MYO RESEARCH DOCUMENT


The effects of the MYO appliance in children with malocclusions of the primary dentition

Kevin Bourk

The myofunctional device variously called: "Munchee," "Chewer" MYO or O.P. device has been extensively researched for the past 30 years both in Australia and Japan.

In Australia, clinical research has shown the "MYO" to be an excellent therapeutic modality in the treatment of open bites and anterior protrusions of the mandible. In Japan research was done at Osaka Dental University, under the chairmanship of the Dean Professor Toyoda Heida, involving faculty members Dr. Masihiko Mine, and Masihiko Yoshihara. Their results, involving plaque control, cranio-facial muscle competence, changes in gnathic relationships, salivary gland secretions, were all positive, suggesting that myofunctional therapy with the "MYO" should be routine therapy for all children, particularly those between the ages of 3 and 6 years, when the stomatognathic system is at its most important state of development. Many members of the Australian Academy of Orthopaedic Orthognathics have found the "MYO" to be a superb adjunct in the field of functional appliance therapy, where it not only gives authority to the cranio-facial musculature, but by therapeutic massage of the oral tissues, it maintains them in states of health through extensive treatment periods.

This exciting information has been researched at Osaka University for some time, with detailed findings to be published by Dr. Yoshihara in 1991.

Speech therapists are now very interested in the myofunctional device, noting that many speech defects in young children are directly related to faulty occlusion.

In cases of severe skeletal or dental malocclusion, the infant should be encouraged to exercise the stomatognathic system for about 30 minutes daily. In such cases improvement may be expected in the occlusion and appearance of the infant in periods sometimes as short as 3 months. As with functional appliance therapy, compliance can be a real problem, and so the dentist needs the help of a "Motivating Kit" which consists of a small album, showing the excellent before and after results, which have been obtained in other infants, after constant daily use.

Where no gross orthodontic problem exists, regular daily use of the myofunctional device (MYO) for about 4 minutes, helps improve the alignment of the anterior teeth and gives authority to all musculature of the stomatognathic system. The appliance if used as directed has excellent preventive potential.

Practitioners involved in treating open bites, and tongue posture problems, have in the past, made use of myofunctional therapists and custom made appliances to discourage abnormal tongue habits. These appliances were constructed with spikes or guards to discourage aberrant tongue posture. Many practitioners found the above methods inconvenient for the parent or the child with unpredictable results. The use of the MYO suits well the philosophy of the functional orthodontist.

When the MYO appliance is placed in the mouth for a sustained period, such as when an infant is watching television, then that infant is trained to breathe throughthe nose. Most functional orthodontists emphasize the importance of nasal breathing for proper facial development.

Dr. R.M. Ricketts found that if the nasal cavity is not developing properly then the palate will frequently be elevated in front. The diet in the modern world is insufficient in fibre content to activate sufficiently the facial and pericranial musculature. There is much truth in the saying that "stasis is the basis of disease."

The MYO provides the necessary exercise to oxygenate and empower the muscles of the stomatognathic system. Just as modern man needs a combination of aerobic and strengthening exercises to keep his body fit so also does one need a non-traumatic exercise for the pericranial, facial and neck musculature.

When MYO therapy is used the blood supply to the musculature has been shown to increase between 6 and 20 minutes. Dr. R.M. Ricketts has stated that the need for early treatment, mentioning that he frequently commenced treatment on 4 and 5 year old children. Now with the availability of the "MYO," treatment may be commenced as early as 3 years. The young bone is very susceptible to environmental influences both good and bad, and many habits such as thumb sucking and mouth breathing can be countered and often completely nullified with MYO therapy.

Osaka Dental University has research work to show that the competence of the orbicularis oris can be doubled in most 3 to 6 year old children in a 3 month period.

TABLE 1 - Development of myodynamic lip force observed in the children who had used OP device for 20 minutes a day continuously for 9 months (Normal occlusion)

Sample Age Before Op 3m later 6m later 9m later
1 3 350 450 600 700
2 3 400 525 700 750
3 3 300 425 550 600
4 3 350 300 425 600
5 3 325 400 650 700
4 3 375 400 450 500
7 3 450 450 500 550
8 3 525 550 700 700
9 4 600 750 850 900
10 4 400 400 550 750
11 4 650 700 850 900
12 4 350 425 470 495
13 4 375 400 475 600
14 4 375 400 600 650
15 5 550 650 650 800
16 5 600 800 1000 1000
17 5 400 500 700 1000
18 5 500 650 725 800
19 5 550 660 800 800
20 5 300 350 500 600
21 5 550 650 700 900
22 5 650 700 850 850
23 5 700 750 900 925
24 5 500 600 60 650
25 6 500 575 625 700
26 6 450 650 650 700
27 6 575 650 1000 1000
28 6 375 450 800 850
29 6 475 550 750 900
30 6 700 650 900 1000

(unit:gram)

Table 2 - Development of myodynamic lip force observed in the children who had used OP device for 20 minutes a day continuously for 9 months (Abnormal Occlusion).

