Types of implants: main characteristics of dental structures

Intramucosal implantation

A type of implantation that involves the installation of mini-implants and is used to obtain extremely strong fixation of removable dentures.
Removable dentures are the most inexpensive type of orthopedic structures, which have a number of disadvantages, including the inability to firmly fix the product in the oral cavity. Especially if removable prosthetics are performed in the upper jaw. Such a prosthesis can easily fall out when eating or talking, and of course this will not bring any pleasant emotions to the person. And what is important: this problem is not solved by gels, which are so widely advertised on TV. Intramucosal implantation or mini-implantation allows you to qualitatively solve the problem of fixing removable dentures, improve the aesthetics of the result of prosthetics, and relieve the patient of problems such as rubbing soft tissues with the denture or impaired diction.

Typically, this type of technology is used when there are contraindications to intraosseous implantation, and if the patient wishes to minimize his costs for dental restoration.

During the operation, special implants consisting of two parts are used. The first part of the system is fixed on a removable denture, the second is implanted into the mucous membrane. Implants of the intramucosal type are installed in holes that the implantologist forms with a bur in the gums. After the implants are implanted, a prosthesis is immediately placed on them, which is easily removed. This makes it possible to carry out high-quality oral hygiene.

USEFUL FACT: Intramucosal implantation can only be carried out if the mucosa is in good condition, namely, if its thickness is at least 2.2 millimeters.

Transosseous implantation

Another type of implantation that modern implantologists have abandoned.
This technology was used for severe bone resorption in the area of ​​the alveolar process and for implantation in the lower jaw. If the diagnosis revealed a similar condition of the bone tissue, implantation could only be carried out using a transosseous method or after an operation to move the nerve located in the lower part of the tooth socket. But such an operation implied additional costs for the patient and not everyone agreed to it, so the doctors offered an alternative - transosseous implantation. The operation used implants of a specific type - in the form of a curved bracket with two pins, which were implanted not in the oral cavity, but in the chin area. Transosseous implantation is a complex technology and a traumatic operation; in addition, this method does not eliminate certain requirements for bone tissue. This type of implantation could not be used if the bone was below 6 millimeters and thinner than 3 millimeters.

Laser dental implantation

Laser implantation is not a separate type of implantation; this is how clinics refer to an operation during which all the incisions necessary for implantation will be made not with a scalpel, but with a laser.

This method of carrying out the operation has its advantages, including:

• Reducing the time required for surgical intervention;
• Reducing the pain of the procedure for the patient and, accordingly, reducing the dose of anesthetic drugs;
• Low traumatism, antibacterial action of the laser;
• There are no stitches, which has a positive effect on tissue recovery time.

There is essentially one downside to the laser type of dental implantation: the high price, which is much higher than the cost of traditional surgery. For comparison, turnkey implantation using a standard set of manipulations and a scalpel can cost from 35,000 rubles, the same operation, with the same implants and procedures, but with a laser - from 60,000 rubles.

USEFUL FACT: Many implantologists do not believe that laser dental implantation provides patients with any significant benefits. The implant healing period remains the same, but the patient’s costs increase significantly.

Express dental implantation

It is also not a separate type of implantation.
For the sake of beautiful advertising, clinics use the sonorous name “express implantation” to designate one-stage implantation, in which the installation of implants and a prosthesis is carried out in one operation. But the advertisement is silent about one very important detail regarding this type of implantation: it can be performed only in cases where the patient has no contraindications to surgery, there is no bone tissue atrophy, and there is enough space in the oral cavity for implantation. That is, if there are initially ideal conditions for implantation.

However, if such conditions exist, then the patient can receive a number of benefits from the use of one-stage implantation:

• Teeth can be restored in the shortest possible time and thus relieve a person from psychological discomfort and the need to limit oneself in the diet.
• One-stage implantation can be carried out in case of diabetes, hepatitis, periodontitis - conditions that are contraindications for other types of implantation.
• The patient's expenses for dental restoration are reduced, since preliminary osteoplasty is not required and, moreover, this implantation technology makes it possible to restore any number of teeth using a minimum of implants (for example, you can restore a full row of teeth with just 4 or 6 implants).
• There is no need to pay for an abutment and gum former, since implants used with one-stage technology are monolithic structures.

You can find out more useful details on one-stage implantation at an appointment with the implantologists of the Firadent clinic, which offers premium services in the field of dentistry!

Navigation implantation

Does not apply to certain types of implantation. This term refers to the use of a special program that allows you to plan in detail the operation to install implants and develop surgical templates for it. The use of templates eliminates inaccuracies when installing implants into the bone and reduces the traumatic nature of the operation. The navigation implantation service is offered to all patients of our premium dentistry in Moscow - Firadent.

Implantation without surgery

Implantation without surgery - this type of technique does not exist. This name is used for advertising and to attract clients and implies the operation is performed in a low-traumatic way, which does not exclude surgical intervention. Yes, the implantologist will not cut the patient’s gums, but to form a bone bed for the implant, he will make holes in the jaw bone with drills.

Types of implantation in complete absence of teeth

In case of complete absence of teeth, one-stage implantation using All-on-4 or All-on-6 technology is used.
These technologies make it possible to completely restore the dentition and use a limited number of implants - 4 or 6. The implants are installed in the jaw according to a certain pattern and then, immediately after the operation, a temporary prosthesis is fixed on them, which, after engraftment of the titanium rods, is replaced with a permanent orthopedic structure.

All-on-4 and All-on-6 have many advantages: these technologies make it possible to quickly restore the dentition, reduce the overall treatment time and costs for the patient, and in addition, they allow you to do without bone grafting even with diagnosed bone tissue atrophy. All-on-4 or All-on-6 are used in cases of complete edentia or when teeth are preserved in the dentition, but their treatment with conservative methods will not be effective and will not provide the opportunity to obtain a solid base for a classic prosthesis.

Dental implantation – what is it?

Patients often imagine the implant as a self-tapping screw, which is screwed into the bone, and a ceramic crown is placed on top, like a cap. And that's almost right. A dental implant is a rod that the doctor inserts under the gum and implants it into the bone. This is an artificial root, the basis of the future tooth. The second part of the structure is the aba between the base and the crown.

