Evidence for antibacterial activity of endodontic gutta-percha cones

Nanomaterials Application in Endodontics

In recent years, nanomaterials have become increasingly present in medicine, especially in dentistry. Their characteristics are proving to be very useful in clinical cases. Due to the intense research in the field of biomaterials and nanotechnology, the efficacy and possibilities of dental procedures have immensely expanded over the years. The nano size of materials allows them to exhibit properties not present in their larger-in-scale counterparts. The medical procedures in endodontics are time-consuming and mostly require several visits to be able to achieve the proper result. In this field of dentistry, there are still major issues about the removal of the mostly bacterial infection from the dental root canals. It has been confirmed that nanoparticles are much more efficient than traditional materials and appear to have superior properties when it comes to surface chemistry and bonding. Their unique antibacterial properties are also promising features in every medical procedure, especially in endodontics. High versatility of use of nanomaterials makes them a powerful tool in dental clinics, in a plethora of endodontic procedures, including pulp regeneration, drug delivery, root repair, disinfection, obturation and canal filling. This study focuses on summing up the current knowledge about the utility of nanomaterials in endodontics, their characteristics, advantages, disadvantages, and provides a number of reasons why research in this field should be continued.

Bacterial Contamination of Gutta-Percha Points From Different Brands and the Efficacy of a Chairside Disinfection Protocol

OBJECTIVE

To evaluate the bacterial contamination of different brands of Gutta-Percha (GP) points routinely used in clinical practice and the efficacy of a chairside disinfection protocol with sodium hypochlorite.

METHODS

GP points (n=240), in sizes A, B, C, D, K15, K20, K25, K30, K35, K40, F1, F2, F3 (Dentsply®, Proclinic®, ProTaper® and R&S®), were randomly sampled from commercial packages already in use. These were added directly to Fluid Thioglycolate Medium (one GP point per tube) and incubated at 37ºC for 21 days. During this period, the presence/absence of turbidity was evaluated. To evaluate the efficacy of a chairside disinfection protocol, all detected contaminated GP points were immersed for 1 minute in 10 mL of 5.25% sodium hypochlorite, followed by 5 minutes in 10 mL of detergent solution (3% Tween 80 and 5% sodium thiosulfate) and a final rinse with 10 mL of sterile distilled water and incubated. The data was analysed using the chi-square test and differences between characteristics of dichotomic variables were performed using the binomial test. The significance level was set at P<0.05.

RESULTS

Bacterial growth was observed in 22.9% of the total study samples. Dentsply® and R&S® showed the highest level of contamination, 47.3% each, although without significant differences to the other commercial brands. The most contaminated GP point size was K30 (16.4%). The chairside disinfection protocol was effective in disinfection of 76.4% of GP points (P<0.001).

CONCLUSION

A real small number of GP points in clinical use harboured bacteria, including after the Chairside Disinfection Protocol that, anyway, proved to be effective. No significant difference was observed between tested commercial brands.

Evaluation of antimicrobial activity and efficacy of herbal oils and extracts in disinfection of gutta percha cones before obturation

Objectives

Literature has shown that micro-organisms contaminate gutta percha (GP) during storage and manipulation. Till date herbal extracts are not explored as an alternative medicament for pre-operative chairside disinfection of GP cones. The purpose of our study was to evaluate the antimicrobial activity and efficacy of lemon grass oil (LG), basil oil (BO), and obicure tea extract (OT) in disinfecting GP cones before obturation.

Materials and Methods

Agar diffusion method was used to evaluate the antimicrobial efficacy of LG, BO, OT, and sodium hypochlorite (control) against common contaminants, namely, Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. One hundred and twenty GP cones were contaminated and cut into 2. First half was placed in the broth and incubated; whereas the second was treated with herbal extracts for 1 minute and then incubated for 24 hours in the broth. Any inhibition in bacterial growth was noted with presence/absence of turbidity. Two-way analysis of variance and χ² test were used to assess the effectiveness of herbal extracts to decontaminate GP.

Results

LG showed the highest inhibition zones (29.9 ± 6.9 mm) for all tested organisms, followed by OT extract (16.3 ± 1.8 mm), sodium hypochlorite (16.0 ± 1.6 mm), and BO (14.5 ± 5.3 mm). Statistically significant difference was observed between LG and other herbal extracts (p < 0.05).

