Influence of the combined effect of desensitizing dentifrices and universal adhesives on dentin bond strength under erosive conditions

Objective: This study aimed to evaluate whether the use of desensitizing dentifrices containing obliterating agents can affect bond strength of eroded/abraded dentin. Methodology: A total of 100 dentin samples were obtained from human molars. The teeth were cut into 3 mm-thickness discs and allocated in five groups (n=20), according to the toothpaste used: WoF – abrasion with fluoride-free toothpaste (Cocoricó); Arg – toothpaste containing arginine (Colgate Sensitive Pro-Relief); Nov – calcium sodium phosphosilicate toothpaste (Sensodyne Repair and Protect); SnF – fluoride-containing toothpaste (AmF/SnCl2/SnF2 – Elmex Erosion); and Control (no erosive/abrasive process). The erosive/abrasive cycle consisted of immersion in citric acid (1%, pH 2.6, 5 min, 4×/day) and abrasion (2×/day, 120–20 sec abrasion, 100 sec immersion) with each toothpaste. During intervals, samples were immersed in artificial saliva. This cycle was performed for five days. Two resin cylinders (2 mm in diameter) were constructed on each sample for the shear bond strength test using a universal adhesive system. The self-etch and etch-and-rinse (Scotchbond Universal) strategies were employed, each in half of the total sample (n=10). Bond strength (MPa) was measured in a shear test and failure modes were assessed with a stereomicroscope. Statistical analysis was performed using the two-way analysis of variance (ANOVA) and Tukey tests (p<0.05). Results: A statistically significant difference was found between the adhesive strategies tested (p<0.001), with the self-etching form showing higher values than the etch-and-rinse. Moreover, no significant differences were observed between the tested toothpastes (p=0.750) and interactions (p=0.438). Conclusion: The use of toothpaste containing obliterating agents does not affect bond strength to dentin subjected to erosive/abrasive conditions when a universal adhesive is used. However, the self-etch strategy might be preferred for eroded/abraded dentin

Influence of thickness and translucency of lithium disilicate ceramic on degree of conversion of resinous materials

In this study was assessed the degree of conversion (DC) of amine-free resin cements light cured through lithium disilicate-reinforced ceramics at different thicknesses and translucency. Specimens were divided into 21 groups (n = 5) according to luting agent used: Variolink Esthetic LC (Light shade), RelyX Ultimate (A1 shade), and Filtek Z350 XT Flow (A1 shade); the ceramic translucency: low (LT) and high (HT); and the ceramic thickness: no ceramic (control), 0.5 mm, 1 mm, and 2 mm. A Teflon mold with (5 x 5 x 0.5 mm) was used to standardize the cement and over it the ceramic block from each group was placed. Set was cured using a polywave LED light (1200 mW/cm2 - Bluephase G2) for 40 s. FTIR spectra of uncured and cured materials was obtained and DC calculated from the height of the peaks 1610 and 1640 cm-1. Data were submitted to ANOVA followed by Tukey?s test (? = 0.05). There was a significant difference for luting agents (p< 0.0001) and translucency (p = 0.025), but not for thickness (p = 0.73). Dual amine-free RelyX Ultimate showed the lowest DC values and higher translucency promoted higher DC. Dual amine-free cement showed the lowest monomer conversion and higher translucency ceramics promoted a higher DC

Protection of calcium silicate/sodium phosphate/fluoride toothpaste with serum on enamel and dentin erosive wear

