5.1 Introduction

The term laser, which stands for light amplification by stimulation of emitted radiation, refers to the production of a coherent form of light, usually of a single wavelength. In dentistry, clinical lasers emit either visible or infrared light energy (nonionizing forms of radiation) for surgical, photobiomodulatory, and diagnostic purposes.

Investigations into the possible intraoral uses of lasers began in the 1960s, not long after the first laser was developed by American physicist Theodore H. Maiman in 1960 [1]. Reports of clinical applications in periodontology and oral surgery became evident in the 1980s and 1990s. Since then, the use of lasers in dental practice has become increasingly widespread.

5.2 Laser-Tissue Interactions

Another type of laser-tissue interaction relevant to the use of lasers in periodontal surgery is nonthermal, whereby visible or infrared laser energy is used at lower power (subablative) levels to elicit photophysical and photochemical events that produce beneficial therapeutic outcomes. Such photobiomodulation outcomes may include alleviation of pain or inflammation and promotion of wound healing and tissue regeneration [4].

Laser energy may be absorbed, reflected, or scattered. However, it is only when the laser is absorbed by the substrate that useful interactions occur. Absorption of the laser energy by the target tissue is dependent on the laser wavelength, tissue composition, pigmentation, and water content.

5.3 Types of Lasers

The commonly used surgical lasers in the dental profession range from 445 to 10,600 nm in wavelength and can be classified based on the types of tissue with which they interact:

5.3.1 Hard Tissue Lasers

Erbium lasers (2780-nm Er,Cr:YSGG and 2940-nm Er:YAG) are well absorbed by water and hydroxyapatite and are mainly used for cutting tooth structure and bone. They can also be used for soft tissue procedures. However, due to their absorption characteristics, they have shallow penetration into soft tissue and provide limited hemostasis.

5.3.2 Soft Tissue Lasers

9250-nm and 10,600-nm carbon dioxide (CO₂) lasers are well absorbed by hydroxyapatite and water. They are used mostly for soft tissue surgery. Like the erbium lasers, they have relatively shallow penetration and provide reasonable hemostasis. The 10,600-nm laser is contraindicated for use on teeth and bone, whereas the 9250-nm laser can be used for cavity preparation and bone modification.

Diode lasers (445, 450, 457, 808, 810, 940, 970, 980, 1064 nm) are absorbed by melanin and hemoglobin and are most commonly used in the general dental office for soft tissue surgery via the aforementioned hot tip methodology. These wavelengths penetrate soft tissue more deeply than the erbium and CO₂ lasers and provide excellent hemostasis. Diode lasers are contraindicated for use on bone.

The Nd:YAG laser (1064 nm) is absorbed by melanin and hemoglobin and, like the diode lasers, has a deeper penetration into soft tissue and provides excellent hemostasis. The use on osseous tissue is contraindicated. The tissue absorption and pulsing characteristics of the Nd:YAG laser make it an effective instrument for treatment of moderate-to-severe periodontal disease.

5.4 Lasers in Periodontal Surgery

Collectively, the erbium, CO₂, diode, and Nd:YAG lasers enable a variety of soft tissue surgical procedures, including gingivectomy [5–7], reduction of gingival hyperplasia [8–11], frenectomy [12–16], operculectomy [17], vestibuloplasty [18, 19], free gingival graft [20–22], second-stage recovery of implants [23–25], incisional and excisional biopsy [26, 27], and fibroma removal [28, 29].

Photobiomodulation studies using various laser wavelengths have demonstrated their ability to promote conditions conducive to wound healing in gingivectomy and gingival graft sites and in the management of periodontal disease [30–37].

Compared to conventional treatment modalities, some of the advantages of the use of lasers in periodontal surgery include control of surgical and postsurgical bleeding, reduced bacteria in the surgical field, reduced need for anesthesia in some cases, reduced need for sutures, reduced or eliminated wound contraction and scarring, decreased postoperative edema and discomfort, and high patient acceptance and preference [26, 38, 39].

