Dental implants surface analysis after exposure to radiation of laser dental systems
Currently, dental implantation is the leading sphere in the rehabilitation complex of patients with secondary complete or partial absence of teeth (missing teeth). Every year more than two million implants are installed around the world, the total number of such patients reached 30 million people in the 1990s of the last century. Scientific observations and clinical investigations demonstrate good results of implantation, allowing to achieve full restoration of chewing efficiency, speech formation and esthetics of the tooth alignment .
A good result of cleaning depends on the quality of surface preparation of the implant neck and how tightly the modules are fitted to each other. The first visit after fixation of permanent superstructure to the implants should be planned 1 month after it. Performance of oral hygiene by patient should be controlled with application of tests. When implants or the structure of the prosthesis are contaminated, they are cleaned with low-speed tips and ultrasonic instruments. Plastic curettes and nylon brushes are usually used. In conclusion, it is necessary to clean the superstructure fixed on the implants. Brushes, superflosses and rubber heads are used. If the supraconstruction is removable, it is recommended to clean it with ultrasound in addition to mechanical cleaning. The use of Perio Flow technology (air-abrasive over- and subgingival treatment with glycine powder with a particle size of 25 µm) (EMS, Switzerland) allows the removal of biofilms without causing visible damage to the implant surface [1–6].
It is unacceptable to use coarse metal tools, as well as conventional scalers designed to remove oral debris from natural teeth. Their use leads to chemical inactivation and physical damage to the surface of the implant. A reaction between the metal of the instrument and the implant metal is possible, the inactivating film on the implant is broken, the implant surface is damaged, and the formation of plaques is increased.
Retaining the bone and creating a biological width at the abutment level provide the necessary stimulation of the bone and contribute to a healthy state of the soft tissues. An important function of soft tissue is to protect the underlying bone. In this case, the bone should be stable in order to maintain soft tissue. In this connection, the structure of the dental implants surface is of great importance. Implantable materials are widely used in dentistry. Many materials contact directly with bone tissue. For decades, the scientists have created new surfaces specially designed to improve the interaction between the implant and bone tissue [1, 5, 7, 12].
Using the latest sandblasting and acid etching technology, it is possible to produce clean and porous implant surfaces so as to provide long-term osseointegration of the dental implant with bone tissue, stability of the implant, to extend the functioning period of the prostetic structure with support on the implant. As a result of the marketing, implants of the following systems were selected for this group of dental implants from widely used in our country: OsseoSpeed, Astra Tech (Astra Tech, Mцllndal, Sweden), Biotech (Aix-en-Provence, France), Liko (Moscow, Russia), Nobel Active (Nobel Biocare, Gothenburg, Sweden), Xive TG (Dentsply friadent, Mayneim, Germany), Dentium (Dentium Co, Seoul, Korea) [1, 5, 8–12].
With the introduction of lasers in clinical dentistry, it became possible to improve the technologies of professional oral hygiene in dentistry. The use of lasers for professional oral hygiene includes bactericidal treatment of the neck and implant upper rings, bone tissue and soft peri-implant tissues. All known dental lasers are used to achieve this: solid-state Er : YAG and Nd : YAG lasers with a wavelength of 2 940 nm and 1 064 nm. Under the impact of the laser energy of the Er : YAG laser, ablation is observed in the tissues, which leads to a layer-by-layer dissection of tissues. The result of the action of the Nd : YAG laser is a homogeneous photothermolysis, the absorption of laser energy by the target tissue and its propagation over the surrounding tissues as a heat to a shallow depth. The use of a laser beam makes it possible to sterilize the bone tissue, implant surfaces protruding above the bone and the inner surface of the peri-implant pocket [6, 13].
Thus, the use of aggressive metal tools and chemical agents for professional oral hygiene adversely affects the surface structure of dental implants. To avoid this, various laser systems are used in dentistry to treat peri-implant pockets during professional oral hygiene and the treatment of mucositis and peri-implantitis. However, no information was found in medical sources concerning the way laser irradiation affects implant surfaces. Advancement of implant surfaces mainly aimed the goal of better and more predictable osseointegration, rather than surface resistance to chemical and physical agents that would be used for professional hygiene. This issue is not sufficiently developed. The use of modern surgical laser technologies probably could contribute to solving this problem. However, the rationale for this requires further research in this direction.
The aim of the investigation was to compare the microstructure of the surface of the implants of different systems after laser exposure at different wavelengths.
MATERIALS AND METHODS
The following dental laser systems were used in the research: Er : YAG DEKA Smart 2940D plus, Nd : YAG DEKA "Smarti A10" performed based on YAG technology (yttrium aluminum garnet), emitting light of infrared spectrum with a wavelength of 2 940 nm and 1 064 nm respectively; "Smart US20D" DEKA laser system (Italy), with a wavelength of 10 600nm (CO2-); Smart Lite DEKA (Italy) laser system with a wavelength of 532 nm (Nd: YAG-CTr); laser device LSP "IRE-Polyus" (Russia), with a wavelength of 970 nm. Implants of the following systems were used as the object of the study: OsseoSpeed, Astra Tech (Astra Tech, Mцllndal, Sweden), Biotech (Aix-en-Provence, France), Liko (Moscow, Russia), Nobel Active (Nobel Biocare, Gothenburg, Sweden), Xive TG (Dentsply friadent, Maingheim, Germany), Dentium (Dentium Co, Seoul, Korea). The samples of implants were divided into study groups depending on the method of exposure. In total, 5 groups of samples were examined (Table 1).
The surface of the implants was exposed using surgical lasers point-wise for 1 second with a power of 1W and 2W. The scanning electron microscopy method was used for the analysis of the microrelief of the implant surface. The samples were placed on a graphite tape, which was fixed to the aluminum table with the other side. The sample prepared in this way was placed in the working chamber of the scanning electron microscope (SEM) LEO 1420 (VP). The analysis was carried out both at a 2–5 micrometer point and at an arbitrarily specified area. Determination of the intensity and number of defects in the case of nonuniform fracture was performed on a digital scale in scores 0 to 5, where 0 indicates the absence of defects, and 5 indicates the presence of a strong damage to the coating; scores 1 to 4 – intermediate degrees of destruction (Table 2). A score system of the destruction of the microrelief of the implant surface after exposure to laser irradiation was performed by comparison with the intact surface of the implants.
RESULTS AND DISCUSSION
When studying the surface of implants according to scanning electron microscopy after radiation with 1 W CO2-laser, the surface of the Nobel Active implant was more damaged (Fig. 1), there was a moderate amount of bubbles, chaotically located cracks, in some places there was a peeling of the implant coating, the structure of the surface of other implants remained intact.
When the power of CO2 laser was increased to 2 W, the signs of damage of various degrees were revealed on all samples in the form of small bubbles, blisters, a small number of chaotically located cracks, flakes and vaporization of the implant coating with the formation of surface defects (Fig. 2).
After the impact of the 1 W Er: YAG laser, only two samples, Biotech BIS-Conic (Fig. 3) and Nobel Active, were affected, to a lesser or greater extent, respectively, a significant number of defects on the surface of the Nobel Active sample – swelling, cracking, flaking, vaporization of the surface with the formation of a continuous defect in the microrelief of the implant. At a power of 2 W, damage to all implant samples ranged from a few subtle defects to continuous surface defects is noted.
The softest laser irradiation on the sample surface was provided by the Nd : YAG-KTP laser (a kind of neodymium laser), at a power of 1 W, the surface of the Nobel Active sample was damaged, a small number of small bubbles appeared on the surface. However, with an increase in power to 2W, two samples, Dentium and Liko, suffered insignificantly, barely noticeable defects in the form of bubbles on the surfaces, and the surface of the Nobel Active implant sample was significantly damaged, melting, cracking with formation of surface defects was observed (Fig. 4).
The most aggressive was the effect of the Nd : YAG laser irradiation in ablation mode, which is used in the clinic. After exposure to a 1 W neodymium laser, there were no intact samples. The degree of destruction of the microrelief is characterized by the range of effects from presence of a significant number of small defects to continuous surface defects, such as melting, blistering and cracking of the surface of the implant samples (Fig. 5). When the power was increased to 2 W, the Nd : YAG laser irradiation led to continuous surface defects: melting, cracking, exfoliation of the implant coating and vaporization of the surface of the implant samples with metal exposure (Fig. 6).
The effect of laser irradiation from the domestic IREE-Polus diode laser in the clinical mode ablation led to a slight disruption of the surface of "OsseoSpeed, Astra Tech" and "Nobel Active" in the form of small bubbles. More significant destruction of the surfaces of these samples (Fig. 7) was observed after increase in power to 2 W, the remaining samples practically did not suffer (Fig. 8).
As a result of the experimental study, the scanning electron data showed significant differences. The greatest degree of destruction of the microrelief of the implant surface is revealed when exposed to Nd : YAG laser irradiation and minimal or no damage to surfaces when exposed to Nd : YAG-KTP laser radiation. With 1 W laser radiation, the least amount of blistering, cracking and delamination on the surface of implants is determined using Nd : YAG-KTP, CO2- and semiconductor IRE-Polyus lasers, and the greatest amount of damage was registered when exposed to Nd: YAG and Er: YAG lasers (Fig. 9).
With 2 W laser exposure, the aggressive influence of irradiation is observed under the influence of Nd : YAG and Er : YAG lasers in the form of complete opening of the upper layer of implant surfaces and a less destructive effect from the irradiation of Nd : YAG-KTP-, IRE-Polyus diode laser and CO2- laser (Fig. 10).
The data of scanning electron microscopy showed significant differences. The greatest damage to the implant surface was detected by exposure to the Nd : YAG laser and minimal or no damage when exposed to Nd : YAG-KTP laser irradiation. When 1 W power was applied, the smallest damaging action was detected using Nd : YAG-KTP, CO2-laser and IRE-Polyus diode laser, and the largest – when exposed to the Nd : YAG and Er : YAG lasers. At a power of 2 W, the aggressive influence of laser irradiation was detected for the Nd : YAG and Er : YAG lasers, and a smaller effect was detected for the Nd : YAG-KTP, IRE-Polyus diode laser and CO2-laser.
The data of scanning electron microscopy states (or proves) that all the laser systems that were used in the investigation can be successfully applied for professional oral hygiene in patients with dental implants. However, it should be borne in mind that the most traumatic effect on the implant surface is provided by the irradiation of Nd : YAG- and Er : YAG lasers. This indicates that these lasers can be used for professional oral hygiene at a lower radiation power – up to 1 W. The smallest damaging effect on the implant surface was revealed by the emission of Nd : YAG-KTP, IRE-Polyus laser and CO2-laser. The power of these lasers for use in professional oral hygiene can be above 1 W.