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Development of dentition & occlusion

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Development of dentition & occlusion

  1. 1. DEVELOPMENT OF DENTITION & OCCLUSION www.indiandentalacademy.com
  2. 2. OVERVIEW  Introduction  Pre-natal development  Post-natal development  Factors affecting occlusal development -General -Local  Clinical implications  Conclusion www.indiandentalacademy.com
  3. 3. INTRODUCTION The development of dentition is an important part of craniofacial growth as the formation, eruption, exfoliation and exchange of teeth take place during this period. This is an assimilation of facts, predictions, studies, in both static and dynamic situations; the factors influencing them and their clinical implications. www.indiandentalacademy.com
  4. 4. PRE-NATAL DEVELOPMENT OF TEETH  Initiation  Bud stage  Cap stage  Bell stage www.indiandentalacademy.com
  5. 5. Initiation: The very 1st sign of tooth development appears late in the 3rd embryonic week. At 6 weeks, the 4 maxillary odontogenenic zones coalesce to form the dental lamina. Morphological changes in the dental lamina occurs in 3 main phases:  Initiation of the entire deciduous dentition –during 2nd month in utero  Initiation of the entire permanent dentition –from 5th month in utero  Initiation of the 1st permanent molar–4 months in utero  Initiation of the 2nd permanent molar-1 yr  Initiation of the 3rd permanent molar-4 to 5 yrs www.indiandentalacademy.com
  6. 6. Bud Stage: Immediately after the formation of Dental lamina, the following take place :  Division for cheek & lip from the Dental arches at the Vestibular furrow.  Increased mitotic activity( knob-like ) corresponding to each deciduous tooth position .  Between the 7th & 8th week both max. & mand. Deciduous tooth buds form.  The 1st buds to form are the mand. Anterior teeth. www.indiandentalacademy.com
  7. 7. Cap Stage:  The growth rate throughout the tooth bud is not uniform & is more active at the periphery.  The Cap stage begins by the 8th week with the appearance of a concavity on the deep surface of the bud.  The epithelium of the cap-shaped tooth organ enlarges & proliferates into deeper connective tissues (ectomesenchyme).  Areas of increased cellular density give rise to non- enamel portions of the tooth & its periodontal matrix.  The Tooth germ, consisting of the Enamel organ, Dental papilla & Dental follicle can be identified. www.indiandentalacademy.com
  8. 8. Bell Stage : In the Bell stage, the Enamel organ differentiates into : -Inner enamel epithelium -Stratum intermedium -Stellate cells -Outer enamel epithelium  Dental papilla cells differentiate into Odontoblasts & Inner enamel epithelium cells into Ameloblasts. They deposit Dentin & Enamel respectively, and withdraw from each other & the DE junction.  The OEE becomes discontinuous & allows entry of cells from the Dental sac, while the Stellate cells are withdrawn to make room for the Crown.  When enamel formation is complete, the crown is fully formed. www.indiandentalacademy.com
  9. 9. Root Formation:  Just before the ameloblasts deposit their matrix, the Cervical loop lengthens due to a proliferation of cells & forms the Hertwigs epithelial root sheath (determines no., size & shape of roots ).  Dentin matrix is deposited against the root sheath & covered by cementum due to the invasion of cementoblasts, which eventually form the PDL . www.indiandentalacademy.com
  10. 10. THEORIES OF TOOTH ERUPTION  Bone remodeling  Root growth  Vascular pressure  Periodontal ligament traction www.indiandentalacademy.com
  12. 12. BIRTH TO COMPLETE PRIMARY DENTITION (Birth- 3yrs)  The tooth buds of all primary teeth are present and in various stages of development at the time of birth.  About 7 to 8 months after birth, all the teeth except the 7’s & 8’s are present in some stage of development.  In a mandible which is less than 1yr of age, a line drawn along the occlusal surfaces passes through the condyle suggesting the lack of ramal growth.  By the 1st year, a normal & desirable dentition will usually exhibit spacing.www.indiandentalacademy.com
