Lisa R. Wilcox

An evaluation of coronal microleakage in endodontically treated teeth. Part III. In vivo study

Root canal therapy was performed on posterior teeth in monkeys using gutta-percha and various sealers for obturation. The access openings were restored with zinc oxide-eugenol. Seventy-two hours later, the temporary restorations were removed and the coronal openings exposed to the oral environment for 1 wk. Following removal, the teeth were placed in dye and cleared to allow visualization of dye penetration. The results showed the presence of dye in teeth in all groups with no significant differences among the groups.

The relationship of root canal enlargement to finger-spreader induced vertical root fracture

The purpose of this study was to assess the effect of lateral condensation forces on the development of vertical root fracture (VRF) in teeth that have undergone controlled, measured internal root reduction (i.e. canal preparation). Thirty-four straight-rooted maxillary anterior teeth were used. For each tooth a simulated PDL was fabricated from a uniform 0.15 mm layer of silicone impression material. The teeth were mounted in resin to facilitate removal for observation. They were radiographed and measured at 2, 4, 6, and 8 mm from the apex. They were prepared with the step-back method so that the canal width was 20% of the total root width at 2, 4, 6, and 8 mm from the apex. They were obturated using a fine finger spreader attached to a jig that produced a static force of 3.3 kg for 15 s after placement of each gp point. Obturation was complete when the spreader did not penetrate apical to 8 mm from the apex. Twenty-four h after obturation the teeth were examined by transillumination for VRF. Teeth not exhibiting VRF were tested further after gp removal and canal enlargement of 30%, 40%, and 50% The teeth were sectioned at 2-mm increments with a diamond wafering saw and examined under stereomicroscope. No VRF occurred at 20% or 30%; 5 teeth fractured at 40% and 7 at 50%. These teeth had root surface craze lines that developed during testing. Craze lines had also developed in all 17 of the remaining unfractured samples. No VRF occurred after testing unless craze lines were previously present.

Endodontic retreatment: evaluation of gutta-percha and sealer removal and canal reinstrumentation.

To examine the appearance of root canal walls after retreatment, 80 extracted teeth were chemomechanically prepared using a stepback flare technique and obturated with gutta-percha and either Roths 801 or AH26 sealers. Four techniques were used to remove gutta-percha and sealer: method 1—heat and files; method 2—heat, files, and Cavi-Endo; method 3—chloroform and files; and method 4—chloroform, files, and Cavi-Endo. The teeth were sectioned longitudinally and the amount of debris remaining was quantitated. The results showed that no technique removed all debris. When AH26 was the sealer, method 4 was significantly less effective. When Roths 801 was the sealer, method 1 was significantly less effective. Teeth obturated using Roths 801 sealer were significantly cleaner after reinstrumentation.

Endodontic Retreatment: Ultrasonics and Chloroform as the Final Step in Reinstrumentation

Forty extracted teeth were instrumented using a step-back flare technique and obturated with gutta-percha and either AH26 or Roths 801 sealer. After 3 months the canals were retreated by removing gutta-percha and sealer with hot instruments followed by chloroform and files. As a final step, the teeth were instrumented using ultrasonics with either chloroform or with NaOCl. Most teeth were well cleaned. No significant differences were found between sealer groups or between the two irrigants as to the ability to remove gutta-percha/sealer.

Endodontic retreatment with halothane versus chloroform solvent

Chloroform has been the most widely used solvent in endodontics, but due to concerns about its safety, alternatives have been sought. The purpose of this study was to compare the effectiveness of gutta-percha removal and time of retreatment between halothane and chloroform used as solvents. Thirty mandibular premolars were prepared, obturated, and stored in a humidor for 14 months, after which they were randomly divided into two groups for retreatment. The teeth were retreated using either halothane or chloroform as the solvent. The time of retreatment was measured to the nearest minute. Retreatment was deemed complete when there was no evidence of gutta-percha or sealer on the files or paper points. Teeth were split longitudinally and photographed. The resulting slides were projected, the canals traced, and the areas of the canal, gutta-percha, and sealer were measured using a sonic digitizer. The results were analyzed statistically by t test. The results showed no significant difference in gutta-percha removal between the two groups. The chloroform group took significantly less time to retreat than halothane (7.7 min. versus 10.8 min, respectively).

Detection of pulpal circulation in vitro by pulse oximetry.

