Effect of Toothpaste Fluoride Concentration on Color Stability of Resin Composites: An In Vitro Study

ABSTRACT Objective: To investigate the effects of two different dentifrice fluoride concentrations on the color stability of the composite. Material and Methods: Twenty-seven specimens (2×4×5 mm) each of microfilled (Gradia, GC, Japan) and nanohybrid (Grandio, VOCO, Germany) composites were prepared. The specimens were randomly divided into six groups (control, Fluoflor caries protection toothpaste with 1450ppm Fluoride (EXW, France), and Fluoflor kids toothpaste with 500ppm Fluoride (EXW, France) (n = 9). The specimens were immersed in a mixture of artificial saliva and toothpaste in a ratio of 1:3 and applied for 60 seconds every 12 hours for 42 days. The control samples were incubated in artificial saliva at 37°C. Primary and secondary color measurements were performed using color parameters (L∗a∗b) with a spectrophotoshade (MHT Optic Research AG, Niederhasli, Switzerland). Data were analyzed using a two-way analysis of variance at a significance level of 0.05. Results: According to the two-way ANOVA analysis, there was no significant difference in color change between the composites and no difference in the level of discoloration between different fluoride concentrations(p>0.05). Also, None of the dentifrices caused clinically significant color changes(∆E˂3.3). Conclusion: No clinically unacceptable color changes were observed in the microfilled and nanofilled composites with different concentrations of fluoride toothpaste.

Cytotoxicity Comparison of a Calcium Silicate-Based Resin Cement versus Conventional Self-Adhesive Resin Cement and a Resin-Modified Glass Ionomer: Cell Viability Analysis

Abstract Objective: To compare the cytotoxicity level of a new calcium silicate-based resin cement (TheraCem) with two commonly used cements, including a conventional self-adhesive resin cement (Panavia SA) and a resinmodified glass ionomer cement (FujiCem2), on the human gingival fibroblast cells after 24 and 48 hours. Material and Methods: Twelve discs of each cement type were fabricated. The extract of cement disks was made by incubating them in the cell medium. Human gingival fibroblast cells were cultured and exposed to cement extracts for 24 h and 48 h. MTT assay was performed on extracts and optical density and cell viability rates were calculated by the spectrophotometer device at 570 nm. Data were analyzed using ANOVA and Tukey HSD tests. Results: The cell viability rates after 24 hours and 48 hours were as follows: TheraCem: 89.24% and 85.46%, Panavia SA: 49.51% and 46.57% and FujiCem2: 50.63% and 47.36%. TheraCem represented the highest cell viability rate. However, no significant difference was noted between Panavia SA and FujiCem2. Time had no significant effect on cell viability. Conclusion: TheraCem exhibited the best results among three tested cements and was considered non-toxic. Panavia SA and FujiCem2 were not significantly different regarding the cell viability rate. Time had no significant effect on the cytotoxicity level of cements (AU).

Comparison the effect of charcoal-containing, hydrogen peroxide-containing, and abrasive whitening toothpastes on color stability of a resin composite; an in vitro study.

BACKGROUND: This study aimed to compare the effects of charcoal-containing, hydrogen peroxide-containing, and abrasive whitening toothpastes on color stability of a resin composite. METHODS: Forty-five specimens were fabricated of spectrum TPH3 composite resin and stored in artificial saliva for 24 h. Baseline color assessment was performed using a spectrophotometer device. Then, the specimens were randomly assigned into 5 experimental groups, namely distilled water (GC), Bencer (GB), colgate optic white (GO), perfect white black (GP) and colgate total whitening (GT) toothpastes. The specimens immersed in coffee solution for 10 min and brushed for 1 min with respective toothpaste and then stored in artificial saliva until the next day. This cycle was repeated for 30 days. After 30 days, the final color assessment was performed using the spectrophotometer. Data were analyzed using one-way ANOVA and Tukey tests. RESULTS: Experimental groups were not significantly different in terms of Δa and ΔE values. However, ΔL and Δb values showed significant difference among the groups. Regarding Δa, GT and GC groups showed red color shift while the other groups showed green color shift. Regarding Δb, all groups showed blue color shift except GT group which showed yellow color shift. CONCLUSION: None of the whitening toothpastes could decrease discoloration caused by the coffee solution to the level below the perceptibility threshold except Colgate Optic White which reduced discoloration within the clinically acceptable perceptibility range.

