Preparation modification for posterior ceramometal restorations with porcelain occlusal surfaces

TIPS FROM OUR READERS

Preparation modification occlusal surfaces D. J. Pipko,

D.M.D.,

for posterior ceramometal restorations with porcelain

and G. J. Hadeed,

D.M.D.

Pittsburgh, Pa.

This article presents a modification of the combination shoulder-chamfer preparation. The proposed modification involves the incorporation of a ledge on the reduced lingual surface of the shoulder-chamfer combination preparation (Figs. 1 and 2). The ledge is prepared at the height of contour of the lingual surface. It is approximately 1 mm in depth in the middle third of the lingual surface and tapers to blend into both of the proximal surfaces. This lingual ledge is prepared after the lingual reduction and the gingival chamfer is accomplished. A fine-tapered round-end diamond instrument with the end diameter of 1.5 mm is used. This modified combination shoulder-chamfer preparation can be placed on the maxillary and mandibular premolars and molars. The modification provides additional space for metal substructure and porcelain, which facilitates ideal facial-

lingual contour for the final restoration. Below this ledge modification on the lingual surface, an all-metal collar extends to the chamfer margin.’ In addition to providing adequate spatial requirements for the porcelain occlusal cermometal restoration, the modification adds retention to the preparation.

Fig. 1. Sectional view of typical preparation (right) and modified combination shoulder-chamfer preparation fkff) on molar.

Fig. 2. Dies of full shoulder shoulder-chamfer preparation

REFERENCE 1. Stein RS, Kuwata M. Crown contours are straight in teeth surfaces emerging from the gingival toward the height of contour. Dent Clin North Am 1977;21:683-9. Reprint requests to: DR. D. J. PIPKO MEDICAL ARTS BLDG., STE. 204 3708 FIFTH AVE. PITTSBURGH,PA 15213

Syringe technique for placement of visible light-curing preparations Thomas

M. Schulein,

(right) and combination (I+) of molar.

bases in conservative cavity

D.D.S., M.S.*

The University of Iowa, College of Dentistry, Iowa City, Iowa

Many practitioners have experienced difficulty in placing cement bases onto the pulpal floors of conservative cavity preparations. With even the smallest applicator instruments, the base is often deposited on the walls of the preparation

*Assistant Professor, Department of Operative Dentistry. THE JOURNAL

OF PROSTHEI’IC

DENTISTRY

perpendicular to the pulpal floor before it can be carried to the intended location. The concept of preventive resin restorations has been introduced and affords a valuable treatment mechanism for teeth with isolated, small carious lesions not involving the entire fissure pattern. When prepared conservatively, the resultant cavities are often quite narrow although often mod385