Inflammatory Response Mechanisms of the Dentine-Pulp Complex and the Periapical Tissues.

The macroscopic and microscopic anatomy of the oral cavity is complex and unique in the human body. Soft-tissue structures are in close interaction with mineralized bone, but also dentine, cementum and enamel of our teeth. These are exposed to intense mechanical and chemical stress as well as to dense microbiologic colonization. Teeth are susceptible to damage, most commonly to caries, where microorganisms from the oral cavity degrade the mineralized tissues of enamel and dentine and invade the soft connective tissue at the core, the dental pulp. However, the pulp is well-equipped to sense and fend off bacteria and their products and mounts various and intricate defense mechanisms. The front rank is formed by a layer of odontoblasts, which line the pulp chamber towards the dentine. These highly specialized cells not only form mineralized tissue but exert important functions as barrier cells. They recognize pathogens early in the process, secrete antibacterial compounds and neutralize bacterial toxins, initiate the immune response and alert other key players of the host defense. As bacteria get closer to the pulp, additional cell types of the pulp, including fibroblasts, stem and immune cells, but also vascular and neuronal networks, contribute with a variety of distinct defense mechanisms, and inflammatory response mechanisms are critical for tissue homeostasis. Still, without therapeutic intervention, a deep carious lesion may lead to tissue necrosis, which allows bacteria to populate the root canal system and invade the periradicular bone via the apical foramen at the root tip. The periodontal tissues and alveolar bone react to the insult with an inflammatory response, most commonly by the formation of an apical granuloma. Healing can occur after pathogen removal, which is achieved by disinfection and obturation of the pulp space by root canal treatment. This review highlights the various mechanisms of pathogen recognition and defense of dental pulp cells and periradicular tissues, explains the different cell types involved in the immune response and discusses the mechanisms of healing and repair, pointing out the close links between inflammation and regeneration as well as between inflammation and potential malignant transformation.

Immunological profile of teeth with inflammatory periapical disease from chronic liver disease patients.

AIM: To evaluate the mRNA expression levels of the cytokines interferon-γ, tumour necrosis factor-α, interleukin (IL)-1ß, IL-10, IL-6, VEGF, and AGT and the chemokine CCL2/MCP-1 in periapical interstitial fluid associated with root canal infections before and after the reduction of the bacterial load using a cleaning procedure. METHODOLOGY: The case group included 11 patients with chronic liver disease, and the control group included 11 healthy patients. Clinical samples were taken from teeth with pulp necrosis. After cleaning and drying the canal, three paper points were introduced into the root canal and passed through the root apex (2 mm) into the periapical tissues for 1 min. The samples were collected immediately after root canal cleaning and 7 days later to characterize those gene expression levels using real-time PCR. The data were subjected to the Shapiro-Wilk and the Wilcoxon tests. RESULTS: In the control group, significantly increased expression of the pro-inflammatory cytokines IFN-γ and TNF-α was observed in teeth with restrained bacterial loads (day 7) (P < 0.05). Similarly, increased TNF-α expression was found on day 7 in the liver group (P < 0.05). No differences were observed in the expression levels of the IL-1ß, IL-10 and, IL-6, MCP-1/CCL-2 and VEGF between the first collection (day 0) and second collection (day 7), over time in either group. CONCLUSION: Chronic liver disease patients exhibited sufficient immunologic ability showing relatively similar expression levels of cytokines, chemokines and angiogenic factors in periapical samples compared with the responses from no-chronic liver disease patients. The outcomes of this study suggest that liver impairment did not compromise the periapical immune response.

[Disinfection effects of MTAD on apical isthmus of the root canal system: a scanning electron microscopic evaluation].

OBJECTIVE: To evaluate the disinfection efficacy of MTAD on Enterococcus faecalis biofilm and smear layer colonization in apical isthums of the root canal system. METHODS: Fifteen extracted human maxillary first premolars with isthmus anatomic structure which confirmed by stereo-microscope were contaminated with E. faecalis in vitro and randomly divided into 5 groups: the first group was not treated serving as a baseline control, the second group was treated by normal saline (NS) serving as negative control, the third group was treated by MTAD , the forth group by 5.25% NaOCl, and the fifth group by 5.25% NaOCl + EDTA. All roots in the latter four groups were instrumented by Protaper rotary files and irrigated with respective irrigant, then the roots were split longitudinally and a scanning electron microscope was used to evaluate the antibacterial activity and smear layer cleaning ability of irrigants on isthmus. RESULTS: In the first group, E. faecalis colonized on the isthmus surface and aggregated together to form biofilm-like microorganism community, some bacteria also colonized in the dentinal tubules. When treated with NS, both smear layer and bacteria remained (median of smear layer score was 5). MTAD can remove partial smear layer, and have limited antibacterial activity, some bacteria embedded in smear layer (the median was 3) and were destroyed; In 5.25% NaOCl treatmentgroup, the smear layer was not removed (median of smear layer score was also 5), but all bacteria on the surface were extinguished. The combined use of 5.25% NaOCl and EDTA produced a cleaner isthmus surface and had marked antimicrobial effect, with the median of smear layer score being only 1. CONCLUSION: MTAD may permeate into the isthmus area of apical root canal system, but only performed a partial effect of disinfection and limited antibacterial activity. Sodium hypochlorite cooperated with EDTA can remove infection effectively in the isthmus area.

