The antimicrobial effect of various endodontic sealers Zuhair Z. Al-Khatib, BDS,a Robert H. Baum, PhD,b Donald R. Morse, BS, DDS, MA (Biol), MA (Psychol), PhD (Nutr),’ Cemil Yesilsoy, DMD, MS,d Satish Bhambhani, BDS, MDS,a and h4. Lawrence Furst, PhD,e Philadelphia, Pa. TEMPLE

UNIVERSITY

SCHOOL

OF DENTISTRY

The antimicrobial activity of an endodontic microbes. Therefore it was decided to test sealers. The sealers used were Grossman’s

sealer can be helpful in destroying any remaining root canal the antimicrobial activity of several commonly used endodontic sealer, Tubliseal, Calciobiotic, Sealapex, Hypocal, eucapercha,

Nogenol, and AH26. Also tested were dry calcium hydroxide powder, calcium hydroxide mixed with saline, and a Teflon formulation. The microbes used were Streptococcus mufans (a gram-positive microaerophile), Sfaphylococcus eureus (a gram-positive facultative anaerobe), and Becteroides endodontelis (a gram-negative obligate anaerobe). The freshly mixed sealers were placed into the prepared wells of agar plates inoculated with the test microorganisms. After varying periods of incubation. the zones of inhibition bacterial growth were observed and measured. Grossman’s sealer had the greatest overall antibacterial activity. However, AH26 had the greatest activity against B. endodonteks. The zinc oxide-eugenol-based sealers had more antimicrobial activity than either the calcium hydroxide-based sealers or eucapercha. (ORAL SURC ORAL MED ORAL PATHOL 1990;70~784-90)

E

limination of the etiologic agents of endodontic diseases is a major aim of clinical practice. Microbes are considered to be the primary etiologic agents in endodontic diseases.lm4In the early stages of pulpitis, the pulp can be sterile but frequently facultative anaerobic stieptococci are found (e.g., Streptococcus mutans, Streptococcus mitis) as well as staphylococcus (e.g., Staphylococcus epidermidis). By the time pulpal necrosis and a radiolucent periapical lesion develop (PN/PL), the root canal flora consists of obligate anaerobes including Bacteroides species (e.g., Bacteroides melaninogenicus, Bacteroides endodontalis, Bacteroides gzkgivalis), fusobacteria, peptococ-

ci, peptostreptococci, and facultative anerobic species.5 In recent studies, obligate anaerobic microbes have been found in certain cases of PN/PL associated with the periapical lesion (generally found with necrotic tissue and abscess cavities).6

aFormer graduate student, Department of Endodontology. bAssociate Professor, Department of Microbiology. cProfessor, Department of Endodontology; former graduate dent, Department of Endodontology. dAssociate Professor, Department of Endodontology. eAssociate Professor, Department of Oral Medicine. 7/15/16365 784

stu-

of

Several studies have examined the effects of microbes and their products in the etiology of endodontic flare-ups and the repair of periapical tissue.4* 5*7 Since microbes are etiologically involved in pulpalperiapical diseases, it is important to eliminate them. Methods commonly used in this regard include instrumentation (e.g., hand, ultrasonic); antimicrobial irrigation (e.g., sodium hypochlorite, hydrogen peroxide); antimicrobial intracanal medication (e.g., calcium hydroxide, formocresol); and systemic antibiotics (e.g., penicillin, erythromycin, cephalosporin, metronidazole, clindamycin).5, ’ In addition, there can be antimicrobial effects from some endodontic filling materials. Solid core materials such as silver cones have antimicrobial effects (oligodynamic properties of heavy metal ions), but their breakdown products are also irritating to the periapical tissues.* The sealer components can also have antimicrobial activity. However, whether or not the antimicrobial properties of endodontic sealer components are advantageous is controversial. Advocates of the use of antimicrobial endodontic sealers consider that the antimicrobial activity would maintain the sterility of the root canal system and thus potentiate repair.9 Opponents claim that for an antimicrobial agent to be effective it should be potent and long acting without

