Technical points of root canal treatment and retreatment after failure

Technical points of apex preparation

01 This step must be completed in the state of isolation of the surgical field. The purpose is to remove the infection and prepare for the subsequent root canal filling, including multiple techniques such as medullary cavity entry and preliminary preparation, positioning of the root canal orifice, root canal dredging, determining the working length, root canal cleaning and shaping, and root canal irrigation. The pulp cavity entry and initial preparation should be based on the anatomy of the tooth, the number of root canals and the distribution type to determine the shape of the pulp cavity, and preserve the normal dental tissue as much as possible. Ultrasonic instruments help to safely remove restorative dentin or other calcifications covering or covering the root canal orifice. Surgical microscopes and optical magnification equipment can provide better magnification and lighting effects, help identify different tissues, operate accurately, and reduce damage. Opening the upper section of the root canal and removing the residual pulp After positioning the root canal orifice, opening the upper section of the root canal first helps the small instruments and irrigation fluid reach the apical one-third area, and helps to remove the residual pulp. Root canal dredging and working length determination During the whole process of root canal preparation, the root canal should be filled with root canal irrigation fluid. Sodium hypochlorite solution is recommended. Unblock the root canal to obtain suitable root canal orientation, thickness and patency. Use an apex locator to determine the working length. When the working length cannot be determined by using the apex locator alone or in doubt, the apex X-ray film inserted with the diagnostic wire should be taken to confirm. The determined working length is the main reference for root canal preparation, irrigation and filling. Root canal cleaning, shaping and flushing Root canal shaping needs to follow the working length, keep the root canal unobstructed and the original direction and taper of the root canal, and prevent debris and irrigation fluid from going beyond the apical hole. When using stainless steel or nickel-titanium rotating instruments, the relevant rules for the use of the instruments should be followed. Ultrasonic instruments for ultrasonic irrigation can help improve the root canal irrigation effect after root canal preparation. Ultrasonic irrigation is recommended after the preparation of infected root canals. Treatment of instrument separation Due to uncertain factors such as root canal anatomy variation, operation difficulties, and instrument material fatigue, occasionally the instrument separation and left in the root canal may occur. In order to prevent the separation of the device, it is necessary to maintain and inspect the device before treatment, and use it in a standardized manner during treatment. Whether to remove the instruments left in the root canal after separation should be determined according to the specific clinical situation and weighing the pros and cons. When deciding not to take it out, the remaining part of the root canal should be filled and the relevant information should be recorded in the medical record. After the root canal preparation, the root canal can be filled immediately after the root canal is prepared, or the medicine can be sealed in the clinic according to the condition, and the root canal can be filled after the clinical situation is suitable. Crown closure requires reliable sealing materials to temporarily fill the medullary cavity at the interval between two visits. For the situation where the temporary sealing material is easy to fall off, it is recommended to use glass ionomer cement or composite resin material. Note on preparation of calcified root canal:

1. A large amount of NaOCl flushing

2. The root canal file slowly enters the root canal

3. Clean the debris of the root canal file and check the root canal file every time.

4. When the working length is reached, it should be determined according to X-ray.

5. Do not use strong acid or alkali to assist preparation

6. Use EDTA paste or liquid to assist preparation

7. Ultrasound assisted preparation

8. Fully expand the root canal orifice and the expanded root canal part.

9. The root canal orifice can be opened with a Nitinol root canal expander. Technical points of root canal filling.

02Current root canal filling technologies include lateral pressure filling technology, vertical pressure technology, hot gutta-percha filling technology, hybrid filling technology and solid core filling technology. It is generally believed that the hot gutta-percha vertical pressure filling effect is the best. The timing of root canal filling is based on the clinical situation. You can choose to fill the root canal immediately after the root canal is prepared, or you can perform root canal filling at an optional time. For cases of inflammatory exudation or clinical symptoms of apical periodontitis, root canal filling should be performed after the symptoms are relieved and the infection control is effective. The basic goal of root canal filling is to use biocompatible and biologically inert materials to seal and clean the formed root canal cavity, prevent leakage, and achieve the purpose of controlling infection, promoting root apex sealing and root apical lesion healing. The main material of the root canal filling material is currently the main clinical application of gutta percha (a mixture of natural gum and zinc oxide), which is used in conjunction with a sealant. Root canal sealer is used in conjunction with gutta percha to seal dentin tubules and fine root canal cavities to increase the seal between the material and the root canal. The new root canal sealing material should have the effect of promoting the growth of normal tissues around the apex. Technical points Before filling, the root canal should be thoroughly rinsed and wiped dry. Choose the right main tip and try the tip. The amount of blocking agent should not be too much. Cold side pressure or hot vertical pressure technology is used to ensure the filling of the root canal, especially the dense one-third of the root canal filling. After the filling is completed, the residual root filling material in the medullary cavity is cleaned, and the root canal orifice and the medullary cavity are effectively sealed. Filling method, quality control standard a, the distance between the filling and the root tip is less than or equal to 2mm.

