Predictable Treatment for “Gummy Smiles” Due to Altered Passive Eruption
A systematic diagnostic approach based on foundational principles
Depending on the degree, excessive gingival tissue display is a major concern for a large number of patients, as it plays a vital role in the overall harmony of a beautiful smile. To predictably treat this condition and achieve a successful esthetic and stable outcome, the contemporary esthetic dentist must have a clear understanding of the dental-gingival complex and its biologic determinants.1,2
As cosmetic dental treatments are becoming more common, dentists must be able to offer the treatment options available to address their patients’ esthetic concerns. With the awareness and emphasis on overall facial esthetics, both patients and dentists are recognizing the importance of how the amount of gingival display can become a critical component in the make-up of an attractive smile.
Altered passive eruption is a condition in which the relationship between teeth, alveolar bone, and the soft tissues creates an excessive gingival display. Often the patient’s initial chief complaint is of short teeth or a “gummy smile.” In the past, these concerns were often overlooked, or the clinical crowns were lengthened with restorative procedures without investigating the etiologic causes. However, patients and dentists alike are becoming aware of the importance of comprehensive facial evaluations.3-5 Currently, the gingival architecture is a vital aspect of any restorative treatment plan, as clinicians recognize how the gingival complex and its parameters relate to the esthetic treatment of short clinical crowns.
This article presents the differential diagnosis for excessive gingival display and the modality used for the treatment of altered passive eruption.
Possible Etiologies
There are a number of clinical conditions that lead to excessive gingival tissue display when smiling.6 Any successful treatment plan must include a proper diagnosis of the true etiology of the condition with a clear understanding of the dental-gingival complex and its deviation from the norm.7-10
The four etiologies of excessive gingival tissue display include hyper-mobile/short upper lip; compensatory eruption/dental alveolar extrusion; vertical maxillary excess; and altered passive eruption. There are also instances in which a combination of etiologies occurs concurrently.
Normal Tooth Eruption
The normal eruption of teeth occurs in two phases, an active and a passive phase. The active eruption phase involves the physical movement of the tooth out of the alveolar bone into position on the occlusal/incisal plane. The passive eruption phase is the exposure of the crown of the tooth due to the apical migration of the gingival tissues. This apical migration in the passive phase of tooth eruption occurs in four distinct stages:6
Stage 1: The teeth reach the plane of occlusion, and the junctional epithelium is on the enamel.
Stage 2: The epithelial attachment rests partly on the enamel and partly on the cementum apical to the cementoenamel junction (CEJ). The base of the sulcus is on enamel.
Stage 3: The junctional epithelium lies totally on the cementum, with the base of the sulcus at the CEJ.
Stage 4: The epithelial attachment lies totally on the cementum, the base of the sulcus is on the cementum, and a portion of the root may be clinically exposed.
Altered Passive Eruption
Altered passive eruption is the failure of the dental/gingival complex to migrate apically past stage 2 and expose the entire clinical crown to obtain a normal position at the base of the sulcus relative to the CEJ.11 It is estimated that this occurs in about 12% of the general population. Clinically, the most obvious sign of altered passive eruption is a short-looking tooth. Normally, the CEJ resides just apical to the free gingival margin of the anatomic crown, and the sulcus depth usually measures 1 to 3 mm. In cases of altered passive eruption, the CEJ might be up to 10 mm apical to the free gingival margin.
Altered passive eruption, as described by Coslet, is further classified into two case types, based on the free gingival margin and osseous crest relationships with the tooth.6 Type 1 presents with a noticeably thicker biotype and wider band of buccal keratinized tissue, while Type 2 exhibits a narrower band of buccal keratinized tissue that appears to fall into a normal width. Types 1 and 2 are further separated into two subgroups, A and B. In the 1A subgroup, the osseous crest is located 1.5 mm to 2 mm apical to the CEJ, while in the 1B subgroup, the osseous crest is found at the level of the CEJ.
As empirical evidence suggests that Type 1B of Coslet’s classification is the most common type of altered passive eruption observed in nature, this article describes a treatment protocol for this subgroup of altered passive eruption.
Diagnosis
When there are multiple etiologies of excessive gingival display, a series of clinical evaluations is warranted for a clear diagnosis in order to recommend and provide the most appropriate treatment.
In the case of diagnosing altered passive eruption, an assessment is made of the patient’s lips in repose and during a smile. If there is excessive gingival display when the patient smiles naturally, the length and mobility of the upper lip must be evaluated. The normal maxillary lip dynamic has a translation of 6 to 8 mm from rest to full smile and up to 10 mm in a hyper-mobile lip scenario. This first step is utilized to rule out a hyper-mobile/short upper lip, for which the treatment may be lip repositioning surgery or reducing lip mobility with botulism toxin.
The clinical exam should include evaluating any maxillary incisal wear to rule out the possibility of compensatory eruption/dental-alveolar extrusion. Dental-alveolar extrusion is most commonly treated with segmental orthodontic intrusion.12
Traditionally, a cephalometric analysis was utilized to evaluate patients with vertical maxillary excess. An alternative method has been proposed by Misch to rule out vertical maxillary excess by using the maxillary canines and their position relative to the upper lips in repose.13 This study indicates that if the tip of the maxillary canines are at the same level as the maxillary lip line with lips in repose, any excessive tissue display when the patient smiles is not likely a result of vertical maxillary excess. A diagnosis of vertical maxillary excess would be indicated if the amount of maxillary canine cusp tip display were 2 mm or greater with the maxillary lip in repose. In Misch’s study, the maxillary canine position to lips in repose had an average dimension within 1 mm of the upper lip, regardless of gender or age. Due to the very narrow range of the canine exposure in the population, it is suggested that this relationship may be used as a more predictable determinant of anterior tooth position.
