Subjects
The initial subjects consisted of 54 patients (18 males and 36 females) who complained of TMD before 2-jaw surgery. Inclusion criteria were: 2-jaw surgery by Le Fort I osteotomy and bilateral sagittal split ramus osteotomy(BSSRO), no history of orofacial trauma, check-up with cone beam computed tomography (CBCT) imaging at 3 periods (T0: preoperative period, T1: postoperative 1 week or less, T2: postoperative 6 months or more). Exclusion criteria were: congenital developmental disorders such as cranio-facial syndromes and clefting, inflammatory TMJ disease such as acute capsulitis and osteoarthritis. On the basis of the criteria, 32 patients were recruited finally. The patients were divided into two groups according to presence or absence of preceding treatments for the purposes of alleviation of TMD and stabilization of condyles before the surgery: The study group consisted of 15 patients that had no preoperative TMD treatments (sex: 4 males and 11 females, mean age: 24.8 ± 2.76 years, range: 21 - 31 years). And the control group consisted of 15 patients had been treated until the symptoms and signs of TMD alleviated (sex: 7 males and 8 females, mean age: 24.4 ± 4.29 years, range: 18 - 31 years). The treatments for stabilization of preoperative TMJ condition included medication therapy, physical therapy, splint therapy, and self-regulation therapy. This study was exempted by the Institutional Review Board at Pusan National University Dental Hospital, and we followed the guidelines of Helsinki Declaration in this study.
Surgical procedure
All patients underwent 2-jaw surgery by 1 experienced surgeon from January, 2007 to June, 2012 in the clinic of Oral and Maxillofacial surgery, Pusan National University Dental Hospital. During the BSSRO, the mandibular proximal segments were manually repositioned and fixated with single miniplate (4 holes) & four monocortical screws (2.0 mm diameter) through intraoral approach. Intermaxillary fixation with the occlusion guided wafer was applied for 1 week after the surgery. Since the 1 week, the postoperative physical trainings for mandibular function were progressed gradually.
Clinical examination of TMD
In this study, we collected the data by self-reported questionnaires and clinical and functional examinations: (1) TMJ pain during function(mouth opening or mastication), (2) TMJ noise on jaw movement, (3) LOM under 35 mm. The study group were examined in three times: before the preceding treatments for TMD, before surgery and 6 months after surgery. The control group were examined in two times: before surgery and 6 months after surgery. Self-reported questionnaire consisted of several questions regarding the subjective changes of TMJ symptoms. Clinical and functional examinations were performed for the diagnosis of TMD according to the Research Diagnostic Criteria for TMD (RDC/TMD) Axis I [14]. The severity of TMJ pain and noise was rated on Numerical Analogue Scales (NAS) composed of 11 rating points. The NAS ranged from 0 to 10 with 0 indicating ‘no symptom and sign’, 10 representing ‘worst possible symptom and sign’, and 5 documenting an intermediate level at ‘moderate symptom and sign’. The change of LOM was evaluated as three grades: ‘improvement (+)’, ‘deterioration (-)’, and ‘no change (0)’.
Analysis of condylar position with 3D CBCT
The patients underwent 3D CBCT imaging with the closed mouth (Pax-Zenith 3D, VATECH, Korea). For ascertainment of positional changes in both condyles, dental CBCT (DCT) images were reconstructed with 3D dental image software (SimPlant Pro Crystal for Intel X86 Platform V13. 0. 1. 4, Belgium). On the basis of three reference planes and twenty-five reference points set up on 3D reconstruction model, fifteen measurements were obtained (Figures 1 and 2, Tables 1 and 2).
Statistical methods
The data were analyzed with a commercial statistical software package (SPSS for windows ver. 20.0). Significances of differences between the times were assessed by the Wilcoxon signed rank test. The significant level is set at P < 0.05.