50 - Microgap formation between a resin-matrix CAD/CAM ceramic and dentin.

Recently, a significant development in dental materials has been implemented with the introduction of resin-matrix CAD/CAM ceramics, which can provide high aesthetics and long-term clinical survival rates of indirect restorations such as inlays, onlays, endocrowns, crowns, and veneers in one single session. Furthermore, dental research has focused on the bonding of these materials to dental tissues by applying various surface modifications. The aim of this in vitro study was to evaluate the potential formation and the size of microgaps at the material/dentin interface after various surface modifications of a resin-matrix CAD/CAM ceramic following artificial aging. Fifty intact human third molars were used in the present study. The teeth were sectioned horizontally in the middle of the cervico-occlusal dimension of the crowns to expose dentin. A resin-matrix CAD/CAM ceramic (Lava Ultimate, 3 M ESPE) and a resin cement (Rely X Ultimate, 3 M ESPE) were tested. The CAD/CAM blocks were sectioned resulting in 50 slabs with 2 mm thickness. Each slab was luted on the tooth surface using the same resin cement. To improve the bond strength, the surface material was modified using the following treatments: Group 1 – no treatment (control); Group 2 – HF + silane; Group 3 – air-abrasion with Al 2 O 3 particles (29 μm); Group 4 – air-abrasion with Al 2 O 3 particles (53 μm); and Group 5 – Er,Cr:YSGG (2780 nm) laser treatment. The 50 pairs of sandwich specimens were then submitted to thermocycling (2000 cycles: 5 ºC – 37 ºC – 55 ºC – 37 ºC) and the specimens transversely cut in the middle and the adhesive interfaces were examined using SEM-EDS. The microgap formation was measured in the scale of μm using the software of the SEM microscope. Almost all the specimens of the control and laser-group were debonded or the microgap was between 10-100 μm. On the other hand, the other 3 groups (29, - 53 μm, HF + silane) presented lower microgap formation and in some cases no microgaps were detected. The best results showed the air-abrasion groups with Al 2 O 3 particles. Different surface modifications of the material presented significant differences in the formation of microgaps at the adhesive interface with dentin after artificial aging, implying also differences in bond strengths among the treatment groups. Air-abrasion pretreatments with Al 2 O 3 particles presented the most beneficial results regarding microgap formation after artificial aging. [ABSTRACT FROM AUTHOR]