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

Planning of the retentive form
If a non-adhesive restoration is to be placed, some mechanical reten-
tion must be included in the preparation. The nature of caries lesions
Principles of direct intervention


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is such that removal of the caries should result in a preparation that is
undercut in cross-section. This general form may provide sufficient
retention for the restoration. However, in a large preparation, 
additional retentive features may need to be provided – these include
undercuts, grooves, boxes etc. and these aspects are addressed later in
this chapter.
Integrity of the restoration
Internal preparation features affect the stresses that occur within 
the restoration. This is particularly important in the case of pro-
ximal lesions in which the placement of a groove in the floor of 
the ‘box’ will minimise the lateral forces to which the restoration is
subjected and thus reduce failure due to fracture of the restorative
material.
A wide range of rotary and hand instruments may be used to
remove unsupported tooth structure and form features within the
remaining tooth structure. Such procedures should always be per-
formed in such a way as to minimise pulpal damage. Completed
preparations must always be meticulously cleaned, dried and then
carefully inspected for evidence of residual caries or small exposures,
which may have been overlooked.
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Chapter 2
Fig. 2.1
Rounded cavity form and position of occlusal contacts relative to 
cavity margins.
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ALTERNATIVE PREPARATION METHODS
Chemomechanical caries removal
Chemomechanical techniques are one of the recently documented
alternatives to traditional mechanical rotary techniques and mechan-
ical non-rotary techniques.
Chemomechanical caries removal involves the application of a 
gel to tooth tissue. This selectively softens the carious dentine, thus
facilitating its removal. Removal of sound tooth structure, the cutting
of open dentinal tubules, pulpal irritation and pain are all reduced
when compared with conventional mechanical methods
12
.
The first commercially launched product for chemomechanical
caries removal was Caridex (National Patent Medical Products Inc.),
initially introduced on the US market in 1985. This system involved
Principles of direct intervention