TLR2 agonist prevents the progression of periapical lesions in mice by reducing osteoclast activity and regulating the frequency of Tregs.

AIM: To evaluate the role of regulatory T lymphocytes (Tregs) in the presence or absence of the synthetic ligand Pam3Cys during the progression of periapical lesion in wild-type (WT) and toll-like receptor 2 knockout (TLR2KO) mice. METHODOLOGY: A total of 130 C57BL/6 male WT and TLR2KO mice were allocated into control (n = 5) and experimental (periapical lesion induction) (n = 10) groups. In specific groups (WT+Pam3cys and TLR2KO+Pam3cys), the synthetic ligand Pam3cys was administered intraperitoneally every 7 days, according to the experimental period (14, 21 and 42 days). At the end of those periods, the animals were euthanized, and the mandible and the spleen were submitted to histotechnical processing. Mandible histological sections were analysed by haematoxylin and eosin, TRAP histoenzymology and immunohistochemistry (FOXP3, RANK, RANKL and OPG). Spleen sections were analysed by immunohistochemistry (FOXP3). RESULTS: The inflammatory infiltrate and bone resorption were more intense in the TLR2KO group compared to the WT group. The animals that received the Pam3cys had smaller periapical lesions when compared to the animals that did not receive the ligand (p < .05). TLR2KO animals showed a significant increase in the number of osteoclasts when compared to TLR2KO+Pam3cys group (p < .05). At 21 days, the WT+Pam3cys group had a lower number of osteoclasts when compared to the WT animals (p = .02). FOXP3 expression was more intense in the WT+Pam3cys groups when compared to the WT animals in the 42 days (p = .03). In the spleen analysis, the WT+Pam3cys group also had a higher expression of FOXP3 when compared to the WT animals at 14 and 42 days (p = .02). Concerning RANKL, there was a reduction in staining in the KOTLR2+Pam3cys groups at 21 and 42 days (p = .03) and a higher binding ratio between RANK/RANKL in animals that did not receive the ligand. CONCLUSION: Administration of the Pam3cys increased the proliferation of Tregs, showed by FOXP3 expression and prevented the progression of the periapical lesion in WT mice. On the other hand, in the TLR2KO animals, Treg expression was lower with larger areas of periapical lesions. Finally, systemic administration of the Pam3cys in KO animals was able to limit the deleterious effects of the absence of the TLR2 receptor.

The effects of NLRP3 inflammasome inhibition or knockout in experimental apical periodontitis induced in mice.

OBJECTIVE: To evaluate the effects of NLRP3 inflammasome inhibition or knockout in experimental apical periodontitis (AP) induced in mice. METHODS: The experimental AP was induced by pulpal exposure. To evaluate NLRP3-specific inhibitor medication (MCC950), WT mice received intraperitoneal injections, while the control received PBS (n = 10). In addition, to evaluate NLRP3 knockout, 35 wild-type (WT) and 35 NLRP3-/- mice were divided into a control group (without pulpal exposure, n = 5) and three experimental groups: after 2, 14 and 42 days after pulpal exposure (n = 10). Microscopic and molecular analyzes were carried out using a significance level of 5%. RESULTS: Exposure to MCC950 did not affect the periapical lesion size after 14 days (P = 0.584). However, exposed mice had a lower expression of IL-1ß, IL-18 and caspase-1 (P = 0.010, 0.016 and 0.002, respectively). Moreover, NLRP3-/- mice showed a smaller periapical lesion after 14 and 42 days (P = 0.023 and 0.031, respectively), as well as a lower expression of IL-1ß after 42 days (P < 0.001), of IL-18 and caspase-1 after 14 (P < 0.001 and 0.035, respectively) and 42 days (P = 0.002 and 0.002, respectively). NLRP3-/- mice also showed a lower mRNA for Il-1ß, Il-18 and Casp1 after 2 (P = 0.002, 0.036 and 0.001, respectively) and 14 days (P = 0.002, 0.002 and 0.001, respectively). CONCLUSIONS: NLRP3 inflammasome inhibition or knockout can attenuate the inflammatory events that result in the periapical lesion (AP) formation after pulpal exposure in mice. CLINICAL RELEVANCE: The NLRP3 inflammasome may be a therapeutic target for AP, and new approaches may verify the impact of its inhibition (through intracanal medications or filling materials) on the bone repair process and treatment success.

