jkaoms Journal of the Korean Association of Oral and Maxillofacial Surgeons J Korean Assoc Oral Maxillofac Surg 1225-1585 2234-5930 Korean Association of Oral and Maxillofacial Surgeons 10.5125/jkaoms.2011.37.1.21 jkaoms-37-21 Original Article The change of frontal ramal inclination (FRI) after orthognathic surgery with laterognathism: posteroanterior cephalometric study YuSang-Jin Department of Oral and Maxillofacial Surgery, FOS Dental Clinic, Seoul, Korea Sang-Jin Yu Department of Oral and Maxillofacial Surgery, FOS Dental Clinic, SM Tower 832 Yeoksam-dong, Gangnam-gu, Seoul, 135-080, Korea. TEL: +82-2-3477-2800 FAX: +82-2-3477-3769 E-mail: sjeenie@hanmail.net 01 2011 10 01 2011 37 1 21 29 14102010 20012011 10022011 Copyright © 2011 Korean Association of Oral and Maxillofacial Surgeons 2011 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Introduction

To compare the change in frontal ramal inclination (FRI) in laterognathism after orthognathic surgery.

 Materials and Methods

Twenty four patients (10 men, 14 women; mean age, 22.8±5.2 years) with minimal facial canting (≤2 mm) and apparent menton deviation (5.9±2.4 mm) who had been operated on to correct facial asymmetry and skeletal CIII malocclusion, were selected. On a preoperative posteroanterior (PA) cephalogram, the FRI of the deviated side and non deviated side, L1 deviation amounts and menton deviation amounts were measured. The FRI differences between both sides were compared, and the correlations between the measured deviated elements and the FRI differences were analyzed. On a postoperative PA cephalogram, the shifting amount of L1, shifting amount of L7 and FRI of both sides were measured, and the correlations between the shifting elements and the change in FRI were analyzed.

 Results

On the preoperative PA cephalogram, the FRI of the non deviated side was significantly greater than those of the deviated side. The differences in FRI, with a menton deviation amount showed a significant correlation. On the postoperative PA cephalogram, the FRI differences between the deviated and non deviated side were decreased significantly and mandibular transverse movement toward central position was noted. The mean shifting amounts of L7 were associated with the amount of change in the deviated side of FRI.

 Conclusion

Transverse shifting of the mandible through orthognathic surgery decreases the FRI difference, which showed laterognathism, and improves the facial contour.

 Frontal ramal inclination (FRI) Laterognathism Mandibular transverse movement Orthognathic surgery Cephalogram References Komori M Kawamura S Ishihara S Averageness or symmetry: which is more important for facial attractiveness? Acta Psychol (Amst) 2009131 13642 Jones BC DeBruine LM Little AC The role of symmetry in attraction to average faces Percept Psychophys 200769 12737 Padwa BL Kaiser MO Kaban LB Occlusal cant in the frontal plane as a reflection of facial asymmetry J Oral Maxillofac Surg 199755 8116 discussion 817. Peck S Peck L Kataja M Skeletal asymmetry in esthetically pleasing faces Angle Orthod 199161 438 Phillips C Bennett ME Broder HL Dentofacial disharmony: psychological status of patients seeking treatment consultation Angle Orthod 199868 54756 Nitzan DW Katsnelson A Bermanis I Brin I Casap N The clinical characteristics of condylar hyperplasia: experience with 61 patients J Oral Maxillofac Surg 200866 3128 Park SH Yu HS Kim KD Lee KJ Baik HS A proposal for a new analysis of craniofacial morphology by 3-dimensional computed tomography Am J Orthod Dentofacial Orthop 2006129 600.e23–34. Hayashi K Muguruma T Hamaya M Mizoguchi I Morphologic characteristics of the dentition and palate in cases of skeletal asymmetry Angle Orthod 200474 2630 Nojima K Yokose T Ishii T Kobayashi M Nishii Y Tooth axis and skeletal structures in mandibular molar vertical sections in jaw deformity with facial asymmetry using MPR images Bull Tokyo Dent Coll 200748 1716 Langberg BJ Arai K Miner RM Transverse skeletal and dental asymmetry in adults with unilateral lingual posterior crossbite Am J Orthod Dentofacial Orthop 2005127 615 discussion 15–6. Ishizaki K Suzuki K Mito T Tanaka EM Sato S Morphologic, functional, and occlusal characterization of mandibular lateral displacement malocclusion Am J Orthod Dentofacial Orthop 2010137 454.e1–9; discussion 454–5. Hwang HS Maxillofacial 3-D image analysis for the diagnosis of facial asymmetry J Korean Dent Assoc 200442 7683 Eun CS Hwang HS Posteroanterior cephalometric study of frontal ramal inclination in chin-deviated individuals Korean J Orthod 200636 3807 Hwang HS Hwang CH Lee KH Kang BC Maxillofacial 3-dimensional image analysis for the diagnosis of facial asymmetry Am J Orthod Dentofacial Orthop 2006130 77985 Sekiya T Nakamura Y Oikawa T Ishii H Hirashita A Seto K Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry Am J Orthod Dentofacial Orthop 2010137 55262 Hashimoto T Fukunaga T Kuroda S Sakai Y Yamashiro T Takano-Yamamoto T Mandibular deviation and canted maxillary occlusal plane treated with miniscrews and intraoral vertical ramus osteotomy: functional and morphologic changes Am J Orthod Dentofacial Orthop 2009136 86877 Pinto AS Buschang PH Throckmorton GS Chen P Morphological and positional asymmetries of young children with functional unilateral posterior crossbite Am J Orthod Dentofacial Orthop 2001120 51320 Goto TK Nishida S Yahagi M Langenbach GE Nakamura Y Tokumori K Size and orientation of masticatory muscles in patients with mandibular laterognathism J Dent Res 200685 5526 Yang HJ Lee WJ Yi WJ Hwang SJ Interferences between mandibular proximal and distal segments in orthognathic surgery for patients with asymmetric mandibular prognathism depending on different osteotomy techniques Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010110 1824 Buranastidporn B Hisano M Soma K Temporomandibular joint internal derangement in mandibular asymmetry What is the relationship? Eur J Orthod 200628 838 Uysal T Sisman Y Kurt G Ramoglu SI Condylar and ramal vertical asymmetry in unilateral and bilateral posterior crossbite patients and a normal occlusion sample Am J Orthod Dentofacial Orthop 2009136 3743 Akahane Y Deguchi T Hunt NP Morphology of the temporomandibular joint in skeletal class iii symmetrical and asymmetrical cases: a study by cephalometric laminography J Orthod 200128 11928 Tallents RH Guay JA Katzberg RW Murphy W Proskin H Angular and linear comparisons with unilateral mandibular asymmetry J Craniomandib Disord 19915 13542 Figures and Tables

