Nickel-titanium rotary instrument fracture: a clinical practice assessment.

AIM: To prospectively determine the incidence of nickel-titanium rotary instrument fracture in an endodontic clinical practice setting. METHODOLOGY: Eleven second year endodontic residents, using four nickel-titanium rotary instrument systems (ProFile, ProTaper, GTRotary and K3Endo) according to the recommendations of the manufacturers, instrumented 3181 canals in 1403 teeth of 1235 patients, in a dental school post-graduate endodontic clinic, in 1 year. The incidence of instrument fracture was determined based on the number of instruments used. When fracture occurred, data were collected concerning the type, size, taper and prior use of the fractured instruments, the length and location of the fragment within the root canal and the curvature of the canal. RESULTS: The overall incidence of instrument fracture was 0.39%. The incidence of fracture for ProFile, ProTaper, GTRotary and K3Endo files was 0.28%, 0.41%, 0.39% and 0.52%, respectively. There was no statistically significant difference between instrument systems. The percentage of teeth in which instruments fractured was 1.9% (0.28% for anterior teeth, 1.56% for pre-molars and 2.74% for molars). A total of 26 instruments fractured, of which 23 had tapers of 0.06 or greater. Most of the fragments were located in the apical third of the root canal, and both the median and mode amongst the fragment lengths were 2 mm. CONCLUSIONS: The low incidence of nickel-titanium rotary instrument fracture supports the continued use of these instruments in root canal treatment.

Fracture of ProFile nickel-titanium rotary instruments: a laboratory simulation assessment.

AIM: To determine the incidence of ProFile nickel-titanium rotary instrument fracture in an endodontic laboratory simulation. METHODOLOGY: Three hundred and sixty dental students used 2880 ProFile nickel-titanium rotary instruments to prepare 1440 simulated root canals in 720 plastic teeth, and another 2880 ProFile nickel-titanium rotary instruments to prepare 1440 natural root canals in 720 extracted teeth. A standardized crown-down rotary instrumentation technique was used, which included measures to prevent fracture. Rotary instrument fracture was monitored during and after completion of the laboratory simulation exercises to determine the incidence of fracture. When fracture occurred, data were collected concerning the size of the instrument, the length of the instrument fragment, the location of the fragment in the canal and the curvature of the canal in which the instrument fractured. RESULTS: The incidence of instrument fracture was 0.41% in plastic simulated canals and 0.31% in natural root canals. The overall incidence of instrument fracture was 0.36%. Of the instruments that fractured 67% were size 25, 0.04 taper; and 81% of the fragments were located in the apical third of the canal. The mean, median and mode of the fragment lengths were all 3 mm. CONCLUSIONS: The low overall incidence of fracture in this study suggests that ProFile rotary instruments are safe for use by dental students in laboratory simulations and that if preventive measures are taken the incidence of instrument fracture can be minimized.

Radiovisiography in the detection of periapical lesions.

The periapical areas of 16 teeth from 6 human mandibular jaw specimens were randomly examined by 3 observers using conventional radiography with Kodak E-speed film and radiovisiography (with variable contrast and with fixed contrast). Each periapical area was examined preoperatively and after #2, #4, #6, and #8 sized bur periapical lesions were created in the cortical bone. The three radiographic methods were compared by repeated-measures ANOVA of the accuracy scores for the 16 periapical lesions. Accuracy increased with size of lesion, but did not vary by method. Repeated-measures ANOVA of the accuracy scores of only the smallest and no lesion condition showed that conventional radiography and radiovisiography (variable contrast) have opposite strengths. Conventional radiography tended to be more accurate in the no lesion condition, whereas radiovisiography using variable contrast was somewhat more accurate in the smallest lesion condition. The accuracy of radiovisiography with fixed contrast was not significantly different from the other two methods.

Effect of rotational speed on the breakage of nickel-titanium rotary files.

Nickel-titanium 0.04-tapered rotary files were evaluated for breakage at different rotational speeds in semicircular bovine bone simulated root canals of identical size and radius for each file size group tested. The bovine bone canals had a radius of curvature of 5 mm and a canal width equivalent to the D1 diameter of the file plus 0.04 mm. Profile instrument #3, #4, and #5 were tested at 150, 250, and 350 rpm. A contra-angle electric handpiece was mounted on an Instron machine that was set to deliver a constant downward speed of 5 mm/min. The electric handpiece and Instron machine were activated until the files broke. The amount of file tip penetration into the semicircular bovine bone canal was measured in degrees with a protractor from a radiographic image taken of the file inside the bone model. Greater degrees of tip penetration indicated greater resistance to breakage. Statistical analysis was done and the results indicated that there was a significant difference for all file sizes in the extent of file tip penetration before breakage. In the rotation range between 150 and 350 rpm the greatest extent of penetration occurred at 150 rpm. This study concluded that 0.04 taper nickel-titanium rotary file breakage is less likely to occur if the files are rotated at lower speeds.

Effect of alendronate on immature human dental root explants.

This study investigated the use of alendronate in the formation of new dentin in vitro. Extracted human premolar and molar teeth with immature apices were grown in tissue culture medium for 60 days. Six control specimens were grown without alendronate in the medium, and 22 experimental specimens were grown with alendronate at [10(-9) M] in the medium. Newly formed dentin was stained with tetracycline and procion brilliant red at days 1 to 3, 30 to 33, and 60. Specimens were decalcified and 5-micron sections were prepared for examination using fluorescent microscopy. New dentin formation was measured in microns at the most apical region, at 125-micron from the apical measurement and at 250-micron from the apical measurement. The alendronate group had 57.15% more growth than the control group at the most apical region, and this difference was significant (p = 0.0001). The results indicate that alendronate at [10(-9) M] is effective in accelerating dentin formation in vitro.

A four-rooted quadrangular maxillary molar.

The endodontic treatment of a maxillary molar with an aberrant root morphology can be diagnostically and technically challenging. This case report is presented to illustrate and describe the endodontic treatment of a four-rooted maxillary molar with a quadrangular root trunk morphology.