ABSTRACT
OBJECTIVES: Hydrogen peroxide (H2O2) surface treatment of fiber posts has been reported to increase bond strength of fiber posts to resin cements. However, residual oxygen radicals might jeopardize the bonding procedure. This study examined the effect of three antioxidant agents on the bond strength of fiber posts to conventional and self-adhesive resin cements. MATERIALS AND METHODS: Post spaces were prepared in forty human maxillary second premolars. Posts were divided into five groups of 8 each: G1 (control), no pre-treatment; G2, 10% H2O2 pre-treatment; G3, G4 and G5. After H2O2 application, Hesperidin (HES), Sodium Ascorbate (SA) or Rosmarinic acid (RA) was applied on each group respectively. In each group four posts were cemented with Duo-Link conventional resin cement and the others with self-adhesive BisCem cement. Push-out test was performed and data were analyzed using 2-way ANOVA and tukey's post-hoc test (alpha = 0.05). RESULTS: There was a statistically significant interaction between the cement type and post surface treatment on push-out bond strength of fiber posts (p < 0.001, F = 16). Also it was shown that different posts' surface treatments significantly affect the push-out bond strength of fiber posts (p = 0.001). H2O2 treated posts (G2) and control posts (G1) cemented with Duo-link showed the highest (15.96 +/- 5.07MPa) and lowest bond strengths (6.79 +/- 3.94) respectively. CONCLUSIONS: It was concluded that H2O2 surface treatment might enhance the bond strength of fiber posts cemented with conventional resin cements. The effect of antioxidants as post's surface treatment agents depends on the characteristics of resin cements used for bonding procedure.
Subject(s)
Humans , Antioxidants , Ascorbic Acid , Bicuspid , Glass , Hesperidin , Hydrogen Peroxide , Reactive Oxygen Species , Resin CementsABSTRACT
As dentin bond strength of the materials containing resin is reduced after bleaching, a delay in bonding for at least one week after bleaching is recommended. The aim of this study was to investigate the neutralizing effect of an antioxidizing agent on the shear bond strength [sbs] of bleached dentin and compare it with a delay of one week before bonding of composite resin [CR] and resin-modified glass-ionomer [RMGI]. Exposed dentin surfaces of 96 sound human molars were divided into eight groups. Buccal dentin surfaces of the specimens in group 1 and 5 were consecutively bonded with CR and RMGI cylinders. The specimens in other groups were bleached for six hours a day for five consecutive days. For the specimens in groups 2 and 6, bonding of CR and RMGI was performed immediately after bleaching, respectively. The specimens in groups 3 and 7 were immersed in distilled water for one week and then CR and RMGI were bonded. For the specimens in groups 4 and 8, 10% sodium ascorbate gel was applied and then CR and RMGI were bonded, respectively. Shear bond strengths of the specimens were measured. Data was analyzed by ANOVA and Tukey test [? = 0.05]. The mean sbs values for groups 1 to 5, 7, and 8 in MPa were 17.055 +/- 2.954, 8.19 +/- 0.941, 16.406 +/- 1.508, 15.640 +/- 3.073, 8.893 +/- 0.620, 8.162 +/- 0.975, 7.584 +/- 0.939, respectively. There were significant differences between the study groups. The specimens of group 6 had pretest failure. Bleaching led to a significant decrease in sbs of CR to dentin immediately after bleaching, and RMGI did not bond in this situation. A delay of one week before bonding and application of sodium ascorbate gel significantly increased the sbs of the evaluated materials to bleached dentin. In the composite groups the delayed subgroup had significantly higher sbs than the sodium ascorbate subgroup. In glass-ionomer groups there were no significant differences in sbs values
ABSTRACT
One of the main problems in esthetic dentistry is closing diastema between teeth with a direct technique without creating the black triangle [gingival embrasure lacking papilla]. Black triangle will ruin the patients' smile and is not desirable. Composite resin used to close diastema should have adequate convexity from gingivo-incisal direction to avoid this problem. Various techniques have been introduced to close diastema, some of which are time-consuming or cannot provide proper contour. This article describes a case in which diastema between two teeth was closed with direct composite resin with minimum amount of time. Although closing diastema with direct composite depends on operator skill in most part, this technique is probably less dependent on operator skill compared to other techniques. Closing diastema between anterior teeth with composite resin with direct technique is conservative and timesaving, and the presented technique which provides adequate contour can be carried out very easily by many dental practitioners