The Michigan School Study cephalometric norms expressed in template form

The Michigan School Study cephalometric norms expressed in template form Richard J. Ackerman, D.D.S., MS.* Kunsas City, MO.

S

everal lateral cephalometric template norms have been published. Krogman and Sassouni’ extensively reviewed the early work. Recently template norms based on the longitudinal Bolton Child Study were presented by Broadbent, Broadbent, and Golden,’ and Krogman and Walker, according to a personal communication, are preparing templates based on the Philadelphia School Study. The mesh analysis of Moorrees and associates,3 based on data from the Stuart Child Study, is a version of the template principle. Growth forecasting, based on the template principle, is employed by Ricketts4 and Johnston .5 Another major longitudinal growth study, the Michigan School Study, has been published by Rio10 and colleagues.6 In this study tabular and graphic presentation of data is listed at yearly intervals from ages 6 through 16 years for boys and girls, respectively. The purpose of the current endeavor was to construct transparent templates from some of these data for both boys and girls for the years 6, 8, 10, 12, 14, and 16. The project was conducted as a cephalometric workshop for residents in orthodontics and pedodontics at the Medical College of Georgia. Methods Age- and sex-specific mean values from the text, An Atlas of Craniofacial Growth,’ were used in reproducing the following cephalometric landmarks by geometric triangulation (Fig. 1 and 2): Nasion (N). Sella (S). Basion (Ba). Condylion (Co). Articulare (Ar). Gonion (Go).

Menton (Me). Gnathion (Gn). Pogonion (Pog). “B” point (B). Infradentale (Id).

Lingual symphyseal arc (LSA). An arc representing symphyseal width at pogonion. The symphyseal point (the radius of the arc) is located at the intersection of a construction line from pogonion, parallel with the mandibular plane, to the posterior border of the mandibular symphysis. *Associate Professor, East 25th St., Kansas

282

Department of Orthodontics, City, MO. 64108.

University

of Missouri

OaOZ-94l6/79/030282+09$Ot.90/0

School

0

of Dentistry,

1979 The C. V. Mosby

650

Co.

Michigan

Fig. 1. Cephalometric indicate the template

landmarks format.

incorporated

School

in the template

Study

(see

norms

text

in template

for definitions).

----

Fig. 2. Template degrees below

format (see Fig. I. and the text for landmark true horizontal.

definitions).

form

Dotted

TR!,!L

HORIZONTAL

Nasion-sella

283

lines

- -

line is oriented

Lower incisor edge (LIE). Lower incisor axis (LIA) . Lower molar mesial contact (LMC). (permanent first molar). The mesial contact of the mandibular first molar relative to the occlusal plane. Occlusal plane (OP). A construction line drawn between the midpoint of a line

5

connecting the maxillary and mandibular incisal tips and the midpoint oi a line connecting the mesial cusp tips of the upper and lower permanent first molars. Upper molar mesial contact (UMC). Upper incisor edge (UIE). Upper incisor axis (UIA). Supradentale (Sd) . “A” point (A). Anterior nasal spine (ANS). Posterior nasal spine (PNS). Pterygomaxillary fissure, inferior point (Ptm). Ethmoid registration point (ERP). Intersection of the sphenoidal plane with the averaged greater sphenoid wing. The line nasion-sella was oriented at 5 degrees below the true horizontal, and templates were drawn for both boys and girls at the ages of 6, 8, 10, 12, 14, and 16 years. The triangulation sequence is listed in Table I. Each template was drawn with a 5H drafting lead on 0.003 inch acetate tracing film independently by the author and by one orthodontic or pedodontic resident. At each age those drawings that did not superpose identically were drawn again in a blind manner by both persons and superposed a second time. In no instance was it necessary to repeat the procedure a third time. The acetate templates, representative of the published data, were reduced photographically 12 percent to compensate for radiographic enlargement in the midsagittal plane.* For clinical usage, the “zero” enlargement prints were traced and duplicated on transparent film by a diazo technique. 7 Results Templates derived for boys and girls at ages 6, 8, 10, 12, 14, and 16 years are shown in Figs. 3 through 14. Discussion The templates are presented with “zero” magnification at the midsagittal plane to facilitate standardized diagnostic use with any cephalometric equipment. The calibration procedure consists of photographically enlarging each template until the 100 mm. scale on the template is the same size as the image of a 100 mm. scale positioned at the midsagittal plane of the cephalostat projected onto the cephalometric film during x-ray exposure. In the Michigan School Study6 the mean for the angle nasion-sella to Frankfort horizontal plane is between 4 and 6.5 degrees for both sexes at almost all ages. ThurowX found, upon evaluating Downs’g sample of twenty children 14.5 + 2.5 years of age with excellent occlusions and balanced facial profiles, that the nasion-sella line was inclined at an angle of 6 degrees below the Frankfort horizontal plane. In another sample consisting of 100 children Downs” reported that the Frankfort horizontal plane was inclined at a mean angle of 1.3 degrees above true horizontal in children looking straight ahead while standing in repose (natural head position). Downs lo also found that, for the individual, reproducibility of the Frankfort horizontal plane is within 1 to 3 degrees of superimposition when indexed on “true” horizontal. Both of these findings were corroborated in a study by Moorrees and Kean.” *Meyers,

R.E.:

Personal

communication.

