Effect of Chemical Challenges on the Properties of Composite Resins.

OBJECTIVE: To evaluate the chemical degradation effect on microhardness and roughness of composite resins after aging. MATERIALS AND METHODS: Specimens (n = 10) were used for Filtek Z350 XT (Z350), Filtek Bulk Fill (BULK), Micerium HRI (HRI), Micerium BIOFUNCION (BIO), and Vittra APS (VITTRA). Microhardness and roughness were performed before and after degradation with the followed solutions: citric acid, phosphoric acid, 75% alcohol, and distilled water. Samples were to a 180-day chemical cycling protocol. After degradation, one sample of each group was selected for scanning electron microscope evaluation. The data were analyzed with normal distribution (Kolmogorov-Smirnov) and similarities of variations for the Bartlett test. ANOVA (two-way) followed by Tukey's test was performed considering treatment and composite resin (P < 0.05). RESULTS: For microhardness and roughness, variations were noted to different solution and resin formulations. Z350 and HRI showed higher microhardness percentage loss, and it was more evident after storage in alcohol (-48.49 ± 20.16 and -25.02 ± 14.04, respectively) and citric acid (-65.05 ± 28.97 and 16.12 ± 8.35, respectively). For roughness, Z350 and VITTRA showed less delta values after alcohol storage (-0.047 ± 0.007 and -0.022 ± 0.009, respectively). HRI had the worst roughness for citric acid (-0.090 ± 0.025). All resins were not statistically different between each other in water and phosphoric acid. CONCLUSION: The formulations of restorative resin materials influenced in degree of surface degradation after 180 days of chemical degradation. Water was considered the solution that causes less degradation for microhardness and roughness evaluations. For microhardness, alcohol was considered the worst solution for Z350 and HRI. For superficial roughness, Z350 and VITTRA showed less degradation in alcohol and citric and phosphoric acid solutions.

Can silver diamine fluoride or silver nanoparticle-based anticaries agents to affect enamel bond strength?

OBJECTIVES: The aim of the current study is to investigate the effect of different anticaries agents, such as experimental agents based on silver nanoparticles (SNPs) and silver diamine fluoride (SDF), on the micro-shear bond strength (µ-SBS) of composite resin applied to intact enamel (IE) or demineralized enamel (DE). MATERIALS AND METHODS: Sixty dental enamel fragments were collected from human third molars and categorized into 6 groups (n = 10): positive control (IE), negative control (DE), IE + SDF, DE + SDF, IE + SNP and DE + SNP. Samples from DE, DE + SDF and DE + SNP groups were subjected to pH cycling; superficial microhardness test was performed to confirm demineralization. Resin composite build-ups were applied to the samples (0.75-mm diameter and 1-mm height) after the treatments (except for IE and DE groups); µ-SBS was also evaluated. Samples were analyzed under a stereomicroscope at 40× magnification to identify failure patterns. Data were subjected to one-way analysis of variance, followed by Tukey's and Dunnett's tests (p < 0.05). RESULTS: There was no significant difference among the IE, IE + SNP, DE + SDF, and DE + SNP groups. The IE + SDF and DE groups recorded the highest and the lowest µ-SBS values, respectively. Adhesive-type failures were the most frequent for all treatments. CONCLUSIONS: Anticaries agents did not have a negative effect on the µ-SBS of composite resin when it was used on IE or DE.

Does Pigment Incorporation into Regular Composite Resins for Posterior Buildups Alter Their Bond Strength?

Posterior build-ups are auxiliary devices to orthodontic treatment which are made with resin-based or glass ionomer composites. Their removal requires care to protect the tooth surface, therefore, pigmented materials are preferred for a better visualization. This study proposed a pigmentation experimental technique of a regular composite resin, evaluating the microshear bond strength test (µ-SBT) of this experimental pigmented resin and comparing with a blue-colored polyacid-modified composite resin, used for posterior buildups. Forty-eight buccal and lingual surfaces of human teeth were used and randomly divided into 4 groups (n=12). The groups were divided into: C (control), regular composite resin; P, regular composite resin pigmented; UBL, Ultra Band Lok™; OB, Ortho Bite™. The composites were bonded using a matrix to obtain microcylinders and prepared for each experimental groups. The samples were then stored in distilled water for 24h at 37°C followed by a µ-SBT. The types of bond failures were evaluated using a stereoscopic magnifying glass (10×). The data were analyzed by ANOVA with Fisher post hoc and Dunnett´s test. Means of µ-SBT± standard deviation (MPa) were: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). The most prevalent type of failure was adhesive (80.4%). Further, was not observed a statistically significant correlation between the bond strength values and failure patterns. The pigmentation of a commercially available resin did not alter the µ-SBT and exhibited similar adhesiveness as a polyacid-modified composite resin.

