1. Etiology of Malocclusion
Graber divided the etiologic factors as general and 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.

2. Etiology of Malocclusion
LOCAL FACTORS 1. Anomalies of number: a. Supernumerary teeth b. 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 7. Delayed eruption of permanent teeth 8. Abnormal eruptive path 9. Ankylosis 10. Dental caries 11. Improper dental restorations.
GENERAL FACTORS 1. Heredity 2. Congenital 3. Environment: a. Prenatal (trauma, maternal diet, German measles, material maternal metabolism b. Postnatal (birth injury, cerebral palsy, TMJ injury) 4. Predisposing metabolic climate and disease: a. Endocrine imbalance b. Metabolic disturbances c. Infectious diseases (poliomyelitis, etc). 5. Dietary problems (nutritional deficiency) 6. Abnormal pressure habits and functionaI aberrations: a -Abnormal sucking b. Thumb and finger sucking c. Tongue thrust and tongue sucking d. Lip and nail biting e. Abnormal swallowing habits (improper deglutition) f. Speech defects g. Respiratory abnormalities (mouth breathing, etc.) h. Tonsils and adenoids i. Psychogenetics and bruxism 7. Posture 8. Trauma and accidents.

3. GENERAL FACTORS

4. Hereditary
Hereditary causes of malocclusion include all factors that result in a malocclusion and are inherited from the parents by the offspring. These may or may not be evident at birth, but are likely to express themselves as the child grows. These can be those influencing the
• Neuromuscular system
• Dentition
• Skeletal structures
•Soft tissues (other than the neuromusculature).

5. Neuromuscular system Neuromuscular system
The anomalies that have been found to possess some inherited component include deformities in size, position, tonicity, contractility, and in the neuromuscular coordination pattern of facial, oral, and tongue musculature. Certain malocclusions may be associated with tongue size or lip length and tonicity and these may be found to reoccur within a family over generations and may be inherited.

6. Dentition
Certain characteristics, especially related to the dentition are definitely inherited. These include:
Size and Shape of the Teeth
Studies on twins have proved that the size and relative shape of the teeth is inherited . Peg shaped lateral are the most commonly seen .

7. Number of Teeth
The number of teeth is a partially inherited characteristic.
It can vary considerably especially in cases with cleft palate and cleidocranial dysostosis. The latter condition is known for the significant hyperdontia generally associated with it.
Hypodontia is more widely seen as compared to hyperdontia. Hypodontia is more commonly seen in the permanent dentition as compared to the deciduous dentition. The most frequently missing teeth are the maxillary lateral incisors

8. Primary Position of Tooth Germ and the Path of Eruption
The position of tooth germs and the path of eruption are considered by some researchers to be inherited.

9. Mineralization of Teeth
Inherited defects of the tooth structure differ from exogenic-induced defects in mineralization as they are present in both the deciduous dentition as well as permanent dentition and are localized in the enamel or the dentine. These may result in malformed teeth and contribute towards producing a malocclusion.

10. Skeletal structures
The underlying basal bone and other associated cranial bone structures are partially inherited. The Class III skeletal pattern is most commonly associated with familial tendencies.

11. Soft tissues (other than the neuromusculature)
These generally include the size and shape of the frenurns especially the maxillary labial frenum. Broad flabby frenums are sometimes repeatedly seen in families. Also included in this microstomia and ankyloglossia.

12. Congenital factors
Congenital defects include those malformations that are seen at the time of birth. These are generally maldevelopments of the 1st and the 2nd branchial arches. The most frequently associated malformations are:

13. Micrognathism: Micrognathia means "small jaw
Micrognathism: Micrognathia means "small jaw." It can affect either of the jaws. The congenital variety is often seen associated with congenital heart disease and the Pierre Robin syndrome. Micrognathism of the maxilla is frequently due to a deficiency in the premaxillary region. Mandibular micrognathia is characterized by severe retrusion of the chin.

14. Oligodontia Also known as Izypodontia, is a rather common condition
Oligodontia Also known as Izypodontia, is a rather common condition. Different teeth seem to be affected in raring degree with the third molars being involved most frequent.

15. Anodontia Anodontia means absence of teeth
Anodontia Anodontia means absence of teeth. True anodontia is extremely rare and may be associated with hereditary ectodermal dysplasia. Cleft lip and palate This is relatively more frequently seen anomaly. It can be identified as early as the 18 to 20th week of pregnancy. It is generally associated with under developed maxilla and related dental disorder.

16. Predisposing metabolic climate and disease
Under this three separate conditions need to be stressed upon: a. Endocrine imbalance b. Metabolic disturbances c. Infectious diseases.

