AETIOLOGY OF MALOCCLUSION

1. AETIOLOGY OF MALOCCLUSION BY DR.OYETOLA FEMI

2. OUTLINE INTRODUCTION HISTORICAL BACKGROUND VARIOUS CLASIFICATION CRITERIA GENERAL AND LOCAL FACTORS (1) GENERAL FACTORS (2) LOCAL FACTORS CLINICAL IMPLICATIONS CONCLUSION

3. INTRODUCTION Malocclusion is a developmental condition caused in most cases by distortion of normal development and only a few cases caused by pathology. Although it is difficult to know the precise cause of most malocclusion but we do know in general what the possibilities are.

4. Occasionally a single specific cause is apparent e.g mandibular defficiency secondary to trauma to TMJ or characteristics malocclusion that occur in some genetic syndromes. More often these problem result from complex interaction among multiple factors that influence growth and devpt (William R Proffit,2005)

5. HISTORICAL BACKGROUND By the middle of 19th century different ideas was put forward to explain possible causes of malocclusion Some attributed it to habit e.g tongue sucking,tongue thrusting and lip sucking,some said it is hereditary and dietary defficiency, Overbite was attributed to mouth breathing and tongue thrusting

6. Here are some of the ealier concepts on the aetiology of malocclusion; -Kingsley: the importance of inter- racial mixtures(marriage) -Talbot: the role of endocrine glands -Rogers: lip habit -Brash: theory of inheritance

7. VARIOUS CLASFICATN METHODS Several attempts has been made to classify malocclusion in the literature among which are; (i)General and local factors (Housten et al,1998,Malcolm Jones,2001) (ii) Hereditary and Environmental/Acquired

8. (iii) T.C white et al 1976 classify malocclusion as; (i) Dental base abnormalities (ii)Pre-eruptive abnormalities-large frenum,tooth germ position (iii)Post eruptive abnormalities-muscular forces like swallowing habit,suckling.Also premature loss of deciduos teeth

9. (iv) William R Proffit 2005, classify aetiology of malocclusion as follows (i) specific causes (ii) Genetic influences (iii) Environmental influences

10. Broad classification into local and general factor will be used for this discussion because it appear simple to understand and is a pointer to the management of patients There is possibilities of interceptive orthodontics practice if cause is due to local causes(Housten et al 1998)

11. GENERAL FACTORS They affect all or greater part of the occlusion. They include; (A) Abnormalities in skeletal relationship (B) Soft tissue factors (C) Disproportion between tooth size and ach length

12. ABNORMALTIES IN SKELETAL RELATIONSHIP Refer to as skeletal factors Include the following abnormalities; (i) Anterior-posterior mal relationship-this result from differential devpt of maxillae and mandible, it is hereditary and ethnic in origin in most cases(Kranus et al 1976).other possibilities are;

13. Foetal intrauterine moulding; pressure against mandible if the head is excessively flex against the chest, or arm pressed against the face

15. Syndromes; Some syndromes are associated with mandibular defficiency and jaw malformation e.g. Pierre Robins sequence,Treacher Collin syndrome,Crouzon syndrome Birth trauma to mandible-damage to TMJ

16. Haematological e.g sickle cell anaemia patient can have Class II skeletal pattern due to maxillary prognatism(Sickle cell gnathopathy Endocrine e.g hypothyrodism(Cretinism)-there is reduce jaw growth as part of overall reduction in body growth

17. Disturbance in Embryonic development- teratogens can disturb jaw growth if introduce at a time when the jaw is developing, it can also lead to cleft lip and palate leading to class III skeletal pattern

18. VERTICAL MALRELATIONSHIP There is excessive facial growth which increases the facial height and could cause skeletal open bite. Can result from mandibular prognatism due to hyperpituitarism Also caused by condylar hyperplasia

19. LATERAL MALRELATIONSHIP Occasionally dental bases is disproportional wide or narrow causing lingual or buccal cross bite of molars although the axial inclination of the teeth appear correct some of the causes of anterior-posterior malrelationship are also responsible for this abnormalities

20. (B) SOFT TISSUE FACTOR These include muscles, lips, tongue and cheek The effects are as follows; (i) Muscle dysfunction e.g Bell palsy-The facial muscle affect the growth of the jaw in two ways; -The formation of bone at the point of muscle attachment depend on the activity of the muscle -Growth of soft tissue carry the jaw downward and forward

