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In vitro disinfection of dentinal tubules by various endodontics irrigants
JOURNALOF ENDODONTICS Copyright © 1999 by The American Association of Endodontists
Printed in U.S.A. VOL. 25, NO. 12, DECEMBER1999
In Vitro Disinfection of Dentinal Tubules by Various Endodontics Irrigants Richard Buck, BS, Paul D. Eleazer, DDS, and Robert H. Staat, PhD
Effectiveness of endodontic irrigants within dentinal tubules of human teeth was evaluated. Midsections of single-rooted teeth were prepared into dentin wedges. The pulpal sides of the sections were exposed to Micrococcus luteus or Bacillus megaterium that grew into the tubules. Irrigants used in the study included: 0.525% NaOCI, 0.12% chlorhexidine, RC Prep, 0.5% betadine iodine, and sterile H20 (as a control). Pulpal surfaces were exposed to an irrigant and then rinsed in sterile water. The samples were then cracked, exposing a fresh surface. Culture of the exposed dentin surfaces showed that selected irrigants reached to the far ends of the dentinal tubules in a concentration sufficient to kill 100% of the M. luteus. However B. megaterium was neither killed nor apparently inhibited by any irrigant. We conclude that endodontic irrigants permeate throughout dentinal tubules, but their effectiveness is dependent on the type of bacteria found within the tubules.
White (4) demonstrated in the human pulp canal that 5.25% NaOCI and 2.0% chlorhexidine were also equally effective. Ringel et al. (5) found 2.5% NaOCI was more effective than 0.2% chlorhexidine. Yoshida et al. (6) showed that ETDA has antibacterial action that is better than saline. Orsatvik and Haapasalo (7) performed landmark studies using bovine dentin samples. They showed NaOC1 and chlorhexidine were comparable disinfectants (7). Vabdaty et al.'s (8) bovine studies were similar. Heling and Pecht (9) used the bovine model to show that camphorated paramonochlorophenol, Ledermix (a steroid containing calcium hydroxide paste), and tetracycline all had effective antibacterial properties. Berutti et al. (10) histologically found bacteria deep in dentinal tubules after irrigation. Safavi et al. (2) demonstrated in human dentinal tubules that calcium hydroxide is an effective medicine that kills bacteria. Due to the concern for residual bacteria after endodontic therapy, the far recesses of the dentin tubules must be considered in disinfection attempts. Not only should one question how far into the tubules endodontic irrigants penetrate, but one should also ask if the irrigants are in sufficient concentration to kill the bacteria. The purpose of this pilot study was to evaluate the effectiveness of NaOCI, chlorhexidine, iodine, RC Prep, and saline in the tubules of human dentin. A second purpose was to determine how far into the dentinal tubules the irrigants flow in a killing concentration.
Persistent infection within the root canal and periapical area is a source of concern in endodontics. Inadequate disinfection of the infected root canal and associated periapical lesion can lead to persistence of the infection. Failed root canal treatments have been attributed to viable bacteria that exist within the root canal and periapical system (l). It has been hypothesized that these viable bacteria within the root canal system and dentin tubules can be a source of reinfection or continued periapical inflammation (2). To prevent reinfection of a treated root canal, it is important to disinfect the pulp space and dentinal tubules thoroughly with an endodontic irrigant or medicine. There have been many studies performed to determine which root canal medicines and irrigants are the most effective. Most commonly, the irrigants studied were sodium hypochlorite (NaOCI) and chlorhexidine. Saline and a variety of other irrigants or medicants have also been studied. Jeansonne, Ringel, and Yoshida each considered the problem of disinfection of root canals by irrigating a pulp canal in vitro, and Bystrom and Sundqvist (3) did so in vivo. Bystrom showed that 0.5% and 5.0% NaOC1 were equally effective. Jeansonne and
