Steve Montgomery

A comparison of weights of debris extruded apically by conventional filing and canal master techniques

Sixty extracted human teeth were divided into three groups of 20 each. Apically extruded debris and irrigant were collected, dried, and weighed by the following three instrumentation techniques: (a) group 1, filing 1 mm short of the foramen; (b) group 2, Canal Master instrumentation to the foramen; and (c) group 3, filing to the foramen (for a relative comparison). The results indicated that all three groups were significantly different from one another. Group 1 had the least amount of debris extruded. Of the two groups instrumented to the foramen, group 3 had twice as much debris extruded as group 2. An apical dentinal plug was frequently found in group 1 and was probably a major reason why this group had the least amount of extruded debris. The significance of this dentinal plug and possible indications for instrumentation to the foramen are discussed.

Another look at root canal instrumentation

Several aspects of root canal instrumentation need additional research. Various factors must be considered in an analysis of instrumentation of the root canal system: the dentin that is cut; the technique used to cut it; the design of the instruments; the material and manufacturing process used to make the instruments; the irrigant used during the procedure; and the anatomic configuration of the root canal system. An analysis of these factors clearly indicates that existing root canal instruments and techniques are less than ideal and, in fact, do not accomplish what is expected of them. Root canals must be properly, but, at the same time, destructive and unnecessary removal of dentin should be kept to a minimum. The Flex-R and Canal Master instruments were developed to address some of the shortcomings of existing instruments and techniques. More scientifically based research is needed to fully evaluate these new instruments and techniques and to develop future instruments.

External cervical resorption after bleaching a pulpless tooth

A tooth with cervical resorption possibly caused by an internal bleaching technique was treated with calcium hydroxide. This case had characteristics in common with the other seven cases that have been described in the literature. Several possible treatment methods are discussed, along with the speculation that internal bleaching of tetracycline-discolored teeth may lead to cervical resorption.

The Effects of Canal Master, Flex-R, and K-Flex Instrumentation on Root Canal Configuration

The purpose of this study was to compare the Canal Master instrument and instrumentation technique (CM/CMI) to Flex-R files used with a balanced force technique (FR/BF) and K-Flex files used with a step-back filing technique (KF/SB). Thirty-six root canals in extracted human mandibular molars were equally divided into three groups. The roots were sectioned, then photographed and evaluated before and after instrumentation. Evaluation included canal shape, direction and extent of transportation, amount of dentin removed, and centering ability. Canal Master instrumentation and Flex-R/balanced force techniques both produced more round preparations than the K-Flex/step-back. All three techniques resulted in canal transportation, although to varying degrees. Flex-R/balanced forces and Canal Master instrumentation transported very little up to a #30, and Canal Master instrumentation transported significantly less after the #45 instrument at mid-root. K-Flex/step-back removed the most dentin while Flex-R/balanced force removed the least in the apical sections and Canal Master instrumentation removed the least at mid-root. The ability of Canal Master instrumentation to keep instruments centered in the canals was significantly better than for K-Flex/step-back.

Chemical decontamination of gutta-percha cones with polyvinylpyrrolidone-iodine

Abstract Commercially available gutta-percha cones can be effectively decontaminated by immersion for 6 minutes or more in polyvinylpyrrolidone-iodine prior to insertion into root canals.

Cervical canal leakage after internal bleaching procedures

The effects that walking bleach procedures had on root canal filling leakage and the extent of dentinal penetration were studied. Forty teeth were divided into four groups: 1—GP, set sealer, no base; 2—GP, set sealer, 2-mm Cavit base; 3—GP, unset sealer, no base; and 4—GP, unset sealer, 2-mm Cavit base. All were bleached for 7 days, fresh bleach was added for another 7 days, then methylene blue dye was placed for 5 days. The extent of dye penetration apically along the roct canal filling and through the dentinal tubules was evaluated. The results indicate that 2 mm of Cavit was sufficient to significantly reduce linear leakage and dentinal penetration. The Cavit should be placed to a level slightly coronal to the facial cementoenamel junction. Teeth with cemental defects demonstrated greater perpendicular dye penetration in the areas of the defects than those with intact cementum. The data from this study suggest the use of a base material over gutta-percha in clinical practice prior to internal walking bleach procedures.

