orthopaedic and orthodontic problems which come to fruition in the
mixed dentition, then to maturity in adolescence, have their genesis
in very early childhood. 1
work (N.P. Martinez et al 2 Southern Illinois Uni.
School of Medicine) on 3 - 5 year old children showed 16% of children
had digital habits, 33% T.M.J. clicks, 67% wear facets and 30% teeth grinding
habits - physiological and physical factors all impacting on genetic development.
occasions when addressing early developing problems I have spoken about
treatment for early Class III (5%), crossbites (17.5%) and openbites (15%).
On this occasion I would like to relate to the Class II malocclusion, which
is the bread and butter of orthopaedic treatment, and with which we have
much success today using Clark, Mew and Bionator appliances in older children.
There is little doubt that genetic structure plays a very important role
in the relationship of the developing mandible to the skull base. We can
know this by observation and inquiry. However, it has taken research workers
such as Potter (Uni. North Caroline) and others such as McNamara, Frankel
and Pancherz to scientifically demonstrate that, in the face, genetic development
is overwhelmed by the environment.
how readily the thumb sucking habit will distort an infant's appearance, showing
that the early bone development is very susceptible to pressure. Observing
this, I find it a little puzzling to understand why treatment is ever delayed.
(Uni. Turku Finland) 3 has shown that the sagittal
relationship in the primary dentition (age 3 years) varies significantly
between those who finally developed a Class II or Class I relationship.
He found that the terminal plane in the normal Class I group of infants
at age 3 years was mesial 1.3mm, and in the children who developed a Class
II relationship was 1.3 mm distally, and that the differential became greater
as age progressed. His results showed that the transverse dimension in
the primary dental arch is impaired in the maxilla, but not in the mandible
in Class II cases.
that the lower arch grows normally, but assumes a more distal position
to occlude with the narrow upper arch. All this makes sense to the clinician
who invariably sees mandibular posterior teeth tipped lingually in Class
II cases, and explains the improved vertical dimension in infants who exercise
their stomatognathic systems with daily "myo" chewing (expanding the
developing maxilla and promoting nose breathing, so essential to
work by 4 K. Maki (Showa Uni. Tokyo) and R. Tanaka
(Uni. Nagaski) shows that mechanical stress (chewing) produces changes
in the density and morphology of the bone, and that cancellous bone adapts
to occlusion induced stress.
of course, is of ultimate importance to the proper functioning of the parotid
gland, whose secretions play such an important role in the overall health
of the oral cavity. A striking example of this is in South Africa where
the workers on the sugar plantations in spite of their frequent and high
consumption of sucrose are caries-free. Their chewing produces a salivary
milieu protecting the oral cavity.
studies continue to emerge from international dental research institutions
highlighting the interdependence of skeletal anatomy. For instance S.
Kapila (Uni. Cal. S.F.) 5 has shown that a medio
lateral deviation of the mandible in the rest position induces asymmetries
both in the internal structure of the bone, and in the cranio-skeletal
morphology of a rapidly growing mammal. And again, H. Joy and D. Carlson
(Uni. Michigan) 6 have shown how early septal deviation
which produces respiratory impairment can cause a reduction in mid facial
growth and malocclusion in rats. So it is not surprising that
a retruded human mandible produces inadequacies both in the physiology
and morphology of the upper skeletal components (cervical spine), and subsequently
in the lumbar area.
we notice this interconnection in the treatment of T.M.J. Dysfunction.
McNamara and Woodside have all shown that when you unload the condyle
with an anterior repositioning device in a young child, you cause stimulation
to growth in the fossa and in the condyle. These studies support Osaka
dental Uni. research which shows that in the young the direction of growth
correlated with the direction of strain.
again Y. Sim and D. Carlson (Uni. Michigan 1994) 7
demonstrated that bite splints used in Rhesus monkeys which increase the
vertical dimension of the mid face also caused 62% increase in the chrondroblastic
layer and marked thickening of the pre-chrondroblastic layer.
(Uni. Baylor) A. Demirjian (Uni. Montreal) 8 in
1991 have shown that rotational and remodeling changes are significantly
greater during childhood than adolescence, and that children in the primary
dentition show the greatest amount of remodeling change. 9
examples will suffice to show the importance of function. The Clarke Appliance
owes much of its success to being a truly functional appliance. The muscles,
bone and joints function in a forward position when eating, and the central
comparator does the remodeling. Secondly K. Yamada and D. Kimmel 10
(School of Med. Crighton) showed that when experimental animals (rats)
4 weeks old chewed hard food (rather than just swallowing soft food) mineral
deposition was markedly increased in the mandible, and condylar cartilage
development proceeded more rapidly - as the following table shows:
important to understand that in the infant the Glenoid Fossa is in the
process of formation. It is in its most rapid state of change in morphology
at age 2-5 years. 11
forward repositioning in the adolescent, where vertical growth in the posterior
alveolus is necessary for final stability, the infant's mandible will, over a
12 month period, remodel to accept the more forward position without
producing the posterior open-bite. (See Fig 1 - 4).
