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STATEMENT OF PROBLEM: Although tapered and cylindrical implants have been widely used, a consensus on which macrogeometry offers better clinical performance is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the influence of different macrogeometries (tapered and cylindrical) on the clinical performance of dental implants. MATERIAL AND METHODS: The study was registered in the international prospective register of systematic reviews (PROSPERO) database (CRD42022347436). A search for clinical studies was conducted in 6 databases to identify randomized controlled clinical trials that evaluated the effectiveness of tapered and cylindrical implants placed in the maxilla or mandible of adult patients that had at least 1 clinical performance parameter as outcome. The risk of bias was evaluated using the revised Cochrane Risk-of-Bias Tool (RoB 2) tool. Meta-analyses on implant survival and success, marginal bone loss (MBL), implant stability (ISQ), and torque insertion (TI) were performed, with the certainty of evidence evaluated using the grading of recommendations, assessment, development, and evaluations (GRADE) checklist. RESULTS: Of the 18 included studies, 7 had a low risk, 6 had some concerns, and 5 had a high risk of bias. Meta-analyses of survival (RR 0.99 [0.97, 1.01]; P=.38; I2=0%), implant success (RR 1.06 [0.99, 1.13] P=.08 I2=0%), 1-month MBL (MD -0.11 [-0.33, 0.10] P=.31 I2=98%), 3 months MBL (MD -0.21 [-0.27, 0.16] P=.26 I2=98%), 6 months MBL (MD -0.29 [-0.60, 0.01] P=.06 I2=74%), 1-year MBL (MD 0.01 [-0.07, 0.09] P=.77 I2=98%) and after 2 years MBL (MD -0.04 [-0.14, 0.07] P=.52 I2=0%), ISQ at implant installation (MD 0.35 [-0.72, 1.42] P=.52 I2=0%), %), after 2 months (MD 0.90 [-1.08, 2.87] P=.37 I2=0%) and at 1 year (MD -0.02 [-1.07, 1.03] P=.97 I2=0%), and insertion torque (MD 3.10 [-1.71, 7.92] P=.21 I2=80%) were statistically similar. However, tapered implants showed higher ISQ than cylindrical implants after 3 months (MD 1.20 [0.39, 2.01] P=.004 I2=17%). The certainty of evidence for the analyzed parameters ranged from high to very low. CONCLUSIONS: Both macrogeometries present good clinical performance, with certainty of evidence ranging from high to very low. Tapered implants showed better secondary stability at 3 months after implant installation, but with low certainty of evidence.
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OBJECTIVES: The relative effect of pH and titratable acidity on tooth erosion remains unclear. We determined the effect of both properties on in vivo salivary pH recovery and on enamel and dentine early erosion in situ. METHODS: Solutions simulating acidic beverages with different pHs (2.5 or 3.5) and titratable acidities (0, 25, or 100 mM citric acid) were tested. In an in vivo study (n = 20 participants), the salivary pH was determined before, during, and up to 2 min after exposure to the tested solutions. In situ, 12 participants exposed enamel and root dentine slabs to the tested solutions simulating a beverage consumption; early erosion was assessed by percentage of surface hardness loss (%SHL). Groups were compared by ANOVA (p < 0.05). RESULTS: Saliva pH was lower after exposure to solutions at pH 2.5, irrespective of titratable acidity; pH recovery took longer for solutions with higher titratable acidities, irrespective of their pHs. In situ, the highest %SHL was observed for the solution with lower pH and higher titratable acidities. The addition of citric acid increased the %SHL by 2.5-3 times in enamel, and at least 5 times in dentine. CONCLUSIONS: Both pH and titratable acidity may play a role on the erosive potential of acidic beverages. CLINICAL RELEVANCE: Acidic beverages with lower pHs promote erosion by an initial acid etching of the surface; those with a higher titratable acidity slow down the salivary pH recovery. Both properties contribute to the overall erosive potential.
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Erosión de los Dientes , Ácidos , Bebidas , Ácido Cítrico , Esmalte Dental , Dentina , Humanos , Concentración de Iones de Hidrógeno , Erosión de los Dientes/inducido químicamenteRESUMEN
This study evaluated the probability of survival, failure mode, and stress distribution of narrow diameter implants (NDIs) with internal implant-abutment conical connection comprised of different taper angles and thread designs. Sixty-three NDIs (Ø 3.5 × 8.5 mm) were divided according to the taper angle (TA), internal diameter (ID), and trapezoidal thread design (TD) (n = 21/group), as follows: (a) 11.5°U (11.5° TA; ID: 2.5 mm; TD: dual threaded); (b) 11.5°S (11.5° TA; ID: 2.5 mm; TD: single threaded); (c) 16°S (16° TA; ID: 2.72 mm; TD: single threaded). They were subjected to step-stress accelerated life testing. The reliability and use-level probability Weibull curves were calculated at 50, 100, and 150 N for a mission of 100,000 cycles and the failure mode was analyzed using a scanning electron microscope. For finite element analysis the von-Mises stress (σvM ) was calculated for the abutment and implant. All groups showed high reliability (above 84%) and failures occurred predominantly in the abutment. In the FEA, 11.5°U showed higher σvM for the implant. All NDIs showed high reliability at clinically challenging loads. The system with greater taper angle showed lower σVm in the implant, and dual threaded implants showed a higher stress concentration in the implant and cortical bone.
