One-Year Evaluation of High-Power Rapid Curing on Dentin Bond Strength.

This study investigated the effect of 3 s light-curing with a high-power LED curing unit on the shear bond strength of bulk-fill composites. Four bulk-fill composites were bonded to dentin with a universal adhesive (Scotchbond Universal Plus): two materials designed for rapid curing (Tetric PowerFill and Tetric PowerFlow) and two controls (Filtek One Bulk Fill Restorative and SDR Plus Bulk Fill Flowable). The 4 mm composite layer was light-cured with Bluephase PowerCure for 20 s at 1000 mW/cm2 ("20 s") or for 3 s at 3000 mW/cm2 ("3 s"). The samples were stored at 37 °C in distilled water and tested after 1, 6 and 12 months. The samples polymerised in the "3 s" mode had statistically similar or higher bond strength than the samples cured in "20 s" mode, except for the Tetric PowerFlow (1 month) and SDR+ (6 month). The flowable materials Tetric PowerFlow and SDR Plus initially showed the highest values in the "3 s" and "20 s" groups, which decreased after 12 months. The bond strength was statistically similar for all materials and curing protocols after 12 months, except for Tetric PowerFill cured with the "3 s" protocol (21.22 ± 5.0 MPa), which showed the highest value. Tetric PowerFill showed the highest long-term bond strength. While "3 s" curing resulted in equal or better shear bond strength, its use can only be recommended for a material with an AFCT agent such as Tetric PowerFill.

Color and Chemical Stability of 3D-Printed and Thermoformed Polyurethane-Based Aligners.

The significant rise in the use of clear aligners for orthodontic treatment is attributed to their aesthetic appeal, enhancing patient appearance and self-confidence. The aim of this study is to evaluate the aligners' response to common staining agents (coffee, black tea, Coca-Cola, and Red Bull) in color and chemical stability. Polyurethane-based thermoformed and 3D-printed aligners from four brands were exposed to common beverages to assess color change using a VITA Easyshade compact colorimeter after 24 h, 48 h, 72 h, and 7 days, as well as chemical stability using ATR-FTIR spectroscopy. The brand, beverage, and manufacturing method significantly influence color stability. ATR-FTIR analysis revealed compositional differences, with variations in response to beverage exposure affecting the integrity of polymer bonds. Color change analysis showed coffee as the most potent staining agent, particularly affecting Tera Harz TC85 aligners, while ClearCorrect aligners exhibited the least susceptibility. 3D-printed aligners showed a greater color change compared to thermoformed ones. Aligners with a PETG outer layer are more resistant to stains and chemical alterations than those made of polyurethane. Additionally, 3D-printed polyurethane aligners stain more than thermoformed ones. Therefore, PETG-layered aligners are a more reliable choice for maintaining the aesthetic integrity of aligners.

Blue Laser for Polymerization of Bulk Fill Composites: Influence on dentin bond strength and temperature rise during curing and co-curing method.

Blue diode lasers are alternative curing devices for dental composites. The aim of this study was to investigate the influence of blue diode laser polymerization on shear bond strength of bulk fill composites to human dentin and temperature rise during two types of polymerization. Composite cylinders of SDR Plus(SDR) and Ever X Flow(EX) were bonded to dentin slabs using Adhese Universal and curing devices blue diode laser (449 nm, 1.6 W) and Power Cure LED. For each material and curing device there were two polymerization approaches: 1)conventional: separate curing of adhesive; 2)co-curing: simultaneous adhesive and composite curing. Polymerization modes for each material in conventional and co-curing(c) approach were: blue laser 2000 mW/cm2 for 5 s (L5 and L5c); blue laser 1000 mW/cm2 for 10 s (L10 and L10c); Power Cure 2000 mW/cm2 for 5 s (LED5 and LED5c); Power Cure 1000 mW/cm2 for 10 s (LED10 and LED10c). Temeperature was measured using thermal vision camera. For SDR, the highest bond strength was 24.3 MPa in L10c, and the lowest 9.2 MPa in LED5c. EX exhibited the highest bond strength(21.3 MPa) in LED5, and the lowest in L5(7.7 MPa). The highest temperature rise for SDR was in L10 and L5 (7.3 and 7.2 °C), and the lowest in LED5(0.8 °C). For EX, the highest temperature rise was in L5 (13.0 °C), and the lowest in LED5 (0.7 °C). Temperature rise was higher during blue laser polymerization, especially at high intensity and with conventional curing. Preferable blue laser curing mode is co-curing at 1000mW/cm2 for 10 s.

