Attending, Department of Implantology, Peking University School of Stomatology, Beijing, PR China; Former ITI Scholar, Department of Prosthodontics, Indiana University School of Dentistry, Indianapolis, Ind.
Professor and Chair, Department of Prosthodontics, Indiana University School of Dentistry, Indianapolis, Ind.
J Prosthet Dent. 2020 Jun;123(6):860-865. doi: 10.1016/j.prosdent.2019.08.013. Epub 2019 Oct 29.
Intraoral scans and virtual interocclusal records (VIRs) are widely used for contemporary prosthodontic treatment of patients with partial edentulism. The accuracy of VIRs in various clinical conditions is unclear.
The purpose of this in vitro study was to investigate whether the span and location of edentulous areas affect the accuracy of VIRs.
Five sets of master stone casts were duplicated from a typodont model (Prosthetic Restoration Jaw Model; Nissin Dental) and then assigned into 5 study groups. Six pairs of interarch markers were placed on the master stone casts as reference points for measurements. The 5 study groups were group 1-Post: 1 posterior tooth missing; group 3-Post: 3 posterior teeth missing; group 6-Ant: 6 anterior teeth missing; group Bil-Post: bilateral posterior teeth missing; and group Dent: completely dentate arch. Master stone casts along with VIRs were scanned 10 times in each group by using an intraoral scanner (IOS) (Dental Wings Intraoral Scanner; Dental Wings Inc). Digital measurement of distances between the interarch markers was obtained on all digitally articulated casts and compared with the manual measurements (with electronic calipers with an accuracy of 0.02 mm). In addition, the differences (absolute values) between the digital and manual measurements were calculated at the edentulous locations for the groups 1-Post, 3-Post, 6-Ant, and Bil-Post and were compared with the corresponding interarch marker positions in the group Dent. Two-sample t tests were used for the statistical analysis (α=.05).
The overall differences (mean ±standard deviation) between digital and manual measurements were group 1-Post: 0.10 ±0.19 mm, group 3-Post: 0.28 ±0.63 mm; group 6-Ant: 0.19 ±0.20 mm; group Bil-Post: 0.28 ±0.25 mm; and group Dent: 0.05 ±0.18 mm. Group Dent was the only group with no significant differences between digital and manual measurements at all 6 interarch marker positions and was used as the reference to analyze the measurements in the edentulous areas. No statistical difference was found (P=.237) at the group 1-Post's edentulous area when compared with the group Dent. In the group 3-Post, the edentulous areas showed statistically significant difference when compared with those of the group Dent (P=.002 and P=.003). In the group 6-Ant, the edentulous areas showed statistical differences when compared with those of the group Dent (P=.019 and P=.008). In the group Bil-Post, only 1 side of the edentulous areas showed statistical differences when compared with group Dent (P=.006 and P=.034).
The span and location of edentulous areas impact the accuracy of VIRs. For a single missing posterior tooth, VIRs could achieve a high level of accuracy comparable with that of the dentate condition. Unilateral and bilateral extended edentulous spans with 3 or more missing posterior teeth and the extended edentulous span in the anterior region all affected the accuracy of VIRs.
口内扫描和虚拟咬合记录（VIR）广泛用于部分牙列缺失患者的当代修复治疗。在各种临床情况下，VIR 的准确性尚不清楚。
本体外研究旨在探讨缺牙区的跨度和位置是否会影响 VIR 的准确性。
从牙列模型（修复牙列模型；Nissin Dental）复制了五套主石模型，并将其分为五组研究。在主石模型上放置了六对颌间标记作为测量的参考点。五组研究分别为：组 1-后牙：1 颗后牙缺失；组 3-后牙：3 颗后牙缺失；组 6-前牙：6 颗前牙缺失；组 Bil-后牙：双侧后牙缺失；组 Dent-全牙弓。使用口内扫描仪（IOS）（Dental Wings Intraoral Scanner；Dental Wings Inc）对每组的主石模型和 VIR 进行了 10 次扫描。在所有数字化铰接模型上获得了颌间标记之间距离的数字测量值，并与手动测量值（电子卡尺精度为 0.02mm）进行了比较。此外，计算了组 1-后牙、3-后牙、6-前牙和 Bil-后牙的缺牙区的数字和手动测量值之间的差值（绝对值），并与组 Dent 的相应颌间标记位置进行了比较。采用两样本 t 检验进行统计分析（α=.05）。
数字和手动测量值之间的总体差异（平均值±标准差）为：组 1-后牙：0.10±0.19mm；组 3-后牙：0.28±0.63mm；组 6-前牙：0.19±0.20mm；组 Bil-后牙：0.28±0.25mm；组 Dent：0.05±0.18mm。组 Dent 是唯一一个在所有 6 个颌间标记位置上数字和手动测量值之间没有显著差异的组，被用作分析缺牙区测量值的参考。在组 1-后牙的缺牙区与组 Dent 相比，未发现统计学差异（P=.237）。在组 3-后牙中，缺牙区与组 Dent 相比存在统计学差异（P=.002 和 P=.003）。在组 6-前牙中，缺牙区与组 Dent 相比存在统计学差异（P=.019 和 P=.008）。在组 Bil-后牙中，只有缺牙区的一侧与组 Dent 相比存在统计学差异（P=.006 和 P=.034）。
缺牙区的跨度和位置会影响 VIR 的准确性。对于单个缺失的后牙，VIR 可以达到与有牙状态相当的高精度。单侧和双侧缺牙跨度较大，缺失 3 颗或更多后牙，以及前牙区缺牙跨度较大，都会影响 VIR 的准确性。
