Content uploaded by Mike Mew
Author content
All content in this area was uploaded by Mike Mew on Dec 15, 2015
Content may be subject to copyright.
Craniofacial dystrophy.
A possible syndrome?
M. Mew1
common ground with other professionals
to either support or detract. This article
proposes a possible pathology underlying
malocclusion, to act as a null hypothesis
to be tested. To avoid preconceptions, a
favourable, anterior rotating,5 horizontal
growth pattern will be referred to as upswing
and the opposite as downswing.
AETIOLOGICAL FACTORS
Masticatory effort
Between the Neolithic and Medieval periods
it was common to completely wear away the
clinical crown by the age of 45.6 This was due to
a tougher, more brous, less caloric diet and
non-nutritive uses, such as leather processing
and tool making. Compared to modern
attrition this suggests a massive reduction in
muscle usage over this time period. The effect
of changes in the action of the masticatory
muscle due to strokes, nerve damage, muscular
dystrophy or animal experiments7 on the
anterior craniofacial structure (ACS) are well
established and well-marked.
Posture
Over the last century and certainly the
last few decades, the incidence of nasal
congestion has risen considerably.8 If the
nasal airway is blocked then the tongue and
mandible are lowered, the lips separated and
the head postured forwards.9 While initially
this facilitates breathing the change can
become habitual. At puberty, as individuals
INTRODUCTION
It is projected that the next generation
will live beyond 90 years and many can
also expect to be dentate for most of this.1
Few, however, will have an ideal occlusion
for a signicant period of this lifespan. The
general dental profession has achieved much
by understanding the causes and pathology
of decay and periodontal disease. However,
despite great efforts there is inadequate
evidence for the orthodontic profession to
draw clear conclusions regarding the causes
and pathology for malocclusion.
What evidence we do have is limited
by the lack of sound theories to test.
It is clear that the environment can, at
times, have a large influence on facial
development and malocclusion, but there
are few theories that explain the observed
environmental effects.2,3 We also seem
to have forgotten that our ancestors had
complete and reasonably good occlusions
from birth to death,4 as do nearly all dentate
vertebrates today.
Opinion articles should act as a platform to
make openly, speculative suggestions, to nd
This article proposes a possible syndrome, craniofacial dystrophy (CFD), as one of the underlying causes of malocclusion
and a range of other symptoms. These symptoms have seen a dramatic rise in the twentieth century, lack a clear aetiology
and are currently treated symptomatically. Over the last 10,000 years there has been a progressive downswing in the
anterior craniofacial structure (ACS), possibly due to a combination of changes in the masticatory effort and the posture of
the tongue and the mandible. If the mouth is postured open and the muscles are weaker the face lengthens, a downswing,
reducing the cross sectional area at the level of the oropharynx. This leads to less space for the tongue, the airway and
the teeth, and is exacerbated by an increasingly evident ‘suckling like’ swallowing pattern. Changes in the shape of the
ACS affect the functions for which this structure is responsible, leading to a range of symptoms, including malocclusion.
Certain compensatory responses are possible to maintain these functions, primarily the airway. These vary between
individuals, may be under genetic inuence and may also inuence the ACS and dentition, at times creating vicious cycles.
become socially aware, lip seal may improve
but it appears that the ‘tongue to palate’
posture is rarely re-established. The effects
of a change in the mode of breathing10,11 and
tongue posture in isolation12 on the AFC are
unequivocal.
Swallowing pattern
In an ideal adult swallow, the tongue should
push upwards, outwards and forward on the
palate and the perioral muscles should be
passive.13,14 This now seems rare, with most
individuals displaying some perioral activity,
with a ‘suckling like’ swallow, that pulls
backwards and inwards on the dentition and
1Lecturer and Clinical Director, London School of
Facial Orthotropics , 16‑18 Pampisford Road, Purley,
Surrey, CR8 2NE
Correspondence to: Dr Mike Mew
Email: mikemew@orthotropics.co.uk;
Tel: +44 (0)20 8660 3695
Accepted 12 February 2014
DOI: 10.103 8/sj.b dj.2014 .4 01
©British Dental Journal 2014; 216: 555-558
• Describes a possible pathological process
underlying malocclusion, which relates
malocclusion with a range of other
diseases and problems.
• Proposes a hypothesis for open discussion
by all members of the dental and medical
profession
• Questions the current assumptions
supporting orthodontic therapy and
proposes a radical shif t in thinking that
extends far beyond the teeth.
IN BRIEF
OPINION
Fig.1 Tracings comparing ancient and
modern (mid twentieth century) skulls –
both have naturally aligned teeth and are
considered good examples of their period.