Root canal conicity determination of primary second molars using nanotomography: An in vitro study.

BACKGROUND: The conicity of the root canals of primary teeth is an important measure for endodontic therapies. However, determining this conicity depends on the methods employed, which requires further investigation. AIM: The aim of this study was to determine the conicity of the root canals of the upper and lower primary second molars using nanotomography (nCT). DESIGN: An in vitro study was performed using nine primary second molars, both upper and lower, subjected to nCT. Comparisons between the diameters of root canals were performed between the thirds (cervical-D0, middle-D5, and apical-D7). The conicity (%) was determined for each root canal from cervical to apical. Data were statistically analyzed with a significance level of 5%. RESULTS: The conicity ranged from 2% to 8% for the upper primary second molars. Significant differences in root canal diameter between the thirds (D0, D5, and D7 points) were observed in the mesio- and distobuccal roots (p < .05), but not in the palatal roots (p > .05). For the lower primary second molars, the conicity ranged from 2% to 17%, as well as significant differences in root canal diameter between the thirds (D0, D5, and D7 points) were observed in all roots (distal, mesiobuccal, and mesiolingual; p < .05). CONCLUSION: The conicity of the upper primary second molars was different from that of the lower ones, which showed a greater variability.

Systemic inhibition of 5-lipoxygenase by MK-886 exacerbates apical periodontitis bone loss in a mouse model.

BACKGROUND: To investigate if 5-LO selective inhibitor (MK-886) could be used for systemic treatment of experimentally induced apical periodontitis in a mouse model. METHODS: Twenty-four C57BL/6 mice were used. After coronal opening, a solution containing Escherichia coli LPS (1.0 µg/µL) was inoculated into the root canals of the lower and upper right first molars (n = 72 teeth). After 30 days apical periodontitis was established, and the animals were treated with MK-886 (5 mg/kg), a 5-LO inhibitor, for 7 and 14 days. The tissues were removed for histopathological and histometric analyses, evaluation of osteoclast number and gene expression for receptor activator of nuclear factor kappa-B (Tnfrsf11a), receptor activator of nuclear factor kappa-B ligand (Tnfsf11), osteoprotegerin (Tnfrsf11b), tartrate-resistant acid phosphatase (Acp5), matrix metalloproteinase-9 (Mmp9), cathepsin K (Ctsk) and calcitonin receptor (Calcr). Statistical data analysis was performed using Kruskal Wallis followed by Dunn's tests (α = 0.05). RESULTS: Administration of MK-886 for 7 days exerted no effect on apical periodontitis progression compared to LPS inoculation without treatment (p = 0.3549), while treatment for 14 days exacerbated bone loss (p < 0.0001). Administration of MK-886 enhanced osteoclastogenesis signaling and osteoclast formation within 7 days (p = 0.0005), but exerted no effect at 14 days (p > 0.9999). After 7 days of treatment, MK-886 induced mRNA expression for Acp5 (p = 0.0001), Calcr (p = 0.0003), Mmp9 (p = 0.0005) and Ctsk (p = 0.0008), however no effect in those gene expression was observed after 14 days (p > 0.05). CONCLUSION: Systemic treatment with MK-886 exacerbated LPS-induced apical periodontitis in a mouse model.

Self-ligating brackets exhibit accumulation of high levels of periodontopathogens in gingival crevicular fluid.

