Local factors in etiology of malocclusion orthodontics

1. LOCAL FACTORS IN ETIOLOGY OF
MALOCCLUSION
Ayana K T
Final year part 1
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Number of slides :25
Time required: 15 mins

2. INTRODUCTION
Eyes cannot see what the mind doesn’t know.
• Malocclusion is a developmental condition.
• In most instances, malocclusion and dentofacial deformity are
caused, not by some pathologic process, but by moderate
distortions of normal development.
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3. GRABER'S CLASSIFICATION
1. Abnormalities of number
• Supernumerary teeth
• Missing teeth
1. Anomalies of tooth shape
2. Abnormal labial frenum : mucosal barriers
3. Premature loss
4. Prolonged retention
5. Delayed eruption of permanent teeth
6. Abnormal eruptive path
7. Ankylosis
8. Dental caries
9. Improper dental restorations
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4. 1.CONGENITALLY MISSING TEETH
• Results from disturbances during the initial stages of formation of a tooth (Initiation and
proliferation)
• ANODONTIA – total absence of teeth
• OLIGODONTIA – congenital absence of many but not all teeth
• HYPODONTIA – absence of only a few teeth
• Usually associated with systemic abnormalities eg: Ectodermal dysplasia (sparse hair, sweat glands
and missing teeth)
• As a general rule, if only one or a few teeth are missing, the absent tooth will be the most distal
tooth of any given type. (Butler’s field theory)
• Rarely is a canine the only missing tooth.
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OLIGODONTIA
ANODONTIA HYPODONTIA

6. 2.MALFORMED AND SUPERNUMERARY
TEETH
• Abnormalities in size results from the disturbances during the
morphodifferentiation stage of development, perhaps with some carry over
from the histodifferentiation stage.
• The most common abnormality is a variation of size, particularly of
maxillary lateral incisors and second premolars.
• About 5% of the total population have a significant tooth size discrepancy.
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7. • Supernumerary teeth results from disturbances during the initiation and
proliferation stages of dental development.
• Most common – mesiodens
• Supernumerary laterals, premolars, fourth molars etc are also seen.
• Has great potential to disrupt normal occlusal development – early removal is
usually required.
• Multiple supernumerary teeth – cleidocranial dysplasia ( missing clavicles, many
supernumerary and unerupted teeth, failure of succedaneous teeth to erupt)
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MESIODENS SUPERNUMERARY TEETH

9. 3.TRAUMATIC DISPLACEMENT OF TEETH
• Trauma during formation of crown of permanent teeth ----enamel
formation is disturbed ---defect in crown of permanent teeth
• Trauma after completion of crown formation of permanent teeth-----crown
may be displaced relative to the root, root formation may stop---permanently
short root.
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10. 4.ANOMALIES OF TOOTH SIZE
• Determined by heredity
• Relatively frequent in the mandibular premolar area
• MACRODONTIA – size of teeth larger than normal (True generalized
macrodontia – pituitary gigantism)
• MICRODONTIA – size of teeth smaller than normal ( Most common – peg
laterals)
• Increase in size ------crowding
• Smaller size --------- spacing
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MICRODONTIA
(PEG LATERAL)
MACRODONTIA

12. 5.ANOMALIES OF TOOTH SHAPE
• Peg lateral – anomaly of both size and shape
• Gemination
• Dens in dente
• Fusion
• Concrescence
• Dilaceration
• Talon cusp
• Congenital syphilis and mulberry molars
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TALON CUSP
CONCRESCENCE
DILACERATION
MULBERRY MOLARS

14. 6.ABNORMAL LABIAL FRENUM
• Frenum is attached to the alveolar ridge at birth with fibres running into
lingual interdental papilla.
• As teeth erupt, alveolar bone is deposited and frenum migrates superiorly
• Some fibres may persist between maxillary central incisors, leading to midline
diastema
• BLANCH TEST
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15. 7.PREMATURE LOSS OF DECIDUOUS TEETH
• Premature loss of deciduous teeth allows the adjacent teeth to migrate into
the space, thereby preventing the eruption of permanent successor.
• The overall arch length tends to decrease as the posterior teeth have a
tendency to migrate mesially (Late mandibular crowding)
• Premature loss of mandibular posterior teeth may lead to forward functional
shift of the mandible ------ pseudo class III
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16. 8.PROLONGED RETENTION AND
ABNORMAL RESORPTION OF DECIDUOUS
TEETH
• Undue retention of deciduous teeth beyond the usual eruption age of their
permanent successor.
• Prolonged retention of primary leads to impaction of permanent tooth or
deflection in its path of eruption.
• Leads to crossbite
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17. 9.DELAYED ERUPTION OF PERMANENT
TEETH
• Causes of delayed eruption:
• Systemic 1) endocrinological and metabolic disease
• 2) congenital diseases
• Local factors 1) congenital absence of permanent tooth
• 2) ectopic crypt position of permanent teeth
• 3) cystic changes in the follicle of permanent teeth
• 4) presence of supernumerary tooth or odontomes
• 5) presence of a thick mucosal barrier due to premature extraction of primary teeth
• 6) premature loss of deciduous teeth leading to thick bony barrier
• 7) deciduous teeth which fail to resorb
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18. 10.ABNORMAL ERUPTIVE PATH
• Can be due to presence of supernumerary tooth, retained deciduous tooth or
root fragments, etc
• ECTOPIC ERUPTION
• Maxillary canine – most common tooth to erupt ectopic.
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19. 11.ANKYLOSIS
• Union of root or part of it directly to the bone.
• Frequently encountered during 6-12 yrs of age period.
• Frequently ankylosed tooth – deciduous lower second molar.
• Accidents or trauma, certain endocrine conditions, congenital diseases like
cleidocranial dysplasia predispose to ankylosis.
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20. 12.DENTAL CARIES
• May lead to premature loss of deciduous or permanent tooth, subsequent
drifting of contiguous teeth, abnormal axial inclination, over eruption and
bone loss.
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21. 13.IMPROPER DENTAL RESTORATIONS
• Can cause break in contacts and subsequent rotations.
• Too tight contact------elongation of either the tooth being restored or
approximating teeth -----functional prematurities.
• Too loose contact -----teeth moving apart, food packing and bone loss.
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22. CONCLUSION
MALOCCLUSION ETIOLOGY
Most common cause Premature exfoliation of primary teeth.
Lower incisor crowding ( imbrication) Arch length tooth size discrepancy ( due to
premature exfoliation of primary teeth)
Class II malocclusion Growth discrepancy
Class III malocclusion Hereditary
Late mandibular crowding Pressure from erupting third molar
Non skeletal anterior crossbite Over retained primary incisors
V – shaped maxillary arch Thumb sucking , tongue thrusting , mouth
breathing
Abnormal muscle activity Tongue thrusting
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24. REFERENCES
1. Contemporary orthodontics, William. R. Proffit , Henry. W. Fields, David.
M. Sarver, 5th edition.
2. Contemporary orthodontics, William. R. Proffit , 3rd edition.
3. Orthodontics: principles and practice, Graber TM, 3rd edition.
4. Textbook of orthodontics, S. Gowri Shankar , 1st revised edition.
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25. THANK YOU
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