Accuracy of the DTC torque control motor for nickel-titanium rotary instruments.

AIM: To determine the torque output and examine the accuracy of five identical DTC torque control (DTC) motors. METHODOLOGY: Torque settings on the DTC motors for the.04 ISO ProFile nickel-titanium (NiTi) rotary instruments were evaluated at 350 r.p.m. A modification of the ANSI/ADA Specification No. 28 setup for the evaluation of torsional properties of endodontic instruments was used. A handpiece was attached to the motor and gripped with a vice. An.07 Orifice Shaper, size 50, was inserted in the handpiece. The instrument tip was clamped in a chuck connected to a torque sensor. The motor was then activated to rotate the instrument in a clockwise direction until reversal of the rotation occurred. The actual torque generated at the reversal of the rotation was recorded. Ten tests were carried out at each torque setting. A new Orifice Shaper was used for each test. The means of the actual torque values generated by the motors at the different torque settings were compared with the torque values claimed by the manufacturer and analysed using analysis of variance and the Student's t-test (alpha = 0.05). RESULTS: The actual torque values were significantly higher than the torque preset on the motors (P < 0.0001) and did not differ significantly among the motors (P > 0.05). CONCLUSIONS: The actual torque deviated from the preset torque and was higher than the reported torque at fracture of several NiTi rotary instruments. The usefulness of these motors is questionable.

An in vitro study of the torsional properties of new and used K3 instruments.

AIM: To compare torque and angle of rotation at fracture of new and used K3 rotary instruments. The relation between size of instrument and torque at fracture was also investigated. METHODOLOGY: Nickel-titanium (Ni-Ti).06 K3 rotary instruments were used in a crown-down manner at 300 r.p.m. to prepare canals in resin blocks. The torque and angle of rotation at fracture of new and the used Ni-Ti.06 K3 rotary instruments (sizes 15-40) were determined according to ANSI/ADA Specification no. 28. Analysis of variance was used to compare the torque and angle of rotation at fracture amongst the different sizes of the new instruments and between new instruments and instruments of the same size, which had been used in resin blocks (alpha = 0.05). The relationship between torque at fracture and size of instrument was subjected to regression analysis. RESULTS: Torque at fracture of the new instruments increased significantly with the diameter. The used instruments (sizes 15, 20, 30, 35 and 40) had lower torque at fracture compared to the new ones (P < 0.0001). The means of angle of rotation at fracture between the different sizes of new instruments were significantly different (P < 0.0001) except for sizes 15-20 (P = 0.2561). The used instruments (sizes 20-40) had lower angle of rotation at fracture compared to the new ones (P < 0.05). A linear relationship was found between the size of the file and the torque at fracture for the new instruments (r2 = 0.84; P < 0.0001) and the used ones (r2 = 0.82; P < 0.0001). CONCLUSIONS: In general, the results suggested that the torque and angle of rotation at fracture were significantly affected by the repeated use of.06 K3 instruments in resin blocks.

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.

Quantitative Analysis by Reverse Phase High Performance Liquid Chromatography of 5-Hydroxytryptamine in the Central Nervous System of the Red Swamp Crayfish, Procambarus clarkii.

The concentrations of 5-hydroxytryptamine (5-HT) in central nervous organs of the red swamp crayfish, Procambarus clarkii, were determined by reverse phase high performance liquid chromatography (RPHPLC) with electrochemical detection. The quantity ranged between 54 and 168 pg/mg wet weight of tissue. The amount is highest in the brain, followed in decreasing order by the thoracic ganglia, subesophageal ganglion, eyestalks, and abdominal nerve cord. Significant increases in the levels of 5-HT in the eyestalks, brain, subesophageal ganglion, and thoracic ganglia occurred in crayfish exposed for three days to continuous light on a white background, whereas the 5-HT levels in these tissues decreased in crayfish kept in darkness. Electrical stimulation of central nervous organs in vitro produced significant decreases in the levels of 5-HT. Fenfluramine (5-HT releaser), 5,6-DHT (5-HT neurotoxin), and reserpine (5-HT depletor) induced significant decreases in the 5-HT levels in the portions of the central nervous system tested.

Clonidine in alcohol withdrawal: a clinical report.

Potential of clonidine in the treatment of alcohol withdrawal reactions was investigated. Clonidine was found to be remarkably effective in alleviating various alcohol abstinence signs in a chronic alcoholic. The usefulness of clonidine and related alpha 2-agonists in the treatment of alcohol withdrawal states is discussed.

Distal retinal pigment of the fiddler crab, Uca pugilator: release of the dark-adapting hormone by methionine enkephalin and FMRFamide.

The neuropeptides methionine enkephalin and FMRFamide, when injected into intact fiddler crabs, Uca pugilator, produce dark adaptation of the distal retinal pigment. Furthermore, both neuropeptides stimulate release of distal retinal pigment dark-adapting hormone activity from the isolated eyestalk neuroendocrine complex. It is hypothesized that both neuropeptides, when injected into intact fiddler crabs, act only indirectly on the distal retinal pigment, by stimulating release of this dark-adapting hormone.

Effects of two tranquilizers, reserpine and chlorpromazine, on neurosecretory cells and the ovary of the fiddler crab, Uca pugilator.

Reserpine produced alterations in neurosecretory cell types I and II in the eyestalk, brain, and thoracic ganglion, most notably a decrease in the amount of stored neurosecretory material. The ovarian index decreased, but the oocyte area increased in the reserpinized crabs. Chlorpromazine did not produce any significant changes in the structure of cell types I and II. In spite of having a normal area, the oocytes in the chlorpromazine injected crabs were devoid of yolk. Neurosecretory cell type III showed no change.

Localization of substance P-like, leucine-enkephalin-like, methionine-enkephalin-like, and FMRFamide-like immunoreactivity in the eyestalk of the fiddler crab, Uca pugilator.

The occurrence and distribution of substance P (SP)-like, methionine-(Met)- and leucine-(Leu)-enkephalin-like, and FMRFamide-like immunoreactivities were determined in the neuroendocrine complex of the eyestalk of the fiddler crab, Uca pugilator, by immunocytochemistry. SP-like immunoreactivity was found in the optic peduncle, sinus gland, medulla externa, medulla interna, lamina ganglionaris, and retinular cells. Met-enkephalin-like and Leu-enkephalin-like immunoreactivity was observed in most of the retinular cells, optic peduncle, sinus gland, medulla terminalis, and lamina ganglionaris. However, Met-enkephalin-like, but no Leu-enkephalin-like, immunoreactivity was seen in the medulla terminalis X-organ. FMRFamide-like immunoreactivity could be seen in all parts of the eyestalk except in the sinus gland, lamina ganglionaris, and retinular cells. FMRF-amide-like activity was especially strong in the three chiasmatic regions connecting the optic ganglia. The possibility that these four peptides may function as neuroregulators in the fiddler crab is discussed.

Inhibition of hypertonic-saline stimulated neurosecretory changes in the freshwater bivalve Indonaia caeruleus (Prashad) by chlorpromazine and reserpine.

In the present paper, the effects of reserpine (RSP) and chlorpromazine (CPZ) on the neurosecretory cells of a saline treated freshwater bivalve, Indonaia caeruleus have been tracked. After saline (0.1 ml of 1.5% NaCl per animal) treatment A and B cells of cerebral and visceral ganglia showed significant increase in cell area, nuclear diameter and decrease in the NSM, while administration of RSP (0.50 mg per animal) and CPZ (0.25 mg per animal), following the saline injection completely inhibited these changes. Physiological implications of these changes are discussed in the light of neurosecretory dynamics.