Current concepts in the use of lasers in periodontal and implant dentistry

Abstract

Lasers have various periodontal applications including calculus removal (Er: YAG, Er, Cr: YSGG lasers); soft tissue excision, incision and ablation; decontamination of root and implant surfaces; biostimulation; bacteria reduction; and osseous surgery. This paper reviews some of the major opportunities for using lasers in periodontal and implant specialty practices. The literature relating to the use of lasers for removal of the pocket epithelium, root conditioning, bacterial reduction and decontamination of infected implant surfaces is discussed, and a summary of the advantages and disadvantages of using lasers for periodontal treatment is provided.

INTRODUCTION

The word “laser” is an acronym for “light amplification by stimulated emission of radiation.” It refers to a device that emits light that is spatially coherent and collimated; a laser beam can remain narrow over a long distance, and it can be tightly focused. When directed at tissues, different interactions result. The absorption, reflection, transmission, and scattering of the laser light vary depending on the wavelength of the laser and the characteristics of the tissue.[1]

Lasers have various periodontal applications including calculus removal (Er: YAG, Er, Cr: YSGG lasers); soft tissue excision, incision and ablation; decontamination of root and implant surfaces; biostimulation; bacteria reduction; and last but not least bone removal (osseous surgery). Certain laser wavelengths (i.e. Er: YAG, Er, Cr: YSGG) are highly absorbed by hydroxyapatite and can be used for bone removal more efficiently than others. In contrast, diode and Nd: YAG lasers are more highly absorbed by hemoglobin and thus should be used when coagulation is desirable. In addition, due to the effect that these wavelengths (diode and Nd: YAG lasers) have on pigmented tissues, they can be used by periodontists for removal of gingival pigmentation and/or reduction of periodontopathogenic black-pigmented bacteria.

The aim of this paper is to present innovative opportunities for using lasers in periodontal and peri-implant surgery and to present new challenging indications of this modern technology for the daily practice.

LASER APPLICATIONS IN PERIODONTOLOGY

Different lasers penetrate to different tissue depths, depending on their wavelength and the type of tissue at which they are directed. For instance, when applied to soft tissues, Nd: YAG lasers (1064 nm) have a penetration depth of approximately 2–3 mm, compared to CO₂ lasers (10,600 nm), which affect the tissue only superficially (0.1–0.3 mm). In addition, CO₂ lasers have a high absorption from the water.

Lasers can be used in a focused beam (for excisions and incisions) and in an unfocused beam (for ablation and coagulation). Some evidence suggests that lasers used as an adjunct to scaling and root planing (SRP) may provide additional benefits.[2]

Lasers in periodontal therapy have been demonstrated to be beneficial for control of bacteremia,[3] better removal of the pocket epithelium in the pockets,[4,5] bacteria reduction,[6,7,8,9] efficient subgingival calculus removal (using Er: YAG lasers)[10] and improvement of periodontal regeneration in animals and humans without damaging the surrounding bone and pulp tissues.[11,12]

There is no doubt that specific protocols must be used to achieve specific goals. Aoki et al.[13] compared various power settings of an Er: YAG laser used for calculus removal in vitro and found that ablation of the tooth substance after laser scaling was generally observed within the cementum. They concluded there is potential for clinical application of the Er: YAG laser in subgingival scaling. The Er: YAG laser is able to remove calculus [Figure 1], an increased loss of cementum and dentin which should be taken into account in clinical situations.[14]

Figure 1.

Extraoral root planing using an Er: YAG laser (with sapphire tip) provides complete calculus removal, a smooth, undamaged root surface, and removal of the cementum

Other clinical investigators have demonstrated significant improvements in periodontal parameters after the use of Er: YAG lasers, compared to SRP.[8] Positive effects of the ErYAG laser in surgical periodontal therapy have also been presented.[15] When the use of an Er: YAG laser was compared to ultrasonics, significant improvement in the investigated clinical parameters was found to result from both therapies.[16] The results were statistically similar in shallow and moderate pockets. A recent prospective, randomized, controlled multicenter study of the two different methods of treatment (Er: YAG laser versus sonic debridement) of persistent periodontal pockets also showed no significant differences in the clinical and the microbiological outcomes.[17]