Effect of whitening toothpastes containing activated charcoal, abrasive particles, or hydrogen peroxide on the color of aged microhybrid composite.

Background: This study aimed to assess the effect of different whitening toothpastes containing activated charcoal, abrasive particles or hydrogen peroxide on the color of aged microhybrid composite. Materials and Methods: In this in vitro, experimental study, 45 composite discs (2 mm × 7 mm) were fabricated of a microhybrid composite. They underwent accelerated artificial aging for 300 h, corresponding to 1 year of clinical service. The composites were then randomly divided into five groups (n = 9). One group served as the control and underwent tooth brushing with distilled water. The remaining four groups underwent tooth brushing with Colgate Total whitening (Gt), Colgate Optic White (Go), Perfect White Black (Gp) and Bencer (Gb) toothpastes in a brushing machine The International Commission on Illumination values (Lm, am, bm) were determined using a spectrophotometer. Color change (ΔE) calculated based on this formula: ΔEm= ([ΔLm] 2 + [Δam] 2 + [Δbm] 2)½. The differences were defined by ΔE1 (after aging-baseline),ΔE2 (after brushing-after aging) and ΔE3 (after brushing-base line). ΔE1 were evaluated to ensure that color mismatch had occurred (ΔE1 > 5.5). Difference in (L, a, b) parameters after aging and after tooth brushing in each group, color parameter changes (ΔL2, Δa2, Δb2, ΔL3, Δa3, Δb3) and ΔE2 and ΔE3 were analyzed and compared using Wilcoxon test and independent sample median test at P = 0.05 level of significance. Results: The color parameter changes, ΔE3 and Δ E2 were not significantly different among the five groups (P > 0.05). In Gp and Gb charcoal a*, b*, and L* after tooth brushing (P < 0.05). In Colgate Optic group, the a* parameter significantly decreased while the L* parameter significantly increased (P < 0.05). Conclusion: The results showed that there is no significant difference in the color change of Spectrum composite following tooth brushing with different whitening toothpastes for two weeks. It should be noted that Δ E3 reached to <3.3 only in charcoal whitening toothpastes.

Degree of conversion and water sorption of self-adhesive and conventional flowable composites: an in vitro study

Aim: Self-adhesive flowable composite resins have been recently introduced to the market. Degree of conversion (DC) and water sorption (WS) are two important parameters affecting the properties of restorative materials. This study aimed to assess the DC and WS of a self-adhesive flowable composite resin in comparison with two conventional flowable composite resins. Methods: Vertise Flow (VF) self-adhesive and Tetric-N Flow (TF) and Grandio Flow (GF) conventional flowable composites were evaluated in this in vitro, experimental study. The DC (n=3) was determined by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The WS (n=7) was measured after 7 days of immersion in artificial saliva accordingto ISO 4049specifications. Data were analyzed by one-way ANOVA and a post-hoc test (p<0.05). Results: VF showed the highest DC percentage (84.3%) followed by GF (72.79%) and TF (68.7%). The latter two had no significant difference (p=0.8). WS was the highest in VF (55.2 µg/mm3), and the two conventional flowable composites had a significant difference in WS (19.5 µg/mm3 in TF and 11 µg/mm3 in GF; p<0.001). Conclusions: Flowable composite resins had significant differences in DC and WS, and VF demonstrated the highest DC and WS

Hydrogen peroxide penetration into the pulp chamber during conventional in-office bleaching and diode laser-assisted bleaching with three different wavelengths.

