These steps are essential for the fabrication of precise impressions, for digital scanning, or for direct placement of restorative materials. Whenever the restorative interface is subgingival, the displacement of gingival tissue is critical for finalizing tooth preparation and impression taking or restorative material placement.¹² With older restorative materials, a common challenge to the dentist was placement of the preparation “finish line” at or below the crest of the gingiva so that the margin did not show. Retraction of the gingival tissues usually was performed mechanically, with retraction cord impregnated with medicaments for hemostasis. Packing of retraction cord around the circumference of the tooth to reflect the gingiva away from the tooth and to absorb crevicular fluids was the conventional technique used for recording the finished preparation margin or to complete placement of the direct restorative material.

Another conventional gingival troughing technique, use of electrosurgery or radiosurgery, allows for contouring of gingival tissues and hemorrhage control. The electrosurgery procedure may be associated with delayed wound healing, with asymmetric gingival heights, crestal bony recession, and moderate postoperative discomfort.¹⁴ In a study of electrosurgical gingival troughing with a fully rectified current on rhesus monkeys, Wilhelmsen et al.¹⁵ showed statistically significant recession of the gingival margin along with apical migration of the junctional epithelium. Deep soft tissue resections close to bone typically produced gingival recession, bone sequestration and necrosis, loss of bone height, furcation involvement, and tooth mobility. Electrosurgery (or radiosurgery) is contraindicated around dental implants¹⁶ and must not be used in patients with any of the following:

Scalpel techniques are used primarily to resect tissue to provide access and visualization of the target site. Scalpel incision surgery may result in gingival attachment loss with apical repositioning, exposure of sensitive root surface to the oral environment, asymmetric gingival margins, and the postoperative pain and discomfort typically associated with periodontal surgery.¹⁸

Dentists who practice laser surgery and laser gingival troughing have reported high patient acceptance and comfort. Neill’s survey²⁰ on self-reported patient comfort after laser gingival troughing revealed that 3 h after treatment, patients were comfortable, with half “extremely” comfortable. The overall pain rating was 1.9 (on a scale of 0.0 to 10.0), indicating that patients experienced minimal to no pain.

Laser vaporization of fibrotic tissue around crown margins is extremely fast, with no bleeding, swelling, or postoperative pain. Predictable stability of the gingival tissue on healing is the rule, with the additional benefit of elimination of pathogens from the periodontal pocket.^21,22

Slightly different techniques are used for each wavelength. The laser dentist must learn the specific procedure and follow the specific protocols for the particular device employed. Once again, it must be emphasized that training is critical in using this technology.

Erbium lasers use thin tips made of sapphire, quartz, or hollow metal for troughing. For use of erbium lasers on soft tissue, the water spray usually is turned off. This precaution aids in hemostasis. CO₂ lasers have thin hollow metal or ceramic tips for troughing. The Nd:YAG and diode lasers use optical fibers of various diameters to perform gingival troughing.

To maximize its efficiency, the tip must be kept free of debris. With CO₂ lasers, a stream of air blown through the hollow tip keeps it patent. Debris may accumulate on the outside of the tip, however, in which case the tip should be wiped down with gauze or replaced. Nd:YAG and diode lasers use glass or quartz fibers, which become dulled and scratched after multiple uses. A dull tip may cut tissue poorly, much like a broken piece of glass, leaving tissue tags.⁷ The tip must therefore be cleaved periodically to ensure optimal results. Some diode lasers are supplied with disposable tips, but the cost of tips is much greater than that incurred with simple recleaving of a standard 3-m optical fiber. The tip also must be “initiated” so that the depth of penetration of the wavelength is minimized, with no deep thermal damage.

During troughing to establish gingival proportions with the diode and Nd:YAG lasers, the clinician may note carbonization on the tissues.^8,23 This layer can be quickly removed using a 3% hydrogen peroxide solution in a minibrush tip syringe (Figures 6-3 and 6-4).

