Ferrari Marco, Giovannetti Agostino, Carrabba Michele, Bonadeo Giovanni, Rengo Carlo, Monticelli Francesca, Vichi Alessandro
Department of Medical Biotechnologies, University of Siena, Italy.
Department of Oral Sciences, Prosthodontics Unit, University "La Sapienza", Roma, Italy.
Dent Mater. 2014 Jul;30(7):e163-8. doi: 10.1016/j.dental.2014.02.004.
Chipping is the most frequent clinical failure of zirconia crowns. Causes of chipping have not been completely understood and different possible reasons have been considered. The study was aimed at evaluating the fracture resistance of 3 different CAD/CAM zirconia frame designs veneered with porcelain.
Thirty extracted sound premolars were divided into 3 groups (n=10). Chamfer preparations were performed, impressions were taken. Three zirconia frame designs (Aadva, GC) were realized: reproduction of the abutment contour (flat design, FD); wax-up as for porcelain-fused-to-metal crowns (PFM); anatomically guided, designed to keep constant the thickness of the overlying porcelain veneering (AG). Porcelain veneering was made with pressure layering technique (Initial Zr, GC). Crowns were cemented utilizing a self-adhesive resin cement (G-Cem, GC). After a 24-h water storage at 37°C, using a universal testing machine (1 mm crosshead speed), crowned teeth were loaded in the central fossa in a direction parallel to the longitudinal axis of the tooth. Load at fracture was recorded in Newtons (N). Digital photographs of the specimens were taken in order to assess failure patterns. Between-group differences in fracture strength were statistically analyzed (One-Way Analysis of Variance, Tukey test, p<0.05).
Load at fractures differed significantly among the groups (p=0.004). AG exhibited significantly higher fracture resistance 1721.6 (488.1) N than PFM 1004.6 (321.3) N and FD 1179.5 (536.2) N, that were comparable. Repairable failures occurred in 80% of AG, 70% of PFM, and 50% of FD specimens.
Anatomically guided zirconia frames resisted significantly higher loads than flat and PFM-like frame designs.
崩瓷是氧化锆全冠最常见的临床失败情况。崩瓷的原因尚未完全明确，人们考虑了各种可能的因素。本研究旨在评估三种不同计算机辅助设计/计算机辅助制造（CAD/CAM）的氧化锆基底设计搭配瓷贴面后的抗折强度。
选取30颗拔除的健康前磨牙，分为3组（每组n = 10）。制备肩台，制取印模。实现了三种氧化锆基底设计（Aadva、GC）：基牙外形复制（平面设计，FD）；金属烤瓷冠（PFM）蜡型；解剖学导向设计，使覆盖瓷贴面厚度保持恒定（AG）。采用压力分层技术进行瓷贴面（Initial Zr，GC）。使用自粘结树脂水门汀（G-Cem，GC）粘结全冠。在37°C下储存24小时后，使用万能试验机（十字头速度1mm），沿与牙长轴平行的方向在中央窝加载戴冠牙。记录断裂时的载荷，单位为牛顿（N）。拍摄试件的数码照片以评估失败模式。对各组间的抗折强度差异进行统计学分析（单因素方差分析，Tukey检验，p<0.05）。
各组间的断裂载荷差异显著（p = 0.004）。AG组的抗折强度显著高于PFM组[1004.6（321.3）N]和FD组[1179.5（536.2）N]，分别为1721.6（488.1）N，后两组相当。80%的AG试件、70%的PFM试件和50%的FD试件出现可修复性失败。
解剖学导向的氧化锆基底比平面设计和类PFM基底设计能承受更高的载荷。
