How to check out MB2 (the fourth tube) in advance? Please give me some advice.

Root canal deficiency is one of the common causes of root canal therapy failure. X-ray apical film is the main means to judge the missing root canal. Regardless of X-ray fluoroscopy, when there is only one root canal in the root, the image of the root canal is always located in the center of the root. When X-ray shows that the root canal image is not in the center of the root, it should be highly suspected that there are other root canals. X-ray offset projection (mesial or distal) can most effectively display and judge the existence of missing root canal, and can determine the position of missing root canal (cheek or tongue). In addition, X-ray offset projection can separate overlapping root canal images, determine the direction and curvature of root canal bending, determine the position of foreign bodies and perforations in root canal, and locate the direction of calcified root canal.

For a single tooth, if the root canal image suddenly changes, there are the following situations: (1) Two root canals are separated by a wider pulp cavity; A wide root canal is divided into two root canals; The overlapping double root canals of premolars and lower anterior teeth began to separate.

When X-ray diagnostic radiography is used, if there is another penetrating ray (root canal image) parallel to the diagnostic filament in the middle and upper part of the root canal, the other canal should be highly suspected.

In addition, being familiar with the anatomy of pulp cavity root canal system and observing the position change of root canal orifice will also help to find the missing root canal.

Two. Treatment of calcified and curved root canals

Root canal calcification is a common problem in root canal therapy, which can cause root canal obstruction and even make root canal orifice difficult to find. Dental pulp calcification is a pathological process caused by external stimulation of dental pulp. The degree of calcification is related to different stimuli, and the difficulty of clinical treatment is different.

1. The pulp opening of curved calcified root canal should be as convenient as possible, and all pulp tips should be removed, sometimes more tooth tissue needs to be sacrificed, and the pulp opening wall should form a straight channel with the root canal wall.

2. Finding and determining the root canal orifice is the key first step to deal with calcified root canals. The most important tools are straight tip probe and root canal probe. The pulp chamber floor is hard dentin. Under certain pressure, the probe can enter a little bit at the root canal orifice and feel stuck. At this time, X-ray should be used to determine whether it is a root canal orifice, and if necessary, a microscope should be used to determine it. Most root canals bend at 1 ~ 2mm, so the cervical dentin should be removed. If you can't find the root canal orifice, you can use 2 # long round drill or ultrasonic wave to enter the root canal orifice 1 ~ 2mm. Black pulp floor and white restorative dentin are the signs of finding root canal orifice. Root canal lubricants (including EDTA) are helpful to find the root canal orifice.

(1) patency and preparation of calcified root canals: 08 # and 10 # files are the most effective tools for expanding root canals. Pay attention to the tip of pre-bending 1mm, mark the bending direction of the file with a plug, dip the tip of the file in root canal lubricant, rinse it with a large amount of flushing agent, and file the root canal file gradually, and repeat it repeatedly, deepening 65438+ each time. When the file reaches the working length, it should be determined according to the X-ray film and pulled up and down to enlarge the root canal to a sufficient working length. After the root canal is unobstructed, various methods can be used for preparation.

(2) Preparation of curved root canal: First, pre-curved root canal file is needed. Pre-curved root canal file can easily pass through the curved part and slide over the obstacle point to reach the apical area. Pre-bending includes file tip pre-bending and full file pre-bending, which are prepared in the opposite direction of bending. The pre-expansion and preparation of root canal orifice and root canal crown 2/3 facilitate the smooth entry of pre-bent root canal files. Select 12 #, 17 #, 22 #, 27 #, 32 #, 37 # and other intermediate root canal files. After the small file is fully prepared, change the file number 1. When preparing to bend the root canal, it should be noted that the working length should be re-determined every 3 # expansion. The root canal is seriously bent, and the initial file can reflect the direction and degree of root canal bending, so we should observe it carefully and pay attention to the deformation of root canal at any time. The primary root canal deformation caused by root canal file is not obvious, but the accumulation of multiple preparation effects will produce greater root canal deformation, resulting in the stenosis of root canal preparation not in the apical area, but in the form of tears a few millimeters away from the apical area. In order to avoid the opening of apical foramen, it is best to remove the cutting ability outside the tip of root canal file. Select the middle root canal file, enlarge the crown of root canal first, and adopt the method of gradual deepening or crown downward preparation. Pay attention to full irrigation and use root canal lubricant; Do not over-rotate the instrument; When the root canal file is difficult to enter, be sure to use the middle number; Prepare slowly. In the preparation of hyperbolic root canal, the crown of root canal should be fully enlarged, and the crown curvature should be removed or straightened as much as possible to obtain a good passage into the apical area. Once the small root canal file reaches the apical area, do not lift it completely. Instead, use a file to pull up and down a few millimeters until the resistance disappears. Otherwise, it may be difficult to re-enter the same pipeline file.

