Environmental influences on malocclusion in orthodontics

1. ENVIRONMENTAL
INFLUENCES ON
MALOCCLUSION
Prepared by : Dr. Ali Waqar Hasan
FCPS Resident Orthodontics
UCMD UOL, Lahore
Supervised by : Dr. Saad Asad
Associate Professor of Orthodontics
UCMD UOL, Lahore

2. INTRODUCTION
 Environmental Influences consist of pressures and
forces related to physiologic activity
 Relationship between anatomic form and Physiologic
function
 If function could affect growth of jaws then altered
function would be a major cause of malocclusion ???
 Chewing exercises & physical therapy as part of
orthodontic treatment ???
 If function plays little or no role in pattern of
development, altering the jaw function would have little
impact ???

3. EQUILIBRIUM
CONSIDERATIONS
 Laws of physics state that, If an object
is subjected to unequal forces then it
will change its position, but it will not
do so, if the forces are balanced or in
equilibrium
 Teeth are in equilibrium!!!
 Tooth moves in response to an
Orthodontic force

4.  Periodontium ( PDL & Alveolar Bone ) can
withstand heavy forces of short duration
 Fluid in PDL acts as a shock absorber,
squeezing out of fluid ??
 Light force of long duration ( 6 hours daily
)
 Imbalance of forces between tongue, lips
and cheeks = Tooth movement will occur

5.  Injury to soft tissue of lips
results in scarring &
contracture = Incisors move
lingually as the lip tightens
 If pressure from tongue &
cheeks removed = Teeth
move outward in response
to tongue
 Light sustained pressures
from the lips, cheeks and
tongue are important
determinents of tooth

6. SUCKING & OTHER HABITS
 All children engage in Non-Nutritive Sucking of Thumb or
Pacifier
 General Rule : Sucking Habits during Primary dentition years
= Little long term effects
 If sucking habits persist beyond permanent dentition :
• Flared & Spaced maxillary centrals
• Lingually positioned Lower Incisors
• Anterior Open Bite
• Narrow upper arch
 Considerable variation in which teeth are affected & how
much

8. BLUE GRASS APPLIANCE
 It consists of a wire that is attached
to the upper molars and extends just
behind the upper front teeth.
 A roller which is made of acrylic is
inserted in this wire.
 This makes it possible for the child
to easily spin it with his tongue.
 In a way the child is being offered a
distraction from his habit and is a
kind of positive reinforcement.

9. ANTERIOR OPEN BITE
 Arises by combination of
interference with normal
eruption of incisors & excessive
eruption of posterior teeth
 Seperation of jaws = alters
equilibrium on posterior teeth
 More eruption of posterior teeth
 1mm of posterior elongation
opens the bite about 2mm
anteriorly

10. NARROW UPPER ARCH
 Although negative pressure created in
mouth during sucking, its not solely
responsible
 Arch Form is affected by alteration in
the balance between tongue & cheek
pressures
 Lowered tongue decreases pressure
on the lingual of upper teeth
 Cheek pressure increased as
buccinator muscle contracts during
sucking.
 Pressures greatest at corners of

11. TONGUE THRUST SWALLOW
 Placement of tongue tip between
incisors during swallowing
 Lab studies indicate = Those who
place tongue tip forward do not
have more tongue force against
the tooth
 Swallowing is not a learned
behavior !!!
 Normal stage in transition from
infantile to adult swallow

12.  Functional Adaptation to close off the front
of mouth and form anterior seal in
individuals with anterior open bite / upper
incisor protrusion
 MODERN VIEWPOINT :
Seen in younger children, represents
transitional stage
Individuals with displaced incisors as
functional adaptation

13.  Tongue thrust swallow simply has too short a
duration of action to produce any tooth
movement
 Pressure from TTS lasts for only 1 second
 Typical individual swallows 800 times during
day and few bouts at night daily
 1000 seconds of pressure amounts to only a
few minutes, not nearly enough to disturb
equilibrium
 TONGUE THRUST SWALLOW IS NOT THE
CAUSE BUT RATHER THE RESULT OF
DISPLACED INCISORS !!!!

14. RESPIRATORY PATTERN
 Altered respiratory pattern changes the
posture of head, jaw and tongue
 In order to breathe from mouth, one has to
lower the mandible, tongue and extend the
head backwards
 Adenoid faces
 Relationship between altered posture, mouth
breathing and development of malocclusion
is not so clear cut

15.  When nose is blocked there is 5 degrees
of change in Craniovertebral angle
 Harvolds classic experiments on monkeys
 Total nasal obstruction is extremely rare in
humans
 Difficult to measure and calculate whether
a person is mouth or nose breather!!!

16.  Only reliable way is to establish how much of
airflow goes through nose and mouth
 Requires special instruments
 Best data = Normal versus Long face children
 Minority of long faced children had 40% nasal
breathing
 Adenoidectomy / Tonsillectomy
 Studies of Swedish children = Long face group
had longer anterior face height

17.  In short mouth breathing can contribute to
the development of orthodontic problems
but it is difficult to indict it as a frequent
etiologic factor
 Other side of the coin ???