Evaluation of pulse oximetry as a potential method of determining pulp vitality was the subject of this research. An in vitro model of pulpal circulation was fabricated to test the design for a dental pulse oximetry sensor. Blood samples equilibrated with hypoxic gas mixtures were circulated through the model by a peristaltic pump. A pulse was simulated by introduction of gas bubbles into the blood circulation. Pulse oximeter readings for saturation were recorded and compared with blood gas analysis results. Statistical analysis revealed no difference between pulse oximetry and blood gas analysis with a highly significant correlation coefficient. Clinical evaluation of this application is currently in progress.

In vitro evaluation of four methods of sealer placement

Sealer is required during root canal obturation, although no studies have shown which method of sealer placement provides the best coverage. This study evaluated and compared four methods of sealer placement: file, lentulo spiral, ultrasonic files, and master gutta-percha cone. Forty mandibular incisors were prepared by a step-back technique. AH26 (0.04 ml) was applied to the placement device, the sealer was placed in the canal, and the canal was obturated with lateral condensation of gutta-percha. The specimens were cleared and evaluated for the presence of the sealer in the apical, middle, and coronal thirds of the canal. The results showed no statistically significant differences among the four groups. The greatest variation in sealer coverage was found in the apical level. Sealer coverage in the coronal and middle thirds was nearly identical regardless of sealer placement technique.

Endodontic retreatment of Thermafil versus laterally condensed gutta-percha

The Thermafil device is becoming a popular obturating material. Because endodontic failures inevitably occur with all techniques, questions of retreatment of Thermafil-obturated teeth will also arise. The purpose of this study was to compare retreatment of Thermafil and laterally condensed gutta-percha. Thirty-five mandibular incisors were prepared with a stepback flare technique and divided into two groups. One group (n = 20) was obturated using Thermafil, the other group (n = 15) was obturated with laterally condensed gutta-percha. The teeth were stored in a humidor for 3 months to allow sealer to set. Retreatment of both groups was accomplished using a combination of heat and chloroform solvent. The time for retreatment was recorded. The teeth were split longitudinally and the amount of gutta-percha remaining in the root canal was measured and analyzed statistically. The results showed that in the coronal one-third of the canal, use of the Thermafil device resulted in significantly more remaining gutta-percha than use of laterally condensed gutta-percha. However, in the apical and middle one-third of the canal the difference in remaining gutta-percha between Thermafil and laterally condensed gutta-percha was not significant. The metal carrier was easily removed and the mean time for retreatment was 6.3 min for Thermafil compared with 5.7 min in the lateral condensation group.

Coronal microleakage of permanent lingual access restorations in endodontically treated anterior teeth

Forty-six intact extracted human anterior teeth were treated endodontically with laterally condensed gutta-percha and sealer. The teeth were restored with a base of either zinc phosphate or temporary stopping and a permanent restoration of either acid etched composite resin with GLUMA as the dentin bonding agent or with Ketac-Fil glass ionomer. The teeth were thermocycled, coated with nail varnish (except for the access), immersed in silver nitrate, developed, and sectioned longitudinally. The linear dye penetration was measured. All restorations permitted leakage into the base. All groups had specimens which leaked into the gutta-percha. There was a tendency for the glass ionomer/zinc phosphate group to leak least, but there were no statistically significant differences among the groups.

Effect of a Final Alcohol Rinse on Sealer Coverage of Obturated Root Canals

An endodontic sealer is required to provide an apical and coronal seal in root canals. No previously reported methods of sealer placement completely coated canal walls. The purpose of this study was to dehydrate canal walls with alcohol and determine if this permitted better sealer coverage. Forty single-rooted teeth were prepared and divided into 4 groups of 10 teeth according to method of sealer placement and final irrigant: (a) by lentulo spiral and (b) file NaOCl, (c) lentulo and alcohol, and (d) file and alcohol. After canal preparation, groups 1 and 2 were irrigated with 1 ml of NaOCl and dried with paper points. Groups 3 and 4 were irrigated with 1 ml of alcohol and dried. AH26 (0.04 ml) dyed with charcoal black was applied to the apical end of the file or lentulo and placed in the canal to coat the walls. Gutta-percha without additional sealer was laterally condensed. Teeth were cleared and evaluated for location and amount of sealer visible. Data were evaluated by Kruskal-Wallis and analysis of variance. The results showed (a) no significant differences among the four groups, (b) all areas had sealer present, (c) the coronal third had > 50% sealer coverage in nearly all teeth, and (d) the middle and apical thirds showed the most variability in sealer coverage.