The class II procedure lends itself to closer examination, since it is one of the toughest and most involved restorative procedures a dentist can perform. It is also the type of case that can easily result in an excessive amount of tooth structure being removed. During a class II, it is extremely important to the long-term health of the dentition that we be as conservative as possible in preparing and restoring class II lesions. Especially important is the preservation of the peripheral rim of enamel, as described by Rainey and Milicich.The marginal ridge is a part of a distinct rim of enamel around the occlusal surface that is one of the main stress distribution structures in a tooth. Once the stress distribution system of the tooth is disturbed by a cavity, this demarcation zone becomes clinically evident. To maintain the integrity of the tooth whenever possible, the operator should complete a tunnel preparation, or slot preparation, or when access permits, treat the lesion as though it were a class III. Certain factors must be considered when deciding which type of preparation to use. Second, in high caries risk patients, slot preparations or class II type preparations may be a better choice than a tunnel preparation. Rapid onset caries with early cavitation is more suitable for slot preparations, while slow onset noncavitated contact point caries is ideal for tunnel preparations. In high caries risk patients, the interproximal demineralization often extends well into the embrasures, and a tunnel preparation will not completely isolate the underlying dentin from the microporous enamel.
.