Antimicrobial

Volume 70 Number 6 Table

e#ect of various endodontic sealers

785

I. Sealers and other preparations used Name

Grossman’s sealer Tubliseal Calciobiotic Sealapex Hypocal Calcium hydroxide Calcium hydroxide mixture Eucapercha Nogenol AH26 Teflon formulation

Active

Source

Sultan Chemists, Inc., Englewood, N.J. Kerr Division, Sybron Corporation, Romulus, Mich. Hygenic Corporation, Akron, Ohio Kerr Division, Sybron Corporation, Romulus, Mich. Ellman International Manufacturing, Inc., Hewlett, N.Y. Sultan Chemists, Inc., Englewood, N.J. Sultan Chemists, Inc., Englewood, N.J. According to D. R. Morse, DDS15 Coe Laboratories, Chicago, Ill. DeTrey Division, Dentsply Ltd., London, England According to L. Love, Ph.D.

irritating the normal periapical tissues. However, at least to some degree, all the currently used endodontic sealers are periapical tissue irritants.8 A few commercial endodontic sealers (e.g., N2 types, and iodoform pastes) claim to sterilize the root canal system. However, they contain formaldehyde and/or iodine, which are irritating and allergy inducing. Formaldehyde is potentially mutagenic and carcinogenic (although this has never been shown from endodontic use). lo The topical use of an antibiotic such as penicillin is highly allergenic and therefore is not recommended. In recent years, the role of host resistance in endodontic diseases has been under consideration.” Some studies have shown evidence of periapical repair even with the presence of microbes in the root canal system. These results underlie the importance of host resistance in destroying or impeding any remaining microbes.5-7 Nevertheless, many patients who come into the office for endodontic treatment have impaired resistance. This can be related to (1) the current use of alcohol and other drugs by many patients, (2) the prevalence of undetected systemic diseases that impede repair such as diabetes mellitus, and (3) the prevalence of stress (which impedes the immune system and can contribute toward flare-ups and incomplete repair). Therefore any and all safe and effective means to help prevent flare-ups and aid in periapical repair may be warranted. This can include the use of an antimicrobial endodontic sealer.

ingredients

Zinc oxide, barium sulfate, bismuth subcarbonate, staybilite resin, sodium borate anhydrate, eugenol Zinc oxide, barium sulfate, oleo resins, oils, thymol iodide, modifiers, eugenol Calcium hydroxide, barium sulfate, molybdenum, eugenol, eucalyptol Calcium hydroxide, barium sulfate, titanium dioxide, zinc stearate Calcium hydroxide, barium sulfate, water base Calcium hydroxide (USP) powder Calcium hydroxide (IJSP) powder, sterile saline Gutta-percha cones, eucalyptol, heat Zinc oxide, barium sulfate, natural resin, salicylic acid, vegetable oil, fatty acids Bismuth oxide, silver powder, titanium oxide, hexamethylene tetra amine, epoxy bisphenol resin Teflon, zinc oxide, and other ingredients

The commonly used endodontic sealers such as zinc oxide-eugenol (ZOE) pastes, Tubliseal, Sealapex, calcium hydroxide pastes, and eucapercha, have been shown to have some antimicrobial activity that, according to some investigators, improved the clinical success of endodontic therapy.*, 12-16 However, no study has directly compared most of the various sealers for antimicrobial activity. The purpose of the present study was to test the antimicrobial activity, by size of zones of inhibition on the surface of agar plates, of several of the major currently used endodontic sealers against microbes that can be found in the pulps, dentinal tubules, and periapexes of teeth diagnosed as having a vital-inflamed pulp, pulpal necrosis, or PN/PL. These sealers were tested against (1) the gram-positive microaerophile Streptococcus mutans; (2) the gram-positive facultative anaerobe Staphylococcus aureus; and (3) the gram-negative obligate anaerobe B. endodontalis (all of which can be found associated with endodontic diseases). MATERIAL Sealers

