Browsing by Author "Lear, Megann"

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    In Vitro Comparison of Direct Attachment Shape and Size on the Orthodontic Forces and Moments Generated by Thermoplastic Aligners During Expansion
    (Wiley, 2025) Lear, Megann; Akbari, Amin; Robertson, Olivia; Magura, Janine; Bojrab, Alexandra; Eckert, George; Chen, Jie; Conley, Richard Scott; Turkkahraman, Hakan; Orthodontics and Oral Facial Genetics, School of Dentistry
    Objective: To evaluate the effects of varying direct attachment shape and size on the forces and moments generated by thermoplastic aligners during simulated expansion. Materials and methods: An in vitro orthodontic force tester (OFT) was used to measure the forces and moments from a typodont where the buccal teeth were translated lingually 0.2 mm to simulate expansion. Hemi-ellipsoid and rectangular attachments with either 0.5 or 1.0 mm thickness were added on upper right first premolar (UR4), second premolar (UR5) and first molar (UR6). Analysis of variance (ANOVA) was used to determine two-way interactions among the factors on the outcomes. Results: The interactions between group and tooth were significant for all outcomes (p < 0.001). The greatest buccal forces (Fy) were observed with 1 mm rectangular attachment on the UR4 (0.78 ± 0.29 N), with 1 mm hemi-ellipsoid attachment on UR5 (0.28 ± 0.21 N) and with 0.5 mm rectangular attachment on UR6 (1.71 ± 0.18 N). The greatest buccolingual moments (Mx) were obtained with 1 mm rectangular attachment on UR4 (5.61 ± 1.43 Nmm), without any attachments on UR5 (3.33 ± 1.73 Nmm) and with 1 mm hemi-ellipsoid attachment on UR6 (4.18 ± 4.31). Conclusion: Direct attachment shape and size had a significant effect on the orthodontic forces and moments generated by thermoplastic aligners during simulated expansion. Although loads varied significantly by tooth morphology and its location in the arch, best forces and moments for expansion were obtained with 1 mm rectangular attachments on UR4s, 1 mm hemi-ellipsoid attachments on UR5s and 0.5 mm rectangular attachments on UR6s.
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    In Vitro Comparison of the Effectiveness of Different Attachment Shapes and Locations on Extrusion of the Upper Left Lateral Incisor Using Thermoplastic Aligners
    (Wiley, 2025) Bojrab, Alexandra; Akbari, Amin; Broyles, Dustin; Magura, Janine; Lear, Megann; Eckert, George; Chen, Jie; Turkkahraman, Hakan; Conley, R. Scott; Orthodontics and Oral Facial Genetics, School of Dentistry
    Objectives: The aim of this study was to compare the effectiveness of different attachment shapes and locations on the extrusion of the upper left lateral incisor (UL2) using thermoplastic aligners. Materials and methods: Seven typodonts were digitally printed with hemi-ellipsoid or rectangular attachments in the incisal, middle or cervical third of the UL2. Five clear aligners were fabricated for each typodont; each was tested twice. Forces and moments were measured with an orthodontic force tester during 0.2 mm simulated extrusion of the UL2. Analysis of variance (ANOVA) was used to determine the effects of group, tooth, and the group-by-tooth interaction on the outcomes. A two-sided 5% significance level was used for all tests. Results: Altering attachment shape and location had a statistically significant effect on the forces and moments generated in each trial (p < 0.01), except for rectangular incisal and hemi-ellipsoid cervical (p > 0.05). The rectangular middle attachment generated the highest extrusive force (Fz = 7.498 N), followed by hemi-ellipsoid cervical (Fz = 6.338 N) and rectangular incisal (Fz = 5.948 N). Conclusions: Varying direct attachment shape and location on the UL2 during extrusion has a significant effect on the forces and moments generated by thermoplastic aligners. The rectangular attachment located in the middle third generated the most effective extrusive force and least unwanted moment. For anchorage teeth, hemi-ellipsoid attachments located in the cervical third were found to be the most effective in minimising the reciprocal intrusive forces and unwanted moments.