Question: What are the Parameters for Esthetic Crown Lengthening?

By Robert A. Lowe, DDS; Elizabeth M. Bakeman, DDS; J. William Robbins, DDS, MA

For minor, localized biologic width and/or esthetic gingival zenith corrections, the Er,Cr: YSGG laser can be used, performing a “closed” surgical technique, instead of a open flap procedure, to make the correction and complete the restorative process without the necessary healing time required for open crown-lengthening surgeries. The soft tissues (epithelial and connective tissue attachments) are resected using a 9-mm, 600-µm tip in the proximal area. The osseous crest is sounded using a periodontal probe to determine its position and topography. Using a 9-mm, 600-µm tip, the laser is then used to remove bone, holding the tip adjacent to the tooth and “walking” the tip across the affected area using a “sewing machine” (up and down movement) to a 3-mm depth. After establishing the corrected crestal level, the bone is “smoothed” by setting the laser at 50 pulses per second and moving the tip in a horizontal direction over the crestal bone. It is important to note that with both of these movements, the tip of the laser is in contact with the bony crest. To blend, or “ramp” the bony crest distally, the tip of the laser is angled away from the tooth, eliminating the slight “trench” and creating a smooth transition to the height of alveolar bone on the adjacent tooth. This can be verified by sounding with a periodontal probe as well. The definitive restoration can be seated 2 to 3 weeks after the closed crown-lengthening procedure. The surgical area will heal by secondary intention around the finished restoration with ideal tooth contours, rather than an ill-fitted temporary restoration. The criteriafor clinical health of the dentogingival complex are pink color (absence of inflammation); reestablishment of a probable gingival sulcus; and absence of bleeding on probing.

The primary indication for esthetic crown lengtheningis short clinical crown height in situations where facial parameters indicate that the tooth or teeth should be lengthened in an apicaldirection. For the most part, alteration of the gingival tissue and thecorresponding subtractive alteration of thebone are confined to the facial aspect ofthe teeth from the mesial to the distal lineangles. The decision to use a subtractiveapproach or to apically reposition the tissue depends on the degree ofattached gingiva at the surgical site. Decisionsregarding the optimal surgical approach inwhich to alter osseous architecture are based on the number of teethto be treated, the relationship of the osseous crest to the freegingival margin facially as well asinterproximally, and the thickness of thealveolus.

Several parameters must be evaluated to determine whether or not crown lengthening is the best approach to achieve the desired result. Certainly the determination must be made whether or not the cervical aspects of the teeth have an influence on the esthetics of the smile by evaluating the visible gingival display during the patient’s most dynamic lip movements.

For patients who do display gingival architecture, tooth size must be evaluated. It is undesirable to increase tooth length in either direction when clinical crown heights are within accepted norms. Normal tooth length with excessive gingival display can be seen in patients with vertical maxillary excess, dentoalveolar extrusion, a short or hypermobile lip, or a combination of the aforementioned. Treatment solutions in these situations include orthodontic intrusion, orthognathic surgery, segmental osteotomy, botox therapy, or a coronally positioned mucosal flap procedure. Determining the specific cause for the problem leads to the most favorable treatment solution.

If the determination is made that a tooth or teeth can benefit from increased length in an apical direction, the degree of incisal attrition must be evaluated. Teeth that have short clinical crowns yet do not exhibit wear as seen in cases of delayed passive eruption are ideal candidates for esthetic crown lengthening. With delayed passive eruption, the cervical aspect of the full anatomic crown remains submerged under the tissue. Crown lengthening in these situations simulates normal apical migration of the osseous crest to a desired position 2 mm apical to the cementoenamel junction. On the other hand, teeth with short clinical crowns that have suffered incisal loss of tooth structure suggest a normal relationship of the osseous crest to the cementoenamel junction. Crown lengthening in these cases will expose tooth structure apical to the cementoenamel junction. Alternative solutions include orthognathic surgery, orthodontic intrusion, and segmental osteotomy.

Esthetic crown-lengthening surgery is a procedure uniquely created to treat altered passive eruption. In this condition, the passive eruption process does not go to completion, resulting inexcessive gingival coverage of the anatomic crowns of the teeth. Twoclinical criteria must be met to make adiagnosis of altered passive eruption. First,the tooth is short by measurement, and second,the clinician cannot palpate the cemento-enameljunction (CEJ) in the sulcus with the tip of anexplorer. There are three goals in the esthetic crown-lengthening surgeryprocedure: 1) the alveolar bone is moved 2 mm apical to the CEJ fromfacial line to facial line angle; 2) the gingival crest is positioned 3 mm coronal to the alveolar crest; and 3) thetissue should be level at the completionof the surgery.

In this procedure, the initial incision is only on the facial surfaces of the affected teeth. A thinning incision of the interdental papillae leaves most of the papillae remaining between the teeth. The incision is made as far distally as is evident in the full smile. A full thickness flap is then reflected. The alveolar bone is thinned over the roots of the teeth and festooned between the roots, if necessary, using a bur in high-speed handpiece with water irrigation. Once the bone is thinned over the roots of the teeth, the Wedelstadt Chisel is used to remove the marginal bone from line angle to line angle. This will generally result in a thicker ledge of marginal bone, which is then thinned with a bullet-nosed diamond bur. The flap is placed in its new position so that the gingival crest is 3 mm coronal to the alveolar crest. The flap is sutured to the remaining interdental tissue with a simple interrupted suture. The suture is generally a 5/0 polygalactic acid suture. If necessary, the interdental tissue is re-contoured to blend with the flap after the flap is sutured. No periodontal pack is used and the patient is instructed to refrain from toothbrushing for one week. Chlorhexidine (0.12%) is used twice a day for the first week. The postoperative course is usually uneventful and over-the-counter medications are used for pain management. The patient returns in 1 week for suture removal.

About the Authors

Robert A. Lowe, DDS
Private Practice
Charlotte, North Carolina

Elizabeth M. Bakeman, DDS
Private Practice
Grand Rapids, Michigan

Clinical Instructor
Kois Center for Advanced Dental Education
Seattle, Washington

J. William Robbins, DDS, MA
Clinical Professor
Department of General Dentistry
University of Texas Health Science Center at San Antonio
San Antonio, Texas

Private Practice
San Antonio, Texas