Different Molten Mold Material Accuracy Of Crowns,

Objective To evaluate the influence of different pattern materials on the marginal precision of wax pattern crowns at different time and marginal precision of casting crown made with different patterns.Methods Standard specimen with 90-degree shoulder and 4-degree convergens was made.4 groups pattern crowns were completed on the plaster dies fabricated from the master standard specimen with four kinds of pattern materials,Casting Pattern Resin,SOFU Hard wax,BEGO Crown wax and common inlay wax.There were 10 pattern crowns in every group.The marginal opening of the pattern crowns were measured under Projection Measuring Instrument at the time of 10,20,30,60,120,240 min.And the marginal opening of casting crowns were also measured.The data were statistically analyzed using one-way ANOVA at a significance level of 0.05 with SPSS 13.0.Results(1) There was no difference between 10 min and other time in Casting Pattern Resin pattern crowns group(p＞0.05);there was significant difference among 10,20,30 min in the remain groups(p＜0.01).(2) The lowest marginal opening was obtained for Casting Pattern Resin crowns,while the common inlay wax crowns produced the highest marginal opening at every period,there was significant difference between the four groups at every periods(p＜0.05).(3) The same results of the casting crown as the pattern crowns were obtained.Conclusion Within the limitations of this study,precision of pattern crowns was affected by the type of pattern materials used and the different periods of time.And Casting Pattern Resin was the best material for pattern crown and casting crown.