Department of Restorative Dentistry, Faculty of Dentistry, Jordan University of Science and Technology (JUST), Irbid, Jordan.
J Prosthodont. 2010 Jun;19(4):263-73. doi: 10.1111/j.1532-849X.2009.00560.x. Epub 2010 Jan 29.
The purpose of this in vitro study was to compare the porcelain fracture resistance between screw-retained, cement-retained, and combined screw- and cement-retained metal-ceramic (MC) implant-supported posterior single crowns; and to investigate the effect of offsetting the occlusal screw-access opening on porcelain fracture resistance of screw-retained and cement-retained MC implant-supported posterior single crowns.
Forty standardized MC molar-shaped restorations were fabricated. The 40 restorations were divided into four groups (SRC, SRO, CRP, and CSC) of 10 specimens each. Group SRC: screw-retained, screw-access hole placed in the center of the occlusal surface; Group SRO: screw-retained, screw access hole placed 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group CRP: cement-retained, zinc phosphate cement was used; Group CSC: cement-retained with a screw-access hole in the center of the occlusal surface. The screw-retained restorations and abutments were directly attached to 3i implant fixtures embedded in acrylic resin blocks. Subsequently, all test specimens were thermocycled and vertically loaded in a universal testing machine at a crosshead speed of 2 mm/min until fracture. Mean values of load at fracture (in N) were calculated in each group and compared with a one-way ANOVA and Tukey's Studentized test (alpha= 0.05).
Mean values of loads required to fracture the restorations were as follows (N): Group SRC: 1721 +/- 593; Group SRO: 1885 +/- 491; Group CRP: 3707 +/- 1086; Group CSC: 1700 +/- 526. Groups SRC, SRO, and CSC required a significantly lower force to fracture the porcelain than did the CRP group (p < 0.05).
The cement-retained restorations showed significantly higher mean fracture loads than the restorations having screw-access openings in their occlusal surface. The position of the screw-access hole within the occlusal surface did not significantly affect the porcelain fracture resistance.
本体外研究的目的是比较螺丝固位、粘结固位和螺丝-粘结固位金属陶瓷（MC）种植体支持的后牙单冠的瓷裂阻力；并探讨在牙合面螺丝通道开口处偏移对螺丝固位和粘结固位 MC 种植体支持的后牙单冠瓷裂阻力的影响。
制作了 40 个标准化的 MC 磨牙形状修复体。这 40 个修复体分为四组（SRC、SRO、CRP 和 CSC），每组 10 个。SRC 组：螺丝固位，螺丝通道位于牙合面中心；SRO 组：螺丝固位，螺丝通道向颊尖方向从牙合面中心偏移 1mm；CRP 组：粘结固位，使用锌磷酸盐粘结剂；CSC 组：牙合面中心有螺丝通道的粘结固位。螺丝固位修复体和基台直接连接到嵌入丙烯酸树脂块中的 3i 种植体夹具上。随后，所有试件均在万能试验机上以 2mm/min 的十字头速度进行热循环和垂直加载，直至断裂。在每组中计算断裂时的负荷平均值（N），并采用单因素方差分析和 Tukey 学生化检验（alpha=0.05）进行比较。
各组修复体断裂所需的平均载荷值（N）如下：SRC 组：1721±593；SRO 组：1885±491；CRP 组：3707±1086；CSC 组：1700±526。SRC、SRO 和 CSC 组断裂瓷所需的力明显低于 CRP 组（p<0.05）。
粘结固位修复体的平均断裂载荷明显高于牙合面有螺丝通道开口的修复体。牙合面螺丝通道的位置对瓷裂阻力没有显著影响。
