Micromorfologia superficial de materiais restauradores esteticos submetidos a diferentes processos de degradação

Orientador : Monica Campos SerraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: Na cavidade bucal, materiais restauradores estão sujeitos a diversos fenômenos de degradação, desencadeados por processos fisicos, químicos e mecânicos, que acometem a micromorfologia superficial das restaurações. Assim, este trabalho, composto por quatro artigos, teve como objetivos: 1) avaliar a micromorfologia superficial de materiais restauradores estéticos imersos em diferentes meios; 2) verificar a intluência do meio de armazenamento sobre a rugosidade superficial de materiais restauradores submetidos à escovação; 3) avaliar a rugosidade superficial de materiais estéticos ao longo da simulação de procedimentos de higienização, representados pela escovação, subseqüente a desafios ácidos; 4) analisar o efeito da aplicação de géis tluoretados na micromorfologia superficial de cimentos de ionômero de vidro modificados por resina e de resinas compostas modificadas por poliácidos. Com base nos protocolos experimentais adotados, concluiu-se que materiais restauradores estéticos apresentaram alterações micromorfológicas, quando submetidos a uma condição de alto desafio ácido. A degradação proporcionada por esse modelo, quando seguido pela escovação, desencadeou a um ionômero de vidro modificado por resina e a uma resina composta modificada por poli ácidos maior lisura superficial do que quando armazenados em água destilada e deionizada ou saliva artificial, enquanto a textura dos compósitos, conseqüente à escovação, não foi influenciada pelo meio de armazenamento. Ao longo dos ensaios de escovação, precedidos por ciclos de pH, a rugosidade superficial de resinas compostas e de resinas compostas modificadas por poliácidos apresentou-se inalterada. Aumento progressivo, intercalado por períodos de estabilização, foi observado na rugosidade superficial de um ionômero de vidro modificado por resina. Como resultado da aplicação de géis tluoretados, ionômeros de vidro modificados por resina e resinas compostas modificadas por poliácidos apresentaram comportamentos peculiaresAbstract: In the oral cavity, restorative materiaIs are subject to severa! Degradation phenomena provided by physical, chemical and mechanical processes, which may impair the surface micromorphology of restorations. This study, composed of four manuscripts, had the following objectives: I) to evaIuate the surface micromorphology of aesthetic restorative materiaIs immersed in different media; 2) to verify the influence of the storage medium on the surface roughness of restorative materiaIs subjected to brushing; 3) to evaluate the surface roughness of aesthetic materiaIs throughout brushing, in a highly acidic simulation; 4) to analyze the effect of fluoride gel applications on the surface micromorphoIogy of resin modified glass ionomers and polyacid-modified composite resins. Under the experimental protocols adopted, it was conc1uded that aesthetic restorative materiaIs demonstrated micromorphological damage when subjected to a highly acidic simulation. The degradation provided by this model, when followed by brushing, produced smoother surfaces in a resin modified glass ionomer and a polyacid-modified composite resin than when they were stored either in distilled-deionised water or in artificial saliva, whereas the texture of composites consequent to brushing were not influenced by the storage media. Throughout the brushing simulation preceded by pH-cyc1ing composite resins and polyacid-modified composite showed steady surface textures. A progressive increase in surface roughness, interspersed with periods of stabilization was observed for a resin-modified glass ionomer. As a result of fluoride gel applications both resin-modified glass ionomers and polyacid-modified composite resins showed erratic behaviorsMestradoDentísticaMestre em Clínica Odontológic

Comportamento de resinas compostas dentais diante de fenomenos tribologicos : influencia de aspectos microestruturais e de condições de contato