3. The discovery and treatment of the second buccal root canal of the upper molar.

Clinically, after root canal treatment of some maxillary molars, the apical lesions of mesiobuccal roots still exist or form new lesions, which are often caused by the absence of MB2. In the past, it was reported that the incidence of mb2 in isolated teeth was 5 1.5%~95.2%, and it was 18.6%~77.2% in clinic. Microscopically, the clinical cure rate of MB2 can reach over 90%.

The mesiobuccal root canals of maxillary molars can be divided into four types: 1 type: from root orifice to apical foramen; Type 2: it enters from two root canal orifices, but merges into a tube above the apical foramen to form the apical foramen; Type 3: two root canal orifices and two apical foramen form two independent root canals; Type 4: Enter the root from a root orifice and form two apical foramen respectively.

MB2 root canals are located near buccal root canals, with a distance of (0.93 ~ 2.438+0) mm. Mb2 root canals are located in the middle of the line between buccal roots and palatal roots (MB-P), with a vertical distance of (0.25 ~ 0.81) mm; The included angle between MB-MB2 and MB-P is 9.99~36. 15 degrees.

Clinical examination of MB2: When the X-ray parallel or offset projection shows that the root canal image or the diagnostic wire is not in the root canal center, we should highly doubt the existence of MB2, follow the relationship between MB2 and other root canal orifices, apply ultrasonic method or long round drill near MB-P line, and remove dentin 1 ~ 2mm appropriately, and then use DG 16 probe or root canal orifice probe to find the root canal orifice, preferably. Care should be taken to avoid excessive search, which will lead to bottom penetration or side penetration.

4. The discovery and treatment of C-shaped root canals of mandibular molars.

Type C root canals mostly occur in mandibular second molars. The incidence of type C root canal system of mandibular second molars in China is very high, ranging from15.8% to 45.5%, which is significantly higher than that in Europe and America (below 8%). Because of the complex root canal shape and root canal variation such as high accessory root canal and communicating branch apex triangle, it is easy to cause root canal loss or three-dimensional imperfection of root canal filling, so the treatment of C-type root canal is considered to be a challenge to clinicians.

Because of the special shape of C-shaped root canal, in order to show the characteristics of C-shaped root canal, Melton et al. classified the shape of C-shaped root canal in vitro. Haddad participated in the classification of C-shaped root canals in 1999, and classified C-shaped root canals into three types: 1 type: continuous C-shaped root canal orifice to apical foramen; Type 2: the root canal orifice is semi-colon-shaped, and dentin separates the independent proximal root canal orifice from the distal C-shaped root canal orifice; Type 3: the root canal orifice is discontinuous, arranged in a C shape, and divided into 2 or 3 independent root canals downward.

C-shaped root canal appears in the fused root. Many scholars think that X-ray can't be used to diagnose C-shaped root canals, but through research, we find that the horizontal X-ray before C-shaped root canal surgery has the following characteristics:

Characteristics of (1) root: A is single, pyramidal, square or nodular, with rope or spindle-shaped X-ray density reduction area in the middle. B image has two roots, the root tips are wide and square, and the root tips of the "two roots" are connected by periodontal ligament images; The trabecular bone, periodontal ligament and root bifurcation between "double roots" are not clearly shown.

