J. Gordon Marshall

Influence of Instrument Size on Root Canal Debridement

Files of Greater Taper (GT) are rotary nickel-titanium files of three tapers (0.06, 0.08, 0.10) with file tips of sizes 20, 30, and 40. The purpose of this study was to compare in an in situ model the efficacy of root canal debridement in the apical 3 mm when instrumenting to a GT size 20 or a GT size 40 at working length. Twenty matched human cadaver teeth with 32 canals were decoronated at the cementoenamel junction and instrumented with rotary Files of GT to either GT size 20 or GT size 40. Sodium hypochlorite, EDTA, and RC Prep were chemical aids for debridement. The teeth were extracted; decalcified; sectioned at 0.5 mm, 1.5 mm, and 2.5 mm from the apex; and prepared for histologic examination and quantification of remaining debris. No differences were found between each level within each apex size group; however, the GT size 20 group left significantly more debris in the apical third compared with the GT size 40 group. A regression analysis showed that the apical third cleanliness could be predicted mainly by instrument size and to a lesser extent by the canal length. Irrigant volume, number of instrument changes, and depth of penetration of irrigation needle were not likely to explain differences in debridement.

Evaluation of Apical Debris Removal Using Various Sizes and Tapers of ProFile GT Files

The purpose of this study was to evaluate the effect of preparation taper using size #20 or size #40 ProFile GT files on the ability to introduce irrigant and remove debris from root canals. Forty-eight bilaterally matched pairs of extracted teeth were instrumented using.04-,.06-,.08-, and.10-tapered files with one tooth of each pair enlarged to size #20 and the other to size #40. The teeth were sectioned at 1 mm and 3 mm from the apex, and the amount of remaining debris was calculated as a percentage of the total lumen area. The following variables were evaluated: apical preparation size, preparation taper, total volume of irrigation, depth of irrigation needle penetration, and number of instrument changes needed to reach working length. Compared with the size #40 preparations, a significantly greater percentage of remaining debris was observed in the size #20 preparations at the 1-mm level for all tapers except the.10 taper group in which there was no significant difference (p = 0.982). There were no significant differences between any groups at 3 mm. Results suggest that debris is more effectively removed using.04,.06, and.08 ProFile GT instruments when the apical preparation size is larger (size #40) compared with size #20 apical preparations. When a taper of.10 can be produced at the apical extent of the canal, there is no difference in debris removal between the two preparations sizes.

An In Vivo Comparison of Two Frequency-based Electronic Apex Locators

The purpose of this study was to compare the accuracy of a two-frequency (Root ZX) and a five-frequency (Endo Analyzer Model 8005) electronic apex locator under clinical conditions. Thirty-two teeth planned for extraction were used. The coronal portion of each canal was flared using Gates Glidden drills and Orifice Shapers. The canals were irrigated with 2.6% sodium hypochlorite. A K-type file was used to determine a separate working length in each canal using the electronic apex locators. The teeth were extracted and the apical 4 mm of each root canal was exposed along the long axis of the tooth. Photographic slides of each canal were projected and the file position in relation to the minor diameter was determined by two investigators. The mean distance between the electronic apex locator working length and minor diameter was 1.03 mm for the Endo Analyzer and 0.19 mm for the Root ZX. A paired sample t test showed that the Endo Analyzer had significantly longer readings beyond the minor diameter than the Root ZX (p < 0.0001). The ability to locate the minor diameter (+/- 0.5 mm) was 90.7% for the Root ZX and 34.4% for the Endo Analyzer Model 8005.

Evaluation of cracks associated with ultrasonic root-end preparation

The purpose of this study was to evaluate the integrity of resected root-end surfaces of extracted human teeth after using ultrasonic tips at low or high frequencies for root-end preparation. Thirty bilaterally matched pairs of single-rooted human teeth had root-end resections using a low-speed diamond saw and were examined for root-end cracks. The matched pairs of teeth were then divided into two experimental groups, with one member of each pair being placed in each group. In group 1, root-end preparations were made with an ultrasonic tip on the lowest frequency setting. The preparations in group 2 were done on the highest power setting. Two investigators again examined the resected root-ends using a stereomicroscope at x20 to x63 and recorded the numbers, types, and location of the cracks. Three types of cracks were observed: canal cracks, intradentin cracks, and cemental cracks. There were significantly more root-ends with cracks after ultrasonic root-end preparation than after root-end resection only. In root-ends that had any cracks, significantly more canal cracks per root occurred when the ultrasonic tip was used on the high-frequency setting for root-end preparation than when the ultrasonic tip was used on the low power setting.

A comparison of four instrumentation techniques on apical canal transportation

The ability of four instrumentation techniques to enlarge and maintain the central axis of 51 curved canals was evaluated radiographically. Curved canals in extracted human teeth were instrumented using a step-back preparation with K-files, crowndown preparation with K-files, sonic instrumentation with Shaper-Sonic files, and the NiTiMatic preparation system. Following coronal preflaring, each canal was instrumented to a #35 file 1 mm from the anatomic foramen. Radiographs were taken with mercury filling the canal system using a specially designed model that allowed for the pre- and postinstrumentation canal to be viewed on the same radiograph. Canal enlargement and apical transportation resulting from the various instrumentation techniques were evaluated using computer analysis. No statistically significant differences were found for canal transportation. Sonic instrumentation significantly increased coronal flaring. The crown-down and sonic techniques produced more ledges. Elbow formation was associated with all instrumentation techniques. The model system developed for this study provided an accurate method of assessing the preparation techniques and the instrument effects on the canal walls.

