Novel multi-axial alveolar distractor — part I: design, manufacture, and mechanical/functional tests

Publication date: Available online 20 February 2019

Source: Journal of Cranio-Maxillofacial Surgery

Author(s): Yang-Sung Lin, Cheng-Hsien Wu, Yuan-Chih Liu, Chun-Li Lin

Abstract

Purpose

This study developed a novel multi-axial alveolar distractor and evaluated its safety and effectiveness by performing various mechanical tests and finite element (FE) analysis.

Materials and methods

A ball-and-socket joint with a high degree of freedom was proposed as the design concept to make the distractor produce a cone trajectory motion range of up to 60° with respect to the transport screw (central axis). This device was manufactured with Ti6Al4V alloy. Mechanical functional tests included four-point bending resistance testing of the base bone plate, pull-out testing of the multi-axial alveolar distractor, welding strength testing between the base bone plate and ball-and-socket joint mechanism, and torque strength testing of the ball-and-socket joint. These tests were performed to ensure the effectiveness and safety of the multi-axial alveolar distractor. The base bone plate FE analysis of four-point bending resistance and pull-out testing of the multi-axial alveolar distractor were performed to confirm the results obtained from the experimental testing.

Results

The bending strength for the four-point bending test and the maximum force for pull-out testing were 530.88 N mm and 716.33 N, respectively. Substantial equivalence FE simulations also found that large deformations for four-point bending and pull-out testing were smaller than those for the commercial alveolar distractor, indicating that our new distractor is as safe and effective as the commercially available device. The maximum debonding torque resistance for ball-and-socket joint mechanism welding strength was 3481.1 N mm, meaning it is unable to fall off during a surgical operation. No damage was found at the welding edge. The maximum average resistance force in the ball-and-socket joint was 30.26 N without rotation, allowing it to resist distraction forces during bone regeneration — an important safety consideration.

Conclusion

The alveolar distractor designed using a ball-and-socket joint concept can achieve multi-axial distraction with various angle adjustments in 3D space. Thorough mechanical/functional tests confirm the effectiveness and safety of our new multi-axial alveolar distractor.

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