Advisor(s)

Chung Kau

Committee Member(s)

J Don Spillers Jr
Quamarul Hassan
Terpsithea Christou

Document Type

Thesis

Date of Award

1-27-2026

Degree Name

Master of Science in Dentistry (MSDent)

School

School of Dentistry

Department

Dentistry

Abstract

Introduction: Within orthodontics, CBCT technology has been used to analyze tooth movement with both fixed appliances and clear aligners. However, little research has evaluated alveolar bone remodeling outcomes in growing patients treated with clear aligner expansion. Methods: This study compared pre-treatment (T0) and post-treatment (T1) CBCTs of Phase I patients treated with clear aligners who had expansion planned in the Invisalign® ClinCheck. CBCTs were collected and analyzed, including 27 maxillary and 22 mandibular arches. The aims were (1) to compare planned vs. actual expansion and (2) to evaluate the arch width (AW) and alveolar bone changes before and after treatment. A ratio of achieved/planned expansion was calculated. Twenty-two measurements were made on T0 and T1 CBCTs by six examiners, and inter-rater reliability was determined. ChatGPT-5 was used to calculate descriptive statistics, paired t-tests, and effect sizes. Both arches were analyzed first as a whole and then again after being divided into two groups based on the magnitude of planned expansion. Results: Maxillary molars achieved 74.9% of planned expansion on average, while mandibular molars achieved 87.5%. All maxillary AW measurements showed significant expansion (p < 0.05), though buccal bone (BB) thickness changes were not significant. Maxillary intermolar angle increased 2.54° (p = 0.018). No significant root-to-BB changes were observed. For mandibular CBCT measurements, all variables showed significant changes except AW at the furcation and BB-to-BB at the distal root apex (DRA). The intermolar angle increased 14.5° from uprighting; AW based on central grooves (CG) and arch width based on buccal cusps (BC) increased significantly, while AW based on DRA decreased. BB-to-BB at the DRA remained stable, and BB-to-BB at the furcation decreased slightly, but not significantly. Furcation-to-BB distances decreased significantly bilaterally. Conclusion: Expansion efficiency findings were comparable to previous studies, with slightly improved outcomes using current clear aligner protocols. While maxillary molar buccal tipping was expected and statistically significant, results indicated that most expansion occurred through bodily movement. AW increased significantly without a significant loss of BB thickness. Mandibular molars primarily underwent buccal tipping/uprighting as they expanded, concurrently erupting into thinner bucco-lingual bone.

Keywords

Alveolar Bone;CBCT;Clear aligners;Expansion

ProQuest Publication Number

32279139

ISBN

9798273349254

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