MAY 2001 THE JOURNAL OF PROSTHETIC DENTISTRY 521 During abutment tooth preparation for fixed partial dentures, the presence of undesirable undercuts, due to clinical complicating factors such as poor visibility and access, frequently is observed. 1 The presence of undercuts may hinder the complete seating of the cast restoration, resulting in the need to recontour the pre- pared tooth and make a new impression. This article presents an easy and quick method for evaluating sin- gle or multiple tooth preparations to detect undercuts before making the final impression. PROCEDURE 1. Make an irreversible hydrocolloid impression after gross tooth reduction using a partial perforated tray, and form the mold with a fast-setting stone. Temporization procedures can be initiated con- comitantly to prevent loss of time. 2 2. Using a pencil such as the analyzing rod of a sur- veyor, hold the lead parallel to the axial wall of the prepared teeth (Fig. 1, A) and draw 2 lines that encompass the entire circumference of the prepared tooth. The first one must be coincident with the junction between the axial wall and the cervical margin (Fig. 1, B), and the other must correspond to the junction between the axial reduction and the external cusp reduction (Fig. 1, C). Note that the A simple method to detect undercuts during tooth preparation for fixed prosthodontics Cláudio R. Leles, a and Marco Antonio Compagnoni b Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil a Postgraduate Student, Department of Dental Materials and Prosthodontics. b Chairman and Professor, Department of Dental Materials and Prosthodontics. J Prosthet Dent 2001;85:521-2. Fig. 1. Procedural steps. A, Determination of axial wall of prepared teeth; B, cervical line; C, occlusal line; D, final aspect of cast; and E, occlusal view of convergence of prepared teeth. B A C D E