Author ORCID Identifier

https://orcid.org/0009-0001-6208-3564

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Restorative Dentistry

Committee Chair

Jerry Bouquot

Committee Co-Chair

Shelby Alexander

Committee Member

Shelby Alexander

Committee Member

Bryan Weaver

Abstract

Objectives: To investigate the effect of various hyperbaric air pressures on the loosening of LOCATOR® (ZEST Anchors, LLC, Escondido, CA USA) overdenture abutments.

The pressure conditions tested are meant to simulate scuba diving conditions in edentulous patients that are restored with implant-retained tissue-supported overdentures. Another sub-goal of this study is to determine whether or not there is a difference in LOCATOR® loosening when the sample is exposed to six cycles/dives as opposed to one cycle/dive.

Methods: 36 ZimVie Tapered Screw Vent Implants with a 3.5mm diameter implant platform, and a 2.5mm diameter (and 1.5mm deep) internal hexagon were placed into resin blocks. LOCATOR® abutments were torqued to 30 N-cm with a digital torque meter. The implants were divided into three different hyperbaric pressure groups: the control (1 atm), 2.8 atm, and 4 atm. Each pressure group was subdivided into two groups: a one cycle (one scuba dive) group and a six cycles group (equivalent to six separate dives). A total of 6 implants were randomly assigned to each group: 1 atm and one cycle, 1 atm and six cycles, 2.8 atm and one cycle, 2.8 atm and six cycles, 4 atm and one cycle, and 4 atm and six cycles. LOCATOR® loosening was evaluated by obtaining the reverse torque values (RTVs) with a digital torque meter, then subtracting this from the initial tightening torque. The mean loss of torque for all groups were calculated, and a two-way ANOVA test was utilized to complete the statistical analysis.

Results: Pressure change was not found to have a statistically significant effect on LOCATOR® loosening (and/or loss of torque). However, the number of cycles did significantly affect the loss of torque, with a confidence of 99%.

Conclusions: Based on the statistical analyses, and eventually a two-way ANOVA test, there was no statistically significant effect of pressure on the loss of torque. That is, the LOCATORS® did not loosen more with pressure or loosen less with pressure. Yet, all groups did exhibit torque loss.

When it comes to the number of cycles, there was a statistically significant effect between one and six cycles. For the 1 atm pressure, increasing the cycles from 1 to 6 caused a 1.54 field increase in loosening; for the 2.8 atm pressure, increasing the number of cycles caused a 1.38-fold increase in loosening; and, for the 4 atm pressure, increasing the number of cycles caused a 1.67-fold increase in loosening. The LOCATOR® loosening exhibited can be a result of the exposure to pressure. This exposure of pressure involves both the compression and decompression that occur to and from the pressure tested.

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