17. a. Endocrine imbalance
Hyperpituitarism (Gigantism,acromegaly) • Accelerated development seen especially of the mandible •Accelerated dental development and eruption • Enlarged tongue and other facial structures including the sinuses • Thickening of the cortical bones • Poor maturation • Osteoporosis • Hypercementosis
Hypopituitarism(Dwarfism)
• Retarded growth
• Decreased linear facial
measurements
• Decreased craniaI base measurements
• May result in an open bite
• Delayed tooth eruption
• Incomplete root formation
with incomplete closure of
the apical foramen

18. b. Metabolic disturbances
Acute febrile diseases are capable of affecting not only the general health of the child but might also affect the dentition and its surrounding hard and soft tissues. they are capable of slowing down growth and may cause delayed tooth eruption.

19. c. Infectious diseases.
The affects of infectious diseases are dependent not only on the severity and duration of the disease but also at what age it affects the child or the mother. The frequently seen diseases are : Osteomyelitis, mumps, tuberculosis, congenital syphilis,…

20. Dietary problems (nutritional deficiency)
Nutritional imbalances in the pregnant mother have been associated with certain malformations in the child as: Hypervitaminosis A • Cleft lip and palate Riboflavin deficiency • Cleft lip and palate (vitamin B12) Folic acid deficiency • Cleft lip and palate • Mental retardation Insulin deficiency • Cleft lip and palate • Retardation Iodine deficiency • Cretinism

21. In a growing child nutritional imbalances can further accentuate an existing problem or may by themselves be capable of producing certain malformations, which may lead to malocclusions. These are Protein deficiency, Vitamin A deficiency, Vitamin B complex deficiency, Vitamin C deficiency , Vitamin D (Rickets).

22. Abnormal pressure habits and functional aberrations
These are possibly the most frequently encountered causes of malocclusion. they are all functional abrasions which produce forces that are abnormal. Since these forces are produced repeatedly over time they are capable of bringing about a permanent deformity in the developing musculoskeletal unit. The deformity produced depends upon the intensity, duration and frequency of the habit. These include:

23. a. Abnormal sucking b. Thumb and finger sucking c
a. Abnormal sucking b. Thumb and finger sucking c. Tongue thrust and tongue sucking d. Lip and nail biting e. Abnormal swallowing habits (improper deglutilion) f. Speech defects g. Respiratory abnormalities (mouth breathing, etc.) h. Tonsils and adenoids i. Psychogenic habits and bruxism.

24. Posture Trauma and accidents
Abnormal postural habits are said to cause
malocclusions, Though not directly. They may be
associated with other abnormal pressure or muscle
imbalances increasing the risk of malocclusion.
Trauma and accidents
Trauma and accidents can be further subdivided into
three categories depending upon the time at which
the trauma occurred, as:

25. Prenatal trauma Prenatal intrauterine trauma is often associated with hypoplasia of the mandible and even facial asymmetries. Trauma at the time of delivery Trauma at the time of delivery or birth injuries as they are more frequently called, have reduced considerably in recent years. Previously forceps injuries to the TMJ could result in ankylosis of the joint, resulting in severely impeded mandibular growth.

26. Postnatal trauma
Postnatal trauma can occur at any age and may affect any region of the orofacial complex. The effect of the trauma is dependent not only on the nature and the region, but also on the timing of the trauma. Trauma often results in dilacerations, deformations and displacements . An orthodontist should be careful of the trauma to the permanent teeth as these might not only be non-vital and undergo extensive root resorption during orthodontic movement but at times may get ankylosed and it might be impossible to move them at all.

27. Local Factors

28. Anomalies of number
Each jaw is designed to hold only a specific number of teeth at a particular age. However, if the number of teeth present increases, or size of teeth is abnormally large, it can cause crowding or hamper the eruption of succedaneous teeth in their ideal positions. Similarly, if the number of teeth present is less than normal then gaps will be seen in the dental arch. The anomalies in the number of teeth can be of two types (1) increased number of teeth or supernumerary teeth and, (2)less number of teeth or missing teeth.

29. The most commonly seen supernumerary tooth is the "mesiodens" (It is usually situated between the maxillary central incisors and can vary considerably in shape. It can be seen erupted or impacted . It is usually conical in shape with a short root and crown. It can occur in the maxilla or in mandible.

30. Supernumerary teeth can cause:
Non eruption of adjacent teeth .
b- Delay the eruption of adjacent teeth.
c.Deflect the erupting adjacent teeth into abnormal
locations .
d. Increase the arch perimeter (increasing the over jet) if in the maxillary arch or decreasing the over jet if seen in the mandibular arch.
e. Crowding in the dental arch

31. Congenitally missing teeth can lead to: a. Gaps between teeth. b
Congenitally missing teeth can lead to: a. Gaps between teeth. b. Aberrant swallowing patterns . c. Abnormal tilting, axial inclination or location of adjacent teeth . d. Multiple missing teeth can cause a multitude of problems .

32. Missing teeth Congenitally missing teeth are far more commonly seen as compared to supernumerary teeth. The term used to describe one or more congenitally missing teeth is true partial anodontia or hypodontia or oligodontia. The most commonly congenitally missing teeth are the third molars, followed by the maxillary lateral incisors .

