Celecoxib treatment dampens LPS-induced periapical bone resorption in a mouse model.

AIM: To evaluate the efficacy of selective and nonselective inhibitors of cyclooxygenase-2 enzymes in the treatment of experimental apical periodontitis induced by bacterial lipopolysaccharide (LPS) in vivo in a mouse model. METHODOLOGY: Thirty-six C57BL/6 mice were used. After access cavity preparation, a solution containing E. coli LPS (1.0 µg µL-1 ) was inoculated into the root canals of the mandibular and maxillary right first molars (n = 72) After 30 days, apical periodontitis was established and the animals were systemically treated with celecoxib, a selective COX-2 inhibitor (15 mg kg-1 ), or indomethacin, a nonselective COX-2 inhibitor (5 mg kg-1 ), for 7 and 14 days. Blocks containing teeth and bone were removed for histopathological and histometric analyses (haematoxylin and eosin), evaluation of osteoclasts numbers (tartrate-resistant acid phosphatase enzyme - TRAP) and immunohistochemistry for RANK, RANKL and OPG. Gene expression was performed using reverse transcription and real-time polymerase chain reaction (qRT-PCR) for RANK, RANKL, OPG, TRAP, MMP-9, cathepsin K and calcitonin receptor. Histopathological, histometric, TRAP, immunohistochemistry and qRT-PCR data were evaluated using Kruskal-Wallis followed by Dunn's test (α = 0.05). RESULTS: Systemic administration of celecoxib for 7 and 14 days prevented periapical bone resorption (P < 0.0001), differently from indomethacin that exacerbated bone resorption at 7 days (P < 0.0001) or exerted no effect at 14 days (P = 0.8488). Celecoxib treatment reduced osteoclast formation in apical periodontitis, regardless of the period of treatment (P < 0.0001 for 7 days and P = 0.026 for 14 days). Administration of celecoxib or indomethacin differentially modulated the expression of genes involved in bone resorption. At 7 days, celecoxib and indomethacin treatment significantly inhibited expression of mRNA for cathepsin K (P = 0.0005 and P = 0.016, respectively) without changing TRAP, MMP-9 and calcitonin receptor gene expression. At 14 days, celecoxib significantly inhibited expression of mRNA for MMP-9 (P < 0.0001) and calcitonin receptor (P = 0.004), whilst indomethacin exerted no effect on MMP-9 (P = 0.216) and calcitonin receptor (P = 0.971) but significantly augmented cathepsin K gene expression (P = 0.001). CONCLUSIONS: The selective COX-2 inhibitor celecoxib reduced osteoclastogenic signalling and activity that dampened bone resorption in LPS-induced apical periodontitis in mice, with greater efficacy than the nonselective inhibitor indomethacin.

IgG4-positive plasma cells are more often detected in chronic periapical lesions arising from permanent rather than primary teeth.

AIM: To characterize plasma cell subsets in chronic periapical lesions affecting permanent and primary teeth. METHODOLOGY: Only chronic periapical lesions without root canal treatment were selected. Twenty-one radicular cysts and 7 periapical granulomas affecting permanent teeth and 19 radicular cysts and 4 periapical granulomas affecting primary teeth were assessed for immunoglobulin (Ig) light chain (kappa and lambda), Ig heavy chain (IgG, IgG4, IgA, IgM and IgD) and plasma cell immunohistochemical markers (MUM1/IRF4, EMA and CD138). The data acquired were analysed by Student's t test, Mann-Whitney U, Friedman test followed by Dunn's multiple comparison test and Spearman's rank correlation. RESULTS: All cases were polyclonal (having similar kappa/lambda light chain ratios). IgG was most abundant compared to other Ig heavy chains (all, P < 0.001); like Ig light chains, but unlike IgA, there was greater expression of IgG in the primary compared to the permanent dentition, for both radicular cysts (P < 0.001) and periapical granulomas (P = 0.53). Notably, IgG4 expression was greater in the permanent than the primary dentition, for both radicular cyst (P < 0.05) and periapical granuloma (P = 0.65). IgM and IgD expression was scarce and variable, whereas plasma cell populations were detected efficiently through EMA, CD138 and MUM1/IRF4 markers, the latter being more sensitive in both dentitions. CONCLUSIONS: There were slight variations in the Ig light and heavy chain profiles in chronic periapical lesions when comparing the permanent and primary dentitions. The ability of IgG4+ plasma cell infiltration to modulate inflammatory responses in chronic periapical lesions arising from permanent as opposed to primary teeth should be considered in future studies.

