RESUMO

O objetivo desse estudo foi analisar, por meio do Método de Elementos Finitos, a distribuição de tensões na estrutura dentária, no ligamento periodontal (LP) e no osso alveolar em um modelo tridimensional do canino (23), primeiro (24) e segundo pré-molares superiores (25) submetidos à ação de cargas axiais e oblíquas. Além disso, objetivou-se avaliar a influência do ponto de contato proximal na distribuição das tensões no modelo de três dentes (M1), comparado a um modelo unitário do 24 (M2). As propriedades mecânicas bem como as condições de contorno e carregamento foram determinadas no programa de elementos finitos Ansys®. Cargas axiais e oblíquas foram aplicadas nas seguintes simulações: C1) Carga axial nos contatos A e B no dente 24; C2) Contato excêntrico no dente 24; C3) Carga oblíqua de 45N, com inclinação de 45o no contato A do dente 24; C4) Carga oblíqua de 45N, com inclinação de 45o no contato B do dente 24; C5) Cargas axiais simultâneas, de 70N na ponta de cúspide do dente 23, 90N nos contatos A e B do dente 24 e de 105N nos contaos A e B do dente 25. Para estimar a possibilidade de falha no esmalte, as tensões máximas principais foram analisadas e deformações máximas e mínimas principais foram analisadas no LP e no osso alveolar, sendo que ambos foram comparados a valores encontrados em outros estudos com metodologia similar. Em C1, a distribuição de tensões foi mais favorável para as estruturas dente-LP-osso, com picos de tensões semelhantes em M1 e M2. Em C2, tensões deslocaramse para apical, devido ao contato entre os dentes 24 e 23 em M1; os picos de tensões foram maiores em M1 do que em M2 no esmalte e no osso e o inverso ocorreu na dentina e no LP. Em C3, tensões de tração concentraram-se na região cervical do esmalte e na furca do dente 24; os picos das tensões no esmalte, osso e LP foram menores em M1 comparado a M2, mas na dentina ocorreu o contrário (M1>M2). Em C4, ocorreu o maior pico de tensão de tração no esmalte, tensões de tração concentraram-se na furca do dente 24; esmalte e dentina comportaram-se de forma similar (M1>M2) e osso e LP também (M1˂M2). Em C5, tensões de tração se concentraram no osso alveolar do dente 23. Os contatos proximais em M1 permitiram a distribuição das tensões de forma mais homogênea para o LP e osso que em M2. Exceto em C1, a distribuição de tensões no esmalte cervical, na dentina, no LP e no osso alveolar diferiram em um modelo unitário comparado a um de três dentes, devido à presença dos contatos proximais.

The direction, type and magnitude of loads on the oclusal surface and also the characteristics of the support structures determines the stress distribution. The aim of this study was to analyze, by the finite element method, the stress distribution on the first superior premolar, in a tridimensional (3D) model subjected to various types of loadings considering the enamel anisotropic or isotropic. The geometric modeling was performed based on a computed tomography (CT) scan. The mechanical properties as well as the loading conditions determined by the Abaqus® finite element program. Axial and oblique loads were applied on the occlusal surface of the first superior premolar in the following conditions: I) 30N axial load applied simultaneously on the occlusal contacts A and B and in the mesial marginal ridge, totaling 90N; II) 90N axial load in the mesial longitudinal edge of the lingual cusp, simulating eccentric contact; III) 45N oblique load with a 45o inclination on theocclusal contact A; IV) 45N oblique load with a 45o inclination on the occlusal contact B. To estimate the possibility of failure in the simulated structures, the maximum principal stress were analyzed and compared to known tensile strength values of the tissues studied. The results showed compression stress on the side in which the load was applied and tensile stress on the opposite side. Tensile stress concentrates mainly in the cervical region of the tooth and in the alveolar insertion bone. Anisotropic models revealed areas of tensile stress concentration smaller than the isotropic models. It was concluded that the isotropic 3D models were suitable for analyzing the stress distribution in teeth, because they are less complex models to build and produced similar results compared to the anisotropic models. The cervical enamel seems to be more susceptible to fracture because of the largest stress concentration on this area, associated with its composition and anatomical characteristics

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A distribuição das tensões ao longo da estrutura dentária é determinada pela direção, o tipo e a magnitude das cargas que incidem na superfície oclusal e pelas características das estruturas de suporte. Este estudo teve como objetivo analisar, através do Método de Elementos Finitos, a distribuição de tensões na estrutura dentária, em um modelo tridimensional (3D) do primeiro pré-molar superior submetido a diferentes tipos de carregamentos, considerando o esmalte anisotrópico ou isotrópico...

