General anesthesia in orthognathic surgeries: does it affect horizontal jaw relations?

The aim of this study was to evaluate the influence of general anesthesia on centric jaw relation (CR) records of orthognathic surgical patients in different postural positions.

Fifty patients undergoing orthognathic surgery at Taleghani Hospital (Tehran, Iran) in 2008 were prospectively studied. CR records were obtained in conscious patients in 2 different positions (upright and supine) 1 day before surgery and in the supine position under general anesthesia. The impressions were made and the corresponding casts were mounted on a semiadjustable articulator. Differences were measured to the nearest 0.10 mm using a caliper. Paired t test and a general linear regression model were used for statistical analysis.

Fifty patients (27 women and 23 men; mean age, 22.5 ± 3.5 yr) were enrolled. Angle Class I (group I), Class II (group II), and Class III (group III) malocclusions were detected in 16% (n = 8), 54% (n = 27), and 30% (n = 15) of patients, respectively. Although mean changes were smaller than 2 mm, statistically significant differences were found by paired t test in all Angle classification groups. No significant differences were found between the supine and conscious and the supine and unconscious patient positions in groups I and III (P > .05). However, in group II, this difference was statistically significant (P = .001). Regarding the impact of anesthesia on CR records of patients with different Angle classes, this study showed a significant effect, particularly in group II. Assessment of the outcome of interest (difference between the supine and conscious and the upright and conscious positions) versus position after adjustment for Angle class using a general linear regression model showed that the difference was significant only for Angle class (β = +0.29; t = 3.05; P = .003).

General anesthesia may not adversely affect the mandibular condylar position in orthognathic patients in a supine position compared with a supine and conscious position. However, among all study groups, group II showed more significant changes in CR records under general anesthesia. Oral and maxillofacial surgeons should be well aware of such changes in these particular positions and avoid possible mismanagement and potential complications.