Etiologic Factors of Malocclusion

1. Etiologic Factors of Malocclusion Orthodontic Research office of Xi’an Jiaotong University Stomatology Hospital Min,Zou

2. Classification According to the Phase that Malocclusion Formed • Congenital causes • Acquired causes

3. Mechanisms of individual malocclusion • Hereditary causes • Environmental causes

4. 一、Hereditary Factors • Hereditary Factors ：The characters has been fixed when the spermatid combined with the oocyte. • Heredity：The transmission of traits encoded in GENES fromparent to offspring.Say that similarity that between the parenthood. • Gene is the basical unit of genetic material. • Malocclusion feature is the polygene determine.

5. Experiments with crossbreed dogs by Stock and Johnson • At the beginning of 19th century，through crossbreeding pure-blood dogs with significant difference on coronal and occlusal relation-ship,the data from p3 shows that the cross breeding dogs appears obvious malocclusion. • Conlusion： Hereditary factors play an important role in the development of malocclusion.

6. Heritability of craniofacial feature > Heritability of teeth arche feature，and the later one is easier affected by the environment factors.Heritability has more effects on the bone proportion,and the teeth relation-ship is more likely influenced by the environment factors.

7. Two pathway of hereditary factors induced malocclusion forming . • The disproportion between the size of tooth and the size of jaw. • The hereditary disproportion between maxillary and mandibular size or shape of maxillary and mandibular ,which would cause improper occlusal relationships.

8. First Race evolution • Transition of living environment：From creeping to upright-walking ,the size of jaw has degenerated .

9. Race evolution • Changes in dietary structure：The function of mastication organ has degenerated gradually.

10. Race evolution • Lopsided degeneration of mastication organ:Muscle>Jaws>Teeth

11. Individual development • Malocclusion has closely related to heredity,and is polygene decided . • Evironmental factors induce various types of malocclusion with diverse manner or intensity through the different expression of genotype when there’r different conditions.

12. Second environment factors The environmental factors cause malocclusion are mainly summarized as following: Long-term habits • Influence on postural position of head,mandibular and the tongue.and these positions are determinants on the pressure of soft-tissue in relaxed state. • Influence on teeth eruption.

14. Two Environmental FactorsFirst congenital causes • Matrix factors • Embryo factors • Common maldevelopment and deficiency：supernumerary tooth、congenital missing tooth、abnormal tooth size • Macroglossia, microglossia • Abnormal labial frenum

15. Second Acquired causes Some acute and chronic diseases：Diseases happened in the growth period can affect the health and the development of the individual. • Chronic consumptions（dyspepsy、tuberculosis），may decrease the food assimilation and destroy the body nutrition state,accordingly,disturb the normal growth of jaws.

16. Rachitis：It is a chronic inanition disease,lacking off ultraviolet radiation, VD,unbalanced calcium and phosphor,multiple sites of abnormal development and calcification of bone,and monstrosity of maxillofacial region.

17. Abnormal incretion • Hyperfunctioning of pituitary • Superfluous growth hormone before bone amalqamation • Acromeqaly • Insufficient function of anterior pituitary

18. Abnormal incretion • Hyperfunctioning of hypothyroid • Insufficient function of hypothyroid Narrow teeth arche,high bony plate,deficient development of mandibular,mandibular deficient development，disordered eruption.

19. Acquired causes Malnutrition • VA lacking Deficiency in development of teeth and bone.Delaying eruption,primary teeth retention,maldevelopment on teeth and peridentium. • VBlacking Stagnant development of teeth and maxillofacial facial region、alveolar ridge shrinking.

20. Acquired causes • VClacking Hypogenesis on enamel,dentin,cementum stroma and teeth tissue,degeneration of cementum cells. • VDlacking Metabolic disorder of bone calcify and the calcium and phosphate metabolism.

21. Functional factors Abnormal suck function （Especially artificial feeding ） • Low feeder peressure on mandibular • High feeder peressure on maxillary • 45° recumbent position,flat nipple,without peressure on maxillary ,timing and ration.

22. Functional factors • Abnormal masticatory function ：Perioral masticatory muscles function brought about by functional stimulation of the teeth, together, jaw growth and development has an important role in promoting. Masticatory function receded, the organizational structure of the masticatory muscles caused by the degradation, the impact of upper and lower jaw development. So modern food, apart from the necessary high-protein, high vitamin, should emphasize the physical traits to food rich in fiber, and rough, and chewy nature.

23. Functional factors Respiratory dysfunction • Mouth breathing, drooping lower jaw, tongue body ---- on the whereabouts of the medial arch support for the loss of the tongue, and lateral cheek muscles still exist on stress ---- arch narrow, upper anterior teeth crowding or protrusion; lip muscle relaxation, the usual broad lip, everted lip; because of the airway from the mouth through the decline in prejudice to the hard palate palate.

24. Functional factors Normal swallowing, the mouth-week masticatory muscles to contract, will be on the mandibular dentition clenching together at the middle position on the lower lip muscle natural closure, tongue is located within the dental arch and teeth contact blade of tongue and hard palate. • A typical baby suck especially artificial feeding: the tongue body is located between the upper and lower alveolar ridge and to maintain contact with the lip to swallow. • Abnormal Swallowing: Tongue is located in upper and lower dentition, the lip should not close the opening and closing, protrusion on the dental arch

25. Functional factors • Muscle dysfunction: perioral muscle mainly through two kinds of influence mandibular growth and development of muscle attachment ① affect bone growth and reconstruction. ② soft tissue system as an important part of its function of normal mandibular growth.

