8.7 OPERATIVE TREATMENT OF PRIMARY TEETH
8.7.1 Pit and fissure caries
Pit and fissure caries is less of a problem in primary teeth than in permanent ones. The
fissures are usually much shallower and less susceptible to decay, so the presence of a
cavity in the occlusal surface of a primary molar is a sign of high caries activity.
Because of this it is quite likely that the children who require treatment of these
surfaces will be young. However, treatment is not difficult and can usually be
accomplished without problem. Infiltration analgesia should be given together with
supplemental intrapapillary injection. Caries is removed using a 330 bur in a high-
speed handpiece. For restoration⎯although, as indicated above, silver amalgam has
not so far been bettered in clinical trial⎯because occlusal caries in the primary
dentition indicates high caries activity, the material of choice may be a resin-modified
glass ionomer cement with its possible caries preventive properties (355HFig. 8.8).
8.7.2 Approximal caries
Silver amalgam
Failure of amalgam itself as well as faults in the cavity design have been the most
commonly reported causes of failure of approximal restorations in primary teeth.
Attempts to overcome these deficiencies and to improve durability have come through
alteration in cavity design and the choice of material used. A reduction in the size of
the occlusal lock, rounded line angles, and minimum extension for prevention all
result in less destruction of sound tooth tissue. In addition, the 'minimal' approximal
cavity with no occlusal 'dovetail' has been described for both amalgam and adhesive
restorations, and incorporates some mechanical retention in the form of small internal
resistance grooves placed with a very small round bur just inside the enamel-dentine
junction. 356HFigure 8.12 (a)-(f) demonstrate the clinical stages in the placement of two-
surface amalgam restorations in the primary dentition.
It is unlikely that the 'perfect cavity design' exists for an amalgam restoration in
primary molars due to certain anatomical features:
- Widened contact areas make a narrow box difficult to achieve.
- Thin enamel means that cracking and fracture of parts of the crown are more
common. - Primary teeth may undergo considerable wear under occlusal stress themselves and
this in turn will affect the restorations.
It is therefore necessary to investigate other materials for use in restoring the primary
dentition.
Composite resin
Composite resin has been used quite widely to restore primary teeth and results are