Schwarz Analysis

schwarz analysis cephalometrics

1. Schwarz Analysis

2. INTRODUCTION A.M.SCHWARZ proposed his analysis for orthodontic diagnosis in the year 1961 to evaluate the lateral cephalometric radiograph making use of standard landmarks on the radiograph. He divided his analysis into two parts . CRANIOMETRY (SKELETAL) and GNATHOMETRY(DENTAL) making use of the spinapalate plane (SpP) ,which is the plane that separates the dentition from skull and also serves as the base plane of the maxilla. Craniometry deals with the evaluation of the skeletal base and the profile , while Gnathometry deals with the evaluation of the dentition

3. CRANIOMETRY(SKELETAL) 5 Reference lines have been used: 2-vertical lines , 3- horizontal line

4. SKELETAL ANALYSIS • INCLINATION ANGLE OR 'J'ANGLE OR ANGLE OF INCLINATION : Angle formed between SpP plane and Pn plane is called inclination angle or j angle. Average : 85±5°(straight face) ≥ anteinclination ≤ retroinclination ( similar to facial angle in Down's)

5. • 'F 'ANGLE OR FACIAL ANGLE: Angle formed between NA plane and NSe plane is called the 'F' angle or Facial angle. Normal value : 85° ≥ ante face (forward displacement of jaw) ≤ retro face (backward displacement of jaw)

6. • ASSESSMENT OF TMJ POSITION: Angle formed between H plane and Pn plane . Normal value : 90 ° ≥ TMJ is inferiorly placed. ≤ TMJ is in supraposition.

7. The SpP plane forms an angle of 5 degrees with the NSe plane

8. ANALYSIS OF FACIAL PROFILE Forehead third of face Nasal third of the face Jaw third of the face

9. The landmarks and lines used by Schwarz for analyzing the profile are : • O-eye point or orbitale. • H- Frankfort horizontal plane connecting the orbitale and the porion(Simons eye-ear plane) tr-trichion(hairline) • n-is the soft tissue nasion. • sn-is the subnasale • pg-is the soft tissue pogonion • gn-is the soft tissue gnathion

10. • tr-n -is the forehead third of the face • n-sn -is the nasal third of the face • sn-gn -is the jaw third of the face • For an average profile the forehead , nasal and jaw thirds are approximately equal in size , the jaw third can be slightly longer(up to 10 percent). • The jaw third is divided into two parts , one third belonging to maxilla and the other two thirds belonging to mandible.

11. 'T' ANGLE • The line T( mouth tangent ) drawn from subnasale to pogonion forms and angle of 10 degrees with the Pn plane,this is called the “T” angle. • In an ideal profile the T line should touch the edge of the lower lip and bisect the upper lip.

12. GNATHOMETRY(DENTAL) • Deals with the Planes between SpP and MP plane. • BASE PLANE ANGLE OR “B” ANGLE: • Angle formed between SpP plane and MP plane .(mandibular plane go-gn) Average : 20±5° ≤ well developed masticatory system. ≥ underdevelopment of the height in the molar region. Gnathic openbite (severly increases if both 'B'angle and gonial angle increases).

13. GONIAL ANGLE : Angle formed between tangent drawn to the body of the mandible (MTI) and tangent drawn to the ramus of the mandible(MT2). Average:123±10°

14. AB ANGLE: The AB angle which is the angle formed between the line connecting point A and point B and the SpP plane. Average : 90°

15. MAXILLOMANDIBULAR ANGLE: Angle formed between line connecting point A and pogonion and the SpP plane. Average : 90° ≥ : Retropositioned mandible in relation to maxilla ,supraposition of TMJ and enlarged 'B' angle. ≤ : Forwardly placed mandible in relation to maxilla infraposition of TMJ and decreased 'B' angle. Every 10 degrees change in the “B”angle corresponds to 7 degrees change in the maxillomandibular angle.

16. • AXIAL INCLINATIONS OF TEETH: • Axial inclinations of the teeth-is the angle formed between the long axis of the teeth and their respective base planes. • The average angles formed by long axes upper central incisors , canines and first premolars to SpP plane should be 70,80 and 90 degrees. • The average angles for lower incisors and canines to the mandibular plane is 90degrees. • 5 degrees variation for all the angles is considered normal.

