The Cleft Palate-Craniofacial Journal 50(4) pp. 381–387 July 2013 ’ Copyright 2013 American Cleft Palate-Craniofacial Association

ORIGINAL ARTICLE Evaluation of Mandibular Hypoplasia in Patients With Hemifacial Microsomia: A Comparison Between Panoramic Radiography and Three-Dimensional Computed Tomography Naoko Takahashi-Ichikawa, D.D.S., Takafumi Susami, D.D.S., Ph.D., Kouhei Nagahama, D.D.S., Ph.D., Kazumi Ohkubo, D.D.S., Ph.D., Mari Okayasu, D.D.S., Ph.D., Nasuko Uchino, D.D.S., Kiwako Uwatoko, D.D.S., Hideto Saijo, D.D.S., Ph.D., Yoshiyuki Mori, D.D.S., Ph.D., Tsuyoshi Takato, M.D., Ph.D. Objective: To compare the accuracy of three-dimensional computed tomography (3D-CT) and panoramic radiography in the evaluation of mandibular hypoplasia in patients with hemifacial microsomia (HFM). Design: Retrospective study of imaging data. Setting: Images selected from the archives of the University of Tokyo Hospital. Subjects: Twenty patients with unilateral HFM who had undergone both panoramic radiography and 3D-CT in the same period. Method: Mandibular deformities were classified according to the Pruzansky classification; eight patients had Grade I deformity and 12 patients had Grade II deformity. Ramus heights were measured on both panoramic radiographs and 3D-CT. Main outcome measures: Magnification in panoramic radiographs and extent of mandibular asymmetry as estimated by the affected/unaffected side ratio based on two methods were examined. The Pearson product-moment correlation coefficient was used to estimate correlations between parameters. Results: The magnification of ramus heights on panoramic radiographs showed large variations in Grade II patients. The affected/unaffected side ratio estimated by the two methods showed a strong correlation in Grade I patients (correlation coefficient 0.99; p , .0001). Conversely, a weak correlation was seen in Grade II patients (correlation coefficient 0.77; p = .0036), and affected/unaffected side ratios from panoramic radiographs were both over- and underestimated. Conclusions: The accuracy of evaluation using panoramic radiography was fairly reliable in Grade I patients. Conversely, accuracy was poor in Grade II patients, and evaluation using 3D-CT seems preferable. The combination of two methods with careful consideration is recommended for clinical applications. KEY WORDS: hemifacial microsomia (HFM), mandibular deformity, panoramic radiography, threedimensional computed tomography (3D-CT)

Hemifacial microsomia (HFM) refers to a broad spectrum of congenital malformations resulting from variable dysmorphogenesis of craniofacial structures derived from the first and second brachial arches. Symptoms usually appear unilaterally as facial asymmetry, although bilateral manifestations are reported in 30% of patients (Posnick, 2000). The regions most often affected by HFM are the external/middle/internal ear and the facial skeleton along with the overlying musculature, cranial nerves, and connective tissues (Gougoutas et al., 2007). Estimated incidences as reported in previous studies vary from 1 in 3,500 to 1 in 26,550 (Hennekam et al., 2010), and HFM is the second most common congenital malformation in the face after cleft lip and/or palate (Murray et al., 1984). Mandibular hypoplasia has been regarded as the landmark of HFM and is always involved to some degree (Kaban et al., 1981; Vento et al., 1991; Gougoutas et al.,

Dr. Takahashi-Ichikawa, Dr. Nagahama, Dr. Okayasu, Dr. Uchino, Dr. Uwatoko, are Orthodontists at The University of Tokyo Hospital, Tokyo, Japan. Dr. Susami is Associate Professor and Chief Orthodontist at The University of Tokyo Hospital, Tokyo, Japan. Dr. Ohkubo and Dr. Saijo are Assistant Professors, Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Tokyo, Japan. Dr. Mori is Associate Professor,Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Tokyo, Japan. Dr. Takato is Professor of the Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Tokyo, Japan. Presented at the 20th Annual Meeting of the Japanese Society for Jaw Deformities, Sapporo, June 2010. Submitted August 2011; Accepted January 2012. Address correspondence to: Dr. Takafumi Susami, Department of OralMaxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. E-mail [email protected]. DOI: 10.1597/11-188 381