Alendronate inhibits osteocyte apoptosis and inflammation via IL-6, inhibiting bone resorption in periapical lesions of ovariectomized rats.

AIM: To evaluate the effect of alendronate (ALN) on the development of periapical lesions induced in ovariectomized rats. METHODOLOGY: Twenty-five rats were divided into three groups: sham (control), ovariectomy (OVX) and OVX + ALN. One day after OVX, animals from the OVX + ALN group received the medication via gavage. After 9 weeks, the first molars of all animals were submitted to periapical lesion induction. After 21 days, the animals were euthanized. Femurs were analysed for bone mineral density. The blocks of bone tissue containing the mandibular first molars were submitted to histotechnical processing and staining with haematoxylin and eosin (HE) for periapical lesion analysis under conventional microscopy. At the same time, the morphometric analysis of the periapical lesion area was performed in the fluorescence mode, as well as the histoenzimology for the quantification of osteoclasts and 4'-6-diamidino-2-phenylindole staining for the quantification of apoptotic osteocytes. In addition, the first maxillary molars were used for analysis of the gene expression of proinflammatory cytokines (IL-1ß, IL-6 and TNF-α) and osteoclastogenesis markers (RANKL/OPG). The results were submitted to ANOVA and Kruskal-Wallis tests and Tukey and Dunn post-tests (significance level of 5%). RESULTS: Ovariectomy reduced bone mineral density of the femur, and treatment with ALN was able to prevent bone loss (P < 0.001). Regarding the microscopic analysis of the periapical region, the sham and OVX + ALN groups had moderately increased periodontal ligament and inflammatory infiltrate, while the OVX group had these parameters increased intensely. The periapical lesions of the OVX group were significantly larger in area in comparison to the other groups (P < 0.001). The OVX group had the largest amount of apoptotic osteocytes, and ALN was able to prevent the apoptosis of these cells, in addition to significantly reducing IL-6 expression (P < 0.05). OVX and ALN had no effect on RANKL/OPG expression and did not influence the number of osteoclasts around the periapical lesion (P > 0.05). CONCLUSION: The hypoestrogenic condition induced by OVX aggravated bone resorption, inducing the death of osteocytes and provoking larger periapical lesions. ALN treatment inhibited osteocyte apoptosis and inflammation via IL-6, inhibiting bone resorption in periapical lesions of ovariectomized rats.

Immunophenotypic quantification of M1 and M2 macrophage polarization in radicular cysts of primary and permanent teeth.

AIM: To quantify M1 and M2 macrophages in radicular cysts of permanent (n = 14 cases) and primary teeth (n = 15 cases). METHODOLOGY: All patients who attended the School of Dentistry Ribeirão Preto, University of São Paulo with primary teeth or permanent molars that were scheduled for extraction and fulfilled the inclusion criteria: absence of pain; presence/absence of fistulae; extensive coronal destruction due to caries lesions without possibility of restoration; pulp necrosis; radiographically visible apical periodontitis; and no previous treatment, were selected. The radicular cysts were removed and subsequently submitted to histopathologic analysis in order to classify the type of inflammatory infiltrate. In addition, CD68 (M1+, M2+) and CD163 (M1-, M2+) markers were quantified through an immunohistochemistry analysis. The data acquired were submitted to a Mann-Whitney test, with a 5% significance level. RESULTS: The patients had a mean age of 38.6 years and 5.9 years for cysts associated with permanent and primary teeth, respectively. In the histopathological analysis, no significant difference (P = 0.87) was found between radicular cysts in primary and permanent teeth regarding the intensity of the chronic inflammatory infiltrate. A significantly greater prevalence of M2 macrophages (P < 0.05) was observed in the lesions of both permanent and primary teeth, even though both M1 and M2 macrophages were detected. No significant difference (P > 0.05) was found for M1 and M2 macrophages associated with the cysts of primary and permanent teeth. CONCLUSION: M1 and M2 macrophages were present in radicular cysts associated with primary and permanent teeth, with a greater quantity of M2 cells. The immunophenotypic quantification of M1 and M2 macrophage polarization in radicular cysts associated with primary and permanent teeth were similar.

