Translucency of value resin composites used to replace enamel in stratified composite restoration techniques.

BACKGROUND: The translucency of enamel shade is a crucial property that affects the color of a layered restoration. OBJECTIVE: This study evaluated the translucency of high-, medium-, and low-value resin composites (4 Seasons, Ivoclar Vivadent, Schaan, Liechtenstein) used to replace enamel in stratified composite restoration techniques. MATERIALS AND METHODS: The color specimens with 12 mm in diameter and various thicknesses (0.5, 1.0, 1.5, 2.0, 3.0, 4.0 mm) were measured after polymerization on a reflection spectrophotometer over white and black backgrounds to calculate the translucency parameter (TP). The statistical analysis of TP was accomplished using two-way analysis of variance (p < 0.05). Significant differences were revealed by the Tukey's Honestly Significant Difference post hoc test. RESULTS: Translucency of the value composite resins was influenced by the value and thickness. Color of value resin composites was dependent on the background contrast at the evaluated thicknesses. CONCLUSIONS: High-value composite resins were more translucent than medium-value composites, which were more translucent than low-value composites. The translucency decreased as the thickness of the specimens increased. CLINICAL SIGNIFICANCE: The results suggest that special attention should be paid to the thickness of the increment of value composite resins when reproducing translucency of natural tooth enamel.

Novel-design ultra-thin CAD/CAM composite resin and ceramic occlusal veneers for the treatment of severe dental erosion.

STATEMENT OF PROBLEM: Ultra-thin bonded posterior occlusal veneers represent a conservative alternative to traditional inlays and complete coverage crowns for the treatment of severe erosive lesions. There is a lack of data regarding selection of the most appropriate material and its influence on fatigue resistance, which may affect restoration longevity. PURPOSE: The purpose of this study was to assess the influence of CAD/CAM restorative material (ceramic vs. composite resin) on fatigue resistance of ultra-thin occlusal veneers. MATERIAL AND METHODS: A standardized nonretentive tooth preparation (simulating advanced occlusal erosion) was applied to 40 extracted molars including removal of occlusal enamel, and immediate dentin sealing (Optibond FL). All teeth were restored with a 0.6 mm-thick occlusal veneer (Cerec3 chairside CAD/CAM system). Reinforced ceramics (Empress CAD and e.max CAD) and composite resins (Paradigm MZ100 and XR (experimental blocks)) were used to mill the restorations (n=10). The intaglio surfaces were HF-etched and silanated (reinforced ceramics) or airborne-particle abraded and silanated (composite resins). Preparations were airborne-particle abraded and etched before restoration insertion. All restorations were adhesively luted with preheated Filtek Z100. Cyclic isometric loading was applied at 5 Hz, beginning with a load of 200N (x5,000), followed by stages of 400, 600, 800, 1000, 1200 and 1,400N at a maximum of 30,000 cycles each. The number of cycles at initial failure (first cracks) was recorded. Specimens were loaded until catastrophic failure (lost restoration fragment) or to a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (α=.008, Bonferroni-method). RESULTS: Empress CAD and e.max CAD initially failed at an average load of 500N and 800N, respectively with no specimen withstanding all 185,000 load cycles (survival 0%); with MZ100 and XR the survival rate was 60% and 100%, respectively. CONCLUSIONS: Both composite resins (MZ100 and XR) increased the fatigue resistance of ultra-thin occlusal veneers (P<.001) when compared to the ceramics evaluated (Empress CAD and e.max CAD).

In vitro fatigue resistance of CAD/CAM composite resin and ceramic posterior occlusal veneers.

STATEMENT OF PROBLEM: Thin, bonded, posterior occlusal veneers constitute a conservative alternative to traditional complete coverage crowns. Information regarding selection of the appropriate material and its influence on fatigue resistance, which may affect the longevity of the restoration, is missing. PURPOSE: The purpose of this study was to assess and compare the fatigue resistance of composite resin and ceramic posterior occlusal veneers. MATERIAL AND METHODS: Thirty extracted molars received a standardized nonretentive tooth preparation (simulating advanced occlusal erosion), including removal of occlusal enamel, exposure of dentin, and immediate dentin sealing (Optibond FL). All teeth were restored with a 1.2-mm-thick occlusal veneer (Cerec 3 chairside CAD/CAM system). The restorations (n=10) were milled from leucite-reinforced and lithium disilicate ceramics (IPS Empress CAD and IPS e.max CAD, respectively) and a composite resin (Paradigm MZ100). The intaglio surfaces of the ceramic restorations were conditioned by hydrofluoric acid etching and silane. Airborne-particle abrasion and silane were used to condition the composite resin restorations. Preparations were airborne-particle abraded and etched. All restorations were bonded with preheated luting material and submitted to cyclic isometric loading at 5 Hz, starting with a load of 200 N (x5000 cycles), followed by stepwise loading of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. The number of cycles at initial failure (first cracks) was recorded. Specimens were loaded for a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (alpha=.016, Bonferroni method). RESULTS: IPS Empress CAD failed at an average load of 900 N, with no specimen withstanding all 185,000 load cycles (survival 0%), while IPS e.max CAD and Paradigm MZ100 demonstrated survival rates of 30% and 100%, respectively. None of the specimens exhibited catastrophic failure, but only cracks limited to the restorative material. CONCLUSIONS: Posterior occlusal veneers made of composite resin (Paradigm MZ100) had significantly higher fatigue resistance (P<.002) compared to IPS Empress CAD and IPS e.max CAD.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin.

