Apical periodontitis development and bacterial response to endodontic treatment. Experimental root canal infections in monkeys with selected bacterial strains

Biological properties versus solubility of endodontic sealers and cements

Endodontic sealers and cements used in root canal treatment have different compositions and properties. Common to all materials is that their primary goal is to fill gaps and voids, making a permanent seal of the root canal system. Furthermore, aspects such as antibacterial properties, cytotoxicity, setting time, solubility and biocompatibility are also crucial and ought to be considered. Over the years, a shift in the view on the importance of these aspects has ocurred. Whereas the antibacterial properties were considered important when the technical factors in endodontics were less developed, the sealing ability and biocompatibility have later been considered the most critical factors. The introduction of tricalcium silicate cements and sealers has led to a renewed interest in material properties, as these cements seem to have good sealing ability and at the same time combine favourable antimicrobial effects with excellent biocompatibility. This review discusses how the various properties of root canal sealers and cements may conflict with the primary aim of providing a permanent seal of the root canal system.

An in vitro evaluation of endodontic sealers and an antibiotic to assess their antimicrobial effect against Enterococcus faecalis

Objective

This study aimed to compare the antimicrobial effect of three endodontic sealers (AH Plus, Mineral trioxide aggregate [MTA] Fillapex, and BioRoot RCS) with and without amoxicillin against E. faecalis.

Methodology

Amoxicillin, equivalent to 10% of the sealers' total weight, was mixed with the sealers. Another batch was prepared without amoxicillin. The direct contact test (DCT) and the agar diffusion test were used to assess the antibacterial effect. Results were analysed using one-way analysis of variance (ANOVA), the F-test, and the Kruskal-Wallis test.

Results

AH Plus significantly suppressed E. faecalis without the addition of amoxicillin in the DCT (p = 0.011), while in the agar diffusion test, BioRoot RCS had a larger inhibition zone than the control (p < 0.001). When amoxicillin was added to the sealers, AH Plus (p = 0.003) and MTA Fillapex (p = 0.042) reduced E. faecalis growth. In contrast, all three sealers showed larger inhibition zones than the control (p = 0.001), with AH Plus displaying a larger inhibition zone than MTA Fillapex (p = 0.042) and BioRoot RCS (p = 0.032).

Conclusions

It was thus concluded that the addition of amoxicillin to endodontic sealers enhances their antimicrobial activity against E. faecalis.

Efficacy of antiseptics for rubber dam sterilization prior to endodontic treatment

PURPOSE

This study investigated the efficacy of various antiseptics for disinfection of rubber dams used during endodontic treatment, the duration of disinfection effectiveness, and the disinfection protocol employed by dental schools in Thailand.

METHODS

The efficacy of 10% povidone-iodine, 1.5% tincture iodine and 70% ethyl alcohol in eliminating Enterococcus faecalis (E. faecalis) and Candida albicans (C. albicans) on the rubber dam was investigated. Time duration of disinfection was evaluated at 0, 30, 60, and 120 min. The two-step disinfection method adopted at Thai dental school was examined. Independent t-test or Kruskal-Wallis followed by a Dunnett's test was used for statistical analysis.

RESULTS

Among the three antiseptics, 10% povidone and 1.5% tincture iodine eradicated the microorganisms completely, whereas 70% ethyl alcohol did not achieve a statistically significant decrease. The duration of sterilization effectiveness was 120 min for 10% povidone-iodine, but bacteria were eliminated only at 0 min by 1.5% tincture iodine. The results also indicated that the two-step protocol scarcely eliminated the microorganisms.

CONCLUSION

The best antiseptic for rubber dam disinfection is 10% povidone-iodine, which remains effective for 120 min. The two-step protocol typically practiced in Thai dental schools needs to be updated. The use of 10% povidone-iodine alone is adequate for complete eradication of E. faecalis and C. albicans.

Present status and future directions - Removal of fractured instruments

Success rate of fractured instrument retrieval varies because it is dependent mainly on several factors including the visibility of the fractured instrument, the length of the fractured instrument in relation to the curvature of the canal, and the techniques applied to each case. This review aims to update the present status on removal of fractured instruments to identify factors and variables that could affect the success of fractured instrument retrieval based on both the preparation techniques and the instrument retrieval techniques. On the other hand, future directions of fractured instrument retrieval should focus on management of non-visible fractured instruments since the removal of those instruments are deemed unpredictable with the current techniques, whereas the removal of visible fractured instruments are considered predictable now. Another possible direction of it is there might be no more instrument fracture due to possible significant changes in the root canal preparation technique which may dispense with the use of rotary instruments.

