Development of occlusion.

1. Development of Occlusion By: Piyush Verma MDS 1 st yr Dept of Pedodontics & Preventive Dentistry

2. Index Introduction Evolution Periods of occlusal development Neo-natal period. Primary dentition period. Mixed dentition period. Permanent dentition period Developmental disturbances Conclusion References

3. Introduction Term occlusion is derived from the Latin word, “ occlusio ”; defined as the relationship between all the components of the masticatory system in normal function, dysfunction and parafunction . An ideal occlusion is the perfect interdigitation of the upper and lower teeth, which is a result of developmental process consisting of the three main events, jaw growth, tooth formation and eruption

4. Evolution To develop a functional occlusion it became necessary for the teeth and bones to develop synchronously. Over a period of time there was loss or fusion of cranial and facial bones, the number of bones have reduced and the dental formula has also undergone changes.

5. Periods of Occlusal Development Occlusal development can be divided into the following development periods: Neo-natal period. Primary dentition period. Mixed dentition period. Permanent dentition period.

6. Neonatal Period (lasts upto 6 months after birth)

7. Gum Pads Alveolar processes at the time of birth- gum pads. Pink in colour , firm and are covered by a dense layer of fibrous periosteum .

8. Gum Pads contd … The gum pad soon gets segmented by a groove called transverse groove , & each segment is a developing tooth site. The pads get divided into ‘ labio-buccal ’ & ‘lingual portion’, by a dental groove. The groove between the canine and the 1 st molar region is called the lateral sulcus , useful for judging the inter arch relationship at a very early stage.

9. Gum Pads contd … The upper gum pad is horse shoe shaped & shows: Gingival groove: separates gum pad from the palate. Dental groove: starts at the incisive papilla, extends backward to touch the gingival groove in the canine region & then moves laterally to end in the molar region . Lateral sulcus .

10. Gum Pads contd … The lower gum pad is ‘U’ shaped and rectangular, characterized by: Gingival groove: lingual extension of the gum pads. Dental groove. Lateral sulcus .

11. Relationship of Gum Pads Anterior open bite is seen at rest with contact only at the molar region. Complete overjet . Class II pattern with maxillary gum pad being more prominent. Mandible is distal to the maxilla of 2.7 mm- male and 2.5- female. ( Sillman JH 1938) The range of variation of this distal relationship is from 0 to 7 mm . . ( Sillman JH 1938)

12. Relationship of Gum Pads Mandibular lateral sulci lies posterior to maxillary lateral sulci . Mandibular functional movements are mainly vertical, and to a little extent antero -posterior. Lateral movements are absent.

13. Neonatal Jaw Relationship A ‘precise bite’ or jaw relationship is not yet seen. Therefore, neonatal jaw relationship cannot be used as a diagnostic criterion for reliable prediction of subsequent occlusion in the primary dentition.

14. Status of Dentition at Birth

15. Precociously Erupted Primary Teeth Natal tooth Neonatal teeth Pre-erupted teeth ’ or ‘ Early Infansive teeth ’ are teeth that erupt during the 2 nd or 3 rd month.

16. Natal/neonatal teeth Classification Hebling (1997) classified natal teeth into 4 clinical categories: 1. Shell-shaped crown poorly fixed to the alveolus by gingival tissue and absence of a root; 2. Solid crown poorly fixed to the alveolus by gingival tissue and little or no root; 3. Eruption of the incisal margin of the crown through gingival tissue 4. Edema of gingival tissue with an unerupted but palpable tooth.

17. Gender Predilection for females Kates et al (1984) reported a 66% proportion for females against a 31% proportion for males. Etiology It has been related to several factors, such as:- Superficial position of the germ Infection or malnutrition Eruption accelerated by febrile incidents or hormonal stimulation, Hereditary transmission of a dominant autosomal gene Osteoblastic activity inside the germ area related to the remodeling phenomenon and hypovitaminosis

18. Natal/neonatal teeth Associated syndromes Hallerman - Streiff Ellis-Van Creveld Craniofacial dysostosis Multiple steatocystoma Congenital pachyonychia Sotos Syndrome.

