CXXC5 orchestrates Stat3/Erk/Akt signaling networks to modulate P. gingivalis-elicited autophagy in cementoblasts.

The keystone pathogen Porphyromonas gingivalis (P. gingivalis) elicits inflammation and autophagy in periodontal tissues. Transcription factor CXXC-type zinc finger protein 5 (CXXC5) and various signals are sensitive to P. gingivalis invasion. Herein, we investigated the P. gingivalis-elicited autophagy activity, the contribution of CXXC5, and the involvement of signals in cementoblasts, tooth root surface cells crucial in periodontal and periapical regions. After coculture with P. gingivalis, cementoblasts exhibited inflammatory cytokine increase, light chain 3(LC3)-I/II conversion, autophagosome activation, and CXXC5 reduction. Cementoblasts with loss and gain of CXXC5 were developed. CXXC5 silencing suppressed autophagy and inflammation, thereby partially compensating for the effects of P. gingivalis, and vice versa. We then screened potential signals and verified the positive participation of Stat3/Akt/Erk networks through specific inhibitor employment. P. gingivalis and CXXC5 induced autophagy through Beclin1 and Atg5 activation. Intriguingly, Annexin V/PI assay and EdU detection revealed that P. gingivalis promoted apoptosis and repressed cell proliferation. In sum, coculture with P. gingivalis enhanced autophagy activity in cementoblasts, which was partially suppressed by CXXC5 downregulation and mediated by Jak/Stat3, PI3K-Akt, and Erk1/2 signaling. This process probably influenced cell apoptosis and proliferation.

Mineralising and antibacterial effects of modified calcium phosphate treatment on human root cementum.

BACKGROUND: Aging population will lead to the increase of incidence of root caries globally. The clinical management of root caries is challenging due to the difficulty in moisture isolation. The root caries is caused by the release of organic acids from cariogenic bacteria which results in the dissolution of cementum and dentin of the root. The purpose of this study is to study the efficacy of modified saturated calcium phosphate solution (CaP) supplement with zinc (Zn(2+)) and/or fluoride (F(-)) in providing root cementum surfaces less susceptible to acid dissolution and bacterial colonization. METHODS: Human root cementum sections from extracted premolars were treated with three modified calcium phosphate solutions (M/A-CaPs) respectively: (A) CaP-F/Zn, supplemented with F(-) and Zn(2+); (B) CaP-F, supplemented with F(-) only; (C) CaP-Zn, supplemented with Zn(2+) only. The surface characteristics of treated cementum sections were investigated using scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR). Following the acid attack and Streptococcus mutans challenge, M/A-CaPs treated cementum surfaces were analysed using inductive coupled plasma (ICP) and SEM respectively. RESULTS: Compared with the control group, M/A-CaPs treated cementum presented significant improvements in resistance to acid dissolution and bacterial colonization. Among M/A-CaPs, the CaP-F/Zn treated cementum surfaces released the lowest amount of Ca(2+) ions (2.11 ± 0.51 ppm) upon acid challenge (n = 3, p < 0.01) and also presented the most significant inhibiting effect against the colonization of S. mutans (n = 180, p < 0.05). CONCLUSIONS: Saturated calcium phosphate solution CaP supplemented with both F(-) and Zn(2+) could be applied as an effective coating material providing acid resistance and antibacterial property on cementum surfaces. The modified calcium phosphate-based solution could be a new treatment strategy to prevent the development of root caries and arrest the further progression of root caries.

Complex Apical Intraradicular Infection and Extraradicular Mineralized Biofilms as the Cause of Wet Canals and Treatment Failure: Report of 2 Cases.

