Fracture strength of minimally prepared resin bonded CEREC inlays.

PURPOSE: This study compared the structural integrity and fracture mode of teeth restored with traditionally and minimally prepared resin-bonded CAD/CAM inlays fabricated from the same material. METHODS: Forty intact maxillary premolars were used and divided into four groups. Two groups were prepared according to a traditional inlay preparation design (2.0 mm occlusal reduction, a 1.5 mm wide proximal box and divergent walls) and two groups were prepared according to a newly proposed minimal preparation design (round shaped cavity with 1.0 mm occlusal reduction, a U-shaped proximal box 1.0 mm wide and parallel walls). Two restorative systems were tested: a composite system comprised of Paradigm MZ100 (3M ESPE) blocks and RelyX Unicem (3M ESPE) resin cement and a ceramic system comprised of ProCAD blocks (Ivoclar-Vivadent) and Variolink II (Ivoclar-Vivadent) resin cement. The inlays were cemented according to the manufacturers' instructions. Each specimen was loaded axially to its occlusal surface at a crosshead speed of 0.5 mm/minute in a universal testing machine until fracture. The fracture load data were analyzed using ANOVA, comparing inlays of the same restorative material. Also, the mode of fracture of the inlays was recorded and analyzed using a non-parametric test (Kruskal-Wallis). RESULTS: In the composite system case, the mean fracture load and SD were 1322 N (+/- 445) for the traditional inlays and 1511 N (+/- 395) for the minimal inlays, while in the ceramic system case, those values were 1135N (+/- 450) for the traditional inlays and 1761 N (+/- 494) for the minimal inlays. Statistical analysis of the results showed that there was no statistically significant difference between the two designs for the composite system, while for the ceramic system, the minimally prepared teeth showed higher mean fracture strength. Non-parametric analysis (Kruskal-Wallis) of the mode of fracture showed that there was no statistically significant difference between traditionally and minimally prepared inlays for both systems (p > .05). CONCLUSIONS: Under the conditions of this experimental study, only the ceramic inlays, when prepared with a minimal preparation design, demonstrated a higher fracture strength as compared to the traditionally prepared teeth. Use of the proposed minimal preparation design did not compromise the immediate post-operative structural integrity of teeth restored either with resin composite or ceramic inlays.

Effect of dual-cured adhesive resin cements on cell proliferation of pulp and human fibroblasts.

PURPOSE: To comparatively evaluate the effects of three dual activated adhesive resin cements on cell proliferation of rat pulp cells (RPC-C2A) and human lung fibroblasts (MRC5). METHODS: The cements tested were RelyX ARC, RelyX Unicem and Panavia F. The cements were prepared according to manufacturers' instructions and placed in contact with the cells. Cell survival was estimated by the sulphorhodamine-B staining assay after 24 and 72 hours and cellular changes in morphology were examined under microscope. RESULTS: All resin cements decreased cell proliferation. The decrease observed was material- and time-dependent. Panavia F was found more potent in decreasing cell proliferation. Differences were found in the effect on cell proliferation among the materials tested, that might be associated to their clinical behavior.