Prevalence of Lateral Radiolucency, Apical Root Resorption and Periapical Lesions in Portuguese Patients: A CBCT Cross-Sectional Study with a Worldwide Overview

Objective:

Apical periodontitis develops when bacteria, or their by products, migrate from the infected root canal system space to the surrounding apical tissues. The objective of the present multi-center cross-sectional study was to analyze the prevalence of lateral radiolucency, apical root resorption and periapical lesions in 7 districts of Portugal using cone-beam computed tomographic (CBCT) assessment.

Methods:

A total of 1,249 CBCT scans, from 11 dental clinics, were screened. Data regarding 22,899 teeth was included. For each tooth the recorded data was the presence of lateral radiolucency, apical root resorption, periapical lesions, previous root canal treatment, missed root canals, length of root canal filling (short, good or overfilling) and type of coronal restoration (intact tooth, non-restored, filling or crown). Differences between districts were tested using chi-squared. A P<0.05 was considered significant.

Results:

The proportion of lateral radiolucency ranged between 0.0% (Aveiro, Braga and Coimbra) and 0.9% (Lisbon), while the prevalence of apical root resorption ranged from 0.0% (Braga and Coimbra) to 3.0% in Setubal. The nationwide proportion of lateral radiolucency was 0.4%, while for apical root resorption was 1.1%. The prevalence of periapical lesions varied from 4.1% (Braga) and 13.0% (Lisbon) with a nationwide proportion of 10.0%. Significant differences were noted between districts (P<0.05).

Conclusion:

The prevalence of lateral radiolucency and apical root resorption were low in all districts. Root canal filled teeth were associated with higher periapical lesions proportions than non-treated teeth. Independently of the assessed district, the periapical status may be influenced by both quality of the endodontic treatment and coronal restoration.

Antibacterial Effect of High-Purity Nisin Alone and in Combination with D-Amino Acids or Chlorhexidine in an Endodontic-Like Biofilm Model

New strategies to eradicate endodontic biofilms are needed. Therefore, we evaluated the effect of high-purity nisin alone and in combination with D-amino acids (D-AAs) or chlorhexidine (CHX) against an “endodontic-like” biofilm model. Biofilms were grown on hydroxyapatite discs for 64 h and treated with nisin, eight D-AAs mixture, nisin + eight D-AAs, 2% CHX, and nisin + 2% CHX. After the 5 min and 24 h treatments, biofilm cells were harvested and total colony-forming units were counted. Differences between groups were tested by two-way ANOVA followed by Tukey’s multiple comparisons test (p < 0.05). Nisin and D-AAs, alone or in combination, were not effective in reducing bacteria after short or long exposure times. After 5 min, treatment with 2% CHX and nisin + 2% CHX resulted in 2 and 2.4-log cell reduction, respectively, compared with the no treatment control (p < 0.001). After 24 h, 2% CHX and nisin + 2% CHX drastically reduced bacterial counts. In conclusion, high-purity nisin alone or in combination with D-AAs did not show antibacterial activity against multispecies biofilms. Moreover, combined treatment using nisin and CHX showed similar antibiofilm activity compared with the use of CHX alone.

Antimicrobial Efficacy of Intracanal Medicaments against E. Faecalis Bacteria in Infected Primary Molars by Using Real-Time PCR: A Randomized Clinical Trial

Aim

This study aimed to compare the antimicrobial efficacy of calcium hydroxide (CH) and triple antibiotic paste (TAP) against E. faecalis bacteria in infected primary molars.

Methods and Materials

Thirty-nine 4–6-year-old children with an infected primary molar were randomly divided into three equal groups (n = 13) to receive either CH or TAP and an untreated control group. Following access cavity preparation, the first microbiological samples (S1) were collected by using absorbent paper points. The canals were prepared and rinsed. Then, CH or TAP was applied in the root canals. Seven days later, the second microbiological samples (S2) were collected. DNA extraction was performed to count E. faecalis bacteria by using real-time PCR for S1 and S2 samples. Data were analyzed through one-way ANOVA and Tukey's test (α = 0.05).

Results

E. faecalis bacteria counts decreased significantly in CH and TAP groups compared with the control group (P ≤ 0.001). However, no statistically significant difference existed between these two groups (P=0.698).

Conclusion

Both TAP and CH have significant antimicrobial effects as intracanal medicament between the treatment sessions in infected primary teeth.

Physical and biological properties of a novel root canal sealer modified by polyhexamethylene guanidine

The key of the root canal therapy is to eliminate the micro-organism infection, fill the root canal tightly and reduce the stimulation to the periapical tissues. However, it is quite difficult to meet all the conditions due to the defect of the material. Here we develop a novel root canal sealer (MZOE), in which zinc oxide eugenol (ZOE) were fabricated with polyhexamethylene guanidine (PHMG), and the PHMG's concentration is 0.8, 1.0, 1.2 and 1.4%. Our investigation tested its physical properties, antibacterial effect to E. faecalis, C. albicans, E. coli, S. aureus and cytotoxicity to human periodontal ligament fibroblasts (HPDLFs). The physical properties of the MZOE conformed to the ISO 6876:2001, and its antibacterial effect was stronger than ZOE (p<0.05), the RGR of HPDLFs was tested between 1 to 24%, belonging to moderate cytotoxicity. It was suggested that MZOE had good physical properties, high antibacterial effect, and moderate cytotoxicity.