The implant is made in 99% of cases from a toxicologically inert titanium alloy. The popularity of the material is due to the following:

• due to the absence of a negative reaction from the body, titanium is an alternative to gold;
• upon contact with air, an oxide film is formed on the surface, facilitating survival;
• the titanium abutment connects well with composite cements and porcelain, so the result of implantation will be durable, almost indistinguishable from a real tooth with a “natural” crown;
• The titanium rod has a small thickness and weight; its installation allows you to maintain diction.

Endodontic-endosseous implantation

Another outdated method. Similar types of dental implants

are almost never used in dentistry. If the method is used, it is to preserve the tooth root. Previously, such implantation made it possible to strengthen mobile teeth. Doctors also treated some bone tissue defects using endodontic-endosseous implantation. The appearance of the implants resembled pins. Introduction into the bone was carried out without an incision. If there was any defect, a fracture, for example, then a structure was inserted through it.

At first glance, the desire to leave at least some part of the tooth seems justified. But the root will become a source of inflammation in the future. That is why modern implantologists believe that there is no point in this. It is better to carry out intraosseous implantation instead, first removing the tooth and its remains completely. The described type of implantation is almost never practiced by dentists.

Benefits of dental implantation

The main advantage of dental implantation: the adjacent tooth is not ground down (prepared), the treatment is local, only in the area of ​​the missing tooth. Also important for patients:

1. An implant in the bone prevents its resorption (bone without functional load quickly atrophies).
2. Artificial teeth on an implant are practically no different from your own.
3. Implantation can sometimes be performed immediately after tooth extraction. This is a one-step technique.
4. Implants replace missing teeth of any length.
5. Implants serve as the basis for a fixed (or removable) prosthesis. Instead of 3 missing teeth, you can install 2 implants, and the middle part with a narrower chewing surface to redistribute the load - a bridge.
6. In some cases, replacing a tooth with a dental implant allows you to replace a removable denture with a fixed one.
7. This is the best fulcrum for a removable denture, fixation improves, and the functional value of the denture increases by 20-25%.

Important: a dental implant in the bone, unlike a tooth, is installed rigidly in the bone and has no degree of mobility. Therefore, they try not to make an “implant-bridge-tooth” design.

Dental implantation allows you to restore several teeth at once

Express implantation

The manipulation is less traumatic than tooth extraction. Such implantation cannot be called an operation. It is carried out using special technology and avoids soft tissue incisions. They are virtually absent. The patient is relieved of unpleasant postoperative sensations. The doctor plans the manipulation in advance thanks to computer technology. Using the data obtained, he creates a surgical guide. It simplifies the operation. After preparing the template, the doctor plans the day of installation of the implants. All actions are carried out according to a strictly verified scheme. All calculations are mathematically correct.

The patient does not have to find free time to visit the dentist, since the procedure requires only 40 minutes to install 10 implants. Prosthetics is also one-step.

Minimal trauma is what modern dental implantation strives for. Types of implants by manufacturers

Different ones are created to best suit each clinical case.

Indications for implantation

Dental implants are installed when the formation of the skeleton is complete and bone growth has stopped. The upper age limit is individual. In orthodontics, there are cases where implantation was carried out for people 70-85 years old. If the patient is relatively healthy, the implant can be installed.

Implantation is indicated if:

• one tooth is missing, and next to it all are healthy (intact) or with limited defects;
• 3 or more teeth are missing in a row, up to complete absence;
• there is an allergic reaction to plastic;
• the patient has illnesses or psychological reasons due to which he cannot wear a removable denture.

Laser dental implantation

This is an innovative way to eliminate dental defects. Advantages of this method:

• minimal trauma;
• speed of execution;
• no complications.

Installing implants with a laser allows you to cope with problems caused by tooth loss. A person cannot chew food normally or pronounce individual sounds. Teeth shift. The health of the jaw joints is also at risk.

Laser implantation is similar to the technology used for classical implantation. However, instead of a scalpel, the doctor uses a laser beam. With its help, he cuts tissue and then installs implants into the bone. Then all he has to do is stitch up the wound. To prevent other teeth from becoming deformed, a plastic prosthesis is placed on the gum. Once the implant has settled in, the dentist cuts the gum again and places the artificial tooth.

The laser cauterizes the blood vessels, so the patient does not lose blood. There is no galvanization effect, since metal particles do not fall on the artificial root.

Other advantages of the method:

1. Small incision area. The person receives minimal damage because the tissue simply evaporates.
2. Save time. In just 30 minutes, the dentist manages to make an incision in the gum, install a dental implant and suture the tissue.
3. Sterility. The laser itself has a bactericidal effect.
4. No side effects. Even the most experienced surgeon cannot guarantee the absence of metal dust on the implant. After the surface of the implants reacts with metal particles, they become electrified. A person faces unpleasant sensations. This is excluded during laser implantation.

Contraindications to dental implantation

Absolute contraindications:

1. Acute infectious diseases.
2. Systemic bone diseases (for example, autosomal dominant osteoporosis type 2), osteogenesis imperfecta, Paget's disease.
3. Blood diseases (polycythemia, leukemia).
4. Recent radiation therapy to the head and neck.
5. Malignant and benign tumors in the upper, lower jaw and soft tissues of the oral cavity.
6. Incomplete teething, incomplete growth of skull bones.
7. Mental instability.
8. Drug addiction and alcoholism.

Relative contraindications to dental implantation:

1. Age under 20 years. The body is growing, the implant will interfere with the normal development of the jaw. In addition, there is not enough bone tissue for implantation.
2. Unsatisfactory condition of the oral cavity (rehabilitation required).
3. Immunological or hematological diseases, decompensated diabetes mellitus.
4. Smoking more than 15-20 cigarettes per day.
5. Bruxism and other parafunctional habits. After implant placement, patients are advised to use plastic mouth guards at night.
6. Long-term use of antibiotics, antidepressants, anticoagulants.
7. Hormonal imbalance (menopause), because During this period, the bones become more loose.
8. Pregnancy, after childbirth and during lactation. Due to hormonal changes, implant installation is possible no earlier than six months after the end of breastfeeding.

When a tooth is missing for a long time, the bone tissue is resorbed. About 20 years ago this was considered a reason for refusal, but now, before implantation, surgery is performed to increase bone volume.

Bone tissue augmentation allows implants to be installed even several years after tooth loss

If we are talking about implantation in the lower jaw, it is moved to the side to prevent the threat of damage to the mandibular nerve. Due to the possible rupture of the nerve, such an operation is performed very rarely and only in a hospital.

