# OT Bridge prosthetic system with different number of screws in all on six maxillary prosthesis: finite element analysis

## TL;DR

This study uses finite element analysis to evaluate how different numbers and positions of screws affect stress distribution in an All-on-six maxillary OT-Bridge prosthesis.

## Contribution

The study introduces a biomechanical evaluation of the OT-Bridge system under varying screw configurations using finite element analysis.

## Key findings

- Bilateral elimination of anterior screws (Group IV) caused the highest stress in the bridge and implants.
- Unilateral elimination of two anterior screws resulted in better stress distribution than bilateral elimination.
- The OT-Bridge remains biomechanically efficient even when one-third of anchoring screws are absent.

## Abstract

The OT-Bridge is reported as a simple versatile rehabilitation technique that guarantees tight stable prosthesis even with absence of few screws. However, to provide implant patients with intriguing prospects for rehabilitation with this system, vast research is still required to understand the biomechanical behavior of the OT-Bridge. This investigation aimed to evaluate the stresses induced in an All-on-six maxillary OT-Bridge prosthesis in different circumstances that vary in number and geometric distribution of the retaining screws using finite element analysis.

This study comprised five test groups based on the number and distribution of the connection screws used to anchor an all-on-six OT-Bridge superstructure as follows; Group I: six screws, Group II: five screws eliminating the right central screw, Group III: four screws with two anterior screws eliminated unilaterally, Group IV: four screws with two anterior screws eliminated bilaterally, and Group V: three screws eliminating both central incisors and right canine screws. The computer simulation was done through three main stages: experimental model designing, SolidWorks modelling, and model analysis using ABAQUS ®. The analysis was run under a unilateral axial load (250 N) and an oblique load (150 N). The maximum generated von Mises Stresses (vMS) for the; bridge, prosthetic screws, seeger rings, equators, fixtures, cancellous bone, and cortical bone were recorded to compare the five test groups.

The highest vMS induced in the bridge (677 and 437 MPa under vertical and oblique load, respectively) were in group IV. The highest equator vMS were in groups III and IV (122, 121.9 MPa) under vertical load, while under oblique load, they were in groups V and III (66.2, 65.7 MPa). The vMS in screws, implants, and two bony segments exhibited the most significant increase in group V. The bilateral anterior screw elimination (group IV) compared to the unilateral elimination (group III) increased the vMS on the bridge, screws, and implants.

The OT-Bridge is considered a biomechanically efficient prosthetic system even in the absence of one-third of the anchoring screws in all-on-six prostheses. However, unilateral rather than bilateral elimination of two anterior screws results in better stress distribution pattern.

Not applicable.