hila hajizadeh

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. 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. 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. 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. Using modified bleaching agents decreased the bond strength of the composite resin to the enamel when it was used immediately after bleaching.

The aim of the present study was to evaluate the effect of glass ceramic insert in the sandwich technique to reduce microleakage in class II composite resin restorations. Sixty sound human upper second premolars were selected and randomly divided into six groups (n=10). Class II box-only cavities were prepared in distal aspects of each tooth with gingival margin located approximately 0.5 mm below the CEJ. Group A (Control) was restored incrementally with Tetric Ceram and a total-etch bonding technique. Group B and C were restored with sandwich technique using a compomer (Compoglass F) or flowable composite resin (Tetric Flow) as the lining material at gingival floor, respectively. Group D, E and F were represented in the same way as group A, B and C and a glass ceramic insert was added to the composite bulk. The specimens were thermo-mechanically cycled, and then immersed in 0.5 % basic fuschin for 24 hours. Dye penetration was detected using a sectioning technique. No significant difference was found between total-etch bonding and sandwich techniques. The placement of an insert caused an increase in microleakage in all groups significantly (P < 0.05). Group D (no liner/ with glass insert) showed the highest amount of microleakage and Group A (no liner/ without glass insert) resulted in the lowest amount of total microleakage. Placement of glass ceramic insert could not decrease gingival leakage. According to the limitation of this study a composite resin restorations with incremental technique is recommended.

Sandwich technique with glass ionomer (GI) has been recommended to overcome gingival microleakage. The study objectives were to compare open and closed sandwich techniques and evaluate GI injection in sandwich restorations. Sixty extracted sound premolar teeth were divided into 4 groups (n=15). A Class II cavity with gingival margin below CEJ was prepared on each tooth. Teeth were restored using glass ionomer (Fuji II LC), adhesive (Single Bond) and resin composite (Z250) as follows: Group 1, Open sandwich, GI injection; Group 2, Open sandwich, placing GI by a probe; Group 3, Closed sandwich, GI injection; Group 4, Closed sandwich technique, placing GI by a probe. Dye penetration was performed by using fushin after thermocycling. Teeth were sectioned then dye penetration was evaluated (0-3 scores) under a stereomicroscope. Statistical analysis was conducted using Kruskal Wallis and Mann-Whitney U tests. The least microleakage was observed in closed sandwich technique with GI injection and the most microleakage was observed in open sandwich using GI by a probe. When comparing the handling techniques, it was shown that using a syringe was significantly better than using a probe (P<0.05). There was no statistical difference between open and closed sandwich techniques although the mean dye penetration happened less in closed technique. According to the results of this study, injection of GI into cavity is recommended because of better access and superior adaptation of GI with cavity walls.

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. Methods & Materials: 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±2.21and 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.