Orientador: Monica Campos SerraTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: A busca pelo aumento na longevidade de restaurações tem impulsionado estudos visando ao aprimoramento de propriedades de resinas compostas. Dentre os aspectos capazes de refinar o desempenho desses materiais, estão a maximização da resistência a processos de desgaste e de biodegradação. Este trabalho, composto por cinco artigos, teve por objetivos: (1) revisar os processos fenomenológicos e moduladores envolvidos em processos de desgaste de resinas compostas; (2) avaliar a influência de fatores microestruturais - tamanho e geometria de partículas de carga - no desgaste e grau de conversão de resinas compostas experimentais e sugerir a relação entre ambas variáveis de reposta; (3) verificar o efeito de condições de contato, proporcionadas por diferentes lubrificantes, no comportamento de uma resina composta no decorrer de ensaios de desgaste abrasivo; (4) correlacionar a rugosidade superficial, resultante do emprego de diferentes métodos de acabamento e polimento, com o desgaste abrasivo com três corpos de resinas compostas e (5) monitorar, através de um modelo in situ, o efeito de diferentes técnicas de acabamento e polimento na textura superficial ao longo do tempo de exposição intrabucal de resinas compostas. Com base nos protocolos experimentais adotados, concluiu-se que com o entendimento dos fenômenos envolvidos no desgaste houve o fornecimento de subsídios e identificação de aspectos capazes de contribuir para o refinamento da resistência ao desgaste de resinas compostas. Demonstrou-se que o tamanho e forma das partículas de carga modularam o desgaste de resinas compostas, sendo que a presença de partículas menores em determinados sistemas mono, bi ou trimodais causou redução na magnitude do desgaste, sem prejuízo ao grau de conversão de resinas compostas. Aparentemente, não houve qualquer relação entre a taxa de conversão de monômeros e o desgaste. Sob o ponto de vista das condições de contato, a interposição e a natureza de lubrificantes foram de grande importância em ensaios de desgaste abrasivo, sendo que um substituto salivar à base de mucina poderia ser considerado o lubrificante de escolha para estudos laboratoriais de desgaste. Ainda com relação às condições de contato, a textura superficial obtida através de diferentes técnicas de acabamento e polimento não se correlacionou com o subseqüente desgaste abrasivo de resinas compostas. No modelo in situ, na dependência da técnica de acabamento e polimento, constatou-se um aumento ou redução na rugosidade de resinas compostas ao longo de sua exposição ao ambiente bucalAbstract: The seeking for the improvement of the longevity of restorations has been directing studies toward refining the resin composites' properties. Of the aspects that contribute to this goal are resistance to wear processes and to biodegradation. This study, comprised of five manuscripts, was undertaken to: (1) review the phenomenological processes and modifiers related to wear of resin composites; (2) evaluate the role of microstructural factors - size and geometry of filler particles - on wear and degree of conversion of experimental composites, while suggesting the relationship between both response variables; (3) assess the effect of contact conditions provided by different lubricants on the behavior of a resin composite over abrasive wear simulations; (4) correlate the surface roughness attained by using different finishing and polishing methods with the subsequent three-body abrasive wear of composites and; (5) monitor, by means of an in situ model, the influence of different finishing and polishing techniques on the surface texture of composites over time of intraoral exposure. On the basis of the experimental protocols adopted herein, it was possible to conclude that the understanding of the wear phenomena provided insights into underlying processes and allowed for the identification of aspects capable of contributing to the refinement of the wear resistance of composites. It was demonstrated that the size and shape of filler particles modulated the wear of composites. Especifically, the presence of small filler particles in certain mono-, bi- or trimodal combinations yielded reduced wear magnitude, without compromising the degree of conversion of composites. Apparently, no relationship was found between degree of conversion and wear. From the standpoint of the contact conditions, the interposition and nature of lubricants played an important role on abrasive wear testings. The mucin-based artificial saliva may be considered the lubricant of choice for laboratory wear studies. Still in respect to the contact conditions, the surface texture attained with different finishing and polishing techniques did not correlate with the subsequent abrasive wear of composites. Under the in situ condition, depending on the finishing and polishing technique, smoothness of composites increased or decreased over time of intraoral exposureDoutoradoDentísticaDoutor em Clínica Odontológic

Viability of using enamel and dentin from bovine origin as a substitute for human counterparts in an intraoral erosion model

