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 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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