Pitchfork Analysis

Orthodontics

1. SEMINAR PRESENTATION Pitchfork Analysis DEPARTMENT OF ORTHODONTICS AND DENTOFACIAL ORTHOPAEDICS. Presented by: Guided by: Dr. Deeksha Bhanotia Dr. Mridula Trehan . M.D.S. Second year. Professor & Head. Department of Orthodontics and Dentofacial Orthopaedics 1

2. Contents: 1.Introducion 2.Superimposition Landmarks 3.Superimposition methods of a. Cranial base b. Maxilla c. Mandible 4.Pitch fork analysis a. Cranial Base Superimposition b. Maxilla c. Mandible 5.Pattern of Craniofacial Growth 6.Measurement of Changes: a. Jaw growth/displacement relative to cranial base b. Tooth Movement relative to basal bone c. Molar relationship and overjet change 7.Reliability 8.Conclusion 2

3. Introduction: A cephalometric superimposition is an analysis of lateral cephalograms of the same patient taken at different times. It is used to evaluate a patient's growth pattern between different ages and to evaluate changes in the dentoalveolar and basal relationships after a course of orthodontic or surgical treatment. Cephalometric procedures and evaluations are considered in the light of; pretreatment objectives, orthodontic treatment modalities used, long-term follow-up of the treatment results and during the retention and post-retention periods. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 3

4. The comparison of cephalometric head films taken at intervals is a method used by researchers and clinician to obtain a general view of growth changes and/or to determine the effect of orthodontic treatment on the jaws and teeth. In growing skulls the various bones move apart from each other at different rates. The anatomic landmarks adjacent to growth locations will move apart more than those further from the growth sites. To determine the effect of growth of treatment, tracings of the head films, are superimposed on those landmarks least affected by growth. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 4

5. 5 Superimposition of the Craniofacial Complex.

6. Superimposition Landmarks: Soon after the discovery of Broadbent’s cephalometer , cephalometrics has been extensively used by anatomists and orthodontists to find out variations in craniofacial morphology and growth of the human face. Traditionally cranial base structures were used to superimpose the lateral cephalogram taken at an interval (or at intervals) to either study the growth of the face and dental arches or evaluate changes due to treatment. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 6

7. The cranial base was considered stable since majority of the growth of the middle cranial base (90–95%) was thought to be completed at 7 years of age. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 7

8. The anatomical anterior cranial base (ACB) extends from foramen caecum to nasion , the middle cranial base from foramen caecum to hypophyseal fossa the posterior cranial base from hypophyseal fossa to foramen magnum. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 8 anterior middle posterior

9. The anterior segment of the cranial base, which extends to a relatively short distance from foramen caecum to nasion , continues to grow into adulthood as a result of growth at bony and frontal sinuses. The posterior segment of the cranial base that extends from hypophyseal fossa to the foramen magnum continues growth into early adulthood as a result of the activity of the spheno -occipital synchondrosis (SOS). Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 9

10. It is the middle segment of the cranial base, which extends from the anterior boundary of the hypophyseal fossa to the foramen caecum anteriorly , and completes its growth earliest in life, reaching 62% of the adult size at birth, 94% between 4 and 7 years of age and 98% of the adult size between 8 and 13 years of age. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 10

11. These structures are internally stable after the fusion of the spheno ethmoid , fronto ethmoid , and inter-sphenoid synchondroses by about 8 years of age. Therefore, these structures were considered as a stable reference for cephalometric superimposition. The points easily identifiable on radiographs and reproducible with accuracy were chosen for superimposition. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 11

12. Cranial Base: Many attempts have been made to overcome the problem of analyzing the growing face in the absence of stable non growing reference lines or anatomic landmarks. Broadbent used the Bolton plane (Bolton point to nasion ) to demonstrate downward and forward growth of the face beneath the cranium. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 12

13. Ricketts elected to use Frankfort plane and pterygoid vertical to create the zero point of a coordinate system. The basic cranial axis ( Ba-nasion ) is used as a baseline for growth analysis. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 13

