Exploring the efficacy of laser-assisted in-office tooth bleaching: A study on varied irradiation times and power settings utilizing a diode laser (445 nm).

The aim of this study was to evaluate the effectiveness of a laser-assisted in-office tooth bleaching treatment, employing a diode laser (445 nm) using different power and time settings. Two hundred human incisors were collected for evaluating tooth color change (ΔΕ00) and whiteness index in dentistry (ΔWID) following laser-assisted tooth bleaching treatment. The specimens were distributed into 25 groups (n = 8) according to laser output power (0.5-2 W) and duration of irradiation (10-60 s) that was applied. ΔΕ00 and ΔWID were evaluated using a spectrophotometer at three points of time (24 h, 1 week and 1 month after treatments). Three-way ANOVA revealed that power, duration of laser irradiation, and time of measurement after bleaching treatments significantly affected both ΔΕ00 and ΔWID(p < 0.05). Furthermore, laser irradiation increased ΔΕ00 and ΔWID at all applied powers compared to the control group (p < 0.05), but this increase was dependent on the duration of irradiation. Laser irradiation significantly increased ΔΕ00 when the duration of operation was 50-60 s at 0.5-1 W, while at 1.5-2 W was significantly increased when the duration was 30-60 s. ΔWID was significant higher in the laser groups compared to the control group at all powers, except for 0.5 W where it was significant higher when the duration was 50-60 s. The outcomes of the study can help in selecting the suitable power settings and duration of laser exposure to achieve the optimal whitening results while ensuring the safety of the tooth pulp.

Impact of erosion and aging simulation on chairside materials.

This study investigates the influence of acid exposure and thermocycling simulating erosion tooth wear, on the optical properties and surface roughness of chairside materials. Resin-ceramic, lithium disilicate, premium zirconium oxide and resin composite material comprise the materials tested. To simulate the dental erosion and aging, specimens from each material were immersed in hydrochloric acid, while the thermocycling procedure included 10,000 cycles. The translucency, the color differences and the surface roughness were calculated. The materials phase composition was tested using X-ray diffraction analysis to evaluate T-M phase transformation. The CIEDE2000 color difference and the translucency parameter were tested different significantly among groups. Data were statistically analyzed via independent samples t-test, and paired samples t-test. The thermocycling procedure and the exposure to the acid solution had different effect on the surface roughness of CAD/CAM materials. The present result demonstrated the negative effect the acid exposure has on the zirconia material in terms of color difference. However, no color differences over the threshold of acceptability were recorded after the thermocycling procedure. Both polymer materials exhibit an increase of the surface roughness when they were immersed in acid but they did not display an increase in roughness when they were thermocycled.