Conclusions

All extracts proved to be potential rapid chairside disinfectants of GP cones with LG showing the highest antimicrobial activity.

Single versus multiple visits for endodontic treatment of permanent teeth

BACKGROUND

Root canal treatment (RoCT), or endodontic treatment, is a common procedure in dentistry. The main indications for RoCT are irreversible pulpitis and necrosis of the dental pulp caused by carious processes, tooth cracks or chips, or dental trauma. Successful RoCT is characterised by an absence of symptoms (i.e. pain) and clinical signs (i.e. swelling and sinus tract) in teeth without radiographic evidence of periodontal involvement (i.e. normal periodontal ligament). The success of RoCT depends on a number of variables related to the preoperative condition of the tooth, as well as the endodontic procedures. This review updates the previous version published in 2007.

OBJECTIVES

To determine whether completion of root canal treatment (RoCT) in a single visit or over two or more visits, with or without medication, makes any difference in term of effectiveness or complications.

SEARCH METHODS

We searched the following electronic databases: Cochrane Oral Health's Trials Register (to 14 June 2016), Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, 2016, Issue 5), MEDLINE Ovid (1946 to 14 June 2016), and Embase Ovid (1980 to 14 June 2016). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform for ongoing trials to 14 June 2016. We did not place any restrictions on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs of people needing RoCT. We excluded surgical endodontic treatment. The outcomes of interest were tooth extraction for endodontic problems; radiological failure after at least one year, i.e. periapical radiolucency; postoperative pain; swelling or flare-up; painkiller use; sinus track or fistula formation; and complications (composite outcome including any adverse event).

DATA COLLECTION AND ANALYSIS

We collected data using a specially designed extraction form. We contacted trial authors for further details where these were unclear. We assessed the risk of bias in the studies using the Cochrane tool and we assessed the quality of the body of evidence using GRADE criteria. When valid and relevant data were collected, we undertook a meta-analysis of the data using the random-effects model. For dichotomous outcomes, we calculated risk ratios (RRs) and 95% confidence intervals (CIs). For continuous data, we calculated mean differences (MDs) and 95% CIs. We examined potential sources of heterogeneity. We conducted subgroup analyses for necrotic and vital teeth.

MAIN RESULTS

We included 25 RCTs in the review, with a total of 3780 participants, of whom we analysed 3751. We judged three studies to be at low risk of bias, 14 at high risk, and eight as unclear.Only one study reported data on tooth extraction due to endodontic problems. This study found no difference between treatment in one visit or treatment over multiple visits (1/117 single-visit participants lost a tooth versus 2/103 multiple-visit participants; odds ratio (OR) 0.44, 95% confidence interval (CI) 0.04 to 4.78; very low-quality evidence).We found no evidence of a difference between single-visit and multiple-visit treatment in terms of radiological failure (risk ratio (RR) 0.91, 95% CI 0.68 to 1.21; 1493 participants, 11 studies, I² = 18%; low-quality evidence); immediate postoperative pain (dichotomous outcome) (RR 0.99, 95% CI 0.84 to 1.17; 1560 participants, 9 studies, I² = 33%; moderate-quality evidence); swelling or flare-up incidence (RR 1.36, 95% CI 0.66 to 2.81; 281 participants, 4 studies, I² = 0%; low-quality evidence); sinus tract or fistula formation (RR 0.98, 95% CI 0.15 to 6.48; 345 participants, 2 studies, I² = 0%; low-quality evidence); or complications (RR 0.92, 95% CI 0.77 to 1.11; 1686 participants, 10 studies, I² = 18%; moderate-quality evidence).The studies suggested people undergoing RoCT in a single visit may be more likely to experience pain in the first week than those whose RoCT was over multiple visits (RR 1.50, 95% CI 0.99 to 2.28; 1383 participants, 8 studies, I² = 54%), though the quality of the evidence for this finding is low.Moderate-quality evidence showed people undergoing RoCT in a single visit were more likely to use painkillers than those receiving treatment over multiple visits (RR 2.35, 95% CI 1.60 to 3.45; 648 participants, 4 studies, I² = 0%).

