A Single-Blind Randomized Trial About the Effect of Hydrogen Peroxide Concentration on Light-Activated Bleaching.

OBJECTIVE: To compare the bleaching efficacy and tooth sensitivity (TS) of two hydrogen peroxide (HP) concentrations (20% and 35%) used for in-office bleaching associated or not with a light-emitting diode (LED)/laser light activation. METHOD: Seventy-seven patients with a right maxillary canine darker than A3 were selected for this single-blind randomized trial. The participants were distributed in four groups: bleaching with 35% HP, 35% HP + LED/laser, 20% HP, and 20% HP + LED/laser. The anterior teeth were bleached in two sessions, using a 35% or 20% HP gel with a one-week interval. Each session had three applications of 15 minutes. For the light-activated groups, the LED/laser energy (Whitening Laser Light Plus, DMC) was employed according to the manufacturer's instructions. The color change was evaluated by subjective and objective methods. Participants recorded TS with five-point verbal and visual analog scales. Color change in ΔE was evaluated by analysis of variance and Tukey tests (α=0.05) and in ΔSGU with Kruskall-Wallis and Dunn test. The absolute risk of TS and TS intensity were evaluated by Fisher exact test and Kruskall-Wallis test, respectively (α=0.05). RESULTS: All groups achieved the same level of whitening, except for the 20% HP group, which showed the lowest degree of whitening in the subjective analysis. The use of light did not increase the absolute risk or intensity of TS. No significant difference among groups was observed when color changes were assessed with the spectrophotometer. CONCLUSION: According to the value-oriented shade guide, the use of LED/laser light activation was able to increase the degree of whitening of the 20% HP group, but this association was not useful for the 35% HP gel. The spectrophotometer, however, did not detect significant differences among groups.

Influence of Isolation Method of the Operative Field on Gingival Damage, Patients' Preference, and Restoration Retention in Noncarious Cervical Lesions.

OBJECTIVES: To evaluate the retention rates, gingival damage, and patients' preferences for adhesive restorations in noncarious cervical lesions (NCCL) associated with the use of rubber dam vs cotton rolls/retraction cord isolation. METHODS: Thirty patients having one pair of similar NCCL on opposing sides of the same arch were enrolled in this study. A total of 60 restorations were placed. In each patient one restoration was placed under rubber dam isolation (RD) using dental retainers, and the other one was placed using cotton rolls/retraction cord (CR/RC) isolation. Dental residents with more than 10 years of clinical experience restored all NCCL using the same adhesive (GO!, SDI Limited, Bayswater, Australia) and composite resin (Ice, SDI). The patients' preferences were recorded. The gingival condition (bleeding, gingival laceration, and gingival insertion level) was evaluated immediately after the restorative procedure and after one week. Gingival sensitivity was also assessed one week after the end of the restorative procedures. The clinical time required to perform each restoration was recorded. The performance of the restorations was assessed using the FDI criteria at baseline and six, 12, and 18 months after clinical service. All criteria evaluated were submitted to appropriate statistical analysis (α=0.05). RESULTS: The retention rates of the restorations at each recall time were not affected by the isolation method (p>0.05). No significant difference between isolation methods was found in regard to patients' preferences (p=0.86), gingival bleeding (p=0.57), laceration (p=0.64), insertion (p>0.52), gingival sensitivity (p=0.52), or chairside time (p=0.77). CONCLUSIONS: The use of CR/RC was shown to be similar to the use of RD in terms of retention rates, patient's preference, gingival damage, and chairside time for adhesive restorations in NCCL.

In vitro longevity of bonding properties of universal adhesives to dentin.

PURPOSE: To evaluate the immediate and 6-month resin-dentin bond strength (µTBS) and nanoleakage (NL) of universal adhesives that contain or do not contain methacryloyloxydecyl dihydrogen phosphate (MDP) and are used in the etch-and-rinse and self-etch strategies. METHODS AND MATERIALS: Forty caries-free extracted third molars were divided into eight groups for µTBS (n=5). The groups were bonded with the Clearfil SE Bond (CSE) and Adper Single Bond 2 (SB) as controls; Peak Universal, self-etch (PkSe) and etch-and rinse (PkEr); Scotchbond Universal Adhesive, self-etch (ScSe) and etch-and-rinse (ScEr); and All Bond Universal, self-etch (AlSe) and etch-and-rinse (AlEr). After composite restorations, specimens were longitudinally sectioned to obtain resin-dentin bonded sticks (0.8 mm(2)). The µTBS of the specimens was tested immediately (IM) or after 6 months of water storage (6M) at 0.5 mm/min. Some sticks at each storage period were immersed in silver nitrate and photo developed, and the NL was evaluated with scanning electron microscopy. Data were analyzed with two-way repeated-measures analysis of variance and Tukey test (α=0.05). RESULTS: At the IM period, PkSe and PkEr showed µTBS similar to the control adhesives (p>0.05) but increased NL pattern and lower µTBS after 6M (p<0.05). ScSe and ScEr showed intermediary µTBS values at the IM period but remained stable after 6 months (p>0.05). AlSe showed the lowest µTBS (p<0.05), but µTBS and NL remained stable after 6M (p>0.05). AlEr showed higher IM µTBS but showed higher degradation after 6M (p<0.05). CONCLUSIONS: Universal adhesives that contain MDP showed higher and more stable µTBS with reduced NL at the interfaces after 6 months of water storage.

A comprehensive laboratory screening of three-step etch-and-rinse adhesives.