This study ascertained whether under dental erosion models that closely mimics the real-life situation enamel and root dentin from bovine origin would be reliable substitutes for human counterparts. Through a 2x2 crossover design, in a first trial, 14 volunteers wore a palatal device containing slabs of bovine and human enamel. Half of the participants ingested (4x daily, for 10 days) orange juice first, crossing over to mineral water, while the remainder received the reverse sequence. In a second trial, volunteers wore devices with slabs of bovine and human root dentin. Except for the duration of each intraoral phase, which lasted 2 rather 10 days, the experiment with root dentin run exactly as for enamel. Dental substrates were analyzed for surface microhardness. Two-way ANOVAs (α=0.05) indicated no difference between the microhardness values recorded for human and bovine enamel (p=0.1350), but bovine root dentin had lower microhardness compared to its human counterpart (p=0.0432). While bovine enamel can reliably substitute its human counterpart in in situ dental erosion models, bovine root dentin does not seem to be a viable alternative to the corresponding human tissue.Este estudo visou avaliar, sob um modelo de erosão dental que se aproxima da realidade clínica, se o esmalte e a dentina radicular bovinos seriam substitutos viáveis aos correspondentes substratos de origem humana. De acordo com um delineamento crossover 2x2, 14 voluntários utilizaram dispositivos palatinos contendo fragmentos de esmalte humano e bovino. Metade dos participantes ingeriu suco de laranja (4x/dia, por 10 dias) e, a seguir, alternou para a ingestão de água mineral, enquanto os demais voluntários receberam a seqüência reversa. Em um segundo experimento, os sujeitos da pesquisa fizeram uso do dispositivo palatino contendo fragmentos de dentina radicular bovina e humana. Exceto pela duração de cada uma das duas fases experimentais (2 ao invés de 10 dias), utilizou-se o mesmo protocolo empregado no estudo em que se comparou o esmalte. Os substratos dentais foram avaliados quanto a sua microdureza superficial. ANOVAs a dois critérios (α=0,05) não indicaram diferença entre os valores de microdureza observados para o esmalte humano e bovino (p=0,1350), porém a dentina radicular apresentou microdureza inferior à humana (p=0,0432). Enquanto o esmalte bovino é um substituto fidedigno do substrato humano em modelos in situ de erosão dental, a dentina radicular bovina não parece ser uma alternativa viável ao tecido humano correspondente.The authors are especially grateful for the valuable participation and cooperation of the volunteers. Thanks are also due to Patricia Marchi, for her technical assistance, and to the Ethylene Oxide Sterilization Center of the Clinical Hospital of the School of Medicine of Ribeirão Preto (USP), for sterilizing the dental slabs. The State of São Paulo Research Foundation (FAPESP, grant #05/01515-8) is acknowledged for providing financial assistance in the form of a scholarship to the first author. This research was partially funded by a grant from the First Projects Program (MCT/CNPq-FAPESP, grant #06/60356-0)

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

Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were sectioned into samples with area between 0.85 and 1.25 mm2 that were submitted to µTBS testing, using a universal testing machine (EMIC) at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests. RESULTS: For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p;0.05), or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>;0.05). Regarding fracture pattern, there was no statistical difference among groups (p=0.0713) and 56.3% of the fractures were adhesive. CONCLUSION: It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor

Effect of green tea extract on bonding durability of an etch-and-rinse adhesive system to caries-affected dentin

Objective Green tea extract has been advocated as a matrix metalloproteinase (MMP) inhibitor; however, its effect on bond durability to caries-affected dentin has never been reported. Thus, the aim of this in vitro study was to evaluate the effect of two MMP inhibitors (2% chlorhexidine and 2% green tea extract), applied after acid etching, on bond durability of an etch-and-rinse adhesive system to caries-affected dentin. Material and Methods Occlusal enamel was removed from third molars to expose the dentin surface, and the molars were submitted to a caries induction protocol for 15 days. After removal of infected dentin, specimens were conditioned with 37% phosphoric acid (15 seconds) and randomly divided into three groups, according to the type of dentin pretreatment (n=10): NT: no treatment; GT: 2% green tea extract; CLX: 2% chlorhexidine. The etch-and-rinse adhesive system (Adper™ Single Bond 2, 3M ESPE, St. Paul, MN, USA) was applied according to the manufacturer's instructions, and composite resin restorations were built on the dentin. After 24 hours, at 37°C, the resin-tooth blocks were sectioned perpendicularly to the adhesive interface in the form of sticks (0.8 mm2 of adhesive area) and randomly subdivided into two groups according to when they were to be submitted to microtensile bond strength (μTBS) testing: immediately or 6 months after storage in distilled water. Data were reported in MPa and submitted to two-way ANOVA for completely randomized blocks, followed by Tukey’s test (α=0.05). Results After 24 hours, there was no significant difference in the μTBS of the groups. After 6 months, the GT group had significantly higher μTBS values. Conclusion It was concluded that the application of 2% green tea extract was able to increase bond durability of the etch-and-rinse system to dentin. Neither the application of chlorhexidine nor non-treatment (NT - control) had any effect on bond strength after water storage

Influência da aplicação do laser de ND: yag na durabilidade de adesão de um sistema adesivo universal à dentina humana