In various forms of periodontal disease, there is no gum tightly covering the tooth. After implantation, food particles will get into the “pocket”, which will lead to inflammation of the bone tissue. Therefore, the gum is formed:

• using a flap transplant from the palate;
• by deepening the vestibule of the oral cavity between the cheek and teeth (vestibuloplasty).

Medical consultation is recommended for people with endocarditis, heart failure, pathology of the endocrine system (thyrotoxicosis, diabetes mellitus, etc.). In case of hemorrhagic diathesis, blood clotting disorders (prothrombin time, or Quick reaction index (more than 30), implant installation is carried out in a hospital setting

Subperiosteal implantation

Types of dental implantation

, like this one, are also not considered modern. Previously, it was performed if the alveolar process was of insufficient height. The patient underwent manipulation if he wanted to save money on the sinus lift procedure. There are partial and complete types of SI. The main problem with partial subperiosteal implantation is determining the exact location of the implant.

First, the doctor makes a tomogram of the jaw. In accordance with the data obtained, the implant model is selected. The dentist creates a layout.

They focus on it when making titanium implants. Mandatory procedures include oral sanitation and pain relief. Excision of the periosteum is performed by a surgeon. Thus, he separates it from the bone. The implant is placed on the bone, after which the periosteum is returned to its place. The doctor puts stitches. After this, all that remains is to wait for the tissue to heal. This process is lengthy and requires at least 3 months. During this period, the patient comes for examination to the doctor. He may order a CT scan to make sure there is no tissue rejection.

The tomogram allows you to get an idea of ​​the position of the implant. It needs to be in the right place. Inflammatory processes, the presence of which is detected during medical examinations, are also unacceptable. Once the tissues have healed, the installation of a removable denture can begin. Anesthesia is also administered when doctors take an impression. The dentist removes the periosteum and applies impression material. Once the impression is ready, it is sent to the laboratory. Here a plaster copy will be made from it. In the meantime, the wound is sutured and treated with an antibacterial agent. It will take 10 to 15 days until the titanium implant is ready. At the next appointment, the periosteum will be opened again. The structure will be installed on the bone, after which the surgeon will return the tissue to its original place and apply sutures.

Types of implants

Fixed implantable prostheses can be intraosseous or extraosseous.

Intraosseous

If you look at the implant carefully, like an orthodontist, you can distinguish not 2, but 3 parts:

• supporting;
• transgingival;
• the largest is intraosseous.

The intraosseous shape of implants is different, repeating or not repeating the shape of the tooth root. It is by these criteria that the types of dental implants are most often classified.

The shape of the intraosseous part of the prosthesis is usually made in the likeness of a tooth root. Then healing after implantation will be quick, and the chewing load will be distributed evenly in the jaw.

Lamellar

The surface of these implants is textured and (or) corrugated. There is also a macro-relief resembling a snake. To allow bone tissue to grow through the prosthesis after implantation, holes are provided in the structure. Their total area does not exceed a third of the area of ​​the intraosseous part.

There are:

• non-separable;
• collapsible, with internal or external thread for installing the head.

Root-like

Root-shaped (endosseous) implants include:

• cylindrical. The intraosseous part is smooth, with a small surface area. It is characterized by the lowest biomechanical performance in the shear test, so the cylindrical part is made textured (bioactive coating). They are produced only collapsible;
• screw. With different thread profiles, detachable and one-piece. The surface can be smooth or rough;
• basal. Longer, with a thread at the end to secure itself in the deep layers of bone.

Mini-implants that are installed for a limited time are also classified as root-shaped. This is not to say that they are thinner or shorter than regular ones. They have a simplified and slightly lighter design for people with osteogenesis disorders.

If the root-shaped implants are not connected to each other, their rotation can occur even after a period of bone tissue regeneration. The most common causes are medical manipulation and chewing load. Therefore, their design includes anti-rotation locks (anchors, holes, longitudinal grooves, etc.).

Types of root-shaped implants

Combined

The intraosseous part of the implant can also be a combination of cylindrical and plate-shaped:

• the central part is a cylinder;
• “lateral roots” - 2 asymmetrically or symmetrically located plates.

This type also includes disc, transmandibular (designed with a bracket and 2 pins) implants. Implants of a combined form are usually detachable.

Extraosseous

For osteoporosis or osteonecrosis of the jaw, extraosseous implants are sometimes used for patients in the older age group.

Subperiosteal

These prostheses are used for the rehabilitation of patients with significant atrophy of the jaw bone tissue. They are screwed into the periosteum on the side of the gum.

Intramucosal

They are used when there is a lack of bone tissue, when the patient refuses augmentation, sometimes as a temporary measure. A small, mushroom-shaped magnet is inserted into the gum. In the future, it serves as the basis for removable orthodontic structures.

Stabilization

When implanted, the prosthesis is mounted on the natural root of the tooth, takes root well, but is considered temporary, since the “base” dries out with age, like any bone tissue.

What is an implant

A dental implant (implant) is an artificial multi-component structure that is installed into bone tissue. After fusion, crowns are fixed to it. In simple terms, an implant is an artificial root that performs all the functions of a lost tooth.

A dental prosthesis is implanted into bone tissue. Then an abutment (periosteal element) and a crown are mounted on it.

Dental implant

Indications for installation are partial or complete edentia, restoration of lost incisors, molars, premolars and canines.

Implantation stages

Installing an implant is a lengthy process. It is necessary for it to take root in the bone, so restoration of the dentition takes 3-6 months.

Planning and preparation

Preparation and planning of surgical intervention is:

1. X-ray examination (orthopantomogram, targeted images, determination of projection distortions). A steel ball is fixed in the area of ​​the proposed permanent prosthesis, and the length of the implant is selected based on the images.
2. Determination of the thickness of the alveolar process of the upper and lower jaw using an osteometer (under anesthesia), determination of the profile of the alveolar process or part of it at the site of the proposed implant on diagnostic plaster models. Based on these data, the diameter of the implant is selected for future implantation.
3. Making a diagnostic plaster model with the restoration of missing teeth (from wax or plastic), taking into account intermaxillary interaction, on the basis of which a radiopaque plastic template is created.
4. Computed tomography examination. Before scanning, all removable metal dentures are removed; dental implantation will be successful if the patient is scanned motionless with his mouth slightly open.
5. Creation of a 3D model of the jaw. Axial sections are obtained on a CT scan, then a computer program creates a three-dimensional image and necessarily visualizes the neurovascular bundle. Since teeth, bones, and soft tissues have different densities, based on research data, the program provides the ability to visualize the outer skin and internal structures, as well as turn off the visibility of various anatomical objects.
6. Determining the type of implants and their installation sites, taking into account the qualitative and quantitative composition of bone tissue (planning the surgical stage of implantation). Taking into account the bone density readings, the optimal location for placing the implant is selected, and the distribution of chewing load is assessed. As a rule, the largest implant that can fit in a given volume is selected.
7. Jaw prototyping. Checking the relationship of installed implants with antagonist teeth or opposing implants.
8. Use of a surgical prototype guide. When the location of the prosthesis is strictly limited (complex anatomical conditions), the implant is positioned at a certain angle. Then, using rapid prototyping, a special surgical template is made, in which titanium cylinders are installed for drilling strictly at a given point and at the correct angle. If there is a deficiency of bone tissue, sinus lift surgery is planned.