This article describes 2 cases that showed persistent intracanal exudation (wet canal) even after several visits of antimicrobial endodontic treatment. Histologic and histobacteriologic investigation was conducted for determination of the cause. The 2 cases involved teeth with apical periodontitis lesions, which presented persistent exudation refractory to treatment after several visits. In case 1, it was not possible to achieve a dry canal, and surgery had to be performed. In case 2, attempts to dry the canal succeeded and the canal was filled, but follow-up examination showed an enlarged apical periodontitis lesion and extraction was performed. Biopsy specimens consisting of the root apex and apical periodontitis lesion for case 1 and the whole root for case 2 were subjected to histologic and histobacteriologic analyses. Both cases showed complex bacterial infection in the apical root, affecting both the intraradicular space and the outer root surface. Case 1 showed bacterial biofilms in ramifications, on untouched walls, and extending to the external root surface to form a thick and partially mineralized structure with high bacterial density. Different bacterial morphotypes were evidenced. Case 2 had a ledge on the apical canal wall created during instrumentation, which was filled with necrotic debris, filling material, and bacteria. The walls of the apical portion of the canal were covered by a bacterial biofilm, which was continuous with a thick extraradicular biofilm covering the cementum and dentin in resorptive defects. The extraradicular biofilm showed areas of mineralization and was dominated by filamentous bacteria. The 2 cases with wet canals and treatment failure were associated with complex persistent infection in the apical part of the root canal system extending to form thick and partially mineralized biofilm structures (calculus) on the outer apical root surface.

Time to shift: from scaling and root planing to root surface debridement.

Non-surgical periodontal treatment has traditionally been based on the notion that bacterial plaque (dental biofilm) penetrates and infects dental cementum. Removal of this infected cementum via scaling and root planing (SRP) was considered essential for re-establishing periodontal health. In the 1980s the concept of SRP was questioned because several in vitro studies showed that the biofilm was superficially located on the root surface and its disruption and removal could be relatively easily achieved by ultrasonic instrumentation of the root surface (known as root surface debridement (RSD). Subsequent in vivo studies corroborated the in vitro findings. There is now sufficient clinical evidence to substantiate the concept that the deliberate removal of cementum by SRP is no longer warranted or justified, and that the more gentle and conservative approach of RSD should be implemented in daily periodontal practice.

A histological study of peripheral dental caries of equine cheek teeth.

Peripheral caries of equine cheek teeth is a poorly described disorder and, in particular little is known of its histopathology. Histological examinations of decalcified sections of 21 equine peripheral caries-affected cheek teeth showed two different patterns of cemental lesions; including progressive enlargement of focal, flask-like lesions leading to breakdown of the adjacent cementum, and secondly; a more generalized flaking-off of thin layers of under-run, surface cementum. A thick layer of plaque and food material usually lay on the surface of affected cementum and also within cemental defects. Gram-stained sections showed large numbers of bacteria within the lacunae and canaliculi of affected peripheral cementum and within associated plaque. Pioneer bacteria were also seen within dentinal tubules of adjacent, normal-appearing dentin. Subgingival extension of peripheral caries lesions with localized periodontal destruction was rare. Grading of peripheral caries lesions by gross examination was found to underestimate the severity of the disorder as compared to histological grading.

Bacterial flora and extraradicular biofilm associated with the apical segment of teeth with post-treatment apical periodontitis.

INTRODUCTION: Microorganisms are able to survive and cause persistent infection in the extraradicular area. The aims of this study were to investigate the primary bacterial flora and the localization of extraradicular biofilm in persistent apical periodontitis lesions. METHODS: Apical root samples from root-end surgery were collected from 23 root-filled teeth with apical periodontitis. Five samples were examined for the presence of biofilm by scanning electron microscopy. Another 5 samples were examined for the presence of biofilm by Brown and Brenn-modified Gram staining. The DNA from 13 samples was processed for amplification via polymerase chain reaction and separated with denaturing gradient gel electrophoresis. Selected bands were excised from the gel and sequenced for identification. RESULTS: The extraradicular biofilm present on the external root surface of treated teeth consisted of abundant, amorphous extracellular material and multiple bacterial species. The following species were detected in the microbial community from the apical samples: Actinomyces sp. oral, Propionibacterium, Prevotella sp. oral, Streptococcus, Porphyromonas endodontalis, and Burkholderia. The prevalence of Actinomyces sp. oral and Propionibacterium were highest (84.6% and 61.5%, respectively). CONCLUSIONS: Extraradicular biofilm was present on the external root surface of treated teeth with persistent periapical lesions. Actinomyces sp. oral and Propionibacterium are likely important contributors to extraradicular biofilm formation and persistent periapical infection.

