Carlos E. del Rio

Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography

Computed tomography was used to evaluate root canals prepared by nickel-titanium (Ni-Ti) hand and stainless steel hand endodontic instruments. Thirty-six single-rooted teeth of similar shape and canal size were divided into three groups. The teeth were scanned by computed tomography before instrumentation. In group A, canals were instrumented using a quarter turn/pull technique with K-flex files. In group B, canals were prepared with Ni-Ti hand files (Mity files) using the same technique as group A. Group C was prepared with Ni-Ti hand files (Mity files) using a reaming technique. Instrumented teeth were again scanned using computed tomography, and reformated images of the uninstrumented canals were compared with images of the instrumented canals. Ni-Ti instruments (Mity file) used in a reaming technique caused significantly less canal transportation (p < 0.05), removed significantly less volume of dentin (p < 0.05), required less instrumentation time (p < 0.05), and produced more centered and rounder canal preparations than K-flex stainless steel files used in a quarter turn/pull technique. The computed tomography imaging system used in this study provided a repeatable, noninvasive method of evaluating certain aspects of endodontic instrumentation.

Longitudinal sealing ability of mineral trioxide aggregate as a root-end filling material

This study evaluated the ability of mineral trioxide aggregate (MTA) to seal the root end effectively. Seventy-six single-rooted, extracted human teeth were cleaned and shaped using a step-back technique. After root-end resection and ultrasonic preparation, 72 root sections were randomly allocated to three groups and filled with dental amalgam and cavity liner, Super-EBA, or MTA. Microleakage was assessed at 24 h, 72 h, 2 wk, 4 wk, 8 wk, and 12 wk, using a fluid filtration measurement system. MTA demonstrated excellent sealing ability throughout 12 wk of fluid immersion, comparable with that observed for Super-EBA. Microleakage in the MTA group, as well as the Super-EBA group, was significantly less (p < 0.05) than in the amalgam group at 24 h, 72 h, and 2 wk. At the subsequent periods, there were no significant differences among the three materials. In this study, MTA was determined to be superior to amalgam, and comparable with Super-EBA in preventing microleakage when used as a root-end filling.

Sealing Quality of a Temporary Filling Material.

Endodontic access cavities were prepared in forty extracted human teeth. The access cavities were obturated with Cavit and tested for leakage with methylene blue. The data suggested that at least a 3.5 mm. thickness of Cavit should be used in order to prevent leakage. Examination under the scanning electron microscope showed areas in which the constituents of Cavit were improperly mixed, which may lead to increased penetration.

Changes in pH at the dentin surface in roots obturated with calcium hydroxide pastes

The purpose of this study was to determine the pH, after defined periods of time, in cavities prepared in the facial surface of the cervical, middle, and apical regions of roots obturated with calcium hydroxide pastes. Root canal instrumentation was performed on 40 recently extracted, single-rooted human teeth. Cavities 1.5 mm in diameter and 0.75 mm in depth were prepared in the cervical, middle, and apical regions of the facial surface of each root. Teeth were randomly divided into four groups. One group was left unobturated and served as a control. The three remaining groups were obturated with either aqueous calcium hydroxide, calcium hydroxide mixed with camphorated monochlorophenol. or Pulpdent pastes. Access cavities and apical foramina were closed with Cavit. Each tooth was stored individually in a vial containing unbuffered isotonic saline. pH at the surface was measured in the cervical, middle, and apical cavities at 0 and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days. Results indicate that hydroxyl ions derived from calcium hydroxide pastes diffused through root dentin at all regions over the experimental period of 120 days. The pattern of pH change at the tooth surface was similar in all regions of the root, regardless of the type of calcium hydroxide paste used. This was a rapid rise in pH from a control value of pH 7.6, to greater than pH 9.5 by 3 days, followed by a small decline to pH 9.0 over the next 18 days, before finally rising and remaining at, or above pH 10.0 for the remainder of the experimental period. Pulpdent paste in the apical region was the only exception in this pattern, producing a pH rise nearly one full unit below the other pastes, pH 9.3. These results indicate that, for all pastes tested, a high pH is maintained at the root surface for at least 120 days.

