Comparison of two negative pressure systems and syringe irrigation for root canal irrigation: an ex vivo study.

AIM: To compare in a laboratory study two negative pressure systems and syringe irrigation, regarding the delivery of a contrast solution (CS) to working length (WL) and into simulated lateral canals and the effective volume of irrigant aspirated during negative pressure irrigation. METHODOLOGY: Twenty single-canaled incisor training models were constructed with six simulated lateral canals each (2, 4 and 6 mm to WL) and a size 40, 0.04 taper apical size canal. Each model underwent all irrigation procedures (EndoVac at WL (EndoVac-0) and WL-2 mm (EndoVac-2), iNP needle with negative pressure (iNPn) and syringe irrigation with the iNP needle (iNPs) and a 30-G side-slot needle placed at WL (SI0) and WL-2 (SI2) mm in a crossover design. CS was delivered at 4 mL min(-1) for 60 s with a peristaltic pump and a recovery device collected the volume (in mL) of irrigant suctioned by the negative pressure groups. The irrigation procedures were digitally recorded, and a still image of the 60-s time-point of irrigation was evaluated for CS distance to WL (in millimetres) after irrigation and penetration into lateral canals (3-point scale). Statistical tests used were Kruskal-Wallis and Dunn's test. RESULTS: EndoVac-0, iNPn and iNPs had median distances of CS to WL of 0 mm, followed by SI0 (0.2 mm), SI2 (0.7 mm) and EndoVac-2 (1.7 mm). There were no significant differences between EndoVac-0, iNPn, iNPs and SI0, but these were significantly different to SI2 and EndoVac-2 (P < 0.05). There were no significant differences between the volume of CS delivered by syringe irrigation and that collected by iNPn (4 mL), but these were significantly greater than EndoVac-0 (2.8 mL, P < 0.001) and EndoVac-2 (2.85 mL, P < 0.001), which were not different to each other (P = 1.0). The irrigation procedures were ineffective at penetration into lateral canals. CONCLUSION: iNPn, EndoVac-0, iNPs and SI0 achieved greater irrigant penetration to WL. iNPn was able to collect a median volume of CS (4 mL) similar to that delivered by syringe irrigation (iNPp, SI0 and SI2). An adequate irrigant penetration into lateral canals could not be achieved by any of the systems.

The effect of endodontic procedures on apical crack initiation and propagation ex vivo.

AIM: To evaluate the potential effects of endodontic procedures (instrumentation and filling) on crack initiation and propagation in apical dentine. METHODOLOGY: Forty extracted single-rooted premolars with two canals were selected, 1.5 mm of the apex was ground perpendicular to the long axis of the tooth and the surface polished. The specimens were divided into 4 groups. The buccal canals of groups A, B and C were enlarged to size 40 with manual K-files. Group A was filled with gutta-percha using lateral condensation and vertical compaction without sealer. Group B was filled with the same method as group A except only lateral condensation was used. Group C was left unfilled, while group D was left unprepared and unfilled. Images of the resected surface were taken after resection (baseline), after canal preparation, after filling and after 4-week storage. The images were then inspected for cracks originating from the canal. RESULTS: A significant effect of preparation on crack initiation (P < 0.05) and no significant effect of filling (P > 0.05) or 4-week storage on crack initiation (P > 0.05) was found (logistic regression). Fisher's exact test revealed a significant effect of filling on crack propagation (P < 0.05) and no effect of 4-week storage on crack propagation (P > 0.05). CONCLUSIONS: Root canal procedures can potentially initiate and propagate cracks from within the root canal in the apical region.

Periapical bone defects of root filled teeth with persistent lesions evaluated by cone-beam computed tomography.

AIM: To evaluate and categorize the bone defects of root filled teeth with persistent periapical lesions by cone-beam computed tomography (CBCT). METHODOLOGY: Slice images of 532 teeth with persistent periapical lesions were obtained by CBCT in 427 patients and were examined by two endodontists. The periapical lesions were categorized into five types according to the characteristics of the bone defect based on CBCT images. The prevalence of each type was determined and analysed statistically at a 5% significance level using logistic regression. RESULTS: Of the 532 teeth analysed, 67% had buccal or labial bone plate defects (type II), 4% palatal or lingual bone plate defects (type III), 7%'through and through' defects (type IV) and 10% apical root protrusions from the bone plate (type V). Mandibular teeth had a significantly greater prevalence of type I lesions (P=0.0005) and a significantly lower prevalence for types IV (P=0.041), V (P=0.001), V-1 (P=0.015) and V-2 (P<0.001) as compared to maxillary teeth. CONCLUSION: CBCT accurately identified the type of periapical bone defect in persistent lesions. Because 10% of the teeth had apical root protrusions, which could not be identified by periapical radiography, the diagnostic information obtained by CBCT was an essential component of the treatment planning process.

