Date of Award

2013

Embargo Period

8-1-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Orthodontics

College

College of Dental Medicine

First Advisor

Jing Zhou

Second Advisor

Richard Duncan

Third Advisor

Luis Leite

Fourth Advisor

Ronald A. Bell

Abstract

Introduction: Miniscrew implants or MSI's are reported to be used by upwards of 80% of orthodontists today, and failure rates can reach as high as 30%. The aim of this study was to identify horizontal buccal cortical bone thickness patterns in the maxilla and mandible and to create MSI placement strategies based upon the identified pattern. Methods: Fifty randomly selected cone beam computed tomography scans or CBCT's from healthy subjects with intact dentitions were studied using one quadrant from a maxillary arch and one from the mandibular arch. 900 maxillary and 900 mandibular cortical bone thickness measurements were made. Measurements came from 3 mesiodistal locations at levels of 4mm and 6mm from the alveolar crest in 3 different regions per arch. Results: Cortical bone thickness levels are significantly thinner at a point bisecting 2 teeth (maxilla 1.19mm and mandible 1.26mm) than the bone adjacent to the teeth (maxilla 1.29mm and mandible 1.19mm) in both arches. Maxillary cortical bone (1.26mm) is significantly thinner than mandibular cortical bone (1.34), and in the mandibular arch it tends to get thicker as you move posteriorly. (1.24mm, 1.36mm, and 1.43mm) The maxillary buccal cortical bone did not increase in thickness as you progress posteriorly (1.26mm, 1.27mm, 1.26mm). The 2 sites with the greatest percentage of measurements less than 1mm (20%) were in the mandible bisecting the canine and premolar at 4mm and 6mm from the alveolar crest. The site with the highest percentage of measurements greater than 1.5mm (50%) was also in the mandible adjacent to the first molar at 6mm from the alveolar crest. Conclusion: Cortical bone thickness is significantly thinner centrally between two teeth when compared to areas adjacent to roots. Cortical bone thickness tends to only exceed the upper limit of what is considered ideal in the posterior mandible between the second premolar and first molar.

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