AUTHORS' CONCLUSIONS

There is no evidence to suggest that one treatment regimen (single-visit or multiple-visit root canal treatment) is better than the other. Neither can prevent all short- and long-term complications. On the basis of the available evidence, it seems likely that the benefit of a single-visit treatment, in terms of time and convenience, for both patient and dentist, has the cost of a higher frequency of late postoperative pain (and as a consequence, painkiller use).

Evaluation of cytotoxicity of two root canal filling materials by MTT assay

The aim of this study was to assess the cytotoxicity of two root filling materials GuttaFlow (GF) and gutta-percha (GP) on mouse fibroblasts cell line L-929. In this study there were four groups: GP and GF were considered as study groups and the other two were negative control groups. GP and GF were prepared according to manufacturer's instruction. L-929 fibroblast cells of mouse were passaged with trypsin (Merck, Germany) after elimination of freeze phase. Adequate trypsin was added to cells and they were prepared with 95% of cell vitality. After 24 h, 150,000 cells were put in each well. The cell and dimethyl methacrylate were used as negative and positive controls. Ten specimens from each group were brought into contact with the culture medium and were incubated under sterilised conditions 24 h later. The cytotoxicity of all samples was assessed by dimethylthiazol diphenyltetrazolium bromide test after 1 h, 24 h and 72 h. The results showed that cytotoxicity of GF was less than GP when assessed at 24 h and 72 h, but there was no significant difference at 1 h. In GF, the most and least cytotoxicity were observed at 24 h and 72 h while cytotoxicity of GP increased with time.

Cytotoxicity evaluation of Activ GP and Resilon cones in vitro

OBJECTIVE

This study was done to evaluate the cytotoxicity of Activ GP and Resilon cones in an in vitro cell culture system.

STUDY DESIGN

Gutta-percha (GP), Activ GP, and Resilon cones were tested in this study. L929 cells were seeded into 96-well plates at 3 x 10(4) cells/well. In one set of experiments, 2-mm segments cut from the tip of GP and Resilon cones were placed into the cell culture wells and incubated for 1, 2, and 3 days. In another set of experiments, 2 20-mm segments of GP, Activ GP, and Resilon cones were incubated in 2 mL cell culture medium for 1 week. Then 100 microL elutes were tested for 24 and 48 h. Cell viability was evaluated by MTT assay. Data were analyzed using 1-way analysis of variance.

RESULTS

When GP, Activ GP, and Resilon segments were placed into cell cultures, cell viability in the Resilon group was significantly greater than in the GP and Activ GP groups at any test time. There was no cell viability difference between the Activ GP and GP groups. When the elutes of GP, Activ GP, and Resilon was placed into cell cultures, the results were the same as using segments of the tested material. The cytotoxicity of GP and Activ GP is greater than that of the Resilon cone. There was no cell viability difference between Activ GP and regular GP.

CONCLUSION

Resilon has better biocompatibility than regular GP and Activ GP cones. The cytotoxicity of Activ GP is similar to that of regular GP.

Single versus multiple visits for endodontic treatment of permanent teeth

BACKGROUND

Root canal treatment (RoCT), or endodontic treatment, is a common procedure in dentistry. The main indications for RoCT are irreversible pulpitis and necrosis of the dental pulp caused by carious processes, tooth cracks or chips, or dental trauma. Successful RoCT is characterised by an absence of symptoms and clinical signs in teeth without radiographic evidence of periodontal involvement. The success of RoCT depends on a series of variables related to the preoperative condition of the tooth, as well as the endodontic procedures.

OBJECTIVES

To compare the effectiveness of single- and multiple-visit RoCT, measured as tooth extraction due to endodontic problems and radiological success.To assess the difference in short- and long-term complications between single- and multiple-visit RoCT.

SEARCH STRATEGY

The following databases were searched for relevant trials: Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE, and EMBASE. Handsearching was performed for the major oral medicine journals. References of included studies and reviews were checked. Endodontics experts were contacted through e-mail. No language limitations were imposed. Date of last search was 6th March 2007.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of patients needing RoCT were included. Surgical endodontic treatment was excluded. The outcomes considered were the number of teeth extracted for endodontic problems; radiological success after at least 1 year, that is, absence of any periapical radiolucency; postoperative pain; painkiller use; swelling; or sinus track formation.