Surgical stage

Dental implantation surgery is performed under anesthesia:

• infiltration, familiar to most local “freezing”;
• conduction, when the anesthetic is injected into the paraneural space.

Most pain during implantation is associated with the crushing of blood against the cancellous bone, as well as increased pressure on the nerve endings. To reduce pain during and after surgery, patients with high blood viscosity are advised to take instant aspirin (500 mg) 30 minutes before. before the start of the operation. In addition, when installing an implant, a constant level of bleeding is important (for this purpose, the bone bed is often washed out). Blood fills the voids between the surface of the implant and the bone, improving osseointegration (engraftment of the implant into bone tissue).

Dental implantation begins with an incision with a disposable scalpel and tilting the mucoperiosteal flaps to the sides. According to the wide flap technique, the incision is made in the middle of the alveolar ridge, and the interdental gingival papillae are carefully dissected. Thanks to this technique, there is no need to make a vertical incision, which leaves a visible scar during healing.

Another cutting technique for implantation is the use of a circular mucotome knife. This ensures minimal invasiveness (penetration of pathogenic microorganisms through the wound) and increases the resistance of the epithelium adjacent to the implant to pathogenic effects. There are no stitches for this incision. Any preparation is carried out with copious cooling with sterile saline solution.

The location and position of the prosthesis depend on the defects of the dentition and anatomical conditions. For example, when multiple implants are installed in an edentulous upper jaw, they will have a fan-shaped divergence due to the anatomical shape and inclination of the jaw itself. Read more about the features of upper teeth implantation here.

If the alveolar bone is well preserved when installing a prosthesis during implantation, several rules are followed:

1. The distance between implants is at least 2-3 mm. Otherwise, the bone remodels and atrophies.
2. The implants are installed at a slight angle to each other in order to evenly distribute the vertical load and reduce the concentration of excess stress.
3. The tilt of the implant is mesio-distal.
4. During implantation, bone tension is taken into account (the difference between the size of the prepared bone bed and the diameter of the subosseous part of the implant). The diameter of the endosseous part should be 0.2-0.5 mm larger. Then it is possible to avoid mobility of the implant and achieve rapid osseointegration.

Be sure to ensure that there is blood in the implant bed. This avoids the formation of air cavities between the bone and the implant. Understanding this fact is a guarantee of peace of mind during implantation.

Remember: dental implantation necessarily involves the formation of blood clots. This is the norm, you should not be afraid of blood.

Before inserting the implant, its surface is moistened with saline solution to reduce friction. If the implantation is one-stage, very often a gum former is immediately installed instead of an obturation screw. During two-stage implantation, mucoperiosteal flaps are hermetically sutured.

Orthopedic stage

The gingival cuff former is replaced with a support head. On the day of implantation, it is possible to manufacture and fix a provisional orthopedic structure (or 1-3 days after surgery). Then an impression is made using impression material, and then the prosthesis itself. This is done by an orthodontist who completes the restoration of the dentition.

The entire sequence of actions (cast, making a jaw model, crown or prosthesis frame) is absolutely similar to making a crown. Production time depends on the material and volume of work.

Postoperative period

On the 11th day after implantation, the sutures can be removed. In areas remote from surgery, patients keep their mouth clean and use chlorhexedine-containing products to rinse. Temporary removable dentures can begin to be worn on the 14th day, but the longer the patient goes without it, the better.

The soft lining, which gradually becomes denser, is changed after 6-8 weeks. In addition, for some implants it is necessary to tighten the transocclusal screws, so a dentist’s control is required after 6 weeks, and then after 3 - 5 months.

How did the different types of implantation come about?

Implantation is one of the most popular orthopedic areas. Since the discovery of the phenomenon of osseointegration, that is, the natural restoration of bone tissue, in 1965, millions of implant surgeries have been performed. At the same time, in each individual case, certain nuances of the structure of the jaw bones and other features of the physiology of the patients were noted, which influenced the course of implantation, and, most importantly, its results. Thus, the technology of the process began to vary depending on the indications and conditions of implantation.

Endosseous, or intraosseous, implantation

This is the most progressive type of dental implantation, the effectiveness of which is recognized by implant surgeons around the world. Its advantageous feature is that the implant is installed in the most natural way - by direct insertion into the bone tissue, which guarantees its good survival and further functionality. Endosseous implantation requires a certain alveolar bone height. If it is not enough, osteoplasty is performed - building up bone tissue and improving its quality.

Today, endosseous implantation most often uses root-shaped dental implants. Extremely rarely, in cases with thin bone, plate implants can be used, and in cases of severe resorption or bone atrophy, implants of combined forms can be used (see Figure No. 1). For this type of implantation, either a one-stage method can be used - installation of an implant and abutment with a temporary crown in one day, or a two-stage method - first installation of an implant, and after 4 - 6 months - an abutment with a permanent crown, depending on the clinical situation of the patient. However, there are other methods of dental implantation.

Basal implantation

A type of implantation called “basal” is used only in cases where the following problem is observed: the need for prosthetics of a large number of consecutive teeth when there is insufficient volume of jaw bone tissue and the impossibility of additional surgery to build it up. In this case, some doctors suggest using basal implants, which are installed in the deep and bicortical layers of bone tissue not from above, as is the case with root-shaped implants, but from the side. Basal implantation involves the simultaneous loading of newly installed implants with bridges.

