Prosthetics on implants in the absence of teeth

More and more patients are turning to the dentist to restore all their teeth, or one jaw completely. Conventional removable dentures, partial dentures and extended metal-ceramic bridges do not meet the high requirements for comfort, aesthetics and durability. All of these goals can be achieved with dental implants.

The technique of jaw implantation in the absence of teeth is significantly different from implantation in the absence of only a few teeth. For example, it is an obvious fact that you do not need to install 32 implants to restore all your teeth. All the details of full dental implantation are outlined in this article.

Methods of prosthetics on implants in the absence of teeth

Prosthetics on implants in the absence of teeth can be divided into 3 types: removable, fixed and conditionally removable.

Removable prosthetics on implants is suitable for those patients who have already used a removable denture, but could not get used to it. Any option of removable prosthetics on implants will greatly improve the quality of life of such patients.

However, if you have never used a removable denture, then psychologically it will not be easy to get used to such a design. In this case, the best option would be fixed or conditionally removable prosthetics on implants. Conditionally removable means that the prosthesis is fixed with screws. It can only be removed by a dentist; the patient uses it as if he were his own teeth.

Implantation of both jaws with simultaneous loading with plastic crowns

More details about each treatment method are described later in this article.

Restoration of chewing teeth – end defect

In a situation where the location or number of teeth does not allow the use of bridges, the cheapest and simplest option is removable dentures. Such orthopedic structures rest on the gum or on the remaining teeth on one side. Reconstruction of the dentition with removable dentures restores chewing and speech activity, as well as the appearance of the patient’s face.

Removable dentures can be rigid or flexible. Representatives of each group have their own advantages and disadvantages. Thus, flexible prostheses are more comfortable, and patients adapt to them faster. However, they do not provide 100% correct transmission of the chewing load, and therefore atrophic processes in the bone are inevitable. Rigid dentures take time to get used to. During the adaptation period, rubbing of the mucous membrane and discomfort are possible. However, such structures are durable, repairable and more accurately transfer the load to the bone, slowing down its subsidence and atrophy.

Rigid prostheses are represented by the following types:

Clasp – metal base, plastic crowns. The possibility of using a clasp denture is determined by the presence of at least six healthy teeth in a row.
Lamellar – acrylic base, plastic crowns. Such dentures can be used both in the absence of molars and in completely edentulous patients.

Among flexible prostheses, silicone and nylon products are popular. They are extremely comfortable. The flexible part adjacent to the gum exactly imitates gum tissue. Fixation is carried out by suction; you can additionally use special adhesives.

An alternative to removable dentures is dental implantation. This is the most physiological way to restore teeth, providing a comfortable, aesthetic and durable result. Such restorations serve the patient for a lifetime, provided proper care and regular visits to the dentist.

Lower jaw implantation

The lower jaw is denser in structure than the upper jaw, so in most cases, 2 to 6 implants are enough to restore all teeth. The integration period for implants in the lower jaw is 3 months.

Removable prosthetics on implants in the lower jaw are carried out on 2-4 implants. The most common option is to install 4 implants with spherical attachments (or locators). The advantages of this method are good fixation of the prosthesis, easy oral hygiene, simplicity of design, and, as a result, its low cost. A removable prosthesis on 2 implants with attachments is used in cases where there is not enough bone tissue to install 4; the fixation of the prosthesis in this case is worse. The disadvantages of this treatment method are that the prosthesis distributes the load not only on the implants, but also on the gums. Under the pressure of the prosthesis, the gums atrophy, so it is necessary to reline the prosthesis on average once a year. The fastening on the attachments also weakens; it is necessary to periodically replace the retention matrices. The service life of the prosthesis itself is about 5 years.

Removable denture on 4 implants with spherical attachments on the lower jaw

The second option for a removable prosthesis on the lower jaw is prosthetics of the lower jaw on a beam on 4 implants. In this case, the load is distributed mainly on the implants and much less on the gums. The fixation of the prosthesis is very tight, the prosthesis feels almost like your own teeth. The prosthesis itself is made of plastic. It completely restores aesthetics and chewing function. The fact that the denture is removable simplifies oral hygiene. A plastic prosthesis is not as rigid as a metal-ceramic or zirconium one, so it is easier for people who have problems with the temporomandibular joint to get used to it. The disadvantage of this treatment method is that a properly manufactured beam prosthesis is comparable in cost to a fixed structure.

One of the main conditions for the long-term functioning of such a prosthesis is that the beam connecting the implants must be very accurately connected to them. For this, multi-unit abutments are used, which ensure precise connection of the implant with the beam; the beam itself must be made on a milling machine. Unfortunately, patients are often offered a bar prosthesis made without multi-unit abutments, or made by casting rather than milling. In this case, the beam will be fixed to the implants with tension, which will lead to a negative result, possibly even to the loss of the implants due to their overload.

