Koichi Muraguchi’s research while affiliated with Kagoshima University and other places

This study aimed to evaluate the effect of three pretreatment conditioners and surface preparations on a composite resin adhesive for a gold alloy. Cast disk specimens were made and bonded with RelyX Unicem luting agent under six surface conditions: 1) polished with No.600 carbide paper, 2) air-abraded with alumina, 3) Alloy Primer metal conditioner was applied after alumina-abrasion, 4) Monobond Plus multipurpose conditioner was applied after alumina-abrasion, 5) M. L. Primer metal conditioner was applied after alumina-abrasion, and 6) Rocatec multipurpose silica-coating system was applied. The bond strengths were determined before and after thermocycling (50,000 cycles). The bond strengths of the alumina-abrasion group were significantly decreased after thermocycling. The Rocatec and M. L. Primer exhibited higher bond strengths than other treatments. The application of metal conditioners and multipurpose surface preparations was recommended for improved bonding between the evaluated adhesive resin and gold alloy.

The aim of this study was to clarify the temperature dependence of color, i.e. the thermochromism of restorative composite resins at typical intraoral temperatures. Five brands of restorative composite resins were used. The CIE L*a*b* color values were measured using a spectrophotometer at specimen temperatures of 4, 23, 37, 60, and 80ºC. The temperature dependence of the refractive index of the materials at 4–80ºC were also determined using a refractometer. The values of L* for all materials decreased, and those of a* and b* for most of the materials increased, with increasing temperature. The color difference (ΔE*) for all materials increased with increasing specimen temperatures. The refractive index of the A4 shade of the materials consistently decreased with increasing temperatures. Most of the materials exhibited perceptible thermochromism related to intraoral thermal conditions. Optical properties that change in response to temperature could help explain the thermochromism of materials.

The purpose of the present study was to evaluate the efficacy of pretreatment on the bonding durability between titanium casting and two acrylic adhesives. Cast titanium disk specimens treated with four polymer-metal bonding systems as follow: 1) air-abraded with 50-70 μm alumina, 2) 1)+Alloy Primer, 3) 1)+M.L. Primer and 4) tribochemical silica/silane coating system (Rocatec System). The specimens were bonded with M bond or Super-bond C&B adhesive. The shear bond strengths were determined before and after thermocycling (20,000 cycles). The surface characteristics after polishing, and for the 1) and 4) preparations were determined. The bond strengths for all combinations significantly decreased after thermocycling. The combination of Super-bond C&B adhesive and 2) led to significantly higher bond strength than the other preparations after thermocycling. The maximum height of the profile parameters for the polishing group was lower than other preparations.

This study evaluated the effects of combined use of metal primers and modified monomers on the bonding of MMA-TBBO resins to pure palladium (Pd). Bonding surface was polished with 600-grit silicon carbide paper and primed with one of these four metal primers: V-Primer, M. L. Primer, Metaltite, or Alloy Primer. Four monomers, including three modified ones, were added to MMATBBO resin. One was a methyl methacrylate monomer containing no adhesion promoting monomers, while the other two modified monomers contained the functional monomer of either V-Primer or Alloy Primer. Bonded specimens were prepared by incremental build-up of MMA-TBBO resin on primed Pd surfaces. Shear bond strengths were measured after thermal cycling. Bonding to Pd was significantly improved when modified monomer containing the functional monomer of Alloy Primer was used in combination with M. L. Primer or Metaltite applied on the bonding surface.

This study investigated the efficacies of adhesive resin cements (Clearfil SA Luting, Maxcem, G-CEM, RelyX Unicem Clicker, Vitremer Paste) for bonding to Ag-Pd-Cu-Au alloy not surface-pretreated with metal primer. For control, Panavia F 2.0 -developed for use with a proprietary metal primer, Alloy Primer- was tested with and without metal primer application. Pairs of alloy disks (10.0 and 8.0 mm in diameters, 3.0 mm thickness) were air-abraded with alumina and bonded with one of the cements. Shear bond strengths (SBSs) were measured before and after 50,000 times of thermocycling. Among Maxcem, RelyX Unicem Clicker and the control, there were no statistical differences in SBS before and after thermocycling. After thermocycling, Clearfil SA Luting exhibited the highest SBS among all the cements. Results showed that Clearfil SA Luting, Maxcem, and RelyX Unicem Clicker were efficacious for bonding to Ag-Pd-Cu-Au alloy after air abrasion surface treatment for the latter.

