Technique Tips: Diagnostic method for assessing the amount of reduction in a crown preparation

Clinical tooth preparations are one of many routine treatments carried out in general and specialist practice. It is a topic that has been extensively researched and documented within academia and the teaching environment, with literature going back many decades and its principles are well illustrated and explained in the classic bibliographical textbooks.^1,2 However, a systematic review found a the lack of occlusal reduction and over tapering to be common in preparations.³ Other studies have found the average margin width to fall below the ideal reduction of 1–1.5 mm.^4,5 The ideal preparation varies depending on the type of restoration and underlying tooth structure (Table 1).

When carrying out a crown preparation, one of the major difficulties encountered is assessing the amount of reduction. Traditionally, a putty index constructed prior to the preparation has been used, which is then sectioned to give a guide as to how much has been reduced during the preparation (Figure 1).