The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

Influence of the duration of treatment using a 10% carbamide peroxide bleaching gel on dentin surface microhardness: an in situ study.

This in situ study evaluated the influence of two home-use tooth bleaching regimes (1 hour/day and 7 hours/day) using 10% carbamide peroxide (Nite White Excel 2Z) on the surface microhardness of dentin over a 21-day period. Nine blocks of dentin derived from the teeth of subjects, each with at least two thirds molar in need of extraction, were obtained from the cervical region and submitted to surface-hardness analysis (Shimadsu HMV/2000), fixed to an intraoral palate device fabricated for each subject, and positioned (3 left side, 3 right side, 3 center) according to experimental group. During the bleaching period, casts bearing the whitening agent were applied to the blocks for 7, 1, and 0 hours, respectively (7 left side, 3 right side, 0 center). After the treatment period, the specimens were once again submitted to microhardness analysis, using the same equipment as before, and then analysis of variance and the Scheffé test were applied to the mean differences between the initial and final evaluations. The results demonstrated that the statistical difference between the 1-hour and 7-hour groups was not significant. However, the 7-hour group, when compared with the control group, demonstrated statistically significant differences with a reduction in microhardness. Despite the occurrence of mineral loss in the 1-hour and 7-hour groups, this difference was only 3.1% and 5.4%, respectively, which allows one to conclude that these values probably have no clinical significance.

Fatigue resistance and crack propensity of large MOD composite resin restorations: direct versus CAD/CAM inlays.

OBJECTIVES: To assess the influence of material/technique selection (direct vs. CAD/CAM inlays) for large MOD composite adhesive restorations and its effect on the crack propensity and in vitro accelerated fatigue resistance. METHODS: A standardized MOD slot-type tooth preparation was applied to 32 extracted maxillary molars (5mm depth and 5mm bucco-palatal width) including immediately sealed dentin for the inlay group. Fifteen teeth were restored with direct composite resin restoration (Miris2) and 17 teeth received milled inlays using Paradigm MZ100 block in the CEREC machine. All inlays were adhesively luted with a light curing composite resin (Filtek Z100). Enamel shrinkage-induced cracks were tracked with photography and transillumination. Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 200 N (5000 cycles), followed by stages of 400, 600, 800, 1000, 1200 and 1400 N at a maximum of 30,000 cycles each. Samples were loaded until fracture or to a maximum of 185,000 cycles. RESULTS: Teeth restored with the direct technique fractured at an average load of 1213 N and two of them withstood all loading cycles (survival=13%); with inlays, the survival rate was 100%. Most failures with Miris2 occurred above the CEJ and were re-restorable (67%), but generated more shrinkage-induced cracks (47% of the specimen vs. 7% for inlays). SIGNIFICANCE: CAD/CAM MZ100 inlays increased the accelerated fatigue resistance and decreased the crack propensity of large MOD restorations when compared to direct restorations. While both restorative techniques yielded excellent fatigue results at physiological masticatory loads, CAD/CAM inlays seem more indicated for high-load patients.

Opalescence of bleached teeth.

OBJECTIVES: To evaluate the influence of tooth bleaching on the opalescence properties of enamel. METHODS: Color of 38 specimens was determined by colorimetric analysis before and after bleaching in the reflectance and transmittance modes. The results were described as CIELab color coordinates. The Opalescent Parameter (OP) was calculated as the difference in yellow-blue color coordinate (CIE Δb*) and red-green color coordinate (CIE Δa*) between the reflected and transmitted colors. RESULTS: Mean OP value of the specimens was 18.9 (±1.6) before bleaching and 16.1 (±1.0) after bleaching. CONCLUSIONS: Bleaching decreases the OP of the specimens (p>0.001). OP decrease was correlated with differences in b* color coordinate in the transmittance mode.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin

Abstract The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

Resumo O objetivo deste estudo foi comparar a resistência à fadiga de dentes restaurados com uma resina composta bulk fill, resina composta convencional de inserção incremental e dentes hígidos sem preparo. Vinte e oito pré-molares maxilares extraídos foram selecionados e divididos em quatro grupos conforme a resina composta e técnica de inserção: controle (C), resina composta convencional com inserção incremental (I) e resina composta bulk fill inserida em três (BF3) ou único incremento (BF1). O preparo das cavidades foi padronizado para todos os grupos. As amostras foram restauradas e submetidas ao testes de resistência à fadiga com uma frequência de 5 Hz. Foram aplicados 5.000 ciclos de carregamento senoidal inicial com valor de força mínima igual a 50 N e força máxima de 200 N. Após, foram aplicados estágios de 30.000 ciclos de carga com a força máxima sendo aumentada gradativamente a cada estágio, para 400, 600, 800, 1000, 1200 e 1400 N. O ensaio foi finalizado ao ser alcançado 185.000 ciclos de carga (número máximo de ciclos de carga), ou na fratura da amostra. A resistência à fadiga foi registrada para comparação usando a curva de sobrevivência de Kaplan-Meier e analisada pelo teste log-rank a um nível de significância de 0.05. As fraturas foram classificadas conforme a posição da falha - acima ou abaixo da junção cemento esmalte (JCE). A análise estatística da curva de sobrevivência de Kaplan-Meier pelo teste log-rank demonstrou diferença significativa entre os grupos (p=0.001). Na análise de fratura somente 28.58% das falhas foram abaixo da JCE para o grupo C, enquanto para os grupos I, BF1 e BF3 foram 42.85%, 85.71% e 85.71%, respectivamente. Os dentes restaurados com a resina composta bulk fill em ambas as técnicas de inserção apresentaram valores de resistência à fadiga similares àqueles dos dentes restaurados com a resina composta convencional pela técnica incremental. Entretanto, dentes hígidos mostraram uma menor porcentagem de fraturas abaixo da JCE e maior resistência à fadiga.

Restauração em dente posterior com resina de baixa contração: relato de caso clínico / Restoration in posterior tooth with a low-shrinkage composite resin: clinical case report

A contração de polimerização ainda é um grande inconveniente dos materiais restauradores adesivos diretos. Com o objetivo de minimizar esse problema, foram introduzidas no mercado resinas de baixa contração. Uma delas é a resina à base de silorano, que combina as vantagens do silorano, o qual lhe confere hidrofobicidade, e o oxirano, que resulta em baixa contração volumétrica. Assim, por suas boas propriedades mecânicas e baixa contração volumétrica, ela é indicada para restaurações em dentes posteriores. O objetivo do presente artigo é apresentar o caso clínico de uma restauração de classe I realizada com resina de baixa contração à base de silorano.

Polymerization shrinkage is a major drawback of direct restorative materials. In order to minimize this problem, low-shrinkage composite resins were introduced. Silorane-based composites combine the advantages of the silorane, which conveys hydrophobicity, and oxirane which results in low volumetric shrinkage. They are indicated for restorations in posterior teeth due to their suitable mechanical properties and low shrinkage. The aim of this paper is to present a clinical case of a Class I restoration performed with low shrinkage silorane-based composite resin.

Adesão aos tecidos dentais modificados por agentes externos / Bonding on dental tissues modified by external agents

A evolução da tecnologia dos sistemas adesivos e o conhecimento disponível sobre adesão aos tecidos dentais duros estão baseados em estudos que avaliam qualidade de adesão, que geralmente são realizados em tecidos dentais sadios. A condição prévia do substrato dental pode alterar a eficiência de uma restauração adesiva. Nesse sentido, sob o ponto de vista clínico, os substratos dentais viáveis para adesão podem estar afetados por cárie ou ainda, em pacientes fumantes, podem estar contaminados pela fumaça do cigarro. Este artigo tem como objetivo fazer uma revisão sobre a influência da condição prévia do substrato dental contaminado por ação bacteriana da doença cárie e pela fumaça do cigarro, na qualidade da adesão...

Evolution of adhesive systems technology and the available knowledge regarding bonding to dental hard tissues are based on studies that evaluate bonding quality, which are routinely undertaken on sound dental tissues. Previous condition of dental substrate can alter bonding effectiveness of an adhesive restoration. Thus, from a clinical standpoint, dental tissues which are feasible for adhesion may be contaminated by caries or even by cigarette smoke. The aim of this article is to discuss the influence of the previous condition of the dental substrate, contaminated either by bacterial action of caries disease or by cigarette smoke, on bonding effectiveness...

