Retention of provisional crowns fabricated from two materials with the useof four temporary cements

Statement of problem. Practitioners often choose resin materials and tempor ary cements with little understanding about their effect on provisional cro wn retention. Purpose. This study evaluated the retention of provisional restorations mad e with 2 materials and cemented with 4 temporary cements. Methods and material. Recently extracted molars were prepared with a nat oc clusal surface, 4-mm axial length and 20-degree angle of convergence. Speci mens were distributed into equivalent groups. Provisional crowns were const ructed for each preparation with polymethyl methacrylate (Temporary Bridge Resin) or bis-acrylic composite (Protemp Garant) and later cemented with Te mp-Bond, Temp-Bond NE, Temrex, and an experimental calcium hydroxide tempor ary cement. A second group with Temrex was evaluated using half the recomme nded liquid. A cementing force of 2.5 kg for 5 minutes was used. After init ial bench set followed by 24 hours in room temperature water, the crowns we re removed with an Instron mechanical testing machine at 0.5 mm/min. A 2-fa ctor ANOVA was used with alpha=.05 (n = 10). Mode of debonding was analyzed with a nonparametric chi-square test of association. Results. Mean dislodgment stresses ranged from 670 to 1072 kPa for polymeth yl methacrylate crowns and 554 to 884 kPa for those made of composite. Diff erences were nearly significant for the type of provisional material (P=.06 1) and the cross-product interaction (P=.376) was not significant, whereas there were significant differences among the cements (P=.002) and the mode of debonding (P=.0034). Conclusions. Excluding Temp-Bond to eliminate a cross-product interaction d emonstrated that the polymethyl methacrylate crowns were 19.3% more retenti ve than the composite crowns (P=.015). There was no statistically significa nt difference among the 4 temporary cements when the manufacturer's mixing instructions were followed (P=.186). However, the thicker consistency Temre x was more retentive than the recommended Temrex mix and Temp-Bond.