An investigation of a potential confounder in ex vivo microbiological studies--the bulk flow of fluid through apical foramina during tooth extraction.

AIMS: To investigate the factors affecting bulk flow of dye and bacterial suspensions into and out of apical foramina during simulated tooth extraction, using an ex vivo model. METHODOLOGY: Sixty extracted, single-rooted, human teeth were accessed, root canals located and in 50 the pulps dissolved; 10 teeth with attached periapical lesions were preserved. The size of apical foramina was determined digitally. The teeth were mounted in vials with polyvinylsiloxane impression material. Part 1: different dyes were inoculated in the coronal half of root canals or cervical 'gingival' margin, respectively, in separate experiments using the same teeth. Tooth extraction movements were simulated and apical penetration of the dye solutions with and without coronal restorations were examined in each case (20 teeth re-used 4 × ). Part 2: the same procedures were repeated on 30 more teeth but using a standard inoculum of Acidovorax sp. Part 3: 10 teeth with attached periapical lesions were inoculated with Acidovorax sp. in the absence of coronal restorations. Bacterial leakage into the periapical lesions was assessed. RESULTS: Coronal restorations significantly reduced the flow of dyes (P=0.002) or bacterial suspension (P=0.001) out of the canals and bacterial suspension into (P=0.02) the canals during simulated tooth extraction. The 'size of apical foramina' were positively correlated with passage of bacterial suspension out of the canal (P=0.04) and from the gingival trough into the canal (P=0.008), in the presence of a coronal restoration. CONCLUSIONS: The presence of coronal restorations, the size of apical foramina and presence of native canal contents with attached periapical lesions, all influenced fluid flow into and out of canals during simulated tooth extraction movements.

Randomized controlled clinical study of veneered zirconia abutments for single implant crowns: Clinical, histological, and microbiological outcomes.

OBJECTIVES: To analyze the effect of veneering of the submucosal part of zirconia abutments and the type of retention (cemented vs screw-retained) on clinical, microbiological, and histological outcomes of single-tooth implant crowns. MATERIAL AND METHODS: A total of 44 patients with a single missing tooth to be replaced by an implant in the anterior region participated in the study. Implants were randomly assigned to receive zirconia-based CAD/CAM reconstructions using either one of four treatment modalities: cement-retained with submucosal veneering (CR-P), cement-retained without submucosal veneering (CR-W), screw-retained with submucosal veneering (SR-P), and screw-retained without submucosal veneering (SR-W). Clinical parameters were assessed at baseline (after crown insertion), at 6 and 12 months. Histological and microbiological analyses were performed at 6 months. Descriptive statistics and the Kruskal-Wallis test were applied. RESULTS: The clinical evaluation revealed, in general, stable peri-implant soft tissues with minimal differences for all measured parameters between the four groups, except for bleeding on probing with the two cemented groups exhibiting higher values at 12 months (35.0% ± 26.5% for CR-W and 25.0% ± 38.8% for CR-P versus 13.1 ± 14.8 for SR-W and 13.0 ± 18.2 for SR-P). The descriptive and semi-quantitative histology showed a trend for a higher inflammatory reaction in the two cemented (a medium to high number of inflammatory cells) compared to the screw-retained groups (low number of inflammatory cells) at 6 months. The microbiological test demonstrated low bacterial counts and a similar distribution in between the groups except for two species (Tannerella forsythia and Peptostreptococcus micros) that were found in higher counts in the cemented groups at 6 months. CONCLUSION: Submucosal veneering of zirconia abutments did not negatively affect the health of the peri-implant tissues. The cemented groups, though, did show a clinical and histological trend to higher levels of inflammation.

Large Bacterial Floc Causing an Independent Extraradicular Infection and Posttreatment Apical Periodontitis: A Case Report.