Different types of brackets seem to influence the disruption of the oral microbial environment. Therefore, the aim of this study was to evaluate the influence of self-ligating brackets on the gingival crevicular fluid levels of the putative periodontal pathogens Aggregatibacter actinomycetemcomitans sorotype a (Aaa), Tannerella forsythia, Fusobacterium nucleatum, and Porphyromonas gingivalis. Sixty samples of crevicular fluid of twenty patients (11 boys and 9 girls) were analysed at baseline (T0) and after 30 (T1) and 60 (T2) days of bonding of the self-ligating (In-Ovation®R, Dentsply, GAC or SmartClip™, 3 M Unitek, Monrovia, CA, USA) and of one conventional bracket (Gemini™, 3 M Unitek, Monrovia, CA, USA) used with elastomeric ligatures. Total DNA from samples was extracted using CTAB-DNA precipitation method and Real-time PCR was performed to analyse bacterial level. Non-parametric Friedman and Wilcoxon tests were used for data analysis (p value of < 0.05). F. nucleatum presented a different level among the different brackets at T1 (p = 0.025), the highest level in the Gemini™ bracket when compared to the SmartClip™ bracket (p = 0.043). P. ginigvalis levels increased in the In-Ovation®R (p = 0.028) at T1. The subgingival levels of bacterial species associated with periodontal disease P. ginigvalis increased in the self-ligating brackets In-Ovation®R.Clinical Relevance: Some kinds of brackets could provide more retentive sites than others, and it seems to modulate the subgingival microbiota, since, in this study, we could observe the increase of the species associated with periodontal disease. Preventive protocols should be adopted in the use of self-ligating brackets.

Photosensitizers attenuate LPS-induced inflammation: implications in dentistry and general health.

Antimicrobial photodynamic therapy (aPDT) is a complementary therapeutic modality for periodontal and endodontic diseases, in which Gram-negative bacteria are directly involved. Currently, there are few evidences regarding the effects of aPDT on bacterial components such as lipopolysaccharide (LPS) and it would represent a major step forward in the clinical use of this therapy. In this context, this study aimed to evaluate the efficacy of different photosensitizers (PSs) used in aPDT in LPS inhibition. Four PSs were used in this study: methylene blue (MB), toluidine blue (TBO), new methylene blue (NMB), and curcumin (CUR). Different approaches to evaluate LPS interaction with PSs were used, such as spectrophotometry, Limulus amebocyte lysate (LAL) test, functional assays using mouse macrophages, and an in vivo model of LPS injection. Spectrophotometry showed that LPS decreased the absorbance of all PSs used, indicating interactions between the two species. LAL assay revealed significant differences in LPS concentrations upon pre-incubation with the different PSs. Interestingly, the inflammatory potential of LPS decreased after previous treatment with the four PSs, resulting in decreased secretion of inflammatory cytokines by macrophages. In vivo, pre-incubating curcumin with LPS prevented animals from undergoing septic shock within the established time. Using relevant models to study the inflammatory activity of LPS, we found that all PSs used in this work decreased LPS-induced inflammation, with a more striking effect observed for NMB and curcumin. These data advance the understanding of the mechanisms of LPS inhibition by PSs.

Alteration of the oral microbiota may be a responsible factor, along with estrogen deficiency, by the development of larger periapical lesions.

OBJECTIVES: To answer the questions: (1) Does reducing estrogen levels influence the microbial composition of the oral cavity? (2) Does the presence of periapical lesion (PL) cause changes in the oral microbiota? (3) Since estrogen deficiency alters the oral microbiota, can this be one of the factors that contribute to the increase of the PL? MATERIALS AND METHODS: Thirty-six rats were divided into four groups: sham (control), ovariectomy (OVX), control with PL (Sham + PL), and OVX + PL. After 9 weeks of OVX, the lower first molars were submitted to PL induction. After 21 days, the microbiological collection of the oral cavity was performed, and the animals were euthanized. The contents were evaluated by the checkerboard DNA-DNA hybridization method, to verify the prevalence of 40 bacterial species (divided into 7 microbial complexes). The blocks containing the lower first molars were submitted to histotechnical processing and staining with hematoxylin and eosin (HE), for the measurement of the periapical lesion area. The results were submitted to ANOVA and Kruskal-Wallis tests and Tukey and Dunn post-tests, with a significance level of 5%. RESULTS: In conditions of estrogen deficiency, there was alteration of the oral microbiota. The OVX groups had a higher amount of bacteria compared to the SHAM group in most of the microbial complexes (p < 0.001). The animals in the control group (with or without lesion) did not present a statistically significant difference (p > 0.001) in any of the microbial complexes. The PLs in OVX animals were significantly higher compared to SHAM animals (p < 0.001). CONCLUSIONS: Hypoestrogenicity conditions interfere in the oral microbiota by increasing the amount of bacteria in the saliva and influencing the progression of periapical lesions. CLINICAL RELEVANCE: This inedited study shows that deficiency of estrogen leads to alteration of the oral microbiota.