Note the difference in molar position, due in
part to changes in arch widths
BRITISH DENTAL JOURNAL VOLUME 216 NO. 10 MAY 23 2014 555
© 2014 Macmillan Publishers Limited. All rights reserved
OPINION
does not support the maxilla. The teeth and
alveolus are pulled inward and backwards,
reducing the tongue space. The suggested
cause has been a lack of breast-feeding,13
however, the author also proposes the early
introduction of semi-solid foods before the
adult swallowing reex is fully developed
as a factor.
COMPENSATORY MECHANISMS
Changes in the shape of the ACS disturb
many of its functions, some of which such
as breathing and swallowing are vital. To
facilitate these, certain compensations are
possible, which vary both at a group and
individual level, inuencing both the signs
and symptoms of craniofacial dystrophy
(CFD).
1. The head can be postured forward by
exing the neck while maintaining the
inclination of the head. This opens the
airway by extending the head
2. The tongue can be moved up out of the
airway, usually with some of its bulk
placed between the teeth in a variety of
positions, affecting mandibular position
(the ‘tongue’ effect).
3. The mandible can be lowered and
postured forwards, backwards, laterally
or remain central. It is inuenced by
the position of the tongue and the need
to maintain a comfortable intercuspal
position (the ‘mandibular’ effect).
The exact nature and sequence of these
compensations is not clear, however, some
exacerbate their causes creating self-
reinforcing ‘vicious’ cycles. For example
both the change in swallowing pattern and
a lower maxilla reduce the tongue space
encouraging a ‘tongue-between-tooth’
posture which encourages a ‘suckling like’
swallowing pattern and reduces the support
of the maxilla.
SIGNS OF CRANIOFACIAL
DYSTROPHY
The entire cranium is affected by a down-
swing; the saddle angle (BSN) increases;
the interpupillary distance decreases; the
temporomandibular joint (TMJ) moves
posteriorly; and the occlusal plane usually
drops anteriorly. The ACS lengthens and
the cross-sectional area at the level of the
oropharynx reduces.
The maxilla and the surrounding bones
are the most affected, both in position
and shape, although their overall volume
remains relatively constant. The direct
forces of the tongue on the palate and
indirect forces via the teeth inuence the
growth direction of the maxilla. When
both are reduced in duration and force, the
maxilla drops down and back (Figs 1 and
2). This reduces the eye support; attens
the cheekbones; narrows the nasal airway;
lengthens the mid facial third; and lowers
the palate, which narrows.
As the maxilla descends and the teeth
over erupt (and are worn less), the mandible
hinges open. The ascending ramus appears
largely unaffected due to remodeling, to
prevent it encroaching on the functional
matrixes of the neck, also, the angle is less
pronounced from less muscular activity.
Consequently the mandible attens and
the gonial angle increases (Fig. 3). There is
usually little variation in its ultimate length,
except in some extreme Class III’s.
SYMPTOMS OF
CRANIOFACIAL DYSTROPHY
Most of the functional systems associated
with the ACS are affected, although in this
article malocclusion will be considered in
more detail, with an attempt to illustrate this
graphically (Figs 4, 5 and 6). There is a wide
variation in incidence due to the variation
in individual’s responses.
Malocclusion
Considering the difficulty in artificially
emulating and maintaining a good occlusion
it seems near miraculous that our ancestors
and other animals achieved this naturally.
This is due to the dentoalveolar compensatory
mechanisms (DCM),3 the balance of the soft
tissues surrounding the dental arches in both
function and posture. The change in the ACS
and the associated compensatory responses
disrupted this system affecting the position
of the teeth.
Ideal occlusion
This is a position prognathic and brachyfacial
of most cephalometric normal values. It is
observed in ideal occlusions,15 attractive faces16
and indigenous populations. It is also called
the Mesolithic norm17 and is not considered a
malocclusion. It is typical of individuals who
rest with their tongues on the roof of their
mouths, lips together and teeth near contact18
with good head, neck and body posture.
‘MANDIBULAR’ EFFECT
Class I
This is the most diverse pattern of
malocclusion extending from very mild
malocclusions with all but the wisdom teeth
in good occlusion, to severe malocclusions
with large downswings and gross dental
crowding. Typically the mandible rests
centrally below the maxilla and the dental
arches are in a Class I relationship as judged
from the rst molar.
Class II
The mandible hinges open and back, and
the tongue moves forwards into the space
provided. Often associated with a forward
head posture.
Class III
The mandible is held forwards, bringing the
tongue forwards, possibly increasing the
length of the mandible.
Cross bite
When the upper dental arch is moderately
narrowed a more comfortable intercuspal
position can be created by shifting laterally
to the left or right, which can account for
some cross bites.
‘TONGUE’ EFFECT
Making an assessment in the intercuspal
position is reproducible but does not always
represent the habitual position and distorts
the examiners viewpoint, especially with
deep bites. At rest the tongue is moved
up out of the airway, usually crossing the
periphery of the dental arches to rest in a
variety of positions.
