1. The Etiology of malocclusion
General factors
Local factors
Skeletal factor
Muscle factor
Dental factor

2. Muscle factors affecting occlusal development
Dr. Ahmed AL-Mayali
B.D.S M.Sc. Ortho.

3. Muscle factors affecting occlusal development
The lips
Vertical plane
Sagittal plane

4. Competent lip
Incompetent lip
Vertical plane

5. Incompetent lip
Skeletal
Soft tissue
importance

6. Sagittal plane
Cl II Cl III

7. Sagittal plane
Mild Cl II sever Cl II

8. The lip-line
Normal

9. Low lip line

10. Not applicable

11. High lip line

12. The tongue
Tongue size
Tongue size = lower jaw
Open bite

13. Tongue posture
Lips apart
Nasal breathing

14. Tongue function

15. Normal swallowing requirement
closure of the lips
Teeth in light occlusal contact
Tongue elevated to the palate
Momentary clenching of the teeth as food pass

16. 1-Tooth apart adaptive swallowing

17. Adaptive swallowing
2-Tooth together adaptive swallowing

18. 3-Swallowing with endogenous tongue thrust

19. Thank you