Case Study: Dental Caries

1.1 Introduction

Dental Caries is a bacterially based disease that progresses when acid produced by bacterial action on dietary fermentable carbohydrates diffuses into the tooth and dissolves the carbonated hydroxyapatite mineral resulting in demineralization. 1 Caries management historically has focused only on the removal of cavitated carious tissue and restoration of the tooth. In modern era, clinicians rely on their vision, dental instruments, and radiography as diagnostic tools but these conventional methods only detect relatively advanced lesions in the enamel. With advent of new emerging technologies for caries diagnosis it helps us as clinicians to detect early, reversible stage of caries and provide timely treatment and prevent

This concept advocated a proximal cavity preparation extending toward the buccal and lingual aspects of the tooth so that contact with adjacent teeth would not be at the margins. The separation of the margins, along with proper restoration contours, according to this concept was thought to promote natural cleansing of the embrasures with saliva and fluids in the diet.2

In 1892 , GV Black put forth his idea of "extension for prevention". His concept stated that :

Extension for prevention of the recurrence of decay after a filling has been made. This extension is always made in the preparation of proximal and gingival 3rd (smooth-surface) cavities. In each case the extension is toward the axial line angles of the tooth.

In smooth surface cavities, that is, in proximal cavities, which do not begin in pit or fissures, but occur in the central portion of an area due to poor hygiene. In these cases the superficial injury to the enamel tends to spread. Hence, the laying out of the outline form of the cavity is done upon a different principle. Objective is to include within the outline of the cavity portions of surface that are liable to decay in the future. This will often require that sound enamel and dentin be cut away to obtain correct outline form and is known as “extension for prevention” of the recurrence of the

Following these traditional cavity preparation techniques, results in large amount of tooth structure removal eventually leading to fracture of posterior teeth.
Various studies have shown that the cavity preparation size has a strong co-relation with the incidence of fracture. Research has shown that fractured cusps are the reason for replacement of 13% of amalgam restorations and restoring these fractures pose a difficult clinical problem.5
Vale in 1956, showed a decrease in the strength of a prepared tooth when its width increased from 1/4th to 1/3th of isthmus width. Teeth with narrow or shallow preparation restorations have least susceptibility to fracture.6 When all factors were considered, it was an MOD cavity restoration which leads to greatest number of cusp