What is dental trephination, in what cases is this procedure performed?

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Endodontic treatment of a tooth involves invading its internal cavities - the pulp chamber and root canals for treatment (vitalization) or removal of the pulp.

The location of the opening may be the bottom of the carious cavity or the undamaged, intact surface of the tooth.

The essence and purpose of manipulation

Tooth trephination (Greek Trypanon - trephine, drill) is the initial stage of endodontic treatment, which involves opening the top of the pulpous chamber, removing the pulp located in the coronal part, and creating access to the mouths of the tooth root canals.

This procedure is also called “crown expansion” or “endodontic coronal preparation.”

It should be noted that trephination does not involve expanding or changing the shape of the dental cavity and penetrating the tooth canals. Its more modest task is to open the crown cavity and provide access to the mouth of the root canals. The operation can be performed on both natural and artificial crowns.

According to the general medical classification, trephination is indicated by code A 16. 07. 092, where “A” means medical, indicating that this is a surgical intervention, “07” - that it is carried out in the oral cavity, and “092” indicates that this the procedure, in fact, is trepanation.

General overview

The term “tooth trepanation” is used to describe the initial phase of endodontic treatment, involving the opening of the upper part of the pulp, the subsequent removal of its contents located in the coronal part, as well as the formation of an area providing access to the root canal orifices. Preparation does not involve adjusting or expanding the shape of the cavity - the goal is opening, without which treatment of the canal passages is impossible. In accordance with the dental classification, code A16.07.092 is used to indicate trepanation.

Indications

Trephination is the first stage of endodontic treatment; it is indicated in all cases where it is necessary to penetrate inside the tooth for its treatment (vitalization or pulp removal, obturation of dental canals, installation of a pin or other operations).

Most often, trepanation is performed in the following cases.

• The presence of a deep carious cavity in the area of ​​the clinical crown of the tooth with a thin or completely absent septum between it and the pulpous chamber.
  Even if the thin wall is preserved, it is capable of allowing pathogenic microorganisms to pass through, resulting in possible infection of the pulp. Therefore, if appropriate symptoms are present, the doctor may consider trepanation of the tooth necessary.
• Chronic or acute pulpitis.
• Any form of periodontitis.

A contraindication to trepanation is the impossibility of restoring the functionality of the tooth and the need for its removal:

• impassable, curved root canals;
• severe periodontal damage;
• tooth root fracture.

In all these cases, the tooth is simply removed.

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Apical microsurgery as an opportunity to save a tooth

Starting from the standard therapeutic protocol to tooth-preserving surgery.

The anatomy of root canals is very complex and varied - there are branches, divergences and repeated closures of the canals, and specific bends. Also, the apex of the tooth itself (its apex) is practically a “tree” of small branches of the main canal.

All this helps to maintain minimal infection in the canals and its ability to continue to develop. In some cases, this infection is very minimal and the body comes to the aid of the doctor, completely blocking it. But sometimes, the infectious process is more active and, turning into a chronic form, slowly continues its development.

Several years after treatment, a focus of inflammation may be accidentally detected on control images, and the question of re-treatment or removal will arise. BUT since the doctor’s main task is to preserve the tooth, it is not always worth removing the tooth right away. After assessing its viability, doctors may suggest an alternative treatment - apical surgery.

Apical surgery is a complex of operations performed by resection of the upper quarter/third of the root.

The inflammatory focus is removed along with the root, and its place is filled with bone tissue.

To carry out these manipulations, an operating microscope or binoculars, ultrasound and microsurgical equipment are used, which allow retrograde filling and elimination of the consequences of periodontitis.

Indications for apical surgery:

• Lack of possibility of repeated endodontic treatment
• Detection of instrument fragments in the extreme third of the canal, or excess material behind the root of the tooth (it is not possible to extract all this through the canal)
• Carrying out therapeutic intervention to no avail (sclerosis of the canals, impossibility of passing the canals due to cements or pins)

The planning of the operation is carried out jointly by the therapist and the surgeon. A CT scan is performed and the chances of a positive outcome are assessed. The surgeon evaluates the volume of bone tissue in the lesion area to understand the possibility of complete restoration of bone tissue.

A treatment plan is drawn up and all the nuances are discussed with the patient.

Let's consider the algorithm for apical surgery using a specific clinical example of patient Sergei, 39 years old. He is undergoing comprehensive rehabilitation at our clinic.

After all the examinations, a lesion was identified in the area of ​​2 central teeth 21,22.

Therapist Zapolskaya M.A. carried out repeated endodontic treatment in advance, the canals were filled with biodentine in the apical third and restored on fiberglass pins. On the day of canal filling, the patient immediately goes into the hands of a surgeon to perform resection of the root apexes (apical surgery).

The surgeon works with binoculars to better assess the surgical field. An incision is made to access the teeth, the flap is removed and the lesion is visualized.

Curettage of the lesion area is performed, treated with ultrasound and antiseptic solutions. The tips of the affected roots are partially resected and polished. The therapist controls the canal filling through the surgical field using a microscope.