19. Natal/neonatal teeth Complications Interfere with feeding Risk of aspiration Traumatic injury to the baby’s tongue and/or to the maternal breast Riga- Fede disease- oral condition found, rarely in newborns manifests as an ulceration on the ventral surface of the tongue or on the inner surface of the lower lip. Caused by trauma to the soft tissue from erupted baby teeth. Riga- Fede disease

20. Diagnosis A radiographic verification of the relationship between a natal and/or neonatal tooth and adjacent structures, nearby teeth, and the presence or absence of a germ in the primary tooth area would determine whether or not the tooth belongs to the normal dentition ( Almeida CM et al 1997) Most natal and neonatal teeth are primary teeth of the normal dentition and are not supernumerary teeth ( Brandt Sk et al 1983) Correspond to teeth of the normal primary dentition in 95% of cases, while 5% are supernumerary (Hawkins C 1932)

21. Treatment If the erupted tooth is diagnosed as a tooth of the normal dentition -- maintenance of these teeth in the mouth is the first treatment option, unless this would cause injury to the baby (Chow MH 1980, Roberts MW 1992) When well implanted-- these teeth should be left in the arch and their removal should be indicated only when they interfere with feeding or when they are highly mobile, with the risk of aspiration (Toledo AO 1996) Reasons for removal -- The risk of dislocation and consequent aspiration, traumatic injury to the baby’s tongue and/or to the maternal breast, ( Kates GA et al 1984)

22. Martins et al (1998) suggested smoothing of the incisal margin to prevent wounding of the maternal breast during breast feeding. If the treatment option is extraction , certain precautions should be taken : Avoiding extraction up to the 10th day of life to prevent hemorrhage Assessing the need to administer vitamin K before extraction (0.5-1.0 mg IM) Considering the general health condition of the baby Avoiding unnecessary injury to the gingiva Being alert to the risk of aspiration during removal.

23. Primary Dentition Period (From around the 6 th month to 6 years)

24. Sequence of Eruption

25. Primary (upper) First evidence of calcification (Weeks in utero) Crown completed (months) Eruption (months) Root completed (years) Central 14 (13-16) 1 1/2 10 1 1/2 Lateral 16 2 1/2 11 2 Canine 17 9 19 3 1/4 1 st molar 15 1/2 6 16 2 1/2 2 nd molar 19 11 29 3 Chronology of Primary Dentition Wheelers…

26. Primary (Lower First evidence of calcification (Weeks in utero) Crown completed (months) Eruption (months) Root completed (years) Central 14 (13-16) 2 1/2 8(6-10) 1 1/2 Lateral 16 3 13( 10-16) 1 1/2 Canine 17 9 20(17-23) 3 1/4 1 st molar 15 1/2 5 1/2 16( 14-18) 2 1/4 2 nd molar 18 10 27 3 Wheelers…

27. Status of Dentition (during primary dentition period)

28. At around 5 – 6 Years There are 48 teeth/parts of teeth present in the jaw. It is at this time that there are more teeth in the jaws than at any other time.

29. Features Of Primary Dentition Spacing - 2 types of dentition are seen: A) Spaced dentition - usually seen in the deciduous dentition to accommodate the larger permanent teeth in the jaws. More prominent in the anterior region, and are called ‘physiological spacing’ or ‘developmental spacing ’. Absence of spaces in the primary dentition is an indication that crowding of teeth may occur when the larger permanent teeth erupt.

30. Features Of Primary Dentition contd … Most subhuman primates have it through out life and use it for interdigitation of the opposing canines. This space is used for early mesial shift. primate spaces’, ‘simian spaces’ or ‘anthropoid spaces’.

31. Features Of Primary Dentition contd … Non- spaced dentition Teeth are present without any spaces in between the teeth Due to narrow dental arches or if teeth are wider than usual Usually indicates in developing permanent dentition but it is not always the case

32. Features Of Primary Dentition contd … Shallow overjet & overbite. Initially a deep bite may occur due to the fact that the deciduous incisors are more upright than their successors. The lower incisal edges often contact the cingulum area of the maxillary incisors. This deep bite is later reduced by: Eruption of deciduous molars. Attrition of incisors. Forward movement of the mandible due to growth.

33. Features Of Primary Dentition contd … Almost vertical inclination of anteriors .

34. Features Of Primary Dentition contd … Ovoid arch form.

35. Molar Relationship The molar relationship in the primary dentition can be classified into 3 types: Straight/flush terminal plane. Mesial step. Distal step.

36. Flush Terminal Plane If the distal surface of maxillary and mandibular deciduous second molars are in the same vertical plane; then it is called a flush terminal plane Normal molar relationship in the primary dentition, because the mesiodistal width of the mandibular molar is greater than the mesiodistal width of the maxillary molar.

37. Mesial Step Distal surface of mandibular deciduous second molar is mesial to the distal surface of maxillary deciduous second molar.

