous canine= c deciduous first molar = d deciduous second molar = e

28. The leeway spaces Maxillary c-d-e minus 3-4-5 is 1.5 to 2 mm per side Mandibular c-d-e minus 3-4-5 is 1.7 mm per side

29. How does Nature cope with the “ incisor liability ” ?

30. The 8 mm rule From 6 to 12 years of age, not counting the inter- dental spacing ( 3 mm ), which is variable; in the mandible on average, we get from 6-9 years of age: ( a) Inter-canine arch width increase 3 mm ( b) Labial positioning of adult incisors 1.3 mm 9 to 12 years of age: ( c) Conserving leeway spaces 3.4 mm The total is 7.7 mm

31. The 8 mm rule  In other words, as a rule of thumb, we can expect a 6 year old child to have mandibular arch-length increase of about 8 mm through the transitional dentition;  Whereas a 9 year old child can only have 3 to 4 mm from conserving the leeway spaces. 6 to 9  4 mm 9 to 12  4 mm

32. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

33. sequences of dental eruption

35. Sequences of dental eruption favorable sequence: - 3 4 5 - 4 3 5 - (3 4) 5 - 3 (4 5)

36. Sequences of dental eruption unfavorable sequence: - 5 4 3 - 5 3 4 - 5 (3 4) -4 5 3

37. Sequences of dental eruption unfavorable sequence: - second molars erupting before the second premolars and/or canines

38. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

39. Methods of predicting arch-length

40. 1. Hixon-Oldfather L1,2 + (345) from x- rays prediction table 3. Nance L1,2 + (345) from x - rays 2. Moyers [ L1,2 ] prediction table for (345) 4. Johnston -Tanaka L1,2 + 10.5= L 345 L1,2 + 11.0= U 345

41. Methods of predicting arch-length 4. Johnston -Tanaka L1,2 + 10.5 = L 345 L1,2 + 11.0 = U 345

42. Methods of predicting arch-length 4. Johnston -Tanaka L1,2 + 10.5 = L 345 L1,2 + 11.0 = U 345

43. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

44. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

45. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

46. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

47. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

48. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

49. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

50. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

51. Factors affecting availability of arch-length 1. Spaces in the dental arch 2. Leeway spaces 3. Sequence of eruption 4. Incisal inclination 5. Potential for buccal expansion 6. Molar distalisation 7. Premature loss of deciduous molars

52. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture x x

53. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

54. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

55. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

56. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10.De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

58. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

59. Factors affecting availability of arch-length 8. Premature loss of deciduous canines 9. Congenitally missing teeth 10. De-rotation of molars and premolars 11. Curve of Spee 12. Skeletal divergence 13. Muscle tonicity 14. Tongue habits and posture

60. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ serial extraction ”

61. How does Nature cope with the “ incisor liability ” ?

62. “ Typical ” serial extraction case - Orthognathic straight facial profile - Lips on the full side - Angle Class I malocclusion - Incisors are slightly proclined - Overbite not more than 30% - Moderate to severe crowding

63. Serial extraction c-d-4 x X x x x x x x x x x

65. V.W. : a serial extraction case

66. L x x x x x x c-d-4

67. x x c-d-4 extracted x x xx x x

68. V.W.: after treatment Fixed appliance placed

69. V.W.: after treatment

70. Another case: S.L.

71. Anterior crossbite corrected x x x x

72. Serial extraction: d-4 x x x x

74. After treatment

75. Sequences of serial extraction 1. c- d- 4 for severe crowding 2. d – c- 4 for moderate crowding 3. e ’ s for congenitally missing second premolars ( when mesial drifting of molars is planned)

76. J.D.- a case with missing 35, 45

80. J.D.: after treatment

81. Guidance of dental eruption A. Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

82. Some general guidelines: 1. Take adequate records as required. A panorex is mandatory. 2. Look at the WHOLE, not just a PART. Also, think long term. 3. Do space maintenance when indicated. Restore deciduous molars. 4. Extract ankylosed deciduous teeth.

83. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space.

84. More general guidelines: 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t just go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe maloposition of incisors.

85. Some general guidelines: 1. Take adequate records as required. A panorex is mandatory. 2. Look at the WHOLE, not just a PART. Also, think long term. 3. Do space maintenance when indicated. Restore deciduous molars. 4. Extract ankylosed deciduous teeth.

