Treating a hypertrophic masseter muscle with botulinum toxin
Shad Jaff and Andrew Culbard demonstrate the use of botulinum toxin to alter the aesthetics of the jawline
The use of botulinum toxin type A for the treatment of hyperactive and hypertrophic masseter is not a new concept. There have been dozens of papers and research articles into its efficacy in reducing the activity and size of the muscle since its first reported use in 1994.
As with most developments in facial aesthetic use of toxin, its initial use was for functional treatment. However, secondary to functional, we also discovered aesthetic improvements in the form of a slimmer jawline and a more youthful V-shaped face, with a better zygomatic-gonial ratio.
Anatomy and function
As with any aesthetic procedure, an in-depth knowledge of anatomy and physiology is required to deliver a satisfactory outcome and avoid unwanted complications.
The masseter muscle is a thick, rectangular muscle of mastication. It consists of a superficial and a deep part, both originating from the zygomatic arch.
The superficial part inserts on the masseteric tuberosity at the outer surface of the mandibular angle, whereas the deep part runs further dorsally to the outer surface of the mandibular ramus. At that point, the muscle can be easily palpated from the oral cavity along the cheek.
Furthermore, part of the deep fibres radiates into the anterior capsule and articular disc of the temporomandibular joint. The parotid gland lies on the lateral side of the masseter with its duct coursing underneath the zygomatic arch across the muscle. As all muscles of mastication, the masseter is supplied by a branch of the mandibular nerve, the masseteric nerve (Figure 1).
The masseter is one of the four muscles of the masticatory apparatus. It elevates the mandible, causing a powerful jaw closure. The contraction of the superior part which runs diagonally to the front moves the mandible forward (protrusion). Furthermore, the muscle helps stabilise tension of the articular capsule of the temporomandibular joint.
Review of literature
An early study in 2003 (Park et al, 2003) used ultrasound and CT measurements to analyse the measurements of the masseter muscles in 45 patients. Twenty-five to 30 units of Botox were injected into each side and followed up at one-, three-, four- and 10-month intervals, noting only relatively satisfactory results but a definite favourable improvement. This showed us that the use of botulinum toxin type A for the contouring of the lower face can be predictable and simple.
A more recent study (Xie et al, 2014), which involved more than 200 cases with individualised dosages ranging from 20-40 units each side, showed a significant muscle thickness decrease of up to 4mm. This allowed for dose reduction and reduced risk of any potential complications, such as speech or masticatory function.
Applying what we know from this, we can dramatically improve a patient’s lower face width, creating a more slender contour and help feminise the face.
Kiliaridis S, Kälebo P (1991) Masseter muscle thickness measured by ultrasonography and its relation to facial morphology. J Dent Res 70(9): 1262-1265
Park MY, Ahn KY, Jung DS (2003). Botulinum toxin type A treatment for contouring of the lower face. Dermatol Surg 29(5):477-483
Xie Y, Zhou J, Li H, Cheng C, Herrler T, Li Q (2014) Classification of masseter hypertrophy for tailored botulinum toxin type A treatment. Plast Reconstr Surg 134(2): 209e-218e
Dr Shad Jaff BDS graduated from Glasgow University with commendation in dental surgery and has been working in a mixed private and NHS practice in Glasgow since. Shad has established two aesthetics clinics in Lanarkshire.
Dr Andrew Culbard BDS MJDF RCS Eng is co-founder and clinical director of Face UK. He was awarded his BDS from study at the University of Glasgow Dental School and later gained membership to the Royal College of Surgeons of England in 2015. A practicing cosmetic dentist, Andrew is also an injectables trainer and has lectured for medical organisations around the UK.
This article was originally published in the June 2017 issue of Aesthetic Dentistry Today. Read more articles like this in Aesthetic Dentistry Today and gain three hours’ verifiable CPD with every issue. Click here to subscribe or call 01923 851 777. Get in touch via Twitter @AesDenToday or facebook.com/AesDenToday.