Laser preparation of hard dental tissues in children. Laser dental treatment for adults and children How much tissue is removed from the tooth

ID: 2015-11-5-R-5855

Samedova D.A., Kochneva A.A.

GBOU VPO Saratov State Medical University named after. IN AND. Razumovsky Ministry of Health of Russia

Summary

This article outlines the mechanisms of action of lasers on hard tooth tissue during preparation and clinical advantages in comparison with the standard preparation method.

Keywords

Preparation, laser, erbium laser, CO2 laser

Review

Introduction. With the development of new technologies in recent years, there has been a steady trend towards an increase in the use of lasers and the development of new laser technologies in all areas of medicine, including dentistry.

Target: study the mechanisms of action of lasers, laser preparation techniques and the clinical benefits of lasers.

Tasks:

1. study the effects of lasers on hard dental tissues;

2. study the technique of preparing hard dental tissues with a laser;

3. compare different types of lasers used in the preparation of hard dental tissues;

4. identify the advantages and disadvantages of lasers

Materials and methods: analysis of scientific articles, dissertations, scientific literature.

Results and discussion. The use of lasers in medicine is based on the photodestructive action of light used in laser surgery and the photochemical action of light used for therapeutic treatment. One of the most important tasks of laser dentistry is the removal of carious damage with the subsequent restoration of the shape and function of the tooth. Lasers vary depending on where their energy is applied - affecting soft and hard tissue. Laser light is absorbed by a specific structural element that is part of the biological tissue. There are devices that combine several types of lasers (for example, for influencing soft and hard tissues), as well as isolated devices for performing specific tasks (lasers for teeth whitening). Lasers have several operating modes: pulsed, continuous, combined. Their power (energy) is selected in accordance with the operating mode.

Most often in dentistry, erbium laser and CO2 laser are used for the preparation of hard tissues. The most studied laser for hard tissue removal currently is the Er:YAG laser (wavelength 2.94 nm).

The mechanism of action of the erbium laser is based on “micro-explosions” of water, which is part of the enamel and dentin, when it is heated by a laser beam. The process of absorption and heating leads to the evaporation of water, microdestruction of hard tissues and the removal of solid fragments from the zone of exposure to water vapor. A water-air spray is used to cool the tissues. The impact effect is limited by the thinnest (0.003 mm) layer of laser energy release. Due to the minimal absorption of laser energy by hydroxyapatite - the mineral component of the chromophore - heating of the surrounding tissue by more than 2°C does not occur.

The mechanism of action of the CO2 laser is based on the absorption of laser light energy by water and heating of tissues, which allows layer-by-layer removal of soft tissues and coagulation of them with a minimal (0.1 mm) zone of thermal necrosis of nearby tissues and their carbonization. Laser ablation of tissue is usually accompanied by an increase in the temperature of the surrounding tissue, which causes melting and carbonization.

The most common indications for the use of CO2 and erbium lasers include:

Preparation of cavities of all classes, treatment of caries and non-carious lesions;

Processing (etching) of enamel to prepare for bonding;

Sterilization of the root canal, impact on the apical focus of infection;

Pulpotomy, stopping bleeding;

Treatment of periodontal pockets;

Implant exposure;

Gingivotomy and gingivoplasty;

Frenectomy;

Treatment of mucosal diseases;

Reconstructive and granulomatous lesions;

Operative dentistry.

The laser device consists of a base unit that generates light of a certain power and frequency, a light guide and a laser tip.

There are different types of handpieces: straight, angled, for power calibration, etc. With water-air cooling for constant temperature control and removal of prepared hard tissue. When working with a laser, it is necessary to use eye protection, because Laser light is harmful to the eyes. The doctor and patient must wear safety glasses during preparation.

Laser preparation technique. The laser operates in pulse mode, sending an average of about 10 beams every second. Each impulse carries a strictly defined amount of energy. The laser beam, hitting hard tissue, evaporates a thin layer of about 0.003 mm. A microexplosion, which occurs as a result of heating water molecules, throws out particles of enamel and dentin, which are removed from the cavity with a water-air spray. The procedure is absolutely painless, since there is no strong heating of the tooth and no mechanical objects (bur) that irritate the nerve endings. This means that when treating caries there is no need for anesthesia. The dissection occurs quite quickly, but the doctor is able to precisely control the process, immediately interrupting it with one movement. The laser does not have the same effect as residual rotation of the turbine after the air supply is stopped. Easy and complete control when working with the laser ensures the highest precision and safety.

For the preparation of tooth enamel, the most effective are laser beams with wavelengths of 1.69 - 1.94 microns, in a pulsed generation mode with frequencies of 3 - 15 Hz and a power of 1 - 5 J / pulse.

Since during dental caries (medium and deep), dentin can practically be in two states - softened (more often) or compacted (the so-called transparent dentin), it turned out to be advisable, quite justified, to prepare it with a laser beam of different wavelengths: softened dentin is prepared with a laser beam with a length waves 1.06 - 1.3 µm at frequencies 2 - 20 Hz and power 1 - 3 J/imp, and compacted (transparent) dentin with a wavelength of 2.94 µm, frequency 3 - 15 Hz and power 1 - 5 J/imp.

