Orthognathic surgery is frequently used to correct dentofacial deformities (DFDs) in skeletally mature, non-growing individuals and has a history spanning over more than 150 years. Despite previous research, questions remain about how this treatment affects the patient’s quality of life, upper airways, and respiratory function.

The overall aim of this PhD thesis was to achieve a greater understanding of how orthognathic surgery affects patients’ quality of life in a Swedish context, with additional aspects regarding upper airway function and breathing.

The thesis comprises four studies.

In Study I, the recommended guidelines were used to translate the English-language Orthognathic Quality of Life Questionnaire (OQLQ) into Swedish (OQLQ-S). A group of 121 patients in four diagnostic groups participated in reliability and validity evaluations of the translated Swedish version of the instrument. The main conclusion was that the data supported the OQLQ-S’s validity, reliability, and comparability with the original English version.

Studies II and IV were prospective longitudinal studies of 62 consecutive patients undergoing orthognathic surgery for aesthetic and functional indications. In Study II, respiratory function was assessed using home cardiorespiratory polygraphy on three occasions: prior to orthognathic surgery and at 3 months and 1 year after surgery. None of the patients had previously been diagnosed with obstructive sleep apnoea (OSA). Surgical displacements were evaluated based on measurements in three dimensions using pre- and postoperative computed tomography. There were only minor changes in respiratory parameters such as the apnoea–hypopnoea index (AHI), the apnoea–hypopnoea index in the supine and non-supine positions, the oxygen saturation index (ODI), and the snore index. There was no significant correlation between surgical displacement and AHI, supine AHI, non-supine AHI, and ODI. There was a weak but significant correlation between vertical displacement of the anterior mandible and the snore index. The main conclusion was that the risk for iatrogenic obstruction of the upper airways seemed low in patients without OSA treated with orthognathic surgery.

In Study IV, oral health-related quality of life (OHRQoL) was evaluated with four questionnaires – OQLQ-S, Oral Health Impact 14 (OHIP-14), the Jaw Function Limitation Scale (JFLS), and the Oral Esthetic Scale (OES) – both before and after surgery and in comparison, to a control group comprising 31 patients without DFDs. On average, DFD subjects who underwent orthognathic surgery reported improvements across all scales and subscales, indicating that the surgery was beneficial. At baseline, the DFD group rated their OHRQoL significantly lower than the control group, but this difference levelled out at follow-up. However, some patients reported unchanged or worse outcomes on some of the instruments’ subscales, mainly decreased jaw mobility and an increased postoperative score in the psychosocial impact domain. The main conclusion was that orthognathic surgery has a positive impact on OHRQoL in DFD subjects.

Study III was a retrospective study of 165 adult OSA patients treated with a mandibular advancement device (MAD). Data on AHI, supine sleep, age, sex, body mass index (BMI), Epworth Sleepiness Scale (ESS) scores, mandibular protrusion, patient-reported use, and adverse effects of the MAD were retrospectively collected from medical records or the Swedish Sleep Apnoea Register. Among the included patients, 27.3% (45/165) had both positional OSA at baseline and a ≥50% difference in the proportions of supine sleep between baseline and follow-up. A generalised linear model indicated that changes in the proportion of supine sleep time had a statistically significant effect on the change in overall AHI from baseline to follow-up, comparable in magnitude to the effect of the MAD. The main conclusion was that changes in the proportion of supine sleep are an important determinant of changes between measurements in overall AHI in many patients treated with MADs. Positional OSA must be acknowledged not only in OSA diagnostics but also in MAD treatment follow-up.