This article describes a case of large persistent posttreatment apical periodontitis associated with 2 maxillary incisors, which was successfully managed by periradicular surgery. Histobacteriologic analysis revealed that the lesion was a granuloma that contained in its body a very large actinomycoticlike colony surrounded by accumulations of polymorphonuclear leukocytes and showing no direct communication with the root canal systems from both teeth. One incisor had no evidence of persistent intraradicular infection, whereas the other exhibited some residual dentinal tubule infection in the apical canal, which may have not significantly contributed to persistent inflammation given the organization and agglomeration of inflammatory cells around the large extraradicular bacterial colony. Findings showed that the main cause of persistent disease was the extraradicular infection in the form of a large bacterial floc, apparently independent of an intraradicular infection and as such only solved by surgery.

Histobacteriologic Conditions of the Apical Root Canal System and Periapical Tissues in Teeth Associated with Sinus Tracts.

INTRODUCTION: This histobacteriologic study described the pattern of intraradicular and extraradicular infections in teeth with sinus tracts and chronic apical abscesses. METHODS: The material comprised biopsy specimens from 24 (8 untreated and 16 treated) roots of teeth associated with apical periodontitis and a sinus tract. Specimens were obtained by periradicular surgery or extraction and were processed for histobacteriologic and histopathologic methods. RESULTS: Bacteria were found in the apical root canal system of all specimens, in the main root canal (22 teeth) and within ramifications (17 teeth). Four cases showed no extraradicular infection. Extraradicular bacteria occurred as a biofilm attached to the outer root surface in 17 teeth (5 untreated and 12 treated teeth), as actinomycotic colonies in 2 lesions, and as planktonic cells in 2 lesions. Extraradicular calculus formation (mineralized biofilm) was evident in 10 teeth. CONCLUSIONS: Teeth with chronic apical abscesses and sinus tracts showed a very complex infectious pattern in the apical root canal system and periapical lesion, with a predominance of biofilms.

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.

Prevalence of Treponema spp. in endodontic retreatment-resistant periapical lesions.

This study investigated the presence of the Treponema species in longstanding endodontic retreatment-resistant lesions of teeth with apical periodontitis, the association of this species with clinical/radiographic features, and the association among the different target species. Microbial samples of apical lesions were collected from twenty-five adult patients referred to endodontic surgery after unsuccessful root canal retreatment. Nested-PCR and conventional PCR were used for Treponema detection. Twenty-three periradicular tissue samples showed detectable levels of bacterial DNA. Treponema species were detected in 28% (7/25) of the cases. The most frequently detected species were T. socranskii (6/25), followed by T. maltophilum (3/25), T. amylovorum (3/25), T. lecithinolyticum (3/25), T. denticola (3/25), T. pectinovorum (2/25) and T. medium (2/25). T. vicentii was not detected in any sample. Positive statistical association was found between T. socranskii and T. denticola, and between T. maltophilum and T. lecithinolyticum . No association was detected between the presence of any target microorganism and the clinical or radiographic features. Treponema spp. are present, in a low percentage, in longstanding apical lesions from teeth with endodontic retreatment failure.

Effectiveness of sodium hypochlorite in preventing inoculation of periapical tissues with contaminated patency files.

The aim of this study was to analyze the effectiveness of 5.25% sodium hypochlorite (NaOCI) in preventing inoculation of periapical tissues with contaminated patency files. Twenty-eight extracted human permanent teeth with single canals were used in the study. Group I teeth were filled with NaOCl, and #15 stainless steel files contaminated with Streptococcus sanguis (ATCC #10556) were allowed to pass through the NaOCI into the culture medium. The teeth in group II were also filled with NaOCl, but the contaminated files used in group II canals were immersed in NaOCl for 10 s prior to being placed into the canals and cultured. The negative control group used sterile files (0% growth), the first positive control group used contaminated patency files in teeth with empty canals (100% growth), and the second positive control group placed contaminated files into broth next to teeth filled with NaOCl (to evaluate potential chlorine leakage; 100% growth). The experimental results showed no positive growth of S. sanguis for groups I and II, indicating that the NaOCl present in the canal after irrigation was sufficient to kill the test organism.

Effect of methotrexate-induced neutropenia on pulpal inflammation in rats.