Effect of root surface treatment with denusomab after delayed tooth replantation.

OBJECTIVES: To evaluate denosumab, a human monoclonal antibody that mimics the effects of osteoprotegerin in bone metabolism, as a topical treatment of root surface to be used prior to delayed tooth replantation. MATERIALS AND METHODS: Thirty-six rats' right incisors were used. Teeth were extracted and divided into: delayed replantation without root surface treatment (control); delayed replantation with root surface treatment with denosumab 60 mg/mL and 30 mg/mL, respectively, for 10 min both experimentals groups. After that, the root canals were filled with calcium hydroxide and replanted. After 15 and 60 days, the animals were euthanized, and the samples were collected and processed for microscopic analysis. Histological sections were performed, and stained with HE to describe the dental characteristics, measure ankylosis, replacement resorption, and dental resorption by conventional microscopy. Also, was performed Brown & Brenn staining and immunohistochemistry for RANKL, OPG, and periostin. RESULTS: Denosumab 60 mg/mL reducted ankylosis (p < 0.0001), replacement resorption (p < 0.0001), and tooth resorption, 60 days after replantation, compared to untreated replanted teeth (p < 0.005). Lower bacterial contamination in root surface in the denosumab treatment groups was found, regardless of the concentration used (p < 0.001). Also, denosumab treatment inhibited the expression of RANKL without modulating OPG. Periostin was observed in periodontal ligament of replanted tooth, although this labelling was absent in the ankylosis areas, in both experimental periods. CONCLUSION: Treatment of the root surface with denosumab at 60 mg/mL of rat teeth before delayed replantation reduced dental root resorption compared with the untreated teeth after 60 days. CLINICAL RELEVANCE: Survival of a replanted tooth has been a challenge in clinical practice. The use of a medication, such as denosumab, to limit dental root resorption represents an important therapeutical approach.

Effect of non-steroidal anti-inflammatory drugs on pulpal and periapical inflammation induced by lipopolysaccharide.

OBJECTIVES: The objective of this study was to evaluate the effect of non-steroidal anti-inflammatory drugs (NSAIDs) in controlling pulpal and periapical inflammation in vivo as a potential coadjutant systemic therapy for pulpitis. MATERIALS AND METHODS: A suspension containing E. coli lipopolysaccharide (LPS; 1.0 µg/µL) was inoculated into the pulp chamber of the first molars of C57BL/6 mice (n = 72), and the animals were treated daily with indomethacin or celecoxib throughout the experimental periods. After 7, 14, 21, and 28 days, the tissues were removed for histopathological, histoenzymology, histometric, and immunohistochemical evaluation. RESULTS: Inoculation of LPS into the pulp chamber induced the synthesis of the enzyme cyclooxygenase-2 (COX-2) in dental pulp and periapical region. Indomethacin and celecoxib treatment changed the profile of inflammatory cells recruited to dental pulp and to the periapex, which was characterized by a higher mononuclear cell infiltrate, compared to LPS inoculation alone which recruited a higher amount of polymorphonuclear neutrophils. Administration of indomethacin for 28 days resulted in the development of apical periodontitis and increased osteoclast recruitment, unlike celecoxib. CONCLUSIONS: NSAIDs indomethacin and celecoxib changed the recruitment of inflammatory cells to a mononuclear profile upon inoculation of LPS into the pup chamber, but indomethacin enhanced periapical bone loss whereas celecoxib did not. CLINICAL RELEVANCE: Celecoxib, a selective COX-2 inhibitor, can change the profile of inflammatory cells recruited to the dental pulp challenged with LPS and might a be potential systemic coadjutant for treatment of pulpitis.

