Alex José Souza dos Santos

Evaluation of microleakage in human, bovine and swine enamels

The suitability of bovine and swine teeth has been evaluated when they are used as substitutes for extracted human teeth in varied researches. This study evaluated in vitro the marginal microleakage in human, bovine and swine enamel. Cubic cavities (2 x 2 x 2 mm3) were prepared in enamel blocks from human, swine and bovine teeth. The cavities were filled with composite resin and conventional glass-ionomer cement. All the samples were thermocycled for 1,000 cycles (5 +/- 2 degrees C - 55 +/- 2 degrees C) and immersed in 2% methylene blue solution for 12 hours. The microleakage was quantified by a spectrophotometric technique. The results were statistically analyzed using ANOVA and Tukeys test. The glass-ionomer cement presented significantly higher leakage means (microg/ml +/- SD) than the composite resin for all substrates (0.0695 +/- 0.01313 vs. 0.0471 +/- 0.0163, p < 0.01). No significant differences were found between bovine and swine enamel (0.0668 +/- 0.0246 vs. 0.0674 +/- 0.0286); however, both presented statistically higher leakage means than human enamel (0.0407 +/- 0.0195, p < 0.01). It was concluded that the microleakage pattern was affected by substrates, and that bovine and swine substrates allow higher marginal leakage than human substrates. The results indicate there should be precaution in the substitution of human substrate in laboratory studies of microleakage.

Effect of irradiation times on the polymerization depth of contemporary fissure sealants with different opacities

The aim of this study was to evaluate the depth of curing of 10 contemporary blue light-activated dental flowable materials at several opacities, influenced by different irradiation times using FT-IR spectroscopy. Fifty-five specimens (n = 5) with a 5-mm diameter and 1-mm thickness of translucent (Opallis Flow T), yellowed (Master Flow A2; Opallis Flow A2; Natural Flow A2; Fluroshield Yellowed), and opaque materials (Master Flow OA2; Natural Flow O; Opallis Flow OA3.5; Opallis Flow OP; Fluroshield White) were obtained at six curing times (10s, 20s, 30s, 40s, 50s, and 60s) using a high-intensity LED (Coltolux, Coltène/Whaledent). The degree of conversion (DC) (%) was obtained using the Nexus 470 FTIR Spectrometer (Nicolet Instruments, USA). The FTIR-ATR spectra for uncured and cured samples were analyzed using a ZnSe crystal. The top and bottom surfaces of the cured specimens were analyzed to obtain the depth of curing. Two-way ANOVA was used to analyze the data. The highest curing depth was obtained by Natural Flow OA2, while the lowest was shown by Master Flow OA2. The shortest curing time generated similar depths of cure in comparison with the most extensive for Opallis Flow A2 and Fluroshield Yellowed. Therefore, depth of curing, influenced by the irradiation time, was dependent on the materials. Using the Natural Flow OA2 opaque sealant and the 10-s curing time for Opallis Flow A2 and Fluroshield Yellowed may represent alternative approaches to sealing tooth fissures.

Step-cure Polymerization: Effect of Initial Light Intensity on Resin/Dentin Bond Strength in Class I Cavities

This in vitro study assessed the effect of a step-cure light curing method on resin/dentin bond strength on the buccal wall of Class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Twenty four box-shaped cavities (C-factor = 4.5) were prepared in dentin. Prime&Bond 2.1 was applied and TPH Spectrum (Dentsply) was inserted using a bulk-filling increment. The composite was light-cured using either a step-cure photoactivation technique or a one-step continuous curing method. For step-cure polymerization, the initial cure intensity was varied by changing the distance between the light source and the resin surface. The light-cured resins were cured using four low light intensities: 150(G1), 200(G2), 250(G3) and 300(G4) mW/cm2. In the continuous exposure curing method, the samples were light-activated for 40 seconds at 740 mW/cm2 and irradiation was applied in a box-shaped cavity and a flat cavity (exposed buccal wall, C-factor = 0.22). Samples were prepared for TBS testing by creating bonded beams (of approximately 0.8 mm2) obtained from the buccal wall. The data were analyzed using one-way ANOVA, Tukey Test and Dunnetts Test at a significance level of 0.05. The mean TBS values for the continuous exposure group in the flat and box-shaped cavities were 24.31 and 10.23 MPa, respectively. The corresponding TBS for step-cure polymerization was 23.13 (G3), 18.83 (G2), 14.87 (G1) and 13.26 MPa (G4). Bond strength values to the cavity wall were lower in the three-dimensional cavities and dependent on the light curing method (p < 0.05). The use of a low initial light intensity (200-250 mW/cm2) for 10 seconds followed by high irradiation intensity provided the best bond strengths, similar to bonding in a flat cavity.

Influence of air abrasion and long-term storage on the bond strength of self-etching adhesives to dentin.

