Can we estimate root axis using a 3-dimensional tooth model via lingual-surface intraoral scanning?

• Published in: American journal of orthodontics and dentofacial orthopedics Vol. 158; no. 5; pp. e99 - e109
• Main Authors: Lim, Seung-Weon, Park, Hunkyung, Lim, Sun-Young, Choo, Hyun-Hee, Baek, Seung-Hak, Hwang, Hyeon-Shik, Cho, Jin-Hyoung
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2020
• Subjects: Dentistry
• ISSN: 0889-5406; 1097-6752
• DOI: 10.1016/j.ajodo.2020.07.032

This research aimed to compare the estimation error of the root axis using 3-dimensional (3D) tooth models at the midtreatment stage between the whole-surface scan (WSS) and lingual-surface scan (LSS) methods. The sample consisted of 208 teeth (26 each of central incisors, canines, second premolars, and first molars in the maxillary and mandibular dentition) from 13 patients whose pre- and midtreatment intraoral scan and cone-beam computed tomography (CBCT) were available. The 3D tooth models were constructed by merging the intraoral-scan crowns and the CBCT-scan roots obtained at the pretreatment stage. To estimate the root axis at the midtreatment stage, we superimposed the individual 3D tooth models onto the midtreatment intraoral scan obtained by the WSS and LSS methods. The midtreatment CBCT scan was used as the gold standard to determine the real root axis. The estimated root axis in terms of mesiodistal angulation and buccolingual inclination was measured in the WSS and LSS methods, and statistical analysis was performed. The estimation errors of the mesiodistal angulation and buccolingual inclination were <2.0° in both methods. The LSS method demonstrated a statistically larger but clinically insignificant estimation error than the WSS method in the mandibular canine (mesiodistal angulation, 1.95° vs 1.62°) and the total tested teeth (mesiodistal angulation, 1.40° vs 1.29°; buccolingual inclination, 1.51° vs 1.41°). Because the estimation errors of the root axis angle using the 3D tooth model by the WSS and LSS methods were within the clinically acceptable range, the root axis can be estimated by both methods. •The 3-dimensional tooth model was constructed using pretreatment 3-dimensional data.•The model was used to monitor changes in the root axis via intraoral scanning.•Lingual-surface scanning and whole-surface scanning methods were used.•Mesiodistal angulation and buccolingual inclination estimation errors were <2.0°.•The root axis can be estimated with whole-surface scanning and lingual-surface scanning methods.