The cavity is filled with bone material and hermetically sealed with a membrane. The membrane is fixed to the surface of the bone tissue with pins (surgical buttons)

The wound is sutured.

After surgery, the patient receives standard drug therapy and performs nursing procedures.

After 3 months, a control CT scan was performed to evaluate the results of the surgery. We are satisfied with the result and continue monitoring and monitoring every 3-6 months.

This clinical case went smoothly and pleased us with its result. However, I would like to note that not every tooth can be saved by apical surgery. To make a decision, the doctor always evaluates many factors - from the anatomy and location of the tooth, to the size of the lesion and the degree of destruction of the crown. The main thing here is to answer honestly the question of the appropriateness of such treatment. If the tooth cannot be restored or surgery can cause great trauma, then you should listen to the doctor and accept removal. If the doctor gives good prognosis and the tooth is strong and reliable, of course it’s worth trying all the ways to save it.

Be a team with your doctor, trust and listen to arguments, make a decision together and then the result will please everyone!

This article used the clinical case of G.V. Khokrishvili. and Zapolskaya M.A.

Preparatory stage

Trepanation should be preceded by a diagnosis, a complete assessment of the condition of the crown of the tooth, its roots, and periodontal tissues.

To achieve this, the following activities are carried out:

• Questioning the patient regarding complaints. Inspection and probing of the tooth to determine the presence and depth of carious cavities in the clinical crown. Assessing the condition of the gums in the area of ​​the problem tooth. If there are fillings, their condition is assessed.
• Electroodontometry. Determination of the condition of the pulp by its reaction to electric current.
• X-ray of the tooth. This is a mandatory and very important stage in endodontic treatment.
  Using fluoroscopy, the number and condition of root canals, their length, and anatomical shape are determined. The shape and dimensions of the pulp chamber, the thickness of its walls and lid are established. The presence of lateral canals, pathological changes in the tooth ligament.

By applying the bur to the radiograph, the required size of the instrument and its correct direction when opening the tooth are determined.

Before treatment, professional cleaning of the entire dental cavity or just a segment of the jaw arch with the element being prepared may be necessary.

The procedure for gaining access to dental canals

To ensure convenience and high quality of root orifice treatment, the dentist needs to ensure a wide opening of the tooth cavity. To do this, he needs to perform the following list of operations:

• Formation of an intradental cavity in full accordance with its anatomical dimensions and shape, as well as the number, location and curvature of the canals.
• Adaptation of the shape of the prepared cavity to make subsequent manipulations as convenient as possible by: creating free access to the root orifices;
• providing a direct approach to the apical foramen;
• preparation for a specific filling technique;
• creating conditions for complete control over the movement of the tool.

Sequence of doctor's actions

Trepanation involves three main stages:

• local anesthesia;
• tooth isolation by applying a rubber dam;
• directly opening the crown.

After anesthesia and the application of a rubber dam, the doctor proceeds directly to trepanation. The preparation is performed using a turbine drill with a diamond or carbide bur with a supply of coolant.

First, the crown is opened - installed by drilling a point connection between the bottom of the carious cavity or the intact surface of the tooth with its internal cavity.

Then the coronal cavity is opened - the edges of the enamel-dentin cap overhanging it are removed. Dentin sawdust and necrotic tissue are washed off with liquid.

The coronal part of the pulp is removed with a sharp excavator and EDTA (sodium salt dihydrate, which softens surface dentin) and disinfectant sodium hypochlorite are supplied into the cavity.

The walls of the cavity and the mouth of the dental canals are not additionally prepared. The main thing is that they are clearly visible and access to the dental canals is provided.

At this point, the trephination of the tooth ends and the next stage of endodontic treatment begins according to indications.

In the video, watch the process of tooth trephination.

Resection stages

• Formation of access
  - the dentist cuts through the gum, exposing the jaw bone. Forms a small hole in the bone tissue (in the projection of the root apex), gaining access to the pathological focus. Often, the bone tissue has dissolved in the projection of the cyst; there is no need to cut out a hole.
• Excision of tissues and correction of the apex
  - the doctor removes the source of inflammation along with the dead apex of the root, cutting it off perpendicular to the upper dental axis (to the level filled with the filling mass). The empty space is filled with osteoplastic material (bone volume is restored faster).
• Suturing
  - suturing the wound area is sometimes performed with the installation of drainage for the outflow of ichor. Drainage is installed between the seams and is removed after 1-2 days.

Root resection takes 40-60 minutes, depending on the location of the tooth. It is easier to intervene on canines and incisors than on multi-rooted units.

Some nuances

The starting point for opening the pulpous chamber should be located at the bottom of the caries lesion or on the intact surface of the tooth closest to the pulp, that is, at the site of the pulp horn. The moment the drill enters the cavity manifests itself as a feeling of “sinking” of the instrument.

When is a rubber dam applied?

There is no consensus. Some experts recommend doing this before opening the cavity, others - after opening. The latter explain their choice by the fact that the absence of a rubber dam at the stage of opening the cavity helps to more accurately guide the tool.

Trepanation technique

Trephination methods vary somewhat depending on the group of teeth and their location (upper or lower jaw).

Technique for preparing incisors and canines

The carious cavity on the cutting surfaces of the incisors and canines is transferred to the lingual/palatal surface, and only then the pulpous chamber is opened.

Preparation of intact incisors and canines begins from their lingual/palatal surface - from its central point. Preparation from the cutting edge can lead to destruction (breakage) of the lateral surface of the incisor or canine. The intact incisors are exposed in the area of ​​the blind fossa.

During trephination, the instrument is first directed perpendicular to the palatal or lingual surface of the canine or incisor. After the hole is formed, the drilling direction is changed to parallel to the longitudinal axis of the tooth.

Trepanation of premolars

In premolars, carious cavities begin to be opened from their bottom in the place closest to the pulp. In this case, they try to transfer the preparation to the chewing surface.

The opening point for intact premolars should be located on the occlusal surface in the middle of the fissures. When drilling, the bur is directed towards the most pronounced tubercle.

The dental cavity should be opened in the palatal-buccal direction. Doing this in a mesial or distal direction is not recommended, since this quite often leads to perforation of the walls of the coronal cavity.

The opened cavity should have a round or oval shape.

Molar preparation

Carious cavities in the molars of the upper jaw are trepanned in the same way as premolars. During opening, the bur is directed in the palatal-buccal direction.

Lower intact molars have their own opening characteristics. The bur entry point should be located in the middle of the longitudinal fissure. The instrument is directed towards the anterior buccal cusp. Unlike maxillary painters, the cavities open in the mesial-distal direction. Buccolingual opening is considered faulty.

The second and third maxillary molars are the most difficult for trephination due to the different structures of their crowns.

Difficulty identifying canal mouths

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Opening and formation of the access cavity and localization of root canals

Author: American Association of Endodontists

The endodontic triad, including biomechanical preparation, disinfection and complete obturation of the root canal space (RC), remains the basis of endodontic treatment (ET). However, even if access to the ostia of the CC and apical foramina is ensured correctly, achieving the goals of this triad will still be labor-intensive. The main goal of EL is to create conditions in which the body can heal on its own. Adequate access is the key to achieving this goal and, accordingly, the success of EL. The purpose of this article is to assist the practitioner in understanding the technique of providing access to the dental cavity and orifices of the oral cavity. A systematic approach to addressing this issue is described below.

Basic principles

The pulp complex is a continuum (continuous structure) starting from the pulp horns and ending at the apical foramen. In order to completely remove the pulp, access to the coronal part must be ensured in such a way that the localization and cleaning of the CC can be carried out fully and without weakening the coronal dentin and enamel.

The process of cleaning and forming the access cavity and CC can be divided into 4 stages: analysis of access, removal of the roof of the tooth cavity, identification of the tooth cavity and the mouths of the CC, instrumentation of the CC.

Access Analysis

Removal of pulp tissue begins with an analysis of the anatomy of the tooth being treated and the anatomy of the surrounding tissue. To completely remove all pulp tissue, it is necessary to identify the coronal and root parts of the pulp complex. According to Krasner and Rankow, the cavity of each tooth is centrally located at the cemento-enamel junction, a feature called the “law of centrality.” Confirmation of this law can be seen in Fig. 1A and 1B.

Rice. 1. Sample slices demonstrating the law of centrality.

The law of centrality can be used to guide the initial formation of access. However, the operator must understand that this law is valid only at the level of the CEJ and is not related to the anatomy of the chewing surface.

Therefore, the initial penetration into the tooth cavity must be made in the center of the central epithelium. Therefore, the doctor must make an approach, mentally imagining the localization of the central epithelium, while ignoring the anatomy of the clinical or artificial crown. As can be seen in Fig. 2, artificial crowns disorientate clinicians, since their anatomy is not centered relative to the CEJ.

Rice. 2. Localization of the central epithelium, which does not correspond to the anatomy of the artificial crown.

Step 1

The first step in gaining access to the dental cavity is physical identification of the shape and location of the CEJ. This is done with the help of a periodontal probe, which is used to examine the circumference of the CEJ to get a mental picture of its size and boundaries, as shown in Fig. 3 A-D.

Rice. 3.AD. Periodontal probing to localize the central epithelium.

After visualizing the CEJ on the occlusal surface, a penetration point is selected. On the surface of the restoration, this point may not be related to the anatomy of the occlusal surface. This can be seen in Fig. 3E, where the correct penetration point on the chewing surface is marked with a blue circle. This point was determined using radiographic examination, periodontal probing, and a mental representation of the CEJ perimeter.

Rice. 3. E. Localization of the primary penetration point, based on determining the perimeter of the central epithelium.

Visualization of the final contour of the tooth cavity can be supplemented by the use of another law related to its anatomy - the law of concentricity. This law states: “the walls of the tooth cavity at the level of the CEJ are concentric with respect to the external contour of the tooth.” The law of concentricity is shown in Fig. 4.

Sample slices demonstrating the law of concentricity.

This law helps clinicians to correctly open the tooth cavity. If there is a convexity of the CEJ, the tooth cavity will also have a corresponding convexity. For example, if a tooth is narrowed mesiodistally, the tooth cavity will also be narrowed in that direction, as shown in Fig. 5a and 5b.

