Microstructural and mechanical analysis of two CAD-CAM lithium disilicate glass-reinforced ceramics

Abstract The aim of this study was to analyze the structural, morphological and mechanical properties of two different lithium disilicate glass-reinforced ceramics for CAD-CAM systems (IPS e.max CAD and Rosetta SM). Five methodologies were used for both ceramics: microstructure (n = 2) was analyzed using x-ray diffraction (XRD); morphological properties (n = 2) were analyzed by scanning electron microscopy (SEM), with and without hydrofluoric etching; porosity (n = 3) was assessed using 3D micro-computed tomography (micro-CT); flexural strength was measured (n =1 0) using the three-point bending test; and bond strength was determined with self-adhesive resin cement (n = 10), using a microshear bond test. After performing all the tests, the data were analyzed using t-Student test and two-way ANOVA. All the tests used a significance level of α = 0.05. High peak positions corresponding to standard lithium metasilicate and lithium disilicate with similar intensities were observed for both ceramics in the XRD analysis. Morphological analysis showed that the crystalline structure of the two ceramics studied showed no statistical difference after acid etching. Additionally, no significant differences were recorded in the number or size of the pores for the ceramics evaluated. Moreover, no differences in flexural strength were found for the ceramic materials tested, or in the bond strength to ceramic substrates for the resin cements. Based on the study results, no significant differences were found between the two CAD-CAM lithium disilicate glass-reinforced ceramics tested, since they presented similar crystalline structures with comparable intensities, and similar total porosity, flexural strength and bond strength.

Influence of furnace type in the crystallization of lithium disilicate on bond strength and flexural strength

Aim: The crystallization step is required for lithium disilicate ceramics to change color, improve the mechanical properties and yield material to support mouth loading. Several furnaces could complete the crystallization process. This study evaluated the flexural and bond strength of lithium disilicate ceramics crystallized by different furnaces with the presence or not of vacum and different holding time. Methods: Forty lithium disilicate samples were divided into two groups: Programat P300 - control group with vacuum and holding time 7 minutes (CG) and FVPlus- experimental group and without vacuum and holding time 25 minutes (EG) and submitted to 2 experimental tests: 3-point flexural strength test and micro shear bond strength test (µSBS). For this test, the surface of the samples was treated and 1mm² of resin cement was applied on the surface. The samples were stored in artificial saliva over 2 time periods (24 hours: T0; 1-month storage: T1). To analyze the morphologic crystals of the ceramics tested, one representative specimen from each group were analyzed by using Scanning Electron Microscopy (SEM). Results: There was no significant difference in 3-point flexural strength test between groups CG and EG (p= 0.984). The µSBS results showed no statistical difference between groups, considering different storage time. There was no difference in the 3-point flexural strength and µSBS for lithium disilicate samples regardless of heat treatment of furnace type. The storage time had no influence on the µSBS. No differences were noted in the shape and size of these crystals when comparing the furnace analyzed by SEM images. Conclusion: Different furnaces did not influence the flexural and bond strength of lithium disilicate ceramics

A importância da hibridização de sistemas de instrumentação no tratamento endodôntico: relato de caso / The importance of instrumentation systems hibridization in endodontic treatment: case report

Introdução: a associação do preparo biomecânico adequado à desinfecção do canal radicular e à obturação satisfatória é importante para que o tratamento endodôntico tenha um prognóstico favorável. A complexidade anatômica dos canais radiculares é um fator limitante na instrumentação e impõe ao operador a necessidade de realizar diferentes manobras para conseguir alcançá-la. Objetivo: relatar um caso de tratamento endodôntico no dente #47, com anatomia complexa e dupla curvatura radicular, em paciente com limitada abertura de boca. Relato de caso: o preparo mecânico foi realizado utilizando-se técnica de instrumentação híbrida, com limas manuais de diferentes tipos (Kerr, Hedströen e Flexofile), brocas Gates-Glidden e limas rotatórias (sistema ProDesign S), que foram associadas na tentativa de aumentar a efetividade da limpeza dos três canais. Entre as sessões, foi utilizada medicação intracanal de hidróxido de cálcio e os canais foram obturados pela técnica de condensação lateral. Conclusão: após o estudo da literatura pertinente e a realização do caso clínico, concluiu-se que por meio da hibridização de sistemas é possível obter um tratamento endodôntico com melhor prognóstico e maior segurança. Ao utilizar o melhor de cada técnica, reforça-se a teoria de que nenhuma delas é totalmente completa e que instrumentos manuais, mesmo com o grande avanço dos aparelhos automatizados, ainda possuem seu valor e continuam sendo essenciais nos protocolos de instrumentação.

Influence of dentistry procedures on masticatory function of dentate patients

Aim: Evaluate the masticatory performance in patients with different clinical situations: patients with natural dentition without restorative and/or orthodontic intervention (Group CG) and patients with restorations and/or orthodontic intervention (Group TG). Subjects received instruction before the experiment, related to masticatory movements. Methods: Three capsules containing the granules were delivered separately to chew for 20 seconds each, controlled by the examiner. One capsule was chewed for 20 seconds only on the left side; the second capsule was chewed for 20 seconds only on the right side; and the third capsule was chewed for 20 seconds to simulate each patient's mastication. The mean data and standard deviation of masticatory function of each patient was calculated. Results: The results obtained in this study showed that there were no statistically significant differences (P < 0.05) between both tested groups (0.0320 ± 0.00716, 0.0436 ± 0.00974). Conclusions: Patients who were submitted to orthodontic and/or restorative procedures, with balanced occlusion could be used as a control group, making easier the patient recruitment. Clinicians and researchers on masticatory performance evaluation could apply the colorimetric method. The colorimetric method was a standardize method, effective and easy to execute. (AU)

Reabilitação protética com componentes dinâmicos ­ relato de caso / Prosthetic rehabilitation with dynamic components ­ case report

Os componentes dinâmicos surgiram como alternativa para reabilitar implantes inclinados em até 20°, possibilitando o restabelecimento da estética, função e reduzindo os custos do procedimento. Sendo assim, o objetivo deste trabalho é apresentar um relato de caso utilizando esses componentes. Durante o exame clínico foi diagnosticado que os implantes apresentavam profundidade gengival rasa, inclinação e paralelismo desfavoráveis. Dessa forma, foi optado pela utilização de pilares retos com componentes dinâmicos, que irão corrigir a inclinação do orifício de acesso do parafuso da prótese definitiva.

Dynamic components were created as an alternative to rehabilitate tilted implants until 20º angled. This component allows aesthetic and function rehabilitation with lower cost comparing to angled abutments. The aim of this study was to present a case report us-ing these dynamic components. The patient presented tilted implants with gingival shallow depth, with unfavourable parallelism. Thus, straight abutment and dynamic components were concomitantly used to correct the access screw hole inclination of final the prosthesis.