Development of dentition

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Presenter:Dr. Jamal GiriResident (1st Year)

Development of dentitionContentsDevelopment of dentition and supporting structures.Mechanism of tooth eruption.Proffits contributions regarding eruption.Clinical implications.

2Dept. of dentistry-PG section, IOM (2011)4th week of Intra uterine life (IUL)

3Dept. of dentistry-PG section, IOM (2011)Development of Branchial archNeural crest cells migrate into the head and neck region (4th week)

4Dept. of dentistry-PG section, IOM (2011)

5Dept. of dentistry-PG section, IOM (2011)6th week of Intra uterine life(IUL)Basal cells of oral epithelium proliferate at a rapid rate.

Condensation of underlying connective tissue.

Formation of primary epithelial band.

6Dept. of dentistry-PG section, IOM (2011)7th week of Intra uterine life(IUL)Primary epithelial band divides into 2 processes:1) Vestibular lamina.

Oral vestibule2) Dental lamina. Tooth bud

7Dept. of dentistry-PG section, IOM (2011)Dental lamina8th-10th week of IUL: Series of swellings corresponding future deciduous teeth.

8Dept. of dentistry-PG section, IOM (2011)Directly from Dental lamina.Deciduous teethLingual extension of Dental laminaSuccessional teethDistal extension of Dental lamina.accessional teeth

9Dept. of dentistry-PG section, IOM (2011)

10Dept. of dentistry-PG section, IOM (2011)Stages of tooth development1)Bud stage.

2)Cap stage.

3)Bell stage.

4)Stage of apposition.

5)Stage of root formation and eruption.11Dept. of dentistry-PG section, IOM (2011)Bud stageStage of initiation.

Formation of Bud shaped enamel (dental) organ.

12Dept. of dentistry-PG section, IOM (2011)AgeTooth Bud formation8-10 weeks (IUL)All the deciduous teeth.4th month (IUL)Permanent first molar.5th month (IUL)Permanent central incisor to first premolar.10th monthPermanent second premolar.1 yearPermanent second molar.4-5 yearsPermanent third molar.13Dept. of dentistry-PG section, IOM (2011)Cap stageStage of proliferation.

Differential growth (more towards periphery).

Formation of tooth germ.

Dental papillaDental sacEnamel organTooth germ14Dept. of dentistry-PG section, IOM (2011)First signs of cellular arrangement.

Enamel organ :Enamel.

Dental papilla : Dentin & pulp

Dental sac : Cementum & periodontal ligament.

15Dept. of dentistry-PG section, IOM (2011)Bell stageStage of histo-morphodifferentiation.

4 distinct cell types present in enamel organ.

The dental lamina disintegrates.

16Dept. of dentistry-PG section, IOM (2011)

17Dept. of dentistry-PG section, IOM (2011)Formation of ameloblast

18Dept. of dentistry-PG section, IOM (2011)Appositional stageReciprocal interaction.

Dentin and enamel formation.

19Dept. of dentistry-PG section, IOM (2011)

20Dept. of dentistry-PG section, IOM (2011)Reduced enamel epitheliumFormed by outer and inner enamel epithelium.

Protect the enamel before eruption.

21Dept. of dentistry-PG section, IOM (2011)Stage of root formation and eruption.

22Dept. of dentistry-PG section, IOM (2011)

23Dept. of dentistry-PG section, IOM (2011)Stages of tooth development

24Dept. of dentistry-PG section, IOM (2011)Genetic basis of tooth development.More than 200 genes involved. Homeobox genes.

