Known Causes of Malocclusion - Orthodontics

1. Nasir Al-Hamlan BDS, MPH, MSc, FDS RCSEd, FDS RCSEd, MOrth RCSEd, FICD
Consultant and Assistant Professor, Orthodontics
King Saud bin Abdulaziz University for Health Sciences
Riyadh, Saudi Arabia
@nhalhamlan
@saudibraces
nasiralhamlan
@nasiralhamlan
The Nature of Orthodontic Problems:
Known Causes of Malocclusion

2. Learning Outcomes:
•To understand the causes of Malocclusions,
•To understand the causes and development of Malocclusions,
•To understand the Specific Causes of Malocclusions,
•To understand how Genetics cause Malocclusions,
•To understand how Environment cause Malocclusions,
•To know the Etiology of Malocclusion in Contemporary Perspective

3. • A malocclusion should be regarded as a developmental condition and does not
represent a single entity.
• Rather, it is the sum of a number of complex occlusal traits, which demonstrate
multifactorial inheritance.
• Although in certain cases specific factors and pathologies can be identified as
the cause of a malocclusion; in the majority, the etiology is less clear.
• In each individual there is a close interaction between genetics and the
environment during development and growth of both the jaws and dentition; it
is at this interface that the etiology of malocclusion lies.
Etiology of Malocclusions

4. Etiology of Orthodontic Problems/Causes of Malocclusion

5. Etiology of Orthodontic Problems/Causes of Malocclusion
• Specific Causes of Malocclusion
o Disturbances in Embryologic Development
o Growth Disturbances in the Fetal and Perinatal Period
o Progressive Deformities in Childhood
o Disturbances Arising In Adolescence of Early Adult Life
o Disturbances in Dental Development
• Genetic Influences
• Environmental Influences
o Equilibrium Consideration
o Masticatory Function
o Sucking and other Habits
o Tongue Thrust
o Respiratory Pattern
• Etiology in Contemporary Perspective
Known Causes of Malocclusion

6. Class I Class II Class III
Skeletal (Jaw) Classification

7. Specific Causes of Malocclusion

8. • Disturbances in Embryologic Development
- Defects in embryologic development usually result in death of the
embryo.
- Most defects in embryos are from genetic origin and/environment.
- Stages of Embryonic Craniofacial Development!
Specific Causes of Malocclusion

9. • Disturbances in Embryologic Development
Examples:
Craniofacial Microsomia
Teratogen: chemical capable of producing embryological defects if given at a critical
time (Pregnancy) e.g. Aspirin-cleft lip and palate,
Specific Causes of Malocclusion

10. • Disturbances in Embryologic Development
Examples:
Treacher Collins syndrome (also called mandibulofacial dysostosis)
Specific Causes of Malocclusion

11. • Disturbances in Embryologic Development
Examples:
Fetal Alcohol Syndrome
Specific Causes of Malocclusion

12. • Disturbances in Embryologic Development
Examples:
Crouzon's Syndrome
Specific Causes of Malocclusion

13. Molding and Birth Injuries: Pressure against the developing face prenatally can lead to distortion
of rapidly growing areas.
Skeletal growth disturbances from:
- Intrauterine Molding:
•Pressure from arm leading to Midface deficiency
•Pierre Robin Sequence: chest pressure to mandible causing facial disproportionate growth
- Birth Trauma
•Forceps delivery may cause TMJ damage leading to underdeveloped jaw ! rare
• Growth Disturbances in the Fetal and Perinatal Period
Pierre Robin Sequence
Specific Causes of Malocclusion

14. Childhood fractures of the jaw: most common reason for childhood facial asymmetry
- Common at condylar neck, 75% recovers spontaneously
Specific Causes of Malocclusion
• Progressive Deformities in Childhood

15. Muscle dysfunction
The facial muscles can affect jaw growth in two ways:
-First, the formation of bone at the point of muscle attachments depends on the
activity of the muscle;
-Second, the musculature is an important part of the total soft tissue matrix
whose growth normally carries the jaws downward and forward.
Specific Causes of Malocclusion
• Progressive Deformities in Childhood

16. Muscle dysfunction
Examples:
Torticollis: excessive muscle contraction (Sternocleidomastoid) analogous to scarring
Specific Causes of Malocclusion
• Progressive Deformities in Childhood

17. • Progressive Deformities in Childhood
Muscle dysfunction
Examples:
Specific Causes of Malocclusion
Missing Masseter Muscles Muscle Weakness Syndrome

18. - Condylar Hyperplasia
- Hemimandibular Hypertrophy
• Disturbances Arising In Adolescence of Early Adult Life
Specific Causes of Malocclusion

19. • Disturbances Arising In Adolescence of Early Adult Life
Real Shrek was a professional wrestler with
acromegaly, a disease that make one's bones grow
uncontrollably and makes one look like Shrek.
- Acromegaly: anterior pituitary
tumor in adult with condylar
cartilage growth
Specific Causes of Malocclusion

20. Anodontia: complete missing of teeth
Oligodontia: missing majority of teeth
Hypodontia: missing several teeth
Ectodermal dysplasia
Sparse hair, absence of sweat glands, Missing teeth
- Permanent teeth arises from primary tooth buds
- If primary teeth are missing, its permanent counterpart is missing NOT vice versa
- Absent teeth are the most distal tooth of any type. e.g. 3rd molar, 2nd premolars,
lateral incisors
• Disturbances in Dental Development
- Congenitally Missing Teeth
Specific Causes of Malocclusion

