Influence of number and position of porcelain specimens in the furnace on flexural strength and translucency

The aim of this study was to investigate the influence of the quantity and positioning of feldspathic ceramic specimens inside the furnace on their flexural strength and translucency. The tested hypotheses were that the arrangement of specimens in the furnance would not influence 1) the translucency or 2) the biaxial strength of the porcelain. Methods: Ninety porcelain specimens were made (1.2 mm thickness and 13.5 mm diameter) and assigned into two main groups (n=15): G1 group - 15 firing cycles containing only one specimen each, always at the center of the refractory; and G5 group - 15 firing cycles containing five specimen each, where one specimen was at the center of the refractory and four specimens positioned equidistantly on the periphery. The translucency test was performed using a spectrophotometer, followed by the flexural strength test, according to ISO 6872:2015. T-student test was performed for both the mechanical and optical obtained data. Results: The flexural strength of the porcelain was not affected by the positioning (center x periphery) of the specimens inside the furnace (p =0.08), but the translucency was affected (periphery > center; p =0.009). Regarding to the number of feldspathic ceramic specimens, the biaxial flexural strength was affected (p =0.025), as well as the translucency (p <0.05). Conclusion: A higher quantity of feldspathic ceramic specimens for each firing cycle decreased its biaxial flexural strength and translucency. Also, specimens positioned at the center of the refractory became less translucent than those positioned at the periphery.

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

Surface treatment and adhesion approaches on polymer-infiltrated ceramic network: influence on the bond strength to resin cement

Aim: To evaluate the effect of different surface treatments and adhesive approaches on the microshear bond strength of resin cement to a polymer-infiltrated ceramic network (PICN). Methods: PICN blocks were randomly assigned into 9 groups (n=10): CTRL: no treatment; HF: 5% hydrofluoric acid etching; HF-S: HF + silane; HF-S-A: HF-S + adhesive (Adper Single Bond 2); HF-UA: HF + universal adhesive (Single Bond Universal); SB: sandblasting with 50 µm Al2O3 particles; SB-S: SB + silane; SB-S-A: SB-S + adhesive; SB-UA: SB + universal adhesive. Resin cement microcylinders (Ø = 0.96 mm; height = 1 mm) (RelyX Ultimate) were built upon the PICN surface after roughness and contact angle measurements. Next, microshear bonding tests (µSBS) were performed (0.5 mm/min) after water storage (37ºC, 90 days) and thermocycling (12,000 cycles; 5ºC-55ºC). Failure modes were observed under stereomicroscope. Bond strength data were analyzed by two-way ANOVA/Tukey's test and t-tests. Kruskal-Wallis/Dunn's tests were conducted for roughness and contact angle data (α = 0.05). Results: A rougher surface and lower contact angles were observed for Sandblasting. HF-S (18.54 ± 2.03 MPa), SB-S (19.00 ± 1.66 MPa) and SB-UA (18.07 ± 2.36 MPa) provided the highest bond strength values, followed by the other treated groups. The CTRL group resulted in lower bond strength (7.18 ± 2.34 MPa). Conclusion: Hydrofluoric acid etching followed by silane application and sandblasting followed by silane or universal adhesive are useful clinical steps to enhance bonding to PICN. Adhesive applications after HF etching have no advantages in bonding to PICN

Effect of a Prebrushing Mouthwash on Color Stability of Composite Resins / Efeito de um Evidenciador de Placa na Estabilidade de Cor de Resinas Compostas

Despite composite resins capacity to mimic dental tissues, they can discolor over time. However, there is no information on the effect of prebrushing mouthwashes on the composite resin staining. This study aimed to evaluate the effect of prebrushing mouthwashes on the color stability of three composite resins. Twenty specimens of each resin were prepared: Filtek Z250 (3M ESPE ­S Paul, MN, USA), Charisma (Heraeus Kulzer GmbH - Hanau - Germany) e EvoluX (Dentsply- Petrópolis - Brazil). Groups were randomly divided accord to the treatment: immersion in prebrushing mouthwash (test group) or immersion in deionized water (control group). Test groups were immersed in 10 ml of prebrushing mouthwash Plax Magic (Colgate-Palmolive, São Bernardo do Campo, SP, Brazil) for 60 s three times a day during 35 days following the manufacturer's instructions. Color measurements were performed after 24 h of specimen's preparation and after 7, 14, 21, and 35 days of immersion time. Results showed that prebrushing mouthwash Plax Magic promoted a color change in all the tested materials and evaluation time. The color change was greater in composite resin Charisma, followed by Z250 and EvoluX. Therefore, prebrushing mouthwash promoted a color change in all the materials used. Composite resin Charisma demonstrated less color stability than Filtek Z250 resin and EvoluX resin, which was the most stable. (AU)

