Schwarz analysis and wits appraisal(final)


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Schwarz analysis and wits appraisal(final)

  1. 1. SCHWARZ ANALYSIS AND WITS APPRAISAL INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.ocm 1
  2. 2. INTRODUCTION Lateral cephalometric radiographs have become indispensable to orthodontists in treatment of patients .. They are important in orthodontic growth analysis, diagnosis,treatment planning, monitoring of therapy and evaluation of final treatment outcome.After the introduction of a standardized radiographic technique using the cephalometer by Broadbent in 1931, different methods to evaluate the lateral cephalometric radiograph was put forward. www.indiandentalacademy.ocm 2
  3. 3. 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 and GNATHOMETRY 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 www.indiandentalacademy.ocm 3
  4. 4. CRANIOMETRY The craniometric reference lines used are NSe,H,SpP, NA, and Pn. Line NSe-is the anterior cranial base,where Se is the entrance of sella turcica. Line NA-is the line drawn from nasion to point A, point A is the anterior end of maxilla. www.indiandentalacademy.ocm 4
  5. 5. The H plane -is the Frankfort horizontal of Simon,is determined by the skin landmarks of the eye and ear points and runs parallel to the NSe plane. The Pn plane is the nasion perpendicular of Dreyfus .This is a line drawn from soft tissue nasion perpendicular to the H plane. The angle formed between the SpP plane and the Pn plane is called the inclination angle or the “J”angle.This is similar to the facial angle of Downs. www.indiandentalacademy.ocm 5
  6. 6. The average value is 85 degrees and this is seen in cases of straight faces.5 degrees variation is accepted as normal.  If the value decreases below the normal,in cases where the jaws slant backwards,then it is considered as retroinclination.  If the angle is increased as in cases of the jaws slanting forward it is termed as anteinclination. www.indiandentalacademy.ocm 6
  7. 7. The SpP plane forms an angle of 5 degrees with the NSe plane The angle formed between the NA plane and the NSe plane is called the “F “ angle or the facial angle , the normal value is 85 degrees.If the value is larger than normal as in case of forward displacement of the jaw,it is considered as anteface.If the value is lesser than normal as in case of backward displacement of jaws,it is considered as retroface. www.indiandentalacademy.ocm 7
  8. 8. Assessment of Temporomandibular joint position is done using the angle formed between the H plane and the Pn plane .the normal value should be 90 degrees. If the angle is larger than 90 degrees then it indicates that the Temporomandibular joint is inferiorly positioned. If the angle is decreased it indicates supraposition of the Temporomandibular joint. www.indiandentalacademy.ocm 8
  9. 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 www.indiandentalacademy.ocm 9
  10. 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(upto 10 percent). The jaw third is divided into two parts,one third belonging to maxilla and the other two thirds belonging to mandible. www.indiandentalacademy.ocm 10
  11. 11.  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. www.indiandentalacademy.ocm 11
  12. 12. GNATHOMETRY Helps to ascertain the important morphological details of various malocclusions. Deals with the evaluation of the dentition which is contained between the two base planes SpP and the MP(mandibular plane go-gn) .Therefore it is independent of the craniometric considerations www.indiandentalacademy.ocm 12
  13. 13. The ANGULAR MEASUREMENTS are  The Base plane angle(“B”angle) which is the angle formed between the SpP plane and mandibular plane,the average should be 20 + or – 5 degrees,if the angle is less than normal it indicates a well developed masticatory system, if the angle is larger it indicates underdevelopment of height in the molar region,it plays an important role in differentiation between the gnathic and the alveolar open bites.gnathic openbite is characterized by severe increase in both the “B” angle and the gonial angle. www.indiandentalacademy.ocm 13
  14. 14. The gonial angle is the angle formed between the tangent drawn to the body of mandible(MT1 )and the tangent drawn to the ramus of mandible( MT2),the average should be 123 degrees plus or minus 10 degrees.  The AB angle which is the angle formed between the line connecting point A and point B and the SpP plane,the average should be 90 degrees. www.indiandentalacademy.ocm 14
  15. 15.  The maxillomandibular angle is the angle formed between the line connecting the point A and pgo(pogonion osseous) and the SpP plane ,the average being 90 degrees. If the angle is increased it indicates retropositioned mandible in relation to maxilla whereas the mandibular length may be normal or deficient.and also indicates the supraposition of the TM Joint and an enlarged “B”angle. www.indiandentalacademy.ocm 15
  16. 16. If the angle is decreased it indicates a forwardly placed mandible in relation to the maxilla.and also indicates infraposition of the TM Joint and decreased “B”angle.Every 10 degrees change in the “B”angle corresponds to 7 degrees change in the maxillomandibular angle.  Axial inclinations of the teeth-is the angle formed between the long axis of the teeth and their respective base planes. www.indiandentalacademy.ocm 16
  17. 17.  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 90 degrees.5 degrees variation for all the angles is considered normal.  Inter incisal angle which is the projection of long axes of the upper and lower central incisors till the point of intersection should be 140 degrees plus or minus 5 degrees. www.indiandentalacademy.ocm 17
