Behaviour of Hero NiTi instruments used by an experienced operator under access limitations.

The purpose of this study was to evaluate the failure incidence of Hero 642 nickel-titanium (NiTi) rotary instruments (HRI) when used by an experienced operator in conjunction with different motors and under limitations of access. HRI were used by an experienced operator in a crown-down technique. The teeth were mounted in resin arches of a phantom head to reproduce limitations of access. In Groups 1, 2, 3 and 4, air, high torque control, low torque control and very low torque control motors were used respectively. Each group included 30 canals in extracted human molars. One set of HRI was used for each canal; the HRI were sterilised before each case. A 2.5% NaOCl solution was used as an irrigant. An experienced operator performed all the cleaning and shaping procedures after application of a rubber dam. The opening of the mouth in the phantom head was standardised for the four groups. Instrument fracture did not occur in any of the groups. The air, high torque control and low torque control motors were as safe as the very low torque control motor when HRI were used by an experienced operator in a crown-down manner at 300 rpm.

Failure of ProFile Ni-Ti instruments used by an inexperienced operator under access limitations.

AIM: The purpose of this study was to evaluate the failure incidence of ProFile nickel-titanium rotary instruments (PRI) when used by an inexperienced operator in conjunction with different motors and under limitations of access. METHODOLOGY: PRI with 0.06 taper were used by an inexperienced operator in a crown-down technique. The teeth were mounted in resin arches of a phantom head to reproduce limitations of access. In groups 1-4, air, high torque control, low torque control and very low torque control motors were used, respectively. Each group included 30 canals in extracted human molars. One set of PRI sizes 40-15 was used for each canal; the PRI were sterilized before each case. A 2.5% NaOCl solution was used as an irrigant. An inexperienced operator performed all the cleaning and shaping procedures after application of a rubber dam. The opening of the mouth in the phantom head was standardized for the four groups. The number of deformed and separated instruments was recorded for the various experimental groups and analyzed statistically for significance with chi-square tests. RESULTS: A high incidence of instrument deformation and separation occurred with the air, high torque control and low torque control motors. Only seven and two instruments deformed and separated, respectively, with the very low torque control motor, whereas at least 23 and 10 instruments deformed and separated respectively with the other motors. CONCLUSIONS: A very low torque control motor was safer than on air, high torque control or low torque control motors when PRI with 0.06 taper were used by an inexperienced operator in a crown-down manner at 170 rpm.

Influence of rotational speed, torque and operator proficiency on failure of Greater Taper files.

AIM: The purpose of this study was to evaluate the influence of rotational speed. torque, and operator experience on the incidence of locking, deformation, and separation of instruments when using a specific Ni-Ti rotary instrumentation technique in extracted human teeth. METHODOLOGY: Greater Taper Ni-Ti rotary instruments (GT) were used in a crown-down technique. In one group (rotational speed evaluation) of canals (n = 300) speeds of 150, 2 50 and 350 r.p.m. (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (evaluation of torque) (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (evaluation of operator proficiency) (n = 300 three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of GT rotary instruments and 100 canals of extracted human molars. Each set of instruments was used in up to 10 canals and sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments was recorded for each group. Statistical analysis was carried out with pairwise comparisons using Fisher's exact tests for each of the failure type. RESULTS: When the influence of rotational speed was evaluated, instrument deformation and separation did not occur in subgroups 1 (150) r.p.m.), 2 (250 r.p.m.), and 3 (350) r.p.m.). Instrument locking occurred in subgroup 3 only. Statistical analysis demonstrated a significant difference between the 150 and 350 r.p.m. groups and between the 250 and 350 r.p.m. groups with respect to instrument locking. In torque evaluation, neither separation, deformation nor locking occurred during the use of the instruments, at 150 r.p.m., and at the different torque values. When the operators were compared, although two instruments were separated in canals prepared by the least experienced operator. Fisher's exact tests did not demonstrate a significant difference between the three subgroups. Instrument locking, deformation, and separation did not occur with the most experienced operator. None of the instruments separated with the trained operator. CONCLUSIONS: Preclinical training in the use of the GT rotary instruments when used with a crown-down technique at 150 r.p.m. was crucial in avoiding instrument separation and reducing the incidence of instrument locking and deformation.