Short-Term Fluoride Release from Ion- Releasing Dental Materials.

Objective: To compare short-term release of fluoride ions from ion-releasing dental restorative materials. Material and methods: Seven experimental groups were prepared using the following six different materials: alkasite (Cention Forte), resin-modified glass ionomer cement (Fuji II LC), bioactive composite (ACTIVA BioACTIVE-RESTORATIVE), fluoride-containing nano-hybrid composite (Luminos UN), coat-free glass hybrid (EQUIA Forte HT), coat-applied glass hybrid (EQUIA Forte HT), and glass ionomer cement (Fuji IX). A total of 40 samples for each group (n=40) were prepared in Teflon molds (8 mm x 2 mm) and placed in polyethylene vials with 5 ml of deionized water. Fluoride release was measured after 6, 24, 48 hours, and for 5 weeks using an ion-selective electrode. The results were expressed in mg/l and the data were statistically analyzed using ANOVA. Results: Significant differences in fluoride release were observed within the first 6 hours (ANOVA p<0.001). EQUIA Forte HT had the highest release, while the other materials showed no significant differences. After 24 hours, EQUIA Forte HT (p<0.001) and Luminos UN (p<0.05) exhibited significantly higher releases, compared to other tested materials. EQUIA Forte HT maintained the highest release at 48 hours (p<0.001), followed by Cention Forte (p<0.05) and Luminos UN (p<0.05). All material pairs showed significant differences in fluoride release at 5 weeks (p<0.001). Conclusion: Coat-free EQUIA Forte HT had the overall highest fluoride release, while Cention Forte demonstrated the greatest increase over time. ACTIVA BioACTIVE-RESTORATIVE exhibited the lowest fluoride release in this study.

Remineralization effects of Er,Cr:YSGG and/or bioactive glass on human enamel after radiotherapy-an in vitro study.

The aim was to evaluate the effects of Er,Cr:YSGG and/or bioactive glass 45S5 (BG) on the chemical and physical properties of enamel after radiotherapy. Third molar crowns were cut in half (buccal-lingually), and the mid part of the labial/oral surface was subjected to different protocols. All samples were treated with standard 70 Gy. After radiotherapy, enamel was treated with either Er,Cr:YSGG (2780 nm; pulse 60 µs) and BG or only BG, and control samples were kept in deionized water. Vickers microhardness, scanning electron microscopy (SEM), and characteristic X-ray spectroscopy (EDS) were performed before, after radiotherapy, and after treatment. Analysis of variance (ANOVA) was used. A significant drop in enamel microhardness was observed after radiotherapy (p < 0.001). After Er,Cr:YSGG and BG or BG alone, there was a significant increase in microhardness (p < 0.001), which was on average significantly higher compared to the initial measurements for Er,Cr:YSGG with BG (p < 0.001), but not observed in BG alone (p = 0.331). After radiotherapy, SEM showed increased surface roughness with eroded prisms. Er,Cr:YSGG and BG or BG alone both showed disorderly packed glass particles on the enamel surface. Radiotherapy noticeably reduced the concentrations of calcium and phosphorus. Er,Cr:YSGG and BG treatment increased the concentrations of calcium, sodium, phosphorus, and silicate. BG treatment alone increased the concetration of calcium and phosphorus. Directly induced radiotherapy led to potential damage of enamel, but afterwards treatment with Er,Cr:YSGG laser and BG resulted in a higher increase of enamel microhardness compared to BG alone, reflecting in a possible better remineralization effect.

Detection of Leachable Components from Conventional and Dental Bulk-Fill Resin Composites (High and Low Viscosity) Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method.