86. Some general guidelines: 1. Take adequate records as required. A panorex is mandatory. 2. Look at the WHOLE, not just a PART. Also, think long term. 3. Do space maintenance when indicated. Restore deciduous molars. 4. Extract ankylosed deciduous teeth.

87. Some general guidelines: 1. Take adequate records as required. A panorex is mandatory. 2. Look at the WHOLE, not just a PART. Also, think long term. 3. Do space maintenance when indicated. Restore deciduous molars. 4. Extract ankylosed deciduous teeth.

88. Upper Nance holding arch and Lower lingual arch

89. S.S.: what NOT to do

91. Some general guidelines: 1. Take adequate records as required. A panorex is mandatory. 2. Look at the WHOLE, not just a PART. Also, think long term. 3. Do space maintenance when indicated. Restore deciduous molars. 4. Extract ankylosed deciduous teeth.

92. C.W.

93. Ankylosed e ’ s

95. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space.

96. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space. // \\

97. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space.

98. Diastema may also be caused by mesiodens- rule it out

99. F.C.: 8 years

101. F.C.: 10 years

102. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space.

103. A.A.: missing 35, 45

104. A.A.: 75, 85 kept

105. More general guidelines: 5. Do not extract deciduous teeth until the succeeding permanent teeth are at least 2/3 root-formed. 6. Discing sometimes is a good measure. 7. Do not treat diastema at “ ugly duckling ” stage. 8. Congenitally missing 5 ’ s and 2 ’ s; decide to hold space or to close space.

106. P.P.: multiple missing teeth

109. Spaces reopened for pontics of upper laterals

110. More general guidelines 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe maloposition of incisors.

111. More general guidelines 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe maloposition of incisors.

112. More general guidelines: 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe maloposition of incisors.

113. More general guidelines: 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe maloposition of incisors.

114. M.W.: blocked out 35,45

116. M.W.: 35,45 unblocked

117. More general guidelines: 9. The lower arch is usually the deciding arch. 10. Individualise, don ’ t go by ‘ averages ’. 11. Watch the midlines. 12. Regain space when indicated. 13. Intercept ectopic eruption or severe malposition of the incisors.

118. E.S.: Missing 22; ectopic 16

119. x x

124. E.S.: Pontic placed for #22

125. B.C.: Ectopic #21,22

128. P.S.: Impacted #11,12

131. K.N.: Supernumerary between 11 and 21

132. x

134. Diastema closed and incisors aligned

136. Please help to prevent this

137. By making the right decisions for this

138. By knowing this

139. Guidance of dental eruption A.Transitional development of dentition B. Various sequences of eruption C. Methods of arch-length prediction D. Factors affecting availability of arch-length E. Management of various degrees of crowding F. Guidelines for “ guidance of eruption ”

140. Keep in mind : 1. Take adequate records to help diagnose and plan treatment with long-term treatment goals in mind. 2. Decide to ‘ omit ’ or to ‘ commit ’ - “ the 8 mm rule ”. 3. Weigh benefits vs. cost for the patient. Intercept only when necessary. Avoid over-treatment in mixed dentition.

141. Keep in mind : 1. Take adequate records to help diagnose and plan treatment with long-term treatment goals in mind. 2. Decide to ‘ omit ’ or to ‘ commit ’ - “ the 8 mm rule ”. 3. Weigh benefits vs. cost for the patient. Intercept only when necessary. Avoid over-treatment in mixed dentition.

142. Keep in mind : 1. Take adequate records to help diagnose and plan treatment with long-term treatment goals in mind. 2. Decide to ‘ omit ’ or to ‘ commit ’ - “ the 8 mm rule ”. 3. Weigh benefits vs. cost for the patient. Intercept only when necessary. Avoid over-treatment in mixed dentition.

143. Keep in mind : 1. Take adequate records to help diagnose and plan treatment with long-term treatment goals in mind. 2. Decide to ‘ omit ’ or to ‘ commit ’ - “ the 8 mm rule ”. 3. Weigh benefits vs. cost for the patient. Intercept only when necessary. Avoid over- treatment in mixed dentition.

144. Thank you for your attention ! The End