This study tested the effects of long-term storage and aluminum oxide air abrasion on the bond strength of self-etching adhesive systems. Extracted human third molars were ground flat with 600-grit SiC paper to expose middle coronal dentin. Clearfil SE Bond and One-Up Bond F were applied to dentin surfaces in accordance with manufacturers instructions with or without previous aluminum oxide 50 microm air abrasion. A crown was built up with the resin composite TPH Spectrum and the specimens were stored in water for 24 hours. The bonded assemblies were vertically sectioned into beams for microtensile bond testing. The beams of each tooth were individually immersed in bottles containing water at 37 degrees C for one day, three and six months; the water was changed daily. The specimens were then subjected to microtensile bond testing. The bond strength data were subjected to ANOVA and Tukey Kramer test. Fractured specimens were analyzed in a scanning electron microscope to determine failure modes. Air abrasion improved Clearfil SE Bond bond strength in the three month evaluation. No significant difference was found between the two adhesives systems, but bond strengths gradually decreased over time. Failure modes varied significantly among groups and were influenced by long-term storage and aluminum oxide air abrasion.

CPP–ACP pretreatment effect on microshear bond strength of simplified etch-and-rinse adhesive systems plus a flowable composite to enamel

This study evaluated the effect of a casein phosphopeptide–amorphous calcium phosphate based paste (MI Paste) on the microshear bond strength (MSBS) of different simplified etch-and-rinse adhesive systems on enamel. Roots were removed from 90 bovine incisors, and the facial enamel was ground flat. Teeth were randomized into nine groups, according to the enamel pretreatment (without or with application of MI Paste for 1 or 2 min) and the adhesive system used (Single Bond, Stae, or Ambar). Composite cylindrical blocks (2 mm height × 1 mm diameter) were built, stored in water for 24 h, and subjected to the microshear test in a universal testing machine with a load of 0.5 mm/min. Failure modes were analyzed using scanning electron microscopy. Data were submitted for statistical analysis by a two-way ANOVA, followed by multiple comparisons with Tukey test (α = 5%). The Ambar group presented the highest MSBS values. Pretreatment with MI Paste for 2 min improved bonding in the Single Bond and Stae groups. In all groups, adhesive failures were most frequent. In conclusion, Ambar presented better performance and did not need any pretreatment. The enamel MSBS of the other simplified adhesive systems was improved by the pretreatment with MI Paste, depending on the time of application.

CLAREAMENTO DENTÁRIO COMO ETAPA PRÉVIA À RESTAURAÇÃO DE DENTES COM ALTERAÇÃO SEVERA DE COR

Introducao: A cor dos elementos dentarios consiste em fator determinante para a harmonia do sorriso, sendo objeto de preocupacao por parte de profissionais e pacientes. Alem da relevância estetica, o clareamento dentario, previo a realizacao do tratamento restaurador, pode orientar a adocao de procedimentos menos invasivos, que contribuam para preservacao da estrutura dentaria. Assim, este relato destaca o papel do clareamento dentario na tomada de decisao do tratamento restaurador. Relato de Caso: Paciente do genero masculino, 30 anos, procurou servico odontologico especializado devido a insatisfacao com o escurecimento dos elementos 11 e 21. Facetas indiretas em cerâmica foram indicadas no planejamento inicial. Previamente a realizacao do tratamento restaurador, foi proposta a realizacao de clareamento dentario dos dentes escurecidos. Apos o sucesso obtido pela associacao das tecnicas de clareamento nao vital em consultorio, e clareamento caseiro, foi tracado novo planejamento, pautando a realizacao de facetas diretas em resina composta. Assim, foram realizadas facetas em resina composta (elementos 11, 12, 21 e 22), instalacao de pinos de fibra de vidro (elementos 11 e 21), alem de ajuste cosmetico (elemento 23), tendo como resultado principal a estetica do sorriso e a satisfacao do paciente. Conclusao: O clareamento dentario, como uma etapa previa ao tratamento restaurador de dentes escurecidos, orientou a definicao do plano de tratamento e contribuiu para adocao de procedimentos menos invasivos. DESCRITORES: Clareamento Dental. Facetas Dentarias. Restauracao Dentaria Permanente.

Impact of adhesive and photoactivation method on sealant integrity and polymer network formation

We evaluated the influence of photoactivation method and hydrophobic resin (HR) application on the marginal and internal adaptation, hardness (KHN), and crosslink density (CLD) of a resin-based fissure sealant. Model fissures were created in bovine enamel fragments (n = 10) and sealed using one of the following protocols: no adhesive system + photoactivation of the sealant using continuous light (CL), no adhesive system + photoactivation of the sealant using the soft-start method (SS), HR + CL, or HR + SS. Marginal and internal gaps and KHN were assessed after storage in water for 24 h. The CLD was indirectly assessed by repeating the KHN measurement after 24 h of immersion in 100% ethanol. There was no difference among the samples with regard to marginal or internal adaptation. The KHN and CLD were similar for samples cured using either photoactivation method. Use of a hydrophobic resin prior to placement of fissure sealants and curing the sealant using the soft-start method may not provide any positive influence on integrity or crosslink density.