The aim of this study was to investigate leachable components (monomers) in high and low viscosity dental bulk-fill resin composites and conventional resin composite materials after polymerization. Six bulk-fill and six conventional dental resin composite materials were used in this study. The samples of each material (three sets of triplicates) were cured for 20 s with irradiance of 1200 mW/cm2 with a LED curing unit and immersed in a 75% ethanol solution at 37 °C. The eluates from each triplicate set were analyzed after 24 h, 7 days or 28 days using liquid chromatography coupled with triple quadrupole tandem mass spectrometry (LC-MS/MS). Detectable amounts of 2-Hydroxyethyl methacrylate (HEMA) were found in both Gradia materials and the amount observed across different time points was statistically different (p ˂ 0.05), with the amount in solution increasing for Gradia and decreasing for Gradia Direct flo. Bisphenol A diglycidildimethacrylate (BIS GMA) was found in Filtek and Tetric materials. Triethylene glycol dimethacrylate (TEGDMA) was detected in all materials. On the other hand, there were no statistically significant differences in the amounts of TEGDMA detected across different time points in either of the tested materials. Monomers HEMA, TEGDMA, 4-dimethylaminobenzoic acid ethyl ester (DMA BEE) and BIS GMA in bulk-fill and conventional composites (high and low viscosity) can be eluted after polymerization. The good selection of composite material and proper handling, the following of the manufacturer's instructions for polymerization and the use of finishing and polishing procedures may reduce the elution of the unpolymerized monomers> responsible for the possible allergic and genotoxic potential of dental resin composites.

Influence of pH Cycling on Erosive Wear and Color Stability of High-Viscosity Glass Ionomer Cements.

The purpose of this in vitro study was to evaluate erosive wear and change in color of high-viscosity glass ionomer cements after pH cycling in two erosive media. There were 3 experimental groups with 22 samples each, (I) EQUIA Forte HT without coat, (II) Fuji IX and (III) Ketac Universal Aplicap. Each group was randomly divided into three subgroups (n = 6-8) further exposed to different environments, (1) distilled water, (2) green tea (pH 3.78) and (3) Aceto balsamico vinegar (pH 3.0). Mass and L* a* b* values were recorded before and after pH cycling. The samples in subgroups 2 and 3 were exposed to the acidic media two times a day for 10 min, over a period of 14 days. The differences among materials and erosive effects of the three media were tested using three-way analyses of variance with post hoc LSD test at the significance level p < 0.05. The effect of pH cycling in Aceto balsamico and green tea was degrading for all three materials. pH cycling in Aceto balsamico caused significantly higher erosive wear than pH cycling in Fuzetea and storage in distilled water, in all materials (p < 0.05). pH cycling in both acidic media and in the control group resulted in a significant change in L* a* and b* (p < 0.05). The L* value decreased significantly and the a* and b* values increased significantly (p < 0.05).

Light transmittance and polymerization kinetics of amorphous calcium phosphate composites.

OBJECTIVES: This study investigated light transmittance and polymerization kinetics of experimental remineralizing composite materials based on amorphous calcium phosphate (ACP), reinforced with inert fillers. MATERIALS AND METHODS: Light-curable composites were composed of Bis-EMA-TEGDMA-HEMA resin and ACP, barium glass, and silica fillers. Additionally, a commercial composite Tetric EvoCeram was used as a reference. Light transmittance was recorded in real-time during curing, and transmittance curves were used to assess polymerization kinetics. To obtain additional information on polymerization kinetics, temperature rise was monitored in real-time during curing and degree of conversion was measured immediately and 24 h post-cure. RESULTS: Light transmittance values of 2-mm thick samples of uncured ACP composites (2.3-2.9 %) were significantly lower than those of the commercial composite (3.8 %). The ACP composites presented a considerable transmittance rise during curing, resulting in post-cure transmittance values similar to or higher than those of the commercial composite (5.5-7.9 vs. 5.4 %). The initial part of light transmittance curves of experimental composites showed a linear rise that lasted for 7-20 s. Linear fitting was performed to obtain a function whose slope was assessed as a measure of polymerization rate. Comparison of transmittance and temperature curves showed that the linear transmittance rise lasted throughout the most part of the pre-vitrification period. CONCLUSIONS: The linear rise of light transmittance during curing has not been reported in previous studies and may indicate a unique kinetic behavior, characterized by a long period of nearly constant polymerization rate. CLINICAL RELEVANCE: The observed kinetic behavior may result in slower development of polymerization shrinkage stress but also inferior mechanical properties.

