Permeation of intrinsic water into ethanol- and water-saturated, monomer-infiltrated dentin bond interfaces.

OBJECTIVES: The aim of this study was to evaluate the formation of dentin bonding interfaces using the water-wet and the ethanol-wet techniques under simulated pulpal pressure, and to assess the effect of adhesive solvent and thermomechanical loading. METHODS: Flat dentin surfaces were restored under 20mm-simulated pulpal pressure following two bonding approaches (water-wet and ethanol-wet bonding) in combination with dental adhesives containing ethanol (Single Bond Plus and Scotchbond Multi-Purpose) or acetone (One-Step Plus and All-Bond 2) as solvent. Half of the restorations of each subgroup were subjected to thermocycling followed by cyclic loading (three teeth per group). Bond strength was measured using the microtensile bond strength test and fitted to a Weibull distribution (α=0.05). Ultrastructural analyses of the interface and leakage/nanoleakage evaluation were performed using confocal scanning microscopy (CLSM) and transmission electron microscopy (TEM). RESULTS: Water permeation through dentin tubules during adhesive application prevented adequate penetration of adhesive monomers into the demineralized collagen matrix in both bonding techniques, but more severely for water-wet bonding. Acetone-solvated adhesives showed worse bonding performance and hybridization than ethanol-based systems when applied in the ethanol-wet mode, both before and after thermomechanical challenge. SIGNIFICANCE: The ethanol-wet bonding technique helps to compensate for water permeation from dentin tubules during the bonding procedures to form more stable dentin bonds, especially when used in conjunction to ethanol-solvated systems.

Clinical effectiveness and tooth sensitivity associated with different bleaching times for a 10 percent carbamide peroxide gel.

BACKGROUND: The daily application time for 10 percent carbamide peroxide (CP) typically is between four and eight hours. However, to the authors' knowledge, no investigators in clinical studies have compared different application times; this is the aim of this study. METHODS: The authors recruited 60 patients and categorized each of them into one of four groups. All participants used 10 percent CP in a bleaching tray. The daily application times were 15 minutes, 30 minutes, one hour or eight hours. Participants bleached their teeth for 16 days and those who were not satisfied with the results extended the bleaching time until they were satisfied. Patients recorded their tooth sensitivity on a 0 to 4 scale. The authors measured the shade changes by using a digital spectrophotometer and shade guide. They performed appropriate statistical analysis of the data (α = .05). RESULTS: Participants in the one- and eight-hour groups bleached their teeth for 18 and 16 days, respectively (P > .05), while statistically longer periods were required for participants in the other two groups (P < .001) to be satisfied with the results. Participants' tooth sensitivity ratings were similar for the 15-minute, 30-minute and one-hour application times (P > .05), and they were statistically lower than those for participants in the eight-hour group. CONCLUSIONS: The eight-hour bleaching protocol yielded faster bleaching; however, participants experienced higher sensitivity levels. The one-hour group most closely approached the eight-hour group with regard to bleaching speed, while those in the one-hour group experienced lower sensitivity levels. CLINICAL IMPLICATIONS: In this study, the difference in bleaching speed between the eight- and one-hour application times after 16 days was small, and the results showed less tooth sensitivity for patients in the one-hour group.