The CEJ: a biofilm and calculus trap.

There is a direct correlation between increasing periodontal probing depth and increasing presence of residual biofilms and calculus. One of the more common areas to find postscaling and root-planing residual biofilm and calculus is the cemento-enamel junction (CEJ)--an area that in most cases is easily accessible. Yet few studies have addressed the question of why the CEJ is a potential biofilm and calculus trap. This article discusses the various anatomical relationships of enamel, dentin, and cementum at the CEJ, the role of CEJ anatomy in the retention of biofilm (with SEM photographs as supporting evidence), and the biological and clinical implications of subgingival residual biofilm and calculus.

Antimicrobial action of intracanal medicaments on the external root surface.

OBJECTIVES: To assess in vitro the antimicrobial action of intracanal medicaments in the external root surface, with or without of cementum. METHODS: After the placement of intracanal medicaments, the coronal and apical openings were sealed. The antimicrobial action of 2% chlorhexidine gel (2%CHX); calcium hydroxide+2% chlorhexidine gel (CH+2%CHX); calcium hydroxide+2% chlorhexidine gel+zinc oxide (CH+2%CHX+ZnO); calcium hydroxide+saline solution (CH+SS) was evaluated against Enterococcus faecalis, Candida albicans, Actinomyces viscosus and Porphyromonas gingivalis. The samples were placed over the agar, and the zones of inhibition of microbial growth were measured after the incubation period. RESULTS: The antimicrobial effects of the medicaments could be ranked from strongest to weakest as follows: 2%CHX, CH+2%CHX, CH+2%CHX+ZnO, CH+SS. No differences among groups were verified in the presence or absence of cementum. CONCLUSIONS: 2%CHX containing medicaments diffused into the dentin and reached the outer surface, exerting antimicrobial action.

Microbial distribution in the root canal system after periapical lesion induction using different methods.

The aim of this study was to evaluate the microbial distribution in the root canal system after periapical lesion induction in dogs' teeth using different methods. Fifty-two root canals were assigned to 4 groups (n=13). Groups I and II: root canals were exposed to the oral cavity for 180 days; groups III and IV: root canals were exposed for 7 days and then the coronal openings were sealed for 53 days. The root apices of groups I and III were perforated, while those of groups II and IV remained intact. After the experimental periods, the animals were euthanized and the anatomic pieces containing the roots were processed and stained with the Brown & Brenn method to assess the presence and distribution of microorganisms. The incidence of microorganisms at different sites of the roots and periapical lesions was analyzed statistically by the chi-square test at 5% significance level. All groups presented microorganisms in the entire root canal system. A larger number of microorganisms was observed on the root canal walls, apical delta and dentinal tubules (p<0.05), followed by cementum and cemental resorption areas. In spite of the different periods of exposure to the oral environment, the methods used for induction of periapical periodontitis yielded similar distribution of microorganisms in the root canal system.

Microbial distribution in the root canal system after periapical lesion induction using different methods

The aim of this study was to evaluate the microbial distribution in the root canal system after periapical lesion induction in dogs' teeth using different methods. Fifty-two root canals were assigned to 4 groups (n=13). Groups I and II: root canals were exposed to the oral cavity for 180 days; groups III and IV: root canals were exposed for 7 days and then the coronal openings were sealed for 53 days. The root apices of groups I and III were perforated, while those of groups II and IV remained intact. After the experimental periods, the animals were euthanized and the anatomic pieces containing the roots were processed and stained with the Brown & Brenn method to assess the presence and distribution of microorganisms. The incidence of microorganisms at different sites of the roots and periapical lesions was analyzed statistically by the chi-square test at 5 percent significance level. All groups presented microorganisms in the entire root canal system. A larger number of microorganisms was observed on the root canal walls, apical delta and dentinal tubules (p<0.05), followed by cementum and cemental resorption areas. In spite of the different periods of exposure to the oral environment, the methods used for induction of periapical periodontitis yielded similar distribution of microorganisms in the root canal system.

