Objective: To compare the residual cement between computer aided design/computer aided manufacturing customized abutments (CCA) and stock abutments (SA), and to evaluate the feasibility of digital measurement for residual cement volume by three-dimensional scanning.
Methods: Twenty master models needed in this study were all taken from one 47-year-old patient with arrested periodontitis, who had already had an implant placed at his right upper central incisor site in the Department of Periodonto-logy, Peking University School and Hospital of Stomatology. After 4 weeks of soft tissue conditioning by means of customized healing abutment, the height of peri-implant soft tissue was measured, from the implant platform to mucosal margin, as 5 mm. Using customized impression coping, the impression was taken and twenty models were fabricated and allocated to 4 groups according to the type of abutments: CCA1 (5 mm transmucosal height CCA, with margin at tissue level), CCA2 (4 mm transmucosal height CCA, with 1 mm submucosal margin), SA1 (3 mm transmucosal height SA, with 2 mm submucosal margin) and SA2 (1 mm transmucosal height SA, with 4 mm submucosal margin). Crowns were cemented to the abutments, which were seated on the working models. Excess cement was removed by a prosthodontic specialist. Thereafter, the volume of residual cement was evaluated by using three-dimensional scanning technique. The area proportion of residual cement was calculated on photographs taken by a single lens reflex camera. The weight of residual cement was weighed by an analytical balance. And the correlation of residual cement volume data with residual cement area proportion or weight of residual cement acquired by traditional methods was analyzed.
Results: Residual cement was observed on all the experiment samples. The residual cement volume of CCA was significantly less than that of SA [(0.635 3±0.535 4) mm3 vs. (2.293 8±0.943 8) mm3, P < 0.001]. Consistently, CCA had less residual cement area proportion and weight than those of SA [area proportion: 7.57%±2.99% vs. 22.68%±10.06%, P < 0.001; weight: (0.001 5±0.001 0) g vs. (0.003 7±0.001 4) g, P < 0.001]. The residual cement volume was strongly correlated with the residual cement area proportion and residual cement weight (r>0.75, P < 0.001).
Conclusion: These in vitro results suggest that CCA minimized the residual cement more effectively than SA. The method to digitally evaluate the residual cement volume is feasible, but its validity and reliability need to be further studied.
目的: 通过体外模型比较计算机辅助设计/计算机辅助制造个性化基台(computer aided design/computer aided manufacturing customized abutments，CCA)与成品基台(stock abutments，SA)对粘接剂残留的影响，同时初步评价数字化三维扫描技术定量评估残留粘接剂的可行性。
方法: 本研究所需20个工作模型皆取自同一例已在北京大学口腔医院牙周科接受了右上中切牙种植手术的患者。通过个性化愈合基台成形植体周软组织后，测得植体平台位于颊侧黏膜下5 mm。利用个性化转移杆取模后灌制20副工作模型，并根据基台种类及粘接边缘位置将工作模型分为四组，每组5个：CCA1(穿黏膜高度5 mm，即平齐黏膜粘接边缘)、CCA2(穿黏膜高度4 mm，即黏膜下1 mm粘接边缘)、SA1(穿黏膜高度3 mm，即黏膜下2 mm粘接边缘)和SA2(穿黏膜高度1 mm，即黏膜下4 mm粘接边缘)。在工作模型上模拟临床粘接过程并清除多余粘接剂后，利用三维扫描技术获得残留粘接剂的体积，利用数码相机拍摄二维图像获得残留粘接剂面积百分比，利用称量的方式获得残留粘接剂的质量，并分析三维扫描方法获取的体积与传统评价方法所得的面积百分比及质量的相关性。
结果: 所有冠-基台复合体粘接边缘均有粘接剂残留。其中，CCA组残留粘接剂的体积明显小于SA组[(0.635 3±0.535 4) mm3 vs. (2.293 8±0.943 8) mm3，P＜0.001]，面积百分比及质量也显著低于SA组[面积百分比：7.57%±2.99% vs. 22.68%±10.06%，P＜0.001；质量：(0.001 5±0.001 0) g vs. (0.003 7±0.001 4) g，P＜0.001]，而三者在CCA组及SA组内差异均无统计学意义(P＞0.05)。三维扫描所得残留粘接剂的体积与传统评价方法所得残留粘接剂的面积百分比及残留粘接剂的质量间均具强相关性(r＞0.75，P＜0.001)。
结论: 与SA相比，CCA能更有效地减少粘接剂的残留。基于三维扫描技术数字化评估残留粘接剂的方法切实可行，但其效度和信度还需进一步研究。
Keywords: Computer-aided design; Dental cements; Dental implant-abutment design; Imaging, three-dimensional; In vitro.