CEPHALOMETRICSIN ORTHODONTICSLecture.pptx

Cephalometric landmarks in Orthodontics

1. CEPHALOMETRICS

2. INTRODUCTION: CEPH – HEAD METRICS – MEASUREMENT CEPHALOMETRY – SCIENTIFIC MEASUREMENTS OF THE DIMENSIONS OF THE HEAD.

3. CEPHALOMETRIC RADIOGRAPHY – IS THE PRODUCTION OF SKULL RADIOGRAPHS WHICH ARE USEFUL IN MAKING MEASUREMENTS OF THE CRANIUM AND ORO-FACIAL COMPLEX.

4. TYPES: LATERAL CEPH P.A PROJECTION OR FRONTAL CEPH OBLIQUE PROJECTION – RT AND LT OBLIQUE TAKEN AT 45 O AND 135 TO THE TO THE LATERAL PROJECTION

5. THE BASICS OF CEPHALOMETRY Cephalometry was invented simultaneously in 1931 by Broadbent in the US and Hofrath in Germany. It derived from the craniostat, a device used to radiograph skulls in various planes of space.

6. The pioneering orthodontists of the first part of this century did not have the means of assessing the skeletal pattern so precisely. It is true that a treatment plan can be carried out without the aid of a lateral skull x-ray. However, the amount of information that is available from a cephalogram is considerable.

7. Cephalometry provides us with, at present, the most sensitive, if not the most perfect tool for assessing the growth of the head and jaws.

8. The lateral skull x-ray allows us to:- (a) assess the dento-skeletal relationships (b) assess the soft-tissue relationships to the underlying hard tissues (c) give a prognosis of treatment (d) predict future growth (with some reservations) (e) assess the results of treatment and growth

9. There is a tendency to regard the lateral skull radiograph as the main source of diagnostic information. It must be stressed that the clinical assessment of the patient, and examination of the study models, are just as important. It is probably a good idea to leave the x-rays until last before making a diagnosis.

10. (A) ASSESSMENT OF DENTO-SKELETAL RELATIONSHIPS The assessment of the relationships of the teeth to the underlying bone from the lateral skull radiograph. Anteroposterior and vertical relationships can be assessed. Transverse relationships can only be adequately evaluated from a postero-anterior view.

11. Overjet and overbite and the angulation of the incisors to their respective bases Relationships of the skeletal bases to each other The "vertical" angular relationships such as the Frankfort-Mandibular plane angle and the Maxillo-Mandibular plane angles Linear measurements of the lower anterior and upper anterior facial heights

12. B) RELATIONSHIPS OF THE SOFT TISSUES TO THE UNDERLYING HARD TISSUES The soft tissue features of interest are: the cant of the nose, the nasolabial angle, the relationship of the lower lip to the upper incisors (are they palatal to the upper incisors? What is the vertical relationship of the lower lip to the upper labial surface?),

13. the relationship of the lower lip at rest to the E- ("esthetic") plane of Ricketts, the labiomental angle, and the thickness of the soft tissue over the pogonion.

14. (C) TREATMENT PROGNOSTICATION A reasonable prognosis of the results of treatment can be given from the lateral skull radiograph. If the patient has stopped growing, the skeletal relationships can be expected to remain largely unchanged during treatment, and any changes observed will be due to tooth movements.

15. In the case of the patient who is still actively growing, care must be taken as these patients are likely to show worsening of their dentoskeletal relationships if further growth is expected. It is advisable not to undertake any treatment until growth has ceased.

16. (D) FORECASTING OF FUTURE GROWTH The prediction of growth has been first dealt by Houston in 1979. The most that we can give a reasonable prediction for is about a year or two in advance. By the age of 9, the human face has achieved 85% of its final adult size. Prediction can be done manually, by adding growth increments, or by computer program.

17. (E) ASSESSMENT OF RESULTS OF TREATMENT AND GROWTH After treatment, the movements of the incisors and other teeth, as well as the results of growth, can be evaluated by superimposition of the post-treatment tracing on the pre-treatment tracing.

