PHYSIOLOGIC TOOTH MOVEMENT ─ ERUPTION AND SHEDDING

PHYSIOLOGIC TOOTH MOVEMENT─ERUPTION AND SHEDDING 高雄醫學大學兒童牙科陳弘森 07-3121101-7008, 7020 hosech@kmu.edu.tw

Eruption • Movement of a tooth through the jaw into the oral cavity.

Pattern of tooth movement • preeruptive movement • eruptive movement • posteruptive movement

Histology of tooth movement • Preeruptive phase • Eruptive phase • Posteruptive phase

Preeruptive phase • Bodily movement • Excentric growth bony remodeling osteoclast

Eruptive phase • Root formation • Periodontal ligament • Dento-gingival juction

Posteruptive phase • Condylar growth • Jaw bone growth

Direction of tooth movement • Axial • Drifting • Tilting • Rotating

Tooth eruption mechanism • The push mechanism • The pull mechanism

Push mechanism • Root growth (Pierce 1887) • Vascular pressure (Constant 1900) • Bone growth (Brash 1928) • Cellular proliferation (Eidmann 1923) • Dental follicle

Pull mechanism • Collagen maturation (Thomas 1967) • Fibroblasts (Ness 1967)

Eruption rates • Mouse • Guinea pig 200-1100 μ m/day • Rabbit • Human 140 μ m/day (5 μ m/day)

Clinical consideration • Early eruption • Delayed eruption • Impacted

Shedding(exfoliation) • Gradual removal of roots and alveplar bone

Shedding of teeth odontoclasts pressure

odontoclasts Cementoclas Dentinoclast

Histology of shedding • Odontoclasts Large multinucleated cell Cytoplasm of vacuole Dense mitochondria Brush border surface Acid phosphatase

Odontoclasts resorption bay (Howship’s lacunae) brush border (ruffled border ; microvilli ) acid phosphatase

Root resorption • resorption period • rest period • repair period

PHYSIOLOGIC TOOTH MOVEMENT ─ ERUPTION AND SHEDDING