A Comparative Study of Cephalometric ...

10.5005/jp-journals-10021-1014

ORIGINAL ARTICLE Neha Agarwal et al

A Comparative Study of Cephalometric Measurements with Digital versus Manual Methods 1

Neha Agarwal, 2Dinesh K Bagga, 3Payal Sharma

ABSTRACT Objective: To evaluate the accuracy of measurements obtained with a digital cephalometric software program. Materials and methods: Digital photographs of 32 cephalograms were imported into the Nemotec digital imaging software. Digital measurements of 41 hard and soft tissue variables generated by the software were compared to those obtained by manual tracings. Reproducibility for each method was assessed using Pearson's correlation coefficient by repeating measurements of all radiographs at an interval of 3 months. A paired t-test was used to detect differences between the manual and digital methods. Results: Both the methods demonstrated a high correlation (r > 0.7) between the first and second measurements indicating good reproducibility. SN-Occ, anterior cranial base length, posterior cranial base length, nasolabial angle, facial height and lower lip length showed clinically significant differences between the measurements obtained from digital and manual methods. Conclusion: Digital measurements obtained with the Nemotec digital imaging software using digital photographs of analog cephalograms were found to be reproducible and comparable to the manual method for most of the variables used in clinical practice except a few which could not be measured accurately with the digital method. Keywords: Cephalometric measurements, Digital imaging, Cephalometric software. How to cite this article: Agarwal N, Bagga DK, Sharma P. A Comparative Study of Cephalometric Measurements with Digital versus Manual Methods. J Ind Orthod Soc 2011;45(2):84-90.

INTRODUCTION Cephalometrics has played a vital role in orthodontic diagnosis and treatment planning and for monitoring treatment and growth changes. Cephalometric analysis performed manually using a tracing sheet on the radiograph is the oldest and the most widely used method. Although radiographic film is quite stable and can retain its information for many years, it is not always a dependable archive medium due to its physical nature.1 Film deterioration has been a major source of information loss in craniofacial biology.2 Digital imaging offers several advantages over conventional film-based radiography: Faster data processing, elimination of chemicals and associated environmental hazards and the ability to alter and improve the image to correct for exposure errors, thus virtually eliminating the need for a second exposure.3

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Postgraduate Student, 2Professor and Head, 3Professor

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Department of Orthodontics and Dentofacial Orthopedics, ITS Center for Dental Studies and Research, Ghaziabad, Uttar Pradesh India Corresponding Author: Neha Agarwal, Postgraduate Student Department of Orthodontics and Dentofacial Orthopedics, ITS Center for Dental Studies and Research, Muradnagar, Delhi-Meerut Road Ghaziabad-201206, Uttar Pradesh, India

Received on: 19/01/11 Accepted after Revision: 27/04/11

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Digital radiographic images are easy to store and facilitate communication. They also require lower levels of radiation.4 Numerous digital cephalometric software programs have been introduced like AO Ceph, Quick Ceph 2000, Dolphin, etc. First generation computer-based analysis systems used digitizer pads for tracing conventional cephalometric films and software programs to compute the measurements. Second generation systems used scanners or digital cameras to export cephalometric images to measurement programs. The third generation systems acquired the digital image by two methods— a charged couple device (direct digitization), where the digital image is produced instantaneously and storage phosphor plates (indirect digitization) to capture the film. But the devices required in both the methods were expensive. Computerized cephalometric analysis may use either a manual or automatic identification of landmarks. Automated systems at present are unable to compete with manual identification in terms of accuracy of landmark position. The landmarks lying on poorly defined structures are difficult to automatically identify due to poor signal-to-noise ratio.5 Earlier studies have shown that computer-aided cephalometric analysis does not introduce more measurement error than hand tracing, as long as landmarks are identified manually.6 Therefore, manually identifying landmarks on screen-displayed digital images for cephalometric analysis may still be the better strategy. For digital cephalometry to be a better tool in clinical orthodontics, the cephalometric analysis, represented by widely JAYPEE

JIOS A Comparative Study of Cephalometric Measurements with Digital versus Manual Methods

used linear and angular measurements, must be as comparable and reliable as it is on a conventional radiographic film. The objectives of the present study were to evaluate the accuracy of digital measurements obtained with a cephalometric software program and compare them to manual measurements from the traditional hand-traced method.

