Effect of group and individual education on shade matching competency of dental students.

PURPOSE: To evaluate the influence of group and individual education on shade matching quality using a visual color competency test to match shade tab pairs from two Vita classical A1-D4 shade guides. METHODS: 60 dental students, 21-25 years old (39 females, 21 males) participated in the study. All participants passed a color deficiency test before the experiment. The examination was voluntary and approved by the corresponding Ethics Committee. Students were randomly divided into three groups (n=20): one control group, NE (no education) and two experimental groups - GE (group education) and IE (individual education). The study was performed in three phases. In the "before" (B - Phase 1) and "after" (A - Phase 3) phase, all groups had to match 16 pairs of tabs from two Vita classical A1-D4 shade guides, with the shade designations hidden by custom letter markings. All tabs were mixed on a gray surface illuminated by color-correcting light. In Phase 2 (between B and A), GE had only group education, while IE received additional individual education and training. The control group did not participate in Phase 2. Means and standard deviations were calculated, and differences were compared using the one-way ANOVA, ANCOVA test, and Student t-test for dependent samples (α= 0.05). RESULTS: The NE group matched 10.3 (3.2) and 10.4 (2.9) tab pairs in the before and after phases, respectively. Corresponding results for GE were 11.1 (2.2) and 14.4 (1.9) and 9.5 (3.6) and 15.0 (1.5) for IE, respectively. In Phase 1 (B), no statistically significant difference was recorded among the groups (P= 0.260). The experimental groups achieved a statistically significant improvement compared with the control group in Phase 3 (A) (P< 0.001). Both experimental groups achieved statistically significant improvement within the group after education, GE (P< 0.001) and IE (P< 0.001). Within the limitations of this study, it was concluded that both experimental groups had statistically significant progress in shade matching. The group that received individual education (IE) made statistically significant progress compared with the group that received group education (GE). No statistically significant difference was found in the results of the control group between Phase 1 and Phase 3 of the study. CLINICAL SIGNIFICANCE: Improving the shade matching ability facilitates the work of dentists and dental technicians and enhances the esthetics of dental restorations.

Coffee-stained tooth enamel color restoration and surface abrasion with whitening and regular toothpaste.

PURPOSE: To evaluate the effectiveness of whitening toothpaste in restoring tooth color after coffee staining and its potential impact on enamel surfaces compared with regular toothpaste. METHODS: Bovine tooth enamel specimens were prepared and stained with coffee solutions before undergoing brushing simulation with different toothpaste slurries (whitening, regular, reference). For precise evaluation, spectrophotometric measurements were taken at intervals to assess color changes using the CIELAB (Commission Internationale de l'Éclairage Lab*) color space. Additionally, profilometric measurements were taken to determine the impact of toothpaste type on the roughness and abraded depth of the enamel surface. To understand the effects of toothpaste and brushing on color change, surface roughness, and abraded depth, while also considering correlations between these factors, the findings were analyzed using mixed-effects models. RESULTS: The whitening toothpaste group demonstrated the highest recovery rate (71%) after 10,000 brushstrokes, followed by the regular toothpaste group (48%) and the reference slurry group (43%). The mixed-effects model analysis revealed that the reference group had a smaller change in lightness (ΔL) than those in the regular toothpaste group. The whitening toothpaste group showed a greater change in lightness on average than those in the regular toothpaste group, with an increase in lightness as the number of brushstrokes increased. According to the roughness and abraded depth data, the whitening toothpaste group was least affected by brushing, while the reference and regular toothpaste groups showed higher levels of roughness and abraded depth at all intervals. CLINICAL SIGNIFICANCE: Gaining a thorough understanding of the effectiveness of whitening toothpaste and its impact on the enamel surface plays a crucial role in refining toothpaste formulations and advancing tooth whitening techniques in dental care.

Working viscosity and non-Newtonian behavior of silicone denture liners.