M A T E R I A L S AND M E T H O D S Four main steps in the protocol included: (i) preparing dentin blocks, (ii) infecting tubules with desired bacteria, (iii) exposing bacteria-laden dentin to selected irrigant, and (iv) culturing viable bacteria within tubules after exposure. Single-rooted extracted teeth were obtained from patients age 33 to 53. Teeth with no root caries damage were selected for the dentin samples. Specifically, the midsection of the teeth were isolated. This provided relative consistency of tubule form and number. Micrococcus luteus and Bacillus megaterium were selected as test bacteria. M. luteus is a Gram-positive, aerobic, nonpathogenic bacterium, which grows yellow on tryptic soy broth. M. luteus is very small (0.9 to 1.8/xm) and thus passes readily into the dentinal tubules. B. megaterium is a Gram-positive, aerobic, nonpathogenic bacterium that grows white on tryptic soy broth that was also selected. It is a 1.2 /xm diameter rod with a length that is several
786
Vol. 25, No. 12, December 1999
times greater than its diameter. It also penetrates readily into dentinal tubules. Endodontic irrigants were selected from those commonly used clinically: 0.525% NaOCI, 0.12% chlorhexidine, and RC Prep. Also, an iodine-based disinfectant that gained prominence in periodontal therapy, 0.5% povidone iodine (dilute Betadine), was also included. The cementum of single-rooted teeth was removed with vigorous instrumentation using periodontal curettes. The crown was removed below the cementoenamel junction with a diamond cutting disk. Pulpal tissue was removed using a barbed broach. The canal was filed using K-files large enough to produce clean white filings. Then, sequentially, two sizes larger files were used to the apex and the step-back technique was performed. Finally, to thin the smear layer, some sample canals were sonicated for 1 min using a MM1500 endosonic handpiece with a #25 Rispisonic (Medidenta, Woodside, NY) file. The apical portion of the root was severed using a diamond cutting disk. Experimental procedures were performed on the middle third of the root that was sectioned into four pieces leaving a wedge of dentin with a pulpal surface, periodontal ligament (PDL) side and cut walls (Fig. 1). Exposed, cut walls lateral to the canal were coated with nail polish to exclude bacteria and disinfectants during the test. The wedges were then sterilized in an autoclave. Trypticase soy broth cultures of the bacteria were grown in an incubator until cloudy. A sterile 8 cm diameter round felt pad was soaked with sterile water to avoid drying and placed in a sterile Petri dish. Four to six 25-mm filter pads were placed in the dish on the felt. Three-tenths milliliter of M. luteus broth or B. megaterium broth was placed on the filter pads. The pulpal side of a sterilized tooth wedge was placed on the middle of each bacteria-laden filter pad (Fig. 2). The Petri dish was incubated for 24 to 26 h. To confirm bacterial migration through the dentinal tubules, the PDL side of a bacteria-laden tooth sample was pressed onto trypticase soy agar to leave an imprint (Fig. 3). When the imprint grew selected bacteria colonies, the presence of viable bacteria throughout the dentinal tubules was confirmed. The irrigants were applied to the pulpal surfaces in the following manner. Six 25-mm filter pads were placed in a dry Petri dish. Three-tenths milliliter of an irrigant was placed on each pad. (Irrigants were contained within the pads and the liquids remained isolated from each other.) Samples were placed pulpal side down on an irrigant-soaked pad for 1 min. Then, samples were gently agitated for 20 s in sterile water using sterile cotton pliers. Next, the samples were grasped using two pairs of flamesterilized needle-nosed pliers and cracked into two pieces. This exposed fresh dentin surfaces. The exposed surfaces were pressed onto an agar plate to leave an imprint (Fig. 4). The surfaces were pressed three times each to ensure a good impression. Growth of the bacteria was monitored after 12 h of incubation. The presence of colonies determined the effectiveness of the irrigant used. Controis with saline showed bacterial growth was present throughout the tubules before irrigant exposure.
RESULTS When the smear layer was thinned via sonication, M. luteus was able to grow throughout the tubules as shown by positive culture of the PDL side of the dentin wedges. All the irrigants penetrated within the tubules in a sufficient concentration to kill all the bacteria, as shown by negative culture of the cracked inner surface
Disinfection of Dentin
787
KEY Section of tooth used as sample ~ t Pulp canal ~ posltton of tooth cuts
FIG 1. Preparation of dentin blocks. Bacteria soaked 25 m m filter p a d
Tooth sample
Felt p a d s o a k e d w i t h w a t e r
FIG 2. Introducing bacteria into the dentinal tubules.
