Dingming Huang

A cone-beam computed tomography study of maxillary first permanent molar root and canal morphology in a Chinese population.

AIM This study evaluated root and canal morphology of permanent maxillary first molars in a Chinese population using cone-beam computed tomography scanning. METHODOLOGY The sample included 775 cone-beam computed tomography images of maxillary first molars; 627 of the subjects had unilateral qualifying molars and 74 had bilateral qualifying molars. The following observations were made: (1) frequency of root and canal numbers, (2) frequency of additional canals in the mesiobuccal root by sex, age, and tooth position, and (3) unilateral and bilateral occurrence of additional canals in the mesiobuccal root. RESULTS Fused roots were present in 2.71% of unilateral qualifying molars. Multiple canals were present in the following frequencies: two canals in 0.31%, three canals in 47.21%, four canals in 50.40%, five canals in 1.75%, and six canals in 0.31% of teeth. Additional canals were detected in 52.24% of mesiobuccal roots, 1.12% of distobuccal roots, and 1.76% of palatal roots. Patients aged 20 to 30 years showed a higher prevalence of additional mesiobuccal root canals. This prevalence did not differ with sex and tooth position. Most (71.11%) of the additional mesiobuccal root canals in subjects with bilateral qualifying molars were symmetric. CONCLUSION Cone-beam computed tomography scanning is an effective method for studying external and internal dental morphology. The root and canal configurations of maxillary first molars in this Chinese population were consistent with previously reported data. More attention should be given to the detection of additional canals in patients between 20 and 30 years of age. These data may facilitate successful endodontic treatment.

Evaluation of the root and canal morphology of mandibular first permanent molars in a western Chinese population by cone-beam computed tomography.

INTRODUCTION The purpose of this study was to evaluate the root and canal morphology of mandibular first permanent molars in a western Chinese population by using cone-beam computed tomography (CBCT). METHODS In this study, 558 samples were examined by CBCT. Details of sex, tooth position, the number of roots and canals, and the canal configuration were recorded. The root canal configuration was categorized and compared according to Vertuccis criteria. RESULTS Overall, 51.4% of the mandibular first permanent molars examined had four canals, and 25.8% had a separate distolingual root. In 48.1% of these, the fourth canal was in the separate distolingual root. In the two-rooted mandibular first permanent molars, 93.9% of the mesial root canals were of type IV, and 62.9% of the distal root canals were of type I. In the three-rooted samples, 94.4% of the mesial root canals were of type IV, and 98.6% of the distobuccal and 100% of the distolingual root canals were of type I. In addition, there was a higher incidence of three-rooted mandibular first permanent molars on the left side than on the right, but this relationship was not significantly correlated with sex. CONCLUSIONS Mandibular first permanent molars commonly have four canals and a higher prevalence for a separated distolingual canal in a western Chinese population.

Associations between Maxillary Sinus Mucosal Thickening and Apical Periodontitis Using Cone-Beam Computed Tomography Scanning: A Retrospective Study

INTRODUCTION This study evaluated the pathologic and spatial associations between apical periodontitis of the maxillary premolars/molars and the maxillary sinus mucosal thickening using cone-beam computed tomography (CBCT) scanning. METHODS CBCT images of 372 patients with 508 exposed maxillary sinuses were inspected retrospectively. Clinical features such as sex and age of the patients and pathologic findings of the maxillary sinus and adjacent teeth were recorded, graded, and analyzed. RESULTS Maxillary sinus mucosal thickening was found in 180 (48.4%) patients and 235 (46.2%) sinuses. The prevalence of maxillary sinus mucosal thickening increased dramatically as the severity of apical periodontitis increased (from 41.5% in those without periodontal disease to 100%). However, the nature of the spatial relationship between the maxillary sinus floor and the infected root tips or between the sinus floor and periapical lesions did not appear to have an effect on the prevalence of maxillary sinus mucosal thickening. Patients over 60 years of age had the highest prevalence of maxillary sinus mucosal thickening. CONCLUSIONS A retrospective inspection of CBCT images revealed that the prevalence and severity of maxillary sinus mucosal thickening were positively associated with the degree of apical periodontitis. CBCT imaging is applicable for the evaluation of the maxillary sinuses and adjacent teeth.