18. Superimposition will show the changes that occur over a period of time in the jaw relationships and the angulation of the teeth. They are sometimes used to show that "orthopaedic" change has taken place, subsequent to the use of headgear or functional appliance treatment.

19. CEPHALOMETRIC EQUIPMENT AND TECHNIQUE Cephalometric radiographs are taken by placing the patient's head in a head holder, with ear pieces to ensure that the face is directed at 90 to the direction in which the film tube is facing. In order to keep the patient's head in the reproducible natural head position (NHP), they should look at their own eyes in a mirror.

20. The patient should be instructed to keep their teeth together in centric occlusion with lips relaxed. The tube should be 5 feet away from the centre of the patient's head, with the film 1 foot away on the other side. The resulting magnification will be between 6% and 10%.

21. TRACING A CEPHALOMETRIC RADIOGRAPH The finished radiograph should be checked for a number of features before it is used for tracing. The teeth should be in occlusion, and the radiograph should be sharp and the structures well-defined, with hard and soft tissues visible.

22. ARMAMENTARIUM USED IN TRACING

23. Acetate film is ideal for tracing, and a hard pencil (4H) should be used to draw the features. Tracing should be done in dark room over light box. The relevant cephalometric points should be identified. The appropriate lines are then drawn on the film, and the angles and proportions measured.

24. Purpose of Cephalometrics Description Cephalometrics helps in description of morphology or growth of a particular individual.

25. Diagnosis Cephalometrics in orthodontia is help full in analyzing the nature of the problem and helps in clarifying it. For example it can help in differentiating face type to differentiate whether the malocclusion is skeletal or dental

26. Prediction Cephalometrics to a certain extent can be useful in predicting the future growth.

27. Treatment Planning By helping in diagnosis and prediction of craniofacial morphology it aids in developing a clear treatment plan.

28. Evaluation of treatment results Recurrent cephalogram helps in evaluation of the results of the treatment. It helps the dentist in knowing whether the treatment is going on expected lines or whether any change is needed.

29. Prognosis Cephalometric evaluation also helps in knowing the prognosis.

30. Limitations of Cephalometrics It gives a two dimensional view of a three dimensional object. There can be error in identification of landmaks thus reliability of Cephalometrics comes down. Errors can be made during tracing procedure Assumptions – various things are assumed in Cephalometrics.

31. Symmetry: The various analysis done on lateral projection are based on the assumption that the patient does not have any skeletal asymmetry in case the patient has any skeletal asymmetry then the results of the analysis may not be accurate. This can be avoided by routine study of P.A. projection.

32. Fallacy of false precision It is found that when we take a series of cephalograms of the same person and does the tracing, locates landmarks and calculates various angles, the angles measured showed a standard error that is each time it differed slightly.

33. Fallacy of ignoring the patient The Cephalometric values should not be taken as fixed goals. Sometimes certain values of a given patient may vary from the mean value. But it may not be an indication for treatment.

34. Thus the patient should be analyzed individually before a treatment plan. Just because the values differ it does not mean that treatment is required. If function and esthatics are satisfied then any deviation from normal of the Cephalometric values can be ignored.

35. Cephalometric Landmarks 2 types Anatomic landmarks These land marks represent actual anatomic structures of the skull. Derived landmarks They are those that have been constructed or obtained secondarily from anatomic structures in a cephalogram.

36. Requirements of landmarks The land mark should be easily seen on a radiograph. It should be uniform in outline and reproducible Landmarks should permit valid quantitative measurements of lines and angles projected from them. They should be valid on living and in the roentgengram.

37. Nasion The most anterior point midway between frontal and nasal bones on fronto-nasal suture.

38. Orbitale The lowest point on the inferior bony margin of orbit

39. Sella The point representing the midpoint of pituitary fossa or sella turcica

40. Basion It is median point of the anterior margin of foramen magum

41. Articulare It is a point at the junction of posterior border of ramus and the inferior border of basilar part of occipital bone.

42. Condylion Most superior point on the head of the condyle

43. Anterior Nasal Spine (ANS) It is the anterior tip of the sharp bony process of the maxilla at the lower margin of the anterior nasal opening.