Step 2

The second step is to determine the angulation of the tooth (mesio-distal inclination). This is done using radiography (Fig. 6) and clinical examination. CBCT can provide information about the vestibulo-oral inclination of the tooth.

Rice. 6. Determination of angulation using radiography. You should pay attention to the inclination of the second molar of the HF. Step 3

The third step, as shown in Fig. 7, is the measurement of the distance from the top of the tubercle to the furcation using a radiogram. Once this distance is determined, a shorter length bur is placed in the handpiece to avoid perforation of the furcation. If a shorter bur is directed directly along the center of the central joint, parallel to the long axis of the tooth, then perforation is practically eliminated.

Rice. 7. Measuring the distance from the occlusal surface to the furcation. Step 4

After all parameters are determined, the primary access point is selected. Its location may vary relative to the occlusal surface of the tooth and will depend on all of the above factors. All recommendations regarding starting access from holes or depressions are erroneous. In some extraordinary cases, the primary access point may even be on the tubercle. The principle follows from this: the internal anatomy of the pulp chamber determines the external contours of the crown. The shape of the crown can be triangular, trapezoidal or irregular.

Access technology

Step 1

Before starting the mechanical component of access formation, all defective restorations and carious tissues must be removed to avoid bacterial contamination during the treatment process.

Step 2

The type and shape of the working surface of the bur is selected individually by the clinician. The most commonly used are spherical carbide (carbide) or diamond and fissure burs. For orthopedic structures, special burs are used to cut metal. After selecting the bur, penetration of the occlusal surface is carried out at the point determined by the above characteristics. The bur must move towards the center of the mentally imagined CEJ until the moment of “falling through” or until the head of the tip touches the tubercle of the tooth. However, “sinking” is felt only when the depth of the tooth cavity is at least 2 mm.

When a doctor evaluates the possibility of treatment on his own or referral to another specialist, it is necessary to take into account the distance from the roof of the tooth cavity to the bottom. Patients with a calcified dental cavity, as shown in Fig. 8, it is better to refer to more experienced specialists with appropriate equipment.

Rice. 8. X-ray of a molar with calcified CC. Step 3

The goal of proper access is to completely remove the roof of the tooth cavity. During the process of removing the roof, there is no need to search for the mouths of the roof, since after its complete removal and, accordingly, completion of the formation of the access, the mouths can be found without much difficulty.

The roof of the tooth cavity can be removed in two ways: place the bur parallel to the long axis of the tooth and open the tooth cavity with lateral movements, or place a spherical bur in the access cavity and, grasping the lateral overhanging edges of the roof, move the bur towards the chewing surface (Fig. 9).

Using various burs to remove the roof of the tooth cavity. The roof of the tooth cavity is sequentially removed, after which the formation of the access can be considered complete. One of the most important steps during this process is when it is determined that access has been completed. In order to accurately determine this point, the doctor needs to know the “law of color change.” The law states that the color of a tooth cavity is always darker than that of the surrounding walls. As long as the walls are light, there is a place where they transition into the darker bottom of the tooth cavity. This connection between the wall and the bottom is shown in Fig. 10, passing through the entire bottom of the tooth cavity.

Rice. 10. Sample section showing the connection between the walls and the bottom of the tooth cavity. Fig. 11. Sample slice demonstrating full access.

The operator knows that the access formation is completed in case of a complete view (360 degrees) of the connection of the bottom and walls of the tooth cavity (Fig. 11). If this connection is not fully visible, the operator will need to remove additional overhanging structures (restorative material, reparative dentin, or overhanging edges of the roof of the dental cavity). This intervention to provide a complete view can be seen in Fig. 12.

Clear visualization of the wall-floor junction is one of the main aspects of providing access for endodontic treatment.

If the doctor cannot carry out this manipulation for any reason, then he must refer the patient to another specialist. In Fig. Figure 12 shows a defective approach where a full view of the wall-to-bottom connection is not visible.

Rice. 13 illustrates full access, where the transition of the walls to the bottom is visualized along the entire perimeter of the tooth cavity.

Rice. 12. Sample of defective access.Fig. 13. Sample of full access.

Estuary localization

The number of CC orifices in each specific tooth should be known in advance before treatment. Although radiographs help in some cases to determine the number of roots, and the average values ​​of the number of roots and CC for each tooth are also known, most often the number and location of the orifices of the CC remain unidentified.

So how does a clinician determine the exact number of CB orifices without causing iatrogenic destruction to the tooth? The only effective and safe way to visualize all formations of the floor of the dental cavity is to use a variety of anatomical landmarks.

There are several laws for identifying the localization of the mouths of the CC:

• I law of symmetry: with the exception of the molars of the HF, the mouths of the CC are equidistant from a line drawn in the mesio-distal direction through the center of the bottom of the cavity (Fig. 14);
• II law of symmetry: with the exception of the HF molars, the mouths of the CC lie on a line perpendicular to the line passing in the mesio-distal direction through the center of the bottom of the tooth cavity (Fig. 15);

Rice. 14.Fig. 15.

