PHYSIOLOGIC TOOTH MOVEMENT─ ERUPTION AND SHEDDING 高雄醫學大學 兒童牙科 陳弘森 , 7020

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

Pattern of tooth movement 1. preeruptive movement 2. eruptive movement 3. 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 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

Clincal consideration  Remnants of deciduous tooth  Retained deciduous tooth  Submerged deciduous tooth

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