Removable denture on a beam fixation on the lower jaw

Fixed prosthetics of the lower jaw are performed on 6 implants with classical implantation. It is also possible to restore teeth on 4 implants using the all-on-4 method, in which case 2 of the 4 implants are placed at an angle of up to 45 degrees. The technique has its pros and cons. All-on-4 will be written about later in this article.

Fixed prosthetics completely imitate your own teeth and are the easiest to tolerate psychologically. During the period of implant integration, the patient uses a temporary removable prosthesis, or dental implantation is carried out with a simultaneous load using a fixed plastic prosthesis. The service life of a plastic prosthesis is 1 year. It can be replaced with metal-ceramic or zirconium after the implants have completely healed. On the lower jaw after 3 months. The implants themselves are not affected.

In the case when a permanent prosthesis is made with screw fixation, we are talking about conditionally removable prosthetics on implants. Conditionally removable means that the prosthesis can only be removed by a dentist. The patient cannot remove it on his own; it feels and functions like his own teeth.

The advantages of screw fixation are that the prosthesis can be removed if necessary. Unlike cemented dentures, which cannot be removed without sawing them. However, the complexity of the design, and as a consequence the cost, is increasing.

Fixed denture on the upper jaw on 6 implants, on the lower jaw on 6 implants

Metal crowns

These crowns can be called the best for prosthetics of chewing teeth only in terms of price: it will be the lowest, and then only if the crown is made of an alloy of ordinary metals. If the crown is made of gold, its price will be equal to the cost of products made of ceramics and zirconium.

Metal crowns are durable and this quality can also be attributed to the advantages of this option, but there are still more disadvantages to prosthetics with metal crowns. Patients are often allergic to metal crowns; they can cause a galvanic effect, in which a person constantly feels the taste of metal in the mouth. To install metal crowns, you have to remove a fairly large amount of tissue from the tooth being ground, and this is bad, because the more a tooth is ground, the more fragile it becomes.

Installation of metal crowns can cause increased abrasion of antagonist teeth and, of course, metal crowns have poor aesthetics. Such a prosthesis is always clearly visible in the mouth. Aesthetics is not a determining factor when it comes to prosthetics for back teeth, but if you want the crown on a chewing tooth to not stand out from the background of other teeth, it is better to initially consider options for crowns made from other materials. Since metal crowns have much more disadvantages than advantages, we cannot call them the best, and we do not offer them to patients of our dental clinic in Moscow - “Aesthetica”.

Upper jaw implantation

The bone tissue of the upper jaw is less dense than that of the lower jaw, therefore, for complete prosthetics on implants in the upper jaw, more implants are needed - from 4 to 8. Healing of implants in the upper jaw occurs within 6 months.

Removable prosthetics of the upper jaw are performed on 4-6 implants. On 4 implants it is possible to install an overdenture with spherical attachments. The overdenture has the same boundaries as a regular removable one; it completely covers the palate. To make a prosthesis on the upper jaw without a palate, you need to install 6 implants. Ball-shaped attachments, locators or a beam can be used as connecting elements. The best fixation of the prosthesis is achieved on a beam. However, the cost of such a prosthesis is comparable to a fixed structure.

For fixed prosthetics of the upper jaw, it is necessary to install from 6 to 8 implants. It is also possible to install a fixed denture on the upper jaw on 4 implants using the all-on-4 technique. It will be written about later in this article.

Installing 6-8 implants in the classical way is the most studied and reliable option for implanting the upper jaw. The number of implants is determined by the presence of bone tissue and the shape of the upper jaw. While the implants are healing, the patient uses a temporary removable prosthesis, or implantation is carried out with a simultaneous load using a fixed plastic prosthesis.

The service life of a plastic prosthesis is 1 year. It can be replaced with metal-ceramic or zirconium after the implants have completely healed. On the upper jaw after 6 months. The implants themselves are not affected.

Just like in the lower jaw, in the upper jaw it is possible to make a permanent screw-retained structure - conditionally removable prosthetics. Only a dentist can remove a screw-retained prosthesis. The patient uses it as if he were his own teeth.

Different implantation options for complete absence of teeth. 8 implants on the lower jaw, 6 implants on each jaw, 8 implants on the upper jaw

Reliable fixation using mini-implantation

For cases where full-fledged classical implantation cannot be carried out, and the patient is completely unprepared to use removable dentures, it is possible to use a conditionally fixed technique. It involves, on the one hand, reliable fixation of the prosthesis, and at the same time the patient has the opportunity to remove and put it on independently. Of course, such fixation does not allow you to restore chewing function in the same way as with conventional implantation, but it allows you to calmly chew food and communicate without fear of the prosthesis falling out of your mouth.

