Influência do desgaste das pontas diamantadas em CAD/CAM na adaptação marginal de dois sistemas cerâmicos reforçados por dissilicato de lítio

Abstract

Purpose. This in vitro study aimed to assess the effect of successive milling in CAD/CAM diamond burs in the marginal misfit of two lithium disilicate ceramic crowns. Material and methods. Initially, 36 standardized composite resin dies were prototyped from a three-dimensional design of a right mandibular first molar with a full-crown preparation generated in CAD software. Ceramic crowns were obtained in CEREC CAD/CAM for each composite resin die and divide according to ceramic system (IPS e.max CAD and Rosetta SM) (n=18). Two diamond burs as a set were used, one set for each group and each 3 total crown millings scanning electron microscopy (SEM) was made them. Crowns marginal misfit was assessed through coronal and sagittal micro-tomographic sectioning, in the vertical and horizontal of crows directions seated in their respective dies, simulating a clinical situation. The data was tabulated and submitted to Two-Way ANOVA and Tukey honestly significant difference (HSD) test with alpha=.05. Results. SEM shows that diamond burs wearing used for milling the crowns presented changes on the superficial morphology after crowns milled for each ceramic system. There was significant difference between the marginal misfit of the crowns for both directions (vertical and horizontal) (p<.001). Significant differences were also verified between ceramic systems in horizontal direction (p<.041) but not in the vertical direction (p<. 465). Also significant differences were detected in the marginal misfit of the crowns at the different milling periods among subgroups (T1-T18) (p<.001) Conclusion. Diamond set burs are deteriorated by successive uses. The crowns marginal misfit of both ceramic systems increased with successive use of the CAD/CAM diamond set burs weariness. IPS e.max CAD showed higher marginal misfit values in horizontal direction, but both systems were similar in vertical direction. In addition, it becoming inappropriate to mill new restorations after 6 milling for Roseta SM and 8 for IPS e.max CAD total ceramic crowns.