Conversion and temperature rise of remineralizing composites reinforced with inert fillers.

OBJECTIVES: Remineralizing experimental composites based on amorphous calcium phosphate (ACP) were investigated. The impact of curing time (20 and 40s), curing depth (1, 2, 3 and 4mm) and addition of inert fillers (barium glass and silica) on the conversion and temperature rise during curing were examined. METHODS: Five ACP-composites and two control composites were prepared based on the light-curable EBPADMA-TEGDMA-HEMA resin. For temperature measurements, a commercial composite was used as an additional control. Conversion was assessed using FT-Raman spectroscopy by comparing the relative change of the band at 1640 cm(-1) before and after polymerization. The temperature rise during curing was recorded in real-time using a T-type thermocouple. RESULTS: At 1mm depth, the ACP-composites attained significantly higher conversion (77.8-87.3%) than the control composites based on the same resin (60.5-66.3%). The addition of inert fillers resulted in approximately 5% lower conversion at clinically relevant depths (up to 2mm) for the curing time of 40s. Conversion decline through depths depended on the added inert fillers. Conversion values higher than 80% of the maximum conversion were observed for all of the ACP-composites at depths up to 3mm, when cured for 40s. Significantly higher total temperature rise for the ACP-composites (11.5-13.1 °C) was measured compared to the control composites (8.6-10.8 °C) and the commercial control (8.7 °C). CONCLUSIONS: The admixture of inert fillers represents a promising strategy for further development of ACP-composites, as it reduced the temperature rise while negligibly impairing the conversion. CLINICAL SIGNIFICANCE: High conversions of ACP-composites are favorable in terms of mechanical properties and biocompatibility. However, high conversions were accompanied with high temperature rise, which might present a pulpal hazard.

Accounting for measurement reliability to improve the quality of inference in dental microhardness research: a worked example.

OBJECTIVES: Dental microhardness experiments are influenced by unobserved factors related to the varying tooth characteristics that affect measurement reproducibility. This paper explores the appropriate analytical tools for modeling different sources of unobserved variability to reduce the biases encountered and increase the validity of microhardness studies. MATERIALS AND METHODS: The enamel microhardness of human third molars was measured by Vickers diamond. The effects of five bleaching agents-10, 16, and 30 % carbamide peroxide, and 25 and 38 % hydrogen peroxide-were examined, as well as the effect of artificial saliva and amorphous calcium phosphate. To account for both between- and within-tooth heterogeneity in evaluating treatment effects, the statistical analysis was performed in the mixed-effects framework, which also included the appropriate weighting procedure to adjust for confounding. The results were compared to those of the standard ANOVA model usually applied. RESULTS: The weighted mixed-effects model produced the parameter estimates of different magnitude and significance than the standard ANOVA model. The results of the former model were more intuitive, with more precise estimates and better fit. CONCLUSIONS: Confounding could seriously bias the study outcomes, highlighting the need for more robust statistical procedures in dental research that account for the measurement reliability. The presented framework is more flexible and informative than existing analytical techniques and may improve the quality of inference in dental research. CLINICAL RELEVANCE: Reported results could be misleading if underlying heterogeneity of microhardness measurements is not taken into account. The confidence in treatment outcomes could be increased by applying the framework presented.

Cytogenetic damage in exfoliated oral buccal cells by dental composites.

