Microorganisms in Root Canal–treated Teeth from a German Population
Isabela N. Rôças, PhD, Michael Hülsmann, Prof Dr med dent, José F. Siqueira Jr, PhD
Posttreatment apical periodontitis is usually associated with persistent or secondary intraradicular infection. This study evaluated the presence and relative levels of 28 bacterial taxa in treated root canals of teeth with posttreatment apical periodontitis from German patients using 16S ribosomal RNA (rRNA) gene probes in a reverse-capture checkerboard hybridization assay. Species-specific polymerase chain reaction (PCR) was also performed to detect Enterococcus faecalis and Candida albicans. Bacterial DNA was detected in all samples. Twenty of the 28 taxon-specific probes tested were reactive with at least one sample. Taxa detected more frequently included Streptococcus species (47%), Lactobacillus species (35%), Dialister invisus (29%), Eubacterium infirmum (29%), Prevotella intermedia (29%), Selenomonas sputigena (29%), Synergistes oral clone BA121 (29%), and Treponema denticola (29%). Only eight taxa were present at levels >105. Of these, streptococci and T. denticola were the most prevalent. Species-specific PCR detected E. faecalis in 47% of the cases and C. albicans in 6%. Findings of this study confirm the strong association between persistent/secondary intraradicular infection and posttreatment apical periodontitis. Most cases harbored a mixed infection, and E. faecalis, if present, was never the most dominant species in the consortium. Several other bacterial taxa were detected, and an involvement with the etiology of posttreatment apical periodontitis is suspected.
Lipoteichoic Acid Partially Contributes to the Inflammatory Responses to Enterococcus faecalis
Jung Eun Baik, BS, Young Hee Ryu, MS, Ji Young Han, MS, Jintaek Im, PhD, Kee-Yeon Kum, DDS, PhD, Cheol-Heui Yun, PhD, Kangseok Lee, PhD, Seung Hyun Han, PhD
Enterococcus faecalis, a pathogenic gram-positive bacterium, is closely related to refractory apical periodontitis. Because lipoteichoic acid (LTA) is considered a major virulence factor of gram-positive bacteria, in the present study, highly pure LTA from E. faecalis was prepared, and its ability to stimulate murine macrophages was investigated in comparison with those of the killed whole cells. Upon exposure to E. faecalis LTA, RAW 264.7 (a murine macrophage cell line) produced a significantly (p < 0.05) high level of tumor necrosis factor-a (TNF-a) and nitric oxide (NO) in a concentration-dependent manner. It is to note that the LTA was able to stimulate Toll-like receptor 2 (TLR2) but not TLR4. Concomitantly, LTA enhanced the DNA-binding activity of a transcription factor, nuclear factor-kappa B (NF-?B), which plays an important role in the transcriptional activation of genes encoding inflammatory mediators. In contrast, heat-killed E. faecalis stimulated both TLR2 and TLR4, whereas the killed E. faecalis whole cells induced significant (p < 0.05) levels of TNF-a and NO in RAW 264.7 cells as their LTA did. These results suggest that LTA partially contributes to E. faecalis–induced inflammatory responses.
Efficacy of Revascularization to Induce Apexification/Apexogensis in Infected, Nonvital, Immature Teeth: A Pilot Clinical Study
Naseem Shah, MDS, Ajay Logani, MDS, Uday Bhaskar, MDS, Vivek Aggarwal, MDS
Endodontic treatment options for immature, nonvital teeth conventionally include surgical endodontics, apexification with calcium hydroxide, or single visit mineral trioxide aggregate plug. A new treatment option of revascularization has recently been introduced. It involves disinfecting the root canal system, providing a matrix of blood clot into which cells could grow, and sealing of the coronal access. The present pilot clinical study was undertaken to evaluate the efficacy of revascularization in 14 cases of infected, immature teeth. Endodontic treatment was initiated, and after infection control, revascularization was performed. The access cavity was sealed with glass ionomer cement. The cases were followed up at regular intervals of 3 months; the range in follow-up was 0.5–3.5 years. The outcomes were as follows. Radiographic resolution of periradicular radiolucencies was judged to be good to excellent in 93% (13 of 14) of the cases. In the majority of cases, a narrowing of the wide apical opening was evident. In 3 cases, thickening of apical dentinal walls and increased root length were observed. The striking finding was complete resolution of clinical signs and symptoms and appreciable healing of periapical lesions in 78% (11 of 14) of cases. Thickening of lateral dentinal walls was evident in 57% (8/14) of cases, and increased root length was observed in 71% (10/14) of cases. None of the cases presented with pain, reinfection, or radiographic enlargement of preexisting apical pathology. This pilot study documented a favorable outcome of revascularization procedures conducted in immature nonvital, infected permanent teeth.