b. The filling is dense, continuous, and the taper is appropriate.

c. After filling, the gutta-percha tip is 2～3mm below the root canal orifice, and the small stuffer is cold pressurized.

d. For under-filled patients, it is necessary to prepare for filling again. In principle, over-filling is not recommended to be repeated. Follow-up and apical surgery if necessary. Current research shows that under the same premise of other factors, the prognosis of overcharge is worse than undercharge. Closure and temporary filling of the pulp cavity From the root canal filling to the permanent restoration of the tooth, the pulp cavity should be tightly sealed to prevent re-infection of the root canal. When the defect is limited to the shape of a pulp hole and a short period of time (such as 1-2 weeks), zinc oxide cement can be used: when the defect is large or requires a long observation period, glass ionomer cement or composite should be used Resin materials. Tooth restoration should be arranged as soon as possible after the completion of the root canal treatment. Timely dental restoration is not only necessary to restore the functional and beautiful teeth, but also to prevent leakage from the crown and ensure the efficacy of root canal treatment. Dental restoration after root canal treatment includes composite resin direct bonding restoration, inlay restoration, full crown restoration and post-core crown restoration. The amount of remaining tooth tissue should be considered during restoration, and the retention and resistance of the pulp cavity should be effectively utilized. For the restoration of posterior teeth, occlusal force and functional requirements should be considered, and restoration methods covering the tip of the tooth should be adopted to avoid tooth splitting. Pay attention to prevent re-infection of the root canal by opening the medullary cavity again during repair. No matter which repair method is used, the integrity and sealing of the root apex 5 mm root filling material should be maintained as much as possible to prevent the infection from the crown from migrating to the root apex. Premature or excessive load may affect or delay the healing of larger periapical bone lesions. For such cases, the observation period should be appropriately extended and permanent dental restoration should be postponed. The healing effect of bone lesions can generally be initially shown on X-ray films after 3 months. Re-treatment after root canal failure 031 Take out the broken instrument The traditional method of taking out the broken instrument includes the following 3 kinds:

①Physical methods, Roig-Greene method, Masserann instrument method, IRS instrument removal system (instrument removal system), ultrasonic extraction method;

②Chemical method, electrolysis method, Wass method;

③Surgery methods, filling method, reverse removal method, apical resection, etc. The casing clamping method (Patent Publication No.: CN103405275A; CN104665940A) invented by Professor Fan Bing makes it easy to take out the broken instruments. Ultrasonic instruments have the irreplaceable advantages of other methods in the removal of root canal fracture instruments or foreign bodies. It is the most effective way to remove root canal fracture instruments or foreign bodies. Most instruments that are broken in the root canal can be used in the root canal microscope by ultrasonic technology. Take it out with the aid of.

2 Repair perforation Perforation is an abnormal passage between the root canal system and the periroot tissue caused by pathological or iatrogenic factors. Mineral trioxide aggregate (MTA) is a new type of biocompatible material. It is in the form of a powder and becomes a gel after mixing with water. It will completely solidify after about 4 hours. MTA can be used to repair accidental perforation of the floor or side wall of the medullary chamber during treatment, and the effect is better. Although accidental perforation can reduce the success rate of root canal treatment, Krupp and other studies have shown that 90 cases of MTA repaired perforated root canal treatment patients have a recovery rate of 73.3% after 3 to 4 years of follow-up. Siew et al. reported that the success rate of using MTA to repair perforations was 80.9%.

3 Pain management and prevention Patients with chronic apical periodontitis, pulpitis and pulp necrosis usually have no spontaneous pain, or the pain is mild. In order to avoid acute periapical periodontitis during the treatment process, the operating procedures should be strictly followed during treatment; the principles of aseptic operation should be strictly followed when handling infected root canals; drug prevention and treatment should be used; ultrasound and laser can also be used And microwave prevention, etc. The root canal preparation procedure adopts the crown-to-root preparation, first remove the spoilage residue in the upper and middle section, and gradually prepare to the root to avoid pushing the infected material out of the root apical hole. 4 Discomfort and pain after root canal treatment Some patients still have persistent pain after root canal treatment. Ricucci et al. reported that the presence of bacterial infection around the root canal is the main cause of pain after root canal treatment, such as the underside of the root canal, within the apical granuloma, and bacterial biofilm on the root surface. Another reason is the presence of micro-leakage. The fifth-generation adhesive (Excite) and the sixth-generation adhesive system used clinically have a deproteinizing effect and can prevent the occurrence of microleakage. Postoperative pain caused by missing root canals is not uncommon.