Vitamin D deficiency is a risk factor for delayed tooth eruption associated with persistent primary tooth.

OBJECTIVE: To verify the association between 25(OH)D level and polymorphisms in the vitamin D receptor gene (VDR) with the disturbance in the dental development and eruption. DESIGN: A total of 183 children from two datasets were evaluated. The first dataset was a case-control (15:15) designed to assess if persistent primary tooth (PPT) is associate with serum 25(OH)D level and with genetic polymorphisms in VDR. The second dataset of genomic DNA samples from 54 children with delayed tooth eruption (DTE) and 99 controls were analysed to verify if genetic polymorphisms in VDR (rs2228570 and rs739837) are associated with DTE. The 25(OH)D and the genotyping/allele distribution were analysed using the T-test and chi-square test, respectively. RESULTS: The level of 25(OH)D in the PPT group (24.9 ± 6.4 mg/mL) was significantly lower than the control (30.0 ± 7.0 mg/mL) (p=.047). Our data show that children with 25(OH)D deficiency are more likely to present PPT (OR = 2.36; 95%CI: 1.51, 3.70). The rs739837 and rs2228570 polymorphisms were not associated with DTE (OR = 1.44; 95%CI: 0.87, 2.39 and OR = 0.80; 95%CI: 0.45, 1.44, respectively). CONCLUSIONS: Vitamin D deficiency is a risk factor for PPT.

Esthetic elastomeric ligatures: Quantification of bacterial endotoxin in vitro and in vivo.

INTRODUCTION: The objective of this study was to evaluate in vitro and in vivo bacterial endotoxin (LPS) adhesion in polyurethane and silicone esthetic elastomeric orthodontic ligatures. The null hypotheses tested were: (1) there is no LPS adhesion in esthetic elastomeric orthodontic ligatures; and (2) there is no difference in the LPS adhesion between different brands of these ligatures. METHODS: For the in vitro study, 4 types of esthetic elastomeric ligatures were used (Sani-Ties and Sili-Ties [Dentsply GAC, Islandia, NY;] and Mini Single Case Ligature Stick and Synergy low-friction ligatures [Rocky Mountain Orthodontics, Denver, Colo]), contaminated or not with endotoxin solution. Replicas of twisted wire and cast stainless steel ligatures were used as control. For the in vivo study, 10 male and 10 female patients, aged 15-30 years, received the same 4 types of ligatures, 1 of each inserted in the maxillary and mandibular canines, randomly. Twenty-one days later, the ligatures were removed, and endotoxin quantification was performed using the Limulus amebocyte lysate test. Data were analyzed (α = 0.05) using the Kruskal-Wallis test and Dunn's posttest or analysis of variance and Tukey's posttest. RESULTS: GAC silicone group had the lowest median contamination (1.15 endotoxin units/mL; P <0.0001) in vitro. In the in vivo study, the GAC silicone group had the lowest mean contamination (0.577 endotoxin units/mL; P <0.001). In both studies, the other groups did not present a significant difference when compared with each other (P >0.05). CONCLUSIONS: LPS exhibited an affinity for all the tested polyurethane and silicone elastomeric ligatures. GAC silicone ligatures presented with lower amounts of LPS attached to their surfaces. Thus, both null hypotheses were rejected.

Radiotherapy impairs adhesive bonding in permanent teeth.

OBJECTIVES: To evaluate the in vitro effects of radiotherapy (RT) on the morphological surface of the enamel and dentin and to determine the best adhesive system and most appropriate time to restore teeth in head and neck cancer patients. METHODS: Sixty third molars were cut into 120 enamel fragments and 120 dentin fragments and divided into four groups (n = 30): G1 (control): nonirradiated, only restorative procedure; G2: restorative procedure immediately before RT; G3: restorative procedure immediately after RT; and G4: restorative procedure 6 months after RT. Each group was divided into two subgroups: Adper™ Single Bond 2 (SB) and Clearfill SE Bond (CL) based on the material used. After RT and restorative procedures, the specimens were subjected to confocal microscopy and shear bond strength test. Data were analyzed using a two-way ANOVA followed by Tukey's test at a significance level of 5%. RESULTS: Morphological changes were observed in both substrates after a cumulative dose of 40 Gy, and after 60 Gy, the changes were more evident in both substrates. CL had the highest strength values in both substrates (p < 0.05), and G2 had the lowest strength values for the enamel and dentin (p < 0.05). CONCLUSIONS: Based on the in vitro study results, we can conclude that RT substantially changes the morphological surface of enamel and dentin and impairs the bond strength. The Clearfill system yielded better results than Adper Single Bond 2, and restoring teeth before RT resulted in the worst results in both substrates.

