Mário Jorge Silva

Effect of ozone gas on the shear bond strength to enamel

Ozone is an important disinfecting agent, however its influence on enamel adhesion has not yet been clarified. Objective: Evaluate the influence of ozone pretreatment on the shear strength of an etch-and-rinse and a self-etch system to enamel and analyze the respective failure modes. Material and Methods: Sixty sound bovine incisors were used. Specimens were randomly assigned to four experimental groups (n=15): Group G1 (Excite® with ozone) and group G3 (AdheSE® with ozone) were prepared with ozone gas from the HealOzone unit (Kavo®) for 20 s prior to adhesion, and groups G2 (Excite®) and G4 (AdheSE®) were used as control. Teeth were bisected and polished to simulate a smear layer just before the application of the adhesive systems. The adhesives were applied according to the manufacturers instructions to a standardized 3 mm diameter surface, and a composite (Synergy D6, Coltene Whaledent) cylinder with 2 mm increments was build. Specimens were stored in 100% humidity for 24 h at 37º C and then subjected to a thermal cycling regimen of 500 cycles. Shear bond tests were performed with a Watanabe device in a universal testing machine at 5 mm/min. The failure mode was analyzed under scanning electron microscope. Means and standard deviation of shear bond strength (SBS) were calculated and difference between the groups was analyzed using ANOVA, Kolmogorov-Smirnov, Levene and Bonferroni. Chi-squared statistical tests were used to evaluate the failure modes. Results: Mean bond strength values and failure modes were as follows: G1- 26.85±6.18 MPa (33.3% of adhesive cohesive failure); G2 - 27.95±5.58 MPa (53.8% of adhesive failures between enamel and adhesive); G3 - 15.0±3.84 MPa (77.8% of adhesive failures between enamel and adhesive) and G4 - 13.1±3.68 MPa (36.4% of adhesive failures between enamel and adhesive). Conclusions: Shear bond strength values of both adhesives tested on enamel were not influenced by the previous application of ozone gas.

Lesões de Abrasão Dentária: Herança de uma Escovagem Traumática?

Resumo A friccao provocada por um agente exogeno numa superficie dentaria pode gerar lesoes de abrasao, quando repetida de forma persistente. A abrasao pode resultar de alguns habitos viciosos, porem, a causa mais referida e a frequencia de uma escovagem exageradamente agressiva dos dentes. Essa e, tambem, a causa com que mais frequentemente se responsabiliza a perda de estrutura dentaria na regiao cervical. Neste artigo serao analisados dois casos clinicos sugestivos de abrasao dentaria devidos a escovagens agressivas. No 1° caso, um paciente do sexo masculino de 60 anos, caucasiano, compareceu numa consulta de rotina sem queixas. Na consulta, observaram-se desgastes cervicais nas superficies vestibulares de pre-molares e molares dos quatro quadrantes, passiveis de terem sido provocados pela accao traumatica de escovagem, de acordo com os dados recolhidos na historia clinica. O 2° caso e de um paciente, tambem do sexo masculino e caucasiano, de 65 anos, que nos procurou para restaurar um dente. Nessa consulta, observaram-se lesoes cervicais vestibulares nos caninos, pre-molares e molares, tambem nos quatro quadrantes, causadas muito provavelmente por uma escovagem agressiva. Estes dois casos sao, no entanto, mais complexos do que aparentam numa primeira observacao. Depois de devidamente analisados, conclui-se que a abrasao pode estar associada uma forte componente erosiva e, a estes dois mecanismos, associam-se muitas vezes fenomenos de abfraccao. Assim, para que o tratamento seja o mais eficaz, e fundamental fazer um correcto diagnostico, que nem sempre e o mais obvio.

Encerramento de Diastemas. Revisão de Conceitos Teóricos a Propósito de um Caso Clínico

Resumo A obtencao de bons resultados no encerramento de diastemas depende de um protocolo de actuacao bem estabelecido. A proposito de um caso clinico, de uma paciente que apresentava multiplos diastemas na regiao anterior da arcada superior e que foi corrigido de uma forma directa com resinas compostas, aborda-se a etiologia dos diastemas e reveem-se nocoes de estetica dentaria e facial que sao muito importantes para o resultado final. O caso e descrito passo a passo, para uma mais facil compreensao dos conceitos teoricos em que se baseia.

Oral yeast colonization throughout pregnancy

Background Recent studies suggest that placenta may harbour a unique microbiome that may have origin in maternal oral microbiome. Although the major physiological and hormonal adjustments observed in pregnant women lead to biochemical and microbiological modifications of the oral environment, very few studies evaluated the changes suffered by the oral microbiota throughout pregnancy. So, the aim of our study was to evaluate oral yeast colonization throughout pregnancy and to compare it with non-pregnant women. Material and Methods The oral yeast colonization was assessed in saliva of 30 pregnant and non-pregnant women longitudinally over a 6-months period. Demographic information was collected, a non-invasive intra-oral examination was performed and saliva flow and pH were determined. Results Pregnant and non-pregnant groups were similar regarding age and level of education. Saliva flow rate did not differ, but saliva pH was lower in pregnant than in non-pregnant women. Oral yeast prevalence was higher in pregnant than in non-pregnant women, either in the first or in the third trimester, but did not attain statistical significance. In individuals colonized with yeast, the total yeast quantification (Log10CFU/mL) increase from the 1st to the 3rd trimester in pregnant women, but not in non-pregnant women. Conclusions Pregnancy may favour oral yeast growth that may be associated with an acidic oral environment. Key words:Oral yeast, fungi, pregnancy, saliva pH.

Influence of Different Solvents on the Morphology of the Hybrid Layer Using Two-Step Etch-and-Rinse Adhesives

To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layers morphology. Four one-bottle etch-and-rinse adhesive systems containing different solvents—Group A: Scotchbond 1XT™– 3 M ESPE, Group B: XP – Bond™ – Dentsply, Group C: Prime&Bond NT® – Dentply, and Group D: One Coat Bond® - Coltène Whaledent—were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used. The hybrid layer thickness average found was 3.23 µm (±0.53) in Group A, 3.13 µm (±0.73) in Group B, 2.53 µm (±0.50) in Group C, and 1.84 µm (±0.27) in Group D. Prime&Bond NT® presented a more inconsistent hybrid layer. The solvent seems to play a significant role in hybrid layer structure and thickness.

Etch-and-Rinse and Self-Etch Adhesives Behavior on Dentin

Hybridization is a key phenomenon in bonding resin-based composite restorations to dentin, and results from a molecular-level interaction between the resin and the demineralized collagen fibrils network. Nanoleakage occurs when small molecules or ions infiltrate into the hybrid layer. Our work aims to evaluate if the type of solvent and adhesive system influences the morphology of the hybrid layer and the occurrence of nanoleakage within it. Human molar teeth were distributed into six groups corresponding to adhesives with different solvents (ScotchbondTM 1XT, XP BondTM, Prime&Bond® NT, One Coat Bond®, AdheSE® and Xeno® V). Dentin disks (specimens) were cut from those teeth. The corresponding adhesive systems and a microhybrid composite (Synergy® D6) were applied onto them. The specimens were thermocycled, fixed, cut, polished, decalcified, dried, and, for nanoleakage evaluation, immersed into a tracer solution. The morphology and nanoleakage analyses were performed with a highresolution scanning electron microscope (field-emission scanning electron microscope —FESEM), and the results were statistically processed. AdheSE® achieved the overall best performance. The type of adhesive, the number of steps, and the solvent seem to play a significant role in hybrid layer morphology and nanoleakage within it. The hybrid layer water absorption can determine the adhesion longevity.