(http://bite-it.helsinki.fi)

Oral Biosci Med 2/2004, S. 77-9125Dept. of dentistry-PG section, IOM (2011)

Patterning of Dentition

26Dept. of dentistry-PG section, IOM (2011)

Oral Biosci Med 2/2004, S. 77-9127Dept. of dentistry-PG section, IOM (2011)Defective initiation

28Dept. of dentistry-PG section, IOM (2011)Defective Proliferation

29Dept. of dentistry-PG section, IOM (2011)Defective histodifferentiation

30Dept. of dentistry-PG section, IOM (2011)Defective morphodifferentiation

31Dept. of dentistry-PG section, IOM (2011)Defective apposition

32Dept. of dentistry-PG section, IOM (2011)Tooth eruptionGreek word:Erumpere- to break out

The process whereby a tooth moves from its developmental position within the jaws to emerge in the oral cavity.

33Dept. of dentistry-PG section, IOM (2011)Theories of tooth eruption.Role of root formation.

Role of bone remodeling.

Role of periodontal ligament.

Role of hydrostatic pressure.

Role of dental follicle.

34Dept. of dentistry-PG section, IOM (2011)Role of root formation.

35Dept. of dentistry-PG section, IOM (2011)Pitfalls:Rootless teeth also erupt (Dentin dysplasia).

Hammock ligament hypothesis.

Root length is not equal to distance of path of eruption.

36Dept. of dentistry-PG section, IOM (2011)Role of bone remodelling.Selective deposition and resorption of bone.

Marks and Cahill studies: when the tooth germ is wired to bone, the bony eruption pathway is still formed.

37Dept. of dentistry-PG section, IOM (2011)Role of periodontal ligament.Formation & renewal of the PDL has been considered a factor.

Pitfalls:1) dentin dysplasia.2) Primary failure of eruption.

38Dept. of dentistry-PG section, IOM (2011)Role of hydrostatic pressure.Van Hassel and McMinn (1972)

Hydrostatic pressure gradient apico-occlusally.

Pitfall:Relatively small study (6 dogs).

39Dept. of dentistry-PG section, IOM (2011)Role of dental follicle.Marks and Cahill.

a pattern of cellular activity involving the reduced enamel epithelium (REE) and the follicles.

Recruitment of osteoclasts & release of proteases.

40Dept. of dentistry-PG section, IOM (2011)

Wise et al, CROBM July 2002 vol. 13 no. 4 323-335 41Dept. of dentistry-PG section, IOM (2011)receptoractivator of nuclear factor kappa B (RANKL)41Study on dogs premolar.

Removal of the follicle from the unerupted tooth prevented the tooth from erupting (Cahill and Marks, 1980).

Leaving the follicle intact and substituting an inert object for the tooth resulted in eruption of the inert object (Marks and Cahill, 1984).

42Dept. of dentistry-PG section, IOM (2011)Proffits contributionMechanism and control of tooth eruption: overview and clinical implications, Orthod Craniofac Res 2009;12:5966.

Tooth eruption is difficult to study:1) erupt slowly.2) Inaccessible for clinical examination.43Dept. of dentistry-PG section, IOM (2011)For eruptive movements. Eruptive force.Clearance of eruption path.44Dept. of dentistry-PG section, IOM (2011)Eruptive force.Remains elusive. E R U P T I O NRoot formationBone remodellingDental follicleHydrostatic pressurePeriodontal ligament45Dept. of dentistry-PG section, IOM (2011)

Clearance of eruption path.Pressure from the eruptive force causes resorption.

An eruption path is cleared and the tooth follows along it.

46Dept. of dentistry-PG section, IOM (2011)Resorption-Eruption uncoupling

Ankylosis47Dept. of dentistry-PG section, IOM (2011)

Primary failure of eruption48Dept. of dentistry-PG section, IOM (2011)The daily rhythm of tooth eruptionAJODO, Volume 107, Issue 1, January 1995, Pages 38-47.

17 subjects ( 10 boys, 7 girls)

41 hour video microscopic observation.

49Dept. of dentistry-PG section, IOM (2011)ResultsMean daily eruption: 71um/day

Small amount of intrusion during Daytime.

Net eruption at night.

Transient intrusion associated with breakfast, lunch, dinner.50Dept. of dentistry-PG section, IOM (2011)

51