Correction of a gingival smile with botulinum toxin A
In some people, most of the gum lining is visible when smiling or laughing. These people also often have well-defined nasolabial folds with deep furrows. Some patients, along with the voluntary shortening of the upper lip, also involuntarily lower the tip of the nose.
There are also patients who develop a transverse fold along the philtrum of the upper lip while laughing or talking. There are also cases when all of the above processes are observed in patients. A horizontal groove along the upper lip is more common in older patients or in those whose skin has been damaged by sun exposure, causing it to lose elasticity and soft tissue volume, which contributes to the formation of wrinkles during movement of the upper lip. Many of these patients smoke.
Functional Anatomy
The aesthetics of the ideal visibility of the tooth when smiling depends on the structural and topographic anatomy, but is approximately three-quarters of the height of the dental crown of the upper incisors, provided that the mucous membrane of the gums is visible no more than 1-2 mm in size. There are many causes of a gingival smile, such as increased space between the lips and excessive contraction of the muscles that lift the upper lip. Additional causes include facial height elongation created by excessive vertical maxillary length, congenital short upper lip, and short crowns, with or without incisor misalignment.
According to Rubin, there are three main types of smile. The first type is the most common (67% of patients) and is characterized by the predominance of the large zygomatic muscle in the movement of the lips. The "canine" smile is the second most common smile (35%) and is characterized by a high elevation of the center of the upper lip, in which fangs are visible. This type of smile is provided mainly by contraction of the muscle that raises the upper lip. The third and least common type of smile is the "tooth smile" (2%). A feature of this smile is the simultaneous separation of the upper and lower lips, with such a smile, all teeth are visible - in whole or in part. This type of smile is the result of contraction of all the muscles that raise the upper lip and the muscles that lower the lower lip.
Patients with normal or enlarged canine smiles tend to have deep nasolabial furrows and well-defined nasolabial folds. These two phenomena usually appear together, since contraction of the levator labii and ala of the nose creates an ascending nasolabial fold, while at the same time lifting the central part of the upper lip upward by several millimeters, which also leads to excessive visibility of the alveolar part of the gum. . In the presence of such hyperkinetic muscles that lift the upper lip, smile asymmetry is often found.
Onabotulinum toxin A dosage for gingival smile correction
Non-surgical upper lip lengthening requires weakening (but not paralyzing) the medial levator lip muscles with injections of onabotulinum toxin A. This can be done with the patient in a reclining position. Palpate the nasopharynx with the tip of your index finger. Excessive pressure in this area can cause discomfort to the patient, so this should be done as quickly as possible. When the patient smiles with this position of the index finger, one can feel the contraction of the muscle that lifts the upper lip and ala of the nose. At the point of maximum muscle thickness, insert the needle into the nasofacial sulcus to a depth of approximately 3-5 mm. Inject 1-2 units of onabotulinum toxin A intramuscularly and directly over the periosteum of the canine fossa. If the central muscles that lift the lip are very strong, an additional unit of ona botulinum toxin A may be needed. This procedure is done only for patients with excessive gingival smile and in whom the levator lip and alar of the nose are palpable.
Another technique is to inject 1-2 units of onabotulinum toxin A into the oral cavity in the abdomen of the two central muscles that lift the upper lip by passing the needle through the gingival-labial sulcus above the alveolar margin at the very point of the nasolofacial sulcus described above. The minimum dose of onabotulinumtoxin A should only relax the central muscles that lift the upper lip so that it does not rise all the way up. If most gingiva is visible in the central part of the lips, 1 unit of onabotulinum toxin A can be injected into the muscle that depresses the nasal septum at the base of the columella.
Complications after onabotulinum toxin A
The risk of treating patients with a gingival smile is very high due to the anatomy of various interdependent muscles and their connections with the skin of the upper lip and the orbicularis oculi. The use of electromyography during the procedure will provide more accurate needle placement and avoid incorrect results during onabotulinum toxin A injections.
Inaccurate needle insertion or overdose in this area can lead to lip ptosis and smile asymmetry, which can be accompanied by buccal sphincter dysfunction, difficulty pronouncing certain sounds, and an inability to move the upper lip during a full smile. The muscles that lift the upper lip can be easily damaged by even the slightest amount of accidental diffusion of onabotulinum toxin A.
According to Prime magazine.
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