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Published on: May 30, 2019
[In vitro study of the effect of 4 edentulous space lengths under Kennedy classification on the precision of digital
Xinyan Zheng1, Jiaxu Xing, Shuyu Sun
1Department of Stomatology, First Affiliated Hospital of Bengbu Medical University; School of Stomatology, Bengbu Medical University. Bengbu 233000, Anhui Province, China.
Purpose:
To investigate the effect of 4 edentulous space lengths under Kennedy classification on the overall precision, accuracy and linear precision of digital impressions through in vitro experiments.
Methods:
Four types of edentulous models were constructed according to Kennedy classification, with 3 physical models of different edentulous numbers made for each classification, totaling 12 models. A desktop scanner was used to collect reference data, and a digital intraoral scanner was adopted to obtain experimental data. Zirconia balls with a diameter of 3 mm were bonded to the midpoints of the edentulous spaces of all models, and the above scanning process was repeated. Geomagic Wrap 2021 software was used for comparative analysis of the scanning data.
Results:
There was no significant difference in precision among the groups (P＞0.05). The accuracy of Kennedy Ⅰ group decreased significantly with the increase of edentulous space length, the accuracy of the group with the smallest edentulous space in Kennedy Ⅱ group was significantly better than that of the group with the largest edentulous space. In Kennedy Ⅲ and Ⅳ group, the accuracy of the group with the smallest edentulous space was significantly better than that of the other two groups. When grouping by the number of missing teeth, Kennedy Ⅲ group showed the best overall precision. Linear precision analysis revealed that the group with the smallest edentulous space in Kennedy Ⅰ group had the optimal linear precision; in Kennedy Ⅱ-Ⅳ groups, the linear precision decreased with the increase of edentulous space length. Kennedy Ⅲ and Ⅳ group showed better linear precision when grouping by the number of missing teeth(P＜0.05).
Conclusions:
The length of edentulous space has significant effect on the precision of digital impressions, with the overall trend that as the space length increases, the overall precision and linear precision of digital impressions decrease accordingly. The presence of free-end edentulism leads to a decrease in the overall precision and linear precision of digital impressions. The linear precision of digital impressions is higher when the missing teeth are located in the anterior part of the dental arch.