ALVEOLAR BONE CHANGES, ROOT RESORPTION, INTRUSION AND DENTAL TIPPING IN CLEAR ALIGNER THERAPY PATIENTS
Date of Award
Summer 7-13-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Dentistry
First Advisor
Dawei Liu
Second Advisor
Dawei Liu
Third Advisor
Shengtong Han
Fourth Advisor
William Lobb
Abstract
Objective: The primary null hypothesis tested was the following: there are no statistically significant changes in dental tipping, alveolar bone height, and alveolar bone thickness at the buccal and palatal aspects of the maxillary and mandibular premolars and molars following clear aligner therapy (CAT) in adults. The secondary null hypothesis tested was the following: there are no statistically significant changes in root resorption or vertical tooth position of the maxillary and mandibular premolars and molars following CAT in adults. Materials and Methods: De-identified CBCT scans of 17 patients were analyzed at two time points: pre-treatment (T1) and post-treatment (T2). Patients received non-extraction CAT with Invisalign ClinCheck ® Technology (Align Technology, San Jose, CA). Buccal and palatal alveolar bone heights were obtained for: maxillary and mandibular first premolars (U4s and L4s) and maxillary and mandibular first molars (U6s and L6s). Buccal and palatal alveolar bone thicknesses were obtained at a level of 3, 6, and 9 mm apical to the cemento-enamel junction (CEJ). Root resorption measurements were obtained by measuring the length of the root before and after treatment. Intrusion was measured on reformatted cephalometric radiographs using cusp tip or central pit distances to the mandibular or palatal plane. Dental tipping of the U4s, L4s, U6s, and L6s was evaluated by measuring the distance from CEJ to CEJ and comparing it to the corresponding lingual cusp tip to cusp tip distance. A paired T-test was used to compare measurements at T1 and T2 and statistical significance was set to p< 0.05. Results: There was a statistically significant increase in CEJ-to-CEJ and cusp tip-to-cusp tip distances for maxillary and mandibular premolars and molars. The change in cusp tip- to-cusp tip distance was greater than the CEJ-to-CEJ change for all premolars and mandibular molars. For alveolar bone height, buccal bone height was lost at all mandibular sites and both U4s (p< 0.05). For bone thickness changes from T1 to T2, there was generally a decrease in buccal bone thickness and an increase in lingual bone thickness with varying levels of significance. For root resorption, the mean change in root length ranged from -0.19mm to -0.64mm with the majority of teeth demonstrating statistically significant root resorption (p< 0.05). For intrusion, mandibular premolars and molars showed a statistically significant positive change in position (p< 0.05), indicating slight extrusion. Conclusions: The primary and secondary null hypotheses were rejected, as significant changes were detected in transverse dental changes, alveolar bone height and thickness, intrusion, and root resorption. CBCTs taken with a smaller voxel size and field of view would improve measurement accuracy.