Resinas compostas para esmalte clareado podem diminuir a luminosidade do substrato nas técnicas restauradoras estratificadas / Marginal integrity analysis through three-dimensional scanner in silorane-based composites

Por meio de análise espectrofotométrica, este estudo avaliou a influência cromática de resinas compostas para esmalte clareado em substrato de resina composta para dentina A2. Sessenta e cinco corpos de prova foram confeccionados e divididos em um grupo controle (GC) e quatro grupos teste (G+cor da resina), da seguinte forma: a) GC, formado por resina para dentina (n=5); b) GXXL, formado por resina para dentina e resina para esmalte clareado XXL (n=15); c) GXL, formado por resina para dentina e resina para esmalte clareado XL (n=15); d) GL, formado por resina para dentina e resina para esmalte clareado L (n=15); e) GM, formado por resina para dentina e resina para esmalte clareado M (n=15). O incremento de resina para dentina acrescentou a espessura única de 2mm, enquanto o incremento de resina para esmalte clareado apresentou três diferentes espessuras, originando, em cada grupo teste, três subgrupos (S): a) S1, 1,2mm; b) S2, 0,8mm; c) S3, 0,4mm. A análise estatística foi realizada com ANOVA, que revelou diferenças significantes na luminosidade dos corpos de prova, conforme demonstrado por comparações feitas por meio do teste de Dunnett. Das quatro resinas para esmalte avaliadas apenas uma elevou a luminosidade do substrato. A aplicação dessas resinas provocou, em todos os grupos teste, alterações cromáticas consideradas clinicamente inaceitáveis (∆3>3,3).

The aim of this study was to perform a spectrophotometric analysis of chromatic influence of composite resins for bleached enamel on a A2-shaded composite resin substrate. Sixty five specimens were distributed in a Control Group (GC = dentin composite resin) and four test groups (GC + enamel composite shade) as following: a) GC, A2 shaded dentin composite resin (n=5); b) GXXL. GC and a composite for bleached enamel (XXL) (n=15); c) GXL, GC and a composite for bleached enamel (XL) (n=15); d ) GL, GC and a composite for bleached enamel (L) (n=15); e) GM, GC and a composite for bleached enamel (M) (n=15). The thickness of the dentin composite was 2,0mm, while the enamel composite presented three different thicknesses, originating three subgroups for each group (1.2mm, 0.8mm, and 0.4mm, i.e., S1, S2, and S3, respectively). Two-way ANOVA and Dunnett’s test for individual comparisons revealed statistically significant differences for luminosity. Only enamel composite increased the substrate luminosity. The application of bleached enamel composite resins resulted in clinically unacceptable chromatic changes in all test groups (Δ3>3.3).

Cimentos auto-adesivos: revisão da literatura ilustrada com caso clínico / Self-adhesive cements: literature review and case report

Este trabalho reúne informações científicas sobre o emprego dos cimentos auto-adesivos e as discute criticamente, em busca de subsídios para o uso seguro desse agente cimentante. A investigação buscou artigos científicos que abrangem assuntos relacionados com adesão, microinfiltração e biocompatibilidade. Adicionalmente, relata um caso clínico que exibe sua técnica para cimentação de coroas de porcelana pura. Apenas um cimento auto-adesivo disponível comercialmente tem seu emprego analisado por vasta literatura. Constata que seu uso é excelente alternativa para a cimentação de restaurações indiretas, no entanto, o condicionamento prévio do esmalte melhora sua interação com esse tecido

The aim of this work was to gather and to discuss scientific information regarding the safe use of self-adhesive cements. The terms “luting”, “microleakage” and “biocompatibility” were searched. A case report of an all-ceramic crown using a self-adhesive cement is presented. There is only commercially available self-adhesive cement which has been extensively reviewed and researched, and its has been suggest that it is an excellent alternative for luting indirect restorations, provided that selective etching of enamel is performed to improve its performance

Clareamento de dente não-vital com a técnica inside-outside / Nonvital tooth bleaching with the inside-outside technique

O clareamento de dentes não-vitais escurecidos é um tratamento conservador que apresenta bons níveis de sucesso. Diversas são as técnicas e os materiais indicados para a execução do protocolo clareador em dentes despolpados. O presente artigo apresenta uma breve revisão da literatura pertinente ao tema e relata um caso clínico realizado com a técnica denominada inside-outside.

