2. ETIOLOGY OF MALOCCLUSION
A NUMBER OF CLASSIFICATIONS OF ETIOLOGIC FACTORS OF
MALOCCLUSION HAVE BEEN PUT FORWARD –
• MOYER’S CLASSIFICATION
• WHITE AND GARDINER’S CLASSIFICATION
• GRABER’S CLASSIFICATION
3. MOYER’S CLASSIFICATION
1. HEREDITY
- NEUROMUSCULAR SYSTEM
- BONE
- TEETH
- SOFT PARTS
2. DEVELOPMENTAL DEFECTS OF UNKNOWN ORIGIN
3. TRAUMA
- PRENATAL TRAUMA AND BIRTH INJURIES
- POSTNATAL TRAUMA
4. PHYSICAL AGENTS
- PREMATURE EXTRACTION OF PRIMARY TEETH
- NATURE OF FOOD
4. 5. HABITS
- THUMB SUCKING AND FINGER SUCKING
- TONGUE THRUSTING
- LIP SUCKING AND LIP BITING
- POSTURE
- NAIL BITING
- OTHER HABITS
6. DISEASES
- SYSTEMIC DISEASES
- ENDOCRINE DISEASES
- LOCAL DISEASES
I. NASOPHARYNGEAL DISEASES AND DISTURBED
RESPIRATORY FUNCTION
II. GINGIVAL AND PERIODONTAL DISEASE
III. TUMOURS
IV. CARIES
7. MALNUTRITION
6. 6. ABNORMAL PRESSURE HABITS AND FUNCTIONAL ABERRATIONS
- ABNORMAL SUCKING
- THUMB AND FINGER SUCKING
- TONGUE THRUST AND TONGUE SUCKING
- LIP AND NAIL BITING
- ABNORMAL SWALLOWING HABITS
- SPEECH DEFECTS
- RESPIRATORY ABNORMALITIES
- TONSILS AND ADENOIDS
- PSYCHOGENICTICS AND BRUXISM
7. POSTURE
8. TRAUMA AND ACCIDENTS
7. LOCAL FACTORS –
1. ANOMALIES OF TOOTH NUMBER [SUPERNUMERARY TEETH, MISSING
TEETH, LOSS DUE TO ACCIDENTS, CARIES ETC.]
2. ANOMALIES OF TOOTH SIZE
3. ANOMALIES OF TOOTH SHAPE
4. ABNORMAL LABIAL FRENUM
5. PREMATURE LOSS OF DECIDUOUS TEETH
6. PROLONGED RETENTION OF DECIDUOUS TEETH
7. DELAYED ERUPTION OF PERMANENT TEETH
8. ABNORMAL ERUPTIVE PATH
9. ANKYLOSIS
10. DENTAL CARIES
11. IMPROPER DENTAL RESTORATIONS
8. ETIOLOGY OF MALOCCLUSION – LOCAL FACTORS
ANOMALIES IN NUMBER OF TEETH
- SUPERNUMERARY TEETH [MESIODENS/PREMOLAR/LATERAL
INCISOR/THIRD MOLAR]. THESE TEETH CAUSE NON ERUPTION
OF ADJACENT TEETH AND CAN DEFLECT THE ERUPTING
ADJACENT TEETH INTO ABNORMAL LOCATIONS.
- MISSING TEETH [THIRD MOLARS/MAX. LATERAL
INCISORS/MAND. SECOND PREMOLARS/MAND. INCISORS/MAX.
SECOND PREMOLARS]. IT MAY BE UNILATERAL OR BILATERA,L
AND CAN OCCUR AS ANOMALIES SUCH AS PRESENCE OF EXTRA
TEETH.
9. ANOMALIES OF TOOTH SIZE
- DIFFERENCE BETWEEN TOOTH SIZE AND ARCH LENGTH, MAY
RESULT IN SPACING OF TEETH. A COMMON ANOMALY IS THE PEG
SHAPED LATERAL INCISORS. TOOTH SIZE ANOMALY CAN ALSO
OCCUR IN THE MANDIBULAR PREMOLARS. FUSION BETWEEN
TWO ADJACENT TEETH MAY ALSO OCCUR.
ANOMALIES OF TOOTH SHAPE
- PEG LATERALS
- LARGE CINGULUM ON A MAX. CENTRAL INCISOR,
PREVENTING ESTABLISHMENT OF NORMAL OVERJET AND
OVERBITE.
- THE MAND. SECOND PREMOLARS MAY HAVE AN ADDITIONAL
LINGUAL CUSP, THEREBY INCREASING THE MESIO-DISTAL
DIMENSION OF THE TOOTH.
- TOOTH SHAPE ANOMALIES CAN ALSO OCCUR AS A RESULT OF
DEVELOPMENTAL DEFECTS LIKE AMELOGENESIS IMPERFECTA.
