An in vitro comparison of apical microleakage after obturation with JS quick-fill or lateral condensation

An in vitro comparison of apical microleakage after obturation with JS quick-fill or lateral condensation

0099-2399/97/2305-0312503.00/0 Printed in U.S.A. VOL. 23, No. 5, MAY 1997 JOURNALOF ENDODONTICS Copyright © 1997 by The American Association of Endod...

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0099-2399/97/2305-0312503.00/0 Printed in U.S.A. VOL. 23, No. 5, MAY 1997

JOURNALOF ENDODONTICS Copyright © 1997 by The American Association of Endodontists

An In Vitro Comparison of Apical Microleakage after Obturation with JS Quick-Fill or Lateral Condensation R. Craig Shakespeare, DMD and Jerome C. Donnelly, DMD

Thirty extracted human single-root teeth were instrumented to #45 file size while creating a continuous coronal taper. Canals were obturated with Roth 801 sealer and either JS Quick-Fill or lateral condensation of gutta-percha. Mean apical linear microleakage of India Ink was evaluated in cleared teeth using a stereomicroscope. Significantly less leakage (p < 0.1) occurred with lateral condensation than with JS Quick-Fill.

Soft tissue fragments and calcified debris were removed by root planing and scaling. Standard lingual and occlusal access preparations were made with a 330 carbide bur and high speed handpiece. Following pulpal access, any residual pulp tissue was removed with barbed broaches (Kerr, Romulus, MI). Flex-R files (Union Broach Corp, Long Island City, NY) were used for all instrumentation with the Balanced Force instrumentation method (2). Patency was determined and insured by pass!ng a #15 file 3 to 4 mm out the apical foramen. The incisal or occlusal edge was sanded to a flat surface to achieve a reproducible reference point. The teeth were instrumented to a size #25 at a length where the file first became visible at the apex. An apical control zone was then developed by instrumentation to size #35 1/2 mm back and to size #45 master apical file (MAF) 1 mm back from the apical constriction. Copious irrigation with sterile saline was used between files, and patency was maintained throughout instrumentation with a # 15 file. Each tooth was instrumented with 04 and 05 McXIM files (NT Co., Chattanooga, TN) to achieve a continuous coronal taper. A Midwest slow speed handpiece was operated in the high torque position with a 10:1 gear reduction attachment running at --360 RPM. The rotary instruments were taken to within 1 and 2 mm short of the apical foramen respectively. Finally, the teeth were flushed with 5 cc sterile saline with a 28-gauge Maxi-Probe needle (Smith & Nephew, Inc., Franklin Park, IL) and the #15 file was passed out the apical constricture to confirm patency before obturation. A standard mix of Roth's 801 sealer (Roth International, Chicago, IL) was used for both obturation techniques tested. All canals were dried with medium and fine paper points just before filling the canals with one of the following obturation methods. JS QuickFill: manufacturer's directions were followed using #35 carriers with stops set 1/2 mm short of the #45 MAF file instrumentation length. The carrier was dipped into sealer to lightly coat the apical f,6 and inserted into the dried canal until resistance was felt. The carrier was then rotated at 6000 RPM with slight apical pressure until stopper length was reached. Continuing rotation at the same speed, the carrier was slowly withdrawn from the canal and the coronal GP was condensed into the orifice with a cold #9/11 condenser. Lateral condensation: a #35 GP master cone was fitted with slight tug back to confirm position at length I/2 mm from the apical constriction. This size was selected as the largest size that would allow a finger spreader to begin condensation within 1 to 2 mm of master cone length. The apical V3 of the master cone was

Total obliteration of the canal space and perfect seal of the apical foramen and accessory canals are the goals to achieve consistently successful endodontic treatment (1). Various methods of placing gutta-percha (GP) and root canal sealer are often used as the root canal obturating materials to achieve these goals. JS Quick-Fill (JS Dental Mfg. Inc., Ridgefield, CT) is a recently introduced mechanically thermoplasticized root canal obturation method. This device has a metallic carrier that is encased in GP. The obturator is placed into the canal until it binds, the slow speed handpiece is actuated, and the GP is thermoplasticized and carried to the apex as the carrier rotates. While continuing carrier rotation, it is slowly removed from the canal leaving a solid core GP canal obturation. No studies could be found that tested the apical seal of teeth obturated with JS Quick-Fill. The purpose of this study was to compare the mean apical leakage after root canal obturation with either JS Quick-Fill or lateral condensation using Roth 801 sealer.

M A T E R I A L S AND M E T H O D S Thirty-four extracted human single-rooted teeth were selected and stored in saline containing a few Thymol crystals. All teeth were radiographed in proximal view to exclude any teeth with multiple canal systems. Teeth were randomly assigned a number and placed in individual 15 ml Vacutainers (Vacutainer, Becton Dickinson Systems, Rutherford, NJ). The teeth were randomly distributed into two test groups of fifteen teeth to evaluate two specific obturation techniques.