(2) The characteristics of medullary cavity A are in a cone-shaped single root. It is often seen that the images of two root canals converge in the apical area of 1/3 and merge into a low-density area of X-ray. A small and blurred third root canal image can be seen between the proximal and distal root canal images.

(3) These X-ray features are helpful to judge the existence of C-shaped root canal before clinical operation.

C-shaped root canals, accessory root canals, communicating branches, apical triangle and other root canals have a high incidence of variation, so we should pay attention to the combination of mechanical preparation and chemical preparation in root canal preparation. If possible, we can rinse the root canal with ultrasonic file and irrigation solution after preparation. After perfecting the root canal preparation, it is best to use hot gutta percha vertical pressure method to fill the root canal, so as to better fill the communicating branches and root canals.

5. Treatment of teeth with undeveloped root tips

Apical hypoplasia can be seen in teeth with inflammatory pulp, pulp necrosis or apical mutiny. The treatment scheme should be determined according to the pulp condition and root development level. Vital pulpotomy is used for young permanent teeth with trauma or dental caries. Ca(oh)2 or root canal cement (MTA) can be used to cover the pulp. Regular observation shows that the formation of roots usually takes 2 ~ 3 years. If it fails, root tip induction or root canal therapy should be performed. Apical induction plasty is suitable for young permanent teeth with incomplete apical development.

The procedure of Ca(oh)2 root tip induction molding: after pulp opening, pulp is pulled out, root canal is ready, and the working length is shorter than the X-ray root tip length. After the finished Ca(oh)2 paste or the mixture of Ca(oh)2 and Baso 4 (9: 1) was mixed with physiological saline, the root canal was filled tightly and the crown was filled tightly, and regular observation was made. The exudate from root tip can dissolve Ca(oh)2 in root canal. Once X-ray shows that Ca(oh)2 in the root canal area is not compact, it should be re-treated and re-filled with Ca(oh)2. After the root tip was formed, the Ca(oh)2 paste was taken out and the root canal was filled. Steps of root tip induction molding of MTA: After root canal preparation, seal and disinfect the root canal with Ca(oh)2 paste for one week, put MTA into the root tip area for 3 ~ 4 mm, and fill it tightly. After the surface of MTA was temporarily sealed with a wet cotton ball for one week, the upper part was filled with gutta percha root and the crown was tightly filled.

In some cases, apexification may fail again after early success, which may be due to insufficient sealing of the root canal system, re-invasion of bacteria and toxins, or longitudinal or transverse fracture of the root canal wall. So at least four to five years of observation. It should be noted that the systematic cleaning and preparation of root canals and the tight filling of crowns are as important as Ca(oh)2 or MTA apical induction materials.

Vertex operation of intransitive verbs

After the failure of root canal therapy, root canal retreatment should be carried out first, and the success rate of root canal retreatment is above 60%. Therefore, only a few cases need apical surgery. Indications of apical surgery: A Anatomical factors: such as calcified blockage and severe bending of root canal, failure to prepare and fill perfect root canal, and extensive absorption in apical area leading to treatment failure. B. Accidents in treatment: equipment breakage, shoulder, perforation and overcharge lead to treatment failure. Root canal obstruction: such as post and core, silver needle, non-removable root filling, amalgam and so on hinder root canal retreatment. D persistent symptoms: after improved root canal treatment, the symptoms did not improve for a long time. After all possible factors are excluded, we can consider conducting apical surgery to find and deal with possible causes, such as root longitudinal fissure, absence of accessory apical foramen, apical bifurcation, perforation, overfilling and so on.

Contraindications for apical surgery: First of all, we should pay attention to the patient's general condition and exclude non-surgical indications. Secondly, apical surgery is prohibited for patients with tooth position, maxillary sinus and mandibular nerve canal, short tooth root and severe periodontal disease.