Bimaxillary protrusion
and anterior open bite
The tongue is postured forwards. In a mild
downswing (mainly vertical at this geometry)
Fig.2 A treated case that illustrates the
opposite effect of CFD. Note that the
mandible does not appear to change length
but angulation, with changes occurring in the
maxillary position and shape
Fig.3 The overall mandibular length for
these twosubjects is almost the same.
However, the overall shape and arch lengths
differ, with the wisdom teeth and incisors
the most affected areas
556 BRITISH DENTAL JOURNAL VOLUME 216 NO. 10 MAY 23 2014
© 2014 Macmillan Publishers Limited. All rights reserved
OPINION
this causes the incisors and alveolus to tip
forward, and in more severe downswings an
anterior open bite is created.
Unilateral open bite
Usually seen with a moderate or severe
downswing. The tongue is postured
laterally separating the teeth. Often seen in
conjunction with other patterns.
Complete open bite
This is usually a Class I situation, being mild
when the tongue covers just the lingual
cusps of the molars and severe when both
cusps are covered, disrupting the pattern of
interdigitation.
Bilateral posterior open bite
(deep bites)
The tongue is postured between the molars
and often premolars preventing their
eruption, but not the canines or incisors,
increasing the freeway space and causing
a deep bite (if assessed in the intercuspal
position). When biting fully together the
incisors interfere, contacting prematurely,
usually distalising the mandible encouraging
a Class II/2 pattern and affecting the TMJ.
Some individuals bite onto these tongue
sections ‘tongue splinting’, which leaves
marks on the lateral borders of the tongue
increasing the depth of bite.
Class III
The tongue is placed low in the mandible
which is held forwards. Being further from
the palate, this leads to a collapse of the
maxillary arch and the whole maxilla in
severe cases.
Each variation is dependent on the
severity of the swing pattern and the
individual’s compensatory responses.
Certain responses are seen at a group level
and may follow genetic predispositions. For
example peoples of Caucasian, Negro and
Mongolian decent have a tendency towards
Class II, bi-maxillary protrusion and ClassIII
patterns respectively. Consistently sealed lips
reduce the downswing, align the anterior
teeth and establish a Class I incisor pattern.
High muscular forces tend to widen the ACS
and upright the teeth, even if these are long
lasting low forces directed through sections
of tongue resting between the teeth.
ADDITIONAL POSSIBLE SYMPTOMS:
AN OVERVIEW.
Breathing
Snoring and sleep apnoea are strongly
associated with craniofacial traits that
is consistent with a downswing and its
effects on the airway.19 The compensatory
mechanisms are effective when conscious
but difficult to maintain when asleep,
leading to the tongue compromising the
airway. The associated health implications
of this are outside the scope of this article.
Ear, nose and throat
Deviated nasal septums, sinusitis and narrow
nasal passages are a product of changes in
the shape of the small bones of the midface.
Glue ear and blockages in the Eustachian
tube are related to a lack of air movement
within the tube, caused by a change in the
swallowing pattern and the architecture of
the nasopharynx.
Bruxism
A less certain postulation is that the tongue
acts as the antagonist against the jaw closing
muscles. In this regulatory system, the
tongue would contact the palate, in a unique
situation as an agonist muscle unattached at
one end, and inhibit the action of the jaw
closing muscles and control the freeway
space. A habitual lowered tongue posture in
infancy would prevent the development of
this system leading to unregulated clenching
and grinding.
Temporomandibular disorders
The TMJ, like any joint, adapts to be centric
in the position in which it is held. If the
habitual postural position is with the jaw
open then this is where the joint adapts to,
so that the condyle is unbalanced, ie superior
and distal, in the intercuspal position. This
only usually becomes symptomatic if the
joint is also loaded in this position, such as
periods of stress or bruxism, in individuals
with reasonable muscle tone.
Body posture changes
A change in the head and neck posture
certainly influences the general body
posture; the reverse is also possible, however,
such discussions are outside the remit of this
article.
CONCLUSION
This immense change in our environment
and masticatory usage seems to have passed
almost unobserved as we are immersed in
our modern lifestyles. This potentially leads
to a distorted view of normal, and may lead
us to overlook its effects and limit our focus
to the genetic inuences. The pathologi-
cal process of CFD proposes a mechanism
to explain the genetic and environmental
interactions. Environmental changes inu-
ence the severity of the malocclusion while
the individual’s responses determine its
characteristics and type. Our genes vary and
while we all have the potential for an ideal
occlusion, our response to the environmental
stresses differs.
