Mouth opening and its influencing through the SII appliance during the night

In twelve patients, 43 nocturnal sleep investigations were carried out telemetrically. These investigations were aimed at contributing towards answering the questions of how large the interocclusal distance is during the night, whether there is a correlation with the growth pattern, and whether this interocclusal distance can be changed by using Class II elastics. The treatment appliance chosen was the SII appliance. During nocturnal sleep, all patients slept with their mouth more or less open. The largest interocclusal distance was found in patients with a vertical growth pattern as well as in one patient in whom an allergic reaction to the house dust mite was later verified. The active phase during nocturnal sleep comprised between 200 and 800 biting actions during the entire sleeping period and corresponded to an activity of about 10 minutes. During nocturnal sleep there were rarely complete mouth closures, even during diverse swallowing actions. Patients with a horizontal growth pattern showed the smallest interocclusal distance, provided that nasal breathing was not obstructed. The additional application of Class II elastics had a positive effect on the interocclusal distance in all patients. A shortening of the protrusive bars must be avoided in all events; otherwise there may be no protrusion when biting together. The long bars of the SII appliance have an influence on the maxilla, because there is contact between maxilla and mandible up to mouth openings of about 14-16 mm.