PURPOSE: To evaluate flow profile and non-Newtonian behavior of 10 different silicone lining materials. METHODS: Ten commercially available silicone lining materials were selected for evaluation. The flow profile and non-Newtonian behavior of each material was measured using a shark fin testing method. Fin height and resultant base thickness were measured with a digital caliper and compared with one-way ANOVA and Student-Newman-Keuls post hoc test and fin base by Kruskal-Wallis one-way ANOVA on ranks with Dunn post hoc test with significance at P< 0.05 for both. RESULTS: Shark fin heights ranged from 9.62 ± 0.86 mm [Reline II (Soft)] to 25.54 ± 0.43 mm [Sofreliner (Medium)]. Shark fin bases ranged from 2.57 ± 0.51 mm [Sofreliner (Medium)] to 10.31 ± 0.57 mm [Reline II (Soft)]. Statistically significant differences were found between certain samples' shark fin heights as well as resultant bases (P< 0.05) indicating different rheological properties. CLINICAL SIGNIFICANCE: Silicone liner materials differ significantly with respect to flow profile and non-Newtonian behavior. While a high flow profile (low viscosity) of an elastomeric impression material improves accuracy, it may be a detriment to a denture lining material that must achieve a critical minimum thickness to provide resilience. Likewise, a low flow profile (high viscosity) material may also pose a disadvantage, requiring excessive compression and possible tissue distortion to achieve the same critical thickness. The results of this study should be considered when selecting the appropriate material for clinical application. Additional studies are indicated to further quantify rheological properties as well as correlate them to physical properties after the complete cure of the material.

Comparison of surface properties of universal shade and conventional resin-based composites after degradation and repolishing.

PURPOSE: To investigate the discoloration, line roughness and gloss of conventional and universal shade resin-based composites. METHODS: Clearfil AP-X (AP-X) and Estelite Sigma Quick (EQ) samples were prepared. Discoloration, roughness, and gloss were measured on mirror-polished, alkaline-degraded, and repolished surfaces. The superficial layer degraded by alkaline immersion (degraded layer) was ground off from the sample surface. After removing the degraded layer, the surface was polished with aluminum oxide powder (1.0 µm and 0.3 µm), to create a repolished specimen. Scanning electron microscopy observations were made of the specimens. RESULTS: The results were compared with those for Omnichroma (OC) from a previous study. All the materials showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials. CLINICAL SIGNIFICANCE: The materials tested showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials.

Effect of low power Er:YAG laser irradiation of CAD-CAM resin-based composites on resin bonding.

PURPOSE: To investigate the effect of painless low-power Er:YAG laser irradiation of conventional and polymer-infiltrated ceramic network (PICN) type CAD-CAM resin-based composites (RBCs) on resin bonding. METHODS: An Er:YAG laser system, phosphoric acid etchant, universal adhesive, RBC, and two types of CAD-CAM RBC block were used. Microtensile bond strength, fracture mode, scanning electron microscopy (SEM) observations of bonding interfaces and CAD-CAM surfaces, and surface roughness of ground and pretreated surfaces were investigated. As pretreatment methods, low-power Er:YAG laser irradiation and air-abrasion with alumina particles were used. RESULTS: The effect of low-power Er:YAG laser irradiation of CAD-CAM RBCs on bonding to repair resin varied depending on the type of CAD-CAM RBCs. CLINICAL SIGNIFICANCE: The low-power Er:YAG laser irradiation of the conventional CAD-CAM RBCs was shown to be effective as a surface pretreatment for resin bonding, while the laser irradiation of PICN-type CAD-CAM RBCs was not effective.

Clinical evaluation of subgingival open sandwich restorations: 3-year results of a randomized double-blind trial.

OBJECTIVES: To provide a 3-year follow-up of previously treated patients to assess and compare the periodontal responses and clinical performance of proximal subgingival open sandwich restorations. MATERIALS AND METHODS: Ninety-five adults participated in the study, with a combined total of 120 compound Class II cavities. These cavities had gingival margins located below the CEJ. Four different restorative materials were used to elevate the dentin/cementum gingival margins of the cavities: resin-modified glass ionomer, glass hybrid, flowable bulk-fill composite, or ion-releasing material, which were then completed with the same overlaying composite. Different periodontal and clinical evaluations, based on the criteria set by the World Dental Federation (FDI) criteria, were performed at different time intervals, including baseline, 6 months, 1, 2, and 3 years. RESULTS: The type of base material did not affect the periodontal evaluations. There were no statistically significant differences between different time intervals or base material groups in any of the evaluated FDI parameters. However, the ion-releasing material scored significantly worse in the radiographic evaluation than any of the other groups. CONCLUSIONS: All tested materials are suitable for proximal subgingival open sandwich restorations, as long as the restoration/tooth margin is at least 2-mm away from the bone crest. CLINICAL SIGNIFICANCE: Clinicians can confidently choose any of the tested materials for proximal subgingival open sandwich restorations, as they have shown good outcomes from both periodontal and clinical perspectives.

