Braga Ssl, Oliveira Lrs, Rodrigues R B, Bicalho A A, Novais V R, Armstrong S, Soares C J
Oper Dent. 2018 Jan/Feb;43(1):81-89. doi: 10.2341/16-338-L. Epub 2017 Oct 4.
To evaluate the effect of flowable bulk-fill or conventional composite resin on bond strength and stress distribution in flat or mesio-occlusal-distal (MOD) cavity preparations using the microtensile bond strength (μTBS) test.
Forty human molars were divided into two groups and received either standardized MOD or flat cavity preparations. Restorations were made using the conventional composite resin Z350 (Filtek Z350XT, 3M-ESPE, St Paul, MN, USA) or flowable bulk-fill (FBF) composite resin (Filtek Bulk Fill Flowable, 3M-ESPE). Postgel shrinkage was measured using the strain gauge technique (n=10). The Z350 buildup was made in two increments of 2.0 mm, and the FBF was made in a single increment of 4.0 mm. Six rectangular sticks were obtained for each tooth, and each section was used for μTBS testing at 1.0 mm/min. Polymerization shrinkage was modeled using postgel shrinkage data. The μTBS data were analyzed statistically using a two-way analysis of variance (ANOVA), and the postgel shrinkage data were analyzed using a one-way ANOVA with Tukey post hoc test. The failure modes were analyzed using a chi-square test (α=0.05).
Our results show that both the type of cavity preparation and the composite resin used affect the bond strength and stress distribution. The Z350 composite resin had a higher postgel shrinkage than the FBF composite resin. The μTBS of the MOD preparation was influenced by the type of composite resin used. Irrespective of composite resin, flat cavity preparations resulted in higher μTBS than MOD preparations ( p<0.001). Specifically, in flat-prepared cavities, FBF composite resin had a similar μTBS relative to Z350 composite resin. However, in MOD-prepared cavities, those with FBF composite resin had higher μTBS values than those with Z350 composite resin. Adhesive failure was prevalent for all tested groups. The MOD preparation resulted in higher shrinkage stress than the flat preparation, irrespective of composite resin. For MOD-prepared cavities, FBF composite resin resulted in lower stress than Z350 composite resin. However, no differences were found for flat-prepared cavities.
FBF composite resin had lower shrinkage stress than Z350 conventional composite resin. The μTBS of the MOD preparation was influenced by the composite resin type. Flat cavity preparations had no influence on stress and μTBS. However, for MOD preparation, composite resin with higher shrinkage stress resulted in lower μTBS values.
采用微拉伸粘结强度（μTBS）测试，评估可流动大块充填树脂或传统复合树脂对扁平或近中-咬合-远中（MOD）洞形预备中粘结强度和应力分布的影响。
将40颗人磨牙分为两组，分别进行标准化的MOD洞形或扁平洞形预备。使用传统复合树脂Z350（Filtek Z350XT，3M-ESPE，美国明尼苏达州圣保罗）或可流动大块充填（FBF）复合树脂（Filtek Bulk Fill Flowable，3M-ESPE）进行修复。使用应变片技术测量凝胶后收缩率（n=10）。Z350分层堆积厚度为两个2.0mm增量，FBF一次性堆积厚度为4.0mm。每颗牙齿制备6个矩形棒，每个切片以1.0mm/min的速度进行μTBS测试。使用凝胶后收缩率数据对聚合收缩进行建模。μTBS数据采用双向方差分析（ANOVA）进行统计学分析，凝胶后收缩率数据采用单向ANOVA和Tukey事后检验进行分析。使用卡方检验分析失败模式（α=0.05）。
我们的结果表明，洞形预备类型和所用复合树脂均会影响粘结强度和应力分布。Z350复合树脂的凝胶后收缩率高于FBF复合树脂。MOD洞形预备的μTBS受所用复合树脂类型的影响。无论使用何种复合树脂，扁平洞形预备的μTBS均高于MOD洞形预备（p<0.001）。具体而言，在扁平洞形预备中，FBF复合树脂的μTBS与Z350复合树脂相似。然而，在MOD洞形预备中，使用FBF复合树脂的μTBS值高于使用Z350复合树脂的。所有测试组中粘结失败均较为普遍。无论使用何种复合树脂，MOD洞形预备产生的收缩应力均高于扁平洞形预备。对于MOD洞形预备，FBF复合树脂产生的应力低于Z350复合树脂。然而，扁平洞形预备中未发现差异。
FBF复合树脂的收缩应力低于Z350传统复合树脂。MOD洞形预备的μTBS受复合树脂类型的影响。扁平洞形预备对应力和μTBS无影响。然而，对于MOD洞形预备，收缩应力较高的复合树脂导致μTBS值较低。
