**6. Obstructive sleep apnea syndrome in orthodontic practice**

As cited above, OSA is associated with numerous craniofacial abnormalities. Orthodontics improvement of dento-facial morphology may have a positive impact on OSA components. Orthodontic professionals should provide treatment for OSA patients as well as diagnose potential OSA patients. Medical history and clinical examination allows orthodontists to identify the risk factors of OSA or signs related to OSA (obesity, allergy, nasal dysfunction, maxillary constriction, retrognathia, long uvula, mouth breathing...) or record some symptoms reported by patients. Moreover, several imaging modalities (lateral and frontal cephalogram, cone beam computed tomography, MRI.) can assist Orthodontic professionals in assessment of this condition.

Orthodontic management of OSA syndrome could be provided to children as a preventive and interceptive modal or to adults by an interdisciplinary management. A significant number of children suffering from respiratory problems and obstructive sleep apnea have nasal obstruction associated with a narrow maxilla that may increase nasal resistance and alter the tongue posture, leading to a narrowing of the retroglossal airway and OSA. Maxillary expansion with orthopedic appliances is very effective in these cases allowing for an increase of nasal cavity dimension. It can be combined with adenotonsillectomy for best results in children with OSA associated with adenotonsillar hypertrophy. [4, 66, 67] Among adults, this expansion can be attained by RME or surgically assisted RME and has been reported to reduce snoring and hyper-somnolence.

Maxillomandibular advancement can also be provided either by surgery or orthopedic systems as therapeutic or preventive measure in OSA cases. A good finishing of dental occlusion is desirable. On the other hand, It has been suggested [68] that the improve‐ ment observed in the respiratory symptoms with surgical MMA, namely apnea/hypopnea episodes, should be correlated with SNA increase after surgery which may help maxillofa‐ cial surgeons establish selective criteria for the surgical approach to sleep apnea syn‐ drome patients. Mandibular advancement in case of retrognathia can be accomplished by oral appliances in adulthood, functional appliance therapy in younger patients, mandibu‐ lar distraction osteogenesis or osteotomies, and is among the most frequently used approaches in OSA management.

Orthodontists can also have a role in the treatment of OSA consequences especially those with nocturnal bruxism, which differs from stress-related bruxism. Sleep bruxism has been shown to be prevalent in children, and correlated with sleep disturbances (microarousals). It is characterized by rhythmic masticatory muscle activity and may be related to the patients' attempt to improve airway patency during episodes of oxygen desaturation via co-activation of jaw opening and closing muscles. Its management requires use of night splints and restor‐ ative dentistry.

In brief, although the bi-directional cause and effect relationship between OSA and craniofacial abnormalities remains to be proven, early identification and treatment of dentofacial disorders may enhance OSA management with respect to preventive and curative approaches. Interdisciplinary professional communication is crucial for the success of global OSA management.