Effect of intercellular adhesion molecule 1 deficiency on the development of apical periodontitis.

AIM: To evaluate the specific role of ICAM-1 in host responses against endodontic infection. METHODS: Apical periodontitis was experimentally induced in the mandibular first molars of ICAM-1 knockout and wild-type (WT) mice by pulp exposure to the oral environment. At 7, 21 and 42 days following pulp infection, the animals were euthanized and the jaws were prepared for analysis under conventional and fluorescence microscopy (histopathologic and morphometric analysis), immunohistochemistry (polymorphonuclear leucocytes), enzyme histochemistry (osteoclasts and cementoclasts) and RT-PCR (IL-1 α, TNF-α, INF-γ, IL-10, RANK, RANKL and OPG). A generalized linear model with GLIMMIX procedure with Satterthwaite approximation method of degrees of freedom, Tukey-Kramer, pseudo-ranking nonparametric, Bonferroni-Holm multiple testing adjustment, analysis of variance (ANOVA) and the Tukey's multiple comparisons tests were used to evaluate the statistical differences between the groups using SAS 9.4 and the GraphPad Prism 5.0 software (α = 0.05). RESULTS: Compared to WT mice, ICAM-1 knockout mice had significantly greater bone resorption (P < 0.05), reduced recruitment of neutrophils to periapical inflammatory tissues (P < 0.05) and an increased number of fibroblasts (P < 0.05) at all experimental periods. The osteoclast number was significantly higher in ICAM-1 KO than that of WT animals at all times (P < 0.05), while there was no significant difference between the groups regarding cementoclasts. At day 21, the level of IL-1α, RANK, RANKL and IL-10 had increased significantly in tissues from ICAM-1 KO versus WT mice (P < 0.05), while no significant difference was observed in TNF-α and OPG levels (P > 0.05). Tissue levels of INF-γ were significantly lower in ICAM-1 KO than those in WT mice (P < 0.05). CONCLUSION: ICAM-1 deficiency impaired the host response against endodontic infection, resulting in increased tissue destruction.

Histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis of tissue response to sealing materials after furcation perforation.

AIM: To evaluate in vivo tissue responses after sealing furcation perforations in dog's teeth with either Biodentine™, mineral trioxide aggregate (MTA) or gutta-percha, by means of histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis. METHODOLOGY: After root canal treatment, perforations were created in the central region of the pulp chamber floor using a round diamond bur and filled with one or other of the materials. The animals were euthanized after 120 days, and the teeth (n = 30) were processed for histopathological analysis of new mineralized tissue formation and collagen fibre reinsertion, immunohistochemical analysis of osteopontin (OPN) and alkaline phosphatase (ALP) and immunofluorescence analysis for bone morphogenetic protein (BMP-2), cementum attachment protein (CAP), bone sialoprotein (BSP), osteocalcin (OCN) and cementum protein1 (CEMP1). Histoenzymology was performed for TRAP activity and osteoclast count. Data were analysed statistically (α = 0.05) using chi-square and Kruskal-Wallis tests. RESULTS: Gutta-percha did not induce mineralized tissue formation. MTA and BiodentineTM formed mineralized tissue in 88% and 92% of specimens, respectively, with no significant difference (P > 0.05). Gutta-percha was associated with scattered collagen fibres parallel to the perforations. Groups treated with MTA or BiodentineTM had partial fibre reinsertion perpendicular to the newly formed mineralized tissue. All materials induced OPN and ALP expression, weakest for gutta-percha and strongest for MTA (P < 0.05). Only MTA induced BMP-2, BSP, OCN, CAP and CEMP1 expression. Osteoclast counts were similar in all groups (P = 0.97). CONCLUSIONS: Mineral trioxide aggregate and BiodentineTM were biocompatible, with formation of mineralized tissue and partial reinsertion of collagen fibres. In addition, the participation of several molecules by which calcium silicate-based materials induce the formation of mineralized tissue were noted, with expression of ALP and OPN mineralization markers, without interference in the number of osteoclasts. Only MTA stimulated the expression of proteins associated with the formation of a cementum-like mineralized tissue.