- DILACERATION - CONDITION IN WHICH THERE IS ABNORMAL
ANGULATION OF THE ROOT. IT OCCURS DUE TO A BLOW TO A
DECIDUOUS TOOTH, WHICH IS TRANSMITTED TO THE
UNDERLYING PERMANENT TOOTH BUD.
10. ABNORMAL LABIAL FRENUM –
- ABNORMALITIES OF THE MAX. LABIAL FRENUM ARE USUALLY
ASSOCIATED WITH A MAXILLARY MIDLINE SPACING. AS THE
TEETH START ERUPTING, ALVEOLAR BONE IS DEPOSITED AND
THE FRENAL ATTACHMENT MIGRATES INTO A MORE APICAL
POSITION. SOMETIMES, A HEAVY FIBROUS FRENUM IS FOUND
ATTACHED TO THE INTERDENTAL PAPILLA REGION. THIS TYPE
OF FRENAL ATTACHMENT CAN PREVENT THE TWO MAXILLARY
INCISORS FROM APPROXIMATING EACH OTHER.
THIS CONDITION IS DIAGNOSED BY A POSITIVE BLANCH TEST.
WHEN THE UPPER LIP IS STRETCHED FOR A PERIOD OF TIME, A
NOTICEABLE BLANCHING OCCURS OVER THE INTER DENTAL
PAPILLA. A MIDLINE IOPA X-RAY REVEALS NOTCHING OF THE
INTER-DENTAL ALVEOLAR CREST.
- MIDLINE DIASTEMAS CAN ALSO OCCUR DUE TO MESIODENS AND
TOOTH SIZE AND NUMBER ANOMALIES.
11. PREMATURE LOSS OF DECIDUOUS TEETH -
- THIS REFERS TO LOSS OF A TOOTH BEFORE IT’S PERMANENT
SUCCESSOR IS SUFFICIENTLY ADVANCED IN DEVELOPMENT AND
ERUPTION TO OCCUPY IT’S PLACE. THIS MAY RESULT IN
MIGRATION OF ADJACENT TEETH INTO THE SPACE AND PREVENT
THE ERUPTION OF THE PERMANENT SUCCESSOR.
PROLONGED RETENTION OF DECIDUOUS TEETH -
- THIS REFERS TO A CONDITION WHERE THERE IS RETENTION OF
THE DEC. TOOTH, BEYOND THE USUAL ERUPTION AGE OF THEIR
PERMANENT SUCCESSOR.
THE REASONS MAY BE –
1 ABSENCE OF UNDERLYING PERMANENT TEETH
2 ENDOCRINAL DISTURBANCES, LIKE HYPOTHYROIDISM
3 ANKYLOSED DECIDUOUS TEETH, THAT FAILS TO RESORB
4 NON-VITAL DECIDUOUS TEETH, THAT DO NOT RESORB
12. DELAYED ERUPTION OF PERMANENT TEETH –
1. CONGENITAL ABSENCE OF THE PERMANENT TEETH
2. PRESENCE OF SUPERNUMERARY TOOTH CAN BLOCK THE ERUPTING
PERMANENT TOOTH
3. PRESENCE OF A HEAVY MUCOSAL BARRIER CAN PREVENT THE
PERMANENT TOOTH FROM EMERGING INTO THE ORAL CAVITY
4. PREMATURE LOSS OF DECIDUOUS TOOTH, CAN RESULT IN DELAYED
ERUPTION OF THE PERMANENT TEETH, DUE TO BONE FORMATION
OVER THE ERUPTING PERMANENT TOOTH
5. ENDOCRINAL DISORDERS LIKE HYPOTHYROIDISM, CAN CAUSE DELAY
IN PERMANENT TEETH ERUPTION
6. PRESENCE OF DECIDUOUS ROOT FRAGMENTS, THAT ARE NOT
RESORBED, CAN BLOCK THE ERUPTING PERMANENT TEETH.
13. ABNORMAL ERUPTIVE PATH –
- THIS CAN BE DUE TO ARCH LENGTH DEFICIENCY, PRESENCE OF
SUPERNUMERARY TEETH, RETAINED ROOT FRAGMENTS OR
FORMATION OF BONY BARRIERS. AS THE MAXILLARY CANINES
HAVE A LONG ERUPTIVE PATH, THEY ARE THE MOST PRONE
TEETH FOR ERUPTING IN AN ABNORMAL POSITION.
ANKYLOSIS –
- IS A CONDITION WHERE A PART OR WHOLE OF THE ROOT
SURFACE IS DIRECTLY FUSED TO THE BONE, WITH THE ABSENCE
OF THE INTERVENING PERIODONTAL MEMBRANE.