Apesar da capacidade das resinas compostas de mimetizar os tecidos dentais, esses materiais podem ter sua cor alterada com o tempo. No entanto, não há informação na literatura sobre o efeito de evidenciadores de placa na estabilidade de cor desses materiais. Este estudo teve por objetivo avaliar o efeito de um evidenciador de placa na estabilidade de cor e três resinas compostas. Para isso, 20 espécimes de cada resina foram preparados: Filtek Z250 (3M ESPE ­S Paul, MN, EUA), Charisma (Heraeus Kulzer GmbH - Hanau - Alemanha) e EvoluX (Dentsply- Petrópolis - Brasil). Os grupos foram aleatoriamente divididos de acordo com o tratamento a ser submetido: imersão no evidenciador de placa (grupo teste) ou imersão em água deionizada (grupo controle). Os grupos teste foram imersos em 10 ml do evidenciador de placa Plax Magic (Colgate Palmolive, São Bernardo do Campo, SP, Brasil) por 60 s três vezes por dia durante 35 dias, de acordo com a orientações de uso do fabricante. As leituras de cor foram feitas após 24 h da preparação dos espécimes e após 7, 14, 21 e 35 dias de imersão. Os resultados mostraram que o evidenciador de placa Plax Magic promoveu alteração de cor em todos os materiais usados e em todos os tempos de leitura. A alteração de cor foi maior na resina Charisma, seguida da Z250 e EvoluX. Portanto, o evidenciador de placa promove alteração de cor em todos os materiais testados. A resina composta Charisma demonstrou menor estabilidade de cor que as resinas Z250 e EvoluX, que, por sua vez, foi a mais estável. (AU)

Dentists' Attitudes towards the Dental Ceramic Choice for Metal-Free Restorations: a Questionnaire Survey / Atitudes de Dentistas Frente à Escolha de Cerâmicas Dentárias para Restaurações Livres de Metal: uma Pesquisa de Questionário

A wide variety of dental ceramics is launched every year. Therefore, clinicians should constantly study and update themselves to correctly indicate these materials. This cross-sectional study aimed to assess the association of dentists' academic aspects with their knowledge and the indication of dental ceramics for metal free restorations. All the dentists from private clinics who affirmed to perform prosthetic treatments on their patients in a Southern Brazilian city were personally invited to this research to avoid dropouts. Participants answered questions related to their knowledge of different dental materials, their information sources and usage frequency of ceramic materials, and related to their academic training/education. Chi-square tests were performed to evaluate the association among the outcomes (knowledge of different materials, information sources considered for material selection and their frequencies of use) and exposure variables (time since graduation and post-graduation degree). Significant associations were also submitted to Chi-square residual analysis. A response rate of 73.3% was reached. The most known and used materials were Y-TZP and porcelain veneered zirconia, respectively, whereas the least known was leucite-based ceramic. The majority of the professionals with at least 25 years since graduation claimed not to know lithium disilicate or leucite-based ceramics, and a significant number of these professionals allow the laboratory prostheses technician to choose the restorative material. In addition, most of dentists with no post-graduation said they did not have knowledge about leucite and lithium disilicate. It was evidenced that continuing education plays an important role in the dentists' attitudes regarding ceramic materials. (AU)