Recontorno cosmético e restaurações adesivas diretas para correção de desarmonias estéticas / Cosmetic recontouring with direct adhesive restorations to correct esthetic alterations

Restaurações adesivas diretas constituem uma das alternativas restauradoras para correção de desarmonias estéticas. Dentre suas principais vantagens destacam-se a excelente estética e a preservação de estruturas dentárias sadias. Essa técnica foi eleita para resolução da presente situação clínica, principalmente por ser uma modalidade de tratamento conservador. O relato do caso consiste na descrição da correção de problemas de alinhamento dentário e diastemas interincisais, por meio da aplicação de técnicas de recontorno cosmético e restaurações adesivas diretas com resina composta, com enfoque no diagnóstico e no planejamento estético.

Moldagem com elastômeros não aquosos: visão atual / Nonaqueous elastomeric impression materials: an up-to-date view

A obtenção de excelência estética em restaurações indiretas depende de correta moldagem. Para esse propósito, os elastômeros não aquosos são materiais extremamente eficazes, pois apresentam propriedades químicas, físicas e mecânicas que permitem a reprodução detalhada dos tecidos moles e duros da cavidade oral. O objetivo deste artigo é apresentar um enfoque clínico sobre os materiais elastoméricos não aquosos existentes quanto a seleção, técnicas de aplicação, interações com outros materiais, métodos de desinfecção e falhas mais comuns na moldagem de restaurações indireta.

Método quantitativos para detecção de lesões cariosas: aplicação clínica / Quantitative methods for detection of caries lesions: clinical relevance

Novos métodos têm sido desenvolvidos e testados com a finalidade de permitir o diagnóstico de lesões cariosas e quantificá-las. O objetivo deste estudo é revisar estudos clínicos que utilizaram a fluorescência a laser (DIAGNOdent) e o método de quantificação da fluorescência induzida pela luz para detecção de lesões cariosas e avaliar qual é a aplicação clínica desses métodos. Os estudos sugerem que o DIAGNOdent pode ser utilizado em conjunto com o exame visual na detecção de lesões de cárie em superfícies oclusais. Em relação ao método de quantificação da fluorescência induzida pela luz, os estudos sugerem que esse método pode ser útil no monitoramento de alterações minerais em lesões de mancha branca presentes em superfícies lisas.

Avaliação da resistência a flexão de resinas compostas fotoativadas por LEDS / Flexural strength evaluation of composite resins light cured by LEDS

O objetivo deste trabalho foi avaliar a resistência a flexão de duas resinas compostas (uma microhíbrida e uma de micropartículas), comparando os dispositivos de LED (luz emitida por diodo) e luz halógena. As amostras foram submetidas ao teste de flexão de três pontos, sendo a resitência calculada em MPa e os resultados submetidos ao teste de Anova. Foi constatado que houve diferença na resistência dos compósitos quando fotoativados por dispositivos diferentes (p<0,05)

Avaliação das propriedades mecânicas de cimentos resinosos de dupla ativação / Evaluation of mechanical properties of dual cure resin cements

O propósito deste estudo foi avaliar a resistência mecânica de quatro cimentos resinosos de dupla ativação (Rely X ARC - 3 M; Enforce - Dentsply; Fill Magic Dual Cement - Vigodent; Variolink II - Ivoclar Vivadent), com ensaios de resistência à compressão e resistência flexural. Os testes foram baseados nos métodos descritos na Especificação n°27 da ANSI/ADA. Os resultados foram analisados por ANOVA e teste de Tukey (p<0,05). No ensaio de resistência à compressão, não foram observadas diferenças estatisticamente entre os quatro cimentos. Com relação à resistência flexural, os cimentos Variolink II e Dual Cement foram estatisticamente superiores em relação ao Rely X ARC, ocorrendo similaridade nos demais casos

Avaliaçäo do "creep" estático em resinas compostas / Creep evaluation on composite resin

Demonstrou-se, através de ensaios mecânicos, que as resinas compostas deformam-se de modo permanente quando submetidas a baixas tensöes e em funçäo do tempo, da mesma forma como pode ocorrer em áreas sujeitas às forças oclusais. Na avaliaçäo dos valores do "creep" estático verificou-se que a deformaçäo permanente aumentou em funçäo do tempo, mas com reduçäo acentuada entre as primeiras 24 horas e uma semana

Degradaçäo de resinas compostas / The composite resin degradation

A degradaçäo físico-química do sistema de resinas compostas manifesta-se após algum tempo, tendo o material entrado em contato íntimo com a saliva ou forças oclusais. A manifestaçäo dos efeitos da fadiga, como conseqüência da degradaçäo hidrolítica da uniäo entre a partícula e o silano, foi avaliada e, em conclusäo, verificou-se que é influenciada näo só por líquidos e forças mastigatórias mas, principalmente, pela natureza química de cada sistema de resinas compostas