Imprint of peripheral side of sample
/ Tooth sample being pressed into a g a r to leave peripheral impression FIG 3. Bacteria in the samples were exposed to irrigants.
FIG 4. Viable bacteria within the tubules were cultured. of the wedges. In nonsonicated canals, tack of colonies indicated that bacteria did not pass into dentinal tubules (Table 1). When sonicated canals were exposed to B. megaterium, colonies grew on the agar at the PDL side impression site and also where cracked inner surface dentin samples were impressed on growth medium. This showed that some bacteria can grow through the tubules, yet not be inhibited by the irrigants tested. Interestingly, nonsonicated samples also yielded bacteria colonies, demonstrat-
788
Journal of Endodontics
Buck et al.
Positive growth on cracked surface showed an irrigant was not effectiveat killing all bacteria.
Bacteria entering from either the pulpal surface or periodontal surface can exist within the dentinal tubules. These viable bacteria could act as reservoirs of contamination, perhaps beginning pathological action if leakage of root canal sealant occurs. Therefore intratubular bacteria can act as a nidus of infection or reinfection. An endodontic irrigant's effectiveness is dependent on many factors. Some advocate canal sonication for mechanical smear layer removal or use of weak acids for chemical removal of the smear layer. Some clinicians recommend extended dressing of canals, whereas others prefer simple irrigation and 1 day treatment. Still others claim mere water irrigation is sufficient. There are many differing thoughts on proper treatment of root canals, as well as many differing experimental results. This study used sonication to thin the smear layer and two different bacteria were used. Using two different bacteria yielded very different results. The small Gram-positive M. luteus was easily killed by all the irrigants. Yet the spore forming B. megaterium persisted after exposure to any of the tested irrigants. This model illustrates extremes of bacterial properties and shows how differently each bacterial species reacts to endodontic irrigants. As demonstrated by this study, irrigants such as NaOC1, RC Prep, Betadine, and chlorhexidine seem to be able to penetrate well into dentinal tubules. Their effectiveness at disinfecting an infected root canal is dependent on the type of bacteria found in the root canal.
ing that some species of bacteria can grow through a thick smear layer. Unfortunately, the smear layer kept the irrigants from penetrating into the tubules in sufficient concentration to kill these bacteria (Table 2).
Drs. Buck, Eleazer, and Staat are affiliated with the Department of Periodontics, Endodontics, and Dental Hygiene, School of Dentistry, University of Louisville, Louisville, KY. Address requests for reprints to Dr. P. D. Eleazer, Department of Periodontics, Endodontics, and Dental Hygiene, School of Dentistry, University of Louisville, Louisville, KY 40292.
TABLE 1. Micrococcus luteus PDL Side NaOCl Chiorhexidine RC Prep Betadine Sterile w a t e r
Cracked Inner Surface
+ + + + + Positive growth Negative growth
+
Negative growth on cracked surface showed an irrigant was effective in killing all bacteria.
TABLE 2. Bacillus megaterium
NaOCl Chlorhexidine RC Prep Betadine Sterile w a t e r
PDL Side
Cracked Inner Surface
+ + + + +
+ + + + +
Positive growth Negative growth
+
DISCUSSION Bacteria can exist within the tubules of both vital and nonvital teeth. Nagoka et al. (11) demonstrated that vital teeth are much more resistant to bacterial invasion than are nonvital teeth, thus demonstrating the protective function of the pulp. Because many endodontic cases deal with nonvital pulps, such teeth can be the site of uninhibited bacterial growth within the tubules. During root canal treatment, remnants of odontoblast processes are retained within the dentinal tubules. The fate of these processes is assumed to be necrosis. This necrotic organic tissue can be a source of nutrients for bacteria living within the tubules. These bacteria can live within the tubules indefinitely if their existence goes unchecked. Placement of a root canal filler on the pulpal surface and a continuous cementum layer on the periodontal side may contain any viable bacteria. However, breach of either of these two protective layers could allow for passage of viable bacteria from the tubules into the body. Not only do bacteria enter the dentinal tubules through a pulpal route, but they also can enter the tubules from the periodontal surfaces. Aadriaens et al. (12) showed that bacteria are present in the dentinal tubules beneath the plaque covering the roots of periodontially involved teeth. Continual periodontal scaling can result in elimination of the protective cementum covering. This may allow for communication to the pulp, proliferation of viable bacteria, or migration of pulpal bacteria into the periodontal spaces.