Expression of TRAF6 and pro-inflammatory cytokines through activation of TLR2, TLR4, NOD1, and NOD2 in human periodontal ligament fibroblasts

OBJECTIVE Human periodontal ligament fibroblasts (HPDLFs) play a crucial role in protecting against oral bacteria in periapical tissue. Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD) are two major forms of innate immune sensors that recognize microbial pathogens and initiate pro-inflammatory signalling. Tumour necrosis factor receptor-associated factor 6 (TRAF6) is an adapter protein for TLR-mediated nuclear factor-κB (NF-κB) signalling pathway activation that induces the production of pro-inflammatory cytokines. The aim of this study was to investigate the expression of TLR2, TLR4, NOD1, and NOD2 in HPDLFs. We also investigated the expression of TRAF6 and pro-inflammatory cytokines induced by the activation of TLRs and NODs. METHODS The expression of TLR2, TLR4, NOD1, and NOD2 was measured by reverse transcription-polymerase chain reaction (RT-PCR), flow cytometry, and immunostaining. HPDLFs were stimulated with TLR and NOD agonists. Then, the expression of TRAF6 was measured by real-time PCR and western blot. Concentrations of IL-1β, IL-6, and IL-8 in the culture supernatants were determined by enzyme-linked immunosorbent assay (ELISA). Finally, by using small interfering RNA (siRNA) for TRAF6, we analysed the production of IL-1β, IL-6, and IL-8 in HPDLFs upon stimulation with TLRs and NODs agonists. RESULTS We found clear mRNA and protein expression of TLR2, TLR4, NOD1, and NOD2 in HPDLFs. The expression levels of TRAF6 and pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) were markedly up-regulated upon the activation of TLRs and NODs. Furthermore, the co-activation of TLRs and NODs had synergistic effect on the production of TRAF6 and pro-inflammatory cytokines. We also found TRAF6 suppression resulted in reduced IL-1β, IL-6, and IL-8 expression upon TLR and NOD agonists challenge. CONCLUSION These findings indicated that TLR2, TLR4, NOD1, and NOD2 are functional receptors in HPDLFs during innate immune responses to invading bacteria, and a combination of signalling through TLRs and NODs leads to the synergistic enhancement of inflammatory reactions in HPDLFs. In addition, TLR and NOD signalling involving TRAF6 contribute to inflammatory responses in HPDLFs.

The Shaping Effect of the Combination of Two Rotary Nickel-Titanium Instruments in Simulated S-Shaped Canals

This study aimed to analyze the ability of ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) combined with Hero642 (MicroMega, Besancon, France) to shape the simulated S-shaped canals. Thirty simulated canals with double curvatures, 30 degrees coronally and 20 degrees apically, were randomly divided into three groups and prepared with different instruments: ProTaper in group 1, Hero642 in group 2, and a combination of ProTaper and Hero642 in group 3. All canals were scanned pre- and postoperatively. Each postinstrumentation image was superimposed with the preoperative one in a computer. The amount of material removed from canal wall after every instrument was measured at 14 points. Statistical analysis was performed by using an analysis of variance test at alpha = 0.05. Canals prepared with rotary ProTaper were straightened progressively after the use of F1, and great transportation was created. Hero642 and the combination instruments maintained the original shape of canal with a little transportation. However, the taper of canals prepared with Hero642 was relatively poor.

Apically extruded debris and irrigant with two Ni‐Ti systems and hand files when removing root fillings: a laboratory study

AIM To compare the amount of apically extruded debris and irrigant produced by two Ni-Ti instruments and hand files when removing root fillings, and to compare two experimental models. METHODOLOGY Sixty single straight root canals in human mandibular premolars were prepared with K-files and filled with gutta-percha and AH Plus sealer. The teeth were randomly divided into three groups of 20 for removal of the root filling material with Reciproc files (Group 1, RP), Mtwo retreatment files (Group 2, MR) or hand files (Group 3, H). Each group was then equally divided into experimental subgroups: A, with 1.5% agar gel model (AG); B, with empty tube model (ET). Apically extruded debris and irrigant was quantified by subtracting the initial weight of the test apparatus without a tooth from its weight after the root canal retreatment. Comparative analysis of the amount of apically extruded debris and irrigant for each of the instruments and the experimental models was performed. Time for gutta-percha removal was recorded. Data were statistically analysed using one-way analysis of variance. RESULTS Removal of root fillings with two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files in both experimental models (P < 0.05). More apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the 1.5% agar gel model (P > 0.05). Significantly more apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the empty tube model (P < 0.05). The time required to remove the root fillings followed Reciproc<Mtwo R<hand files (P < 0.05). CONCLUSIONS All the instruments produced apically extruded debris and irrigant. The two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files. A 1.5% agar gel can provide resistance to apically extruded debris and irrigant and may represent the clinical situation better than the empty tube model.

Mangiferin: a possible strategy for periodontal disease to therapy.

Periodontitis is one of the most widespread infectious inflammatory diseases, characterized by chronic bacterial infection of the supporting structures of the teeth, leading to tooth loss in adults. Mangiferin, a naturally occurring glucosylxanthone, has recently gained great attention, owing to potent antioxidant, anti-inflammatory, antidiabetic, immunomodulatory, and antitumor properties. These studies confirm that mangiferin, exert excellent antioxidant effect and act rapidly in the face of oxidative stress. Meanwhile, mangiferin could significantly inhibit the expression of pro-inflammatory cytokines. Especially, treated with mangiferin, the alveolar bone loss of rats with experimental periodontitis has been remarkably reduced. Given these bioactivity exhibited for mangiferin, we hypothesized that mangiferin may play an efficient role in therapy of periodontitis, which may offer new therapeutic options for the management of patients with periodontitis.

