Effect of fiber-reinforced direct restorative materials on the fracture resistance of endodontically treated mandibular molars restored with a conservative endodontic cavity design.

OBJECTIVE: This study aimed to evaluate the fracture strength of teeth restored using fiber-reinforced direct restorative materials after endodontic treatment with a conservative mesio-occlusal access cavity design. MATERIALS AND METHODS: A total of 100 extracted intact mandibular first molars were selected and distributed into a positive control group where teeth left intact and the following four test groups comprised of teeth with conservative mesio-occlusal access cavities that had undergone root canal treatment (n = 20/group): access cavity without restoration (negative control), bulk-fill resin composite with horizontal glass fiber post reinforcement, fiber-reinforced composite with bulk-fill resin and bulk-fill resin composite. Following thermocycling (10,000 cycles), fracture resistance was measured using a universal testing machine. Statistical analyses (one-way analysis of variance and the Tamhane test) were performed, and statistical significance was set at p < 0.05. RESULTS: Groups with minimally invasive access cavities had lower fracture strength than intact teeth, regardless of the restoration material (p < 0.05). Fiber-reinforced composite groups demonstrated higher fracture strength than bulk-fill resin composite alone (p < 0.05). Fracture types varied among groups, with restorable fractures predominant in the fiber-reinforced composite groups. CONCLUSION: This study suggests that using fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, can effectively enhance the fracture strength of endodontically treated teeth with conservative access cavities. However, using only bulk-fill resin composite is not recommended based on the fracture strength results. CLINICAL SIGNIFICANCE: When teeth that undergo endodontic treatment are restored using a conservative access cavity design and fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, the fracture strength of the teeth can be effectively increased.

Evaluation of Enamel Surfaces Treated with a Desensitizing Agent Containing CPP-ACP Before or After In-Office Bleaching.

PURPOSE: To evaluate the effects of desensitizing MI Varnish (GC America) applied before or after bleaching on the mineral component of enamel and surface topography. MATERIALS AND METHODS: The coronal portions of 10 freshly extracted bovine teeth were segmented for a total of 40 specimens. Enamel specimens obtained from each tooth were randomly divided into four groups (n = 10): Group A = no bleaching; Group B = bleaching with 40% hydrogen peroxide (HP); Group C = MI Varnish applied before bleaching; and Group D = MI Varnish applied after bleaching. The calcium (Ca) and phosphorus (P) levels of the specimens in each group were determined by energy dispersive spectroscopy (EDS). Morphologic changes were observed using scanning electron microscopy (SEM). One-way ANOVA and Tukey HSD tests were used for statistical analyses (α = .05). RESULTS: The mean Ca content of Group B was significantly lower than those of Groups A, C, and D (P < .05). The mean Ca content of Group C was significantly lower than that of Group A (P < .05). There was no significant difference in Ca content between the other groups (P > .05). The mean P content of Group A was significantly higher than those of Groups B to D (P < .05). There was no significant difference in P content between Groups B to D (P > .05). CONCLUSIONS: Application of MI Varnish before or after in-office bleaching was effective in reducing mineral loss. However, applying MI Varnish after bleaching was more effective.

The Effect of Food-Simulating Liquids on Surface Features of Single-Shade Universal Composites: An In Vitro Study.

