Avaliação da precisão do posicionamento da mandíbula na telerradiografia lateral para o planejamento cirurgico de cirurgia ortognática

Abstract

This study evaluated the positioning of the mandible in lateral cephalograms used in orthognathic surgery planning. The sample comprised 20 adult male patients aged from 18 to 40 years old with Angle class III type skeletal malocclusion, belonging to the Oral and Maxillofacial Surgery and Traumatology outpatient clinic at PUCRS, who underwent two diagnostic radiographic shots, using as reference positions for performing lateral cephalograms, the natural head position (NHP) and the spinal column perpendicular to the ground. In order to perform the first lateral cephalogram, the patients were instructed while closing their mouth, to position the tip of the tongue in the most posterior region of the hard palate possible until the first tooth contact. Prior to the performance of the second lateral cephalogram, an occlusal record was made with part of a number 7 wax plate that was delicately cut in the appropriate shape of the patient's dental arch prior to the execution of the radiographic examination. It was observed that the mandible remained anteriorly positioned in cephalograms performed using the NHP method in relation to the NHP + occlusal wax registration method (p>0.05), which was effective in keeping the positioning of the mandible in the centric relation position during the pre-surgical lateral cephalogram procedure. The subsequent surgical treatment to correct the facial pattern was performed using rigid internal fixation, and the analyzes were carried out based on cephalograms performed before surgery (T0), in the immediate postoperative period (T1) and 6 months after surgery (T2). The stability of mandibular recoil was compromised in the horizontal direction, with a recurrence of 37.75% at point B, and 45.85% at point Pg, due to the counterclockwise rotation of the mandible between the postoperative periods, which occurred due to the best post-surgical intercuspation and muscular adaptation of the patient to the new skeletal position, causing a more anterior repositioning of the mandible.