Minimal intervention Dentistry

Pit and Fissure – Enlarged lesion

Description
This cavity design modification is generally required where there has been extensive loss of core dentine to the extent that a cusp is at risk of a split at the base (Ref #4, Chapt. 10, p 154). The cavity margin will be at least half way up the cusp incline and the occlusal load on the remaining cusp will lead to the cusp flexing and splitting.

The basic principles of cusp protection (Ref #4, Chapt. 10, p 154) have been dealt with in several previous publications and the same principals apply with this cavity design.

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figure1	This is a technique exercise on an extracted tooth to illustrate this cavity and its restoration. There is an extensive lesion on the occlusal of an upper second molar.
figure2	The cavity preparation is reasonably conventional and includes a protective design to protect the disto-buccal cusp which was under load particularly in lateral excursion. Note there is softened demineralised dentine left on the floor particularly in relation to the pulp chamber.
figure3	A substantial layer of a high strength glass-ionomer has been laid down on the floor to encourage remineralisation.
figure4	The lesion has been restored with amalgam. Aesthetics is of no concern in this region, the occlusal load is expected to be high and the disto-buccal cusp requires support and protection.
figure5	The restored tooth has been sectioned to demonstrate the thickness of the GIC base and the protective design of the amalgam restoration. Note the shallow nature of the occlusal carving. This required some minor modification of the opposing cusp but the result is considerable reduction in lateral load on the disto-buccal cusp and therefore an increase in longevity.