Mini-implants are very thin implants; they are a one-piece structure; the prosthesis is immediately fixed on them, without the use of additional superstructures. The lower part of the mini-implant - its main body - is similar to a thin screw; it is installed into the jaw bone transgingivally - without cutting the gums, and the outer, smaller part, shaped like a ball, serves as a stopper for the prosthesis. Mini-implants are used to fix a removable denture on the jaw; in this case, the denture is also called an overdenture. A small bone volume is not an absolute contraindication; after installing mini-implants, a prosthesis can be installed immediately. Such implants are not used as a support for crowns, only for fixing a removable denture, acting as a retainer.

The spherical heads of mini-implants are snapped into special locks installed inside the prosthesis.

The mini-implant is made of titanium and is similar to a screw, but much smaller. There are significantly fewer contraindications for their installation than for classic root-shaped implants, only extreme cases of systemic diseases.

This type of implant is installed through surgery; it is possible to use implant templates. It is very important to maintain strict hygiene during this period of time and follow all doctor’s instructions.

All-on-4

The All-on-4 technique (all-on-four) was developed by Nobel Biocare. It involves the installation of 4 implants on one jaw with simultaneous loading with a fixed prosthesis on a screw fixation. The 2 outermost implants are placed at an angle of up to 45 degrees, which allows you to bypass anatomically difficult places: the maxillary sinuses in the upper jaw and the nerve exit site in the lower jaw.

Initially, the All-on-4 technique was positioned as minimally invasive, without bone grafting. However, for successful functioning it is necessary to install sufficiently long implants, because 4 implants must bear the load of the entire dentition. Unfortunately, not all patients have the required alveolar ridge height. Installing shorter implants may result in one of the implants not taking root due to increased load. And then everything-on-four will turn into nothing-on-three. This is why patients are offered “all-on-4 modifications”, for example All-on-6 (all-on-six implants), because Installing an additional 2 implants significantly reduces the risks.

3-6 months after implantation using the All-on-4 method, gaps appear between the prosthesis and the gum, because This is why gum remodeling occurs after implantation. It is necessary to either reline the existing prosthesis or replace it with a permanent one - metal-ceramic or zirconium.

Professional dental hygiene

Professional hygiene is necessary before tooth extraction or implantation to reduce the microbial load. In this situation, removal of all dental plaque is also necessary for the treatment of periodontitis and elimination of gum inflammation.

After professional removal of plaque and tartar, the hygienist selected products for independent oral hygiene that will most effectively remove dental plaque and prevent gum inflammation, and taught a technique for brushing teeth that does not injure the gums.

Bone grafting for jaw implantation

The more implants are installed, the greater the likelihood that the existing bone tissue will not be enough to install implants and it will be necessary to build it up. Bone deficiency can be in thickness (very thin bone) or in height (close to the maxillary sinuses in the upper jaw, nerve in the lower jaw).

If there is a slight lack of bone tissue in thickness, one-step bone grafting with the installation of implants is possible. It is also possible to carry out a sinus lift (a type of bone tissue augmentation when the distance to the maxillary sinus is insufficient) with the one-step installation of implants.

If there is a large deficiency of bone tissue, operations are first performed to build it up (open sinus lift, harvesting and replanting of a bone block), and after 3-6 months, implantation is performed. In this case, the total duration of treatment can be from one to one and a half years.

Stages of treatment

The first stage is preparation for orthodontic treatment. Preparation includes x-ray diagnostics, sanitation of the oral cavity and removal of the required number of teeth.

The second stage involves fixing the structure. An initial thin arch with a round cross-section profile is installed. Further in the treatment process, the doctor changes the arcs from a smaller cross-sectional diameter to a larger one. At the final stages, rectangular rigid arches are used.

On average, it is necessary to visit a doctor from once a month when treating with ligature models to once every 2-2.5 months when treating with self-ligating systems. At the end of the second stage of treatment, the doctor removes the braces using enamel-safe forceps. The remaining adhesive is removed from the surface of the teeth with a low-abrasive bur, and the tooth is polished with a brush using a polishing paste.

The third stage is the retention period. The results of orthodontic treatment are stabilized with the help of permanent retainers and aligners.

The duration of treatment depends on the complexity of the anomaly being corrected, the individual anatomical characteristics of the patient and the professionalism of the orthodontist. The speed of tooth movement is influenced by the design of the brace: self-ligating systems can provide faster results in 1-2 years. Treatment with ligature models lasts on average 2 to 3 years.

Some dental anomalies are corrected using removable hard aligners. When treated with aligners, the patient is given a set of several rigid aligners that differ in shape. The patient changes the aligners independently every two weeks. Once every month and a half, the patient visits the orthodontist to assess the progress of treatment. Mouthguards are worn constantly: the device is removed only when eating and brushing teeth.

How to avoid bone grafting?

There are proven methods that allow you to reliably restore teeth on one or both jaws without additional operations to build bone tissue.