BACKGROUND AND AIMS: Penetration of hydrogen peroxide into the pulp chamber and subsequent tooth hypersensitivity is a common concern in dental bleaching. The aim of this study was to assess the penetration of hydrogen peroxide (H2O2) into the pulp chamber in diode-laser activated bleaching with different laser wavelengths. MATERIALS AND METHODS: Fifty extracted human maxillary anterior teeth were collected and divided into five groups(n = 10). Group 1: conventional in-office bleaching using Opalescence Boost gel. Group 2: Bleaching with Biolase Laser White 20 gel activated by 980 nm diode laser. Group 3: Bleaching with Biolase Laser White 20 gel activated by 810 nm diode laser. Group 4: Bleaching with Biolase Laser White 20 gel activated by 940 nm diode laser. Group 5: No bleaching control group.After bleaching, the solution into the pulp chamber was collected and analyzed using a spectrophotometer. The recorded data were compared with a standard sample and the results were analyzed and compared using one-way ANOVA and Tukey's HSD tests. RESULTS: In all bleached groups, H2O2 had infiltrated into the pulp chamber. The highest level of penetration was noted in group 2 (2.32 ± 0.25 µg), while the lowest level was noted in group 3 (1.85 ± 0.33 µg). The difference in this regard was significant between groups 2 and 3 (P = 0.024), but the differences between other groups were not statistically significant (P ≥ 0.42). CONCLUSION: Considering the results of this study, it can be stated that hydroge peroxide penetration in to pulp chamber in diode laser activation of bleaching agent according to manufactures instruction is not higher than in-office bleaching. The wavelength of diode laser had significant effect on penetration of hydrogen peroxide into pulp chamber.

Degree of Conversion of Resin-Modified Glass Ionomer Cement Containing Hydroxyapatite Nanoparticles.

OBJECTIVES: Hydroxyapatite (HA) nanoparticles are used to improve the physical and mechanical properties of glass ionomers (GIs). This study aimed to assess the effect of addition of different weight percentages of nano-HA on degree of conversion (DC) of Fuji II LC GI cement using a spectrometer. MATERIALS AND METHODS: In this in vitro experimental study, 30 samples were fabricated of Fuji II LC (improved) GI cement in six groups (n=5) containing 0%, 1%, 2%, 5%, 7% and 10wt% nano-HA. The obtained paste in each group was subjected to Fourier-transform infrared spectroscopy (FTIR) before curing to assess the monomer to polymer DC percentage. The paste was then light-cured and underwent FTIR again. One-way ANOVA was applied to compare the DC percentage of different groups. Pairwise comparisons were performed using the Tukey's test. RESULTS: The DC was 57.88±0.57% in 0%, 60.04±0.63% in 1%, 66.92±0.54% in 2%, 65.5±0.71% in 5%, 51.49±0.24% in 7% and 50.09±0.32% in 10% nano-HA group. The difference in DC among the groups was statistically significant (P<0.0001). The highest DC was noted in 2% nano-HA and the lowest DC was found in 10% nano-HA group. Pairwise comparisons revealed significant differences between the groups in DC (P<0.0001). CONCLUSION: Increasing the weight percentage of nano-HA to 2% increased the DC but increasing the nano-HA weight percentage over 5% decreased the DC of resin-modified glass ionomer cement (RMGIC). The highest DC was noted in 5w% and 2w% nano-HA groups. Thus, 5w% and 2w% nano-HA can be used to improve the DC of RMGIC.

Effect of Three Wavelengths of Diode Laser on the Efficacy of Bleaching of Stained Teeth.

OBJECTIVES: Light irradiation and heat have been used to accelerate the process of tooth bleaching. This study aimed to assess the efficacy of conventional bleaching compared to laser-bleaching using three different wavelengths of diode lasers. MATERIALS AND METHODS: In this in-vitro experimental study, 40 extracted human central incisors were immersed in a coloring solution made of tea, coffee, and cola for 21 days. The L*, a*, and b* color parameters were measured before and after the immersion using spectrophotometry. The teeth were then randomly divided into four groups (n=10) as follows: group 1: 810-nm diode laser + Biolase Laser White 20, group 2: 940-nm diode laser + Biolase Laser White 20, group 3: 980-nm diode laser + Biolase Laser White 20, and group 4: conventional bleaching with Opalescence Boost without laser irradiation. One-way analysis of variance (ANOVA) was used to assess the effect of laser type and bleaching technique on color parameters. RESULTS: The 940-nm (ΔE=28.5896) and 810-nm laser groups (ΔE=21.2382) showed the highest and the lowest bleaching efficacy, respectively; however, the groups were not significantly different in terms of bleaching efficacy (P>0.05). CONCLUSION: Laser-bleaching with 810-, 940- and 980-nm wavelengths of diode laser has an efficacy similar to that of conventional bleaching but in a shorter period. No difference was noted between different laser wavelengths in terms of bleaching efficacy.