Matters needing attention in apical surgery: 1 Length and angle of apical resection: 3mm parallel resection of apical area can remove more than 93% of the major accessory root canals, which is a suitable resection length. The traditional cutting slope is 45 degrees, which is convenient for observation and operation. At present, it is considered that the cutting surface less than 10 degree is ideal. 2. Root tip preparation: The ideal method is to prepare the head with ultrasound, prepare 3mm along the root canal direction, remove the contents of the root canal and prepare the root canal to form an inverted retention form. 3 apical inverted filling materials: there are many inverted filling materials, such as amalgam, glass ionomer cement, IRM, super EBA and MTA. The most ideal material at present is MTA. Hemostasis is very important in apical surgery. Anesthetic drugs containing adrenaline can be used to press the gauze containing adrenaline into the bone cavity, and ferrous sulfate solution or calcium sulfate can be used to help stop bleeding. 5 After backfilling, the bone cavity should be washed with normal saline before suture to avoid debris staying in the bone cavity.

Seven. Treatment of internal and external root resorption

The causes of internal and external root resorption are different, and the treatment methods and prognosis are also different. Therefore, internal and external absorption should be distinguished according to X-ray and clinical manifestations, and appropriate treatment methods should be selected.

X-ray apical films and occlusal flaps are used to distinguish internal and external root resorption: the internal absorption boundary is smooth and symmetrical, the root canal at the absorption site is thick, the external absorption boundary is rough, the density is different, and it is gnawing and asymmetrical, and the original contour of the root canal can be found before the root canal is destroyed. When offset projection is used, the relationship between internal absorption and root canal position remains unchanged. At the same time, the external absorption position changes. Internal absorption starts from the inner wall of pulp cavity or root canal and is related to pulpitis and bacterial infection. Generally asymptomatic, found in multi-position X-ray photography. Root canal therapy should be carried out as soon as possible. The prognosis of infected tissue is good after resection, otherwise further development will cause perforation of root canal wall. It is difficult to remove the infected tissue in the internal absorption site, so full irrigation or ultrasonic oscillation irrigation is an effective cleaning method, and the root canal is sealed with Ca(oh)2 paste for one week before root filling. Because of irregular internal absorption, it is best to use hot gutta percha vertical pressure technology for root filling. If the internal suction is too large and the root canal wall is very thin, excessive pressure should be avoided, and Ca(oh)2 paste and gutta percha should be used for root filling. The perforation of root canal wall is relatively small. Ca(oh)2 paste can be used for root filling for 3 months, and then root filling can be carried out after inducing the formation of hard tissue. Or root canal filling and restoration with MTA. The larger perforation of root canal wall can be repaired by MTA or surgery in root canal. Periapical surgery can consider absorption in the near apical area, and root cutting can be considered for multiple teeth.

Root resorption begins with periodontal tissue, and the reasons are mostly trauma, excessive corrective force, embedded teeth, tooth bleaching, and periapical periodontitis of replanted teeth. The treatment of periapical exoabsorption caused by periapical periodontitis is the same as that of internal absorption, and other factors cause periapical exoabsorption by corresponding treatment and root canal treatment.

Eight. Removal of damaged instruments

In the process of root canal treatment, instruments may break, and smooth, prepared and perfect root canal filling will lead to the failure of treatment. Therefore, it is necessary to take out or pass the foreign body in the root canal. There are many methods to remove the broken instruments in root canal, including ultrasound, H-file, cannula and apical surgery. The main reasons for the broken instruments are: 1 the root canal file itself is unqualified, or the file is rusted after being soaked in disinfectant for too long; 2. Improper use, skipping or overexertion of root canal file during root canal preparation; 3. Because of the aging of teeth, the root canal is too thin and curved; Repeated use of 4-tube file leads to metal fatigue; Nickel-titanium instruments are generally not damaged by naked eyes under fatigue.

Equipment and operation techniques for taking out broken instruments in root canals by different methods;

Establishment of (1) access: in clinical operation, after X-ray confirmed the position of broken needle, under the observation of root canal microscope (magnification 10 ~ 20 times), the root canal file with handle was inserted into the root canal until the coronal section of broken needle was marked with a plug to determine the depth of broken needle. Then prepare the root canal at the upper part of the broken needle to 30 ~ 40 # with K file or H file, grind the tips of 2 # and 3 # with GG drill to make the plane diameter of the tip of GG drill larger than the diameter of the broken needle, prepare the root canal from the root canal orifice to the position of the broken needle with 2 # or 3 # adjusted GG drill, and establish a channel to make the root canal at the upper part of the broken needle clear, which is convenient for microscope observation and intraoperative operation.

