Correction of square jaw with low angles using mandibular “V-Line” ostectomy combined with outer cortex ostectomy

Correction of square jaw with low angles using mandibular “V-Line” ostectomy combined with outer cortex ostectomy

Abstract

Objective.To evaluate the feasiblility and effectiveness of correction for square jaw with low angle using mandibular “V-Line” ostectomy combined with outer cortex ostectomy.

Study design.From July 2005 to November 2007, 31 patients that had square faces with low angles were treated with mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy. All the patients had standard frontal and lateral cephalometric radiographs, panoramic radiographs, and were photographed preoperatively and postoperatively to assess their face contour. The alteration of mandibular angle and width of lower face was observed for 6 to 24 months postoperatively.

Results.Postoperative appearance of all 31 cases showed that the width of lower face was reduced expectedly; the gonial angle and the mandibular plane angle were increased effectively. The final aesthetic outcomes were quite satisfactory in all cases for both the surgeons and the patients

Conclusions.A slender oval facial outline as the fashionable aesthetics could be achieved by using mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy. It might be a feasible and a reasonable surgical procedure for correction of square jaw with low angle.

Keywords: square jaw; low angle;“V-Line” ostectomy; mandibular outer cortex ostectomy

In Oriental culture, a woman who has a wide and square face is thought to be of forceful or unfriendly character. A prominent mandibular angle produces a characteristic quadrangle, coarse, and masculine appearance. So, oriental women prefer to have an ovoid facial contour, which symbolizes a kind and gentle nature. Recently, because of the influence of fashion and films, not only women but also men dislike having square facial contours. Nowadays, even the ovoid face is unacceptable as more and more women prefer slender oval faces or so called "melon seed face" in Asian terms. The so called “melon seed face” makes one look intelligent, beautiful and delicate thus many Orientals who have a square face pursue such contour by undergoing various cosmetic surgeries.

After Legg’s first report of masseteric hypertrophy, a lot of researchers attempted to correct square jaw by surgical methods which lead to refined and innovative surgical procedures. In East Asia, nowadays, the surgical resection for correction of square jaw via intraoral approach is a routine procedure. ^1，2，.3 However, majority of squared jaw patients have severe form characterized by a definite square shaped face with low angle deformity. "Square jaw with low angle deformity" means that the gonial angle is below 120 degrees or approximately 90 degrees, and the mandibular plane angle is less than 30 degrees（Fig.1a）.

The appearance shows the mandible with too flat or flagging mandibular outline. However, while correcting square jaw, the traditional operation methods that only reduce the mandibular width (G0-G0) （Fig.1b）might not increase the mandibular plane angle⁴, and usually do not have a good clinical outcome. Therefore, depending on the appearance characteristics and aesthetic conceptions of the square jaw deformity patients or beauty yearning people, we use "V-Line" ostectomy procedure combined with mandibular outer cortex ostectomy by intraoral approach to correct square jaw with low angle. It is named "V-Line" ostectomy because of the "V" shape formed by two lines of ostectomy on both sides of mandible. This surgical procedure can effectively change the mandibular outline, increase the mandibular plane angle and mandibular angle, upgrade the curve of lower face, make the flat mandibular inferior margin or flagging mandibular outline steeper and smooth, and satisfy the aesthetic request of patients.

PATIENTS AND METHODS

PATIENTS

From July 2005 to November 2007, there were a total of 31 patients in this study who received Mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy to correct the lower facial contour. The patients ranged from 20 to 31 years. Their chief complaint was square facial contour. Out of these patients, 7 cases had asymmetric lower mandible margin and 15 cases had square chin.

Facial appearance characteristics: wide lower face in anterior view; gonial angle less than 120 degrees or approximately 90 degrees; mandibular plane angle less than 30 degree in lateral view; the mandibular inferior border too flat; or flagging mandibular outline. 15 cases had prominent masseteric hypertrophy, and 17 cases had buccal fat pad hypertrophy. The purpose was to change the lower facial contours and satisfy the aesthetic requirements. All the patients had frontal and lateral cephalometric radiographs, panoramic radiographs, and were photographed preoperatively to eliminate or minimize osseous pathological change and tumor and to analyze the mandibular symmetry, the degrees of the gonial angle, and the shape of mandible. Communication with the patient comprehensively about the characteristics of the patient's facial contours was done. At the same time, the line of ostectomy according to the adjustment of mandibular plane angle, the location of mandibular canal and the form of mental region was designed.

Operative Technique

All patients were performed under general anesthesia using nasotracheal intubation. The surgical procedures were performed intraorally. The incision was made from the anterior edge of the ascending ramus in the upper teeth occlusal plane, extending to the central incisor on the buccal side, along the oblique line of the mandible. It was deepened to the periosteum and then was dissected along the subperiosteal plane exposing the lateral cortex of the ramus, the mandibular body region, and the mental region. Precautions were taken when exposing the mental nerve. Same procedure was followed on the other side and exposed to complete the surgery area.