Effect of Laser-assisted and Conventional In-office Bleaching on Monomer Release from Microhybrid and Nanohybrid Composite.

BACKGROUND AND AIMS: Bleaching might affect structural properties of composite materials, and lead to monomer release. This study aimed to evaluate the effect of Laser-assisted and conventional in-office bleaching on the release of BIS-GMA, TEGDMA, and UDMA monomers from a nanohybrid and a microhybrid BIS-GMA based composite. MATERIALS AND METHODS: 32 samples of each composite, were divided into 4 subgroups; subgroup 1: Conventional in-office bleaching (CIB) with the Opalescence Boost PF 38% gel, subgroup 2: Laser-assisted bleaching (LBO) with the Opalescence Boost PF 38% gel, subgroup 3: Laser-assisted bleaching (LBH) with the JW Power bleaching gel, subgroup 4: (CO) control without bleaching. All the samples were immersed in tubes of 2cc Ethanol 75% medium. The released monomers were analyzed using the high performance liquid chromatography (HPLC) method 24 h, 7, and 28 days. Data's were analyzed by Univariate Analysis of Variance test followed by Tukeys HSD. RESULTS: The amount of TEGDMA monomer released was not significant. However, nanohybrid composites showed significantly more monomer release than microhybrid composites (P < 0.05). For UDMA the interaction was significant only after 1 week. In microhybrid composites, the CO subgroup showed more monomer release than LBH and LBO. In nanohybrid composites, LBH showed more monomer release than CIB and CO subgroups. For BIS-GMA monomers the interaction was significant at all time periods and the LBH subgroup of nanohybrid composite had significantly more BIS_GMA release in comparison to other subgroups. CONCLUSION: Bleaching by laser with JW Power Bleaching gel led to more monomer release in nanohybrid composite.

Effect of Intracanal Post Space Treatments on Push-Out Bond Strength of Fiber Posts to Root Dentin.

OBJECTIVES: The main disadvantage of fiber posts is their low bond strength to root canal wall. The aim of the present study was to assess the effect of different root canal post space treatments on push-out bond strength of fiber posts to root canal dentin. MATERIALS AND METHODS: After post space preparation in 40 endodontically treated human premolars, the teeth were randomly divided into four experimental groups: Group 1: control group, group 2: Endsolv R, group 3: ultrasonic cleaning, group 4: Clearfil Repair. Afterwards, the posts were bonded with Panavia F 2.0 bonding cement. The bond strength of fiber posts to root canal wall in the middle part of canal was evaluated following thermocycling using push-out test. Data were analyzed using one-way ANOVA and Tamhane's multiple comparisons test. The failure mode of each group was determined under a stereomicroscope. RESULTS: There was a significant difference in the mean push-out bond strength among the groups (P<0.05). The lowest bond strength was noted in the control group. The control group had significant differences with ultrasonic and Clearfil Repair groups (P<0.05). The bond strength of Endsolv R group increased; however, it was not significant (P>0.05). CONCLUSIONS: It seems that ultrasonic cleaning and Clearfil Repair can modify the root canal wall and significantly increase the bond strength of fiber posts.

Effect of addition of Nano hydroxyapatite particles on wear of resin modified glass ionomer by tooth brushing simulation.