O objetivo deste estudo foi avaliar a distribuição microbiana no sistema de canais radiculares após indução de lesões periapicais em dentes de cães por diferentes métodos. Cinqüenta e dois canais radiculares foram divididos em 4 grupos (n=13). Grupos I e II: canais radiculares foram expostos por 180 dias; grupos III e IV: canais radiculares foram expostos por 7 dias e então as aberturas coronárias foram seladas por 53 dias. Os ápices radiculares dos grupos I e III foram arrombados, enquanto os dos grupos II e IV foram mantidos intactos. Após os períodos experimentais, os animais foram mortos e as peças foram processadas e coradas pelo método de Brown e Brenn para avaliação da presença ou ausência e distribuição dos microrganismos. A incidência de microrganismos nas diferentes regiões das raízes e lesões periapicais foi analisada estatisticamente pelo Teste Qui-Quadrado em nível de 5 por cento de significância. Todos os grupos apresentaram microrganismos em todo o sistema de canais radiculares. Um maior número de microrganismos foi observado nas paredes do canal radicular, delta apical e túbulos dentinários, seguido pelo cemento e áreas de reabsorção cementária. Apesar de utilizar diferentes períodos de exposição dos canais radiculares ao meio bucal, os métodos usados para indução das lesões periapicais permitiram semelhante distribuição de microrganismos no sistema de canais radiculares (p>0,05).

Incipient caries lesions on cementum by mono- and co-culture oral bacteria.

OBJECTIVES: There is increasing prevalence of root caries. We hypothesized different biofilms will cause varying demineralization in cementum. This study investigated the extent of demineralization of cementum by oral biofilm formed from three major cariogenic microorganisms: Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces israelii. Sound cementum tooth blocks were incubated with mono-, bi-, and tri-species combinations of the bacteria under investigation. MATERIALS AND METHODS: The matrix (amide I) and phosphate content of the lesions was analyzed by Fourier-transform infrared spectroscopy (FTIR), and calcium and phosphorus levels were analyzed by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDX). RESULTS: The log[amide I:HPO(4)(2-) absorbance] values showed that A. israelii mono-culture caused significantly more demineralization than the other bacterial cultures. log[Ca:P] showed that all carious lesions were confined to the cementum. CONCLUSIONS: Oral biofilm arising from bacterial species A. israelii alone was the most cariogenic of those tested and produced the most demineralization in incipient carious lesions in cementum.

Effect of two different approaches for root decontamination on new cementum formation following guided tissue regeneration: a histomorphometric study in dogs.

BACKGROUND AND OBJECTIVE: The aim of the present study was to evaluate comparatively the effect of two different approaches for root decontamination on new cementum formation following guided tissue regeneration (GTR). MATERIAL AND METHODS: Nine mongrel dogs were used to obtain bilateral chronic class III furcation defects by placing cotton ligatures around both third mandibular premolars. The teeth were randomly assigned to receive one of the following treatments: scaling and root planing, by means of hand and rotatory instruments, in order to remove soft and hard deposits as well as all root cementum (group A); or removal of only soft microbial deposits, by polishing the root surface with rubber cups and polishing paste, aiming for maximum root cementum preservation (group B). Both groups were treated with GTR, with the use of resorbable polyglycolic-lactic acid membranes (RESOLUT XT). RESULTS: Four months later, data analysis showed that a superior length (mm) (3.59 +/- 1.67 and 6.20 +/- 2.26 for groups A and B, respectively; p = 0.004) and a thicker layer (microm) (18.89 +/- 9.47 and 52.29 +/- 22.48 for groups A and B, respectively; p = 0.001) of new cementum was achieved by keeping the root cementum in place during root decontamination (group B). Regardless of the treatment modality, the new cementum was predominantly of a reparative, cellular extrinsic and intrinsic fiber type. CONCLUSION: Within the limits of the present study, it may be concluded that root cementum preservation may affect the new cementum formation following GTR in class III furcation defects, and the treatment modality did not influence the type of newly formed cementum.