Objective: To evaluate the effect of a toothpaste containing calcium silicate/sodium phosphate/fluoride associated or not to the boost serum (BS) against erosive tooth wear (ETW) on enamel and dentin. Methodology: Bovine enamel and dentin specimens were subjected to an erosion-abrasion cycling model (1% citric acid - pH 3.6 -2 min / artificial saliva – 60 min, 4×/day, 5 days). Toothbrushing was performed for 15 s (2 min exposed to slurry), 2×/day, with the toothpastes (n=10): control without fluoride (Weleda), Arg/Ca/MFP (Colgate Pro-Relief), Si/PO4/MFP (Regenerate-Unilever), and Si/PO4/MFP/BS (Si/PO4/MFP with dual BS – Advanced Enamel Serum-Unilever). The effect of treatments on the eroded tissues was assessed by surface microhardness in the first day, and surface loss (SL) resulting from ETW was evaluated by profilometry (μm) after three and five days. Additional dentin specimens (n=5/group) were subjected to 20,000 brushing cycles to verify the abrasivity of the toothpastes. Data were subjected to ANOVA and correlation tests (5%). Results: For enamel, no difference in microhardness was observed among the treated groups, and similar SL was obtained after 5 days. For dentin, Si/PO4/MFP/BS resulted in higher microhardness values, but none of the groups presented significantly lower SL than the control. There was no significant correlation between SL and abrasiveness. Conclusion: The calcium silicate/sodium phosphate toothpaste and serum increased microhardness of eroded dentin, but they did not significantly reduce enamel and dentin loss compared to the non-fluoride control toothpaste. The abrasiveness of the toothpastes could not predict their effect on ETW

Bonding performance of universal adhesives with concomitant use of silanes to CAD/CAM blocks

ABSTRACT Objective: This study assessed whether the use of a silane coupling agent influence the bond strength of two universal adhesives to ceramic or resin CAD/CAM blocks. Methods: Forty-eight samples were obtained from each resin nano-ceramic hybrid block (RCBs) and lithium disilicate ceramic blocks (LD). Samples were treated with silane with MDP (Monobond - S-MDP), silane without MDP (Prosil - PS), and no silane application (Control - Ctr) followed by universal adhesive with silane (UAS) and without silane (UA) (n=8). Three polyurethane tubes (1.5 mm of internal diameter) were positioned in each sample treated surface and filled with a dual cured resin cement. Bond strength was assessed by microshear bond strength test and failure analysis was performed for all samples. Results: For the RCBs, UAS presented the highest bond strength values (p=0.004). Silane application was not significant in bond strength values (p=0.444). For LD, silane application was significant in bond strength values (p<0.001), but the adhesive was not (p=0.066). Failure analysis showed high prevalence of adhesive failures for both substrates. Conclusion: A silane-containing universal adhesive promoted the best bond strength results to the resin nano-ceramic hybrid block. For bonding to a glass-ceramic CAD/CAM material, additional silane (without MDP) application presented the best results

Minimal intervention in dentistry : which is the best approach for silorane composite restoration repairs?

This study aimed to evaluate surface treatments, adhesives and composites for repairing silorane based restorations. One hundred and twenty truncated cones (2 mm smaller diameter and 4 mm larger diameter) made of silorane composite were divided in 12 g

Efeito do diâmetro da ponta aplicadora de carga e do orifício central da base no desempenho biomecânico do teste de push-out: avaliação experimental e validação por análise em elementos finitos