Incidence of periradicular pathoses in endodontic treatment failures

Biopsy reports from 150 periradicular tissue specimens obtained from teeth refractory to nonsurgical endodontic therapy were reviewed. The specimens were submitted by postdoctoral dental students in the Department of Endodontics, and the biopsy reports were prepared by oral pathologists at the University of Texas Health Science Center at San Antonio. The study found that 59.3% of the periradicular lesions were granulomas, 22% cysts, 12% scars, and 6.7% other pathoses. The majority (56%) of endodontically treated cases which failed to heal were recognized within 2 yr after the completion of therapy. The most common location for surgical retreatment was the anterior maxilla, followed by the posterior maxilla, the posterior mandible, and the anterior mandible. The periapical granuloma was the predominant pathosis at each location.

Histological evaluation of ultrasonic and sonic instrumentation of curved root canals

Fifty extracted human mandibular first and second molars with mesial canal curvatures of 18 to 35 degrees were randomly divided into five groups. After routine endodontic access and canal length determination, one of the mesial root canals was instrumented using tap water and one of the following instrumentation methods: (a) hand instrumentation; (b) ultrasonic instrumentation with the Cavi-Endo unit; (c) ultrasonic instrumentation with the Enac unit; (d) sonic instrumentation with the Medidenta unit; and (e) sonic instrumentation with the Endostar 5 unit. The other mesial canal was used as a control. The mesial roots were decalcified, serially sectioned, stained with hematoxylin and eosin, and blindly evaluated using the light microscope. The mean canal wall planing and soft tissue debridement scores were compared by analysis of variance. There was no statistically significant difference among the groups for wall planing or soft tissue debridement.

Comparison of mechanical and standard hand instrumentation techniques in curved root canals

The original and postinstrumentation shapes of the mesial root canal system of 12 mandibular molars were compared after being instrumented with a mechanical handpiece and a hand instrumentation technique. Area of dentin removed and amount and direction of transportation were evaluated in relation to degree of root canal curvature. Pre- and postinstrumentation measurements were taken of the root canal system in the cervical, middle, and apical thirds. The mechanical handpiece removed dentin and transported the root canal more than the hand instrumentation in the cervical and apical thirds. Both techniques transported to the distal in the cervical third and to the mesial in the apical third. In the middle third, the mechanical handpiece transported more to the mesial and the hand instrumentation more to the distal. Degree of root canal curvature had no influence on the amount of dentin removed or transportation of the root canal.

A computerized method for evaluating root canal morphology.

Access was performed on nine extracted single-rooted permanent human premolars. Complete debridement of the root canal system was accomplished by running high volumes of NaOCl through them for 90 min. Volumes of the root canal system and access preparation were calculated for each specimen by weighing the teeth, filling them with contrast medium at a known density, and reweighing them. Radiographs were taken of each tooth at known angles with the contrast medium in place. Then each tooth was cross-sectioned at known distances from the anatomical apex. Microscopic measurements were made of canal diameter on each cross-section. The radiographs of each tooth were evaluated by a computerized digital image processing program. Computerized calculations of canal volume and diameter were made and compared with the actual measurements taken from each tooth. The data were analyzed by paired t tests. Results indicate this computerized method for evaluating diameter of root canals to be accurate within 0.1 mm of actual measurements. The volumetric data differed significantly. The difference was probably due to voids in the contrast medium. Overall, this technique appears to be very accurate in determining the anatomy of root canal systems.

Corrosion of endodontic silver cones in humans: a scanning electron microscope and X-ray microprobe study

Analyses with the scanning electron microscope and the X-ray microprobe were performed on 13 silver cones removed from 12 patients. The cones showed changes that ranged from surface dulling to black corrosion and pitting. Sulfur and chlorine were detected at the apical end of the cones and in the biopsy specimens of periapical tissues.

Effect of nickel-titanium engine-driven instrument rotational speed on root canal morphology.

Thirty-six mesial canals in 18 extracted human mandibular molars were randomly allocated to three experimental groups. Specimens were prepared and evaluated using a modified Bramante technique. Teeth were sectioned at the midroot and apical regions. Canals were prepared with the Lightspeed instruments rotating at 750, 1300, or 2000 rpm. Digitized uninstrumented and instrumented canal images were compared via subtraction software. There was no significant difference (p <0.05) among the three experimental groups in the amount of dentin removed, canal transportation, or the ability of the instrument to remain centered in the canal.