Slimming the Jaw Muscle and Temple Changes: A Surprising Link

A small 2020 study looked at nine women who had a neuromodulator injected into the large chewing muscle at the angle of the jaw. As expected, the jaw area became less bulky, but the researchers also measured a modest increase in fullness at the temples. The finding is interesting because it suggests that treating one part of the face can change another, though it comes from a very small group and needs confirming.

Why this was studied

The masseter is the thick muscle you can feel at the back of your jaw when you clench your teeth. In some people it is large, either naturally or because of clenching and grinding, which can make the lower face look square or wide. Small doses of botulinum toxin type A, placed into the muscle, relax it so that it gradually becomes less bulky over several weeks. Our article on jaw clenching and masseter treatment explains that treatment in more detail.

The research team had noticed something unexpected in their own practice: after masseter treatment, some patients' temples seemed less hollow. Temple hollowing is a common sign of ageing and is usually treated with filler. The researchers wanted to check whether the change they thought they were seeing could actually be measured.

What the researchers did

The study drew on a group of nine women, average age about 35, who were being treated for enlarged masseter muscles. Each received the same total dose into the masseters on both sides. Some were treated with a single injection point per side and others with several smaller injection points spread across the muscle, so the team could also compare the two approaches.

Three-dimensional scans of the whole face were taken before treatment and again 16 weeks later. Two independent assessors rated both masseter prominence and temple hollowness using standard rating scales, and the scans were used to calculate the volume of the temple area directly.

What they found

Masseter prominence dropped clearly on the rating scale, which matches what is already well known about this treatment. Temple hollowness scores also improved, typically by one point on the scale, with one person improving by two. On the 3D scans, the temple area gained an average of just under 2 cubic centimetres of volume, although that average varied widely from person to person.

The single-point and multi-point techniques produced similar results on every measure. The authors suggest a likely explanation: when the masseter is relaxed, the temporalis, another chewing muscle that sits under the temple, may take on more of the work of chewing. A muscle that works harder can become a little fuller, which would make the temple look less hollow.

How strong is this evidence?

This is early, exploratory evidence. It is useful for raising a question, but it cannot settle one. Key limits include:

• Nine participants is a very small number, and all were relatively young women. The results may not apply to men or to older adults, whose temple hollowing often relates to fat and bone changes.
• No comparison group was left untreated, so the study cannot rule out other reasons for change over 16 weeks.
• The temple measurements were added partway through a larger trial, which is one reason the group was so small.
• The muscle explanation was not directly tested. The authors note that recording muscle activity would be needed to confirm that the temporalis is responsible.
• Industry links: the lead author disclosed working with the manufacturer of the neuromodulator used.

The report also did not present side-effect data, so it adds nothing new on safety. The authors themselves describe this as a possible additional effect of jaw treatment, not a new way to treat the temples.

What it means for you

The broader message is one many clinicians already share: the face works as a connected system. Muscles, fat, bone and skin influence one another, and a change in one area can show up somewhere else. That is a good reason for a whole-face assessment rather than treating each feature in isolation, which our article on facial balancing discusses.

For someone considering masseter treatment, this study does not mean you should expect fuller temples. Any change seen was small, varied between people, and has not been confirmed in larger groups. If temple hollowing bothers you, it is better to discuss it as its own concern. Options are covered in our article on temple hollowing and filler.

It is also worth remembering the usual points about masseter treatment. Results build over several weeks and fade over months, so repeat treatment is usually needed to maintain the effect. Possible side effects include tenderness, bruising, temporary chewing fatigue and, uncommonly, a change in smile if the product spreads to nearby muscles. Neuromodulators are not used during pregnancy or breastfeeding, or in people with certain nerve and muscle conditions.

Questions to ask at your consultation

• Is my wide jaw mainly muscle, bone, fat or a combination?
• Do I clench or grind, and should my dentist also be involved?
• How might relaxing the masseter affect other areas of my face?
• How long does treatment typically last, and what happens if I stop?

Frequently asked questions

Will masseter treatment make my temples look fuller?

Possibly a little, but this has only been measured in a handful of people. It should not be the reason for choosing jaw treatment, and many people may notice no change at all.

Could relaxing the jaw muscle make my temples look more hollow?

This study found the opposite on average, but it was too small to describe every possible response. Your clinician can look at your temples and jaw together before treatment and at follow-up.

Does the number of injection points matter?

In this study, one point and several points per side gave similar results. Injection pattern is still chosen individually, based on muscle size, shape and safety around nearby structures.

If you are wondering whether jaw slimming suits you, a consultation at HealthPark Medical Aesthetics can include a full-face assessment and a frank discussion of what the evidence does and does not show.

Source

Nikolis A, Enright KM, Rudolph C, Cotofana S. Temporal volume increase after reduction of masseteric hypertrophy utilizing [a botulinum toxin type A product; brand name omitted]. Journal of Cosmetic Dermatology, 2020. Read the study