**12. Mandibular advancement devices (MADs)**

MADs were first described by Pierre Robin in 1934 in the treatment of a patient with micrognathia as a modified monobloc in order to reposition the mandible in a more forwarded position and open the airway. This advancement makes the attached soft tissues and tongue stretch and stabilize; by this way, oro- and hypopharyngeal airways enlarge.

displacement of the mandible also decreases the gravitational effect of the tongue in supine position and enlarges the velopharynx by stretching the palatoglossal and palatopharyngeal

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Tongue-retaining devices were first described by Cartwright and Samelson in 1982 [28]. During sleeping and in supine position, the tongue and all gravity-dependent tissues tend to fall posteriorly. With TRDs, the tongue is prevented from dropping posteriorly by suction created when the patient forces the tongue into a hollow bulb built into the device. The forward position of the tongue increases the volume and decreases the resistance of upper airway. The superiority of TRDs over MADs is that they can be used for edentulous patients [10–12, 16, 17, 19, 20, 23, 25, 31].

Edentulous OSA patients, OSA patients who have TMJ disorders, OSA patients with big tonsils and large tongues, OSA patients who have less than six teeth per arch, hypothyroidism,

Severe periodontal diseases, bruxism, chronic nasal obstruction, patients who are unable to

The TRD appliance can be fabricated from soft copolymer materials by the technician to the OSA patient individually, or standard fabricated appliances can be used to the patient.

arches (**Figures 1** and **2**).

**13. Tongue-retaining devices (TRDs)**

**Figure 2.** Two-piece, activation-optioned MAD appliance.

**Figure 1.** One-piece, non-activation MAD appliance.

and sleep position–related apnea-hypopnea occurrence.

move their tongue anteriorly, and obese OSA patients.

**13.1. TRD indications**

**13.2. TRD contraindications**

**13.3. TRD appliance construction**

MAD appliances can be divided into several groups: monobloc-style one-piece or twin block-style two-piece, available to activation or unavailable to activation, teeth-supported or teeth- and tissue-supported, and soft- or hard-materialed. All of these appliances increase the distance between soft palate and posterior wall of the pharynx and enlarge the space between tongue root and posterior region of the oropharynx.

Tooth- and tissue-supported, soft-materialed, activation-optioned MAD appliances are reported to be more successful in OSAS treatment. One-pieced or two-pieced appliance design does not affect the treatment success.

MAD-type oral appliances are found the most effective type of oral appliances in OSAS treatment [10–12, 17, 19, 23, 25–30].
