Basic principles in the preparation of cavities in primary teeth

Date: 2015-10-07; view: 556.

Traditional cavity preparations for class I and class II lesions include areas that have carious involvement and, in addition, those areas that retain food and plaque material and may be considered as areas of potential carious involvement. A flat pulpal floor is generally advocated. However, a sharp angle between the pulpal floor and the axial wall of a two-surface preparation should be avoided. Rounded angles throughout the preparation will result in less concentration of stresses and will permit better adaptation of the restorative material into the extremities of the preparation. Although the traditional class I cavity preparation and restoration may occasionally be the most practical treatment for a tooth under certain circumstances, such treatment is currently obsolete for most class I lesions. The traditional treatment has been replaced, for the most part, by conservative caries excavation and restoration using a combination of bonding restorative and sealant materials. Likewise, the traditional class II cavity preparation and restoration, though not yet considered obsolete, is currently used less frequently as steadily improving restorative materials with therapeutic and bonding capability are developed. In the traditional class II cavity preparation for amalgam, the buccal and lingual extensions should be carried to self-cleansing areas. The cavity design should have greater buccal and lingual extension at the cervical area of the preparation to clear contact with the adjacent tooth. This divergent pattern is necessary because of the broad, flat contact areas of the primary molars and because of the distinct buccal bulge in the gingival third. Ideally, the width of the preparation at the isthmus should be approximately one third the intercuspal dimension. The axiopulpal line angle should be beveled or grooved to reduce the concentration of stresses and to provide greater bulk of material in this area, which is vulnerable to fracture. Because many occlusal fractures of amalgam restorations are caused by sharp opposing cusps, it is advisable to identify these potentially damaging cusps with articulating paper before cavity preparation. The slight reduction and rounding of a sharp opposing cusp will reduce the number of such fractures.