Comparison of zygoma plates and infrazygomatic crest miniscrews used open bite treatment: A 3-dimensional finite element study.

INTRODUCTION

This study aimed to evaluate infrazygomatic crest (IZC) miniscrews, which represent a new approach to maxillary posterior tooth intrusion and extra-alveolar skeletal anchorage, using 3-dimensional finite element stress analysis to predict the clinical usability instead of zygoma plates.

METHODS

Six different models were developed. The direction of the intrusion force was generated parallel to the maxillary first molar, and the posterior bite-block intrusion appliance was connected with 2 steel arches. A zygoma plate, stainless steel (SS)-IZC miniscrew, and a titanium alloy (TiA)-IZC miniscrew were used as anchorage units, and 200 g and 400 g of intrusion forces were applied. The cortical bone, spongious bone, stress values, and displacements in the anchorage unit were examined. The anchored materials were considered nonosseointegrated.

RESULTS

Zygoma plates formed low-stress values under 200 g and 400 g of force. The greatest stress and displacement occurred in the first miniscrew that fixed the plate. SS-IZC miniscrews gave lower stress and displacement values than TiA-IZC miniscrews. The most stress was detected inferior to the screw-to-bone contact in IZC miniscrews.

CONCLUSIONS

Considering the initial value of resorption in cortical bone, it is predicted that SS-IZC and TiA-IZC miniscrews can be used in the clinic under 200 g of intrusion force, although there is not as little stress and displacement as for zygoma plates. Under 400 g of intrusion force, clinical use cannot be recommended because of the critical stress value they generate in the cortical bone.