Treatment Planning for Functional Anomalies
The general rule that, in orthodontics, it is seldom necessary to take action at an early age does not apply as much to functional abnormalities as it does to morphological deviations. Disturbed function can unfavorably influence the development of the dentition and the growth of the facial skeleton. Hence it can be desirable to correct deviant function at a relatively early age (shortly after emergence of the permanent incisors).
In the area of planning treatment for functional abnormalities, consideration is given to mouth breathing, abnormal tongue position, abnormal lip position and activity, deviant habits (such as digit sucking), forced bites and gnathological anomalies.
As stated, for general health purposes, breathing through the nose is preferred to mouth breathing because air inhaled through the nose is cleaned, humidified and warmed better than air taken in through the mouth. In fact, the olfactory senses depend on sampling air through the nose. Many investigators and clinical workers have emphasized the importance of nasal breathing influencing the harmonious development of the dentition and the face,224 225 251 although a causal relationship has not been properly shown.285
Mouth breathing is often just a part of the wider concept called the “adenoid face”, the characteristics of which are a long narrow face, a large anterior lower face height, a steeply sloping lower border of the mandible, inactive lips lacking tone, a short upper lip, an open mouth, maxillary incisors practically continually visible, and a low degree of “facial animation”. Enlarged adenoids are, correctly or not, blamed for this condition, thus giving rise to the term “adenoid face”. This has also not been proved to be a casual relationship.37
Children who resume nasal breathing after adenoidectomy do indeed exhibit a somewhat changed pattern of growth of the facial skeleton. The changes are rather inconsiderable223 and do not justify the supposition that “adenoid faces” are caused by enlarged adenoids, or other conditions that have restricted nasal passages.
With most children showing restricted nasal passages, hypertrophied and inflamed adenoids are not the chief causes. Usually other factors are responsible for the restriction.243 For instance, allergies and septum deviation are more likely to be the cause. The effective treatment of nasal allergies is not often possible. Operative intervention, such as correction of septum deviation before facial growth has finished, can unfavorably affect the eventual shape of the nose. It is not possible to secure an adequate improvement in nasal patency in all children and adults.
When patients have a mouth breathing habit, it should be ascertained if nasal patency is sufficient for nose breathing to be learned (3.4.3.). Nose breathing is important in securing normal physiological conditions of the orofacial region, particularly during the period in which the permanent incisors emerge. A closed mouth and harmonious distribution of the muscular forces that act upon the teeth are of special importance in achieving and keeping good dental alignment.
Children who have been mouth breathing for a long time frequently have a short, thick, incompetent upper lip and a voluminous curled-over lower lip. With changing from mouth breathing to nose breathing in such cases, lip exercises should be prescribed (9.4) usually shortly after transition of the incisors. The patient must be aware of the importance of the change in the way of breathing and be prepared to devote himself to achieving it. If no obstructions remain, and it is possible to close the mouth, then with sufficient motivation it should be possible to learn to automatically breathe through the nose.
The therapies can be applied to eliminating unwanted habits are discussed in Section 9.5. Here it is enough to say that it is recommended that, on going to sleep, adhesive tape is used to hold the lips shut because especially in the beginning, it is difficult (while asleep) not to slip back into old habits.
Mouth breathers with good nasal patency (habitual mouth breathers) will have to practise consciously to achieve subconscious nasal breathing. Patients for whom an obstruction has been removed do not necessarily automatically go on to nose breathing once a patent airway is established. If this is not happening, help and support may be needed to realize the change.
Children who have taken to mouth breathing as the result of enlarged adenoids, will normally be found to resume nose breathing once the further growth of the facial skeleton and the simultaneous reduction of adenoid tissue occurs and consequently restores nasal patency.
A new-born child has a tongue that is relatively large when compared with the other structures of the face. At rest it lies between the maxillary and mandibular alveolar crests. During suckling the tongue is positioned under the nipple and in contact with the lower lip; on swallowing the lips are contracted. Later, the pattern of swallowing changes as the infant is put onto solid food. The lip activity is reduced, the masticatory muscles bring the dental arches into contact, and the tip of the tongue is placed in contact with the lingual surfaces of the maxillary incisors. Not all children make these changes completely; at the age of 6 years, approximately 50% of children have a pattern of swallowing in which there is no occlusal contact. About 15% of adults continue to swallow, without bringing their teeth together.
The changing in the swallowing pattern and the positioning of the tip of the tongue more dorsally at rest, are related to the difference in intensity of growth of the tongue and the structures embracing it. The face, and especially the mandible, grow more rapidly and catch up with the tongue, which had at an early age already attained a considerable proportion of its adult size. More room becomes available for the tongue; it can be held within the dental arches and swallowing can proceed without the tongue being interposed between the arches.
In children the space available for the tongue can sometimes be encroached upon by severe enlargement of the tonsils and adenoids. Their hypertrophy makes it necessary to hold the tongue forward to provide an airway. In cases of gross enlargement of the tonsils, the base of the tongue has to be held forward, particularly in swallowing food. When later, at about the age of 9 years, the lymphoid tissues begin to regress, space for the tongue returns. Accompanying this there is also an increase in tongue space due to the growth of the facial skeleton and its appurtenances.
When the tongue is relatively large, or takes up a ventral position, it is held between the incisors anteriorly and also sometimes between the posterior teeth. Consequently, an open bite exists.
Digit suckers also often have open bites. When swallowing, the tongue is placed in the open space so as to secure good closure with the lips. This is to prevent food or fluid leaking out of the mouth.302 If the sucking habit is discarded and there are no additional functional disturbances, the open bite can close spontaneously and the tongue will resume a normal swallowing pattern.
If a lack of space for the intra-oral functioning of the tongue is not corrected, then the open bite will not decrease and the further growth of the face will be influenced by this. In such situations, the anterior face height increases more than does the posterior height. The mandibular lower border slopes more steeply and the chin moves downwards and slightly, or not at all, to ventral.
The different aspects of tongue position, swallowing, open bites and facial growth have been discussed above to show that there are no valid arguments for instituting myofunctional therapy in order to attempt to modify so-called abnormal patterns of swallowing and tongue position. Those “abnormalities” are a response to anomalies which myofunctional therapy does not attempt to remove.132 Interposition of the tongue at an early age is a normal phenomenon, inherent with the different rates of growth of the tongue and the jaws. With maturity, tongue interpositioning ceases in most cases, and the open bite vanishes. Open bites due to sucking habits usually vanish when the habit stops. In these cases tongue interposition is adaptive and needs no further attention. In cases involving excessive increases in lymphoid tissue with resulting abnormality of tongue position, reduction of that lymphoid tissue is followed by spontaneous improvement in tongue position. Sometimes surgical removal of the tissue might be indicated.364 If the tongue interposition is a symptom of such a shortage of space for intra-oral functioning that facial growth will be influenced by it, then instituting myofunctional therapy could not be expected to produce any significant effect on that influence.
Repeatedly, and convincingly, it has been proved that with speech therapy it is possible to permanently improve the action of the tongue in speech and subconsciously retain the learned pattern. However, there is a great difference between speaking and swallowing. Speaking is a conscious learned activity, while swallowing is an unconscious automatic function that depends on reflexes. There are no data from which it can be concluded that the pattern of swallowing can be permanently changed by myofunctional exercises, nor that such exercises would reduce the seriousness of an orthodontic anomaly.364
“Review of data from studies published to date has convinced the Joint Committee for Dental and Speech Pathology that neither the validity of the diagnostic label ‘tongue thrust’, nor the contention that myofunctional therapy produces significant consistent changes in oral form or function, has been adequately documented. There is insufficient scientific evidence to permit differentiation between normal and abnormal, or deviant patterns of deglutition, particularly as such patterns might relate to occlusion and speech.
There is unsatisfactory evidence to support the belief that any patterns of movement defined as tongue thrust by any criteria suggested to date should be considered abnormal, detrimental or representative of a syndrome. The few suitably controlled criteria and appropriate quantitative assessment of therapy have demonstrated no effects on patterns of deglutition or oral structure. This research is needed to establish the validity of tongue thrust as a clinical entity. In view of the above, and despite our recognition that some dentists call upon speech pathologists to provide myofunctional therapy, at this time there is no acceptable evidence to support claims of significant, stable, long-term changes in the functional patterns of deglutition and significant, consistent alterations in oral form. Consequently, the Committee urges increased research efforts, but cannot recommend that speech pathologists engage in clinical management procedures with the intent of altering functional patterns of deglutition”.192
Finally, it can be said that application of forms of myofunctional therapy thus far developed, in order to improve so-called anomalous patterns of swallowing and tongue position, is generally senseless. If one nonetheless feels compelled to use such therapy, then it should at least be restricted to attempts to improve the rest position of the tongue and lips and not started before the age of 10 years.246 302 Although, in connection with the dominance of tongue function, it has been advocated that surgical reduction might be warranted in some cases, this is not considered here. In particular, there is insufficient certainty that such intervention—except in extreme situations—would achieve the desired result.169
Many children, whose permanent incisors have emerged, have poor lip closure. The lower lip lies against the incisal edges of the maxillary incisors and, depending on the size of the overjet, is more or less curled-over. The upper lip in such cases is usually short and underdeveloped, and functions minimally in speaking. This picture is associated principally with a large overjet.
It is recommended that in such cases a normal lip closure be striven for. Whether or not this can be achieved will depend on the possibility of breathing through the nose normally, as well as on the morphological conditions. There must naturally be sufficient lip tissue present to bridge the opening. With large overjets for example, this is not always the case.
To improve lip position and activity, some exercises can be suggested. For example, the upper lip should extend itself as far as possible down over the maxillary incisors and, in addition, should try to go right over the incisal edges and pull inwards. If the maxillary incisors are in labioversion the patient should try to place the lower lip against the labial surface of the upper lip. Besides this, it should pull inwards as strongly as possible.141 From an investigation during which these exercises were done at least ten minutes per day over a period of one year, it appeared that lip position notably improved: both lips were longer and the upper lip thinner.184
There are other exercises with the aid of which an improvement in lip position and activity can be sought, such as extending the upper lip down outside the lower lip, or the reverse movement; and closing the incisors into edge-to-edge contact and then moving the lips to and fro over the/>