Disruption and bactericidal indices depicted in polygonal graphs to show multiple outcome effects of root canal irrigant supplements on single- and dual-species biofilms

OBJECTIVES

The aims of this study were to (1) investigate the relative time-dependent disruption and bactericidal effects of detergent-type surfactants on single- or dual-species biofilms of root canal isolates and (2) to examine the utility of polygonal graphs for depiction of biofilm disruption and cell killing.

MATERIALS AND METHODS

Single-species biofilms of Streptococcus sanguinis, Enterococcus faecalis, Fusobacterium nucleatum and Porphyromonas gingivalis were grown on nitro-cellulose membranes for 72 h and immersed in Tween®80, cetyltrimethylammoniumbromide (CTAB), and sodium dodecyl sulphate (SDS) for 1-, 5- or 10-min (n = 3 per test). The number of viable and non-viable bacteria "disrupted" from the biofilm and those "remaining-attached" was determined using a viability stain in conjunction with fluorescence microscopy. The data were analysed using non-parametric Kruskal-Wallis test with 5% significance level.

RESULTS

Gram-negative obligate anaerobes were more susceptible to cell removal than gram-positive facultative anaerobes. The majority of cells were disrupted after 1-min of exposure; however, the extent varied according to the agent and species. CTAB and SDS were more effective than Tween 80™ at disrupting biofilms and killing cells but all agents failed to achieve 100% disruption/kill.

CONCLUSIONS

Biofilm disruption and cell viability were influenced by the species, the test agent and the duration of exposure. CTAB and SDS were more effective in biofilm disruption than Tween 80™. Graphical depiction of biofilm disruption- and viability-outcomes provides an alternative means of simultaneously visualising and analysing relative efficacy in different domains.

CLINICAL RELEVANCE

Surfactants were not as effective at biofilm disruption as NaOCl but may be added to other non-disruptive antibacterial agents to enhance this property.

Effect of Intracanal Medicaments on Pull-Out Bond Strength of Fiber Post Cemented with a Self-Adhesive System

OBJECTIVES

 This study aimed to assess the effect of four intracanal medicaments on pull-out bond strength of fiber posts.

MATERIALS AND METHODS

 A total of 65 single-rooted, single-canal teeth were selected and decoronated. Root canals were prepared and after rinsing were randomly divided into five groups (n = 13). G₁: calcium hydroxide (CH), G_2: CH plus chlorhexidine (CH+CHX), G₃: triple antibiotic paste (TAP), G₄: double antibiotic paste (DAP) were applied in the canals in the four groups. The control group (G₅) received no medicament. After 4 weeks, the medicaments were rinsed off and the canals were filled with gutta-percha. Post space was then prepared in root canals for the placement of glass fiber posts and self-adhesive cement (Panavia F2). After cementation, they were subjected to pull-out bond strength test.

STATISTICAL ANALYSIS

 Data were statistically analyzed using one-way analysis of variance and Tukey test.Results The pull-out bond strength values were significantly different in the groups (p < 0.001). The highest values of bond strength were seen in G₂, G₁, and G₃ (359.97 ± 81.26, 333.79 ± 98.96, 309.27 ± 78.07), respectively. There was no significant difference between G₄ and G₅ (p = 0.75).

CONCLUSION

 The results showed that CH, CH+CHX, and TAP enhanced the pull-out bond strength of fiber post to root canal wall as compared to the control group.

Root Canal Microflora

Modern day endodontics is undergoing a massive change with the introduction of new molecular based techniques for microbial identification. This review focuses on the microbiota in untreated and root-filled canals. It will also describe briefly the recent developments in microbial identification and the mechanisms by which certain species of microbes are able to invade and establish themselves in the root canal.

Evaluation of the Effect of Enterococcus faecalis Biofilm on the 2% Chlorhexidine Substantivity: An In Vitro Study

INTRODUCTION

The aim of this study was to correlate the bacterial viability and the presence of 2% chlorhexidine (CHX) solution on dentin by means of confocal laser scanning microscopy and high-performance liquid chromatography for 48 hours, 7 days, and 30 days.