14. DENTAL CARIES -
- CARIES CAN LEAD TO PREMATURE LOSS OF DECIDUOUS OR
PERMANENT TEETH, THEREBY CAUSING MIGRATION OF THE
ERUPTING TEETH, ABNORMAL AXIAL INCLINATIONS AND SUPRA
ERUPTION OF OPPOSING TEETH.
IMPROPER DENTAL RESTORATIONS -
- OVERCONTOURED OCCLUSAL RESTORATIONS CAN LEAD TO
PREMATURE CONTACTS, LEADING TO FUNCTIONAL SHIFT OF
THE MANDIBLE, DURING JAW CLOSURE, WHEREAS UNDER
CONTOURED OCCLUSAL RESTORATIONS, CAN PERMIT
SUPRA ERUPTION OF THE OPPOSING TEETH.
15. ETIOLOGY OF MALOCCLUSION – GENERAL FACTORS
HEREDITY –
AS THE CHILD IS A PRODUCT OF PARENTS WHO HAVE DISSIMILAR
GENETIC MATERIAL, HE MAY INHERIT CONFLICTING TRAITS FROM BOTH
THE PARENTS, RESULTING IN ABNORMALITIES OF THE DENTOFACIAL
REGION.
ANOTHER REASON FOR GENETICALLY DETERMINED MALOCCLUSION IS
THE RACIAL, ETHNIC AND REGIONAL INTER-MIXTURE.
THERE ARE A NUMBER OF HUMAN TRAITS WHICH ARE INFLUENCED BY
GENES, LIKE -
• TOOTH SIZE
• ARCH DIMENSION
• CROWDING/SPACING
• TOOTH SHAPE ANOMALIES
• TOOTH NUMBER ABNORMALITIES
• OVERJET
• INTER-ARCH VARIATIONS
• FRENUM
16. CONGENITAL DEFECTS [BIRTH DEFECTS] –
GENERAL CONGENITAL FACTORS –
• ABNORMAL STATE OF MOTHER DURING PREGNANCY
• MALNUTRITION
• ENDOCRINOPATHIES
• INFECTIOUS DISEASES
• METABOLIC AND NUTRITIONAL DISTURBANCES
• ACCIDENTS DURING PREGNANCY AND CHILD BIRTH
• INTRA-UTERINE PRESSURE
• ACCIDENTAL TRAUMATIZATION OF THE FETUS BY EXTERNAL FORCES
LOCAL CONGENITAL DEFECTS –
• JAW DEVELOPMENT ABNORMALITIES DUE TO INTRA-UTERINE POSITION
• CLEFTS OF THE FACE AND THE PALATE
• MACRO AND MICROGLOSSIA
• CLEIDO CRANIALDYSOSTOSIS
17. ENVIRONMENT –
PRE-NATAL FACTORS –
ABNORMAL FETAL POSTURE, MATERNAL FIBROIDS, AMNIOTIC LESIONS,
MATERNAL DIET AND METABOLISM, MATERNAL INFECTIONS AND DRUGS
LIKE THALIDOMIDE DURING PREGNANCY, CAN CAUSE GROSS
DEFORMITIES.
POST-NATAL FACTORS -
• FORCEPS INJURY TO TMJ DURING DELIVERY, CAUSING ANKYLOSIS
OF TMJ. THE PATIENT ALSO SHOWS RETARDED MANDIBULAR
GROWTH.
• CEREBRAL PALSY
• CONDYLAR FRACTURES MAY ALSO CAUSE GROWTH RETARDATION
• PROLONGED USE OF MILWAUKEE BRACES CAN CAUSE MANDIBULAR
GROWTH RETARDATION
18. PREDISPOSING METABOLIC CLIMATE AND DISEASE –
THE REASONS MAY BE –
1 ENDOCRINE IMBALANCE – [HYPOTHYROIDISM,
HYPERTHYROIDISM, HYPOPARATHYROIDISM,
HYPERPARATHYROIDISM]
2 METABOLIC DISTURBANCES
DIETARY PROBLEMS / NUTRITIONAL DEFICIENCY
POSTURE
ACCIDENTS AND TRAUMA
19. White And Gardiners Classification
1. Dental Base Abnormalities
Antero-posterior malrelationship
Vertical malrelationship
Lateral malrelationship
Disproportion of size between teeth and basal
bone
Congenital abnormalities
20. 2. Pre eruption Abnormalities
Abnormalities in position of developing tooth
germ
Missing Teeth
Supernumerary teeth and teeth abnormal in
form
Prolonged retention of deciduous teeth
Large labial frenum
Traumatic injury
21. 3. Post eruption Abnormalities
Muscular –
1) Active muscle form
2) Rest position of musculature
3) Sucking Habits
4) Abnormalities in path of closure
Premature loss of deciduous teeth
Extraction of permanent teeth
