Clinical Study Of The Blocked Canals

Blocked canals were often met in the clinic and the treatment was very difficult and time-consuming, sometimes accompanying with the sequela of transportation and perforation. The common reasons of block include calcified canals, obturation and foreign materials and so on. Many studies were made on the removal of gutta-percha and metal obstacles. But as for the resinifying treated teeth and calcified canals there was seldom reported. The purposes of this thesis were to investigate the retreatment of the resinifying treated teeth and the calcified pulp teeth and analyze factors affecting the success of retreatment.The clinic study of the retreatment of failed resinifying treated teeth To study how to remove the FR resin from the resinifying treated teeth and renegotiate the canals, analyze the factors affecting negotiation. Collecting 56 resinifying teeth that need retreatment, the symptoms and radiography outcome were recorded. Before the retreatment, the X-ray film was taken and read to affirm the direction and position of the curvature. If the canals were curved, the coronal parts of the canals were flared-up with G-burs to reduce the curvature before the negotiation. After removing the coronal obturation, the orifices were located under the dental microscopy. The 15# K-file was used to explore the degree of the polymerized FR resin. If the 15# K-file could deepen into the canals, it was proven the FR resin was partly polymerized and 15 K-file was used to remove the FR resin, then 20#,25#,30#,35# files were used in turn. The canals were irrigated with 2.5% NaOCl when changing the file. If the 15 H-file could not deepen into the canals, the LN was used to remove the FR resin from the orifices and then rechanged to ultrasonic files along the trace of FR resin to remove the resin. If the canals were curved the FR resin was removed to the middle 1/3 with ultrasonic files, 15# or 10# K-file was rechanged to remove the FR resin with picking or stroking action until to the apex. At the meanwhile the canals were irrigated with 2.5% NaOCl. During the negotiation, X-ray films were taken to observe and adjust the direction of negotiation when necessary. It was thought as FR resin complete removal that the canals were smooth and the file was no FR resin. The working length was determined with the X-ray film.If the file could not reach the apex, it was thought as failure. After negotiation, the canals were reinstrumented with hybrid preparation technique, filled with cold gutta-percha by lateral condensation technique. The tooth was restored and recalled periodically. During the retreatment the negotiated canals, broken files, perforation and the incidence of postoperation pain were recorded. The results were analyzed statistically. It was found that 42 cases were successfully retreated and 14 cases failed including 3 cases perforated, 1 case file broken. 16 cases had postoperative pain. All of the premolars were successfully retreated. The success rate of cases with apical radiolucent area was significantly higher than that of no apical radiolucency (P<0.05). The interval length of two treatments had significant effect on the outcome of negotiation (P<0.05).There was significant difference between the incidence of postoperative pain and apical lesion (P<0.05). The results showed that the length of two-treatment interval, apical lesion and teeth positions had significant effects on the success rate of the retreatment.The treatment of calcified canalsThe aim of this study was to investigate how to treat the cases with calcified canals and what affect the treatment outcome. 35 teeth with calcified canals, which need root canal treatment, were collected. The present and past histories of the teeth were collected and the clinic examination and periodontal and apical status were recorded. The X-ray films with different angle were taken. The calcified degree and position was determined. The treatment plan was made. When treatment the pulp was accessed at first. If the pulp chamber was also calcified, the pulp was obtained...