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PREPARATEON FOR AND CONSTRUCTION OF BAKED PORtXLAlN CROWNS AND INLAYS THOMAS B. SHARP, D.D.S." Emory University, School of Dentistry, Atlanta, Ga. T HE PARAMOUNT REASON E’OR the use of restorations of fused porcelain is its natural esthetic quality. It more closely si mulates the appearance of tooth ename l than any other material, with color and form remaining constant. The inherent weakne ss of porcelain lies in its friabil ity; therefore, usage in full coverage is limited to the anterior teeth in favorable incisal relationships. Vacuum -fired porcelain has increased the strength and improved the color saturation, hue, and brill iance over the usual baked porcelain. Porcelain inlays are used in Class III and V cavities, principally, when esthetic factors are of prime importan ce. Class IV cavities may be restored with porcelain inlays, but usually jacket crowns are mor e practical. TREAT.MENT PLANNING The diagnosis for porcelain crowns begins with a visual clinical examination. The eight upper anterior teeth are the usual concern oi the youthful and inter- mediate age groups. Disfigurement may be produced by unsightly diastem as and peg-sha ped teeth (often lateral incisors). Whe n these exist, well-formed , normal central incisors may be present with a 1.0 mm. diastema at the median lin e. The peg lateral in- cisors are dwarfed by comparison, and each may have a considerable diasterna mesially and distally. The m edian diastema may be closed in 2 or 3 days with orthodontic rubber bands around the two central incisors and secured with gold ligature wire. The lateral incisors can be prepared, and jacke t crowns constru cted, establishing the mesial and distal con tacts. The distal conta cts would be high, at the gingiv al fi of the tooth, perm itting a very slight but delicate diastema to appear in the incisal curve. The superior labial frenum attached at the gingivae usually atrophies under the pressure created by the continuous contacts of the si x anterior teeth, and rarely is it necessary to have it removed surgically. Other causes of disfi gurement are: ( 1) extensive caries and/or weaken ed restorations involving the incisal angles, (2) pitted and hypoplastic ename l tesuft- ing from eruptive fevers and childhood diseases, (3) unsightly gold restorations, (4) discolored teeth from devitali zation, (5) mottled e namel from endemic Auoro- sis, (6) trau matic injuries, or fractures, and (7) malposed teeth. Presented as a clinic before the American Academy of Restorative Dentistry. Chicago, Ill., Feb. 2, 1968. Received for publication Feb. 20, 1958. *Associate jn Clinical Crown and Bridge Dentistry. 1 13
