Can size 20, .04 taper rotary files reproducibly create a glide path for the self-adjusting file? An ex vivo study in MB canals of mandibular molars.

AIM: To test and compare the effectiveness and safety of two size 20, .04 taper rotary files that were used to create a glide path for the self-adjusting file (SAF) in curved canals of mandibular molars. METHODOLOGY: Forty mandibular molars with curved mesial roots and narrow MB root canals were selected based on a passage of size 15 K-files to WL; size 20 K-files could not reach WL. Only roots with no visible microcracks were included. Two types of size 20 rotary files were used for glide path preparation, the new Pre-SAF size 20, .04 taper file and the ProFile size 20, .04 taper, which served as the reference and control. Both files were used with 3-4 pecking strokes, which brought them to WL. Two parameters were tested whether the glide path allowed manual insertion of a 1.5-mm SAF file to WL and whether the procedure caused microcracks in the root dentine. Paired t-tests were used to compare the groups. RESULTS: Glide path preparation with both files allowed the manual insertion of the SAF file to WL in all 20 root canals, with no difference between the two groups. No cracks were detected after the procedure in any of the roots in either group. CONCLUSIONS: Both types of size 20, .04 taper rotary files were effective for glide path preparation for the SAF file in curved canals. Neither file type caused microcracks in root dentine.

Apical debris extrusion associated with oval shaped canals: a comparative study of WaveOne vs Self-Adjusting File.

OBJECTIVES: The aim was to evaluate ex vivo apical debris extrusion associated with WaveOne and Self-Adjusting File instruments when used in oval canals. METHODS: Twenty-four extracted human mandibular premolars with oval-shaped canals were assigned in two equal groups. Following coronal cavity preparation, a glide path was created. Group A was subjected to canal preparation using a WaveOne primary file, which was used along with syringe and needle irrigation and 10 mL of 2.4 % NaOCl solution, followed by flushing with 10 mL of 17 % EDTA solution, activation with EndoActivator for 1 min and final flushing with 10 mL of 2.4 % NaOCl solution, and activation for 30 s. Group B, the SAF system was used with continuous simultaneous irrigation, provided by the system's pump. The irrigant was supplied at 5 mL/min, alternating every minute between 2.4 % NaOCl solution and 17 % EDTA solution, over a total of 4 min followed by final flushing with 10 mL of 2.4 % NaOCl solution. Extruded apical debris from each root canal was collected into a preweighed glass vial and dried. The mean weight of the debris from each group was assessed and analyzed statistically. Both systems resulted in apical debris extrusion. RESULTS: The WaveOne system was associated with a statistically significant greater mean mass of apically extruded debris (2.18 ± 0.44 mg) than the SAF system (0.49 ± 0.33 mg, permutation-based Wilcoxon test, p < 0.001). CONCLUSION: Both WaveOne and the SAF systems were associated with apical debris extrusion. The amount of debris extruded by the WaveOne system was 4.4 times greater than that extruded by the SAF system. CLINICAL RELEVANCE: The results of the present ex vivo comparative study cannot be directly applied to the clinical situation. Difference between both groups remains completely unclear; maybe the amount of extrusion is harmless in both groups or similarly deleterious for the periradicular tissues in both groups or may be dose-related to the amount of the extruded material.

Towards antibacterial endodontic sealers using quaternary ammonium nanoparticles.

AIM: To change and characterize the antibacterial properties of endodontic sealers by incorporating low concentrations of insoluble antibacterial nanoparticles (IABN). METHODOLOGY: The antibacterial effect against Enterococcus faecalis was evaluated by (i) agar diffusion test (ADT), (ii) direct contact test (DCT) and (iii) scanning electron microscopy (SEM). IABN were incorporated into AH Plus (Dentsply, DeTrey Konstanz, Germany) and GuttaFlow (Coltène Whaledent, Langenau, Germany) at concentrations of 0.5%, 1% or 2% weight/weight. Bacterial growth rates were analysed using ANOVA followed by Tukey's test. RESULTS: The antibacterial tests demonstrated total bacterial growth inhibition using AH Plus samples incorporating 2% weight/weight IABN after 4 weeks (P < 0.005). DCT showed total growth inhibition of up to 6 logs in viable count in AH Plus samples incorporating IABN and up to 4 log in count in GuttaFlow incorporating IABN (P < 0.005). Significant differences were found between the unmodified sealers and the experimental groups. No antibacterial effect was observed in the ADT, indicating IABN were not diffusing into the agar. Furthermore, SEM indicated bacterial cell wall damage and lysis. CONCLUSIONS: AH Plus and GuttaFlow incorporating low concentrations of IABN exhibited significant and stable antimicrobial properties.