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UNLABELLED: Secondary caries is still the main cause of restoration replacement, especially on the root surface. OBJECTIVE: This in vitro study evaluated the cariostatic effects of fluoride-containing restorative materials associated with fluoride gels, on root dentin. MATERIALS AND METHODS: A randomized complete block design was used to test the effects of the restorative systems, fluoride regimes and the interactions among them at different distances from restoration margins. Standardized cavities were prepared on 240 bovine root specimens and randomly assigned to 15 groups of treatments (n=16). Cavities were filled with the following restorative materials: Ketac-Fil (3M-ESPE); Vitremer (3M-ESPE); Dyract/Prime & Bond NT (Dentsply); Charisma/Gluma One Bond (Heraeus Kulzer) and the control, Z250/Single Bond (3M-ESPE). The specimens were subjected to a pH-cycling model designed to simulate high-caries activity. During the cycles, 1.23% acidulated phosphate fluoride, 2.0% neutral sodium fluoride or deionized/distilled water (control) was applied to the specimens for 4 min. The surface Knoop microhardness test was performed before (KHNi) and after (KHNf) the pH cycles at 100, 200 and 300 mm from the margins. Dentin microhardness loss was represented by the difference in initial and final values (KHNi - KHNf). Data were analyzed by Friedman's and Wilcoxon's tests, ANOVA and Tukey's test (α=5%). RESULTS: The interaction of restorative systems and topical treatments was not significant (p=0.102). Dentin microhardness loss was lowest closer to the restoration. Ketac-fil presented the highest cariostatic effect. Vitremer presented a moderate effect, while Dyract and Charisma did not differ from the control, Z250. The effects of neutral and acidulated fluoride gels were similar to each other and higher than the control. CONCLUSION: Conventional and resin-modified glass ionomer cements as well as neutral and acidulated fluoride gels inhibit the progression of artificial caries adjacent to restorations. The associated effect of fluoride-containing restorative materials and gels could not be demonstrated.

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Secondary caries is still the main cause of restoration replacement, especially on the root surface OBJECTIVE: This in vitro study evaluated the cariostatic effects of fluoride-containing restorative materials associated with fluoride gels, on root dentin. MATERIALS AND METHODS: A randomized complete block design was used to test the effects of the restorative systems, fluoride regimes and the interactions among them at different distances from restoration margins. Standardized cavities were prepared on 240 bovine root specimens and randomly assigned to 15 groups of treatments (n=16). Cavities were filled with the following restorative materials: Ketac-Fil (3M-ESPE); Vitremer (3M-ESPE); Dyract/Prime & Bond NT (Dentsply); Charisma/Gluma One Bond (Heraeus Kulzer) and the control, Z250/Single Bond (3M-ESPE). The specimens were subjected to a pH-cycling model designed to simulate high-caries activity. During the cycles, 1.23 percent acidulated phosphate fluoride, 2.0 percent neutral sodium fluoride or deionized/distilled water (control) was applied to the specimens for 4 min. The surface Knoop microhardness test was performed before (KHNi) and after (KHNf) the pH cycles at 100, 200 and 300 mm from the margins. Dentin microhardness loss was represented by the difference in initial and final values (KHNi - KHNf). Data were analyzed by Friedman's and Wilcoxon's tests, ANOVA and Tukey's test (α=5 percent). RESULTS: The interaction of restorative systems and topical treatments was not significant (p=0.102). Dentin microhardness loss was lowest closer to the restoration. Ketac-fil presented the highest cariostatic effect. Vitremer presented a moderate effect, while Dyract and Charisma did not differ from the control, Z250. The effects of neutral and acidulated fluoride gels were similar to each other and higher than the control. CONCLUSION: Conventional and resin-modified glass ionomer cements as well as neutral and acidulated fluoride gels inhibit the progression of artificial caries adjacent to restorations. The associated effect of fluoride-containing restorative materials and gels could not be demonstrated.

