American journal of dentistry最新文献

Purpose: To investigate the effect of over-etching and subsequent use of different adhesive application approaches including active, double, preheated, and ultrasonic application on dentin bond strength.

Methods: Dentin specimens from sound human third molars were prepared and allocated into six groups (n= 10 per group). In Group 1 (negative control), the dentin specimens were over-etched with phosphoric acid for 30 seconds, and a two-step etch-and-rinse adhesive (Prime & Bond XP; Dentsply Sirona) was applied for 20 seconds according to the manufacturer's instructions. In test Groups 2-5, the application of the adhesive varied: In Group 2, the adhesive was actively rubbed into the dentin surface, whereas in Group 3, a second adhesive layer was applied after light-curing of the first one. In Group 4, the adhesive was heated to 68°C prior to application, and in Group 5, the adhesive was ultrasonically activated. Acid-etching for 15 seconds and adhesive application for 20 seconds was performed in the positive control group (Group 6) according to the manufacturer's instructions. After light-curing and composite build-up [Ceram.x Spectra ST (HV); Dentsply Sirona], microtensile bond strength and fracture types were determined. Data were statistically analyzed by Kruskal-Wallis rank test, followed by post-hoc pairwise comparisons using Conover tests and P-value adjustment according to Holm (α= 0.05).

Results: Active, double, preheated, or ultrasonic adhesive application showed no significant effect on dentin bond strength when compared to the control groups. Predominantly adhesive failures were observed in all groups.

Clinical significance: A modification of adhesive application by using active, double, preheated, or ultrasonic application does not improve bonding to accidentally over-etched dentin.

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.

Purpose: To evaluate the influence of different surface treatments on the clinical behavior of non-carious cervical sclerotic lesions (NCCLs) over an 18-month follow-up period.

Methods: 128 NCCLs from 32 volunteers were randomized into four groups (n=32): G1-control, without preoperative treatment of the dentin surface; G2, dentin conditioning with 17% ethylenediaminetetracetic acid (EDTA) for 2 minutes; G3, increase in dentin surface roughness with diamond bur and G4, increase in dentin surface roughness with diamond bur + dentin conditioning with 17% EDTA for 2 minutes.

Results: Differences between groups were tested using the Friedman test (α= 0.05). A questionnaire was administered to volunteers about risk factors related to NCCLs. The relationship between the questionnaire data and the clinical performance of the restorations was analyzed using the multiple logistic regression test (α= 0.05). The variables related to parafunctional habits, anxiety and/or depression were significantly related to the manifestation of postoperative sensitivity. Roughening the sclerotic dentin with a diamond bur increased postoperative sensitivity within 12 months. The presence of parafunctional habits and anxiety/depression may lead to postoperative sensitivity.

Clinical significance: Roughening the sclerotic dentin with a diamond bur increased postoperative sensitivity within 12 months.

Purpose: To determine caries inhibition potential of conventional and bulk-fill bioactive composites around restorations.

Methods: Enamel and dentin blocks were prepared using a diamond saw under water irrigation, finished (SiC, 600- and 800-grit) and polished (SiC 1,200, final polish= 0.2 μm). Blocks were then selected through enamel surface microhardness, and enamel and dentin standard cavities were restored (n=10/group) with conventional bioactive composite (Beautifil II, BTF), bulk-fill bioactive composite (Activa BioACTIVE, ACT), glass-ionomer cement (Ionofil Plus, ION), conventional composite (GrandioSO, GSO), and bulk-fill composite (Admira Fusion X-TRA, ADM). Afterwards, the blocks were subjected to pH cycling: 4 hours in demineralization and 20 hours in remineralization solutions for 7 days, before being cut in the middle. One half was used to calculate the carious lesion area (ΔS) using values obtained by cross-sectional microhardness (CSMH) testing. The other half was submitted to polarized light microscopy (PLM) and scanning electron microscopy (SEM). The % of internal gap formation (GAP) of restorations' replicas were analyzed under SEM. Data were analyzed by ANOVA and Tukey test (α= 5%).

Results: In terms of CSMH, ION group exhibited the lowest ΔS values, with no significant difference to ADM. The composites BTF and ACT were similar to each other (P< 0.05) and to their negative controls (GSO and ADM), respectively. ION showed lower caries formation under PLM, whereas the GSO group presented a greater demineralized area. ION presented the highest % of internal GAP formation. Bioactive composites (BTF and ACT) were similar to their corresponding conventional ones (GSO and ADM) in terms of GAP formation.

Clinical significance: The glass-ionomer cement was more effective in inhibiting the formation of caries lesions around restorations. Because of the glass-ionomer cement's limited application in high load-bearing areas, the conventional bioactive composite would be a promising clinical choice.

Purpose: To compare Candida albicans adhesion and quantify the biofilm formed on thermopolymerizable (T.PMMA) and 3D printing (3D.PMMA) polymethyl methacrylate through quantitative and qualitative analyses.

