February 14, 2008

Amelogenesis - The Formation of Enamel A.Hard Tissue Formation B.Amelogenesis C.Structure of Enamel D.Clinical Correlations E.Enamel versus Dentin

ENAMEL vs DENTIN Enamel Spindles

ENAMEL vs DENTIN Striae of Retzius

ENAMEL vs DENTIN Perikymata

Enamel: Primary versus Permanent Teeth * Similar enamel structure [except at tooth surface where primary teeth more likely to have a “prismless” surface (lacks enamel rods)] * Enamel is about twice as thick in permanent teeth * Postnatal enamel more highly pigmented, so…. enamel of primary teeth whiter than permanent teeth (believed due to primary tooth enamel formed prenatally, not subject to some environmental factors)

Enamel Rod Basics Enamel rod: * represents “mineralized trail” taken by ameloblast * diameter of corresponds to the diameter of columnar ameloblast that formed it * rods vary in length…short near cervix, in pits & in fissures * inclination of rods varies more inclined near cusps, almost vertical near cervix

DENT 5315 & DH 2215 Dentin-Pulp Complex 1 February 14, 2008 A.Dentinogenesis B.Root Formation C.Dentin-Pulp Complex D.Dentin Classification E.Clinical Correlations

Hard Tissue Formation Bell Stage

Dentinogenesis - Secretory Stage

Dentinogenesis acellular zone separates ameloblasts from dental papilla

Dentinogenesis First sign of dentin formation.

Dentinogenesis arrows show von Korff’s fibers

Pulp Odontoblasts Dentin Tubules Dentinogenesis Odontoblasts have a cell process.

Dentinogenesis Note: trapped odontoblast processes at dentino- enamel junction (DEJ) Odontoblasts have a cell process.

Dentinogenesis DEJ - Trapped Odontoblastic processes

Dentinogenesis Odontoblastic cell processes in dentin tubules

Dentinogenesis Note: collagen fibers & odontoblastic processes in tubules

Dentinogenesis Note: mineralization foci forming mantle dentin Odontoblasts produce organic matrix & crystals.

Dentinogenesis Note: predentin layer

Root Formation Proliferation of cells from “cervical loop” Cervical Loop

Root Formation Formation of Hertwig’s epithelial root sheath.

48 Hertwig’s Epithelial Root Sheath

Root Formation Sheath grows around dental papilla/future pulp.

THE DENTIN-PULP COMPLEX

Root Formation & Periodontium

Root Formation 56 Formation and narrowing of apical foramen.

The Completed Root PDL 123 Pulp Incremental layering of cementum. Alveolar bone

Apicoectomy THE DENTIN-PULP COMPLEX

Green Arrows: “Rests of Malassez” (remnants of Hertwig’s epithelial root sheath) 135 Periodontal Ligament Space