Comparative evaluation of effect of chlorhexidine application on dentin bond strength with two different adhesives after ER, CR: YSGG phototherapy: an in vitro study.

This study aimed to assess the efficacy of phototherapy with an Er, Cr:YSGG laser on the bond strength of dentin using two different adhesive systems after chlorhexidine (CHX) application. Twenty-four non-carious human molar teeth were separated into three main groups: negative control Group A (Group A), CHX and phototherapy with an Er, Cr:YSGG laser (Group PC), and CHX with conventional diamond bur (no phototherapy) (Group C). These groups were divided into two subgroups based on adhesives: Clearfil Universal Quick Bond and Clearfil SE Bond. To evaluate the microtensile bond strength, the occlusal enamel surfaces of the teeth were removed with a low-speed, water-cooled diamond bur to expose hard dentin tissue. The teeth within Group PC were treated with Er, Cr:YSGG phototherapy. The surfaces were then disinfected with 0.2% chlorhexidine gluconate. Subgroups were applied according to the manufacturer's instructions using the adhesive systems mentioned above. Following adhesive application, the teeth were restored with composite resin. A microtensile bond strength test was performed on the test sticks obtained from the teeth using a universal test device. Data were analyzed using variance analysis (ANOVA) at a significance level of p < 0.05. Among all groups, the highest bond strength was achieved with Clearfil SE Bond with CHX + phototherapy (45.6 ± 4.2), while the lowest was achieved with Clearfil Universal Quick Bond without phototherapy (control group) (27.0 ± 6.7) (p < 0.05). Phototherapy with Er, Cr: YSGG following chlorhexidine application enhanced the bond strength of both the bond systems (p < 0.05).

Effect of the cavity disinfectant containing chitosan on dentin bonding strength after radiotherapy.

INTRODUCTION: This study aimed to compare the bond strength of teeth treated with radiotherapy with two cavity disinfectants (Chlorhexidine gluconate, a chitosan-containing agent). METHODOLOGY: Eighteen newly extracted, non-carious human third molar teeth were used. The teeth were randomly divided into two main groups, treated and/or non-treated with radiotherapy, then separated into three subgroups for disinfectant agent application (CHX, chitosan, control). A total dose of 70.2 Gy was given over 39 days using a linear radiation accelerator for radiotherapy. After applying the cavity disinfectant, the teeth were restored with composite resin to obtain the stick. All bond strength values from sticks were measured using a universal testing machine. The data were analyzed with ANOVA and Chi-square test at a p < 0.05. RESULTS: Among all groups, Group CH, with no radiotherapy application and containing a chitosan-disinfectant agent, showed the highest bond strength (44.7 ± 8.2). In contrast, Group RC with radiotherapy and disinfectant-free showed the lowest bond strength value (29.1 ± 3.5). The highest bond strength values were obtained after applying the chitosan-containing agent in all groups. CONCLUSIONS: Radiotherapy application had a negative effect, while the use of disinfectant agents had a positive effect on the bond strength.

Effects of different bleaching application time on tooth color and mineral alteration.

BACKGROUND: The effects of HP-based products upon dental enamel are inconclusive. PURPOSE: The purpose of this study was to evaluate the colour and mineral changes caused by the bleaching agent applications at different durations on the enamel surface. BASIC PROCEDURES: 60 caries-free lower central incisor extracted for periodontal reasons were standardized for enamel and dentin thickness after cone-beam computed tomography (CBCT) measurements in terms of mineral (n = 24) and colour change (n = 36). All teeth were divided into 3 groups according to different bleaching durations for colour (n = 12) and mineral change (n = 8) measurements. The samples for mineral change were examined with the -energy scattering X-ray (EDX, JSM-6390 LV, Jeol Inc., Japan) device before and 2 weeks after the application. For colour change, the measurement of the samples was performed with spectrophotometer device (VITA EasyShade 4.0, Germany). Opalescence Boost PF 40% (Ultradent Products, USA) was applied for 20 min (min) in Group 1, 40 min in Group 2 and 60 min in Group 3. In order to determine the efficacy of bleaching, colour measurements were repeated at 24 h, 7 and 14 days after the application. In the intragroup comparison, Friedman and Wilcoxon tests were used for non-normally distributions, while repeated variance analysis and paired t test were used for normally distributions in dependent variables. In the intergroup comparison, ANOVA and LSD tests were used for normally distributions, while Kruskal-Wallis and Dunn tests were used for non-normally distributions in independent variables. p < 0.05 was considered significant. MAIN FINDINGS: In the study, statistically significant difference was observed between all groups in terms of colour change at different measurement times (p < 0.05). The highest ΔE00 values were observed in Group 3 (ΔE003 = 8.37 ± 2.15); the lowest value was observed in Group 1 (ΔE001 = 4.74 ± 1.26). Ca values were similar increase among all groups (p > 0.05). The highest Ca values were observed in Group 3 (69.91 ± 5.34); the lowest value was observed in Group 2 (66.08 ± 1.50). P values were similar increase among all groups (p > 0.05). The lowest P values were observed in Group 3 (26.54 ± 5.92); the highest value was observed in Group 2 (29.86 ± 2.26). PRINCIPAL CONCLUSIONS: Effective whitening was achieved in all study groups. When the results are evaluated as versatile in terms of bleaching effectiveness and mineral change, the most ideal bleaching duration was determined as 40 min (Group 2).