References 1. Sundqvist G, Figdor D, Persson S, Sjogren U. Microbiological analysis of teeth with failed endodontie treatment and the outcome of conservative retreatment. Oral Surg Oral Med Oral Patho11998;85:86-93. 2. Safavi KE, Spangberg LS, Langeland K. Root canal dentinal tubule disinfection. J Endodon 1990; 16:207-10. 3. Bystrom A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35-40. 4. Jeansonne M J, White RR. A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. J Endodon 1994;20:276-8. 5. Ringel AM, Patterson SS, Newton CW, Miller CH, Mulhern JM. In vivo evaluation of chlorhexidine gluconate solution and sodium hypochlorite solution as root canal irrigants. J Endodon 1982;8:200-4. 6. Yoshida T, Shibata T, Shinohara T, Shunji G, Sekine I. Clinical evaluation of the efficacy of EDTA solution as an endodontic irrigant. J Endodon 1995;21:592-3. 7. Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9. 8. Vahdaty A, Pitt Ford TR, Wilson RF. Efficacy of chlorhexidine in disinfecting dentinal tubules in vitro. Endod Dent Traumatol 1993;9:243-8. 9. Heling I, Pecht M. Efficacy of Ledermix paste in eliminating Staphylococcus aureus from infected dentinal tubules in vitro. Endod Dent Traumatol 1991;7:251-4. 10. Berutti E, Marini R, Angeretti A. Penetration ability of different irrigants into dentinal tubules. J Endodon 1997;23:725-7. 11. Nagaoka S, Miyazaki Y, Eiu HJ, Iwamoto Y, Kitano M, Kawagoe M. Bacterial invasion into dentinal tubules of human vitai and non-vital teeth. J Endodon 1995;21:70-3. 12. Adriaens A, De Boever JA, Loesche WJ. Bacterial invasion in root cementum and radicular dentin of periodontally diseased tooth in humans. J Periodontol 1988;59:222-30.
Printed in U.S.A. VOL. 25, NO. 12, DECEMBER1999
In Vitro Disinfection of Dentinal Tubules by Various Endodontics Irrigants Richard Buck, BS, Paul D. Eleazer, DDS, and Robert H. Staat, PhD
Effectiveness of endodontic irrigants within dentinal tubules of human teeth was evaluated. Midsections of single-rooted teeth were prepared into dentin wedges. The pulpal sides of the sections were exposed to Micrococcus luteus or Bacillus megaterium that grew into the tubules. Irrigants used in the study included: 0.525% NaOCI, 0.12% chlorhexidine, RC Prep, 0.5% betadine iodine, and sterile H20 (as a control). Pulpal surfaces were exposed to an irrigant and then rinsed in sterile water. The samples were then cracked, exposing a fresh surface. Culture of the exposed dentin surfaces showed that selected irrigants reached to the far ends of the dentinal tubules in a concentration sufficient to kill 100% of the M. luteus. However B. megaterium was neither killed nor apparently inhibited by any irrigant. We conclude that endodontic irrigants permeate throughout dentinal tubules, but their effectiveness is dependent on the type of bacteria found within the tubules.
White (4) demonstrated in the human pulp canal that 5.25% NaOCI and 2.0% chlorhexidine were also equally effective. Ringel et al. (5) found 2.5% NaOCI was more effective than 0.2% chlorhexidine. Yoshida et al. (6) showed that ETDA has antibacterial action that is better than saline. Orsatvik and Haapasalo (7) performed landmark studies using bovine dentin samples. They showed NaOC1 and chlorhexidine were comparable disinfectants (7). Vabdaty et al.'s (8) bovine studies were similar. Heling and Pecht (9) used the bovine model to show that camphorated paramonochlorophenol, Ledermix (a steroid containing calcium hydroxide paste), and tetracycline all had effective antibacterial properties. Berutti et al. (10) histologically found bacteria deep in dentinal tubules after irrigation. Safavi et al. (2) demonstrated in human dentinal tubules that calcium hydroxide is an effective medicine that kills bacteria. Due to the concern for residual bacteria after endodontic therapy, the far recesses of the dentin tubules must be considered in disinfection attempts. Not only should one question how far into the tubules endodontic irrigants penetrate, but one should also ask if the irrigants are in sufficient concentration to kill the bacteria. The purpose of this pilot study was to evaluate the effectiveness of NaOCI, chlorhexidine, iodine, RC Prep, and saline in the tubules of human dentin. A second purpose was to determine how far into the dentinal tubules the irrigants flow in a killing concentration.
