THERORIES OF TOOTH ERUPTION

Resource FacultyPrabhat Ranjan PokharelHead of department

Rajesh GyawaliAssistant professor

Jamal GiriAssistant professor

DEPARTMENT OF ORTHODONTICSPRESENTERNabin Chaudhary

Contents

• Root elongation theory(Hammock ligament theory)• Bone remodeling• Periodontal ligament contraction theory• Vascular pressure theory• Pulp constriction theory• Dental follicle theory

Physiologic tooth movement• Tooth eruption• Migration or drift of tooth• Changes in tooth position during

mastication

• Active eruption• Passive eruption• Anatomical crown• Clinical crown

Phases of tooth eruption

• Pre-eruptive phase• Eruptive phase(4 stages:root form-ation,penetration,movement,occlusalcontact)• Post-eruptive phase

Patterns of tooth movement

• Pre-eruptive phase1. Bodily(drifting) movement2. Eccentric growth• Eruptive phase1. Axial(occlusal) movement2. Drifting(bodily) movement3. Tilting(tipping) movement4. Rotating movement

• Post-eruptive phase1. axial

ROOT ELONGATION THEORY

proliferating root impinges on a fixed base, thus converting an apically directed

force of the tooth into occlusal movement

Fallacies

o rootless tooth erupts

o Some teeth erupt more than the total length of the roots

o Teeth erupt even after the complete formation of the root

Therefore root formation is accommodated during tooth eruption and is a consequence,

not a cause, of the eruption process.

• According to Harry Sicher, a band of fibrous tissue(cushion hammock ligament) exists below the root apex spanning from one side of alveolar wall to another.

Ligament was never found histologically

BONE REMODELING

• The end result of bone remodeling is a considerable bone deposition at the bottom of the socket• selective formation and resorption of bone brings about eruption.

• Fallacies : • alveolar bone remodeling which occurs around the root,endby bone

deposition, is the outcome and not the cause of axial tooth movement

PERIODONTAL LIGAMENT CONTRACTION THEORY• CONTRACTILE ELEMENTS - COLLAGEN AND FIBROBLASTS

CONSTRICTION

Force initiated by fibroblast

Transmitted to extracellular compartment via fibronexus and collagen

bundles by root formation

ERUPTION

• Fallacies

• Examples of PDL being present but tooth not erupting and rootless

teeth erupting have been reported.

• Fallacies

• Examples of PDL being

present but tooth not

erupting and rootless

teeth erupting have

been reported.

A –fibroblasts

B –adherence type intercellular junctions

C – fibronexus, attached to collagen by fibronectin

D – deposition of collagen

E – resorption of collagen

PULP CONSTRICTION THEORY

• Growth of root dentin and constriction of pulp --- sufficient pressure to move tooth occlusally• Fallacies

• Pulpless teeth erupt at same rate as normal teeth

• Premature extraction of deciduous molar: premolar do erupt

without any growth of dentin or pulp constriction

VASCULAR PRESSURE THEORY

• THE VASCULAR PRESSURES are present in pulpal tissues as well as in the

periodontal ligament

• The pressure exerted by the blood vessels at the apex of the tooth help

in eruption of teeth

• Fallacies

• The pressure exerted is not enough to help in eruption of teeth

• Teeth erupt even when the vascular supply is cut

DENTAL FOLLICLE THEORY

• Specific cellular changes occur in and around the follicle when a

tooth erupts.

• Source for new bone-forming cells and osteoclasts

• Teeth eruption is delayed or absent in animal models and human

diseases that cause a defect in osteoclast differentiation

• Tooth eruption is definitely a multifactorial process involving all • or few factors of the above or other factors like Control of Endocrine Glands Pressure from muscular action Effect of Nutrition Inherent tendency of teeth to erupt

Facts

• Rate of eruption• Intraosseous=1-10µm/day

• Extraosseous=75 μm/day

• Root formation ( tomes 1872 )• Bone remodeling ( brash 1928 )• Dental follicle ( marks and cahill 1984)• Periodontal ligament ( thomas 1967 )• Hydrostatic pressure ( sutton and graze 1985 )• Pulpal pressure ( v . Korff 1935 )