The Journal of Adhesive Dentistry, 03/2007

Purpose: The aim of this study was to evaluate the effectiveness of previous dental substrate treatments on the bond strength of two self-etching adhesives. Materials and Methods: One hundred bovine incisors were sectioned at the cementoenamel junction. The labial tooth surface was ground to obtain flat superficial dentin. Teeth were randomly divided into two groups (n = 50): Clearfil Protect Bond and One Up Bond F. The specimens of each group were subdivided into five groups, according the dental substrate treatment, and then the adhesive system was applied as follows (n = 10): C: control, without previous treatment; TA: 37% phosphoric acid etching on enamel and dentin for 15 s; PA: 37% phosphoric acid etching only on enamel for 15 s; SB: Al2O3 sandblasting on dental surface; EDTA: enamel and dentin conditioning with 24% EDTA gel, pH 7.0. Resin composite blocks were fixed to the dental surfaces with dual-polymerized resin cement. Samples were sectioned in the mesiodistal direction and were trimmed to reduce the cross-sectional area to approximately 1.2 mm2. They were tested at a crosshead speed of 0.5 mm/min on a testing machine. Microtensile bond strength values from enamel, superficial dentin, and deep dentin were compared. Mean microtensile bond strength values were expressed in MPa and were analyzed by two-way ANOVA (2 x 3 x 5) and Tukey's tests. Results: A significant difference was observed for interaction (p = 0.00001) among the factors. The highest mean bond strength to enamel was found with previous phosphoric acid etching, and to dentin when EDTA was previously applied. Conclusion: The most indicated previous treatment for increasing the bond strength to enamel and dentin simultaneously is EDTA for both self-etching adhesive systems used. Keywords: dentin bonding, microtensile test, resin-dentin bond strength

Purpose: To compare marginal adaptation in enamel and dentin after different surface treatments before and after longterm simultaneous thermal and mechanical stresses in a mixed Class V restoration. Materials and Methods: Thirty-six V-shaped mixed Class V cavities were prepared in extracted human molars and treated as follows: group 1: 30 s ozone exposure (Heal Ozone, Kavo); group 2: 20 s air abrasion with 50 µm Al2O3 particles (Dento-prep, Rønvig); group 3: 20 s exposure to 27 µm SiOx powder (RONDOflex, Kavo with CoJet powder, 3M-ESPE); group 4: control (no treatment). Cavities were restored with a light-cured composite material (Tetric Ceram, shade A2, Ivoclar Vivadent) using a self-etching adhesive system (Syntac Clasic, Ivoclar Vivadent) with H3PO4 conditioning of the enamel. Each group was evaluated in respect to marginal adaptation before and after mechanical and thermal loading under simulated dentinal fluid. Results: Even if loading significantly influenced marginal quality in all groups (paired t-test, p 0.05), the percentages of "continuous margin" of all groups in enamel ranged between 93.2% and 92.3% before and 84.1% and 76.9% after loading and were not significantly different (ANOVA and Scheffe's post-hoc test, p > 0.05). Continuous margin in dentin ranged from 98.9% to 94.2% before and from 95.9% to 76.4% after loading, and significant differences were observed between groups treated with ozone vs control before and after loading and CoJet vs control group after loading (ANOVA and Scheffe's post-hoc test, p 0.05). Conclusion: Surface treatment with ozone and silica coating may significantly decrease marginal quality in dentin without negatively influencing marginal quality in enamel. Keywords: marginal adaptation, ozone, CoJet, Al2O3

Purpose: To evaluate the effect of saliva contamination on the microleakage of an etch-and-rinse adhesive and a selfetching adhesive. Materials and Methods: Class V cavity preparations at the cementoenamel junction were made on the buccal and lingual surfaces of 40 freshly extracted human molars. The teeth were randomly assigned into two groups for different adhesives: Group I, Single Bond (two-step etch-and-rinse adhesive) and Group II, Futura Bond NR (one-step self-etching adhesive). The adhesive materials were applied according to their manufacturers' recommendations. The specimens were then further subdivided into five subgroups (A-E; n=8): group A, contamination before adhesive curing; group B, contamination before adhesive curing and re-application of adhesive; group C, contamination after adhesive curing; group D, contamination after adhesive curing and re-application of adhesive; and group E, no contamination (control). Contamination of adhesive surfaces was performed with fresh natural saliva and the saliva was removed by a gentle air blast. The specimens were restored with Z250 hybrid composite. After thermocycling (500x, 5°C to 55°C) and immersion in 0.5% basic fuchsin, the dye penetration was evaluated under a stereomicroscope. Statistical analysis was performed with the Kruskal-Wallis test at p 0.05. Results: No statistically significant differences were found among the contamination subgroups on the enamel or on the dentin for either group (p > 0.05). There was no significant difference in leakage between Group I and Group II for any subgroup (p > 0.05). Conclusion: Contamination of adhesives with saliva before and after adhesive curing did not worsen the microleakage of the two-step etch-and-rinse adhesive Single Bond or the one-step self-etching adhesive Futura Bond NR. Keywords: saliva contamination, etch-and-rinse adhesive, self-etching adhesive, microleakage