• law of color change: the color of the bottom of the tooth cavity is always darker than the color of the walls (Fig. 16, A and B);

Rice. 16. A-B.

• I law of localization of the mouths: the mouths of the CC are always located at the point of transition of the walls into the bottom of the tooth cavity (Fig. 17);
• II law of localization of mouths: the mouths of the CC are located at the tops of the wall-bottom connection (Fig. 18).

Once the wall-bottom connection is clearly visualized, all laws of symmetry and location of orifices can be used to determine their exact position and number.

If you look at the localization of the mouths at the bottom of the tooth cavity in Fig. 19, then knowledge of the l and ll laws of symmetry indicates not only the presence of the 4th mouth, but also its exact location.

The laws of localization of mouths l and ll can be used to determine their number and location. Since all orifices may be located along the wall-bottom junction, any black spots, indentations or white spots that are observed elsewhere (on the walls or dark bottom) should be ignored to avoid perforation. ll law of localization of mouths helps to focus on their exact location. The vertices or corners of the geometric shape of the dark bottom of the tooth cavity will indicate the exact location of the orifices. If the CC is calcified, then this apical position will determine the need for the bur to penetrate the reparative dentin of the upper part of the CC (Fig. 20).

Rice. 19. Localization of mouths using symmetry laws. Fig. 20. Sample sections showing the vertices of the floor of the tooth cavity. l and ll laws of localization of orifices in combination with the law of color change are often the only possible indicators of the presence and localization of the second CC in the bucco-medial root of the first molar of the HF (Fig. 16). In Fig. 16A shows the bottom of a tooth cavity; along the wall-floor junction there is an angle between the orifices of the bucco-medial and palatal CC. l and ll laws of localization of orifices indicate the presence of a second CC in the buccal-medial root, as can be seen in Fig. 16B. This orifice is present in the vast majority of HF molars; it can be located at different distances from the orifice of the first CC, but is always located along the line of connection between the wall and the bottom of the tooth cavity.

All of the above laws apply to all teeth with the exception of high-frequency molars. They are especially valuable in cases of unusual anatomy. Pay attention to the schematic representation of the bottom of the tooth cavity of the second premolar tooth in Fig. 21(A). Knowledge of the laws of the anatomy of the bottom of the tooth cavity will immediately indicate the presence of three CCs in this tooth (Fig. 21 (B)).

Localization of the mouth of the third CC using the laws of the anatomy of the bottom of the tooth cavity. Another example of the value of knowing the anatomy of the bottom of the tooth cavity can be seen in Fig. 22(A), which shows a LM molar sectioned along the CEJ. In accordance with the laws of the anatomy of the bottom of the tooth cavity, it can be argued that there are only two CCs in this tooth. Their location is shown in Fig. 22(B). However, the physician should be aware that the number of orifices does not always correlate with the number of CCs. Sometimes there may be several CCs at one mouth.

Anatomy of the dental cavity, demonstrating the presence of two CCs in the molar of the lower jaw. Despite all our attempts to ensure high-quality access, problems may still arise during the treatment process. Listed below are the most common problems faced by practitioners and how to resolve them.

Schematic representation of problems and options for eliminating them

Problem: inability to localize the bottom of the tooth cavity due to excessive bleeding. Cause: pulp tissue of the tooth cavity or CC. Methods of elimination: 1. Expand access by removing the roof of the tooth cavity without touching the bottom (you cannot touch the bottom of the tooth cavity without completely visualizing the wall-bottom connection). 2. Place a hemostatic agent into the tooth cavity. 3. Use a pulp extractor to remove pulp tissue.

Problem: inability to determine the location of the bottom of the tooth cavity due to inadequate removal of the roof of the tooth cavity. Reasons: 1. Wrong choice of primary access point. 2. Inability to visualize the wall-bottom connection at 360 degrees. Elimination methods: return to the previous bur (spherical or fissure) and continue opening the tooth cavity until the wall-bottom connection is completely visualized.

Problem: inability to determine the location of the bottom of the tooth cavity due to inadequate lighting. Reasons: 1. Too little access. 2. Presence of crowns or restorations. 3. Lack of smooth surfaces on the walls and bottom of the tooth cavity (usually due to the use of too small spherical burs). Methods of elimination: 1. Enlarge the access cavity until the wall-bottom connection is completely visualized. 2. Remove the restoration material. 3. Use additional lighting devices (LED headlamps or operating microscope) if you have a crown. 4. Smooth out all irregularities on the walls and bottom of the tooth cavity using spherical burs.

Problem: calcifications, denticles. Cause: degenerative processes in the pulp Methods of elimination: after completely removing the roof of the tooth cavity and stopping the bleeding, use a non-aggressive spherical bur to smooth the bottom of the tooth cavity to remove calcification and clearly visualize the wall-bottom connection.

Problem: inability to determine the location of the bottom of the tooth cavity due to the overhang of the restoration material over the tooth cavity. Reason: inadequate removal of all restoration material before the start of access formation (in particular, with carious cavities of class 5, the restoration material can be introduced into the tooth cavity). Remedy: remove all restoration material before starting access.

