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A 3-Month Reduction in the Maximal Voluntary Bite Force Following a Single Injection of Botulinum Neurotoxin Into the Masseter Muscles Bilaterally
TAKE-HOME MESSAGE
- In this prospective study designed to evaluate the duration of maximal voluntary bite force (MVBF) reduction after a single injection of 25 U of botulinum neurotoxin A (BoNT A) into the masseter muscles bilaterally in individuals seeking esthetic treatment of self-perceived bulky masseters, a significant reduction in MVBF was observed in the test group but not in the control (no intervention) group at 3 months. At 6 and 12 months after injection, no significant reduction in MVBF was observed. However, visual improvement of lower facial contouring was observed for more than 3 months.
- BoNT A injections into the masseter muscles are administered by physicians and dentists for various off-label uses, including as an esthetic treatment to reduce the masseter volume or to treat bruxism. This was the first study to include parameters that could be measured objectively. BoNT A–induced reduction in the masseter's strength may ameliorate bruxism and mitigate pathological dental wear or failure of dental restorations.
abstract
This abstract is available on the publisher's site.
Access this abstract nowBACKGROUND
Previous studies concerning the effect of botulinum toxin in masseter muscle have mainly reported effects observed through inspection of facial features or differences in pain levels. One systematic review of studies utilizing objective measurements reported that long-term muscular effect of botulinum neurotoxin injections into masseter muscle was inconclusive.
OBJECTIVE
To evaluate the duration of reduced maximal voluntary bite force (MVBF) after botulinum toxin intervention.
METHODS
The intervention group was comprised of individuals seeking aesthetic treatment for masseter reduction (n = 20), the reference group (n = 12) comprised of individuals with no intervention. Intervention through 25 units of Xeomin® (Merz Pharma GmbH & Co KGaA, Frankfurt am Main, Germany) botulinum neurotoxin type A injected into the masseter muscles bilaterally (totalling 50 units). A reference group did not receive any intervention. MVBF was measured in Newtons using a strain gauge meter at the incisors and first molars. MVBF was measured at baseline, at 4 weeks, 3 months, 6 months, and after 1 year.
RESULTS
Both groups were similar in terms of bite force, sex and age at baseline. MVBF remained similar compared to baseline in the reference group. At 3 months, a significant reduction at all measurement points was observed in the intervention group; at 6 months, this reduction was no longer significant.
CONCLUSION
A single intervention of 50 units of botulinum neurotoxin results in a reversible MVBF reduction of at least 3 months, although a visually discernable reduction may be more long-lasting.
Additional Info
Disclosure statements are available on the authors' profiles:
Duration of bite force reduction following a single injection of botulinum toxin in the masseter muscle bilaterally: A one-year non-randomized trial
J Oral Rehabil 2023 May 01;50(5)343-350, M Ågren, Y Nanchaipruek, P Phumariyapong, C Apinuntham, S Rakchart, M Pettersson, R WanitphakdeedechaFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Whether treatment goals are for esthetic changes, managing pain, or treating bruxism, the dental clinician needs to establish the correct neuromodulator dose, provide the expected duration of efficacy, and predict possible long-term changes. In this article, a single dose of 50 units of botulinum neurotoxin (Xeomin®; Merz Pharma GmbH & Co KGaA) was injected into the masseters (25 U bilaterally) in the intervention group of 20 female participants (selected using exclusion criteria of a history of temporomandibular joint pain, pregnancy, and edentulous spans) for either esthetic changes or for the treatment of bruxism. A reference (nontreatment) group of 12 female participants was also evaluated. A baseline maximal voluntary bite force (MVBF) measured in Newtons was taken and repeated at specific time intervals following a single botulinum toxin dose using a custom strain gauge meter placed in the anterior, right, and left posterior areas. This provided data regarding the measurable changes in both the reference and treatment groups over the study duration of 12 months. The first molar bite force measurement demonstrated a significant reduction in the treatment group, which declined gradually over time. Both treatment groups had a reduction in MVBF at 3 months and showed desired esthetic changes (reduced muscle size with effects declining over time). The reference group showed a slight increase in the right first molar MVBF in the same period. The ability to quantify the patient’s baseline bite force and utilize this diagnostic information to determine the treatment goals, dosage, efficacy of treatment, and recommended frequency of retreatment is invaluable for the clinician. Adding a bite force test in my neuromodulator practice has helped with data collection, informed consent, and monitoring of patient outcomes.