apart. All measurements were automatically calculated by the tracing software. The following cephalometric measurements were obtained:

MATERIALS AND METHODS

Rakosi-Jarabak Analysis

Thirty-two pretreatment cephalometric radiographs of adequate diagnostic quality with identifiable craniofacial structures and landmarks were selected for the study (Fig. 1). The cephalometric analysis was done by two methods: 1. Manual 2. Digital

1. Saddle angle (N-S-Ar) 2. Articular angle (S-Ar-Go) 3. Gonial angle (Ar-Go-Me).

Manual Method Each lateral cephalogram was traced using a 0.3 mm lead pencil on an acetate matte tracing paper, 0.003 inch × 8 inch × 10 inch. The tracings were done on a view box with the tracing paper securely positioned over the radiograph with a masking tape. Both midline and bilateral images were traced, with all bilateral images bisected and, thereafter, treated as midline structures. All linear measurements were rounded to the nearest 0.5 mm and angular measurements to the nearest 0.5°. Digital Method The digital image of each cephalogram was acquired using a digital camera (SONY DSC H50, 9.1 Megapixel) after taping it to the view box. The images were imported to the Nemotec digital imaging software (version 6.0) and the cephalometric landmarks were identified on the displayed image by using a mouse controlled cursor linked to the tracing software (Fig. 2). The image enhancement features of the software, like brightness, contrast adjustment and magnification were used as needed to identify individual landmarks as precisely as possible. The images were calibrated by identifying two crosshairs 10 mm

Hard Tissue Measurements Angular Measurements

Steiners Analysis 1. 2. 3. 4. 5. 6. 7. 8.

SNA angle SNB angle ANB angle U1 to NA L1 to NB Interincisal angle SN-mandibular plane angle (SN-GoGn) SN-occlusal plane angle.

Downs Analysis 1. Facial angle (FH-N-pog) 2. Angle of convexity (N-ptA to A-pog). Tweeds Analysis 1. FMA 2. IMPA 3. FMIA. Linear Measurements Rakosi-Jarabak Analysis 1. Anterior cranial base length (Se-N) 2. Posterior cranial base length (S-Ar).

Fig. 1: Cephalometric landmarks taken into consideration for the study

The Journal of Indian Orthodontic Society, April-June 2011;45(2):84-90

Fig. 2: Lateral cephalogram with digital tracing

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Steiners Analysis

Statistical Analysis

1. U1 to NA 2. L1 to NB.

Intraexaminer error was evaluated by repeating tracings of all radiographs (performed 3 months apart) and using the Pearson’s correlation coefficient as a measure of standardized covariance. Systematic error (differences in measurements related to the methods investigated) was calculated by using paired t tests based on equality of variance between the digital and manual tracings. A p-value of 0.05 was used as the minimal level of statistical significance.

Downs Analysis U1 to A-Pog Ratios 1. Jarabak ratio—Posterior facial height (S-Go) × 100: Anterior facial height (N-Me) 2. UAFH (N-ANS)/LAFH (ANS-Me). Soft Tissue Measurements Angular Measurements

RESULTS Table 1 shows that the correlations between first and second observations were strong (r > 0.7) for both the methods showing good reproducibility of measurements due to minimal intraexaminer variability.

Arnett-Bergman Analysis Hard Tissue Measurements 1. Nasolabial angle 2. Upper lip angle 3. Angle of convexity. Linear Measurements Arnett-Bergman Analysis 1. Upper lip thickness 2. Lower lip thickness 3. Chin thickness (Pog-Pog´) 4. Facial height (N´-Me´) 5. Upper lip length (Sn-upper lip inferior) 6. Lower lip length (lower lip superior –Me´) 7. Maxillary height (Sn-maxillary incisor tip) 8. Mandibular height (mandibular incisor tip-Me´) 9. TVL-Pog´ 10. TVL-Nasal projection 11. TVL-Point A´ 12. TVL-Point B´ 13. TVL-Glabella. Ratios 1. Upper lip –lower lip length ratio 2. UAFH (G-Sn)/LAFH (Sn-Me´). The digital measurements obtained with the cephalometric software were compared to those of the manual method. Method of Determining Accuracy The accuracy of the measurements obtained by the digital method would be considered acceptable provided they met the following conditions:7,8 1. The intraclass correlation coefficient, r > 0.75, which would show good reproducibility of the method 2. Mean measurement differences between digital and manual methods were less than 2 units (1 unit = 1 mm for linear measurements and 1° for angular measurements). 86