BACKGROUND: Recently, incorporation of nanohydroxyapatite (NHA) has been suggested to improve the mechanical properties of glass ionomers (GIs). This study aimed to assess the effect of addition of NHA on wear of resin modified glass ionomer (RMGI) by tooth brushing simulation. MATERIAL AND METHODS: In this in vitro, experimental study, NHA in 1, 2, 5, 7 and 10wt% concentrations was added to Fuji II LC RMGI powder, and 48 samples (5×5mm) in five experimental and one control group (n=8) were fabricated. After polishing, cleaning and incubation at 37°C for three weeks, the samples were weighed and subjected to tooth brushing simulation in a toothpaste slurry according to ISO14569-1. Then, they were weighed again and the weight loss was calculated. The data were analyzed using one-way ANOVA and Tukey's test. RESULTS: The highest and the lowest weight loss was found in the 0% NHA (-1.052±0.176) and 5% NHA (-0.370±0.143) groups, respectively. Wear was significantly higher in 0% NHA group (P<0.05). No difference was detected in wear between 2 and 5wt% NHA or among 1, 7 and 10wt% NHA groups. Significant differences were noted in wear between 2 and 5wt% NHA and 1, 7 and 10wt% NHA groups (P<0.001). CONCLUSIONS: Incorporation of up to 10wt% of NHA increases the wear resistance of Fuji II LC RMGI. This increase was the highest when 2 and 5wt% NHA were added. Key words:Glass ionomer, hydroxyapatites, nanoparticles, dental restoration wear.

Shear Bond Strength of Two Types of Glass Ionomer to Bleached Dentin: Effect of Delayed Bonding and Antioxidant Agent.

BACKGROUND: Studies have shown a reduction in bond strength of composites and glass ionomer to bleached enamel and dentin. Several methods have been proposed to reverse compromised bond strength. OBJECTIVE: The aim of this study was to evaluate the effect of delayed bonding and application of antioxidant agent on the bond strength of reinforced self-cured (Fuji IX) and light-cured glass ionomers (Fuji II LC) to bleached dentin. MATERIAL: Eighty extracted third molars were randomly divided into 8 groups. Buccal dentin surfaces received different treatments: Two control groups: no treatment + bonding Fuji IX or Fuji II LC. Two immediate bonding groups: bleaching + bonding Fuji IX or Fuji II LC. Two delayed bonding groups: bleaching + 7 days delay + bonding Fuji IX or Fuji II LC. Two sodium ascorbate application groups: Bleaching + application of 10% sodium ascorbate + bonding Fuji IX or Fuji II LC. All samples were tested for shear bond strength. Two-way analysis of variance (ANOVA) was used to compare the mean and standard deviations among groups, followed by the Tukey's test for significant interaction. RESULTS: No statistically significant difference was detected in shear bond strength of Fuji IX to bleached or normal dentin. Although a significant reduction was found shear bond strength values of Fuji II LC to bleached dentin, no significant difference was observed between no bleaching group and those treated with 10% sodium ascorbate or 7 days of delay in bonding for both types of glass ionomer. CONCLUSION: Bleaching had no significant effect on shear bond strength of Fuji IX to dentin; this type of GI can be used immediately after bleaching.

Effect of different endodontic sealers on push-out bond strength of fiber posts

Despite the increasing demand for fiber-reinforced composite (FRC) posts, their bonding to root canals is still subject to debate. Endodontic sealers may affect the bond strength between fiber posts and root canal dentin. Aim: To compare the effects of different sealers on fiber post bond strength. Methods: Sixty teeth were divided into 4 groups according to obturation method: GI, gutta-percha without any sealers; GII, gutta-percha and AH26 resin-based sealer; GIII, RealSeal point and RealSeal resin-based sealer, GIV, Guttaflow. Fiber posts were cemented into root canals. Specimens were sectioned, and the bond strength was measured in the middle area. The failure mode was evaluated. Data were analyzed by one-way ANOVA and post hoc test. Results: The highest bond strength was observed in the control group (2.95±1.12), and the least was in the Guttaflow group (1.15±0.78). There was a significant difference between bond strengths of the control and Guttaflow groups and between AH26 and Guttaflow groups (p<0.05). The failure mode was mainly adhesive between dentin and resin cement in all groups. Conclusions: Sealers may have a negative effect on the bond strength of fiber posts to root canal dentin.