Stress distribution produced by correction of the maxillary second molar in buccal crossbite.

The purpose of this study was to evaluate the stress distribution produced in the dentoalveolar system by a maxillary posterior crossbite appliance used for the correction of maxillary second molars in buccal crossbite. A photoelastic model was fabricated using a photoelastic material (PL-3) to simulate alveolar bone and ivory-colored resin teeth. The model was anteriorly and posteriorly observed with a circular polariscope and photographically recorded before and after activation of the maxillary posterior crossbite appliance. An uncontrolled palatal tipping and a rotating force were generated when the traction force was applied on the palatal surface of the maxillary second molar. A controlled tipping and an intrusive force were generated when the traction force was applied on the buccal surface of the maxillary second molar.