METHODS

One hundred twenty-three extracted human teeth were used. Samples were divided into 4 groups according to the solution (CHX or saline) and the presence of Enterococus faecalis biofilm. Samples were kept in contact with 5 mL of the solution for 5 minutes. Each group was divided into 3 subgroups according to the evaluation period (n = 10). Statistical analysis was performed by using the Kruskal-Wallis test, the Mann-Whitney U test (P < .05), and the Spearman rank correlation coefficient (P < .01).

RESULTS

There was a negative correlation between the percentage of live cells and the amount of remaining CHX (P = .000). CHX significantly reduced the percentage of viable cells compared with saline after 48 hours (P = .007). Differences were maintained in the 7-day evaluation period (P = .001). After 30 days, the CHX group presented an increase of viable cells, thereby becoming similar to saline (P = .623). Simultaneously, the remaining CHX was significantly reduced in the 30-day specimens (P = .000).

CONCLUSIONS

The results of this study indicate that 2% CHX solution was detected for 48 hours and 7 days with a low percentage of viable cells. The presence of microorganisms on human dentin did not affect 2% CHX maintenance.

Physicochemical and biological properties of a novel injectable polyurethane system for root canal filling

A root canal sealer with antibacterial activity can be efficacious in preventing reinfection that results from residual microorganisms and/or the leakage of microorganisms. In the present study, a series of injectable, self-curing polyurethane (PU)-based antibacterial sealers with different concentrations of silver phosphate (Ag₃PO₄) were fabricated. Subsequently, their physicochemical properties, antibacterial abilities, and preliminary cytocompatibilities were evaluated. The results indicated that the fabricated PU-based sealers can achieve a high conversion rate in a short amount of time. More than 95% of the isocyanate group of PU sealers with 3 wt% (PU3) and 5 wt% (PU5) concentrations of Ag₃PO₄ were included in the curing reaction after 7 hours. With the exception of those for film thickness for PU5, the results of setting time, film thickness, and solubility were able to meet the requirements of the International Organization for Standardization. The antibacterial tests showed that PU3 and PU5 exhibit stronger antimicrobial effects than that achieved with 1 wt% Ag₃PO₄ (PU1) and AH Plus (positive control) against Streptococcus mutans. The cytocompatibility evaluation revealed that the PU1 and PU3 sealers possess good cytocompatibility and low cytotoxicity. These results demonstrate that the PU3 sealer offers good physicochemical and antimicrobial properties along with cytocompatibility, which may hold great application potential in the field of root canal fillings.

Antimicrobial activity of calcium hydroxide and chlorhexidine on intratubular Candida albicans

This study investigated the efficacy of calcium hydroxide and chlorhexidine gel for the elimination of intratubular Candida albicans (C. albicans). Human single-rooted teeth contaminated with C. albicans were treated with calcium hydroxide, 2% chlorhexidine gel, calcium hydroxide plus 2% chlorhexidine gel, or saline (0.9% sodium chloride) as a positive control. The samples obtained at depths of 0–100 and 100–200 µm from the root canal system were analyzed for C. albicans load by counting the number of colony forming units and for the percentage of viable C. albicans using fluorescence microscopy. First, the antimicrobial activity of calcium hydroxide and the 2% chlorhexidine gel was evaluated by counting the number of colony forming units. After 14 days of intracanal medication, there was a significant decrease in the number of C. albicans colony forming units at a depth of 0–100 µm with chlorhexidine treatment either with or without calcium hydroxide compared with the calcium hydroxide only treatment. However, there were no differences in the number of colony forming units at the 100–200 µm depth for any of the medications investigated. C. albicans viability was also evaluated by vital staining techniques and fluorescence microscopy analysis. Antifungal activity against C. albicans significantly increased at both depths in the chlorhexidine groups with and without calcium hydroxide compared with the groups treated with calcium hydroxide only. Treatments with only chlorhexidine or chlorhexidine in combination with calcium hydroxide were effective for elimination of C. albicans.

Comparative evaluation of pH and antibacterial effect of various calcium hydroxide combinations on E. faecalis and its effect on root strength: An in vitro study

AIM

To evaluate and compare the pH and antibacterial property of Ca(OH)(2) combined with iodine potassium iodide (IKI) or chlorhexidine (CHX) on E. faecalis and to assess and compare their effect on fracture resistance of root dentin.

MATERIALS AND METHODS

CHX (0.5%) The following test materials were used: Group I Calcium hydroxide + saline, Group II Calcium hydroxide + CHX (0.5%) and Group III Calcium hydroxide + IKI (2%). For antibacterial activity, 60 root dentin blocks (20 in each group) were infected by E. faecalis followed by placement of medicaments. At the end of 24 h and 7 days, 10 samples from each group were randomly chosen and assessed for antibacterial activity. For evaluation of root strength, 30 teeth were used and stored in sterile saline after placement of medicament. At the end of 30 days, samples were subjected to fracture resistance testing on the Universal Strength Testing Machine. Hounsfield strength testing machine, UK pH of the various calcium hydroxide combinations was determined with a digital pH meter.

