ETIOLOGY OF MALOCCLUSION• The various classifications proposed are:• White and Gardiners classification• Salzmanns classification• Moyers classification• Grabers classification.
White and Gardiners classification• This was one of the first attempts to classify malocclusion.• It tried to make a distinction between the skeletal and dental etiologic factors.• It also tried to distinguish between pre-eruptive and post- eruptive causes.
DENTAL BASE ABNORMALITIES• 1. Antero-posterior mal relationship• 2. Vertical mal relationship• 3. Lateral mal relationship• 4. Disproportion of size between teeth and basal bone• 5. Congenital abnormalities.
PRE·ERUPTION ABNORMALITIES• 1. Abnormalities in position of developing tooth germ• 2. Missing teeth• 3. Supernumerary teeth and teeth abnormal in form• 4. Prolonged retention of deciduous teeth• 5. Large labial frenum• 6. Traumatic injury.
POST·ERUPTION ABNORMALITIES• 1. Musculara. Active muscle forceb. Rest position of musculaturec. Sucking habitsd. Abnormalities in path of closure• 2. Premature loss of deciduous teeth• 3. Extraction of permanent teeth.
SALZMANNS CLASSIFICATIONSalzmann defined three definite stages in which malocclusions are likely to manifest:• 1. The genotypic• 2. The fetal environment• 3. The postnatal environment.• Since different factors effect these different stages hence, the division of the etiologic factors into prenatal, postnatal, functional and environmental or acquired.
PRENATAL• 1. Genetic - included malocclusions transmitted by genes, where the dentofacial anomalies may or may not be in evidence at birth.• 2. Differentiative - malocclusions that are inborn, engrafted in the body in the prefunctional embryonic developmental stage. Can be subdivided into:a. General-effect the body as a wholeb. Local-effect the face, jaws and teeth only.• 3. Congenital - can be hereditary or acquired but existing at birth. Can be subdivided as:a. General or constitutionalb. Local or dentofacial.
POSTNATAL• Developmental• A. Generala. Birth injuriesb. Abnormalities of relative rate of growth in different body organsc. Hypo- or hypertonicity of muscles which may eventually affect the dentofacial development and functiond. Endocrine disturbances which may modify the growth pattern and eventually affect dentofacial growthe. Nutritional disturbancesf. Childhood diseases that affect the growth patterng. Radiation.
• B. Locala. Abnormalities of the dentofacial complex:• 1. Birth injuries of the head, face and jaws• 2. Micro- or macrognathia• 3. Micro- or macroglossia• 4. Abnormal frenal attachments• 5. Facial hemiatrophy.b. Abnormalities of tooth development:• 1. Delayed or premature eruption of the deciduous or permanent teeth• 2. Delayed or premature shedding of deciduous teeth• 3. Ectopic eruption• 4. Impacted teeth• 5. Aplasia of teeth.
B. Local• 1. Malfunction of forces exerted by the inclined planes of the cusps of the teeth• 2. Loss of forces caused by failure of proximaI contact between teeth• 3. Temporomandibular articulation disturbances.• 4. Masticatory and facial muscular hypo- or hyperactivity• 5. Faulty masticatory functions, especially during the tooth eruption period• 6. Trauma from occlusion• 7. Compromised periodontal condition.
ENVIRONMENTAL OR ACQUIREDA. General• 1. Disease can affect the dentofacial tissues directly or by affecting other parts of the body indirectly disturb the teeth and jaws.• 2. Nutritional disturbances especially during the tooth formation stage.• 3. Acquired endocrine disturbances that are not present at birth• 4. Metabolic disturbances• 5. Trauma, accidental injuries• 6. Radiation.• 7. Tumours.• 8. Surgical pathologies.
B. Local• 1. Disturbed forces of occlusion• 2. Early loss of deciduous teeth• 3. Prolonged retention of deciduous teeth• 4. Delayed eruption of permanent teeth• 5. Loss of permanent teeth• 6. Periodontal diseases• 7. Temporomandibular articulation disturbances• 8. Infections of the oral cavity• 9. Pressure habits• 10. Traumatic injuries including fractures of the jaw bones.
MOyERS CLASSIFICATION• Moyer identified etiologic sites, from where the variations were expected to arise. These sites included:A)the craniofacial skeleton,B) the dentition,C) the orofacial musculature, andD)other soft tissues of the masticatory system.He based his classification on the premise that various factors may contribute to cause variations at these sites, more often in groups rather than individually.
• 1. Heredity• 2. Developmental defects of unknown origin• 3. Trauma:a. Prenatal trauma and birth injuriesb. Postnatal trauma• 4. Physical agents:a. Premature extraction of primary teethb. Nature of food• 5. Habits:a. Thumb sucking and finger suckingb. Tongue thrustingc. Lip sucking and lip biting• d. Posture• e. Nail biting• f. Other habits
• 6. Diseases:a. Systemic diseasesb. Endocrine disordersc. Local diseases:• • Nasopharyngeal diseases and disturbed respiratory function• • Gingival and periodontal disease• • Tumours• • Caries:- Premature loss of deciduous teeth- Disturbances in sequence of eruption of permanent teeth- Early loss of permanent teeth• 7. Malnutrition.
GRABERS CLASSIFICATION• Graber divided the etiologic factors as general or local factors and presented a very comprehensive classification.• This helped in clubbing together of factors which make it easier to understand and associate a malocclusion with the etiologic factors.
GENERAL FACTORS• 1. Heredity• 2. Congenital• 3. Environment:a. Prenatal (trauma, maternal diet, German measles, material maternal metabolism, etc).b. Postnatal (birth injury, cerebral palsy, TMJ injury)• 4. Predisposing metabolic climate and disease:a. Endocrine imbalanceb. Metabolic disturbancesc. Infectious diseases (poliomyelitis, etc).
• 5. Dietary problems (nutritional deficiency)• 6. Abnormal pressure habits and functional aberrations:a. Abnormal suckingb. Thumb and finger suckingc. Tongue thrust and tongue suckingd. Lip and nail bitinge. Abnormal swallowing habits (improper deglutition)f. Speech defectsg. Respiratory abnormalities (mouth breathing, etc.)h. Tonsils and adenoidsi. Psychogenetics and bruxism• 7. Posture
• LOCAL FACTORS• 1. Anomalies of number:a. Supernumerary teethb. Missing teeth (congenital absence or loss due to accidents, caries, etc.).• 2. Anomalies of tooth size• 3. Anomalies of tooth shape• 4. Abnormal labial frenum: mucosal barriers• 5. Premature loss• 6. Prolonged retention