Aesthetic crown lengthening is a surgical procedure to correct a “gummy smile,” or to make the teeth appear longer. It is aesthetically driven and usually requires crown lengthening on the just the buccal surface of the teeth in question.
It has been reported that 14 percent of all women and 7 percent of all men have a “gummy smile.”1 When dentists and lay people were polled and shown pictures, most agreed that gingival display up to 2 millimeters was considered normal and pleasing to the eye, while anything more than 3mm of gingival display was considered less attractive.2
Sulcus depth varies, depending on which tooth in the mouth and where on the tooth you’re probing. Assuming that you’re dealing with a periodontally healthy situation, 1–3mm would be deemed within “normal limits” for a sulcus depth. We then will assume the epithelial attachment to be around 1mm, and the connective tissue attachment to be around 1mm as well.2 This usually equates to 3mm from the free gingival margin to the bone on the direct facial, and around 4.5mm on the interproximal areas from the tip of the papilla to the crest of the bone. The only way to know this before surgery is through bone sounding. I always recommend sounding before flapping the tissues, so I can ascertain if I am dealing with a normal, high or low crest situation.4
Some common causes of a “gummy smile” include:
Hyperactive upper lip
What it means: This patient looks “normal” in repose, but shows an excessive amount of gingiva when smiling. Tooth size is normal. The average translation from repose to full smile for women is 7mm; for males, 8mm.
Treatment option: Botox to help immobilize the hyperactive lip.
Short upper lip
What it means: These patients will typically show more than half of the centrals in repose. They will have a “Bugs Bunny” appearance, and may show excessive gingival display when smiling. Tooth size is normal. The average lip length, measured in repose, is from the base of the nose to the inferior border of the lip and is 21mm on average in women and 23mm in men.
Treatment option: Plastic surgery options to lengthen the upper lip.
Vertical maxillary excess
What it means: Essentially, there is too much maxillary bone in the vertical dimension. Tooth size is normal and there is normal lip length and not a hyperactive upper lip. When these patients smile, an excessive amount of gingiva of the maxillary teeth is noticed—usually symmetrically throughout the entire visible smile.
Treatment options: LeFort surgery; lip stat/tuck procedure; orthodontic intrusion.
What it means: Patients with very deep bites, missing lower anterior teeth or worn-down lower anterior teeth are subject to this. Because the maxillary anterior teeth have extruded but not the posterior teeth, the gingiva follows the extrusion of the teeth and thus is shown more when smiling.
Treatment option: Orthodontically intruding the maxillary anterior teeth that have extruded (would ideally then require orthodontics on all maxillary and mandibular teeth to re-establish correct occlusion).
Incisal wear and superuption
What it means: The maxillary teeth have superupted (referring to the anterior teeth only in this scenario) because of occlusion/bruxism.
Treatment options: Orthodontically intruding the maxillary anterior teeth that have extruded (would ideally then require orthodontics on all maxillary and mandibular teeth to re-establish correct occlusion); aesthetic crown lengthening and crowns.
Altered passive eruption
What it means: Too much bone and gingiva are present on the teeth. The teeth will appear shorter and more square shaped. Occlusion is unrelated to this.
Treatment options: Asthetic crown lengthening; gingivectomy, if minimal amount of resection.
Certainly, a combination of the above conditions can exist. This will complicate the diagnosis and likely require interdisciplinary care with a periodontist, oral surgeon, restorative dentist or orthodontist.
This article will focus mainly on altered passive eruption, produced when excessive gum overlaps the enamel limits. The resulting appearance is of short clinical crowns, giving the sensation of “hidden teeth.”
The principles for biologic width and crown lengthening noted in my article about functional osseous crown lengthening in the February 2018 issue of Dentaltown all apply, and the same parameters are followed. We still anticipate a 2mm soft tissue attachment and a 1–2mm sulcus, so we will crown-lengthen accordingly.
Once we have determined that we want to lengthen the teeth, the first question to address will be assessing how long we want the teeth to be and whether we will lengthen the teeth from a gingival direction, an incisal direction or a combination of the two. A diagnostic wax-up often is needed to make this determination within the context of the patient’s smile and occlusion.
The next question is whether restorations will be placed, or if it’s a case of just crown lengthening (bone and tissue). If you don’t plan to place crowns or veneers, exposing the roots may not be a good thing. It could limit the amount of tissue and bone that is removed, and thus not allow the ideal tooth length to be created. For example, if a patient presented with short teeth because of incisal wear but was not planning on having crowns or veneers, then it would be impossible to lengthen the teeth enough to re-create the ideal tooth length without exposing the roots. In a young patient, this may lead to root sensitivity. It may also lead to unaesthetically shaped teeth if the coronal portion of the tooth and the roots don’t have the same color or confluence.
A third factor to consider is how much attached gingiva there is. During most aesthetic crown lengthening cases, the first step is to perform a gingivectomy before flapping the tissues. If there is an inadequate amount of attached gingiva, a gingivectomy will require the patient to undergo a soft-tissue graft later. Another option would be to apically position the gingival flap instead of performing the gingivectomy. This is certainly more challenging.
So, once we’re ready perform an aesthetic crown lengthening, we should have some parameters to follow. For instance, the height-to-width ratio of maxillary anterior teeth is generally about 1.2 : 1. Most centrals and canines are 10–11mm long, while laterals are 8–9mm. (Obviously, this will vary slightly for those with very small or very large teeth.) The idea here is to create teeth that look natural and harmonious with each other. The gingival zenith should be at the same line for canines and centrals, with the laterals being as much as 1.5mm short of that but acceptable to be on the same line. Asymmetries of the teeth on the contralateral side look “off.”
Other factors to consider
Is the patient’s plane of occlusion even with the lower border of the upper lip in full smile? If not, one side may show more gingiva than the other side in full smile. The ideal appearance has the lower border of the top lip at the level of the free gingival margin, so a canted occlusal plane that seeks to accomplish this will end up with one side having longer teeth than the other side. Somewhere a compromise will have to be made unless crowns are made to even this up. If the patient has a “Popeye” smile where in full smile one side goes higher than the other side, the acceptable way to treat this would be to then crown-lengthen to the ideal, based on the incisal edge position.
How many teeth show in the smile? Does the patient show only the front six teeth, or can you see back to the molars? It is unnatural to see large #6–11 with short posterior teeth. This is why we typically will crown-lengthen to the premolars, but this may require exposing some root surface.
1. Robbins, JW. Differential diagnosis and treatment of excess gingival display. Pract Periodontics Aesthet Dent. 1999;11:265-272.
2. Kokich, VO Jr., Kiyak, HA, Shapiro, PA. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Dent. 1999;11:311-324.
3. Gargiulo, AW, Wentz, FM, Orban, B. Dimensions and relations of the dentogingival junction in humans. J Perio 1961;32:261–267.
4. Kois, J. Altering gingival levels: The restorative connection, Part 1: Biologic variables. J Esthet Dent. 1994;6:3–9.