Effect of open windows on airborne contamination and its topographical distribution in the dental operatory.

Aerosols produced by dental handpieces represent a permanent risk of disease transmission in the dental environment. The current study evaluated the effects of natural ventilation (open windows) on Streptococcus mutans airborne contamination by dental handpieces in simulated clinical conditions. A dental phantom was placed on a dental chair at a standard university dental clinic operatory. An S. mutans suspension was infused into the phantom's mouth while an operator performed standardized dental procedures using low (contra-angle) and high speed (turbine) dental handpieces or an ultrasonic scaler, with windows open or closed. Selective medium Petri dishes were placed in 18 sites of the operatory environment to evaluate contamination topographically. Sites were clustered as: wall, floor, ceiling, dental chair, and cabinet. Contamination was expressed as log10 CFU/cm2 . A linear mixed model analysis was used, nesting the sites within each ventilation and handpiece combination. Open windows significantly reduced contamination. The high-speed handpiece provided the highest contamination, followed by the ultrasonic scaler and the low-speed handpiece. Contamination values were much smaller at the ceiling, and much larger at the chair. Opening windows produced more homogeneous contamination of the operatory compared to closed windows. Natural ventilation during dental procedures decreases contamination and affects its topographical distribution.

Periodontopathic bacterial adhesion to different restorative materials used to elevate proximal subgingival margins.

This study compared the periodontopathic bacterial adhesion to four restorative materials used for deep margin elevation at 2, 24, and 48-h after incubation. Discs were produced from four restorative materials: resin modified glass ionomer, glass hybrid, flowable bulk fill resin composite, and bioactive ionic resin. Root dentin was used as control. Specimens were coated with saliva and used to culture a biofilm comprised of three strains of periodontopathic bacteria; Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans. Bacterial adherence was assessed by colony count assay, crystal violet staining, and visualized using confocal laser scanning microscopy. Data were analyzed by two-way ANOVA followed by Tukey's post hoc tests. The adhesion values for the control specimens were significantly higher than for other materials, while those for the flowable bulk fill were significantly lower than for any other material within all evaluation assays. The 2-h incubation period showed the lowest adhesion values regardless of the group. The 48-h adhesion values were higher than the 24-h results in all groups except the flowable bulk fill. Microscopic imaging partially supported the findings of the measurements. In terms of periodontopathic bacterial adhesion, the tested flowable bulk fill may be preferable for subgingival use over other tested materials.

Dentin abrasion using whitening toothpaste with various hydrogen peroxide concentrations.

PURPOSE: To compare the amount of abrasion of four whitening toothpastes, two conventional toothpastes, and seven experimental toothpastes with varying concentrations of hydrogen peroxide. METHODS: Bovine dentin specimens were treated with the four whitening toothpastes (containing three different concentrations of hydrogen peroxide: 0.75%, 1.50%, and 2.80%), two conventional toothpastes without hydrogen peroxide, seven experimental toothpastes (concentrations of hydrogen peroxide: 0.75%, 1.50%, 3.0%, 4.50%, 6.0%, 7.50%, and 9.0%), and distilled water. After 10,000 strokes of toothbrushing, the amount of abrasion on the dentin surface was measured with a contactless 3D surface profiler (n= 8). The pH of all solutions, the weight percentages of the particles, and the component of particles in the toothpaste were analyzed. The correlations between the dentin abrasion, pH, and weight percentages of the particles in the toothpastes were investigated. RESULTS: The amount of abrasion of the two conventional toothpastes were 1.1-3.6 times higher than those of the four whitening toothpastes. Likewise, the pH of the conventional toothpaste was higher than those of the other whitening toothpastes. No significant differences were found among the four whitening toothpastes. The four whitening toothpastes consisted of a relatively lower weight percentage of particles compared to the two conventional toothpastes. A strong positive correlation was observed between the dentin abrasion and the weight percentages of the particles (r= 0.913; P< 0.05). Furthermore, no significant differences in the amount of abrasion were observed between the specimens treated with seven experimental toothpastes and those treated with distilled water. CLINICAL SIGNIFICANCE: The whitening toothpastes containing less than 9% hydrogen peroxide did not seem to harm the dentin surface significantly. These findings can serve as a reference for consumers, patients, and dental professionals.