Fig.4 The estimated effect of antroposterior
mandibular rest position (horizontal) and
swing pattern on the occurrence of Ideal and
Class I occlusal patterns
Fig.5 The estimated effect of antroposterior
mandibular rest position (horizontal) and
swing pattern on the occurrence of Class II and
ClassIII occlusal pattern, and micrognathia
Fig.6 The estimated effect of antroposterior
lingual rest position (horizontal) and swing
pattern on the occurrence of bimaxillary
protrusion, anterior open bite and bilateral
posterior open bite-deep bite
BRITISH DENTAL JOURNAL VOLUME 216 NO. 10 MAY 23 2014 557
© 2014 Macmillan Publishers Limited. All rights reserved
OPINION
CFD provides a new way of looking at
malocclusion and challenges existing
beliefs, which is never easy. If accepted,
it also leads to the socially uncomfortable
conclusion that the facial development
of most modern humans is not attaining
its full genetic potential. Discussing this
can be an emotive issue; while people are
happy to acknowledge manifestly crooked
teeth, many nd an implied criticism of
their facial development too personal,
particularly so if that criticism relates to their
children. Fatalism is often more comfortable
than determinism.
It is important that our profession works
together to consider the possibility of a
better solution to this problem, since the
possible ramications extend far beyond
teeth. Although we cannot turn the clock
back, and changing posture, habits or
muscle tone is extremely difcult, it is vital
to understand the aetiology and pathology
of malocclusion.
Following scientic protocol the concept
of craniofacial dystrophy is proposed in
an open forum to encourage debate and
responses. Attempts to constructively
critique or falsify this hypothesis with quality
evidence and sound logic are welcomed.
Further information on this complex
subject is available at www.orthotropics.
com/craniofacialdystrophy
1. Ofce for National Statistics. Historic and projected
data from the period and cohort life tables, 2012-
based. ONS, 2013. Online article available at http://
www.ons.gov.uk/ons/rel/lifetables/historic‑and‑
projected‑data‑from‑the‑period‑and‑cohort‑life‑
tables/2012‑based/index.html (accessed March
2014).
2. Moss ML. The functional matrix hypothesis
revisited. 1.The role of mechanotransduction. Am J
Orthod Dentofacial Orthop 1997; 112: 8–11.
3. Solow B. The dentoalveolar compensatory
mechanism: background and clinical implications.
Br J Orthod 1980; 7: 145–161.
4. Corruchini RS. How anthropology informs the
orthodontic diagnosis of malocclusion’s cause. New
York: The Edwin Mellen Press, 1999.
5. Björk A, Skieller V. Facial development and tooth
eruption. An implant study at the age of puberty.
Am J Orthod 1972; 62: 339–383.
6. Brothwell DR. Digging up bones. 2nd ed. London:
British Museum, 1972.
7. Hohl TH. Masticatory muscle transposition in
primates: effects on craniofacial growth.
J Maxillofac Surg 1983; 11: 149–156.
8. Stewart M, Ferguson B, Fromer L. Epidemiology and
burden of nasal congestion. Int J Gen Med 2010; 3:
37–45.
9. Vig PS, Showfety KJ, Phillips C, Experimental
manipulation of head posture. Am J Orthod 1980;
77: 258–268.
10. Harvold EP, Vargervik K, Chierici G. Primate
experiments on oral respiration. Am J Orthod 1981;
79: 359–372.
11. Linder‑Aronson S. Adenoids: their effect on mode of
breathing and nasal airow and their relationship
to characteristics of the facial skeleton and the
dentition. Acta Otolaryngol Suppl 1970; 265: 1–132.
12. Harvold, EP, Vargervik K, Chierici G. Primate
experiments on oral sensation and dental
malocclusions Am J Orthod 1973; 63: 494–508.
13. Barrett RM, Hanson ML. Oral myofunctional
disorders. Saint Louis, Missouri: The Mosby
Company, 1974.
14. Jones B. Normal and abnormal swallowing: imaging
in diagnosis and therapy. 2nd ed. New York: Spinger‑
Verlag, 2003.
15. Platou C, Zachrisson BU. Incisor position in
Scandinavian children with ideal occlusion. A
comparison with the Ricketts and Steiner standards.
Am J Orthod 1983; 83: 341–352.
16. Peck H, Peck S. A concept of facial esthetics. Angle
Orthod 1970; 40: 284–318.
17. Mew J R C. In Search of Our Direct Ancestor: An
anthropological and orthodontic summary. Dental
Historian 2013; 59: 33‑38
18. Mew J. The aetiology of malocclusion. Can the tropic
premise assist our understanding? Br Dent J 1981;
151: 296–302.
19. Cistulli PA. Craniofacial abnormalities in obstructive
sleep apnoea: implications for treatment.
Respirology 1996; 1: 167–174.
558 BRITISH DENTAL JOURNAL VOLUME 216 NO. 10 MAY 23 2014
© 2014 Macmillan Publishers Limited. All rights reserved