Table 2 shows that the saddle angle, articular angle, SNB, L1-NB, interincisal angle, facial angle and FMA did not show statistically significant differences between the digital and manual methods, but gonial angle, SNA, ANB, U1-NA, SNGoGn, SN-Occ, angle of convexity, IMPA and FMIA showed significant differences in the two methods. The linear measurements for the anterior cranial base, posterior cranial base, U1-NA and U1-A-Pog were found to be significantly different in the two methods except L1-NB which showed no statistically significant difference. For both the hard tissue ratios, Jarabak ratio and UAFH/ LAFH, the differences between the two methods were found to be statistically significant. Soft Tissue Measurements Table 3 shows that the difference between the measurements by the two methods was found to be statistically significant for the angular variables of nasolabial angle and angle of convexity, whereas no difference was seen in upper lip angle. Statistically, significant differences in the linear measurements of upper lip thickness, facial height, upper lip length, lower lip length, maxillary height, mandibular height, TVLnasal projection and TVL -Point A’ were observed. No statistically significant difference was seen in lower lip thickness, chin thickness, TVL-Pog´, TVL-Point B´ and TVLGlabella. A statistically significant difference between the measurements by the two methods was seen for the soft tissue ratio UAFH/LAFH. No statistically significant difference was seen in UL/LL. Table 4 shows that saddle angle, articular angle, SNB, ANB, U1-NA, L1-NB, interincisal angle, facial angle, FMA, U1-NA (linear), L1-NB (linear), U1-APog, Jarabak ratio, UAFH/LAFH, upper lip angle, lower lip thickness, chin thickness, TVL-Pog´, TVL-point A´, TVL-Glabella showed measurement differences

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JIOS A Comparative Study of Cephalometric Measurements with Digital versus Manual Methods Table 1: Reproducibility of measurements for manual and digital methods S. no.

Parameter

Manual Difference* (mean ± SD)

Digital Correlation coefficient

Difference* (mean ± SD)

Correlation coefficient

Hard tissue measurements 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Saddle angle Articular angle Gonial angle SNA angle SNB angle ANB angle U1-NA L1-NB Interincisal angle SN-GoGn SN-Occ Facial angle Angle of convexity FMA IMPA FMIA Ant. cranial base Post. cranial base U1-NA L1-NB U1 to A-Pog Jarabak ratio UAFH/LAFH ratio

0.03 ± 1.03 –0.06 ± 1.10 –0.15 ± 0.98 –0.09 ± 0.96 –0.31 ± 0.96 0.21 ± 1.36 –0.31 ± 0.93 –0.21 ± 0.94 –0.09 ± 0.99 0.12 ± 1.00 –0.28 ± 0.95 –0.21 ± 0.97 –0.12 ± 0.97 –0.18 ± 0.96 –0.18 ± 0.96 0.37 ± 1.40 –0.5 ± 0.80 –0.18 ± 0.99 0.12 ± 1.00 –0.12 ± 0.97 0 ± 1.00 –0.18 ± 0.64 –0.01 ± 0.03

0.98 0.99 0.99 0.92 0.95 0.86 1.00 0.99 1.00 0.99 0.98 0.97 0.98 0.99 0.99 0.99 0.98 0.98 0.97 0.97 0.98 0.99 0.85

–0.13 ± 0.64 –0.2 ± 0.48 0.05 ± 0.58 0.07 ± 0.51 –0.06 ± 0.51 0.01 ± 0.94 –0.18 ± 0.5 –0.05 ± 0.37 0.03 ± 0.53 –0.21 ± 0.43 0.01 ± 0.46 –0.1 ± 0.43 –0.3 ± 0.33 –0.2 ±0.42 –0.37 ± 0.45 –0.6 ± 0.43 –0.33 ± 0.53 –0.35 ± 0.27 –0.2 ± 0.28 –0.23 ± 0.26 –0.25 ± 0.33 –0.11 ± 0.51 –0.02 ± 0.07