Does pigment incorporation into regular composite resins for posterior buildups alter their bond strength?

Abstract Posterior build-ups are auxiliary devices to orthodontic treatment which are made with resin-based or glass ionomer composites. Their removal requires care to protect the tooth surface, therefore, pigmented materials are preferred for a better visualization. This study proposed a pigmentation experimental technique of a regular composite resin, evaluating the microshear bond strength test (µ-SBT) of this experimental pigmented resin and comparing with a blue-colored polyacid-modified composite resin, used for posterior buildups. Forty-eight buccal and lingual surfaces of human teeth were used and randomly divided into 4 groups (n=12). The groups were divided into: C (control), regular composite resin; P, regular composite resin pigmented; UBL, Ultra Band Lok™; OB, Ortho Bite™. The composites were bonded using a matrix to obtain microcylinders and prepared for each experimental groups. The samples were then stored in distilled water for 24h at 37°C followed by a µ-SBT. The types of bond failures were evaluated using a stereoscopic magnifying glass (10×). The data were analyzed by ANOVA with Fisher post hoc and Dunnett´s test. Means of µ-SBT± standard deviation (MPa) were: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). The most prevalent type of failure was adhesive (80.4%). Further, was not observed a statistically significant correlation between the bond strength values and failure patterns. The pigmentation of a commercially available resin did not alter the µ-SBT and exhibited similar adhesiveness as a polyacid-modified composite resin.

Resumo Levantes de mordida posterior são dispositivos para o tratamento ortodôntico confeccionados com resinas compostas ou materiais ionoméricos. Cuidado com a remoção destes se faz necessário para proteção da superfície dentária; para tanto, materiais pigmentados são preferidos por proporcionar melhor visualização. Este estudo propõe uma técnica de pigmentação experimental de resinas compostas convencionais, avaliando a resistência ao microcisalhamento (µ-SBT) na interface de união da resina experimental e superfície de esmalte dental e comparando-a com materiais comercialmente disponíveis para a confecção de levantes de mordida. Quarenta e oito superfícies de dentes humanos foram selecionadas aleatoriamente e divididos em quatro grupos (n=12), de acordo com o material adesivo utilizado: C (Controle, resina composta convencional); P (pigmentação experimental da resina composta convencional); UBL (Ultra Band Lok®); OB (Ortho Bite®). Microcilindros foram preparados para cada tipo de compósito utilizando uma matriz de silicone. As amostras foram mantidas em água destilada por 24h a 37°C, antes da realização do µ-SBT. Os padrões de fratura foram avaliados através de uma lupa estereoscópica com magnificação de 10x. ANOVA com pós teste de Fisher e teste de Dunnett foram utilizados para avaliar os dados. As médias obtidas do µ-SBT ± desvio padrão (MPa) foram: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). O tipo de fratura mais prevalente foi a adesiva (80.4%). Além disso, não foi observada correlação estatisticamente significante entre os valores de resistência de união e os padrões de fratura. A técnica de pigmentação experimental não alterou os resultados de µ-SBT da resina composta convencional e mostrou adesividade semelhante à dos compósitos modificados por poliácidos utilizados neste estudo.

Evaluation of the effects of whitening mouth rinses combined with conventional tooth bleaching treatments.

OBJECTIVES: The aim of the present study was to evaluate the effect of whitening mouth rinses alone and in combination with conventional whitening treatments on color, microhardness, and surface roughness changes in enamel specimens. MATERIALS AND METHODS: A total of 108 enamel specimens were collected from human third molars and divided into 9 groups (n = 12): 38% hydrogen peroxide (HP), 10% carbamide peroxide (CP), 38% HP + Listerine Whitening (LW), 10% CP + LW, 38% HP + Colgate Plax Whitening (CPW), 10% CP + CPW, LW, CPW, and the control group (CG). The initial color of the specimens was measured, followed by microhardness and roughness tests. Next, the samples were bleached, and their color, microhardness, and roughness were assessed. Data were analyzed through 2-way analysis of variance (ANOVA; microhardness and roughness) and 1-way ANOVA (color change), followed by the Tukey post hoc test. The Dunnett test was used to compare the roughness and microhardness data of the CG to those of the treated groups. RESULTS: Statistically significant color change was observed in all groups compared to the CG. All groups, except the LW group, showed statistically significant decreases in microhardness. Roughness showed a statistically significant increase after the treatments, except for the 38% HP group. CONCLUSIONS: Whitening mouth rinses led to a whitening effect when they were used after conventional treatments; however, this process caused major changes on the surface of the enamel specimens.