Pesquisas sobre pré-tratamento da dentina têm sido desenvolvidas a fim de minimizar os efeitos da degradação da interface adesiva e aumentar a longevidade da adesão. A irradiação com laser Neodmiyum: ítrio-aliminum granada (Nd:YAG) promove alterações morfológicas e estruturais na dentina que podem favorecer a estabilidade da resistência de união ao longo do tempo. Este trabalho visou avaliar, in vitro, o efeito do uso do laser de Nd:YAG na resistência de união (RU), imediata e em longo prazo, bem como modo de falha (MF), de um sistema adesivo universal (SAU) à dentina humana, aplicado no método convencional e autocondicionante. Trinta e dois terceiros molares humanos hígidos tiveram suas porções oclusais removidas para exposição da dentina e foram aleatoriamente divididos em 4 grupos (n=8), de acordo com modo de aplicação do SAU (Single Bond Universal, 3M ESPE), autocondicionante ou convencional, e da irradiação da superfície com laser de Nd:YAG (100mJ/10Hz) ou não (controle). As superfícies de dentina foram restauradas com resina composta (FiltekTM Z350 XT, 3M ESPE). Após 24 hs, os blocos dentina-resina foram seccionados em amostras em forma de “palitos” (1mm2 de área adesiva), os quais foram aleatoriamente divididos conforme o tempo de armazenamento em água (AA) após restauração: 24 horas e seis meses. Os palitos foram submetidos ao teste de microtração em máquina universal de ensaio com velocidade de 0.5mm/min. A análise do MF foi realizada por meio de um esteromicroscópio (30x). Os resultados de RU (MPa) foram submetidos ao teste de ANOVA a três critérios (a= 0,05) e os dados de MF a estatística descritiva (%). Não houve interação tripla significativa entre os fatores em estudo (p = 0,603). A irradiação com Nd:YAG resultou em valores significativamente maiores de RU (p = 0,031), independente do modo de aplicação de SAU ou tempo de AA. RU foi estatisticamente semelhante quando SAU foi empregado no modo convencional ou autocondicionante (p < 0,001), tenha sido irradiada ou não a dentina, tanto no tempo 24 horas quanto após 6 meses de AA. A RU foi significativamente reduzida após 6 meses de armazenamento (p = 0,007), independentemente se a dentina foi ou não irradiada e da forma pela qual o sistema adesivo universal foi aplicado. Houve predomínio de falhas adesivas em todos os grupos. Conclui-se que o laser de Nd:YAG afetou positivamente a resistência de união do sistema adesivo universal, independente de seu modo de aplicação, à dentina. No entanto, sua aplicação à dentina não promoveu estabilidade da união ao longo dos 6 meses de armazenamento em água

Titanium dioxide nanotubes incorporated into bleaching agents: physicochemical characterization and enamel color change

Titanium dioxide nanotubes are nanostructures that can accelerate the oxidation reaction of bleaching procedures and promote a more effective whitening effect. Objective: This study evaluated physicochemical properties of bleaching agents incorporated with titanium dioxide (TiO2) nanotubes, and the effects on tooth color change at different periods. Methodology: 40 premolars were treated according to the following groups (n=10): CP - 10% carbamide peroxide (1 hour daily/21 days); CPN - CP incorporated into TiO2; HP - 40% hydrogen peroxide (three 40-minute sessions/7 days apart); HPN - HP incorporated into TiO2. Color shade was evaluated at five different periods (baseline, after 7, 14 and 21 days of bleaching, and 7 days after end of treatment) according to Vita Classical, CIELab and CIEDE2000 scales. Mean particle size (P), polydispersity (PO) and zeta potential (ZP) were evaluated using dynamic light scattering. Data on the different variables were analyzed by mixed model tests for measures repeated in time (ZP e L*), generalized linear models for measures repeated in time (P, PO, Vita Classical and b*), and Friedman and Mann-Whitney tests (a* and color change/ΔE and ΔE00). Results: CP and CPN presented higher P, higher PO and lower ZP than HP and HPN (p≤0.05). All groups showed a significant decrease in Vita Classical color scores after 7 days of bleaching (p<0.05), and HPN presented a greater significant reduction than the other groups. L* increased in TiO2 presence, in all groups, without any differences (p>0.05) in bleaching time. A significant reduction occurred in the a* and b* values for all the groups, and HPN presented lower a* and b* values (p<0.05) than CPN. ΔE was clinically noticeable after 7 days, in all groups, and all groups resulted in a perceptible color change according to ΔE00. Conclusion:TiO2 did not influence physicochemical properties of the bleaching agents. HPN presented more effective tooth bleaching than CP

Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were sectioned into samples with area between 0.85 and 1.25 mm(2) that were submitted to µTBS testing, using a universal testing machine (EMIC) at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests. RESULTS: For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p<0.05). No statistical difference between restorative systems was shown for Class I cavity model (p>0.05), or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05). Regarding fracture pattern, there was no statistical difference among groups (p=0.0713) and 56.3% of the fractures were adhesive. CONCLUSION: It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor