Written by
Lalit Matai, Pharmacist Prescriber (GPhC 2086556) & Clinical Director, MediGlow Aesthetics & Health
If you’ve been researching jawline slimming or teeth grinding treatment, you’ve probably come across a lot of before-and-after photos – and not very much explanation of how it’s actually done, or why it matters who does it.
At MediGlow, we think you deserve to understand exactly what happens during your treatment, why we do things the way we do, and how our approach keeps you safe while delivering results you’ll love. So let’s talk honestly about masseter botulinum toxin – one of our most popular treatments – and what separates a great outcome from a disappointing one.
What Is the Masseter, and Why Does It Matter?
The masseter is a powerful jaw muscle that runs along the lower side of your face, connecting your cheekbone to your jawline. Its job is to help you chew – but in many people, it becomes enlarged over time due to teeth grinding (bruxism), jaw clenching, or simply genetics.
When this muscle becomes overdeveloped, it can give the lower face a wide, square appearance. A small amount of botulinum toxin injected into this muscle causes it to gradually relax and reduce in size – softening the jawline, creating a more oval or V-shaped facial contour, and relieving the tension and discomfort that comes with grinding and clenching.
The results can be genuinely transformative. But – and this is important – only if the injections are placed correctly.
The Part Most Clinics Don’t Tell You About
Here’s something that surprises many of our patients: the masseter sits right next to a thin muscle called the risorius — one of the muscles responsible for your smile.
The risorius runs very close to the surface of the skin at the front edge of the masseter. It’s delicate, it’s shallow, and it plays a meaningful role in how your smile moves. If botulinum toxin spreads into this muscle – even accidentally – it can cause your smile to look flat, uneven, or asymmetric. This is one of the most distressing complications associated with jaw slimming injections, and it is entirely avoidable with the right technique.
This anatomical relationship is well established in the published literature – Bae and colleagues (2014) specifically mapped the risorius muscle’s position relative to the masseter for exactly this reason, providing the anatomical basis clinicians now use to define safe injection zones.
The risorius also connects to neighbouring muscles that influence the corners of the mouth. Disrupting this balance – even subtly – can change the way your face moves in a way that’s immediately noticeable to you and those around you.
We tell you this not to alarm you, but because understanding the anatomy is exactly what makes our approach different.
How We Inject – and Why We Do It This Way
Our technique is built around three principles: correct placement, correct depth, and correct angulation. Here’s what that means for you.
We Target the Bulk of the Muscle
Before any injection, we ask you to clench your teeth. This causes the masseter to contract and firm up beneath the skin, making the muscle clearly palpable. We work in the thick, posterior portion of the muscle – toward the back of the jawline – rather than toward the front or the top. This is where the treatment has the most impact, and where you are furthest from the delicate structures at the front of the face.
We Stay Well Away from the Danger Zone
We deliberately avoid the front third of the masseter. This is the border where the risorius muscle sits just beneath the skin, and no injection should be placed in this region. Our injection points are positioned in a carefully defined safe zone – mapped by anatomical studies and informed by the peer-reviewed literature on this treatment.
We Inject Deep – and Point Posteriorly
Because the risorius is superficial – sitting just under the skin – injecting deep into the muscle body creates meaningful physical distance between the product and this vulnerable structure. Our needles are directed into the belly of the masseter and angled slightly posteriorly, driving the injectate further into the safe zone toward the back of the jaw. This combination of depth and direction is one of the most important technical safeguards in this treatment.
The Dose We Use – and Why
Our standard protocol uses three injection points per side, with 8 units of botulinum toxin at each point. This gives 24 units per side, and 48 units in total across both sides of the face.
| Points per side | Units per point | Total (both sides) |
| 3 | 8 units | 48 units |
This is not arbitrary. Research by Kim et al. (2005) established the three-point technique as safe and effective for both jawline contouring and bruxism. Studies by Wu (2017) and Hexsel et al. (2012) demonstrated reliable, measurable reduction in muscle volume at comparable doses, with MRI-confirmed atrophy and high patient satisfaction.