STATISTICAL ANALYSIS

Kruskal Wallis test, Mann Whitney U test, and one-way ANOVA test for intergroup comparison and Wilcoxon's signed rank test and student's paired t test for intragroup comparison.

RESULTS

Group III showed significantly greater antibacterial activity against E. faecalis, followed by group II and control group. There was no statistically significant change in the pH and root strength values among all the groups.

CONCLUSION

The present study revealed that IKI or CHX in combination with Ca(OH)2 is an effective medicament against E. faecalis.

Relationship between files that bind at the apical foramen and foramen openings in maxillary central incisors--a SEM study

Considering that instrumentation of the apical foramen has been suggested for root canal infection control, this study analyzed the relationship between the files that bind at the apical foramen and the foraminal openings in 50 maxillary central incisors. After preparation of the pulp chamber, access to the canal was obtained with #1 and 2 LA Axxess and K-files with tip cut were inserted up to the apical foramen until binding was felt. The files were fixed with methyl cyanoacrylate and the tooth-file sets were cross-sectioned 10 mm short of the apex. Scanning electron microscopic analysis was carried out and files and foraminal areas were measured using Image Tool software. Statistically significant difference (p<0.0001) was found between files and the apical foraminal areas. The mean foraminal area was 3.8 times larger than the mean file area. The results of this study suggest that it would require 4 files of greater size beyond the one that bound to the foramen in order to allow a better relationship between files and apical openings of maxillary central incisors.

Prevalence of apical periodontitis and endodontic treatment in a Kosovar adult population

Background

Despite numerous studies on the prevalence of apical periodontitis (AP) and endodontic treatment in diverse geographical populations, there are currently no data on the prevalence of these conditions in populations of adults native to Kosovo. Therefore, little is known about how widespread these conditions are, and whether there is any correlation between root canal treatment and AP. The purpose of our research was to address this anomaly by investigating AP and endodontic treatment in an adult Kosovar population based on radiographic examination.

Methods

The sample used for this study consisted of randomly selected individuals referred to the University Dentistry Clinical Center of Kosovo in the years 2006-2007. Orthopantomographs of 193 patients were evaluated. The periapical status of all teeth (with the exception of third molars) was examined according to Ørstavik's Periapical Index. The quality of the root canal filling was rated as 'adequate' or 'inadequate' based on whether all canals were filled, the depth of fill relative to the radiographic apex and the quality of compaction (absence/presence of voids). Data were analyzed statistically using the Chi-square test and calculation of odds ratios.

Results

Out of 4131 examined teeth, the prevalence of apical periodontitis (AP) and endodontic treatment was 12.3% and 2.3%, respectively. Of 95 endodontically-treated teeth, 46.3% were associated with AP. The prevalence of AP increased with age. The prevalence in subjects aged over 60 years old (20.2%) was higher than in other age groups. A statistically significant difference was found for the frequency of endodontically-treated teeth associated with AP in the 40-49 year age group (P < 0.001). Of some concern was the discovery that only 30.5% of the endodontically-treated teeth examined met the criteria of an acceptable root canal filling. Inadequately root-filled teeth were associated with an increased AP risk.

Conclusions

The prevalence of AP and the frequency of endodontically-treated teeth with AP in this Kosovar population are higher than those found in other countries. Inadequate root canal fillings were associated with an increased prevalence of AP.

Inorganic chemistry of defensive peroxidases in the human oral cavity

The innate host response system is comprised of various mechanisms for orchestrating host response to microbial infection of the oral cavity. The heterogeneity of the oral cavity and the associated microenvironments that are produced give rise to different chemistries that affect the innate defense system. One focus of this review is on how these spatial differences influence the two major defensive peroxidases of the oral cavity, salivary peroxidase (SPO) and myeloperoxidase (MPO). With hydrogen peroxide (H(2)O(2)) as an oxidant, the defensive peroxidases use inorganic ions to produce antimicrobials that are generally more effective than H(2)O(2) itself. The concentrations of the inorganic substrates are different in saliva vs. gingival crevicular fluid (GCF). Thus, in the supragingival regime, SPO and MPO work in unison for the exclusive production of hypothiocyanite (OSCN(-), a reactive inorganic species), which constantly bathes nascent plaques. In contrast, MPO is introduced to the GCF during inflammatory response, and in that environment it is capable of producing hypochlorite (OCl(-)), a chemically more powerful oxidant that is implicated in host tissue damage. A second focus of this review is on inter-person variation that may contribute to different peroxidase function. Many of these differences are attributed to dietary or smoking practices that alter the concentrations of relevant inorganic species in the oral cavity (e.g.: fluoride, F(-); cyanide, CN(-); cyanate, OCN(-); thiocyanate, SCN(-); and nitrate, NO(3)(-)). Because of the complexity of the host and microflora biology and the associated chemistry, it is difficult to establish the significance of the human peroxidase systems during the pathogenesis of oral diseases. The problem is particularly complex with respect to the gingival sulcus and periodontal pockets (where the very different defensive stratagems of GCF and saliva co-mingle). Despite this complexity, intriguing in vitro and in vivo studies are reviewed here that reveal the interplay between peroxidase function and associated inorganic chemistry.