Effectiveness and SEM-EDX analysis following bleaching with an experimental bleaching gel containing titanium dioxide and/or chitosan.

The aim of this study was to evaluate the bleaching effectiveness and mineral alterations following the use of experimental bleaching gels that included 6% hydrogen peroxide (HP), titanium dioxide (TiO2) and/or chitosan in comparison with the routinely used 35% HP bleaching gel. Thirty-six maxillary anterior teeth were divided into three groups according to bleaching agent as follows: Group 1: 6% HP + TiO2, Group 2: 6% HP + TiO2 + chitosan, Group 3: 35% HP. Tooth colour was measured with a spectrophotometer before bleaching and after sessions one and two on days 14 and 30, respectively. Colour changes were assessed with the CIEDE2000 and CIELab formulas. Mineral analysis was performed with a scanning electron microscopy-energy dispersive X-ray (SEM-EDX) device before and 14 days after application. The enamel surfaces of randomly selected samples from each group were analysed by SEM. Two-way ANOVA was used to compare differences between groups. All tested materials resulted in significantly increased bleaching compared to the initial colour values (p < 0.05). Group 3 showed significantly more whitening compared to the other groups after the first and second sessions (p < 0.05). However, Group 2 presented prolonged whitening efficiency and reached a bleaching level similar to the 35% HP treatment after 14 and 30 days. The results of the CIEDE2000 and CIELab formulas were found to be correlated (r > 0.6). The increases in Ca were similar in Groups 2 and 3 (p > 0.05) and were significantly higher than that in Group 1 (p < 0.05). p was similarly decreased among all groups (p > 0.05). The combination of 6% HP, chitosan and TiO2 appears to constitute a promising material for tooth whitening, showing good bleaching efficiency and acceptable mineral alterations.

Effects of a Newly Developed Experimental Bleaching Agent on Tooth Color and Shear Bond Strength of Composite Resins.

PURPOSE: To evaluate the bleaching efficacy and shear bond strength (SBS) of composite restorations performed immediately after bleaching with a newly developed experimental bleaching agent, including 6% hydrogen peroxide (HP), titanium dioxide (TiO2), and/or chitosan (CS). MATERIALS AND METHODS: We randomly divided 132 maxillary anterior teeth into 2 study groups, 60 teeth for color analysis and 72 teeth for the SBS test. For color analysis, teeth were divided into 5 subgroups. For SBS analysis, teeth were divided into 6 subgroups according to bleaching agent: group C (control): no bleaching; group 35HP: whiteness 35% HP; group 6HP: 6% HP; group HPC: 6% HP+CS; group HPT: 6% HP+TiO2; group HPTC: 6% HP+ TiO2+CS. The teeth were measured with a spectrophotometer before and 24 h after the bleaching, and calculated with the CIEDE2000 formula. SBS test was evaluated in composite restorations immediately after bleaching, using a universal testing machine. Statistical analysis was performed using ANOVA. RESULTS: The highest ∆E00 values were observed in group 35HP (4.2 ± 1.2); the lowest value was observed in group 6HP (1.7 ± 0.6) (p < 0.05). The values for groups HPC and HPT were similar to each other and significantly lower than the value for 35HP (p < 0.05 and p > 0.05, respectively). Group HPTC was similar to 35 HP (p > 0.05). For SBS, all groups except those containing chitosan showed significantly decreased bond strength compared to the control (p < 0.05), while groups HPC and HPTC had values similar to the control (p > 0.05). Group C (28.02 ± 6.81) had the highest value, while group 35HP (17.02 ± 7.79) had the lowest SBS value. CONCLUSION: With the newly developed agent, the bond strength immediately after bleaching was found to be similar to the control group. Its bleaching efficacy was similar to that of routinely used bleaching agents.

Analysis of enamel structure and mineral density after different bleaching protocols using micro-computed tomography.

OBJECTIVE: This study aims to investigate the effect of three different bleaching applications on structural integrity, mineral volume (MV) and density of the enamel by using micro-computed tomography (Micro-CT) and evaluate the colour effectiveness using CIEDE2000. MATERIALS AND METHODS: Twenty-four maxillary premolar teeth were divided into three groups (n = 8) (group 1: 40% HP gel with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser activation; group 2: 40% HP gel with diode laser activation; group 3: 16% CP gel). Bleaching protocols were applied and colour alteration was obtained. Data were calculated with CIEDE2000 before and after bleaching. A Micro-CT was used to scan the specimens before and after the bleaching application. Statistical analysis was performed by ANOVA. RESULTS: No significant difference was observed between the groups for colour changes (p > .05). Micro-CT analysis showed significant differences in structural thickness, structural separation, mineral density and MV for the different ROIs before and after bleaching for all groups (p<.05). CONCLUSIONS: All of the bleaching methods represented similar efficiency. However, bleaching with Er,Cr:YSGG laser was less harmful to enamel in comparison with other bleaching methods. The present results may be useful for establishing a numerical standard for the change in bleaching with laser systems in dental hard tissues.