The purpose of this study was to determine the role of neutropenia in pulpal inflammation. We investigated the effect of methotrexate-induced neutropenia on pulpal inflammation in rats. Pulpal inflammation was produced by pulpal exposure. Thirty-six rats were divided equally into control and experimental groups. The control animals received no injection, whereas the experimental animals were injected with 7.5 mg/kg of methotrexate once a day for 3 days before the pulpal exposure. The pulp was exposed in the mandibular first molar of all animals, and the exposed areas were left open. Animals were killed at 2, 4, and 7 days thereafter. Before they were killed, peripheral blood was taken. The number of total leukocytes and neutrophils in the peripheral blood of experimental animals was significantly decreased compared with those of control animals. The methotrexate-induced neutropenia resulted in the initiation of a bacterial invasion into the pulpal tissue and an increase in pulpal necrosis, as well as lessened abscess formation. Histometrically, the area of pulpal necrosis in experimental animals was significantly greater than that in the control animals. Immunohistochemically, the neutropenia resulted in inhibition of the infiltration by neutrophils. These results suggest that the neutrophil plays an important role in the defense against bacteria in pulpal tissue.

Radiographic evaluation of the effect of endotoxin (LPS) plus calcium hydroxide on apical and periapical tissues of dogs.

The aim of this study was the radiographic evaluation of the apical and periapical region of dog teeth submitted to intracanal bacterial endotoxin (lipopolysaccharide, LPS), associated or not with calcium hydroxide. After removal of the pulp, 60 premolars were divided into four groups and were filled with bacterial endotoxin (group 1), bacterial endotoxin plus calcium hydroxide (group 2), saline solution (group 3), or periapical lesions were induced with no treatment (group 4), for a period of 30 days. Similar periapical lesions were observed in groups 1 and 4. The lamina dura was intact in groups 2 and 3. Bacterial endotoxin (LPS) caused radiographically visible periapical lesions, but when associated with calcium hydroxide, this endotoxin was detoxified.

[The first isolation of Torulopsis glabrata (Anderson) Lodder from dental granulomas]. / Primo isolamento di Torulopsis glabrata (Anderson) Lodder da granulomi dentali.

Three Torulopsis have been isolated from two hundred or so dental granulomas. Torulopsis glabrata has been observed in cases of ophthalmopathy, infections of the oral cavity, lung infections, endocarditis and septicaemia. Apical lesions due to Torulopsis glabrata are not typical of mycosis but are generic of dental granulomas. The histological granulomatous character prevails. Experimental infections have been obtained from this fungus. Human infections by Torulopsis glabrata have been described. These infections are induced particularly in subjects with their immunity systems depressed by prolonged cortisone therapy. Their systematic position and morphology in optical microscopy have been examined in accordance with current views.

[Bacterial recolonization in the guided regeneration of the inter-radicular periodontal tissues]. / La ricolonizzazione batterica nella rigenerazione guidata dei tessuti parodontali interradicolari.

The present experimental study has been undertaken in order to analyse clinically and microbiologically the formation of new periodontal attachment in class II furcation lesions in mandibular molars, comparing healing after surgical conventional therapy and after guided periodontal tissue regeneration technique using non-resorbable membranes and evaluating at the same time, with cultural anaerobic technique, the influence on healing of the bacterial recolonization of some periodontally pathogenic species. Clinical results have demonstrated that, after therapy, may occur a certain discrepancy between soft and hard tissue regeneration and that the bone tissue shows a different pattern of apposition in the horizontal and vertical direction. Microbiological data have underlined the significance of surgical instrumentation in the guided inter-radicular periodontal tissue regeneration and have confirmed the necessity of maintaining the healing sites free from the main periodontal pathogens.

[Periapical lesions of mixed etiology: bacterial and foreign body]. / Lesioni periapicali ad eziologia mista: batterica e da corpo estraneo.

After a review of the literature on periapical lesion pathogenesis, we studied histological, immunological, and bacteriological examinations of 10 overfilled teeth with periapical lesions. We found, in our research, a bacteriological etiology with foreign body reactions.

Resinifying therapy in endodontics. II--Histological and bacteriological evaluation.

This study was conducted on six rabbits, six rats and six human permanent teeth to evaluate histologically the effect of resin resorcinol in the periapical areas, the bacteriological aspect of the resin and the penetration of resin in the dentinal tubules. After 12 days period of observation plenty of lymphocytes and macrophages were evident along with granulomas which are suggestive of the tendency of the resin to stay longer. It was observed that the resin penetrate approximately three fourth distance inside the dentinal tubules. In the last phase the resin was found to be effective against the eight commonly found micro organisms. Though the histological results indicated that the periapical tissue would take longer time for complete repair, yet clinically the tooth functions well. Resinifying therapy is effective and economical method in root canal treatment.

Chronic periapical lesions: correlations with clinical finding.

