A Spectrophotometric Study on Light Attenuation Properties of Dental Bleaching Gels: Potential Relevance to Irradiation Parameters

The influence of delivery power losses and full operating parametry on the effectiveness of diode visible-near infra-red (445-1064 nm) laser therapy in dentistry-a multi-centre investigation

The development of protocols for laser-assisted therapy demands strict compliance with comprehensive operating parametry. The purpose of this investigation was to examine the accuracy of correlation between laser control panel and fibre emission power values in a selection of diode dental lasers. Through retrospective analysis using successive systematic review and meta-analysis, it is clear that there is inconsistency in the details, and possible inaccuracies in laser power applied and associated computed data. Through a multi-centre investigation, 38 semi-conductor ("diode") dental laser units were chosen, with emission wavelengths ranging from 445 to 1064 nm. Each unit had been recently serviced according to manufacturer's recommendations, and delivery fibre assembly checked for patency and correct alignment with the parent laser unit. Subject to the output capacity of each laser, four average power values were chosen using the laser control panel-100 mW, 500 mW, 1.0 W, and 2.0 W. Using a calibrated power meter, the post-fibre emission power value was measured, and a percentage power loss calculated. For each emission, a series of six measurements were made and analysed to investigate sources of power losses along the delivery fibre, and to evaluate the precision of power loss determinations. Statistical analysis of a dataset comprising % deviations from power setting levels was performed using a factorial ANOVA model, and this demonstrated very highly significant differences between devices tested and emission power levels applied (p < 10-142 and < 10-52 respectively). The devices × emission power interaction effect was also markedly significant (p < 10-66), and this confirmed that differences observed in these deviations for each prior power setting parameter were dependent on the device employed for delivery. Power losses were found to be negatively related to power settings applied. Significant differences have emerged to recommend the need to standardize a minimum set of parameters that should form the basis of comparative research into laser-tissue interactions, both in vitro and in vivo.

Effects of tooth bleaching protocols assisted by Er,Cr:YSGG and diode (980 nm) lasers on color change of resin-based restoratives

OBJECTIVE

To evaluate color change of three resin-based restorative materials after two laser-assisted in-office tooth bleaching protocols using Er,Cr:YSGG and diode (980 nm) lasers.

MATERIALS AND METHODS

A nanohybrid composite resin (EP), a Bis-GMA free composite resin (EPBio) and a resin-matrix CAD-CAM ceramic (HC) were tested. Ninety specimens were prepared and stored in artificial saliva. Group 1 received an in-office bleaching treatment using 40% H₂ O_2. The same bleaching procedure was assisted by Er,Cr:YSGG laser in Group 2 and by a diode laser (980 nm) in Group 3. Color measurements were performed using a double-beam UV-Vis spectrophotometer at four time intervals (before, 24 h, 15 and 30 days), converted to L*, a*, and b* units of the CIELAB color space and assessed on the basis of 50:50% acceptability (ΔΕ_ab * = 2.7 and ΔΕ₀₀  = 1.77) and 50:50% perceptibility (ΔΕ_ab * = 1.2 and ΔΕ₀₀  = 0.81) thresholds. Three-way ANOVA with repeated measurements was used for statistical analysis of the data.

RESULTS

Color and whiteness changes did not exceed the established 50:50% acceptability thresholds. EP presented the highest color change after the bleaching followed by EPBio and HC (p ≤ 0.05). Three-way ANOVA revealed that type of material and time interval significantly affected color change (p ≤ 0.001).

CONCLUSIONS

The tested bleaching treatments assisted by Er,Cr:YSGG and diode (980 nm) lasers did not induce unacceptable color and whiteness changes in the resin-based restorative materials.

CLINICAL SIGNIFICANCE

The tested Er,Cr:YSGG and diode (980 nm) laser-assisted tooth bleaching protocols which may be recommended to accelerate the clinical procedures cannot affect the color of the existing resin-based restorations in case they are accidentally exposed on the bleaching gel and laser irradiation.

Spectrophotometric evaluation of the effectiveness of Er,Cr:YSGG laser-assisted intracoronal tooth bleaching treatment using different power settings

BACKGROUND

Non-vital tooth discoloration is a common condition in dental practice. The aim of this in vitro study was to evaluate the efficacy of intracoronal bleaching treatments of non-vital teeth either activated or not by Er,Cr:YSGG laser (2780 nm) operating at 1.25 or 2.5 W.

METHODS

Twenty four human canines were artificially stained after implementation of root canal treatment. Subsequently, the teeth were randomly divided into three groups (n = 8): Group 1 (control) received intracoronal bleaching treatment with a bleaching gel containing 35 % hydrogen peroxide for 40 min, Group 2 received the same treatment assisted with Er,Cr:YSGG laser (2780 nm) operating at 1.25 W average power for 30 s and Group 3 received the same treatment with Group 2, but the average power was adjusted to 2.5 W. The bleaching treatments repeated after one week. Spectrophotometric analysis of tooth color change (ΔE) was implemented 7 days after both bleaching sessions.

RESULTS

The results of two-way ANOVA revealed that there was a tendency of no significant difference in color change between the three experimental groups (p = 0.063). However, the between-group comparisons showed that laser 2.5 W group had significantly higher ΔE than the control group after the first bleaching session. Moreover, a significant interaction between bleaching treatment and number of applications was detected (p = 0.026).

CONCLUSIONS

Er,Cr:YSGG laser irradiation significantly increased ΔE only after the first bleaching session when operating at 2.5 W. After the second bleaching session ΔE was not different compared to the control group, irrespectively of the laser power settings.