Masahiro Aida

Adhesion of composite to porcelain with various surface conditions.

This study evaluated the adhesion of composite resin to five different surface conditions of porcelain samples that were treated with three kinds of silane agents. Two of these were commercially available Porcelain Liner M and Tokuso Ceramic Primer, and one was an experimental agent. The commercially available silane agents gave high bond strengths without hydrofluoric acid etching, which gave the greatest roughness on the porcelain surface. One component of these commercially available silane agents was gamma-methacryloxypropyl trimethoxysilane, and the other was the carboxylic acid. As a result of the effective formation of siloxane bonds by mixing with acid solution, porcelain surface conditions did not affect the bond strengths.

The influence of surface conditions and silane agents on the bond of resin to dental porcelain

The influence of porcelain surface condition and the application of silane agents on the adhesion between resin and dental porcelain were investigated. The experimental variables included three porcelain surface preparations, as polished, etched with phosphoric acid, or etched with hydrofluoric acid and three kinds of commercially available silane coupling agents. The shear bond strength between the light-cured composite and the dental porcelain was measured after one-day immersion in 37 degrees C water. Samples without the silane agent application were also tested as controls. Without the silane agent, hydrofluoric acid-etched specimens had a higher bond strength than polished or phosphoric acid-etched specimens. The combination of hydrofluoric acid-etching and an application of Cosmotech Porcelain Primer increased the bond strengths more than that of phosphoric acid-etching. With the application of Laminabond Porcelain Primer or Optec Silane Coupling Agent, high bond strengths were obtained regardless of the porcelain surface condition. Therefore, it seems the chemical reactions between the porcelain surface and silane agents were responsible for the high shear bond strengths.

Effect of Reacted Acidic Monomer with Calcium on Bonding Performance

We determined the number of reacted and unreacted 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) molecules with calcium during the demineralization process of hydroxyapatite or dentin by 10-MDP-based one-step (Clearfil Tri-S Bond, TS) or two-step self-etch adhesive (Clearfil SE Bond Primer, SE). We then examined the effects of the number of reacted and/or unreacted 10-MDP molecules on the initial bond strength and bond durability of the resultant adhesive layer. The null hypotheses were that (1) the etching efficacy of tooth apatite by 10-MDP used in TS was the same as that in SE, and (2) the unreacted 10-MDP polymer included within the adhesive layer does not affect bond durability. Addition of hydroxyapatite or dentin to the TS and SE resulted in decreases in the NMR peak intensities for 10-MDP. The peak intensity for 10-MDP showed a greater reduction in SE than in TS, consistent with the observation that SE provided significantly higher initial mean bond strengths than TS. Further, the unreacted 10-MDP polymer within the adhesive layer did not decrease the mean bond strength, despite the application of 20,000x thermo-cycling.

Degradation-stage Effect of Self-etching Primer on Dentin Bond Durability

It is well-known that self-etching primers can be altered. However, the effects from altered primers on the dentin bond durability have yet to be thoroughly identified. In this study, we examined the effects from 5 altered Liquid A primers in different stages of degradation—where 2-hydroxyethylmethacrylate (HEMA) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP), used in Liquid A primers, were altered by the hydrolysis of the methacryloxy ester portion in the HEMA and MDP—on the hybrid layer’s quality and dentin bond durability. The hypothesis was that degradation stages of altered Liquid A primers have no effect on the hybrid layer’s quality and on dentin bond durability. Bond strengths, obtained after thermo-cycling, were strongly dependent on the degradation stage of the altered Liquid A primer. Alterations of self-etching primers reduced dentin bond durability and decreased the created hybrid layer’s quality.

A selective medium for Rothia mucilaginosa and its distribution in oral cavities

A selective medium for Rothia mucilaginosa (RMSM) was developed to examine the population of R. mucilaginosa in oral cavities. The growth recovery of R. mucilaginosa on RMSM was 85.1% relative to HI medium. R. mucilaginosa was detected at 3.4% of total bacteria from stimulated saliva of 8 subjects.

A novel selective medium for the isolation and distribution of Rothia dentocariosa in oral cavities.

Rothia dentocariosa is an indigenous microbial flora of dental plaque. To examine the bacterium population in oral cavities, a novel selective medium, designated RDSM, was developed for the isolation of R. dentocariosa. RDSM was prepared by adding 0.5 μg/ml of lincomycin, 10 μg/ml of colistin, and 40% sucrose to Heart Infusion (HI). Average growth recovery of R. dentocariosa on RDSM was 93.8% that of HI medium. Growth of other bacteria including Rothia mucilaginosa, Neisseria, Actinomyces, or streptococci was remarkably inhibited on the selective medium. Clinical efficacy was evaluated by the recovery of R. dentocariosa on RDSM from the stimulated saliva samples of 8 volunteers. R. dentocariosa was detected at 2.6 (range: 1.0-4.6) % to total bacteria of 8.0×10(7)CFU/ml on BHI in their oral cavities. The new selective medium, RDSM, was highly selective for R. dentocariosa and was useful for the isolation of R. dentocariosa from clinical samples.

Zirconia surface modification by a novel zirconia bonding system and its adhesion mechanism

OBJECTIVE Bonding to zirconia has been of great interest over the last 10-15 years. The aim of this study was to develop a zirconia bonding system and clarify its adhesion mechanism. METHODS A zirconia primer was prepared using tetra-n-propoxy zirconium (TPZr) and water. A silane primer was also prepared using γ-methacryloyloxypropyltrimethoxysilane (γ-MPS) and hydrochloric acid. After the zirconia primer was applied to the oxidized zirconia surface, the silane primer was applied to the ZrO2-functionalized layer and the resin cement was applied to the silane-modified layer. Ceramic Primer II was used as a typical MDP-based ceramic primer. Shear bond strengths were measured using a universal testing machine. To clarify the enhancing mechanism of the zirconia bonding system, X-ray photoelectron spectroscopy (XPS) analyses were performed. RESULTS The zirconia bond strength was affected by the surface wettability of zirconia, and the compositions of TPZr and water utilized in the zirconia primer. When the zirconia primer, consisting of 10μL TPZr and 13μL water, was applied to the zirconia surface that had been oxidized by H2O2 above 10%, the maximum bond strength of 8.2MPa was obtained. The mechanism of the zirconia bonding system was established as follows: the hydrolyzed zirconium species formed a more reactive ZrO2-functionalized layer on the oxidized zirconia surface, and the hydrolyzed γ-MPS species adsorbed on that layer introduces a chemical bonding to the resin. SIGNIFICANCE The novel zirconia bonding system enhanced the bonding performance of the resin, and showed a greater bond strength than an MDP-based ceramic primer.