After laser preparation, there are no chips or scratches in the cavity. Under the influence of the laser, microflora dies, which minimizes the risk of cross-infection. In this case, the CP does not require antiseptic treatment. Laser is acceptable for small lesions with direct access. Preparation of larger cavities can be time-consuming and labor-intensive. The procedure is painless, since there is no strong heating of the tooth and the duration of the laser pulse is approximately 200 times less than the time threshold for pain perception.

Clinical benefits of lasers. Under the influence of laser light on the hard tissues of the tooth, the metabolism of the cellular elements of the pulp increases. When irradiated with laser light, structural changes occur in the enamel, promoting an increase in the content of calcium and phosphorus, reducing the acid dissolution of the enamel. An in vitro study of the effect of a laser beam on hard dental tissues showed its high photomodifying and recalcifying properties.

Compared to rotary instruments, the laser has a huge advantage. Laser treatment is non-contact, which allows direct cooling of the treatment area with a water spray. Patients perceive the laser positively mainly due to the non-contact processing and the absence of drilling sounds compared to traditional instruments. In addition, due to the absence of pain from pressure and elevated temperature, anesthesia is often not required. This is especially beneficial when treating children, when it is necessary to use the most gentle techniques. The water content of tissue is one of the most important factors in the issue of preparation efficiency: tissue layers with lower water content will have less volume of excision per unit time.

And this is one of the reasons why more pulse energy is required when processing enamel than when working on dentin, since the water content in healthy enamel is about 12% of its volume, and in healthy dentin it is about 24%.

The water content in carious tissue is much higher than in healthy tissue, and it can vary depending on the volume of the lesion. The higher the water content of the tissue, the greater the volume and speed of excision. As tooth dehydration increases during treatment, the effectiveness of excision may decrease. In this regard, the use of a water spray not only ensures cooling of the tooth to a safe temperature, but also increases the absorption of laser radiation.

The time a doctor spends treating one patient is reduced by more than 40%. Time savings are achieved due to the following reasons:

1. Less time for psychological preparation of the patient for treatment;

2. There is no need for premedication and anesthesia, which takes from 10 to 30 minutes.

3. No need to constantly change burs and tips - work with only one tool;

4. Finishing of the edges of the cavity is not required;

5. There is no need for etching of enamel - the cavity is immediately ready for filling.

The disadvantages of laser treatment include the high cost of equipment and the high professional requirements placed on the dentist and the high cost of treatment; if the technique is violated, soft tissue injury may occur.

Conclusions:

When studying the mechanism of action of lasers during the preparation of hard tooth tissues, we found that the laser beam, hitting the hard tissues, evaporates a thin layer of about 0.003 mm.
We studied the laser preparation technique (the laser operates in a pulsed mode, sending an average of about 10 rays every second, a micro-explosion that occurs as a result of heating water molecules, throws out particles of enamel and dentin, which are removed from the cavity with a water-air spray).
We compared different types of lasers, their wavelength, power and what types of tissues they act on (erbium and CO2 lasers)
Currently, the advantages of using lasers in dentistry have been proven by practice and are undeniable: safety, accuracy and speed, absence of undesirable effects, limited use of anesthetics - all this allows for gentle and painless treatment, acceleration of treatment time, and therefore creates more comfortable conditions for the doctor, and for the patient.

Literature

Bakhareva E.G., Khalturina O.A., Lemeshkina V.A. Laser technologies in dentistry // Health and education in the XXI century N4, 2012, p. 483
Anosov V.A. Laser preparation of hard dental tissues // Kuban Scientific Medical Bulletin, N 4, 2002, P.25-27.
Khramov V.N., Chebakova T.S., Burlutskaya E.N., Danilov P.A. Dental pulse-periodic neodymium laser // Bulletin of VolSU 2011, P.9 - 13.
Ed. L.A. Dmitrieva, Yu.M. Maksimovsky. Therapeutic dentistry: manual: national. hands GEOTAR-Media, 2009, 912 p.
Prokhonchukov A.A., Zhizhina N.A., Nazyrov Yu.S. Method for preparing hard dental tissues. Patent for invention No.: 2132210. June 27, 1999
Melcer J. Latest treatment in dentistry by means of the CO2 laser beam // Lasers surg. med. - 1986. - Vol. 6 (4). - P. 396-398.
Melcer J., Chaumette M. T., Melcer F., Dejardin J., Hasson R., Merard R., Pinaudeau Y., Weill R. Treatment of dental decay by CO2 laser beam: preliminary results // Laser surg. med. - 1984. -Vol. 4 (4). - P. 311-321.
Hibst R. Technik, wirkungsweise und medizinische anwendung von holmium-und erbium-lasern. Habilitationsschrift // Ecomed verlag.- Landsberg, 1996. - P. 135-139.
Cavalcanti B. N., Lage-Marques J. L., Rode S. M. Pulpal temperature increases with Er: YAG laser and high-speed handpieces //J. prosthet dent. - 2003. - Vol. 90 (5). - P. 447-451.
Drisovannaya O. N. Modern laser technologies in the treatment of hard dental tissues // Kuban Scientific Medical Bulletin. N 6, C. 20
Dubova L.V., Konov V.I., Lebedenko I.Yu., Baev I.V., Sinyavsky M.N. Thermal effect on the coronal pulp of a tooth with a microsecond ND:YAG laser // Russian Dental Journal, N5, 2013, pp. 4-8.
Chechun N.V., Sysoeva O.V., Bondarenko O.V. Modern aspects of preparation in therapeutic dentistry. Altai State Medical University. pp. 127-130.
Shumilovich B.R., Suetenkov D.E. The state of mineral metabolism of enamel depending on the method of preparation of hard tooth tissues in the treatment of caries // Pediatric dentistry and prevention. 2008. T. 7. No. 3. pp. 6-9.