0.99 1.00 1.00 0.98 0.99 0.94 1.00 1.00 1.00 1.00 0.99 0.99 1.00 1.00 0.97 0.97 0.99 1.00 1.00 1.00 1.00 1.00 0.86

–0.17 ± 0.39 –0.15 ± 0.44 –0.12 ± 0.33 0.02 ± 0.39 0.01 ± 0.44 0.01 ± 0.36 –0.05 ± 0.43 –0.15 ± 0.36 –0.21 ± 0.31 –0.18 ± 0.36 –0.22 ± 0.27 0.14 ± 0.25 –0.1 ± 0.26 –0.003 ± 0.32 –0.02 ± 0.44 0.09 ± 0.39 –0.009 ± 0.09 –0.01 ± 0.03

1.00 1.00 1.00 0.98 0.97 0.97 1.00 0.99 1.00 0.99 1.00 1.00 1.00 0.98 1.00 0.99 0.94 0.85

Soft tissue measurements 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Nasolabial angle Angle of convexity Upper lip angle Upper lip thickness Lower lip thickness Chin thickness Facial height Upper lip length Lower lip length Maxillary height Mandibular height TVL-Pog´ TVL-nasal projection TVL-point A´ TVL-point B´ TVL-glabella UAFH/LAFH UL/LL

–0.500 ± 0.84 –0.219 ± 0.94 –0.31 ± 0.93 0.06 ± 0.94 –0.21 ± 0.9 –0.28 ± 0.95 –0.31 ± 0.93 –0.65 ± 0.7 –0.43 ± 0.87 –0.12 ± 0.97 –0.56 ± 0.75 0.37 ± 0.94 –0.21 ± 0.94 0.07 ± 0.96 –0.01 ± 0.97 0.37 ± 0.89 –0.03 ± 0.057 –0.01 ± 0.02

1.00 0.99 0.99 0.92 0.89 0.79 0.99 0.95 0.97 0.94 0.98 0.99 0.91 0.75 0.98 0.98 0.88 0.91

*Difference between two duplicate measurements r > 0.9—almost perfect correlation; r > 0.7—strong correlation; 0.5 < r > 0.7—moderate correlation; 0.3 < r > 0.5—mild correlation

of less than one unit. The parameters with measurement differences between 1 and 2 units were gonial angle, SNA, SN-GoGn, angle of convexity, IMPA, angle of convexity (soft tissue), TVL-nasal projection, TVL-B´, FMIA, upper lip thickness, maxillary height and mandibular height. The parameters showing measurement differences of less than 2 units have fair degree of accuracy to be clinically acceptable. The parameters showing measurement differences of more than two units by the two methods were: I. Hard tissue parameters: 1. SN-Occ angle 2. Anterior cranial base length 3. Posterior cranial base length.

II. Soft tissue parameters: 1. Nasolabial angle 2. Facial height 3. Lower lip length. DISCUSSION 15 out of 23 hard tissue measurements showed statistically significant differences in the digital and manual methods. A majority of these measurements depend on landmarks, such as articulare, gonion, porion, menton, gnathion, orbitale and point A, which lie on poorly defined outlines or low contrast areas. Previous studies by Houston et al,9 Gregston et al10 and Santoro et al11 on manual and computerized methods have found


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Neha Agarwal et al Table 2: Comparison of hard tissue cephalometric measurements obtained by manual and digital methods using student’s t test S.no.

Parameter

Manual (mean ± SD) Digital (mean ± SD)

Difference (mean ± SD) t-value

p-value

Angular measurements 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Saddle angle Articular angle Gonial angle SNA angle SNB angle ANB angle U1-NA L1-NB Interincisal angle SN-GoGn SN-Occ Facial angle Angle of convexity FMA IMPA FMIA

124.78 ± 5.52 144.34 ± 7.29 121.03 ± 7.90 83.19 ± 2.31 79.00 ± 3.16 4.19 ± 2.68 27.81 ± 10.58 28.50 ± 7.52 118.44 ± 17.12 28.13 ± 6.35 19.34 ± 4.56 85.88 ± 3.88 7.13 ± 5.37 25.28 ± 5.58 98.78 ± 7.69 54.94 ± 8.98

