Resistance to traction forces in mini-implants used in Ortohodontics depending on the insertion angle

Resumo

For maximum anchorage in orthodontics, mini-implants have been used for various tooth movements without causing unwanted reactive forces on the teeth. The purpose of this study was to evaluate the mechanical resistance to traction of mini-implants to be evicted from bone and assess whether they can increase their tensile strength depending on its insertion angle (60 and 90o). Pig hip cuts were used for the placement of 5 mini-implants which were inserted with a 60o angulation and a 90o angulation. Ten new 2.5 mm (neck) x 1.6 (diameter) x 8 mm (length) with fl at head self- drilling mini-implants were used (MOSAS Dewimed. Germany). They were subjected to perpendicular tensile forces, using a universal mechanical testing machine (Instron) with a loading rate of 1 mm/min. The results were analyzed using Student’s t test. It was observed that 90o angulation mini-implants had better resistance (7.40 ± 2.68 Mpa) than 60o angulation ones (4.21 ± 0.58 Mpa). 90o angulation mini-implants could be a better option for orthodontic treatment due to their higher resistance to traction forces thus improving stability.

Key words: Anchorage, miniscrews, tensile strenght.