Problem: inability to localize the bottom of the tooth cavity due to loss of landmarks. Reasons: 1. Using the occlusal surface as the starting point for access formation. 2. Problem with determining the inclination and rotation of the tooth. 3. Loss of landmark in the form of a circle along the central nervous system. 4. Wrong choice of angulation for primary access. Methods of elimination: 1. Correctly determine the orientation of the tooth before starting access formation. 2. Correctly mentally imagine the CES. 3. Remove the rubber dam to avoid loss of landmarks. 4. Select the appropriate penetration angle for the bur during initial access.

Problem: perforation of the bottom of the tooth cavity. Reasons: 1. Premature attempt to identify the mouths of the CC. 2. Incorrect measurement of the distance from the occlusal surface to the furcation. 3. Incorrect identification of the wall-to-bottom connection. 4. Inadequate access. Elimination methods: 1. Remove the roof of the tooth cavity before determining the location of the mouths of the CC. 2. Obtain a 360 degree view of the wall-bottom connection. 3. Use a bur of shorter length than the distance from the occlusal surface to the furcation. 4. Direct the bur along the center of the CES perimeter.

Problem: perforation of the lateral wall of the tooth cavity. Reasons: 1. Misconception about CES. 2. Incorrectly chosen angle when creating access. 3. Using the occlusal surface as a guide to begin penetration. Elimination methods: 1. Remove the roof of the tooth cavity before determining the location of the mouths of the CC. 2. Obtain a 360 degree view of the wall-bottom connection. 3. Direct the bur along the center of the CES perimeter. 4. Select the primary point of penetration based on the idea of ​​the central nervous system.

Conclusion

To increase the likelihood of success of endodontic treatment, it is necessary to remove the pulp as completely as possible. In order to achieve this, it is necessary to find the mouths of all CCs. The only rational way is to use the laws of the anatomy of the bottom of the tooth cavity. To do this, it is necessary to create an access in such a way as to visualize the connections of the walls and the bottom of the tooth cavity along the entire perimeter. This article describes clinical conditions that may interfere with such imaging. The article is also supplemented with a schematic representation of possible problems that arise during the treatment process, and options for their prevention and elimination.

Amet Tabakov Kirill Kulik

Possible complications

Coronal preparation is less risky in terms of complications than root preparation. However, they still happen:

• Perforation of the wall of the pulpous chamber. The reason is the carelessness of the dentist, the wrong choice of instrument, the lack of an x-ray, which determines the shape of the cavity.
  If the hole is small and the perforation site is located above the periodontal groove, the defect can be easily eliminated - with the help of cement.

  If the hole is larger than 1.5 mm, and the perforation is located below the periodontal groove, there is a risk of filling material leaking into the periodontium, which can lead to inflammation.

• Broken tool. Occurs due to excessive application of force, the use of low-quality instruments, poor condition of the crown, and the doctor ignoring the shape of the cavity.
• Change in color (darkening) of the crown . The reasons are a violation of the operating mode of the tool (high speed, lack of cooling), improper processing of the cavity walls.
• Pain. They may appear after the instrument enters the periodontium, when working without cooling, or due to poor-quality antiseptic treatment (re-infection).

In general, complications are caused by preparation errors, lack of cooling, incorrect choice of instrument, and lack of high-quality x-rays. To avoid them, you need to strictly follow the operation protocol.

Nuances and features of the procedure on different teeth

You now know what trepanation of a tooth crown is. However, when preparing different teeth, there are some nuances:

• incisors and canines: drilling and opening of the pulp chamber is carried out through the lingual or palatal surface. Opening from the outside is not carried out due to the risk of breaking off or destroying the cutting edge, which will lead to disruption of the functionality of the tooth and loss of its aesthetics. For work, the doctor selects burs of small or medium diameter (No. 2 or No. 4), their rotation speed during the process should be minimal,
• molars and premolars: they are opened on the chewing surface in the fissure area. The doctor gives the emerging cavity a rounded shape for subsequent high-quality filling. Manipulations are performed using burs larger than those used for incisors and canines.

If a patient is aged (over 60 years) undergoing treatment, then the degree of tissue preparation should be less than in younger people. This is due to the smaller size of the tooth cavity.

Large burs are not suitable for trepanation, because their vibrations can lead to tissue destruction and root fracture.

Reviews

The vast majority of visitors to dental offices are familiar with tooth trephination, which everyone simply calls “drilling.”

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Main types of tooth preparation

In modern dental practice, five main methods of tooth preparation are used:

• tunnel;
• laser;
• ultrasonic;
• chemical;
• air-abrasive.

Tunnel preparation

For tunnel turning of abutment teeth, turbine units are used, equipped with speed regulators, as well as metal or diamond tips.

Advantages of the tunnel view

The main advantage of this technique is the ability to control the thickness of the removed layer of dental tissue.

Disadvantages of the tunnel view

The disadvantages of tunnel grinding of teeth include:

• severe overheating of the enamel;
• increased risk of injury to the soft tissues of the mouth if the technique of performing the procedure is violated;
• a high probability of cracks and microscopic chips appearing on hard dental tissues when using worn out or low-quality instruments.