38. Distal Step Distal surface of mandibular second deciduous molar is more distal to the distal surface of the maxillary second deciduous molar

39. Canine relationship Relationship of maxillary & mandibular deciduous caninnes is one of the most stable in primary dentition Classified as: Class 1 Class 2 Class 1 Class 2

40. Mixed Dentition Period

41. Mixed Dentition Period (Around 6 years- 12 years) The mixed dentition period can be divided into three phases: First transitional period. Inter-transitional period. Second transitional period.

42. First Transitional Period

43. Eruption of 1 st Permanent Molar The location & relation of the 1 st permanent molar depends much upon the distal surface of the upper & lower 2 nd deciduous molar.

44. Transition to Class I Molar Relation The shift in lower molar from a flush terminal plane to a class I relation can occur in two ways: Early shift. Late shift.

45. Early Shift Early shift occurs during the early mixed dentition period. Since this occurs early in the mixed dentition, it is called early shift.

46. Late Shift This occurs in the late mixed dentition period and is thus called late shift .

47. Leeway Space of Nance Described by Nance in 1947 Maxilla : 0.9 mm/segment = 1.8 mm. Mandible: 1.7 mm/segment = 3.4mm.

48. Although the deciduous posterior segment of teeth is larger than the permanent segment, converse is true of the anterior segments Nance did not consider large difference in mesiodistal size between the deciduous incisor teeth & their permanent successors– arch needs to be looked in its totality Maxillary incisors, as a group in one quadrant– 3.2to 3.5 mm larger Mandibular incisors, as a group in one quadrant – 2.4 to 2.5 mm larger The latter figures balance out or cancel the 1.7 mm of so called leeway space

49. Moorrees -- measurements of deciduous & permanent teeth in the mouths obtained by longitudinal studies, there is no leeway space Total no. of permanent teeth destined to replace total no. of deciduous teeth in an average child – slighly less than 1mm more space in mandibular arch, 6mm more in maxillary arch 1.7 mm leeway space taken up by the larger permanent incisors, requires more distal eruption of permanent canines Allows reduction of incisor crowding in mandibular arch

50. If the permanent molars were allowed or even encouraged to drift mesially and utilize the leeway space – no enough room in the arch for the incisor segment Initially – permanent incisors are forced into a crowded position If molars are held stable, incisors will utilize the leeway space, ultimately the average mandibular arch will have enough room for proper alignment

51. Secondary spacing Term was coined by Baume Observed in closed primary dentition Secondary spacing can also occur during the eruption of permanent central incisors

52. Distal Step When the deciduous second molars are in a distal step, the permanent first molar will erupt into a class II relation. This molar configuration is not self correcting and will cause a class II malocclusion despite Leeway space and differential growth.

53. Mesial Step Primary second molars in mesial step relationship lead to a class I molar relation in mixed dentition. This may remain or progress to a half or full cusp class III with continued mandibular growth .

54. Influence of terminal plane on the position of 1 st permanent molar Distal Step – 23.3% incidence, abnormal, Class II- 38.6% Straight terminal plane – 49.2% incidence, Class I or II Mesial Step - <2mm 26.7%, class I 58.9% >2mm 0.8%. Class III- 2.5%

55. Exchange of Incisors During the first transitional period the deciduous incisors are replaced by the permanent incisors. The mandibular central incisors are usually the first to erupt. The permanent incisors are considerably larger than the deciduous teeth they replace. This difference between the amount of space needed for the accomodation of the incisors and the amount of space available for this, is called ‘ Incisal liability ’. The incisal liability is roughly about 7.6 mm in the maxillary arch & about 6 mm in the mandibular arch (Wayne).

56. Transition of Incisors The incisal liability is over come by the following factors: Interdental physiological spacing in the primary incisor region. (4 mm in maxillary arch & 3 mm in mandibular arch)

57. Transition of Incisors contd … Increase in inter-canine arch width: Significant amount of growth occurs with the eruption of incisors and canines.

58. Transition of Incisors contd … Increase in anterior length of the dental arches: Permanent incisors erupt labial to the primary incisors to obtain an added space of around 2-3 mm.

59. Transition of Incisors contd … Change in inclination of permanent incisors: Primary teeth are upright but permanent teeth incline to the labial surface, thus decreasing the inter- incisal angle from about 151 degrees in the deciduous dentition to 124 degrees in the permanent dentition. This increases the arch parameter.

60. Inter-Transitional Period This is a stable phase where little changes take place in the dentition. The teeth present are the permanent incisors and first molar along with the deciduous canines and molars. This phase prepares for the second transitional phase. Some of the features of this stage are: Any asymmetry in emergence and corresponding differences in height levels or crown lengths between the right and left side teeth are made up.

