ABSTRACT
Statement of Problem: Bleaching systems with different concentrations and applications are widely used to improve the visual appearance of the teeth, but one of the complications of these materials is reduction of bond strength for immediately bonding to the bleached enamel
Objective: The aim of this study was to evaluate the influence of using different modified hydrogen peroxide bleaching agents on the shear bond strength of composite resin bonded to the bleached enamel
Materials and Methods: Forty-eight sound extracted premolar teeth were collected, sectioned 1 mm below the CEJ to detach the root. The proximal surfaces of the teeth were flattened using diamond disks and silicon carbide papers to achieve flat homogeneous enamel surfaces without exposure to the dentin. The teeth were randomly divided into four groups as follows [n = 12]: group 1: bleaching with 35% hydrogen peroxide gel; group 2: bleaching with 35% hydrogen peroxide gel contained [casein phosphopeptide-amorphous calcium phosphate [CPP-ACP]; group 3: bleaching with 35% hydrogen peroxide gel combined with fluoride; and group 4: bleaching with 35% hydrogen peroxide applying one week before resin restoration placement. Composite resin, Clearfil AP-X [Kuraray, Tokyo, Japan], was bonded on each tooth in the mould [4 mm diameter × 3 mm height] using Clearfil SE Bond [Kuraray, Tokyo, Japan]. After 24 hours of storage and 1000 cycles of thermocycling, the shear bond strength of the specimens at a cross-head speed of 0.5 mm/min was measured in MPa. Data were analyzed using ANOVA and Tukey's post-hoc test
Results: The minimum and maximum mean shear bond strength values were observed in groups 2 [15.82 +/- 4.41] and 4 [21.00 +/- 3.90], respectively. Multiple comparisons of groups revealed no significant differences among the groups except between group 4 and all the other groups. The most common type of failure was adhesive
Conclusion: Using modified bleaching agents decreased the bond strength of the composite resin to the enamel when it was used immediately after bleaching
ABSTRACT
Due to the disadvantages of self cure composites, application of light cure composites is suggested in orthodontics but light transmission through metal brackets is in doubt. The aim of this study was to compare shear bond strength [SBS] of Ideal Maccoo and Brilliant composites in bonding steel and ceramic brackets. Eight intact first upper premolars were collected for this experimental invitro study and randomly divided into 4 equal groups. The buccal surfaces were etched and cured by visible light after applying margin bond resin. In the first group Ideal Maccoo composite was applied on the steel bracket base [SI group], bracket positioning in the correct location was done and then curing was performed by visible light for 40 seconds [20 seconds from occlusal and 20 seconds from gingival]. In the second group fascination ceramic brackets with Ideal Maccoo composite [CI group], in the third group ceramic brackets with Brilliant composite [CB group] and in the fourth group steel brackets with Bralliant composite [SB group] were bonded to teeth with the same method. SBS was measured by Zwick testing Machine. To compare the groups, Kolomgrov-Smironov, two way analysis of variance, one way analysis of variance and Tukey tests were used. Mean SBS was 9.71 +/- 3.37, 7.36 +/- 4.40, 5.58 +/- 2.21 and 12.36 +/- 5.77 in SI, CI, CB and SB groups respectively. Tukey test showed significant difference between SB and CB groups [P<0.001], no significant differences was detected between CI and SI, SI and SB and between CI and CB. Ideal Maccoo and Brilliant light cure composites had good capabilities in steel bracket bonding whereas ceramic brackets had lower shear bond strength. In bonding ceramic brackets only Ideal Maccoo composite showed acceptable results