(2) Ultrasonic extraction method: ultrasonic instrument (85-264VAC, SATELEC), replaceable K file, ET20/ET40 root canal expander. Clinically, other root canals were sealed with cotton balls, and then the broken needle root canals were established under the microscope. Then, ultrasonic power is set at the root canal treatment file, and the ultrasonic K file is gently pressed down on the crown, so that the ultrasonic K file or ET20/ET40 enters between the broken needle and the root canal wall until the upper part of the broken needle vibrates counterclockwise around the broken needle. In most cases, the broken needle often floats out with the washing liquid or is taken out by the file.

(3)H-files removal method: after the channel is established, a certain gap is formed around the broken needle by ultrasonic method, three H-files are inserted around the broken needle, and the three H-files are rotated counterclockwise, so that the broken needle is tightly bitten and removed. Suitable for removing broken spiral packing and H file.

(4) Casing extraction method: After the access is established, ultrasound (1/3) exposes the crown of the broken needle in the root canal, breaks the outer sleeve of the needle sleeve, and inserts the wedge into the sleeve. At this time, the broken needle will wedge out of the side window at the tip of the cannula. At this time, take out the cannula and wedge, and the broken needle will be taken out with the child.

(5) Clamp-out method: If the broken needle is located at 1/3 of the root canal, the broken needle can be taken out with forceps after the access is established, or it can be taken out with forceps after the broken needle is shaken loose by ultrasound.

(6) Auxiliary extraction method of pulp-pulling needle: when the instrument is broken and the pulp-pulling needle is pulled out, or when the screw filler is used, it is used to try to take off the broken needle with the barb of the pulp-pulling needle.

Although there are many ways to take out broken instruments, there are still many broken instruments that are difficult to take out. There are two main reasons that affect the removal of broken instruments: one is the root canal depth, cross-sectional diameter and root canal curvature where the broken needle is located. Generally speaking, if the broken instrument length of 1/3 can be exposed, it can often be taken out; If the broken instrument is in a straight root canal, it is easier to take it out; If the broken instrument is located at the root canal bend, the dentin thickness allows the passage from the root canal orifice to the crown of the instrument to be established, and the broken needle can also be taken out; However, if the broken needle is located below the root canal bend to the apical area, it is difficult to establish a safe passage and take out the broken needle instrument. Secondly, the type of broken instruments is also an important factor affecting the removal. It is easier to take out broken instruments such as spiral fillers; However, nickel and titanium may break again under the heat of ultrasonic wave, which is difficult to take out.

Attention should be paid to the following points when taking broken needle instruments: 1 When using ultrasonic to take broken needles from multiple tooth positions, the broken needles may flow from one root canal to another root canal orifice. To prevent this from happening, cotton balls should be placed in other root canals or other root canals should be filled in advance; Under the heating of ultrasonic wave, the nickel-titanium instrument may break again and fall deeper into the root canal. Therefore, attention should be paid to avoid excessive power when taking needles by ultrasound to prevent excessive heat production. In order to avoid lateral puncture or pushing the broken needle out of the apical foramen, we should have a clear vision when removing the dentin around the broken needle to avoid exerting force on the broken needle.

Prognostic observation: Not all broken instruments will affect the effect of root canal therapy. Whether the broken needle is taken out or passed through, the preparation, cleaning and filling of the deep root canal can be completed. If the broken instrument is wedged into the root canal at the apical part and cannot be taken out, the root canal is basically clean, the affected tooth has no clinical symptoms, and the instrument liquid that has not been taken out plays the role of root filling. Preparation and root filling should be carried out, and regular observation should be made, and apical surgery should be carried out if necessary. If the broken instrument exceeds the apical foramen, it is feasible to perform apical surgery after the inflammation of the affected tooth is eliminated. Preparation and root filling can be performed, regular observation can be made, and apical surgery can be performed if necessary.