As already partly said above, preparation occurs as follows: the laser operates in a pulsed mode, sending an average of about 10 beams every second. Each impulse carries a strictly defined amount of energy. The laser beam, hitting hard tissue, evaporates a thin layer of about 0.003 mm. A microexplosion that occurs as a result of heating water molecules throws out particles of enamel and dentin, which are immediately removed from the cavity with a water-air spray. The procedure is absolutely painless, since there is no strong heating of the tooth and no mechanical objects (bur) that irritate the nerve endings. This means that when treating caries there is no need for anesthesia. The dissection occurs quite quickly, but the doctor is able to precisely control the process, immediately interrupting it with one movement. The laser does not have the same effect as residual rotation of the turbine after the air supply is stopped. Easy and complete control when working with the laser ensures the highest precision and safety.

After the laser, there are no cracks or chips left on the enamel, which inevitably form when working with burs.

In addition, the cavity after laser preparation remains sterile and does not require long-term antiseptic treatment, because laser light destroys any pathogenic flora.

When the laser unit is operating, the patient does not hear the unpleasant noise of the drill that frightens everyone. The sound pressure generated by laser operation is 20 times less than that of a high-quality imported high-speed turbine. This psychological factor is sometimes decisive for the patient when choosing a place of treatment.

In addition, as already noted, laser preparation is a non-contact procedure, i.e. None of the components of the laser system is in direct contact with biological tissues - preparation occurs remotely. After work, only the tip is sterilized. It should be noted that prepared particles of hard tissue along with infection are not thrown out with great force into the air of the dentist’s office, as happens when using a turbine. During laser preparation, they do not acquire high kinetic energy and are immediately deposited by a spray jet. All this makes it possible to organize a sanitary and epidemiological operating regime for a dental office that is unprecedented in its safety, allowing to reduce to zero any risk of cross-infection, which is especially important today. Such a level of infection control should undoubtedly be appreciated by both sanitary and epidemiological services and patients.

In addition to undoubted practical advantages, the use of a laser can significantly reduce the cost of treatment. Working with a laser, the doctor almost completely eliminates burs, etching acid, and antiseptic treatment of carious cavities from everyday expenses, and the consumption of disinfectants is sharply reduced. The time spent by a doctor on treating one patient is reduced by more than 40%!

Time savings are achieved due to the following reasons:

Less time for psychological preparation of the patient for treatment;

There is no need for premedication and anesthesia, which takes from 10 to 30 minutes;

There is no need to constantly change burs and tips - work with only one tool;

Finishing of the cavity edges is not required;

There is no need for etching of enamel - the cavity is immediately ready for filling;

Roughly calculating the time required to carry out the above manipulations, every dentist will agree that it is slightly less than half of the total appointment time. If we add to this the significant savings in consumables, tips, burs, etc., then we will receive undoubted proof of the economic feasibility and profitability of using a laser in the daily practice of a dentist.

To summarize, we can highlight the following undoubted advantages of laser preparation of hard dental tissues:

No drill noise;

Virtually painless procedure, no anesthesia required;

Time savings up to 40%;

Excellent surface for bonding to composites;

No enamel cracks after preparation;

No etching required;

Sterilization of the surgical field;

No cross infection;

Saving consumables;

Positive reaction from patients, lack of stress;

A high-tech image of a dentist and his clinic.

Now we can say with firm confidence that the use of lasers in dentistry is justified, cost-effective and is a more advanced alternative to existing methods of treating dental diseases.

This technology has a great future, and the widespread introduction of laser systems into dental practice is only a matter of time.

Tooth preparation is an irreversible process, so it is very important that it is carried out by an experienced specialist in compliance with all standards and requirements.

This is one of the key stages in preparing for the installation of a crown, which means that not only the structural features of the teeth should be taken into account, but also the individual characteristics of the patient himself.

What is tooth preparation

Preparation is the same drilling process that most patients are so afraid of. In simple terms, this is the “grinding” of a damaged tooth, which allows you to create additional space used in the restoration process. In this procedure, the top layers of enamel and surface tissue are ground using a special device equipped with high-speed tips and diamond burs.