Hydrogen Peroxide Induces Heme Oxygenase–1 and Dentin Sialophosphoprotein mRNA in Human Pulp Cells
Kyung-San Min, DDS, PhD, Hwa-Jeong Lee, MS, Suk-Ho Kim, DDS, PhD, Sun-Kyung Lee, MS, Hyung-Ryong Kim, DDS, PhD, Hyun-Ock Pae, PhD, Hun-Taeg Chung, MD, PhD, Hong-In Shin, DDS, PhD, Suk-Keun Lee, DDS, PhD, Eun-Cheol Kim, DDS, PhD
Although the induction of heme oxygenase–1 (HO-1) by hydrogen peroxide (H2O2) has been reported, the HO-1 and odontoblastic differentiation-inducing effects against H2O2have not been clarified in human pulp cells. In this study, we investigated whether HO-1 is involved in the protective mechanisms against the cytotoxic effects of H2O2 by using a cell viability assay, and we examined the production of dentin sialophosphoprotein (DSPP) and other mineralization markers by using reverse transcriptase–polymerase chain reaction in human pulp cells. H2O2decreased cell viability but increased HO-1 and DSPP expression in a concentration- and time-dependent manner. Antioxidants and inhibitors of HO-1, phosphatidylinositol-3'-kinase, extracellular signal-regulated kinase, and p38 mitogen-activated protein kinase blocked H2O2-induced cytotoxicity and the expression of HO-1 and DSPP mRNA in pulp cells. These data suggest that the induction of HO-1 by H2O2 in pulp cells plays a protective role against the cytotoxic effects of H2O2 and stimulates DSPP expression, resulting in premature odontoblast differentiation through pathways that involve phosphatidylinositol-3'-kinase, p38, and extracellular signal-regulated kinase.
Single-step Apical Barrier Placement in Immature Teeth Using Mineral Trioxide Aggregate and Management of Periapical Inflammatory Lesion Using Platelet-rich Plasma and Hydroxyapatite
Hemalatha Hiremath, MDS, Neerav Gada, MDS, Yogesh Kini, MDS, DNB, Sadanand Kulkarni, MDS, Shoeb Sheikh Yakub, MDS, Sandeep Metgud, MDS
We present here a case report of a tooth with an immature root with a large periapical lesion. The open apex was managed by placing an apical barrier using mineral trioxide aggregate, and the periapical lesion was treated surgically. A combination of platelet-rich plasma (PRP) and hydroxyapatite graft (HA) was used to achieve faster healing of the periapical lesion. The case was followed up for 11 months. The indications and advantages of apical barrier placement, periapical surgery, and the role of PRP and HA in postsurgical healing are discussed.
