Surface Deterioration of Indirect Restorative Materials

Abstract The objective of this work was to evaluate the effects of in vitro and in situ biodegradation on the surface characteristics of two resin cements and a hybrid ceramic system. One hundred and eighty specimens (4X1.5mm) of each material (Maxcem Elite, NX3 Nexus and Vita Enamic) were made and randomly distributed in twelve groups (n=15) according to the material and biodegradation method. The specimens were then submitted to the following challenges: storage in distilled water 37 ºC for 24 h or 7 days, storage for 7 days, at 37 ºC, in stimulated saliva or in situ. The in situ stage corresponded to the preparation of 15 intraoral palatal devices, used for 7 days. Each device presented 3 niches, where a sample of each materials was accommodated. Specimens from both saliva and in situ groups suffered a cariogenic challenge, corresponding to the application of a solution of 20% of sucrose, 10 times throughout each day. After each biodegradation method, the surface roughness (Ra), Vickers hardness (VHN) and scanning electron microscopy (SEM) analyzes were performed. The data collected were evaluated by Levene test, two-way ANOVA and Tukey`s test (α=5%). The in situ challenge promoted the greater biodegradation, regardless of the material. Regarding the materials, the Vita Enamic VHN was negatively affected by all biodegradation methods and the Nexus NX3 presented better performance than the self-adhesive cement tested. Therefore, within the conditions of this work, it was concluded that in situ biodegradation can affect negatively the surface characteristics of indirect restorative materials.

摘要 本研究旨在评估体外（in vitro）与原位（in situ）生物降解对两种树脂水门汀（resin cements）及一款混合陶瓷系统表面特性的影响。每种材料制备180个规格为4×1.5mm的试样，按材料类型与生物降解方式随机分为12组（每组n=15）。随后对试样开展以下处理：于37℃蒸馏水中储存24小时或7天；于37℃模拟唾液（stimulated saliva）内储存7天；或实施原位生物降解。原位降解阶段需制备15个口内腭部装置，每个装置设有3个槽位，分别容纳三种材料的试样，装置佩戴于口内7天。模拟唾液组与原位降解组的试样均接受致龋挑战（cariogenic challenge）：每日10次涂抹20%蔗糖溶液。在每种生物降解处理完成后，分别对试样开展表面粗糙度（Ra）、维氏硬度（VHN）检测及扫描电子显微镜（SEM）观察。采用莱文检验（Levene test）、双因素方差分析（two-way ANOVA）与图基检验（Tukey's test）对采集的数据进行分析，显著性水平设定为α=5%。结果显示，无论受试材料类型如何，原位降解引发的生物降解程度均更为显著。就材料而言，Vita Enamic的维氏硬度会受到所有生物降解方式的负面影响，而NX3 Nexus的表现优于受试的自粘接树脂水门汀。综上，在本研究的实验条件下，原位生物降解可对间接修复材料的表面特性产生负面影响。