First of all, it’s worth talking about the positions in which implants are installed. Humans have a total of 32 teeth, 16 teeth on each jaw. The 2 outer teeth are wisdom teeth; they do not bear a functional load, therefore they are not restored during prosthetics. Of the remaining 14 teeth (7 on each side), the most problematic in terms of restoration are the sixth and seventh teeth (counting from the center). They are located close to the maxillary sinus in the upper jaw and to the nerve in the lower jaw. It is precisely to restore the sixth and seventh teeth that lengthy osteoplastic operations are necessary.

According to the recommendations of the international association of implantologists ITI - International Team for Implantology , in the case of complete absence of teeth, it is necessary to restore the dentition up to the sixth tooth inclusive (12 teeth on each jaw). This method completely restores both the function of the jaw and the aesthetics of the smile. At the same time, additional risks associated with the close location of anatomically important formations (maxillary sinuses and nerve) are avoided.

In this case, the implants are installed in the anterior part of the jaw, and the outer ones in the area of the fifth teeth (the so-called Frankfurt University protocol ). Subsequently, a one-piece fixed prosthesis is installed on them. Combining all implants into a single structure compensates for lateral chewing loads and ensures full functioning of the entire jaw with only 6 implants in the lower jaw and 6-8 in the upper jaw.

Another problem is a deficiency of bone tissue thickness ( thin bone ). To avoid bone grafting in this case, it is possible to use thin implants. However, not all systems guarantee that their thin implants can withstand the load of full jaw prosthetics. Such guarantees are provided by German implants Ankylos , and the Straumann has developed a special alloy of titanium and zirconium, which allows thin implants to function without building up bone tissue, it is called Straumann Roxolid .

And lastly, if there is a deficiency of bone tissue both in height and width, a possible solution is to install short and thin implants, but in larger quantities. Instead of 6 standard ones - 8 short ones. The total length of the implants in this case will be equal.

Tooth roots

The processes of bone tissue - the roots of the tooth, hold it in the jaw - and in this they are very similar to the roots of plants. But, in addition, in each root process there is a void inside - this is the root canal. The same nerve fibers and capillaries that go higher into the pulp, and from below are brought out into the jaw through a tiny hole at the tip of the tooth root, are laid in it, like wires in a protective cable. This hole is called apical.

Depending on the type and size of the tooth, there may be one root, or there may be two.

Which implants to choose?

Today there are more than 3,000 implant systems in the world. However, not all of them can boast a long history of observations and clinical trials around the world. There are also some implant systems that, despite their reliability, are not very common in Russia. This may lead to difficulties in terms of delivery of original components of implant systems.

It is worth choosing only generally recognized implant systems, which are used by different doctors independent of each other. Otherwise, the patient risks finding himself in a situation where no one can help him.

An important point when choosing an implant system is the type of implant-abutment connection. It determines how long the implant will last. The most reliable today is the conical implant-abutment connection with the effect of switching platforms. It is able to withstand greater loads compared to a flat connection, is leak-tight and does not cause resorption of bone tissue around the implant.

The healing of implants is affected by the purity of the titanium from which they are made. The most common is Grade 4 - commercially pure titanium. Grade 1,2,3 alloys are even purer. Grade 5 – less pure, contains impurities of vanadium and aluminum.

The surface of each implant is a unique patented technology, because... It is on the surface of the implant that osseointegration occurs—the fusion of the implant with the bone tissue. Serious implant manufacturing companies conduct a lot of research, proving that their implants are integrated not only in standard situations, but also, for example, in people suffering from diabetes or bleeding disorders. The following systems meet all these requirements: Straumann (Switzerland), Ankylos (Germany), Astra tech (Sweden), Nobel biocare (USA/Sweden). Among the inexpensive systems, we can highlight Osstem implants (South Korea). They have proven themselves throughout the world as a reliable and economical implant system.

Fundamentals of occlusion and biomechanics of the jaws: a new look at old concepts

A deep understanding of the basics of occlusion and biomechanics of the jaws is one of the most important and necessary components for providing comprehensive patient rehabilitation in dental practice. Knowledge of the principles of differential diagnosis of pain, planning of future iatrogenic intervention, as well as algorithms for the treatment of prosthetic disorders provides the doctor with all the necessary tools for further normalization of the patient’s dental status.

An orthopedic doctor simply cannot do without understanding how significant the concept of occlusion is not only in pathology, but also in a state of stable and adequate function. The formation of appropriate occlusal schemes is based on the redistribution of acting forces, because, in fact, it is precisely because of the excess of such indicators that diseases, pathologies and dysfunctions of the elements of the dentofacial apparatus arise.

Occlusal disorders can manifest themselves in the form of various structural damage to the dental status, such as pathological abrasion, fractures, and premature wear of restorative structures. In addition to the latter, functional pathologies are characterized by tooth mobility, loss of volume of soft and hard tissues, muscle pain, as well as pain and noise in the joints (the so-called clattering), limitation and impairment of movements of the lower jaw, remodeling changes in bone tissue in the structure of the temporomandibular joint . In such cases, patients form so-called parafunctional habits, the presence of which he himself does not know. Clinically, signs of such are manifested by excessive wear of one’s own teeth and various types of restorative structures present in the oral cavity.