The mandibular angle and the lower margin were exposed completely with Shea's light guided retractors. The cutting line designed from the mental region to the posterior edge of the ascending ramus was performed with a reciprocating saw, and deepened to the lingual cortex of the mandible（Fig. 2a,b）. The finger was placed on the mucous membrane on the lingual side to experience the depth of the cut while operating, and once the lingual cortex of the mandible was completely cut off, cutting was stopped. The cut bone was chiseled gently with the osteotome, and the attachment of medial pterygoid and mylohyoid muscle was detached. Finally, the mandibular inferior margin was removed.

The outer cortex ostectomy (MASO) apply the methods similar to those described by Han and Kim^5，6（Fig 2c,d,e）. The resected mandibular inferior margin and mandibular outer cortex were harvested（Fig 3）.

The step that was formed from the vertical cutting line of mandibular outer cortex ostectomy was smoothened by an electronic bone file or a large sized burr. For some patients with strong masseter, myectomy⁷ of the internal part of masseter was performed and for some with buccal fat pad hypertrophy, “buccal fat pad resection” was performed. The incision was sutured. Negative pressure drainage was applied. Antibiotics were used for 3 to 4 days, and a bulky pressure dressing was applied for 5 days postoperatively in all cases.

Results

The Mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy were performed successfully in all cases. No severe complication and unexpected fractures of the mandible body, ramus, or condyle was observed. Postoperative recovery was uneventful, and all wounds healed by primary intention without local infections.

In the 6~24 months postoperative follow-up period, no facial paralysis or trismus was observed in any of the patients. Transient sensory disturbance of the skin around the mental nerve area was observed in 13 cases, but all recovered within 4 months. Postoperatively, the gonial angle improved to 120~ 130 degrees, the mandibular plane angle improved to 25~ 35 degrees in lateral view, and the mandibular width decreased. The contours of the lower face were efficiently changed in anterior view and lateral view, and the final aesthetic outcomes after the Mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy for square jaw were quite satisfactory in all cases for both surgeons and patients.

Clinical Cases

Case 1

A 26-year-old woman who had had a constant complaint about the shape of her wide lower face sought treatment for a square jaw.

Facial appearance characteristics: In anterior view, the lower face was wide and symmetrical, the gonial angle was 90 degrees, and lower mandibular plane angle was 0 degree in lateral view, with square chin but not too weak and buccal fat pad hypertrophy. In March 2006, the mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy and buccal fat pad resection were performed on this patient. In subsequent visit 12 months after the operation, the postoperative contour was improved expectedly, the mandibular plane angle was improved to 35 degrees, and mandibular angle was improved to 125 degrees. The appearance showed that the lower face was narrowed and symmetrical in anterior view, the mental region became slick, and the facial proportion was suitable. The contour of lower mandible margin was smooth and steep from mental region to mandibular angle region. The final outcome was very satisfying. (Fig.4,5)

Case 2

A 24-year-old man sought treatment for a prominent mandibular angle and square chin.

Facial appearance characteristics: In anterior view, the lower face was wide and angular, the gonial angle was 100 degrees, and the lower mandibular plane angle was 10 degrees in lateral view, with square and dull chin, and masseteric hypertrophy. In May 2007, the mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy and masseter myectomy were performed on this patient. In subsequent visit 12 months after the operation, the mandibular plane angle was improved to 30 degrees, and mandibular angle was improved to 130 degrees. The appearance showed the lower face was slender oval, the facial proportion was suitable, and the contour was smooth and natural. The final outcome was very satisfying. (Fig.6)

Discussion

A square face contour gives a strong, masculine and unattractive impression, which generally is regarded as an aesthetic problem for women or even for some men in Oriental culture. Due to the fashion trends put forth by the celebrities on television and magazines, most of the Orientals are in a favour to own a slender oval face shape. Not only those who have abnormal shape of their lower face, but also those who have normal ones are pursuing their face shapes to be just like some of the celebrities. Therefore, the people who want to do contouring surgery are intended on showing a better, slender, oval and lifting curve with superb outlines of their chins, which will make them look sharp and attractive. ^8，9 Analyzing face contours indicates that the gonial angle is around 120 degrees, the mandibular plane angle is around 25~30 degrees in lateral view, and the contour of the lower face is slender oval in anterior view in those who are considered beautiful. However, the majority of squared-jaw patients with severe forms and with definite square-shaped mandible have low angle deformity. The appearance shows the flat mandibular inferior margin, or flagging mandibular outline, and an obviously squared face. In order to make the square face become a “slender oval face”, the mandibular inferior margin needs to be sloped and the mandibular plane angle must be corrected.