PURPOSE: To evaluate the possible geno/cytotoxic effects of dental composite materials by assessing the frequency of micronuclei formation and other nuclear abnormalities in the exfoliated buccal epithelium. METHODS: Swabs were taken from the buccal mucosa of 85 young healthy subjects. All participants had healthy dentition or dentition restored only with composite materials. Genotoxicity and cytotoxicity was assessed by micronucleus assay. RESULTS: The results indicated no significant difference in number of oral mucosa cells with micronuclei in subjects with different numbers of composite restored tooth surfaces (P= 0.476). Also, the number of restored surfaces had no effect on nuclear alterations closely related to cytotoxicity, such as karyolysis (P= 0.572), karyorrehexis (P= 0.573) and picnosis (P= 0.765). CLINICAL SIGNIFICANCE: Despite doubts about the safe clinical use of resin composites, this study found no evidence that composite materials trigger long-term cytogenetic damage in the epithelial cells of buccal mucosa in humans. There is no objective and quantifiable evidence of genotoxicity induced by composite restorative materials in clinical practice.

Microhardness of Bulk-Fill Composite Materials

The aim of the study was to determine microhardness of high- and low-viscosity bulk-fill composite resins and compare it with conventional composite materials. Four materials of high-viscosity were tested, including three bulk-fills: QuiXfi l (QF), x-tra fi l (XTF) and Tetric EvoCeram Bulk Fill (TEBCF), while nanohybrid composite GrandioSO (GSO) served as control. The other four were low-viscosity composites, three bulk-fill materials: Smart Dentin Replacement (SDR), Venus Bulk Fill (VBF) and x-tra base (XB), and conventional control material X-Flow (XF). Composite samples (n=5) were polymerized for 20 s with Bluephase G2 curing unit. Vickers hardness was used to determine microhardness of each material at the surface, and at 2-mm and 4-mm depth. GSO on average recorded significantly higher microhardness values than bulk-fill materials (p<0.001). The low-viscosity composite XF revealed similar microhardness values as SDR, but significantly lower than XB (p<0.001) and significantly higher than VBF (p<0.001). Microhardness of high-viscosity bulk-fill materials was lower than microhardness of the conventional composite material (GSO). Surface microhardness of low-viscosity materials was generally even lower. The microhardness of all tested materials at 4 mm was not different from their surface values. However, additional capping layer was a necessity for low-viscosity bulk-fill materials due to their low microhardness.

Real-time local experimental monitoring of the bleaching process.

OBJECTIVE: The purpose of this article was to investigate a new setup for tooth bleaching and monitoring of the same process in real time, so to prevent overbleaching and related sideeffects of the bleaching procedure. BACKGROUND DATA: So far, known bleaching procedures cannot simultaneously monitor and perform the bleaching process or provide any local control over bleaching. MATERIALS AND METHODS: The experimental setup was developed at the Institute of Physics, Zagreb. The setup consists of a camera, a controller, and optical fibers. The bleaching was performed with 25% hydrogen peroxide activated by ultraviolet light diodes, and the light for monitoring was emitted by white light diodes. The collected light was analyzed using a red-green-blue (RGB) index. A K-type thermocouple was used for temperature measurements. Pastilles made from hydroxylapatite powder as well as human teeth served as experimental objects. RESULTS: Optimal bleaching time substantially varied among differently stained specimens. To reach reference color (A1, Chromascop shade guide), measured as an RGB index, bleaching time for pastilles ranged from 8 to >20 min, whereas for teeth it ranged from 3.5 to >20 min. The reflected light intensity of each R, G, and B component at the end of bleaching process (after 20 min) had increased up to 56% of the baseline intensity. CONCLUSIONS: The presented experimental setup provides essential information about when to stop the bleaching process to achieve the desired optical results so that the bleaching process can be completely responsive to the characteristics of every individual, leading to more satisfying results.

Temperature rise during experimental light-activated bleaching.