Bone morphogenetic protein 2-induced human dental pulp cell differentiation involves p38 mitogen-activated protein kinase-activated canonical WNT pathway

Both bone morphogenetic protein 2 (BMP2) and the wingless-type MMTV integration site (WNT)/β-catenin signalling pathway play important roles in odontoblast differentiation and dentinogenesis. Cross-talk between BMP2 and WNT/β-catenin in osteoblast differentiation and bone formation has been identified. However, the roles and mechanisms of the canonical WNT pathway in the regulation of BMP2 in dental pulp injury and repair remain largely unknown. Here, we demonstrate that BMP2 promotes the differentiation of human dental pulp cells (HDPCs) by activating WNT/β-catenin signalling, which is further mediated by p38 mitogen-activated protein kinase (MAPK) in vitro. BMP2 stimulation upregulated the expression of β-catenin in HDPCs, which was abolished by SB203580 but not by Noggin or LDN193189. Furthermore, BMP2 enhanced cell differentiation, which was not fully inhibited by Noggin or LDN193189. Instead, SB203580 partially blocked BMP2-induced β-catenin expression and cell differentiation. Taken together, these data suggest a possible mechanism by which the elevation of β-catenin resulting from BMP2 stimulation is mediated by the p38 MAPK pathway, which sheds light on the molecular mechanisms of BMP2-mediated pulp reparative dentin formation.

Distribution of Porphyromonas gingivalis fimA Genotypes in Chronic Apical Periodontitis Associated with Symptoms

INTRODUCTION Porphyromonas gingivalis (P. gingivalis) is an anaerobic bacterium involved in root canal infections whose fimbriae are classified into six genotypes (types I-V and Ib) based on nucleotide sequence. Accumulated evidence suggests there is significant association between P. gingivalis and some clinical symptoms of periodontal diseases. The present study aims to determine the prevalence of P. gingivalis fimA genotypes in apical periodontitis and to investigate the correlation between P. gingivalis fimA genotypes and clinical symptoms. METHODS Samples were obtained from 158 infected root canals with apical periodontitis. DNA was extracted and analyzed with a polymerase chain reaction-based identification assay. Odds ratios, 95% confidence intervals, and contingency coefficient were calculated for associating the fimA-specific genes with clinical symptoms. RESULTS P. gingivalis was detected in 39.9% of the inflected root canal samples and was found in 44.5% of P. gingivalis-positive specimens with symptoms. Types II (69.4%) were the most frequent in the symptomatic cases followed by type IV (32.7%). The occurrence of type I (64.3%) was significantly higher than any other genotypes in the asymptomatic apical periodontitis, whereas type II and type Ib were not identified. Statistical analysis revealed that the occurrences of types II, IV, and Ib fimA were associated with greater risk of clinical signs (swelling, sinus tract, or intracanal exudates) than type I. CONCLUSIONS Results from this study reinforce the association between P. gingivalis-specific fimA genotypic clones and apical periodontitis, indicating that fimA genotypes (types II, IV, and Ib) were related to the etiology of symptomatic periradicular diseases.

Occurrence of Dentinal Microcracks in Severely Curved Root Canals with ProTaper Universal, WaveOne, and ProTaper Next File Systems

INTRODUCTION This study aims to compare the incidence of dentinal microcracks produced by the ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), WaveOne (Dentsply Maillefer), and ProTaper Next (Dentsply Maillefer) file systems during root canal procedures in severely curved canals using a dyeing technique. METHODS Sixty extracted human molars with 25° to 40° root curvatures were divided into 3 groups of 20 canals each. ProTaper Universal, WaveOne, and ProTaper Next file systems were used for root canal procedures. Untreated root canals of 60 molars served as negative controls. After preparation, all roots were stained with 1% methylene blue for 24 hours. Roots were then sectioned at the most curved plane and 2 mm below and above the most curved plane with a low-speed saw under cold water. A stereomicroscope was used to inspect dentinal microcracks at 60× magnification, and differences between these 3 instrument groups were analyzed using the chi-square test. RESULTS The ProTaper Next system induced less complete and incomplete dentinal microcracks compared with the ProTaper Universal and WaveOne systems (P < .05), and there were no significant differences between the ProTaper Universal and WaveOne systems (P > .05). The ProTaper Universal and WaveOne systems induced significantly more complete cracks in the plane 2 mm above the most curved plane compared with either of the other 2 planes (P = .004). CONCLUSIONS The ProTaper Next system induces less dentinal microcracks during root canal procedures in severely curved root canals compared with the ProTaper Universal and WaveOne systems.