Award Date

5-1-2021

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Dental Medicine

First Committee Member

Brian Chrzan

Second Committee Member

Joshua Polanski

Third Committee Member

James Mah

Fourth Committee Member

Courtney Coughenour

Number of Pages

89

Abstract

The aim of this study was to analyze and compare the bone depth at various postulated miniscrew insertion angles in both the Infrazygomatic Crest (IZC) and Distal Infrazygomatic Crest (DIZC) regions. Furthermore, root morphologies of the maxillary 1st and 2nd molars and their effect on bone depth and the various miniscrew insertion angles were analyzed.

A total of 69 CBCT images were collected from pre-orthodontic adult patients at the UNLV orthodontic residency clinic. Bone depth measurements were made at 8 postulated miniscrew insertion angles starting at 40° up to 75°. All measurements were recorded from the buccal bone at the “insertion point,” which was measured 5 mm apically from the CEJ of both the maxillary 1st and 2nd molars. Bone depth measurements were categorized by measurement outcome, meaning that whatever structure the measurement encountered. Three (3) outcomes were utilized: 1) Sinus floor contact, 2) Root contact, and 3) No bone measurement. Lastly, root morphology was recorded based on whether the root was converging toward root apices or diverging as viewed from the coronal slice. Descriptive statistics were used to analyze bone depth as well as the probability of outcome for each location. A student t-test was utilized to compare bone depth between both the IZC and DIZC regions.

Results showed that the overall bone depth in the IZC is 3-9mm and had a small percentage of measurements that contacted the sinus floor ranging from 0% to 39% from the 40°-75° angles respectively. Conversely, the DIZC had an average of 4-9mm but with a much larger percentage of measurements contacting the sinus floor. The probability of contacting the sinus floor was at least 55% at 60° and increased to 77% at the highest angle of 75°. The average bone depth when contacting the sinus floor in the DIZC was 7.2-8.98 mm. Root morphology was found to have no statistically significant impact on bone depth in both the IZC and DIZC regions.

The conclusions of our study show that the DIZC is a preferred location for miniscrew placement where bone depth is greater and potential for sinus floor contact is greater. The ideal insertion angle was 60° - 70° with an average bone depth in this range of 8.0-8.5 mm. Lastly, our method of measurement is one that can be employed by the typical clinician to measure bone depth and predictability if access to a CBCT is available.

Keywords

Infrazygomatic Crest; Miniscrew; Orthodontics; Skeletal Anchorage; Temporary Anchorage Device

Disciplines

Dentistry

File Format

pdf

File Size

2800 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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