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School Study norms in template form

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Table I. Geometric triangulation sequenceused in template construction Landmark NS Ba Me GO

Gn Ar co pots ANS PNS ERP Ptm vertical B Id LIE LIA LSA A Sd UIE

UIA Ptm OP UMC LMC

plane

I

Derivation NS line 5” below true horizontal S-Ba at N-S-Ba angle Intersection of N-Me and Ba-Me Intersection of Me-Go and S-Go S-Gn at N-S-Gn angle Intersection of Go-Ar and N-Ar Intersection of Gn-Co and S-Co Intersection of Go-Pog and S-Pog Intersection of N-ANS and Ba-ANS Intersection of ANS-PNS and S-PNS Intersection of N-ERP and PNS-ERP A line through ERPat ANS-PNSto Ptm vertical planeangle Intersection of S-B and Go-B Intersection of S-Id and Me-Id Intersection of S-LIE and Me-LIE A line through LIE at S-N to LIA angle Peg-LSA Intersection of S-A and Ba-A Intersection of S-Sd and Id-Sd Intersection of S-UIE and ANS-UIE A line through UIE at S-N to UIA angle Intersection of UIE-Ptm and Ptm vertical plane A line through bisection of UIE-LIE at OP-Ptm vertical plane angle Measured from vertical projection of UIE onto OP Measured from vertical projection of LIE onto OP

In deriving the templates presented in the current article, determination of the specific location of the Frankfort horizontal plane (that is, orbitale-porion) was not possible with the data presented in An Atlas of Craniofucial Growth.6 Therefore, on each template nasion-sella was arbitrarily oriented at 5 degrees below a horizontal line passing through nasion. In using the templates as diagnostic overlays, two implications apply to this orientation. First, true horizontal can be substituted for the Frankfort horizontal plane in determining any cephalometric angular measurement. Second, if the lateral cephalogram is taken in natural head position, assessment of nasion-sella normality is possible. The importance of this latter information is apparent if one considers patients in whom the cranial base is high or low relative to nasion; interpretation of any craniofacial landmark in reference to N-S will be affected. In the form of transparent templates, drawings of cephalometric norms can be used as diagnostic aids by laying them directly over lateral head plates on the view box. Persons unfamiliar with template usage will find a checklist helpful (Fig. 15). However, this formal analysis can soon be eliminated as the procedure becomes intuitive. I use the templates as follows: The lateral cephalogram (which was taken in natural head position) is placed on the view box and an appropriate transparent template is superposed on best fit of the entire head. The position of nasion is evaluated. The template is then superposed at nasion in true horizontal position (that is, parallel to the upper and lower edges of the film). The cranial base is evaluated, and an assessment is made of the horizontal and vertical relationships of the maxilla and the mandible. Items noted at this time are upper and lower face height anteriorly and posteriorly, position of mandibular articulation (im-

T

Fig.

Fig. Fig. Fig. Fig. Fig.

3. 4. 5. 6. 7. 8.

Six-year male template. Eight-year male template. Ten-year male template. Twelve-year male template. Fourteen-year male template. Sixteen-year male template.

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School Study norms in template form

. . . . . . . . . . .. . . . . .. . . .. . . .. . . . . . . . . . .

Fig. Fig. Fig. Fig. Fig. Fig.

9. 10. 11. 12. 13. 14.

Six-year female template. Eight-year female template. Ten-year female template. Twelve-year female template. Fourteen-year female template. Sixteen-year female template.

287

CEPHALOMETRIC 7‘hblPLATE ANALYSIS: CHECKLIST OF SUSPECTED DYSPLASIA

Reference

Trait

Superposition #l

Subjective best fit of template

#2 True horizontal indexed at nasion

Template

~

Variation

Discrepancy Between Norm and Headplate (I/)

High

Nasion

LOW

I

i

High Low

i

I

Anterior total face height (N to Me)

Long Short

i

i

Posterior total face height (S or true horizontal to Go)

Long Short

i

i

Upper face height, anterior (N to ANS)

Long Short

i

i

Upper face height, posterior (S-N & ERP or true horizontal to Ptm, PNS)

Long Short

I

i

Cranial

Palatal

base

cant (ANS-PNS)

l

Lower face height, anterior (ANS to Me)

Long Short

Mandibular

Steep Flat

Position

Occlusal

plane (Go-Gn)

( 1 ( 1

High Low Anterior Posterior

of condyle

plane (OP)

Horizontal position of maxilla (Ptm, PNS, ANS, A: best fit collectively)

Anterior Posterior Continued

Fig.

