Effect of number of uses and sterilization on the instrumented area and resistance of reciprocating instruments

Objectives

This study evaluated the effect of repeated uses and autoclaving in the instrumented area, fracture resistance, and time of instrumentation of thermally treated nickel-titanium reciprocating systems.

Materials and Methods

Two hundred simulated canals were instrumented using Reciproc Blue and WaveOne Gold. Each file was used up to 10 times or until fracture. The instrumented area was measured in pre- and post-operative images, using ImageJ software. Kaplan-Meier survival analysis evaluated the number of uses of instruments before fracture. Instrumented area and time of instrumentation were analyzed by Mann-Whitney U test and Kruskal-Wallis. Correlations among the number of uses and instrumented area were measured. The level of statistical significance was set at p < 0.05.

Results

Reciproc Blue presented a higher estimated number of uses in comparison with WaveOne Gold (p = 0.026), but autoclaving did not affect the resistance to fracture of instruments (p > 0.05). The instrumented area was different among the evaluated groups (p = 0.039), and the instrumented area along the uses of both tested instruments was reduced. With the time of instrumentation, there was also a significant difference among the evaluated groups; the groups without sterilization cycles were faster, in comparison to those submitted to autoclaving (p = 0.010).

Conclusions

Reciproc Blue was more resistant than WaveOne Gold, suffering later fracture. Additionally, the sterilization cycles did not influence the estimated number of uses of thermally treated reciprocating instruments, but the instrumented area of root canals was reduced along with the repeated uses of both instruments.

Endodontic treatment during COVID-19 pandemic

Aim: This study evaluated, by the application of questionnaires, the impact of the COVID-19 pandemic on the clinical routine and inspection by the competent authorities, on the flow of patients in the office, as well as on possible changes in Endodontic treatment costs and the amounts charged to patients. Methods: This cross-sectional study was conducted from May 2nd, 2020 to May 6th, 2020, using an online questionnaire with a convenience sample. The inclusion criterion was professionals who perform endodontic treatments in daily clinical practice and who professional setting is private practice. The questionnaire brought questions about the impact on costs and the amount charged to the patient. Results: A total of 1042 questionnaires were answered from all the different states of Brazil, by professional who usually perform Endodontic treatment, and who is working in private practice. A total of 1010 (96.9%) respondents affirm it was necessary to modify the protective equipment in endodontic treatment due to pandemic and longer intervals between appointments was cited by 922 (88.5%), economically affecting the dental practice. There was no association between routine changes and economic impacts with gender, professional experience, area of residence or education level. Conclusion: In conclusion, most dental professionals recognized changes in the routine of endodontic treatment during the COVID-19 pandemic. They have a perception of increase in endodontic costs, and reduction in the volume of patients.

12-Year Follow-Up of Regenerative Endodontic Treatment of Immature Permanent Upper Incisors with Acute Abscess

This case report discusses the endodontic treatment of a 7-year-old girl who suffered trauma (intrusion) to the immature upper central incisors secondary to a fall from a bicycle. Thirty days after the accident the patient was brought by her mother for clinical and radiographic assessment with a chief complaint of swelling and tenderness to percussion and palpation. Acute apical abscess associated with immature teeth were diagnosed. A decision was made to perform regenerative endodontic treatment. Access cavities were made and the root canals were disinfected by irrigation with 2.5% sodium hypochlorite. Final irrigation was performed with 17% EDTA. Due to pain and presence of secretions, 2% chlorhexidine gel was applied as an intracanal medicament. Seven days later, at the second visit, the root canals were once again disinfected and the canals of the right and left permanent upper central incisors were filled with double antibiotic paste (metronidazole/ciprofloxacin) and calcium hydroxide paste, respectively. Zinc oxide was mixed in both pastes. At the third visit, after 21 more days, the pastes were removed and the periapical areas were stimulated with a #80 K-file to encourage clot formation within the pulp cavities. A mineral trioxide aggregate (MTA) paste cervical plug was placed and the teeth were restored with glass ionomer cement. Radiographs and CBCT scans demonstrated complete root formations. The patient has been followed for 12 years, with evidence of clinical success throughout.

Influence of reuse and cervical preflaring on the fracture strength of reciprocating instruments

Objective:

This study sought to assess the influence of cervical preflaring and reuse after resterilization, on fracture strength and plastic deformation and/or surface cracking in reciprocating nickel–titanium [NiTi] endodontic instruments after root canal instrumentation of extracted human teeth.

Materials and Methods:

Forty engine-driven reciprocating NiTi instruments (20 Reciproc^® [RC], VDW; 20 WaveOne^® [WO], Dentsply) were used in root canal instrumentation of extracted human molars. A total of 485 human upper molars with similar anatomical features were selected and randomly distributed across four groups according to the instrumentation procedures performed (G1 and G3: RC; G2 and G4: WO). Reciprocating instruments were used as per manufacturer instructions. In groups G3 and G4, cervical preflaring was performed prior to instrumentation. After each use of each instrument, sterilization was repeated and scanning electron microscope (SEM) images were obtained to check for plastic deformations and/or cracks on instrument surfaces. Each instrument was used repeatedly until fracture occurred.

Results:

Regardless of flaring, RC files exhibited greater fracture strength than WO instruments (P <0.01) with and without preflaring. Cervical preflaring significantly reduced the risk of instrument fracture (P <0.01). No plastic deformations were observed before fracturing. However, cracks were found on WO instruments shortly after their first use. RC and WO instruments resisted fracturing after autoclave sterilization.

Conclusions:

Cervical preflaring allowed a significant increase in the number of times RC and WO files could be reused safely.