124.56 ± 5.64 145.10 ± 7.43 119.88 ± 8.31 84.38 ± 2.81 79.16 ± 3.63 5.09 ± 2.68 26.85 ± 10.34 29.29 ± 7.53 118.45 ± 16.97 29.49 ± 6.15 22.97 ± 3.45 86.18 ± 3.41 8.61 ± 5.56 25.59 ± 5.54 99.98 ± 8.34 53.43 ± 8.84

0.23 ± 2.36 –0.76 ± 2.35 1.15 ± 2.51 –1.19 ± 1.91 –0.16 ± 1.32 –0.91 ± 1.24 0.97 ± 2.44 –0.79 ± 2.67 –0.02 ± 2.53 –1.37 ± 2.10 –3.63 ± 2.74 –0.31 ± 2.74 –1.48 ± 2.15 –0.31 ± 2.67 –1.2 ± 3.09 1.51 ± 3.94

0.540 – 1.827 2.587 –3.532 –0.683 –4.143 2.236 –1.682 –0.035 –3.671 –7.493 –0.640 –3.900 –0.662 –4.016 3.599

0.593 0.077 0.015** 0.001*** 0.500 < 0.001*** 0.033* 0.103 0.972 0.001*** < 0.001*** 0.527 < 0.001*** 0.513 < 0.001*** 0.001***

3.29 ± 1.70 2.86 ± 1.96 0.90 ± 2.09 0.04 ± 1.37 0.53 ± 1.15

10.95 8.264 2.432 0.180 2.587

< 0.001*** < 0.001*** 0.021** 0.858 0.015**

–0.56 ± 1.12 –0.03 ± 0.08

–2.804 –2.118

0.009** 0.042*

Linear measurements 1. 2. 3. 4. 5.

Ant cranial base Post cranial base U1-NA L1-NB U1 to A-Pog

73.38 ± 4.2 37.50 ± 4.91 7.66 ± 7.66 7.63 ± 3.75 9.84 ± 5.05

70.08 ± 4.2 34.64 ± 4.91 6.76 ± 3.95 7.58 ± 3.75 9.32 ± 5.05 Ratios

6. 7.

Jarabak ratio UAFH/LAFH

68.47 ± 5.64 0.79 ± 0.06

69.03 ± 5.63 0.82 ± 0.09

NS—not statistically significant; *p < 0.05—significant; **p < 0.01—very significant; ***p < 0.001—most significant

Table 3: Comparison of soft tissue measurements obtained by manual and digital methods using student’s t test S.no.

Parameter

Manual (mean ± SD)

1. 2. 3.

Nasolabial angle Angle of convexity Upper lip angle

103.28 ± 16.12 18.03 ± 5.88 15 ± 8.95

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Upper lip thickness Lower lip thickness Chin thickness Facial height Upper lip length Lower lip length Maxillary height Mandibular height TVL-Pog´ TVL-nasal projection TVL-point A´ TVL-point B´ TVL-glabella

1. 2.

UAFH/LAFH UL/LL

Digital (mean ± SD)

Difference (mean ± SD)

t-value

p-value

–3.67 ± 2.38 –1.08 ± 2.33 0.95 ± 3.14

–8.707 –2.612 1.707

< 0.001*** 0.014** 0.098

1.74 ± 1.68 –0.64 ± 2.08 0.12 ± 1.40 4.04 ± 3.57 1.78 ± 1.44 3.65 ± 2.61 1.53 ± 1.49 1.66 ± 2.44 –0.54 ± 1.57 1.17 ± 1.84 –0.63 ± 1.04 –1.03 ± 6.26 0.53 ± 1.68

5.850 –1.750 0.479 6.404 7.017 7.920 5.825 3.854 –1.948 3.583 –3.422 –1.831 1.768

< 0.001*** 0.090 0.636 < 0.001*** < 0.001*** < 0.001*** < 0.001*** 0.001*** 0.061 0.001*** 0.002*** 0.077 0.087