[Failure in the orthodontic treatment of impacted maxillary canines].

Maxillary canine impaction occurs in 1-3% of most Western populations and its orthodontic treatment is often difficult. Failure to resolve the impaction is not uncommon and may lead to malpractice lawsuits. The information in the literature about the reasons for non-resolution of this condition is sparse and unsubstantiated. This encourages the dispensing of inappropriate treatment that may result in severe tooth, soft and hard tissue damage as well as a prolonged treatment period. This review describes the epidemiology, pathogenesis and the wide range of reasons that may lead to failure to resolve the canine impaction. It shows that a lack of appreciation of anchorage demands and inaccurate positional diagnosis of the 3-D location and orientation of impacted teeth are the major reasons for failure. In addition, the review shows that invasive cervical root resorption (ICRR) is a frequently undiagnosed or unrecognized cause of failure of orthodontic resolution of impacted canines, and should be distinguished from replacement resorption (ankylosis). Corrective measures which may lead to successful treatment are further recommended. Special emphasis is placed on the crucial role of cone beam computerized tomography in the accurate radiographic diagnosis and early detection of pathology of impacted tooth and damage to adjacent anchor teeth. The importance of teamwork in achieving the best treatment outcome is stressed.

The effectiveness of a self-adjusting file to remove residual gutta-percha after retreatment with rotary files.

AIM: To test the efficacy of a two-stage retreatment method in which the Self-Adjusting File (SAF) is used to remove root canal filling residue left in the canal after using ProTaper Universal retreatment files. METHOD: One of the curved mesial canals of 25 extracted mandibular molars was instrumented up to ProTaper F2, followed by NiTi K-files up to size 45 and filled. Radiographs of these canals served as a pre-treatment control, which was later compared with those of the same canals after each stage of the retreatment procedure. Stage 1 consisted of ProTaper Universal D1-D3 retreatment files, which were used to remove the bulk of root filling material, followed by stage 2 in which a SAF file was applied to remove the remaining root canal filling residue. The amount of the radiopaque material in each third of the canal was evaluated before and after each stage, using bucco-lingual and mesio-distal radiographs. The amount of residue was expressed as the per cent of the root canal filled area, as measured in the pre-treatment control. The difference between the control and results of the first and second stages of retreatment was analysed using the Wilcoxon signed-rank test. RESULTS: Radiopaque residue was present after the use of the ProTaper Universal rotary files in 7.8 (± 12.9)%, 12.9 (± 13.9)% and 34.7 (± 22.8)% of the coronal, mid-root and apical areas, respectively. Following the supplementary application of the SAF, the amounts of residue were reduced to 2.6 (± 3.7)%, 4.1 (± 5.7)% and 6.7 (± 9.4)% of the coronal, mid-root and apical canal areas, respectively (P < 0.01 for the coronal and mid-root and P < 0.001 for the apical third). CONCLUSION: No system removed the root filling materials entirely. The use of the SAF after rotary instrumentation using ProTaper Universal retreatment files resulted in a significant reduction in the amount of filling residue in curved canals of mandibular molars.

The efficacy of five techniques for removing root filling material: microscopic versus radiographic evaluation.

AIM: To test and compare the efficacy of five methods for the removal of root filling material and to test the hypothesis that radiographs fail to represent the real extent of remaining material on canal walls. METHODOLOGY: Fifty maxillary anterior single-rooted teeth with straight root canals were selected. The coronal third of each root canal was prepared with Gates-Glidden drills to number 3, whilst the apical two-thirds were prepared with manual K-files to size 40. Root fillings were performed using lateral compaction with gutta-percha and AH-26. After full setting, the coronal third of the root filling was removed with Gates-Glidden drills and the teeth divided into five groups (n=10). The remaining root filling material was then removed with either Hedström files and chloroform (25 µL), using size 40 as the last file, SafeSider files, using a NiTi Pleezer reamer with a 0.06 taper followed by size 40 reciprocating file, with or without chloroform, or ProTaper Universal retreatment files (D2, D3) with or without chloroform. Reaching working length with no more gutta-percha on the last file was defined as the endpoint for all procedures. The presence of remaining filling material was first evaluated radiographically and then by the microscopic evaluation of split roots. The time required to accomplish the procedure was also recorded. anova and anova with repeated measures were used for statistical analysis of the results. RESULTS: Overall, 11-26% of the canal wall remained covered with filling material; no significant difference was found between the groups. The mechanized methods were faster than manual removal of filling material (P < 0.01); the use of solvent did not speed up the mechanized procedures. Radiographic evaluation failed to adequately and reliably detect the extent of filling material remaining on the canal walls, which was later observed by microscopic evaluation. CONCLUSIONS: All methods left root canal filling material on the canal walls. Radiographic evaluation failed to detect the extent of remaining root filling material, which could only be detected using microscopy.

