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JOURNAL OF ENDODONTICS Copyright © 1993 by The American Association of Endodontists
VOL. 19, NO. 2, FEBRUARY1993
Sealing Ability of Three Materials Used to Repair Lateral Root Perforations Luke G. Moloney, MDSc, Sophie A. Feik, MDS, and Graham Ellender, MDSc, PhD
management is due to technical difficulties in sealing the perforation without overfilling (3). Surgical treatment involves a procedure similar to retrograde filling. A class I preparation is prepared in the perforation and an appropriate material is used to fill the defect. Many materials have been used in the repair of root perforations and it is generally agreed that determination of their sealing ability and biocompatibility are important. Amalgam has been shown to provide a superior seal when compared with a number of other materials such as guttapercha and Cavit (4, 5). The use of two coats of cavity varnish with the amalgam resulted in a significant improvement in the apical seal of retrograde fillings (6, 7). EBA cement, a reinforced zinc-oxide eugenol cement, has high compressive and tensile strengths, neutral pH, and low solubility. It is radiopaque, demonstrates good adhesion to dentin and seals well in retrograde cavities (4, 8-10). Silver glass-ionomer cement, a product of sintering pure silver to aluminosilicate, is a potentially useful material in surgical endodontics. It has the following favorable properties: bonding to dentin, radiopacity, rapid set, and ease of delivery. In vitro studies of silver-glass ionomer cement have found that Ketac-Silver seals retrograde cavities as well, or better, than amalgam and cavity varnish (11, 12). The aim of this experiment was to address and compare the sealing ability of amalgam, EBA, and silver-glass ionomer cements in the repair of lateral root perforations. The extent of microleakage was determined by penetration of the radioisotope, calcium-45, using a combined in vivo/in vitro model.
Thirty-five extracted single-rooted human teeth were decoronalized, root filled with AH-26 and guttapercha, and perforated at the apical one third level. Repairs of the lateral perforations were carried out with three materials: amalgam plus cavity varnish, EBA cement, and silver glass-ionomer cement. Negative controls were not perforated and positive controls had unrepaired perforations. The roots were then implanted subcutaneously in rats for 5 days to place the materials in a surgical environment. Following retrieval, the roots were placed in a solution containing 20 p.Ci/ml of calcium-45 for 7 days to measure microleakage. They were rinsed, sectioned, and autoradiographs of the repaired perforations were made. The autoradiographs were projected onto a screen and the extent of penetration of the radioisotope measured. Statistical analysis showed that the EBA cement group exhibited significantly less leakage than the silver glass-ionomer cement group (p < 0.05). No differences were found between the other groups. It was concluded that EBA cement provides a superior seal in lateral root perforations to silver glass-ionomer cement while amalgam was intermediate between the two.
A root perforation can be defined as "an artificial opening in a tooth or its root created by boring, cutting or pathologic resorption, which results in a communication between the root canal and the periodontal tissues" (1). Perforations are commonly caused by rotary instruments during attempts to locate calcified canals or during post space preparation. There are a number of methods for treating perforations depending on their location, level relative to the gingival sulcus, age, and size. Surgical treatment of perforations is indicated where coronal access is not possible. However, surgery is limited by the position of the perforation. As most perforations occur on the buccal and mesial root surfaces of upper anterior teeth, surgical treatment is often possible (2). This form of treatment has been found to be slightly superior to conservative management. The lesser tendency to heal following conservative
MATERIALS AND M E T H O D S Thirty-five single-rooted freshly extracted human teeth with one canal were used in this study. There were three experimental groups of 10 teeth and 5 control teeth. Following removal of adherent soft tissues and calcified deposits, the teeth were decoronalized and the canals were filled with guttapercha (Progress Gutta-Percha points; Rudolph Gunz & Co. Pty Ltd., Melbourne, Australia) and AH-26 (DeTrey/Dentsply, DeTrey Division, Dentsply Ltd., Weybridge/Surrey, England). The coronal access cavity was closed with Cavit (ESPE, Seefeld/Oberbayern, Germany) and sticky wax and the apical 2 m m of the root coated with sticky wax. The roots were then mounted on a jig and perforated with a 112 flat fissure bur (Ash, Amalgamated Dental Trade Dis59
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Moloney et al.
