Clinical Diagnosis And Treatment Of Calcified Root Canals

Endodontic diseases and periapical diseases are common clinical oral diseases, and the currently widely recognized treatment method isroot canal therapy (RCT). With the widespread development of root canal therapy, more and more calcified root canals are found during the treatment. Conventional root canal preparation often fails to clear the root canal and accurately establish root canal access. Blind exploration or preparation can easily lead to root canals. Wall side penetration or formation of steps will cause greater difficulties for subsequent treatment. This article will review the related research on calcified root canal treatment.

Classification of calcified root canals

Calcified root canals can be divided into partial calcification and complete calcification according to the X-ray dental film images. Partial calcification is manifested as the pulp cavity image is not obvious, the root canal image is reduced but clearly visible, and the complete calcification is almost invisible on the X-ray dental film. The root canal image or image is not clear. Clinically, according to the location of calcification, it can be divided into calcification of the medullary compartment, 1/3 of the crown of the root canal, 1/3 of the middle of the root canal, and 1/3 of the apical calcification. There is also a special type of calcified root canal, called root canal calcification (calcific metamorphosis, CM), which is the characteristic rapid hard tissue deposition in the root canal after pulp injury, which usually occurs in patients with tooth concussion or subluxation trauma. tooth. It is manifested by the deposition of hard tissue in the root canal, root canal obstruction, and yellowing and discoloration of clinical crowns

The mechanism of calcified root canal

Root canal calcification is a manifestation of dental pulp calcification, which can be an age-related change. As we age, the number of blood vessels in the pulp tissue decreases and collagen fibers increase. At the same time, secondary dentin deposits, the lumen shrinks, and the root canal is narrowed, eventually causing varying degrees of calcification or blockage in the root canal.

Dental pulp calcification can also be an active restoration response of the dental pulp. The dental pulp tissue produces a defense response under stimuli such as caries, periodontal disease, trauma, abrasion, etc., and the permeability of damaged dental pulp cells increases. The influx of ions increases, and the intracellular phosphate groups co-precipitate with it. The denatured and necrotic dental pulp cells are used as the calcification center to form calcification foci, and the odontoblasts accelerate the secretion of reactive dentin, which ultimately leads to the calcification of the dental pulp to form a pulp stone Or diffuse calcification, blocking the root canal.

Preoperative evaluation of calcified root canals

Calcified root canal is the current difficulty in clinical treatment. The treatment failure rate is 20% to 70%. The degree and range of root canal calcification are important factors that affect the success rate of treatment. Therefore, effective assessment of the degree of root canal calcification and the difficulty of treatment is the treatment of calcification. The important premise of root canal mainly includes two aspects: imaging evaluation and clinical evaluation. It is worth noting that not all calcified root canals need root canal treatment. The teeth without clinical symptoms and X-ray periapical abnormalities do not need to undergo root canal treatment immediately. The choice is made according to the specific clinical needs.

Methods of establishing calcified root canal channels

Detection method of root canal orifice calcification:

Root canal omission is one of the common reasons leading to root canal treatment failure, and root canal and root canal orifice calcification is the main cause of root canal omission. There are a variety of methods to explore the root canal orifice in clinic, such as: micro-ultrasound technology, imaging examination, staining method, immersion method, transillumination method, etc., which can help the surgeon to improve the discovery rate of calcified root canal orifice.

Preparation methods for calcification in the root canal:

At present, the calcified root canal can be dredged mainly through the physical preparation of instruments and chemical reagents.

Application of Type C Pioneer File

The C-type Pioneer File is a manual instrument designed for narrow, curved and calcified root canals. Compared with the K file, its tip has high hardness and no cutting ability, good posterior toughness and strong flexural resistance, and it is easy to enter narrow and blocked root canals. , Passing through the space around the calcification, and better adapting to the curvature of the root canal, maintaining the original shape and direction of the root canal, and avoiding deviation or perforation. The efficiency of dredging calcified root canals has been affirmed by scholars. In the study by Cai Huaxiong and others, the success rate of K file combined with EDTA group to dredge molar curved calcified root canals was 50.4%, while the success rate of C-type pioneer file combined with EDTA group was 83.8%. No complications occurred. For difficult molar calcification root canals such as curved or lower root canal calcification, when the use of ultrasonic instruments is limited, the C file combined with EDTA can be used to dredge in stages to improve the success rate of treatment.