Methods: The specimens were made (n= 39/material) by conventional polymerization (T.PMMA) and designed in Autodesk Meshmixer software, followed by 3D printing (3D.PMMA) - CAD-CAM method. After the roughness standardization, the monospecies biofilm of C. albicans (ATCC 10231) was submitted to adhesion analysis, verifying the quantification and microbial load, in triplicate, by the methods of counting colony forming units (CFU/mL) and staining with crystal violet, followed by optical density reading, respectively. Qualitative analyses were performed by scanning electron microscopy to analyze the surface characteristics of the specimens and biofilm formed. The Mann-Whitney U test was used for comparisons between resins regarding the count of CFU/mL (log¹⁰+ 1) and optical density values (P≤ 0.05).

Results: T.PMMA (5.78 ± 0.43) had a CFU/mL count (P< 0.001) higher than 3D.PMMA (4.84 ± 0.39). There was a difference between C. albicans biofilm accumulation (P< 0.001), in which on T.PMMA (1.59 ± 0.31) was higher than 3D.PMMA (1.10 ± 0.14). The qualitative analyses corresponded to the quantitative ones and allowed the visualization of more porosities in T.PMMA.

Clinical significance: The adhesion (microbial load and biofilm accumulation) of C. albicans was lower in the 3D printed polymethyl methacrylate when compared to the thermopolymerizable model.

Purpose: This secondary analysis further analyzed variations in the 50:50% perceptibility and acceptability thresholds (PT and AT, respectively) pertaining to light, medium, and dark tooth-colored specimen sets.

Methods: Primary raw data from the original study was retrieved. Visual thresholds (Perceptibility - PT and Acceptability - AT) were analyzed among the three specimen sets - light, medium, and dark. The Wilcoxon signed-rank test was used for paired specimens, and the Wilcoxon rank-sum nonparametric test was used for independent specimens (α= 0.001).

Results: The 50:50% CIEDE2000 PT and AT values were significantly higher for the light-colored specimen set when compared with the medium and dark-colored specimens: 1.2, 0.7, 0.6, respectively (PT) and 2.2, 16, 14 (AT), respectively (P< 0.001). Independent of the observer group, the highest PT and AT values were always found for the light-colored specimen sets (P< 0.001). Dental laboratory technicians had the lowest visual thresholds, but not significantly different from the other observer groups studied (P> 0.001). Similarly, all research sites had statistically higher visual thresholds for the light-colored specimen set than for the medium- or dark-colored sets, except for two sites that showed statistically similar results for medium-colored specimens but were significantly different from the dark-colored set. Among the different research sites, sites 2 and 5 registered significantly higher PT thresholds for the light specimens (1.5 and 1.6, respectively), and site number 1 had a significantly higher AT threshold relative to the other sites. The 50:50% perceptibility and acceptability thresholds were significantly different among light-, medium-, and dark-colored specimens for different research sites and observer groups.

Clinical significance: The visual perception of color difference related to light-, medium-, and dark-colored specimens varied based on observer group and their geographic location. Therefore, a greater understanding of factors that affect visual thresholds, with the observers being "the most forgiving" for color differences among the light shades, will allow diverse clinicians to overcome some of the challenges of clinical color matching.

Purpose: Two clinical trials were conducted to investigate the oral and perioral irritation and sensitization potential of a tooth whitening leave-on-gel alone and in combination with a whitening toothpaste, each containing 1.0% of the active ingredient potassium monopersulfate (MPS).

Methods: Both clinical trials were Institutional Review Board (IRB) approved, double-blind, randomized, and parallel group designed studies. For the MPS leave-on gel study, 200 qualifying and consented subjects were randomly assigned to two groups: (1) 0.1% hydrogen peroxide (H₂O₂) gel pen (34 subjects); and (2) 0.1% H₂O₂ + 1.0% MPS gel pen (166 subjects). Subjects used the assigned products according to instructions provided and returned on Days 22 and 36 for oral and perioral tissue examination (pre-challenge). At the Day 36 visit, the subject applied the assigned gel on site (challenge) and received oral and perioral tissue examinations 1 and 24 hours following the application to detect any post-challenge tissue reactions. For the MPS toothpaste/MPS gel pen study, 200 qualifying and consented subjects were randomly assigned to three groups: (1) Placebo toothpaste + placebo gel pen (66 subjects); (2) 1.0% MPS toothpaste + 1.0% MPS gel pen (67 subjects); and (3) 1.0% MPS toothpaste + placebo gel pen (67 subjects). The study design and procedures were the same as those for the MPS gel pen study described above.

Results: For the MPS gel pen study, 192 subjects completed the study. None of the eight dropouts was related to the product use. The demographic data were comparable between the two groups. No evidence of tissue irritation and sensitization was detected in any subjects at any visit, and the findings were comparable between the groups. The detected and self-reported tissue issues were minimal and minor, and they were comparable between the two groups. For the MPS toothpaste/MPS gel pen study, 200 subjects were enrolled with 12 dropped from the study, resulting in an overall dropout rate of 6%. Of the 12 that did not complete the study, none were due to product-related use. The demographic data were comparable among the three groups. The detected and self-reported tissue issues were minimal and minor, and they were comparable among the three groups.

Clinical significance: Potassium monopersulfate (MPS) at the active concentration of 1.0% in the tooth whitening leave-on-gel and the toothpaste plus the gel did not cause oral/perioral irritation nor sensitization.