The solvent effects of calcium hydroxide irrigating solution on bovine pulp tissue

The solvent effects of calcium hydroxide irrigating solution (used alone and in combination with sodium hypochlorite) on bovine pulp tissue were studied. Forty pieces of pulp tissue weighing 90 mg each were treated with calcium hydroxide solution alone, calcium hydroxide and sodium hypochlorite alternated, sodium hypochlorite alone, and saline alone. Each piece of tissue was treated for 32 min. Desiccated pretreatment and posttreatment weights were compared. There was no significant difference between the dissolution capability of calcium hydroxide solution used alone and of saline. No significant difference was noted between calcium hydroxide solution and sodium hypochlorite used alternately, and sodium hypochlorite used alone. However, both of these groups were significantly more effective at dissolving tissue than calcium hydroxide solution alone or saline. Calcium hydroxide solution was an ineffective solvent of pulpal tissue. If tissue dissolution is desired during root canal therapy, the use of calcium hydroxide solution as the sole irrigant is no more effective than saline.

Effectiveness of a brush in removing postinstrumentation canal debris

The purpose of this study was to evaluate the effectiveness of a brush in removing debris in the root canal after endodontic instrumentation. Seventeen extracted human maxillary first molars with mesiobuccal canal curvatures of 25 to 35 degrees were divided into two groups. After endodontic access and determination of working length, one group was hand instrumented to a #45 file and the other group to a #35 file at the working length. After the teeth were sectioned at the working length and at 2, 4, and 6 mm from the working length, they were evaluated for debris remaining in the canal space. The specimens were reassembled, brushed with an Endobrush, and reevaluated. The scores for instrumentation alone (controls) and instrumentation plus brushing were compared with paired t tests. Instrumentation with brushing was significantly better than instrumentation alone in debriding the root canal.

Effect of Restoration Thickness on the Sealing Ability of TERM

An in vitro study was done using a fluid filtration device to compare microleakage of Temporary Endodontic Restorative Material (TERM) at various thicknesses. Forty-four extracted mandibular molars had their roots removed at the cementoenamel junction, occlusal table flattened, and a standardized endodontic access made in the crown. The teeth were restored with TERM in thicknesses of 1, 2, 3, and 4 mm, and quantitatively measured for leakage (microliters/min) at intervals of 1 and 24 h and 1, 3, and 5 wk. Thermocycling was accomplished at the 5-wk interval. Positive controls received 4-mm-thick IRM or gutta-percha restorations and were measured at 24 h only. Repeated measures of analysis of variance found no significant difference (p < 0.05) in leakage values in any group over time or between any of the different thicknesses. Positive controls showed significantly more leakage than all other groups. TERM maintained as tight a seal at 1-, 2-, and 3-mm thicknesses as it did at 4 mm and may be suited for clinical situations where less than 4 mm of restorative space exists.

Evaluation of thermafil obturation of curved canals prepared by the canal master-U system

A dye penetration study was performed to compare the apical seals obtained with laterally condensed gutta-percha and Thermafil. The sample group contained 40 teeth with curved canals which had been prepared with the Canal Master-U System. Canal curvature was measured and the teeth were decalcified, cleared, and linear dye penetration was measured. Thermafil had statistically more linear leakage as verified by a Wilcoxon test (p < 0.001). Thermafil also had greater variability in the apical seal than did laterally condensed gutta-percha as verified by an F test (p < 0.001). A Spearman correlation analysis (p > 0.05) showed that there was no correlation between root curvature and linear dye penetration.