OBJECTIVES: This study evaluated several bonding (microtensile bond strengths [µTBS], nanoleakage [NL], and in situ degree of conversion [ISDC] on dentin) and mechanical properties (ultimate tensile strength [UTS], degree of conversion [DC], water sorption [WS], and solubility [SL] in water) of four three-step etch-and-rinse adhesives in the short term. METHODS: A total of 28 molars were used in this study. The dentin surfaces were bonded with the following adhesives: All-Bond 3 (ALB3); Fusion Duralink (FSDL); Optibond FL (OBFL), and Scotchbond Multi-Purpose (SBMP). After each adhesive-system application, composite resin build-ups were added. For bonding tests, specimens were sectioned in order to obtain bonded sticks. The sticks were divided to be tested for µTBS (0.5 mm/min), for NL (n=2), and ISDC (n=2). For NL, they were immersed in 50% silver nitrate and analyzed by scanning election microscopy. For ISDC, the hybrid layer was evaluated by micro-Raman spectroscopy. An hourglass-shaped matrix (UTS) or disk-shaped matrix (WS and SL) was filled with primer and adhesive (1:1 ratio) and light-polymerized. For UTS evaluation, the specimens were tested under tension. For WS and SL, specimens were desiccated and stored in distilled water to evaluate water diffusion kinetics over a 28-day period. The DC of the adhesives was evaluated by Fourier transformed infrared spectroscopy. The data from each test were analyzed by appropriate statistical methods. RESULTS: OBFL resulted in the highest µTBS, lower NL, higher ISDC and DC, and higher UTS than other adhesives (p<0.05), as well as lower WS (similar to ALB3 and FSDL) and SL (similar to ALB3 and SBMP) (p>0.05). ALB3 showed a higher NL and the lowest DC value. FSDL showed the highest NL and SL and the lowest ISDC. SBMP showed the lowest pattern of WS (p<0.05)CONCLUSION: OBFL showed the best results in all the properties evaluated, and it can be considered the gold standard of the three-step etch-and-rinse adhesive systems.

Immediate adhesive properties to dentin and enamel of a universal adhesive associated with a hydrophobic resin coat.

OBJECTIVES: To evaluate the effect of acid etching and application of a hydrophobic resin coat on the enamel/dentin bond strengths and degree of conversion (DC) within the hybrid layer of a universal adhesive system (G-Bond Plus [GB]). METHODS: A total of 60 extracted third molars were divided into four groups for bond-strength testing, according to the adhesive strategy: GB applied as a one-step self-etch adhesive (1-stepSE); GB applied as in 1-stepSE followed by one coat of the hydrophobic resin Heliobond (2-stepSE); GB applied as a two-step etch-and-rinse adhesive (2-stepER); GB applied as in 2-stepER followed by one coat of the hydrophobic resin Heliobond (3-stepER). There were 40 teeth used for enamel microshear bond strength (µSBS) and DC; and 20 teeth used for dentin microtensile bond strength (µTBS) and DC. After restorations were constructed, specimens were stored in water (37°C/24 h) and then tested at 0.5 mm/min (µTBS) or 1.0 mm/min (µSBS). Enamel-resin and dentin-resin interfaces from each group were evaluated for DC using micro-Raman spectroscopy. Data were analyzed with two-way analysis of variance for each substrate and the Tukey test (α=0.05). RESULTS: For enamel, the use of a hydrophobic resin coat resulted in statistically significant higher mean enamel µSBS only for the ER strategy (3-stepER vs 2-stepER, p<0.0002). DC was significantly improved for the SE strategy (p<0.00002). For dentin, the use of a hydrophobic resin coat resulted in significantly higher dentin mean µTBS only for the SE strategy (2-stepSE vs 1-stepSE, p<0.0007). DC was significantly improved in groups 2-stepSE and 3-stepER when compared with 1-stepSE and 2-stepER, respectively (p<0.0009). CONCLUSIONS: The use of a hydrophobic resin coat may be beneficial for the selective enamel etching technique, because it improves bond strengths to enamel when applied with the ER strategy and to dentin when used with the SE adhesion strategy. The application of a hydrophobic resin coat may improve DC in resin-dentin interfaces formed with either the SE or the ER strategy. On enamel, DC may benefit from the application of a hydrophobic resin coat over 1-stepSE adhesives.

Effect of bur roughness on bond to sclerotic dentin with self-etch adhesive systems.

PURPOSE: To evaluate the effect of bur roughness on bond strength values and conditioner pattern of two-step self-etch adhesives applied on sclerotic dentin. METHODS: The roots of 48 bovine incisors were removed and the crowns were divided into four groups: the control group (CO) teeth were left untreated or the teeth were slightly roughened with coarse-, medium-, or fine-grit diamond burs. Next, the teeth were subdivided and Clearfil SE Bond (CSE) and Adper SE Bond (ASE) were applied according to the manufacturers' instructions. Composite resin (Opallis) buildups were incrementally constructed on the bonded surfaces. After storage for 24 hours in distilled water at 37°C, the teeth were sectioned into sticks (area of 0.8 mm(2)). The sticks were stressed until failure by tensile forces (0.5 mm/min). Additionally, eight bovine teeth were treated as previously described, and after adhesive application, the surface was rinsed off and examined by scanning electron microscopy to measure the relative number of open tubules (OT). Data (MPa) were analyzed by two-way analysis of variance and Tukey test (p=0.05). RESULTS: CO showed the highest bond strength values (p<0.05). As regards OT, the lowest mean was observed for CO (p<0.05) and the highest was found after application of CSE or ASE (p<0.05).