Oral stereognostic ability and masticatory performance in denture wearers.

This study examined the relationship between masticatory performance and oral stereognostic ability in 71 dentate individuals and 64 denture wearers. Stereognosis was evaluated in denture wearers with and without dentures in place. No significant differences (P > .05) were noted between the stereognostic scores of either group, with both groups correctly identifying approximately 68% of the items. This suggests that the receptors in the periodontal ligament are of minimal importance in the oral detection of shape and that the loss of teeth and placement of dentures does not diminish the perception of shape differences. Correlations between masticatory performance and stereognostic measures ranged in magnitude from 0.01 to 0.12 (P > .05). Further studies employing smaller test forms may be needed to assess the role of stereognosis on food manipulation during mastication.

Reuse of silver-palladium ceramic metal.

The effect of various percentages of reused silver-palladium alloy on the bond strength of porcelain was considered. All-new metal and once-cast alloy with the addition of 50% new metal produced the highest bond values. Once-cast alloy with less than 50% new metal produced bond strength values that were significantly lower. When using this silver-palladium alloy, 50% new alloy should be added to each casting button, and buttons with questionable casting history should not be used.

Effect of opaque porcelain application on strength of bond to silver-palladium alloys.

The opaque porcelain layer for porcelain-fused-to-metal restorations is critical for success. This investigation examined opaque porcelain application using one- and two-layer techniques with respect to their effect on the strength of bond to three silver-palladium alloys. There were no significant differences in the flexural bond strengths of the three alloys for the one- and two-layer opaque application techniques. With respect to bond strength, these results afford flexibility in the choice of the one- or two-layer techniques.

Effects of cooling methods on silver-palladium castings.

Cast metal specimens for three ceramic metals were subjected to two different types of cooling procedures after casting. One method involved the rapid cooling of the casting as soon as the red glow of the button disappeared. The other method allowed the castings to bench cool to room temperature. Hardness, bond strength, and microstructural determinations lead to the following conclusions. 1. Vickers hardness values for W-1 and Rx-91 alloys for each cooling regimen were not significantly different. Statistically higher hardness values were obtained for the quenched specimens of JP-5 alloys compared with the bench-cooled specimens. 2. Cooling of W-1 and JP-5 alloy specimens by quenching resulted in higher bond strengths than for specimens that were bench-cooled to room temperature. However, bench-cooling Rx-91 alloy lead to higher bond strengths than did quenching. 3. For all of the alloys examined, quenching produced a smaller grain structure than did bench-cooling. 4. From the standpoint of the parameters tested and the saving of processing time, quenching of the silver-palladium ceramic alloys examined is the cooling procedure of choice for W-1 and JP-5 alloys.

Effect of metal surface treatment on ceramic bond strength.

This study indicates that the unaltered specimens of both alloys produced the lowest bond values; for the gold-palladium alloy, a short degassing period (manufacturer's recommendation) and a 10-minute degassing period resulted in significantly lower bond strengths than those observed with the aluminum oxide and the steam cleaning treatments; and all treatments of the silver-palladium alloy gave comparable bond strengths to that obtained with the manufacturer's recommendation for surface treatment. Because the simplified methods gave equivalent or higher bond strength values than the manufacturer's recommendations, and because of the time saving, we recommend the following procedures for the porcelain-alloy systems tested: After casting and investment removal, use an abrasive to remove casting irregularities and to modify or correct the surface that will receive porcelain. Create a uniform matte finish on the surface that is to receive porcelain by pressure blasting with 50 micron aluminum oxide particles, or steam clean the surface for 30 seconds, or both. Proceed with opaquing.

Composite resin repair of porcelain denture teeth.

An effective temporary repair of fractured poreclain denture teeth involves abrasive treatment of the fractured tooth surface followed by a composite resin buildup. This study has demonstrated that the best potential retention of the composite buildup can be obtained through abrasive treatment by a course diamond stone.