The purposes of this study were twofold: (1) to examine the effects of bleaching on the bond strength of an adhesive to bovine tooth surfaces; and (2) to explore the effectiveness of an ascorbic acid application in preventing the deterioration of bonding ability due to bleaching. In the experimental groups, ascorbic acid was applied to the bleached bovine tooth surfaces. In the control groups, the tooth specimens were bleached but no ascorbic acid application was carried out. All bonded specimens were subjected to shear bond test, and the data were statistically analyzed with two-way ANOVA and Bonferroni's test (p=0.05). Bond strengths to the bleached specimens were significantly lower than those of non-bleached specimens. No statistical differences were found in bond strength between the bleached and non-bleached groups when the ascorbic acid treatment was carried out. Results of this study suggested that ascorbic acid application was effective in preventing the reduction of bonding ability to bleached teeth.

The purpose of this study was to evaluate the effect of thermal cycling on the surface texture of restorative materials. Disk-shaped specimens made of seven resin composites (Beautifil: BF; Esthet-X: EX; Filtek Supreme: FS; Inten-S: IS; Point 4: PT; Solare: SR; and Venus: VS) were finished with 1-microm alumina suspension, and then thermocycled between 4 and 60 degrees C in distilled water for 20,000 or 50,000 cycles with a dwell time of 60 seconds. Staining susceptibility and mean surface roughness, Ra, were examined, and surface texture was observed by scanning electron microscopy. Dye penetration test showed that the surfaces of all resin composites were more stained after thermal cycling. Mean Ra of all resin composites, except PT, significantly increased after 50,000 thermal cycles. Dislodgement of filler particles was observed for all resin composites after thermal cycling, except FS. It was concluded that thermal cycling significantly affected the surface texture of the seven examined resin composites.

This study investigated the stability of a resin-paint material (Master Palette)--which was developed for chairside shade modification of composite restorations--by evaluating its bond strength to indirect resin composite and surface degradation. Bond strength was evaluated with four surface treatments including an application of methylene chloride, airborne particle abrasion with 50 microm aluminum oxide, and additional applications of bonding agents after air-abrasion. The surface roughness (Rz value) of both the resin-paint and indirect resin composite before and after thermo-cycling (4-60 degrees C, 50,000 cycles) was also evaluated. All data were statistically analyzed by two-way ANOVA and Boneferroni's test (p=0.05). It was found that bond strength was improved by bonding agent application (14.9+/-1.9 MPa to 18.6+/-2.2 MPa, p<0.0054) after thermo-cycling. As for surface roughness, its results after thermo-cycling (2.7+/-0.2 microm, p<0.001) demonstrated that the resin-paint needed further improvements to maintain the original surface texture.

目的: 本研究では, 新規に開発された反応性有機質複合フィラー含有硬質レジン人工歯の審美的性質を評価する目的で, 色素浸漬試験による色調変化を従来の硬質レジン人工歯と比較した.方法: 実験には, 新規硬質レジン人工歯デュラクロスフィジオ (以下DPとする) と4種類の市販硬質レジン歯を用いた. 試験片は, 義歯技工ステップを加えた場合と加えない場合の2種類の条件で作製した. 完成した試験片は, 0, 5, 000, 10, 000回のいずれかの回数の水中熱サイクルを負荷してから, カレー溶液あるいは塩基性フクシン溶液中に一定時間浸漬した後, 色調変化を測定した. また, カレー溶液色素浸漬試験では, 浸漬後の試験片を蒸留水中に保管した場合の色調を測定して, 色調の回復程度を観察した. また, 色素浸漬試験前後の人工歯の表面性状を走査電子顕微鏡で観察した.結果: カレー溶液浸漬後, 新規人工歯DPはほかの人工歯と同様に着色が認められたが, その程度は小さかった. また, 蒸留水保管3日後における色調回復の程度は, DPが最も大きかった. 塩基性フクシン溶液浸漬後でも, DPの色調変化は, ほかの2種類の人工歯より小さかった.結論: 新規硬質レジン人工歯DPは, 従来の硬質レジン人工歯よりも着色しにくいことが明らかになった. また, 義歯の洗浄を徹底することによって, 義歯使用中の着色を防止できる可能性が示された.