Today, basal dental implantation cannot be classified as a modern type of dental implantation. The opportunity to avoid additional surgery to restore bone volume may have its advantages in terms of finances and time spent, but there is no need to talk about the reliability of this procedure. Therefore, many leading specialists in the field of implantology either do not use basal implantation in practice at all, or consider it only as a temporary solution to the problem of missing teeth for elderly patients.

Endodontic-endosseous implantation

Endodontic-endosseous implantation is one of the outdated techniques that is practically not used today. Its main goal is to preserve the tooth root. This implantation technique was used to strengthen mobile teeth, in cases of bone tissue defects, periodontitis, cysts, dental fractures and other situations. The implants, similar to pins, were inserted into the bone tissue through the tooth canal without the need for an incision in the gum. In cases involving resection of root tips, removal of cysts, or fracture of teeth, the pin was inserted into the bone tissue directly through the defect.

The very idea of ​​preserving at least some part of the tooth can be considered commendable. But does it make sense to leave a destroyed root, which at any moment can become a source of inflammation? Modern implantologists answer this question unequivocally - no. Carrying out endosseous or intraosseous implantation together with tooth extraction will be the best solution in this situation. This fact confirms the almost complete refusal of doctors from this type of implantation.

Subperiosteal implantation

This technology of dental implantation does not belong to modern methods, but it is worth mentioning as a historical reference about implantology. Subperiosteal implantation was carried out when the height of the alveolar process, the bone bed of the tooth formed by parts of the upper and lower jaws, was insufficient, in cases where it was impossible to perform bone grafting or the patient wanted to save on it. The procedure involved placing an implant under the periosteum, the connective tissue surrounding the bone. That is, the base for future teeth was not introduced from the side of the tooth socket, but was attached to the side surface, under the gum.

For subperiosteal implantation, subperiosteal implants were used, which were a metal frame with supports protruding into the oral cavity (see Figure No. 2). They were made individually based on a cast of the jaw bone tissue. Subperiosteal dental implantation could take place in either one or two stages. The bone size for this type of implantation required at least 5 mm in height.

Intramucosal implantation

It is known that partially and completely removable dentures are very inconvenient to use. Intramucosal implantation helps make removable dentures more comfortable for patients and improves the aesthetics of their smile. It is used to improve the fixation of removable dentures in cases of atrophy of the alveolar process in the upper jaw, as well as in cases of developmental defects of the palate, when classical endosseous implantation is impossible or the cost of the procedure is an acute issue for the patient.

This technique is also called mini-dental implantation and is carried out using special intramucosal implants, which consist of two parts: the first part is attached to a removable denture, and the second is installed directly into the oral mucosa. The implants are fixed into small hole-shaped depressions in the gums, formed using a special bur. They are immediately fitted with a denture, which can later be easily removed for oral hygiene. The only prerequisite for this type of implantation is the thickness of the mucosa - at least 2.2 mm.

Transosseous implantation

Transosseous dental implantation has also become history. It was used for significant resorption of the alveolar ridge (the tip of the alveolar process, which is formed after tooth loss) of the lower jaw. Such a diagnosis was considered an absolute contraindication for any type of implantation, since if the bone tissue above the mandibular canal is less than 10 mm, then the inferior alveolar nerve can be damaged during the operation. To eliminate this problem, an operation could be performed to move it, but in cases where the patient expressed a desire to save money, transosseous implantation was used.

To perform transosseous dental implantation, dental implants were used in the form of a curved bracket with two pins that were installed on the chin, and not in the oral cavity. It happened as follows. A small incision was made on the outside of the lower jaw, and an arc-shaped bracket was fixed. The pins were inserted into the bone in such a way that they passed right through it. Protruding in the oral cavity, they later served to secure removable dentures (see Figure No. 3). In order to carry out this operation, bone tissue was required to be at least 6 mm in height and at least 3 mm in thickness.

Laser dental implantation

Along with various types of implantations, dental clinics offer dental implantation using lasers. The essence of the method is that all cuts are made not with a scalpel, but with a laser beam. It is believed that laser dental implantation takes less time and is less painful for the patient, which makes it possible to reduce the dose of anesthetics. In addition, it is practically bloodless due to instant coagulation of blood vessels, and also has an additional antibacterial effect. Patients are also attracted by the absence of surgical sutures, which is believed to contribute to faster and better tissue healing.

Laser dental implantation is more expensive compared to the traditional implant procedure. The price difference will be approximately 30 - 60% depending on the category of the clinic. For example, in one of the Moscow dentistries, the basic cost of traditional dental implantation ranges from 20,000 to 35,000 rubles, while laser implantation will cost the patient more - from 40,000 to 60,000 rubles. Many doctors believe that there is no big difference between these procedures, but whether it is worth overpaying is up to you to decide.

Express implantation

This term is more advertising than scientific. This refers to conventional endosseous or intraosseous implantation using a one-stage technique that offers the installation of an implant and a dental crown in one visit. The so-called rapid dental implantation is intended, in principle, to attract patients to the implantation procedure. Unfortunately, victims of advertising only find out at an appointment with a specialist that this method is not suitable for everyone. In order to carry out express implantation, ideal conditions for the operation are necessary - the absence of general contraindications, a sufficient volume of bone tissue and the availability of space for installing the implant.

Implantation without surgery

Dental implantation without surgery is another advertising gimmick and nothing more. We are talking about minimally invasive intraosseous implantation, which is carried out using the transgingival method. The implantologist, without cutting the gums, uses special drills to make a hole in the bone, where the implant is then installed. Again, this method has its contraindications and is not suitable for everyone. In any case, this cannot be called non-surgical dental implantation.

Types of implantation

Based on the mutual influence of implants and oral tissues (hard, soft), several types are distinguished.

Endodonto-endosseous

Dental implantation, which uses a pin and various fixation elements in bone tissue. The pin is placed in the dental canal, so for the orthodontist, due to special manual skills, this is one of the most difficult implantations.

Endosseous

Otherwise, intraosseous. The most popular implantation, with good results of engraftment and distribution of occlusal load. The implant is inserted into the bone through a mucoperiosteal flap. The intraosseous part is made in the form:

• screw;
• plates;
• cylinder.

In addition to prosthetics of 1 tooth, this type is used in the all-on-four and all-on-six implantation method in the case of complete absence of teeth. Implants (4 or 6) will be the basis for attaching the bridge. The new All-on-3 (Trefoil) implantation method has been used since 2017, 3 implants are used, the acrylic prosthesis is permanent, manufacturing takes 1 day. Also suitable for full dental implantation.