Effectiveness of Different Laser-Assisted In-Office Bleaching Techniques: 1-Year Follow-Up.

Objective: The aim of this study was to evaluate color longevity after different bleaching techniques. Background: Laser-activated bleaching methods are gaining popularity due to decreased chair time and increased patient compliance. However, the longevity of such methods has not been stated clearly. Methods: Sixty patients were divided into the following three groups (n = 20); group 1: chemical bleaching with 35% hydrogen peroxide (HP) gel, group 2: bleaching with 35% HP gel with diode laser activation, and group 3: bleaching with 35% HP gel with Er,Cr:YSGG laser activation. Color changes (ΔE*) were calculated by using two different formulas: (i) CIELAB (ΔEab) and (ii) CIEDE2000 (ΔE00) with a spectrophotometer before treatment, 24 h after treatment 3, 6, and 12 months after treatment. Evaluation of postoperative sensitivity was performed before and immediately after treatment, followed by re-evaluation 24 h and 1 week after treatment. Results: For ΔEab calculation, no significant difference was observed during both intra- and inter-group evaluations (p > 0.05). For ΔE00 calculation, no significant intergroup difference was observed (p > 0.05), whereas significant intragroup differences between the values of after treatment, 6-12 months. In the chemical bleaching group, increased postoperative sensitivity was observed after 24 h (p < 0.001). In the diode-laser-activated group, postoperative hypersensitivity was detected at 24 h and 1 week. No significant hypersensitivity was observed in the Er,Cr:YSGG-laser-activated group (p > 0.05). Conclusions: All three techniques provided efficient bleaching. Chemical and diode-activated bleaching methods resulted in slight sensitivity after application, whereas Er,Cr:YSGG-laser-activated bleaching did not cause sensitivity.

Evaluation of the cytotoxic and genotoxic effects of different universal adhesive systems.

OBJECTIVES: The objective of this study was to evaluate and compare the cytotoxicity and genotoxicity of different universal adhesive systems in the mouse fibroblast cell line L929. MATERIALS AND METHODS: L929 (mouse fibroblast) cells were exposed to G-Premio Bond (GPB) (GC Europe, Belgium), Prime&Bond Universal (Dentsply Sirona, USA), Universal Bond Quick (Kuraray, USA), Single Bond (SB) Universal (3M ESPE, USA), and Tokuyama Universal Bond (TB) (Tokuyama, USA). Cell viability was assessed by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide test, whereas oxidative DNA damage was assessed by determining the 8-hydroxydeoxyguanosine level using an enzyme-linked immunoassay kit. Statistical analysis was performed by one-way analysis of variance, followed by Bonferroni post hoc tests. RESULTS: Cytotoxic and genotoxic effects of TB and SB Universal groups were significantly higher than the other groups (P < 0.05). Among the adhesives tested, GPB (93.0 ± 1.3) had the least cytotoxicity, while TB (67.3 ± 3.0) had the most cytotoxic effect. In terms of genotoxicity, GPB (2.2 ± 0.3) had the least genotoxic effect, while Tokuyama Bond Universal (4.17 ± 0.4) had the most genotoxic effect. CONCLUSIONS: Universal adhesive systems used in dentistry have cytotoxic and genotoxic effects in live cells. Universal adhesive systems should, therefore, be used with caution due to their cytotoxic and genotoxic effects in clinical applications.

Effect of fibre-reinforced composite on the fracture resistance of endodontically treated teeth.

The aim of this study is to evaluate the fracture resistance of root-filled teeth restored with fibre-reinforced composite (everX posterior). Fifty mandibular molars were divided into five groups (n = 10). Group 1: no treatment was applied (intact teeth). Group 2-5: canals were prepared and root filled. Group 2: no coronal restoration was placed. Group 3: teeth were coronally restored with composite. Group 4: composite restorations were performed following polyethylene fibre insertion at the cavity base. Group 5: composite resin placed over everX posterior. After thermocycling (5-55°C, 5000×), fracture resistance was measured. Mean force load for each sample was recorded in Newtons (N). Results were statistically analysed with one-way analysis of variance and post hoc Tukey's tests. The mean force required to fracture samples and standard deviations are as follows: group 1: 2859.5 ± 551.27 N, group 2: 318.97 ± 108.67 N, group 3: 1489.5 ± 505.04 N, group 4: 1958.3 ± 362.94 N, group 5: 2550.7 ± 586.1 N. everX posterior (group 5) was higher than groups 2, 3 and 4 (P < 0.05). There were no significant differences between everX posterior and intact teeth (P > 0.05). Placing fibre-reinforced composite under composite increased the fracture strength of root-filled teeth to the level of intact teeth.