Prosthodontics, Department of Surgery, Faculty of Medicine, University of Salamanca (USAL), C/Alfonso X el Sabio, s/n, Campus de Unamuno, E-37007 Salamanca, Spain.
J Dent. 2012 Dec;40(12):1081-9. doi: 10.1016/j.jdent.2012.09.001. Epub 2012 Sep 12.
To evaluate the incidence of prosthetic complications in implant-retained crowns made with UCLA castable abutments and to identify possible risk factors with a view to establishing recommendations to help predict the success of such restorations.
A cohort follow-up study was carried out in 71 partially dentate patients rehabilitated with 93 implant-retained single crowns. Data regarding socio-demographic background, anatomical features, implant-, and prosthesis-related variables were recorded. The incidence rate (%), relative risk (RR) and odds ratio (OR) were applied for predictive risk factors. ANOVA and Student t-tests were used to compare quantitative variables, the chi-square test was used to compare proportions and also a logistic regression analysis was performed. The statistical significance was set at α = 0.05.
Two implants (2.2%) were lost during the first year of function. The incidence of prosthetic complications in the observed mean period (26.2 ± 15.4 months) was 11.9%, consisting of screw loosening (10.8%) and ceramic fracture (1.1%). A higher tendency for prosthetic complications was noticed in posterior mandibular crowns restoring saddles longer than 10 mm with mesiodistal cantilevers longer than 6mm, having natural antagonists, after long-term use (>20 months), with initial torque values superior than 30 Ncm.
Screw loosening is the most frequent complication in implant-retained crowns fabricated with UCLA abutments cast in cobalt-chromium. Nevertheless, the connection usually remains stable after retightening the screws. A high survival rate was recorded, and these prostheses may be a suitable treatment option.
Based on the study findings, the risk of prosthetic complications is expected to increase when long-span posterior edentulous areas are rehabilitated with single implant-supported crowns. The antagonist occlusal plane should be restored to prevent torsional forces and overloading. Implant systems with initial torque values less than 30 Ncm should be selected.
评估使用 UCLA 可铸造基台制作的种植体固位冠的修复体并发症发生率，并确定可能的危险因素，以期为这类修复体的成功提供预测建议。
对 71 名部分牙列缺失患者的 93 个种植体单冠修复体进行了队列随访研究。记录了社会人口统计学背景、解剖学特征、种植体和修复体相关变量的数据。应用发生率（%）、相对风险（RR）和比值比（OR）评估预测性危险因素。采用 ANOVA 和 Student t 检验比较定量变量，采用卡方检验比较比例，同时进行逻辑回归分析。统计显著性水平设定为α=0.05。
在功能的第一年有 2 个种植体（2.2%）丢失。在观察的平均时间（26.2±15.4 个月）内，修复体并发症的发生率为 11.9%，包括螺丝松动（10.8%）和陶瓷断裂（1.1%）。在后牙下颌后牙区，当修复体长度超过 10mm 的鞍状区域，具有超过 6mm 的近远中悬臂，存在天然对颌牙，使用时间较长（>20 个月），初始扭矩值大于 30 Ncm 时，修复体并发症的发生率有更高的趋势。
在使用钴铬铸造 UCLA 基台制作的种植体固位冠中，螺丝松动是最常见的并发症。然而，在重新拧紧螺丝后，连接通常仍保持稳定。记录到了较高的存活率，这些修复体可能是一种合适的治疗选择。
根据研究结果，当用单个种植体支持的牙冠修复长跨度后牙缺失区时，预计修复体并发症的风险会增加。应恢复对颌牙的牙合平面以防止扭转力和过载。应选择初始扭矩值小于 30 Ncm 的种植体系统。
