Extrusion of debris after use of rotary nickel-titanium files with different pitch: a pilot study.

The aim of this investigation was to quantitatively compare the amount of debris extruded apically from curved canals when using rotary nickel-titanium files with different pitches and sequences of use under the same preparation technique. Thirty-six extracted human maxillary and mandibular molars with curved root canals were used. They were divided into two groups of 18 teeth each prepared by one of two different sequences with NRT files (MANI Inc., Tochigi, Japan). Each group was further divided into three subgroups according to file pitch length (short, medium and long). The debris extruded apically was collected in glass vials. The liquid inside was dried and the debris in each group was weighed and compared. Two-way analysis of variance and Fisher's PLSD test were used to evaluate differences between the extruded debris weights among the experimental groups. No statistically significant difference was observed between two sequences. There were significant differences in sequence 1 between the short pitch group and the others. Also, there were significant differences between the long pitch and others in sequence 2, except between the short and medium pitches. In conclusion, short pitch design resulted in significantly less amount of debris extrusion compared with the other pitch lengths.

Root canal medicaments.

The ultimate goals of endodontic treatment are complete removal of bacteria, their byproducts and pulpal remnants from infected root canals and the complete seal of disinfected root canals. Intracanal medicaments have been thought an essential step in killing the bacteria in root canals; however, in modern endodontics, shaping and cleaning may be assuming greater importance than intracanal medicaments as a means of disinfecting root canals. Until recently, formocresol and its relatives were frequently used as intracanal medicaments, but it was pointed out that such bactericidal chemicals dressed in the canal distributed to the whole body from the root apex and so might induce various harmful effects including allergies. Furthermore, as these medicaments are potent carcinogenic agents, there is no indication for these chemicals in modern endodontic treatment. Today, biocompatibility and stability are essential properties for intracanal medicaments. The more modern meaning of intracanal dressing is for a blockade against coronal leakage from the gap between filling materials and cavity wall. Calcium hydroxide has been determined as suitable for use as an intracanal medicament as it is stable for long periods, harmless to the body, and bactericidal in a limited area. It also induces hard tissue formation and is effective for stopping inflammatory exudates. Single-visit endodontics, where intracanal medicaments are not used, is generally not now contraindicated and various reports have shown that the clinical outcomes between single- and multiple- visit endodontics are similar. There is no reason to counsel against single-visit endodontics: however, if multiple-visit endodontics is chosen, calcium hydroxide is recommended to be used as an intracanal medicament.

In vitro evaluation of the accuracy of five different electronic apex locators for determining the working length of endodontically retreated teeth.

The aim of this study was to evaluate the accuracy of five electronic apex locators (EALs) in determining the working length (WL) of teeth after removal of the root canal obturation materials. A total of 32 extracted straight, single-rooted teeth were used. The actual canal length (AL) was determined and the WL was established by subtracting 0.5 mm from the AL. The root canals were instrumented and divided into two groups. One group (n = 6) served as control, while the other group (n = 26) was the experimental group. In the experimental group, the root canals were obturated using vertically compacted gutta-percha with AH 26 sealer. In both groups, the access cavities were restored with a provisional restoration and stored for 15 days at 37 degrees C and 100% humidity. The root canal obturation material was removed, and the teeth were then mounted in an experimental apparatus. Five EALs were used: Dentaport ZX, ProPex, Foramatron D10, Apex NRG and Apit 7. For the electronic measurement of canal length, a size 25 K-file was used. During measurement, the canal was irrigated with 2.5% sodium hypochlorite. The difference (D) between the AL and the electronically determined length (EDL), AL-EDL, was calculated and recorded for each measurement. Data were analysed by two-way anova and Fisher's PLSD test. In both groups, statistically significant differences were found among the EALs (P < 0.01). In conclusion, the Dentaport ZX, ProPex and Foramatron D10 were more accurate than the other two EALs in determining the WL in teeth after removal of the root canal obturation materials. However, the Apex NRG and Apit 7 were also reliable for determination of the WL in the majority of the cases.

Accuracy of three different electronic apex locators in detecting simulated horizontal and vertical root fractures.

