Functional tongue space is critical for each patient. Inadequate functional tongue space can be a cause of anterior tongue thrusting. This can cause anterior or lateral dental open bites that are difficult to close. Adequate functional tongue space is also very important in sleep apnea. Inadequate functional tongue space can contribute to a posterior posturing of the tongue during sleeping, which can cause snoring and airway obstructions.
Inadequate functional tongue space can cause chronic inadvertent biting of the lateral border of the tongue, a primary site of squamous cell carcinoma.
In my 33 years of clinical orthodontics, I have seen a number of adult patients who have a history of orthodontic treatment with extractions of four bicuspid teeth and later four third molars. A significant number of these patients often complain of difficulty in swallowing because their tongue feels too crowded, so orthodontists should take the amount of functional tongue space into account when considering such extractions.
To diagnose functional tongue space, begin the clinical examination by listening to the patient speak. Is normal speech encumbered? Encourage patients to answer common questions to begin this process. Ask questions about "noisy eating habits." Ask the patient to swallow. Watch for anterior tongue thrust or abnormal lip and tongue motion.
On the initial opening wide of the mouth, observe the most posterior molars. Does the tongue billow out over the lower molars? Are the most posterior mandibular molars lingually proclined into the tongue? If you observe the most posterior molars proclined into the tongue, imagine the molar movement required to upright these molars and move them slightly laterally. Now visualize the amount of bodily maxillary movement required to reposition the maxillary molars vertically over the uprighted mandibular molars.
If the most posterior mandibular molars require uprighting and lateral expansion, and the maxillary molars require bodily lateral movement (usually accomplished with bonded rapid palatal expansion with bite planes), the total effect of these movements may significantly gain arch space. This could solve some crowding problems without extractions.
You can also verify deficient functional tongue room by noting scalloping along the lateral border of the tongue or fissuring of the tongue. Muscles normally do not fold or scallop unless forced to do so by inadequate functional space.
The reader may find these important diagnostic observations helpful in making the all-important extraction or nonextraction decision.
—Michael C. Alpern, DDS, MS, Port Charlotte, Fla
