Effectiveness of four electronic apex locators to determine distance from the apical foramen.

AIM: To evaluate the accuracy of four electronic apex locators (EAL) in the apical region (0-3 mm short of the foramen) and to compare the precision of the readings on the display with the real position of the file in the root canal. METHODOLOGY: Twenty single-rooted extracted teeth with round root canals were used. The canal orifices were preflared, and the length to the major foramen was determined visually under a microscope. Canals were enlarged, so that a size 15 file fitted well inside the canal. Teeth were mounted in acrylic test tubes filled with physiologic saline solution. Electronic length was determined in the region between the major foramen and 3 mm short of it in 0.5 mm steps with the Dentaport ZX, Root ZX mini, Elements Diagnostic Unit and Apex Locator and Raypex 5 using files of size 10 and size 15. The data were analysed using linear regression between true length and EAL reading, Bland-Altman plots and nonparametric tests at a significance level of alpha = 0.05. RESULTS: The major foramen was detected by all EALs. With a measurement file positioned directly at the major foramen, meter readings were equivalent to a position 0.01-0.38 mm away. For the Dentaport ZX, a better accuracy using the size 15 file for the area 0-1.5 mm short of the apex was found. The differences in measurements between the two files were smaller for the other EALs. In linear regression, a good linearity for Dentaport ZX and Root ZX mini and moderate linearity for Elements Diagnostic Unit and Apex Locator and Raypex 5 were found. The slope of the measurement curve was too low (0.37-0.57) for the Raypex 5 and almost optimal for the Dentaport ZX (1.01-1.05). The Root ZX mini and the Elements Obturation Unit produced lower slope values and especially the Elements Obturation Unit revealed much higher SDs at the different measurement levels. CONCLUSION: Amongst the four EALs, the Dentaport ZX and Root ZX mini had the best agreement between true lengths and meter readings. For the Raypex 5, an interpretation of the colour-coded zones as distance to the foramen cannot be recommended and might lead to erroneous interpretations.

SEM evaluation of root canal debridement with Sonicare CanalBrush irrigation.

AIM: To determine the efficacy of Sonicare CanalBrush irrigation for root canal cleaning. METHODOLOGY: Fifty human molar root canals were shaped with sequential NiTi rotary instruments up to size F3 (size 30, 0.09 taper; ProTaper system) and then enlarged apically with a Profile size 40, 0.04 taper. Five different irrigation protocols were tested (n = 10 canals per group) with 2 mL of distilled water (control, group I) or 2.5% NaOCl (control group II and test groups III, IV and V) between instrument size changes. Group III-IV received a final rinse with 17% EDTA for one min. This was extended by 30 s in group IV, whereas group V received this additional 30 s of 17% EDTA sonically dispersed with a Sonicare CanalBrush. For cleanliness evaluations, roots were split longitudinally, examined with scanning electron microscopy and scored according to Hülsmann et al. (1997) for debris and smear layer on the surface of the root canal wall. Walls were assessed at the coronal, middle and apical thirds. Data were analysed with the Kruskal-Wallis and Mann-Whitney tests. RESULTS: Irrigation with 17% EDTA significantly reduced debris and smear layer scores (P < 0.05) compared to controls. The coronal and middle thirds had lower debris and smear layer scores than the apical third (P < 0.05). In all thirds, sonic agitation of the irrigant with a CanalBrush (group V) resulted in significantly cleaner canal walls compared to all other groups (P < 0.05). CONCLUSIONS: Irrigation by agitation with the Sonicare CanalBrush improved root canal debridement in the coronal, middle and particularly the apical thirds of the root canal.

Micro-CT evaluation of residual material in canals filled with Activ GP or GuttaFlow following removal with NiTi instruments.

AIM: To assess the efficacy of removing Activ GP or GuttaFlow from canals using NiTi instruments. METHODOLOGY: Root canals in 55 extracted pre-molars were prepared to apical size 40, 0.04 taper. The teeth were imaged with micro-CT, and 30 teeth selected that had consistent apical size and taper of the shaped canals. They were randomly assigned to root filling with either the glass-ionomer-based ActivGP system (n = 15) or the polyvinylsiloxane-based GuttaFlow system (n = 15). After 2 weeks, canals were retreated stepwise with size 40-50 EndoSequence 0.04 taper instruments. Micro-CT scans (8 mum) were taken after use of each instrument to detect root filling residue in the coronal, middle and apical segment, and the retreatment time recorded. Residue, expressed as percentage of canal surface area, was compared between groups with t-tests, and within groups with repeated measures anova and Bonferroni-adjusted pairwise comparisons. Retreatment time was analysed with one-way anova. RESULTS: The percentage of sealer residue-coated canal surface was consistently highest (P < 0.001) in the apical third of canals, and it did not differ significantly between the two root filling groups. Stepwise enlargement from size 40 to 50 significantly decreased the amount of sealer residue in both groups (P < 0.001). Retreatment time did not differ significantly between groups. CONCLUSIONS: Both root fillings with ActivGP and GuttaFlow were removed with nickel-titanium rotary instruments. Enlargement of canals up to two sizes beyond the pre-retreatment size was necessary to minimize the amount of sealer remaining.

Antimicrobial activity of various 'active' gutta-percha points against Enterococcus faecalis in simulated root canals.

AIM: To test the antimicrobial activity of various gutta-percha points against Enterococcus faecalis in simulated root canals. METHODOLOGY: Root canals were simulated by inoculated glass capillaries. A 2.5 microL increment of a suspension of E. faecalis was placed into 10 simulated root canals together with Calcium Hydroxide(R) points (CHP), Calcium Hydroxide Plus(R) points (CH+P), active points(R) (AP), conventional gutta-percha points (CP) (Coltène Whaledent, Langenau, Germany) or no points (NP) (control) (each n = 2). The points and simulated root canals were flushed with 2 mL of sterile saline solution after 10 min or after 5 h of anaerobic incubation (37 degrees C, 100% humidity). Dilution sequences until 10(-3) and 10(-4) were prepared and plated on agar plates. The original suspension, diluted until 10(-6) and 10(-7), served as another control. The numbers of colony forming units were counted after 24 h. This experimental procedure was repeated 15 times. RESULTS: Without gutta-percha points, bacteria grew threefold in number within 5 h. With CHP and CH+P bacterial counts at 10 min and 5 h were approximately 50% compared with the control. AP killed all bacteria within 5 h. With CP, bacteria proliferated more than without points (counts at 5 h 177% of NP). Except for CHP versus CH+P differences between groups were statistically significant (Mann-Whitney test, P < 0.01). CONCLUSIONS: In this experimental model, the potential of CHP and CH+P to kill E. faecalis was limited. CP stimulated bacterial growth. AP killed all bacteria after 5 h.