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

Removal of caries
With access established, caries is removed, first from around the
amelodentinal junction and then, working apically, towards the areas
overlying the pulp. When caries extends down to a vital pulp, one
should aim to remove all soft, stained, infected dentine leaving either
some stained but firm dentine or possibly some slightly softened,
unstained dentine protecting the pulp from exposure. The rationale
for this is that affected dentine (rather than infected dentine) may be
retained and remineralised with the use of a therapeutic liner. It is
common to experience difficulties in distinguishing between dentine
that should be removed, and that which should be left. Fluorescence-
aided caries excavation
5
or a caries detector dye have been suggested
as aids in such situations, but may actually lead to over-preparation
6
.
The area of the amelodentinal junction must always be made completely
Principles of direct intervention


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caries-free, although again the necessity for this has recently been
questioned.
Development of final form
Once the caries has been removed, before proceeding to create the
final cavity form, it is necessary to consider the biological, functional
and mechanical demands that will be placed on the final tooth-
restorative ‘system’. In particular, the following should be considered.
Minimisation of the effect of preparation on 
tooth strength
Any preparation will weaken a tooth and predispose it to fracture. To
minimise this effect, all internal line angles should be rounded.
Choice of restorative material
The material to be used is dictated largely by the size of the
cavity/preparation and an assessment of the functional demands 
that will be placed on the tooth-restorative system. If the tooth is 
non-functional then mechanical properties of the material will not be
a large consideration, but for a large preparation in a functional tooth
a material that is strong (e.g. amalgam) and able to withstand the
stresses encountered during function will be required. The choice of
material will influence the final form of the preparation, particularly
the cavo-surface angle (more critical with amalgam restorations) and
presence of retentive features (more required with non-adhesive
restorations).