Bacterial Leakage with Mineral Trioxide Aggregate or a Resin-Modified Glass Ionomer Used as a Coronal Barrier

The purpose of this study was to evaluate gray mineral trioxide aggregate (MTA), white MTA, and Fuji II LC cement as coronal barriers to bacterial leakage. Seventy-eight, matched, human teeth were obturated with gutta-percha. In group I, 18 pairs received a 3-mm barrier of gray or white MTA. In group II, 18 pairs received a 3-mm barrier of gray MTA or Fuji cement. Three pairs were used as positive (obturated without barrier) and negative (covered with epoxy resin) controls. A dual-chamber leakage model utilizing salivary microbes was used for the evaluation. Leakage was recorded when turbidity was observed. All controls behaved as expected. In group I, three gray MTA and three white MTA samples leaked. In group II, one gray MTA and three Fuji samples leaked. There was no statistically significant difference in leakage between gray and white MTA or gray MTA and Fuji at 30, 60, or 90 days. Gray and white MTA or Fuji II can be recommended as a coronal barrier for up to 3 months.

The effect of intramuscular injection of steroid on posttreatment endodontic pain

Fifty patients participated in this controlled double-blind study. The results showed that, when compared with a placebo, injection of the steroid (dexamethasone, 4 mg) significantly reduced both the incidence and severity of pain at 4 h posttreatment and reduced pain at 24 h posttreatment. Other patient and treatment factors such as age, sex, tooth number, pulp and periapical status, and number of appointments had no effect on posttreatment pain. However, posttreatment pain did correlate with the presence of pretreatment pain in both incidence and severity.

Effect of Early Coronal Flaring on Working Length Change in Curved Canals Using Rotary Nickel-Titanium Versus Stainless Steel Instruments

This in vitro investigation examined pre- and postinstrumentation working length (WL) measurements in curved root canals. The conditions compared were combinations of (a) stainless steel hand files + Gates Glidden drills (SS) versus nickel-titanium rotary files (Ni-Ti); and (b) early coronal flaring (flaring completed before WL determination) versus late coronal flaring (flaring completed after WL determination). Coronal flaring was accomplished for the SS group using Gates Glidden drills and for the Ni-Ti group using rotary Ni-Ti files (n = 15/group). WL was determined before coronal flaring, immediately after coronal flaring, and again after canal preparation. Results indicated that WL decreased for all canals as a result of canal preparation. The mean decrease in WL was significantly greater for the SS group (-0.48 mm +/- 0.32) than for the Ni-Ti group (-0.22 mm +/- 0.26). Less change in WL occurred in both groups when initial WL was determined after coronal flaring (SS: -0.12 mm +/- 0.13, Ni-Ti: -0.14 mm +/- 0.25).

Efficacy of irrigation with rotary instrumentation.

The purpose of this study was to evaluate the efficacy of a handpiece-mounted irrigation device and compare it to irrigation with a syringe and needle in the apical 5 mm of the root canal system. Twenty matched pairs of extracted teeth were used. The only variable within each matched pair was the method of irrigation. A syringe and needle were used in group A and the handpiece-mounted system in group B. Sections 1, 3, and 5 mm from the working length were examined microscopically, and images of the slides were digitized. The percentage of canal space occupied by pulpal and dentinal debris was calculated to be 6% +/- 12.7% in group A, versus 3.8% +/- 7% in group B (p = 0.264). The percentages at each level were as follows: 1 mm from the working length, 14.1% +/- 19% for group A and 5% +/- 7.5% for group B; 3 mm from working length, 1.8% +/- 5.4% for group A and 3.9% +/- 6.9% for group B; and 5 mm from working length, 3.1% +/- 7.7% for group A and 2.6% +/- 7.3% for group B. In group A, there was significantly more debris in the 1-mm section than in the 3- or 5-mm sections. In group B, the differences between levels were not significant. There was no significant difference in the amount of debris remaining in the apical 5 mm of canals when comparing the handpiece-mounted irrigation device to irrigation with a syringe and needle. The average times for instrumentation in group A (needle irrigation) and group B (Quantec-E irrigation system) were 8.7 +/- 2.7 min and 6.5 +/- 1.9 min, respectively. Group B was associated with statistically significant shorter instrumentation time (p < 0.0005). An average of 12.5 +/- 4.9 ml of irrigant was used in group A and 17.3 +/- 4.8 ml in group B. The difference was statistically significant (p < 0.0005).

Evaluation of cracks associated with ultrasonic root-end preparation of gutta-percha filled canals

Many clinicians use ultrasonics for root-end preparations. The purpose of this study was to evaluate resected root-end surfaces of bilaterally matched human teeth for cracks before and after ultrasonic root-end preparation. Twenty matched pairs of extracted single rooted teeth were divided into two experimental groups. In group 1, root-end resection was performed on uninstrumented teeth. In group 2, root-end resection was performed after the canals were instrumented and filled with gutta-percha. All teeth in both groups received root-end preparations using ultrasonic instrumentation at low power. Two examiners evaluated the root-ends after root-end resection and again after root-end preparation using zoom magnification of 20x to 63x. The number, types, and location of cracks were mapped. There were no significant differences when gutta-percha filled roots were compared to uninstrumented roots with regard to the number or type of cracks after root-end resection or root-end preparation. In addition, there were no significant differences in the number or type of cracks following root resection and ultrasonic root-end preparation when compared to teeth with root resection alone.