Does the acidity of self-etching primers affect bond strength and surface morphology of enamel?

Purpose: This study examined the ultrastructure and microtensile bond strengths (TBS) of self-etching (with different acidity) and conventional adhesive systems bonded to unground enamel. Materials and Methods: Resin composite (Filtek Z250) buildups were bonded to unground enamel surfaces of third molars after adhesive application with the following materials: Clearfil SE Bond (CSE); Optibond Solo Plus Self-Etch (OP); Tyrian Self Priming Etching (TY), and the controls Scotchbond Multi-Purpose Plus (SBMP) and Single Bond (SB). Six teeth were assigned to each material. After storage in water for 24 h at 37 degrees C, the bonded specimens were sectioned into beams of approximately 0.8 mm(2) and subsequently subjected to mu TBS testing at a crosshead speed of 0.5 mm/min. The average values were subjected to one-way ANOVA (alpha = 0.05). The effect of surface conditioning of each material was observed under scanning electron microscopy (SEM). Results: The highest resin-enamel bond strength was observed for SBMP (22.7 +/- 5.2) and SB (26.7 +/- 5.2 MPa). The lowest mean bond strengths were 10.9 +/- 3.2 and 7.8 +/- 1.5 MPa for TY and OP, respectively. CSE showed an intermediate performance (18.7 +/- 4.6 MPa). An overall increase in porosity was evident along the entire enamel surface treated with the self-etching primers; however, no selective demineralization similar to that with 35% phosphoric acid was observed. Conclusion: The highest bond strength means and the more retentive etching pattern were observed for the two-step etch-and-rinse adhesives. Among the self-etching systems studied, Clearfil SE Bond should be preferred.82758

Overview of Clinical Alternatives to Minimize the Degradation of the Resin-dentin Bonds

The incorporation of hydrophilic and acidic resin monomers substantially improved the initial bonding of contemporary etch-and-rinse (ER) and self-etch (SE) adhesives to intrinsically wet dental substrates, providing quite favorable immediate results, regardless of the bonding approach used. However, in the long term, the bonding effectiveness of most simplified ER and SE adhesives drop dramatically. This review examines the fundamental processes that are responsible for the aging mechanisms involved in the degradation of the resin-bonded interfaces and some possible clinical approaches that have been effective in minimizing or even preventing the degradation of the adhesive interfaces produced with simplified adhesives. The incorporation of some of the feasible approaches - described in this review - may improve the quality of the adhesive restorations performed in clinical practice, while manufacturers develop bonding materials that are less susceptible to the aging mechanisms present in the oral environment

Influence of specimen size and regional variation on long-term resin-dentin bond strength

Objectives: Verify whether the dimension of a bonded specimen stored prior microtensile testing and its regional variation may affect the resin-dentin bond strength (BS) over time. Methods: Thirty human third molars had a flat dentin surface exposed and all peripheral enamel removed. Two adhesive systems (Single-Bond and One-Step) were applied and composite resin crowns (Z250) were constructed. Teeth were divided into three groups (n = 5). Group A specimens were sectioned to obtain sticks to be tested in tension (0.5 mm/min) immediately. Group B specimens were stored in water for 6 months, before sectioning and testing. Group C specimens were sectioned; the sticks were stored for 6 months and tested. In groups A and B, the origin of the sticks, periphery and inner regions was controlled. Bond strength (BS) was expressed as an index that considers cohesive failures and estimated values of premature debonded specimens. One-way ANOVA and Tukey's test (alpha = 0.05) were used to compare groups A, B and C, and a second analytical approach (A and B) employed a two-way ANOVA (time versus regional differences) for each adhesive system. Results: For Single-Bond (SB), the BS for specimens in group A was higher than for groups B and C. For One-Step (OS), the BS in group A was higher than for B, which was in turn higher than for C. In the second group approach, no difference was found when the test was performed immediately; however, after 6 months, the inner sticks from group B showed significantly higher BS. Significance: (1) The amount of decrease in BS is dependent on the specimen size; (2) the decrease in BS was greater for peripheral specimens than more centrally located specimens. (C) 2004 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.21322423

Long-term efficacy of in-office and at-home bleaching: A 2-year double-blind randomized clinical trial

Purpose: This parallel, double-blind randomized clinical trial evaluated the 2-year bleaching efficacy and sensitivity produced by at-home (AH) and in-office (IO) bleaching therapies. Methods: 60 participants with tooth color darker than C2, without restorations in the anterior dentition and older than 18 years old, were randomly allocated into two groups to receive either IO with 35% hydrogen peroxide or AH with 16% carbamide peroxide. Color was recorded at baseline (BA); 1-week (1W); end of the treatment (ET); and 2 years (2Y) after bleaching, using the Vita Classical shade guide. The perception of TS was recorded on a 0-4 scale during and 2Y after bleaching. The variation in shade guide units (Delta SGU) from BA vs. 1W was compared to Delta SGU from BA vs. 2Y using paired t-test. The percentage of subjects who reported TS was evaluated by Fisher's exact test. The intensity of TS was evaluated by a Mann-Whitney test (alpha=0.05). Results: Both bleaching techniques demonstrated equivalent and significant tooth color shade lightening. No significant color rebound occurred after 2Y for both techniques (P = 0.77 and 0.87, for AH and IO respectively). The absolute risk of TS was similar for IO and AH (P= 0.12), however the intensity of TS was significantly higher for IO (P= 0.001). No subjects reported sensitivity after 2Y. (Am J Dent 2012:25:199-204).25419920