33. Anomalies of tooth size
Only two anomalies of tooth size are of interest to an orthodontist-microdontia and macrodontia, involving one or more teeth. The most commonly seen form of localized microdontia involves the maxillary lateral incisors. The tooth is called a 'peg lateral"

34. Anomalies of tooth shape
Anomalies of tooth shape include true fusion, gemination, concrescence, talon cusp, and 'dens in dente'. Dilaceration is also an anomaly of the tooth shape in which there is a sharp bend. or curve in the root or crown. It generally does not effect orthodontic treatment planning but may complicate the extraction of the affected tooth.

35. Abnormal labial frenum
At birth the labial frenum is attached to the alveolar ridge with some fibers crossing over and attaching with the lingual dental papilla. As the teeth erupt, bone is deposited and the frenal attachment migrates superiorly with respect to the alveolar ridge. Some fibers may persist between the maxillary central incisors. These fibers which persist between these teeth are capable of preventing the two central incisors from coming into close and cause Midline diastema.

36. Premature loss of deciduous teeth
The premature loss of a deciduous tooth can lead to malocclusion only if the succedaneous tooth is not sufficiently close to the point of eruption. ln other words, the permanent successor does not erupt for sometime following the loss of the deciduous tooth, during which the adjacent teeth get time to migrate in its space. This can lead to a decrease in the over all arch length as the posterior teeth have a tendency to migrate mesially. This might cause the permanent successor to erupt malpositioned or get impacted or cause a shift in the midline (in case of anterior teeth).

37. Prolonged retention of deciduous teeth
Whatever the reason for the prolonged retention of deciduous teeth, they have a significant impact on the dentition. Which ever deciduous tooth may be retained beyond the usual eruption age of their permanent successor, is capable of causing: Buccal/labial or palatal/lingual deflection in its path of eruption; or Impaction of the permanent tooth.

38. Most commonly impacted tooth is the maxillary canine (third molars not taken into account). The reasons for this include: i. It is the last anterior tooth to erupt ii. Space occupied by the deciduous canine is less than the mesiodistal width of the permanent canines ill. The premolars might migrate mesially leaving limited space for the canines to erupt iv. It has the longest path of eruption v. Controversially, as it may seem, it is the only tooth to erupt after root completion.

39. Delayed eruption of permanent teeth
Nature has provided for a particular sequence for the eruption of individual teeth in each arch. This sequence of eruption has a certain amount of flexibility built into it as well; but if one of the teeth does not occupy its designated place in this sequence there is a likelihood of migration of other teeth into the available space. As a result the tooth whose eruption has been delayed might get displaced or impacted. Whatever the reasons for the delay in eruption it is important from a clinicians point of view to maintain and if required to create space for its eruption. Proper knowledge of preventive and interceptive orthodontics can definitely reduce the occurrence of rnalocclusions, if not prevent them from occurring; this can significantly reduce the severity of the malocclusion,

40. Abnormal eruptive path
Generally each tooth travels on a distinct path since its inception to the location at which it erupts. Tt can deviate from this eruption path because of many reasons .The tooth that most frequently erupts in an abnormal location is the maxirnally canine . Various reasons have been attributed for this behavior. These include: It travels the longest distance, from near the floor of the orbit to the cover of the arch.

41. It is the last anterior tooth to erupt and loss in arch length-anterior or posterior may impinge on the space required for it Abnormal position of the tooth bud. Ideally it should slide along the distal aspect of the root of the lateral incisor. Any problem in the position of the lateral incisor may divert the erupting canine. Since it has the longest path and is travelling for the longest time duration all other factors which might affect any tooth have a greater likelihood of effect it to erupt.

42. Ankylosis
Ankylosis is a condition which involves the union of the root or part of a root directly to the bone, i.e. without the intervening periodontal membrane Ankylosis or partial ankylosis is encountered relatively frequently during the mixed dentition stage. Ankylosis of teeth is seen more commonly associated with certain infection endocrine disorders and congenital disorders, e.g. Cleidocranial dysostosis, but these are rare occurrences.

43. Dental caries
Proximal caries are especially to blame for the reduction in arch length. This might be brought about by migration of adjacent teeth and/or tilting of adjacent teeth into the space available and/or supra-eruption of the teeth in the opposing arch. Caries can also lead to the premature loss of deciduous or permanent teeth. A substantial reduction in arch length can be expected if several adjacent teeth involved by proximal caries are left unrestored. This is especially true for deciduous molars. Premature loss of deciduous or permanent teeth can by themselves cause malocclusion, as explained earlier.

44. Improper dental restorations
Malocclusions can be caused due to improper dental restorations. Under contoured proximal restoration can lead to a significant decrease in the arch length especially in the deciduous molars. Over contoured proximal restorations might bulge into the space to be occupied by a succedaneous tooth and result in a reduction of this space. Overhang or poor proximal contacts may predispose to periodontal breakdown around these teeth. Premature contacts on over contoured occlusal restoration can cause a functional shift of the mandible during jaw closure, under-contoured occlusal restorations can lead to the supra-eruption of the opposing dentition.