Novel endodontic sealers induce cell cytotoxicity and apoptosis in a dose-dependent behavior and favorable response in mice subcutaneous tissue.

OBJECTIVES: The objective of the present study is to evaluate the in vitro cytotoxicity and in vivo biocompatibility of two novel endodontic sealers: RealSeal XT1 and Sealapex Xpress on the subcutaneous connective tissue of mice. MATERIALS AND METHODS: The cytotoxicity was assessed by cell viability using the MTT assay (one-way ANOVA), trypan blue test (Mann-Whitney) and cell apoptosis by flow cytometer. For the subcutaneous study, polyethylene tubes filled with the sealers were implanted in 70 BALB/c mice: 6 experimental groups (n = 10/group) and 2 control groups with empty tubes (n = 5/group). At the end of experimental periods (7, 21, and 63 days), the tissue was removed and histotechnically processed. Angioblastic proliferation and edema (Fisher's exact test) were evaluated, besides thickness measurement (µm) of the reactionary granulomatous tissue and neutrophil counts (Kruskal-Wallis and Dunn's post test; Mann-Whitney) (α = 0.05). RESULTS: MTT assay, trypan blue, and analysis of apoptotic cells showed a dose-dependent direct effect: the more diluted the sealer, the less cytotoxic. Regarding the angioblastic proliferation and edema, difference between the sealers at 7 and 63 days occurred (p < 0.05). Both endodontic sealers initially promoted perimaterial tissue reaction as a foreign body granuloma and thus stimulated favorable tissue responses. CONCLUSIONS: Both sealers showed a dose-dependent effect and promoted satisfactory subcutaneous tissue response; the sealer Sealapex Xpress was less cytotoxic and more biocompatible than RealSeal XT. CLINICAL RELEVANCE: The step of root canal filling during endodontic treatment is highly important for the preservation of the periapical tissue integrity. Subcutaneous reaction to endodontic sealers enables scientific basis for clinical use.

Influence of therapeutic cancer radiation on the bond strength of an epoxy- or an MTA-based sealer to root dentine.

AIM: To evaluate the influence of radiation on root canal sealer push-out bond strength to dentine and sealer/dentine interface in teeth filled with AH Plus (Dentsply Ind. Com. Ltda, Petrópolis, RJ, Brazil) and MTA Fillapex (Angelus Ind. Prod. Odontológicos S/A, Londrina, PR, Brazil). METHODOLOGY: Thirty-two maxillary canines were selected and randomly assigned to 2 groups (n = 16): one group was not irradiated, and the other was subjected to a cumulative radiation dose of 60 Gy. Root canals were prepared with the Reciproc system (VDW GmbH, Munich, Germany), and each group was divided into 2 subgroups (n = 8) according to the sealer - AH Plus or MTA Fillapex - using the single-cone filling technique. Then, 1-mm-thick dentine slices were obtained from each root third for the push-out test to evaluate sealer bond strength to dentine and for scanning electron microscopy (SEM) to examine the sealer/dentine interface. Failure mode after debonding was determined with a stereomicroscope at ×25 magnification. Bond strength data were analysed by two-way anova with a split-plot design and post hoc Tukey's test (α = 0.05). RESULTS: Significantly lower bond strength (P < 0.0001) was obtained after irradiation (0.71 ± 0.20 versus 0.97 ± 0.29 MPa) and in specimens filled with MTA Fillapex (0.70 ± 0.18 MPa) compared with AH Plus (1.00 ± 0.27 MPa). Percentage of adhesive failures increased after radiation in all root thirds in the teeth filled with AH Plus. SEM revealed more gap-containing regions and fewer tags at the sealer/dentine interface in irradiated specimens, with more tag formation and fewer gaps with AH Plus sealer. CONCLUSIONS: Radiation was associated with a decrease in the push-out bond strength of sealers to intraradicular dentine and formation of more gaps and fewer tags at the sealer/dentine interface regardless of the sealer.