OBJECTIVES: The aim of this study was to evaluate the relationship between periapical lesions with and without clinical symptoms. MATERIAL AND METHOD: This study was performed on cases with chronic periapical lesion diagnosis. During oral surgery procedures, 80 tissue samples were obtained. Anamnesis data were taken from each subject included in the study. Periapical tissue samples were processed for laboratory procedures including: histological and pathological examination of lesions by light microscopy analysis and microbiological status assessment by qualitative and semi-quantitative analysis of bacteriological findings. RESULTS AND CONCLUSION: The results obtained illustrate that symptomatic apical periodontitis was more frequent with teeth without previous endodontic therapy. Even though a pathological type of periapical inflammation is significantly associated with the presence or absence of clinical symptoms (p=0.0002), they do not have an effect on making a clinical diagnosis. Statistical analysis showed no significant difference (p>0.05). Comparative analysis of symptom persistence and infection severity was performed. It was found that positive symptoms were in relation to the quantity of the bacterial growth only in the group previous endodontically treated and these two factors do show relation with an accuracy of 95%. The growth of a mixture of several, mainly anaerobic, bacterial species is closely related to the presence of clinical symptoms.

Preliminary molecular analysis of bacterial composition in periapical lesions with primary endodontic infections of deciduous teeth.

BACKGROUND: The bacterial composition of periapical lesions in deciduous teeth has not been well documented. This study was designed to explore the bacterial compositions, especially the dominant bacteria in periapical lesions using 16S rRNA sequencing. METHODS: Tissue samples were collected from 11 periapical lesions in deciduous teeth with primary endodontic infections. DNA was extracted from each sample and analyzed using 16S rRNA cloning and sequencing for the identification of bacteria. RESULTS: All DNA samples were positive for 16S rRNA gene PCR. One hundred and fifty-one phylotypes from 810 clones were identified to eight phyla, and each sample contained an average of 25.9 phylotypes. In addition, 59 phylotypes were detected in more than two samples, and Fusobacterium (F.) nucleatum (8/11), Dialister (D.) invisus (8/11), Campylobacter (C.) gracilis (7/11), Escherichia (E.) coli DH1 (6/11), Aggregatibacter (A.) segnis (6/11), and Streptococcus (S.) mitis (6/11) were the most prevalent species. Furthermore, 45 as-yet-uncultivated phylotypes were also identified. CONCLUSIONS: Chronic periapical lesions in deciduous teeth contained polymicrobial infections. F. nucleatum, D. invisus, C. gracilis, E. coli DH1, A. segnis, and S. mitis were the most prevalent species detected by 16S rRNA sequencing.

Surgical endodontic treatment of refractory periapical periodontitis with extraradicular biofilm.

OBJECTIVE: This study explored the effect of surgical endodontic treatment of refractory periapical periodontitis with extraradicular biofilm. STUDY DESIGN: Endodontic surgery was conducted on a case of refractory periapical periodontitis with extraradicular biofilm. During the procedure, the samples of periapical tissues were collected for microbiologic analysis. The resected root ends were observed under scanning electron microscope. The patient was recalled every 3 months to evaluate the treatment effect for 1 year. RESULTS: The samples yielded 1 type of facultative anaerobic bacteria (Streptococcus sanguis) and 2 types of obligate anaerobic bacteria (Porphynomonas endodontalis and Prevotella oralis). Mature bacteria biofilms were formed on the surface of the root apexes. At the 1-year recall visit, the radiograph and the clinic examination showed the refractory periapical periodontitis was cured successfully. CONCLUSIONS: The periapical bacterial biofilm may contribute to the refractory periapical periodontitis. Endodontic surgery is a good option for definitive removal of an established extraradicular infection.

Prevalence of Treponemaspp. in endodontic retreatment-resistant periapical lesions

This study investigated the presence of the Treponema species in longstanding endodontic retreatment-resistant lesions of teeth with apical periodontitis, the association of this species with clinical/radiographic features, and the association among the different target species. Microbial samples of apical lesions were collected from twenty-five adult patients referred to endodontic surgery after unsuccessful root canal retreatment. Nested-PCR and conventional PCR were used for Treponema detection. Twenty-three periradicular tissue samples showed detectable levels of bacterial DNA. Treponema species were detected in 28% (7/25) of the cases. The most frequently detected species were T. socranskii (6/25), followed by T. maltophilum (3/25), T. amylovorum (3/25), T. lecithinolyticum(3/25), T. denticola (3/25), T. pectinovorum (2/25) and T. medium(2/25). T. vicentii was not detected in any sample. Positive statistical association was found between T. socranskiiand T. denticola,and between T. maltophilumand T. lecithinolyticum. No association was detected between the presence of any target microorganism and the clinical or radiographic features. Treponemaspp.are present, in a low percentage, in longstanding apical lesions from teeth with endodontic retreatment failure.