44. Posterior Nasal Spine (PNS) Process formed by the united projecting ends of the posterior border.

45. Porion Superior most point on the external acoustic meatus.

46. Gonion (Go) It is the lowest posterior and most out ward point on the angle of the mandible.

47. Pogonion (Pog) The most anterior prominent point on the chin in the median plane.

48. Gnathion (Gn) It is the most anterior and inferior point of the bodychin.

49. Menton It is the most inferior midline point on the mandibular symphysis

50. Infradentale (Id) The highest inter dental point on the alveolar mucosa between the mandibular central incisors. (Highest and most anterior point).

51. Point B or Supramentale It is the most posterior midline point in the concavity of the mandible between the most superior point on the alveolar bone

52. Subnasale (Sn) A skin point, the point at which the nasal septum merges inferiorly with the integument of upper lip.

53. Point A or Sub Spinale Deepest point on the midline contour of the alveolar process between the anterior nasal spine and prosthion.

54. Prosthion (Pr) The lowest interdental point on the alveolar mucosa in the median plane between the maxillary central incisor.

55. REFERENCE PLANES: S-N PLANE: (SELLA- NASION) Represents Anterior cranial base.

56. Frankfurt Horizontal Plane: Porion to Orbitale.

57. Palatal Plane: From ANS to PNS.

58. Occlusal Plane: Anatomical and Functional

59. Mandibular Plane: From Gonion to either Menton or Gnathion.

60. Y-axis: Nasion to Sella to Gnathion

61. DOWN ANALYSIS: Introdused by W B Down. Considered ‘position of the mandible could be used in determining whether or not faces were balanced.’ The “ideal” profile, which represents the best harmony of features or beauty, is the one in which the position of the mandible is orthognathous, that is neither retrusive nor protrusive.

62. Considers Frankfort horizontal plane as reference plane. 20 white subjects( 12-17 yrs) Boys and Girls are 1:1 ratio. All individuals having excellent occlusion. Down redused his observation to the following four basic facial types:

63. Retrognathic: Recessive lower jaw.

64. Mesognathic or Orthognatic: Ideal or average lower jaw

65. Prognathic: Protrusive lower jaw

66. True Prognathism: Pronounced protrusion of the lower face ( i,e both the jaws)

67. SKELETAL PATTERN:

68. FACIAL ANGLE: To measure , the degree of retrusion or protrusion of lower jaw. Facial line (N-Pog) intersect the F-H Plane. Mean – 87.8 Range – 82-95 Angle – Promint chin Angle– Retrusive chin

69. ANGLE OF FACIAL CONVEXITY: By the intersection of line from Nasion to Point A and line from Point A to Pogonion. Revels the convexity or concavity of the skeletal profile. Positive Angle – Convex profile – Class II Negative Angle – Concave profile – Class III Mean – 0 Range – -8.5 to +10

70. A-B PLANE ANGLE: Formed by line joining Point A to Point B AND line joining Nasion to Pogonion. Indicative of Maxillo-Mandibular relationship in relation to Facial plane. Mean - -4.6 Range – 0 to -9 . Large –ve angle – Class II Positive angle – Class III

71. MANDIBULAR PLANE ANGLE: Formed by the line joining tangent to lower border of mandible to F-H Plane. Mean – 21.9 Range – 17 to 28 Increased angle- Unfavorable growth pattern which complicates the treatment and prognosis.

72. Y (GROWTH) AXIS: Formed by the line joining Sella to Gnathion and F-H Plane. Larger angle- ClassII tendency and vertical growth pattern. Smaller angle- ClassIII tendency and horizontal growth pattern. Mean – 59.4 Range – 53-66

73. DENTAL PATTERN:

74. CANT OF OCCLUSAL PLANE: Here Occlusal plane is the line bisecting overlapping cusps of first molar and incisal overbite. Angle between Occlusal plane and F-H Plane. Mean - +9.3 Range - +1.5 to +14

75. INTERINCISAL ANGLE: Line passing through incisal edge and apex of root of maxillary and mandibular incisors. Mean – 135.4 Range – 130 to 150 Small angle- Proclined incisors Large angle- Retroclined incisors.