Absence of interleukin 22 affects the oral microbiota and the progression of induced periapical lesions in murine teeth.

AIM: To evaluate the absence of IL-22 on the progression of periapical lesions in wild-type (WT) and IL-22 knockout (IL-22 KO) mice. METHODOLOGY: The evaluation of the oral microbial profile of mice was performed by Checkerboard DNA-DNA hybridization from saliva samples. Periapical lesions were induced in manbibular first molars by pulpal exposure and evaluated after 7, 21 and 42 days (n = 15). Haematoxylin-eosin-stained sections were analysed under conventional and fluorescence microscopy to evaluate the tissue features and size of periapical lesions and tartrate-resistant acid phosphatase histoenzymology (TRAP), Brown & Brenn staining and immunohistochemistry. The scores of the number of bacterial cells present in the oral cavity were analysed by the Mann-Whitney test, and the results and comparisons for periapical lesion size and number of osteoclasts were subjected to one-way anova and Bonferroni's post-test (α = 0.05). RESULTS: Significant differences were observed for bacterial load between the groups of animals for 6 bacterial species (P < 0.05), with five species found in higher levels in the WT group, and one in the IL-22 KO group. WT mice had significantly larger periapical lesions (P < 0.05) between 7 and 42 days and between 21 and 42 days, with an increase in the mean size and number of osteoclasts. IL-22 KO mice had an increase in periapical lesion size and number of osteoclasts between 7 and 21 days (P < 0.05). No differences were found between bacteria localization in the root canal system between the experimental groups. Small variations related to the location of immunostaining were found between the groups. CONCLUSION: This study revealed differences in the composition of oral microbiota between mice that may be taken into account in the susceptibility to infections and development of periapical lesions. The absence of IL-22 in mice resulted in smaller periapical lesions with fewer osteoclasts at the final experimental period, suggesting the participation of IL-22 in the host immune and inflammatory response to a periradicular infection.

The treatment of a maxillary lateral incisor with unusual morphology with long-term follow-up.

AIM: To report the treatment of an unusual combination of one dens evaginatus and two dens invaginatus in a single tooth and its healing outcome after 10 years. SUMMARY: The long-term outcome of a maxillary lateral incisor with dens evaginatus combined with two Oehlers type II dens invaginatus and a large periradicular lesion in an 11-year-old female treated endodontically and restoratively is described. The endodontic treatment included intracanal medication with calcium hydroxide and canal filling using a thermoplastic root canal filling technique. The crown was restored with conventional composite resin. During periodic clinical and radiographic follow-up, the patient remained symptom free, and the periradicular region was completely healed, meeting both aesthetic and functional expectations after 10 years. KEY LEARNING POINTS: The co-occurrence of dens evaginatus and two dens invaginatus in the same tooth is an unusual finding that compromises aesthetics and predisposes the patient to dental pulp infection. The complex morphology observed in this case represented both endodontic and restorative challenges.

Pulpal and periapical response after restoration of deep cavities in dogs' teeth with Filtek Silorane and Filtek Supreme XT systems.