Sample Age Before Op 3m later 6m later 9m later
1 3 200 225 225 350
2 3 250 300 350 375
3 3 200 200 350 400
4 3 100 150 250 300
5 3 400 450 500 500
6 3 250 400 700 750
7 3 100 325 400 500
8 3 150 400 650 675
9 4 175 200 525 650
10 4 250 300 400 525
11 4 300 350 500 700
12 4 200 150 300 350
13 4 500 550 700 700
14 4 150 250 700 725
15 4 250 400 700 750
16 4 150 350 1000 1000
17 4 450 500 700 850
18 5 250 400 700 750
19 5 175 200 525 550
20 5 300 350 500 500
21 5 150 250 700 725
22 5 200 450 800 950
23 5 250 450 60 750
24 5 250 450 800 800
25 5 300 450 600 950
26 5 350 500 800 825
27 5 400 500 800 800
28 5 375 400 550 550
29 5 325 400 600 625
30 5 500 700 750 750
31 6 400 550 700 950
32 6 400 600 600 700
33 6 500 500 550 700
34 6 500 750 750 900
35 6 425 500 650 700
36 6 475 500 600 600
37 6 375 400 550 900
38 6 350 400 600 600
39 6 325 450 600 625
40 6 300 350 400 400

(unit:gram)

Note that the figures for children suffering abnormal occlusion are, after nine months' use of the MYO, generally better than those for children with normal occlusion.

They have scientifically shown that which we have always intuitively known that young children with developing malocclusions, always have impaired competence of the orbicularis oris. (See tables one and two)

Chewing on the device produces a copious salivary flow up to 30 times the resting flow rate, and certainly many times greater than any chewing gum which is currently being advertised as important in the remineralisation of interproximal enamel during the 20 minutes following food intake.

The MYO was originally called the "Chewing Brush" and the O.P. (Oral Prophylactic) device because of its capacity to physically remove plaque. As used by a child as a cleaning device only, it was shown to be about 20% more effective than a toothbrush, being exceptionally efficient on the lingual surface of the teeth.

As a therapeutic modality in the field of the physical therapist the myofunctional device may have an important part to play, both as a diagnostic device, and as an aid to treatment, when the occlusion is causing pathology in the cervical spine.

There are many instances in daily dental practice where a patient may gain help from the myofunctional device.

Case Reports

Case number 1: A.G. is a female aged 3 years and 4 months with a severe open bite and speech impairment related to the dental problem. (Fig 1) The child and mother were motivated for about 15 minutes on how to use the MYO. A.G. began chewing on the appliance twice daily for 2 minutes. This time was gradually increased to 4 minutes in a month. The open bite closed at the rate of 1 mm a month. (Fig 2)

Fig. 1 A.G. is 3 years, 4 months old
with a severs open bite and speech
impairment.
Fig. 2 A.G. is shown posttreatment
with an excellent occlusal
relationship.

Currently, it is recommended in cases of this type that the child exercise with the appliance for 10 minutes daily after the first month and to leave it in the mouth for another 30 minutes. This results in faster improvement.

Case number 2: J.F. is a 2 1/2 year old female with severe Class III malocclusion (Fig 3) that was observed at age 2 years. Treatment was postponed until now and consisted of a Sim-type upper sagittal appliance with bands on the second primary molars. This appliance was activated for 3 months. The cross bite was corrected at this time, but it took another 3 months for the posterior to contact. (Fig 4)

Fig. 3 J.F. is 2.5 - years-old with
a severe Class III Malocclusion
Fig. 4 J.F. is 3 - years - old with
a Class I occlusion

All the time J.F. was chewing the MYO twice daily for 4 minutes.

Case number 3: A.E. is a 4 year 11 months old boy (Fig 5) who used the MYO appliance for a total of 18 months. The action of the MYO is thought to improve functionally of the musculature and esthetically the teeth and face. Perhaps all infants need aerobics for the face to keep the stomatognathic system developing to its full genetic potential.

 
 
 
Fig. 5 A.E. begins to use the appliance.
 
Fig. 6 A.E. is half way through the treatment
 
Fig. 7 A.E. is completed after 18 months of using the MYO.
 

Case number 4: S.B. shows a 48 hour plague accumulation that has been stained. (Fig 8) After 3 minutes of chewing with the MYO most of the stained plaque has been removed (Fig 9). After 6 months of using the MYO, the open bite has been reduced and a normal occlusion is the result.

 
 
 
Fig. 8 S.B. shows stained 48 hour plaque accumulation
 
Fig. 9 S.B. uses the MYO for 3 minutes to clean her teeth.
 
Fig. 10 S.B.: after 6 months of using the MYO excellent occlusion is achieved
 



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