iraqui

J Bagh College Dentistry Vol. 22(3), 2010 Iraqi cephalometric norms

Orthodontics, Pedodontics and Preventive Dentistry 123

Iraqi cephalometric norms using McNamaras analysis Mohammed Nahidh, B.D.S., M.Sc. (1) ABSTRACT Background: This study aimed to establish the cephalometric norms for Iraqis using McNamara's analysis and to verify the existence of sexual dimorphism. Materials and Methods: 75 dental students, (33 males and 42 females) having normal occlusion, were chosen for this study. Each student was subjected to clinical examination and digital true lateral cephalometric X-ray. The radiographs were analyzed using AutoCAD program 2006 to measure the distances and angles. Descriptive statistics was obtained for the measured variables for both genders and independent- samples t-test was performed to evaluate the genders difference. Results and Conclusions: The maxilla is protrusive in males in comparison with females, the effective midface and mandibular lengths, lower facial height are significantly higher in males, and the Frankfort mandibular plane angle is significantly higher in females. The females show retrusive mandibles with slight retrusive upper incisors in comparison with males, while both genders show the same lower incisor position. Key words: McNamara's analysis, cephalometric norms. (J Bagh Coll Dentistry 2010;22(3):123-127). INTRODUCTION

Since the introduction of cephalometrics by Broadbent (1) in 1931, a number of different analyses have been devised such as that of Downs (2-4), Steiner (5-7), Harvold (8) and Ricketts (9-11).

McNamara (12) suggested that a need has arisen for a method of cephalometric analysis that is sensitive not only to the position of the teeth within a given bone but also to the relationship of the jaw elements and cranial base structures one to another because he felt that clinical orthodontics has seen the advent of numerous orthognathic surgery procedures which allow three-dimensional repositioning of almost every bony structure in the facial region and of functional appliance therapy which presents new possibilities in the treatment of skeletal discrepancies. So, in 1984, McNamara (12) introduced his analysis which was derived, in part, from the principles of the cephalometric analyses of Harvold (8) and of Ricketts (9-11), although other aspects, such as the construction of the Nasion perpendicular and the point A vertical, are presumed to be original. He thought that his method of analysis represents an effort to relate teeth to teeth, teeth to jaws, each jaw to the other, and the jaws to the cranial base.

In an effort to create a clinically useful analysis, McNamara (12) divided the craniofacial skeletal complex into five major sections: maxilla to cranial base, maxilla to mandible, mandible to cranial base, dentition, and airway.

(1) Assistant lecturer / Department of Orthodontics, College of Dentistry, University of Baghdad

The purposes of this study were to establish the cephalometric norms for Iraqi adults using McNamaras analysis and to verify the existence of sexual dimorphism. MATERIALS AND METHODS Sample

The sample included under and postgraduate students in the College of Dentistry. The age ranged between 18-33 years. 75 subjects (33 males and 42 females) were selected having normal occlusion, full permanent dentition regardless the third molars, with no history of orthodontic/ oro-facial surgery, facial trauma or deformity. The Instruments 1. Kidney dish. 2. Dental mirrors. 3. Sterilizer (Memmert, Germany).

The Equipments 1. X-Ray Unit (The Planmeca ProMax X-

ray unit) 2. Analyzing Equipments

a) Pentium IV portable computer. b) Analyzing software (AutoCAD 2006).

Method Each student was examined clinically and

subjected to the digital true lateral cephalometric X-ray. The individual was positioned within the cephalostat with the sagittal plane of the head vertical, the Frankfort plane horizontal, and the teeth were in centric occlusion. Every lateral cephalometric radiograph was analyzed by AutoCAD program to calculate the linear and angular measurements. Once the picture was imported to the AutoCAD program, it will appear in the master sheet on which the points



and planes were determined, and then the angular and linear measurements were obtained. The angles were measured directly as they were not affected by magnification, while the linear measurements were divided by scale for each picture to overcome the magnification. Cephalometric Landmarks, Planes, and Measurements Cephalometric Landmarks 1. Point A (Subspinale): The deepest

midline point on the premaxilla between the Anterior Nasal Spine and Prosthion (2).

2. Point S (Sella): The midpoint of the hypophysial fossa (13).

3. Point N (Nasion): The most anterior point on the nasofrontal suture in the median plane (13).

4. Point Cd (Condylion): The most posterosuperior point on the outline of the mandibular condyle (12).

5. Point Pog (Pogonion): It is the most anterior point on the mandible in the midline (2).

6. Point Gn (Gnathion): A point located by taking the midpoint between Pogonion and Menton points of the bony chin (14).

7. Point Me (Menton): The lowest point on the symphyseal shadow of the mandible seen on a lateral cephalograms (14).

8. Point Go (Gonion): A point on the curvature of the angle of the mandible located by bisecting the angle formed by the lines tangent to the posterior ramus and inferior border of the mandible (14).