Modern dental technologies have made great strides forward, so unpleasant sensations such as discomfort and pain are practically absent. However, most patients are still afraid of this procedure due to psychological factors. To avoid this, you need to understand a little about the process technology.

Why is the procedure needed?

As mentioned above, the procedure is necessary to prepare the tooth for the further restoration process. Unfortunately, modern dentistry has no other option, so grinding is necessary in any case of restoration.

The thing is that by nature the tooth has an irregular geometric shape, which does not allow the prosthesis to be installed tightly enough. Therefore, the convex side walls must be carefully sanded to give them the correct conical shape. It allows you to install the crown in such a way as to avoid the slightest gaps and prevent the recurrence of caries or other problems.

In what cases is the procedure performed?

This procedure is necessary in almost every case of oral restoration:

Restoration and replacement of already installed fillings. Turning is necessary if the old filling has significant defects.
Recovery after fractures. Often not only the shape is disrupted, but also increased sensitivity appears.
Restoration of birth defects.
As part of other restorative treatments. Grinding of supporting teeth when installing a prosthesis.

Indications for preparation

In addition to installing crowns, there are some other indications for the procedure.

During the enamel removal procedure, a carious process may be detected, in which case it must also be removed to avoid spreading to neighboring teeth. In addition, infected dentin remains in the cavity, which must also be removed.

Another case in which grinding will be necessary is deep caries damage to several teeth at once. In this case, before starting any restoration actions, it is necessary to remove all carious tissue and fill the cavities with temporary fillings. Only after this can the restoration process begin.

Teeth preparation methods

Each restorative dentist knows several grinding techniques and determines in which case each of them is most suitable for the patient.

The main preparation methods include:

Advantages and disadvantages of each method

It is impossible to single out any of the preparation methods separately, since they are selected individually for each case of restoration and treatment. However, each method has certain pros and cons.

Ultrasonic method

The ultrasound procedure has virtually no disadvantages. Ultrasound does not affect pulp tissue, the small amount of heat generated cannot overheat dentin or enamel, and there are no chips or cracks. In addition, the procedure is carried out as painlessly as possible.

Laser tooth preparation

The laser procedure is carried out almost silently, the treated tissues do not heat up, and cracks and chips do not form. However, this method is only used for surface treatment.

Tunnel preparation

Tunnel machining is one of the most common, as it is the easiest to use and allows precise control of the thickness of the surface being ground. This method, unlike others, has several key disadvantages.

The enamel overheats greatly during the procedure, so the installation must have a special cooling device. If the instrument is of poor quality or is heavily worn, then there is a risk of cracks, and if the technique is violated, even injury to the soft tissues of the oral cavity is possible.

Chemicals

The chemical method also allows you not to heat the tissue, it is painless, and even microcracks are absent when used. The main disadvantage of chemical exposure is the duration of the procedure.

Air abrasive method

Air abrasive treatment is painless, without generating excessive heat and quite quickly. However, this method is practically not used independently, since it only affects the upper layers. It is used in combination with other methods to prepare teeth for the installation of permanent structures.

Types of ledges during turning

The ledge is the hard tissue remaining after turning, on which the future prosthesis will be attached. They are divided into several types:

Knife-shaped. Used for installation of solid cast structures. Its width is 0.3-0.5 mm.
Rounded. It is also called grooved. It is used for metal-ceramic prostheses. Has a thickness from 0.8 mm to 1.3 mm.
Brachial. It is considered the most durable, reliable and aesthetic type of ledge. Its width is on average 2 mm.

Stages of the preparation procedure

Turning is carried out in several stages; in total, 6 clinical stages can be distinguished:

Features of the procedure

Depending on the structure you plan to install, grinding may vary.

Crown preparation

If you plan to install solid structures, then turning begins from the side surfaces to avoid damage to adjacent teeth.

For metal ceramics, depulpation will also be required. The doctor removes 2 mm of thickness from each side and selects the shape of the ledge that matches the chosen design. For metal ceramics, the enamel surface is left rough to ensure maximum adhesion.

For a porcelain crown, the tooth is ground into a cone shape, with the ledge plunging into the gum by about 1 mm.

If the crown is made of zirconium, then the ledge has a shoulder-shaped or rounded shape, with clearly defined boundaries.

Turning for veneers

Since veneers are external overlays, the main attention during preparation is paid to the front surface of the tooth enamel. The lateral sides are processed either while maintaining interdental contact, or the boundaries of the ledges are brought to the inner side (in this way the maximum aesthetic effect is achieved).

For tabs

An inlay is a partial denture that is inserted into a tooth cavity. When preparing, it is very important to maintain all angles and maintain even walls of the cavity so that the prosthesis is in contact with the tissue as closely as possible.

Turning for dentures

The procedure is necessary in case of installation of bridges. Since bridges are similar in principle to crowns, preparation is carried out according to the same scheme.

Steaming during splinting

Since splinting is a procedure that secures the dentition and prevents loosening, it implies maximum preservation of hard tissue. Before installation, minimal grinding of the enamel is carried out.

