Mechanical Properties, Wear Resistance, and Reliability of Two CAD-CAM Resin Matrix Ceramics.

Background and Objectives: There are limited data regarding the behavior of resin matrix ceramics for current CAD-CAM materials. Further studies may be beneficial and can help clinicians planning to use these materials during prosthodontic rehabilitation. The aim of this study was to evaluate and compare the flexural strength and strain distributions, filler content, wear, and reliability of two resin matrix ceramic CAD-CAM materials. Materials and Methods: Two resin matrix ceramics, Ambarino High-Class (AH) and Vita Enamic (VE), were tested for flexural strength (n = 24), wear (n = 10), and reliability (n = 18). Thermogravimetric analysis was used to determine the percentage of filler by weight, and digital image correlation (DIC) was used for strain analysis in flexural strength test. Reliability of each resin matrix ceramic was compared after accelerated lifetime testing of crowns using a two-parameter Weibull distribution. Data of flexural strength, wear, and thermogravimetry were analyzed by independent t-tests with significance level at 5%. Results: The results of DIC analysis were analyzed by a qualitative comparison between the images obtained. The materials tested showed different flexural strength (p < 0.05) and strain distributions. The filler content was the same as informed by manufacturers. No difference was observed in the wear or reliability analysis (p > 0.05). The flexural strength of material AH was superior to VE, and the strain distribution was compatible with this finding. Conclusions: The two resin matrix ceramics tested showed similar behavior in wear and reliability analysis. Both can provide safe use for dental crowns.

Biocompatible silver nanoparticles incorporated in acrylic resin for dental application inhibit Candida albicans biofilm.

BACKGROUND: Although silver nanoparticles (SNP) have proven antimicrobial activity against different types of microorganisms, the effect of SNP incorporation into acrylic resin to control Candida albicans biofilm formation aiming at the prevention of Candida-associated denture stomatitis has not yet been fully elucidated. OBJECTIVES: This study aimed to evaluate the antimicrobial effect of an acrylic resin containing SNP on C. albicans biofilm growth, the flexural strength of this material and tissue reaction in the subcutaneous connective tissue of rats to SNP. METHOD: SNP were synthesized through silver nitrate reduction by sodium citrate. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to verify the size and colloidal stability. SNP were added to acrylic resin monomer (Lucitone 550) at 0.05, 0.5 and 5 vol%. The antimicrobial effect against C. albicans (ATCC 10231) was investigated by the enumeration of colony-forming units (CFUs) and SEM. The three-point bending test was performed to analyze the flexural strength. Tissue reaction was evaluated after 7 and 60 days of implantation in the connective tissue of Wistar rats. RESULTS: Spherical particles of 5 and 10 nm were obtained. SNP at 0.05 and 0.5% incorporated into acrylic resin was effective in reducing C. albicans biofilm growth (p < .001). SEM revealed that the material was able to disrupt C. albicans biofilm formation and did not reduce the flexural strength compared to control (p > .05). The inflammatory response observed 60 days after implantation SNP in the subcutaneous tissue was similar to control. CONCLUSION: It was concluded that SNP addition at 0.05 and 0.5% into acrylic resin exhibited antimicrobial effects against C. albicans biofilm, did not interfere in the flexural strength and may be considered biocompatible.

Survival of all-ceramic restorations after a minimum follow-up of five years: A systematic review.

OBJECTIVE: The purpose of this systematic review was to compare the survival and complication rates of all-ceramic restorations after a minimum follow-up time of 5 years. DATA SOURCES: A comprehensive search of studies published from 2005 to November 2015 and listed in the PubMed/MEDLINE, Scopus, and Cochrane Library databases was performed in accordance with the PRISMA statement. Two reviewers independently analyzed the abstracts. Relevant studies were selected according to predetermined inclusion criteria. RESULTS: Twenty-nine studies were selected for the final analysis from an initial yield of 514. Only four studies fulfilled the requirement of having a randomized design, and 25 studies were prospective with a mean follow-up period of 5 to 16 years. Overall, the 5-year complication rates were low. The most frequent complications were secondary caries, endodontic problems, ceramic fractures, ceramic chipping, and loss of retention. CONCLUSION: This systematic review showed that all-ceramic restorations fabricated using the correct clinical protocol have an adequate clinical survival for at least 5 years of clinical service with very low complication rates. Minor ceramic chipping and debonding did not affect the longevity of the restorations. CLINICAL RELEVANCE: Long-term clinical performance of all-ceramic restorations manufactured using various ceramic systems provides clinical evidence of complications and long-term management of these restorations. Available evidence indicates the effectiveness of many ceramic systems for numerous clinical applications. Correct planning and a rigorous technical execution protocol increase clinical success. Studies of ceramic prostheses indicate more problems with ceramic failure and debonding.