Implants for endosseous implantation

Subperiosteal or subperiosteal

Dental implantation is recommended when alveolar bone degeneration is evident. First, an impression is made from the bone, and an implant is made from it. Then it is installed under the mucoperiosteal flap. For an orthodontic surgeon, such implantation is a top flight, since due to limited space and bone structure, it is difficult to choose a rational design that will not subsequently affect the dentition and correctly distribute the chewing load. With the advent of 3D modeling, the percentage of unsuccessful implantations has decreased, however, in difficult cases it is better to contact a dental clinic with extensive experience, since significant difficulties arise during the installation process.

Intramucosal

It is also called insert implantation. The implant resembles a button, very small. The bone is not drilled; installation occurs in the mucous tissue of the alveolar processes. The risk of installing an implant is minimal

Submucosa

In the literature for dentists, there is a second name - submucosal type. The easiest type of implantation, the risk of surgery is reduced to zero. Magnets are inserted into the transitional fold, creating a valve zone and retention (holding) of removable dentures.

Transosseous

When the atrophy of the lower jaw is clearly expressed, implants are installed through it in the intermental region and secured to the basal edge.

Implantation methods for complete absence of teeth

Trefoil

Trefoil technology is a new method of dental implantation. The technique was created exclusively for the restoration of teeth in the lower jaw with complete edentia. The advantage of the technology is that the permanent fixed prosthesis is installed immediately on the day of implantation on a titanium bar with an innovative fixing mechanism, which ensures passive fit of the orthodontic structure. The base follows all the curves of the real lower jaw, and adaptive connections hold the artificial roots in the correct position. The use of a small number of implants significantly reduces the cost of prosthetics.

All-on-4

The All-on-4 method is a patented development of Nobel Biocare. The operation according to the protocol involves the installation of only four implants to restore all the teeth in the jaw. Immediately after implantation, provided there is good primary stability, titanium roots can be loaded with a fixed prosthesis. The peculiarity of the operation is that the implants are fixed in the lateral part of the upper jaw at an angle of 45 degrees, bypassing the maxillary sinuses. Abutments with inclined fastening (multi-unit) are selected for them. The two remaining implants are installed at right angles to the front teeth. Implantation using the All-on-4 method is especially effective in cases where it is not possible to grow bone tissue due to the physiological characteristics of the patient’s body.

All-on-6

The All-on-6 technique is an improved All-on-4 implantation technology. Two titanium rods are fixed vertically in the frontal zone, four - in the chewing sections at an angle of about 60 degrees. The implants do not affect the maxillary sinuses. Compared to the All-on-4 technology, when using the All-on-6 protocol, the chewing load is distributed more evenly due to the increased number of implants.

Techniques

Basic surgical techniques in orthodontics include one-stage and two-stage implantation.

Two-stage

Standard implantation, which can be performed in any dental office.

Stage 1

The gum flaps are cut and moved back, clearing the bone for the implant. An axial guide channel is created with a 2-2.5 mm drill, and it is expanded with a drill of a larger diameter.

When the root portion of the implant is screw-shaped, the bone is manually threaded using taps. Then the endosseous element is screwed in using the implant lead.

If cylindrical implants are used, the bed is formed using a reamer or a special cutter. When using combined implants, first the cylindrical part is formed using fissure burs, and then preparation for the plates is carried out.

The intraosseous part of the implant is installed just below the height of the alveolar ridge. To protect against bone tissue getting inside the implant, the canal is closed with a plug, the gum flaps are raised and sutured.

Stage 2

It is carried out no earlier than 2-3 months, when it becomes clear that the root-like part of the implant is successfully engrafting. After activation of local anesthesia, the gum is excised again and the plug is removed. After flushing the canal, the upper part of the implant is screwed in. Additional incisions are sutured.

Two-stage implantation technique

One-stage

It differs from the two-stage procedure in that after implantation the entire implant protrudes into the oral cavity. It is installed by cutting the gum, or in a simplified way. This is the so-called bloodless implantation technique (no stitches are applied):

1. The mucous tissue and periosteum are excised with a perforator.
2. The bone bed is prepared with a drill, circular saw, or fissure bur.
3. The implant is installed.

These methods of dental implantation give the same long-term results. If there are any doubts about the patient’s compliance with hygienic requirements for the cleanliness of the oral cavity, they resort to a two-stage procedure. Then the possibility decreases:

• accumulation of food plaque and bacteria on the surface of the implant;
• development of the inflammatory process;
• implant rejection.

If oral hygiene is maintained, the implant is installed in one go.

Indications and contraindications

Contraindications to the installation of implants are diseases and dysfunctional disorders that lead to a significant deterioration of the patient’s condition. These include type 2 diabetes, collagenosis, malignant neoplasms, blood clotting disorders, diseases that lead to a decrease in the regenerative abilities of bone tissue. It is not recommended to carry out dental implantation in the presence of acute inflammatory diseases of the oral mucosa, periodontitis, malocclusion and rapid tooth wear (including bruxism), diseases and anatomical features of the structure of the upper and lower jaw that preclude the installation of implants. Most of these contraindications are relative, that is, if the patient’s condition improves or the cause that makes implantation difficult is eliminated, it can still be performed.

Classic clinical indications for dental implantation are the following dental defects:

• Single. Simply put, it is the absence of one tooth when there are normal healthy teeth next to the defect. In this case, installing an implant will avoid grinding down adjacent teeth to install a bridge.
• Limited. If there are no 2-3 teeth in the dentition, but due to some circumstances it is not possible to install a bridge (or for the same reason - reluctance to grind down adjacent teeth), an implant can become a support for the prosthesis.
• Terminal. The last teeth in the dentition are usually used as support for the installation of dentures. If there is no such support point, then it is impossible to install a prosthesis. For prosthetics on implants, such a problem does not exist - they can be installed anywhere, including in place of missing teeth at the end of the dentition.
• Complete absence of teeth. Until recently, there was only one option for prosthetics in such cases - removable prosthetics. Now such patients are fitted with implants, which become a support for fixed dentures. Prosthetics on implants is especially indicated for edentia, which is accompanied by a decrease in the height of the alveolar processes. There is also a psychological nuance: many people are simply not mentally prepared to wear removable dentures.

And finally, the most important indication for dental implantation is the patient’s desire. If he wants to have beautiful and functional teeth, no one can forbid him from doing so.

How are dentures attached?