21. - Lateral incisor & second premolar variations,
- Mesiodent is the most common supernumerary teeth,
- Tooth Size and Shape
Fusion VS Gemination
• Disturbances in Dental Development
- Malformed and Supernumerary Teeth
Specific Causes of Malocclusion

22. 1. Trauma to primary tooth can damage permanent tooth bud,
2. Premature loss of primary tooth causes permanent teeth to drift
3. Direct injury to permanent teeth
1. Disturbances in Dental Development
- Traumatic Displacement of Teeth
Specific Causes of Malocclusion
Dilaceration

23. Genetic Influences

24. Hapsburg Jaw in German Royal Family
• Inherited disproportion of teeth VS jaw size
• Inherited disproportion between size and shape of the upper VS
lower jaw
◇ Are jaw and tooth size inherited independently or are they linked?
Can outbreeding lead to an increase in malocclusion?
Hawaii: Polynesian, Japanese, Chinese, European melting pot. If tooth and jaw were
inherited independently then we would see high prevalence of malocclusion….. Not seen.
Genetic Influences
Lauweryns et.al concluded 40% of dental and facial variation that
leads to malocclusion can be attributed to genetic factors

25. Achondroplasia:
- Short limbs
- Midface deficiency because the cranial base synchondroses do not grow to
displace the maxilla
Genetic Influences

26. Environmental Influences

27. • Equilibrium Consideration
- Equilibrium theory and development of the dental
occlusion
Can abnormal function cause malocclusion?
o Constant pressure from lips, cheeks and tongue creates
equilibrium
o Loss of cheek causing teeth to flare out
o Increased tongue pressure
- Magnitude of force: Heavy intermittent pressure like
chewing has no effect on tooth movement.
- Duration of force: causes a shift in equilibrium
threshold of 6 hrs in human is needed.
Environmental Influences

28. Environmental Influences
• Masticatory Function
Pressure from chewing activity affects dental facial development:
1. Greater use of jaw ! increase dimension of jaw and dental arches?
2. Less use of jaw ! underdevelopment with crowding??

29. • Masticatory Function
- Function and Dental Arch Size
- Heavy intermittent force of mastication should have no effect on
tooth position.
- But what about dental arch size? Does masticatory activity
widen base dental arches? Eskimo with widen dental arches
reflecting diet.
- Malocclusion is a disease of civilization: changes to modern
diet, with changes in dental occlusion!
Environmental Influences
Genetic drift towards smaller jaw + dietary changes! better explanation for modern
malocclusion

30. • Masticatory Function
- Biting Force and Eruption
- Long face adult have less bite force than normal face.
- Long face and normal face children have similar bite force.
- However, Conclusion: it’s not muscle activity that leads to long face. There is no cause and effect.
Environmental Influences

31. • Sucking and Other Habits
Rule: sucking habits during the primary
dentition years has little long term effect
If continued into permanent dentition:
(Needs 6 hrs or more to produce dental movement)
1. flared and space upper incisors,
2. lingually tipped lower incisors,
3. open bite
4. narrow upper arch
Environmental Influences

32. • Sucking and Other Habits
Environmental Influences
- Musical instruments causing malocclusion: clarinet, violin, viola
- Sleeping habits in which of the head rested on the chin---Class II Malocclusion
- Sleeping on one side of the face or child leans the side of the face against one hand

33. • Tongue Thrusting
- Swallowing is not a learned behavior, it is at subconscious level
- Tongue thrust in adult (especially those with anterior open bite) mimics infantile swallow
Environmental Influences
◆ It’s a transitional stage for young children from infantile to adult swallow,
◆ In any individual of any age with anterior openbite to create anterior seal

34. • Respiratory Pattern
* Primary determinant of tongue position, and jaw posture.
-Mouth breather : lower mandible and tongue, tip head backward
-Increase facial height , posterior teeth super-erupt, anterior open
bite, increase mandibular angle, narrow maxillary arch
Environmental Influences
Over-eruption of posterior teeth leading to open bite 1mm posterior opening = 2 mm anteriorly
Adenoid

35. • Respiratory Pattern
Environmental Influences
- Allergies and obstruction can increase nasal resistance,
- Size of nostril is the limiting factor in nasal airflow,
- Pharyngeal / adenoid tonsil can cause partial obstruction,
- Nasal obstruction immediately changes head tip by 5 o and the jaws moved apart,
- Mandibular Prognathism seen in monkey with complete nasal blockage

36. • Respiratory pattern
Environmental Influences
Mouth breather with Adenoid Face
- Constricted upper arch, protruding
teeth, lip separated at rest, most are not
obligatory mouth breathers, may breath
through nose
- Total nasal obstruction is highly likely to alter the pattern of
growth and lead to malocclusion and long-face pattern,
- Majority of individuals with the long-face pattern have no
evidence of nasal obstruction,
MOUTH
BREATHING
PATHWAY
(UNTREATED)
NORMAL
PATHWAY OF
FACIAL
DEVELOPMENT

37. - Complete nasal blockage causing mandible to rotate back and down!
• Respiratory Pattern
Environmental Influences

38. Swedish Study
Kids requiring adenoidectomy have:
-Increased facial height
-Maxillary constriction
-Steep mandibular plane
-Upright incisors
1.After adenoidectomy, mandibular plane angle returns
toward norm, but never reach it
• Respiratory Pattern
Environmental Influences

39. Etiology in Contemporary Perspective

40. Etiology in Contemporary Perspective
• No simple explanations for malocclusion in terms of oral function.
• Research has not yet clarified the precise role of heredity as an etiologic
agent for malocclusion.
• The etiology of most orthodontic problems is difficult because several
interacting factors probably played a role.