The purpose of this study was to evaluate the surface and intrapulpal temperatures after treatments with different bleaching gels subjected to different types of light activation. A K-type thermocouple and infrared thermometer were used to measure the temperature increase during the 15- or 30-min treatment period. Light-emitting diode with a center wavelength of 405 nm (LED405), organic light-emitting diode (OLED), and femtosecond laser were tested and compared to ZOOM2. The tooth surface was treated with five bleaching agents and Vaseline which served as a control.The generalized estimating equation (GEE) model was applied for testing the differences in temperature increase. The ZOOM2 light source led to the largest increase in mean pulpal and tooth surface temperatures of 21.1 and 22.8 °C, followed by focused femtosecond laser which increased the pulpal and surface temperatures by up to 15.7 and 16.8 °C. Treatments with unfocused femtosecond laser, LED405, and OLED induced significantly lower mean temperature increases (p < 0.001 for each comparison with ZOOM2 and focused femtosecond laser), both in the pulp chamber (up to 2.7, 2.5, and 1.4 °C) and at the tooth surface (up to 3.2, 3.4, and 1.8 °C). Significant differences between pulp chamber and tooth surface measurements were obtained for all types of bleaching gel, during treatments with ZOOM2 (p < 0.001), LED405 (p < 0.001), and unfocused (p < 0.001) and focused femtosecond laser (p ≤ 0.002). Different bleaching agents or Vaseline can serve as an isolating layer. Focused femtosecond laser and ZOOM2 produced large temperature increases in the pulp chamber and at the tooth surface. Caution is advised when using these types of light activation, while LED405, OLED, and unfocused femtosecond laser could be safely used.

Effect of temperature on post-cure polymerization of bulk-fill composites.

OBJECTIVES: To investigate the 24h post-cure polymerization and the effect of temperature on the post-cure polymerization of one conventional and three bulk-fill composite materials. METHODS: A conventional composite GrandioSO (GR) and three bulk-fill composites: Tetric EvoCeram Bulk Fill (TECBF), Quixfil (QF) and X-tra fil (XF) were investigated. The samples were cured for 20s with irradiance of 1090mW/cm(2). Composite samples were divided into two groups: the "room-temperature" group (RT, n=5) and the "body-temperature" group (BT, n=5) and they were stored in dark at 20°C and 37°C, respectively. Measurements of degree of conversion (DC) were made immediately after curing (0h) and 24h post-cure (24h). To analyse the extent of post-cure DC increase, the DC values of 0h-RT/24h-RT and 0h-BT/24h-BT were compared. To analyse the difference in DC between RT and BT, the DC values of 0h-RT/0h-BT and 24h-RT/24h-BT were compared. RESULTS: DC increase 24h post-cure was significant for all composites and ranged between 6.3% and 8.2% in RT and between 12.5% and 15.7% in BT. All composites demonstrated a higher DC in 24h-BT compared to 24h-RT. The difference was statistically significant for GR, TECBF and QF. CONCLUSIONS: All composites demonstrated a significant post-cure effect after 24h. Post-cure temperature increase from 20°C to 37°C yielded a higher post-cure DC increase. CLINICAL SIGNIFICANCE: Due to the temperature effect on the final DC, studies performed at composite samples at room temperature may record more inferior properties than these attained in the oral cavity.

Optical effects of experimental light-activated bleaching procedures.

OBJECTIVE: The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures. BACKGROUND DATA: The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching. MATERIALS AND METHODS: Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy. RESULTS: Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis. CONCLUSIONS: The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

Atmospheric Pressure Plasma Jet as an Accelerator of Tooth Bleaching.

OBJECTIVE: To study the effect of atmospheric pressure plasma (APP) jet as a potential accelerator of the degradation of hydrogen peroxide in bleaching gels which could lead to better and faster bleaching. MATERIAL AND METHODS: 25 pastilles of hydroxylapatite were colored in green tea for 8 hours and were randomly divided into five groups (n = 5). The bleaching process was performed with 30% and 40% hydrogen peroxide (HP) gel alone and in conjunction with helium APP jet. During the bleaching treatment, optical emission spectroscopy and non-contact surface temperature measurement using pyrometer were performed. Color of the pastilles was determined by a red-green-blue (RGB) colorimeter. PH values of bleaching gels were measured before and after the plasma treatment on additional 10 pastilles using a pH meter with contact pH electrode. RESULTS: The color measurements of pastilles before and after the treatment showed that treatment with APP jet improved the bleaching effect by 32% and 15% in the case of 30% and 40% HP gel. Better results were obtained approximately six times faster than with a procedure suggested by the bleaching gel manufacturer. Optical emission spectroscopy proved that plasma has a chemically active role on the gel. After the APP treatment, pH values of bleaching gels dropped to about 50-75% of their initial value while the surface temperature increased by 8-10˚C above baseline. CONCLUSION: The use of plasma jet provides more effective bleaching results in a shorter period of time without a significant temperature increase which may cause damage of the surrounding tissue.