Persistent infection within the root canal and periapical area is a source of concern in endodontics. Inadequate disinfection of the infected root canal and associated periapical lesion can lead to persistence of the infection. Failed root canal treatments have been attributed to viable bacteria that exist within the root canal and periapical system (l). It has been hypothesized that these viable bacteria within the root canal system and dentin tubules can be a source of reinfection or continued periapical inflammation (2). To prevent reinfection of a treated root canal, it is important to disinfect the pulp space and dentinal tubules thoroughly with an endodontic irrigant or medicine. There have been many studies performed to determine which root canal medicines and irrigants are the most effective. Most commonly, the irrigants studied were sodium hypochlorite (NaOCI) and chlorhexidine. Saline and a variety of other irrigants or medicants have also been studied. Jeansonne, Ringel, and Yoshida each considered the problem of disinfection of root canals by irrigating a pulp canal in vitro, and Bystrom and Sundqvist (3) did so in vivo. Bystrom showed that 0.5% and 5.0% NaOC1 were equally effective. Jeansonne and
M A T E R I A L S AND M E T H O D S Four main steps in the protocol included: (i) preparing dentin blocks, (ii) infecting tubules with desired bacteria, (iii) exposing bacteria-laden dentin to selected irrigant, and (iv) culturing viable bacteria within tubules after exposure. Single-rooted extracted teeth were obtained from patients age 33 to 53. Teeth with no root caries damage were selected for the dentin samples. Specifically, the midsection of the teeth were isolated. This provided relative consistency of tubule form and number. Micrococcus luteus and Bacillus megaterium were selected as test bacteria. M. luteus is a Gram-positive, aerobic, nonpathogenic bacterium, which grows yellow on tryptic soy broth. M. luteus is very small (0.9 to 1.8/xm) and thus passes readily into the dentinal tubules. B. megaterium is a Gram-positive, aerobic, nonpathogenic bacterium that grows white on tryptic soy broth that was also selected. It is a 1.2 /xm diameter rod with a length that is several
786
Vol. 25, No. 12, December 1999
times greater than its diameter. It also penetrates readily into dentinal tubules. Endodontic irrigants were selected from those commonly used clinically: 0.525% NaOCI, 0.12% chlorhexidine, and RC Prep. Also, an iodine-based disinfectant that gained prominence in periodontal therapy, 0.5% povidone iodine (dilute Betadine), was also included. The cementum of single-rooted teeth was removed with vigorous instrumentation using periodontal curettes. The crown was removed below the cementoenamel junction with a diamond cutting disk. Pulpal tissue was removed using a barbed broach. The canal was filed using K-files large enough to produce clean white filings. Then, sequentially, two sizes larger files were used to the apex and the step-back technique was performed. Finally, to thin the smear layer, some sample canals were sonicated for 1 min using a MM1500 endosonic handpiece with a #25 Rispisonic (Medidenta, Woodside, NY) file. The apical portion of the root was severed using a diamond cutting disk. Experimental procedures were performed on the middle third of the root that was sectioned into four pieces leaving a wedge of dentin with a pulpal surface, periodontal ligament (PDL) side and cut walls (Fig. 1). Exposed, cut walls lateral to the canal were coated with nail polish to exclude bacteria and disinfectants during the test. The wedges were then sterilized in an autoclave. Trypticase soy broth cultures of the bacteria were grown in an incubator until cloudy. A sterile 8 cm diameter round felt pad was soaked with sterile water to avoid drying and placed in a sterile Petri dish. Four to six 25-mm filter pads were placed in the dish on the felt. Three-tenths milliliter of M. luteus broth or B. megaterium broth was placed on the filter pads. The pulpal side of a sterilized tooth wedge was placed on the middle of each bacteria-laden filter pad (Fig. 2). The Petri dish was incubated for 24 to 26 h. To confirm bacterial migration through the dentinal tubules, the PDL side of a bacteria-laden tooth sample was pressed onto trypticase soy agar to leave an imprint (Fig. 3). When the