Objectives: This study aimed to investigate the microhardness, surface roughness, and field emission scanning electron microscopes (FE-SEM) images of three different single-shade composites (Essentia Universal, Omnichroma, and Vittra APS Unique) in food simulation liquids such as ethanol, citric acid, and distilled water. Materials and Methods: Three single-shade universal composites were selected for this study. For each composite resin group, 92 samples (5-mm diameter and 2-mm depth) were prepared in plexiglass molds (N = 276). Then, samples were separated into four groups randomly consisting of 23 samples each (10 for hardness, 10 for roughness, and 3 for FE-SEM analysis). Three groups were immersed in food-simulating liquids (FSL)-citric acid (0.02N), distilled water, and 75% ethanol stored in a glass at 37°C for the next 7 days to simulate a wet oral environment. Control samples were stored in an opaque-light-proof box at room temperature. After the conditioning period, roughness and microhardness were measured, and FE-SEM analysis was performed. For statistical analysis, the two-way analysis of variance and Tukey honestly significant difference tests were used to evaluate roughness and microhardness (P < 0.05). Results: There was a statistically significant difference between the composites in terms of roughness and hardness averages (P = 0.001; P < 0.05). Omnichroma showed the most surface changes in ethanol storage, whereas Vittra Unique showed the most surface changes in citric acid storage such as Essentia. Conclusion: FSL that mimic various oral environments affect single-shade universal resin composite restorations.

The Effect of In-Office Bleaching with Different Concentrations of Hydrogen Peroxide on Enamel Color, Roughness, and Color Stability.

The aim of this study is to evaluate the effectiveness of in-office bleaching in esthetic dentistry on the roughness and color stability of the enamel surface, using different concentrations of hydrogen peroxide (HP). Fifty human incisors were randomly divided into 5 groups (n = 10). No bleaching was performed in the control group. For these groups, concentrations of 40% HP with fluoride (F), 35% HP with calcium (Ca), 25% HP with nano-hydroxyapatite (nHA) and 18% HP with nHA were used for bleaching in the test groups. Surface roughness was assessed at baseline after bleaching occurred. Color measurements were first obtained at baseline, then after the first and second sessions of bleaching, and, finally, after the staining protocol. Scanning electron microscopy and atomic force microscopy were performed. Statistical analysis was conducted with a one-way ANOVA, followed by a post hoc Tukey's test and a paired-samples t-test (p < 0.05). All the bleaching gels used exhibited a similar color change (p > 0.05). Bleaching gels containing 18% HP with nHA and that containing 35% HP with Ca caused less surface roughness of the enamel. Of these concentrations, 25% HP with nHA caused the most surface roughness and no significant difference was observed, compared with 40% HP with F. The highest coloration after bleaching was observed in 40% HP with F and 25% HP with nHA. The lowest coloration was obtained in 35% HP with Ca and 18% HP with nHA but no significant difference was observed between them and the control group. A concentration above 18% HP does not increase the bleaching effectiveness. The results show that 18% HP with nHA and 35% HP with Ca resulted in the least increase in enamel surface roughness when compared to high-concentrate HP; however, it also prevented recoloration after bleaching.

Instrumental and visual evaluation of the color adjustment potential of different single-shade resin composites to human teeth of various shades.

OBJECTIVE: The study aims to evaluate the color adjustment potential (CAP-I, CAP-V) of different single-shade resin composites. MATERIALS AND METHODS: The shades of 40 human incisors were determined using a spectrophotometer, with the teeth divided into four groups of the same shade (n = 10). The following single-shade resin composites were tested: Omnichroma, Charisma Diamond One, Vittra Unique, and Essentia Universal. The specimens were prepared as "dual" and "single." Standardized cavity preparations (diameter, 7 mm; depth, 2 mm) were prepared in human incisor teeth and then restored for dual specimens. Composite duplicates of human incisors were prepared with resin composites for single specimens (n = 10). The color match of these specimens to that of unrestored human incisors was compared, and the color difference (ΔE*) was calculated. Independent observers conducted a visual evaluation of the specimens and scored them. CAP-I and CAP-V values were determined. A one-way analysis of variance test was used for statistical analysis (p < 0.05). RESULTS: There was no statistically significant difference between the CAP-V and CAP-I values of the tested single-shade resin composites (p > 0.05). All the materials tested had acceptable color-matching potential. CONCLUSIONS: In terms of color matching, there were no significant differences between the different tooth shades of all the tested resin composites. CLINICAL RELEVANCE: Single-shade resin composites have acceptable CAP. The use of single-shade resin composites can reduce in-chair clinical times by minimizing the time spent on shade selection.