Duration-dependent susceptibility of endodontic pathogens to calcium hydroxide and chlorhexidene gel used as intracanal medicament: an in vitro evaluation

The aim of this study was to evaluate the effective duration of antimicrobial activity of a calcium hydroxide-based medicament (Apex Cal) and 2% chlorhexidene gluconate gel against selected endodontic pathogens (Enterococcus faecalis, Candida albicans, Porphyromonas gingivalis, and Prevotella intermedia). The agar diffusion test was used to determine the antimicrobial activity. Chlorhexidene gluconate gel showed the largest inhibitory zones. The antimicrobial action of both medicaments decreased significantly with time, with calcium hydroxide showing no antimicrobial action after 72 hours. In conclusion, 2% chlorhexidene gel showed better antimicrobial activity than calcium hydroxide, and the effective antimicrobial action of both medicaments decreased after 48 hours.

The Influence of Root Canal Sealer on Extended Intracanal Survival of Enterococcus faecalis With and Without Gelatinase Production Ability in Obturated Root Canals

Enterococcus faecalis can survive for extended periods in obturated root canals. In this study, the hypotheses tested were that long-term survival of E. faecalis is dependent on (1) the type of endodontic sealer and (2) the capacity for microbial gelatinase activity, a potential "virulence" trait identified previously in clinical isolates. Root canals of extracted human canines (n=95) were inoculated with either E. faecalis OG1RF or its gelatinase-negative mutant E. faecalis TX5128. After 48 hours of incubation at 37 degrees C, canals were obturated with gutta-percha and either the epoxy-resin-based AH-Plus (Dentsply, De Trey, Konstanz, Germany), the silicone-based RoekoSeal (Coltène/Whaledent, Langenau, Germany), or zinc oxide eugenol-based Roth's sealer (Root Canal Cement Type 801; Roth International Ltd, Chicago, IL). Access cavities were sealed. After 8 months of incubation at 37 degrees C, viable E. faecalis was recovered from more teeth sealed with RoekoSeal (95%) compared with AH-Plus (40%) (p=0.0004, Fisher's exact test) and Roth's sealer (45%) (p=0.0012, Fisher's exact test). In the RoekoSeal groups, viable counts of E. faecalis OG1RF were higher than E. faecalis TX5128 (p=0.03, Mann-Whitney U test) suggesting that gelatinase activity plays a role in long-term survival of E. faecalis in obturated root canals.

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics, non-phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.

Primer sensitivity: can it influence the results in Enterococcus faecalis prevalence studies?

BACKGROUND/OBJECTIVE

Recent polymerase chain reaction (PCR)-based studies have shown significant variability in the prevalence of Enterococcus faecalis cases with nonhealing endodontic infections. This variability may be, at least in part, due to the differences in sensitivities of the primers used. The purpose of this study was to compare the sensitivity of 3 sets of PCR primers which have been reported in the endodontic literature.

METHODS

The 3 primers sets used were: group 1) tuf gene-based primers with genus-level specificity; and groups 2 and 3) 16S rDNA-based primers that were E. faecalis specific. Three strains of E. faecalis at concentrations of 10(2)-10(8) cells/mL were included in this study.

RESULTS

The PCR amplification of E. faecalis strains with the 3 primer pairs showed that group 1 primers consistently had the highest sensitivity, followed by group 2 and group 3 (P<.0001).

CONCLUSION

A tuf-based PCR identification assay followed by direct sequencing would yield accurate and consistent prevalence rates of E. faecalis in endodontic infections.

Photodynamic Therapy for Endodontic Disinfection

The aims of this study were to investigate the effects of photodynamic therapy (PDT) on endodontic pathogens in planktonic phase as well as on Enterococcus faecalis biofilms in experimentally infected root canals of extracted teeth. Strains of microorganisms were sensitized with methylene blue (25 microg/ml) for 5 minutes followed by exposure to red light of 665 nm with an energy fluence of 30 J/cm2. Methylene blue fully eliminated all bacterial species with the exception of E. faecalis (53% killing). The same concentration of methylene blue in combination with red light (222 J/cm2) was able to eliminate 97% of E. faecalis biofilm bacteria in root canals using an optical fiber with multiple cylindrical diffusers that uniformly distributed light at 360 degrees. We conclude that PDT may be developed as an adjunctive procedure to kill residual bacteria in the root canal system after standard endodontic treatment.