There are different opinions regarding the relationship between the state of occlusion and disorders of the temporomandibular composition. According to the most extensive literature reviews, such associations are rather weakly expressed, as evidenced by the fact that when correcting occlusal relationships, it is not always possible to prevent the development and progression of joint pathologies. Based on the available data, the following conclusions can be drawn: only the absence of traumatic occlusal injuries, which are manifested by the action of excessively high parafunctional forces exceeding the adaptive capabilities of the body, ensures complete prevention of the occurrence of pathologies and dysfunctions, or the presence of such in the acceptable adaptation range. This conclusion is evidence-based, regardless of how ideal or non-ideal the occlusal schemes of each individual patient are. On the other hand, with prolonged exposure to excessive occlusal forces, the development of corresponding dysfunctions and diseases occurs regardless of the characteristics of a particular occlusal scheme. The corresponding pathological types of occlusion only further aggravate the course of related prosthetic diseases.

From the above it follows that if the doctor is fully familiar with the specifics of occlusal movements in a particular patient, and also understands their impact on the condition of soft and hard tissues, muscles and joints, then he can ensure the formation of such occlusal patterns that would be the most stable and least traumatic for each specific patient. In other words, understanding the basics of occlusion helps doctors not only plan future interventions, but also predict the functional rehabilitation of prosthetically compromised patients. The main connecting link between the pathology of the temporomandibular joint, the state of occlusion and the functional disorder of the dentofacial apparatus is the repeated action of excessive occlusal load, which goes beyond the adaptive range of the body. Based on this, the author considers it wrong to separate the dynamics of the application of force on human tissue from disorders and diseases developing in the same tissues - after all, in fact, these processes are of an indirect cause-and-effect nature.

The question is different: what is the true connection between the existing parafunction, the state of occlusion and functional deviations of the dentofacial apparatus. In order to understand how the jaw functions and where occlusion begins, you need to repeat in detail the anatomy of the masticatory muscles, the temporomandibular joint, and, of course, the teeth, taking into account the functional parameters of each of the above-mentioned components. After analyzing the anatomy, you should focus on how the relationship between the upper and lower jaws is generally formed, taking into account the occurrence of static and dynamic contacts between the surfaces of antagonist teeth. After this, the data obtained during the analysis can be implemented into a plan for future iatrogenic intervention aimed at eliminating structural disorders of the dentition and aesthetic problems, while ensuring not only the functional comfort of the dentofacial apparatus, but also the stability of the achieved results of complex rehabilitation.

In the course of analyzing the features of anatomy and intermaxillary relationships, doctors should look for key parameters of each of these components, on the basis of which they will subsequently make a decision regarding one or another possible treatment plan.

In this article, the author will refer to the concept of dental treatment planning, which takes into account changes in the facial profile during iatrogenic interventions, developed by Frank Spear. With significant destruction of the tooth structure, the main occlusal landmarks are simply lost, and the pathology goes beyond the boundaries of possible dental-alveolar compensation. Consequently, the clinician’s task is also to restore the supporting occlusal points of the intermaxillary relationship, and then, based on their stability, carry out further prosthetic rehabilitation. When implementing an approach to treatment taking into account changes in the facial profile, it is possible to ensure successful prosthetic reconstruction of the bite, based precisely on the position of the supporting occlusal landmarks.

Pankey rules and the concept of optimal occlusion

Dr. LD Pankey, being a pioneer and developer of comprehensive approaches to dentition restoration, proposed a specific concept that helps critically evaluate occlusion both during systemic dental rehabilitation and during everyday dental care:

When the condyle of the jaw is completely in the glenoid fossa, all the posterior teeth exhibit equal and uniform contact, while the anterior teeth only lightly touch the opposing teeth.
When the jaws are clenched, neither the teeth nor the lower jaw move.
When the mandible moves in any direction, none of the back teeth contact faster or more strongly than the teeth in the anterior region.

Having analyzed these features, we can take a fresh look at the specifics of the anatomy of the dentofacial apparatus.

Anatomy of the temporomandibular joint

In Photo 1 you can see that the condyle of the mandible is in very close contact with the biconcave disc of the joint. These elements of the joint are located inside the capsule, which is protected behind by retrodiscal ligaments, and below, by means of capsular ligaments, is attached to the neck of the condylar process. Anteriorly, the superior portion of the lateral pterygoid muscle attaches to both the disc and the neck of the condylar process, while the inferior portion of the muscle attaches only to the neck of the condyle. Behind the joint is the external auditory canal. Anterior and superior to the condyle is the eminence, and directly above it is the glenoid fossa. The articular surfaces are covered by fibrocartilage, which is a smooth structure, and is supported by synovial fluid. The latter lubricates the surfaces of the joint, providing them with nutrients and oxygen, as well as ensuring the removal of possible debris. In the structure of the capsule, the number of blood tissues is very limited, or they may be completely absent.