This dosing approach is also consistent with findings from Ahn, Horn and Blitzer (2004), who studied masseter reduction protocols specifically in Asian patients, and Choe et al. (2005), whose work on lower face contouring outcomes supports comparable dose ranges for predictable, conservative results.
The consensus across published evidence is that this dose range achieves meaningful results without over-treating the muscle or compromising your ability to chew comfortably.
For patients with more significant muscle bulk or severe bruxism, we may consider a modest increase at a follow-up visit – but we always start conservatively. Your safety and your function come before speed of results.
What to Expect After Treatment
Results from masseter botulinum toxin are gradual – which is exactly how good aesthetic treatment should feel.
- Weeks 1–2: The muscle begins to relax; bruxism symptoms often improve first
- Weeks 4–6: Visible softening of the jawline begins
- Weeks 8–12: Full cosmetic result with maximum muscle reduction
- Ongoing: Most patients return every 4–6 months initially; intervals often extend over time as the muscle progressively reduces
There is no downtime. Some patients experience mild tenderness at the injection sites for a day or two. Serious complications, when the treatment is performed correctly, are rare.
Why This Matters When Choosing Your Practitioner
Jawline slimming with botulinum toxin is not a high-risk procedure – but it does require genuine anatomical knowledge and technical discipline. The difference between a clinician who understands the risorius, injects at the right depth, and respects the boundaries of the safe zone – and one who does not – can be the difference between a result you love and a smile you don’t recognise.
At MediGlow, our injectors are Independent Prescribers with specialist training in facial anatomy and aesthetic medicine. We believe that expertise should be visible and explainable – not just claimed.
If you have questions about this treatment or anything else we offer, we welcome a consultation. Book at medi-glow.co.uk or visit us at The Glen Clinic, Glasgow.
Frequently Asked Questions
How much does masseter Botox cost in Glasgow?
At MediGlow, masseter botulinum toxin treatment is priced per session based on dose and technique required. Book a consultation for a personalised quote.
How long does masseter Botox last?
Most patients see results lasting 4 to 6 months initially. As the muscle progressively reduces in size with repeated treatment, many patients find the interval between sessions extends over time.
Will masseter Botox affect my smile?
Not if performed correctly. The risk of smile asymmetry comes from injecting too far forward into the danger zone near the risorius muscle. At MediGlow, injections are placed in the safe posterior zone specifically to avoid this complication.
Can masseter Botox help with teeth grinding?
Yes. Many patients notice improvement in bruxism symptoms within the first 1 to 2 weeks, often before the cosmetic jawline change becomes visible.
Is masseter Botox painful?
Most patients describe mild discomfort similar to a quick pinch. There is no downtime, though some tenderness at injection sites can occur for a day or two.
How many units of Botox does masseter slimming require?
At MediGlow, our standard protocol uses 24 units per side (48 units total), based on a three-point injection technique supported by published clinical research. Your prescriber may adjust this at a follow-up based on your individual response.
Clinical References
- Kim NH, Chung JH, Park RH, Park JB. The use of botulinum toxin type A in aesthetic mandibular contouring. Plast Reconstr Surg. 2005;115(3):919–930.
- Wu WT. Masseter reduction with botulinum toxin type A for cosmetic jawline contouring. Plast Reconstr Surg. 2017;139(4):983–991.
- Hexsel D, Hexsel C, Siega C. Botulinum toxin type A for the treatment of masseter hypertrophy and cosmetic changes to the lower face. Expert Rev Neurother. 2012;12(11):1357–1365.
- Ahn J, Horn C, Blitzer A. Botulinum toxin for masseter reduction in Asian patients. Arch Facial Plast Surg. 2004;6(3):188–191.
- Choe SW, Cho WI, Lee CK, Seo SJ. Effects of botulinum toxin type A on contouring of the lower face. Dermatol Surg. 2005;31(5):502–507.
- Bae JH, Choi DY, Lee JG. The risorius muscle: anatomic considerations with reference to botulinum neurotoxin injection for masseteric hypertrophy. Dermatol Surg. 2014;40(12):1334–1339.
Content produced for educational and informational purposes. Individual results vary. All treatments at MediGlow are carried out by qualified Independent Prescribers.