Genotoxic effect of two bleaching agents on oral mucosa.

AIM: To analyze the genotoxic effect of two hydrogen peroxide-containing bleaching products on oral mucosal cells. MATERIALS AND METHODS: The research was conducted on 22 individuals divided into two groups. Group 1 used ZOOM2 and group 2 the Opalescence BOOST bleaching agent. Specimens of the gingival and the upper lip mucosa were obtained before, immediately after, and 72 h after the bleaching procedure and were analyzed using a micronucleus test. RESULTS: Seventy-two hours after bleaching treatment with BOOST, samples collected from the oral mucosa exhibited a statistically significant increase of all genotoxicity markers, with large effect sizes (Cohen's d>0.8) observed in the total number of micronuclei (MN), number of cells with 3+ MN, karyolysis and bi-nuclear cells. ZOOM2 treatment showed a significant increase, with medium-to-large effect sizes, in the number of cells with 1 MN, karyolysis, nuclear buds and bi-nuclear cells. CONCLUSION: Both preparations demonstrated potential genotoxic effects.

Time dependent accuracy of dental radiometers.

Inadequate intensity of the polymerization light source can compromise the quality and longevity of dental composite restorations. In order to maintain optimal strength of polymerization devices, regular control of polymerization units is necessary. The aim of this study was to compare the accuracy of two radiometers in the measurement of light intensity of photopolymerization devices concerning the time point of measurement. Light intensity measurements of 16 halogen and 8 LED curing lights were performed using three different devices at the beginning as well as 10 and 40 seconds after the start of illumination. Two were handheld radiometers: Bluephase meter (BM) and Cure Rite (CR), while an integrating sphere (IS) represented the reference device. Data were statistically analyzed using Friedman's test and Wilcoxon signed-rank test (p < 0.05). The values at the beginning and after 10 seconds measured by BM were significantly higher than the measurements by IS, whereas CR showed higher values after 10 and 40 seconds. Both commercial radiometers tended to overestimate the light intensity of LED and halogen curing units when compared to the reference device. The time point of measurement influences the output value. The heating of radiometers was proposed as a possible explanation for the inaccuracy.

Surface changes of enamel and dentin after two different bleaching procedures.

Bleaching agents have effect on chemical/physical and morphological structure of enamel and dentin that must be taken into account when this therapy is used. The aim of this in vitro study was to evaluate the effects of two bleaching agents containing a high concentration of hydrogen peroxide for professional use on human enamel and dentin surface and to evaluate the potential remineralizing effect of amorphous calcium phosphate gel (ACP). Twenty-five human third molars were divided into two groups and dissected in half and both surfaces were bleached with either ZOOM2 or Opalescence BOOST for 3 x 15 minutes. Vickers microhardness of enamel and dentin was measured before, after the bleaching treatment, and after treatment with artificial saliva and ACP gel or 2-week storage in deionized water. Surface microstructure was evaluated using scanning electron microscopy. The mixed model ANOVA and Wilcoxon Rank Sum test were used. Both bleaching agents showed significant reduction in surface microhardness (p < 0.001 for both BOOST and ZOOM2 application). ZOOM2, which had a lower pH value showed greater decrease in surface microhardness (p = 0.005) compared to BOOST. Post-treatment with artificial saliva and ACP showed significant increase in surface microhardness (p < 0.001). After the bleaching procedure, enamel and dentin surface microstructure showed mild or slight alterations with no loss of superficial structure. In conclusion, both bleaching agents resulted in reduction in surface enamel and dentin microhardness. Treatment with ACP led to increase in surface microhardness, improved surface roughness, and enhanced remineralization of the hard dental tissues.