Minimally interventive restorative care of teeth with molar incisor hypomineralization and open apex-A 24-month longitudinal study.

AIM: To assess the efficacy of treatment using a minimally invasive approach (selective removal of carious tissue, restoration and preventive strategies) in immature permanent molars with MIH. DESIGN: A total of 281 patients, aged 6-8 years, with carious lesions (ICDAS 5-6), severe MIH, and incomplete root formation (one tooth/patient) were included. After clinical and radiographic examinations, selective carious tissue removal was performed, and the teeth received interim restoration for 6 months and were then restored with composite resin. Clinical and radiographic follow-up was undertaken, 6, 12, 18, and 24 months. A protocol of preventive oral care measures was established and repeated at each follow-up, including diet counselling, oral hygiene instruction, dental plaque control, and topical application of fluoride varnish containing CPP-ACP. All clinical procedures and evaluations were done by a single operator. RESULTS: Clinical and radiographic success was observed 24 months after treatment in 96.8% of the cases. Failures were due to enamel fracture at restoration margins, resulting in pulpitis and absence of apex closure. CONCLUSION: Selective removal of carious tissue, interim, and subsequently definitive restoration, combined with home and professional preventive measures, maintained marginal integrity of restorations in immature permanent molars with severe MIH, confirmed by pulp vitality and occurrence of apexogenesis.

RANKL is associated with persistent primary teeth and delayed permanent tooth emergence.

BACKGROUND: Tooth eruption is a process that is not fully understood. AIM: To evaluate whether genetic polymorphisms for RANK/RANKL/OPG are associated with delayed tooth emergence. To evaluate whether the relative expression of this genes is associated with persistent primary teeth. DESIGN: To evaluate whether genetic polymorphisms for RANK/RANKL/OPG could be involved in delayed tooth emergence, saliva samples from 160 children, aged 6-13 years old, were analysed. To test if there is correlation between gene expression of RANK/RANKL/OPG in children with delayed tooth emergence and persistent primary teeth, periapical tissue from 15 children with persistent primary teeth and from 15 control subjects were collected for qPCR analysis. RESULTS: Fifty-six children with delayed tooth emergence (35%) had at least one permanent tooth with delayed emergence. The T allele in RANKL (rs9594738) increased the risk of delayed tooth emergence (P = 0.02; OR = 1.71, 95%CI 1.09-2.75). The relative gene expression for RANKL and the ratio RANKL/OPG in children with delayed tooth emergence and persistent primary teeth were lower compared to controls (P = 0.02 and P = 0.005, respectively). CONCLUSIONS: Data suggest that the polymorphism rs9594738 in RANKL is associated with delayed permanent tooth emergence. Moreover, reduced relative gene expression of RANKL in periapical tissue is associated with persistent primary teeth.

Genetic polymorphism in RANK is associated with mandibular size.

OBJECTIVE: The aim of this study was to evaluate the association between genetic polymorphisms in RANK, RANKL and OPG with maxillary and mandibular dimensions in humans. DESIGN: DNA extracted from saliva and the rs3826620, rs9594738 and rs2073618 polymorphisms in RANK, RANKL and OPG, respectively, were analysed by real-time PCR. Four linear measurements (Co-Gn, GoPg, Co-Go and PTM-A) from lateral cephalograms were examined for the evaluation of craniofacial measurements. ANOVA testing and a multivariate linear regression analysis, adjusted for age and gender, were used for statistical analysis, with an alpha of 5%. Hardy-Weinberg equilibrium was also evaluated using the chi-square test within each polymorphism. SETTING: School of Dentistry of Ribeirão Preto, University of São Paulo. PARTICIPANTS: A total of 100 unrelated non-syndromic Brazilian Caucasian subjects were included in this study. RESULTS: The polymorphism in RANK was associated with a higher Go-Pg measurement (p = .039). In the multivariate analysis, adjusted for age and gender, the polymorphism in RANK was associated with Go-Pg (p = .017) and Co-Gn (p = .043). CONCLUSION: The polymorphism rs3826620 in RANK is associated with the mandibular size.

