PDF: Endodontic Cavity Preparation


A standard radiograph (left) in buccolingual projection provides only a two-dimensional view of what is actually a three-dimensional problem. 




If a mesiodistal x-ray projection could be made (right), one would find the pulp of the maxillary second premolar to be flat tapering “ribbon” rather than round “thread” visualized on the initial radiograph. The final ovoid occlusal cavity preparation (F) will mirror the internal anatomy rather than the buccolingual x-ray image.

Read also: Obturation of Root Canal Systems

Coronal preparation of a maxillary first molar illustrating the major principle of endodontic cavity outline form: the internal anatomy of the tooth (pulp) dictates the external outline form. This is accomplished by extending preparation from inside of the tooth to the outside surface, that is, working from inside to outside.

Endodontic cavity preparation, mandibular first molar, superimposed on inlay, restoring proximal-occlusal surfaces. Black’s outline form of inlay is related to the external anatomy and environment of the tooth, that is, the extent of carious lesions, grooves, and fissures and the position of the approximating premolar. 

A triangular or rhomboidal outline form of endodontic preparation, on the other hand, is related to the internal anatomy of the pulp. No relationship exists between the two outline forms.