imprint grew selected bacteria colonies, the presence of viable bacteria throughout the dentinal tubules was confirmed. The irrigants were applied to the pulpal surfaces in the following manner. Six 25-mm filter pads were placed in a dry Petri dish. Three-tenths milliliter of an irrigant was placed on each pad. (Irrigants were contained within the pads and the liquids remained isolated from each other.) Samples were placed pulpal side down on an irrigant-soaked pad for 1 min. Then, samples were gently agitated for 20 s in sterile water using sterile cotton pliers. Next, the samples were grasped using two pairs of flamesterilized needle-nosed pliers and cracked into two pieces. This exposed fresh dentin surfaces. The exposed surfaces were pressed onto an agar plate to leave an imprint (Fig. 4). The surfaces were pressed three times each to ensure a good impression. Growth of the bacteria was monitored after 12 h of incubation. The presence of colonies determined the effectiveness of the irrigant used. Controis with saline showed bacterial growth was present throughout the tubules before irrigant exposure.
RESULTS When the smear layer was thinned via sonication, M. luteus was able to grow throughout the tubules as shown by positive culture of the PDL side of the dentin wedges. All the irrigants penetrated within the tubules in a sufficient concentration to kill all the bacteria, as shown by negative culture of the cracked inner surface
Disinfection of Dentin
787
KEY Section of tooth used as sample ~ t Pulp canal ~ posltton of tooth cuts
FIG 1. Preparation of dentin blocks. Bacteria soaked 25 m m filter p a d
Tooth sample
Felt p a d s o a k e d w i t h w a t e r
FIG 2. Introducing bacteria into the dentinal tubules.
Imprint of peripheral side of sample
/ Tooth sample being pressed into a g a r to leave peripheral impression FIG 3. Bacteria in the samples were exposed to irrigants.
FIG 4. Viable bacteria within the tubules were cultured. of the wedges. In nonsonicated canals, tack of colonies indicated that bacteria did not pass into dentinal tubules (Table 1). When sonicated canals were exposed to B. megaterium, colonies grew on the agar at the PDL side impression site and also where cracked inner surface dentin samples were impressed on growth medium. This showed that some bacteria can grow through the tubules, yet not be inhibited by the irrigants tested. Interestingly, nonsonicated samples also yielded bacteria colonies, demonstrat-
788
Journal of Endodontics
Buck et al.
Positive growth on cracked surface showed an irrigant was not effectiveat killing all bacteria.
Bacteria entering from either the pulpal surface or periodontal surface can exist within the dentinal tubules. These viable bacteria could act as reservoirs of contamination, perhaps beginning pathological action if leakage of root canal sealant occurs. Therefore intratubular bacteria can act as a nidus of infection or reinfection. An endodontic irrigant's effectiveness is dependent on many factors. Some advocate canal sonication for mechanical smear layer removal or use of weak acids for chemical removal of the smear layer. Some clinicians recommend extended dressing of canals, whereas others prefer simple irrigation and 1 day treatment. Still others claim mere water irrigation is sufficient. There are many differing thoughts on proper treatment of root canals, as well as many differing experimental results. This study used sonication to thin the smear layer and two different bacteria were used. Using two different bacteria yielded very different results. The small Gram-positive M. luteus was easily killed by all the irrigants. Yet the spore forming B. megaterium persisted after exposure to any of the tested irrigants. This model illustrates extremes of bacterial properties and shows how differently each bacterial species reacts to endodontic irrigants. As demonstrated by this study, irrigants such as NaOC1, RC Prep, Betadine, and chlorhexidine seem to be able to penetrate well into dentinal tubules. Their effectiveness at disinfecting an infected root canal is dependent on the type of bacteria found in the root canal.
ing that some species of bacteria can grow through a thick smear layer. Unfortunately, the smear layer kept the irrigants from penetrating into the tubules in sufficient concentration to kill these bacteria (Table 2).