14. The most widely accepted and most conventional method of assessing overall dento facial change is to superimpose two serial tracings with point registration at sella and the S-Na lines superimposed one over the other. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 14

15. The displacement of nasion up or down during growth at the frontonasal suture cannot be disregarded. Bjork studies however showed that in 90% of cases only a very small changes can be detected, while in the remaining cases, growth changes amounted to +-1mm with only two exceptions where the difference was 2mm. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 15

16. Positional changes resulting from growth or treatment can also be evaluated using a grid system. The system entails superimposing headfilm tracings along the anterior cranial base with sella as a point of registration. The Grid is formed by a line dropped from sella perpendicular to the occlusal plane. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 16

17. Changes in the position of the maxilla and mandible can then be measured in reference to the grid. To evaluate growth/Displacement of the maxilla and mandible and to register movements of upper and lower molars and incisors, Johnson developed Pitchfork analysis. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 17

18. Maxilla Among the most popular superimposing method of maxilla is that of superimposing serial headfilms along the palatal plane from ANS to PNS with the films registered at ANS (McNamara). To more accurately assess maxillary dental changes, Downs recommended that the nasal floor in the headfilms be made to coincide and the tracings registered on the anterior surface of maxilla, thereby eliminating the problem of change in the region of ANS. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 18

19. To eliminate the possible appositional changes at ANS, the Research Workshop on Cephalometrics in 1960 advocated superimposition of the superior and inferior surfaces of Hard palate. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 19

20. Using implants, Doppel et al compared various maxillary superimposition methods and concluded that for clinical purposes the method of maxillary superimposition that most closely approximates implant superimposition is as follows: the anterior and posterior contours of the zygomatic arches are superimposed allowing for the floor of the orbit to be raised more than the palatal plane is lowered in a ratio of 1.5:1 Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 20

21. Mandible To evaluate intramandibular change, the method agreed on by a workshop on cephalometry conducted in 1960 was that of superimposing radiographs along the lower border of the mandible and on the inner table of the symphysis . Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 21

22. Various accepted mandibular planes are: 1. Tangent to the lower border of the mandible. 2. A line extending from gonion to gnathion , both points which are variable. 3. A plane joining gonion to menton , likewise with variable points. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 22

23. Other superimposition method is by Bjork , who uses natural reference structures in the growth analysis of the mandible. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 23

24. By superimposing two radiographic tracings taken at different ages and orienting them with reference to those structures, growth pattern of mandible can be estimated with fairly high degree of accuracy. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 24

25. Pitch fork Analysis Given by Dr. Lysle E.Johnston and presented in the British Journal of Orthodontics 1996. The purpose of this analysis is to describe a method of cephalometric analysis design, that has evolved over the past two decades and which is designed specifically to measure the dental and skeletal effects that combines to produce the occlusal changes that are the goals of treatment. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 25

26. The change in the molar and incisor relationship can be expressed as an exact algebraic sum: Positive= If it reduces overjet / Corrects a class II. Negative= If it increases the overjet . Accordingly, this accounting can support comparisons of change between treatments and between treatment phases, not only with respect to magnitude, but also source( ie skeletal or dental). Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 26

27. The Pitchfork analysis uses Apical base changes (ABCH) ie the sum of maxillary and mandibular translatory growth relative to cranial base. It represents the net effect of skeletal growth , usually the amount that the mandible has outgrown the maxilla. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 27

28. Thus Apical base Changes (ABCH) plus upper and lower molar movement equals the change in molar relationship. Apical base Changes (ABCH) plus upper and lower incisor movement equals change in overjet . Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 28

29. The pitch fork analysis thus requires that the skeletal change is measured as actual physical displacement, rather than apparent change in the position of a landmark due to surface remodeling. Thus measurements must be executed with respect to landmarks that have a good chance of being physically the same at both time points. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 29

30. The present analysis of occlusal change employs three general superimpositions---- a. Cranial base b. Maxilla c. Mandible Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 30

31. Cranial Base Superimposition Sella (S) and Nasion (Na) undergo change by local remodeling during the growth period. However , the literature argues that the bony anatomy from the anterior half of sella turcica to the region of foramen caecum and the internal outline of the frontal bone is suffiently stable to support meaningful anterior cranial base superimposition. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 31

