Effect of laser irradiation during in-office tooth bleaching on surface properties of resin-based restorative materials.

This study evaluated the changes in surface properties of three resin-based restorative materials after two laser-assisted, in-office tooth bleaching protocols using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) or diode (980 nm) lasers. A nanohybrid composite (Enamel Plus HRi), a Bis-GMA-free composite (Enamel Plus HRi Bio Function), and a resin-matrix CAD-CAM ceramic (Shofu Block HC) were tested. Forty specimens for each material were prepared and divided into four groups (n = 10/group). The control specimens did not undergo any bleaching treatment, whereas group 2 received bleaching with 40% hydrogen peroxide (H2O2), while groups 3 and 4 underwent the same bleaching procedure with the use of diode (980 nm) or Er,Cr:YSGG lasers, respectively. Surface microhardness and roughness measurements were conducted using a Vickers tester and an optical profilometer. Microhardness was lower in bleached specimens, with the nanohybrid composite exhibiting the largest difference from the no bleaching group. For the Bis-GMA-free composite the microhardness difference between no bleaching and laser-assisted bleaching were smaller than seen for the conventional bleaching technique. Surface roughness was higher in bleached specimens, with nanohybrid composite showing the largest differences from the control specimens. The examined laser-assisted tooth bleaching protocols were found not to impact surface microhardness and roughness of the tested resin-based specimens and they are deemed suitable for clinical use.

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 O2. 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 (ΔΕab * = 2.7 and ΔΕ00  = 1.77) and 50:50% perceptibility (ΔΕab * = 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.

Safe use of chemicals and risk communication among dentists and dental students in Greece.

Use of chemicals, most often classified for intrinsic hazards, is rather common among dentists. To date, no data have been recorded in the European Union (EU) on dentists' awareness regarding the safe use of chemicals. In the EU regulatory framework, two Regulations with wide applications, namely Regulations (EC) 1907/2006 (REACH) and 1272/2008 (CLP), have been introduced to protect human health and the environment and clearly communicate hazards posed by chemicals to workers and consumers. The aim of this study was to assess the extent of comprehension of hazard communication of chemicals among Greek dentists. For this, a closed-ended, anonymous and validated questionnaire was initially distributed to a total of 300 Greek dentists, both professionals and university students, over a period of 4 months. The collected data from 240 final responders were subjected to statistical analysis (frequencies, percentages, chi-square (χ2) and significance (p < 0.05)). The vast majority (90%) of the interviewed dentists are not aware of the CLP. Main sources of information regarding chemical hazard and safe use was the supplier through direct communication (90%), while some dentists also consulted the product labels (39%) and the material safety data sheets (54%). Regarding hazard communication, the perceived information from the pictograms is confusing to the vast majority of the dentists (86%), especially for systemic hazards (carcinogenicity and/or reproductive toxicity). In addition, 88% of the professional dentists have not noticed any changes in the labelling of chemical products, which also shows the low input of labels to hazard communication. On the other hand, 90% of the responders always utilize personal protective equipment (PPE), although it is not clear whether this PPE is adequate. In conclusion, rising awareness campaigns are needed, in collaboration with universities and dental care professional associations, to inform dentists about the safe use of chemicals not only to ensure protection of their own health but also to contribute to environmental sustainability.