Mitsuhiro Tatsuta

Influence of atmospheric pressure low-temperature plasma treatment on the shear bond strength between zirconia and resin cement

PURPOSE Zirconia exhibits excellent strength and high biocompatibility in technological applications and it is has therefore been investigated for clinical applications and research. Before setting prostheses, a crown prosthesis inner surface is sandblasted with alumina to remove contaminants and form small cavities. This alumina sandblasting causes stress-induced phase transition of zirconia. Atmospheric-pressure low-temperature plasma has been applied in the dental industry, particularly for adhesives, as a surface treatment to activate the surface energy and remove contaminants. The purpose of this study was to examine the influence of atmospheric-pressure low-temperature plasma treatment on the shear bond strength between zirconia and adhesive resin cement. METHODS The surface treatment method was classified into three groups: untreated (Cont group), alumina sandblast treatment (Sb group), and atmospheric-pressure low-temperature plasma treatment (Ps group). Adhesive resin cement was applied to stainless steel and bonded to zirconia. Shear adhesion tests were performed after complete hardening of the cement. Multiple comparisons were performed using a one-way analysis of variance and the Bonferroni method. X-ray diffractometry was used to examine the change in zirconia crystal structure. RESULTS Statistically significant differences were noted between the control and Sb groups and between the control and Ps groups. In contrast, no statistically significant differences were noted for the Ps and Sb bond strength. Atmospheric-pressure low-temperature plasma treatment did not affect the zirconia crystal structure. CONCLUSIONS Atmospheric-pressure low-temperature plasma treatment improves the bonding strength of adhesive resin cement as effectively as alumina sandblasting, and does not alter the zirconia crystal structure.

Quantitation of occlusal condition in the frame of reference on the cranio-facial system.

本研究の目的は, 頭蓋顔面系を基準とした三次元咬合診査法を開発し, その評価パラメータについて検討することである.被験者として健常有歯顎者2名と, 顎機能異常患者2名を選択した.5%MVC以下のLight Clenchingと30%MVCの咬合力を発揮させて採得した2種類のシリコーンバイトを試料として, 非接触形状計測を行った.シリコーンバイトの三次元構築データから上下顎歯間距離60μm以下の領域を咬合接触域として抽出し, 咬合接触域の傾斜方向と面積を個歯ベクトル, 歯列ベクトルとして表示した.頭部エックス線CTから, 頭蓋顔面骨の三次元構築データを抽出した.頭蓋顔面骨の解剖学的な標点から, 頭蓋顔面系の基準座標を右手座標系にて設定した.テフロン球をマーカーとして, シリコーンバイトと頭蓋顔面骨の三次元構築データの位置合わせを行った.上下顎歯列咬合面の重ね合わせにより, 咬みしめ強度の増加に伴う下顎歯列の変位から下顎変位を推定した.三次元咬合診査法における非接触形状計測の再現性と測定精度を調べる実験を行ったところ, 再現性は高く, およそ±20μmの計測精度を有していることが確認された.健常者ではLight Clenching, 30%MVC間での下顎変位が小さく, 咬合接触状態はほぼ左右均等で変化の小さい様相を呈した.顎機能異常患者では習慣性閉口位における早期接触により下顎変位が生じていることが観察された.以上のことから, 頭蓋顔面系を基準とした三次元咬合診査法を開発し, 咬合接触状態および咬みしめ強度の増加に伴う下顎変位を定量的かつ視覚的に把握することが可能となった.