Cephalometric landmarks and measurements used in this study: FRI of deviated side, FRI of non deviated side, amount of menton deviation, amount of U1 deviation, amount of L1 deviation, linear L7 of deviated side, linear L7 of nondeviated side.(FRI: frontal ramal inclination)

Diagram of FRI change after parallel shifting of mandibular body.(FRI: frontal ramal inclination)

Superimposition of 3-dimensional computed tomography of preoperation and postoperation.

Preoperative deviated amounts in laterognathism

Case Age/Sex Deviated site Amont of Me deviation Amount of L1 deviation Amount of U1 deviation Amount of canting correction FRI� of non deviated side FRI� of deviated side Differential amount of FRI�
1 19.3/F Rt. 8.0 4.2 2.8 1.5 17.6 10 7.6
2 18/F Lt. 7.0 4.5 0.5 2.0 11.3 6 5.3
3 27.9/F Lt. 3.3 1.0 1.0 0.0 11.4 5.8 5.6
4 17.8/F Lt. 6.5 5.2 2.8 0.0 15.8 6.3 9.5
5 27.4/M Lt. 5.5 1.2 0.5 0.0 10 1.9 8.1
6 17.7/F Rt. 5.0 6.8 3.2 0.0 12.2 7 5.2
7 23.8/F Rt. 1.5 1.5 1.6 1.0 9.5 6.3 3.2
8 30.9/M Lt. 6.0 3.1 −4.5 −1.0 8.7 0.2 8.5
9 24.9/F Rt. 9.5 6.2 2.5 2.0 13.1 8 5.1
10 36.4/M Lt. 7.5 5.5 2.5 1.5 12 4.5 7.5
11 22.6/F Lt. 7.6 3.8 1.5 0.0 11.7 5 6.7
12 18.8/M Rt. 6.6 4.5 1.0 1.5 11.5 6.5 5.0
13 25.7/F Lt. 10.5 6.0 2.3 2.0 16 5.4 10.6
14 18.5/M Lt. 5.8 4.2 1.5 1.0 8.00 5.00 3.0
15 17.9/F Lt. 5.2 1.5 0.5 1.0 6.20 −1.0 7.2
16 24.2/F Lt. 5.7 4.6 0.5 −2.0 14.8 11.7 3.1
17 17/F Rt. 5.0 5.8 3.2 1.0 14.9 11.5 3.4
18 24.8/M Lt. 2.6 2.1 1.0 0.0 6.8 3.8 3.0
19 20.8/M Lt. 3.0 1.5 −2.2 2.0 10 6.4 3.6
20 23/M Lt. 4.5 5.2 1.2 0.0 4.1 −1.2 5.3
21 19.5/F Lt. 2.9 3.2 2.9 1.0 12.4 9.2 3.2
22 17.5/F Lt. 9.7 5.9 1.5 1.0 10.2 2.1 8.1
23 31.2/M Lt. 4.8 2.6 2.7 −2.0 14.8 9.5 5.3
24 22/M Lt. 8.9 5.9 4.2 2.0 12.9 3.8 9.1
Mean     5.9 4.0 1.4 0.6 11.5 5.6 5.9
SD     2.4 mm 1.8 mm 1.8 mm 1.2 mm 3.3� 3.5� 2.3�

Postoperative shifting amounts of deviated elements in laterognathism

Case L1 shifting amount L7 shifting amount of deviated side L7 shifting amount of non-deviated side Mean L7 shifting amount FRI� of deviated side FRI� of non deviated side FRI� change amount of deviated side FRI� change amount of non deviated side
1 6.5 4.2 4.0 4.1 15.3 15.8 5.3 −1.8
2 5.5 4.0 3.5 3.8 10.1 9.5 4.1 −1.8
3 4.2 2.7 2.0 2.4 9.8 10.5 4.0 −0.9
4 5.5 4.2 3.2 3.7 10.1 14.0 3.8 −1.8
5 3.0 2.8 2.7 2.8 5.5 7.6 3.6 −2.4
6 6.1 4.6 3.6 4.1 12.2 13.1 5.2 0.9
7 1.0 2.9 3.2 3.1 9.1 8.3 2.8 −1.2
8 5.5 4.1 3.6 3.9 5.1 5.8 4.9 −2.9
9 7.0 5.8 5.9 5.9 13.4 10.5 5.4 −2.6
10 6.0 2.9 1.7 2.3 7.5 11.2 3.0 −0.8
11 4.8 3.8 3.8 3.8 9.5 10.2 4.5 −1.5
12 5.0 5.1 4.0 4.6 13.6 13.5 7.1 2.0
13 8.0 6.5 4.5 5.5 12.0 10.5 6.6 −5.5
14 7.7 4.2 3.4 3.8 10.0 6.2 5.0 −1.8
15 3.5 3.0 4.2 3.6 5.9 3.3 6.9 −2.9
16 5.1 3.1 2.9 3.0 15.0 13.4 3.3 −1.4
17 4.5 4.7 4.4 4.6 15.8 13.5 4.3 −1.4
18 3.0 3.0 2.7 2.9 6.1 4.8 2.3 −2.0
19 4.1 4.9 2.3 3.6 12.1 8.7 5.7 −1.3
20 6.1 5.2 3.2 4.2 5.1 5.2 6.3 1.1
21 4.2 2.4 2.7 2.6 13.0 9.8 3.8 −2.6
22 5.4 5.5 5.2 5.4 9.7 8.5 7.6 −1.7
23 3.1 3.5 4.0 3.8 14.5 12.0 5.0 −2.8
24 3.8 3.7 3.0 3.4 8.1 10.5 4.3 −2.4
Mean 4.9 4.0 3.5 3.8 10.4 9.9 4.8� −1.6
SD 1.6 mm 1.1 mm 1.0 mm 0.9 mm 3.4� 3.2� 1.4� 1.5�

(FRI: frontal ramal inclination, SD: standard deviation)

Comparison of FRI and difference between non deviated side and deviated side in laterognathism (�)

  Non deviated side Deviated side Difference Significance
  Mean±SD Mean±SD Mean±SD Significance
Preoperative FRI� 11.5±3.3� 5.6±3.5� 5.9±2.3� *

P<0.001, paired t-test, FRI: frontal ramal inclination, SD: standard deviation)

Pearson correlation between FRI difference and U1 midline deviation, L1 midline deviation, menton deviation amount in laterognathism (preoperation)

  U1 midline deviation (mm) L1 midline deviation (mm) Menton deviation (mm)
Difference of FRI� between deviated and non deviated side 0.058 0.256 0.679*

0.679: P<0.001, FRI: frontal ramal inclination)

Comparison of FRI after operation (postoperative FRI�- preoperative FRI�)

  Preoperative FRI� Mean±SD Postoperative FRI� Mean±SD Difference� Mean±SD Significance
Non deviated side 11.5±3.3� 9.9±3.2� −1.6±1.5� *
Deviated side 5.6±3.5� 10.4±3.4� 4.8±1.4� *

P<0.001, paired t-test, FRI: frontal ramal inclination, SD: standard deviation)

Comparison of FRI and FRI change amount between non deviated side and deviated side after operation (�)

  Non deviated side Mean±SD Deviated side Mean±SD Difference Mean±SD Significance
Postoperative FRI� 9.9±3.2 10.4±3.4 −0.4±2.2 NS
Change amount of FRI� after operation −1.6±1.7 4.8±1.4 3.1±2 *

P<0.001, paired t-test, FRI: frontal ramal inclination, SD: standard deviation, NS: not significant)

Comparison of difference between L1 shifting amount and mean L7 shifting amount after operation

  L1 shifting amount Mean±SD L7 shifting amount Mean±SD Difference Mean±SD Significance
Difference (preoperative distance-postoperative distance) 4.9±1.6 3.8±0.9 1.18±1.36 *

P<0.001, paired t-test)

Pearson correlation between FRI changes and L1 shifting amount, L7 shifting amount (deviated site, non deviated site, mean) after operation

  L1 shifting amount (mm) L7 shifting amount (deviated side, mm) L7 shifting amount (non deviated side, mm) Mean L7 shifting amount (mm)
FRI� change of deviated site after operation 0.414* 0.704**   0.723**
FRI� change of non deviated site after operation −0.056   −0.229 −0.120

FRI: frontal ramal inclination

P<0.05

P<0.001)