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Implantes Dentales , Fenómenos Biomecánicos , Diseño de Implante Dental-Pilar , Análisis del Estrés Dental , Análisis de Elementos Finitos , Ensayo de Materiales , Probabilidad , Reproducibilidad de los Resultados , Estrés MecánicoRESUMEN
Biofilm fluoride reservoirs may be a source of fluoride to the fluid phase during a sugar challenge reducing tooth mineral loss. However, the evidence for that is conflicting and has not been studied in biofilms containing different fluoride levels. In order to test fluoride release from biofilms with distinct fluoride concentrations, biofilms were grown in situ exposed to a combination of placebo, calcium and fluoride rinses forming biofilms with no (fluoride-free rinses), low (fluoride-only rinses) or high (calcium followed by fluoride rinses) fluoride concentrations, and collected before and 5 min after a sucrose challenge. Rinsing with fluoride increased fluoride concentration in the biofilm (p < 0.05), mainly when a calcium pre-rinse was used before the fluoride (p < 0.05). However, after a sugar challenge, no significant increase in the biofilm fluid fluoride concentration was observed, even in the fluoride-rich biofilms (p > 0.05). Fluoride-rich biofilms do not release fluoride to the fluid phase during a sugar challenge.
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Biopelículas , Cariostáticos , Fluoruros , Calcio , Fluoruros/farmacocinética , Concentración de Iones de Hidrógeno , Minerales , SacarosaRESUMEN
OBJECTIVE: To evaluate the reliability and failure mode of zirconia-reinforced lithium silicate (ZLS) molar crowns of different thicknesses. METHODS: Monolithic ZLS molar crowns (0.5mm, 1.0mm, and 1.5 mm thickness) were modeled and milled using a CAD/CAM system (n = 21/group). Crowns were cemented on dentin-like epoxy resin replicas with a resin cement. The specimens were subjected to single load-to-failure test for step-stress profiles designing. Mouth-motion step-stress accelerated-life test was performed under water by sliding an indenter 0.7 mm lingually down on the distobuccal cusp until specimen fracture or suspension. Use level probability Weibull curves and reliability were calculated and plotted. Polarized-light optical microscope and scanning electron microscope (SEM) were used to characterize fracture patterns. RESULTS: Irrespective of crown thickness, beta (ß) values were higher than 1 and fatigue accelerated failures. While 0.5 mm ZLS crowns exhibited a significant reduction in the probability of survival at 200N, 300N and 400 N mission loads (69%, 41% and 19%, respectively), no significant difference was observed between 1.0 mm and 1.5 mm crowns. Both thicknesses have maintained the survivability at approximately 90%. Failure primarily comprised bulk fracture where radial cracks originated from the cementation surface beneath the indenter loading trail and propagated towards the cervical margin. SIGNIFICANCE: 1.5 mm- and 1.0 mm-thickness monolithic ZLS crowns presented higher probability of survival compared to 0.5 mm crowns. Bulk fracture was the chief failure mode, regardless of thickness.
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Porcelana Dental , Litio , Cerámica , Diseño Asistido por Computadora , Coronas , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Ensayo de Materiales , Reproducibilidad de los Resultados , Silicatos , CirconioRESUMEN
Streptococcus mutans are considered the most cariogenic bacteria, but it has been suggested that Candida albicans could increase their cariogenicity. However, the effect of this dual-species microorganisms' combination on dentine caries has not been experimentally evaluated. Biofilms of C. albicans, S. mutans and C. albicans + S. mutans (n = 12/biofilm) were grown in ultra-filtered tryptone yeast extract broth culture medium for 96 h on root dentine slabs of known surface hardness and exposed 8 times per day for 3 min to 10% sucrose. The medium was changed 2 times per day (after the 8 cariogenic challenges and after the overnight period of famine), and aliquots were analyzed to determinate the pH (indicator of biofilm acidogenicity). After 96 h, the biofilms were collected to determine the wet weight, colony-forming units, and the amounts of extracellular polysaccharides (soluble and insoluble). Dentine demineralization was assessed by surface hardness loss (% SHL). The architecture of the biofilms was analyzed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Data were analyzed by ANOVA followed by Tukey's test (α = 0.05). The dual-species C. albicans + S. mutans biofilm provoked higher % SHL on dentine (p < 0.05) than the S. mutans and C. albicans biofilm. This was supported by the results of biofilm acidogenicity and the amounts of soluble (6.4 ± 2.14 vs. 4.0 ± 0.94 and 1.9 ± 0.97, respectively) and insoluble extracellular polysaccharides (24.9 ± 9.22 vs. 18.9 ± 5.92 and 0.7 ± 0.48, respectively) (p < 0.05). The C. albicans biofilm alone presented low cariogenicity. The images by CLSM and TEM, respectively, suggest that the C. albicans + S. mutans biofilm is more voluminous than the S. mutans biofilm, and S. mutans cells interact with C. albicans throughout polysaccharides from the biofilm matrix. These findings show that C. albicans enhances the cariogenic potential of the S. mutans biofilm, increasing dentine demineralization.
