Microscopic evaluation of three endodontic files pre- and postinstrumentation.

K-type files, Sureflex NiTi files, and FlexoFiles were evaluated morphometrically as they come from the manufacturer, and after being used to instrument root canals 1, 3, and 5 times in maxillary premolars. Evaluation was made using a stereomicroscope at x40 magnification and photomicrographs. The abnormalities found after instrumentation were submitted for statistical analysis. It was concluded that small-sized stainless-steel instruments should be discarded after one use. On the other hand, #30 stainless-steel K-files could be used up to three times and #30 stainless-steel FlexoFiles up to five times. Sureflex NiTi instruments, even after five times, did not show appreciable abnormalities in shape. It is strongly recommended that small-sized nickel-titanium instruments should be discarded after five uses.

An evaluation of sterilization of endodontic instruments in artificial sponges.

The ability to sterilize endodontic files inserted into synthetic sponges was tested. Sponges were subjected to 5 cycles of either dry heat (Driclave) or steam under pressure (autoclave) sterilization. Sterilization was corroborated by microbiological tests. The sponges and files were pre-sterilized separately using steam under pressure. One hundred eighty files contaminated with Bacillus stearothermophilus spores (experimental and positive control) and 60 noncontaminated files (negative control), were inserted into 60 sponges. After each cycle, each file and a portion of sponge surrounding the file were transferred aseptically to tubes containing trypticase soy broth culture medium for bacteriological analysis. None of the tubes containing files and portions of sponges that were subjected to autoclave grew Bacillus stearothermophilus spores. Two of 60 (3.33%) of the tubes that were subjected to sterilization by Driclave demonstrated bacterial growth. Although the sponges tolerated the dry heat cycles well physically, sterilization was achieved in only 96.67% of the cases.

Torsional testing of the Lightspeed nickel-titanium instrument system.

Revolutions to separation and maximum torque at failure of 216 Lightspeed instruments were determined in an instron using a clockwise rotation. After instruments failed, the distance the instrument separated from the tip was measured. Comparison of the results with existing ANSI/ADA specification no. 28 showed that the Lightspeed far exceeded the values of the specification for revolution to failure. On the other hand, torque to failure results showed that instrument sizes 20 and 25 exceeded the specification, whereas instrument sizes 30 through 50 were below the minimum values. Half-size instruments were not compared, because specifications for half-sizes do not exist. Comparison between mean torque values and instrument shaft diameters of the Lightspeed previously reported showed a near linear relationship up to and including instrument size 50, but overall torque to failure increased exponentially when related to shaft diameter (coefficient of determination = 0.9923). Lightspeed instruments separated 2.32 +/- 0.60 mm from the tip, generally within the land area or at the beginning of the shaft. Scanning electron microscopic observation of the Lightspeed instrument fracture site showed two distinct areas. There was a striated concentric area in the periphery of the fracture characteristic of a brittle or cleavage fracture and a corrugated area in the center of the fracture characteristic of a ductile fracture.

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.

pH changes at the surface of root dentin when using root canal sealers containing calcium hydroxide.

The purpose of this study was to investigate long-term pH changes in cavities prepared in root surface dentin of extracted teeth after obturation of the root canal with gutta-percha and a variety of sealers containing calcium hydroxide. After cleaning and shaping, root canals in 50 recently extracted, human single-rooted teeth were divided into five groups. Each of four groups was obturated with gutta-percha and either Sealapex, Sealer 26, Apexit, or CRCS, all of which contain calcium hydroxide. The remaining group served as the control and was not obturated with gutta-percha or sealer. Cavities were prepared in the facial surface of the roots in the cervical and middle regions. The pH was measured in these dentinal cavities at the initiation of the experiment, and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days after obturation. Results indicate that the pH at the surface of the root does not become alkaline when calcium hydroxide cements are used as root canal sealers. Regardless of the sealer used, the observed pattern of pH change was not different from that seen in the control group of roots that were not treated with sealer. It is concluded that calcium hydroxide-containing cements, although suitable for use as root canal sealants, do not produce an alkaline pH at the root surface. If such a pH change is related to treatment of root resorption, these sealants do not contribute to this treatment.

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.

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.

Morphometric video analysis of the engine-driven nickel-titanium Lightspeed instrument system.

Two hundred and sixteen Lightspeed instruments were evaluated microscopically for the presence of corrosion, surface debris, and alloy defects. The instruments were assessed morphometrically for consistency of physical design and dimensions by measuring and analyzing eight parameters of the instrument pilot tips, heads, and shafts. Results from visual inspection showed that none of the instruments were corroded; 23 presented surface porosities, and 17 had sharp strips of alloy. Data obtained by morphometric analysis indicated the mean diameter of the head of only 7 of 18 sizes met the +/- 0.02 mm allowable tolerance set forth by the American Dental Association (ADA) Specification No. 28. Observation and video analysis indicated that instruments of the same size adhere to the same basic design, but that morphometric variations do exist. The visual and intersize analysis indicated that the Lightspeed is not an instrument of any one determined shape that changes only in diameter. Rather, it is a series of instruments that show gradual shifts in both size and shape as the instrument size increases. Lightspeed instruments are a new type of nickel-titanium endodontic instrument that cannot be evaluated using the standards proposed by the American National Standards Institute/ADA Specification No. 28 for files and reamers.

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.

A comparison of root canal preparations using Ni-Ti hand, Ni-Ti engine-driven, and K-Flex endodontic instruments.