AND METHODS

The various sealers that were used are shown in Table I. Cultures

and media

Cultures of Streptococcus mutans, ATCC 6715, and Staphylococcus aureus were obtained from the

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Fig. 1. A representative brain-heart infusion agar plate that was coated with 0.2 ml of Streptococcus mutans and contained wells of the various test sealers; growth pattern after 48-hour interval. 1 = Grossman’s sealer; 2 = Sealapex; 3 = Tubliseal; 4 = Hypocal; 5 = Calciobiotic; 6 = dry calcium hydroxide; 7 = eucapercha. Arrows indicate zones of inhibition.

laboratory stock of the Microbiology Department, Dental Unit, Temple University School of Medicine. Cultures of B. endodontalis, ATCC 35406, were obtained from the American Type Culture Collection (Bethesda, Md.). The Streptococcus mutans culture was grown in trypticase soy broth (BBL Inc., Cockeysville, Md.) and the Staphylococcus aureus culture was grown in brain-heart infusion broth (BHIB, Difco Laboratories, Detroit, Mich.). Chopped meat carbohydrate broth (CMC, Carr-Scarborough Microbiologicals, Inc., Stone Mountain, Ga.) and/or chopped meat broth (CM, Scott Laboratories, Inc., Fiskeville, R.I.) were used to maintain and grow the B. endodontalis culture. Experimental

procedure

The surfaces of fresh brain-heart infusion plates were spread with 0.2 ml of Streptococcus mutans or Staphylococcus aureus actively growing in BHIB. Four wells of 5 mm depth and 4 mm diameter were punched in the agar plates and filled with the test sealers. One well was left empty as a negative control. The Streptococcus mutans agar plates were incubated, under enhanced carbon dioxide, in candle jars kept at 37” C. The plates were observed at 24 hours, 48 hours, and 7 days. The Staphylococcus aureus agar plates were incubated aerobically at 37” C and were observed at the same time intervals as the Streptococcus plates. The diameters of the zones of bacterial inhibition around each well were measured in millimeters. The entire experiment was repeated six times, and a mean diameter was determined for each sealer. Greater diameters of zones of inhibition were

ORAL

SURGORAL

MEr) ORALPATHOL December 1990

interpreted to indicate greater antimicrobial activity of the involved sealers. Blood agar plates for growing the obligate anaerobes were made with the use of rabbit erythrocytes (Rockland Inc., Gilbertsville, Pa.), according to the Holdeman and colleagues. VP1 manual.” For each experiment, fresh rabbit blood was added to the agar just before the Petri dishes were poured. The plates were then allowed to solidify. Each plate was spread with 0.2 ml of B. endodontalis that was actively growing in CMC or CM broth. A single well, 5 mm deep and 4 mm in diameter, was punched in each plate. After being mixed according to manufacturer’s (or developer’s) instructions, each of the various sealers was placed in an individual well. The plate bottoms were pressed into tops covered (on the open side) with pieces of filter paper containing several drops of glycerin. This was to provide a seal. The plates were placed in jars rendered anaerobic by the Gas Pak hydrogen-carbon dioxide system (BBL Laboratories, Cockeysville, Md.). They were incubated at 37” C for up to 35 days. The diameters of the zones of inhibition for each sealer were measured in millimeters. As with the brain-heart infusion plates, similar interpretations were made with respect to the zones of inhibition and antimicrobial activity. The measurements were taken at 7 and 35 days because at least 7 days are required for growth of B. endodontalis cultures to be visible. Statistical

analysis

Statistical analysis was not performed because of the difference of diffusibility in the agar of the various sealers. For example, eugenol-containing sealers diffuse markedly as contrasted with the slight diffusibility of calcium hydroxide-containing sealers. Hence, we merely made a semiqualitative comparison with the understanding that the results could not be completely transferable to the in vivo situation. RESULTS Activity versus

