Investigation of implant internal screw loosening under hyperbaric conditions: An in vitro study

The internal screw has an essential role in carrying abutment and prosthesis loading. Some dental implant patients such as scuba divers, mineworkers, and hyperbaric oxygen patients are exposed to hyperbaric atmospheres. The aim of this study was to investigate internal screw loosening under hyperbaric conditions.

Forty-two dental implants were placed into plexiglass blocks. Abutments were fixed with internal screws by 25 Ncm torque force. Groups were set as control, 2.8-bar air pressure, and 4-bar air pressure groups. Hyperbaric groups were subdivided and exposed to either one or six cycles. Removal torque values were measured with a digital torque meter. Data were analyzed statistically using analysis of variance and Tamhane's T2 tests, considering p < 0.05 as the level of statistical significance. Internal screw threads were qualitatively observed under magnification.

Four-bar groups showed the lowest removal torque values among all groups (p < 0.001). 2.8-Bar groups did not show significant differences compared with control groups. There was no statistically significant difference between the one and six pressure cycle subgroups in each group. All internal screw threads had various deformations.

Four-bar air pressure had a significant effect on internal screw loosening. Internal screw tightening protocols should be reconsidered for patients exposed to advanced hyperbaric conditions.