ABSTRACT
In Asian and Western countries, the desire for beauty has been regarded as one of the basic instincts of mankind. In days gone by, with no development in transportation and communication, esthetic standards differed depending on regional, racial, and national groups. However, in modern times, a universal standard for beauty is being established due to globalization by the remarkable developments in transportation and communication. This phenomenon might be explained by the fact that the esthetic standard of both Western and Asian countries has merged, or it might be accounted for by the fact that the Westerners have an aspiration for Asian beauty, while Easterners have a desire for Western beauty. Since Northeastern Asians, including Koreans,
belong ethnically to the Mongolian race, they tend congenitally to have a well-developed mandible compared to Westerners. The well-developed mandible makes the face look more quadrangular. Whether it is congenital or acquired, a developed masseter muscle makes the face look wider. This is bad for women esthetically, because a square face gives a masculine image. From the view of an esthetic standard, it is more desirable for the bigonial distance (width of lower face) to be narrower than the bizygomatic distance (width of mid-face). The classical standard bigonial to bizygomatic ratio was 9:10, but a narrower bigonial distance has become preferred in recent years (Figure 21.1). The size of the mandible, the volume of muscle that
surrounds the mandible, and the subcutaneous fat tissues determine the width of the lower third of the face. In a case of overdeveloped mandible, it can be corrected by bone resection, and excessive fat tissues can be removed by liposuction. However, if the main factor is masseter hypertrophy, a treatment for the masseter muscle itself is essentially needed. In the historical background of treatment for masse-
teric hypertrophy and square-angled jaw, in 1880 Legg first described benign masseteric hypertrophy as a condition characterized by the enlargement of the
masseter muscle.1 Since then, conservative treatments, including systemic medications with stabilizers or sedatives and reconfirmation, have been used to treat benign masseteric hypertrophy. Gurney, in 1947, performed masseteric resection through an extraoral incision.2 The operation resected 75% of the total masseter muscle and did not cause loss of the masticatory capacity. In 1951, Converse used the intraoral route to resect the masseteric muscle and the bone together (unpublished work). In 1989, Whitaker presented a method to reduce the width of the lower facial portion by resection of the mandible cortical layer and themassetericmuscle.4 Baek et al found out that the masseteric muscle volume was reduced over time as the muscle tone deteriorated, even though only the mandible was resected.5-7 Experiments in rabbits proved that the unused masseteric muscle shows akinetic atrophy after ostectomy of the mandible. There is also a viewpoint that masseter atrophy occurs after resection of the mandibular angle around the masseter insertion, because this reduces the tone of the masseter muscle. According to these viewpoints, surgical treatments for a square-angled mandible have been frequently applied even in cases of muscular hypertrophy. Muscle resection could be an alternative; however, direct resection of the masseter muscle can result in considerable bleeding or facial nerve injury. Moreover, it is technically impossible to create even contour lines using exact resection of a definite muscle volume. In addition, scar tissues or contracture that remains in the muscle after muscle resection can lead to trismus when the patient opens his mouth. Furthermore, mandible resections for masseter atrophy have sometimes resulted in unexpected outcomes owing to a structural change in the mandible. Smyth, in 1994, reported that the masseter muscle
was reduced by using the application of botulinum toxin A (Dysport®) in seven cases of masseter hypertrophy.9 This clinical experiment was carried out for the purpose of confirming the effect of botulinum toxin A injection on masseter hypertrophy as well as determining the influence on pain. As a result, as well as a reduction in volume of the masseter muscle, bruxism and clenching habits were stopped. Botulinum toxin A injection was an innovative event in that
period when surgery was the mainstream of treatment for masseter hypertrophy. In the same year, Moore and Wood presented a case of treating bilateral masseteric hypertrophy accompanying temporomandibular disorder (TMD) by using botulinum toxin A.10