Secondary caries adjacent to bulk fill resin composite restorations lined with fluoride agents.

PURPOSE: To evaluate the potential secondary caries reduction of bulk-fill resin composite restorations treated with different fluoride (F)-based agents prior to restoration placement. METHODS: 25 upper extracted molars received Class V cavities on both buccal and lingual surfaces with an enamel margin and root surface margin. The teeth were randomly assigned into five groups with five teeth per group (n=10). The treatment groups were: control group, with no treatment; the other groups received treatment using different F-based agents prior to bonding. All teeth were restored using a selective etch bonding technique and bulk fill resin composite. All teeth received 10,000 thermal cycles followed by immersion in demineralizing solution to produce artificial caries-like lesions. Polarized light microscope evaluation was performed on longitudinal sections (30 enamel lesions and 30 root surface lesions per group). Lesion depth and wall lesions for both enamel and root surface adjacent to the restorations were evaluated. RESULTS: Both lesion depths and frequency of wall lesions in the enamel and root surfaces in all treatment groups were significantly reduced compared with the control group. Among the different F-based agents, no significant difference was seen on the enamel or root surface lesion depth, showing a similar presence of enamel and root cavosurface wall lesions. CLINICAL SIGNIFICANCE: F-based agent treatment of adjacent enamel and root surfaces prior to placement of restorative materials provided resistance to the development of secondary caries during an in vitro caries model.

Comparative evaluation of subgingival scaling and polishing techniques on dental material surface roughness.

PURPOSE: To evaluate and compare the effects of different scaling and polishing techniques on the surface roughness of four different restorative materials. METHODS: 72 specimens were prepared, molded to a size of 8.0 by 2.0 mm, and cured according to the manufacturers' instructions. The specimens were stored at 37°C for 24 hours and then thermocycled for 5,000 cycles (from 55°C to 5°C) to simulate 6 months of clinical use. Surface roughness (Ra/average and Rz/max-overall heights) was calculated using a stylus profilometer by subtracting the simulated treatments of hand scaling, ultrasonic scaling, and air polishing from the baseline measurements. The difference in Ra and Rz data were compared independently for each measurement using a two-way ANOVA on Ranks and the Holm-Sidak test, with α< 0.05 used to determine significance. RESULTS: Irrespective of the scaling or polishing technique employed, flowable bulk fill demonstrated the lowest Ra and Rz values. Hand scaling exhibited the highest roughness and variability among the other techniques, regardless of the materials tested (P< 0.001). Air polishing with glycine resulted in the lowest roughness values across all tested materials, with the exception of the tested bioactive restorative material group. CLINICAL SIGNIFICANCE: Regarding surface roughness, air polishing with glycine may be an effective and safe intervention for periodontal maintenance of subgingival restorations compared to the other tested scaling methods.

Longterm abrasive and erosive effect of whitening toothpaste on dentin surface.

