Eight special problems of root canal therapy

I. omission of root canal findings

Omitting the root canal is one of the common causes of root canal treatment failure. Periapical X-ray diagnosis means missing the root canal. No matter how the X-ray radiographic angle, when there is only one root canal, root canal is located in the central image is always the root. When the X-ray shows that the root canal image is not in the central part of the tooth, there is a high suspicion of other root canals. X-ray offset (near or mid) is the best way to show and assess the presence of missing root canals and to determine the location of the missing root canals (cheeks or tongue). In addition, the X-ray offset can separate the overlapping root canal images, determine the direction and curvature of the root canal bend, determine the location of foreign bodies and perforation in the root canal, and locate the calcification, the direction of the root canal and so on.

For the single root canal teeth, if the image changes suddenly, prompting the following: from the medullary cavity separated large two root canals; a wide root tube into two root canal; premolar and anterior teeth by double root canal began to separate.

When using X-ray radiography, if there is another penetrating ray (root canal image) parallel to the diagnostic wire in the upper part of the root canal, another tube should be highly suspected.

In addition, familiarity with the anatomy of the medullary root canal system and observation of the change in the location of the root canal orifice will also help to find the missing root canals.

Two. Treatment of calcified and curved root canals

It is a common problem in root canal treatment. It can cause root canal obstruction and even difficult to find the root canal orifice. Pulp calcification is the pathological change process of dental pulp subjected to external stimulation. The degree of calcification is related to different stimuli, and the clinical treatment is difficult.

1. for curved calcified root canals, the opening of the root canal should be as convenient as possible. Removal of the entire crest of the bone, and sometimes the need to sacrifice more dental tissue, should lead to a straight line through the wall of the root canal.

2. finding and determining the root canal orifice is a critical first step in dealing with calcified root canals. The most important tools are the straight head dental tip probe and the root canal orifice probe. The bottom of the pulp chamber is a hard dentin. The probe can enter a little at the root canal at a certain pressure and has a sense of obstruction. This time the X-ray is used to determine whether it is the root canal orifice and should be microscopically determined if necessary. Most of the root canal at 1 ~ 2mm bending, cervical dentin should be removed; if you still can't find the root canal, can use 2 oblong drill or ultrasonic root canal into 1 ~ 2mm. The dark pith floor and the white restoration dentin are the marks for the root canal mouth. Root canal lubricants (including EDTA) are helpful in finding the root canal orifice.

(1) patency and preparation of calcified root canals:

No. 08 and No. 10 file is the most effective tool for expanding Roberto tube, pay attention to the tip of the 1mm pre bending, bending direction by the stop mark file, the file tip dipped in root canal lubricant, with a large number of cleaning, the root canal file gradually into the file repeatedly, each time, grow 1 ~ 2mm. When the file reaches the working length, it should be determined according to the X - ray and made up and down movements, so that the root canal can be extended to the length of work. After the root canal is unobstructed, various methods can be used to prepare it.

(2) preparation of curved root canals:

First, bend the root canal file, and the pre curved root canal file is easy to reach the tip through the bend. Pre bending is divided into two kinds. The end of the file is pre bent and the whole file is pre bent. The root canal orifice and root canal crown 2/3 are pre expanded and ready to facilitate pre curved root canal file smoothly.  Select the middle number root canal file, such as 12, 17, 22, 27, 32, 37. The small file is fully prepared and then replaced with the next file. When bending the root canal, each extension of 3 should be taken to re confirm the length of the work.  Serious curved root canal, the initial file can reflect the direction and extent of the root canal bending, should be carefully observed, pay attention to the deformation of the root canal at any time. A root canal file caused by pipe deformation is not obvious, but the cumulative effect of repeated preparation will produce large deformation resulting in the root canal, root canal stenosis in the apical area, but far from the apical area of a few millimeters, a teardrop. In order to avoid the opening of the apical hole, it is better to remove the cutting ability on the outside of the apex of the root canal file. Select the middle number of root canal file, root canal crown extension first, and adopt the method of step by step or crown downward preparation. Pay attention to adequate irrigation and use of root canal lubricant; do not over rotate the appliance; when root canal files are difficult, use intermediate numbers; slow down when necessary.

The root canal crown should be fully extended when the root canal is prepared, and the crown curve can be removed or straightened as far as possible to obtain a good passage into the root tip area. Once the small root canal file reaches the tip area, the file should not be fully put forward. To file with a few millimeters up and down until the resistance disappears. Otherwise, it may be difficult even if the same pipe file is re entered.

Three. The discovery and treatment of the second root canals (MB2) of the upper molars and mesial roots

Clinically, lesions of the mesial root of the mesial teeth still exist or become new lesions after the root canal treatment of some maxillary molars, often due to the omission of MB2. In the past, the incidence of MB2 in the isolated teeth was 51.5%~95.2%, and the clinical rate was 18.6%~77.2%. The clinical treatment rate of MB2 was more than 90% by microscopy.

The maxillary molars can be divided into 4 types:

Type 1: from one root orifice to one apical foramen;

Type 2: enter from the two root canals, but above the apical foramen, fuse into a single tube to form a apical foramen

Type 3: two root canals and 2 apical pores formed 2 independent root canals;

Type 4: enter the root from a root orifice and form 2 apical pores.

The root canal orifice of MB2 was located in the mesial buccal root canal, and the distance between MB2 and MB was (0.93~2.01) mm. The MB2 root canal orifice is located near the root canal