Graduation Date

Fall 12-15-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Programs

Medical Sciences Interdepartmental Area

First Advisor

Meenakshi Vishwanath, BDS, MS, M.Dent.Sc

Second Advisor

Po-Jung Chen, D.D.S., M.D.S., M.Dent.Sc

Third Advisor

James Wahl, Ph.D.

Fourth Advisor

Thomas Petro, Ph.D.

Abstract

Purpose: The purpose of this study was to 1. experimentally (in vitro) quantify the force system acting on the molar and the incisor when a tip-back bend is placed on an auxiliary spring mounted on a base archwire and create a prediction model 2. to compare the type of tooth movement obtained from the prediction model (in-vitro) and the clinical outcome (in-vivo) data obtained from a previously conducted clinical trial. Methods: A computerized 3-dimensional (3D) orthodontic force tester (OFT) was used to quantify and compare the force systems generated from different combinations of tip-back bend archwires and base archwires. A combination of Stainless Steel (SS) base archwires and tip-back archwires of different sizes and materials: Nickel Titanium (NiTi), Beta Titanium (TMA), and SS were tested. Based on power analysis, 10 samples of each combination were tested. The in vivo portion of the study involved retracing and measuring 13 deidentified lateral cephalometric images from the prospective clinical trial. Results: In vitro analysis: The 3D force system of a tip-back bend can be quantified, and the force system of the molar and incisor were captured. For both forces and moments, the .017” x .025” SS and .019” x .025” SS tip-back bend archwires were statistically significant at p p £ 0.25). The tooth movement on the incisor was not significant which differed from the in-vitro analysis. Conclusions: Tip-back bend placed on archwires of high modulus of elasticity and increased dimensions, increases the magnitude of the forces and moments produced on the molar and the incisor. A .017” x .025” NiTi tip-back bend archwire with a .016” x .022” SS base archwire does not accomplish a force system needed for Class II correction via molar distalization.

Comments

2023 Copyright, the authors

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