METAL-FREE Crowns Fracture Load USING Different Cements

METAL-FREE CROWNS FRACTURE LOAD USING DIFFERENT CEMENTS.

Objectives: This study evaluated the fracture load and fracture pattern of metal-free crowns cemented with different cements through mechanical test and finite element analysis. Methods: 4 groups (n=32) were obtained from 128 bovine roots that received metal posts and resin cores and were restored with ceramic systems- feldspatic (FE), leucite-reinforce-Cergogold (CG), di silicate reinforced-Empress (EM) - and laboratory processed resin - Adoro (AD). Each group was divided into 4 (n=8) according to the cement used: zinc phosphate (ZF); dual resin self-bonding - RelyX UNICEM (UN); autopolymerizing resin - Cement Post (CP); glass ionomer - Ketac Cem (KE). Manufactures' insctructions were followed for all the materials. After cementation the specimens were submitted to load in the EMIC DL machine at the speed of 0.5 mm/min. The fracture loads were recorded and submitted to 2-way ANOVA and Tukey test (p<.05) which indicated significant differences for both the material and cement, as well as their interaction. Results: mean values of fracture load (N) and statiscal analysis for the interaction were: EM-UN 1450±248a; EM-KE 1437±241a; EM-ZF 1331±187a; AD-UN 947±367ab; EM-CP 846±237abc; CG-UN 758±337bc; AD-KE 693±214bc; AD-ZF 695±273bc; CG-KE 653±146bcd; CG-ZF 637±186bcd; FE-UN 596±127bcd; FE-CP 615±198bcd; CG-CP 613±223bcd; AD-CP 553±333cd; FE-KE 479±115cd; FE-ZF 378±116d (lowercase letters indicate difference statistically significant). The fracture pattern and finite element analysis, through measuring of stress in the cement thickness, indicated that materials with higher modulus of elasticity concentrated more stress and, interacted with adhesive cementation, resulted in more injuries for underlying structure. Conclusion: Results from mechanical and finite element analysis indicated that the cement influenced the strength and the fracture pattern from the restorative systems. The choice of the association material/cement can lead to higher values of strength but result in catastrophic tooth fracture.