Calcitonin Gene-related Peptide Receptor Expression in Alternatively Activated Monocytes/Macrophages During Irreversible Pulpitis
Javier Caviedes-Bucheli, DDS, MSc, Gloria Cristina Moreno, DDS, MSc, María Paula López, DDS, Ana Milena Bermeo-Noguera, DDS, Gloriana Pacheco-Rodríguez, DDS, Adriana Cuellar, MSc, Hugo Roberto Muñoz, DDS, MSc
The purpose of this study was to quantify the percentage and the mean fluorescence intensity of viable alternatively activated monocytes/macrophages (AAMø) CD163+ positive for calcitonin gene-related peptide receptor (CGRPr) within the total AAMø population in human dental pulp. Pulp tissue samples were collected from teeth with a clinical diagnosis of irreversible pulpitis (n = 13), pulps with induced inflammation (n = 13), and normal pulps (n = 13). All samples were labeled to identify positive cells for CGRPr and CD163 using a flow cytometry assay. Results demonstrated that a high percentage of total viable AAMø CD163+ expressed CGRPr on their membranes (72.12% in healthy pulp, 62.20% in irreversible pulpitis, and 58.01% in induced pulpitis). Significant differences were found between mean AAMø CD163+ fluorescence for CGRPr according to pulp condition, being greater in irreversible pulpitis. It can be concluded that AAMø CD163+ are expressed during normal and inflammatory processes, supporting the hypothesis that they could exercise an anti-inflammatory action that could be controlled by CGRP signaling after its binding.
Differential Patterns of Receptor Activator of Nuclear Factor Kappa B Ligand/Osteoprotegerin Expression in Human Periapical Granulomas: Possible Association with Progressive or Stable Nature of the Lesions
Renato Menezes, DDS, MS, PhD, Thiago Pompermaier Garlet, DDS, MS, Ariadne Letra, DDS, MS, PhD, Clóvis Monteiro Bramante, DDS, MS, PhD, Ana Paula Campanelli, MS, PhD, Rita de Cássia Figueira, MS, Mari Claide Sogayar, PhD, José Mauro Granjeiro, MS, PhD, Gustavo Pompermaier Garlet, DDS, MS, PhD
Receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) are expressed in apical periodontitis, suggesting a role for these molecules during lesion development. However, the profiles of RANKL/OPG expression in periapical lesions remain unknown. In this study we investigated the patterns of RANKL and OPG mRNA expression by real-time polymerase chain reaction in human periapical granulomas (N = 44) and compared them with sites presenting characteristic bone resorbing activity: healthy (n = 14) and orthodontically stretched and compressed periodontal ligament (n = 26), healthy gingiva (n = 24), chronic gingivitis (n = 32), and chronic periodontitis (n = 34) samples. Both RANKL and OPG mRNA expression was higher in periapical granulomas when compared with healthy periodontal ligament. Distinct patterns of RANKL and OPG expression ratio were found in the granulomas and in different physiologic and pathologic conditions, with characteristic bone resorption activity potentially being indicative of the stable or progressive nature of the lesions. Lesions with radiographic image smaller than 5 mm showed higher RANKL/OPG expression than images greater than 5 mm. Periapical granulomas presented heterogeneous patterns of RANKL and OPG expression, ranging from samples with RANKL/OPG ratio similar to that seen in sites with minimal or absent bone resorption to samples with RANKL/OPG expression pattern comparable with active bone resorption sites.
Immunohistochemical Analysis of Nestin, Osteopontin, and Proliferating Cells in the Reparative Process of Exposed Dental Pulp Capped with Mineral Trioxide Aggregate
Momoko Kuratate, DDS, Kunihiko Yoshiba, DDS, PhD, Yoshimi Shigetani, DDS, PhD, Nagako Yoshiba, DDS, PhD, Hayato Ohshima, DDS, PhD, Takashi Okiji, DDS, PhD
This study investigated the reparative process of mechanically exposed pulps capped with mineral trioxide aggregate (MTA). Maxillary first molars of 8-week-old rats were MTA-capped for 1–14 days, and 5-bromo-2′-deoxyuridine–labeled proliferating cells and immunoreactivity for nestin and osteopontin were analyzed. MTA capping caused mild necrotic changes followed by progressive new matrix formation and calcified bridging. Proliferating cells peaked at 3 days when matrix formation was inconspicuous. Nestin-expressing cells appeared at 3 days, were arranged beneath the newly formed matrix at 5 days, and showed odontoblast-like morphology by 14 days. Osteopontin immunoreactivity was detected just beneath the necrotic area after 1 day. These findings suggest that pulpal responses to MTA capping involve proliferation and migration of progenitors followed by their differentiation into odontoblast-like cells, a mechanism basically similar to those to calcium hydroxide. Osteopontin might play a triggering role in initiation of the pulpal reparative process.