Staphylococcus

Streptococcus

mutans

and

aureus

Twenty-four-hour interval. The results are summarized in Table II. The zones of inhibition were greatest with Grossman’s sealer (a eugenol-containing sealer) against both microorganisms. Calciobiotic (a calcium hydroxide-eugenol sealer) had the second highest antimicrobial activity against Streptococcus mutans while Tubliseal (a resin-eugenol sealer) had the second highest antimicrobial activity against Staphylococcus aureus.

Plain calcium hydroxide powder was more effective than Hypocal (calcium hydroxide-containing paste) against both Streptococcus mutans and Staphylococcus aureus. Sealapex (calcium hydroxidecontaining

Antimicrobial

Volume 70 Number 6

efect of various endodontic sealers

Table II. Zones of inhibition by diameter in millimeters from antimicrobial preparations against three microorganisms during four time periods (microaerophile Streptococcus Time

Mean

Sealer

Microorganisms and facultative

mutans *SD

activity of sealers and other Microorganism (obligate anaerobe)

anaerobe)

Staphylococcus

787

aureus

Bacteroides

Mean

*SD

Time

endodontalis

Mean

*SD

16.40 14.60

5.60 4.50

12.60

5.20 3.00

Grossman’s h 48 h and 7 d 24

7.50 7.50

1.65 1.65

4.66 4.83

0.98 0.93

35

7d

5.22 5.22

2.05 2.05

2.67 2.67

0.77 0.77

35

7.00 7.16

1.44 1.78

2.17 2.17

1.18

7d

1.18

35

2.00 1.66

1.70 1.57

1.17 1.17

0.77 0.77

35

d

Tubliseal h 48 h and 7 d 24

7d d

9.80

Calciobiotic h 48 h and 7 d 24

d

14.20

12.60

3.10 2.40

d

4.00 7.60

8.90 9.60

d

0.00 0.00

0.00 0.00

d

4.00 7.60

8.90 9.60

d

0.00 0.00

0.00 0.00

d

9.00 13.20

5.20 3.60

d

6.10 5.90

2.90 2.40

d

17.50 21.60

3.50 7.40

d

0.00 0.00

0.00 0.00

Sealapex h 48 h and 7 d 24

7d

Hypocal h 48 h and 7 d 24

1.48

1.08

1.25

0.88

0.67 0.67

0.49 0.49

35

7d

1.75

0.75 0.81

1.oo 0.92

0.77 0.86

35

Calcium hydroxide h 48 h and 7 d 24

h 48 h and 7 d 24

1.16

Calcium hydroxide mixture Eucapercha

24 h 48 h and 7 d

0.75 2.16

7d 7d 35

1.17 3.06

0.54 0.54

0.30 0.30

7d 35

Nogenol h 48 h and 7 d 24

7d

AH26

35

-

h 48 h and 7 d 24

7d 35

Teflon formulation

h, HOWS; d, days; SD, standard

deviation;

-

-

h 48 h and 7 d 24

-,

-

unable to test because of time and/or

sealer) had more antimicrobial activity than Hypocal against both microbes and was better than calcium hydroxide powder against Streptococcus mutans. Eucapercha had less antimicrobial activity than either Hypocal or calcium hydroxide powder against both microbes. Because of technical problems, calcium hydroxide mixture, Nogenol, AH26, and the Teflon formulation were not tested against the two microbes. Forty-eight-hour interval. The results are summarized in Table II. With Grossman’s sealer, there was no change with Streptococcus mutans and a slight increase in the antimicrobial effect against Staphylococcus aureus. With Calciobiotic, there was a slight increase in antimicrobial activity against Streptococcus mutans and no change with Staphylococcus aureus. With Tubliseal, there was no change with both microorganisms. With Hypocal, there was a slight

procedural

7d 35

technicalities.