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2007). Mandibular hypoplasia may range from mild flattening of the condylar head to complete agenesis of the condyle, ascending ramus, and glenoid fossa. Mandibular hypoplasia in combination with maxillary hypoplasia frequently results in malocclusion and, depending on the severity of the maxillomandibular deficiency, an upward occlusal cant to the affected side (Gougoutas et al., 2007). To evaluate mandibular deformity in patients with HFM, panoramic radiographs and cephalograms have been used. Changes with facial growth or with treatments such as functional orthodontic appliances or mandibular distraction have been examined using these radiographic modalities (Kaban et al., 1981; Sarnas et al., 1982; Rune et al., 1983; Murray et al., 1984; Melsen et al., 1986; Silvestri et al., 1996; Polley et al., 1997; Meazzini et al., 2005, 2008). However, these methods produce variable results and thus decrease in precision according to head position and magnification. The alternative modality to evaluate HFM is threedimensional computed tomography (3D-CT). The first study to use 3D-CT in patients with HFM was reported in 1988 by Marsh et al. and many studies have since been reported (Marsh et al., 1989; Ono et al., 1992; Yune, 1993; Huisinga-Fischer et al., 2001). This modality enables more accurate depiction of all craniofacial bony structures compared to conventional methods. The main advantage of 3D-CT is the accuracy in dimensional measurements, but a high radiation dose is needed. Panoramic radiography and cephalometric radiography still offer advantages from the perspective of radiation dose and convenience in daily clinical practice. Given these differences, the thoughtful combination of panoramic radiography, cephalometric radiography, and 3D-CT seems effective for evaluating facial deformities in HFM patients and changes with growth or treatments. However, to the best of our knowledge, no studies have clarified relationships between these methods. The present study measured mandibular ramus height in patients with HFM using the two methods of panoramic radiography and 3D-CT in order to evaluate relationships and differences between these modalities. The effective combination of panoramic radiography and 3DCT was discussed based on the results of this study. MATERIALS AND METHODS Patients Twenty patients (11 males, 9 females) who had undergone both panoramic radiography and 3D-CT in the same period were selected from the archives of the Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics at the University of Tokyo Hospital (Table 1). Mean age of patients at the time of examination was 11.3 years (range, 5 years 7 months to 23 years 8 months). The affected side was the right side in seven patients and the left in 13 patients. Mandibular hypoplasia in patients was classified

TABLE 1

Details of 20 patients with hemifacial microsomia

Parameters

Distribution

Sex (male/female) Age at examination (years) Mean (range)

11/9 11.3 (5–23)

Affected side Right Left

7 13

Pruzansky classification Grade I Grade II

8 12

according to the following Pruzansky classification (Pruzansky, 1969). Grade I: Characterized primarily by a difference in size from the assumed normal side in the same person. Morphological characteristics of the ramus were clearly present. Grade II: The condyle, ramus, and sigmoid notch, although still identifiable, were grossly distorted and the mandible was strikingly different in size and shape from any concept of the norm. Grade III: The mandible presented either a grossly distorted ramus with loss of identifiable landmarks or complete agenesis of the ramus. The present study included eight patients with Grade I deformity and 12 patients with Grade II deformity. Measurement of Mandibular Ramus Height Using Panoramic Radiography In the evaluation using panoramic radiography, mandibular ramus height was measured according to a modification of the methods of Habets et al. (1988) (Fig. 1). All films were traced and measured. A tangent of the posterior outline of the mandibular ramus (Line A) and a line perpendicular to Line A and tangential to the outline of the condylar head (Line B) were drawn. The point of contact was defined as the condylion (Cd: the most superior point on the condylar head). A tangent to the posterior outline of mandibular body (Line C) and a bisector of the angle between Lines A and C were drawn (Line D). The intersection of the mandibular outline and Line D was defined as the gonion (Go: the boundary point between the mandibular body and ramus). Distance between Cd and Go was measured as the ramus height (RH). Measurement of Mandibular Ramus Height Using 3D-CT Each patient underwent volumetric computed tomography (CT) using an Aquilion ONE multi-slice CT scanning system (Toshiba Medical Systems, Tochigi, Japan). Slice thickness was 0.5 mm. Slice data were taken for the region extending from the chin to at least 3 to 4 mm above the

Takahashi-Ichikawa et al., EVALUATION OF MANDIBULAR HYPOPLASIA BY 3D-CT

FIGURE 1 Measurement of mandibular ramus height using panoramic radiography. A: A ramus tangent line (Line A). B: A line perpendicular to Line A and tangential to the outline of the condylar head (Line B). C: A tangent to the posterior outline of the mandibular body (Line C). D: A bisector of the angle between Lines A and C (Line D). Cd = condylion; Go = gonion; RH = ramus height (Cd - Go).