Even though the push-out test is widely used, its parameters aren t well established in literature. The aim of this study was to evaluate the influence of indenter and base diameters on push-out test results, by means of laboratorial and finite element analysis (FEA). Three bases with different central orifices diameters (2.5, 3.0, and 3.5 mm) and three diameters of indenters (0.5, 1.0, and 1.5 mm) were used. For the push-out test 90 bovine incisors with similar roots were selected and had its coronal part removed, leaving a root remanescent of 15 mm. These roots were prepared and restored with the fiberglass post White Post nº3 (FGM, Brazil) and RelyX Unicem (3M ESPE, USA). The roots were randomly divided into nine groups and two slices of 1 mm height were obtained from the cervical third of each one. All slices were analyzed in an optical microscope and the higher and smaller diameter of the post was determined by software of digital measurement for the bonding surface area (mm²). For the push-out test the slices were placed in the center of the base orifice, with the side of the higher diameter of the post facing downwards, allowing its extrusion during the test. A compressive load was applied with constant velocity of 0.5 mm/min, until failure of the system occurs. The bonding resistance (MPa) was calculated by the ratio between the load (N) required to cause failure of the system and the bonding area (mm²) of the post. Statistical analysis were made with ANOVA two-way and Tukey s test (p<0.05). All slices were analyzed with stereoscopic magnifying glass (40x) and classified into six failure pattern. FEA was performed using 3D models in the MARC/MENTAT software, following the same parameters of the laboratorial test. Modified von Mises stress, principal maximum stress, shear stress and tensile component were analyzed. Bond strength values significantly lower only for the smaller indenter (0,5mm). The failure pattern indicated that larger bases and small indenter lead the samples to fail more cohesively (dentin or post). FEA showed that the diameter base size had more significant influence on the stress distribution than the indenter. The indenter diameter and base size influence on stress generation and the experimental results of push-out tests. The association of failure mode and stress distribution analysis using FEA is important to better explain bonding test performance. The use of specific indenter and base diameter sizes for specimens originated by different root third should be pursued.Fundação de Amparo a Pesquisa do Estado de Minas GeraisMestre em OdontologiaO teste de push-out é largamente utilizado para avaliar a resistência adesiva de materiais no interior do canal radicular, determinando procedimentos clínicos e caracterizando materiais. Porém, seus parâmetros não estão bem estabelecidos na literatura. O objetivo desse trabalho foi avaliar a influência do diâmetro da ponta aplicadora de carga e do orifício central da base no desempenho do ensaio de push-out, por meio de ensaio laboratorial e método por elementos finitos (MEF). Três bases com diferentes diâmetros do orifício central (2,5; 3,0 e 3,5mm) e três pontas (0,5; 1,0 e 1,5mm) foram testadas. Para o ensaio laboratorial 90 raízes de incisivos bovinos retilíneas, com 15mm de comprimento e dimensões semelhantes foram utilizados. Estas foram preparados e restauradas com o pino de fibra de vidro White Post nº3 (FGM, Brasil) e RelyX Unicem (3M ESPE, USA). As raízes restauradas foram aleatoriamente divididas em nove grupos e duas fatias de 1 mm de espessura foram obtidas do terço cervical de cada uma. Todas as fatias foram analisadas em microscópio ótico e o maior e menor diâmetro do pino foi determinado por meio de software de medição digital para cálculo da área adesiva (mm²). Para realização do teste de push-out, as fatias foram centralizadas sobre o orifício central da base com o lado de maior diâmetro do pino voltado para baixo, permitindo sua extrusão durante o teste. Na sequência, foi realizado carregamento de compressão com velocidade constante de 0,5 mm/min, até ocorrer falha do sistema e a resistência adesiva (MPa) foi calculada pela razão entre a força (N) necessária para causar falha e área da superfície adesiva (mm²) do pino. A análise estatística foi realizada com ANOVA fatorial (3x3) seguido do teste de Tukey (p<0,05). Todas as fatias foram observadas com lupa estereoscópica com aumento de 40x e classificadas em seis tipos de padrão de falha em função da localização das mesmas. O MEF foi realizado com modelos 3D no software MARC/MENTAT, seguindo os mesmos parâmetros do ensaio laboratorial. As tensões analisadas foram von Mises modificado, tensão máxima principal, tensões de cisalhamento e tração. Os valores de resistência adesiva foram significantemente menores apenas para a menor ponta (0,5mm). A análise do padrão de falha indicou que bases maiores e pontas menores tendem a causar falhas coesivas (dentina ou pino). MEF mostrou que o diâmetro da base tem maior significância na distribuição de tensões do que a ponta. Os diâmetros da ponta e o da base influenciam na distribuição de tensões e nos resultados experimentais do teste de push-out. A associação do padrão de falha e da distribuição de tensões usando MEF é importante no entendimento do comportamento biomecânico do teste. O uso de pontas e bases específicas para amostras de diferentes terços radiculares deve ser preconizado