Incidence of accessory canals in Japanese anterior maxillary teeth following root canal filling ex vivo.

AIM: To investigate the vertical and horizontal distribution and the incidence of accessory canals in Japanese maxillary anterior teeth following root filling. METHODOLOGY: The study included maxillary teeth; 69 central incisors, 61 lateral incisors and 31 canines. After the canal systems had been dyed and root canal instrumentation had been carried out, all prepared canals were filled with gutta-percha without using sealer. Transparent specimens were then obtained and examined with a digital microscope for horizontal and vertical distributions of accessory canals. RESULTS: The incidence of teeth with accessory canals in the apical 3 mm was 46%, 29% and 38% for the maxillary central incisors, lateral incisors and canines, respectively. The horizontal distribution was mainly buccal for central incisors, palatal for lateral incisors and distal and palatal for canines. There was a significant difference (P < 0.05) between the apical 3 mm and the rest of the root (16%, 20% and 19% for the maxillary central incisors, lateral incisors and canines, respectively) in terms of the presence of accessory canals. CONCLUSIONS: A high percentage of accessory canals can be found in apical 3 mm of the root. The horizontal distribution of accessory canals differed amongst the tooth types studied.

The effect of working length and root canal preparation technique on crack development in the apical root canal wall.

AIM: To evaluate the effects of working length and root canal preparation technique on crack development in the apical root canal wall. METHODOLOGY: Seventy extracted mandibular premolars were mounted in a resin block with simulated periodontal ligaments and divided into seven groups according to preparation technique and working length: group A, step-back preparation with stainless steel files with working length set at the apical foramen and defined as root canal length (CL); group B, same as for A, except that the working length was CL-1 mm; group C, crown-down preparation with Profile instruments followed by an apical enlargement sequence with CL as working length and group D, same as for C, except that the working length was CL-1 mm. Groups E, F and G served as controls. Groups E and F were prepared only with the crown-down sequence up to CL and CL-1 mm, respectively. Group G was left unprepared. Digital images of the apical root surface (AS) were recorded before preparation, immediately after instrumentation and after removing the apical 1 mm (AS-1 mm) and 2 mm (AS-2 mm) of the root end. RESULTS: Working length significantly affected crack development at AS (P < 0.05). Preparation technique significantly affected crack development at AS-1 mm (P < 0.05). At AS-2 mm, there was no significant difference between preparation technique and working length in terms of crack development on the canal wall. CONCLUSION: Root canal preparation alone, regardless of the technique used, can potentially generate cracks on the apical root canal wall as well as the apical surface. Working 1- mm short of the apical foramen might produce fewer cracks in the apical region.

Distance from file tip to the major apical foramen in relation to the numeric meter reading on the display of three different electronic apex locators.

AIM: To establish and compare the relationship between the distance from the file tip to the apical foramen and the numeric meter reading on the display of three different electronic apex locators (EALs). METHODOLOGY: A total of 12 extracted intact, straight, single-rooted human teeth with complete roots were used. The actual root canal length (AL) was determined after access preparation. For the electronic measurements with each EAL, silicon stops were fixed with auto-polymerizing resin to size 15 K-files at AL and 0.5, 1, 2, 3, 4 mm short of AL. The data was analysed by two-way anova and Tukey's honestly significant difference (HSD) test for multiple comparisons amongst EALs. Additionally, one-way anova and Tukey's HSD test were carried out for multiple comparisons amongst the measurements of each EAL. RESULTS: There was a statistically significant difference amongst all EALs in indicating the position of file tips in relation to the major foramen (P < 0.05). The correlation between the meter reading and the position of the file tip from the apical foramen was statistically significant in the three EALs. There were significant differences amongst the measurements at distances from 0 to 2 mm in Justy III. In Dentaport, significant differences were found from 0 to 1 mm. However, the E-Magic Finder showed significant differences from 0 to 0.5 mm. CONCLUSIONS: Justy III was more capable of displaying the intracanal position of the file tip from the major foramen in mm whilst advancing through the root canal during electronic measurements than the Dentaport and E-Magic Finder Deluxe.