Application of Nitinol System

Nickel-titanium instruments have good flexibility, can conform to the curved direction of the root canal, and reduce complications such as root canal perforation. Its large taper design can relieve the false appearance of root canal calcification caused by root canal obstruction and bending. Some scholars have proposed that the tip of the nickel-titanium instrument has no cutting force, and the forward guiding force generated in the blocked root canal can be used to break through the calcified part by means of a "percussion drill". Zhao Junjun et al. used nickel-titanium instruments combined with EDTA to re-dug the calcified root canals that failed to dredge the C-type Pioneer file combined with EDTA. The dredging success rate was 65.71%, but the problem of device separation was also found in the study. The application of nickel-titanium instruments in the treatment of calcified root canals still needs further research.

Micro-ultrasound technology

The micro-magnification system can provide good light and magnification effects, helping the surgeon to accurately determine the direction of the root canal and the distribution of calcifications. The cavitation effect, sound wave effect, stirring effect, and thermal effect produced by ultrasound can improve the dissolution and removal of dentin debris and smear layer, remove calcification in the root canal, and dredge the narrow root canal. Combining the high-efficiency cutting function and oscillation effect of the micro-amplification system with the ultrasonic instrument is applied to the calcified root canal, so that the fine ultrasonic tip can accurately act on the working area and effectively remove the calcified material in the root canal.

Many scholars have combined ultrasonic instruments and micro-amplification systems to treat calcified root canals and have achieved good results, increasing the discovery rate of calcified root canals and the success rate of dredging to 74.0% to 90%. However, the application of micro-ultrasound in the treatment of calcified root canals has certain limitations. This technique has high requirements for physicians, and requires preliminary microscopy basic training and standardized operation. Calcification is located in the lower part of the root canal and at the curved part. Due to the unclear vision and the inability of ultrasonic instruments to adapt to the curvature of the root canal, ultrasonic instruments should be used with caution to avoid complications such as steps, root canal deviation, and lateral penetration.

Chemistry preparation

Cation chelating agents such as ethylenediaminetetraacetic acid (EDTA) and NaClO are commonly used clinical root canal irrigation solutions. EDTA can complex with calcium ions in calcified tissue to dissolve it, and NaClO can dissolve organic matter including collagen matrix. Sayin et al. found that when EDTA and NaClO are used in combination, they can remove more calcium ions, help demineralize dentin, and generate a large number of bubbles to efficiently remove the dentin smear layer, while helping the device to obtain lubrication and higher cutting ability . Some scholars have shown that temporary sealing of EDTA reagent in the root canal for 1 week can increase the rate of calcification and obstruction of the root canal. However, some scholars believe that the use time of EDTA should be controlled within 1 min. More than 10 minutes will excessively erode the dentin, which is not conducive to tooth preservation; some scholars believe that the chelating agent only plays the role of lubricating and removing the smear layer in the short time of root canal dredging. There is no obvious effect of removing calcifications. At present, the effectiveness and safety of EDTA in dredging calcified root canals remain to be studied.

CT guide technology

In recent years, CT guide technology has also been used in the treatment of calcified obstructed root canals. It is modeled on the production of oral implant guides, and CBCT is used to establish a precise guide track for dredging partially or completely calcified root canals, which can reduce the risk of perforation. This technology has been applied to the clinic, and its safety and clinical feasibility have been confirmed. Meer et al. and Krastl et al. used CBCT and intraoral scanners to obtain dental information, computer software processed the data to construct a three-dimensional structure, and finally used 3D printing technology to make personalized guide plates and instruments, and successfully treated the anterior teeth with calcified root canals.

Domestic scholars have also reported the use of 3D guides combined with micro-ultrasound technology to successfully dredge the calcified root canals of the anterior teeth. But at present, the scope of application of this technique is narrow, and it is only suitable for straighter root canals or the straighter crown of curved root canals. There is no systematic research on the application of calcified root canals, and further research and development are needed.

In summary, the diagnosis and treatment of calcified root canals are full of difficulties, requiring high theoretical knowledge and technical requirements for the operator, as well as good cooperation from the patient. Before treatment, the surgeon should have accurate cognition and judgment on the condition of root canal calcification and the difficulty of treatment. At present, there is no single technology that can treat calcified root canals independently. The treatment should be rationally selected according to clinical needs, and multiple treatments can be combined in order to obtain better treatment results.