Mechanical properties evaluation of an orthodontic miniscrew system for skeletal anchorage

Orthodontic anchorage control is a fundamental chapter of a successful orthodontic therapy: mini-screws have been commonly used to increase absolute anchorage with no need for patient compliance, therefore reducing treatment time. The purpose of this study was to analyze the mechanical performance of a self-tapping surgical stainless steel mini-screw system.

Data concerning the mechanical properties of a stainless steel mini-screw system subjected to torsional and flexural forces were collected. The sample consisted of 10 AISI 316LVM surgical stainless steel 1.5mm in diameter mini-screws and 10 surgical stainless steel 2mm in diameter mini-screws manufactured by Leone. The devices were inserted into a polyurethane block. Maximum torsional resistance was measured by a torque meter (series MG MARK-10); flexural strength was registered with a universal tester (series 4300 INSTRON), equipped with a 2518-809 5 kg load cell.

Torsional test: at a 26.5 N cm force magnitude yielding was observed on 1.5mm diameter mini-screws and at 48.3N cm on 2mm diameter mini-screws. Flexural test: 1.5mm diameter mini-screws plastically deformed with a loading value of 105,4N and 2mm diameter mini-screws deformed when load exceeded 216.7 N.

The evaluated surgical stainless steel mini-screw system withstood greater force magnitude compared to other commercially available mini-screw systems (titanium and titanium alloy); therefore the examined mini-screw system is provided with greater mechanical properties.