decrease in antimicrobial activity against Streptococcus mutans and no change against Staphylococcus aureus. Calcium hydroxide powder showed a slight decrease in antimicrobial activity against both microorganisms. With Sealapex, there was a slight decrease in antimicrobial activity against Streptococcus mutans and no change with Staphylococcus aureus. With eucapercha, there was a moderate increase in antimicrobial activity against Streptococcus mutans and no change with Staphylococcus aureus. Because of technical problems, calcium hydroxide mixture, Nogeneol, AH26, and the Teflon formulation were not tested against these two microorganisms. In Fig. 1, a representive agar plate is given showing the zones of inhibition of various sealers at 48 hours against Streptococcus mutans. Seven-day interval. The results are summarized in

788

Al-Khatib

et al.

Fig. 2. A representative section from a blood agar plate that was coated with 0.2 ml of B. endodontalis and contained a well with Grossman’s sealer; growth pattern after 7-day interval. Arrows indicate zone of inhibition.

Table II. They show that there was no change in the antimicrobial activity of all of the sealers from the 48-hour period through the 7-day period. Activity versus

6. endodontalis

Seven-day interval. The results are summarized in Table II. The largest zone of inhibition was found with AH26, and the next largest was Grossman’s sealer. Next in order was Calciobiotic followed closely by Tubliseal. In descending order, eucapercha, Nogenol, Sealapex, and calcium hydroxide powder were the remaining sealers with antimicrobial activity. Hypocal, calcium hydroxide mixture, and the Teflon formulation showed no antimicrobial activity. In Fig. 2, a representative blood agar plate is given showing the zone of inhibition of Grossman’s sealer at 7 days against B. endodontalis. Thirty-five-day interval. The results are summarized in Table II. Hypocal, calcium hydroxide mixture, and the Teflon formulation still showed no antimicrobial activity. There were slight decreases in the zones of inhibition with Grossman’s sealer, Nogenol, Tubliseal, and Calciobiotic. AH26, Sealapex, and calcium hydroxide powder showed a slight increase in the zones of inhibition. Eucapercha had a moderate increase in the zone of inhibition. The top three sealers in terms of zones of inhibition at 35 days were AH26, Grossman’s sealer, and eucapercha. DISCUSSION

The subsequent findings must be qualified by the knowledge that the size of the zone of bacterial inhibition of an antibacterial substance on microbiologic plates depends on (1) the toxicity of the substance for the particular bacterium and (2) the diffusibility of

ORAL

SURG

ORAL

MELI ORAL PATHOI. December 1990

the substance in the test medium being used. The diffusibility of the agent is a function of its (a) hydrophilicity or hydrophobicity, (2) size, and (3) rate of release from the insoluble matrix in which it is bound. 17aThese variables are difficult to control for in vitro. Consequently, to determine their true antimicrobial effectiveness, in vivo testing is essential to determine the biocompatibility of the materials. With this in mind, the findings from this study show that the various endodontic sealers differ in their antimicrobial activity as indicated by zones of inhibition. The sensitivity of the three types of microorganisms (gram-positive microaerophile, gram-positive facultative anaerobe, gram-negative obligate anaerobe) to the antimicrobial activity also varied with the same sealer. With all sealers, no change in the zone of inhibition against Streptococcus mutans and Staphylococcus uureus occurred after 48 hours. The maximum zone of inhibition against B. endodontalis varied with the sealers. With Grossman’s sealer, Tubliseal, Calciobiotic, and Nogenol, it was achieved by 7 days. With Sealapex, calcium hydroxide powder, eucapercha, and AH26, it was achieved by 35 days. Grossman’s sealer was highly effective against all of the microorganisms that were tested. Also quite effective were Tubliseal and Calciobiotic. The high eugenol content of all three sealers may explain their antimicrobial activity. Cox and coworkers14 have shown that ZOE is an effective bactericidal agent against Staphylococcus aureus and an effective bacteriostatic agent against Streptococcus viridans. The results were apparently due to the eugenol content because zinc oxide alone had no antimicrobial activity against those microorganisms. Hume** has shown that in the dentin immediately beneath the ZOE, the concentration of eugenol is sufficient to inhibit bacterial metabolism. Furthermore, if the ZOE contacts wet tissue, the eugenol concentration increases. In other studies on carious dentin,19y 2o ZOE was found to be a more effective antibacterial agent than calcium hydroxide. Using L-cells in the in vitro millipore test system, Yesilsoy and Feiga121 showed that the ZOE-containing sealers (e.g., Roth’s sealer) had a greater cytotoxicity effect than any of the other sealers tested. According to Onose and associates,22 with the use of Staphylococcus aureus, Streptococcus faecalis, and Escherichia coli, the Grossman’s sealer type cement, Fill Canal, was active only immediately after its preparation. In contrast, in the present study with Grossman’s sealer, as time progressed, it was observed that usually there was either an increased antimicrobial effect or the sealer maintained its antimicrobial effectiveness at a constant level. As in the present study, Stevens and Grossman23 found Grossman’s

