Cephalometrics in orthodontics

The uses and application of cephalometrics in orthodontics

1. Cephalometrics in Orthodontics By , Dr.Dineshwarran Rajendran 21 January 2015

2. Contents Introduction Types History Uses Equipment Positioning of the P atient Evaluation of Radiograph Landmarks and Planes Analysis References

3. Introduction Cephalometry The analysis and interpretation of standardized radiographs of facial bones - Using standardized skull radiograph to assess facial, dental and skeletal relationships as well as airway analysis

4. Types Lateral Cephalogram Lateral view of skull X-ray beam perpendicular to the patient's sagittal plane Frontal Cephalogram Anteroposterior view of skull X -ray beam perpendicular to the patient’s coronal plane

5. History Cephalometry was modified from anthropological studies and craniometry (study of cranium) Introduced in 1931 by Broadbent (USA) and Hofrath (Germany ) Clinical application of cephalometry was introduced by Downs

6. Uses In orthodontic diagnosis and treatment planning . Assesment of horizontal/vertical skeletal relationship, incisor position/inclination, soft tissue profile Orthognathic surgery Helps in classification of skeletal and dental abnormalities. Helps in evaluation of treatment results . Post-functional to assess skeletal/dental relationship Plan retention and monitor post retention phase Helps in predicting growth related changes . Research purpose

7. Equipment Collimated X-ray source - 5 feet from midsagittal plane of patient Cephalostat - head positioner(with 2 ear rods and forehead clamp ) Aluminium wedge/ Barium paste - increases soft tissue definition Film - placed 1.5-1.8 foot behind midsagittal plane of patient with rare earth metal intensifying screen

8. Cephalostat

9. Positioning of the patient Frankfurt Horizontal plane should be parallel to floor. Ear rods stabilize the patient on the horizontal plane. Forehead clamp should be fixed for vertical plane stabilization of patient. Patient is made to close the mouth in centric occlusion.

10. Evaluation of Cephalometric Radiograph Important to examine radiograph for any abnormalities or pathology Eg . Sella turcica increase in size in pituitary tumor Digitizing Illuminated radiograph viewing screen which is connected to computer. Specialized software used to produce tracing Hand Tracing Carried out in a darkened room with light viewing box (X-ray viewer) and all but the areas being traced should be shielded out Acetate sheets used as transparency facilitates landmark identification Sharp pencil used ( 0.3mm leaded propelling pencil) Acetate sheet to be secured using masking tape and tracing oriented in the same position as patient when X-ray taken Bilateral landmarks , unless directly super imposed, an average of two should be taken

11. Cephalometry Tracing

12. Landmarks and planes Sella : Centre of the pituitary fossa of the sphenoid bone Nasion : Junction of frontonasal suture Basion : Most anterior point of foramen magnum Anterior Nasal Spine : Most anterior midpoint of ANS of maxilla Posterior Nasal Spine : Most posterior midpoint of PNS of palate A- Point : Most concave point of alveolar process of maxilla B- Point : Most concave point of alveolar process of mandible Menton : Most inferior midpoint of the chin on the outline of mandibular symphysis Pogonion : Most anterior midsaggital point along convexity of chin Gonion : Midpoint along curvature of angle of mandible between inferior border of body and posterior border of ramus Condylion : Most superior point of mandibular condyle Gnathion : Most anteroinferior point on mental symphysis Orbitale : Most inferior point of infraorbital rim Porion : Most superior point of external accoustic

13. Landmarks

14. Horizontal planes S.N. Plane – sella to nasion . F.H. Plane – orbitale to porion . Occlusal plane – plane bisecting posterior occlusion. Palatal plane – ANS to PNS of palatine bone. Mandibular plane – gonion to gnathion . Vertical planes A- Pog line – point A on maxilla to pogonion on mandible. Facial plane – nasion to pogonion , Facial axis – ptm point to gnathion . Planes

15. Analysis Examples Down's Steiner Rickett Harvold McNamara Sassouni Wits by Johnston Wylie Tweed

16. Downs Analysis First published by Downs in 1948 Most frequently used cephalometric analysis According to Downs, “ Balance of face is determined by position of mandible ” Frankfurt Horizontal plane used as reference plan to degree of retrognathism or prognathism

17. Skeletal Perimeters Facial angle I nferior angle formed by intersection of nasion-pogonion plane and F.H. plane. A verage value : 87.5 o ( 82 o - 95 o )

18. Significance : Indication of antero - posterior positioning of mandible in relation to upper face. - Increased in skeletal class III with prominent chin - Decreased in skeletal class II

19. Angle of convexity Nasion -point A to point A – pogonion . Average value : 0 o ( - 8.5 o - 10 o ).

20. Significance : - Positive angle suggest a prominent maxillary dental base in relation to mandible. - Negative angle is indicative of prognathic profile

21. A-B plane angle Point A – point B to nasion – pogonion . Average value : -4.6 o ( -9 to o )

22. Significance : Indicative of maxillo mandibular relationship in relation to facial plane. - Negative since point B is positioned behind point A. - Positive in class III malocclusion or class I malocclusion with mandible prominence

23. Y-Axis Sella gnathion to F.H. plane. Average value: 59.4 o ( 53 to 66 o ) Significance : Indicates growth pattern of a individual Increased in Class II facial patterns – Vertical growth pattern of mandible Decreased in Class III facial patterns – Horizontal growth pattern of mandible

24. Mandibular plane angle Intersection of mandibular plane with F.H. Plane. Average value : 21.9 o ( 17 to 28 o )

25. Dental Parameters Cant of occlusal plane Occlusal plane to F.H. plane Average value : 9.3 o ( 1.5 o - 14 o ) Gives a measure of slope of occlusal plane relative to F.H. Plane .

26. Inter incisal angle Angle between long axes of upper and lower incisors. Average value : 135.4 o ( 130 o - 150.5 o ) Increased in class I bimaxillary protrusion.

27. Incisor occlusal plane angle This is the inside inferior angle formed by the intersection between the long axis of lower central incisor and the occlusal plane and is read as a plus or minus deviation from a right angle Average value : 14.5 o ( 3.5 o - 20 o ) An increase in this angle is suggestive of increased lower incisor proclination .

28. Incisor mandibular plane angle This angle is formed by intersection of the long axis of the lower incisor and the mandibular plane. Average value : 1.4 o (-8.2 o - 7 o ) An increase in this angle is suggestive of increased lower incisor proclination .

29. Upper incisor to A- pog line This is a linear measurement between the incisal edge of the maxillary central incisor and the line joining point A to pogonion . Average value : 2.7 mm(-1 - 5 mm) The measurement is more in patients presenting with upper incisor proclination .

30. Soft tissue Analysis Rickett’s E-plane Line joining the soft tissue chin and tip of nose. In balanced face, lower lip lie 2mm ( ± 2mm) anterior to this line and upper lip little further posterior

31. Facial plane Line between soft tissue nasion and soft tissue chin. In well balanced face, the Frankfort plane should bisect the facial plane at an angle about 86 o and point A should lie on it

32. The Holdaway line Line from the soft tissue chin to upper lip. In a well proportioned face, if extended, should bisect the nose

33. References An introduction to orthodontics, Laura Mitchell (3 rd edition) Radiographic Cephalometrics , Alexander Jacobson Contemporary Orthodontics, William R. Proffit (4 th edition) Comparisons of the Consistency and Sensitivity of Five Reference Lines of the Horizontal Position of the Upper and Lower Lip to Lateral Facial Harmony, The Orthodontic Cyberjournal

34. Thank You