Compensation of pathological tooth mobility impact on the static occlusal maxillo-mandibular relationship registration with the use of intraoral scanner

Abstract

Introduction. Ones of the factors that affect the accuracy of maxillo-mandibular static occlusion relationship registration using intraoral scanning technology are fremitus and pathological mobility of teeth, since such can provoke the dislocation of the teeth as graphical objects within the structure of the received scan under the influence of contact with teeth-antagonists in comparison with the position of the same teeth, which was registered when the jaws were non-occluded. Objective of the research. To evaluate the possibility of compensating the impact of pathological mobility, as well as the phenomenon of fremitus on spatial deviations of teeth during the registration of static interocclusal maxillo-mandibular relationship with the use of intraoral scanner. Materials and methods. Approbation of approaches used to compensate the influence of pathological mobility and fremitus on the accuracy of intraoral bite scanning was carried out only among patients who were clinically diagnosed with 1st degree of pathological tooth mobility (up to 1 mm in the buccal-lingual direction), or with the clinical phenomenon of fremitus. A total of 34 sets of intraoral scans (upper jaw, lower jaw, and a scan-record of the static occlusal maxillo-mandibular relationship) were obtained from 34 patients with signs of pathological mobility or fremitus of individual teeth, while for each patient 3 different bite-scans were obtained (without implementation of any approaches to compensate the influence of pathological mobility or fremitus of the teeth; with segmentation of areas characterized with pathological mobility or fremitus during the registration of the static occlusal maxillo-mandibular relationship; bite scanning while using the teeth without any signs of pathological mobility as stable references). Evaluation of the effectiveness of above-mentioned practical approaches aimed at compensating the influence of pathological mobility and fremitus of teeth on the accuracy of intraoral scanning during the registration of static occlusal maxillo-mandibular relationship was carried out by processing the received intraoral scans in the Medit Link software (Medit Corp., Seoul, South Korea) with further determination of teeth spatial deviations within the registered scans in the Medit Design application. Results and discussions. The range of deviations obtained for spatial position of teeth, which were characterized by the presence of pathological mobility and/or fremitus signs, and which were included within the digital occlusal scan, was 189-456 μm compared to position of the same teeth within the structure of the non-occluded mandibular or maxillary scans, without implementation of any additional measures aimed at compensating the impact of existing pathological mobility. Segmentation (trimming) of teeth with signs of pathological mobility or those with signs of fremitus from scans of upper and lower jaws, made it possible to reach the range of spatial deviations of teeth that were included within the digital occlusal scan up to 116-216 μm compared to the position of such teeth within the structure of the nonoccluded mandibular or maxillary scans. Statistically significant differences were confirmed only for the maximum values of spatial deviations when comparing approaches with segmentation (trimming) of teeth with signs of pathological mobility or fremitus, and such without the implementation of any additional measures aimed at compensating the influence of pathological mobility/fremitus (p < 0,05). Conclusions. Segmentation (trimming) of teeth with signs of 1st degree pathological mobility and/or signs of fremitus helped to reduce the range of the spatial deviations for teeth included within the structure of bite scans in comparison with position of such teeth, which was registered on non-occluded lower or upper jaws’ scans. However, proposed approach characterized by only limited effectiveness and partially compensated the negative impact of pathological mobility and fremitus phenomena on the accuracy of registering static interocclusal maxillomandibular relationship with the use of intraoral scanner in conditions where the range of tooth mobility does not exceed 1 mm, because no statistically significant difference was noted regarding minimum and maximum values of spatial deviations when comparing the approach with segmentation (trimming) of teeth with signs of pathological mobility or fremitus, and one that included the registration of static occlusal relationship only within the boundaries of teeth without any signs of pathological mobility (p > 0,05).