| BOTulInumTOxIn A | articLe
Exaggerated upper gummy smile Some individuals have a tendency to reveal an excessive amount of their upper gum mucosa when they smile or laugh. Consequently, they attempt only to smile partially when being photographed or during social interactions. These individuals also tend to have sharply defined nasolabial folds with deep furrows. Some patients, in conjunction with the inadvertent
shortening of their upper lip causing an exaggerated gingival smile, are also plagued with exhibiting an involuntary lowering of the tip of their nose. There are still others who also form a transverse furrow across the philtrum of their upper lip when they speak, laugh, or smile. Occasionally, the same person will exhibit a combination of all of these changes. A horizontal furrow across the upper lip is usually seen in older individuals or in those whose photodamaged skin has reduced elasticity and soft tissue bulk, causing the lax upper lip skin to wrinkle easily with every lip movement. many of these individuals also have a history of smoking tobacco.
Functional anatomy The aesthetics of ideal tooth exposure when smiling varies according to structural and topographic anatomy, but has been loosely calculated to be three quarters of the dental crown height of the upper incisors and no more exposure than 1–2 mm of upper gum mucosa (23,24). There are many reasons for a ‘gingival smile’. It can be the result of an increase in the interlabial space combined with an excessive contraction of the upper lip levators, producing an excessive amount of exposure of the gums on smiling or laughing (25,26). Additional causes include an elongation of facial height created by an excessive vertical length of the maxilla, a genetically short upper lip, and a short crown length, with or without malpositioning of the incisors (27). According to Rubin, there are three patterns of smiles
by which an individual is identified (28,29). The first and most commonly encountered type of smile (67% of patients) is when the zygomaticus major dominates the movement of the lips. This is called the ‘mona lisa’ smile, and is initiated with a sharp elevation and outward pull of the corners of the mouth, and then a soft elevation of the centre of the upper lip, revealing approximately 80% of the incisors. The canine smile is the second most commonly
identified smile pattern (35%) and is characterized by a high elevation of the centre of the upper lip, exposing the canine teeth before the rest of the upper lip is elevated. The canine smile can produce anywhere from a partial central dental reveal to an exaggerated full denture show with a certain amount of gingival exposure. This pattern of smile is produced predominantly by the contraction of the levator labii superioris elevating the upper lip. When the contraction of the levator labii superioris is intense and severe, a gummy smile results. The third and least commonly seen smile pattern is
the full denture smile, which is seen in approximately 2% of patients. This smile is characterised by the
simultaneous separation of both the upper and lower lips, in which both the upper and lower dentures have partial or full exposure. This type of smile is the result of the contraction of all the upper lip levators and lower lip depressors around the mouth at the same time. Commonly found with a simple canine or exaggerated
canine smiles are individuals with deep nasolabial furrows and highly mounded nasolabial folds. These two conditions usually are found together, because contraction of the levator labii superioris alaeque nasi creates an ascending steep medial nasolabial fold while lifting the central upper lip a few extra millimetres, which can also over-expose the alveolar gingiva. With such hyperkinetic upper lip levators, asymmetric smiles are not uncommon.
prime-journal.com | May 2011 ❚ 29
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