From the Research
The recommended dose of botulinum toxin (Botox) for masseter muscle injections is 10 units per side, as supported by the most recent and highest quality study 1. This dose has been shown to be effective in reducing the frequency of bruxism episodes, decreasing pain levels, and reducing muscle spasms associated with nocturnal bruxism. The injection should be administered into the thickest part of the masseter muscle, usually divided into 3-5 injection points per side. Before injection, the patient should be asked to clench their teeth to identify and mark the bulkiest portion of the muscle. The injections should be placed at least 1 cm away from the mandibular border to avoid affecting adjacent muscles like the risorius or depressor anguli oris. The procedure is performed using a 30-gauge needle, with injections placed deep into the muscle body. Results typically appear within 1-2 weeks and last 3-6 months. Patients should be informed that maximum effect may take up to 4 weeks to develop. This treatment works by temporarily blocking acetylcholine release at neuromuscular junctions, causing partial muscle atrophy and reduced muscle bulk. Potential side effects include temporary difficulty chewing, asymmetric smile, or bruising at injection sites. Treatment should be avoided in pregnant women, those with neuromuscular disorders, or patients taking aminoglycoside antibiotics. It is also important to note that the use of botulinum toxin for masseter hypertrophy has been supported by other studies, including a systematic review that found it to be a safe and effective treatment option 2, 3. However, the most recent and highest quality study 1 supports the use of a lower dose of 10 units per side, which should be taken into consideration when making treatment decisions. Additionally, a study on the complications of botulinum toxin injection for masseter hypertrophy found that the incidence of side effects can be minimized by injecting within the recommended safety zone and avoiding important local structures 4. Overall, the use of botulinum toxin for masseter muscle injections is a safe and effective treatment option, and the recommended dose of 10 units per side should be considered in clinical practice.