レジンコンポジットのヒト象牙質に対する接着強度に及ぼす硬化配置法時の圧力の影響

Effect of pressure during curing placement technique on bond strength of resin composite to human dentin.

抄録

目的:

セルフエッチングボンディングプロトコルを用いて，硬化時の圧力が象牙質に対するレジンコンポジットの接着強さに及ぼす影響を評価・比較する．

PURPOSE: To evaluate and compare the effect of pressure during curing on resin composite bond strength to dentin using a self-etch bonding protocol.

方法:

20本のヒトの歯を歯根膜の中間まで切断し、標準化されたスメア層を受けた。準備された歯は、以下の2つのグループ（n= 10/グループ）にランダムに割り当てられた：（1）硬化中に圧力をかけない（コントロール）または（2）硬化中に圧力をかける。コントロール群の歯は，ナノハイブリッドレジンコンポジットを4 mmの厚さで2回に分けて硬化させ，コンポジットプレースメント器具を用いて適合させ，万能接着剤で接着した．各グループはさらに2つのサブグループに分けられ，一方は24時間後に切開して微小引張接着強さ（μTBS）試験を行い（即時サンプル；n=5），もう一方は切開してμTBS試験を行う前に1万回の熱サイクル（TC；n=5）試験を行った．得られた破壊パターンを実体顕微鏡で評価した。さらに、各サブグループの代表的な1つの標本を、内部修復物/象牙質界面の定性的な顕微鏡による形態学的分析に供した。データは二元配置分散分析とTukey' post hoc testにより解析し、P<0.05の値を統計的に有意であるとみなした。

METHODS: 20 human teeth were cut to the mid-coronal dentin and received a standardized smear layer. The prepared teeth were randomly assigned to the following two groups (n= 10/group): (1) without pressure during curing (control) or (2) with pressure during curing. Teeth in the control group received a 4 mm-thick buildup of a nanohybrid resin composite in two separately cured increments, adapted using a composite placement instrument, and bonded with a universal adhesive, while teeth in the treatment group were restored with the same adhesive and resin composite but a plexiglass pressure cylinder was used to apply pressure while each increment was cured. Each group was further divided into two subgroups, one of which was sectioned and subjected to microtensile bond strength (µTBS) testing after 24 hours (immediate samples; n= 5), while the other was subjected to 10,000 thermal cycles (TC; n= 5) prior to sectioning and µTBS testing. The resulting failure patterns were assessed under a stereomicroscope. In addition, one representative specimen from each subgroup was subjected to qualitative microscopic morphological analysis of the internal restoration/dentin interface. Data were analyzed by two-way ANOVA followed by Tukey' post hoc test and values with P< 0.05 were considered to be statistically significant.

結果:

TC後のμTBS値は，加圧硬化群がコントロールよりも有意に高い値を示したが（P< 0.05），TCはすべてのμTBS値に有害な影響を及ぼした．顕微鏡検査では、硬化過程で加圧した試料に比べ、コントロールの試料はレジンコンポジット部にボイドが多く見られた。

RESULTS: After TC, the group cured with pressure exhibited significantly higher µTBS values than did the control (P< 0.05), although TC had a detrimental effect on all µTBS values. Microscopic examination revealed that the control specimens had more voids in the resin composite part, relative to specimens that were under pressure during the curing process.

臨床的意義:

レジンコンポジット硬化時の圧力印加は、象牙質との接着強度に好影響を及ぼすと考えられる。

CLINICAL SIGNIFICANCE: Pressure application during curing of resin composite may have a positive effect on bond strength to dentin.