Objective: The aim of this study was to evaluate the degree of conversion and surface hardness of two bulk-fill composites and one incremental-fill composite. Methods: Bulk-fill composites (x-tra fil, Voco; QuiXfil, Dentsply) and incremental-fill composite (Grandio, Voco) were used. Twenty five cylindrical specimens (5 Â 4 mm) were made from each material in Teflon molds. Mold was filled in one increment for the bulk-fill composites and in two increments for the incremental-fill composite. Specimens were stored dry in dark at room temperature for 24 h before testing. Degree of conversion (DC) was determined using Fourier transform infrared spectroscopy (FTIR). A microhardness tester was used to measure the Vickers hardness number (VHN) on top and bottom surfaces of each specimen. Data for DC and VHN were analyzed by ANOVA and pair-wise Newmanekeuls test. Results: X-tra fill recorded significantly the highest DC, while no significant difference was noted between the other two composites. The VHN mean values of all composites tested were significantly different from each other (P < 0.0001), either in top or bottom surface, with Grandio showed the highest mean value and QuiXfil showed the lowest mean value. Only QuiXfil recorded no significant VHN difference between its top and bottom surfaces. There was no significant difference in bottom/top hardness ratio% among materials. Non significant Correlation between VHN and DC was noted. Conclusions: X-tra fil showed the most DC performance. Incremental-fill composite showed higher VHN than bulk-fill composites. Differences in DC and VHN values among materials proved to be a material dependent.

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Objectives: To assess the influence of thermocycling following application of fluoride resin agent on shear bond strength (SBS) of metal orthodontic brackets bonded with two self-etching primers (SEPs). Materials and methods: Eighty extracted upper premolars were randomly divided into 4 equal groups (n=20) and stainless steel brackets were bonded to their buccal surfaces as follows: group 1, teeth were conditioned with Transbond Plus SEP (3M Unitek, Monrovia, Calif), then brackets were bonded with Transbond XT adhesive (3M Unitek) and no fluoride resin applied; group 2, teeth were bonded as in group 1, and subsequently a fluoride-releasing resin (Ortho-Coat, Pulpdent, Watertown, Mass) was applied ; group 3 teeth were conditioned with Clearfil Protect Bond antimicrobial SEP (Kuraray Medical, Osaka, Japan), then brackets were bonded with Transbond XT adhesive and no fluoride resin applied; and in group 4, the same protocol for brackets bonding as in group 3 was used followed by an application of Ortho-Coat. All specimens were stored in distilled water (24 h., 37 o C) then, half of each group (n=10) subjected to SBS debonding and the other half (n=10) were thermocycled before debonding. The adhesive remnant index (ARI) score was also recorded after debonding. The data of SBS and ARI scores were statistically analyzed by using 3-way ANOVA and Chi-Square test, respectively Results: The application of Ortho-Coat had no significant effect on SBS values of both SEPs, either before or after thermocycling. SBS values of both SEPs were not significantly changed by thermocycling whether Ortho-Coat was applied or not. No significant difference was noted between the two SEPs in any application condition. No significant differences were found in the ARI scores. Conclusions: The application of fluoride-releasing resin had no negative effect on SBS of metal brackets bonded with the two SEP systems. Thermocycling had no effect on SBS of the both SEPs either with or without fluoride-releasing resin application.