Drs. Buck, Eleazer, and Staat are affiliated with the Department of Periodontics, Endodontics, and Dental Hygiene, School of Dentistry, University of Louisville, Louisville, KY. Address requests for reprints to Dr. P. D. Eleazer, Department of Periodontics, Endodontics, and Dental Hygiene, School of Dentistry, University of Louisville, Louisville, KY 40292.
TABLE 1. Micrococcus luteus PDL Side NaOCl Chiorhexidine RC Prep Betadine Sterile w a t e r
Cracked Inner Surface
+ + + + + Positive growth Negative growth
+
Negative growth on cracked surface showed an irrigant was effective in killing all bacteria.
TABLE 2. Bacillus megaterium
NaOCl Chlorhexidine RC Prep Betadine Sterile w a t e r
PDL Side
Cracked Inner Surface
+ + + + +
+ + + + +
Positive growth Negative growth
+
DISCUSSION Bacteria can exist within the tubules of both vital and nonvital teeth. Nagoka et al. (11) demonstrated that vital teeth are much more resistant to bacterial invasion than are nonvital teeth, thus demonstrating the protective function of the pulp. Because many endodontic cases deal with nonvital pulps, such teeth can be the site of uninhibited bacterial growth within the tubules. During root canal treatment, remnants of odontoblast processes are retained within the dentinal tubules. The fate of these processes is assumed to be necrosis. This necrotic organic tissue can be a source of nutrients for bacteria living within the tubules. These bacteria can live within the tubules indefinitely if their existence goes unchecked. Placement of a root canal filler on the pulpal surface and a continuous cementum layer on the periodontal side may contain any viable bacteria. However, breach of either of these two protective layers could allow for passage of viable bacteria from the tubules into the body. Not only do bacteria enter the dentinal tubules through a pulpal route, but they also can enter the tubules from the periodontal surfaces. Aadriaens et al. (12) showed that bacteria are present in the dentinal tubules beneath the plaque covering the roots of periodontially involved teeth. Continual periodontal scaling can result in elimination of the protective cementum covering. This may allow for communication to the pulp, proliferation of viable bacteria, or migration of pulpal bacteria into the periodontal spaces.
References 1. Sundqvist G, Figdor D, Persson S, Sjogren U. Microbiological analysis of teeth with failed endodontie treatment and the outcome of conservative retreatment. Oral Surg Oral Med Oral Patho11998;85:86-93. 2. Safavi KE, Spangberg LS, Langeland K. Root canal dentinal tubule disinfection. J Endodon 1990; 16:207-10. 3. Bystrom A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35-40. 4. Jeansonne M J, White RR. A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. J Endodon 1994;20:276-8. 5. Ringel AM, Patterson SS, Newton CW, Miller CH, Mulhern JM. In vivo evaluation of chlorhexidine gluconate solution and sodium hypochlorite solution as root canal irrigants. J Endodon 1982;8:200-4. 6. Yoshida T, Shibata T, Shinohara T, Shunji G, Sekine I. Clinical evaluation of the efficacy of EDTA solution as an endodontic irrigant. J Endodon 1995;21:592-3. 7. Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9. 8. Vahdaty A, Pitt Ford TR, Wilson RF. Efficacy of chlorhexidine in disinfecting dentinal tubules in vitro. Endod Dent Traumatol 1993;9:243-8. 9. Heling I, Pecht M. Efficacy of Ledermix paste in eliminating Staphylococcus aureus from infected dentinal tubules in vitro. Endod Dent Traumatol 1991;7:251-4. 10. Berutti E, Marini R, Angeretti A. Penetration ability of different irrigants into dentinal tubules. J Endodon 1997;23:725-7. 11. Nagaoka S, Miyazaki Y, Eiu HJ, Iwamoto Y, Kitano M, Kawagoe M. Bacterial invasion into dentinal tubules of human vitai and non-vital teeth. J Endodon 1995;21:70-3. 12. Adriaens A, De Boever JA, Loesche WJ. Bacterial invasion in root cementum and radicular dentin of periodontally diseased tooth in humans. J Periodontol 1988;59:222-30.