A Novel Abutment Screw Head Design with an Integrated Retrieval Feature: An In Vitro Study.

Background/

Objectives

This study aimed to present the design of a novel abutment screw head featuring an integrated retrieval mechanism and to evaluate the retrievability of four prototype designs.

Methods

In this in vitro mechanical study, the modified screws were produced by replicating the macrogeometry of the Brånemark and Klockner VEGA abutment screws and incorporating a secondary screw chamber below the original one, with a 1.0 mm or 0.9 mm hexagonal design. Sixty screws were manufactured, fifteen for each group: BC0.9, BC1.0, KC0.9, and KC1.0. Retrieval success and the relationship between peak tightening and loosening torque were evaluated (α = 0.05).

Results

All screws tolerated tightening at a torque 20% above the manufacturer's recommendation. Most specimens from BC0.9 and KC0.9 failed during loosening, while all specimens in BC1.0 and KC1.0 were successfully retrieved. Regarding peak tightening torque and the loosening-to-tightening ratio, neither prototype exhibited a statistically significant correlation. BC1.0 demonstrated a statistically significant positive correlation between peak tightening torque and peak loosening torque, whereas KC1.0 showed a weaker relationship; detailed correlation coefficients and p-values are reported in the Results.

Conclusions

Under the in vitro conditions tested, the prosthetic screw incorporating a 1.0 mm secondary retrieval head demonstrated reliable retrieval performance, supporting its potential as a simple retrieval system. These findings represent a proof-of-concept and require further mechanical and clinical investigation before clinical application.