The Expression and Role of Stromal Cell–derived Factor-1α–CXCR4 Axis in Human Dental Pulp
Long Jiang, DDS, MDS, Ya-Qin Zhu, DDS, PhD, Rong Du, DDS, MDS, Ying-Xin Gu, DDS, MDS, Lie Xia, DDS, MDS, Feng Qin, DDS, MDS, Helena H. Ritchie, PhD
Recent reports have suggested that the stromal cell–derived factor (SDF)-1α–CXCR4 axis has a direct effect on stem and progenitor cell recruitment in muscle and neural tissue repair after injury. No information is available about SDF-1α or CXC chemokine receptor 4 (CXCR4) in dental tissues. The aim of this study was to assess the expression of SDF-1α and its receptor, CXCR4, in healthy or inflamed human dental pulp and to evaluate the effects of SDF-1α on dental pulp cells (DPCs) in both proliferation and migration in vitro. Immunohistochemical staining and reverse-transcription polymerase chain reaction detected weak expression of SDF-1α and CXCR4 in healthy dental pulp and strong expression of SDF-1α and CXCR4 in inflamed dental pulp. A methylthiazol tetrazolium assay showed that SDF-1α could not promote DPCs proliferation. A transmigration assay, however, indicated that SDF-1α enhanced DPCs migration, which could be abolished by anti-CXCR4 antibodies. Taken together, these results imply that the SDF-1α–CXCR4 axis may play a role in the recruitment of CXCR4-positive DPCs toward the damaged sites.
Root Form and Canal Morphology of Jordanian Maxillary First Premolars
Lama Awawdeh, BDS, MSc, PhD, Hassan Abdullah, BDS, MSc, Aladdin Al-Qudah, BDS, PhD, FDSRCPS/Glasgow
This study was conducted to investigate root canal morphology of maxillary first premolars in a Jordanian population. Six hundred maxillary first premolars were collected, stained, and decalcified. Cleared teeth were examined and the following features were evaluated: (1) number of roots, (2) presence of furcation grooves, (3) location of apical foramina, (4) number and types of root canal, (5) number of lateral canals and isthmi, and (6) frequency of apical deltas. Of the six hundred maxillary first premolars 30.8% has one root, 63.2% has two, and 5.2% has bifid roots. Concerning root canal morphology, 79.7% had two canals with two separate apical foramina, whereas 3.3% of the teeth possessed type I canal systems. All two rooted maxillary first premolars showed furcation groove in the buccal roots. Maxillary first premolars are mainly two rooted and mostly have two canals. The presence of furcation groove should be kept in mind during both endodontic and prosthodontic procedures.
Is Adhesive Cementation of Endodontic Posts Necessary?
Michael Naumann, DMD, Guido Sterzenbach, Martin Rosentritt, Florian Beuer, Roland Frankenberger
Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups (n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequent static loading. Significant differences between the experimental groups regarding load capability and fracture patterns were observed. The conventional non-adhesive post cementation is less reliable to withstand simulated functional forces compared to adhesive approaches.
Evaluation of Smear Layer: A Comparison of Automated Image Analysis versus Expert Observers
Roy George, BDS, MDS, Edward B. Rutley, BSc, BDSc, MDSc, Laurence J. Walsh, PhD, DDSc
Consistent and reproducible evaluation techniques of the smear layer in root canals in scanning electron microscopy studies are needed when comparing various instruments and techniques. In this study, the performance of 3 experienced blinded evaluators applying the Hulsmann technique was compared with a digital analysis method. Smear layer in the apical third of root canals of 35 freshly extracted teeth prepared by using nickel-titanium rotary instruments, Er:YAG and Er,Cr:YSGG lasers was scored on coded images. There was good agreement between the digital analysis method and the different evaluators (kappa analysis) across the range of the Hulsmann scores. Image analysis might be useful for evaluating the degree of smear layer removal in endodontic research.