All scientific indicators
point in the direction of early treatment of Class II malocclusion. The research
has been done and the evidence is clear. It remains for this knowledge to be transferred
into general clinical practice.
Fig. 1 Developing Class II Malocclusion in a child aged
3 years 6 months.
Fig. 2 Repositioning of mandible after 1 year of treatment (MYO Munchee
and a MEW III device)
This child's problem was a closed bite with a trapped mandible. He was also, as evidenced by
the wearing down of his teeth, a nocturnal grinder.
These photos demonstrate that such problems can be rectified
easily at an early age.
B.T.'s Class II Malocclusion was fairly typical.
When treatment commenced, BT was 3 years and 10 months old.
Fig. 3 Developing Class II Malocclusion.
As indicated by the red line, the
deciduous molar position is 1.3 mm distal to the terminal plane.
Fig. 4 The problem is fully corrected by 12 months' MYO Munchee therapy.
were taken, and a bite recorded; the anteriors were in an edge to edge
relationship, but 1.3mm apart.
repositioning appliance was constructed, in this case a Mew III. Composite
was added to the buccal of the upper E's to provide positive retention
for the clasps. The child was examined monthly. Bone and joint changes
take place slowly. The child should exercise with the myo (which is set
in a Class I relationship) for 10 minutes daily. This gives stimulation
to all bones, joints and muscles of the Stomagnathic System and facilitates
morphological change. Young children manage the appliance much the same
way as their older siblings. After about 12 months the child will tend
to close into a Class I position. To consolidate this relationship composite
is added to the deciduous canines to proprioceptively encourage the mandible
to permanently assume the desired Class I relationship. It will be noted
that there is no space between the upper and lower 2nd deciduous molars.
simple methods may be used to relieve a genetic predisposition to faulty
development. The mandible may be genetically short, and if the maxilla
is also influenced by environmental factors such as frequent head colds,
then what is likely is a potentially serious developing Class II malocclusion.
Fig. 5 A severe case of Class II Malocclusion.
Fig. 6 Improvement after 13 months of MYO Munchee treatment
Treatment in this case was as follows:
1. To free
the entrapped mandible with an upper Sagittal.
2. To institute
good function with daily Myo chewing.
3. Use a
ramp (even while eating) to encourage forward positioning of the mandible
after the anterior teeth have been moved forward with the sagittal appliance.
This patient had no problem functioning with the ramp.
was added to the canines to proprioceptively reposition the mandible.
late' mindset is under serious challenge, with work such as this demonstrating
excellent results from very early correction.
Unlike later treatment, early intervention with the use of MYO devices improves
musculature and bony structures. There is a general improvement in appearance.
This is shown clearly in the pictures below, which really are "the last word" in this debate.
Fig. 7 At 3 years 6 months this child is exhibiting
the gross facial disfiguration associated with
Class II Malocclusion.
Fig. 8 At age 7 MYO Munchee and orthopaedic therapy
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Potter, J. Dent Res. 1990 Abstr. 1836. "A Twin Half-Sib Model For Occlusal
Verada, J. Dent Res. Abstr. 2098, 1993 "Skeletal Development of CII Malocclusion
In Early Childhood".
Maki, Y. Shibaski, T. Fuklihara J.D.R. 1991 "Relationship Between Bone
Density And Stress In The Growing Mandible".
Tanaka, H. Murakami, T. Kitahara, H. Suzuki. J.D.R. 1991 Abstr. P.797
"Relationship Between Stress And Trabecular Pattern In Mandible While
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Kapila, A. Miller, D. Curtis, D. Hatcher J.D.R. 1990 Abs. 1844 "Effect Of Lateral Deviation Of Mandibular Growth On Cranio Mandibular Function".
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And Mid Facial Growth In Rats."
E. Harkness, J.D. Res. Abstr. 1214 Special Issue 1993 - "Association Between
Head Posture And Dental Occlusion".
Y. Michaeli, M. Terespolsky. J.D.R. 1990 Abstr. 1397 - "The Effect Of
Combined Occlusal And Mechanical Forces On PDL Of Rat Incisor".
D. Kimmel, J. Dent Res. 1990 Abstr. 1816 - "Soft Diet Effects On Mandibular
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Correspondence - Uni. Manitoba Winnipeg.