Uma grande variedade de cerâmicas é lançada no mercado a cada ano. Portanto, os clínicos devem se manter em constante estudo e atualização para indicar corretamente o uso desses materiais. Assim, este estudo transversal teve por objetivo avaliar a associação entre aspectos acadêmicos de dentistas com seus conhecimentos e as indicações de cerâmicas dentárias para uso em restaurações livres de metal. Para isso, todos os dentistas de clínicas privadas que afirmaram realizar tratamentos protéticos em seus pacientes em uma cidade do sul do Brasil foram pessoalmente convidados a participar desta pesquisa para evitar desistências. Os participantes responderam a questões relacionadas ao seu conhecimento sobre diferentes materiais dentários, suas fontes de informação, a frequência de uso de materiais cerâmicos, e, também, sobre sua formação acadêmica. Testes qui-quadrado foram realizados para avaliar a associação entre os desfechos (conhecimento de diferentes materiais, fontes de informação consideradas para a seleção do material e sua frequência de uso) e as variáveis de exposição (tempo desde a graduação e grau de pós-graduação). As associações significativas foram submetidas à análise de resíduos do qui-quadrado. A taxa de resposta obtida foi de 73,3%. O material mais conhecido e usado foi a Y-TZP e zircônia recoberta por porcelana, respectivamente, enquanto que o material menos conhecido foi a cerâmica a base de leucita. A maioria dos profissionais com pelo menos 25 desde a graduação afirmaram não conhecer as cerâmicas a base de dissilicato de lítio ou leucita, e um significativo número desses profissionais permitem que o técnico em prótese dentária escolha o material restaurador. Ainda, a maioria dos dentistas sem pós-graduação disseram não conhecer as cerâmicas a base de dissilicato de lítio ou leucita. Concluiu-se que a educação continuada é um fator determinante nas atitudes de dentistas em relação aos materiais cerâmicos. (AU)

Optical Properties of a Glass Ceramic and an Indirect Resin Composite: Effects of Polishing and Staining / Propriedades Ópticas de uma Cerâmica Vítrea e uma Resina Composta Indireta: Efeitos do Polimento e Manchamento

Little information is available about the optical behavior of glass ceramics and indirect resin composites. This study aimed to evaluate if an indirect resin composite can present similar behavior of color stability and translucency to a glass ceramic after polishing and aging in staining beverage. Specimens of a dental ceramic (IPS e.max Ceram) and an indirect resin composite (SR Adoro) were made. Half the specimens of each material were polished with disc-shaped tips. Groups were divided according to aging media: distilled water or immersion in red wine for 20 min/day during 30 days. CIE L*a*b* coordinates were measured with a spectrophotometer at baseline and after 30 days of aging. Color change was calculated by CIEDE2000 and translucency was calculated by contrast ratio (CR). Statistical analysis were performed with ANOVA and Tukey tests. Aging in red wine caused perceptible color change in both materials. Polishing only increased color change of indirect composite when aged in red wine. Ceramic groups showed greater opacity than the composite in all measurements. The indirect composite remained more translucent and results showed that it is capable of presenting color stability similar to a ceramic. However, polishing seems to increase its color change. (AU)

Pouca informação comparando o comportamento óptico de cerâmicas vítreas e resinas compostas indiretas estão disponíveis na literatura. O objetivo deste estudo foi avaliar se uma resina composta indireta pode apresentar comportamento semelhante a uma cerâmica vítrea em relação à estabilidade de cor e translucidez após polimento e envelhecimento em meio altamente pigmentante. Espécimes de uma cerâmica vítrea (IPS e.max Ceram) e uma resina composta indireta (SR Adoro) foram preparados. Metade dos espécimes de cada material foram polidas com pontas de polimento. Os grupos foram divididos conforme o meio de armazenamento: água destilada ou vinho tinto por 20 min/dia durante 30 dias. As coordenadas CIEL*a*b* foram medidas com espectrofotômetro previamente e após os 30 dias de armazenamento. A alteração de cor foi calculada pela equação CIEDE2000 e a translucidez foi calculada por razão de contraste. A análise estatística foi realizada pelos testes ANOVA e teste de Tukey. O armazenamento em vinho levou a uma alteração de cor perceptível nos dois materiais. O polimento apenas causou alteração de cor na resina composta indireta quando imersa em vinho tinto. A resina composta indireta manteve-se mais translúcida e os resultados mostraram que esse material é capaz de apresentar estabilidade de cor semelhante à cerâmica. No entanto, o polimento parece aumentar sua alteração de cor. (AU)