Limitations of laser use in dentistry include the relatively high cost of the instruments, the requirement of specialized training, and the strict adherence to safety precautions such as the need to protect nontarget tissues from laser exposure and the need for patients and operatory personnel to wear protective laser-specific eyewear. Optimum clinical results are achieved when proper technique and laser parameters are used, in accordance with manufacturer’s directions and specified treatment protocols.

5.5 Lasers in Periodontal Treatment

The use of lasers for the treatment of periodontal disease has a lengthy history, with some reports dating from the early 1990s.

Reports of the use of erbium lasers to treat periodontal pockets began to appear in 2001, some 4 years after commercial availability in clinical dentistry. Manufacturers of erbium lasers have tried to develop protocols to treat periodontal disease but have only anecdotal reports and no human histological evidence to back up claims of regeneration. Some practitioners use erbium lasers to remove or contour osseous tissues after a flap is made. These devices can also remove calculus, but because they cannot differentiate calculus from dentin and cementum, or determine where the calculus ends and the tooth surface begins, their use in calculus removal can lead to undesirable ditching of the root surface [40, 41].

Carbon dioxide lasers are not amenable to treating periodontal disease as they have no selectivity in removing diseased tissue and can heat the bone and teeth which is not desired in the treatment of periodontal disease. Anecdotal reports of their use within the periodontal pocket exist, but their rigid delivery system tips do not readily lend themselves to accessing the full depth of the pocket without first laying a flap. In 1995, Israel et al. investigated whether de-epithelialization with a CO₂ laser at the time of flap surgery would enhance the formation of connective tissue attachment. Indeed, a 90-day postoperative assessment showed positive results in one of the two patients treated [42].

A popular use of diode lasers is sulcular debridement and bacterial reduction within the periodontal pocket, performed either by dentists or dental hygienists. The first reports of such procedures were published in 1997, 1 year after diode lasers were introduced in dentistry. Effectiveness of treatment varies, and some studies have shown that scaling and root planing (SRP) with diode laser use shows no greater benefit than SRP alone [43–47]. Human histological studies of new attachment or regeneration have not yet appeared in the literature.

The Nd:YAG laser has the longest history in periodontal pocket therapy and treating periodontitis, dating from 1991, 1 year after introduction of this laser device in clinical dentistry [5, 48, 49]. Its flexible fiber-optic delivery system facilitates minimally invasive access within periodontal pockets (Fig. 5.1). In 1994, Gold and Vilardi showed that the use of a pulsed Nd:YAG laser inside a periodontal pocket will specifically remove the diseased tissue and leave intact rete ridges to facilitate new attachment of the gingiva to the root surface [50].

Subsequent human histological investigations using one particular Nd:YAG laser (PerioLase MVP-7, Millennium Dental Technologies, Cerritos, Calif., USA) in a well-defined clinical protocol established the ability of this protocol to achieve periodontal regeneration in patients presenting with moderate-to-severe periodontal disease. Based on independent studies conducted by Yukna et al. [51] and Nevins et al. [52], in March 2016, the US Food and Drug Administration granted marketing clearance to the PerioLase Nd:YAG laser for true regeneration of the attachment apparatus (new cementum, new periodontal ligament, and new alveolar bone) on a previously diseased root surface when used specifically in the LANAP^® protocol.

The full-mouth LANAP procedure (Figs. 5.2 and 5.3) involves using a digitally pulsed Nd:YAG laser to remove diseased epithelium from the periodontal pocket, leaving the rete ridges intact, and reduce pathogens within the periodontal pocket. Scaling and root planing (SRP) is then performed with a piezo scaler. Osseous modification/decortication is performed to induce bleeding and release stem cells and growth factors. The Nd:YAG is then used for hemostasis, to establish a stable fibrin clot, activate growth factors, and upregulate gene expression. The Nd:YAG laser-induced hemostasis allows patients on anticoagulants to be treated without taking them off their medications. Occlusal adjustment, essential in any regenerative procedures, is performed at the time of surgery (Fig. 5.4) and throughout periodontal maintenance during the first year post-LANAP treatment.