The influence of porcelain thickness and opacity on the polymerization of two dual activated (microfine and hybrid) and one light irradiated (hybrid) resin cements was assessed by hardness measurements. The surface microhardness values of the upper and lower surface of 1 mm thick resin cement specimens were determined. Specimens were polymerized using 40s irradiation beneath different thicknesses and opacities of porcelain discs. The results showed that increasing the thicknesses and opacity of the porcelain produced a statistically significant decrease in microhardness of the resin-based cements. The effect of attenuation is less for the microfine cement than for the hybrids. In the case of hybrid cements, the light activated material performed better than the dual activated cement.

Objectives The aim was to examine the influence of short-fiber composite (SFC) core on the fracture-behavior of different types of indirect posterior restorations. In addition, the effect of thickness ratio of SFC-core to the thickness of the veneering conventional composite (PFC) on fracture-behavior of bi-structured composite restorations was evaluated. Materials and methods MOD cavities with removed palatal cusps were prepared on 90 intact molars. Five groups of direct overlay restorations (n = 10/group) were fabricated having a SFC-core (everX Flow) with various thicknesses (0, 1, 2, 3, 4 mm) and layer of surface PFC (G-aenial Anterior), remaining the thickness of the bi-structure restoration to be 5 mm. Four groups of CAD/CAM-made restorations (Cerasmart 270 and e-max CAD) were fabricated either with 2-mm layer of SFC-core or without fiber reinforcement. Intact teeth (n = 10) were used as control group. Restorations were statically loaded until fracture. Fracture patterns were evaluated visually. Data were analyzed using ANOVA (p = 0.05). Results With indirect overlay restorations, no statistically significant differences (p > 0.05) were observed in the load-bearing capacities between restorations reinforced by 2-mm SFC-core (bi-structured) and those fabricated from plain restorative materials. ANOVA displayed that direct overlay restorations made from 4-mm layer thickness of SFC-core had significantly higher load-bearing capacities (3050 ± 574 N) (p < 0.05) among all the groups tested. Conclusions Restorations (direct/indirect) combining SFC-core and a surface layer of conventional material demonstrated encouraging achievement in reference to fracture behavior. Clinical relevance The use of flowable short-fiber composite as reinforcing base with large direct and indirect restorations may result in more repairable failure.

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The effects of desensitizer, disinfectant, saliva, blood, and hydrogen peroxide on the tensile bond strength between adhesive and ceramic as well as between adhesive and dentin were examined. Sixty 7×3 mm pressed ceramic discs of IPS e.max were fabricated and randomly assigned to six groups of different dentin surface treatments (control, desensitizer, disinfectant, saliva, blood, and hydrogen peroxide). Representative samples of fractured specimens were observed by SEM (scanning electron microscopy). There were significant differences between the control group and saliva, blood, and hydrogen peroxide groups (p<0.05). However, there were no significant differences between any other dentin surface treatment groups (p>0.05). Results of this study suggested that only saliva, blood, and hydrogen peroxide influenced the tensile bond strength between dentin and ceramic.

The aim of this paper was to evaluate the fracture resistance and failure type of maxillary incisor teeth, rebuilt with various types of post-core restorations and full crowns made of either direct conventional particulate filler composite (PFC, G-aenial Anterior, GC, Tokyo, Japan) or indirect CAD/CAM restorations (composite Cerasmart 270 and glass ceramic LiSi Block from GC). One hundred (n = 10/group) central incisors were cut and divided into 10 experimental groups restored with different approaches. In approach A, teeth were restored with a core build-up composite (Gradia Core, GC) for a core and full crown of PFC. Approach B had teeth restored using composite core and prefabricated fiber posts, and a complete crown of either PFC or CAD/CAM. Approach C contained teeth restored with a core of short fiber-reinforced composite (everX Flow, GC) and prefabricated fiber posts, and a complete crown of either PFC or CAD/CAM. In approach D, the teeth had a core of short fiber-reinforced composite only, and a complete crown of either PFC or CAD/CAM restorations. The root canals were prepared, and when posts were used, they were luted with either a dual-cure resin cement (LinkForce, GC) or everX Flow. As the control, sound teeth (n = 10) were used. Restorations were quasi-statically loaded until fracture. Failure type was visually investigated. The interface between the fiber post and luting cement was investigated using SEM, before and after completion of the loading test. The data were analyzed by analysis of variance (p = 0.05) followed by Tukey’s test. None of the restorative approaches restored the fracture load strength of intact teeth (p < 0.05). Restorations with additional fiber posts (Approaches B and C) had higher load-bearing capacity (p < 0.05) than restorations without fiber posts (Approaches A and D). Restorations that had short fiber-reinforced composite cores with or without fiber posts presented more repairable failures. Using short fiber-reinforced composite as post-luting and core build-up material with conventional fiber posts proved to be a promising method to strengthen severely damaged incisors.