Purpose: To evaluate the marginal adaptation of mixed Class V cavities restored with Clearfil Protect Bond (Kuraray), Clearfil SE Bond (Kuraray), and two experimental combinations of both marketed adhesives, after fatigue and water storage. Materials and Methods: Four groups (Clearfil Protect Bond, Clearfil SE Bond, Exp. 1 and Exp. 2) of Class V cavities were restored with a microhybrid restorative composite (Clearfil APX, Kuraray). The marginal quality of these restorations was quantified by evaluation of gold-coated epoxy replicas with scanning electron microscopy before loading, after loading, and after a 12-month period of water storage. Data from marginal adaptation along the total margin length, on enamel, and on dentin were analyzed with the Wilcoxon signed rank test for differences within a group and with Kruskal-Wallis in order to assess the differences between groups. The Bonferroni test was used for post-hoc comparisons, and the confidence level was set to 95%. Results: The mean percentages (±SD) of "continuous margin" of the total marginal length ranged from 79.5% (±13.3) to 62.2% (±10.4) and from 70% (±11) to 61% (±15.1) after loading and after storage, respectively. No significant differences could be detected among the different groups. However, the marginal adaptation of Clearfil Protect Bond remained the most stable of all materials tested, as no significant differences were detected between the percentages of continuous margins before loading, after loading, or after storage. Conclusions: The use of an antibacterial adhesive system was as effective as the conventional two-step self-etching adhesive in the marginal adaptation of Class V restorations. Keywords: marginal adaptation, water storage, MDPB, antibacterial monomer, hydrolytic stability, enamel, dentin

Purpose: To evaluate the effect of different surface treatments of composite resin blocks on the adhesive properties of indirect composite restorations. The null hypothesis tested was that none of the performed surface treatments would produce greater bond strength. Materials and Methods: The crowns of 80 extracted molars were transversally sectioned next to the pulp to expose flat, deep dentin surfaces. Eighty-eight cylindrical composite specimens measuring 3.5 mm in diameter and 10 mm in height were prepared and randomly divided into 4 groups (CG, HFSiG, SaG, SaSiG), which respectively received the following treatments: control (CG): etching with 9.5% HF acid gel and application of a silane (HFSiG); sandblasting (SaG) with 50- µm Al2O3 from a distance of 10 mm at a pressure of 2.5 bars for 10 s; combination of sandblasting and silanization procedures (SaSiG). Two composite specimens of each group were analyzed with SEM, while the remaining twenty cylindrical specimen were bonded to dentin samples using a two-step adhesive system and a thin layer of composite. After 24 h storage and 5000 thermocycles, all specimens were loaded to failure under tension in a universal testing machine. The mean differences of each group were analyzed with the Kruskal-Wallis test, while multiple comparisons were made using the Ryan-Einot-Gabriel-Welsch Range test. P-values less than 0.05 were considered to be statistically significant in all tests. The fracture pattern of bonded specimens was also evaluated by SEM. Results: SEM analysis showed morphological changes in each group. The mean values (in MPa) of TBS (± SD) for groups CG, HFSiG, SaG, and SaSiG were 11.17 ± 3.48, 10.81 ± 5.19, 16.51 ± 3.45 and 16.55 ± 3.16, respectively. Statistical analysis showed that the bond strength was significantly affected by surface treatment (p 0.001). Multiple comparison analysis identified statistically significant differences for CG and HFSiG vs SaG and SaSiG (p 0.05), while no significant differences were found for the comparisons CG vs HFSiG and SaG vs SaSiG (p > 0.05). Only a few adhesive failures were recorded (CG: 0.5%; SaG: 0.4%; HFSiG: 0.5%; SaSiG: 0.7%). The null hypothesis was rejected. Conclusion: Composite surface treatments are important for adhesion of indirect composite restorations. Roughening the composite area of adhesion, sandblasting, or both sandblasting and silanizing can provide statistically significant additional resistance to tensile load. Hydrofluoric acid etching with silane treatment did not reveal significant changes in tensile bond strength. These findings suggest that sandblasting treatment was the main factor responsible in improving the retentive properties of indirect composite restorations. Keywords: tensile bond strength, composite, surface treatments

