Fracture incidence of instruments from a single-file reciprocating system by students in an endodontic graduate programme: a cross-sectional retrospective study.

AIM: To assess the fracture incidence of instruments from single-file reciprocating systems when used by students in an endodontic graduate programme. METHODOLOGY: Dental records and periapical radiographs of patients treated by students on an endodontic graduate programme using reciprocating systems were assessed. Data on tooth type, number of treated root canals, number of fractured instruments, fragment size, angle, radius, arc length and position of root canal curvature where fractures occurred were tabulated for analysis. The risk of fracture was calculated for each group of teeth, root canal and root thirds, whilst the incidence of fractures reported for the reciprocating systems was compared using the chi-squared test at 5% significance level. RESULTS: Overall, 2056 root canals (826 teeth) from 810 patients were included. The incidence of fractured files from single-file reciprocating systems in relation to a number of instrumented canals was 0.92%. Fracture rates of 0.84% and 0.93% were found in 830 and 1226 root canals instrumented with WaveOne and Reciproc systems, respectively. No significant differences were observed between the systems. The highest fracture rate was 52.6% in the mesiobuccal root of mandibular molars. The central angle, radius and arc length of the curvature of root canals where the instruments fractured ranged from 58° to 84°, from 1.7 to 7.2 mm and from 2.4 to 7.6 mm, respectively. CONCLUSION: The use of WaveOne and Reciproc single-file reciprocating systems in an endodontic graduate programme was associated with a low incidence of instrument fractures.

Influence of reciprocating single-file and rotary instrumentation on bacterial reduction on infected root canals.

AIM: To compare the bacterial reduction achieved with reciprocating and rotary systems during root canal preparation. METHODOLOGY: Sixty distobuccal root canals of maxillary molars were contaminated with Enterococcus faecalis broth culture. After an incubation period of 21 days, bacterial samples were collected and cultured on m-Enterococcus agar plates. The root canals were divided into five groups, according to the system used for instrumentation: WaveOne, Reciproc, ProTaper, Mtwo and manual instrumentation. The negative controls consisted of five uncontaminated root canals that were subjected to the same instrumentations as each of the experimental groups. Bacterial samples were collected immediately and 7 days after instrumentation. Statistical analysis was performed by paired t-tests and anova tests. RESULTS: Compared with the samples before instrumentation, the bacterial count was significantly reduced after instrumentation in all groups, with no significant difference in bacterial count reduction amongst the reciprocating, rotary and manual techniques. However, the samples tested 7 days after instrumentation showed significantly higher bacterial counts than the samples tested immediately after instrumentation. CONCLUSIONS: All systems tested reduced bacterial counts to a similar level.

Histological evaluation of the osteoinduction capability of human dentine.

Aim To assess whether human dentine has the potential to promote the development of calcified tissues when implanted in the muscle tissue of mice. Methodology Root canals in extracted human teeth were instrumented to produce dentine fragments. The dentine fragments produced were divided into two. In group 1, fragments were demineralized and sterilized. In group 2, the fragments were not submitted to any additional treatment. The dentine fragments were then implanted in the muscle of mice. In group 3, the muscles were implanted with rehydrated lyophilized human bone powder. Animals were killed following test periods of 7, 15, 30, 60, 120 and 180 days, the fragments were removed together with adjacent muscle and examined under light microscopy to assess calcification. Results Areas of calcification were observed in groups 1 and 3 after a period of 180 days. In group 2, the surrounding tissues displayed only chronic inflammatory infiltration. Conclusions On the basis of the experimental model adopted in this study, fibroblast-rich connective tissue formed in groups 1 and 3, which could reflect an osteoinductive process. Further studies are suggested to identify which dentinal factors are capable of inducing the formation of a calcified matrix.