Laser preparation

For laser preparation, pulsed lasers are used to heat the water contained in the hard dental tissues and destroy the integrity of the enamel and dentin. Pieces of sanded fabric are cooled and removed using a special air-water mixture.

Advantages of the laser type

The advantages of laser tooth preparation include:

• high turning speed;
• safety (no equipment elements rotating at high speed);
• absence of noise from the operation of laser equipment;
• low heating temperature of the treated tissues;
• no cracks or chips on the edges of the pin.

Ultrasonic preparation

With ultrasonic preparation, the grinding of teeth is carried out due to high-frequency vibration of the dental instrument under the influence of ultrasound.

Advantages of Ultrasonic View

The main advantages of this method are:

• no negative effect of ultrasonic waves on pulp tissue;
• release of a small amount of thermal energy that is not capable of causing significant overheating of dentin and enamel;
• painlessness;
• no chips or cracks on the pin stacks.

Air abrasive preparation

When using air-abrasive tooth preparation, instead of a drill with a rotating drill, an abrasive-air mixture is used, supplied to the desired area under high pressure. When abrasive powder gets on enamel or dentin, tissue destruction occurs.

Advantages of the air-abrasive type

The advantages of this turning method are:

• absence of tissue overheating and excessive vibration;
• high speed of the procedure and its relative simplicity;
• maintaining the maximum volume of dental tissue;
• painlessness of the performed manipulations.

Chemical preparation

The chemical preparation method of teeth involves softening enamel and dentin using acids and other active chemicals.

Advantages of the chemical type

The advantages of this technique include:

• absence of microcracks and chips on the treated surface;
• painlessness;
• absence of thermal damage to dental tissues.

Disadvantages of the chemical type

The only disadvantage of chemical preparation is the long duration of the procedure.

How is tooth preparation done?

The choice of preparation method directly depends on:

• clinical situation,
• technical equipment of the dental clinic,
• client's wishes.

Grinding of pulpless teeth is carried out without anesthesia (except for those cases when the doctor has to use special threads to move the gums back). If the procedure is performed on living (vital) teeth, the patient may require local anesthesia.

Grinded teeth are necessarily protected with temporary crowns. This allows you to keep damaged dental tissues in an acceptable condition until they are covered with a permanent prosthesis.

Teeth preparation should be carried out only in specialized medical institutions that have positively proven themselves in the dental services market. Only a professional and competent approach to the procedure allows not only to achieve the desired result, but also to avoid the development of complications.

Stages of treatment: how to prepare, install a crown on a tooth

Below we will analyze in detail each of the stages of prosthetics with crowns, and if you want to get advice directly from a specialist, call and make an appointment with the orthopedic doctors of our dental clinic in St. Petersburg - “Unident”. An initial consultation with an orthopedist at our clinic is provided free of charge!

Inspection and diagnostics

The treatment process begins with a visit to the office of an orthopedic dentist.
The specialist will carefully examine the patient’s oral cavity, identify existing problems, and, if necessary, prescribe a number of additional diagnostic measures. Based on the information collected from the clinical case, the orthopedist will draw up a detailed treatment plan and also offer the patient all possible prosthetic options. A well-designed treatment plan necessarily takes into account not only the installation of a dental crown, but also additional procedures:

• Removal of teeth, restoration and treatment of which is impossible for objective reasons;
• Preliminary treatment of diagnosed diseases of teeth and gums;
• Treatment of tooth canals and their filling (carried out when deciding to depulp a tooth before installing a crown);
• Professional oral hygiene. Sanitation of the oral cavity before prosthetics must be carried out to completely remove hard and soft plaque from the surface of the teeth. The event will allow you to most accurately select the crown to match the color of the patient’s natural tooth enamel, and will also have a positive impact on the quality of treatment.

The preparation of a treatment plan is completed by selecting a specific type of dental crown, after which the total cost of prosthetics is calculated and the timing of its implementation is specified.

Preparatory stage

The duration of the preparatory stage depends on what procedures will need to be carried out before prosthetics to ensure a high-quality and durable result. Below we will consider in detail all the possible stages of preparation for dental prosthetics with crowns.

Depulpation

A few years ago, before installing crowns, teeth were depulped without fail.
But modern orthopedists, if the clinical case allows, strive to keep teeth viable and do without removing the nerve. A tooth with preserved pulp is not deprived of adequate nutrition with minerals and nutrients, and does not acquire increased fragility. Crowns installed on living teeth last longer, but unfortunately, it is not always possible to refuse pulp removal. Most often, the front teeth are depulped, but the chewing dental units are kept alive. They have a fairly large area of ​​the natural crown, in them the distance from the enamel to the pulp chamber is much greater, and therefore the risk of nerve bundle burns when installing a crown will be minimal.

The decision on the advisability of preliminary pulp removal is also made based on the number of roots, which may vary for different teeth. If you plan to install a crown on a single-rooted tooth, the depulpation procedure is mandatory. When treating single-rooted teeth, the risk of pulp burn is too high, and thermal damage to the sensitive nerve bundle is fraught with the occurrence of an inflammatory process under the installed crown. To prevent such negative consequences, single-rooted teeth are depulped, the canal cavities are treated with antiseptic agents and filled with gutta-percha.