DATA COLLECTION AND ANALYSIS

Data were collected using a specific extraction form. The validity of included studies was assessed on the basis of allocation concealment, blindness of the study, and loss of participants. Data were analysed by calculating risk ratios. When valid and relevant data were collected, a meta-analysis of the data was undertaken.

MAIN RESULTS

Twelve randomised controlled trials were included in the review. Four studies had a low risk of bias, four a moderate risk, and another four had a high risk of bias. The frequency of radiological success and immediate postoperative pain were not significantly different between single- and multiple-visit RoCT. Patients undergoing single-visit RoCT reported a higher frequency of painkiller use and swelling, but the results for swelling were not significantly different between the two groups. We found no study that included tooth loss and sinus track formation among its primary outcomes.

AUTHORS' CONCLUSIONS

No difference exists in the effectiveness of RoCT, in terms of radiological success, between single- and multiple-visit RoCT. Most short- and long-term complications are also similar in terms of frequency, although patients undergoing a single visit may experience a slightly higher frequency of swelling and are significatively more likely to take painkillers.

Effects of Short-term Chemical Disinfection of Gutta-Percha Cones: Identification of Affected Microbes and Alterations in Surface Texture and Physical Properties

The aims of this study were to identify microorganisms on the surface of gutta-percha (GP) cones using a polymerase chain reaction (PCR) and to evaluate the sterilization effect of 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and ChloraPrep on these bacteria. Alterations of the surface texture and physical properties of GP cone after chemical sterilization were compared. A total of 150 GP cones were randomly selected in endodontic clinics, and a PCR assay was performed to identify the contaminating microorganisms. After inoculation with the same microorganisms followed by drying for 1 day, the GP cones were immersed in the three chemical disinfectants. The sterilization effects were assessed by measuring the turbidity and through subculturing. The changes in surface texture were observed by scanning electron microscopy, and Instron 5500 (Instron Corp, Canton, MA) was used to measure the tensile strength and elongation rate of the GP cones after chemical sterilization. Statistical analysis was performed. Results indicate that 19.4% of GP cones from the clinic were contaminated, and all the species belonged to the genus Staphylococcus. Three chemical disinfectants were all effective in the rapid disinfection of GP cones against Staphylococcus spp, and 1-minute immersion of the GP cones was adequate for disinfection. Microphotographs of the NaOCl-soaked cone showed a cluster of cuboidal crystals. The tensile strength between the NaOCl- and CHX-soaked groups was significantly different (p<0.05), but there was no significant difference between the NaOCl- and ChloraPrep-soaked groups (p>0.05). All disinfectants significantly increased the elongation rate of the GP cones compared with fresh GP cones (p<0.05), especially in the ChloraPrep (Medi-flex, Leawood, KS). These results show that the three chemical disinfectants are effective agents for the rapid sterilization of GP cones. However, further research will be needed to determine the clinical relevance of the changes in physical properties.

Disinfection of artificially contaminated Resilon cones with chlorhexidine and sodium hypochlorite at different time exposures

OBJECTIVE

The aim of this study was to evaluate the efficiency of chlorhexidine (CHX) and sodium hypochlorite (NaOCl) solutions on Resilon cones that were artificially contaminated with microbial samples of Enterococcus faecalis or Candida albicans at various concentrations and time exposures.

STUDY DESIGN

Resilon cones artificially contaminated with E faecalis or C albicans were left in contact with 1% NaOCl, 5% NaOCl, and 2% CHX disinfecting solutions for 1 and 5 minutes. The cones were then individually transferred to the test tubes, which contained 10 mL of thioglycollate media, and were incubated at 37 degrees C for 7 days. The antimicrobial activities of tested agents were determined by microbial growth.

RESULTS

All of the Resilon cones contaminated with E faecalis or C albicans could be disinfected with 1% and 5% NaOCl for 1 and 5 minutes and with 2% CHX for 5 minutes. Three of 7 Resilon cones contaminated with E faecalis and 1 of 7 Resilon cones contaminated with C albicans could not be disinfected with 2% CHX at 1 minute of treatment.

