Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

Injuries to developing teeth
The close relationship between the apices of primary teeth and their
permanent successors explains why injuries are easily transmitted
from the primary to the permanent dentition. Traumatic injuries to
developing teeth may influence their future growth and maturation.
When the injury occurs during the initial stages of development,
enamel formation can be seriously disturbed owing to interference
with a number of stages in ameloblast development.
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Chapter 4
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Resorption
Transient root resorption occurs frequently in traumatised teeth
2
and
in those undergoing orthodontic treatment. It is normally without
clinical significance. Pressure resorption in the permanent dentition
seen during tooth eruption is also seen in orthodontic movement of
teeth
3
and usually manifests as a shortening of the roots. It may be
quite destructive if diagnosed late.
Root resorption sustained by infection is the most important clinical
condition from an endodontic point of view. It can occur either on 
the root surface (external resorption), or in the root canal (internal
resorption). Replacement or endosteal root resorption is seen in teeth
that have suffered dentoalveolar ankylosis because of necrosis of the
periodontal ligament.
Internal root resorption
It has been shown that bacterial infection is a prerequisite for internal
resorption
4
. This process seems to be elicited by irritation from bacte-
ria or their products within the dental tubules derived from caries,
fractures or anatomical defects. Sometimes, resorptive defects are
noted radiographically in root-filled teeth and this may be attributed
to percolation of oral fluids via a defective coronal restoration or peri-
odontal pocket and lateral canals etc. When seen radiographically,
internal resorption is a definite indication that endodontic treatment
is required. Clinically, there is necrosis in the pulp chamber and in the
root canal to a level coronal to the resorption lacunae. Root treatment
is complicated by the problems associated with removal of tissue
from a resorptive defect and any remnants may contribute to failure.
The treatment of choice is to use sodium hypochlorite as an irrigant
and to dress the canal with calcium hydroxide paste, replacing at 2–3-
week intervals before filling with gutta-percha. A thermo-softened
filling method may be indicated if there is extensive resorption.