Purpose: To evaluate the effect of cervical margin relocation (CMR) for crowns designed using CAD/CAM technology, and made of pre-cured resin or lithium disilicate, before and after thermomechanical loading. The test hypothesis was that the marginal quality of the crowns would not be influenced by the CMR with composite resins before or after thermomechanical loading.
Materials and Methods: Standard crown preparations were created in 40 human molars. The margins were located
in enamel, except for the mesial proximal box, where the cervical margin was 2.0 mm below the cementoenamel
junction, with 4.0 mm in the buccolingual and 2.0 mm in the mesiodistal dimension. For the CMR technique, a
2-mm layer of conventional or flowable composite resin was applied to the mesial box. Using the Cerec CAD/CAM
system, 40 standard crowns were prepared, and restorations were luted using a dual-curing adhesive cement. SEM
analysis was performed using epoxy resin replicas before and after loading to assess the marginal quality of interfaces
of the mesial proximal box with CMR/crown and the distal face of the tooth without CMR. Statistical differences
between groups were analyzed using the Kruskal-Wallis test and Bonferroni’s post-hoc test.
Results: The null hypothesis was accepted, since no statistically significant differences were found in marginal
quality before and after thermomechanical cycling (p > 0.05).
Conclusion: The implementation of CMR before and after thermomechanical cycling had no effect on the quality of
cervical margins. To establish whether CMR is a suitable procedure for the adhesive luting of composite resin
crowns in deep proximal boxes, additional studies are required.