CONCLUSIONS

In conclusion, these results demonstrated that 1% and 5% NaOCl solutions are effective agents for disinfecting Resilon cones in 1- or 5-minute treatments. Two percent CHX was only effective after 5 minutes of treatment.

Cultivable microbial flora associated with persistent periapical disease and coronal leakage after root canal treatment: a preliminary study

AIM

To identify the cultivable bacterial flora in root filled teeth with persistent periapical lesions and to locate their distribution within the root canal system using an in vitro sampling protocol.

METHODOLOGY

Eight freshly extracted root filled teeth were collected from the Oral and Maxillo-facial Surgery Department, Eastman Dental Hospital. Seven teeth were associated with persistent apical periodontitis and also showed evidence of coronal leakage. Teeth were transferred to an anaerobic chamber immediately after careful extraction and sectioned transversely to give a crown (in all but one case) and two root segments (coronal and apical). Two samples were obtained from each segment, one from dentine and the other from the restoration or gutta-percha (GP) root filling (46 sites in total). The samples were dispersed, serially diluted and cultured on blood agar and fastidious anaerobic agar (with 5% defibrinated horse blood). The primary growth was subcultured to obtain pure isolates, which were identified by routine microbiological techniques and commercial enzyme tests.

RESULTS

A total of 252 strains were isolated from all the teeth. Of all the isolates, the most prevalent bacteria were Gram-positive facultative anaerobes 189/252 (75%) with staphylococci (48/252, 19%), streptococci (44/252, 17%), enterococci (20/252, 8%) and Actinomyces species (20/252, 8%) being found in most of the teeth (6/8, 6/8, 5/8, 5/8 and 7/8, respectively). Of the obligate anaerobes (17%), peptostreptococci (7%) were also present in most teeth (7/8). A statistical association between bacterial flora and site (crown/coronal/apical) or surface (dental/GP/restoration) could not be shown.

CONCLUSIONS

The predominant group of bacteria in root filled teeth with persistent apical periodontitis and coronal leakage was Gram-positive facultative anaerobes of which staphylococci followed by streptococci and enterococci were the most prevalent.

The antimicrobial efficacy of 'MGP' gutta-percha in vitro

AIM

To determine whether 'MGP' gutta-percha (Westport, CT, USA), a commercially available gutta-percha containing iodoform, inhibits the growth of potential endodontic pathogens.

METHODOLOGY

Inocula of Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus sanguis, Fusobacterium nucleatum and Actinomyces odontolyticus were spread onto the surface of agar plates. 'MGP' gutta-percha cones presoaked in sterile water were transferred to the inoculated agar and incubated at 37 degrees C aerobically or anaerobically as required for optimal growth. Identical studies were performed using iodoform-free gutta-percha and sterile paper disks saturated with 10% povidone-iodine. Following incubation, zones of inhibition around the 'MGP' gutta-percha, iodoform-free gutta-percha and disks were evaluated.

RESULTS

Povidone-iodine inhibited all the strains. Iodoform-free gutta-percha inhibited S. sanguis and A. odontolyticus. 'MGP' gutta-percha inhibited S. aureus, S. sanguis, A. odontolyticus and F. nucleatum. Neither iodoform-free gutta-percha nor 'MGP' gutta-percha inhibited growth of E. faecalis, E. coli or P. aeruginosa.

CONCLUSIONS

Compared to iodoform-free gutta-percha, iodoform-containing 'MGP' gutta-percha had an inhibitory effect in vitro on S. aureus and F. nucleatum, but not on E. faecalis, E. coli or P. aeruginosa.

In vitro cytotoxicity of medicated and nonmedicated gutta-percha points in cultures of gingival fibroblasts

This investigation was designed to test the cellular toxicity of two medicated (Roeko activ point and Roeko Calcium Hydroxide) and four nonmedicated brands of gutta-percha (GP) points (Antaeos, DeTrey White, Roeko color, and Roeko Top color). The test points were transferred into a culture medium including the GP-point material with a concentration of 6 mg/ml, and eluates were obtained after 72 h. Five milliliters of each eluate were pipetted onto fibroblast cultures, incubated, and subsequently stained. Mitotic rates, cell densities, and the distribution of normal cells, pathologically altered and dead cells were determined and correlated with control cell cultures. Roeko activ point (containing chlorhexidine) resulted in the highest number of dead cells. The difference was statistically significant in comparison with all other materials. Concerning all parameters mentioned, the cytotoxicity of the points containing calcium hydroxide (Roeko Calcium Hydroxide) was not significantly different from all other points tested, with the exception of those containing chlorhexidine. All tested gutta-percha materials caused cytotoxic reactions in varying extents. Taking into consideration the limitations of an in vitro experiment, points containing calcium hydroxide and nonmedicated points seem to be the most recommendable products for clinical use.

Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms

AIM

The purpose of the present study is to evaluate the healing of periapical lesions of teeth with positive and negative canal cultures at the time of obturation, and to evaluate the periapical healing of teeth treated in one visit (without) or in two visits with an interappointment dressing of calcium hydroxide.

METHODOLOGY

Thirty-nine patients received root-canal treatment. In the first visit, teeth were instrumented, and 18 of these teeth were filled (after microbiological sampling) with calcium hydroxide in sterile saline. The other 21 teeth were obturated with gutta-percha and AH-26 sealer after microbiological sampling. Four weeks later, the teeth with calcium hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer. Healing of periapical radiolucency was recorded over a period up to 4.5 years.

RESULTS

In both the treatment groups, the size of the periapical lesions reduced significantly during the follow-up period. Complete radiographic healing was observed in 81% of the cases in the one-visit group, and in 71% of the cases in the two-visit group. The probability of success increased continuously over time for both treatment groups. Seven out of eight cases (87.5%) that showed a positive root-canal culture at the time of obturation healed. The number of colony forming units (CFU) in six out of eight positive canals was <10(2) CFU mL(-1).

CONCLUSIONS

Within the limitations of this study, no significant differences in healing of periapical radiolucency was observed between teeth that were treated in one visit (without) and two visits with inclusion of calcium hydroxide for 4 weeks. The presence of a positive bacterial culture (CFU<10(2)) at the time of filling did not influence the outcome of treatment.

Efficacy of chemical sterilization and storage conditions of gutta-percha cones

AIM

The objective of the present study was to assess the efficacy of 2.5% sodium hypochlorite and 2.2% glutaraldehyde ('Cidex') as sterilizing agents for gutta-percha cones. The efficacy of storage of gutta-percha cones in the presence or absence of paraformaldehyde was also evaluated.

METHODOLOGY

Gutta-percha cones artificially contaminated with a suspension of Bacillus stearothermophilus (ATCC/7953) were treated with either 2.2% glutaraldehyde for 10, 15, 30 and 60 min and 10 and 12 h, or 2.5% sodium hypochlorite for 5, 10 and 15 min. The cones were then incubated in thioglycollate medium for the determination of microbial growth. In parallel, additional sterile gutta-percha cones were stored in sealed containers with or without paraformaldehyde tablets for 30 days. The containers were opened 30 min a day and exposed to the environment of a functioning dental clinic. Twelve cones were removed weekly from the containers to determine whether contamination had occurred.

RESULTS

The results showed that 2.5% sodium hypochlorite was effective after 5, 10 and 15 min, whereas 10 and 12 h contact with 2.2% glutaraldehyde was necessary to obtain sterilization. There was no contamination of the gutta-percha cones when stored with or without paraformaldehyde.

CONCLUSIONS

Sodium hypochlorite (2.5%) and 2.2% glutaraldehyde ('Cidex') proved to be effective as sterilizing agents for gutta-percha cones, with sodium hypochlorite requiring shorter periods of use. No difference was observed between the two methods of cone storage.

Antibacterial properties of electron beam-sterilized Gutta-Percha cones

The purpose of the study was to determine the effect of electron beam sterilization on gutta-percha cones (GPCs) at different times after sterilization. An agar diffusion test was used with -one aerobic bacterium (Bacillus subtilis) and five oral anaerobic bacteria (Fusobacterium nucleatum, Peptostreptococcus micros, Porphyromonas gingivalis, Propionibacterium acnes, and Veillonella parvula). With each microorganism 30 agar plates were prepared, evenly distributed among three groups (group 1: unsterilized GPCs; groups 2 and 3: GPCs sterilized by electron beam irradiation 5 months and 5 yr before, respectively). One GPC of the selected group was placed in each plate. After incubation the area of inhibition was read on the agar plates. Inhibition of growth was significantly different for the tested microorganisms. However no significant difference was observed between the sterilized and unsterilized GPCs. Both the tested sterilized and unsterilized GPCs impair the growth of endodontic pathogens, with no influence of the time elapsed since sterilization.