9. Point ANS (Anterior Nasal Spine): It is the tip of the bony anterior nasal spine in the median plane (13).

10. Point Or (Orbitale): The lowest point on the inferior rim of the orbit (14).

11. Point Po (Porion): The most superiorly positioned point of the external auditory meatus (14).

12. Point Ba (Basion): The lowest point on the anterior margin of the foramen magnum in the median plane (13).

13. Posterosuperior aspect of the pterygomaxillary fissure (PTM) (12).

Cephalometric Planes 1. Mandibular plane (MP): Formed by a

line joining Gonion and Menton (13). 2. Sella-Nasion (SN) plane: It is the

anteroposterior extent of anterior cranial base, formed by a line joining Sella turcica and Nasion (13).

3. N-A plane: Formed by a line joining points A and N (13).

4. Frankfort plane: A line passing through the points Porion and Orbitale (14).

5. Nasion- Basion (N-Ba) plane: A line from Nasion to Basion (9).

6. Nasion perpendicular (NP) line: A vertical line drawn from Nasion perpendicular to Frankfort horizontal (12).

7. A-Pog line: A line drawn from point A to Pogonion (2).

8. PNP line: A vertical line drawn through point A parallel to the Nasion perpendicular (12).

9. A line from posterosuperior aspect of the pterygomaxillary fissure (PTM) to Gnathion (12).

Cephalometric Measurements The cephalometric measurements below

were obtained according to McNamara (12): 1. Maxilla to cranial base

o Nasion Perpendicular to point A (NP-A): The perpendicular distance between Nasion perpendicular and point A. An anterior position of point A is a positive, and a posterior position is a negative value.

o SNA angle: The angle between lines S-N and N-A. It represents the angular anteroposterior position of the maxilla to the cranial base.

2. Maxilla to Mandible o Effective mid-facial length (Co-A): The

length from Condylion to point A. o Effective mandibular length (Co-Gn):

The length from Condylion to Gnathion. o Maxillomandibular differential (MM

difference): The mid-facial length is subtracted from the mandibular length.

o Lower anterior face height (LAFH): The distance from ANS to Menton.

o Mandibular plane angle (FMA): The angle between anatomic Frankfort horizontal and the line drawn along the lower border of the mandible through Gonion and Menton.

o Facial axis angle (FAA): The angle formed by line constructed from the posterosuperior aspect of the pterygomaxillary fissure (PTM) to Gnathion relative to the cranial base, which is represented by a line joining Basion to Nasion.

3. Mandible to cranial base o Pogonion to Nasion perpendicular (Pog-

NP): The perpendicular distance between Pogonion and Nasion perpendicular. An anterior position of



Pogonion is a positive value and posterior position is negative value.

4. Dentition o Upper incisor to point A (U1-PNP): The

perpendicular distance between the facial surface of the upper incisor and the line passing through point A parallel to N-perpendicular (PNP line).

o Lower incisor to A-Pog plane (L1-A-Pog): The perpendicular distance between the facial surface of the lower incisor and the point A- Pogonion plane.

Statistical Analysis All the data of the sample were subjected

to computerized statistical analysis using SPSS version 15 (2006) computer program. The statistical analysis included: 1. Descriptive Statistics; mean, standard

deviation (SD) and statistical tables. 2. Inferential Statistics; independent-

samples t-test for the comparison between both genders.

In the statistical evaluation, the following levels of significance are used:

P > 0.05 NS Non-significant 0.05 P > 0.01 * Significant 0.01 P > 0.001 ** Highly significant

P 0.001 *** Very highly significant RESULTS

Table 1 showed the descriptive statistics and genders difference. For ease the measurements were divided into 4 major groups: 1. Maxilla to cranial base

The mean value of the measurements relating the maxilla to the cranial base are higher in males than in female with a highly significant difference between both genders regarding SNA angle and non-significant difference regarding NP point A. 2. Maxilla to Mandible

In all of the measurements representing the relation between the maxilla to mandible in McNamara's analysis, the males showed significantly higher mean values than females except for FMA when the mean value of this angle is higher significantly in females. On the other hand, the facial axis angle is higher in males with a non-significant difference. 3. Mandible to cranial base

The females showed higher mean value of Pogonion to Nasion perpendicular than males with a non-significant difference between both genders.

4. Dentition The mean value of position of upper

incisor relative to PNP is insignificantly higher in males than females, while the position of lower incisor relative to A-Pog line is the same in both genders with a non-significant difference. DISCUSSION

Odeh (15) stated that cephalometric values for the Iraqi population are yet to be investigated and the international values available may not necessarily apply to Iraq.

