Abstract
Objective: The aim of this study was to evaluate the effect of displacement patterns of the molar teeth in response to different asymmetric headgear loading using 3D finite element method. Methods: A series of twenty-five facebow with different left vs. right outer bow length and different expansion of left vs. right were designed. The non-favored side (right side) was shortened at intervals of 10 mm, and favored side (left side) was expanded 10 degree greater than right side and 5 degree expansion were successively added. At the first phase, each side received 200-g load, implying the neck strap to displace toward shorter arm. At the second phase, a total of 400-g load was applied to the ends of the outer bow. Because of the neck strap displacement, the shorter arm received greater load than the left side, the magnitude of the applied force to each side depended on difference of left vs. right outer bow length and expansion. Results: All systems were effective in promoting asymmetric distal movement of the molars. However, the asymmetrical facebow with the 40 mm shortening and 25 degree expansion outer bow when unequal force applied could be used in asymmetric mechanics. Medial and occlusal displacing forces were observed in all systems. Conclusions: Both equal and unequal force application is effective for molar distalization. Expansion of the outer bow in the affected side and shortening of the outer bow in the normal side were effective to produced differential distal molar movement.
Highlights
Headgear was introduced at the first time in early1800s, until now, different modifications have been used.[1]
The first part consisted of the evaluation of molar movement when the applied loads were similar in left and right side, and the second part consisted of the evaluation of various load applied to left vs. right side
Part one: equal force » Anteroposterior displacement – The results revealed that the affected side underwent greater movement toward posterior than right side (Fig 2)
Summary
Headgear was introduced at the first time in early1800s, until now, different modifications have been used.[1]. Different treatment modalities have been introduced to distalize maxillary molars to overcome patient compliance, such as palatal bar, repelling magnets, Nitinol coil spring, K-loops, superelastic wires, Wilson arches, Jones jig appliances, pendulum appliances, distal jet appliances and recently temporary anchorage devices (TAD).[1] Compared with these appliances, headgear is the better choice because of restricting effect of maxillary growth and dental movement to correct Class II relationship.[3] In some instances, there is unilateral Class II malocclusion (Class II subdivision), in which one side presents Class II molar relationship, while the other side is Class I Such situation requires an asymmetric force system. It is based on the separation of the analysis shape into subdomains through finite elements that could predict the mechanical behavior of the object under varied loading conditions.[5,6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