Fastening the prosthesis after implantation depends on whether it will be removable or not.

Fixed prosthetics

In this case, the prosthesis is installed by an orthodontic surgeon once. Fastening can be using locking mechanisms or dental cement.

For cement

The prosthesis is attached to the head of the implant using dental cement. There are no holes for screws - the dentition looks solid. Fast production and low costs, coupled with speed of installation, made cement fastening widespread.

Flaws:

1. Such fastening poses a risk of an inflammatory process under the prosthesis if cavities remain in the cement fixation between the gum and the prosthesis.
2. If it is necessary to remove the prosthesis, parts of it may be damaged.
3. If the intramaxillary space is small, a small abutment is placed, the fastening becomes less reliable, and there is a risk of losing the crown.
4. Difficult to remove remaining cement.

On attachments

The prosthesis is securely attached to the implants using clasps and attachments. The shapes of the locks are different; they can be located on the outside of the crown or on the inside.

Removable dentures

Removable dentures are attached differently.

Screw fixation

The prosthesis can be attached with a screw to the implant:

• to the intraosseous part;
• to the head.

If a custom abutment is made, it is secured with a lateral screw.

1. Advantages of screw fixation:
2. If necessary (broken, chipped abutment), it is easy to unscrew and replace.
3. Does not interfere with contouring implants during soft tissue restoration.
4. The reason for the screw breaking is the incorrect distribution of the chewing load; for the orthodontist this is a clear signal with a ready-made sequence of actions.

Flaws:

1. Some increase in gum volume.
2. Visibility of access holes (they are covered with filling material).
3. A larger channel for the root part of the implant in the bone.

Push-button fastening

To secure the prosthesis, 2 implants are sufficient; push-button locks in the form of a ball or coupling are used.

Magnetic fixation

Usually magnets are soldered to the abutment. This fixation holds the prosthesis well when opening and closing the mouth, however, when chewing (horizontal movements), the prosthesis may move to the side, because the magnet cannot resist the horizontal shear force. Frequent shifts are one of the causes of complications of dental implantation, as they loosen the implant.

Beam mount

The design splints several implants (2-4), preventing their loosening. Therefore, the fixation of the prosthesis is strong, much better than a push-button one. Sometimes beam fastening is combined with telescopic or locking elements, and expanded with additional beams. Then the pressure on the gums decreases and the likelihood of inflammation decreases.

Prosthesis with beam type fastening

Telescopic system

The prosthesis with cylindrical or conical holes in the crowns is simply placed on top of 4 implants. This is one of the massive designs; when you wear it, your facial features change slightly. But with such fastening there are practically no complications of the mucous tissue under the prosthesis.

Plate implants

Plate implants have a special shape that extends into the bone, which is distinguished by its flatness. In appearance, they really look more like a plate. Plate implants are used for prosthetics of anterior teeth, where the bone is thinnest, so it is impossible to install an intra-root structure with a wide diameter. Plate implants allow for long-distance implantation, which is especially advantageous when prosthetizing several front teeth at the same time.

Which dental implantation method to choose?

The method, implant and type of prosthesis are selected individually after an examination; it is not chosen by the patient (although his wishes are listened to), but by a collegial surgeon, orthodontist and dental technician. Therefore, you need to contact specialists with many years of experience.

They take into account indications and contraindications for dental implantation based on X-ray and other studies, and simulate the implantation process using dental computer programs. However, they usually offer several options (crown - metal ceramics or zirconium dioxide, type of prosthesis, etc.), since the price of dental services depends on the materials used.

Dental implantation in Khimki – prices

Currently, there are quite a lot of dental implantation clinics , Moscow , of course, is no exception. However, many people are put off by the prices of dental implants in Moscow . It is worth admitting that the prices for dental implantation in Moscow are really quite high. This is determined by the rather high cost of the dental implantation systems themselves, and the rather labor-intensive process of preparing for the procedure and its implementation. Often, prices for installing a dental implant in Moscow are inflated due to the “status” of the clinic and the prohibitively high costs of renting premises, purchasing equipment and consumables.

If you are looking for a good clinic and want to get the best price/quality ratio, pay attention to the Apex-D dental implantation clinic, which installs dental implants in Khimki . Highly professional specialists with extensive experience in dental implantology, working on modern equipment, having at their disposal a wide selection of dental implantation systems - all this will allow you to install implants that best meet your requirements and wishes. The doctors of our clinic will help you choose implants that fully correspond to any clinical situation that requires prosthetics on implants. Well, the prices will satisfy patients with different income levels; in any case, we will select the most acceptable prices for dental implants in Moscow .

FAQ

1. Can implants fail to take root? Yes, this happens.

2. Do I need to change implants and when? Implants need to be replaced in case of fractures, breakage, chipping of the implant, transocclusal screws, suprastructures, etc. Contact your orthodontist if your implant becomes loose.

3. How much does an implant cost? The price of a high-quality prosthesis (with a crown) and labor is on average 50 thousand rubles. Economy segment 15-30 thousand rubles.

4. Which crowns are the most durable? Crowns made of zirconium dioxide and metal ceramics.

Literature:

1. Dental implantation: textbook / N.E. Rural, . R.T. Bulyakov, E.I. Galieva, O.A. Gulyaeva, S.V. Viktorov, A.V. Trokhalin, I.O. Short
2. Zhusev A.I., Remov Yu.A. Dental implantation. Success Criteria
3. Paraskevich V.P. Dental implantology: basic theory and practice
4. Sudnev I., Mikhailov I., Goldstein E. Dental implantation. New level of prosthetics
5. Trezubov V.N., Shteingard M.Z., Mishnev L.M. Orthopedic dentistry. Applied materials science

Moscow metro station Zvezdnaya, Danube Avenue, 23

Subperiosteal implants

Implants are used if the bone tissue is severely deficient. It is impossible to install other types of implants into such bone, so subperiosteal structures are placed under the gum, located between the bone and the periosteum. The subperiosteal structures are quite fragile in appearance, but due to their shape they are held tightly in place.

Advantages and disadvantages of dentures using the implantation method

Advantages:

• Reliability of dentures
• Long (lifetime) service life
• Great aesthetics
• Possibility of restoring from one to all units of the dentition
• Large selection of options for orthopedic products (crowns, bridges, complete dentures)
• Safety for adjacent elements (no need to grind)

Flaws:

• Risk of implant rejection
• Possibility of complications in the postoperative period
• High price
• A large number of contraindications
• Long term osseointegration

How to make a choice?

