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ObjectiveTo evaluate the effect of different surface treatments of nickel chrome (NiCr) with the type of metal primer monomers on the conventional tensile bond strength (CTBS) of resin cement.MethodsForty disks of NiCr alloy were prepared for CTBS test and grouped as follows: group (1) no surface treatment (control group), group (2) oxide layer only, group (3) air abrasion, and group (4) air abrasion with an oxide layer. Each main group was subdivided into two subgroups (n = 5) depending upon the type of metal primer used for metal treatment. All specimens were bonded with resin cements. The CTBS was tested using a tensile testing machine. The data were statistically analyzed with One-way ANOVA, Two-way ANOVA, and T-test at 0.05 level of significance.ResultsSignificant differences in the mean value of the CTBS between different surface treatments (P ≤ 0.05) were observed. Tukey's test showed that air abrasion surface treatment had the highest mean value followed by the air abrasion with an oxide layer and oxide layer only. The control group showed the lowest value of significant difference compared to all treated groups (P ≤ 0.05).ConclusionsCTBS of self-adhesive resin cement to NiCr is dependent on surface treatment. Two types of the metal primer of different monomer contents 10-methacryloyloxydecyldihydrogenphosphate (MDP) or Thiophosphoricmethacrylate (MEPS) show similar behavior on the tensile bond strength.

The aim of this study was to evaluate the regional mechanical properties of flowable composites with different initiation systems under free and constrained conditions. Forty cavities fabricated in resin blocks with or without bonding treatment were bulk-filled with Estelite Flow Quick (EFQ) or Palfique Estelite LV (ELV), followed by light irradiation for 10 or 30 seconds. Each specimen was sliced to three slabs parallel to the long axis. The middle slab was serially sliced from top to bottom to harvest three sticks for ultimate tensile strength (UTS) measurement. The remaining slabs were polished for microhardness (KHN) measurement. The results indicated that the UTS and KHN of both flowable composites decreased toward the bottom of the cavity and increased with prolonged light irradiation time. At the upper cavity region, UТS values of the bonded groups were significantly lower than those of the unbonded groups, except for the 10-second light irradiation group of EFQ. As for KHN, the values did not change significantly for both flowable composites between the unbonded and bonded groups.

The aim of this study was to evaluate the micro-shear bond strength (µSBS) of one and two steps self-etch adhesive systems after enamel bleaching with photo-activated bleaching systems of different hydrogen peroxide (HP) concentration. Occlusal enamel of forty intact human molars were flattened and assigned into four groups. GI Unbleached, GII, GIII, and GIV were bleached with Pyrenees (3.5% HP), GC TiON (20% HP), and Hi-Lite (35% HP) respectively. Enamel treatment with one and two steps self-etch adhesives (Clearfil S3 Bond- S3, and Clearfil SE Bond-SE) then micro-tubes were fixed on enamel and filled with AP-X composite (n=5). Bond was tested with the universal testing machine. Data were analyzed using two-way ANOVA and Tukey’s tests at 5 % level of significance. The µSBS was significantly different between adhesives (F=154.46; p<0.05) and bleaching systems (F=77.33; p<0.05) with significant interaction. Specimens bonded with S3 shows a significantly lower μSBS than those bonded with SE (p<0.05) in all groups. For both adhesives the bleached groups demonstrate lower µSBS than unbleached except specimens bleached with Pyrenees and bonded with SE (p>0.05). A significant difference was observed between groups of the bleaching systems (p<0.05). Different peroxide concentrations photo-activated bleaching systems adversely affect μSBS of one and two steps self-etch adhesives. Low concentration system (Pyrenees) does not influence the bond strength of two steps adhesive.