supraorbital margin. A three-dimensional (3D) surface image of the facial skeleton was reconstructed on a ZIOSTATION system 610 (ZIOSOFT, Tokyo, Japan). The 3D reference planes were defined as follows. The horizontal reference plane (XY plane) was the Frankfurt horizontal plane (FH plane), constructed on the unaffected side of the porion (Po: highest midline point on the roof of the external auditory meatus) and bilateral orbitale (Or: lowest point on the infraorbital margin of orbit). The coronal plane (ZX plane) was perpendicular to the XY plane, passing through the bilateral supraorbital notches. The midsagittal plane (YZ plane) was perpendicular to the XY and ZX planes, passing through nasion (Na: the most frontal median point of the frontonasal suture). After determining the reference planes, shape of mandible was extracted and RH was measured bilaterally. The condylion (Cd: the most superior point of the condylar head) and the anthropometric Go (the most protruded part of the mandibular angle) were used as landmarks. Landmarks were first designated on the lateral view of the 3D surface model of the mandible, and y and z coordinates were determined. The frontal view was then displayed, and the x coordinate was determined. The 3D distance between Cd and Go was measured as the RH in 3DCT evaluation (Fig. 2).

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FIGURE 2 Measurement of mandibular ramus height using 3D-CT. Cd = the most superior point on the condyle head; Go = the most protruded part of the mandibular angle; RH = ramus height (Cd - Go).

Evaluation of the Magnification in Panoramic Radiographs In the comparison of RHs between panoramic radiography and 3D-CT, values from 3D-CT measurement were assumed to represent actual distances. Magnifications from panoramic radiography were calculated as panoramic radiograph/3D-CT ratios. These calculations were preformed for affected and unaffected sides. Evaluation of Mandibular Asymmetry The extent of mandibular asymmetry was evaluated by affected/unaffected side ratios of RH in both panoramic radiographs and 3D-CT measurements. Statistical Analysis and Approval of the Institutional Review Board The Pearson product-moment correlation coefficient was used to estimate correlations between magnifications of panoramic radiographs on the affected and unaffected sides, and between the extent of mandibular asymmetry in panoramic radiographs and 3D-CT measurement. The

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TABLE 2

Mandibular Ramus Heights Measured Using Panoramic Radiograph and 3D-CT and Affected/Unaffected Ratio* Panoramic Radiograph

Patient/Grade Affected Side

3D-CT

Right

Left

Affected / Unaffected Ratio

Right

Left

Affected / Unaffected Ratio

Grade I 1 2 3 4 5 6 7 8

L L L R L R L L

57.3 60.9 50.3 52.6 69.2 58.5 71.6 52.6

54.6 47.7 47.9 53.6 66.7 63.3 69.0 50.3

0.95 0.78 0.95 0.98 0.96 0.89 0.96 0.95

48.7 52.4 37.8 45.6 47.8 42.0 60.2 46.3

47.4 37.7 35.3 46.2 47.0 48.4 58.0 43.9

0.97 0.72 0.93 0.99 0.98 0.87 0.96 0.95

Grade II 9 10 11 12 13 14 15 16 17 18 19 20

R L L R L R L R L R L L

49.1 63.1 73.9 42.2 69.6 38.6 48.9 27.4 56.8 45.1 74.5 53.9

66.6 29.0 53.6 68.5 56.3 42.8 27.1 57.7 51.0 76.9 61.5 43.4

0.74 0.46 0.73 0.62 0.81 0.90 0.56 0.47 0.90 0.59 0.83 0.81

36.2 55.4 59.1 37.4 56.8 25.4 40.0 28.0 47.3 25.9 53.2 42.3

57.0 22.2 48.9 58.0 43.1 37.5 16.2 47.5 44.8 63.5 50.2 27.0

0.64 0.40 0.83 0.65 0.76 0.68 0.41 0.59 0.95 0.41 0.94 0.64

* Eight patients had Pruzansky Grade I deformity (patients 1 to 8); 12 patients had Grade II deformity (patients 9 to 20). R5Right; L5Left; 3D-CT5three-dimensional computed tomography.

correlation coefficient and p value were calculated using Prism software (Graph Pad Software, La Jolla). Values of p # .05 were considered significant. This study was approved by the institutional review board of University of Tokyo (No.2945).