It is necessary to determine the type of structure:

1. Root-shaped dental implants are usually used in the classical clinical picture, when no pathologies are found in the body, and the bone tissue has optimal parameters.
2. Plate structures are used when it is necessary to restore the front row.
3. Combined dental implants are used for complex restorations. They are relevant during operations after injuries and injuries.
4. Subperiosteal structures are used when the condition of bone tissue is unsatisfactory.
5. Mini-implants allow you to secure temporary structures, removable dentures, or restore 1-2 teeth for aesthetic purposes.

It is necessary to determine the manufacturer of the structure.

When choosing, focus on financial capabilities:

1. Cheap designs of various types are manufactured mainly in Russia and the CIS countries.
2. More expensive are the well-known designs of the Israeli company Alpha Bio.
3. There are also super-premium dental systems. They are produced by Swedish and Swiss manufacturers such as Nobel Biocare and Astra Tech. Each implant is a piece of work by experienced craftsmen. Manufacturers provide a lifetime warranty on all dental structures.

Don't know which dental implants to choose? Our specialists will help you navigate the variety of types of products and their manufacturers. They will answer all questions. The specialist will be able to begin implantation as soon as possible using the appropriate type of products.

Types of dental implant installation

Based on the clinical situation, the doctor chooses the installation option. Among the types of implants, it is necessary to choose those that are suitable in a particular case. To fix an artificial root in the jaw, the following methods are used:

• Patchwork . The doctor creates access to the bone by making a soft tissue incision and exfoliating a small area. Next, it forms a bed for the implant by drilling.
• Minimally invasive . It involves installing pins according to an individual surgical template. The titanium root is installed without incisions, by puncture. The doctor simply screws it into the bone.
• In the socket of an extracted tooth . The method involves installing an artificial rod immediately after removing the unit. Used after a planned extraction (not for an inflammatory disease).
• Lateral . The most traumatic method, involving extensive damage to soft tissues. The gum is peeled off from the side of the jaw, then the doctor drills a hole for the implant. Rarely used.

Basal implantation

The method is used most often in specific clinical cases when there is a lack of bone tissue and there is a need to install several teeth in a row at once. At the same time, there is no possibility of increasing the base for the implant. This method uses a single-moment load. The implants themselves are installed not in the lower base of the bone tissue, but in the side. This method allows you to solve the problem of missing several teeth in a row, but the healing process is quite long and painful.

When is implantation needed?

• Lack of separate units;
• loss of row segments;
• complete edentia;
• loss of all teeth as a result of periodontal disease;
• planned removal of units.

Using titanium roots, single row defects are eliminated. Complex protocols are used for complete edentia, as well as for subsidence of the alveolar ridge as a result of prolonged use of dentures. Using high-tech materials, implantation is carried out even in the presence of chronic diseases, bad habits, and pathologies of the oral mucosa.

Cost of the service: what is included in turnkey implantation, and what will have to be paid separately?

The price of two-stage implantation will depend on the type of implantation system that will be chosen. Traditional implantation is widely used in modern dentistry, so it is not surprising that implantation systems for it are offered in a wide variety of types and by different manufacturers. You can choose a budget option for implants, or you can opt for premium designs with a lifetime guarantee.

USEFUL TO KNOW: The cost of the implantation system and all its components is a significant factor in determining the price of implantation in general. Which implant option do you prefer? This question is best asked to a doctor, but we draw your attention to the fact that the result of implantation largely depends not on the type of titanium screw that will be implanted, but on the level of professionalism of the doctor performing the operation. The slightest mistake can cause the titanium screw to fail and cause various complications.

Therefore, before implantation, it is worth studying information not only on products of different brands: be sure to find out all the details about the clinic where you plan to undergo the procedure, and the level of training of its specialists.

In addition to the price of implantation systems, the cost of the turnkey service also includes an examination, a panoramic image, consultation with an implantologist, drawing up a treatment plan, anesthesia necessary to relieve pain, implantation of a titanium screw, and installation of components.

USEFUL TO KNOW: The price of a permanent crown that will be placed on an implant is not included in the price of turnkey implantation. You will have to pay separately for its production and installation. The amount of expenses will depend on the type of orthodontic structure and the material of its production. The most expensive option at the moment is structures made of zirconium dioxide.

Additional procedures (osteoplasty, caries treatment, oral cavity sanitation) are not included in the price of implantation; they will need to be paid separately.

One-stage implantation

This is a technology that allows the patient to use prostheses within a few hours after surgery.

The procedure is carried out as follows:

• preparation: consultation, examination for contraindications, taking impressions;
• pain relief using local anesthesia or general anesthesia;
• incision of gingival tissue (if the operation is performed transgingivally, cutting of soft tissue is not required);
• formation of a bone bed - a hole for the implant is drilled in the bone;
• implantation of an artificial root;
• suturing;
• installation of a temporary prosthesis.

The use of a prosthesis in this case is a mandatory requirement of the installation protocol. Permanent dentures are placed on the patient after the implant has completely healed, that is, after 3-6 months.

Immediate loading implantation allows you to restore chewing functions and smile aesthetics in just one day, while simultaneously preventing bone tissue atrophy.

How many stages?

If the entire procedure takes one day, this is a one-stage installation (express implantation). Its execution requires more complex manipulations, since the structure is solid. A suitable option for minimal changes in bone structure.

A two-step method is preferred. At the first stage, the implant is installed, after 1.5-4 months the crown is installed. Advantages – a more convenient method for the dentist, since it is easier for the specialist to monitor the body’s reaction to the implant. It is also convenient to control the speed and completeness of fusion of the implanted structures. If a permanent crown becomes damaged, it can be easily replaced.

How does implantation work?

The duration of implantation depends on the chosen technique, but in each case the procedure is divided into 4 stages:

• planning;
• preparation for surgery;
• surgery to install an implant;
• fixation of a crown or bridge.

Before proceeding with the operation, it is necessary to determine whether intervention is possible in a particular case. During planning, the implantologist assesses the condition of the oral cavity and jaw bone tissue, studies the patient’s medical history to exclude contraindications to the procedure.

Implantation is a complex operation that cannot be performed for some chronic pathologies. To exclude them, the patient takes blood tests and takes an x-ray of the jaw bones. At this stage, the doctor decides on the need for prosthetics and gives recommendations on the choice of technique.