Transverse, Vertical, and Antero-posterior changes between Tooth-borne versus Dresden Bone-borne Rapid Maxillary Expansion: A Randomized Controlled Clinical Trial

• Author / Creator

  Ling, Connie

• Objectives: 1) To identify accurate and easily repeatable (intra-examiner reliability) 3-D landmarks in the cranial base, maxilla, and mandible which can be used to quantify treatment changes after rapid maxillary expansion (RME). 2) To compare the transverse, vertical and antero-posterior, skeletal and dental post-treatment changes for the Dresden Bone-borne expander, 4-band Tooth-borne expander, and an untreated control group. Methods: Fifty adolescents with maxillary transverse constriction were randomly assigned into one of three groups according to type of expander: 2-point Dresden-type Bone-borne RME (B-RME; n = 17, mean age = 14.1 years), 4-band Tooth-borne RME (T-RME; n = 17, mean age = 13.7 years), or the untreated control group (n = 16, mean age = 13.3 years). The Dresden B-RME had a unique set-up where one side was anchored by a temporary anchorage device (TAD-side), and the other side was anchored to a shortened implant (implant-side). Cone-beam computed tomography (CBCT) scans were taken at 0.3-mm voxel size before treatment (T1), and 6 months later (T2). The CBCT data were coded, and then loaded into 3-D visualization software (AVIZO 8.1 software) by a blinded examiner for measurement. The transverse, vertical and sagittal changes of the maxilla was evaluated. Dental changes at the level of the pulp horn, buccal alveolar bone and root apex were evaluated on upper molars, upper premolars, upper canines, and lower molars. Repeated measures Multivariate analysis of variance (rm-MANOVA) and Bonferroni post-hoc tests were performed to identify significant differences between groups at each landmark and time-point. Results: Transverse a) T-RME group showed symmetrical maxillary premolar and molar expansion. b) The B-RME appliance configuration showed asymmetrical maxillary molar expansion. c) The TAD-anchor side of B-RME, showed greater molar crown displacement (mean 1.84 mm) than the Implant-anchor side, with statistical significance of p<.015. Antero-posterior d) T-RME group showed anterior displacement of molar apex and premolar crown (mean < 1.5 mm), compared to other groups, with statistical significance (p<.05). e) No significant antero-posterior changes were found for B-RME group. Vertical f) T-RME showed some dental vertical extrusion of premolar and molar crowns (< 1.8 mm ; p<.05), relative to control group. g) No significant dental vertical changes were found for the B-RME group. Minimal skeletal superior displacement at infra-orbital foramen (IORB) was noted for B-RME group (mean < 1.3 mm ; p<.05), relative to control group. h) Vertical changes were minimal and non-significant between the B-RME and T-RME groups. Posterior versus Anterior transverse discrepancy i) T-RME group showed greater expansion between upper molars than between upper canines (1.6 mm more per side), with statistical significance (p<.002). No statistical significant differences were found between inter-molar and inter-premolar expansion. j) In the B-RME group, both the TAD- and Implant-sides showed greater inter-molar expansion than inter-canine. This difference was 1.1 mm on the Implant-side, and 1.9 mm on the TAD-side, with statistical significance (p<.001). k) In the B-RME group, only the TAD-side showed greater inter-molar expansion than inter-premolar (1.3 mm; p<.001). This was not statistically significant on the Implant-side. Dental to Skeletal Ratio l) The B-RME group showed a smaller ratio of dental to skeletal expansion compared to T-RME group. The dental to skeletal ratio of expansion in the T-RME group, was roughly 40:60, with 42% dental expansion, 27% alveolar, 31% sutural. The dental to skeletal ratio of expansion in the B-RME group was approximately 20:80, with 17% dental expansion, 40% alveolar, and 43% sutural. Conclusions: The decision to use B-RME or T-RME in adolescents depends upon operator preferences and specific dental and skeletal considerations for the patient. B-RME may be preferred in patients with missing permanent posterior teeth, or periodontal/endodontically compromised dentition, or when a lower ratio of dental to skeletal expansion is desired. Based solely on this study's sample, T-RME may be more effective for patients with similar severity of transverse maxillary constriction at the molar level and premolar levels. Meanwhile, B-RME may be more effective for patients with greater constriction at the bilateral maxillary molar level than the premolar level. In addition, the Dresden B-RME appliance configuration produced asymmetrical molar expansion. Placement of the TAD-anchor on the side of more severe maxillary transverse constriction may be helpful in cases with more pronounced maxillary arch asymmetry.

• Subjects / Keywords

  • Cone-beam Computed Tomography
  • Accuracy and Reliability
  • 4-band Hyrax Tooth-borne expander
  • Dresden Bone-borne expander
  • Maxillary Transverse Constriction
  • Rapid Maxillary Expansion
  • Three-dimensional Reference Plane Analysis
  • Cephalometry
  • Three-dimensional Anatomical Landmarks

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R31Z4240Z

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.