TABLE 3

Magnification in the Panoramic Radiographs*

Patient/Grade

Affected Side

Unaffected Side

Grade I 1 2 3 4 5 6 7 8

1.15 1.27 1.36 1.15 1.42 1.39 1.19 1.14

1.18 1.16 1.33 1.16 1.45 1.31 1.19 1.14

Grade II 9 10 11 12 13 14 15 16 17 18 19 20 Average

1.36 1.30 1.10 1.13 1.31 1.52 1.67 0.98 1.14 1.72 1.22 1.61 1.35

1.17 1.14 1.25 1.18 1.23 1.14 1.22 1.21 1.20 1.21 1.40 1.27 1.30

* The values from 3D-CT measurement were assumed to be actual distances. The magnifications in the panoramic radiographs were calculated as panoramic radiograph/3DCT ratios.

RESULTS Mandibular RHs measured using both panoramic radiography and 3D-CT are shown in Table 2. Magnifications of RH on panoramic radiographs are shown in Table 3 and Figure 3. Mean magnification on the affected side in all patients was 1.35 (range, 0.98 to 1.72). Mean magnification on the unaffected side was 1.30 (range, 1.14 to 1.45). Large variations were found on the affected side in all patients (correlation coefficient, 0.17; p 5 .4608) (Fig. 3A). In Grade I patients; however, magnifications in each patient were relatively constant on the affected and unaffected sides, and a significant correlation was found between sides (correlation coefficient, 0.90; p 5 .0023) (Fig. 3B). Conversely, no significant correlation was found in Grade II patients (correlation coefficient, 0.08; p 5 .7949) (Fig. 3C). Affected/unaffected side ratios calculated as a parameter of mandibular asymmetry are also presented in Table 2. Ratios calculated from panoramic radiography and 3D-CT were similar in Grade I patients. However, in many Grade II patients, differences between the two methods were large. Affected/unaffected side ratios calculated from panoramic radiography were both over- and underestimated in comparison with ratios from 3D-CT. Figure 4 shows the correlation between affected/unaffected side ratios between panoramic radiography and 3D-CT. Significant correlations were found in affected/unaffected side ratios in all patients (correlation coefficient, 0.88; p , .0001) (Fig. 4A), with prominent correlations in Grade I patients (correlation coefficient, 0.99; p , .0001) (Fig. 4B). Conversely, the correlation was weak in Grade II patients (correlation coefficient, 0.77; p 5 .0036) (Fig. 4C).

Takahashi-Ichikawa et al., EVALUATION OF MANDIBULAR HYPOPLASIA BY 3D-CT

FIGURE 3 Magnification of ramus height on panoramic radiographs. A: All patients. B: Pruzansky Grade I patients. C: Pruzansky Grade II patients. Ramus heights from 3D-CT measurements were assumed to represent actual distances, and magnifications in panoramic radiographs were calculated as the panoramic radiograph/3D-CT ratio.

DISCUSSION Morphological changes in patients with HFM after facial growth or with treatments such as functional orthodontic appliances or mandibular distraction have been examined using panoramic or cephalometric radiography (Kaban et al., 1981; Rune et al., 1981; Sarnas et al., 1982; Rune et al., 1983, Melsen et al., 1986; Silvestri et al., 1996; Polley et al.,1997; Meazzini et al., 2005, 2008). However, twodimensional (2D) radiographs show several limitations in evaluating mandibular asymmetry. In panoramic radiographs, structures in the middle of the tomographic layer are sharply depicted, whereas those in the periphery are unclear. Outside the layer, all structures are blurred and magnified (Miles et al., 1993; White and Pharoah, 1999). Any angulations of the x-ray beam, recording plane, or the object in the path of the beam will

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FIGURE 4 Comparison of the extent of mandibular asymmetry (affected/ unaffected side ratio) evaluated by panoramic radiography and 3D-CT. The relationship between affected/unaffected side ratio as evaluated by 3D-CT and that by panoramic radiography of all patients was investigated using Pearson’s correlation coefficient test.

result in distortions of the recording image and the image will demonstrate either elongation or foreshortening (Cullinan, 1994; Batenburg et al., 1997). As for mandibular asymmetry, Laster et al. (2005) examined the accuracy of measurements in panoramic radiographs and reported accuracies in detecting mandibular asymmetry of 67%, 70%, and 47% for ideal, rotated, and shifted skull positions, respectively. They concluded that panoramic radiographs should be used with caution in making absolute measurements or relative comparisons, and that measurements such as those assessing posterior mandibular facial symmetry may be unreliable. Van Elslande et al. (2008) undertook a systematic review of the diagnosis of mandibular asymmetry on panoramic radiographs and found that vertical measurements, although more accurate than horizontal or angular measurements, still do not provide a true representation of the real objects. They advised caution in assessing mandibular asymmetry using panoramic radiography.

