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    Depth of cure and microhardness of a new composite vs. bulk-fill composites
    (AMBER PUBLICATION, 2019) Cetin, Ali Riza.; Hataysal, Ahmet Ercan.; Kaplan, Taibe Tokgoz.; Botsali, Murat Selim.
    Aim: To compare the depth of cure of new composite with bulk fill resin composites through using Vickers hardness profiles (VHN). Materials and Methods: New composite and four bulk fill composite materials were examined: Tetric N Ceram (R) Bulk Fill, X-tra base, Compon, Filtek Posterior Bulk Fill, Sonic FiIITM. Eight specimens of each material type were prepared in teflon molds which contained a slot of dimensions (8 mm x 4 mm x 2 mm), and a top plate. The molds were irradiated from one end. All specimens were stored at 37 degrees C for 24 h, before measurement. The Vickers hardness was measured as a function of depth of material, at 1 mm intervals. Data were analyzed by one-way ANOVA using Turkey post hoc tests (p=0.05). Results: The maximum VHN ranged from 46.7 to 68.1, whilst the 80% of max. WIN ranged from 374 to 54.5. The depth corresponding to 80% of maximum VHN ranged from 5.5 to 7 mm. This was taken as the depth-of cure. Discussion: In this study, VHN, 80% VHN and depth profile properties of different Bulk Fill resin composites were measured and compared with the new composite by the determination of their VHN/depth profiles. There were statistically significant differences between different bulk fill composite materials in terms of max. VHN and depth of cure, corresponding to 80% of max. VHN. Depth of cure is related to the clinical success of restoration. When a more extensive polymerization and crosslinking occurs,greater VHN results are obtained. According to the manufacturer's claims bulk fill composites can be applied up to 4 mm, or even 5 mm in one time. In general, adequate polymerization along the recommended depth in bulk fill composites is critical to the long-term stability of restorations. According to the results of our research, the manufacturers' claim was approved for these materials. Conclusion: New composite can be cured to an acceptable post-cure depth as Bulk fill resin composites, according to the manufacturers' claims. X-tra base had the greatest depth of cure among the composites examined.
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    The effect of antioxidant treatment on the shear bond strength of different bonding systems to bleached enamel
    (JOURNAL EVOLUTION MEDICAL & DENTAL SCIENCES, 2019) Cetin, Ali Riza.; Yildirim, Cihan.; Unlu, Nimet.; Cobankara, Funda Kont.
    BACKGROUND Nowadays, teeth whitening has become an important procedure in dental practice. According to results of previous studies, the bond strength values of bonded restorations are decreased when the teeth have been whitened with an office or home bleaching technique. The aim of this in-vitro study is to explore the effect of antioxidant implementation on enamel after whitening on the shear bond strength to enamel surface. METHODS The buccal enamel surfaces of 100 extracted teeth were divided non randomly into two groups for bonding with Single Bond [Group A] (3M ESPE) or Clearfil SE [Group B] (Kuraray). Each group was then divided into five random subgroups: 1. the negative control group (NC) received no whitening treatment [Group Al and Group B1]; 2. whitened with 15% carbamide peroxide and that received no antioxidant agents [Group A2 and Group B2]; 3. whitened with 15% carbamide peroxide and implemented 10% sodium ascorbate (SA) [Group A3 and Group B3]; 4. whitened with 35% hydrogen peroxide and that received no antioxidant agents [Group A4 and Group B4]; 5. whitened with 35% hydrogen peroxide and implemented 10% sodium ascorbate [Group A5 and Group B5]. After the restorations were done with a composite (Clearfil ST, Kuraray), they were shear-tested until failure. Two-way analysis of variance (ANOVA) test and Tukey's multiple comparisons test were used to check shear bond strength data at a significance level of p= 0.05. RESULTS Shear bond strength values of used bonding systems immediately after bleaching to whitened enamel, were significantly lower than those of non-whitened enamel (p<0.05). No statistically significant differences in shear bond strengths were found for two adhesive systems, when the antioxidant implemented groups were compared with the non-whitened group (Control) (p>0.05). Thus, the enamel bond strengths of the bonding systems were reversed following sodium ascorbate treatment. CONCLUSIONS It was concluded that the antioxidant sodium ascorbate application could fully neutralize the destructive actions of whitening agents on shear bond strength.