Development of tooth- Introduction and Histology

Introduction to development of tooth. Oral histology describing bud stage, cap stage and bell stage.

1. DEVELOPMENT OF TOOTH PROF. DR. ARUN TOM DEPT OF ORAL PATHOLOGY

2. Stomodium

3. Primary Epithelial Band Oral epithelium Primary epithelial band Thickening of oral epithelium due to proliferation of basal cells Earliest event in the origin of each dental organ Progresses to form horse shoe shaped thickening Mesenchyme

4. Primary Epithelial Band Primary epithelial band divide in to Dental lamina Lingual extension (successional lamina) Distal extension Vestibular lamina

5. Dental Lamina Primordium for the ectodermal portion of primary teeth Activity extends for 5years Fate: Breaks up by mesenchymal invasion Remnant is called Cell Rest of Serres which persists as epithelial pearls of islands in the jaws or gingiva

6. Initiation of Tooth At 10 points little knobs growing in to ectomesenchyme

7. Patterning Determination of specific tooth types at their correct positions

8.  Odontogenic homeobox code model of dental patterning. Epithelial FGF8 and BMP4 expressed during early initiation induce the mesenchymal expression of a number of homeobox -containing genes in the underlying mesenchyme as overlapping domains that provide the spatial information necessary to determine tooth type.  A,  Domains of Barx-1 and Dlx-1/-2 expression overlap in the mesenchyme of the presumptive molar region, whereas domains of Msx-1, Msx-2, and Alx-3 overlap in presumptive incisor mesenchyme.  B,  Mouse dental pattern. Incisors deriving from Msx-1/Alx-3 expressing cells; molars deriving from Barx-1/Dlx-1/-2 expressing cells.  C,  Human dental pattern. Premolars and canines can be derived from the same odontogenic code as that observed in mice by virtue of the overlapping domains of gene expression. Thus canines and premolars may be derived from cells expressing Dlx-1/-2 and Msx-1, for example. (From McCollum MA, Sharpe PT:  Bioessays  23:481, 2001

9. Tooth germ For descriptive purpose tooth germ classified in to (morphologic) Bud Stage Cap Stage Bell Stage Enamel Organ Dental Papilla Dental Sac

10. Enamel Knot Enamel Knot knob like enlargement Densely packed cells Signaling centre FGF-4 & Slit-1 markers for knot formation

11. Apposition

12. Clinical consideration Lack of initiation: Anodontia Oligodontia (partial anodontia ) Abnormal initiation: Supernumerary teeth (hyper dontia ) Supplemental teeth Dilaceration Twinning Fusion ( synodontia ) Germination ( Schizodontia ) Peg shaped Hypo calcification &hypo meneralization