76. INCISOR-OCCLUSAL PLANE ANGLE: Relates lower incisor to their functioning occlusal plane. Mean – +14.5 Range - +3.5 to +20 Positive angle-proclined incisors. Negetive angle- Retroclined incisors

77. INCISOR MANDIBULAR PLANE ANGLE: Formed by the intersection of Mandibular Plane to Long axis of lower incisor. Mean – 1.4 Range - -8.5 to +7 Positive angle- Proclined incisor Negetive angle- Retroclined incisor

78. PROTRUSION OF MAXILLARY INCISORS: It is the linear measurement between the incisal edge of the maxillary central incisor and line joining Point A and Pogonion. Mean – +2.7mm Range – -1.0 to +5mm Reading is negative if incisal edge lies behind line and positive if it is front.

79. STEINER ANALYSIS: By Cecil C Steiner Divided the appraisal in to various sub groups, skeletal, dental and soft tissue. Reference plane is Sella- Nasion (S-N).

80. LAND MARKS AND PLANES USED IN STEINERS ANALYSIS:

81. SKELETAL PARAMETERS:

82. MAXILLA TO THE CRANIAL BASE (S-N-A Angle): Denotes antero-posterior position of maxilla to cranium. Mean – 82 Larger angle – Prognathic Maxilla Smaller angle – Retrognathic Maxilla

83. MANDIBLE TO THE CRANIAL BASE (S-N-B ANGLE): Denotes antero-posterior position of mandible to cranium. Mean – 80 Larger angle – Prognathic mandible Smaller angle – Retrognathic mandible

84. RELATIONSHIP OF MAXILLA TO THE MANDIBLE (A-N-B ANGLE): Provides general idea of the antero-posterior discrepancy of the Max- Mand Apical bases. Mean - +20 angle- ClassII angle- ClassIII

85. OCCLUSAL PLANE ANGLE: Occlusal plane is drawn through the region of overlapping cusps of premolars and molars. Angle formed between occlusal and S-N Planes. Mean - 14

86. MANDIBULAR PLANE ANGLE: Mandibular plane is drawn between Gonion and Gnathion. Angle formed between Mandibular and S-N Plane. Mean – 32 Increased or decreased angle- Unfavorable growth pattern which complicates the treatment and prognosis.

87. DENTAL PARAMETERS:

88. MAX INCISOR POSITION ( I TO NA) : Both angular and linear. Relative antero-posterior location and axial inclination of upper incisor to N-A Line. 4 mm and 22

89. MAND INCISOR POSITION ( I TO NB) : Both angular and linear. Relative antero-posterior location and axial inclination of lower incisor to N-B Line. 4 mm and 25

90. INTERINCISAL ANGLE: Relative position of upper and lower incisors. Mean – 130 Larger angle – Proclined incisors. Small angle – Retroclined incisors.

91. LOWER INCISOR TO CHIN (HOLDAWAY RATIO): The degree of prominence of chin contributes to the determination of placement of teeth in the arch. Ideally the distance between labial surface of lower incisor and hard tissue chin to the N-B Line should be equal i.e 4mm.

92. A 2mm discrepancy between the measurements is acceptable; 3mm is less desirable, but tolerable. If the discrepancy is more than 4mm, however, corrective measures are generally indicated.

93. SOFT TISSUE ANALYSIS: The lips in well balanced faces, should touch the line extending from soft tissue contour of chin to middle of the ‘S’ formed by the lower border of the nose.

94. TWEED ANALYSIS: FMA – 25 (FH Plane to Mandibular Plane). FMIA – 65 (FH Plane to Long axis of lower incisor). IMPA – 90 (Mandibular Plane to Long axis of lower incisor).

95. WITTS APPRAISAL: In the Witts appraisal, Points A and B are projected to the functional occlusal plane, which is drawn through the posterior teeth. Then A-B difference is measured. In well proportioned faces, the A-B difference is -1mm for men and is 0mm for women.

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