Influência do torque e da ciclagem mecânica na manutenção da pré-carga e resistência à fratura de parafusos de retenção em diferentes junções parafusadas / Influence of torque and mechanical cycling in preload maintenance and resistance to fracture of retaining screws in different implant-joints

Sendo o afrouxamento e fratura dos parafusos de retenção as principais complicações em próteses implantossuportadas, o objetivo deste estudo foi avaliar a manutenção da pré-carga e ocorrência destas fraturas em parafusos de pilares UCLA, para implantes de conexão hexagonal externa e cone Morse, em função do torque aplicado (recomendado pelo fabricante, torque obtido através de aperto manual e sem torque), submetidos à ciclagem mecânica. Sequencialmente, investigou-se a resistência à fratura desses parafusos por meio do teste de compressão. Utilizou-se 36 implantes embutidos em poliuretano divididos em 6 grupos. De forma randomizada, os espécimes pertencentes ao grupo sem torque foram submetidos a ciclagem mecânica e os dos grupos torque recomendado pelo fabricante e torque manual foram submetidos a aplicação do torque e mensuração da pré-carga remanescente, antes e após a ciclagem mecânica. Sendo os parafusos submetidos ao teste de resistência a fratura por meio do ensaio de compressão. O torque remanescente foi significantemente menor (p<0,05) após a ciclagem mecânica. Ao se comparar os dois tipos de conexão, não houve diferença em relação o torque remanescente (p>0,05). Para os diferentes tipos de torque, observou-se que quando se aplicou o torque recomendado pelo fabricante o torque remanescente foi significativamente maior (p<0,05) quando comparado ao grupo que recebeu o torque manual. Três parafusos fraturaram, equivalendo a 8,33%. No teste de resistência a compressão os parafusos novos apresentaram as maiores médias para a força máxima e também para deformação na força máxima, havendo diferença estatisticamente significativa (p<0,05) ao se comparar com os parafusos ciclados. Dos 12 parafusos novos, 6 fraturaram durante o teste. Para os parafusos ciclados, houve a mesma quantidade de fratura. A maior média para força de ruptura (FR) ocorreu nos parafusos novos. Conclui-se então que a ciclagem mecânica e os diferentes valores de torque de inserção, sendo estes abaixo do que se recomenda o fabricante, interferiram negativamente nos valores de pré-carga dos parafusos de retenção nas condições avaliadas e embora os parafusos submetidos a ciclagem tenham apresentado uma menor média de força de ruptura, a diferença encontrada não apresentou poder estatístico que comprovasse sua influência na fratura dos parafusos de retenção testados(AU)

Being loosening and fracture of retention screws the main complications in implantsupported prostheses, this study aimed to evaluate the preload maintenance and the occurrence of fractures at screws of UCLA-type abutment for implants with external connection and Morse Taper, due to the applied torque (recommended by the manufacturer, torque obtained by manual tightening and no torque), submitted to mechanical cycling. Sequentially, the fracture resistance of these screws through the compression test.was investigated by the compression test on a universal testing machine. Thirty-six implants embedded in polyurethane were used and divided into 6 groups. Randomly, the specimens belonging to the group without torque underwent mechanical cycling and groups of recommended by the manufacturer torque and manual torque underwent torque application and measurement of the remaining preload, before and after mechanical cycling. The screws were submitted to the fracture resistance test by the compression test. The preload maintenance was significantly lower (p <0,05) after mechanical cycling. When comparing the two types of connection, there was no difference regarding to preload maintenance (p>0,05). For different types of torque, it was observed that, when it was applied the recommended by the manufacturer torque, the preload maintenance was significantly higher (p <0,05) compared to the group that received the manual torque. Three fractured, being equivalent to 8,33%. The new screws showed the highest average for maximum strength and deformation at full strength, with a statistically significant difference (p <0.05) when compared with the cycled screws. Of the 12 new screws, 6 fractured during the test. The highest average for fracture strength (FS) also occurred on the new screws. It was concluded that the mechanical cycling and different insertion torque values, which are lower than recommended by the manufacturer, negatively interfered on the preload maintenance of the retention screws of bolted joints in the evaluated conditions and although the screws submitted to cycling have presented a lower tensile strength average, the difference found did not present statistical power that would prove their influence on fracture of the tested retention screws(AU)