  18. 18. The interincisal angle is reduced in cases where there is an enlarged B angle in spite of the inclinations of the teeth being normal . LINEAR MEASUREMENTS Distance between Nasion and Se(sella entrance) is considered the length of anterior cranial base ,average value ranging between 60mm-70mm. Length of body of mandible measured along the mandibular tangent MT1,average value should be anterior cranial base + 3 mm. www.indiandentalacademy.ocm 18
  19. 19. 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 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 www.indiandentalacademy.ocm 19
  20. 20. 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 . www.indiandentalacademy.ocm 20
  21. 21.  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 www.indiandentalacademy.ocm 21
  22. 22. 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 and 14-16mm in adults. www.indiandentalacademy.ocm 22
  23. 23. 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. www.indiandentalacademy.ocm 23
  24. 24. WITS APPRAISAL Various cranial reference planes have been used as baselines from which to determine the degree of jaw dysplasia..these reference planes deal with cranial architecture and as such are useful in relating the jaws to the cranium. Measurements from the cranial base, however do not always provide a reliable expression of anteroposterior jaw relationships in the dentoalveolar complex. www.indiandentalacademy.ocm 24
  25. 25. The ANB angle (difference between SNA and SNB angles is the most commonly used measurement for appraising the anteroposterior disharmony of the jaws.the average ANB angle is 2 degrees.angles greater than the mean indicate class II skeletal disharmony and smaller angles are indicative of class III skeletal base. Although the ANB angle is a reliable indication of anteroposterior jaw relationship,there are many situations in which this reading cannot be relied on . As in cases with rotation of jaws. www.indiandentalacademy.ocm 25
  26. 26. The Wits appraisal was developed in an effort to reduce inconsistencies found within angle ANB when both the rotational effect of the jaws relative to cranial reference planes and the anteroposterior spatial relationship of nasion relative to the jaws are considered. The wits appraisal is a measure of the extent to which the jaws are related to each other. This appraisal relates point A and point B to the occlusal plane, providing a measurement of the anteroposterior relationship of the jaws nearer the teeth than is provided by the angle ANB. www.indiandentalacademy.ocm 26
  27. 27. The Wits appraisal uses a constructed occlusal plane, which is the plane of maximum intercuspation of posteriors. Perpendicular lines are drawn from points A and B to this occlusal plane. The points on the occlusal plane is named AO and BO. From these points on the occlusal plane, a measurement is made in millimeters. www.indiandentalacademy.ocm 27
  28. 28. Positive values occur when point A is anterior to point B, and negative values occur when point B is anterior to point A. www.indiandentalacademy.ocm 28
  29. 29. The average jaw relationship according to wits reading is –1.0mm for men and 0mm for cases of skeletal class II point BO would be located well behind point AO(positive reading)whereas in skeletal class III the wits reading would be negative(point BO is ahead of point AO). The severity of anteroposterior disharmony depends on the amount of deviation of wits reading from the mean. www.indiandentalacademy.ocm 29
  30. 30. Since the introduction of wits appraisal,various papers addressing the subject have been published.  Roth and Martina et al recognized the ANB angle as an invalid measure of sagittal skeletal disharmony because of it being affected by rotations and variations in the sagittal and vertical jaw dimensions relative to the cranial base.  According to Roth two factors affect the wits reading,they are occlusal plane angle and vertical alveolar dimensions. www.indiandentalacademy.ocm 30
  31. 31.  If the distance between point A and point B is increased then the wits reading also increases…so Roth gave an alternate procedure whereby a standard distance of 50 mm is used along the A-B line .  According to him the anteroposterior effect of wits appraisal of changes in occlusal plane could be used for determining changes in the molar relationship relative to the occlusal plane. www.indiandentalacademy.ocm 31
  32. 32. This technique is possible only if the first molars move on arcs with centers at A and B.  Since Jacobson defined the functional occlusal plane only as "the line drawn through the region of maximum cuspal inter digitation," the diagnosis of "anteroposterior jaw discrepancy" by means of the Wits appraisal may incorporate a large inherent error arising from the subjectivity of the method. www.indiandentalacademy.ocm 32
  33. 33. Various attempts have therefore been described to reproduce the occlusal plane in a more satisfactory manner . www.indiandentalacademy.ocm 33
  34. 34. Wits appraisal is a linear measurement and not an analysis itself.It is simply adjunctive diagnostic aid that may prove useful in assessing the extent of anteroposterior skeletal dysplasia and determining the reliability of the ANB angle. www.indiandentalacademy.ocm 34
  35. 35. CONCLUSION Identification of landmarks and interpretation of findings of a three dimensional object on a two-dimensional image cannot be regarded as truly stable. No single parameter in cephalometry should be relied on entirely and interpreted as an absolute value,Correlation between the linear and angular measurements is a must for interpretation. www.indiandentalacademy.ocm 35
  36. 36. REFERENCES…. Textbook of radiographic cephalometry by Alexander Jacobson. A practical evaluation of the X-ray headplate by A.Martin Schwarz (original article )(AJO-Aug 1961) www.indiandentalacademy.ocm 36
  37. 37. Thank you For more details please visit www.indiandentalacademy.ocm 37