Experimental and numerical investigations of fracture and fatigue behaviour of implant-supported bars with distal extension made of three different materials

Abstract

The aim of this study was to investigate experimentally the fatigue and stability of three bar materials with distal extension at the molar region and to numerically analyse the biomechanical properties of the bar materials connected to overdentures in a patient individual model. A milled bar was designed for the mandible on four implants in the canine and second premolar region. Three bar materials were investigated: titanium (Ti), cobalt chromium (CoCr), and polyetherketonketon (PEKK). Firstly, static and fatigue tests were performed based on EN ISO 14801 in a commercial permanent loading set-up. Unilateral axial force was applied on the distal extension of the bars. Secondly, numerical models were created. Different bar materials and loading scenarios were analysed. The static fracture limit of the three materials was 1,750 N, 780 N, 310 N for Ti, CoCr, and PEKK, respectively. The Wöhler curves showed comparable fatigue limits of 200 N, 160 N, and 150 N for titanium, CoCr, and PEKK, respectively. The stress at the distal extension was 2,600 MPa (Ti), 1,000 MPa (CoCr), and 270 MPa (PEKK). All loading simulations with the PEKK bar showed higher stresses in the implants and in the bone bed as well as higher displacements of the over denture in comparison to metal bars. PEKK showed different mechanical behaviour compared to Ti and CoCr. The distribution of stresses within the PEKK bar was wider than the area of loading which probably leads to fatigue of the whole bar and not only the part under load.

Strain Evaluation of Peek Cantilever Bars Around Implants Assisted Mandibular Overdentures (In Vitro Study)

“…In addition, these study findings are consistent with the findings of Mochalski et al, study where the stresses in the implants and the bone bed around the implants displayed higher values under axial load with the Ti bar than with the PEEK bar (27).…”

Evaluation of Fracture Resistance of Long Span Implant Supported Fixed Dental Prostheses Fabricated from Different CAD/CAM Materials.

“…There are limited data revealing fracture resistance of PEKK; The obtained results were in agreement with Mochalski et al, (2021) (39) who did a study to investigate the fracture and fatigue behavior of implant supported bars with distal extension milled from three different materials (titanium, cobalt chromium , and PEKK). The static fracture limit of the three materials was 1,750 N, 780 N, 310 N for Ti, CoCr, and PEKK, respectively.…”

“…(5,28,(32)(33)(34)(35)(36)(37) Several studies evaluated the fracture load of PEKK restorations, the results were between (310-2037N). (29,33,38,39) In the posterior region, the average masticatory force is 300 N. (40) The length of the bridge determines the amount of stress in the prosthesis.. (41) As a result, longer restorations are likely to face higher tensile stresses, particularly when employed in high-stress regions like the posterior region. The occlusal forces in FDPs are passed to the surrounding structures via pontics, connectors, and abutments, with the connector region experiencing the most stress.…”

Axial and Non-axial Retention Forces of Milled Titanium Bar Versus Locator-Milled Titanium Bar Attachments in Implant-Supported Maxillary Overdenture: An In Vitro Study

“…As a result, the construction is more robust, stronger, and lighter in weight. The CAD/CAM bars are machined from a high-quality titanium alloy, resulting in a one-piece structure that is both lighter and stronger, improving patient comfort and confidence (23) .…”