Unlocking the Path to Optimal Restorative Esthetics
Crown lengthening is crucial for addressing issues including caries, fractures, and altered passive eruption, ultimately enhancing both function and esthetics in restorative dentistry. By carefully planning and modeling restorative contours, clinicians can ensure ideal gingival relationships and tooth display for each patient, leading to beautiful, effective outcomes.
Indications for crown lengthening include caries or tooth fracture at or below the gingival margin, teeth with excessive occlusal loss, teeth with insufficient interocclusal space for a required restorative procedure and altered passive eruption (APE). The treatment plan is predicated on the diagnosis and goals of definitive therapy.1
Esthetic crown lengthening or anatomical crown exposure aims to provide the correct dentogingival relationship in cases of APE or gingival enlargement. Such procedures may or may not include osseous resection and are usually limited to the facial surface of the teeth involved. The appearance of short clinical crowns can lead to the suspicion of APE. Clinical evaluation is performed with the aid of an explorer to identify the presence or absence of an intrasulcular cementoenamel junction (CEJ). The CEJ should be located at the level of the gingival margin or in the dental sulcus. The inability to identify the CEJ on short clinical crowns leads to a diagnosis of APE.2
Functional crown lengthening improves restorative access by exposing more tooth structure for a prosthesis. This procedure always requires osseous resection, which is usually performed circumferentially. Commonly accepted crown preparation guidelines include a minimal occlusocervical dimension of 4 mm for molars, and 3 mm for other teeth.3 The occlusocervical-to-faciolingual dimensional ratio should be at least 0.4 for the preparation to provide adequate resistance and retention form. These dimensions are used as a guideline when reestablishing the coronal tooth structure necessary to enable the restoration of a compromised tooth. When possible, a supragingival finish line is preferred, and subgingival finish lines should not extend into the epithelial attachment.3
Prior to proceeding with any crown lengthening procedure, a restorative plan should be determined. In cases involving the maxillary anterior teeth, restorative treatment plans should consider esthetic guidelines. The location of anterior teeth in space can be broken down into their vertical and horizontal position. The vertical position of anterior teeth is guided by the desired amount of tooth display at rest. Maxillary anterior tooth display at repose tends to decrease with age. The average 30- to 39-year-old shows around 1.5 mm of the maxillary central incisors, and this value decreases around 0.5 mm each decade.4 These dimensions help determine age-appropriate display of the anterior teeth. Phonetics and esthetics guide the horizontal position of these teeth. Once these positions are determined, it is clinically desirable for the incisal edges to parallel the lower lip line (also known as the smile line).5
Definitive restoration contours may be modeled using an analog or digital approach. An analog approach requires maxillary and mandibular diagnostic casts mounted in either centric relation or maximum intercuspation, depending on whether the restorative treatment is conformative or rehabilitative. A digital approach requires a surface scan of the maxillary and mandibular dentition and design software. Prior to proceeding with surgical treatment, the proposed restorative contours should be modeled intraorally. This offers both the provider and patient an opportunity to make modifications to the treatment plan prior to providing care that is irreversible. The location and contours of the definitive restorations will determine the desired location of the gingival margins.
References
- Rosenberg ES, Garber DA, Evian CI. Tooth lengthening procedures. Compend Contin Educ Gen Dent. 1980;1:161–172.
- Dolt AH, Robbins JW. Altered passive eruption: an etiology of short clinical crowns. Quintessence Int. 1997;28:262–272.
- Goodacre CJ, Campagni WV, Aquilino SA. Tooth preparations for complete crowns: an art form based on scientific principles. J Prosthet Dent. 2001;85:363–376.
- Vig RG, Brundo GC. The kinetics of anterior tooth display. J Prosthet Dent. 1978;39:502–504.
- Lombardi RE. The principles of visual perception and their clinical application to denture esthetics. J Prosthet Dent. 1973;29:358–382.
This information originally appeared in Saltz AE, Antonella AB. Decision-Making in Esthetic and Functional Crown Lengthening. Decisions in Dentistry. March 2022;8(3)30-33.