Volume 70 Number 6

sealer had good antimicrobial activity against an obligate anaerobic microorganism (Bacteroides fragilis). However, this microbe is not typically found in the oral cavity. Part of the antimicrobial effectiveness of Calciobiotic may also be attributable to the calcium hydroxide content. However, the other calcium hydroxidecontaining materials had variable antimicrobial activity. The best was Sealapex followed in descending order by calcium hydroxide powder, Hypocal, and calcium hydroxide-saline mixture (which showed no antimicrobial activity with the organisms tested). Possibly related to the different test microorganisms used, Chohayeb and Cole24 did not find Sealapex to be an effective antimicrobial agent. In addition to being relatively biocompatible and inducing hard tissue formation,2S, 26 calcium hydroxide has been shown to have antimicrobial activity in dentin, the pulp, and periapex. 19,20~27-30The antimicrobial activity is most likely related to the alkaline pH of the calcium hydroxide. However, the pH can vary in the different calcium hydroxide preparations that were used in the present study. Other possible reasons for the variable results with the different calcium hydroxide preparations are as follows: 1. There were differing amounts of unreacted calcium hydroxide in the set pastes. 2. The pastes varied in their readiness to undergo hydrolysis. 3. The pastes contained different additives, some of which could have had antimicrobial activity. AH26 had good antimicrobial activity against the obligate anaerobe tested (B. endodontalis). This may be related to the silver (oligodynamic effect of heavy metal ions), hexamethylene tetranium, and epoxy bisphenol resin components. Stevens and Grossman23 also found that AH26 had good antimicrobial activity against an obligate anaerobic microorganism (B. fragilis) . Eucapercha had good, relatively long-lasting antimicrobial activity against the obligate anaerobe (B. endodontalis) and slight antimicrobial activity against the other microorganisms. Previous studies have shown that eucalyptus oil has antimicrobial activity with low tissue toxicity. 31-33Nogenol had some antimicrobial activity against the obligate anaerobe tested (B. endodontalis). This may be related to the presence of the resin component. Although sterilization of the root canals and periapex is ideal, in clinical practice it is not possible. Regardless, all efforts should be made to reduce endodontic microbes to a minimum. This includes instrumentation, irrigation, intracanal medication, antibiotics (when required), and obturation. When a root canal is completely instrumented and irrigated, and the patient has no untoward clinical manifesta-

