ORAL HEALTH EVIDENCE-BASED PRACTICE PROGRAM
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Title The Use of Botulinum Toxin for Treatment of Gummy Smiles
Clinical Question Is the use of Botulinum toxin an effective treatment option for patients presenting with excessive gingival display otherwise known as gummy smile?
Clinical Bottom Line The use of Botulinum toxin for treatment of a gummy smile is effective if the gummy smile is a result of hyperactivity of the lip.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 18249285Polo/200830 Hispanic subjects aged 15-41 years old presenting with gummy smileCase Series
Key resultsSubjects identified to have a gummy smile due to facial muscle hyperactivity were injected with Botulinum toxin in the facial muscles deemed responsible. An average lip drop of 5.2 mm compared to baseline was noted 2 weeks after injection (P < 0.00001). This result gradually decreased to final follow up at 24 weeks. At 24 weeks, gingival display was still reduced compared to baseline.
#2) 21093661Mazzuco/201016 Female subjects presenting with gummy smileCase Series
Key resultsSubjects were injected with Botulinum toxin in facial muscles deemed responsible for their specific type of gummy smile (Anterior, Posterior, Mixed, Asymmetric). At decrease in gingival display of 75% was noted for all subjects 20 – 30 days post injection. Results lasted for 3-5 months.
#3) 15750541Polo/20055 female subjects, 16-23 years old presenting with gummy smileCase Series
Key resultsSubjects identified to have a gummy smile due to facial muscle hyperactivity were injected with Botulinum toxin. An average of 4.2 mm decrease in gingival display was noted at 2 weeks post injection. Subjects were followed for 16 weeks.
Evidence Search Botulinum toxin, gummy smile
Comments on
The Evidence
These studies show promising results however are limited by lack of sample size calculation, randomization and absence of a control. Furthermore, only Polo 2008 provides statistical analysis of results. These limitations reduce the internal validity of the studies. Little evidence exists for this technique and randomized control trials are needed to strengthen the evidence pertaining to the use of Botulinum toxin in the treatment of gummy smile.
Applicability Applicable to dental practitioners seeking a conservative option for treatment of patients with gummy smiles resulting from lip hyperactivity.
Specialty/Discipline (General Dentistry) (Orthodontics) (Periodontics) (Prosthodontics) (Restorative Dentistry)
Keywords Botulinum toxin, gummy smile, excessive gingival display, cosmetic dentistry
ID# 2312
Date of submission: 08/03/2012spacer
E-mail suttonk@livemail.uthscsa.edu
Author Kirk Sutton
Co-author(s)
Co-author(s) e-mail
Faculty mentor/Co-author Kevin M. Gureckis, DMD
Faculty mentor/Co-author e-mail gureckis@uthscsa.edu
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
post a rationale
by Kirk Sutton (San Antonio, Texas) on 09/18/2012
Botulinum Toxin is derived from the bacteria Clostridium botulinum which produces seven distinct neurotoxins A through G. Botulinum Toxin A (BTX-A) is the most commonly used subtype in humans and acts through preventing the release of acetylcholine (ACH) into the neuromuscular junction therefore inhibiting down stream muscles contraction. BTX-A works specifically on SNARE proteins (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) in the nerve terminus. SNARE proteins are on the intra-cellular vesicles which contain ACH and on the cell membrane and facilitate the fusion of vesicles with the cell membrane and subsequent release of ACH into the synaptic cleft. Neuromuscular activity returns over a period of 3 months as new smaller nerve endings develop to help regain function. Moreover, original nerve conduction is restored during this time as new SNARE proteins are produced in the original nerve terminus. BTX is used for the treatment of gummy smile via injection into strategic locations of the face thereby inhibiting action of 5 primary muscles involved in the movement of the lip during smile. These muslces include: levator labii superiouris alaeque nasi, levator labii superioris, zygomaticus minor. zygomaticus major and risorius. References: Christian, M. & Solish, N. (2007). Botulinum Toxin Injections. In S. Wolvertons (2nd ed.) Comprehensive Dermatologic Drug Therapy (pp. 851-861). Philidelphia: Saunders Elsevier and PMID: 21093661.
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