17. • INTERINCISAL ANGLE: Angle formed between long axis of the upper and lower central incisor. Average:140±5° ≥ Retroclination ≤ Proclination

18. • Pn TO OCCLUSAL PLANE : Angle formed between Pn plane and occlusal plane. Pn - Soft tissue Nasion perpendicular to H plane(Frankfort horizontal plane). Average : 75 °

19. • Pn to mandibular plane: Angle formed between Pn plane and mandibular plane(go-gn). Pn - Soft tissue Nasion perpendicular to H plane(Frankfort horizontal plane). Average : 65°

20. • Palatal plane to occlusal plane: Angle formed between palatalplane and occlusal plane. Average : 8-10°

21. • OCCLUSAL PLANE TO MANDIBULAR PLANE: Angle formed between occlusal plane and mandibular plane (go-gn). Average : 10-12°

22. LINEAR MEASUREMENTS • EXTENT OF ANTERIOR CRANIA BASE: From sella entrance to Nasion. Average : 60-70mm(68mm)

23. • EXTENT OF ASCENDING RAMUS: Measured from go to condylion. Average : 50mm(55.6mm)

24. • EXTENT OF MAXILLARY CRANIAL BASE: Measured from ANS to PNS. Average : 51.9mm(47.5mm)

25. • EXTENT OF MANDIBULAR BASE: Measured from gonion to pogonion. Average - 79mm(71mm) Length of body of mandible measured along the mandibular tangent MT1,average value should be anterior cranial base + 3 mm.

26. Length of ramus-measured from gonion upwards to the point where it intersects the H plane(average-50mms). The length of the maxilla is measured along the SpP plane from the projected point A to the outline of pterygomaxillary fissure as it crosses the spina palate plane. The average value is 47.5mm. The average length of the jaws is calculated in comparison with the anterior cranial base , the average length ratio of anterior cranial base to upper jaw should be 10:7

27. The average length ratio of upper jaw to the mandibular corpus should be 2:3 . The average length of NSe and pogonion-gonion line is 20:21 or 60:63. The length ratio of mandibular body to that of mandibular ramus is 7:5. The average length ratio between the upper incisors and upper molars to SpP=lower incisors and the lower first molars to the mandibular plane which is =5:4 .

28. The average length ratio of upper incisor (oi) to lower incisor (ui ) and upper first molar (om1)lower first molar (um1) which is equal to 2:3. For all sagittal malocclusions a variation of 5 degrees or 5mm is acceptable because the distance between the two buccal cusps of the maxillary first molar is equal to 5 mm,so a 5mm shift is a must to shift the occlusion from normal to a class II or class III

29. SOFT TISSUE LINEAR MEASUREMENT Soft tissue thickness in the jaw region is also considered in linear measurements of profile. • The average horizontal distance from subnasale to NA line is 12mm in children and14-16mm in adults.

30. • Horizontal distance of upper lip to upper central incisor= 12 mm. • The distance of lower lip to the labial surface of the lower incisors = 12 mm. • The average chin cushion = 10mm and • soft tissue thickness at gnathion = 6 mm.

31. Dental Axial inclinations of the teeth to palatal plane : upper central incisors - 70±5° upper canine - 80±5° upper Ist Premolar - 90±5° Axial inclinations of the teeth to mandibular plane : lower incisors - 90±5° lower canine - 90±5° Interincisal angle Your Footer Here - 140±5°

32. Pn to occlusal plane - 75° Pn to mandibular plane - 65° palatal plane to occlusal plane - 8-10° occlusal plane to mandibular plane - 10-12° Base plane or B angle - 20±5° Gonial angle - 123° maxillomandibular angle - 90° AB angle - 90°

33. SKELETAL • Se-N - 68mm • Corpus mandibular -71mm • Mandibular ramus -50mm • Upper jaw length -47.5mm • SpP NSe plane -5° • SpP Perpendicular from N': J angle -85° • Na-Nse -85° • H plane-Nse -5° • H plane-Perpendicular from N* -90°

34. Length relation of the jaws: • N-Se / pog-gonion - 60:63 • Ramus / mandibular corpus - 5:7 • Upper jaw / mandibular corpus - 2:3 Soft tissue thickness : • Sn-A - 14-16mm • Upper lip - 12mm • Lower lip - 12mm • Chin cushion - 10mm • Soft tissue at gnathion - 6mm

35. REFERENCE A .M.Schwarz -A practical evaluation of the x- ray head plate - Am.J.orthodontics august :1961 vol- 47

36. THANK YOU