Treatment of diseases of teeth and gums

If, during a visual examination of the oral cavity, the doctor discovers caries, signs of the development of an inflammatory process - these conditions must be eliminated before installing crowns.
If the tooth is significantly destroyed by caries, the doctor removes the affected tissue and restores the crown part by installing a durable filling. Pulpitis and periodontitis are treated according to a more complex scheme, which includes treatment of dental canals and filling them. A high-quality and durable filling must be placed on the tooth, otherwise it may fall out, and the installed crown will fall out along with it. In case of severe destruction of a dental unit, its coronal part can be restored in different ways:

• Installing a seal on the pin. A pin is a special structure in the form of a rod, which is inserted into the root canal of the tooth and acts as a reliable support for the filling;
• Stump tab. Inlays for dental restoration are made in a dental laboratory and are installed, like a pin in a canal, but are also fixed in the crown of the tooth.

If a tooth is severely damaged, it is recommended to restore it with an inlay, which is considered more reliable and durable than a conventional filling or installation of a filling on a pin.

Preparatory activities are completed with professional oral hygiene. Sanitation is necessary for the complete and high-quality elimination of dental plaque, which is a favorable environment for the proliferation of pathogenic organisms, in addition, the procedure will allow you to accurately select the color of the crown for installation so that it matches as closely as possible the shade of the natural enamel of the patient’s teeth.

Preparation

Preparation or grinding of teeth is a procedure that the doctor performs before taking impressions.
During the preparation, the tooth enamel will be ground down to the thickness of the future crown. During the grinding process, a drill is used: with its help, the tooth is given a certain shape that can provide the most durable fixation to the installed crown. If living, non-pulp teeth are subjected to preparation, the procedure can be very unpleasant and painful for the patient, and therefore local anesthesia is used before it is performed. The thickness of the enamel removal will depend on the type of crown that will be subsequently placed on the prepared tooth. A maximum of natural tissue is removed from the tooth to install ceramic and metal-ceramic crowns; the enamel is ground down to a minimum before prosthetics with cast crowns.

After the tooth has been prepared, a stump remains, from which the doctor will take impressions to produce crowns.

Laboratory stage

An impression is taken from the ground teeth. To obtain a high-quality, anatomically accurate impression of teeth, a specialized highly elastic mass is used to produce a crown. Using impressions, a dental technician in the laboratory will make a plaster model of the patient’s teeth, which will be used to make crowns for further installation. Dental crowns can be made from a variety of materials - alloys of precious and non-precious metals, ceramics, zirconium dioxide, metal ceramics. The type of crowns for installation is selected based on the characteristics of a specific clinical situation, the patient’s preferences, his wishes for the level of aesthetics, as well as financial capabilities.

The timing of its production will depend on the type of raw material from which the crown will be made. The company has been producing crowns made of ceramics and metal-ceramics for a long time. So that the patient does not have to walk with an unsightly stump during the entire period of crown production, a temporary immediate prosthesis is placed on it for this period. Temporary crowns are made of plastic, and their installation allows you to relieve the patient from psychological discomfort, as well as protect prepared and vulnerable teeth from the action of pathogenic microflora and harmful environmental factors.

Fitting and installation of dental crowns

When the dental technician makes the crown frame, the patient will be invited to the clinic for fitting.
During fitting of the frame part of the crown, the tightness of its fit to the surface of the tooth stump is assessed. If the fit is insufficient, food debris and bacteria will get under the installed crown, and all this can lead to the onset of an inflammatory process. If during fitting the crown fits perfectly on the stump, the frame is sent to the laboratory, where it will be covered with ceramic mass. The finished crown is tried on a second time and during the second fitting it will be fixed with temporary cement mortar. A second check is required to assess the quality of contact between the prosthesis and the opposing teeth, and if it goes well, the crown will be installed on the tooth using permanent cement. The process of permanently installing a crown on a tooth takes place according to the scheme described below:

• The inside of the crown is covered with a layer of cementing solution, after which the crown is put on the tooth;
• A tooth with a crown is exposed to light, which accelerates the hardening process of the cement mortar;
• All excess cement mixture is carefully removed, since it is a rather caustic substance and, if it comes into contact with soft tissue, can cause severe burns.

The treatment ends with a detailed consultation from the orthodontist on the care of the prosthesis and oral cavity after prosthetics. Compliance with the specialist’s recommendations guarantees the absence of negative side reactions and complications after crown installation.

Causes of toothache under a crown

The list of factors that can provoke an inflammatory process even under a recently installed crown is:

1. Hypothermia of the body.
2. Decreased immunity; previously suffered acute respiratory diseases; viral infections.
3. Failure of the crown (i.e. the crown has expired its service life) each orthopedic design has its own service life, therefore, in order to avoid pain in the tooth under the crown, it is necessary to undergo a professional examination. dental examination every 6 months.
4. Chronic dental injuries. (if the filling on the antagonist tooth is too high)
5. Acute injury (fall and bruise or damage in a fight).