In 1991, Al-Sahaf (16) conducted a lateral cephalometric study to evaluate the Iraqi cephalometric norms and investigate the growth pattern in a sample of 380 school boys and girls aged from 9 to 17 years. She did not depend on one analysis, but she took 7 angular and 7 linear measurements and obtained the norms for Iraqis.

Al-Dawoody (17) established the Iraqi cephalometric norms in the adolescents of the Mosul city using Downs and Steiner's analyses, while Al-Tamimy (18) established the Iraqi cephalometric norms in a sample aged 8-10 year old using Ricketts analysis.

There are some studies conducted to establish the cephalometric norms using McNamaras analysis in different countries, and others compare their results with McNamaras norms (19-21). In Iraq, this is the first study that establishes the Iraqi cephalometric norms using McNamaras analysis.

As mentioned in the results, for ease the measurements were divided into 4 major groups: 1. Maxilla to cranial base

The results indicated that the maxilla is prognathic in males when compared with females; this comes in agreement with McNamara (12). In comparison with other population, Miyajima et al. (19) reported nearly a similar mean values for both measurements in both genders while Wu et al. (20) and Al-Barakati and Talic (21) reported a relatively retrusive maxillary position in comparison with McNamara (12), Miyajima et al. (19) and the present study and this may attributed to the difference in the ethnic group (Table 2). 2. Maxilla to Mandible

Regarding the effective midface and mandibular lengths and lower facial height, the measurements are higher significantly in males than females; this comes in agreement with many researches (12,19-21). On the other hand, these measurements are less than of McNamara (12) and Miyajima et al. (19) for Caucasian and Japanese respectively, and Al-Barakati and Talic (21) for



Saudi sample while they are higher than that of Wu et al. (20) due to the age factor.

The inclination of the mandibular plane to the Frankfort plane is significantly higher in females in comparison with males; this comes in agreement with the previous findings (12,19,21).

The mean value of the facial axis angle is insignificantly higher in males than females and this comes in agreement with Miyajima et al. (19). The higher mean values of lower anterior facial height and facial axis angle indicated that the males have tendency towards excessive vertical development of the face. 3. Mandible to cranial base

The results indicated that the females showed more retrusive mandible than males although it is insignificant; this comes in agreement with McNamara (12) and Miyajima et al. (19) for Caucasian and Japanese respectively, on the other hand, they are less than of Wu et al. (20) and Al-Barakati and Talic (21) who reported a relatively retrusive mandibular position in males. 4. Dentition

The upper incisors showed insignificant proclination in males more than females; this agrees with Al-Barakati and Talic (21) and disagrees with McNamara (12), Miyajima et al. (19) and Wu et al. (20) who reported a nearly similar mean values.

The lower incisors showed nearly the same position in both sexes with a non-significant difference and this agrees with McNamara (12) and Wu et al. (20), while disagrees with Miyajima et al. (19) whose female sample showed more protrusive incisors and Al-Barakati and Talic (21) who reported more lower incisor proclination in males in comparison with females.

Generally, the lower incisors are more protrusive in the present study in comparison with McNamara (12). REFERENCES 1. Broadbent BH. A new X-ray technique and its

application to orthodontia. Angle Orthod 1931; 1(2): 45-66.

2. Downs WB. Variations in facial relationship: their significance in treatment and prognosis. Am J Orthod 1948; 34(10): 812-40.

3. Downs WB. The role of cephalometrics in orthodontic case analysis and diagnosis. Am J Orthod 1952; 38(3): 162-82.

4. Downs WB. Analysis of the dentofacial profile. Angle Orthod 1956; 26(4): 191-212.

5. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953; 39(10): 729-55.

6. Steiner CC. Cephalometrics in clinical practice. Angle Orthod 1959; 29(1): 8-29.

7. Steiner CC. The use of cephalometrics as an aid to planning and assessing orthodontic treatment. Am J Orthod 1960; 46(10): 721-35.

8. Harvold EP. The activator in interceptive Orthodontics. 1st ed. St. Louis: The C. V. Mosby Company; 1974. p. 41-56.

9. Ricketts RM. The influence of orthodontic treatment on facial growth and development. Angle Orthod 1960; 30(3): 103-33.

10. Ricketts RM, Bench RW, Hilgers JJ, Schulhof R. An overview of computerized cephalometrics. Am J Orthod 1972; 61(1): 1-28.

11. Ricketts RM. Perspectives in the clinical application of cephalometrics. Angle Orthod 1981; 51(2): 115-50.

12. McNamara JA Jr. A method of cephalometric evaluation. Am J Orthod 1984; 86(6): 449-69.

13. Rakosi T. An atlas and manual of cephalometric radiography. 2nd ed. London: Wolfe medical publications Ltd.; 1982. p. 35, 40-1.