Failure of ProFile instruments used with high and low torque motors.

AIM: The purpose of this study was to evaluate the failure incidence of ProFile nickel-titanium rotary instruments when used in conjunction with different motors and a specific instrumentation technique. METHODOLOGY: ProFile Ni-Ti rotary instruments (PRI) with 0.06 taper were used in a crown-down technique. In groups 1, 2 and 3, an air, a high torque and a low torque motor were used, respectively. Each group included 30 canals in extracted human molars. One set of PRI sizes 40-15 was used for each canal; they were sterilized before each case. A 2.5% NaOCl solution was used as an irrigant. The number of deformed and separated instruments was recorded for the various experimental groups. RESULTS: Instrument separation did not occur in any of the three groups. One and two instruments were deformed when using the air and high torque motors, respectively. CONCLUSIONS: The results indicated no difference between the three motors with respect to the incidence of instrument failure. The results suggest that the use of PRI in a crown-down manner with air control motors was safe.

Influence of rotational speed, torque and operator's proficiency on ProFile failures.

AIM: The purpose of this study was to evaluate the influence of rotational speed, torque, and operator experience with a specific Ni-Ti rotary instrumentation technique on the incidence of locking, deformation and separation of instruments. METHODOLOGY: ProFile Ni-Ti rotary instruments (PRI) sizes 40-15 with a 6% taper were used in a crown-down technique. In one group of canals (n = 300) speeds of 150, 250 and 350 rpm (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (n = 300) three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of PRI and 100 canals of extracted human molars. Each set of PRI was used in up to 10 canals and then sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments for the different groups, and within each part of the study was analysed statistically for significance with chi-squared tests. RESULTS: In group 1 only one instrument was deformed in the 150-rpm group and no instruments separated or locked. In the 250-rpm group instrument separation did not occur, however, a high incidence of locking, deformation and separation was noted in the 350-rpm group. In general, instrument sizes 30-15 locked, deformed and separated. Chi-squared statistics showed a significant difference between the 150 and 350 rpm groups but no difference between the 150 and 250 rpm groups with regard to instrument separation. Overall, there was a trend toward a higher incidence of instrument deformation and separation in smaller instruments. Locking and separation occurred during the final passage of the instruments, in the last (tenth) canal in each subgroup. In the second group, neither separation nor deformation and locking occurred during the use of the ProFile instruments, at 150 rpm, and at the different torque values. In the third group, chi-squared analysis demonstrated that significantly more instruments separated with the least experienced operator. Instrument locking, deformation, and separation did not occur with the most experienced operator. CONCLUSIONS: Preclinical training in the use of the PRI technique with crown-down at 150 rpm were crucial in avoiding instrument separation and reducing the incidence of instrument locking and deformation.

Cyclic fatigue of ProFile rotary instruments after clinical use.

AIM: The purpose of this study was to evaluate cyclic fatigue of .06 ProFile Ni-Ti rotary instruments after clinical use in molar teeth. METHODOLOGY: In group 1, instruments size 40-15 were used in a crown-down technique using 2.5% NaOCl as an irrigant. Fifty-two molars were included and 13 sets of Profile Ni-Ti rotary instruments were used. Each set of instruments was used in four molars, and was steam autoclaved before each use. Group 2 (10 sets of new ProFile Ni-Ti rotary instruments) was the control group. Cyclic fatigue was tested by rotating the instruments in a 90 degrees metallic tube until they broke. RESULTS: One-way analysis of variance did not show any statistically significant differences amongst the files from both groups regarding cyclic fatigue. CONCLUSIONS: It was concluded that sterilization and clinical use in the presence of NaOCl did not lead to a decrease in the number of rotations to breakage of the files.

Cyclic fatigue of Profile rotary instruments after simulated clinical use.