The most common questions

Many patients are keenly interested in the question of what exactly dissection is, since this term is not widely used. We tried to answer the most common questions that patients have.

How much tissue is removed from a tooth?

The amount of fabric removed depends not only on the purpose for which the turning is performed, but also on the characteristics of the surface and its primary dimensions.

According to the rules for preparing hard dental tissues in orthopedics, on average the maximum cut is 2 mm, but it can be more.

For example, to install inlays, you need to leave at least 0.5 mm of tissue on each side adjacent to the prosthesis.

Thus, the amount of fabric sewn entirely depends on its original amount.

Is it painful to prepare a tooth?

Modern technologies in dentistry have come a long way. However, on a psychological level, most patients find any procedure painful. The latest methods make it possible to make even such a procedure as dissection completely painless.

How long does the procedure take?

How long the procedure will take will depend on the preparation method chosen by the doctor and the purpose for which it is done. On average, one visit to the doctor will take from 30 minutes to 2 hours, depending on the overall restoration plan.

Is it possible to install a prosthesis without preparation?

Unfortunately, it is impossible to properly install a prosthesis without grinding. There are several gentle methods that allow you to avoid grinding down the teeth adjacent to the prosthesis, but no more.

Can dissection be performed on children?

It is possible to perform grinding on children, but young patients are the most problematic, as they have a very negative attitude towards the devices used for dental procedures.

In addition, milk teeth, due to their anatomy, do not allow complex procedures.

The simplest method of child dissection is considered to be chemical, as it causes the least discomfort. Now dentists are looking for an alternative way to restore baby teeth.

Why do my teeth and gums hurt after preparation, and what can I do about it?

Incorrectly performed preparation often destroys the gingival margin, causing inflammation. In this case, experts recommend using anti-inflammatory drugs or performing a laser procedure. If this problem is not taken care of in time, periodontitis may develop.

Consequences and complications

Complications can only arise if the procedure is performed poorly. Most often they involve inflammation of the gums.

However, if all the affected tissues have not been removed, secondary caries may develop, which will lead to the loss of the supporting tooth.

In order to avoid problems and complications after preparation, it is very important to choose an experienced specialist. To do this, you need to contact a trusted clinic and first read the reviews.

In addition, it is necessary to choose the right method for carrying out the procedure; this can only be done by an experienced doctor.

There is no need to delay or postpone treatment until later, since without timely medical intervention you may encounter more unpleasant consequences and even lose a tooth.

Plan Introduction Lasers and laser installations in dentistry: description, classification and characteristics Effect of lasers on tissue Interaction of laser with hard dental tissue Mechanism and features of laser preparation of hard dental tissues List of references

Introduction. In the 1960s, the first lasers for medical purposes were introduced. Since then, science and technology have made huge leaps in development, allowing the use of lasers for a huge number of procedures and techniques. In the 90s, lasers made a breakthrough in dentistry; they began to be used to work with soft and hard tissues. Currently, in dentistry, lasers are used for the prevention of dental diseases, in periodontics, therapeutic dentistry, endodontics, surgery and implantology. The use of lasers is an appropriate method for daily assistance to dentists in many types of work. For some procedures, such as frenulotomy, lasers have proven so clinically effective that they have become the gold standard among physicians. They allow you to work in a dry field, which provides excellent visibility and reduces operating time. With lasers, the likelihood of scarring is very low and virtually no stitches are required. They also ensure absolute sterility of the working field, which in most cases is an absolute necessity, for example when sterilizing a root canal.

Lasers and laser devices in dentistry: description, classification and characteristics Laser devices produce different wavelengths that interact with certain molecular components in animal tissues. Each of these waves affects certain tissue components - melanin, hemosiderin, hemoglobin, water and other molecules. In medicine, lasers are used to irradiate tissues with a simple therapeutic effect, for sterilization, for coagulation and resection (operational lasers), as well as for high-speed tooth preparation. Laser light is absorbed by a specific structural element that is part of the biological tissue. The absorbing substance is called a chromophore. They can be various pigments (melanin), blood, water, etc. Each type of laser is designed for a specific chromophore, its energy is calibrated based on the absorbing properties of the chromophore, as well as taking into account the field of application.

Laser interactions with calcium-containing tissues have been studied using various wavelengths. Depending on such laser parameters as pulse duration, discharge wavelength, penetration depth, the following types of lasers are distinguished: pulsed dye, He-Ne, ruby, alexandrite, diode, neodymium (Nd: YAG), goldmium (No: YAG), erbium (Er: YAG), carbon dioxide (CO 2). In medicine, lasers are used to irradiate tissues with a preventive or therapeutic effect, sterilization, for coagulation and cutting of soft tissues (operational lasers), as well as for high-speed preparation of hard dental tissues. Lasers produce surface changes in enamel such as crater formation, melting and recrystallization. In dentistry, the CO 2 laser is most often used to treat soft tissues and the erbium laser is used to prepare hard tissues. There are devices that combine several types of lasers (for example, for treating soft and hard tissues), as well as isolated devices for performing specific highly specialized tasks (lasers for teeth whitening).

