Myofunctional therapy is treatment aimed at changing muscle (Myo = muscle) function and thereby influencing jaw growth
and the position of the teeth.
Myofunctional therapy is not new to orthodontics with claims in the past of nasal congestion or a tongue thrust swallow causing open bites.
However, it has been demonstrated that even in children with the most extreme nasal congestion requiring removal of their adenoids and
tonsils, this profound change and invasive procedure had only a very minor influence on their facial growth (1.7° difference which you would
not notice without measuring it).
Similarly, tongue thrust swallowing is a normal adaptation to having an open bite (you place your tongue between the teeth to seal the front while you swallow). Even though swallowing can generate quite high forces, you do not swallow enough to actually move teeth (we swallow an average 1000 times per day which is ~17 minutes of swallowing – it takes ~6 hours of force daily to start to move teeth). Teeth can be moved with very light forces but it has to be over this threshold of ~6 hours to achieve this.
However habits, such as placing thumbs, lips or tongues, between the teeth can be sufficiently long enough to influence the position of the teeth which can require intervention such as reminder strategies or reminder appliances in some cases. The patient below had a thumb habit that with some reminder strategies stopped the habit resulting in the open bite improving without any further treatment being required at that time (photos at the start, 12 months and 30 months later).
It has been suggested to check your child during sleep and if their lips are apart, they need some form of treatment. However, when we are younger many children have their lips apart anyway which normal growth would improve with no treatment. This needs to be evaluated on a case by case basis as some have excessive vertical facial growth but many would simply need monitoring over time.
Lip growth catches up with vertical facial growth from ages 9 to 13 dramatically reducing lip separation with no treatment (Vig. American Journal of Orthodontics 1979;75:405-415).
The graph on the right shows this improvement (circled) in lip separation with normal growth. A study in the American Journal of Orthodontics and Dentofacial Orthopedics (Klocke. 2002;122:353-8) observed 14 children with open bites at age 5. By the age of 9, only 3 had an open bite and only 1 by 12 years of age. Very early treatment has been suggested at the age of 5 to 8 years old to correct open bites but it can be seen from this study that many would improve with no treatment.
This is not to say that early treatment is not indicated as in some cases certain conditions may need monitoring to assess whether treatment is required at a later stage and some benefit from early treatment such as expansion for crossbites which interfere with the bite.
Myofunctional appliances have also been around in various forms for many years. These can include lip shields and screens, eruption guidance appliances (pictured) and trainer appliances such as the T4K™. Although claims are made that they alter muscle function resulting in improved facial growth, better alignment and more stable results, what evidence is there to support these claims?
There are a number of studies examining the clinical effects of eruption guidance appliances and the T4K™ (Keski-Nisula. American Journal of Orthodontics and Dentofacial Orthopedics 2008;133:254-60; Methenitou. Journal of Pedodontics 1990; 14:219-30; Usumez. Angle Orthodontist 2004;74:605-609; Janson. American Journal of Orthodontics and Dentofacial Orthopedics 2007;131:717-28) . These studies provide clinical evidence as to the compliance and effect of these appliances.
These appliances are available in limited sizes and one size is selected to suit an individual rather than being custom made from an impression of the teeth. Possibly because of this poorer fit, the study by Keski-Nisula found 31% of patients did not wear the appliance and the study by Janson excluded 35% of cases from the study. A randomised trial of the T4K™ versus a custom made Activator appliance (Idris. Eur J Paediatr Dent. 2012;13:219-24) found the custom made Activator caused less discomfort than the T4K™ and was more acceptable.
All four studies showed that with 13 – 36 months of treatment, protrusion of the top teeth was reduced by an average of only 1.5 to 2.5mm. The study by Janson also followed patients over time and found the small 2mm improvement in crowding virtually completely relapsed to the initial state which does not support the claim of improved stability. A 2mm improvement in bite depth was also unstable and relapsed leaving only 0.5mm of change.
A 2mm change is considered a minor improvement and could be treated once all teeth have erupted in one phase of treatment once all the adult teeth have erupted. This resulted in a reduced overall treatment time as well as potentially less cost than doing 2 or more phases of treatment from the age of 5 to 8 onwards.
Clinical trials in the both the USA (Tulloch. American Journal of Orthodontics and Dentofacial Orthopedics 2004;125:657-67) and the United Kingdom (O’Brien. American Journal of Orthodontics and Dentofacial Orthopedics 2009;135:573-9) where patients were randomly assigned to early or late treatment have shown that when patients were treated early for much more severe protrusions (7mm rather than 2mm) they could be treated equally as well by delaying treatment until all the baby teeth had been lost. T
he result of treating later (~ age 12-13 years of age) was a shorter overall treatment and less cost. However a case can be made for early treatment to reduce protrusive teeth when the appearance or function is concerning the patient or for a small reduction in the risk of trauma to the front teeth.
So if you are unsure about whether early treatment is indicated for your child, consult your orthodontist as to whether early treatment is indicated or whether simply monitoring your child is indicated to achieve the most efficient and cost-effective method at the most appropriate time.