PURPOSE: To evaluate the amount of dentin loss following immersion in or toothbrushing with whitening toothpaste (WT) containing hydrogen peroxide (HP) and citric acid (CA). Additionally, the amount of dentin loss after brushing with a WT alone or in combination with a conventional toothpaste was assessed, and the effects of HP and CA solutions on the dentin surface were investigated. METHODS: Bovine dentin specimens (n= 350) were randomly assigned to seven solutions of various compositions as toothpaste: The specimens assigned to each solution were then further divided into five treatment groups (n=10 each) : Group A = 1-hour immersion in each solution (ES); Group B = 10,000 brushing in ES; Group C = 1-hour immersion in ES + 10,000 brushing in ES; Group D = 1-hour immersion in ES + 10,000 brushing in reference slurry (RS); Group E = 10,000 brushing in ES + 10,000 brushing in RS. The amount and pattern of dentin loss were determined, and the surfaces were observed using noncontact profilometry. RESULTS: The WT (pH 5.0) caused lower dentin loss than RS after a single brushing cycle; however, the extent of dentin loss after 1 hour of immersion in the WT was significantly greater than that in the RS. Among the specimens treated with WT, a significant difference in dentin loss was observed between Group C and Groups D and E (P< 0.05) but not between Groups D and E. The surfaces exposed to CAS1, CAPB, and WT exhibited U-shaped patterns of dentin loss after brushing or immersion, whereas a wedge-shaped pattern was observed in those that underwent brushing with the RS. CLINICAL SIGNIFICANCE: The effects (dentin abrasion) of a whitening toothpaste containing hydrogen peroxide and citric acid when used in combination with a conventional toothpaste were similar to those seen with the continuous use of a conventional toothpaste alone.

Microhardness of different thicknesses of bulk fill composites.

PURPOSE: To compare the microhardness values and bottom/top hardness ratios of different composites after being cured in 2 or 4 mm increments. METHODS: Two bulk fill composites, methacrylate-based and ormocer-based, and one conventional composite were tested. 36 cylindrical discs were prepared (n=12/composite, with six for 2 mm, and six for 4 mm thickness) by pressing each composite into a mold between two glass slides covered by Mylar strips. The top and bottom surfaces of each sample were evaluated using a Buehler hardness tester for Knoop microhardness, with a 50 g static load applied for 10 seconds at three different locations of the central part of each sample. The bottom/top hardness ratio was calculated for each sample. The Knoop microhardness data and bottom/top ratio percentages were analyzed using two-way repeated measures ANOVA and Holm-Sidak post hoc test, with significance at P< 0.05. RESULTS: The tested methacrylate-based bulk fill had the highest overall microhardness among the three tested composites. All three composite types showed a significant difference in microhardness between the top and bottom of the 4 mm discs. The bottom/top ratio percentages differed significantly for both tested bulk fill composites across different thicknesses. Both tested bulk fill materials had a bottom/top ratio of ≥ 80% at the deepest level of a 4 mm increment. CLINICAL SIGNIFICANCE: The type of material significantly affected both the bottom and top microhardness values under the experimental conditions used. While both tested bulk fill composites showed a decline in microhardness at the bottom of the 4 mm depth, they had clinically acceptable microhardness ratios at greater depths.

Effect of toothpaste tablets on gloss and surface roughness of resin-based composite materials.

PURPOSE: To evaluate the effects of toothpaste tablets on the gloss and surface roughness of resin-based composite materials and determine the relationship between gloss and roughness. METHODS: Rectangular jigs were designed and printed. Wells (2 mm deep x 7 mm diameter) were filled with Filtek Supreme Ultra A2B, light-cured and polished. A small-area glossmeter was used for gloss (GU) measurements and a profilometer for roughness measurements (Ra) at baseline and after challenge with each toothpaste. An automated tooth-brushing machine was set at 120 strokes/minute for a total of 10,000 strokes to evaluate four test groups with 16 specimens in each group. NC: Brushing with distilled water; TABS: Colgate Anywhere Travel Tooth Tabs; CP: Colgate Cavity Protection Toothpaste and AW: Colgate Whitening Advanced Toothpaste. Kruskal-Wallis test was used to test the difference in gloss and surface roughness among the groups and Pearson correlation was used to compare the relationship between gloss and roughness. RESULTS: There was no statistically significant difference in gloss and roughness among the four groups at baseline. At post-brushing, there was a statistically significant difference among the groups (P< 0.001) with increased roughness and decreased gloss for CP and AW when compared to TABS. There was a statistically significant correlation between post-brushing roughness and post-brushing gloss (P< 0.001, rho: -0.815). Thus, the higher the surface roughness the lower the gloss. CLINICAL SIGNIFICANCE: Toothpaste tablets retain better gloss and roughness of resin-based composite materials when compared to conventional toothpastes.

Perceptions of dental students, dental faculty, practicing dentists and industry dental professionals on the acquisition of dental competencies and clinical skills in the Dominican Republic.