15. Diagnostic

analysis

form.

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School Study norms in template form

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Fig. 15 (Cont’d).

Superposition

#3 Palatal plane (AN.5PNS, Ptm best fit collectively)

#4 Mandibular body (Me, LSA, Go-Gn: best fit collectively)

INTERPRETATION

Trait

Variation

Horizontal position mandible (LSA, Me, B: best fit collectively)

Anterior Posterior

Maxillary dental height, incisors (UIE)

Supraerupted lnfraerupted

Maxillary dental height, molars (OP at UMC)

Supraerupted lnfraerupted

Horizontal position of incisors (UIA)

Bodily forward Bodily back

Inclination of incisors (UN

Proclined Retroinclined

Horizontal position of molars (UMC)

Anterior Posterior

Corpus length (Go-Gn)

Excessive Diminished

Ramus length (Go-AriCo)

Excessive Diminished

Gonial angle (Ar-Go-Me)

Excessive Diminished

Mandibular dental height, incisors (LIE)

Supraerupted lnfraerupted

Mandibular dental height, molars (OP at LMC)

Supraerupted lnfraerupted

Horizontal position of incisors (LIA)

Bodily forward Bodily back

Inclination of incisors VA)

Proclined Retroinclined

Horizontal position of molars (LMC)

Anterior Posterior

Chin (Pog & Gn relative to LSA, Me, B)

Excessive Diminished

OF FINDINGS:

Discrepancy Between Norm and Headplate (4

( ) ( 1

plied from the location of condylion), cant of the palatal plane. cant and level of the occlusal plane, cant of the mandibular plane. horizontal position of the maxilla, and horizontal position of the mandibular symphyseal area. The template is then superposed on the palatal plane and these maxillary features are evaluated: vertical and horizontal position of the anterior alveolar base, vertical and horizontal position and inclination of the incisors, and vertical and horizontal position of the permanent first molars. The template is superposed a fourth time on the mandibular body. indexing in the symphyseal area of the corpus. These mandibular features are then evaluated: corpus length, ramus height, gonial angle, prominence of chin, vertical and horizontal position and inclination of the incisors, and vertical and horizontal position of the permanent first molars. A discussion of the interpretation and implications gleaned from these diagnostic findings is not the intent of the present article. Summary and conclusions User-calibrated cephalometric templates have been presented for boys and girls at the ages of 6, 8, 10, 12, 14, and 16 years. The templates were derived by geometric triangulation from normative data published in An Atlas ofCraniofucial Growth.’ A technique for using the templates diagnostically has also been presented. The author wishesto thank Dr. Ronald M. Lorber and the following orthodontic and pedodontic residents for their assistancein deriving the templates: D. Mark Babcock, Burch G. Cameron, Thomas E. Doyle, JosephM. Greene, Thomas C. Field, John E. Horvath, H. Kenneth Shoaf, III, and Robert M. Willard. Also, I wish to thank Ms. Carole Barber for typing the manuscript. REFERENCES

1. Krogman,W. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

M., and Sassouni, V.: Syllabus in roentgenographic cephalometry, Philadelphia, 1957, Philadelphia Center for Research in Child Growth. Broadbent, B. H., SC., Broadbent, B. H., Jr., and Golden, W. H.: Bolton standards of dentofacial growth, St. Louis, 1975, The C. V. Mosby Company. Moorrees, C. F. A., van Venrooij, M. E., Lebret, L. M. L., Glatky, C. B., Kent, R. L., Jr., and Reed, R. B.: New normsfor the meshdiagramanalysis,AM. J. ORTHOD. 69: 57-71, 1976. Ricketts, R. M.: On growth prediction, J. Clin. Orthod. 9: 340-362, 1975. Johnston, L. E.: A simplified approach to prediction, AM. J. ORTHOD. 67: 253-257, 1975. Riolo, M. L., Moyers, R. E., McNamara, J. A., Jr.. and Hunter, W. S.: An atlas of craniofacial growth, Ann Arbor, 1974, Center for Human Growth and Development, The University of Michigan. Ackerman, R. J., Jr.: Full-scale color transparencies of cephalometric tracings, J. Clin. Orthod. 10: 62-64, 1976. Thurow, R. C.: Atlas of orthodontic principles, St. Louis, 1970, The C. V. Mosby Company, pp. 52-58. Downs, W. B.: Variations in facial relationships: Their significance in treatment prognosis, AM. I. ORTHOD. 34: 812-840, 1948. Downs, W. B.: Analysis of the dentofacial profile, Angle Orthod. 26: 191-212, 1956. Moorrees, C. F. A., and Kean, M. R.: Natural head position, a basic consideration in the interpretation of cephalometric radiographs, Am. J. Phys. Anthropol. 16: 213-234, 1958.