Hisanori Kurashige

In vitro evaluation of the effect of thermal and mechanical fatigues on the bonding of an autopolymerizing soft denture liner to denture base materials using different primers.

PURPOSE This in vitro study evaluated the effect of priming procedures on bonding of an autopolymerizing silicone denture liner (Sofreliner) to a denture base material after fatigue processes using cyclic thermal stressing and repetitive mechanical stressing. MATERIALS AND METHODS Denture base specimens were fabricated by use of an autopolymerizing denture base resin and Co-Cr alloy into a cylinder shape 8-mm diameter and 4-mm high. The bonding surfaces of denture base specimens were polished with 600-grit silicon carbide paper. Resin denture base specimens were pretreated with applications of resin primer (Sofreliner Primer or Reline Primer for resin). Metal specimens were pretreated with application of metal primer (Reline Primer for metal) or coated with adhesive resin (C&B Metabond) followed by application of resin primer (Sofreliner Primer). Tensile specimens were fabricated by polymerizing a 2-mm thickness of Sofreliner between a pair of pretreated denture base cylinders. Repetitive mechanical stressing was performed by using a University of Alabama-type wear-testing apparatus as a stress generator. Vertical 75 N load with 15 degrees rotation was applied 66,700, 133,300, 266,700, and 400,000 times, then residual tensile resistance to failure was measured. Seven specimens were fabricated for 16 groups--four cyclic loading groups for four pretreatment groups. Residual tensile resistance to failure of specimens before the fatiguing process and after 5000, 10,000, 20,000, and 30,000 thermocycles were used as reference. The mean values of each group were statistically analyzed by three-way ANOVA and Bonferroni/Dunn test at a 95% confidence level. Failure modes were assessed for all specimens measured. RESULTS In the denture-bonded groups, residual tensile resistance to failure of Sofreliner Primer-treated group was significantly higher than that of the Reline Primer at each thermocycling interval (p < 0.0001) and up to 133,300 times of cyclic loading (p < 0.0001). In the metal-bonded groups, residual tensile resistance to failure of the intermediate adhesive resin group was higher than the metal primer-applied group up to 5000 thermocycles (p < 0.0001); however, there was no significant difference between them after 66,667 cyclic loads (p= 0.1698). Although adhesive resin-coated specimens of metal-bonded groups showed mixed failure, metal primer-applied groups and both denture-bonded groups consistently revealed cohesive failure of the soft denture liner after cyclic loading. CONCLUSIONS Application of Sofreliner Primer for a resin denture base provided better bonding after thermocycle and cyclic load testing than did Reline Primer. Using an intermediate adhesive resin layer on a Co-Cr denture base material improved the bonding for up to 5000 thermocycles; however, it did not affect cyclic loading parameters.

Study on Endurance Property of Adhesion Systems Evaluated by Long-Term Immersion Test in Different pH Solutions.

目的: 接着耐久性をin vitroで検討する長期浸漬試験は蒸留水中で行われてきた. しかし, 口腔内のpH値は, 2.3-8.0まで変化するとされている. そこで, 口腔内pHの上下限値と同じpHの溶液中で浸漬試験を実施して, 蒸留水浸漬の場合との接着耐久性の違いを検討した.方法: 3種類の歯科用合金および歯科用陶材を被着体として, 接着試験片を作製した. これらをpH2.3の乳酸水溶液, pH8.0の炭酸水素ナトリウム水溶液およびpH6.0の蒸留水の3種類の浸漬液に最長で36カ月まで浸漬した. 浸漬終了後, 剪断接着強さを測定した.結果: 金銀パラジウム合金およびCo-Cr合金をスーパーボンドC&Bで接着した場合には, 蒸留水 (pH6.0) 浸漬において接着強さの著しい低下を生じた. 金銀パラジウム合金およびNi-Cr合金をパナビア・フルオロセメントで接着した場合には, 乳酸水溶液 (pH2.3) 浸漬において接着強さが著明に低下した. また, 被着体が陶材の場合には, すべての接着強さ測定において陶材の凝集破壊が生じたため, 接着耐久性の検討は行えなかった.結論: 歯科用合金, 接着用表面処理が異なっても, 接着性レジンおよび浸漬液のpHが同じであれば, 接着耐久性には類似した傾向が認められた.