21. (ii) Short lips-leads to proclination of anteriors,increase overjet and occasionally open bite (iii)Tongue-e,g Macroglossia (iv) Cheek/lip defect-causes displacement or proclination of the teeth to the affected regions

22. (C)TOOTH SIZE AND ARCH LENGTH DISPROPORTION Basically hereditary in origin Patient inherit small arch from one parent and large tooth size from other parent leading to crowding Or a combination of large arch and small tooth size resulting in spacing

23. LOCAL FACTORS Affecting one or two adjacent and/or opposing teeth, effects are localised to the mouth They produce a local disturbance in dental devpt that become more severe the longer it continue to operate Such factor can be intercepted with advantage

24. VARIATION IN TOOTH NUMBER Can result from any of the following (A) CONGENITALLY MISSING TEETH. -result from disturbances during the initial stages of tooth formation in which the tooth bud failed to develop -Anodontia is rare, it occur when all the tooth buds failed to develop and so the patient has no teeth in the mouth

25. -Oligodontia is congenital absence of many teeth -Hypodontia is the absence of only few teeth -Hypodontia is more commonly seen than oligodontia

26. Congenitally missing tooth contd Congenitally missing tooth may be associated with ectodermal dysplasia ED consist of sparse hair, absence of sweat gland and xtically missing teeth. As a general rule. if only one or few teeth are missing, the absence will be the most distal tooth of any giving type (Williams Proffit 2005) i.e. if molar it is 3rd,if premolar it is second and if incisor it is lateral. Rarely is canine the only missing tooth. Missing teeth could result in spacing.

27. (ii)Premature loss of deciduos teeth or unplanned extraction of perm. Teeth -Result in loss of space -Extraction of perm, teeth can result in spacing in adult (iii)Supernumenary teeth -Additional teeth found in the mouth -can be supplemental if have the same anatomy as the surrounding teeth -Result in crowding -Examples are;mesiodens,paramolar,distomolar -Can be associated with cleidocranial dysplasia and Gardner�s syndromes (iv) Retained deciduous

28. (B)VARIATION IN TOOTH FORM Malformed tooth e.g. peg shape lateral Macrodontia Microdontia Additional cusps Invigilation Evagination

29. (C) INTERFERANCE WITH ERUPTION Classically seen in Cleidocranial dysplasia which include; -Sclerotic bone -Heavy fibrous gingival -Supernumerary teeth.

30. (D)ABNORMALTIES IN TOOTH POSITION Ectopic eruption-Occurs when teeth are not erupting on their normal position on the arch Canine may erupt labially,palatally or rotated so also other teeth in the mouth Transposition e.g laterals taking the position of cannie,results in occlussal disharmony Traumatic displacement of teeth

31. (E) LOCAL DISTURBANCE IN SOFT TISSUE Pressure law states that �an object subjected to unequal forces will be accelerated and thereby move to a different position in space� Disturbances in the resultant forces which act to maintain the teeth in the ach will eventually lead to malocclusion The disturbances exist in diverse forms

32. HABIT -Thumb sucking-proclination of upper incissor,retroclination of lower incissor,anterior open bite and deep palatal vault -Finger sucking-ant. Open bite -Tongue sucking -Tongue thrusting-anterior open bite -Arm sucking -Lip sucking

33. Mouth breathing-An abnormal respiration pattern which can interfere with occlusion as it could result in open bite High frena attachment �Can cause displacement of centrals, can also lead to diastema which may be considered as malocclusion in some places

34. Positive association between pacifiers use and posterior cross bite and reduced upper arch width. Probable mechanism �Sucking activity in the cheeks �Reduced palatal support as the tongue takes a lower position

35. Impact of infant sucking habits Digit and dummy sucking resulted in increased tendency to tongue thrust. Tongue thrust related to: open bites, overjet, and Class II malocclusion. Sucking habits influence the aetiology of malocclusion Melsen B, et al.1979

36. Rutruded chin and elevated upper lip from lip sucking

37. Patient with sucking habit

38. ANTERIOR OPEN BITE FROM THUMB SUCKING

39. Arm sucking

40. Adult tongue thrusting can lead to spacing

41. Spaces created from the same patient

42. (F) LOCAL PATHOLOGY/INFECTION Cysts Cancrum oris Trauma Tumour e.g Ameloblastoma

43. CONCLUSION It can not be over emphasise that the knowledge of the causes of malocclusion goes a long way in the management especially those that can be intercepted

44. THANK YOU VERY MUCH