Antimicrobial

e#ect of various endodontic sealers

789

tions (e.g., pain, swelling), there are most likely few remaining microbes within the root canal, its branches, the dentin, or the periapex (unless there has been leakage or anachoresis that took place between visits). Therefore the need for an endodontic sealer with strong antimicrobial properties is questionable, especially since the antimicrobial effect of the various sealers is nonspecific (related to toxic effects) and can cause periapical tissue destruction as well as antimicrobial activity. Nevertheless, as part of the obturation process, the use of an antimicrobial endodontic sealer can be another helpful adjunct to the removal or destruction of endodontic microorganisms. However, it would appear to be preferable to use a sealer that has relatively mild antimicrobial activity and low tissue toxicity (e.g., eucapercha, Sealapex) than a sealer that has strong antimicrobial activity and high tissue toxicity (e.g., Grossman’s sealer, Tubliseal). SUMMARY

The antimicrobial effects of several types of endodontic sealers were tested against Streptococcus mutans, Staphylococcus aureus, and B. endodontalis. Wells were prepared in agar plates inoculated with each of the test microorganisms. The wells were filled with each of the freshly mixed sealers. After incubation, the zones of inhibition of bacterial growth were observed and measured. Grossman’s sealer was the most effective antimicrobial agent against all three microorganisms used. However, AH26 was most effective against B. endodontalis. The ZOE-based sealers had a greater antimicrobial effect than did the calcium hydroxide-based sealers or eucapercha, but relative to possible toxic effects, it appears preferable to use the latter sealers because of their slight antimicrobial effects but minimal tissue toxicity properties. REFERENCES 1. Sundqvist GK. Bacterial studies of necrotic pulps [Umei, University Odontological Dissertation No. 71 Umea, Sweden; University of Umea, 1976. 94 pp. 2. Matusow RJ. Acute pulpal-alveolar cellulitis syndrome. 1. Clinical isolates of bacterial isolates from pulps and exudates of intact teeth, with a description of a specific culturing technique. ORAL SURG ORAL MED ORAL PATHOL 1979;48:70-6. 3. Keudell K, Conte M, Fujimoto L, Ernest M, Berry HG. Microorganisms isolated from pulp chambers. J Endod 1976; 2:146-8. 4. Pakman LM, Baum RH, Seltzer S, Krasner P, Gross M, Carol J. Root canal infections: symptoms vs. bacterial isolates. Abstracts American Society of Microbiology No. C-38, 281, 1980. 5. Morse DR. Microbiology and pharmacology. In: Cohen S, Burns RC, eds. Pathways of the pulp. 4th ed. St. Louis: The CV Mosby Co, 1987:364-96. 6. Tronstad L, Barnett F, Riso K, Slots J. Extraradicular endodontic infections. Endod Dent Traumatol 1987:3:86-90. 7. Morse DR, Furst ML, Lefkowitz RD, D’Angelo DD, Esposito JV. A comparison of erythromycin and cefadroxil in the prevention of flare-ups from asymptomatic teeth with pulpal necrosis and associated periapical pathosis. ORAL SURG ORAL MED ORAL

PATHOL

1990;69:619-30.

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et al.