tributors Ltd., London, England; DeTrey, Gesellschaft, Germany) at 15 degrees to the long axis of the root. These perforations were angled to approximate the clinical situation of a misdirected bur during attempts to locate a calcified canal. Perforation defects were then repaired with one of the three test materials; Ketac-Silver (ESPE), amalgam (Valiant Palladium enriched; L. D. Caulk and Co., Division of Dentsply International Inc., Milford, DE) plus cavity varnish (Fuji Varnish; G-C Dental Industrial Corp., Tokyo, Japan), or EBA cement (Stailine Super EBA; Staident International, Staines, Middlesex, England). Positive controls had no repairs to the perforations and negative controls were not perforated. In an attempt to simulate the clinical situation, the repaired roots were implanted subcutaneously in the suprascapular region of rats for 5 days. This allowed exposure of the materials to extracellular fluids and defense cells in an attempt to reproduce the surgical conditions to which these materials would be exposed. Following initial set of the repair materials, the repaired roots were implanted, five per rat, each in individual sutured pockets. Five days later the rats were killed and the roots were carefully dissected out and placed in a solution of 20 uCi/ml of calcium-45. Calcium-45 as calcium chloride is the most widely used isotope in marginal leakage studies because it is easily obtained and, being a weak ~ emitter, it produces sharp autoradiographs. Ionic exchange of calcium-45 with the calcium of the apatite crystals of the calcified substance can also occur. Radioactive calcium readily enters dentinal tubules and exchanges with nonradioactive calcium in the dentin matrix (13). This exchange is so efficient that only 1% of radioactive calcium that enters the tubules in diffusion studies actually reaches the surface (14). Calcium-45 thus acts as a permanent marker of microleakage. After 7 days in this solution, the roots were rinsed in running water for 20 h, mounted with sealing wax on a specially constructed jig, and sectioned with an Isomet slowspeed diamond saw (Buehler Ltd., Lake Bluff, IL). The sectioning cut was approximately l-ram wide and made along the long axis of the root at an angle to divide the root through the perforation repair and along the filled root canal. Care was taken to section the teeth to show the full length of the perforation defect and the filled root canal (Fig. 1). The width of the cut meant that one section was obtained from each root. A series of autoradiographs were then produced. Different exposure times and films were used to produce the sharpest and clearest images. Three sets of autoradiographs were made using Kodak Industrex SR film (Eastman Kodak Co., Rochester, NY). The root sections were placed on the emulsion side of the film, and 12-, 24-, and 48-h exposures were made. The images were magnified, projected, traced, and the extent of microleakage measured in millimeters. The method of evaluating the autoradiographs used in this study is a modification of a previously used technique where photomicrographs of sectioned teeth were projected onto a screen and traced (7, 15, 16). The extent of microleakage was determined by the amount of darkening along the repair material/defect wall accompanied by penetration of radioisotope into the dentinal tubules. Because some of the 12- and 24-h autoradiographs were impossible to read adequately due to underexposure, the final measurements were made on the 48-h exposures only. All of
FiG 1. Three experimental roots sectioned to show root filling (GP) and full length perforation repair. Repair materials are silver-glass ionomer cement (K) (Ketac-Silver), EBA cement (E), and amalgam plus cavity varnish (A) (original magnification x3).
FiG 2. Autoradiograph of tooth root with perforation repaired with EBA cement. Leakage can be seen extending approximately half way along the defect (arrows) (original magnification x5).
the 48-h exposures showed enough detail to be read (Figs. 2 to 4). The true length of each perforation was determined from radiographs taken of the repaired perforations prior to implantation. An analysis of variance was carried out to test the significance of the results. A posteriori analysis of the measurements using Tukey's test was then performed to determine the level of significance between groups. RESULTS Of the 30 experimental roots, 2 were excluded from the study: 1 from the Ketac-Silver group because of an incorrect plane of section and the 1 from the amalgam plus cavity varnish group due to cracking. Of the remaining teeth, all showed some leakage.
Vol. 19, No. 2, February 1993
FIG 3. Autoradiograph of tooth root with perforation repaired with amalgam plus cavity varnish. Note minimal amount of leakage extending less than one third along the perforation (arrow) (original magnification x5).
Positive controls showed leakage the full extent of the defects accompanied by leakage into the associated dentinal tubules. Negative controls showed no penetration of isotope into the root canal system. The mean leakage for the three experimental groups is shown in Table 1. An analysis of variance comparing the three experimental groups revealed that the means of these samples were significantly different (Table 2). A posteriori analysis of these results using Tukey's test was carried out to compare results between groups. The differences in leakage between amalgam plus cavity varnish and Ketac-Silver, and amalgam plus cavity varnish and EBA cement were not significant. There was, however, a significant difference between EBA cement and Ketac-Silver (p < 0.05) showing that EBA cement provided a significantly superior seal in perforation repairs compared with Ketac-Silver. DISCUSSION
Sealing Lateral Root Perforations
FIG 4. Autoradiograph of tooth root with perforation repaired with Ketac-Silver. Note maximum amount of leakage of radioisotope extending to root canal system (arrow) (original magnification x5).