Influence of residual bacteria on periapical tissue healing after chemomechanical treatment and root filling of experimentally infected monkey teeth

The purpose of this study was twofold: first, to determine the influence on the healing of the periapical tissues when selected bacterial strains and combinations thereof remain after root canal treatment; and, second, the relationship to healing of the quality of the root filling. In eight monkeys, 175 root canals, previously infected with combinations of four or five bacterial strains and with radiographically verified apical periodontitis, were endodontically treated, bacteriologically controlled, and permanently obturated. After 2-2.5 yr, the periapical regions were radiographically and histologically examined. Of these teeth, 48 root canals were also examined for bacteria remaining after removal of the root fillings. When bacteria remained after the endodontic treatment, 79% of the root canals showed non-healed periapical lesions, compared with 28% where no bacteria were found. Combinations of residual bacterial species were more frequently related to non-healed lesions than were single strains. When no bacteria remained, healing occurred independently of the quality of the root filling. In contrast, when bacteria remained, there was a greater correlation with non-healing in poor-quality root fillings than in technically well-performed fillings. In root canals where bacteria were found after removal of the root filling, 97% had not healed, compared with 18% for those root canals with no bacteria detected. The present study demonstrates the importance of obtaining a bacteria-free root canal system before permanent root filling in order to achieve optimal healing conditions for the periapical tissues.

Coaggregation interactions between oral and endodontic Enterococcus faecalis and bacterial species isolated from persistent apical periodontitis

Interactions between Enterococcus faecalis and other species found in root canal infections might be important for the development and persistence of periapical disease. The aim of this study was to investigate the coaggregation interactions between E. faecalis clinical isolates and species previously shown to survive and induce apical periodontitis in monkeys: Peptostreptococcus anaerobius, Prevotella oralis, Fusobacterium nucleatum, and Streptococcus anginosus. Intergeneric coaggregation assays were conducted in duplicate with observations scored immediately at 0 h, 1 h and 24 h after mixing of combinations of strains. All E. faecalis strains (n = 53) coaggregated with F. nucleatum; E. faecalis did not coaggregate with P. anaerobius or S. anginosus. One strain, E. faecalis E1, coaggregated with P. oralis, with aggregates visible at 1 h. Coaggregation interactions between E. faecalis and F. nucleatum observed in this study suggest a potential role for this combination in endodontic infections.

Detection and quantitation of E. faecalis by real-time PCR (qPCR), reverse transcription-PCR (RT-PCR), and cultivation during endodontic treatment

Enterococcus faecalis is frequently recovered from refractory endodontic infections and has been implicated in endodontic treatment failures. This study compared real-time quantitative PCR (qPCR) assay to cultivation for E. faecalis detection and quantitation during endodontic treatment. A reverse-transcription PCR (RT-PCR) assay was also developed to detect the bacterium clinically in the viable but nonculturable (VBNC) state. Intra-canal samples (n = 87) were collected upon access, post-instrumentation/irrigation and postcalcium hydroxide treatment from 15 primary and 14 refractory infections involving 29 single-rooted teeth, and analyzed by the three methods. The bacterium was up to three times more prevalent in refractory than primary infections at each collection step. Overall, qPCR detected significantly more E. faecalis-positive teeth and samples than cultivation (p < 0.001). VBNC E. faecalis was detected by RT-PCR in four samples that were negative by cultivation. These findings support qPCR and RT-PCR as more sensitive methods than cultivation for detecting E. faecalis in endodontic infections.

The relation between apical periodontitis and root-filled teeth in patients with periodontal treatment need

AIM

To investigate a number of clinical and treatment variables that might have influenced the prevalence of apical periodontitis in root-filled teeth in a population of periodontally compromised patients.

METHODOLOGY

This investigation was a retrospective cross-sectional study on data collected from periodontal charts in addition to intra-oral full-mouth radiographs from patients attending the Department of Periodontology of the Dental School of the Ghent University Hospital. Periodontal parameters (clinical attachment loss and the lowest marginal bone level, the history of periodontal treatment), endodontic treatment (length, homogeneity and overall quality of the root filling) and the quality of coronal restorations were related to the prevalence of apical periodontitis. A total of 272 root-filled teeth in 94 patients were evaluated.

RESULTS

The periapical condition was significantly influenced by the quality of the root filling and the coronal filling (P < 0.05). More apical periodontitis was seen when the coronal level of the root filling exceeded the marginal bone level (P < 0.005). The marginal periodontal condition seemed to influence the periapical status. Teeth with apical periodontitis were associated with significantly more extended marginal bone loss (P < 0.001). Significantly less apical periodontitis was seen in patients that had received marginal periodontal treatment (P < 0.005), compared with untreated periodontal patients.

