Periodontal health is not jeopardized, even though the Invisalign system aligners cover all the teeth and the keratinized gingiva in part. This could be attributed to the fact that aligners are removable and thus allow unimpeded oral hygiene.

Although all the teeth and parts of the keratinized gingiva are covered nearly all day during Invisalign treatment, the periodontal risk is lower than that associated with fixed lingual appliances. This may be due to the fact that aligners are removable, permitting unimpeded oral hygiene. In contrast, the lingual tooth surfaces are very difficult to clean when fitted with a fixed appliance.

In order to investigate the difference in tongue movement between visceral (infantile) and somatic (mature) swallowing patterns, 12 visceral (seven females, five males) and 14 somatic (eight females, six males) swallowers were examined with the B+M-mode ultrasound technique. Movements of the tongue tip and submental musculature during swallowing were recorded on video cassette and evaluated with a personal computer. The results demonstrated that the tongue dorsal surface, which was thought to be ideal for observing tongue function, was not suitable for differentiating between visceral and somatic swallowing patterns. Conversely, the movements of the genioglossus muscle were found to be identical within groups but significantly different (P < 0.01) from each other between the two swallowing patterns. Therefore, the genioglossus muscle can serve as a reliable means for differentiating between visceral and somatic swallowers.

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Invisalign therapy seems particularly attractive to a clientele comparable to that for the lingual technique. Patients show high acceptance, since they become accustomed to the aligners very quickly and do not suffer much impairment. If indicated, Invisalign therapy should thus be considered an alternative to the lingual technique for esthetically-demanding patients. This applies especially to patients who cannot be treated by the lingual technique because of the inevitable speech impairment.

M-mode ultrasonography provides valid information on tongue movements without any side-effects and is thus a useful tool in the diagnosis and research of tongue functions in orthodontics and dentistry.

Hypodontia and malformation are almost regular dental characteristics in patients suffering from ectodermal dysplasia. The distribution of absent teeth deviates remarkably from the general population. Treatment requires an interdisciplinary approach including orthodontics, prosthodontics and oral surgery.

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