Nine. Acute attack during root canal therapy

Acute attacks during root canal therapy include pain between appointments and reaction after filling. Although the treatment process is very careful, postoperative pain and swelling are sometimes inevitable and unpredictable. Most of the postoperative reactions were mild discomfort (40%), about 25% cases would have moderate and severe pain, and 2% ~ 4% cases would have acute attacks. Postoperative reaction is related to the patient's condition, dental pulp and root tissue and treatment steps. Patients with preoperative pain and swelling, pulp necrosis or acute periapical periodontitis are more likely to have acute attacks. Using long-acting anesthetics, improving root canal shaping and cleaning, giving analgesics and preparing patients psychologically can effectively reduce the pain between two appointments. Therefore, it is very necessary to tell patients the possible situation, degree and duration of postoperative pain. Prophylactic use of antibiotics has little effect on relieving postoperative pain and is unnecessary, but for patients with infection or systemic diseases, antibiotics should be used under the guidance of doctors. When acute apical symptoms or abscesses occur, the pulp cavity should be opened or cut and drained. Mild to moderate pain can take aspirin and ibuprofen; Ibuprofen and codeine can be taken for moderate and severe pain, and hormone drugs are generally not used. In addition, the use of long-acting local anesthetics is also helpful to delay the severe pain of root canal treatment. X. Analysis of factors influencing the long-term curative effect of root canal therapy

1. Dental pulp status before root canal therapy: The dental pulp status before root canal therapy is a controversial influencing factor. It is generally believed that the success rate of root canal therapy for living teeth is higher than that for dead teeth.

2. Root tip status before root canal therapy: Root tip mutiny before root canal therapy will reduce the success rate of root canal therapy by 7.5%~ 14%. However, it is still controversial whether the size of apical mutiny affects the long-term effect of root canal therapy.

3. Root canal preparation methods and filling techniques: There is no significant difference in the influence of different preparation methods on the success rate of root canal treatment; The success rate of cold lateral pressure filling is higher than that of no lateral pressure filling, and the success rate of full-length root canal filling is higher than that of apical filling alone, but the difference is not statistically significant. The size of the main file for root canal preparation has no obvious effect on the long-term curative effect of root canal treatment.

4. Root canal filling materials: the combination of gutta percha tip and root canal filling paste is the most commonly used method in clinic. There are many problems in root canal filling with paste or silver needle combined with paste, which is not a desirable method.

5. Apical filling quality: divided into two factors: apical filling position and apical filling density. The evaluation standard of root tip area abroad is the same: the distance between root canal filling and X-ray root tip position is 0 ~ 2 mm, and insufficient filling or excessive filling will reduce the effect of root canal treatment. In addition, if the apical area is not tightly filled, the long-term effect of root canal therapy will be significantly reduced. The root tip area is not tightly filled, which makes microorganisms have living space; However, there are many apical lateral branches in root canals. Under the condition of not dense filling, tissue fluid is easy to penetrate and provide nutrition for bacteria, which eventually leads to the failure of root canal treatment.

6. Crown restoration after root canal therapy: Crown restoration should be a necessary step to improve root canal therapy. Without good crown restoration, the long-term effect of root canal therapy will be affected.

7. Recurrent accidents in root canal therapy: lateral penetration and broken instruments in root canal therapy have certain influence on the effect of root canal therapy. The main reason is that the root canal preparation, irrigation and filling are difficult under the condition of lateral puncture or broken instruments, which leads to an increase in the failure rate of root canal treatment; However, with the application of root canal microscope, ultrasound and good repair materials (such as MTA), the accidents in root canal treatment can be dealt with in time and the long-term curative effect can be improved.

By consulting the literature, the above factors have a significant impact on the long-term curative effect of root canal therapy: the filling quality of apical area, the apical state before root canal therapy and the crown restoration after root canal therapy. Therefore, ensuring the position and three-dimensional compactness of apical fillings, properly sealing the medicine according to the pulp condition, and timely crown restoration and quality assurance after treatment are the prerequisites for obtaining good long-term root canal treatment. I don't know.