In modern clinical dentistry, the application scope of lasers has also been extended to the field of oral implantology. Different laser systems have various indications in the multiple phases of implant treatment and for the management of complications. These clinical options include today:
- soft tissue surgery before implant placement or at the stage of implant uncovering (second stage surgery),
- during the loading phase,
- for the treatment of peri‐implantitis,
- for implant removal and,
- for implant placement.
The different indications of laser use for clinicians using dental implants are described extensively in the literature. The reader is advised here to study these papers to understand better the interactions between lasers and titanium surfaces and also to evaluate the scope of practice, as a standard of care, when lasers are involved in implant dentistry (Romanos et al. 2009a, 2013).
This chapter presents clinical applications, including step‐by‐step illustrations, where different laser systems are used in various stages of treatment with dental implants.
6.2 Laser‐Assisted Surgery Before Implant Placement and Implant Exposure
Before implant surgery, the implant bed may be modified using different laser systems. Specifically, areas with high attachment of muscles (i.e. frenum), insufficient width of keratinized mucosa, reduced depth of the vestibulum, presence of soft tissue benign tumors (e.g. fibromas, papillomas), and leukoplakia and other oral mucosal conditions (e.g. lichen planus) should be treated before implant placement (see also Chapter 3).
For the surgical exposure of endosseous (two‐staged) submerged healed dental implants, the use of the CO2 laser is recommended (Catone 1997). The implant surface can reflect the beam; therefore, a temperature increase of the implant body and the peri‐implant hard and soft tissues does not take immediately place. For the protection of the adjacent soft tissues, use of instruments (e.g. metal spatula and matrices) is recommended.
Another alternative seems to be the Er:YAG laser (Arnabat‐Domínguez et al. 2003), but the Er,Cr:YSGG laser also provides advantages and superior esthetic benefits compared to the scalpel (Arnabat‐Domínguez et al. 2010). This laser can uncover implants and allows apical position of the tissue, increasing the width of attached mucosa.
In vitro studies showed that the irradiation of different implant surfaces with the CO2 laser does not change the surface characteristics of the implant (Romanos et al. 1997). Previous morphological studies using a scanning electron microscopy (SEM) showed that the CO2 laser irradiation of machined, sandblasted, and titanium plasma‐sprayed (TPS) and hydroxyapatite (HA)‐coated implants does not cause damage to the implant surface, using different power settings (2–4 W) in the continuous (Figure 6.1) as well as pulsed mode. However, in the superpulsed mode, oxidation‐related discolorations of the implant surface were reported, as well as extensive melting (Deppe et al. 1998). Recent studies by Park et al. (2012) showed no changes on titanium (Ti) surfaces after CO2 laser irradiation, compared to irradiation with the Er,Cr:YSGG and Er:YAG laser. The latter presented surface changes on Ti disks according to the power output. The CO2 laser irradiation did not affect the surface of Ti disks, irrespective of the power output.
In contrast to the use of CO2 laser, the application of a pulsed Nd:YAG laser led to severe damage of implant surfaces. Block et al. (1992) reported irreversible changes in HA‐coated implants. Extensive melting, porosity alterations, cracks, and ruptures of the HA‐coating of IMZ implants, as well as on sandblasted and Ti‐ plasma‐sprayed implants were shown (Figure 6.2).
However, SEM studies demonstrated changes (Figure 6.3) in the surface pattern of implants when they were irradiated with a diode 810 nm laser (unpublished data) compared to a diode 980 nm laser (Romanos et al. 2000). Therefore, more studies in this field with specific parameters should be performed to evaluate the power settings of diode lasers in implant dentistry to avoid postoperative complications. In another in vitro study, it was found out that strong absorption of the Nd:YAG laser lead to a biologically, not tolerant temperature rise (Romanos et al. 1996)
Similarly, the temperature can be clinically unacceptable when the continuous wave mode is used for diode lasers (810 or 980 nm) over an irradiation period of 15–20 seconds. Therefore, professional advanced training and exact knowledge about the power settings for the use of diode lasers is very important to avoid complications in the final clinical outcome (Geminiani et al. 2012; Leja et al. 2013).
In contrast to that, recent studies with thermo‐elements showed that during laser surgery using the CO2 laser in the continuous mode, the temperature rises. For example, in a few seconds a temperature rise of 20 °C can be reached, when it is used the continuous mode with a power of 4–6 W. Using the pulsed mode of CO2 lasers, no significant overheating of the implant is caused at an output power of up to 6 W (Ganz 1994; Geminiani et al. 2012; Leja et al. 2012).
The coagulation of soft tissues using laser‐assisted implant exposure is very good. The incision is carried out in the middle of the alveolar crest or in the area where the implant was placed according to the surgical (prosthetic) guide. The use of a punch for removal of the peri‐implant mucosa with the CO2 laser is no longer recommended because this method leads to loss of tissue especially keratinized mucosa. Abutments (sulcus formers) are then connected with the implant after surgical exposure. Usually, impressions for the completion of the prosthetic restoration can be carried out after 10 days.
The use of the Er:YAG family of lasers may be used near metal surfaces and especially dental implants. However, the use of air and water is important to control the temperature rise. The parameters of the Er:YAG laser application seems to be sensitive and may have dramatic effects on the temperature levels (Geminiani et al. 2011; Leja et al. 2012). The recommendations for clinicians who use the Er:YAG or the Er,Cr:YSGG lasers are to follow strictly the manufacturer guidelines but also to study the current literature.
6.3 Laser Application During Function
The most frequent problem in implant dentistry during the functional phase is the growth of peri‐implant gingival hyperplasia, of unknown etiology, especially in cases with removable implant‐supported restorations, which can affect the long‐term prognosis of implants (Adell et al. 1981, 1986; Lekholm et al. 1986; Engquist et al. 1988). In this field, the CO2 laser, as well as the diode laser, can be applied successfully. Hyperplasia is usually removed with the continuous laser beam of the CO2 laser and output power of approximately maximum 4 W. Peri‐implant soft tissues will be ablated to create a smooth, tissue morphology (gingivoplasty). This surgical treatment needs sometimes to be carried out in several sessions. For diode lasers, a significantly lower power of 2–3 W (with initiator) is usually sufficient for soft tissue excisions.
Other surgical corrections of the peri‐implant soft tissues may be necessary during implant loading, such as removal of muscular attachments (frenectomy) and vestibuloplasty (Figure 6.4; see also Chapter 3). In such surgical interventions, additional suturing is not necessary. Wound healing succeeds usually without complications. The charring may serve as a wound dressing, and it is more common in the application of the CO2 laser.
6.4 Laser Applications in Peri‐implantitis Treatment
Peri‐implant diseases have increased in the last few years. Studies by Zitzmann and Berglundh (2008) presented peri‐implant inflammatory reactions over 50% for peri‐implant mucositis and a maximum of 43% for peri‐implantitis. However, peri‐implantitis has been defined recently as a peri‐implant infection with bleeding on probing, suppuration, and a progressive crestal bone loss. Other signs of inflammation (i.e. pain) may be included (Albrektsson et al. 2012a). Based on this definition and the recent analysis of the literature, the frequency of peri‐implantitis and implant failures are commonly less than 5% over 10 years of follow‐up for modern implants using established protocols (Albrektsson et al. 2012b).
Laser use in the field of the peri‐implantitis treatment does not seem to be an evidence‐based approach. One reason for that is that there is no possibility of having randomized‐controlled split‐mouth clinical trials on the treatment of peri‐implant diseases. Many case series and clinical reports present the application of various laser wavelengths for the decontamination of failing implants. Early case reports showed the effects of the use of a diode laser for the decontamination of implant surfaces with an output power of 1 W and 20 seconds application period (under noncontact fiber). Specifically, a significant reduction of the pathogenic bacteria (Porphyromonas gingivalis and fusobacteria) was observed (Hartmann and Bach 1997).
Other microbiological studies showed bacteria (especially Bacillus subtilis) reduction on implant surfaces with various surface patterns, after Nd:YAG laser irradiation. Only one output power up to 3 W was studied. However, the risk of metal overheating should be taken into consideration. An absolute bacteria elimination (i.e. sterilization) could not be observed (Block et al. 1992). For this reason, and also because of the severe damage of the implant surface after irradiation with the Nd:YAG laser, the use of this laser might be avoided in peri‐implantitis therapy.
In contrast to the Nd:YAG laser, it was confirmed in another in vitro study that, after contamination of implant surfaces with pathogenic bacteria (Porphyromonas gingivalis), the bacteria can be reduced by the CO2 laser irradiation (Purucker et al. 1998). A significant reduction of bacteria was observed in samples of irradiated surfaces, in comparison to the nonirradiated titanium surfaces (Figures 6.5 and 6.6).
Some animal experiments and clinical studies showed that the use of the CO2 laser can be promising for the peri‐implantitis therapy (Figure 6.7). Based on an animal study in dogs, the progression of the inflammatory osseous reduction can be prevented around the implant, without leaving thermal damages in the osseous bed, when implants are irradiated with the CO2 laser. Of particular interest is the new bone formation on peri‐implant osseous defects after decontamination with the CO2 laser (Figure 6.8) in close contact with the implant surface (re‐osseointegration). Furthermore, implant surfaces could be decontaminated using appropriate parameters, without changes of the surface pattern (Deppe et al. 1998).
In contrast to the use of the CO2 laser for implant surface decontamination, Schmage et al. (2012) also showed inefficient cleaning of implant surfaces using an Er:YAG laser (Key Laser 3, KaVo Dental, Biberach, Germany). Another study also stated that surface alterations may occur with the Er:YAG laser (Kreisler et al. 2002). Compared to numerous studies by the group of Schwarz et al. (2005, 2006), who promoted the use of Er:YAG laser in the treatment of peri‐implant diseases (Schwarz et al. 2005, 2006), there is evidence that the radiological bone fill after decontamination of failing implants with the Er:YAG laser is not predictable, especially when the peri‐implant lesions are advanced (Schmage et al. 2012; Schwarz et al. 2012).
In contrast to that, the use of CO2 laser for decontamination of peri‐implant infrabony defects (before bone augmentation) seems to be a predictable method with a long‐term success, also when these lesions are advanced (Romanos and Nentwig 2008; Romanos et al. 2009a, b).
Also, of significant importance is the improvement of corrosion resistance of laser‐irradiated titanium surfaces due to surface melting and rutile (TiO2) formation. Studies indicate that rutile particles are less bioreactive than titanium particles (wear‐related debris from the implant surface) and, therefore, higher biocompatibility of titanium‐based implants modified with an outer surface layer of rutile is expected (Vallés et al. 2006). This was also tested in human osteoblast cultures as well (Vallés et al. 2008), promoting this surface modification of implants due to the modulation of secretion of mediators associated with bone resorption, such as interleukin 6 (IL‐6) and prostaglandin (PGE‐2).
In contrast to the use of CO2 lasers, pulsed Nd:YAG lasers were used to modify the surface of hydroxyapatite‐coated dental implants and showed changes of the coating, alterations of the surface phase composition, as well as the morphology. These changes were not acceptable for biomedical applications. However, repetitive passes with the pulsed laser did not help to seal the cracks that formed (Cheang et al. 1996).