Color and translucency stability of CAD/CAM restorative materials

Aim: This study assessed the color and translucency stability of a polymer infiltrated ceramic network (PICN) and compared it with a resin composite (RC) and a feldspathic ceramic (FEL). Methods: Disc-shaped samples of a PICN (Vita Enamic), a feldspathic ceramic (Vitablocks Mark II), and a resin composite (Brava block) were prepared from CAD/CAM blocks. PICN and RC surfaces were finished with a sequence of polishing discs and diamond paste. FEL samples received a glaze layer. The samples were subjected to 30-min immersions in red wine twice a day for 30 days. CIEL*a*b* coordinates were assessed with a spectrophotometer at baseline and after 15 and 30 days of immersion. Color alteration (ΔE00) and translucency parameter (TP00) were calculated with CIEDE2000. Average roughness was measured before the staining procedures. Color difference and translucency data were analyzed with repeated-measures ANOVA and Tukey's tests. Roughness was analyzed with the Kruskal-Wallis test. Results: Roughness was similar among the experimental groups. All materials had their color alteration significantly increased from 15 to 30 days of staining. PICN reached an intermediate ΔE00 between FEL and RC at 15 days. PICN revealed a color alteration as high as the composite after 30 days. No statistical difference was observed regarding translucency. Conclusion: PICN was not as color stable as the feldspathic ceramic at the end of the study. Its color alteration was comparable to the resin composite when exposed to red wine. However, the translucency of the tested materials was stable throughout the 30-day staining

Polishing of ground y-tzp ceramic is mandatory for improving the mechanical behavior

Abstract It evaluated the effect of aging by Low Temperature Degradation (LTD), executed after post- processing surface treatments (polishing, heat treatment and glazing), on the surface characteristics (micromorphology and roughness) and on the structural stability (phase transformation and mechanical behavior-flexural strength and structural reliability) of a ground yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. Discs of Y-TZP (VITA In-Ceram YZ) were manufactured (ISO:6872-2015; 15 mm in diameter and 1.2 ± 0.2 mm in thickness) and randomly assigned into 10 groups according two factors: "aging" in 2 levels (with or without) and "surface treatment" in 5 levels (Ctrl: as-sintered; Gr: grinding with coarse diamond bur; Gr + HT: grinding plus heat treatment; Gr + Pol: grinding plus polishing; Gr + Gl: grinding plus glazing). Roughness (n=30), biaxial flexural test (n=30), phase transformation (n=2), and surface topography (n=2) analyses were performed. Aging led to an intense increase in monoclinic (m) phase content for all the tested conditions, being the as-sintered samples (Ctrl= 65.6%) more susceptible to the t-m phase transformation. Despite of increasing the m-phase content, aging was not detrimental for characteristic strength (except to the grinding condition). There was no significant reduction in the Weibull modulus after surface treatments. Additionally, heat treatment and glazing after grinding led to a decrease in characteristic strength, while polishing presented the highest characteristic strength values. Thus, polishing is mandatory after grinding the Y-TZP ceramic, while performing glazing or heat-treatment alone after grinding lead to the worst mechanical performance.

Resumo Este estudo avaliou o efeito do envelhecimento através da degradação a baixas temperaturas (low temperaturare degradation - LTD) após a realização de tratamentos de superfície pós- sinterização (polimento, tratamento térmico e glaze) nas características superficiais (micromorfologia e rugosidade), e na estabilidade estrutural (transformação de fase e comportamento mecânico - resistência flexural e confiabilidade estrutural) de uma cerâmica de zircônia tetragonal policristalina estabilizada por ítria (Y-TZP) desgastada. Discos de cerâmica Y-TZP (VITA In-Ceram YZ) foram confeccionados (ISO:6872-2015; 15mm de diâmetro e 1,2 ± 0,2mm de espessura) e randomicamente divididos em 10 grupos de acordo com dois fatores: "envelhecimento" (com e sem) e "tratamento de superfície" (Ctrl - sem tratamento; Gr - desgaste com ponta diamantada grossa; Gr + HT - desgaste mais tratamento térmico; Gr + Pol - desgaste mais polimento; Gr + Gl - desgaste mais glazeamento). Foram realizadas as análises de rugosidade (n=30), flexão biaxial (n=30), transformação de fase (n=2) e topografia de superfície (n=2). O envelhecimento levou a um aumento intenso no conteúdo de fase monoclínica (m) em todas as condições testadas, sendo observada uma maior susceptibilidade de transformação de fase t-m nas amostras do grupo controle (Ctrl= 65.6%). Apesar de provocar elevada transformação de fase, o envelhecimento não apresentou efeitos negativos nos desfechos avaliados. Não houve redução significativa do módulo de Weibull após os tratamentos. Além disso, o tratamento térmico e o glaze após desgaste levaram a uma redução da resistência característica, enquanto que o grupo polimento apresentou o mais alto valor de resistência característica. O glaze e o tratamento térmico geraram o pior desempenho mecânico, portanto a realização do polimento após desgaste de uma cerâmica Y-TZP é obrigatória.

Eficácia de dois métodos de degermação das mãos / Effectiveness of two methods of hands degermation

A lavagem das mãos reduz as bactérias da pele, diminuindo as taxas de infecções. Há várias técnicas de higienização das mãos, devendo o profissional escolher a mais adequada. OBJETIVOS: este trabalho avaliou a eficácia da lavagem cirúrgica das mãos e antebraços com escova impregnada com clorexidina a 2%, comparando com o método de fricção das mãos e antebraço com sabonete líquido contendo clorexidina a 2%. MATERIAIS E MÉTODOS: foram analisadas amostras das pontas dos dedos polegar e indicador, palma da mão e antebraço, de 40 alunos do curso de Odontologia da UNIFRA. A primeira degermação realizada foi com a escova impregnada com clorexidina a 2%, e, sete dias após, os mesmos participantes degermaram as mãos com sabonete contendo clorexidina a 2%. As amostras foram coletadas em placas contendo meio Ágar Base Sangue, identificadas e levadas ao laboratório de microbiologia. RESULTADOS:os mostraram que o método de fricção com sabonete contendo clorexidina a 2% apresentou melhores resultados. CONCLUSÃO: a higienização das mãos pelo método de fricção com sabonete contendo clorexidina a 2% foi mais eficaz quando comparada à realizada com escova impregnada com clorexidina a 2%, sugerindo um método de preparo pré-cirúrgico das mãos mais rápido, eficaz e menos oneroso... (AU)

ABSTRACT Hand washing reduces the amount of skin bacteria, thus contributing to reducing infection rates. There are several techniques for hand washing and the health professional should choose the most appropriate one. OBJECTIVES: This study evaluated the effectiveness of surgical hands and forearms washing made with brush impregnated with 2% chlorhexidine, compared with the friction method of hands and forearms with liquid soap containing 2% chlorhexidine. MATERIALS AND METHODS: We analyzed tip of the thumb and index finger, palm and forearm from 40 students of Dentistry from UNIFRA. The first protocol antisepsis was performed with a brush impregnated with 2% chlorhexidine, and seven days later, the same participants washed their hands with soap containing 2% chlorhexidine. The samples were collected in plates containing Blood Agar Base, identified and taken to the microbiology laboratory. RESULTS:The method of rubbing the soap containing 2% chlorhexidine performed better. CONCLUSION: Hand hygiene by friction method with soap containing 2% chlorhexidine is more effective than the one performed with brush impregnated with 2% chlorhexidine, suggesting a faster, effective and less costly presurgical hand preparation... (AU)