AIM: The purpose of this study was to evaluate cyclic fatigue of Profile Ni-Ti rotary instruments (PRIs) after dry heat sterilization and up to 10 times simulated clinical use. METHODOLOGY: Instruments of size 40-15 were used in a crown-down technique. Three groups were included in this study. In groups 1 and 2, each set of instruments was used in five and 10 canals, respectively. Group 3 was the control group. NaOCl at a concentration of 2.5% was used as an irrigant. Each set of instruments was sterilized before each use. RESULTS: The PRI size 40 demonstrated the lowest incidence of rotations to breakage. One-way analysis of variance and Turkey's HSD test showed statistically significant differences among different file sizes within each group. CONCLUSIONS: The results showed that dry heat sterilization and simulated clinical use in the presence of NaOCl did not lead to a decrease in the number of rotations to breakage of the files.

Microleakage of a new and an old Kerr root canal sealers.

This study sought to evaluate the microleakage of two Kerr root canal sealers (old and new formulas of the Pulp Canal Sealer). Sixty anterior teeth were used. After cleaning and shaping to a size 30 file, the teeth were obturated with the vertical condensation of gutta-percha with either the old or the new root canal sealer. Apical microleakage was determined using pressurized fluid filtration at 90 min, 1 day, and 1, 4, 12, 18, and 24 wk after root canal obturation. The results showed that leakage tended to increase over time for the two groups. Also, no significant difference was found in microleakage between the old and the new formulas of the root canal sealer.

Influence of the removal of coronal gutta-percha on the seal of root canal obturations.

The purpose of this study was to compare the quality of the coronal seal of lateral and vertical condensations after removal of the coronal gutta-percha with two different techniques. One hundred single-rooted human teeth with one root canal were used. After cleaning and shaping, the teeth were divided into 4 equal groups. In groups 1, 3 and 2, 4 vertical and lateral condensations were performed respectively. Then, the coronal portion of gutta-percha was removed with heat-carriers alone for groups 1 and 2 and with heat-carriers and compaction for groups 3 and 4. Apical microleakage was determined using pressurized fluid filtration measured at different time intervals up to 24 wk. The results showed that the alternation of heat-carriers and compaction enhances the quality of the coronal seal. The obturation with the vertical condensation technique resulted in a better seal independently of the gutta-percha removal technique.

An evaluation of 2% lidocaine with different concentrations of epinephrine for inferior alveolar nerve block.

The purpose of this study was to compare the degree of anesthesia obtained with 2% lidocaine with three different concentrations of epinephrine for inferior alveolar nerve block. Using a repeated measures design, 30 subjects randomly received an inferior alveolar injection using masked cartridges of each solution at three successive appointments. The first molar, first premolar, lateral incisor, and contralateral canine (control) were blindly tested with an Analytic Technology pulp tester at 3-min cycles for 50 min. No statistically significant differences in success and failure were found among the 1:50,000, 1:80,000, and 1:100,000 concentrations of epinephrine.

Evaluation of lidocaine in human inferior alveolar nerve block.

The purpose of this study was to measure the degree of anesthesia following the administration of 3.6 ml of 2% lidocaine solutions with either 1:50,000, 1:80,000, or 1:100,000 for inferior alveolar nerve block and to compare the results with those obtained following the administration of 1.8 ml of the same solutions (1). With the use of a repeated measures design, 30 subjects randomly received an inferior alveolar injection at three successive appointments. The first molar, first premolar, lateral incisor, and contralateral canine (control) were blindly tested with an Analytic Technology pulp tester at 3-min cycles for 50 min. The degree of anesthesia was comparable for the three solutions following the administration of 3.6 ml of each solution. Retrospective evaluation showed that the volume of the solution influenced the degree of anesthesia.

Sealing ability of the vertical condensation with different root canal sealers.

This study evaluated the influence of various root canal sealers on the quality of the apical seal of vertically condensed gutta-percha. One hundred and twenty human anterior teeth with single canals were used. After cleaning and shaping to an apical size 30 file, the teeth were divided into 4 equal groups of 30 teeth each and obturated with vertically condensed gutta-percha. In group 1, no sealer was used. In groups 2, 3, and 4, Kerr Pulp Canal Sealer, Roth 801, and AH 26 were used, respectively. Apical microleakage was determined using pressurized fluid filtration measured at different time intervals up to 24 wk. The no-sealer group showed significantly more apical leakage than the other groups. Kerr Pulp Canal Sealer was significantly better than Roth 801 and AH 26 at 24 wk.

