Abstract
BackgroundOrthodontic root resorptions are frequently investigated in small animals, and micro-computed tomography (μCT) enables volumetric comparison. Despite, due to overlapping histograms from dentine and bone, accurate quantification of root resorption is challenging. The present study aims at (i) validating a novel automated approach for tooth segmentation (ATS), (ii) to indicate that matching of contralateral teeth is eligible to assess orthodontic tooth movement (OTM) and root resorption (RR), (iii) and to apply the novel approach in an animal trial performing orthodontic tooth movement.MethodsThe oral apparatus of three female mice were scanned with a μCT. The first molars of each jaw and animal were segmented using ATS (test) and manually (control), and contralateral volumes were compared. Agreement in root volumes and time efficiency were assessed for method validation. In another n = 14 animals, the left first upper molar was protracted for 11 days at 0.5 N, whereas the contralateral molar served as control. Following ATS, OTM and RR were estimated.ResultsATS was significantly more time efficient compared to the manual approach (81% faster, P < 0.01), accurate (volume differences: − 0.01 ± 0.04 mm3), and contralateral roots had comparable volumes. Protracted molars had significantly lower root volumes (P = 0.03), whereas the amount of OTM failed to reveal linear association with RR (P > 0.05).ConclusionsWithin the limits of the study, it was demonstrated that the combination of ATS and registration of contralateral jaws enables measurements of OTS and associated RR in μCT scans.
Highlights
Orthodontic root resorptions are frequently investigated in small animals, and micro-computed tomography enables volumetric comparison
Eligibility of approach for tooth segmentation (ATS) for automated tooth segmentation Automated tooth segmentation was successfully achieved in all animals
When comparing the tooth and root volumes with the respective reference value from manual approach (MA) segmentation, the Bland-Altman analyses revealed a mean difference of 0.01 mm3 for tooth roots and 0.03 mm3 for the teeth (Fig. 4)
Summary
Orthodontic root resorptions are frequently investigated in small animals, and micro-computed tomography (μCT) enables volumetric comparison. The present study aims at (i) validating a novel automated approach for tooth segmentation (ATS), (ii) to indicate that matching of contralateral teeth is eligible to assess orthodontic tooth movement (OTM) and root resorption (RR), (iii) and to apply the novel approach in an animal trial performing orthodontic tooth movement. Micro computed tomography (μCT) is a complementary tool enabling high-resolution volumetric analyses of bone and tooth micro-morphometry. [8,9,10,11,12,13,14] In principle, the 3D-orthodontic tooth movement (OTM) can be computed even from end-point analyses, and they. At the time being, the majority of studies performed 2D linear measurements in the volumetric data sets, comparable to 2D histology, or they mechanically separated murine teeth from bone prior to scanning. Marker-based Watershed algorithms (WS) have been successfully used to segment computed tomography images with overlapping histograms. [22, 23] this approach may be applicable in the orthodontic field
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