Dental Flossing and Proximal Caries in the Primary Dentition: A Systematic Review.

PURPOSE: To evaluate in a systematic review whether the use of dental floss in primary teeth is associated with a reduction in incidence of proximal caries. MATERIALS AND METHODS: Searches were performed using the following databases: PubMed MEDLINE, Web of Science, Bireme, Scopus and The Cochrane Library. Only 5 studies were eligible for inclusion. The quality assessment and bias control of the studies were carried out based on the Fowkes and Fulton Guideline. The study concept was first registered in the international prospective register of systematic reviews (PROSPERO). RESULTS: Flossing was professionally performed in one study and self-reported (by parents or by the children) through questionnaires in all other 4 studies. In the first study, the authors concluded that daily interdental flossing resulted in a significant reduction in the incidence of proximal caries in deciduous teeth during a 20-month period. Two cross-sectional studies found that the use of interdental floss did not show any relevant association with the prevalence of caries; one study found that a higher the frequency of flossing was associated with higher caries experience, and the other found an association between severe caries and the use of dental floss, independently of the flossing frequency. CONCLUSION: There is only one study in the current literature showing evidence of an association between the use of dental floss and proximal caries reduction on primary dentition. However, the use of dental floss should never be discouraged. Healthy habits acquired in childhood continue throughout adult life, with numerous oral- and general-health benefits.

Comparison between one-session root canal treatment with aPDT and two-session treatment with calcium hydroxide-based antibacterial dressing, in dog's teeth with apical periodontitis.

To evaluate one-session endodontic treatment with aPDT and two-session treatment with calcium hydroxide (CH)-based dressing in dog's teeth with apical periodontitis. After experimental induction of apical periodontitis, 48 teeth were randomly assigned to the following groups: groups OS/aPDT120d and OS/aPDT180d (one-session treatment with aPDT) and groups TS/CH120d and TS/CH180d (two-session treatment with CH-based dressing-control groups). The animals were euthanized after 120 and 180 days. After histotechnical processing, microscopic and radiographic analyses were performed. Data were analyzed by Kruskal-Wallis and Fisher's exact tests (α = 0.05). Groups TS/CHs presented repaired resorbed cemental areas, with collagen bundles and few inflammatory cells. In groups OS/aPDTs, the areas of cemental resorption were not repaired with reduced presence of cells and fibers. In the analysis of the apical closure, fluorescence microscopy and percentage of radiographic reduction of lesions, there was significant difference between groups TS/CH120d and OS/aPDT120d and between TS/CH180d and OS/aPDT180d (p < 0.05). Groups TS/CHs had weak RANKL expression and positive immunostaining for RANK and OPG. In OS/aPDT120d, there was positive immunostaining for RANKL. In OS/aPDT180d, the three osteoclastogenesis markers were expressed. The results using aPDT were worse than those obtained with two-session endodontic treatment using a CH-based dressing in teeth with apical periodontitis.

Enamel permeability and resistance to acid challenges after systemic use of sodium alendronate: a study in rat teeth.