INTRODUCTION: This study gathered perceptions from four stakeholder groups in the Dominican Republic (DR) regarding acquiring professional dental competencies and clinical skills. MATERIALS AND METHODS: Researcher-created surveys covering core dental competencies and clinical skills were distributed to stakeholder groups associated with nine different DR dental programs. Respondents included 153 undergraduate dental students, 153 dental faculty members, 108 practicing dentists (who had graduated in the past 5 years) and 42 industry professionals (who hire and supervise dentists). Data were examined using descriptive statistics, univariate ANOVA and multiple linear regressions. RESULTS: Dental school students and recent graduates now practicing dentists in the DR reflected moderate to solid confidence that they had learned most of the dental skills and competencies covered in the survey. Industry professionals were a bit less confident overall, while dental faculty offered the lowest scores, although those were often still in the moderately confident range. ANOVAs revealed significant differences when broken down by individual university dental programs. Regressions also revealed that individual university dental programs significantly predict confidence that dental skills and competencies were achieved. CONCLUSION: Data show that DR's dental stakeholder groups generally felt optimistic about the learning occurring. However, the lower mean scores and higher standard deviations from faculty responses raise concern, as do the significant differences between individual dental programs and the dental program itself a significant predictor. Further review of programs is needed, and a national set of dental competencies should be considered in this country.

Effect of mold enclosure and chisel design on fatigue bond strength of dental adhesive systems.

To examine the effect of mold enclosure and chisel design on macro shear fatigue bond strengths of dental adhesive systems. The fatigue bond strength testing was conducted with two commercially available dental adhesive systems, (1) OptiBond eXTRa and (2) Scotchbond Universal, for bonding a resin composite (Filtek Supreme Ultra) to both enamel and dentin using a mold enclosure and a non-mold enclosure with a knife-edge and two sized notched-edge chisel assemblies for loading. As a loading reference for the fatigue testing, macro shear bond strengths of the adhesive systems to enamel and dentin were conducted using a mold enclosure and a knife-edge chisel assembly. The shear bond strengths with the mold enclosure using knife-edge chisel assembly did not exhibit a significant difference between the adhesive systems for either enamel or dentin. The fatigue bond strengths of bonded specimens demonstrated significant differences when comparing the mold enclosure and non-mold enclosure, but not between knife-edge and notched-edge chisel assemblies. The fatigue bond strengths of dental adhesive systems demonstrated significantly higher values when using mold-enclosed bonded specimens than a non-mold enclosure, regardless of type of chisel assembly.

Effect of whitening dentifrices on toothbrush abrasion on composites.

PURPOSE: To evaluate the laboratory long-term effect of various whitening dentifrices on the surface roughness of two brands of resin composite (TPH ST, Filtek Bulk Fill One) using a mechanical toothbrushing simulation. METHODS: Thirty-two samples each of Filtek and TPH were fabricated in ring molds 10 x 1 mm. Samples were randomly grouped (n=8; four groups), according to dentifrice used; Crest 3D, Optic White, Hello (charcoal), and Aim as control. Samples were brushed in mixed solutions containing deionized water and dentifrice at 150 gf for 10,000x with rotation to ensure uniform brushing. Surface roughness was measured both before (baseline) and after the mechanical toothbrushing simulation using a stylus profilometer. Data collected was compared independently for each treatment using two-way ANOVA and SNK with α< 0.05 for significance. RESULTS: The data showed that TPH was more susceptible to the abrasive nature of three of the whitening dentifrices tested [Crest 3D, Optic White, and Hello (charcoal) ]. Filtek also exhibited significant susceptibility to the abrasive nature of Hello. Aim showed the least or minimal amount of abrasion. CLINICAL SIGNIFICANCE: TPH ST composite was more susceptible to the abrasive nature of the three whitening dentifrices tested [Crest 3D, Optic White, and Hello (charcoal)]. Filtek also exhibited significant susceptibility to the abrasive nature of Hello. Aside from the data supporting the clinical efficacy of TPH compared to Filtek, clinicians should inform patients of the abrasive capacity of all whitening dentifrices, especially those that are charcoal based.