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Biopelículas , Candida albicans/patogenicidad , Dentina/microbiología , Streptococcus mutans/patogenicidad , Desmineralización Dental , Animales , Bovinos , Humanos , Técnicas In VitroRESUMEN
OBJECTIVE: To characterize the mechanical properties of different coating methods of DLC (diamond-like carbon) onto dental implant abutment screws, and their effect on the probability of survival (reliability). METHODS: Seventy-five abutment screws were allocated into three groups according to the coating method: control (no coating); UMS - DLC applied through unbalanced magnetron sputtering; RFPA-DLC applied through radio frequency plasma-activated (n=25/group). Twelve screws (n=4) were used to determine the hardness and Young's modulus (YM). A 3D finite element model composed of titanium substrate, DLC-layer and a counterpart were constructed. The deformation (µm) and shear stress (MPa) were calculated. The remaining screws of each group were torqued into external hexagon abutments and subjected to step-stress accelerated life-testing (SSALT) (n=21/group). The probability Weibull curves and reliability (probability survival) were calculated considering the mission of 100, 150 and 200N at 50,000 and 100,000 cycles. RESULTS: DLC-coated experimental groups evidenced higher hardness than control (p<0.05). In silico analysis depicted that the higher the surface Young's modulus, the higher the shear stress. Control and RFPA showed ß<1, indicating that failures were attributed to materials strength; UMS showed ß>1 indicating that fatigue contributed to failure. High reliability was depicted at a mission of 100N. At 200N a significant decrease in reliability was detected for all groups (ranging from 39% to 66%). No significant difference was observed among groups regardless of mission. Screw fracture was the chief failure mode. SIGNIFICANCE: DLC-coating have been used to improve titanium's mechanical properties and increase the reliability of dental implant-supported restorations.
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Tornillos Óseos , Carbono/química , Materiales Biocompatibles Revestidos/química , Pilares Dentales , Diamante/química , Fenómenos Biomecánicos , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Módulo de Elasticidad , Dureza , Ensayo de Materiales , Reproducibilidad de los Resultados , Estrés Mecánico , Propiedades de Superficie , Titanio/químicaRESUMEN
STATEMENT OF PROBLEM: Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture. PURPOSE: The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture. MATERIAL AND METHODS: Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone. RESULTS: In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone. CONCLUSIONS: A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the prosthesis and could minimize the incidence of fracture.
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Implantes Dentales de Diente Único , Prótesis Dental de Soporte Implantado , Prótesis de Recubrimiento , Aleaciones de Cromo/química , Diseño Asistido por Computadora , Aleaciones Dentales/química , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Diseño de Dentadura , Retención de Dentadura , Análisis de Elementos Finitos , Humanos , MandíbulaRESUMEN
STATEMENT OF PROBLEM: Which post-and-core combination will best improve the performance of extensively damaged endodontically treated incisors without a ferrule is still unclear. PURPOSE: The purpose of this in vitro study was to investigate the restoration of extensively damaged endodontically treated incisors without a ferrule using glass-ceramic crowns bonded to various composite resin foundation restorations and 2 types of posts. MATERIAL AND METHODS: Sixty decoronated endodontically treated bovine incisors without a ferrule were divided into 4 groups and restored with various post-and-core foundation restorations. NfPfB=no-ferrule (Nf) with glass-fiber post (Pf) and bulk-fill resin foundation restoration (B); NfPfP=no-ferrule (Nf) with glass-fiber post (Pf) and dual-polymerized composite resin core foundation restoration (P); NfPt=no-ferrule (Nf) with titanium post (Pt) and resin core foundation restoration; and NfPtB=no-ferrule (Nf) with titanium post (Pt) and bulk-fill resin core foundation restoration (B). Two additional groups from previously published data from the same authors (FPf=2mm of ferrule (F) and glass-fiber post (Pf) and composite resin core foundation restoration; and NfPf=no-ferrule (Nf) with glass-fiber post (Pf) and composite resin core foundation restoration), which were tested concomitantly and using the same experimental arrangement, were included for comparison. All teeth were prepared to receive bonded glass-ceramic crowns luted with dual-polymerized resin cement and were subjected to accelerated fatigue testing under submerged conditions at room temperature. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees with a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied every 15000 cycles. The specimens were loaded until failure or to a maximum of 1000 N (140000 cycles). The 6 groups (4 groups from the present study and 2 groups from the previously published study) were compared using the Kaplan-Meier survival analysis (log-rank post hoc test at α=.05 for pairwise comparisons). RESULTS: None of the tested specimen withstood all 140 000 cycles. All specimens without a ferrule were affected by an initial failure phenomenon (wide gap at the lingual margin between the core foundation restoration/crown assembly and the root). NfPfP, NfPt, and NfPtB had similar survival (29649 to 30987 mean cycles until initial failure). NfPfB outperformed NfPt and NfPtB. None of the post-and-core foundation restoration materials were able to match the performance of the ferrule group FPf (72667 cycles). In all groups, 100% of failures were catastrophic. CONCLUSIONS: The survival of extensively damaged endodontically treated incisors without a ferrule was slightly improved by the use of a fiber post with a bulk-fill composite resin core foundation restoration. However, none of the post-and-core techniques was able to compensate for the absence of a ferrule. The presence of the posts always adversely affected the failure mode.
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Coronas , Incisivo , Técnica de Perno Muñón , Diente no Vital/rehabilitación , Animales , Bovinos , Cerámica/química , Resinas Compuestas/química , Materiales Dentales/química , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Técnicas In Vitro , Titanio/químicaRESUMEN
AIM: This study aimed to evaluate the influence of surface free energy (SFE) of denture base and liner materials on Candida albicans biofilm development. METHODS: Discs were fabricated using poly(methyl methacrylate) acrylic resin and poly(ethyl methacrylate) denture liner, according to the manufacturers' instructions. For SFE test, discs were pellicle-coated with saliva alone, saliva + blood plasma, or blood plasma alone. Candida albicans biofilms were allowed to form on pellicle-coated discs for 48 h. Biofilms were evaluated for cell counts, metabolic activity, and structural characteristics at adhesion phase (after 1.5 h of development) and at biofilm maturity (after 48 h of development). Data were analyzed by anova and Tukey tests using a significance level of 5%. RESULTS: Saliva + blood plasma pellicles had a higher SFE compared to pellicles of saliva or blood plasma alone (P < 0.001). Differences in SFE by pellicle-coating did not affect the cell counts, metabolic activity, or structure at the adhesion phase (P > 0.05). In contrast, the presence of blood plasma resulted in higher cell counts, biovolume, and thickness of mature biofilms on both materials (P < 0.001). CONCLUSIONS: Increases in SFE from pellicle-coating leads to robust mature C. albicans biofilms on both denture materials.
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Biopelículas , Candida albicans/fisiología , Materiales Dentales/química , Bases para Dentadura/microbiología , Alineadores Dentales/microbiología , Candida albicans/citología , Recuento de Colonia Microbiana , Película Dental/microbiología , Humanos , Ensayo de Materiales , Metilmetacrilatos/química , Microscopía Confocal , Plasma , Polimetil Metacrilato/química , Distribución Aleatoria , Propiedades de Superficie , Tensión SuperficialRESUMEN
AIM: Confocal laser-scanning microscopy (CLSM) was carried out to investigate the exopolysaccharide matrix of Candida albicans (C. albicans) biofilms developed on denture material under dietary carbohydrate exposure. METHODS: Biofilms were developed on poly(methyl methacrylate) discs in culture media without (control) or with supplementation by glucose or sucrose for 72 h. For the CLSM analysis, biofilms were labeled with concanavalin A (ConA) during its development. Afterwards, biofilms were also labeled with SYTO-9. To confirm the results, the matrix was investigated by the phenol-sulfuric method. Data were analyzed by anova, followed by Tukey's test, with the level of significance set at 5%. RESULTS: The use of ConA during biofilm development provided effective labeling of the exopolysaccharide matrix. The exposure to sucrose resulted in biofilms with the highest exopolysaccharide matrix biovolume (P < 0.05). The characterization obtained by CLSM was confirmed by the phenol-sulfuric method. CONCLUSION: Confocal laser-scanning microscopy was found to be an effective tool for investigating the exopolysaccharide matrix of C. albicans biofilms, and exposure to sucrose resulted in increased matrix production.
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Biopelículas , Candida albicans/ultraestructura , Polisacáridos Fúngicos/ultraestructura , Candida albicans/química , Candida albicans/metabolismo , Concanavalina A , Medios de Cultivo , Materiales Dentales/química , Polisacáridos Fúngicos/análisis , Glucosa/metabolismo , Humanos , Microscopía Confocal/métodos , Compuestos Orgánicos , Polimetil Metacrilato/química , Distribución Aleatoria , Saliva/microbiología , Coloración y Etiquetado , Sacarosa/metabolismo , Propiedades de SuperficieRESUMEN
AIM: The objective of the present study was to determine if blood plasma proteins could change the proteome of the acquired denture pellicle by label-free quantitative proteomics. As pellicle proteome modulates the interaction between substrates and Candida cells, we investigated its effect on the surface free energy (SFE) of the coated resin and on Candida albicans phospholipase and aspartyl proteinase activities. METHODS: Poly(methylmethacrylate) discs were exposed to saliva (control) or saliva enriched with blood plasma (experimental group). The pellicle proteome was analyzed by mass spectrometry coupled with liquid chromatography. SFE was determined by acid-base technique. After biofilm formation, phospholipase and proteinase activities were determined accordingly to classic plate methods. Data were analyzed by two-way anova and Tukey test (P < 0.05). RESULTS: α-Amylase, cystatins, mucins, and host-immune system proteins were the main proteins identified in the control group. Fibrinogen and albumin were observed only in the experimental group. Coated discs of the experimental group presented an increased SFE (P < 0.05). For both enzymes tested, the experimental group showed higher proteolytic activity (P < 0.001). CONCLUSION: Blood plasma changes the proteome of the acquired denture pellicle, increasing surface free energy and the activity of Candida albicans phospholipase and aspartyl proteinase.
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Proteasas de Ácido Aspártico/análisis , Proteínas Sanguíneas/fisiología , Candida albicans/enzimología , Película Dental/fisiología , Bases para Dentadura , Fosfolipasas/análisis , Polimetil Metacrilato/química , Adulto , Biopelículas , Proteínas Sanguíneas/análisis , Cromatografía Liquida/métodos , Cistatinas/análisis , Película Dental/química , Femenino , Fibrinógeno/análisis , Humanos , Inmunoproteínas/análisis , Técnicas In Vitro , Masculino , Mucinas/análisis , Proteoma/metabolismo , Distribución Aleatoria , Albúmina Sérica/análisis , Tensión Superficial , Espectrometría de Masas en Tándem/métodos , alfa-Amilasas/análisisRESUMEN
BACKGROUND: The microwave energy is an efficient disinfection method; however, it can generate high temperatures that can result in distortion of the dentures. OBJECTIVES: To evaluate whether the addition of an enzymatic cleanser to microwave disinfection regimen would disinfect dentures with shorter irradiation time. MATERIALS AND METHODS: Seven resin discs colonized with Candida albicans biofilm were placed on the palatal surface of sterile dentures to be randomly assigned to the following treatments: immersion in distilled water for 3 min with 0 (DW), 1 (DW + M1), 2 (DW + M2), or 3 min (DW + M3) of microwave irradiation; or immersion in denture cleanser for 3 min with 0 (DC), 1 (DC + M1), 2 (DC + M2) or 3 min (DC + M3) of irradiation. After the treatments, the viable cells were counted by a blinded examiner. The temperature was measured immediately after irradiation. The data were analyzed by ANOVA and Tukey post hoc tests (α = 0.05). RESULTS: No viable cells were found after DC + M2, DC + M3, and DW + M3 treatments, of which DC + M2 achieved the lowest temperature. No significant difference was found between the effectiveness of DW, DW + M1 and DC treatments (p > 0.05). CONCLUSION: Within the limits of this study, the association of a denture cleanser and microwave energy is efficient to disinfect dentures in lower irradiation time and temperature.
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Desinfectantes Dentales/uso terapéutico , Limpiadores de Dentadura/uso terapéutico , Dentaduras , Desinfección/métodos , Microondas/uso terapéutico , Resinas Acrílicas/química , Resinas Acrílicas/efectos de la radiación , Biopelículas/efectos de los fármacos , Biopelículas/efectos de la radiación , Candida albicans/efectos de los fármacos , Candida albicans/efectos de la radiación , Recuento de Colonia Microbiana , Calor , Humanos , Ensayo de Materiales , Viabilidad Microbiana/efectos de los fármacos , Viabilidad Microbiana/efectos de la radiación , Polimetil Metacrilato/química , Polimetil Metacrilato/efectos de la radiación , Propiedades de Superficie , Factores de Tiempo , Agua/químicaRESUMEN
PURPOSE: The objective of this study was to evaluate the effect of different immersion times in denture cleansers on surface roughness (SR) of two resilient denture liners (RDL) after the cleanliness of Candida albicans biofilm. METHODS: Poly(methyl methacrylate) (PMMA) resin discs (10x1.5 mm) were relined with a 1.5 mm layer of RDL (PMMA or silicone-based). The initial SR of each specimen was measured and C. albicans biofilm was developed for 48 h. Subsequently, the discs were randomly assigned for one of four cleansing treatments (n=8): two alkaline peroxide (soaking for 3 or 15 min), 0.5 percent sodium hypochlorite (10 min) or distilled water as control (15 min). After the treatments, the SR was measured again. Data were analyzed by ANOVA and the Tukey post-hoc test (α=0.05) RESULTS: No differences were found between the cleansing treatments evaluated (P>0.05). The PMMA-based liner exhibited higher SR than silicon-based (P<0.001); however, both liners showed higher SR after the reatments compared with the baseline values (P<0.001). CONCLUSION: Within limitations of this study, it can be concluded that the surface roughness of RDL increased after the immersion in denture cleansers, independently of the time of immersion.
OBJETIVO: O objetivo deste estudo foi avaliar o efeito de diferentes tempos de imersão em limpadores químicos sobre a rugosidade de superfície ( RS)de reembasadores resilientes após a simulação da limpeza de biofilmes de Candida albicans. METODOLOGIA: Discos (10x1,5 mm) de poli(metilmetacrilato) (PMMA) foram cobertos com uma camada de 1,5 mm de reembasador resiliente (a base de PMMA ou silicone). A RS inicial de cada espécime foi mensurada e biofilmes de C. albicans desenvolvidos por 48 h. Em seguida, os espécimes foram submetidos aleatoriamente a um dos tratamentos (n=8): duas soluções alcalinas a base de peróxido (imersão por 3 ou 15 min), hipoclorito de sódio a 0.5 por cento (10 min) ou água destilada como grupo controle (15 min). Após o tratamento, a RS foi mensurada novamente. Os resultados foram analisados por ANOVA e teste Tukey (α=0,05). RESULTADOS: Não houve diferença estatística entre os tratamentos (P>0,05). O reembasador a base de PMMA apresentou maior RS que os de silicone (P<0,001); entretanto, ambos apresentaram um aumento da RS após os tratamentos (P<0,001). CONCLUSÃO: Dentro das limitações deste estudo, conclui-se que a RS dos reembasadores resilientes aumenta após a imersão em limpadores químicos, independentemente do tempo de imersão.
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Desinfección , Limpiadores de Dentadura/efectos adversos , Alineadores Dentales , Propiedades de SuperficieRESUMEN
Because low-fluoride toothpaste (500 p.p.m. F) has not clearly been shown to be effective for controlling caries in caries-active children, this experimental in situ study was conducted to evaluate whether its effect, when compared with a conventional toothpaste (1,000-1,500 p.p.m. F), would depend on the cariogenic challenge. During four phases of 14 d each, 14 volunteers used 500 or 1,100 p.p.m. F toothpaste and wore palatal appliances containing deciduous enamel slabs, on which biofilm was accumulated and exposed to 20% sucrose solution at frequencies increasing from two to eight times per day. The F concentration was determined in the biofilm formed, and enamel demineralization was assessed by surface hardness loss (% SHL) and integrated area of hardness x lesion depth (DeltaS). The F uptake by enamel was also determined. Fluoride in biofilm fluid and solids was statistically higher when conventional F toothpaste was used. The toothpastes did not differ statistically in terms of % SHL, DeltaS, and F in enamel, but only the conventional F toothpaste significantly reduced caries-lesion progression according to the frequency of sucrose exposure. The findings suggest that the high-F availability in biofilm, resulting from the use of conventional toothpaste compared with low-F toothpaste, may be important for reducing caries-lesion progression in conjunction with a high frequency of sucrose exposure.
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Biopelículas , Cariogénicos/administración & dosificación , Cariostáticos/uso terapéutico , Esmalte Dental/patología , Sacarosa en la Dieta/administración & dosificación , Fluoruros/uso terapéutico , Desmineralización Dental/etiología , Diente Primario/patología , Pastas de Dientes/uso terapéutico , Adolescente , Adulto , Disponibilidad Biológica , Cariogénicos/efectos adversos , Cariostáticos/análisis , Cariostáticos/farmacocinética , Estudios Cruzados , Caries Dental/etiología , Caries Dental/microbiología , Caries Dental/prevención & control , Esmalte Dental/metabolismo , Placa Dental/metabolismo , Placa Dental/microbiología , Sacarosa en la Dieta/efectos adversos , Progresión de la Enfermedad , Método Doble Ciego , Fluoruros/análisis , Fluoruros/farmacocinética , Dureza , Humanos , Factores de Tiempo , Desmineralización Dental/microbiología , Desmineralización Dental/prevención & control , Cepillado Dental , Pastas de Dientes/análisis , Adulto JovenRESUMEN
PURPOSE: Clinicians are still confused about the choice of repair method, which depends on factors such as the length of time required for processing, the mechanical strength of the repaired material, and the effect of stress concentration in the acrylic resins before the repair. The aim was to determine the impact and flexural strength characteristics, such as stress at yield, Young's modulus, and displacement at yield of denture base resins fractured and repaired by three methods using heat-, auto-, and visible light-polymerized acrylic resins. MATERIAL AND METHODS: For impact and flexural strength tests, 18 rectangular specimens measuring 50 x 6 x 4 mm(3) and 64 x 10 x 3.3 mm(3), respectively, were processed using Impact 2000, Lucitone 550, Impact 1500, and QC-20 acrylic resins. Fracture tests were performed according to ISO1567:1999. Afterward, all fractured specimens were stored in distilled water at 37 degrees C for 7 days, and then repaired with (1) the same acrylic resin used for specimen fabrication (n = 6), (2) an autopolymerized acrylic resin (TruRepair, n = 6), and (3) a visible light acrylic resin (Versyo.com, n = 6). The repaired specimens were again submitted to the same fracture tests, and the failures were classified as adhesive or cohesive. Data from all mechanical tests after repair by the different methods were submitted to two-way ANOVA, and mean values were compared by the Tukey test. RESULTS: All acrylic resins showed adhesive fractures after impact and flexural strength tests. Differences (p < 0.05) were found among repair methods for all acrylic resins studied, with the exception of displacement at yield, which showed similar values for repairs with auto- and visible light-polymerized acrylic resins. The highest values for impact strength, stress, and displacement at yield were obtained when the repair was made with the same resin the specimen was made of. CONCLUSION: Denture base acrylic resins repaired with the same resin they were made of showed greater fracture strength.
Asunto(s)
Resinas Acrílicas/química , Recubrimiento Dental Adhesivo/métodos , Materiales Dentales/química , Bases para Dentadura , Reparación de la Dentadura/métodos , Resinas Acrílicas/efectos de la radiación , Análisis de Varianza , Recubrimiento Dental Adhesivo/instrumentación , Materiales Dentales/efectos de la radiación , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Reparación de la Dentadura/instrumentación , Elasticidad , Humanos , Docilidad , Estrés MecánicoRESUMEN
Since the anticaries effect of a dentifrice with low fluoride concentration and low pH is unknown, the aim of the present study was to evaluate in situ the enamel remineralizing ability of this type of formulation. A double-blind crossover design employing 3 phases of 45 days was conducted. Six adult volunteers wore palatal devices containing 6 previously demineralized human dental enamel slabs, which were subjected 3 times a day to one of the following treatments: non-fluoridated dentifrice (negative control); dentifrice containing 1, 100 microg F/g, pH 7.0 (positive control); dentifrice containing 550 microg F/g, pH 5.5 (experimental). At the end of each phase, enamel remineralization was assessed in terms of cross-sectional microhardness, and loosely as well as firmly bound fluoride formation was determined on the enamel surface. Fluoridated dentifrices were more effective than the negative control in forming loosely and firmly bound fluoride on enamel (P < 0.05). However, the positive control formed more loosely bound fluoride than the other treatments (P < 0.05). Microhardness analysis showed that the fluoridated dentifrices were more effective than the negative control (P < 0.05) in remineralizing dental enamel, although no statistically significant difference was observed between them. Thus, the experimental dentifrice was shown to be effective in remineralizing dental enamel, and this may be attributable to its ability to form firmly bound fluoride on enamel.
Asunto(s)
Cariostáticos/administración & dosificación , Cariostáticos/farmacocinética , Esmalte Dental/metabolismo , Dentífricos/química , Fluoruros/administración & dosificación , Fluoruros/farmacocinética , Remineralización Dental/métodos , Adulto , Cariostáticos/uso terapéutico , Estudios Cruzados , Caries Dental/tratamiento farmacológico , Dentífricos/uso terapéutico , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Fluoruros/análisis , Dureza , Humanos , Concentración de Iones de Hidrógeno , Electrodos de Iones Selectos , Fluoruro de Sodio/uso terapéuticoRESUMEN
In situ dental biofilm composition under sugar exposure is well known, but sugar effect on the genotypic diversity of S. mutans in dental biofilm has not been explored. This study evaluated S. mutans genotypic diversity in dental biofilm formed in situ under frequent exposure to sucrose and its monosaccharide constituents (glucose and fructose). Saliva of 7 volunteers was collected for isolation of S. mutans and the same volunteers wore intraoral palatal appliances, containing enamel slabs, which were submitted to the following treatments: distilled and deionized water (negative control), 10% glucose + 10% fructose (fermentable carbohydrates) solution or 20% sucrose (fermentable and EPS inductor) solution, 8x/day. After 3, 7 and 14 days, the biofilms were collected and S. mutans colonies were isolated. Arbitrarily primed polymerase chain reaction (AP-PCR) of S. mutans showed that salivary genotypes were also detected in almost all biofilm samples, independently of the treatment, and seemed to reflect those genotypes present at higher proportion in biofilms. In addition to the salivary genotypes, others were found in biofilms but in lower proportions and were distinct among treatment. The data suggest that the in situ model seems to be useful to evaluate genotypic diversity of S. mutans, but, under the tested conditions, it was not possible to clearly show that specific genotypes were selected in the biofilm due to the stress induced by sucrose metabolism or simple fermentation of its monosaccharides.