OBJECTIVE: This study evaluated, histopathologically, the pulpal and periapical response to a silorane-based resin (Filtek Silorane) and a methacrylate-based nanoparticle resin (Filtek Supreme XT) in deep cavities in dogs, having zinc oxide and eugenol-based cement (ZOE) as a control. METHODS: The tooth/bone blocks were collected after 10 and 90 days and processed for microscopic analysis of the dentin, pulp, and periapical tissues using a score system. Data were analyzed statistically by Kruskal-Wallis and Dunn post-test (α=0.05). RESULTS: At 10 days, the pulp, connective tissue, and periodontal ligament showed normal characteristics. No resorption areas were observed. Both resins caused significantly less (p<0.05) periapical and pulpal inflammatory response than ZOE. At 90 days, for all materials, the connective pulp tissue was healthy and dense, with a normal blood vessel system. The apical and periapical region had normal structure and thickness. CONCLUSIONS: The use of the Filtek Silorane and the Filtek Supreme XT resins caused no adverse pulpal and periapical reactions after restoration of deep dentin cavities in vivo.

Preliminary study of the inflammatory response to subcutaneous implantation of three root canal sealers.

AIM: To evaluate the kinetics of the inflammatory tissue response to three root canal sealers using a physicochemical method for quantification of the enhanced vascular permeability and histopathological analysis. METHODOLOGY: Twenty-eight male Wistar rats randomly assigned to four groups according to the evaluation periods (1, 3, 7 and 14 days) were used to assess the vascular permeability and histopathological reaction to RoekoSeal, AH Plus and Sealapex (new formulation) sealers, using saline and Chloropercha as negative and positive controls, respectively. Seven rats were sacrificed per period. The biocompatibility of the sealers was evaluated spectrophotometrically and histopathologically. RESULTS: At day 14, Sealapex produced significantly more inflammatory exudate than AH Plus and RoekoSeal (P < 0.05); however, there was no significant difference between AH Plus and RoekoSeal (P > 0.05). Sealapex (new formulation) was the most irritating sealer, producing severe inflammation with the presence of multinucleated giant cells. RoekoSeal was the most biocompatible sealer, producing the least amount of inflammatory exudate. CONCLUSIONS: RoekoSeal root canal sealer was biocompatible when implanted in connective tissue.

Accuracy of the iPex multi-frequency electronic apex locator in primary molars: an ex vivo study.

AIM: To evaluate ex vivo the accuracy of the iPex multi-frequency electronic apex locator (NSK Ltd, Tokyo, Japan) for working length determination in primary molar teeth. METHODOLOGY: One calibrated examiner determined the working length in 20 primary molar teeth (total of 33 root canals). Working length was measured both visually, with the placement of a K-file 1 mm short of the apical foramen or the most coronal limit of root resorption, and electronically using the electronic apex locator iPex, according to the manufacturers' instructions. Data were analysed statistically using the intraclass correlation (ICC) test. RESULTS: Comparison of the actual and the electronic measurements revealed high correlation (ICC = 0.99) between the methods, regardless of the presence or absence of physiological root resorption. CONCLUSIONS: In this laboratory study, the iPex accurately identified the apical foramen or the apical opening location for working length measurement in primary molar teeth.

NLRP12 Attenuates Inflammatory Bone Loss in Experimental Apical Periodontitis.