–0.06 ± 0.07 –0.01 ± 0.03

–5.270 –1.284

< 0.001*** 0.209

Angular measurements 106.95 ± 15.94 19.11 ± 5.67 13.93 ± 8.79 Linear measurements 13.34 ± 2.29 13.53 ± 1.85 12.09 ± 1.49 122.84 ± 7.8 21.38 ± 2.32 44.56 ± 3.88 25.56 ± 2.68 47.75 ± 3.89 –10.91 ± 5.73 14.78 ± 2.15 –1.80 ± 1.23 –11.02 ± 4.48 –8.00 ± 4.1

11.60 ± 1.91 14.18 ± 1.78 11.98 ± 1.36 118.81 ± 6.53 19.59 ± 2.18 40.91 ± 4.35 24.03 ± 2.72 46.09 ± 4.43 –10.37 ± 5.43 13.62 ± 2.8 –1.17 ± 1.34 –9.99 ± 6.32 –8.53 ± 3.5

0.98 ± 0.1 0.47 ± 0.06

1.05 ± 0.09 0.48 ± 0.06

Ratios

NS—not statistically significant; *p < 0.05—significant; **p < 0.01—very significant; ***p < 0.001—most significant

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JIOS A Comparative Study of Cephalometric Measurements with Digital versus Manual Methods Table 4: Distribution of cephalometric parameters according to the level of measurement difference (MD) between manual and digital methods MD < 1

1 < MD < 1.5

1.5 < MD < 2

MD > 2

Hard tissue angular 1. Saddle angle 2. Articular angle 3. SNB angle 4. ANB angle 5. U1-NA 6. L1-NB 7. Interincisal angle 8. Facial angle 9. FMA Hard tissue linear 1. U1-NA 2. L1-NB 3. U1-APog Hard tissue ratios 1. Jarabak ratio 2. UAFH/LAFH Soft tissue angular 1. Upper lip angle Soft tissue linear 1. Lower lip thickness 2. Chin thickness 3. TVL-Pog´ 4. TVL-point A´ 5. TVL-glabella Soft tissue ratios 1. UAFH/LAFH 2. UL/LL

Hard tissue angular 1. Gonial angle 2. SNA angle 3. SN-GoGn 4. Angle of convexity 5. IMPA Soft tissue angular 1. Angle of convexity Soft tissue linear 1. TVL-nasal projection 2. TVL-point B´

Hard tissue angular 1. FMIA Soft tissue linear 1. Upper lip thickness 2. Upper lip length 3. Maxillary height 4. Mandibular height

Hard tissue angular 1. SN-Occ Hard tissue linear 1. Anterior cranial base 2. Posterior cranial base Soft tissue angular 1. Nasolabial angle Soft tissue linear 1. Facial height 2. Lower lip length

Linear measurements in millimeters; angular measurements in degrees

difficulties in locating the landmarks Ar, Gn, Go, Po, Or, lower incisor apex, Me, Point A and Pog. While different reference planes may be constructed to assist in identifying points Gn, Go and Me during hand tracing, this may not be possible with on-screen digitization. Previous studies by Baumrind and Frantz,12 Lim and Foong,13 Gravely and Benzies14 have reported tracing difficulties of the incisor position and variation in incisor angular measurements between tracing methods. The SN-Occ measurement is affected by the double images of the occlusal surfaces of the teeth, interfering with easy identification of the occlusal plane. Also the occlusal plane is marked automatically on the digital image and may not correspond to that drawn in the manual method. The differences in the UAFH/LAFH (NANS/ANS-Me) ratio can be explained by the difficulty in locating Me and ANS. According to Chen et al8 the uncertainty in locating the Me point may be caused by the difficulty of delineating a landmark on a curved anatomical boundary. The uncertainty in locating ANS point may result from delineating the most anterior point of blurred anatomical outlines. 11 out of 18 soft tissue measurements showed significant differences in the manual and digital methods. Very few studies in the literature have evaluated soft tissue measurements due to the uncertainty in identifying soft tissue landmarks. The landmarks Li, Ls, Me´, Pog´, Sn and Point A´ were difficult to locate which may account for the measurement differences. According to Cooke and Wei15 lip prominence points are poor landmarks to identify. During conventional hand tracing,