61. Inter-Transitional Period contd … Root formation of emerged incisors, and molars continues, along with concomitant increase in alveolar process height.

62. Inter-Transitional Period contd … Resorption of roots of deciduous canines and molars.

63. Second Transitional Period The second transitional period is characterized by the replacement of the deciduous molars and canines by the premolars and permanent canines respectively. At around 10 years of age the deciduous canines shed, but just before the shedding there is a transient or self correcting malocclusion seen in the maxillary incisor region between the age of 8 – 9 years.

64. Ugly Duckling Stage (Broadbent’s phenomenon) Around the age of 8 - 9 years, a midline diastema is commonly seen in the upper arch, which is usually misinterpreted by the parents as a malocclusion. Its typical features are: Flaring of the lateral incisors. Maxillary midline diastema .

65. Ugly Duckling Stage contd … Crowns of canines on young jaws impinge on developing lateral incisor roots, thus driving the roots medially and causing the crowns to flare laterally.

66. Ugly Duckling Stage contd … The roots of the central incisors are also forced together, thus causing a maxillary midline diastema .

67. Ugly Duckling Stage contd … With the eruption of the canines, the impingement from the roots shift incisally thus driving the incisor crowns medially, resulting in closure of the diastema as well as the correction of the flared lateral incisors.

68. Ugly Duckling Stage contd … Hence this unaesthetic metamorphosis, eventually leads to an aesthetic result.

69. Self correcting anomalies

70. Sequence of Eruption The canines in the upper arch erupt only after the premolars have replaced the deciduous molars, whereas the canine erupt before the premolars in the lower arch.

71. Second Transitional Period contd … Favorable occlusion in this area is largely dependent on: Favorable eruption sequence. Satisfactory tooth size to available space ratio. Attainment of normal molar relation with minimum diminution of space available for the bicuspids.

72. Second Transitional Period contd … Eruption of permanent second molars Before emergence- second molars, oriented in a mesial & lingual direction Teeth- formed palatally , guided into occlusion by Cone Funnel mechanism , upper palatal cusps (cone) slides into the lower occlusal fossa (funnel) Arch length is reduced by mesial eruptive forces Thereby, crowding if present is accentuated

73. The Permanent Dentition Period

74. The Permanent Dentition This period is marked by the eruption of the four permanent second molars.

75. Nolla’s Stages of Tooth Development Moyers In 1960 Nolla studied the stages of tooth development using panoramic & postero -anterior radiographs .

76. The Permanent Dentition contd … Calcification begins at birth with the calcification of the cusps of the first permanent molar and extends as late as the 25 th year of life. Complete calcification of incisor crowns take place by 4 – 5 years and of the other permanent teeth by 6 – 8 years except for third molars.

77. Permanent (Upper) First evidence of calcification ( weeks in utero) Crown completed (months) Eruption ( months) Root completed (years) Central 3-4 mo 4-5 yr 7-8 yr 10 Lateral 10-12 mo 4-5 yr 8-9 yr 11 Canine 4-5 mo 6-7 yr 11-12 yr 13-15 1 st premolar 1 1/2 -1 3/4 yr 5-6 yr 10-11 yr 12-13 2 nd premolar 2-2 1/4 yr 6-7 yr 10-12 yr 12-14 1 st molar At birth 2 1/3 -3 yr 6-7 yr 9-10 2 nd molar 2 1/3 -3 yr 7-8 yr 12-13 yr 14-16 3 rd molar 7-9 yr 12-16 yr 17-21 yr 18-25 Chronology of Permanent Dentition Wheelers…

78. Permanent (Lower) First evidence of calcification ( weeks in utero) Crown completed (months) Eruption ( months) Root completed ( years) Central 3-4 mo 4-5 yr 6-7 yr 9 Lateral 3-4 mo 4-5 yr 7-8 yr 10 Canine 4- 5 mo 6-7 yr 9-10 yr 12-14 1 st premolar 1 3/4 -2yr 5-6 yr 10-12 yr 12-13 2 nd premolar 2 1/4 -2 1/2 yr 6-7 yr 11-12 yr 13-14 1 st molar At birth 2 1/2 -3yr 6-7 yr 9-10 2 nd molar 2 1/2 -3yr 7-8 yr 11-13 yr 14-15 3 rd molar 8-10 yr 12-16 yr 17-21 yr 18-25 Wheelers…

79. The Permanent Dentition contd … The permanent incisors develop lingual to the deciduous incisors and move labially as they erupt.

