Avaliação das coroas de dissilicato de lítio obtidas por sistemas CAD/CAM de consultório e pela técnica de prensagem a quente por meio da adaptação marginal utilizando a micro-tomografia computadorizada

Abstract

Objectives: The current study evaluated the marginal fit of lithium disilicate crowns fabricated by different chairside CAD/CAM systems (CEREC and E4D) and hot-pressed technique using micro-CT. Methods: A human mandibular premolar was mounted with its adjacent teeth on a typodont model, and prepared for an all-ceramic crown. In the first group, the control group P, five restorations were fabricated from lithium disilicate glass ceramics, using a combination of the lost-wax and hot-pressed technique. Five different impressions, designs and crowns were made for each CAD/CAM system: group C, scanned with CEREC, using a thin layer of titanium dioxide powder, and group E, scanned with E4D, without powdering. Each crown was fixed. All specimens were scanned using a micro-CT to obtain images for marginal gap measurements. Fifty-two measurements were done for each specimen (n=260). Three independent examiners were calibrated prior to the measurements of the marginal gaps. Results: Considering the percentage of vertical marginal gap up to 75 μm, the results were: P 83.85%, C 83.85% e E 65%. The percentages of horizontal measurements with overextension of the crowns were: P 19.61%, C 21.16%, and E 23.85% Conclusions: Within the limitations of this study, it was concluded that vertical misfit below 75 μm, the group had 35% of the E4D values greater than desired, against 16.25% of the groups Pressed and CEREC, apparently having worse performance. As the horizontal misfit three techniques had the same performance with 20% of overextension areas, suggesting that all techniques can be improved.