14. Caufield PW. Tracing technique and identification of landmarks. In Jacobson A (ed). Radiographic cephalometry from basics to videoimaging. 1st ed. Chicago: Quintessence publishing Co.; 1995. p. 60-1.

15. Odeh FD. Assessment of jaw and dental relationship by the use of lateral skull radiographic cephalometry. Iraqi Dent J 1983; 10: 72-82.

16. Al-Sahaf NH. Cross - sectional study of cephalometric standards and associated growth changes. A master thesis, Department of Pedodontics, Orthodontics, and Preventive Dentistry, University of Baghdad, 1991.

17. Al-Dawoody AD. Cephalometric standards for Iraqi adolescents in Mosul city using Downs and Steiner's analyses. A master thesis, Department of Pedodontics, Orthodontics, and Preventive Dentistry, University of Mosul, 2001.

18. Al-Tamimy EA. The reliability of Ricketts' analysis using cephalometric tracing on Iraqi sample aged 8-10 year. Mustansiria Dent J 2006; 3(2): 159-68.

19. Miyajima K, McNamara JA Jr, Kimura T, Murata S, Iizuka T. Craniofacial structure of Japanese and European-American adults with normal occlusions and well-balanced faces. Am J Orthod Dentofac Orthop 1996; 110(4): 431-8.

20. Wu J, Hgg U, Rabie ABM. Chinese norms of McNamara's cephalometric analysis. Angle Orthod 2007; 77(1): 1220.

21. Al-Barakati SF, Talic NF. Cephalometric norms for Saudi sample using McNamara analysis. Saudi Dent J 2007; 19(3): 139-45.



Table 1: Descriptive statistics and genders difference

Descriptive statistics Genders difference d.f.= 73 Male (N=33) Female (N=42) Variables Mean S.D. Mean S.D.

t-test p-value

NP-A (mm) 1.6 2.87 0.67 2.4 1.53 0.12 (NS) SNA (degree) 83.75 3.29 81.8 3.02 2.72 0.008 ** Co-Gn (mm) 121.37 5.2 111 4.47 9.03 0.000 *** Co-A (mm) 93.22 3.95 85.5 3.18 9.32 0.000 *** MM difference (mm) 28.15 3.53 25.7 3.34 3.02 0.003 ** LAFH (mm) 68.75 4.89 63.4 4.42 4.97 0.000 *** FMA (degree) 21.69 3.71 23.9 4.81 -2.19 0.03 * FAA (degree) -0.61 3.28 -0.19 3.91 -0.48 0.62 (NS) Pog-NP (mm) -0.09 4.45 -1.44 5.0 1.21 0.22 (NS) U1-PNP (mm) 6.44 2.34 5.91 1.66 1.15 0.25 (NS) L1-A-Pog (mm) 3.99 2.25 4.01 1.69 -0.03 0.97 (NS)

Table 2: The mean values of the variables comprising the McNamara's analysis in different

populations

Author (s) McNamara (12) Miyajima et al.(19) Wu et al. (20) Al-Barakati and Talic (21) Present study

Year 1984 1996 2007 2007 2010 Age Adults Adults 12 years Adults Adults

Country USA Japan China Arabia Saudi Iraq Sex Male Female Male Female Male Female Male Female Male Female

Number 38 73 26 28 200 205 36 29 33 42 NP-A (mm) 1.1 0.4 2.5 2.3 -0.75 -0.53 -2 -0.2 1.6 0.67 SNA (degree) 83.9 82.4 82.2 82.1 81.78 81.97 - - 83.75 81.8 Co-Gn (mm) 134.3 120.2 125.5 118.8 113.95 113.32 133.4 124.9 121.37 111 Co-A (mm) 99.8 91 91.4 86.3 87.90 85.93 101.7 98.2 93.22 85.5 MM diff. (mm) 34.5 29.2 34.1 32.5 26.06 27.39 31.8 26.8 28.15 25.7 LAFH (mm) 74.6 66.7 75.1 72.7 66.14 64.39 76.1 68.9 68.75 63.4 FMA (degree) 21.3 22.7 22.3 26.1 27.81 26.10 24.9 25 21.69 23.9 FAA (degree) 0.5 0.2 -4.2 -3.5 -5.51 -3.83 2.8 2.9 -0.61 -0.19 Pog-NP (mm) -0.3 -1.8 0.3 -1.7 -7.45 -4.88 -6.1 -5.9 -0.09 -1.44 U1-PNP (mm) 5.3 5.4 5.7 6 7.34 7.86 6.2 4.3 6.44 5.91 L1-A-Pog (mm) 2.3 2.7 4 4.9 6.35 6.26 4.4 3.6 3.99 4.01

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