  13. 13.  The 1st primary tooth to erupt is the lower central incisor between 6&8 months of age, followed by the U.Centrals, U.Laterals & L.Laterals.  The 1st primary molar erupts by about the 14th month.  The primary cuspids & 2nd primary molars erupt by about 2 1/2 yrs of age.  The primary teeth are quite upright whereas the permanent incisors have a labial inclination & the permanent posteriors have a mesial tilt.  There is evidence of vertical growth as signified by the superior positioning of the condyle to the occlusal plane. www.indiandentalacademy.com
  14. 14. FIRST INTERTRANSITIONAL PERIOD( 3-6 yrs ) This is the period between the completion of eruption of Primary dentition & the emergence of the Permanent teeth. According to Baume(1950)  Primate Space(Type I Spacing)  Terminal plane Space for the 6’s is achieved by  Tuberosity apposition in the maxilla.  Ramal resorption in the mandible. The tooth buds of the 4’s & 5’s begin to form.www.indiandentalacademy.com
  15. 15. FIRST TRANSITIONAL PERIOD( 6-8 yrs ) Eruption of the 1st permanent molars :  The Terminal plane is very important in determining the interocclusal relationship of the 1st permanent molars. -Vertical plane type -Mesial step type -Distal step type www.indiandentalacademy.com
  16. 16. Exchange of incisors :  The primary incisors begin to exchange with the permanent incisors before & after the eruption of the 6’s.  The total sum of the M-D width of the 4 permanent incisors is > that of the primary incisors by about 7mm in the maxilla & 5mm in the mandible. Incisor liability(Mayne 1968 ) -Interdental spacing in primary incisors should exist. -Intercanine archwidth growth should occur. - Intercanine archlength should increase through anterior positioning of the permanent incisors. -Favourable size ratio between the primary & permanent teeth. www.indiandentalacademy.com
  17. 17. SECOND INTERTRANSITIONAL PERIOD( 8-10 yrs ) This period is referred to as the “Mixed Dentition period”/ “Ugly Duckling stage” ( Broadbent 1937 ) .  Vertical dimension of the face increases thus increasing the alveolus to accommodate the roots.  Max. Tuberosity& Mand. Ramal activity makes room for the 7’s.  Max. cuspids are lateral to the nose, mand. cuspids close to the mand. borders.www.indiandentalacademy.com
  18. 18.  Premolars are in the bifurcation of their antecedents with evidence of their resorption.  The “GABLE EFFECT” : -The mand. cuspids & bicuspids are in the shape of a ‘V’, in sequence, in relation to the occlusal plane. -The sequence of eruption being 3,4,5 in the mandible, 3 makes its way much ahead of 4 & 5. www.indiandentalacademy.com
  19. 19. SECOND TRANSITIONAL PERIOD( 10- 12 yrs )  Here, exchange of teeth occurs between c,d,e & 3,4, 5.  Emergence of 7’s takes place by virtue of increase in arch-circumference, after the Dental arch upto 6, is established .(mixed to permanent )  During the exchange & emergence, smooth utilization of “Leeway space” & “Primate space” takes place.  The sequence of eruption of the lateral teeth in: Maxilla - 4, 3, 5 ( 3,4,5 /4,5,3 are exceptions ). Mandible - 3,4, 5. www.indiandentalacademy.com
  20. 20. ADULT DENTITION  This is considered to be between 18 & 25 yrs, when the roots of the permanents are completed and the 8’s have erupted.  Nose & chin become more prominent to enhance profile.  Cranio-facial growth gives finishing touches to the face by pneumatization of the Sinuses & apposition at the Glabella.  Increase in jaw growth continues ( mandible ) to accommodate the 8’s.www.indiandentalacademy.com
  21. 21. FACTORS AFFECTING OCCLUSAL DEVELOPMENT  GENERAL FACTORS 1.Skeletal Factors 2.Muscle Factors 3.Dental factors  LOCAL FACTORS www.indiandentalacademy.com