Apical periodontitis is an inflammatory disorder that results from the host immune response to microbial infection through the dental pulp, leading to alveolar bone destruction. The nod-like receptor 12 (NLRP12) is an atypical intracellular sensor of the NLR family that is involved in the negative regulation of several inflammatory conditions and also osteoclastogenesis. However, the role of NLRP12 in the regulation of immune response and bone loss induced by bacterial infection remains unclear. Here we investigated the development of apical periodontitis in wild-type (WT) and NLRP12 knockout (NLRP12-/-) mice by using micro-computed tomography together with histological, immunohistochemical, and molecular analyses. We found that NLRP12-/- mice are highly susceptible to apical periodontitis induced by bacterial infection, which is associated with an elevated infiltration of neutrophils and macrophages, periapical lesion extension, and alveolar bone destruction. Furthermore, NLRP12-/- mice showed a high expression of inflammatory cytokines ( Il1b, Il6, and Tnfa) and the osteoclastogenic markers ( Rankl and Acp5) in the periapical tissues. Consistent with this observation, NLRP12-/- mice showed an increased number of tartrate-resistant acid phosphatase-positive cells lining the apical periodontitis site, which was associated with augmented expression of the osteoclast effector genes, Ctsk and Mmp9. Mechanistically, NLRP12-deficient preosteoclasts showed elevated IκB-α degradation and p65 phosphorylation when stimulated with receptor activator of nuclear factor (NF)-κB ligand (RANKL). Similarly, increased IκB-α degradation was observed in the periapical tissue of NLRP12-/- mice. Furthermore, our in vitro study showed that preosteoclasts from NLRP12-/- mice exhibited higher RANKL-induced osteoclastogenesis, which was synergistically amplified by interleukin-1ß and tumor necrosis factor α (mimicking an inflammatory periapical milieu). In conclusion, our data show that NLRP12 exhibits a protective role in the periapical bone destruction by attenuating inflammation and osteoclastogenesis through negative regulation of the NF-κB pathway.

Ex vivo evaluation of the accuracy of two electronic apex locators during root canal length determination in primary teeth.

AIM: To evaluate ex vivo the accuracy of two electronic apex locators during root canal length determination in primary incisor and molar teeth with different stages of physiological root resorption. METHODOLOGY: One calibrated examiner determined the root canal length in 17 primary incisors and 16 primary molars (total of 57 root canals) with different stages of root resorption based on the actual canal length and using two electronic apex locators. Root canal length was measured both visually, with the placement of a K-file 1 mm short of the apical foramen or the apical resorption bevel, and electronically using two electronic apex locators (Root ZX II--J. Morita Corp. and Mini Apex Locator--SybronEndo) according to the manufacturers' instructions. Data were analysed statistically using the intraclass correlation (ICC) test. RESULTS: Comparison of the actual root canal length and the electronic root canal length measurements revealed high correlation (ICC = 0.99), regardless of the tooth type (single-rooted and multi-rooted teeth) or the presence/absence of physiological root resorption. CONCLUSIONS: Root ZX II and Mini Apex Locator proved useful and accurate for apex foramen location during root canal length measurement in primary incisors and molars.

Biofilm on the apical region of roots in primary teeth with vital and necrotic pulps with or without radiographically evident apical pathosis.

AIM: To evaluate, by scanning electron microscopy (SEM), the presence of biofilms on the external surfaces of the apical third of roots of human primary teeth with vital or necrotic pulps with and without radiographically evident periradicular pathosis. METHODOLOGY: Eighteen teeth were selected: group I - normal pulp (n = 5), group II - pulp necrosis without radiographic evidence of periapical pathosis (n = 7) and group III - pulp necrosis with well-defined radiographic periapical pathosis (n = 6). After extraction, the teeth were washed with saline and immersed in 0.03 g mL(-1) trypsin solution for 20 min. The teeth were then washed in sodium cacodilate buffer and stored in receptacles containing modified Karnovsky solution. The teeth were sectioned, dehydrated in an ethanol series, critical-point dried with CO(2), sputter coated with gold and the external root surface in the apical third examined by SEM. RESULTS: In the teeth of groups I and II, the apical root surfaces were covered by collagen fibres, with no evidence of bacteria (100%). In the teeth of group III, the root apices had no collagen fibres but revealed resorptive areas containing microorganisms (cocci, bacilli, filaments and spirochetes) in all cases (100%). CONCLUSION: Microorganisms organized as biofilms on the external root surface (extraradicular infection) were detected in primary teeth with pulp necrosis and radiographically visible periapical pathosis.

