[Comparative study of crown retention on composite core by glassionomer luting cement, adhesive resin and zinc phosphate after thermocycling]

One of the important points in dentistry is retentive strength of crown on teeth or bridge on abutments. One the effective factors in retention is cement type and its relation to core buildup materials. One of the core buildup materials which has a wide usage in Iran, is the commercial Core Max II composite. The aim of this study is to compare the retention of cemented crowns by zinc phosphate, glassionomer and resin cements of panavia F on Core Max II dies. In this research silver cast alloy crowns were made on 90 similar dies of core max II, these dies were divided to 3 groups of 30: In each group the crowns were cemented on Core Max II dies with one of three cements. Then the crowns were pulled tensively in Instron machine, and the results were analyzed with SPSS V.11.5 software. In this study the analytic tests of ANOVA and Tuky test were used [alpha= 0.05]. According to quantitative analysis between 3 cements glassionomer, zinc phosphate and panavia F had significant difference [P=0.001]. The evaluation of mode of failure revealed that the most common failure pattern in panavia F was cohesive in core [80%], which reveals more retention between core, panavia [as cement] and crown, however in glassionomer this was [26/7%], and there was no cohesive failure in zinc phosphate. Considering retentive characteristics when the Core Max II composite cores are made the best cements are panavia F and glassionomer respectively