Influence of polymerization time on properties of dual-curing cements in combination with high translucency monolithic zirconia

Purpose: The aim of this in vitro study was to assess conversion degree (DC), micro-hardness (MH) and bond strength of two dual-curing resin cements employed under translucent monolithic zirconia irradiated with different time protocols. Methods: 84 square shaped samples of 1 mm thickness were prepared from high translucency zirconia blocks and divided into two groups (n = 24) according to the cement employed: (1) Rely-X Ultimate; (2) Panavia SA. Each group was further divided into 3 subgroups (n = 8) according to the irradiation time: (a) no light; (b) 20 s; (c) 120 s. Light curing was performed 60 s after the sample was placed on the diamond support of a FT-IR spectrophotometer with a high power multiLED lamp. Final DC% were calculated after 10 min. After 24 h, Vickers Test on the cement layer was performed. The same protocol was used to lute composite cylinders in order to evaluate microshear bond-strength test. ANOVA and Bonferroni tests were performed to find differences between MH and bond-strength to zirconia, while for DC% the Scheirer\u2013Ray\u2013Hare two-way test was used. Results: The two cements reached higher DC% in subgroup (b) and (c). As concern MH, statistics showed an increase in curing time was able to improve MH significantly. Bond-strength was not affected by irradiation time only for Panavia SA. Conclusions: The first null hypothesis has to be rejected since DC% and MH of the dual-cements tested were influenced by the curing time. The second null hypothesis is partially rejected since the bond strength was influenced by the curing time only for Rely-X Ultimate

Influence of surface coating sealer on resin composite water absorption and discoloration: An in vitro study

Purpose: This in vitro study evaluated the efficacy of surface coating sealer (SCS) in reducing the amount of water absorption and stain formation in resin composites. Methods: To evaluate the amount of water sorption, 40 stainless steel round molds (n=10 per composite) were filled with Filtek Supreme XTE; Venus Diamond; Clearfil Majesty ES-2; Gradia Direct Anterior. Groups were further divided into two subgroups (n=5) according to the presence/absence of SCS (Easy Glaze,VOCO). Their masses were measured at baseline and reweighed at 1,4,12and20 weeks. For staining evaluation, 48 composite resin discs, 2 mm thick, were obtained with the same composites and SCS was applied on a single surface of each sample. After baseline color assessment, samples were immersed in vials containing 5 mL of six different staining solutions. Color evaluation was performed again after 1,4,12and20 weeks. Three-way ANOVA was performed to evaluate either differences in weight gain and color changes (p<0.05). Results: A significant protective action of SCS (p<0.001), but not of the composites (p=0.366) was found. Differences in weight and color change were not influenced by the resin composite, but uniquely by the presence of the coating on the surface of the samples. SCS are well-established materials for polishing and protecting composite restorations from water sorption and color changes. Different staining solutions can still produce different effects on composite resins

Influence of operator experience on non-carious cervical lesion restorations: Clinical evaluation with different adhesive systems

Purpose: To evaluate the influence of operator experience on adhesive technique and to assess the clinical performances of two different adhesive systems. Methods: 90 cervical lesions in 42 subjects, with a mean age of 52.4 years (range between 32-63) were selected. Lesions were divided into two groups according to operator experience (n= 42 restorations performed by a skilled operator, n= 48 restorations performed by five unexperienced operators) and further divided into two subgroups according to the adhesive system used: three-step etch-and-rinse (Optibond FL) or one step self-etch (G-Bond). Adhesives were applied according to manufacturers' instructions. Subjects underwent follow-up at 12, 24, and 36 months and restoration retention, enamel and dentin marginal integrity, marginal discoloration, caries occurrence, post-operative sensitivity, and preservation of tooth vitality were evaluated according to USPSH criteria. ANOVA test was performed to evaluate the influence of the adhesive system, the operator experience, and aging on restorations. Results: Operator experience (expert vs. inexperienced), aging time (12,24, or 36 months), and the adhesive system (self-etch vs. etch-and-rinse) all affected the results statistically, as did the interaction between the adhesive system and operator experience