CONCLUSIONS

Signs of periodontal disease, as reflected by marginal bone loss, are of importance for the periapical condition of root-filled teeth. Efforts should be taken in preventing spread of infection through the periodontal-endodontic pathway by periodontal infection control and a high quality of root filling and coronal filling. Care should also be taken to seal the coronal cavity up to the level of the root filling, where it is advisable to reduce the coronal level of the root filling below or at least at the level of the surrounding marginal bone.

In vitro antibacterial activity of endodontic sealers

OBJECTIVES

To evaluate the antibacterial activity of four endodontic sealers: one epoxy resin sealer (AH Plus), two zinc oxide eugenol (ZOE)-based sealers (Endomèthasone, Pulp Canal Sealer), and one sealer containing both ZOE and orthophenilphenol (Vcanalare).

METHODS

A direct contact test (DCT) was performed. A 10 microl suspension of Enterococcus faecalis was placed on the test material 20 min, 24 h and 7 days after mixing. Bacteria were allowed to directly contact the sealers for 1h at 37 degrees C. Bacterial growth was then spectrophotometrically measured every 30 min for 7 h, and again after 24 h as well.

RESULTS

All freshly mixed sealers showed complete inhibition of bacterial growth. Similar results were obtained with the 24-h-old samples, with the exception of AH Plus. Vcanalare was the only sealer still inhibiting bacterial growth 7 days after mixing.

CONCLUSIONS

The antimicrobial activity of the tested sealers depends on the time interval between mixing and testing. All sealers exhibit bactericidal effect when freshly mixed, but only Vcanalare extended this effect until 7 days after setting.

Enterococcus Spp. in Endodontically Treated Teeth with and without Periradicular Lesions

The purpose of this study was to determine if Enterococcus spp. are more prevalent in endodontically treated teeth with periradicular lesions compared with teeth that require retreatment but have no periradicular rarefaction. Fifty-eight teeth that had received root canal therapy more than 1 yr previously and required retreatment were included. Designation of lesion versus no lesion was determined by two experienced endodontists. DNA extraction and PCR amplification were performed using ubiquitous 16S rDNA bacterial primers, as well as Enterococcus spp.-specific primers. The results showed that the overall prevalence of bacteria was 90% and Enterococcus spp. was 12%. chi analysis revealed a statistically significant relationship between the presence of a lesion and the presence of bacteria, as detected by the universal primers (p = 0.032). Using logistic regression, a statistically significant relationship was found between teeth with normal periapex and the presence of Enterococcus spp. (p = 0.023). This study revealed that bacteria are significantly associated with endodontic treatment failure but enterococci are not associated with disease.

Effect of E. faecalis on the release of serine proteases elastase and cathepsin G, and collagenase-2 (MMP-8) by human polymorphonuclear leukocytes (PMNs)

AIM

To measure the release of hydrolytic enzymes [elastase, cathepsin G and collagenase-2 (MMP-8)] from human polymorphonuclear leukocytes (PMNs) during interaction with strains of Enterococcus faecalis isolated from endodontic infections.

METHODOLOGY

Six E. faecalis strains isolated from treatment resistant cases of apical periodontitis were included in the study. Overnight cultures of the microbes were used for the experiments. PMNs were isolated using the Ficoll Paque technique, and their vitality was assessed throughout the experiments by the Trypan Blue exclusion test. A known amount of microbes and PMNs were mixed in PBS at +37 degrees C in air, and the release of elastase, cathepsin G and MMP-8 was measured at 0, 20, 60 and 120 min after initiation of incubation. The activities of elastase and cathepsin G were analysed by spectrophotometer assays using specific synthetic peptide substrates, and MMP-8 by western immunoblotting quantitated by computer densitometry. PMNs incubated in buffer without any added microbes served as negative controls, cells incubated with 5 ng mL(-1) phorbol myristic acetate (PMA) served as a positive control. The 95% confidence interval was used to compare the relative amount of elastase and cathepsin G released from the samples.

RESULTS

One E. faecalis strain induced a similar or higher elastase, cathepsin G and MMP-8 release than the positive control, whereas the other five strains induced only moderate or no release of the three enzymes examined as compared with the negative and positive controls. Western immunoblot revealed that released MMP-8 had molecular sizes of 60 and 75 kDa representing active and latent forms of MMP-8. In addition, >110 kDa high molecular size and a fragmented 20-30 kDa MMP-8 species could be observed.

CONCLUSIONS

The majority of the E. faecalis strains induced little or no release of hydrolytic enzymes from the PMN cells. The finding may partly explain the clinical observation that root canal infections dominated by E. faecalis are usually symptom free.