Effect of immersion into solutions at various pH on the color stability of composite resins with different shades

OBJECTIVES: This study examined the color changes of a resin composite with different shades upon exposure to water with different pH. MATERIALS AND METHODS: Nanohybrid resin composites (Filtek Z350XT, 3M ESPE) with four different shades (A2, A3, B1, and B2) were immersed in water with three different pH (pH 3, 6, and 9) for 14 day. The CIE L*a*b* color coordinates of the specimens were evaluated before and after immersion in the solutions. The color difference (DeltaE*) and the translucency parameter (TP) were calculated using the color coordinates. RESULTS: DeltaE* ranged from 0.33 to 1.58, and the values were affected significantly by the pH. The specimens immersed in a pH 6 solution showed the highest DeltaE* values (0.87 - 1.58). The specimens with a B1 shade showed the lowest DeltaE* change compared to the other shades. TP ranged from 7.01 to 9.46 depending on the pH and resin shade. The TP difference between before and after immersion in the pH solutions was less than 1.0. CONCLUSIONS: The resulting change of color of the tested specimens did not appear to be clinically problematic because the color difference was < 1.6 in the acidic, neutral, and alkaline solutions regardless of the resin shade, i.e., the color change was imperceptible.

Microtensile bond strength of all-in-one adhesive to caries-affected dentin / 대한치과보존학회지

The purpose of this study was to evaluate the effect of multiple application of all-in-one dentin adhesive system on microtensile bond strength to caries-affected dentin. Twenty one extracted human molars with occlusal caries extending into mid-dentin were prepared by grinding the occlusal surface flat. The carious lesions were excavated with the aid of caries detector dye. The following adhesives were applied to caries-affected dentin according to manufacturer's directions; Scotchbond(TM) Multi-Purpose in SM group, Adper Prompt L-Pop(TM) 1 coat in LP1 group, 2 coats in LP2 group, 3 coats in LP3 group, Xeno(R) III 1 coat in XN1 group, 2 coats in XN2 group, and 3 coats in XN3 group. After application of the adhesives, a cylinder of resin-based composite was built up on the occlusal surface. Each tooth was sectioned vertically to obtain the 1 x 1 mm2 sticks. The microtensile bond strength was determined. Each specimen was observed under SEM to examine the failure mode. Data were analyzed with one-way ANOVA. The results of this study were as follows; 1. The microtensile bond strength values were; SM (14.38 +/- 2.01 MPa), LP1 (9.15 +/- 1.81 MPa), LP2 (14.08 +/- 1.75 MPa), LP3 (14.06 +/- 1.45 MPa), XN1 (13.65 +/- 1.95 MPa), XN2 (13.98 +/- 1.60 MPa), XN3 (13.88 +/- 1.66 MPa). LP1 was significantly lower than the other groups in bond strength (p 0.05). 2. In LP1, there were a higher number of specimens showing adhesive failure. Most specimens of all groups except LP1 showed mixed failure.