OBJECTIVES: To evaluate the enamel resistance and permeability of rat teeth to acid challenges after systemic use of sodium alendronate. MATERIALS AND METHODS: Eighteen Wistar rats (36 teeth), aged 36-42 days (200-230 g), were assigned into two groups: alendronate group (n = 20 teeth), which received two weekly doses of 1 mg/kg of alendronate, via gavage; and a non-alendronate group (n = 16 teeth), which received only distilled water. After 60 days, the animals were killed, the maxillary incisors were extracted and used for the artificial induction of the caries lesion (pH cycling regimen) and erosion area (immersion cycles in cola-type soft drink) and for the enamel permeability test (dye penetration). The teeth were divided into alendronate group (n = 10) or non-alendronate group (n = 8) for each test. The quantitative response variables were the percent longitudinal change in Knoop microhardness (%LMC), the enamel carious/erosion lesion area (CELA) and enamel permeability. RESULTS: Groups were not significantly different (p > 0.05) with regard to the %LMC and enamel permeability (25.58 µm ± 12.73 and 25.40 µm ± 4.6 for the experimental and control groups, respectively). For CELA, it was not observed significant difference (p > 0.05) between the non-alendronate group (24.08 ± 1.36 and 25.22 ± 1.60, for caries and erosion, respectively) and the alendronate group (25.46 ± 1.60 and 25.0 ± 1.26) for caries and erosion, respectively). CONCLUSIONS: Based on the methodological conditions and the presented results of this study, sodium alendronate did not affect the longitudinal microhardness, demineralisation lesion area or permeability of the enamel after acid challenge; therefore, alendronate did not become the enamel of rats more resistant. CLINICAL RELEVANCE: The systemic alendronate treatment for 60 days did not change the enamel of rats regarding the susceptibility to acids.

Three-Dimensional Micro-Computed Tomography Analyses of Induced Periapical Lesions in Transgenic Mice.

The aim of this study was to evaluate the three-dimensional (3D) parameters given by the micro-computed tomography (µCT) analysis of experimentally induced periapical lesions in wild type (WT) and knockout mice for the interleukin 22 (IL-22 KO). Periapical lesions were induced in the mandibular first molars of wild type and IL-22 KO mice (n = 12 teeth/group). The animals were euthanized after the experimental periods of 7, 21 and 42 days. The mandibles were removed and exposed to µCT scanning. The analyses were performed by the CTAn software for the tree-dimensional parameters: Tissue Volume (TV), Lesion Volume (LV), Tissue Surface (TS), Lesion Surface (LS), Intersection Surface (IS), and Trabecular Pattern factor (Tb.Pf). After that, the tissue was subjected to routine histologic procedures and to immunohistochemistry analysis. Statistical analysis was performed in the GraphPad software. A t-test was used to compare the differences between the groups with significance level of 5%. The evaluation of the 3D parameters showed statistical significant difference between the groups only at the latest period of periapical lesion development (42 days), for the TV, LV, TS, LS and IS parameters. The immunohistochemistry evaluation confirmed the immunostaining for IL-22 only in the WT mice, surrounding the periapical lesion. There were no differences regarding the trabecular alveolar bone (Tb.Pf) that could influence the lesion development. In conclusion, the 3D parameters showed that the absence of IL-22 leads to detectable differences at 42 days of lesion progression, resulting in smaller periapical lesions.

Correlation Between Histomorphometric and Micro-computed Tomography Analysis of Periapical Lesions in Mice Model.

Periapical lesions are processes mediated from bacterial invasion on the pulp tissue, which results in inflammatory process and bone resorption. Animal models have been used for the study of cell interactions and inflammatory responses involved in periapical lesion. The use of different methods for morphometric evaluation of this lesion has been reported. However, due to the limitation of 2D methods, computerized microtomography (µCT) has been indicated. Therefore, the aim of this study was to evaluate the correlation between the histomorphometric measures of periapical lesions and the µCT analysis obtained in an animal experimental model. Briefly, the periapical lesions were induced by pulp exposal and after the experimental periods (7, 21 and 42 days) the mice were euthanized. The mandibles were evaluated under the µCT scanning and then were subjected to the routine histologic procedures, stained with hematoxilin and eosin. The periapical lesions were measured by the specific softwares of each technique. A weak correlation among the histomorphometric measurement and the 2D µCT analysis (r(2)= .204) and between the histomorphometric measurement and the 3D µCT analysis (r(2)= .237) was observed. A strong correlation between the 2D and 3D µCT analysis (r(2)= .867) was observed. Thereby, it can be concluded that the µCT is a method that allows a precise volumetric scanning and represents an important tool for morphometric evaluation.