Removal of the pocket epithelium

Lasers are also used for soft tissue periodontal applications. The Nd: YAG was the first laser wavelength to be compared to the scalpel for treating periodontal pockets[5] and controlling bacteremia and gingival bleeding.[5,18] The probing pocket depth and bleeding index scores were reduced using the pulsed Nd: YAG laser. Furthermore, clinical evaluation of soft tissue biopsies taken from human subjects using the Nd: YAG laser versus a curette presented a complete removal of the epithelium of the pocket after use of the pulsed Nd: YAG laser compared to the curette.[4] Similar effects presented in pig jaws (in vitro) after the use of a 980 nm diode laser with 2–4 W power settings and continuous wave compared to the conventional curette.[19]

There are advantages in the postsurgical outcomes with the removal of pocket epithelium. A recent clinical study in India showed that the modified Widman flap with removal of the pocket epithelium was more effective in reducing mean probing depth compared to access flap with intrasulcular incision. It showed greater gain of clinical attachment and demonstrated less gingival recession.[20]

When deep periodontal pockets are present, removal of the pocket epithelium using a glass laser fiberoptic offers benefits. With or without flap elevation and a conventional periodontal access flap procedure, the pocket epithelium will be removed from the inner and the outer part of the pocket. Depending on how the patient heals, the epithelium can later be ablated every 7–10 days from the outer part of the pocket, usually under the use of topical anesthesia, in order to control apical migration. This can result in long-term, stable connective tissue attachment, without gingival recession [Figure 2]. The principle underlying this approach is guided tissue regeneration; it has been called “laser-assisted guided tissue regeneration.”[21] This approach should be evaluated in different prospective clinical studies involving many patients and following exactly the same protocol in order to establish that it is a technological improvement that should be incorporated routinely in daily practice.

Figure 2.

(a) Preoperative clinical condition; (b) clinical condition after laser-assisted scaling and root planing in conjunction with a de-epithelialization of the oral and sulcular epithelium for pocket reduction using an Nd: YAG laser; (c) stable long-term clinical condition (5 years postoperative)

Both clinical case series and clinical research have shown the potential of this application using the CO₂ laser, since the noncontact handpiece is able to ablate tissues very quickly, controlling the epithelial cell proliferation and further apical migration of a long junctional epithelium. Israel et al.[11] were able to demonstrate histologically the effects of this de-epithelialization technique in humans. The technique involves using the CO₂ laser to remove (ablate) the inner part of flap after conventional periodontal flap elevation [Figure 3] and then using the same method in the outer part of the flap to achieve epithelial retardation. Case series in patients with generalized advanced periodontal disease have shown that the laser de-epithelialization technique leads to good results [Figure 4] without the need for multiple membrane therapy.[22,23]

Figure 3.

CO₂ laser de-epithelialization immediately after flap closure. The tissue ablation of the superficial layer of the epithelium is responsible for the epithelial retardation and further improvement of the connective tissue attachment

Figure 4.

Follow-up 1-year after surgical treatment (PPD = 3 mm) using the CO₂ laser de-epithelialization method; (a) compared to apical repositioning flap for pocket elimination; (b) observe the significant gingival recession at the control site

Laser root conditioning

The use of CO₂ lasers to decontaminate root surfaces has been investigated, providing more information about the exact power settings and parameters required to avoid root damage. Barone et al.[24] showed that a defocused, pulsed CO₂ laser is able to create smooth and clean root surfaces compared to a focused, continuous wave; the latter leads to melting and root surface damage. Later studies using the same parameters for CO₂ lasers reported root conditioning with a better fibroblastic activity, cellular proliferation, and greater fibroblast attachment.[25] Different clinical case reports have demonstrated these advantages of CO₂ laser de-epithelialization.[26]

This technique has also been used in clinical studies and has shown that coronal flap advancement in conjunction with CO₂ laser root conditioning leads to improvements in clinical parameters and long-term tissue stability after 15 years, compared to the modified Widman periodontal flap procedure.[27] The authors concluded that this laser technique seemed to have greater effects and should be used in treating deep periodontal pockets (more than 7 mm deep).

Bacterial reduction

A laser application that has been especially promoted in the past is for the reduction of bacteria in pockets, due to the high absorption of specific laser wavelengths by the chromophores. Initially, the use of an Nd: YAG laser was shown to reduce the load of Porphyromonas gingivalis and Prevotella intermedia.[28]

A study by Assaf et al.[29] is of special interest. Using a diode laser in conjunction with ultrasonic scaling for treatment of gingivitis, they were able to show a significantly lower incidence of bacteremia in the diode + ultrasonic group (36%) compared to the ultrasonic only group (68%). They suggested that diode lasers should be used to prevent bacteremia, especially in immuno-compromised patients.

Using a 980 nm-diode laser to reduce periodonto-pathogenic bacteria in patients with aggressive periodontitis has also been investigated. Kamma et al.[30] confirmed that it was possible to reduce the total bacterial load in pockets without use of any systemic antibiotic therapy.

Clinical case series with 10 patients using in the same patient (in a randomized protocol) SRP in conjunction with 980 nm-diode laser, SRP and an Nd: YAG laser and SRP with photodynamic therapy (PDT), showed that the PDT was able to reduce significantly the bacteria in the pockets and provide a predictable clinical outcome for 3 months. In contrast to that, the use of Nd: YAG laser was not very beneficial and was similar to the control (SRP) group.[31] Due to the bacteria reduction, and the reduced bleeding on probing provided by the PDT, the PDT was recommended for periodontal patients especially for the maintenance appointments.

Laser applications in implant dentistry

The use of lasers in implant dentistry has been discussed extensively.[32] Many clinicians want to know if lasers can be used to treat peri-implantitis, but it is impossible today to investigate this question using randomized clinical trials due to the lack of comparable test and control sites.[33] However, there are applications for lasers in implant dentistry, including for second stage surgery,[34] removal of peri-implant soft tissues, and decontamination of failing implants.[35] Serious concerns about the implant overheating followed by melting of the implant surface have been raised,[36,37] along with concerns about a lack of re-osseointegration following treatment of peri-implantitis with lasers. Recent systematic reviews have focused on the latter question and provided more information about how implants can re-stabilize following implant surface laser decontamination.[38] Deppe et al.[39] showed that CO₂ laser decontamination of the surface of implants placed in dogs allowed new bone to grow and be in contact with the implant surface (re-osseointegration). In vitro studies of osteoblasts have confirmed these effects for CO₂ and Er, Cr: YSGG lasers.[40]

Previous clinical case series were able to demonstrate new bone fill [Figure 5] and long-term success of failing implants that were decontaminated with a CO₂ laser.[41,42,43,44]

Figure 5.

(a) Peri-implant infrabony defect due to peri-implantitis; (b) after cleaning of the defect with conventional curettes, CO2 laser irradiation of the implant surface and surrounding bone allows sufficient decontamination to enable further bone grafting; (c) immobilization of a collagen membrane around the defect in order to stabilize grafting material (bovine mineral, cancellous bone) immediately before flap closure; (d) preoperative radiograph demonstrating the peri-implant defect before laser decontamination; (e) postoperative radiograph at the 6 months follow-up shows significant bone fill (asymptomatic lesion)

The main advantage of using CO₂ laser irradiation on implant surfaces is that this wavelength does not pose the risk of overheating,[45] unlike other wavelengths, such as that of diode, Nd: YAG, and Er: YAG lasers.[46,47] A significant increase of the implant surface temperature has been demonstrated when irradiating implant surfaces with a diode laser in vitro for more than 10 s.[46,47,48] It is possible that authors have presented unsuccessful and nonpredictable clinical results from their studies because of overheating resulting from inconsistent power settings.[49] Recent systematic reviews have shown that there is limited information available about laser-assisted decontamination of implant surfaces, with high heterogeneity of results and a low number of included studies. However, although information is limited about the clinical application of CO₂ (10.6 µm) lasers in the surgical treatment of peri-implantitis, its use appears promising.[50]

Further clinical trials and multicenter studies should be performed to improve the effects of laser treatment of periodontal and peri-implant diseases and to develop standardized protocols so that lasers may be used in a predictable way in daily practice.

The following summary of advantages and disadvantages of using lasers for periodontal therapy is based on the literature and the author's experience.

Advantages of using lasers in the periodontal therapy include

1. Less pain

2. Less need for anesthetics (an advantage for medically compromised patients)

3. No risk of bacteremia

4. Excellent wound healing; no scar tissue formation

5. Bleeding control (dependent on the wavelength and power settings);

6. Usually no need for sutures

7. Use of fewer instruments and materials and no need for autoclaving (economic advantages)

8. Ability to remove both hard and soft tissues

9. Lasers can be used in combination with scalpels (however, the laser is a tool and not a panacea).

Disadvantages of using lasers in periodontal therapy include

1. Relatively high cost of the devices

2. A need for additional education (especially in basic physics)

3. Every wavelength has different properties

4. The need for implementation of safety measures (i.e. goggle use, etc.).