Purpose: To evaluate the effect of cyclical mechanical loading on the bond strength of a fiber and a zirconia post bonded to root dentin. Materials and Methods: Forty single-rooted human teeth (maxillary incisors and canines) were sectioned, and the root canals were prepared at 12 mm. Twenty randomly seleced specimens received a quartz fiber post (FRC) (D.T. Light-Post) and 20 others received a zirconia post (ZR) (Cosmopost). The posts were resin luted (All Bond 2 + resin cement Duo-link) and each specimen was embedded in epoxy resin inside a PVC cylinder. Ten specimens with FRC post and 10 specimens with ZR post were submitted to fatigue testing (2,000,000 cycles; load: 50 N; angle of 45 degrees; frequency: 8 Hz), while the other 20 specimens were not fatigued. Thus, 4 groups were formed: G1: FRC+0 cycles; G2: FRC+2,000,000 cycles; G3: ZR+0 cycles; G4: ZR+2,000,000 cycles. Later, the specimens were cut perpendicular to their long axis to form 2-mm-thick disk-shaped samples (4 sections/specimen), which were submitted to the push-out test (1 mm/min). The mean bond strength values (MPa) were calculated for each tooth (n = 10) and data were submitted to statistical analysis (α = 0.05). Results: Two-way ANOVA revealed that the bond strength was significantly affected by mechanical cycling (p = 0.0014) and root post (p = 0.0325). The interaction was also statistically significant (p = 0.0010). Tukey's test showed that the mechanical cycling did not affect the bonding of FRC to root dentin, while fatigue impaired the bonding of zirconium to root dentin. Conclusion: (1) The bond strength of the FRC post to root dentin was not reduced after fatigue testing, whereas the bonding of the zirconia post was significantly affected by the fatigue. (2) Cyclical mechanical loading appears to damage the bond strength of the rigid post only. Keywords: mechanical cycling, fiber post, zirconia post, adhesive cementation, push-out test, fatigue test, clinical study

Purpose: The purpose of this in vitro study was to measure the microtensile bond strength of a nanofilled composite resin to human dentin after nonvital bleaching at different post-bleaching time intervals, and to analyze the fracture mode under SEM. Materials and Methods: Thirty-six sound human maxillary premolars extracted for orthodontic reasons were prepared in a standardized manner, and randomly assigned to four groups (n = 9): non bleached (control) (NB); bleached with sodium perborate and 35% hydrogen peroxide (SP-HP); bleached with 35% hydrogen peroxide (HP); and bleached with 37% carbamide peroxide (CP). Each group was subdivided into 3 subgroups (n = 3): restored immediately (R0); restored after 7 days (R7); and restored after 14 days (R14). The teeth were stored in distilled water for 24 h, sectioned 4 mm below cementoenamel junction, and the crown was serially sectioned to obtain sticks (0.9 mm2 cross section) for microtensile bond strength testing. The µTBS samples were attached to a universal testing machine (Instron, model 4444), using a Geraldeli's device. The test was performed until the fracture of the specimens, and all specimens were analyzed under a scanning electron microscope (Philips XL-30). Results: Two-way ANOVA (p = 0.05) revealed that there were no statistically significant differences of bond strength values for the bleaching agents used, or at different post-bleaching time intervals. Conclusion: It was concluded that the definitive restoration can be accomplished immediately after nonvital bleaching treatment. Keywords: tensile bond strength, nonvital bleaching, microtensile bond strength test, scanning electron microscopy

Tooth anomalies such as fusions and geminations present a considerable challenge for the practitioner. Functional, esthetic, periodontal, orthodontic, and psychological problems have been described. Quite often, the surgical measures taken lead to a considerable burden for the patient and to subsequent treatment. This report presents the treatment of a 15-year-old male bearing 2 × 2 fused incisors with different tissue structures in the maxilla. No surgical measures were performed; instead, restorative and orthodontic departments cooperated to achieve an adequate treatment result with a minimally invasive approach. Keywords: restorative dentistry, orthodontics, fused incisors, minimally invasive treatment