Sealing furcation perforations with silver glass ionomer cement: an in vitro evaluation.

Furcation perforations sealed with silver glass ionomer cement (Chelon Silver) were evaluated in vitro compared with amalgam. Access cavities were prepared in 25 extracted human molar teeth. The coronal orifices of the root canals were sealed with amalgam and varnish. Naturally occurring coronal leakage through the intact pulp chamber floor was determined quantitatively for each tooth, using a modified fluid transport model, under pressure of 1.2 Atm. Each tooth was then disconnected from the system, perforated at the furcation, and the perforation sealed with either Chelon Silver (10 teeth) or amalgam (10 teeth); five remaining teeth served as a negative control. After incubation for 24 h at 37 degrees C in 100% humidity, teeth were reconnected to the modified fluid transport system, and coronal leakage under pressure was evaluated at 1, 2, 6, 15, and 24 h. Leakage through each tooth was compared with that of its own intact pulp chamber floor before perforation and the groups compared with each other. No significant difference was found between the mean leakage of the intact pulp chamber floors of the two groups. Chelon Silver had a significantly better sealing ability than amalgam (p < 0.01): leakage rate of 0.007 and 0.017 microliter/min, respectively. It is concluded that Chelon Silver could be an adequate sealer for furcation perforations.

The effect of immediate vs. delayed post space preparation on the apical seal of a root canal filling: a study in an increased-sensitivity pressure-driven system.

A 5 mm remaining length of root canal filling, after post space preparation, is commonly assumed to maintain sealing ability similar to that of the intact filling. Post spaces were prepared either immediately using hot pluggers, or later, using drills. The sealing ability of the fillings, 5 mm remaining length, were compared with each other and with an intact root canal filling control, using radioactive tracer in a pressure-driven system. When no pressure was applied, no differences could be detected between either of the groups and the control. When a pressure of 120 mm Hg was applied to the same teeth, the control group clearly maintained a better seal than each of the experimental groups, which did not significantly differ from each other. These results suggest that (a) the pressure-driven system was more sensitive than the passive leakage assay that failed to detect differences even at 14 days; (b) a remaining root canal filling of 5 mm was inferior to the intact root canal filling; and (c) the immediate post space preparation with hot pluggers did not differ from a delayed preparation with drills.

Improving the seal of amalgam cores with cemented dowels: a comparative in vitro radioactive tracer study.

Amalgam cores with cemented dowels are commonly used to restore endodontically treated teeth. These restorations were widely studied for their mechanical properties; however, less is known about their sealing ability. The effect of the cement type used for the dowel and that of a bonding agent application were studied in a radioactive tracer coronal leakage study. The sealing ability of posts and cores was also compared with that of 5 mm remaining root canal fillings. Composite luting cement provided a better seal than zinc phosphate cement. The seal provided by 5 mm root canal fillings was poorer than that provided by posts and cores. High variability in seal quality was found among all types of posts and cores studied. This may indicate that the seal provided by cemented dowels with amalgam cores is unpredictable. Because neither the remaining root canal filling nor the post and core may be trusted alone for a seal, each should be performed with the greatest care and both covered with a crown as soon as possible.

Effect of repeated vertical loads on microleakage of IRM and calcium sulfate-based temporary fillings.

Temporary fillings are commonly used to seal endodontic access cavities between visits. IRM and Cavidentin were selected to represent two widely used groups of temporary filling materials. The first is a reinforced zinc oxide-eugenol preparation that is mixed at chairside, whereas the second is a ready-to-use calcium sulfate-based material that gained popularity due to its convenience of application. The seal provided by the aforementioned materials was studied using a radioactive tracer quantitative assay. When compared as passive temporary filling, the two provided a similar quality of seal. However, when subjected to repetitive "occlusal" cyclic loading of 4 kg, IRM was clearly superior to the calcium sulfate-based material. Whereas IRM maintained a reasonable seal, the calcium sulfate-based fillings deteriorated and lost the ability to seal. These results suggest that even though calcium sulfate-based materials may be useful when not subjected to any occlusal forces, IRM should be preferred whenever occlusal loads may be applied. Furthermore it is demonstrated that testing such materials for microleakage with no reference to mastication forces may be of limited value.

Sensitivity of oral bacteria to 254 nm ultraviolet light.

AIM: To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. METHODOLOGY: The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer. RESULTS: Direct exposure to relatively low doses of UV light (2-7 mJ cm(-2)) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells microm(-2) were present in the light path, the UV light dose had to be increased by a factor of x10 to achieve 100% elimination of the bacteria in an inner layer. CONCLUSIONS: The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.