Changes in sleep and airway variables in patients with obstructive sleep apnea after mandibular advancement splint treatment Whitney R. Mostafiz, a,b David W. Carley, c Maria Grace C. Viana, a Serina Ma, d Oyku Dalci, d M. Ali Darendeliler, d Carla A. Evans, a,e Budi Kusnoto, a Ahmed Masoud, f and Maria Therese S. Galang-Boquiren a Chicago, Ill, New York, NY, Sydney, New South Wales, Australia, Boston, Ma, and Jeddah, Saudi Arabia Introduction: Obstructive sleep apnea (OSA) is an extensive public health problem that imposes considerable morbidity. Mandibular advancement splint (MAS) therapy is a well tolerated treatment, but success rates are diffi- cult to predict. Our objective was to investigate the relationship of oropharyngeal airway dimensions, sleep char- acteristics, patient biometrics, and treatment response within an OSA patient sample. Methods: Records of 33 adults were assessed retrospectively with the use of Dolphin 3D and Image J to measure the airway on pretreat- ment supine cone-beam computed tomography images and derived lateral cephalograms. The patients used Somnodent (Somnomed; Crows Nest, Australia) MAS appliances, which were titrated over 6-8 weeks. Appliance titration measurements and pre- and posttreatment polysomnograms were assessed. Respiratory disturbance index (RDI), absolute and percentage changes in RDI, non–rapid eye movement (NREM) RDI, rapid eye movement (REM) RDI, supine and nonsupine NREM and REM RDI, and minimal blood-oxygen saturation variables were evaluated. The associations of measurements from 2D and 3D minimal anterior- posterior linear distance and 3D airway variables with MAS treatment response were estimated. Results and Conclusions: Combined effects of baseline total airway volume, body mass index, neck circumference, location of minimal cross sectional area, and OSA severity were associated with treatment response. Patients with higher initial OSA and more superiorly located airway constriction showed enhanced treatment response to MAS ther- apy. Airway constriction due to maxillofacial disproportions rather than soft tissue obstruction also showed better treatment response. No significant relationships were found in lateral cephalogram measurements. (Am J Orthod Dentofacial Orthop 2019;155:498-508) O bstructive sleep apnea (OSA) is an extensive pub- lic health problem that imposes considerable morbidity. Although continuous positive airway pressure (CPAP) is the criterion standard of treatment, it often produces suboptimal results because of variable patient adherence. 1 The American Academy of Dental Sleep Medicine (AADSM) 2 has recommended oral appli- ance therapy for mild-moderate OSA, but the under- standing of underlying mechanisms that offer treatment through oral appliances is poorly under- stood. 3 Orofacial anatomy is an important factor to consider. OSA patients are thought to have a significantly larger tongue, creating an anatomic imbalance of the upper airway. 4-6 According to Tsuiki et al, 7 a more caudal and larger tongue correlates with increased lower face dimensions, significantly longer mandibular plane to hy- oid bone (MP-H) distance, and excessive soft tissue. A reduction in diaphragm and upper airway muscle activity during the transition from awake to non–rapid eye movement (NREM) sleep also leads to a 2- to 5-fold in- crease in upper airway resistance. Apneic events are more a Department of Orthodontics, College of Dentistry, University of Illinois, Chicago, Ill. b Department of Orthodontics, New York University, New York, NY. c College of Nursing, College of Medicine, University of Illinois, Chicago, Ill. d Department of Orthodontics, University of Sydney, Sydney, New South Wales, Australia. e Department of Orthodontic, Henry M. Goldman School of Medicine, Boston, Ma. f Department of Orthodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia. All authors have completed and submitted the ICMJE Form for Disclosure of Po- tential Conflicts of Interest, and none were reported. Address correspondence to: Maria Therese S. Galang-Boquiren, UIC Department of Orthodontics, 801 S. Paulina Street, Room 131 M/C 841, Chicago, IL 60611; e-mail, mgalang@uic.edu. Submitted, April 2017; revised and accepted, May 2018. 0889-5406/$36.00 Ó 2019 by the American Association of Orthodontists. All rights reserved. https://doi.org/10.1016/j.ajodo.2018.05.022 498 ORIGINAL ARTICLE