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TABLE 1. Linear leakage in MM from the apical extent of GP/sealer Specimen Number 1L 2Q 3Q 4Q 5Q 6Q 7L 8Q 9Q 10L 11L 12L 13Q 14Q 15L* 16L 17L 18Q 19Q 20Q 21L 22L 23L 24Q 25Q 26L 27Q 28L 29L 30L 4C 3C Mean Std Dev Total samples

Evaluator 1 (JD) QF

LC

Evaluator 2 (CS) C

QF

1

LC

C

1

9 0 11 4.5 4.25

9 0 11 4.5 4.25 0.5

0.5

0 0 5.25

0 0 5.25

10 1

3.25 8

3.25 8 1 2

1.5 3.75 2.25

1.5 3.75 2.25 2 3 2.5

2 3 2.5 1.75 7.5

1.75 7.5 0 0 1 1 0

9 11

9 11 4.64 3.30 15

1.38 1.48 14

4.50 3.04 15

1.38 1.48 14

2 Sample Student's t-test for difference between means: LC vs Q = Reject null hypothesis p < .01 * Sample destroyed during processing Key: QF, JS Quick-Fill, LC, Lateral condensation, C, Control

coated with a thin coat of sealer and inserted into the canal. Lateral condensation was completed using a size 1A finger spreader (LD Caulk Division, Dentsply International Inc., Milford, DE) and medium-fine GP accessory points (Hygenic Corporation, Akron, OH) with the apical 2 mm dipped into sealer before insertion. The coronal GP was heat seared from the orifice and cold condensed with a #9/11 condenser. All 30 teeth were sealed coronally with amalgam (Valiant, Caulk, Dentsply) restorations and replaced in individual glass Vacutainers wrapped in wet gauze sponges to maintain 100% humidity. Four additional teeth instrumented in a similar fashion were used as controls. A single #35 master cone of GP was inserted without sealer and the canal was coronally sealed with amalgam. Each tooth was air dried. Clear acrylic nail polish was applied to the entire tooth surface for the negative controls and all surfaces except the apical 2 mm for the other teeth. The first coat was allowed to dry and a second coat was applied using magnification loupes (Orascoptic Research, Inc., Madison, WI). A shallow well was constructed and the apical ½ of the teeth was suspended into a bath of India Ink (Pelikan, Hannover, Germany) for 7 days. No attempt was made to establish a vacuum

system because teeth were sealed coronally with amalgam (3). The teeth were removed after 7 days, rinsed with running water, and lightly scrubbed to remove ink residue from the external surface before returning them to 15 cc Vacutainers. The teeth were then soaked in acetone for 2 h to remove the nail polish. They were inspected under magnification to insure the complete removal of the acrylic nail polish. Teeth were air dried and prepared for clearing. Each tooth was flushed with 20 to 30 ml distilled water and patted dry. The remainder of the clearing sequence was completed with the teeth in their individual glass Vacutainers. Five ml o/" 5% Nitric acid (HNO3) was placed in each glass tube. The nitric acid was changed each day and the teeth were agitated regularly. The teeth were bathed in 5% HNO 3 for a total of 84 h at which time they were determined to be fully decalcified. Teeth were rinsed in running water and placed in numbered containers with 50 ml of distilled water and allowed to soak for 8 h. The teeth were agitated hourly and the distilled water was changed every 2 h. Dehydration of the teeth was completed by placing them in ascending concentrations of ethyl alcohol (Aaper Alcohol and Chemical Co., Shelbyville, KY) (Etoh) beginning with 80%. The

