Bleaching-induced tooth sensitivity with application of a desensitizing gel before and after in-office bleaching: a triple-blind randomized clinical trial.

OBJECTIVES: This randomized triple-blind clinical trial, split-mouth design, evaluated the application effect of the desensitizing gel before and after in-office bleaching on tooth sensitivity. MATERIALS AND METHODS: In one group, the desensitizing gel was applied for 10 min before the bleaching with 35% hydrogen peroxide, and then application of placebo gel after (n = 90). In the other group, the desensitizing gel was applied before and after the bleaching procedure for 10 min (n = 90). The primary outcome was pain intensity assessed with a numeric rating scale and a visual analog scale. Color was evaluated by means of a digital spectrophotometer and a shade guides. RESULTS: The proportion of patients that experienced pain in the side of before application was 90% (95% CI 82 to 94.6%), while the side of before and after was 93% (95% CI 86.2 to 96.9%), without significant difference between groups (OR = 0.25; 95% CI 0.005 to 2.52; p = 0.37). Pain was correlated in both groups, for the NRS scale (p < 0.0001) and the VAS scale (p < 0.0001) in all assessment periods. Significant whitening was detected, and no significant difference of color change was observed between groups (p > 0.45). CONCLUSIONS: The application of the desensitizing agent did not influence the effectiveness of bleaching, but it was not efficient in reducing the sensitivity, when applied before the procedure, or before and after. CLINICAL RELEVANCE: The use of a desensitizing gel before or after in-office bleaching does not reduce incidence or intensity of tooth sensitivity.

Mechanical and microbiological properties and drug release modeling of an etch-and-rinse adhesive containing copper nanoparticles.

OBJECTIVES: To evaluate the effect of addition of copper nanoparticles (CN) at different concentrations into a two-step etch-and-rinse (2-ER) adhesive on antimicrobial activity (AMA), copper release (CR), ultimate tensile strength (UTS), degree of conversion (DC), water sorption (WS), solubility (SO), as well as the immediate (IM) and 1-year resin-dentin bond strength (µTBS) and nanoleakage (NL). METHODS: Seven adhesives were formulated according to the addition of CN (0, 0.0075, 0.015, 0.06, 0.1, 0.5 and 1wt%) in adhesive. The AMA was evaluated against Streptococcus mutans using agar diffusion assay. For CR, WS and SO, specimens were constructed and tested for 28 days. For UTS, specimens were tested after 24h and 28 days. For DC, specimens were constructed and tested after 24h by FTIR. After enamel removal, the ER was applied to dentin. After composite resin build-ups, specimens were sectioned to obtain resin-dentin sticks. For µTBS and NL, specimens were tested after 24h and 1-year periods. All data were submitted to statistical analysis (α=0.05). RESULTS: The addition of CN provided AMA to the adhesives at all concentrations. Higher CR was observed in adhesives with higher concentration of CN. UTS, DC, WS and SO were not influenced. For µTBS an increase was observed in 0.1 and 0.5% copper group. For NL, a significant decrease was observed in all groups in comparison with control group. After 1-year, no significant reductions of µTBS and no significant increases of NL were observed for copper containing adhesives compared to the control group. SIGNIFICANCE: The addition of CN in concentrations up to 1wt% in the 2-ER adhesive may be an alternative to provide AMA and preserve the bonding to dentin, without reducing adhesives' mechanical properties evaluated.

Influence of Conditioning Time of Universal Adhesives on Adhesive Properties and Enamel-Etching Pattern.

OBJECTIVES: To evaluate the effect of application protocol in resin-enamel microshear bond strength (µSBS), in situ degree of conversion, and etching pattern of three universal adhesive systems. METHODS AND MATERIALS: Sixty-three extracted third molars were sectioned in four parts (buccal, lingual, and proximals) and divided into nine groups, according to the combination of the main factors-Adhesive (Clearfil Universal, Kuraray Noritake Dental Inc, Tokyo, Japan; Futurabond U, VOCO, Cuxhaven, Germany; and Scotchbond Universal Adhesive, 3M ESPE, St Paul, MN, USA)-and enamel treatment/application time (etch-and-rinse mode [ER], self-etch [SE] application for 20 seconds [SE20], and SE application for 40 seconds [SE40]). Specimens were stored in water (37°C/24 h) and tested at 1.0 mm/min (µSBS). The degree of conversion of the adhesives at the resin-enamel interfaces was evaluated using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data were analyzed with two-way analysis of variance and Tukey test (α=0.05). RESULTS: In general, the application of the universal adhesives in the SE40 produced µSBS and degree of conversion that were higher than in the SE20 (p<0.01) and similar to the ER mode. The deepest enamel-etching pattern was obtained in the ER mode, followed by the SE40. CONCLUSIONS: The active and prolonged application of universal adhesives in the SE mode may be a viable alternative to increase the degree of conversion, etching pattern, and resin-enamel bond strength.

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.