TABLE 1. Leakage measured in millimeters from 48-h exposure autoradiographs Tooth
1 2 3 4 5 6 7 8 9 10
--* 3.5 1.0 1.25 1.5 2.0 3.75 1.25 2.0 1.25
2.0 1.5 2.0 2.5 1.0 1.75 1.75 1.25 2.0 1.0
2.25 4.0 2.5 -1.75 2.25 1.5 2.75 3.5 3.75
No. Mean Median SD
9 1.94 1.50 1.01
10 1.68 1.75 0.49
9 2.69 2.50 0.88
• - - , Specimens deleted because of technical failure.
The objective of this study was to compare the sealing ability of three materials used to repair iatrogenic root perforations. The amount of leakage was established by measuring the length of penetration of a radioisotope along the total length of the perforation defect. Results of the leakage assessments indicated that there was a significant variation among the three groups. Comparisons between groups revealed that EBA cement sealed significantly better than Ketac-Silver. These results support earlier findings in retrofillings, which showed that EBA cement provided a superior apical seal (10, 17). Leakage of amalgam has been investigated in a large number of studies, since it is a commonly used surgical endodontic material to which other newer materials are compared. There have been many conflicting results regarding the sealing ability of amalgam. Differing results of dye leakage studies appear to be related to differences in cavity depth, whether cavity varnish was used, and the presence or absence of a root filling. Leakage of amalgam retrofillings has been shown to vary between 0 and 100% of the total depth of the retrograde cavity (18-20).
In studies comparing the sealing ability of amalgam to other materials, varying results also have been obtained. Using 2-ram retrograde cavities, Bondra et al. (9) found that the seal of amalgam was signifcantly inferior to that of EBA cement. Time is an important variable associated with amalgam in surgical endodontics. Delivanis and Tabibi (5) have shown that the seal of amalgam in retrograde cavities in vivo is better after 6 months than it is initially. The deposition of corrosion products is thought to improve the seal of amalgam (8). In this study the 12-day experimental period may not have been long enough to allow the amalgam group to develop an optimum seal. However, the depths of the perforation defects, being up to 10 mm, may have favored this material. The observed superior sealing ability of EBA cement appears to correlate well with other studies using a variety of methods. Beltes et al. (4), using ingress of methylene blue dye, found EBA cement sealed better than amalgam, glass ionomer cement, or heat-sealed gutta-percha. Bondra et al. (9), also using methylene blue dye, found no leakage past 2-mm retrograde cavity preparations filled with EBA cement. They
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Moloney et al. TABLE 2. One-factor analysis of variance*
Amalgam cavity/varnish 1.94 1.02
EBA 1.68 0.24
T R T M T SS
5.20 p = 0.033
3 Ketac-Silver 2.69 0.78 Variance of Mean Variance Means 0.68
* x: groups 1,2, and 3; Y: leakageof radioisotope. 1"dfN, degreesof freedombetweengroups; dfD, degreesof freedomwithin groups; TRTMT SS, sum of squareswithin groups.
.also reported that EBA cement sealed retrograde cavity preparations significantly better than amalgam. The Ketac-Silver repairs in this study showed the largest variation in sealing the perforations. These results are contrary to the findings of Schwartz and Alexander (10) who found that silver-glass ionomer cement provided a significantly superior retrograde seal than amalgam plus cavity varnish. The difference is possibly due to technique (i.e. perforation repairs compared with retrograde fillings) and different leakage markers (i.e. calcium-45 compared with methylene blue dye). However, the delivery system used with the silver-glass ionomer may have caused problems in this study because of the difficulty in condensing the material into a long, narrow defect, such as a perforation. The clinical significance of microleakage in surgical endodontics has not been elucidated. However, the possible presence of bacteria in the root canal system of nonvital teeth makes it appropriate to aim for the best possible seal when repairing lateral root perforations. Of the materials tested, it appears that EBA cement offers a comparatively superior seal to Ketac-Silver. Amalgam plus cavity varnish would also appear to provide a satisfactory seal. Long-term sealing and biocompatibility studies also need to be carried out before definitive recommendations can be made regarding the clinical use of these materials in sealing root perforations. The authors would like to acknowledge the assistance of Professor Harold Messer, Dr. Garry Nervo, and Dr. Alan Malcolm in the design of the experiment and in preparation of the manuscript. Dr. Moloney is a former postgraduate student, School of Dental Science, Faculty of Medicine and Dentistry, University of Melbourne, Melbourne, Victoria, Australia and is currently in private endodontic practice in Camberwell and parttime clinical endodontics, Royal Dental Hospital, Melbourne. Dr. Feik is a senior lecturer, School of Dental Science, Faculty of Medicine and Dentistry, University of Melbourne. Dr. Ellender is a senior lecturer, School of Dental Science, Faculty of Medicine and Dentistry, University of Melbourne. Address requests for reprints to Dr. Luke Moloney, 2 Victoria Road, Camberwell, Victoria, Australia 3124.
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