A typical laser device consists of a base unit, a light guide and a laser tip, which the doctor uses directly in the patient’s oral cavity. For ease of use, various types of handpieces are available: straight, angled, for power calibration, etc. All of them are equipped with a water-air cooling system for constant temperature control and removal of prepared hard tissue. When working with laser equipment, special eye protection must be used. The doctor and patient must wear special glasses during preparation. It should be noted that the danger of vision loss from laser radiation is several orders of magnitude less than from a standard dental photopolymerizer. The laser beam does not scatter and has a very small illumination area (0.5 mm² versus 0.8 cm² for a standard light guide). The laser operates in a mode that sends out an average of about ten beams every second. The laser beam, hitting hard tissue, evaporates a thin layer of about 0.003 mm. The dissection occurs quite quickly, but the doctor can control the process by immediately interrupting it with one movement. After laser preparation, an ideal cavity is obtained: the edges of the walls are rounded, whereas when preparing with a turbine, the walls are perpendicular to the tooth surface, and after that additional finishing has to be carried out. In addition, the cavity after laser preparation remains sterile, as after long-term antiseptic treatment, since laser light kills pathogenic flora.

In addition, the cavity after laser preparation remains sterile, as after long-term antiseptic treatment, since laser light kills pathogenic flora. Laser dissection is a non-contact procedure; the components of the laser system do not directly contact the tissues - dissection occurs remotely. In addition to the undoubted practical advantages, the use of a laser helps to significantly reduce the cost of treatment. By working with a laser, you can completely eliminate burs, antiseptic solutions, and acid for etching enamel from everyday expenses. The time spent by the doctor on treatment is reduced by more than 40%.

Effect of lasers on tissue In vitro studies have shown that CO 2 laser irradiation prevents the progression of carious lesions by up to 85 percent, which is comparable to daily use of fluoride toothpaste. Subsequent studies showed that similar effects are typical for erbium lasers up to 40 -60 percent, respectively. There is also a device that is based on an Er:YAG laser - a laser hydrokinetic system, or LGKS. The mechanism of action on hard tissues of this system consists in “micro-explosions” of water included in the enamel and dentin when it is heated by a beam. The process of absorption and heating leads to microdestruction of hard tissues and leaching of enamel and dentin particles from the cavity with a water-air spray. The effect of laser on hard dental tissues will be discussed in more detail below.

In a number of studies, prepared tooth surfaces are evaluated for their ability to form adhesion to various bonding agents. He-Ne and Nd:YAG systems create a weaker bonding surface that can be achieved with acid etching. CO 2 lasers cause changes in the enamel, depending on what wavelength is used, but in general the bonding to these surfaces is superior to that produced by acid etching of the enamel. Electron microscopy showed that LGCS makes surfaces clean and does not form a smear layer. Temperature assessment of teeth shows that in vitro prepared cavities on human teeth and in vivo prepared cavities on the teeth of pre-anesthetized dogs do not produce any adverse temperature effects on the pulp. Pathohistological studies in molars in animals and humans have shown that the pulp tissue does not undergo any pathological changes. Also, no changes were noted in odontoblasts. The mechanism of action of a CO 2 laser on soft tissues is based on the absorption of laser light energy by water and heating of tissues, which allows layer-by-layer removal of soft tissues and coagulation with a minimal (0.1 mm) zone of thermal necrosis of nearby tissues and their carbonization.

Interaction of the laser with the hard tissue of the tooth The laser beam is unique in that it compresses the energy of the laser output into a small, directed and focused beam of highly coherent monochrome light. The properties of the laser beam allow it to be focused to a very small spot, which makes it possible to achieve the highest energy density with low pulse energy and makes it possible to carry out truly unique procedures. Er:YAG laser with a wavelength of 2.940 nm is the best laser of choice for procedures on hard dental tissues due to the highest percentage of absorption in water and hydroxyapatite. The radiation absorption of the Er:YAG laser (2.940 nm) in enamel is 2 times higher than that of the Er:YSGG laser (2790 nm). Extremely high absorption in water allows you to effectively remove or cut hard tissue using microflashes. (see Fig. 1) When pulses are sent to a small spot on the tooth tissue, the water in this spot heats up very quickly until it evaporates. This effect is called ablation. It results in the removal of a small amount of the target tissue. A specially developed temporary structure of laser pulses (Fotona's VSP technology - Variable Square Pulsations, "rectangular pulses of variable duration") allows achieving very effective removal of hard tooth tissue without side thermal effects. The treated surface remains durable, smooth, clean and free of cracks.

