Yasushi Hibino

Relationship between the strength of glass ionomers and their adhesive strength to metals

OBJECTIVES The objective of this study was to examine the possible correlation between the strength of glass ionomers and their adhesive strength to metals. METHODS Three different brands of glass ionomers mixed at four different P/L ratios were evaluated. The compressive and diametral tensile strengths of the cements were determined. The shear bond strengths were determined between four different types of dental casting alloys and the cement made with the different P/L ratios. RESULTS Significant (p < 0.05) increases in the bond strength to any of the metal surfaces were found in the cement specimens mixed at the highest P/L ratio compared to those mixed at the lowest P/L ratio. For two glass ionomers (FI and DNT), the specimens prepared at the highest P/L ratio showed significantly greater diametral tensile strength than those prepared at the lowest P/L ratio (p < 0.05). SIGNIFICANCE The present study showed a significant correlation between diametral tensile strengths and bond strengths. It is suggested that the use of glass ionomers with high mechanical strength is an important factor of enhancing the adhesion to metal surfaces.

Effects of surface microtopography of titanium disks on cell proliferation and differentiation of osteoblast-like cells isolated from rat calvariae

The surface topography of implant fixture is an important factor affecting the osseointegration. We herein demonstrated the effects of surface microtopography of titanium disks on proliferation and differentiation of osteoblast-like cells isolated from rat calvariae. Titanium disks with machine surface (MS), rough surface (R1) and rough surface combined with small cavities (R2) were used in an in vitro culture system. Rough surfaces (R1 and R2 disks) induced stronger osteoblast proliferation and differentiation (BGP and sclerostin mRNA expressions and calcium content) than the smooth surface (MS disk). Furthermore, surface microtopography of R2 disk, which was rough with small cavities, more strongly induced cell proliferation and mineralized bone matrix production than R1 disk. Our results suggest that surface microtopography influences osteoblast proliferation and differentiation. R2 disk, which is rough with small cavities, may be used in implant fixtures to increase osseointegration.

Influence of monomer content on the viscoelasticity, water sorption and solubility of experimental fluorinated soft lining materials

The influence of monomer content on the viscoelasticity, water sorption and solubility of experimental fluorinated soft lining materials was investigated. Changes in the viscoelastic properties of the materials were also examined after thermal cycling. Four fluorinated soft lining materials containing different amounts of methoxy diethylene glycol methacrylate (MDGMA) and tridecafluorooctyl methacrylate (13FMA) were prepared. The viscoelastic displacement for specimens containing 13FMA was found to be less than that without 13FMA (p<0.05), and the values tended to decrease with increasing 13FMA content. Reduction of the MDGMA content and addition of 13FMA caused a decrease of water sorption and solubility (p<0.05). Thermal cycling was found to affect the viscoelastic deformation of the specimens without 13FMA and those specimens with relatively large amounts of 13FMA.

Effect of Various Reinforcing Materials for Resin Denture Base

目的: PMMA (Polymethylmethacrylate) レジンは広く臨床で用いられているが, 義歯床の強度を増加する必要が生じた場合, 補強線を用いることが多い. しかしながら, 義歯の破折線は補強線に沿って発生する傾向が見受けられ, この一因子として, 補強線とPMMAレジンが化学的に結合していないことが考えられる. これに対し, 臨床においては金属接着プライマーや4-META (4-methacryloxyethyl trimellitate anhydride) 含有ンジンなどを用い, 補強線と床用レジンとの接着を求めてきた. 本研究は, レジン床義歯に対する補強効果を検討する目的で, 繊維製補強材ならびに金属製補強芯を用い, それぞれの補強効果を比較検討した.方法: 三点曲げ試験, レジンの填入圧による繊維製補強材の断面積変化および色素浸入試験を行い, 熱サイクル負荷の有無について検討した.結果: 熱サイクル負荷を加えない試料の三点曲げ試験の結果, コントロールと比較し, Connect, Fiber-Spiintは近似した値となり, そのほかの補強材は若干高い値を示した. 各種繊維製補強材は低加圧状態で重合した場合と比較し, 加圧することにより圧縮されることが確認された. 色素浸入試験の結果, 熱サイクル負荷を加えない場合, Ribbond, Conn. ect, Fiber-Splintに色素浸入が認められたが, Vectris, 補強芯では認められなかった. また, 熱サイクル負荷を加えた場合, Vectrisを除く繊維製補強材の色素浸入量が増加した.

Casting Junction between Gold-coated Keeper of Magnetic Attachment and Ag-Pd-Au Cast Alloy

目的: 磁性アタッチメントキーパー表面に金コーティングを施すことにより, キーパーと金銀パラジウム合金との鋳接が確実に行えるかについて検討した.方法: 市販の金コーティングされたキーパーと, 金コーティングされたキーパーならびに金コーティングを施さない試作キーパーを用いた. 試作キーパーは市販のキーパーを改変し, 金コーティングの厚みは4ならびに10μmとした. キーパー上に円柱状のワックス棒を盛り上げ埋没し, 通法に従い, 市販の金銀パラジウム合金にて鋳接を行った. 鋳接強さの測定は万能試験機を用いて室温大気中にて行った. また, 鋳接後の試料断面をエックス線マイクロアナライザーにて観察を行った.結果: 市販品を含め, 金コーティング層から金パラジウム合金表面に対して金濃度の緩やかな減少がみられた. 金コーティングされたキーパーでは, 酸化層が介在しない合金とキーパー表面の緊密な接合が観察された. 金コーティングされたキーパーの鋳接強さは, 金コーティングを施さない試料と比較して有意に大きな値を示した.結論: 金コーティング層の存在は鋳接操作に伴う酸化層の生成を最小限にし, 金コーティングされたキーパーと鋳造用合金との鋳接強さを増加させると推察された.