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Conventional cephalometric radiography also shows limitations in assessing facial asymmetry. On lateral cephalometric radiographs, structures in the right and left sides are depicted on the same view, and identification of anatomical structures on specific sides is difficult. Magnifications of both sides also differ, and comparisons of structure sizes have poor reliability. Frontal cephalometric radiographs are often used for the evaluation of facial asymmetry; however, the vertical dimension is substantially affected by the head position and is unsuitable for distance measurement (Athanasiou and Van der Meij, 1995). In patients with HFM, deformity and malposition of the ears makes the head position unreliable, and reproducibility is poor. To overcome these problems, the combination of multidimensional cephalography was devised and used for the evaluation of facial asymmetry (Kaban et al., 1981; Rune et al., 1981; Grayson et al., 1983), but these methods still have limitations in terms of head position and accuracy of landmarks. With the progress of 3D imaging technology, more accurate analysis of the craniofacial complex has become possible. Several computer 3D methods have been developed to assist with diagnosis, treatment planning, and prediction of outcomes (Halazonetis, 2005). In the field of dentistry, 3D-CT is widely used for the following reasons: (1) Actual measurements can be obtained; (2) a spatial image of the craniofacial structures can be produced; (3) the frame of reference can be defined freely; (4) inner structures can be observed by removing the outer surfaces; and (5) hard and soft tissues can be observed independently by changing threshold densities for organs (Ono et al., 1992; Yune, 1993). Patients with HFM have been discussed in several reports on 3D-CT (Marsh et al., 1989; Ono et al., 1992; Yune, 1993). Huisinga-Fischer et al. (2001) reported a method of CT-based size and shape determination of the craniofacial skeleton in an attempt to design a better system of craniofacial classification for bony deformities in patients with HFM. Images from 3D-CT conquer the problems of panoramic radiography, such as sensitivity to positioning error and variability in magnification factors (Tronje et al., 1981; Batenburg et al., 1997; Van Elslande et al., 2008). Despite the usefulness and versatility of CT, the high cost of 3D-CT reconstruction and the high radiation dose required represent key disadvantages. As a result, 3D-CT should be used in conjunction with conventional 2D radiography at present. The present study attempted to clarify the accuracy of measurements from panoramic radiography for the evaluation of mandibular deformity and asymmetry. Accuracy was considered to be largely affected by the severity of mandibular deformity. Several classifications for HFM have been proposed in an effort to define, tabulate, and communicate clinical findings (Pruzansky, 1969; Laurifzen et al., 1985; Kaban et al., 1988; Vento et al., 1991; Gougoutas et al., 2007). Among these, the Pruzansky system is the simplest and most widely accepted. This system grossly classifies deformities, and we considered

these features to be suitable for our purpose. Unfortunately, no patients with Grade III deformity underwent both panoramic radiography and CT in the study period at our hospital. We thus compared Grade I and II patients in this study. In our study, magnifications on panoramic radiographs of the affected side varied more widely (0.98 to 1.72) than those on the unaffected side (1.14 to 1.45) (Table 3). This was more prominent in Grade II patients, and no significant correlation between both sides was found (Fig. 3C). Conversely, magnifications on both sides were relatively constant in Grade I patients, and a significant correlation was found (Fig. 3B). These results showed that measurement of RH using panoramic radiographs in Grade I patients is fairly reliable and useful for the examination of mandibular deformity. Affected/unaffected side ratios of RH were used as a parameter of the severity of mandibular asymmetry. Ratios evaluated by measurements from panoramic radiography and 3D-CT showed significant correlations in all patients (correlation coefficient, 0.88) (Fig. 4A). This correlation was more prominent in Grade I patients (correlation coefficient, 0.99) but was low in Grade II patients (correlation coefficient, 0.77). In Grade II patients, affected/unaffected side ratios calculated from panoramic radiographs were both over- and underestimated in comparison with those from 3D-CT. These results show that evaluation of mandibular deformity in Grade I patients using panoramic radiographs is fairly reliable when taken in the appropriate manner. Conversely, measurement is unreliable in Grade II patients, and thus accurate evaluation using 3D-CT is preferable. However, CT requires a radiation dose of 2.5 mSv, about 60-fold greater than that in panoramic radiography (0.04 mSv). This has to be taken in critical phases. From the results of this study, we are considering the following general rules in our department. In Grade I patients, 3DCT should be taken once before surgical or orthodontic treatment to accurately evaluate the deformity, if the patient or parent agrees after being provided with information on the advantages and disadvantages of 3DCT. Panoramic radiography can be used for monitoring changes with growth or treatment. In Grade II patients, evaluation using 3D-CT seems essential for accurate examination of the deformity. In addition to examination before treatment, 3D-CT should be performed after treatment involving major positional changes, such as orthognathic surgery, facial bone distraction, or long-term orthodontic treatment. Panoramic radiography can also be used in a complementary manner. If the cost and radiation dose of 3D-CT decrease substantially in the future, 3D-CT will take the place of conventional 2D radiography. CONCLUSIONS The present study compared the accuracy of 3D-CT and panoramic radiography in the evaluations of mandibular