32. Specifically, Bjork and Skieller (1983) suggest that the following “natural reference structures” be employed: a. the anterior wall of sella turcica (and its point of intersection with the lower contours of the anterior clinods ) b. the greater wings of the sphenoid c. the cribriform plate d. the orbital roofs e. the inner surface of the frontal bone. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 32

33. Maxilla Best -fit registration for the maxilla is both the: a. zygomatic process of the maxilla(right and left side averaged). b. on the bony anatomical details superior to the incisors. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 33

34. The superior and inferior surfaces of the posterior hard palate assist in orientation and to minimize the probability of gross errors in antero -posterior registration. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 34

35. Mandible For the purpose of measuring tooth movement relative to basal bone, mandibular regional superimposition commonly is effected via a mandibular and a lingual- symphysis registration. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 35

36. Implant studies, however, suggest that greater validity can he achieved by using the mandibular canal, tooth germs (prior to the initiation of root formation), and the individual bony architecture in the labial aspect of the symphysis ( Bjork and Skicller , 1983: Dibbets , 1990; Fig. 5). Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 36

37. Unfortunately, many of these bony details are often absent, difficult to see, or distorted by among-series variation in head placement. When, as is sometimes the case, nothing seems to match (except, perhaps, bony details within the symphysis ), the mandibular plane can be used as a substitute orientation line, especially if there has been minimal growth between cephalograms . Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 37

38. Indeed, if there has been little change in overall size, any superimposition that seems to show marked growth rotation probably is wrong. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 38

39. The pattern of craniofacial growth Before the measurement of skeletal and dental change is examined, it should be noted that the three superimpositions described here can also be useful in illustrating the overall pattern of growth. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 39

40. When each tracing has been executed in appropriate detail, ' fiducial lines' ( arbitrary straight lines several inches long marked on either end with registration crosses ) are drawn adjacent to cranial base, maxilla, and mandible of one tracing. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 40

41. Once the fiducial lines have been transferred through out the series, they serve not only to record the superimpositions to facilitate the process of measurement (and re-measurement), but also to provide a greatly simplified picture of change seen from the vantage point of any of the three facial areas. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 41

42. When the cranial base fiducial lines are superimposed , the seperation of the mandibular and maxillary fiducial lines represents the translatory growth --- both in amount and angulation --- of the jaws relative to cranial base. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 42 Fiducial lines

43. Measurement of change: Although the face undergoes widespread change during orthodontic treatment, only effects that are felt at the level of the occlusion can have a direct impact on the molar and incisor relationships. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 43

44. The occlusion, therefore, represents the 'bottom line', the site at which change in the upper and lower jaws comes together and is integrated. For this reason, the pitchfork analysis measures change projected onto the plane of occlusion. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 44

45. Accordingly, the pitchfork analysis uses a functional' occlusal plane ( FOP) similar to that suggested by Jenkins ( 1955) and defined as “ the average occlusal plane of the buccal teeth, including canine and first permanent molar· ” Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 45 Functional occlusal plane

46. As used here, Functional Occlusal Plane is 'a best-lit line passing through the occlusal overlap in the region of the first molars, premolars and canines (especially when premolars have been extracted).” 46

47. Thus it is insensitive to incisor movement, it is representative of the bulk of the buccal occlusion, and it is relatively stable over time, although its angulation with respect to cranial base tends to decrease slightly and progressively as the mandible outgrows the maxilla. Unfortunately, the functional occlusal plane also tends to he technically challenging. It can serve as the basis of an analysis of change only if great care is exercised during the execution of the tracings. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 47

48. Firstly, it is important to remember that Functional Occlusal Plane is defined mostly by the premolars and first permanent molars, the second and third molars, and incisors must he ignored. Secondly, the line is placed by inspection. either with respect to the radio-opacities created by cuspal overlap or to the radiolucencies scattered among cusps along the line of the occlusion. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 48

49. When a two-film series is to be analysed the maxilla are superimposed, and the two Functional Occlusal Plane then they are averaged by inspection to yield a Mean Functional occlusal plane (MFOP) which is passed through to each tracing. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 49

