Can Botox of the Masseter muscle result in bone loss, and should I be concerned?

Thank you for your very interesting question. Bone loss after masseter Botulinum toxin ('botox') injections does sound scary. You are probably quite worried about complications developing since you have been undergoing them. Hope I can clarify your doubts!

Can Botox of the Masseter muscle result in bone loss, and should I be concerned?

Studies do show that yes, repeated injections of Botox into the masseter can produce bone changes in the mandible. In a Korean study involving 20 patients, a series of Botox injections into the lower third of the masseters produced reductions in the volume of the mandibular angle. This, however, is not as alarming as it sounds.

It is normal for a bone to respond to disuse or load reduction by decreasing in size and thickness. This may not have any clinical significance or functional impact. The Korean study actually showed a reduction in the volume of the mandibular angle, which may actually help to slim the facial shape in patients who have pronounced or strongly square-shaped face due to not just masseter enlargement but a prominent mandibular angle.

There are also other studies that indicate bone loss in the temporomandibular joint (TMJ) that opens and closes the mouth after Botox. This may not be clinically relevant given that:

1. The studies were done in animals, not humans.

2. The studies were done to investigate the effect of Botox on TMJ pain, in which masticatory muscles other than the masseters are injected.

3. The bone loss on the TMJ was shown to be reversible.

4. In masseter Botox we generally only relax the lower part of the masseter muscles, hence there is still loading on the TMJ, thus it shouldn't produce similar effects as the animal studies.

I perform Botox injections to the masseters very frequently. I have not encountered any problems with bone loss or TMJ problems after masseter Botox over the years.

Hope this reassures you!

Warmest regards,

Dr Wan Chee Kwang

References

1. Lee et al. Repeated injections of botulinum toxin into the masseter muscle induce bony changes in human adults: A longitudinal study. Korean J Orthod. 2017 Jul;47(4):222-228.

2. Raphael et al. Osteopenic consequences of botulinum toxin injections in the masticatory muscles: a pilot study. Journal of Oral Rehabilitation, 41(8), 555–563. J Oral Rehabil 41: 555–563.

3. Dutra et al. Loading of the Condylar Cartilage Can Rescue the Effects of Botox on TMJ. Calcif Tissue Int. 2018 Jul;103(1):71-79.

Hi Michelle!

The massetor acts on ur jawbone and helps chewing. Like all the bones in your body, a lack of muscular action on them would cause a decrease in bone density, that’s why exercise is recommended to increase bone density and prevent osteoporosis in the elderly.

Botox of the massetor reduces the action of chewing, and thus may cause some bone resorption. However the effect is minimal and has not caused any complications to patients in my practice or in the literature.

Hope that helps!

Regards,

Dr Harvey Ho

Botox of the masseter muscles relaxes the masster muscles and are useful in hypertrophied masseters and for facial shaping, i.e. getting a more defined jawline.

It does not affect the bone at all, as the botox is injected into the masseter muscle bulk, and hence does not result in bone loss. Botox exerts its action on muscles and not on bone.

Hope that answers your query.

There is no need to worry. There is no evidence that Botox of the masseter (jaw muscle) causes bone loss. Botox works by weakening the masseter over a period of 3-4 months to cause a reduction in muscle size. It does not affect the bone in any way.

Cheers! Dr Terence Tan