Takahashi-Ichikawa et al., EVALUATION OF MANDIBULAR HYPOPLASIA BY 3D-CT

hypoplasia in patients with HFM. The magnification of RHs in panoramic radiography showed large variations in Grade II patients. From the two methods, affected/ unaffected side ratios, used as a parameter of mandibular asymmetry, showed a strong correlation in Grade I patients but a weak correlation in Grade II patients. Ratios from panoramic radiographs were both over- and underestimated. From these findings, the accuracy of evaluation using panoramic radiography seems fairly reliable in Grade I patients. Conversely, accuracy is poor in Grade II patients; thus, evaluation using 3D-CT appears essential. Considering the high radiation dose and cost of 3D-CT, the combination of these two methods with careful consideration is recommended in clinical applications. REFERENCES Athanasiou AE, Van der Meij AJW. Posteroanterior (frontal) cephalometry. In: Athanasion AE, ed. Orthodontic Cephalometry. London: Mosby-Wolfe; 1995:141–162. Batenburg RH, Stellingsma K, Raghoebar GM, Vissink A. Bone height measurements on panoramic radiographs: the effect of shape and position of edentulous mandibles. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1997;84:430–435. Cullinan AM, Cullinan JE. Radiographic quality. In: Allen AM, Benert M, Gibbons T, eds. Producing Quality Radiographs. 2nd ed. Philadelphia: JB Lippincott; 1994:114–132. Gougoutas AJ, Singh DJ, Low DW, Bartlett SP. Hemifacial microsomia: clinical features and pictographic representations of the OMENS classification system. Plast Reconstr Surg. 2007;120:112e–120e. Grayson BH, McCarthy JG, Bookstein F. Analysis of craniofacial asymmetry by multiplane cephalometry. Am J Orthod. 1983;84:217–224. Habets LL, Bezuur JN, Naeiji M, Hansson TL. The orthopantomogram, an aid in diagnosis of temporomandibular joint problems. II. The vertical symmetry. J Oral Rehabil. 1988;15:465–471. Halazonetis DJ. From 2-dimensional cephalograme to 3-dimensional computed tomography scans. Am J Orthod Dentofacial Orthop. 2005;127:627–637. Hennekam RCM, Krants ID, Allanson JE. Branchial arch and oral-arcal disorders. In: Motulsky AG, Harper PS, Scriver C, Epstein CJ, Hall JG, eds. Gorlin’s Syndromes of the Head and Neck. 5th ed. New York: Oxford University Press; 2010:879–887. Huisinga-Fischer CE, Zonneveld FW, Vaandrager JM, Prahl-Andersen B. CT-based size and shape determination of the craniofacial skeleton: a new scoring system to assess bony deformities in hemifacial microsomia. J Craniofac Surg. 2001;12:87–94. Kaban LB, Mulliken JB, Murray JE. Three-dimensional approach to analysis and treatment of hemifacial microsomia. Cleft Palate J. 1981;18:90–99. Kaban LB, Moses MH, Mulliken JB. Surgical correction of hemifacial microsomia in growing child. Plast Reconstr Surg. 1988;82:9–19. Laster WS, Ludlow JB, Bailey LJ, Garland Hershey H. Accuracy of measurements of mandibular anatomy and prediction of asymmetry in panoramic radiographic images. Dentomaxillofac Radiol. 2005;34:343–349.

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