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Objetivo: Caracterizar os pacientes atendidos no programa de manutencao preventiva (MP) e relacionar as necessidades de tratamento apresentadas com os intervalos de retorno prescritos. Metodo: Foram coletados dados secundarios de prontuarios de pacientes da MP, no ano de 2008, relativos a idade, genero, e intervalo de tempo decorrido desde a ultima consulta. Registrou-se a presenca ou ausencia de alteracoes sistemicas, uso de medicamentos, dor ou desconforto bucal, desordem oclusal e lesoes de mucosa. Foram comparados os dois ultimos Indices Periodontais Comunitarios (CPI) e Indices de Placa Visivel (IPV). As variaveis necessidade de tratamento e tempo decorrido desde a ultima consulta foram comparadas pelo teste-t, com nivel de significancia de 5%. Resultados: A amostra consisti u de 115 individuos, 60,9% do genero feminino e 39,1% do masculino, com media de idade de 25,40 (ñ13,34) anos. A porcentagem dos que faziam uso regular de medicamentos (22,61%) foi maior que a observada para a presenca de alteracoes sistemicas (19,13%). Dos 67,83% que apresentaram necessidade de tratamento, 52,56% tinham necessidade de atencao primaria, 6,41% somente secundaria e 41,03% em ambos os niveis de atencao. O intervalo medio de tempo decorrido desde a ultima consulta (12,76 ñ 6,62 meses) apresentou baixa correlacao com as variaveis alteracoes sistemicas (r= 0,0174), uso de medicamentos (r= 0,0714), dor e desconforto bucal (r= 0,0357), lesoes de mucosa (r= 0,0357), necessidade de tratamento (r= 0,0368). Nao houve diferenca estatistica significativa entre os intervalos de retorno prescritos para individuos que tinham ou nao necessidade de tratamento (p=0,6958). Conclusao: Existe uma falta de sistematizacao na determinacao de intervalos de MP, ressaltando a necessidade de estudos prospectivos para estabelecer criterios baseados na classificacao de risco individual, que possam ser aplicados ao ensino da disciplina e a pratica profissional.

Objective: To characterize the patients enrolled in a preventive maintenance (PM) program, and to correlate their treatment needs with the prescribed and recall intervals. Method: Secondary data - age, gender and time interval elapsed since the last dental appointment - were collected from the charts of patients attending the PM program in 2008. The presence or absence of systemic alterations, use of medications, oral pain or discomfort, oclusal disorder and mucosal lesions was recorded. The last two Community Periodontal Indexes (CPI) and Visible Plaque Indexs (VPI) were compared. The variables treatment needs and time interval elapsed since the last dental appointment were compared by the t-test at 5% significance level. Results: The sample was composed by 115 individuals, 60.9% were females and 39.1% were males with mean age of 25.40 (ñ 13.34) years. The percentage of those who made regular use of medications (22.61%) was higher than that observed for the presence of systemic alterations (19.13%). From the 67.83% that had treatment needs, 52.56% needed primary attention, 6.41% only secondary attention and 41.03% needed both levels of attention. The mean time interval elapsed since the last appointment (12.76 ñ 6.62 months) had a low correlation with the variables systemic alterations (r= 0.0174), use of medications (r= 0.0714), oral pain and discomfort (r= 0.0357), mucosal lesions (r= 0.0357) and treatment needs (r= 0.0368). There was no statistically significant difference among the recall intervals prescribed for individuals who had or not treatment needs (p=0.6958). Conclusion: There is a lack of systematization in the determination of PM intervals, reinforcing the need for prospective studies to reestablish criteria based on the classification of individual risks that can be applied to the teaching of Integrated Clinic discipline and professional practice.

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