Microflares are indicated in the form of stars, water in the form of cubes, and solid particles in the form of dots. A study of ablation of hard tooth tissue with an Er:YAG laser showed that there is a direct and pronounced effect of the duration of the laser pulse on the speed of preparation of enamel and dentin. To effectively prepare enamel, very short laser pulses must be used (eg, 100 to 150 microseconds), whereas the speed of dentin preparation is essentially the same with pulse widths ranging from 100 to 350 microseconds. The rate of removal of a particular tissue depends on the percentage of water content. Enamel contains on average 4% water, while dentin contains 10%. Carious dentin contains even more water. Based on the described interaction of Er: YAG laser radiation with tooth tissues, it is necessary to highlight its following advantages over classical mechanical treatment: selective effect on carious dentin; high speed of tissue processing; improved adhesion of filling materials due to the absence of a smear layer; preventive effect of enamel photomodification; psychological comfort of the patient, the possibility of treatment without anesthesia.

The study was carried out at AALZ (Germany). Average volume removed in 10 seconds: Enamel: PFN laser 0.65 mm 3 VSP laser 4.43 mm 3 Turbine 5.5 mm 3 Dentin: PFN laser 1.90 mm 3 VSP laser 4.68 mm 3 Turbine 5.3 mm 3

A water-air spray is used to cool the tissues. The impact effect is limited to the thinnest (0.003 mm) layer of laser energy release. Due to the minimal absorption of laser energy by hydroxyapatite - the mineral component of the chromophore - heating of the surrounding tissues by more than 2 o. C doesn't happen. Now, after such a spatial excursion into the depths of theoretical biophysics, let's move on to the practical application of laser technologies in dentistry. Indications for the use of laser almost completely repeat the list of diseases that a dentist has to deal with in his work. The most common and popular indications include: Preparation of cavities of all classes, treatment of caries; Processing (etching) of enamel; Sterilization of the root canal, impact on the apical focus of infection; Pulpotomy; Treatment of periodontal pockets; Exposure of implants; Gingivotomy and gingivoplasty; Frenectomy; Treatment of mucosal diseases; Reconstructive and granulomatous lesions; Operative dentistry.

The mechanism and features of laser preparation of hard dental tissues As already partly said above, preparation occurs as follows: the laser operates in a pulsed mode, sending an average of about 10 rays every second. Each impulse carries a strictly defined amount of energy. The laser beam, hitting hard tissue, evaporates a thin layer of about 0.003 mm. A microexplosion that occurs as a result of heating water molecules throws out particles of enamel and dentin, which are immediately removed from the cavity with a water-air spray. The procedure is absolutely painless, since there is no strong heating of the tooth and no mechanical objects (bur) that irritate the nerve endings. This means that when treating caries there is no need for anesthesia. The dissection occurs quite quickly, but the doctor is able to precisely control the process, immediately interrupting it with one movement. The laser does not have the same effect as residual rotation of the turbine after the air supply is stopped. Easy and complete control when working with the laser ensures the highest precision and safety.

After laser preparation, we obtain an ideal cavity prepared for filling. The edges of the cavity walls are rounded, whereas when working with a turbine the walls are perpendicular to the tooth surface, and we have to carry out additional finishing after preparation. After laser preparation this is not necessary. But the most important thing is that after laser preparation there is no “smear layer”, since there are no rotating parts capable of creating it. The surface is absolutely clean, does not require etching and is completely ready for bonding. After the laser, there are no cracks or chips left on the enamel, which inevitably form when working with burs. In addition, the cavity after laser preparation remains sterile and does not require long-term antiseptic treatment, since laser light destroys any pathogenic flora. When the laser unit is operating, the patient does not hear the unpleasant noise of the drill that frightens everyone. The sound pressure generated by laser operation is 20 times less than that of a high-quality imported high-speed turbine. This psychological factor is sometimes decisive for the patient when choosing a place of treatment.

In addition, as already noted, laser preparation is a non-contact procedure, i.e. none of the components of the laser system is in direct contact with biological tissues - the preparation occurs remotely. After work, only the tip is sterilized. It should be noted that prepared particles of hard tissue along with infection are not thrown out with great force into the air of the dentist’s office, as happens when using a turbine. During laser preparation, they do not acquire high kinetic energy and are immediately deposited by a spray jet. All this makes it possible to organize a sanitary and epidemiological operating regime for a dental office that is unprecedented in its safety, allowing to reduce to zero any risk of cross-infection, which is especially important today. Such a level of infection control should undoubtedly be appreciated by both sanitary and epidemiological services and patients. In addition to undoubted practical advantages, the use of a laser can significantly reduce the cost of treatment. Working with a laser, the doctor almost completely eliminates burs, etching acid, and antiseptic treatment of carious cavities from everyday expenses, and the consumption of disinfectants is sharply reduced. The time spent by a doctor on treating one patient is reduced by more than 40%!

Time savings are achieved due to the following reasons: Less time for psychological preparation of the patient for treatment; There is no need for premedication and anesthesia, which takes from 10 to 30 minutes; There is no need to constantly change burs and tips - work with only one tool; Finishing of the cavity edges is not required; There is no need for etching of enamel - the cavity is immediately ready for filling; Roughly calculating the time required to carry out the above manipulations, every dentist will agree that it is slightly less than half of the total appointment time. If we add to this the significant savings in consumables, tips, burs, etc., then we will receive undoubted proof of the economic feasibility and profitability of using a laser in the daily practice of a dentist.

To summarize, we can highlight the following undoubted advantages of laser preparation of hard dental tissues: Lack of drill noise; Virtually painless procedure, no anesthesia required; Time savings up to 40%; Excellent surface for bonding to composites; No enamel cracks after preparation; No etching required; Sterilization of the surgical field; No cross infection; Saving consumables; Positive reaction from patients, lack of stress; A high-tech image of a dentist and his clinic. Now we can say with firm confidence that the use of lasers in dentistry is justified, cost-effective and is a more advanced alternative to existing methods of treating dental diseases. This technology has a great future, and the widespread introduction of laser systems into dental practice is only a matter of time.

References 1. Babaeva E. O. Lasers in dentistry: from divine origins to the latest developments. // Dentistry today. – 2002 - No. 8 (21). 2. Bgramov R.I. Using a pulsed CO 2 laser in bone and osteoplastic operations of the maxillofacial region in an experiment. // Dentistry. - 1989. - T. 68, No. 3. - p. 17 -19. 3. Burger F. Lasers in dentistry // Maestro. – 2000 - No. 1 – p. 67 -75. 4. Laser dentistry: Inf. Bull. "Dent-Inform". - 2000 - No. 1 - p. 21 -25. 5. Applied laser medicine: Educational and reference manual. / Ed. H. P. Berliena - M.: Interexpert, 1997. - 346 p. 6. Prokhonchukov A. A., Zhizhina N. A. Lasers in dentistry. - M.: Medicine, 1986. - 174 p.

Preparation of carious cavities in modern dentistry is carried out using the following methods: 1. Laser preparation; 2. preparation using an air-abrasive device; 3. chemomechanical preparation

Laser preparation of carious cavities

Operating principle of a pulsed laser: The laser beam heats the water contained in the hard tissues of the teeth, causing micro-destructions in the enamel and dentin. Then, cooling occurs and particles of enamel and dentin are immediately removed from the oral cavity using a water-air spray.

Benefits of using laser:

The use of laser systems makes it possible to reduce the likelihood of cross-infection to zero, due to the fact that particles of hard tissue are immediately deposited by an aerosol jet.
The use of anesthesia is not required, since preparing the cavity for filling is painless.
When using a pulsed laser, costs for a number of additional tools and preparations are reduced, such as burs, disinfectants, acid for etching, antiseptics for treating carious cavities, etc.
Preparation of a carious cavity with a laser is a quick procedure; the dentist has the opportunity, if necessary, to immediately interrupt it with one movement.
After using the laser, there is no need for additional processing of the cavity walls, since they immediately acquire rounded edges, and there are no chips or scratches on the bottom and walls.
The laser unit works very quietly, does not heat the teeth too much and does not cause mechanical damage to the nerve endings.
Upon completion of the preparation, only the tip is sterilized, since this procedure is practically contactless.

Preparation using an air abrasive device

This method of preparing a carious cavity uses an air flow mixed with a special powder.

Typically, powder made from baking soda, silicon or aluminum oxide is used. When the aerosol under pressure collides with the hard tissue of the tooth, the latter turns into dust.

Advantages of using an air abrasive device:

Fast and simple procedure,
for superficial caries anesthesia is not required,
It is possible to treat several teeth in one visit,
when treating a caries cavity, more healthy tooth tissue remains,
the treatment area remains dry, which facilitates the installation of composite fillings,
the risk of chipping tooth tissue is reduced.

Precautionary measures when carrying out air abrasive processing:

Before the procedure begins, the doctor treats the patient’s oral cavity with antiseptic solutions,
if the patient has contact lenses, they must be removed before the procedure;
the soft tissues of the patient’s oral cavity are isolated using cotton swabs, the lips are lubricated with Vaseline;
the use of air abrasive treatment is contraindicated in areas where there is exposed cement or metal-ceramic crowns;
the abrasive flow should be directed from a distance of 3-5 mm at an angle of 30-60° to avoid aerosol getting on the surface of the gums and damaging the epithelium;
After air-abrasive treatment, in order to reduce tooth sensitivity, remineralization of hard tissues is recommended. It is advisable for the patient to refrain from smoking for three hours;
the doctor and the patient use personal protective equipment (mask, goggles, protective screens);
the aerosol is removed using an aspirator - a “vacuum cleaner”.

Contraindications to the use of an air-abrasive method of preparation: an allergic reaction to the powder, HIV, bronchopulmonary diseases, hepatitis, acute infectious diseases of the oral cavity, pregnancy.

Chemomechanical preparation of carious cavities

The method of chemomechanical preparation consists of chemical and instrumental treatment of carious cavities.

For chemical treatment of carious cavities, various substances are used, such as lactic acid, the drug “Karydex”, a set of gels “Kariklinz”, etc.

First, the cavity is drilled using a bur, after which chemicals are applied. With their help, the dentin is softened, then removed with an instrument, and the cavity is washed with water.