Bactericidal effect on S. mutans using N-TiO2 with combined treatment of low concentration H2O2 and visible light.

PURPOSE: To test the feasibility of nitrogen-doped TiO2 nanoparticles in the killing of Streptococcus mutans (S. mutans) for short term treatment. METHODS: For the study, S. mutans were treated with the combinations of N-TiO2, visible light, and without/with 0.5% H2O2 inclusion. Visible light was irradiated for 3 minutes one time. RESULTS: Methylene blue solution was degraded (bleached) 5-30% by one of N-TiO2 (or TiO2) + visible laser (405 or 660 nm) +0.5% H2O2 conditions owing to almost linearly producing free radicals through photocatalysis. Antibacterial outcomes treated with N-TiO2 were slightly better than those by TiO2 regardless of test condition. Also, killing of S. mutans treated with 405 nm laser was slightly better than those by 660 nm laser. CLINICAL SIGNIFICANCE: S. mutans can be eliminated using N-TiO2 with clinically acceptable light (wavelength, intensity) and low concentration H2O2 condition under short term treatment.

Teeth whitening using nitrogen doped-TiO2 nanoparticles and hydrogen peroxide under visible light irradiation.

PURPOSE: To test the efficacy of nitrogen doped-TiO2 (N-TiO2) nanoparticles (NPs) on teeth whitening under visible light irradiation. METHODS: N-TiOV2 NPs were prepared by the sol-gel method, using TiN as a precursor. Their light absorbance and crystal structures were characterized. Photocatalytic reactions were tested using methylene blue (MB) and extracted teeth. For the extracted teeth, carbomer gel, without or with 3% H2O2, and light irradiated, with subsequent evaluation of the color differences. RESULTS: Unlike ordinary TiO2, N-TiO2 showed high absorbance after 400 nm. N-TiO2 prepared with TiN as a precursor showed rutile phase over the TiN structure. For MB solution, N-TiO2 with 3% H2O2 showed the maximum decrease in absorbance after laser irradiation. Observing the effect on teeth, N-TiO2+3% H2O2+405 nm laser treatment achieved approximately 25% higher whitening than that by 15% H2O2 during the same treatment time. Higher H2O2 concentrations may offer faster results. CLINICAL SIGNIFICANCE: N-TiO2 nanoparticles (without or with 3% H2O2) show better whitening of teeth as compared to 15% H2O2, if used with a visible laser for 5 hours. The potential on N-TiO2 nanoparticles to be used as a tooth whitener needs to be further explored to reduce its application time.

Effect of pressure during curing placement technique on bond strength of resin composite to human dentin.

PURPOSE: To evaluate and compare the effect of pressure during curing on resin composite bond strength to dentin using a self-etch bonding protocol. METHODS: 20 human teeth were cut to the mid-coronal dentin and received a standardized smear layer. The prepared teeth were randomly assigned to the following two groups (n= 10/group): (1) without pressure during curing (control) or (2) with pressure during curing. Teeth in the control group received a 4 mm-thick buildup of a nanohybrid resin composite in two separately cured increments, adapted using a composite placement instrument, and bonded with a universal adhesive, while teeth in the treatment group were restored with the same adhesive and resin composite but a plexiglass pressure cylinder was used to apply pressure while each increment was cured. Each group was further divided into two subgroups, one of which was sectioned and subjected to microtensile bond strength (µTBS) testing after 24 hours (immediate samples; n= 5), while the other was subjected to 10,000 thermal cycles (TC; n= 5) prior to sectioning and µTBS testing. The resulting failure patterns were assessed under a stereomicroscope. In addition, one representative specimen from each subgroup was subjected to qualitative microscopic morphological analysis of the internal restoration/dentin interface. Data were analyzed by two-way ANOVA followed by Tukey' post hoc test and values with P< 0.05 were considered to be statistically significant. RESULTS: After TC, the group cured with pressure exhibited significantly higher µTBS values than did the control (P< 0.05), although TC had a detrimental effect on all µTBS values. Microscopic examination revealed that the control specimens had more voids in the resin composite part, relative to specimens that were under pressure during the curing process. CLINICAL SIGNIFICANCE: Pressure application during curing of resin composite may have a positive effect on bond strength to dentin.