This study used a modified Bramante technique and new digital subtraction software to compare root canals prepared by nickel-titanium (Ni-Ti) hand, Ni-Ti engine-driven, and stainless steel hand endodontic instruments. Sixty mesial canals of extracted human mandibular molars were randomly divided into five groups. The roots were embedded in clear resin and cross-sectioned in the apical and mid-root areas. 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 in group A. Group C was prepared with NT Sensor engine-driven files. Group D canals were prepared with Ni-Ti Canal Master "U" hand instruments. Group E was prepared with engine-driven Ni-Ti Lightspeed instruments. Digitized images of the uninstrumented canals were compared with images of the instrumented canals. Engine-driven Ni-Ti instruments (Lightspeed and NT Sensor file) and hand instrumentation with the Canal Master "U" caused significantly less canal transportation (p < 0.05), remained more centered in the canal (p < 0.05), removed less dentin (p < 0.05), and produced rounder canal preparations than K-Flex and Mity files. Engine instrumentation with Lightspeed and NT Sensor file was significantly faster than hand instrumentation (p < 0.05).

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.

Cavitational bone defect: a diagnostic challenge.

A patient with a history of trauma to the maxillary left anterior region presented with chronic pain of unknown etiology. Root canal therapy and periradicular surgery failed to resolve the persistent pain. A second surgical procedure revealed a bone cavity superior and distopalatally to the apex of the maxillary left lateral incisor. The suspected etiology was necrotic bone removed from the bone cavity.

Histological evaluation of ultrasonic debridement comparing sodium hypochlorite and water.

Twenty extracted human mandibular first and second molars with mesial canal curvatures of 18 to 35 degrees were randomly divided into two groups. Following routine endodontic access and canal length determination one of the mesial root canals was ultrasonically instrumented, using tap water in the first group or 2.6% sodium hypochlorite irrigation in the other. In both groups the other mesial canal was used as a control. The mesial roots were decalcified, serially sectioned, and stained with hematoxylin and eosin. Wall planing and soft tissue debridement were blindly evaluated using the light microscope. Mean canal wall planing and soft tissue debridement scores were compared by multiple t tests. Sodium hypochlorite, in conjunction with ultrasonic instrumentation, was more effective than tap water in wall planing when the entire root length was considered. Sodium hypochlorite, in conjunction with ultrasonic instrumentation, was more effective than tap water in soft tissue debridement in the middle third of the canal. Both irrigants were ineffective in conjunction with ultrasonic instrumentation in removing soft tissue from the main canal, the isthmus between canals, the canal fins, and the multiple branches or deltas often encountered in the apical one-third of the canal.

Reactions of rat odontogenic tissues to heat.

Twenty-four Wistar rats were anesthetized and 200 degrees C heat was applied for 4 minutes to each mandibular left first molar. Eight of these rats were then killed at 2, 8, and 14 weeks. The subject and control teeth were radiographed and compared. They were then prepared for histologic evaluation and scored for levels of inflammation in both the pulpal and periradicular tissues. Furcal, interproximal, and apical radiographic changes were found at all three time intervals. These changes involved progressively larger percentages of teeth at 8 and 14 weeks. Histologically, complete necrosis and/or abscess formation were found in the coronal portions of all experimental pulps. With time, inflammatory changes increased in intensity and progressed through the radicular pulps, resulting in necrosis or calcific changes and, finally, inflammatory changes in the periradicular areas. The pathosis created by the application of heat was devoid of microorganisms as evaluated by the Brown and Brenn stain.

Comparison of the Canal Master endodontic instrument and K-type files for enlargement of curved root canals.

Twenty mandibular molars with 40 mesial curved root canals were instrumented with a circumferential technique using K files and the Canal Master instrumentation technique by junior dental students whose only endodontic experience had been completion of a preclinical endodontic course. Preoperative and postoperative radiographs were taken facially and mesially with instruments in place. The canals were evaluated radiographically for transportation 1 mm and 4 mm from the apex. The mesial roots were cross-sectioned at the same level. The sections were evaluated for roundness of the canal preparation. It was concluded that the Canal Master instrumentation technique transported the root canal less and produced rounder preparations than the K file circumferential technique. There appears to be a greater tendency for breakage with the Canal Master.

Temperature changes in thermoplasticized gutta-percha: a comparison of two ultrasonic units.

With the use of an extracted human tooth as in vitro model, this study measured temperature changes in the surface of gutta-percha while it was being ultrasonically thermoplasticized. Two sources of ultrasonic oscillation were used: a Cavitron 2001 ultrasonic unit with a file in a PR-30 insert and an ENAC ultrasonic unit with a plugger or file. Temperature elevation in the apical third of the tooth was minimal with either instrument (1.66 degrees C to 3.74 degrees C). The temperature rise in the middle third was higher with the ENAC unit, although probably still within clinically acceptable limits (range, 6.35 degrees C to 19.10 degrees C). The time taken for each unit to thermoplasticize the gutta-percha and reach a predetermined distance in the experimental model was recorded and defined as instrument efficiency. The Cavitron unit that had the PR-30 insert with a No. 25 file required 0.48 sec/mm, whereas the ENAC unit with a No. 25 file required 10.83 sec/mm and the ENAC unit with a plugger required 8.38 sec/mm. It appears that the Cavitron unit with a PR-30 insert was more than 22 times as efficient as the ENAC unit for thermoplasticizing gutta-percha under the experimental conditions used in this study.

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.

Cutaneous sinus tracts of dental etiology.

Intermittently draining cutaneous sinus tracts in the area of the face and neck may be caused by chronic dental infection. Diagnosis of the cause may be challenging but is the key to successful therapy. Two cases of these uncommon lesions are presented; one involved a mandibular molar and the other a mandibular incisor. Nonsurgical endodontic treatment was performed. Healing was rapid and uneventful.