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teeth were replaced in washed glass Vacutainers with 5 ml of 80% Etoh and allowed to sit for 12 h. The 80% Etoh was drained and replaced with 5 ml of 90% Etoh for 2 h. After 2 h, the 90% solution was similarly drained and replaced with 100% Etoh and allowed to remain for 2 more h. The teeth were air dried and placed in 6 ml of Methyl Salicylate (Plastodent, Inc., Bronx, NY) to clear them. Teeth were maintained in the Methyl Salicylate solution for storage and final evaluation using a stereomicroscope (Stemi SR, Zeiss, West Germany). Ten teeth were randomly selected and linear dye leakage was determined independently by both authors and compared to verify calibration of measurement methods. Leakage length was determined to the nearest 0.25 mm from the canal exit from the tooth, or from the vertex if the canal exit was not visible. The results of the pilot calibration were evaluated and the variance between examiners was no greater than the accuracy limits of the instrument. The two authors then independently measured the leakage for all teeth in the study. Each tooth was evaluated blindly without knowing the obturalion technique. The values were then subjected to statistical analysis using paired comparison t-tests with statistical significance being p < 0.5. RESULTS Apical microleakage results are shown in Table 1. Negative controls showed no microleakage and positive controls showed complete canal penetration. One lateral condensation specimen was destroyed in processing. Lateral condensation showed significantly less mean apical microleakage than JS Quick-Fill (p < 0.1). DISCUSSION The general impression of the authors in this study was that the JS Quick-Fill was fast and easy to use. These would be desirable clinical assets if an effective root canal obturation results. These findings, however, indicated that lateral condensation of GP provides a significantly better apical seal than JS Quick-Fill in canals obturated with Roth 801 sealer. Other factors may affect the seal of JS Quick-Fill and could be examined in future studies. These include the degree and variability of canal taper. This could effect the ability to thermoplasticize the GP by affecting friction as the GP and carrier rotate against the canal walls. Canal curvature could be a positive or negative factor concerning an effective apical seal. Additionally, varying the method of sealer placement may provide a method of improving apical seal. The sealer was placed into the canal on the tip of the JS Quick-Fill device while inserting the rotating carrier into the canal as the GP was thermoplasticizing. This did not exactly duplicate the way sealer was placed for the lateral condensation method. The cartier is binding the walls during the rotary insertion into the apical % of the canal due to the bulk of the GP coating on the carrier. With lateral condensation the sealer is carried into the apical region of the canal on the GP cone before the GP binds at the apical seat and condensation begins. This variation of sealer placement must be considered when evaluating these results. The manufacturer recommends placing only a small amount of sealer onto the tip of the JS Quick-Fill obturator before insertion into the canal. Other methods of sealer placement might improve the apical seal. In plastic blocks or on extracted teeth, sealer placed into the canal before carrier insertion appears to be displaced out

the apex or coronal orifice during carrier insertion into the canal. It is possible, however, that more is retained within the canal, too, thus improving the apical seal. The first mm of apical canal preparation in this study provided a more abrupt step-back than the gradual taper created by Allison et al. (4) in their study evaluating leakage after lateral condensation of GP. An apical control zone (5) was created in this study as the #35 file was used % mm from the deepest file penetration and the #45 1 mm from it. This abrupt step-back creates a firm apical seat to place either a #35 or #45 master cone against. Using the #35 cone provided the ability to place the spreader to about 1 to 2 mm from the extent of apical preparation as suggested by Allison et al (4).

Results of this study can be compared to those of Allison et al (6), who used nonstandard GP master cones and lateral condensation of GP. They found that the close adaptation of the master cone to the lateral canal walls was not as important as the ability to deeply penetrate a spreader to within at least 2 mm of the preparation depth after fitting a master cone with slight tug back. Apical leakage correlated well with the depth of spreader penetration and was not related to poor lateral adaptation to the canal walls as evidenced by radiographs. The #35 cone inserted 1/2 mm from the apical constriction was selected in this study because it provided slight tug back and deeper spreader penetration than a #45 cone placed 1 mm from the apical extent of preparation. Mean apical leakage in this study of 1.38 mm approximates the depth of spreader penetration. It is uncertain if other variations of cone fitting would have affected the leakage results. It is unknown if the difference in leakage between the tested obturation methods would be significant clinically. The range of apical microleakage appears to be within that found by other investigators as summarized in the study by Saunders et al (7). These results show lateral condensation of GP, a clinically successful obturation technique, produced in vitro apical microleakage ranging of 0.12 to 9.25 ram. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. Dr. Shakespeare is a Major and former Resident in the Advanced Education in General Dentistry Program 2-Year, Fort Hood, TX, currently stationed in Korea. Dr, Donnelly is retired and the former Chief of Endodontics, U.S. Army Dental Activity, Fort Hood, TX. Address requests for reprints to Dr. Jerome C. Donnelly, 3001 Oakwood Drive, Harker Heights, TX 76548.

References 1. Nguyen NT in Cohen S, Bur0s RC. Pathways of the pulp, 5th ed. St. Louis: CV Mosby, 1991:186. 2. Roane JB, Sabala CL, Duncan MG. The "balanced force" concept for instrumentation of curved canals. J Endodon 1985;11:203-11. 3. Dickson SS, Peters DD. Leakage evaluation with and without vacuum of two gutta-percha fill techniques. J Endodon 1993;19:398-403. 4. Allison DA, Weber CR, Walton RE. The influence of the method of canal preparation on the quality of apical and coronal obturation. J Endodon 1979; 5:298-304. 5. Roane JB. Principles of preparation using the balanced force technique. In: Hardin JF, ed. Clark's clinical dentistry. Vol. 1. Philadelphia: J.B. Lippincott Co., 1991:3-4. 6. Allison DA, Michelich RJ, Walton RE. The influence of master cone adaption on the quality of the apical seal. J Endodon 1981;7:61-65. 7. Wu MK, Wesselink PR. Endodontic leakage studies reconsidered. Part I. Methodology, application and relevance. Int Endodon J 1993;26: 37-43.