50. This averaging is aided, once again, by the use of a lined acetate strip. When change is to be measured in a series of more than two films, the Mean Functional Occlusal Plane is obtained by averaging the initial and final functional occlusal planes. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 50

51. Once the Mean Functional Occlusal Plane has been established and transferred to all tracings in the series, regional superimposition within cranial base, maxilla, and mandible is used to measure the various components of antero -posterior change that make up the tines of the pitchfork. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 51

52. Jaw growth/displacement relative to cranial base In the anterior cranial base, 'wing point' ( W, the point at which the greater wings of the sphenoid crosses jugum sphenoidale ) commonly serves as a registration point and is used here as the cranial-base reference point from which maxillary and mandibular displacement are measured . Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 52

53. To maximize both its validity and reliability, the anterior-cranial-base fiducial line is used to pass W from one tracing through to the others in the series. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 53

54. To measure displacement of the maxilla relative to cranial base (MAX), the maxillary fiducial lines are superimposed and the separation of the W points measured parallel to Mean Functional Occlusal Plane (MFOP) (Figs 3 and 4) Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 54

55. Mandible: The separation of D-points is measured parallel to Mean Functional Occlusal Plane ( MFOP) (Fig. 4). This measurement represents Apical Base Change (ABCH), the growth/displacement of the mandible relative to maxillary basal bone. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 55

56. Since the mandible outgrows the maxilla, ABCH commonly is positive. Whatever its sign (and cause), mandibular displacement relative to cranial base (MAND) then can be estimated by subtraction: MAND = ABCH- MAX. For example, if the maxilla underwent 3 mm of forward translatory growth, and the mandible out-grew it by 4 mm, MAND = 4 - (-3) = 7 mm. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 56

57. These three measurements abstract the sagittal growth of the jaws and, together with tooth movement, account for change in molar relationship and overjet . Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 57

58. Tooth movement relative to basal bone Tooth movement is measured parallel to Mean Functional Occlusal Plane from the vantage point of a superimposition within either the maxilla (Fig. 7) or mandible (Fig. 8) Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 58

59. Molar crown movement is measured at the mesial contact point, root movement from the point at which the long axis is crossed by a line drawn between the apices of the buccal roots. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 59

60. Crown movement is the algebraic sum of root movement and a component due to tipping. Thus, the tipping component can be estimated by subtracting root movement from crown movement. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 60

61. The same procedure can be applied to the incisors; however, it may be less important to resolve separate tipping and bodily effects here than in the molar region. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 61

62. Molar relationship and overjet change' The change in molar relationship is measured by registering on the mesial contact point of one molar (upper or lower) and then measuring the separation of the contact point of the other. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 62

63. the change in overjet , by registering on the averaged incisal edge of the upper or lower incisors and then measuring the displacement of the averaged incisal edge in the other arch (Fig. 9). Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 63

64. Reliability: The reliability of this technique as a whole can he estimated from double-determinations. In past studies of Class II treatment, 5-10 percent of the subjects were selected at random, and their cephalograms retraced and re-measured. Based on Dahlberg's formula Based on Dahlberg's formula may he seen, most standard deviations lie in the regi0n of 0·5-0·7 mm. 64

65. In any event, power calculations based on the present data imply that samples of about 30 have a reasonable probability (say, 80-90 per cent) of resolving treatment effects in the range of 0.5 -1·0 mm. 65

66. Conclusion: This method of Cephalometric analysis is designed to provide an integrated accounting of the source-skeletal growth or tooth movement. Each of the components is measured separately , however as a group they sum to provide a “complete” explanation of changes in overjet and molar relationship . 66

67. References 1. Jacobson A. Radiographic Cephalometry , Quintessence Publishing Co ; 1955 2. Kharbanda OP. Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities,3 rd edition, Elseiver ; 2020 3. Lysle E., Johnston Jr. Balancing the Books on Orthodontic Treatment: An Integrated Analysis of Change . British Journal Of Orthodontics.1996;23:2:93-102 67

68. 68