A Revolving Temporary Anchorage Cap Connecting to an Orthodontic Miniscrew Using In Vitro Experimental Testing: Safety and Biomechanical Evaluations.

PURPOSE: This study is to develop a plastic revolving (translation and rotation) temporary anchorage cap (TAC) as the orthodontic anchor and evaluate its biomechanical safety and clinical used feasibility.

MATERIALS AND METHODS: The TAC was designed to connect onto a mini-implant head with 45-degree switching unit and extended arm for tying an orthodontic elastic chain/coil spring. The removal force between the TAC and mini-implant head and torque resistance on the mini-implant/bone interface were performed to evaluate the biomechanical safety. Clinical molar uprighting and mesial drive application were performed to reveal the TAC feasibility/capacity.

RESULTS: The removal force was 43.95 N (>finger-pulling force 9.3 N) to prevent the TAC from detaching, and the torque resistance was 159.25 N·mm to maintain micromotion smaller than 30.4 μm between the screw and bone. The strain value in using TAC treatment was found to be about 2 times that of traditional tracing (without using TAC) in molar uprighting/mesial drive application.

CONCLUSIONS: The plastic revolving TAC can provide optional use with translation/rotation features to change the angles and directions in orthodontic tractions and increase treatment efficiency under biomechanical safety considerations.