Use of flap surgery with osseous resection is the traditional method of choice when crown margins will impinge on the biologic width. Rotary instruments have long been used to recontour the alveolar structure. Bone recontouring can be achieved conventionally with fissure or diamond burs, using copious amounts of water, or with bone chisels. Thinning of the bone around the tooth or teeth reduces craters or ridges that create sharp, uneven soft tissue topography. Sufficient bone is removed to create a 3-mm space between the crest of the bone and the new restoration’s finishing-line margin. However, poor esthetics may result from enlarged gingival embrasures, root sensitivity, transient mobility, or root resorption.²⁴

In some cases, the need for osseous recontouring may be localized to one specific area because of the presence of a subgingival restoration, carious lesion, or fractured cusp. Erbium lasers may be useful in localized osseous tissue removal for establishing a new biologic width without raising a gingival flap. In allowing for careful removal of osseous tissue in a closed-flap technique, along with soft tissue removal, the clinician can create the biologic width for the final restoration and complete the impressions for the indirect restoration in the same appointment.²⁵ The closed-flap, hard tissue crown-lengthening procedure is very technique-sensitive and is not recommended for the novice laser dentist; advanced training in open-flap periodontal surgery is highly recommended.

Erbium lasers have end-cutting tips with a water spray that prevents the surgical site from overheating, in contrast with the rotary friction heat released by conventional burs. Collateral thermal tissue damage when using erbium lasers is less than with conventional techniques.⁴ The use of rotary diamond or carbide burs for osseous tissue removal risks possible damage to adjacent tooth structure. Healing after conventional osseous surgery is associated with swelling and postoperative pain.²⁶ Bleeding from a conventional (blade) incision typically will compromise visualization of the surgical site, in contrast with a laser incision, and visualization is critical in working on osseous structure. The risk of bony damage caused by dissipated heat from rotary burs outweighs the risk of trauma from a water-cooled erbium laser when correct parameters are used.

The procedure starts by measuring the amount of needed reduction of the bony crest. End-cutting then commences. While maintained in parallel orientation with the root surface, the laser tip is advanced to penetrate the crestal bone to the desired depth. Miniature osteotomies are produced with the laser tip. Once at the desired depth, the laser tip is withdrawn and moved 1 to 2 mm laterally, and the next osteotomy is performed to the desired depth. This sequence continues across the facial or buccal, mesial, distal, and lingual walls until the entire circumference is treated, if necessary.²⁵

Once the cut is completed, the laser tip is inserted into the osteotomy site. A swiping motion in the mesial or distal direction is performed to remove any osseous tags between osteotomy sites. Soft smoothing of the underlying bone removes troughs or craters and creates a scalloped topography from the facial surface to interproximal surface.²⁵ The gingival tissue is essentially a marker of underlying bone, and preservation of the interproximal bone height will prevent loss of the interproximal papillae. A literature review revealed that the contact area between teeth should be positioned 5 mm incisal to the height of the interproximal bone to maintain the papillae.²⁷ Provisionalize the area, and allow 3 to 4 weeks for healing before taking the final impression. Once again, it must be pointed out that a closed-flap osseous procedure is a “blind” procedure and is not recommended for laser dentists to perform until they have extensive experience and training with their units.

If conventional (rotary or bone chisel) open-flap osseous recontouring is performed, any laser wavelength (or a scalpel) may be used to open and reflect the flap. With a laser incision for full-thickness flap reflection rather than conventional techniques, visualization of the bony crest is enhanced because bleeding is minimal. The surgical site is cleaner, free of blood, and more “sterile,” because the laser destroys bacteria as it incises the soft tissue.

The bone should be contoured so that the bone structure has no craters or ledges. If any of these defects are present, the overlying soft tissue will become thick, hindering good impression taking, in addition to resulting in deep probing depth after the restoration is cemented. Before suturing, it is essential to ensure that the flaps are without tension and preferably covering where the eventual crown margin will be placed. Flaps will not lie correctly if the bone is not contoured properly.¹¹

Sutures should be removed within 7 to 10 days. If crown lengthening is performed correctly, the impression can be made 3 to 6 weeks after the open-flap surgery for posterior teeth and a few weeks later for anterior teeth, for which soft tissue esthetics is critical (Figure 6-5) (see also Chapter 4).

Emergence profile is critical for gingival health and esthetic contours. Axial contours of the prepared tooth structure will be reflected in the final restoration contours as well. The contact point of the restoration(s) will influence