Dental Pulp Tissue Engineering with Stem Cells from Exfoliated Deciduous Teeth
Mabel M. Cordeiro, DDS, MS, PhD, Zhihong Dong, MD, PhD, Tomoatsu Kaneko, DDS, PhD, Zhaocheng Zhang, MD, PhD, Marta Miyazawa, DDS, MS, PhD, Songtao Shi, DDS, PhD, Anthony J. Smith, BSc, DDS, PhD, Jacques E. Nör, DDS, MS, PhD
Stem cells from human exfoliated deciduous teeth (SHED) have been isolated and characterized as multipotent cells. However, it is not known whether SHED can generate a dental pulp-like tissue in vivo. The purpose of this study was to evaluate morphologic characteristics of the tissue formed when SHED seeded in biodegradable scaffolds prepared within human tooth slices are transplanted into immunodeficient mice. We observed that the resulting tissue presented architecture and cellularity that closely resemble those of a physiologic dental pulp. Ultrastructural analysis with transmission electron microscopy and immunohistochemistry for dentin sialoprotein suggested that SHED differentiated into odontoblast-like cells in vivo. Notably, SHED also differentiated into endothelial-like cells, as demonstrated by B-galactosidase staining of cells lining the walls of blood-containing vessels in tissues engineered with SHED stably transduced with LacZ. This work suggests that exfoliated deciduous teeth constitute a viable source of stem cells for dental pulp tissue engineering.
A Comparison of Four Pulpotomy Techniques in Primary Molars: A Long-term Follow-up
Deniz Sonmez, DDS, PhD, Saziye Sari, DDS, PhD, Tuğba Çetinbaş, DDS
The study evaluated the effects of formocresol (FC), ferric sulphate (FS), calcium hydroxide (Ca[OH]2), and mineral trioxide aggregate (MTA) as pulp dressing agents in pulpotomized primary molars. Sixteen children each with at least four primary molars requiring pulpotomy were selected. Eighty selected teeth were divided into four groups and treated with one of the pulpotomy agent. The children were recalled for clinical and radiographic examination every 6 months during 2 years of follow-up. Eleven children with 56 teeth arrived for clinical and radiographic follow-up evaluation at 24 months. The follow-up evaluations revealed that the success rate was 76.9% for FC, 73.3% for FS, 46.1% for Ca(OH)2, and 66.6% for MTA. In conclusion, Ca(OH)2is less appropriate for primary teeth pulpotomies than the other pulpotomy agents. FC and FS appeared to be superior to the other agents. However, there was no statistically significant difference between the groups.
The Properties of a New Endodontic Material
Saeed Asgary, DDS, MS, Sima Shahabi, DDS, PhD, Tahereh Jafarzadeh, DDS, PhD, Sara Amini, DDS, MS, Sanam Kheirieh, DDS
The purpose of this study was to analyze the physical properties and chemical compositions of a new experimental cement (NEC) and compare them with mineral trioxide aggregate (MTA); pH, working time, setting time, dimensional changes following setting, flow, film thickness, and chemical composition of NEC and MTA were assessed. For chemical compositions, all specimens were imaged and analyzed by scanning electron microscopy and electron probe microanalysis (EPMA). The physical properties were performed according to ISO 6876:2001. Working time, pH, and dimensional changes of NEC and MTA showed similar results. Shorter setting time was obtained with the NEC compared with MTA (p < 0.05). The NEC showed more flow than MTA. In addition, the film thickness of the NEC was considerably less than the MTA (p < 0.01 and p < 0.001, respectively). EPMA investigations indicated that lime (CaO) was the dominant compound in NEC and MTA; however, other compounds were significantly different. It was concluded that the chemical composition of NEC is different compare with MTA; it can be concluded that the NEC exhibits acceptable physical properties.