Er:Yag laser irradiation of the microbiological apical biofilm.

One problem in cases of healing-resistant periapical lesions is to eradicate the contamination at the periapical area. This contamination is due to the microbiological biofilm formed by microorganisms and their subproducts lodged in apical third of the root, on both cementum and dentin surface. Paraendodontic surgery consists of the mechanical removal of harmful agents to promote healing and periapical health. The purpose of this study was to assess the results of Er:YAG laser irradiation on the apical root third of newly extracted teeth to eliminate microbial contamination on root apex surface. Apical irradiation was performed with an Er:YAG laser device using an experimental contact tip, at 100 mJ, 10 Hz, 1 W, 39 J/cm(2), 3 times on the target area. SEM analysis showed the elimination of part of the irradiated cementum and the formation of small roughened without exposing the subjacent dentin. Vaporization of the remaining periodontal tissue and removal of microbiological apical biofilm (MAB) were also observed on the irradiated areas. Under the tested conditions and based on the findings of this study, Er:YAG laser may be considered effective for removal of microbiological apical biofilm.

Er: Yag laser irradiation of the microbiological apical biofilm

One problem in cases of healing-resistant periapical lesions is to eradicate the contamination at the periapical area. This contamination is due to the microbiological biofilm formed by microorganisms and their subproducts lodged in apical third of the root, on both cementum and dentin surface. Paraendodontic surgery consists of the mechanical removal of harmful agents to promote healing and periapical health. The purpose of this study was to assess the results of Er:YAG laser irradiation on the apical root third of newly extracted teeth to eliminate microbial contamination on root apex surface. Apical irradiation was performed with an Er:YAG laser device using an experimental contact tip, at 100 mJ, 10 Hz, 1 W, 39 J/cm², 3 times on the target area. SEM analysis showed the elimination of part of the irradiated cementum and the formation of small roughened without exposing the subjacent dentin. Vaporization of the remaining periodontal tissue and removal of microbiological apical biofilm (MAB) were also observed on the irradiated areas. Under the tested conditions and based on the findings of this study, Er:YAG laser may be considered effective for removal of microbiological apical biofilm.

A problemática dos casos envolvendo pacientes portadores de lesões periapicais resistentes é a eliminação da infecção que atinge a região periapical. Esta infecção é composta por microrganismos e seus subprodutos alojados no cemento e dentina do terço apical, sob forma de biofilme microbiano. A execução da cirurgia paraendodôntica com vistas à promoção da saúde do periápice, invariavelmente resume-se em remover mecanicamente os agentes causadores da doença, com objetivo de proporcionar a reparação. O propósito deste estudo foi avaliar o resultado da irradiação com laser de Er:YAG no terço apical de dentes recém extraídos com relação à infecção microbiana na superfície do ápice radicular. O laser Er:YAG foi empregado para irradiação de ápices radiculares, com ponteira experimental de contato (Chisel, Morita co.), utilizando energia de potência de 100 mJ, 10 Hz, por 3 vezes em área delimitada no terço apical das raízes. Os resultados do estudo em microscopia eletrônica de varredura mostraram a eliminação do tecido periodontal remanescente juntamente com quantidade significativa de microrganismos. Portanto, pode-se concluir que o laser de Er:YAG nas condições experimentais testadas mostrou-se efetivo na remoção de microrganismos do tecido periodontal contaminado e do cemento sem expor a dentina subjacente.

