Batson Emily R, Cooper Lyndon F, Duqum Ibrahim, Mendonça Gustavo
Former Resident, Department of Prosthodontics, University of North Carolina at Chapel Hill School of Dentistry, Private practice, Colorado Springs, Colo.
Director and Stallings Distinguished Professor, Graduate Prosthodontics, University of North Carolina at Chapel Hill School of Dentistry, Chapel Hill, NC.
J Prosthet Dent. 2014 Oct;112(4):770-7. doi: 10.1016/j.prosdent.2014.05.002. Epub 2014 Jun 28.
Computer-aided design and computer-aided manufacturing (CAD/CAM) generated restorations are gaining popularity. However, limited clinical evidence is available for single-unit posterior CAD/CAM restorations fabricated with established and newer crown materials.
The purpose of this clinical study was to assess the restoration quality of and gingival response to CAD/CAM fabricated posterior single-tooth restorations with different processing technologies.
Twenty-two individuals in need of posterior complete coverage crowns were recruited under an institutional review board approved protocol. Teeth were randomized to 1 of 3 groups: metal ceramic, lithium disilicate, and monolithic zirconia. An unprepared or minimally restored tooth on the contralateral side was chosen as a control tooth for gingival measurements with each participant. Teeth were prepared and scanned intraorally by 1 of 3 experienced practitioners. A total of 32 restorations were digitally designed and fabricated with either milling technology or rapid-prototype printing and casting with conventional porcelain application. Restorations were evaluated with modified United States Public Health Service criteria for contour, marginal adaptation, occlusion, and shade. Gingival crevicular fluid volume and bleeding on probing were recorded preoperatively, at 1-month and 6-month postcementation visits. Polyvinyl siloxane impressions were made of the buccal margin of cemented restorations and evaluated with microcomputed tomography to assess marginal adaptation (horizontal discrepancy). The Mantel Haenszel row mean score was used to assess whether the crown systems differed with respect to the modified United States Public Health Service criteria. Linear mixed models were used to assess whether the average gingival volumes were affected by the explanatory variables (crown system, tooth status [treated vs control], or visit). A generalized estimating equation approach was used to assess whether bleeding on probing was affected by the explanatory variables. One-way ANOVA was used to assess marginal discrepancy values among the crown systems (α=.05 for all tests).
Twelve metal ceramic, 10 lithium disilicate, and 10 zirconia restorations were fabricated for 22 participants. Zirconia restorations were significantly different from the other 2 crown systems (P<.001) with respect to occlusion. No occlusal adjustment was needed on 80% of the zirconia restorations. The average gingival crevicular fluid volumes did not differ among crown systems, between treated and control groups, or over time. The average horizontal marginal discrepancy was significantly different between lithium disilicate and zirconia crowns (P=.027), with zirconia crowns having the least amount of horizontal marginal discrepancy.
Given the small sample size and limitations of this study, CAD/CAM-generated restorations for posterior teeth made from different materials had acceptable clinical results.
计算机辅助设计与计算机辅助制造（CAD/CAM）制作的修复体越来越受欢迎。然而，关于使用成熟及新型牙冠材料制作的单单位后牙CAD/CAM修复体的临床证据有限。
本临床研究的目的是评估采用不同加工技术的CAD/CAM制作的后牙单颗修复体的修复质量及牙龈反应。
在机构审查委员会批准的方案下招募了22名需要后牙全冠修复的个体。牙齿被随机分为3组中的1组：金属陶瓷、二硅酸锂和整体式氧化锆。选择对侧未预备或轻度修复的牙齿作为每位参与者牙龈测量的对照牙。由3名经验丰富的从业者中的1名在口内对牙齿进行预备和扫描。总共32个修复体通过铣削技术或快速原型打印并结合传统瓷应用进行数字化设计和制作。根据修改后的美国公共卫生服务标准对修复体的外形、边缘适合性、咬合和色泽进行评估。在术前、粘固后1个月和6个月的随访中记录龈沟液体积和探诊出血情况。对粘固修复体的颊侧边缘制取聚醚橡胶印模，并通过微型计算机断层扫描进行评估以评估边缘适合性（水平差异）。使用Mantel Haenszel行平均得分来评估牙冠系统在修改后的美国公共卫生服务标准方面是否存在差异。使用线性混合模型来评估平均牙龈体积是否受到解释变量（牙冠系统、牙齿状态[治疗组与对照组]或随访时间）的影响。使用广义估计方程方法来评估探诊出血是否受到解释变量的影响。使用单因素方差分析来评估牙冠系统之间的边缘差异值（所有检验的α = 0.05）。
为22名参与者制作了12个金属陶瓷修复体、10个二硅酸锂修复体和10个氧化锆修复体。氧化锆修复体在咬合方面与其他2种牙冠系统有显著差异（P <.001）。80%的氧化锆修复体无需进行咬合调整。牙冠系统之间、治疗组与对照组之间以及不同时间的平均龈沟液体积没有差异。二硅酸锂和氧化锆牙冠之间的平均水平边缘差异有显著不同（P = 0.027），氧化锆牙冠的水平边缘差异最小。
鉴于本研究的样本量较小及局限性，不同材料的CAD/CAM制作的后牙修复体具有可接受的临床结果。