The aim of this in vitro study was to evaluate the accuracy of three electronic apex locators (EALs): Root ZX, Foramatron D10 and Apex NRG, in the detection of fractures in teeth having simulated horizontal and vertical root fractures. A total of 90 extracted intact, straight, single-rooted teeth were divided into six groups of 15 teeth each. In Groups A, B and C, an incomplete horizontal fracture was simulated by preparing a horizontal incision in the coronal, middle or apical portion of the root until the circumferential half of the canal was exposed in the horizontal plane respectively. In Groups D, E and F, an incomplete vertical root fracture was simulated by preparing a vertical straight incision to expose the canal in the coronal, middle or apical portion of the root all the way in the longitudinal plane respectively. The simulated fractures were 0.25 mm in thickness in all groups. The teeth were embedded in 1% agar and the canals were irrigated with saline solution during electronic measurement. Detection of the simulated root fractures was established with a size 10 K-file when the meter value reached 'APEX' on each EAL. In Groups A, B and C, Kruskal-Wallis tests revealed that there were no statistically significant differences between the three EALs. However, statistically significant differences were found among the EALs in Groups D, E and F (P < 0.0001, one-way anova and Tukey's post-hoc test). In conclusion, the three EALs tested were accurate and acceptable clinical tools in the detection of horizontal root fractures. However, the three EALs were unreliable in detecting the position of vertical root fractures.

Debris retention and wear in three different nickel-titanium rotary instruments.

The aim of this in vitro study was to compare three nickel-titanium (Ni-Ti) rotary instruments: EndoWave, K3 and ProFile, with respect to their debris retention and wear. Thirty simulated root canal models made from resin blocks with 40 degrees canal curvature were used. They were divided into three groups of 10 samples each; EndoWave, K3 and ProFile were used in Groups A, B and C respectively. They were prepared with four serial size files. The weight of each file was measured to evaluate debris retention and wear at four representative time points: prior to root canal preparation (W1), immediately after root canal preparation (W2), after ultrasonic cleaning (W3), after further additional cleaning (W4). The weight of debris on each file after root canal instrumentation and ultrasonic cleaning was calculated as D1: (W2 - W4) and D2: (W3 - W4) respectively. Also, wear of the file was calculated as WF: (W1 - W4). There was a significant difference in the amount of debris remaining on the file among the three files; EndoWave retained more debris (D1) than K3 and ProFile (P < 0.001, one-way anova). ProFile had the largest amount of debris (D2) remaining after ultrasonic cleaning (P < 0.001). Wear was not detectable in this study. Under the conditions of this study, immediately after root canal preparation, EndoWave retained the largest amount of debris, while ProFile retained the most debris even after ultrasonic cleaning.

An experimental study on the vasoconstriction effect of calcium hydroxide using rat mesentery.

Calcium hyroxide has been used for eliminating persistent intracanal exudation. In order to address the mechanism behind this action, we investigated whether calcium hydroxide solutions cause the constriction of microvessels in the mesenteric microcirculation bed of rats. The exteriorised mesentery from anaesthetised rats was spread in a chamber, and arterioles, venules and capillaries were viewed under a digital microscope. Various concentrations of calcium hydroxide solutions were applied for 10 sec, and the diameter of the microvessels was recorded. In arterioles, calcium hydroxide solutions caused rapid and transient constriction. A statistically significant difference versus original diameter was detected 1 min after the application of 4.0 x 10(-3) mol/l and 1.0 x 10(-2) mol/l solutions (p < 0.05, one-way analysis of variance and Tukey-Kramer test). No statistically significant constriction occurred in capillaries and venules. It was concluded that the arteriolar constriction might be an explanation for the exudation-controlling effect of intracanal calcium hyroxide dressings.

[Incident and accident reports in Tokyo Medical and Dental University Dental Hospital (FY 2001-2002)].

In 2002, the Dental Hospital of Tokyo Medical and Dental University set up a working group for risk management. This working group analyzed 225 incident and accident reports submitted to the hospital in 2001 and 2002. Each report was analyzed with regard to "type," "place," "reporter," "severity," and "cause" in order to diagnose hospital safety and prevent future incidents and accidents. The cause of incidents and accidents was analyzed using the SHEL model, where S stands for Software, H for Hardware, E for Environment, and L for Liveware. The severity of the consequence was classified into 6 levels, where level 0 = "error not applied," level 1 = "not affected," level 2 = "watch and see or additional test," level 3 = "treatment," level 4 = "aftereffect," and level 5 = "death." The incidents and accidents judged to have potentially high risk were given a score of "+H," irrespective of the level. The results of the analyses revealed that most of the incidents and accidents happened in "wards," "operation rooms," and "oral surgery clinics." This is probably because the incident and accident reporting system is well established by nurses working in these clinics. Additional analysis revealed that most of the reports were written and submitted by nurses. The frequencies of "treatment procedure," "misuse of dental instruments," "mis-prescription," "falling down" and "needlestick" related incidents and accidents were the highest and were caused mainly by L and S. There were only 3 accidents above level 4, however, less severe cases were given a score of +H due to the high potential risk involved.