Influence of calcium hydroxide intracanal dressings on the prognosis of teeth with endodontically induced periapical lesions

AIM

This prospective clinical study explored the influence of calcium hydroxide as an interappointment dressing on the healing of periapical lesions associated with pulpless teeth that had not been endodontically treated previously. This was achieved by comparing the prognosis after a two-visit root canal treatment with that following a one-visit treatment.

METHODOLOGY

Seventy-three patients were recruited having one tooth with an endodontically induced lesion. Of these patients, 67 could be re-examined. Calcium hydroxide was placed in the instrumented root canals of 31 teeth for at least one week and the treatment finished at the second visit. Thirty-six teeth were root canal treated at one visit. The criteria for success were the absence of signs and symptoms indicating an acute phase of periapical periodontitis and radiographically a periodontal ligament space of normal width. Methods for event time analysis were used to evaluate and compare the prognosis of both treatment approaches.

RESULTS

The probability that complete periapical healing will take place increased continuously with the length of the observation period. In both treatment groups the likelihood that the root canal treatment yields a success within an observation time of five years exceeded 90%. A statistically significant difference between the two treatment groups could not be detected.

CONCLUSIONS

From a microbiological perspective, one-visit root canal treatment created favourable environmental conditions for periapical repair similar to the two-visit therapy when calcium hydroxide was used as antimicrobial dressing. One-visit root canal treatment is an acceptable alternative to two-visit treatment for pulpless teeth associated with an endodontically induced lesion.

Microbial flora of sinus tracts and root canals of non-vital teeth

The occurrence of bacteria in 12 endodontically induced periodontal lesions associated with sinus tracts was examined. The microbial flora encountered in the sinus tract was compared with that of the root canal of the involved teeth which had not experienced any prior endodontic therapy. All microbiological samples taken from the sinus tract and from the root canal system contained bacteria. Seventy-one strains were detected in the extraradicular lesions. Of the anaerobic species, Fusobacterium nucleatum (7 strains), Prevotella intemedia (4 strains) and P. oralis (4 strains) were most frequently found. In the group of the facultative anaerobes Streptococcus spp. were predominant. Ninety-four strains were isolated from the root canal system of the 12 teeth. P. intermedia (6 strains), P. buccae (5 strains), F. nucleatum (5 strains) and Lactobacillus plantarum (5 strains) were most common. In 9 cases, species present in the root canal could be revealed in the extraradicular lesions. It was concluded that a variety of microorganisms were capable of colonizing endodontically induced, extraradicular lesions clinically characterized by sinus tracts.

In vitro cytotoxicity of root canal filling materials: 1. Gutta-percha

Gutta-percha (GP) has been the most widely used root canal filling material because of its well-known low toxicity. The inertness of GP, however, was challenged recently. The purpose of this study was to evaluate the toxicity of marketed endodontic GP using the radiochromium release test. Fourteen commercially available and three experimental GP brands were tested. Raw GP, zinc oxide, and barium sulfate, which were considered major components of GP points, and zinc ions were also evaluated. The material was spread to cover the bottom of testing wells after being dissolved in chloroform or warmed. A labeled suspension of L929 cells was added to the wells. After incubation at 37 degrees C for 4 and 24 h, extracellular radiochromium in the culture medium was measured and calculated in percentage of the total intracellular label. Spontaneous release of radiochromium was used as control and the results were considered to be within normal limits either at 4 or 24 h. All chloroform-dissolved GP showed low toxicity at 4 h, whereas warmed GP showed statistically significant differences at 4 h. Both dissolved and warmed GP were toxic at 24 h. The raw materials and barium sulfate were not toxic, whereas zinc oxide and zinc ions showed marked toxicity. All GP points tested were toxic at longer observation periods, and the toxicity was attributed to leakage of zinc ions into the fluids.