Effectiveness of in-office bleaching treatment with different activation techniques on tooth color changes and sensitivity: A randomized clinical trial.

PURPOSE: To investigate the effectiveness of different light activation methods for in-office bleaching agents in terms of color change durability and tooth sensitivity (TS). METHODS: 80 subjects were randomly divided into four groups (n= 20). A bleaching agent (40% H2O2) was activated using a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, an 810-nm diode laser, a light-emitting diode (LED), and conventional (chemical) treatment. The CIE L*a*b* system and ΔE* values were used to measure color changes in the teeth using a spectrophotometer. TS was measured using the visual analogue scale (VAS). The measurements were performed before the treatment, immediately afterwards, and 2 weeks, 1 month, and 6 months later. A P< 0.05 was accepted as statistically significant. RESULTS: The most statistically significant color change occurred in the 2nd week (⏊E2) in all groups (P< 0.05). However, the most color change in the 2nd week (ΔE2) occurred in the Nd:YAG group, yet there was no statistically significant result between Nd:YAG and LED (P< 0.05). After the procedure (VAS2), a statistically significant increase in TS was observed in all groups (P< 0.05), with the highest sensitivity observed in the LED group; significant differences were observed between the LED and the other groups (P< 0.05). CLINICAL SIGNIFICANCE: Although all light activation techniques showed noticeable color changes, the conventional technique showed appreciable color change at the 6-month follow-up. Nd:YAG and diode laser activation can be preferable alternatives to LED and conventional activation in clinical practice as they bleach more and faster, decrease the number of sessions and chair time, and cause minimum sensitivity.

Effect of surface finishing treatments on the color stability of CAD/CAM materials.

PURPOSE: The aim of this study was to evaluate the effect of different surface finishing processes on the color stabilities of lithium disilicate glass-ceramics, zirconia-reinforced lithium silicate ceramics, and resin nanoceramics after artificial ageing. MATERIALS AND METHODS: 216 samples were prepared from 3 different CAD/CAM materials (LAVA Ultimate, IPS e.max CAD, VITA Suprinity) with A1 HT color at a size of 14 × 12 mm and a thickness of 0.5 ± 0.05 mm. Color measurements of the samples were performed with a spectrophotometer using color parameters and CIE Lab color system on a gray backing between baseline color and after 5000 cycles of artificial ageing in 4 stages (i.e. the first measurement before the treatment, the second measurement after polishing, the third measurement after cement application, and the fourth measurement after artificial ageing). The results were evaluated using the Variance analysis and Fisher's LSD test. RESULTS: Resin nanoceramics (LU) exhibited higher color change values than zirconia-reinforced lithium silicate (VS) and lithium disilicate (EC) ceramics after artificial ageing. Manual polishing and glazing resulted in similar color change for LU and VS (P>.05). In the EC group, glazing provided statistically different results as compared to the manual polishing and control groups (P<.05). Among the ceramic groups, color change values of the subgroup, which was treated by glazing, of the zirconia-reinforced lithium silicate (VS) and lithium disilicate (EC) samples were below the clinically acceptable level (ΔE < 3.5). CONCLUSION: The lowest color change for all stages was observed in Vita Suprinity.

Effect of Laser Etching on Glass Fiber Posts Cemented with Different Adhesive Systems.

BACKGROUND: Glass fiber-reinforced posts have been preferred frequently because of some physical properties similar to the dentin, chemically bonding to dentin, biocompatibility, and esthetics. OBJECTIVE: This study aimed to evaluate the microleakage and bond strength of glass fiber posts cemented with various adhesive systems on laser-etched root canal walls. METHODS: Roots of 120 human mandibular premolars were divided into two groups for push-out bond strength test and the microleakage test (n = 60). Erbium-doped yttrium-aluminum-garnet (Er:YAG) laser etching of the root canal walls was carried out on half of the specimens in both test groups. The laser-treated and laser-nontreated groups were divided again into three subgroups (n = 10). Glass fiber posts (everStick Post) were luted using three different resin cements: total-etch (Variolink N), self-etch (Panavia F 2.0), and self-adhesive (Rely X Unicem). Three dentin discs were obtained from each root, and the bond strength of the glass fiber posts was measured by push-out tests. The dye penetration method was used to investigate coronal microleakage. In addition, surface treatments and the bonding interfaces were observed using scanning electron microscope. RESULTS: The highest bond strengths were observed for the total-etch and self-adhesive resin cement groups with laser etching (p < 0.05), and the lowest bond strength was obtained for the self-etch resin cement group (p < 0.05). There were no statistically significant differences in terms of microleakage (p > 0.05), except for the self-adhesive resin cement group (p < 0.05). CONCLUSIONS: Er:YAG laser etching enhances the bonding strength of glass fiber posts. In addition, laser etching can reduce microleakage of self-adhesive resin cement.