Influence of operator proficiency on the sealing ability of the vertical condensation.

This study sought to evaluate on a long-term basis the quality of the apical seal of the vertical condensation performed by three operators with different levels of proficiency in vertical compaction. Ninety anterior teeth were used. After cleaning and shaping to a size 30 file, the teeth were divided into three equal groups. Then, vertical condensation was performed. Apical microleakage was determined using pressurized fluid filtration at 90 min, 1 day, and 1, 4, 12, 18, and 24 wk after root canal obturation. Leakage tended to increase over time for the three groups. Teeth obturated by an inexperienced operator showed greater long-term leakage.

Comparison of three files to prepare curved root canals.

Flex-R, Ultra-Flex (Ni-Ti construction), and K-type files were compared using a circumferential filing technique on 96 extracted human maxillary molars. Buccal canals with minimal initial curvature of 24 degrees were used. The maximal initial curvature was 52 degrees. Canal curvature was measured before and after filling, and changes were analyzed statistically. The angle of curvature was better maintained with the Flex-R and Ultra-Flex files.

Influence of plugger penetration on the sealing ability of vertical condensation.

This study sought to evaluate the influence of plugger penetration on the sealing ability of vertical compaction. Ninety anterior teeth were used. After cleaning and shaping to a size #30 file, these teeth were divided into three equal groups (A, B, and C) according to the level of plugger penetration set at 5, 7, and 9 mm short of the working length, respectively. Then vertical compaction was performed. Apical microleakage was determined using pressurized fluid filtration at 90 min, 1 day, and 1, 4, 12, 18, and 24 wk after root canal obturation. Leakage tended to increase over time for the three groups. The deeper plugger penetration groups (A and B) showed significantly less apical leakage than group C.

Influence of apical enlargement on bacterial infection during treatment of apical periodontitis.

This study sought to evaluate the influence of apical enlargement and 1-wk calcium hydroxide dressing on bacterial infection of root canals. Sixty single-rooted teeth were used. Half of these teeth were prepared to a size 25 file and the other half to a size 40 file. Then the root canals were dressed with calcium hydroxide for 1 wk. Bacterial sampling showed significant reduction of bacterial growth during the treatment. No statistically significant difference was noted between the size 25 and 40 file groups after instrumentation, and after 1-wk calcium hydroxide dressing.

Apical enlargement: influence on the sealing ability of the vertical compaction technique.

This study sought to evaluate the influence of apical enlargement on the sealing ability of vertical compaction. Sixty anterior teeth were used. Half of these teeth were prepared to a size 25 file and the other half to a size 40 file. Then vertical compaction was performed. Apical microleakage was determined using pressurized fluid filtration at 90 min, 6 h, 1 day, 4 days, and at 1, 2, 4, 8, 12, 16, and 24 wk after root canal obturation. Leakage tended to increase over time for both groups. The size 25 file group showed significantly less apical leakage than the size 40 file group.

Apical enlargement: influence on overextensions during in vitro vertical compaction.

This study evaluated the apical movement of gutta-percha master cones under in vitro vertical compaction. A split natural tooth model was used. The gutta-percha cones were first fitted at 0.5 and 1.0 mm short of the apical end of a canal instrumented up to a size 25 file and then condensed. Then the canal was cleaned of gutta-percha and reshaped up to a size 40 file, other cones fitted and obturated. Photographs were taken before and after compaction and measurements were made. The canals instrumented to a size 40 file had significantly more overextensions than those instrumented to a size 25 file.

Elongation and movement of the gutta-percha master cone during initial lateral condensation.

This study evaluated gutta-percha master cone elongation and apical movement during initial lateral condensation. A split natural tooth model was used. Measurements on photographs taken before and after initial spreading were made. The results showed that both elongation and total cone displacement occur.

Master core apical movement during compaction: evaluation of two in vitro models.

This study evaluated two in vitro models (a split hard metal model and a split natural tooth model) for the assessment of master cone apical movement. Gutta-percha cones were fitted 0.5 and 1.0 mm short of the apical ends of the artificial canals. Photographs were taken before and after vertical or lateral compaction and measurements were made. The results demonstrated no significant difference between the two models.