26. Four Oral habits • Sucking habit : there is the corpus callosum fingers and fingers are curved, such as diagnosis suck phenomenon refers to an important indication of the habit.

27. Habit of sucking caused by mistake .All types and suck mean the type and position of buccal muscle contraction tension and sucking at the time of the relevant position. The severity of these with the amount of sucking, duration, frequency and other factors.

28. Oral habits Tongue habits: Tongue Thursting: the tougue tip between the incisors protruding forward to put in contact with the elevated lower lip. Licking teeth: a. Palatal tongue at teeth teeth ---- dump lip, tongue tooth gap at b. labial teeth tongue ---- dump, competent single tooth crossbite Lolling， opening and closing of anterior teeth, mandibular protrusion, Noodles 1 / 3 high to increase . Cheek muscle strength: on arch stenosis; occlusal posterior teeth posterior teeth to open so that to continue elongation, lower down, after the rotation.

30. Oral habits Lip habit: occurred in the 6-15 years old. ---- To bite the upper lip anterior crossbite ----To bite the lower lip .anterior lip dump, space + under the tongue dump teeth, crowding ---- deep overbite malocclusion, large ultra-Hop

31. Oral habits • Unilateral chew habits: excessive development of the functional side of mandible, masticatory muscles developed; Disuse lateral hypoplasia, facial asymmetry, submental point and the center line to the function of lateral deflection. Habit of biting objects.Sleep habits.

32. Fifth Local disturbance in primary and the mixed dentition • premature shedding of deciduous tooth • deciduous tooth retention • Abrasio shortage of primary canine • Primary teeth subside

33. premature shedding of deciduous tooth • Early eruption of permanent dentition • Sequence of permanent tooth eruption disorders

34. （六）骨性错合的病因 Genetic approach Defects in embryonic development Trauma Functional factors

35. Some scholars think that the growth of abnormal bone formation of Hopewell mistake caused primarily by genetic factors, the person holding such an opinion is not to change the growth type, but put the emphasis was placed on the treatment of dentition can not be changed to adapt to the skeleton type. Instead, put those same look for the growth of abnormal environmental factors from those who actively attempt to change the environment, the pursuit of successful treatment.

36. Summary heredity environment

37. Summary

38. Classification of Malocclusion Orthodontic Research office of Xi’an Jiaotong University Stomatology Hospital Min,Zou

39. Angle Ideal Occlusion • Old Glory----ideal normal occlusion:Fully preserved teeth (32), upper and lower teeth in the dentition with a very neat, sharp upper and lower teeth fossa relationship entirely correct, the satisfactory relationship between upper and lower dentition.

40. Andrews six keys A. correct molar relationship B. correct crown angulation C. correct crown inclination D. tight interproximal contacts E. absence of rotations F. a flat curve of Spee

41. Angle’s Classification • The traditional classification methods of malocclusion raised in 1899 Orthodontics, is currently one of the most widely used international classification methods. Theoretical basis: The maxillary first molars are the "key", so the malocclusion are caused by mandibular deformities or mesal/distal dislocation. Simply put, regarding the maxillary first molar as the benchmark ,the occlusal relation ship will be divided into mesiocclusion,neutroclusion, and distoclusion.

42. Class I, neutroclusion • All the middle bit, the maxillary first molar in the cheek near the sharp bite on the mandibular first molar in the cheek near the trenches, such as oral teeth neatly arranged without dislocation, the call of normal together; such as dentition in existence when the wrong tooth known as the neutral or the first category mistake Hopewell Hopewell mistake. • The first mistake can be combined as follows: crowding, protrusion on the dental arch, double arch protrusion, maxillary anterior crossbite, deep overbite combined anterior, posterior teeth buccal / lingual and so on to the dislocation.

43. class II, distoclusion • Lower molar distally positioned relative to upper molar,line of occlusion not specified. • Mild distaloclusion • Complete distaloclusion

44. class II, distoclusion • class II, division 1：Distal molar relationship,with upper anterior teeth protrusion. • class II, division 1，subdivision：Distal molar relationship in one side of dental arche,and neutroclusal relationship in another side,with upper anterior teeth protrusion.

45. class II, division 1：deep overbite,deep overjet,hypodeveloped muffle

46. class II, distoclusion • class II, division 2：Distal molar relationship,with upper anterior teeth lingua inclination. • class II, division 2，subdivision：Distal molar relationship in one side of dental arche,and neutroclusal relationship in another side,with upper anterior teeth lingua inclination.

47. class II, division 2： deep overbite combined with lingua inclination

48. Class III, mesioclusion • All the middle bit, the maxillary first molar in the cheek near the sharp bite on the mandibular first molar in the buccal sulcus near the near the Medium. If the lower back 1 / 4 molar or 1 / 2 premolar distance, that is, upper and lower first molar Constant Medium cheek near the relatively sharp, the mistake known as mild distal start together or combined distal mistake. If the lower jaw continues to retreat, that is, near the maxillary first molar in the buccal occlusal tip in the first permanent molars in between the second premolar, and known as the fully distal molar relation ship. .

49. class III • classIII, subdivision：mesiocclusal molar relationship in one side of dental arche,and neutroclusal relationship in the other side. • Openbite and crossbite in front teeth

50. Angle’s Classification • Characteristics of the basic scientific theory and easy to be understood • Clarify the confuse concept of dental relationship in past • Significant guiding for clinical diagnosis and treatment design