Localization of Porphyromonas gingivalis-carrying fimbriae in situ in human periodontal pockets.

Fimbriae, which are involved in adherence, constitute an important pathogenic factor of Porphyromonas gingivalis. In vivo, however, the distribution of P. gingivalis-carrying fimbriae is unknown. The localization of P. gingivalis-carrying fimbriae was examined in situ. From 19 patients with severe periodontitis and P. gingivalis, we obtained 20 teeth with periodontal tissue attached, with and without immunolocalized fimbriae. Eleven teeth were subjected to light microscopy, 9 to electron microscopy. In 6 of the 11 samples examined, we detected positive reactions with an anti-P. gingivalis-fimbriae serum, located in the cementum-attached plaque area in the deep pocket zones. In the so-called 'plaque-free zones', P. gingivalis-carrying fimbriae were immunocytochemically observed to reside in contact with the dental cuticle in 6 of the 9 samples examined. These findings suggest that P. gingivalis-carrying fimbriae are strongly related to adherence to the root surface at the bottoms of human periodontal pockets.

EM evaluation of bacterial biofilm and microorganisms on the apical external root surface of human teeth.

The aim of this study was to evaluate the presence of bacterial biofilm on the external surface of the root apex in teeth with pulp necrosis, with and without radiographically visible periapical lesions, and in teeth with a vital pulp. Twenty-one teeth were extracted, eight with pulp necrosis and periapical lesions, eight with pulp necrosis without radiographically visible periapical lesions, and five with a vital pulp. The roots were sectioned, and the root apexes (+/- 3 mm) were processed for scanning electron microscope evaluation. The surface of the apical root was evaluated for the presence of microorganisms, root resorption, and biofilm. There were no microorganisms on the apical root surface of either teeth with pulp vitality or with pulp necrosis with no radiographically visible periapical lesions. Microorganisms were always present in teeth with pulp necrosis and radiographically visible periapical lesions. These included cocci, bacilli, and filaments and the presence of an apical biofilm. Apical biofilm is clinically important because microbial biofilms are inherently resistant to antimicrobial agents and cannot be removed by biomechanical preparation alone. This may cause failure of endodontic treatment as a consequence of persistent infection.

In vitro effect of laser irradiation on cementum-bound endotoxin isolated from periodontally diseased roots.

BACKGROUND: In a previous study, we evaluated the in vivo effects of an Nd:YAG laser on periodontal disease by measuring crevicular interleukin (IL)-1beta levels before and after laser application. It was found that laser therapy was less effective than traditional scaling and root planing. These results might be due to incomplete removal of microbial residues and cementum-bound endotoxin on root surfaces by the laser. In this study, we explored the in vitro effectiveness of an Nd:YAG laser for the elimination of cementum-bound endotoxin by measuring IL-1beta changes in stimulated monocytes. METHODS: Fresh human monocytes were harvested from adults without periodontitis and grown in RPMI 1640 medium. Diseased cementum particles were collected and prepared from teeth with untreated periodontitis and were irradiated with 5 levels of laser energy. Cementum particles were subjected to endotoxin testing by a limulus amebocyte lysate (LAL) assay and then were incubated with cultured monocytes. Production of IL-1beta in stimulated monocytes was measured by enzyme-linked immunosorbent assay and quantified by spectrophotometry. RESULTS: The endotoxin unit (EU) of diseased cementum was 18.4 EU/mg, which seemed to be remarkably lower than that of common periodontal pathogens including Porphyromonas gingivalis (381) at 15,300 EU/mg/ml, Prevotella intermedia (ATCC 25611) at 227 EU/mg/ml, and Fusobacterium nucleatum (ATCC 25586) at 1,987 EU/mg/ml. Monocytes subjected to stimulation by diseased cementum particles without laser irradiation produced 124 to 145 pg/ml IL-1beta, 9- to 18-fold higher than that of unstimulated monocytes (7.07 to 15.95 pg/ml). Diseased cementum particles after irradiation with various energy levels of the Nd:YAG laser could still stimulate monocytes to secrete 89 to 129 pg/ml IL-1beta. No statistically significant difference was found in the production of IL-1beta induced by diseased-bound cementum with or without laser irradiation. CONCLUSIONS: The Nd:YAG laser varying from 50 mJ, 10 pps to 150 mJ, 20 pps, for 2 minutes, did not seem to be effective in destroying diseased cementum endotoxin.