different reference planes may be constructed to identify the innermost point of a curve; therefore nasolabial angle, which is constructed on a curve, may show great variation. According to Chen et al8 the measurement differences of less than 2 units (mm or degree) are generally within one standard deviation of norm values in conventional cephalometric analysis. The parameters with measurement differences of more than 2 units were hard tissue measurements SN-Occ, anterior cranial base length and posterior cranial base length as well as soft tissue measurements nasolabial angle, facial height and lower lip length. Thus, out of a total 41 hard and soft tissue measurements, only six measurements showed clinically significant differences. This is in agreement with the results of Chen et al8 and Schulze et al16 who stated that although statistically significant differences between digitized and analog measurements existed, they were clinically insignificant (less than 2 units). CONCLUSIONS The following conclusions were drawn from the study: 1. All the measurements showed clinically acceptable reproducibility in the digital method (r > 0.7—strong correlation) 2. Digital measurements obtained from digital photographs of analog cephalograms were found to be reproducible and


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comparable to the manual method for all the measurements undertaken in this study except the hard tissue variables of SN-Occ, anterior cranial base length and posterior cranial base length and soft tissue variables nasolabial angle, facial height and lower lip length, which showed clinically significant differences. These parameters could not be measured accurately with the digital method 3. Nemotec digital imaging software can be reliably used with good accuracy for the measurements of most of the parameters used in routine clinical practice 4. Further research needs to be done on the evaluation of growth changes or treatment effects by superimposition of radiographs by the digital method. REFERENCES 1. Geelen W, Wenzel A, Gotfredsen E, Kruger M, Hansson LG. Reproducibility of cephalometric landmarks on conventional film, hardcopy, and monitor-displayed images obtained by the storage phosphor technique. Eur J Orthod 1998;20:331-40. 2. Melsen B, Baumrind S. Clinical research application of cephalometry. In: Athanasiou A (Ed). Orthodontic cephalometry (2nd ed). St Louis: Mosby-Wolfe 1995;181-202. 3. Quintero JC, Trosien A, Hatcher D, Kapila S. Craniofacial imaging in orthodontics: Historical perspective, current status and future developments. Angle Orthod 1999;69:491-506. 4. Naslund EB, Kruger M, Petersson A, Hansen K. Analysis of low-dose digital lateral cephalometric radiographs. Dentomaxillofac Radiol 1998;27:136-39. 5. Forsyth DB, Shaw WC. Digital imaging of cephalometric radiology: Advantages and limitation of digital imaging (Part 1). Angle Orthod 1996;66:37-42.

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6. Gravely JF, Benzies PM. The clinical significance of tracing error in cephalometry. Br J Orthod 1984;11:44-48. 7. Grybauskas S, Balciuniene I, Vetra J. Validity and reproducibility of cephalometric measurements obtained from digital photographs of analogue headfilms. Stomatologija, Baltic Dental and Maxillofacial Journal 2007;9:114-20. 8. Chen YJ, Chen SK, Yao JC, Chang HF. The effects of differences in landmark identification on the cephalometric measurements in traditional versus digitized cephalometry. Angle Orthod 2004;74:155-61. 9. Houston WJ. The analysis of errors in orthodontic measurements. Am J Orthod 1983;83:382-90. 10. Gregston M, Kula T, Hardman P, Glaros A. A comparison of conventional and digital radiographic methods and cephalometric analysis software: Hard tissue (I). Semin Orthod 2004;10(3):204-11. 11. Santoro M, Jarjoura.K, Cangialosi.T. Accuracy of digital and analogue cephalometric measurements assessed with the sandwich technique. Am J Orthod Dentofac Orthop 2006;129:345-51. 12. Baumrind S, Frantz RC. The reliability of head film measurements. Landmark identification. Am J Orthod 1971a;60:111-27. 13. Lim KF, Foong KW. Phosphor-stimulated computed cephalometry: Reliability of landmark identification. Br J Orthod 1997;24:301-08. 14. Gravely JF, Benzies PM. The clinical significance of tracing error in cephalometry. Br J Orthod 1974;1:95-101. 15. Cooke MS, Wei SH. Cephalometric errors: A comparison between repeat measurements and retaken radiographs. Australian Dental Journal 1991;36:38-43. 16. Schulze RK, Gloede MB, Doll GM. Landmark identification on direct digital versus film-based cephalometric radiographs: A human skull study. Am J Orthod Dentofac Orthop 2002;122:635-42.

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