The influence of storage time and cutting speed on microtensile bond strength

Purpose: The aim of this study was to verify the influence of the storage time and the cutting speed during specimen preparation on the bond strength of a single-bottle adhesive to dentin. Materials and Methods: A flat dentin surface was exposed in 36 human third molars. The adhesive system (Single Bond) was applied according to the manufacturer's instructions, and composite resin crowns (Z250) were constructed incrementally. Specimens were stored for 10 min, 24 h, or 1 week in distilled water at 37degreesC before being longitudinally sectioned in both the "x" and "y" directions at different cutting speeds (0.5, 1.6, and 2.6 m/s) to obtain sticks with a cross-sectional area of approximately 0.8 mm(2). The specimens were tested in a tensile load machine (0.5 mm/min) and the fracture mode analyzed. A two-way ANOVA with storage time (3 levels) and cutting speed (3 levels) as factors was used to compare the mean microtensile bond strengths. Results: Highly significant main effects and interaction (p < 0.0001) were detected. The highest mean bond strength was obtained with a storage time of 1 week and cutting speed of 2.6 m/s. The lowest mean was found when the specimens were prepared immediately after composite resin placement and sliced at 0.5 m/s. Conclusion: Both the storage time and the cutting speed may affect the bond strength results. Therefore, these variables must be controlled in microtensile bond strength tests.6171

Clinical Effects of Prolonged Application Time of an In-office Bleaching Gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objective: The aim of this study was to evaluate whether the use of a gel applied for 1 x 45 minutes would have the same bleaching rate and tooth sensitivity levels when compared with 3 x 15-minute applications. Methods: In-office bleaching was performed in 30 participants with 35% hydrogen peroxide gel. In one group (n=15; 3x15 minutes), the bleaching agent was refreshed every 15 minutes, three times at each bleaching appointment. In the other group (n=15; 1x45 minutes) the gel was left undisturbed on the buccal surfaces of all teeth for 45 minutes at each bleaching appointment. This protocol was repeated after one week. The bleaching evaluation was completed by two blinded, calibrated evaluators who compared the baseline color of the maxillary anterior teeth with a value-oriented shade guide after each period. The patients recorded the tooth sensitivity on a 0-4 scale. The color changes were evaluated by appropriate tests (alpha=0.05). The percentage of patients with tooth sensitivity and its intensity were also statistically analyzed (a=0.05), respectively. Results: The use of gel for a single 45-minute period (1x45 minutes) decreased the bleaching efficacy (p<0.05) 86.7%, and 100% of patients from the 3 x 15-minute and 1 x 45-minute groups, respectively, experienced tooth sensitivity (p=0.22). The intensity of sensitivity was lower for the 3 x 15-minute applications (p=0.04). Conclusions: A 35% hydrogen peroxide gel for in-office bleaching preferably should be applied in three 15-minute applications because 1 x 45 minutes reduces the bleaching speed and slightly increases the intensity of tooth sensitivity.366590596Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [301937/2009-5, 303933/2007-0

Membrane Permeability Properties of Dental Adhesive Films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)This study evaluated the permeability properties of five experimental resin membranes that ranged from relatively hydrophobic to relatively hydrophilic to seal acid-etched dentin saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents or as solutions solvated with ethanol (70% resin/30% ethanol). The quality of dentin sealing by these experimental resins was expressed in terms of reflection coefficients calculated as the ratio of the effective osmotic pressure to the theoretical osmotic pressure of test solutions. The effective osmotic pressure produced across resin-bonded dentin was induced in hypertonic solutions (CaCl(2) or albumin) at zero hydrostatic pressure. The outward fluid flow induced by these solutions was brought to zero by applying an opposing negative hydrostatic pressure. The least hydrophilic resins blends, R1 and R2, exhibited significantly (p < 0.05) higher reflection coefficients than the most hydrophilic resins (R4 and R5) in both conditions of dentin saturation (water and ethanol). The reflection coefficients of neat resins were, in general, significantly higher when compared with their corresponding solvated versions in both conditions of dentin saturation. In dentin saturated with ethanol, bonding with neat or solvated resins, resulted in reflection coefficients that were significantly higher when compared with the results obtained in dentin saturated with water. Reflection coefficients of CaCl(2) (ca. 1 x 10(-4)) were significantly lower (p < 0.05) than for albumin (ca. 3 x 10(-2)). Application of hydrophobic resins may provide better sealing of acid-etched dentin if the substrate is saturated with ethanol, instead of water. (c) 2007 Wiley Periodicals. Inc. J Biomed Mater Res Part B: Appl Biomater 88B: 312-320, 200988B2312320National Institute of Dental and Craniofacial ResearchCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES