Avaliação da microdureza ao redor de restaurações de compósito confeccionadas com sistemas adesivos contendo fluoretos

The purpose of this study was to evaluate the microhardness of dental enamel around composite restorations bonded with fluoride-containing adhesive systems (FCAS), after thermo- and pH-cycling protocols. Standardized cylindrical cavities were prepared on enamel surfaces of 175 dental fragments, which were randomly assigned into seven experimental groups (n=25). Four groups used FCAS: Optibond Solo (OS); Prime&Bond 2.1 (PB); Syntac Sprint (SS) and Tenure Quick (TC). Other groups consisted of "Sandwich" technique restoration (STR) (glass ionomer liner + hydrophobic adhesive resin /restorative composite) or used Single Bond with (SB) or without (SBWC) cycling protocols. Adhesive systems were applied according to manufacturers' instructions and cavities were restored with a microfilled composite (Durafill VS). After finishing and polishing, all groups were submitted to 1,000 thermal cycles (5 ºC and 55 ºC) and to demineralization (pH 4.3) and remineralization (pH 7.0) cycling protocols, except for SBWC group. The Knoop microhardness of enamel surfaces were measured around restorations. Indentations were recorded at 150, 300 and 450-mm from the cavity wall. Data were analyzed by two-way ANOVA and Duncan's Test (a=0.05%). Means ± SD of enamel microhardness for the groups were (Kg/mm²): SBWC: 314.50 ± 55.93ª ; SB: 256.78 ± 62.66b; STR: 253.90 ± 83.6b; TQ: 243.93 ± 68.3b; OS: 227.97 ± 67.1c; PB: 213.30 ± 91.3d; SS: 208.73 ± 86.6d. Means ± SD of microhardness for the distances 150, 300, 450mm from the cavity wall were, respectively: 234.46 ± 77.81ª; 240.24 ± 85.12ª; 262.06 ± 79.46b. SBWC group, which was not submitted to thermo- and pH-cycling protocols, showed the highest enamel microhardness mean value and the FCAS resulted in lower microhardness values. At 450 mm from the cavity wall, the enamel microhardness increased significantly.O objetivo deste estudo foi avaliar a microdureza do esmalte dental ao redor de restaurações em compósito que utilizaram sistemas adesivos contendo fluoretos (FCAS), após tratamento dessas superfícies restauradas aos protocolos de ciclagem térmica e pH. Cavidades cilíndricas padronizadas foram preparadas em 175 superfícies de esmalte de fragmentos dentais, os quais foram aleatoriamente divididos em sete grupos (n=25). Quatro grupos utilizaram os FCAS: Optibond Solo (OS); Prime&Bond 2.1 (PB); Syntac Sprint (SS) e Tenure Quick (TC). Outros grupos consistiram em restaurações "Sandwich" (STR - ionômero de vidro como base + restauração em composíto) ou utilizaram Single Bond com (SB) ou sem (SBWC) ciclagens. Os sistemas adesivos foram aplicados segundo as instruções dos fabricantes e as cavidades restauradas com compósito microparticulado (Durafill VS). Após o acabamento e polimento, todos grupos foram submetidos a 1.000 ciclos térmicos (5 ºC e 55 ºC) e a um protocolo de ciclagem de pH (desmineralização-pH 4,3 e remineralização-pH 7,0), exceto para o grupo SBWC. A microdureza das superfícies de esmalte foi mensurada ao redor das restaurações. Indentações foram feitas nas distâncias de 100, 300 and 450-mm da parede cavitária. Os dados foram analisados pela ANOVA (2 fatores) and Teste de Duncan (5%). Os valores médios ± DP da microdureza do esmalte para os grupos foram (Kg/mm²): SBWC: 314,50 ± 55,93ª ; SB: 256,78 ± 62,66b; STR: 253,90 ± 83,6b; TQ: 243,93 ± 68,3b; OS: 227,97 ± 67,1c; PB: 213,30 ± 91,3d; SS: 208,73 ± 86,6d. As médias ± DP de microdureza para as distâncias 150, 300, 450 mm da parede cavitária foram, respectivamente: 234,46 ± 77,81ª; 240,24 ± 85,12ª; 262,06 ± 79,46b. O grupo SBWC que não foi submetido aos protocolos de ciclagem térmica e pH mostrou a maior média de microdureza do esmalte e os FCAS resultaram nos menores valores de microdureza. Na distância de 450 mm da parede cavitária, a microdureza apresentou aumento significativo

Obliteration of Dentinal Tubules by Desensitizing Agents Based on Silver Fluoride/Potassium Iodide or Pre-Reacted Glass Particles: An in Vitro Study

Objective: To evaluate the efficacy of desensitizing agents for the obliteration of dentinal tubules subjected or not to a simulated oral environment. Material and Methods: Dentinal discs (n=8) treated with Riva-Star (RS) or PRG-Barrier-Coat (PRG) were submitted (cycled) or not submitted (control) to erosive-abrasive-thermal cycles and evaluated using scanning electron microscopy/energy dispersive spectroscopic analysis. The variables analyzed were tubule obliteration and dentin surface chemical composition. Data were analyzed by non-parametric tests (p<0.05). Results: The cycled and control groups did not differ significantly for the responses in each material. The PRG control and cycled groups had fewer visible tubules and a higher proportion of totally obliterated tubules than the RS groups. The percentages of silver coverage were higher in the RS-control than in the RS-cycled. There was a significant inverse correlation between the presence of silver and non-obliterated tubules (R=-0.791; p<0.001). The percentages of carbon, aluminum, strontium, and potassium were significantly higher in the PRG-control and PRG-cycled compared to the RS control. The percentages of calcium, phosphorus, and silver were significantly higher in the RS compared to the PRG groups. PRG-control showed a higher percentage of boron than RS-control. Conclusion: PRG promoted greater tubule obliteration than SR. Simulated stress did not affect the obliterating effect of each agent. Greater silver coverage corresponded to a lower proportion of non-obliterated tubules in RS. Carbon, aluminum, strontium, boron, and potassium predominated in the dentin surface treated with PRG, while calcium, phosphorus, and silver prevailed in RS groups

Efeito cariostático de restaurações adesivas em superfícies radiculares: estudo in vitro

Dental materials that release fluoride have been shown to be effective in caries inhibition around restorations. Adhesive materials would also be effective in caries inhibition by sealing and protecting cavity margins from acidic demineralization. This in vitro study tested the hypothesis that composite restorations with a dentin adhesive system have a caries preventive effect similar to that of an adhesive material with fluoride - glass-ionomer cement - on root surfaces. Twenty roots from extracted sound third molars were embedded in polystyrene resin and ground flat. Standardized cavities were prepared in leveled root surfaces and randomly restored with (a) Chelon-Fil (Espe) or (b) Z100/SingleBond (3M). Baseline indentations were measured at 100, 200 and 300 mum from the occlusal margins of each restoration and the surface microhardness values were obtained using a Knoop diamond indenter. A 2.0 mm wide margin around the restorations was submitted to a pH-cycling model, at 37ºC. After that, surface microhardness was measured again, as it was before. The differences between baseline and final surface microhardness were considered for statistical analysis. The median values of differences were (a): -3.8; -0.3; -1.0; and (b): 3.3; 2.5; 1.7, for the distances of 100, 200 and 300 mum, respectively. The Kruskal-Wallis test did not show statistically significant difference between 100, 200 and 300 mum distances in each tested group. There was no difference between the studied materials at the distances of 200 and 300 mum. Chelon-Fil was statistically different from Z100/SingleBond, at 100 mum (pMateriais restauradores que liberam íons flúor e/ou promovem adesão à estrutura dental têm sido relacionados com a inibição do desenvolvimento de lesões de cárie adjacentes às restaurações. A hipótese testada neste estudo foi a de que o uso de resina composta/sistema adesivo tem efeito cariostático semelhante a um material adesivo que libera íons flúor - cimento de ionômero de vidro - sobre a superfície radicular adjacente às restaurações. Foram utilizadas 20 raízes de terceiros molares humanos extraídos, embutidas em resina de poliestireno e planificadas. Cavidades padronizadas foram preparadas e restauradas aleatoriamente com (a) Chelon-Fil (Espe) ou (b) Z100/SingleBond (3M). Valores iniciais (KHNi) de microdureza superficial Knoop da dentina foram obtidos a 100, 200 e 300 mim da margem oclusal das restaurações. Uma área de 2,0 mm ao redor da restauração foi delimitada e submetida à indução de cárie artificial. Obtiveram-se, então, os valores finais (KHNf) de microdureza, nas mesmas condições e localizações da leitura inicial. As diferenças entre KHNi e KHNf foram consideradas para a análise estatística. As medianas de KHNi - KHNf nas distâncias de 100, 200 e 300 mim foram para (a): -3,8; -0,3; -1,0; e para (b): 3,3; 2,5; 1,7. O teste de Kruskal-Wallis não evidenciou diferença significativa entre as distâncias dentro de cada grupo. Às distâncias de 200 e 300 mim, não houve diferença significativa entre os materiais avaliados. À distância de 100 mim, (a) diferiu significativamente de (b) (p < 0,05). Sob as condições deste estudo, o cimento de ionômero de vidro apresentou maior potencial cariostático que a resina composta com sistema adesivo dentinário

Caries inhibition around adhesive restorations in roots: in vitro study

Dental materials that release fluoride have been shown to be effective in caries inhibition around restorations. Adhesive materials would also be effective in caries inhibition by sealing and protecting cavity margins from acidic demineralization. This in vitro study tested the hypothesis that composite restorations with a dentin adhesive system have a caries preventive effect similar to that of an adhesive material with fluoride - glass-ionomer cement - on root surfaces. Twenty roots from extracted sound third molars were embedded in polystyrene resin and ground flat. Standardized cavities were prepared in leveled root surfaces and randomly restored with (a) Chelon-Fil (Espe) or (b) Z100/SingleBond (3M). Baseline indentations were measured at 100, 200 and 300 mum from the occlusal margins of each restoration and the surface microhardness values were obtained using a Knoop diamond indenter. A 2.0 mm wide margin around the restorations was submitted to a pH-cycling model, at 37ºC. After that, surface microhardness was measured again, as it was before. The differences between baseline and final surface microhardness were considered for statistical analysis. The median values of differences were (a): -3.8; -0.3; -1.0; and (b): 3.3; 2.5; 1.7, for the distances of 100, 200 and 300 mum, respectively. The Kruskal-Wallis test did not show statistically significant difference between 100, 200 and 300 mum distances in each tested group. There was no difference between the studied materials at the distances of 200 and 300 mum. Chelon-Fil was statistically different from Z100/SingleBond, at 100 mum (p<0.05). Under the studied conditions, the glass-ionomer cement had a higher caries preventive effect than the composite/dentin adhesive restorations.Materiais restauradores que liberam íons flúor e/ou promovem adesão à estrutura dental têm sido relacionados com a inibição do desenvolvimento de lesões de cárie adjacentes às restaurações. A hipótese testada neste estudo foi a de que o uso de resina composta/sistema adesivo tem efeito cariostático semelhante a um material adesivo que libera íons flúor - cimento de ionômero de vidro - sobre a superfície radicular adjacente às restaurações. Foram utilizadas 20 raízes de terceiros molares humanos extraídos, embutidas em resina de poliestireno e planificadas. Cavidades padronizadas foram preparadas e restauradas aleatoriamente com (a) Chelon-Fil (Espe) ou (b) Z100/SingleBond (3M). Valores iniciais (KHNi) de microdureza superficial Knoop da dentina foram obtidos a 100, 200 e 300 mim da margem oclusal das restaurações. Uma área de 2,0 mm ao redor da restauração foi delimitada e submetida à indução de cárie artificial. Obtiveram-se, então, os valores finais (KHNf) de microdureza, nas mesmas condições e localizações da leitura inicial. As diferenças entre KHNi e KHNf foram consideradas para a análise estatística. As medianas de KHNi - KHNf nas distâncias de 100, 200 e 300 mim foram para (a): -3,8; -0,3; -1,0; e para (b): 3,3; 2,5; 1,7. O teste de Kruskal-Wallis não evidenciou diferença significativa entre as distâncias dentro de cada grupo. Às distâncias de 200 e 300 mim, não houve diferença significativa entre os materiais avaliados. À distância de 100 mim, (a) diferiu significativamente de (b) (p < 0,05). Sob as condições deste estudo, o cimento de ionômero de vidro apresentou maior potencial cariostático que a resina composta com sistema adesivo dentinário.11311

Analysis of Bone-implant Interfacial Stress during Disocclusion in Complete Implant-supported Prosthesis: A Finite Element Study

Aim: Little is known about the biomechanical behavior of disocclusion patterns in implant-supported prostheses. Thus, the aim of the present study was to analyze the stresses generated at bone-implant interface during different patterns of disocclusion in an implant-supported lower complete denture without free distal ends using the three-dimensional (3-D) finite element method. Study Design: Finite element method. Methods: A 3-D model of a complete denture supported by five inter-foraminal implants and two distal was developed (CAE software Abaqus). A canine guide disocclusion (CG) was simulated applying a nodal load of 15 N at an angle of 45° on the canine tooth prosthesis, while to a bilateral balanced occlusion (BBO) a similar load pattern was applied at four distinct points, bilaterally. Linear elastic static analysis was used to compare the magnitude of maximum and minimum principal stresses at bone-implant interface for each simulation. Results: The disocclusion pattern generated during CG exhibited a greater stress concentration at the bone-implant interface of the distal implant on the working side. BBO showed a more homogeneous stress distribution pattern at the bone-implant interface of the two distal implants. Anterior implants showed lower stress concentration. Conclusions: Bilateral balanced occlusion (BBO) resulted in a more favorable stress distribution in this complete implant-supported prosthesis model

Obliteration of Dentinal Tubules by Desensitizing Agents Based on Silver Fluoride/Potassium Iodide or Pre-Reacted Glass Particles: An in Vitro Study

Objective: To evaluate the efficacy of desensitizing agents for the obliteration of dentinal tubules subjected or not to a simulated oral environment. Material and Methods: Dentinal discs (n=8) treated with Riva-Star (RS) or PRG-Barrier-Coat (PRG) were submitted (cycled) or not submitted (control) to erosive-abrasive-thermal cycles and evaluated using scanning electron microscopy/energy dispersive spectroscopic analysis. The variables analyzed were tubule obliteration and dentin surface chemical composition. Data were analyzed by non-parametric tests (p<0.05). Results: The cycled and control groups did not differ significantly for the responses in each material. The PRG control and cycled groups had fewer visible tubules and a higher proportion of totally obliterated tubules than the RS groups. The percentages of silver coverage were higher in the RS-control than in the RS-cycled. There was a significant inverse correlation between the presence of silver and non-obliterated tubules (R=-0.791; p<0.001). The percentages of carbon, aluminum, strontium, and potassium were significantly higher in the PRG-control and PRG-cycled compared to the RS control. The percentages of calcium, phosphorus, and silver were significantly higher in the RS compared to the PRG groups. PRG-control showed a higher percentage of boron than RS-control. Conclusion: PRG promoted greater tubule obliteration than SR. Simulated stress did not affect the obliterating effect of each agent. Greater silver coverage corresponded to a lower proportion of non-obliterated tubules in RS. Carbon, aluminum, strontium, boron, and potassium predominated in the dentin surface treated with PRG, while calcium, phosphorus, and silver prevailed in RS groups

Standard of disocclusion in complete dentures supported by implants without free distal ends: analysis by the finite elements method

OBJECTIVE: The occlusal patterns are key requirements for the clinical success of oral rehabilitation supported by implants. This study compared the stresses generated by the disocclusion in the canine guide occlusion (CGO) and bilateral balanced occlusion (BBO) on the implants and metallic infrastructure of a complete Brånemark protocol-type denture modified with the inclusion of one posterior short implant on each side. MATERIAL AND METHODS: A three-dimensional model simulated a mandible with seven titanium implants as pillars, five of them installed between the mental foramen and the two posterior implants, located at the midpoint of the occlusal surface of the first molar. A load of 15 N with an angle of 45º was applied to a tooth or distributed across three teeth to simulate the CGO or BBO, respectively. The commercial program ABAQUS(®) was used for the model development, before and after the processing of the data. The results were based on a linear static analysis and were used to compare the magnitude of the equivalent stress for each of the simulations. RESULTS: The results showed that the disocclusion in CGO generated higher stresses concentrated on the working side in the region of the short implant. In BBO, the stresses were less intense and more evenly distributed on the prosthesis. The maximum stress found in the simulation of the disocclusion in CGO was two times higher than that found in the simulation of the BBO. The point of maximum stress was located in the neck of the short implant on the working side. CONCLUSIONS: Under the conditions of this study, it was concluded that the BBO pattern was more suitable than CGO for the lower complete denture supported by implants without free distal ends

Efeito cariostático de restaurações adesivas em superfícies radiculares: estudo in vitro

Materiais restauradores que liberam íons flúor e/ou promovem adesão à estrutura dental têm sido relacionados com a inibição do desenvolvimento de lesões de cárie adjacentes às restaurações. A hipótese testada neste estudo foi a de que o uso de resina composta/sistema adesivo tem efeito cariostático semelhante a um material adesivo que libera íons flúor - cimento de ionômero de vidro - sobre a superfície radicular adjacente às restaurações. Foram utilizadas 20 raízes de terceiros molares humanos extraídos, embutidas em resina de poliestireno e planificadas. Cavidades padronizadas foram preparadas e restauradas aleatoriamente com (a) Chelon-Fil (Espe) ou (b) Z100/SingleBond (3M). Valores iniciais (KHNi) de microdureza superficial Knoop da dentina foram obtidos a 100, 200 e 300 mim da margem oclusal das restaurações. Uma área de 2,0 mm ao redor da restauração foi delimitada e submetida à indução de cárie artificial. Obtiveram-se, então, os valores finais (KHNf) de microdureza, nas mesmas condições e localizações da leitura inicial. As diferenças entre KHNi e KHNf foram consideradas para a análise estatística. As medianas de KHNi - KHNf nas distâncias de 100, 200 e 300 mim foram para (a): -3,8; -0,3; -1,0; e para (b): 3,3; 2,5; 1,7. O teste de Kruskal-Wallis não evidenciou diferença significativa entre as distâncias dentro de cada grupo. Às distâncias de 200 e 300 mim, não houve diferença significativa entre os materiais avaliados. À distância de 100 mim, (a) diferiu significativamente de (b) (p < 0,05). Sob as condições deste estudo, o cimento de ionômero de vidro apresentou maior potencial cariostático que a resina composta com sistema adesivo dentinário.Dental materials that release fluoride have been shown to be effective in caries inhibition around restorations. Adhesive materials would also be effective in caries inhibition by sealing and protecting cavity margins from acidic demineralization. This in vitro study tested the hypothesis that composite restorations with a dentin adhesive system have a caries preventive effect similar to that of an adhesive material with fluoride - glass-ionomer cement - on root surfaces. Twenty roots from extracted sound third molars were embedded in polystyrene resin and ground flat. Standardized cavities were prepared in leveled root surfaces and randomly restored with (a) Chelon-Fil (Espe) or (b) Z100/SingleBond (3M). Baseline indentations were measured at 100, 200 and 300 mum from the occlusal margins of each restoration and the surface microhardness values were obtained using a Knoop diamond indenter. A 2.0 mm wide margin around the restorations was submitted to a pH-cycling model, at 37ºC. After that, surface microhardness was measured again, as it was before. The differences between baseline and final surface microhardness were considered for statistical analysis. The median values of differences were (a): -3.8; -0.3; -1.0; and (b): 3.3; 2.5; 1.7, for the distances of 100, 200 and 300 mum, respectively. The Kruskal-Wallis test did not show statistically significant difference between 100, 200 and 300 mum distances in each tested group. There was no difference between the studied materials at the distances of 200 and 300 mum. Chelon-Fil was statistically different from Z100/SingleBond, at 100 mum (p<0.05). Under the studied conditions, the glass-ionomer cement had a higher caries preventive effect than the composite/dentin adhesive restorations

Cariostatic effect of fluoride-containing restorative systems associated with dentifrices on root dentin

Objective. The aim of this in vitro study was to evaluate the interaction between two sources of fluoride (restorative systems and dentifrices) in inhibiting artificial root caries development. Methods. One hundred and eighty tooth segments were embedded in polyester resin, and sanded flat. Cylindrical cavities 1.0 mm-deep and 1.5 mm-diameter were prepared in root dentin and randomly restored by fluoride-containing restorative systems: Ketac-fil/Espe (Ke), Fuji II LC/GC Corp (Fj), F2000/3M (F2), Surefil/Dentsply (Su) or a control: Filtek Z250/3M (Z2). Ten experimental groups were made to test the association among the five restorative systems and two dentifrices: with F - (Sensodyne Baking Soda) or without F- (Sensodyne Original) (n = 18). After surface polishing, a 1 mm-wide margin around the restorations was demarcated and initial dentin surface Knoop microhardness values (KHNi) were obtained. The specimens were submitted to a pH-cycling model, and to applications of slurries of dentifrice. Afterwards the final dentin surface Knoop microhardness values (KHNf) were measured. Results. The differences between KHNi and KHNf, and the covariate KHNi were considered by the ANCOVA and Tukey's test (α = 0.05). The interaction between restorative system and dentifrice was statistically significant (p = 0.0026). All restorative systems provided some protection against artificial caries challenge when associated with the fluoride-containing dentifrice treatment. The means (standard deviation) of reductions in Knoop hardness values for systems associated with the fluoride-containing dentifrice were: Ke: 40.0(1.02)a, Fj: 41.9(1.02)b, F2: 43.3(1.04)c, Su: 43.5(1.00)c, Z2: 44.0(1.02)c; and with the non-fluoride-containing dentifrice were: Ke: 42.9(1.02)a, Fj: 44.7(1.01)b, F2: 45.2(1.09)bc, Su: 46.0(0.99)c, Z2: 46.6(0.99)c (statistical differences were expressed by different letters). Conclusion. The cariostatic effect shown by the fluoride-containing dentifrice could enhance that shown by Ketac-fil and Fuji II LC, and could mask that shown by F2000. © 2002 Elsevier Science Ltd. All rights reserved