80. The Permanent Dentition contd … The premolars develop below the diverging roots of the deciduous molars .

81. The Permanent Dentition contd … At approximately 13 years of age all permanent teeth except third molars are fully erupted .

82. Features of Permanent Dentition Coinciding midline. Class I molar relationship.

83. Features of Permanent Dentition contd … Vertical overbite of about one third the clinical crown height of the mandibular central incisors. Overjet and over bite decreases throughout the second decade of life due to greater forward growth of the mandible.

84. Andrews keys to normal occlusion Key I – Molar relationship MB cusp of the max 1 st molar falls into the mesiobuccal groove of the mand 1st molar and that the distal surface of the DB cusp of the upper first permanent molar should make contact and occlude with mesial surface of the MB cusp of the lower second molar .

85. Andrews keys to normal occlusion Key II Crown angulation (Tip) The angulation of the facial axis of every clinical crown should be positive The gingival portion of the long axis of the all crowns must be distal than the incisal portion.

86. Andrews keys to normal occlusion Key III Crown inclination In upper incisors, the gingival portion of the crown’s labial surface is lingual to the incisal portion. In all other crowns, including lower incisors, the gingival portion of the labial or buccal surface is labial or buccal to the incisal or occlusal portion.

87. Andrews keys to normal occlusion Key IV – Rotations The fourth key to normal occlusion is that the teeth should be free of undesirable rotations.

88. Andrews keys to normal occlusion Key V – Tight contacts contact points should be tight (no spaces). In absence of abnormalities such as genuine tooth size discrepancies, contact point should be tight.

89. Andrews keys to normal occlusion Key VI – Occlusal plane or curve of spee The curve of Spee should have no more than a slight arch. Intercuspation of teeth is best when the plane of occlusion is relatively flat. A deep curve of spee results in a more contained area for the upper teeth, making normal occlusion impossible.

90. Andrews keys to normal occlusion Key VII – Correct tooth size or the bolton’s ratio Bennett and McLaughlin in 1993 gave seventh key to normal occlusion. i.e. the upper and lower tooth size should be correct.

91. Roth (1981) added some functional keys to the previous six keys to normal occlusion by Andrew: a) Centric relationship and centric occlusion should be coincident. b) In protrusion, the incisors should disclude the posterior teeth, with the guidance provided by the lower incisal edges passing along the palatal contour of the upper incisors. c) In lateral excursions of the mandible, the canine should guide the working side whilst all other teeth on that and the other side are discluded . d) When the teeth are in centric occlusion, there should be even bilateral contacts in the buccal segments.

92. Abnormalities in dental arch Arch Length Discrepancy Crowding Spacing Deviation in no. of teeth- Absence of teeth ( Agenesis) Supernumerary teeth

93. Absence of teeth ( Agenesis) Sequece of agenesis is – 3 rd molar > Mand . 2 nd premolars > Max Lateral Incisors > Max. 2 nd Premolar

94. Absence of teeth ( Agenesis)

95. Supernumerary teeth

96. Deviation in tooth size Its relative in nature All teeth combined > or < relative to size of jaws or head. Crowding Spacing Deviation in size of individual teeth Tooth size Discrepancy

97. Tooth size Discrepancy

98. Ankylosis Frequent in mand deciduous molars. In permanent 2 types Due to abnormal position within jaw Max perm. Canine Due to lack of space Mand 3 rd molar

99. CONCLUSION In its simplest of definition, occlusion is the way the maxillary and mandibular teeth articulate, but in reality dental occlusion is a much more complex relationship, because it not only involves the study of the teeth, but also their morphology and angulations, the muscles of mastication, the skeletal structures, the temperomandibular joint, and the functional jaw movements. In addition to this, it also involves the relationship of the teeth in centric occlusion, in centric relation, and even during function, and because all this, requires neuromuscular coordination, occlusion should also involve an understanding of the neuromuscular systems, and if we need to determine an abnormal course of development, it is the responsibility of we ‘ pedodontists ’ to have an adequate knowledge on these subjects, to help us differentiate abnormal from normal, before initiating therapy.

100. References Handbook of Orthodontics: Robert E. Moyers. Orthodontics the art & science: S. I. Bhalajhi . Textbook of Orthodontics: M.S. Rani . Textbook of Pediatric Dentistry: S.G. Damle . Dental Anatomy, Physiology & Occlusion: Wheeler. Textbook of Pedodontics : Shoba Tandon . Textbook of Orthodontics: Samir E. Bishara . Contemporary orthodontics – Proffit Textbook of Pedodontics : Koch. Orthodontics principles and practice: T. M. Graber.

101. Thank You.