In 1949, Adams proposed a surgical method for masseteric hypertrophy correction to change the square face⁷. However, as muscular hypertrophy was indicated as the main problem in these surgical methods, a partial excision was recommended. Later, Converse proposed the mandibular angle ostectomy thorough both extraoral and intraoral approach¹⁰for correction of square face. However, the operation was related to straight line ostectomy of mandibular angle that usually forms the angular process in the middle of the mandibular body, termed “the second mandibular angle”. Baek et al, Yang, and Park proposed refined methods for prominent mandibular angle to overcome this disadvantage.^11-14 .In these methods, naturally curved outlines of the mandibular angles were obtained through two, three, or four ostectomies. It was thought to be more rational than the straight linear ostectomy method, but also more complicated. Furthermore, the lines linking ostectomies together did not always present a symmetrical curve, and couldn’t modify the mandibular inferior margin efficiently.

In recent years, the lower face contour surgeries pay particular emphasis on the correction of posterior mandibular body, and neglect the importance of the middle part and the mental region. It makes the anterior displacement about the mandibular center of gravity, and the postoperative outcomes present ponderous anterior mandibular body and dull chin.

Outer cortex ostectomy and its refined surgical procedures were then developed and used for aesthetic surgery. It only reduced the width between mandibular angles in anterior view^2，4-6，15 .The flat mandibular inferior margin couldn’t be steepened. Furthermore, the flagging mandibular angle couldn’t be lifted upward only through outer cortex ostectomy. Therefore, the ideal postoperative appearance couldn’t be completely achieved ¹⁶.The “V-line” ostectomy procedure can eliminate the mandibular inferior margin, and efficiently increase the gonial angle and mandibular plane angle. The cosmetic goal is to improve the contour of mandibular inferior margin and steepen the lower face distinctively. Many patients with a squared face and low angle need not only angle resection but also a reduction of the mandibular thickness.

The “V-line” ostectomy procedure combined with outer cortex ostectomy minimizes and narrows the lower face, and achieves the “melon seed” facial contour as the fashionable aesthetics. The “V- line” ostectomy is designed according to the appearance of the patient. The key point in the procedure is the line of ostectomy. The slope degree of the ostectomy lines is determined by the location of mandibular canal, shape of mental region, and the adjustment of lower mandibular plane angle. The new gonial angle (Ar-Go-Me) is formed by the posterior edge of the ascending ramus and the ostectomy line. The point of ostectomy line on the posterior edge of the ascending ramus is determined by the distance from auricular lobule to gonial angle postoperatively.

When we analyze a woman who is considered beautiful, the appropriate distance between the auricular lobule and the new gonial angle is around 2cm on a body-surface projection. If the ostectomy is overdone and makes the new gonial angle either too close to or on the auricular lobule, then the face contour would be unnatural especially in the lateral view.

The line of ostectomy, usually 3mm below the mental foramen, reaches forward and downward at a point in the mental region that is under the apices of the canines. The point is usually the corner of the mental region. The line of ostectomy stops here to avoid the formation of a second mandibular angle. The procedure effectively prevents the formation of the square chin and the anterior displacement about the mandibular center of gravity, and helps shape a pleasing and natural contour of the lower face in the frontal and the lateral view.

The indications of “V-line” ostectomy procedure are square jaw with low angle, over expanded mandibular angle, flagging or convex mandibular inferior margin, and asymmetrical inferior margin with both sides not on the same horizontal plane. The condition for the adapted case is patient with longer ascending ramus of mandible with the appearance showing the distance from auricular lobule to preoperative gonial angle greater than 2cm. For a case with the shorter ascending ramus of mandible, the better procedures would be “V-line” ostectomy procedure combined with the genioplasty. It can make the mental region longer and increase the slope of mandibular inferior margin, so that the facial contour would become slender oval in accordance with the fashionable aesthetics.

Conclusions

This study shows that a slender oval facial contour as the fashionable aesthetics could be achieved by using mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy. It might be a feasible and a reasonable surgical procedure for correction of square jaw with low angles.

References

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Figure Legends

Fig.1.a: Lateral cephalometric radiographs b: Frontal cephalometric radiographs

1.The gonial angle (Ar-Go-Me) 2. The mandibular plane angle (MP-FH) 3. the mandibular width (Go-Go)

Fig. 2. “V-Line” ostectomy (a,b) and mandibular outer cortex ostectomy(c,d,e)

Fig.3. The excised mandibular inferior margin and mandibular outer cortex

Fig.4. Preoperative views of a 26-year-old woman in Case 1(a,c). Postoperative views after mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy and buccal fat pad resection(b,d)

Fig.5. Case 1. Panoramic radiographs: preoperative (a) and postoperative (b); lateral cephalometric radiographs: preoperative(c) and postoperative (d); frontal cephalometric radiographs: preoperative (e) and postoperative (f)

Fig.6. Preoperative views of a 24-year-old man in Case 2(a,c). Postoperative views after mandibular “V-Line” ostectomy combined with mandibular outer cortex ostectomy and internal part of the masseter myectomy (b,d)