Photo 1. Classic diagram of the anatomy of the temporomandibular joint.

When analyzing a joint, it is necessary to note the most important relationships of its individual components. First, there is the close condyle/disc/fossa connection. Essentially, they are in as much contact as possible, allowing the joint to withstand the necessary loads. On the other hand, this form of connection of the elements ensures the anatomical and functional integrity of this organ during dynamic movements of the lower jaw. In certain articular pathologies, this relationship is disrupted, which leads to permanent functional changes. It is obvious that the variation in the size, volume and shape of the temporomandibular joint is quite significant, and these differ greatly from person to person. Historically, we have assumed that the dimensions of the condylar process are relatively stable. However, recent research has established that the size of this anatomical structure can change and adapt over time and depending on the prevailing circumstances. A striking example is the increase in condyle size when using night guards. Due to the protrusion of the mandible to maintain patency of the upper airway, the condyle also remodels, increasing in size. Thus, it is obvious that this bone structure can not only adapt to functional conditions, but also change its shape, increasing in its geometric parameters. Consequently, the previously determined dimensional stability is very, very relative. As the first occlusal guideline, the doctor can use the position of the condyle during the registration of the centric relation, which is the most desirable. Firstly, the central ratio is a parameter that, with adequate execution technique, can be quite accurately and easily recorded. In addition, this position of the structures is repeatable, and it can be restored even if the position of the teeth changes or the contact between them is disrupted. A stable joint in this position has the ability to withstand significant loads, and the lateral pterygoid muscle can remain in a passive state even with strong clenching of the jaws (photo 2, 3).

Photo 2. Muscles that lift the mandible on the right side.

Photo 3. Muscles that lift the mandible on the left side.

Anatomy of the masticatory muscles

The function of raising the lower jaw is provided by three masticatory muscles. With parafunctional habits, such as bruxism, these masticatory muscles can develop significant force acting on all structures of the dentofacial apparatus. The masticatory muscle starts from the zygomatic arch and is attached to the lower edge of the lower jaw. The force vector of this muscle is directed upward and forward. The cross-sectional thickness of the masticatory muscles justifies the fact why they can develop the most significant strength indicators, located anterior to the temporomandibular joint. The temporalis muscle begins in the area of the temporal fossa and the deep part of the temporalis fascia. It is directed medial to the zygomatic bone and forms a tendon that is attached to the coronoid process of the mandible, and also passes into the region of the retromolar fossa distal to the last molar of the mandible. Since the muscle splits along its course, the action vectors of its force also diverge: the anterior component is directed upward and slightly anteriorly, while the posterior component is directed upward and posteriorly. This feature should be taken into account when diagnosing pain symptoms arising in the area of this particular muscle.

The medial pterygoid muscle consists of two heads: the main part of the muscle begins directly above the medial surface of the lateral pterygoid plate, while the superficial head begins from the maxillary tubercle and the pyramidal process of the palatine bone. The fibers of this muscle are directed downward laterally and posteriorly, and through the tendon are woven into the lower and posterior parts of the medial surface of the angle and ramus of the mandible. Insertable fibers connect this muscle with the masseter, forming common tendon slings, which allows both muscles to jointly perform the function of raising the mandible.

All of the above anatomical factors determine the direction vector of forces when activating the above-mentioned muscles. First, the directions of force of all three muscles shape the position of the condyle in the glenoid fossa: anteriorly and superiorly opposite the eminence and slightly medially, so that the medial pole of the condyle is the most load-bearing side of the joint. In other words, if we exclude the action of interdental contacts, then it is these muscles that determine the most superior position of the condyle, thereby ensuring close contact between the condyle, disc and glenoid fossa. The digastric muscle is one of the main muscles that lowers the lower jaw and opens the mouth. It begins in the area of the mastoid notch, forms a tendon along its path, and ends at the lower border of the mandible near the symphysis on the side of the digastric fossa. Since this muscle lowers the jaw, pain in this area is a rather unusual symptom. The lateral pterygoid muscle moves the lower jaw laterally and also forward. The upper head of this muscle starts from the infratemporal wing of the sphenoid bone, and the lower head starts from the lateral pterygoid plate. The muscle is woven in two bundles into the neck of the condylar process and the articular disc. Part of its function is to coordinate the position of the disc relative to the condyle to maintain the desired functional relationship, but in addition it provides support for the mandible in an eccentric position during intense clenching or bruxing when appropriate jaw movement is required to achieve maximum intercuspidation at existing tooth contacts . The three main levator muscles produce much more force than the lateral pterygoid muscle, therefore it must provide sufficient contraction to counteract the aforementioned elevator muscles. If these parameters do not correspond, painful sensations and even spasms may occur, which indicate a violation of muscle function.