Purpose: To evaluate the effectiveness of five alkaline peroxide-based effervescent tablets in reducing both biofilms and the food layer adhered on the cobalt-chromium surface.

Methods: Cobalt-chromium metal alloy specimens were contaminated with Candida albicans, Candida glabrata, Streptococcus mutans and Staphylococcus aureus. After biofilm maturation, the specimens were immersed in Polident 3 Minute, Polident for Partials, Efferdent, Steradent, Corega Tabs or distilled water (control). Residual biofilm rates were determined by colony forming units counts and biofilm biomass. In parallel, to investigate the denture cleaning capability of effervescent tablets, artificially contaminated removable partial dentures were treated with each cleanser. Data were analyzed by Kruskal-Wallis followed by Dunn post hoc test or ANOVA followed by Tukey post hoc test (α= 0.05).

Results: None of the hygiene solutions reduced C. albicans biofilm. Efferdent and Corega Tabs promoted reduction of C. glabrata biofilm, while Steradent was favorable against S. aureus biofilm. For S. mutans, lower biofilm rates were observed after immersion in Polident for Partials and Steradent. The effervescent tablets showed good cleaning performance, removing an artificial layer with carbohydrates, proteins, and fats, however, they were not effective in removing aggregated mature biofilm.

Clinical significance: The different effervescent tablets presented favorable antimicrobial activity against C. glabrata, S. mutans and S. aureus on cobalt-chromium surfaces and showed cleaning capability. However, for an appropriate biofilm control, a complementary method should be evaluated since none of the peroxide-based solutions reduced C. albicans biofilms or substantially removed aggregated biofilm.

Purpose: To evaluate denture cleansing solutions regarding the surface roughness and color stability of two resilient liners with distinct optical characteristics used for the maximum recommended period of use.

Methods: The specimens of each resilient liner, transparent and white, were randomly distributed into groups (n= 15) of a daily 20-minute immersion simulation of 0.25%, 0.5% and 1% sodium hypochlorite (SH) and 4% acetic acid solutions. Surface roughness (Ra) and color stability (ΔE CIELab formula and NBS systems) were measured after 7, 14, 21, 30, 60, 90, 180, and 270 days. The factors of variations analyzed were material, solutions, and time of immersion. Statistical analysis used three-way ANOVA and Tukey tests (Ra), and repeated measure ANOVA (ΔE and NBS systems), P< 0.05.

Results: For Ra analysis, the variations occurred regardless of time and solution, as the white liner showed the greatest changes (P< 0.001). Regarding interactions between solution and time, in the period of 21 days until 270 days, Ra was equivalent for all solutions (P= 0.001). ΔE analysis showed a difference between solutions (P= 0.000) and interaction between time and solution (P= 0.000). For the transparent liner, the greatest changes were found for 1% SH after 60 days, however, at 270 days there was a color change equivalence with 0.5% SH, while 4% acetic acid solution showed intermediate values. For the white liner, 1% SH showed the highest color changes for all evaluated times, and the other evaluated solutions were similar after 270 days. For both resilient liners, 0.25% SH showed the smallest changes for the evaluated properties.

Clinical significance: The changes found were dependent on the concentration of the solution used, as well as the length of exposure to the solution. In addition, the white resilient liner showed to be less susceptible to color changes. For both resilient liners, 0.25% sodium hypochlorite showed the least changes for the evaluated properties.

Purpose: To evaluate the mechanical properties of two brands of bulk-fill resin composites placed in a single increment up to 4 mm thickness via a novel mechanical strength test and provide related explanations.

Methods: Light transmission (LT), translucency parameter (TP), color difference (ΔE), Vickers hardness (HV) of two bulk-fill resin composites (Filtek Bulk Fill Posterior, Tetric N-Ceram Bulk Fill) and two conventional resin composites (Z100, Spectrum TPH) were evaluated. A novel flexural strength (FS) test method was applied for bulk-fill resin composite to determine the FS value of the bottom composites at depths of 1, 2, 3, and 4 mm after 24 hours of aging treatment (3 months water storage and 15,000 thermal cycles). The conventional resin composites were also tested for FS and all the FS results were subjected to Weibull analysis. Degree of conversion (DC) in the bulk-fill resin composites, light-cured at depths of 1, 2, 3, and 4 mm and conventional resin composites at depths of 2 and 4 mm, were assessed by FTIR.

Results: Both bulk-fill resin composites showed higher light transmission and translucency than that of conventional ones at each of the same thicknesses (1, 2, 3, 4 mm), wherein their flexural strength was not affected by depth. The Weibull analysis suggested both bulk-fill resin composites achieved good reliability and structural integrity under each curing thickness. Vickers hardness was affected by the material type and thickness. Bulk-fill resin composites showed a decrease in degree of conversion between 1 mm and 4 mm, but both were over 55%.

Clinical significance: Filtek Bulk Fill Posterior, Tetric N-Ceram Bulk Fill achieved acceptable mechanical properties when cured at depths of up to 4 mm, which was beneficial from their optical and polymerized properties.