Er:YAG laser: antimicrobial effects in the root canals of dogs' teeth with pulp necrosis and chronic periapical lesions.

OBJECTIVE: Our goal in this study was to evaluate the antimicrobial effect of Er:YAG laser applied after biomechanical preparation of the root canals of dog's teeth with apical periodontitis. BACKGROUND DATA: Various in vitro studies have reported effective bacterial reduction in infected root canals using Er:YAG laser. However, there is no in vivo research to support these results. METHODS: Forty root canals of dogs' premolar teeth with pulp necrosis and chronic periapical lesions were used. An initial microbiological sample was taken, and after biomechanical preparation was carried out, a second microbiological sample was taken. The teeth were divided into two groups: Group I-biomechanical preparation was taken of root canals without Er:YAG laser application; Group II-biomechanical preparation was taken of root canals with Er:YAG laser application using 140-mJ input, 63-mJ output/15 Hz. After coronal sealing, the root canals were left empty for 7 days at which time a third microbiological sample was taken. The collected material was removed from the root canal with a #40 K file and placed in transport media. It was serially diluted and seeded on culture dishes selective for anaerobes, aerobes, and total streptococci. Colony-forming units per milliliter (CFU/mL) were counted. RESULTS: Groups I and II showed an increase of CFU/mL for all microorganisms 7 days after treatment, being statistically significant for anaerobes in Group I and for anaerobes and total streptococci in Group II. When comparing CFU/mL of Groups I and II, there was a statistically significant increase after 7 d for total streptococci in Group II. CONCLUSION: Er:YAG laser applied after biomechanical preparation did not reduce microorganisms in the root canal system.

Root canal morphology of primary molars: a micro-computed tomography study.

AIM: This was to investigate the root canal morphology of primary molar teeth using micro-computed tomography. METHODS: Primary maxillary (n = 20) and mandibular (n = 20) molars were scanned at a resolution of 16.7 µm and analysed regarding the number, location, volume, area, structured model index (SMI), area, roundness, diameters, and length of canals, as well as the thickness of dentine in the apical third. Data were statistically compared by using paired-sample t test, independent sample t test, and one-way analysis of variance with significance level set as 5%. RESULTS: Overall, no statistical differences were found between the canals with respect to length, SMI, dentine thickness, area, roundness, and diameter (p > 0.05). A double canal system was observed in the mesial and mesio-buccal roots of the mandibular and maxillary molars, respectively. The thickness in the internal aspect of the roots was lower than in the external aspect. Cross-sectional evaluation of the roots in the apical third showed flat-shaped canals in the mandibular molars and ribbon- and oval-shaped canals in the maxillary molars. CONCLUSIONS: External and internal anatomy of the primary first molars closely resemble the primary second molars. The reported data may help clinicians to obtain a thorough understanding of the morphological variations of root canals in primary molars to overcome problems related to shaping and cleaning procedures, allowing appropriate management strategies for root canal treatment.

TNF-alpha promotes an odontoblastic phenotype in dental pulp cells.

Dental pulp cells can differentiate toward an odontoblastic phenotype to produce reparative dentin beneath caries lesions. However, the mechanisms involved in pulp cell differentiation under pro-inflammatory stimuli have not been well-explored. Thus, we hypothesized that the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) could be a mediator involved in dental pulp cell differentiation toward an odontoblastic phenotype. We observed that TNF-alpha-challenged pulp cells exhibited increased mineralization and early and increased expression of dentin phosphoprotein (DPP), dentin sialoprotein (DSP), dentin matrix protein-1, and osteocalcin during a phase of reduced matrix metalloproteinase (MMP) expression. We investigated whether these events were related and found that p38, a mitogen-activated protein kinase, differentially regulated MMP-1 and DSP/DPP expression and mediated mineralization upon TNF-alpha treatment. These findings indicate that TNF-alpha stimulates differentiation of dental pulp cells toward an odontoblastic phenotype via p38, while negatively regulating MMP-1 expression.