8. Seltzer S. Endodontology: biologic considerations in endodontic procedures. 2nd ed. Philadelphia: Lea & Febiger, 1988: 450-3. 9. Matsumiya S, Kitamura H. Histopathological and histobacteriological studies of the relation between the condition of sterilization of the interior of the root canal and the healing process of periapical tissues in experimentally infected root canal treatment. Bull Tokyo Dent Co11 1960;1:1-19. 10 Morse DR. Immunological aspects of pulpal-periapical disease: a review. ORAL SURG ORAL MED ORAL PATHOL 1977; 43:436-51. 11. Morse Dr, Koren LZ, Esposito JV, et al. Asymptomatic teeth with necrotic pulps and associated periapical radiolucencies: relationship of flare-ups to endodontic instrumentation, antibiotic usage and stress in three separate practices at three different time periods. Parts l-5. Int J Psychosom 1986;33:5-87. 12 Grossman LI. Antimicrobial effects of root canal cements. J Endod 1980;6:594-7. 13. Pup0 J, Biral RR, Benatti 0, Abe A, Valdrighi L. Antimicrobial effects of endodontic filling cements on microorganisms from root canals. ORAL SURG ORAL MED ORAL PATHOL 1983;55:622-7. 14. Cox ST, Hembree JH, McKnight JP. The bactericidal potential of various endodontic materials for primary teeth. ORAL SURG ORAL MED ORAL PATHOL 1978;45:947-54. 15. Morse DR, Mann C, Esposito JV. Gutta-percha/eucapercha. Part II. Indications, representative cases,and pitfalls management. Compend Cont Ed Dent 1988;8:772-80. 16. Grubb TC. Studies on antibacterial vapors of volatile substance. J Am Pharmaceut Assoc 1958;47:272-5. 17. Holdeman LV, Cato EP, Moore WEC, eds. Anaerobe laboratory manual. 4th ed. Blacksburg, Virginia: VP1 Anaerobe Lab, 1977. 17a. Barry AL, Thornsberry C. Susceptibility test procedures: diffusion test procedures. In: Lennette EH, ed. Manual of clinical microbiology. 3rd ed. Washington, DC: American Society for Microbiology, 1980:463-79. 18. Hume WR. The pharmacologic and toxicological properties of zinc oxide-eugenol. J Am Dent Assoc 1986;113:789-91. 19. Fisher FJ. The effect of calcium hydroxide water paste on microorganisms in carious dentin. Br Dent J 1972;133:19-21. 20. Fisher FJ. The effect of three proprietary lining materials on microorganisms in carious dentin. An in vivo investigation. Br Dent J 1977;143:231-5. 21. Yesilsoy C, Feigal R. Effects of endodontic materials on cell

ORAL SURG ORAL MED ORAL PATHOL December 1990

22.

23. 24. 25.

26. 27. 28. 29. 30.

31. 32. 33.

viability across standard pore size filters. J Endod 1985;ll: 401-7. Onose H, Yanazaki M, Kuruda T. Studies on the antibacterial effects of various medicaments used in root canal therapy. Part 3: antibacterial effect of the pulp capping and root filling agents. J Nihon Univ Sch Dent 1969;11:120-8. Stevens RH, Grossman LI. Antimicrobial effect of root canal cements on an obligate anaerobe organism. J Endod 1981; 7~266-7. Chohayeb AA, Cole M. Evaluation of antimicrobial properties of various root canal sealers. Abstract No. 25. J Endod 1987;13:134. Holland R, deMello W, Nery MJ, Bernabe PFE, de Souza V. Reaction of human periapical tissue to pulp extirpation and immediate root canal filling with calcium hydroxide. J Endod 1977;3:63-7. Holland R, DeSouza V. Ability of a new calcium hydroxide root canal filling material to induce hard tissue formation. J Endod 1985;11:535-43. McComb D, Ericson D. Antimicrobial action of new proprietary lining cements. J Dent Res 1987;66:1025-8. Apont A, Hartsook J, Crowley M. Indirect pulp capping success verified. J Dent Child 1966;33:164-6. Safavi KE, Dowden WE, Introcaso JH, Langeland K. A comparison of antimicrobial effects of calcium hydroxide and iodine-potassium iodide. J Endod 1985;11:454-6. Bystrbm A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumatol 1985;1:170-5. Morse DR, Wilcko JM, Pullon PA, Furst ML, Passo SA. A comparative tissue toxicity evaluation of the liquid components of gutta-percha root canal sealers. J Endod 1981;7:545-50. Morse DR, Martell B, Pike CG, et al. A comparative tissue toxicity evaluation of gutta-percha root canal sealers. Part I. Six-hour findings. J Endod 1984;10:246-9. Morse DR, Martell B, Pike CG, et al. A comparative tissue toxicity evaluation of gutta-percha root canal sealers. Part 1. Forty-eight-hour findings. J Endod 1984;10:484-6.

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