  22. 22. General Factors  Skeletal factors : Conditions that affect jaw growth are ; 1. Any pathological condition 2. Inherited & acquired congenital malformation 3. Trauma or infection during the growing years www.indiandentalacademy.com
  23. 23. The teeth are set in the jaws and hence jaw relationship will have an influence on that of the dental arches. Jaw relationships can be considered as : 1. Jaws in relation to the cranial base 2. Jaws in relation to each other -Skeletal Cl.I, II & III -Buccal cross-bite/ lingual occlusion -High gonial angle-increased V.D Low gonial angle-decreased V.D 3. Alveolar bone in relation to basal bone www.indiandentalacademy.com
  24. 24.  Muscle factors : Final tooth position is largely governed by muscle action, particularly muscles of the lips, cheeks & tongue.  Lip form  Lip activity  Tongue size, resting position & function  Adaptive resting posture or adaptive swallowing  Endogenous tongue thrust  Thumb & finger sucking  Neutral zone www.indiandentalacademy.com
  25. 25.  Dental factors : The third major factor affecting occlusal development is the relationship between the size of the dentition & the size of the jaws. But it is more realistic to consider dentition size in relation to the dental arch size, than to jaw size.  Effects of excessive dentition size -Overlapping & displacement of teeth -Impaction of teeth -Space closure after extractions www.indiandentalacademy.com
  26. 26. Effects of early loss of primary teeth -Function & oral health -Over-eruption of opposing teeth -Psychological effects on child & parent -Position of permanent teeth Effects of asymmetric loss of primary teeth Space maintenance www.indiandentalacademy.com
  27. 27. Local Factors :  Aberrant developmental position of individual teeth -Trauma -Malposed crown -Dilacerated root -Unknown etiology( perm. Max. canines )  Presence of supernumerary teeth -Supplemental (teeth of normal form ) -Conical (the mesiodens ) -Tuberculate (usually palatal to the upper centrals, delaying their eruption ) www.indiandentalacademy.com
  28. 28.  Developmental Hypodontia Hypodontia can modify the occlusion & position of the teeth by virtue of its effects on : -The form of the teeth -The position of the teeth -The growth of the jaw  The Upper Labial Frenum This may cause median diastema. Other possible causes are : -Hypodontia -Supernumerary teeth -Generalized spacing -Proclination of upper incisors -Heredity www.indiandentalacademy.com
  29. 29.  Buccal Crossbite : -Bilateral Crossbite -Unilateral Crossbite -The Incisal Overbite www.indiandentalacademy.com
  30. 30. CLINICAL IMPLICATIONS  Normal versus Ideal occlusionNormal versus Ideal occlusion  Models of occlusionModels of occlusion  Occlusal Adaptive MechanismsOcclusal Adaptive Mechanisms www.indiandentalacademy.com
  31. 31. Normal vs Ideal occlusion  ‘Normal’ implies variations around an average or mean value  ‘Ideal’ connotes a hypothetical concept or goal  It is perfectly proper and practical to accept at the end of treatment , an arrangement of the teeth within the jaws in positions that are neither ideal nor normal but may be stable in a particular person’s face. www.indiandentalacademy.com
  32. 32. Models of occlusion  Occlusion is the common theme of all branches of dentistry, but the concepts of occlusion held by practitioners of different fields are different.  The best occlusion, and hence the best model of occlusion , is that which adapts best through time. www.indiandentalacademy.com
  33. 33. Occlusal Adaptive Mechanisms STAGE DENTITION BONE MUSCULATURE Developing dentition Eruption and tooth movement Growth Learning, imprinting Healthy adult dentition Wear, extrusion,anterior component Repair Supportive occlusal reflexes Deteriorating adult dentition Reconstructive dentistry Resorption pathology Traumatic occlusal reflexes: protective occlusal responses Edentulous adult Prosthetic dentistry Resorption Loss of sensory input www.indiandentalacademy.com
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