8: Lasers in Fixed Prosthetic and Cosmetic Reconstruction

8 Lasers in Fixed Prosthetic and Cosmetic Reconstruction

This chapter describes the clinical applications of laser dentistry with respect to soft tissue and hard tissue alterations for prosthetic and cosmetic reconstruction. Clinical advantages of laser use clearly benefit both dentist and patient. A clear field of vision resulting from excellent hemostasis and moisture control allows the dentist to perform all procedures with precision. Major advantages of laser use include reduced intraoral bleeding, much less postoperative pain, and remarkably less swelling compared with conventional techniques such as electrosurgery.

The procedural techniques routinely encountered during fixed prosthetic and cosmetic reconstruction include the following:

Before each of these procedures is discussed, the role of various laser wavelengths and biologic width in cosmetic and prosthetic reconstruction is reviewed.

Laser Wavelengths for Cosmetic/Prosthetic Procedures

Biologic Width

Biologic width is defined as the combined height of connective tissue and epithelium that isolates the bone from the oral cavity. It is the distance from the most apical extent of a dental restoration to the osseous crest necessary to maintain periodontal health10 (Figure 8-1).

The biologic width distance is approximately 2 mm, with about 1 mm of the 2 mm composed of the connective tissue attachment and 1 mm consisting of the junctional epithelium. Because it is impossible to restore a tooth perfectly to the precise coronal edge of the junctional epithelium, the 1 mm of depth of the sulcus can be added to the biologic width to establish a margin of safety.10

This distance is important to consider when fabricating dental restorations, because the dentist must respect the natural architecture of the gingival attachment to avoid complications. The problem is not the restoration but rather bacteria, which will always find shelter in the interface between the restorative margin and the tooth structure. When restorative procedures do not take these considerations into account and violate biologic width parameters, the following three possible issues may arise10 (Figure 8-2):

Soft Tissue Troughing With and Without Gingivoplasty

The gingival trough is defined as the narrow space between the free margin of the gingival epithelium and the adjacent enamel of a tooth.11 At times, permanent alteration of the gingival contours around a tooth or teeth is necessary to ensure a superior, long-lasting cosmetic restoration. The outcome of a direct or indirect restoration is related to the dentist’s ability to control the surgical site. In controlling the site for delivery of a superior restoration, lasers provide the following functions:

These steps are essential for the fabrication of precise impressions, for digital scanning, or for direct placement of restorative materials. The displacement of gingival tissue is critical for finalizing tooth preparation and impression taking or restorative material placement.12 A common challenge to the dentist is placement of the preparation “finish line” at or below the crest of the gingiva so that the margin does not show. Retraction of the gingival tissues can be performed mechanically with the 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 is the conventional technique used to record the finished preparation margin or to complete placement of the direct restorative material.

Conventional Techniques

A technique widely used for gingival retraction is a double-cord technique for subgingival reflection of tissue. Removing the second (top) retraction cord before injecting the impression material or creating an optical impression allows for complete capture of the finish line. This time-consuming technique has its disadvantages, including potential injury to the periodontal ligament if excessive force is used; difficulty in removing the retraction cord without creating bleeding, and postoperative discomfort.13

Another conventional gingival troughing technique, electrosurgery or radiosurgery, allows for contouring of gingival tissues and hemorrhage control. Healing after electrosurgery can produce a delayed wound-healing response, asymmetrical 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 repeatedly produced gingival recession, bone sequestration and necrosis, loss of bone height, furcation involvement, and tooth mobility. Electrosurgery (or radiotherapy) is contraindicated around dental implants16 and must not be used in patients with pacemakers, with previous radiation to the jaws, with poorly controlled (or uncontrolled) diabetes, or with blood dyscrasias, immunodeficiencies, or other diseases that cause delayed or poor healing.10

Scalpel techniques are primarily used 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, asymmetrical gingival margins, and the postoperative pain and discomfort typically associated with periodontal surgery.17

Laser Troughing

In contrast to conventional techniques, laser troughing allows for clear, clean visualization of gingival margins. Most lasers are excellent coagulation devices, with minimal to no bleeding. Unlike blade or electrosurgical techniques, laser gingival troughing with a laser gingivectomy can be performed at the same appointment as impression taking. The patient saves a trip to the office, greatly reducing valuable chair time. The ease with which necrotic tissue debris is removed from around the preparation finish line simplifies impression taking. Retraction cord is not necessary for reflection around the tooth or teeth; no placement or removal of cord from multiple pockets is required when taking impressions of multiple teeth or a full arch. Laser treatment causes no recession or repositioning of the gingival margin.18 Laser troughing promotes an ideal environment for current impression scanning devices.

Dentists who practice laser surgery and laser gingival troughing have reported high patient acceptance and comfort. Neill’s survey19 on patient comfort after laser gingival troughing revealed that 3 hours after treatment, patients were comfortable, with half “extremely” comfortable. The overall pain rating was 1.9 (scale of 0.0-10.0), indicating patients experienced minimal to no pain.

Laser vaporization of fibrotic tissue around crown margins is extremely fast, with virtually no bleeding, swelling, or postoperative pain. There is predictable stability of the gingival tissue on healing, with the additional benefit of elimination of pathogens from the periodontal pocket.20,21

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.

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

Procedure

The laser troughing procedure is simple to perform. The laser tip is placed parallel to the long axis of the tooth, barely into the periodontal sulcus. The tip should glide circumferentially around the margin of the tooth, with slight to no resistance. Watch for any yellowing of the gingival tissue, which will indicate thermal collateral damage.

To maximize its efficiency, the tip must be kept free of debris. With CO2 lasers, a stream of air blown through the tip keeps the hollow tip patent. Debris may accumulate on the outside of the tip, however, in which case the tip should be wiped down with dry gauze or replaced. Nd:YAG and diode lasers use glass/quartz fibers, which become dulled and scratched after multiple uses. A dull tip may cut tissue poorly, like cutting tissue with 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 multiuse disposable tips, but the cost of tips is much greater than simply using a standard 3-meter optical fiber. The tip must also be “activated” 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.8,22 This can be quickly removed with a 3% hydrogen peroxide diffusing-brush syringe (Figures 8-3 and 8-4).

Crown-Lengthening Procedures

Crown-lengthening procedures have progressively become more driven by esthetics because of the increasing popularity of “smile enhancement” procedures. Crown lengthening is a surgical procedure performed to expose a greater gingivoincisal length of tooth structure, usually to restore the tooth prosthetically. This involves excising a small amount of gingival tissue around the tooth and predictably removing a given height of only gingival tissue (soft tissue crown lengthening) or both gingival tissue and alveolar bone (osseous crown lengthening). Although many general dentists perform this procedure, many others refer crown lengthening to a periodontist or oral surgeon. Conventional techniques of osseous crown lengthening generally involve a full-thickness flap procedure to establish the new gingival level.10

Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 8: Lasers in Fixed Prosthetic and Cosmetic Reconstruction
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