Participation of bacterial biofilms in refractory and chronic periapical periodontitis.

The aim of this study was to examine morphologically the participation of extraradicular biofilm in refractory periapical periodontitis. Six teeth and five extruded root filling gutta-percha points associated with refractory periapical periodontitis were investigated by scanning electron microscope. In nine of 11 samples examined, bacterial biofilms were seen at the extraradicular area. The gutta-percha surface was covered with glycocalyx-like structures, and filaments, long rods, and spirochete-shaped bacteria were predominant in the extraradicular sites. Planktonic cells, which were filaments and spirochete-shaped bacteria, emigrated from the glycocalyx structures in some spots. In the extracted teeth, biofilm consisting of both bacteria and glycocalyx-like structures were observed on the periapical root surfaces. Next to the residual periodontal ligament, a few filaments, rods, and fusiforms were attached on the healthy cementum surface. The present findings suggested that bacterial biofilms formed in the extraradicular areas were related to refractory periapical periodontitis.

A mouse model of inflammatory root resorption induced by pulpal infection.

OBJECTIVE: The present study was undertaken to determine the frequency and extent of apical root resorption associated with induced periradicular lesions in mice. STUDY DESIGN: Bone and root resorption was quantified by using two- and three-dimensional micro-computed tomography (mu-CT) in the lower first molars of mice subjected to pulp exposure and infection. RESULTS: mu-CT measurements showed significant apical resorption in exposed and infected teeth, resulting in an average distal root shortening of 12.7% (P <.001 vs unexposed). These findings were confirmed with three-dimensional reconstituted images that showed thinning and shortening of the distal root. Tartrate-resistant acid phosphatase clastic cells were associated with resorption lacunae on the cementum of root apices, as well as on bone at the periphery of the periradicular lesions. Brown and Brenn staining showed the presence of bacteria in dentinal tubules adjacent to resorbed cementum. CONCLUSIONS: Apical root resorption is a prominent and consistent finding associated with periradicular infection in the mouse. This species represents a convenient model for studying the pathogenesis of inflammatory root resorption in vivo.

Viable bacteria in root dentinal tubules of teeth with apical periodontitis.

Two sets of teeth with apical periodontitis were collected at different geographic locations to study the identity of bacteria left in the root dentinal tubules. Root dentin of 20 of these teeth was cultured from three locations between pulp and cementum (A, B, and C). In addition dentin from eight teeth was examined histologically. Using the culturing technique bacteria were found in 77% of the dentin samples from set 1 (Amsterdam) and in 87.5% of the dentin samples from set 2 (Glasgow). At greater distance, in layer C, from the pulp bacteria were found in 62% (13 of 21) of the dentin samples. Twenty-three percent (3 of 13) of set 1 and 25% (2 of 8) of set 2 contained >50,000 colony-forming units/mg of dentin in layer C. In layers closer to the pulp higher numbers of anaerobic bacteria and gram-positive rods were found, as well as a larger number of bacterial species. Histological sections showed bacterial penetration in dentinal tubules in 5 of 8 teeth. In the other three teeth where the colony-forming units/mg recovered was <10,000, no histological signs of tubule penetration was seen. It seems clear that, in more than half of the infected roots, bacteria are present in the deep dentin close to the cementum and that anaerobic culturing of dentin is more sensitive than histology to detect these bacteria.