Posterior teeth relationship

Pankey's first rule states that by positioning both condyles in centric relation, the posterior teeth form simultaneous and uniform contact, while the anterior teeth contact either slightly less or to a similar degree (Plates 4, 5).

Photo 4. Teeth contacts on the upper jaw.

Photo 5. Teeth contacts on the lower jaw.

Essentially, every type of occlusal design, regardless of condylar position, involves achieving multiple tooth contacts. With this ratio, the bite force is distributed more evenly over a larger number of tooth surfaces. In addition, maximal contact does not require activation of the lateral pterygoid muscles to maintain the mandible in the desired eccentric position. On the other hand, by ensuring simultaneous contact of the tooth cusps with flat bite pads, it is possible to guarantee the direction of the acting force down the long axis of the teeth, excluding the influence of deflecting lateral components (photo 6).

Photo 6. Areas of contact between the cusps.

It is the latter that provoke various structural damage to teeth, restorations, soft tissues and bone crest. And finally, with adequate contact of the posterior teeth, optimal distribution of the functional forces of the muscles that lift the mandible is ensured on both temporomandibular joints. When contact is ensured only in the area of the incisors, 60% of the total force generated by the muscles that lift the mandible is transferred to both joints, while with contact of the second molars this figure decreases to 5%. Posterior tooth contact is especially critical for painful and unstable joints.

Functional system assessment

Assessment of the functional system is a stage of diagnosing all conditions of the functioning of the dentofacial apparatus in each individual patient. The beginning of this stage is an analysis of how the patient talks to the doctor, and the idea of this approach was first proposed by Bob Barkley and later improved by Pankey. Barkley came to the conclusion that it is best when any disorders in a patient are diagnosed not only by the treating team of doctors, but also by the patient himself during diagnostic procedures. Therefore, a history review is a key initial aspect of treatment. A thorough and comprehensive patient examination algorithm was precisely described by William Lockard in his book “The Exceptional Dental Practice”.

Assessment of the functional state of the dental system includes diagnostics:

temporomandibular joints
masticatory muscles
range and pattern of movements of the lower jaw
analysis of static and dynamic tooth contacts.

The overall goal of a functional examination is to collect as much data as possible in order to determine whether the patient’s dental condition is stable or not. If the system is unstable, the doctor needs to determine where the structural damage occurred, what pathology could provoke it, and what type of dysfunction arose as a result. It is extremely important to consider all possible influencing factors before making a final diagnosis. Sometimes it happens that certain violations of functional parameters can be identified only at the end of the diagnostic process, or even between patient visits, based on his own complaints and comments that arose during a comprehensive examination. The order of diagnostic manipulations is determined by the attending physician himself, therefore the author developed the algorithm presented in the article himself, based on existing clinical experience. The first stage of diagnosis remains the assessment of joint function.

This step involves obtaining answers to the following questions:

Do you feel pain when palpating your joints? If so, what is the nature of these sensations and how strong are they?
Do you feel noises when moving your joints? If so, at what point in the movement and what is the nature of the sound? Is it painful?
Is the movement of the lower jaw free and unrestricted? Are there any deviations? If so, how significant are they and in what direction are they observed?
Can the joints withstand the forces or loads placed on them?

Positioning at the 12 o'clock position allows the doctor to examine the patient along the long axis of the head and at the same time analyze the existing deviations in movements and symmetrical relationships. In adult patients, full mouth opening exceeds 40 mm, and in some patients this parameter even goes beyond 50 mm. The lateral movement of the lower jaw is normally about 10 mm. In this case, the doctor must determine whether pain occurs during lateral movements? Do the ranges of lateral motion differ in any particular direction? The nature of the movements of the lower jaw is determined simultaneously by the state of the condylar process, disc, articular fossa and tubercle, as well as the stability of the lateral pterygoid muscles and the muscles that provide mouth opening. It is logical that movements in a damaged or unstable joint will be more limited than movements in a healthy state of the dental system. Therefore, assessment of the initial parameters of movements in the joint is a mandatory stage of a complex diagnostic algorithm. In addition, it is very important to record the position of the joint in the centric relation position. The author uses the bimanual centric relation technique developed by Dawson, as well as a leaf calibrator, a luchiu jig, and various types of frontal stoppers. The lack of contact in the area of the posterior teeth allows the muscles that elevate the mandible to position the condylar head more highly before the disc-fossa complex of the joint limits its position. The use of front stoppers is a fairly reliable method for recording centric relation. The patient is asked to stick the lower jaw forward and repeat this several times in the position of the frontal stopper - in this way it is possible to achieve activation of the muscles that understand the lower jaw. Initial attempts to determine the centric relation may be unsuccessful due to disc impairment, or fluid swelling within the joint capsule, not to mention possible spasms of the lateral pterygoid muscles. In such cases, the doctor will be able to determine only a preliminary central ratio. As the joints and muscles stabilize, more accurate centric relation parameters can be determined. Using the same three recording methods above, the doctor can also test the ability of the joints to tolerate force applied to them. In other words, the physician can determine whether the present condyle/disc/fossa condition is stable and healthy enough to withstand the forces of normal functional loading or even parafunctional conditions? In most cases, joint instability is caused by disorders such as inflammation, disc lesions, disturbances between the constituent surfaces, and pain in the area of attachment of the lateral pterygoid muscle to the condyle and disc. By repeated protrusive and retrusive movements of the patient using a sheet calibrator and a Lucia Jig, the condition of the joint and the lateral pterygoid muscle can be diagnosed. Adaptation to stress is tested using a bimanual technique, increasing the upward pressure force. After diagnosing the joint, they begin to evaluate muscle function. This part of the inspection is to determine the following:

condition of the three muscles that lift the mandible. Is there any discomfort during palpation? What is the approximate cross-sectional thickness of the muscle? What level of tension is present when they are active? How does the patient react to palpation performed by the doctor?
condition of the lateral pterygoid muscles. Does pain occur with palpation or the action of any other factor?
condition of the muscles of the floor of the mouth.
condition of the muscles in the neck and shoulders.

Palpation of each of these muscles is slightly different, but the doctor should palpate as many of them as possible. The physician should increase the pressure gently and slowly while observing the patient's response while rating their pain response on a scale of 1-2-3 (mild to moderate to severe). In addition, the clinician should analyze the relative cross-sectional thickness of the masseter and temporalis muscles, as this parameter is a reliable indicator of the patient's ability to generate loads of a certain force during jaw clenching or towing. Based on existing observations, it is known that patients with a shallower mandibular angle tend to have thicker masticatory muscles, which in turn allows them to generate more force during function.

And finally, the doctor needs to determine the nature of tooth contacts at different jaw ratios for a final understanding of the patient’s functional state. First, the first contact at centric relation must be determined, which will be considered the critical cutoff point, even if the patient has not reached the stage of restoration of centric relation. For this manipulation, the author uses a bimanual technique and a sheet calibrator. In addition, for the same purpose, you can use the “luchiu jig”, deprogramming the patient’s masticatory muscles, and then proceed to the bimanual technique with a progressive increase in the thickness of the calibrator sheets: this is how it is possible to evaluate the upper movement of the condyle deep into the articular fossa, and as a result, the area of occurrence of the most early contact in the dental area. This manipulation helps the clinician form an idea of the need to correct the corresponding vertical and horizontal components in order to achieve maximum contact between the antagonist teeth. To perform such a correction, it may be necessary to use various treatment methods, while at the same time it is necessary to evaluate whether such an intervention will be so effective as to compensate for all the changes in the dentofacial apparatus expected during its implementation, or whether performing it as a whole will be considered inappropriate.

conclusions

Understanding the anatomy of the joints, muscles and dentition, as well as their relationship, helps the doctor to objectively assess the parameters of the bite and the function of the dentofacial apparatus. This knowledge determines the adequacy of the choice of one or another treatment approach, based on the specific clinical conditions of each individual patient. Determining the forces generated during function and parafunctional states is a key step in diagnosing and solving the main clinical problems associated with occlusion and its constituent components. The following article will examine the features of the relationship of the anterior teeth and the dynamics of the movement of the lower jaw in case of malocclusion and various dysfunctions, including pathological abrasion of teeth. In addition, the concepts of treatment planning based on changes in the patient’s appearance remain promising in the structure of algorithms for restoring articulatory patterns, while helping to reduce the destructive influence of excessive forces on the state of the entire functional system.

Source: stomatologclub.ru

How much does implantation cost if there are no teeth?

Despite the apparent high cost of implantation in the absence of teeth, it may turn out to be more profitable than restoring already hopeless teeth. In addition, the service life of implants is unlimited. Treatment is carried out in stages and is also paid for.

So, the price of jaw implantation in the absence of teeth depends on the type of structure (removable, fixed) and the implant system. For example, the cost of jaw implantation using the classical method with a one-time load with a non-removable plastic prosthesis ranges from 350,000 rubles. The price of a zirconium prosthesis on implants for one jaw starts from 200,000 rubles.

You can get acquainted with the prices for implantation in the absence of teeth by clicking on this link.

Author of the article: Akhtanin Alexander Alexandrovich. Dentist-implantologist, orthopedist. He trained for a long time in Berlin, Germany. Member of the international association of implantologists ITI - International Team for Implantology.

Installation of braces

A general understanding of how dental braces work, the design and installation process of the system is important for everyone. There are two installation options: direct and indirect method.

The direct method involves manually installing and positioning each bracket on a tooth directly in the patient’s mouth. Fixation is carried out on a light-curing material. The indirect method involves positioning the system on a plaster model. The braces are transferred from the model to the mouthguard. The mouthguard is formed individually for each patient. Next, glue is applied, the mouthguard is put on the teeth, and the braces are fixed in a predetermined position for each jaw in turn.