Effect of Shortened Irrigation Times with 17% Ethylene Diamine Tetra-acetic Acid on Smear Layer Removal after Rotary Canal Instrumentation
Koichi Saito, DDS, MS, Terry D. Webb, DDS, MS, Glen M. Imamura, DDS, MS, Gary G. Goodell, DDS, MS, MA
The purpose of this study was to evaluate whether irrigation times of 1 minute or less with 1 mL of 17% ethylene diamine tetra-acetic acid (EDTA) effectively removed the smear layer from root canals after rotary instrumentation. Forty single-canal teeth were decoronated, instrumented, and divided into 3 experimental groups (n = 10). Ten teeth served as positive and negative controls. The experimental groups received a final rinse with 1 mL of 17% EDTA for 1 minute, 30 seconds, or 15 seconds followed by a final 3-mL rinse with 6% NaOCl. Teeth were split longitudinally and prepared for scanning electron microscopy imaging. Digital images (350×) of the approximate center of the coronal, middle, and apical sections were graded for quality of smear layer removal by 3 endodontists. Data were analyzed with nonparametric tests, with significance level set at α = .05. Significantly greater smear layer removal was found in the 1-minute EDTA irrigation group than the 30-second or 15-second groups.
The Influence of Cavity Design and Glass Fiber Posts on Biomechanical Behavior of Endodontically Treated Premolars
Carlos Jose Soares, DDS, MS, PhD, Paulo Vinicius Soares, DDS, MS, Paulo Cesar de Freitas Santos-Filho, DDS, MS, Carolina Guimaraes Castro, DDS, Denildo Magalhaes, Antheunis Versluis, PhD
The aim of this study was to evaluate the effect of cavity design and glass fiber posts on stress distributions and fracture resistance of endodontically treated premolars. Fifty extracted intact mandibular premolars were divided into 5 groups (n = 10): ST, sound teeth (control); MOD, mesio-occlusal-distal preparation + endodontic treatment (ET) + composite resin restoration (CR); MODP, mesio-occlusal-distal + ET + glass fiber post + CR; MOD2/3, mesio-occlusal-distal + two thirds occlusal-cervical cusp loss + ET + CR; and MODP2/3, mesio-occlusal-distal + two thirds cusp loss + ET + glass fiber post + CR. The specimens were loaded on a cusp slope until fracture. Fracture patterns were classified according to four failure types. Stress distributions were evaluated for each group in a two-dimensional finite element analysis. The fracture resistance of the MODP, MOD2/3, and MODP2/3 groups was significantly lower than the ST and MOD groups (p < 0.05). The loss of dental structure and the presence of fiber post restoration reduced fracture resistance and created higher stress concentrations in the tooth-restoration complex. However, when there was a large loss of dental structure (MODP2/3), the post reduced the incidence of catastrophic fracture types.
Fractographic Analysis of K3 Nickel-Titanium Rotary Instruments Submitted to Different Modes of Mechanical Loading
Fabiola Ormiga Galvão Barbosa, MSc, José Antônio da Cunha Ponciano Gomes, DSc, Marcos Cesar Pimenta de Araújo, DSc
The aim of the present study was to analyze the fracture surface of nickel-titanium K3 rotary files submitted to different modes of mechanical loading. Torsional and flexural fatigue tests were realized separately in 2 groups of files. Additional 2 groups of files were tested in mixed loading modes, torsional test after incomplete flexural fatigue test and flexural fatigue test after incomplete torsional test. Scanning electronic microscopy observation was used to make a fractographic analysis of the files under test. The files fractured during torsional resistance tests showed fractographies with a central area containing dimples, which are oval-shaped depressions in the microstructure in places of high local plastic deformation. The peripheral area of these files' fractographies presented a flattened aspect without dimples. The fractographies of the files fractured by flexural fatigue presented one area with radial striations and another area containing dimples. The fractographic patterns observed when mixed loading modes were imposed correspond to the pattern defined by the second stage test. The patterns established for the fractured files provide consistent bases to explain the fracture process in clinical conditions by fractographic analysis.