**7. Classification**

10 seconds will lead to decrease oxygen supply to vital organs such as the heart and brain which result in many sign and symptoms. Excessive daytime sleepiness, memory loss, impaired concentration, morning headache, decreased manual dexterity, libido and decrease

Systemic complications of OSA includes cardiovascular and neurocognitive disorders and death. Periods of apnea, prevent effective gaseous exchange at the alveoli which lead to hypoxia and hypercapnia. Apnea dependent hypoxia and hypercapnia increase sympathetic neural tone, which in turn cause vasoconstriction and increase in sympathetic nerve activity. Sympathetic nerve function rises progressively during apnea and is enhanced further by arousal. Increase in the sympathetic tone is the major cause of cardiovascular complications. OSA is associated with hypertension [16-18], arrhythmia, myocardial infarction [16, 19, 20], and congestive heart failure [16]. During the obstruction episodes there are marked changes in blood flow in cerebral arteries. Netzer et al reported 80% changes in cerebral blood flow in cerebral arteries [21]. During periods of apnea there is rapid increase in cerebral blood flow followed by rapid fall to below baseline levels after apnea periods. Fluctuation in cerebral blood flow along with many physiologic changes may lead to stroke [16]. Mortality rate of OSA can reach up to 30% in 15 years if left untreated [22]. Excessive daytime sleepiness could contribute to high rates of road traffic accidents. Studies show RTA among OSA patients is 1.3

Maxillomandibular advancement is considered a telegnathic surgery, which involves maxil‐ lary and mandibular osteotomies to enlarge posterior airway space. Telegnathic surgery is derived from the Greek words *tele,* which means "over a distance," and *gnathis,* which relates to the jaws, whereas orthognathic surgery is derived from the Greek words, ortho, which means, "to straighten," and *gnathis meaning "jaw".* OSA patients are usually middle age, obese, mostly males with significant comorbid medical conditions; on the other hand patients with dentofacial abnormalities are young with no sex prevalence (male or female) and usually in a

There are no major differences in the surgical techniques although the goals of therapy are different. In orthognathic surgery the goal is to correct the occlusion and improve esthet‐ ics while in telegnathic surgery the optimal goal is to relieve upper airway obstruction. Orthodontic treatment is a must for all patients with dentofacial deformities who are going for orthognathic surgery. In OSA patients accepting the existing bite can be used if the patient does not want to go through the lengthy orthodontic treatment. Surgical move‐ ment in the orthognathic surgery patient are dependent upon the esthetic requirement as well as occlusion correction, whereas in OSA patients a larger surgical movement of the maxilla and mandible should be done (up to 10mm) with the main concern being open‐

sexual performance [16].

396 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

good health.

ing the posterior airway space [25, 26].

to 7 times higher than the general population [23, 24].

**6. Orthognathic surgery vs. telegnathic surgery**

Respiratory disturbance index (RDI) represents the number of obstructive respiratory events per hour of sleep. An RDI of 5 is the upper limit of normal.

RDI= (apnea+hypopnea ÷ total sleep time) × 60 [27].

OSA is classified into mild, moderate and severe depending on the respiratory disturbance index (RDI) and oxyhemoglobin desaturation (SaO2).

**Mild OSA** is when RDI 10-30 and SaO2 >90%,

**Moderate OSA** is when RDI 30-50 and SaO2 >85%, and

**Severe OSA** is when RDI >50 and SaO2 <60% [28].
