比色英文版Chapter 51.ppt

Provisional Coverage Chapter 51 Introduction Provisional coverage is a temporary protective covering that is temporarily cemented to a prepared tooth for a single crown or to abutment teeth for a bridge preparation. Purpose of Provisional Coverage Reduces sensitivity and discomfort in the prepared tooth. Maintains the function and esthetics of the tooth. Protects the margins of the preparations. Prevents shifting of the adjacent or opposing teeth. Fig. 51-1 Types of provisional coverage. Custom Provisional Coverage The most common type of provisional coverage used for crown and bridge preparations. The technique can be used for either posterior or anterior crowns or bridges. Criteria for Constructing Provisional Coverage Must be esthetically acceptable to the patient. The contours are similar to those of the natural tooth. The cervical margin is smooth and fits snugly. Does not extend below the margin of the preparation. The occlusal surface is aligned with the occlusal plane of the adjacent teeth. When cemented, it remains stable, stays in place, and is comfortable for the patient. Can be readily removed without damage to the tooth or adjacent tissues. Preformed Polymer Crowns Provisional shell-like crowns that are designed specifically for premolars and molars. These shells are made from a polymer material that is designed with anatomic features of natural teeth. Fig. 51-8 Preformed polymer crown. Aluminum Crowns An aluminum crown is available in a range of sizes. The crown surface may be anatomic or nonanatomic. The crown is sized, contoured, and cemented in place. Fig. 51-13 Aluminum crown cemented. Preformed Polycarbonate Crowns The preformed polycarbonate crown is tooth?colored and is selected for anterior teeth where appearance is important. These crowns are available in a variety of sizes, shapes, and shades. Fig. 51-14 Size and shape of a polycarbonate crown. Home Care Instructions for Provisional Coverage Bite and chew