Asunto(s)
Biopelículas/crecimiento & desarrollo , Carbohidratos de la Dieta/metabolismo , Boca/microbiología , Streptococcus mutans/crecimiento & desarrollo , Sacarosa/metabolismo , Técnicas de Tipificación Bacteriana , Recuento de Colonia Microbiana , Estudios Cruzados , ADN Bacteriano/análisis , Esmalte Dental/microbiología , Método Doble Ciego , Variación Genética , Genotipo , Humanos , Monosacáridos/metabolismo , Valores de Referencia , Especificidad de la Especie , Streptococcus mutans/genética , Streptococcus mutans/metabolismo , Estrés FisiológicoRESUMEN
This study evaluated the internal adaptation, porosity, transverse and impact strength of three denture base polymers: (1) conventional heat-polymerized, (2) microwave-polymerized, and (3) injection-molded resins. Internal adaptation was measured by weighing a vinyl polysiloxane film reproducing the gap between the denture base and the metallic master model of an edentulous maxilla. The measurements were performed immediately after finishing and after 30-day storage in water. Porosity was evaluated by weighing each specimen in air and in water using an analytical scale balance. Transverse strength test (three-point bending test) was performed using a universal machine under axial load, at a crosshead speed of 5 mm/min. Impact strength test (Charpy's test) was performed with a 40 kJ/cm load. Data were analyzed by ANOVA and Tukey test (alpha = 0.05). Internal adaptation, porosity, transverse and impact strength varied according to the type of acrylic resin and the processing technique. The injection-molded resin showed better internal adaptation compared with the conventional heat-polymerized and the microwave-polymerized resins, particularly after 30 days, but there was no relevant improvement of porosity, transverse and impact strength.
Asunto(s)
Resinas Acrílicas/química , Bases para Dentadura , Ensayo de Materiales , Metacrilatos/química , Resinas Acrílicas/síntesis química , Mecánica , Metacrilatos/síntesis química , Polímeros/síntesis química , Polímeros/química , PorosidadRESUMEN
In situ dental biofilm composition under sugar exposure is well known, but sugar effect on the genotypic diversity of S. mutans in dental biofilm has not been explored. This study evaluated S. mutans genotypic diversity in dental biofilm formed in situ under frequent exposure to sucrose and its monosaccharide constituents (glucose and fructose). Saliva of 7 volunteers was collected for isolation of S. mutans and the same volunteers wore intraoral palatal appliances, containing enamel slabs, which were submitted to the following treatments: distilled and deionized water (negative control), 10 percent glucose + 10 percent fructose (fermentable carbohydrates) solution or 20 percent sucrose (fermentable and EPS inductor) solution, 8x/day. After 3, 7 and 14 days, the biofilms were colleted and S. mutans colonies were isolated. Arbitrarily primed polymerase chain reaction (AP-PCR) of S. mutans showed that salivary genotypes were also detected in almost all biofilm samples, independently of the treatment, and seemed to reflect those genotypes present at higher proportion in biofilms. In addition to the salivary genotypes, others were found in biofilms but in lower proportions and were distinct among treatment. The data suggest that the in situ model seems to be useful to evaluate genotypic diversity of S. mutans, but, under the tested conditions, it was not possible to clearly show that specific genotypes were selected in the biofilm due to the stress induced by sucrose metabolism or simple fermentation of its monosaccharides.
A composição do biofilme dental in situ exposto a açúcares é bem conhecida, mas o efeito dos açúcares na diversidade genotípica de S. mutans no biofilme dental ainda não foi explorada. Este estudo avaliou a diversidade genotípica de S. mutans no biofilme dental formado in situ sob frequente exposição à sacarose e seus monossacarídeos constituintes (glicose e frutose). Primeiramente, saliva de voluntários foi coletada para isolamento de S. mutans e os mesmos voluntários usaram um dispositivo intraoral palatino, contendo blocos de esmalte, que foram submetidos 8x/dia aos seguintes tratamentos: água destilada e deionizada (controle negativo), solução de glicose 10 por cento + frutose 10 por cento (carboidratos fermentáveis) e solução de sacarose 20 por cento (fermentável e indutor de PEC). Após 3, 7 e 14 dias, os biofilmes foram coletados e colônias de S. mutans foram isoladas. A técnica de reação em cadeia de polimerase usando primers arbitrários (AP-PCR) demonstrou que o genótipo salivar foi detectado em quase todas as amostras de biofilme, independente do tratamento, e parece refletir aqueles genótipos presentes em maiores proporções no biofilme. Além do genótipo salivar, outros foram encontrados nos biofilmes, mas em uma menor proporção e foram distintos entre os tratamentos. Os dados sugerem que o modelo in situ é útil para a avaliação da diversidade genotípica de S. mutans. Porém, nas condições do presente estudo, não foi possível demonstrar que genótipos específicos foram detectados no biofilme devido ao estresse induzido pelo metabolismo da sacarose ou fermentação de seus monossacarídeos.