Abstract
BackgroundBased on low-dose radiation Cone-bean computed tomography (CBCT) images, This study aims to establish a space coordinate system, which offers more precise and comparable evaluation on changes of maxillary third molars influenced by orthodontic treatment with premolar extraction in adults. The system suggests promising application prospect in future studies related to CBCT superimposition and evaluation for its feasibility and efficiency.MethodsForty-nine maxillary third molars from 27 patients (mean age, 20.78 years) were included. CBCT images were obtained before and after orthodontic treatment with premolars extracted (mean treatment duration, 31.47 months). The changes in the position, angulation, and rotation of the third molars were evaluated with a space coordinate system using four landmarks: anterior nasal spine (ANS), posterior nasal spine (PNS), left and right orbitales.ResultsAfter orthodontic treatment, the third molars moved forward (adjusted mean, 1.44 mm) (p < 0.001) and downward (adjusted mean, 2.87 mm) (p < 0.001) accompanied by outward rotation of the crowns (adjusted mean, 5.38°) (p = 0.001), while changes in angulation were insignificant.ConclusionsThis was the first study to systematically investigate the spatial position change of maxillary third molars in adult patients who received orthodontic treatment with premolar extraction. During the process, maxillary third molars moved downward and forward accompanied by outward rotation of the crowns. Orthodontists should take tooth movement potential into consideration when making extraction plans.
Highlights
Based on low-dose radiation Cone-bean computed tomography (CBCT) images, This study aims to establish a space coordinate system, which offers more precise and comparable evaluation on changes of maxillary third molars influenced by orthodontic treatment with premolar extraction in adults
The inclusion criteria were: (1) patients with CBCT images taken before orthodontic treatment (T1) and after the treatment (T2) were available, (2) patients who were 18 to 30 years of age at Before treatment (T1), (3) patients with one or two maxillary premolars extracted during orthodontic treatment, and (4) patients with third molar images in relevant tooth extraction sites existed in both pretreatment and posttreatment CBCT images
Fourty-nine maxillary third molars from 27 patients were selected for analysis
Summary
Based on low-dose radiation Cone-bean computed tomography (CBCT) images, This study aims to establish a space coordinate system, which offers more precise and comparable evaluation on changes of maxillary third molars influenced by orthodontic treatment with premolar extraction in adults. Extraction of premolars, as a routine orthodontic treatment for reducing protrusion or crowding of dental arch, has been widely used in the correction of severe. Pan et al BMC Oral Health (2020) 20:321 related to complications [4], among which possible late incisor crowding and post-orthodontic relapse are main concerns of orthodontists [5]. A systematic review published in 2017 [11] demonstrated favorable changes in the eruption rate, retromolar space, and angulation of third molars, especially in maxillary. Due to various reference lines and inconsistent measurements, the level of evidence was relatively low
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