[Effect of root canal curvature on canal length measurement on digital image of human lower mandibular permanent incisor].

OBJECTIVE: To investigate the effect of canal curvature on measured precision in canal length of human lower mandibular permanent incisors imaged by direct digital radiograph. METHODS: With Trophy digital X-ray system, 299 Chinese lower mandibular permanent incisors were selected to take the direct digital X-ray photography in both facial to lingual (L-T) and proximal directions (M-D). Two operators familiar with endodontic knowledge estimated the canal length by means of on-screen DDR with 2-and 3-click measurements. RESULTS: The true canal length of Chinese lower mandibular permanent incisors was (19. 54 +/- 1.62) mm. The tooth root canal length on digital image was overestimated with 3-click measurement (P < 0.05), and the canal length with 2-click measurement was almost similar to the true canal length from the facial-lingual direction X-ray photography (P > 0.05). The less than 1 mm difference between the estimated canal and the true canal length was above 95%. The canal length was underestimated with 2-click measurement as the curvature severity increased. CONCLUSION: Direct digital radiography system is applicable to estimate the canal length in clinic as the accuracy is very good. The curved canal length should be estimated with 3-click measurement.

[Morphology of cross-sectioned root canal in Chinese mandibular permanent incisors].

OBJECTIVE: To identify morphological features of cross-sectioned root canal in Chinese mandibular permanent incisors. METHODS: Twenty mandibular permanent incisors were selected in this study. The tooth roots were embedded in resin and transversely sectioned with a low-speed diamond saw. The number of root canal and the morphology and isthmus of the root canal were observed under a stereo-microscope, which included the measure of the canal diameter. RESULTS: The double root canal comprised 22.5%, 30.0%, and 15.0% in crown third, middle third, and apical third root canals of the mandibular permanent incisors, respectively. The long oval canal comprised 44.8%, 77.0%, and 44.5% in crown third, middle third, and apical third root canals, respectively. The canal isthmus comprised 62.5%, 75.0%, and 48.7% in crown third, middle third, and apical third root canals, respectively. The diameter of buccal-lingual canal was at least 2 times of the diameter of mesial-distal canal. CONCLUSION: The cross-sectioned root canal morphology in Chinese mandibular permanent incisors varies considerably. But most have long oval and canal isthmus, which imposes a great challenge for root canal therapy.

[Porphyromonas gingivalis induced interleukin-6 expression by Nod/Rip2-mediated signaling pathway].

OBJECTIVE: To investigate into the signaling pathway of Porphyromonas gingivalis (P. gingivalis) on cytokine expression in human dental pulp cells (HDPC). METHODS: Anaerobic method was employed to culture P. gingivalis, and then HDPC were intracellularly infected by P. gingivalis. The extraction of total RNA, real-time quantitative polymerase chain reaction (qPCR) and enzyme linked immunosorbent assay (ELISA) was used for mRNA expression of Nods and Rip2, protein secretion of interleukin-6 (IL-6). RESULTS: HDPC expressed Nods, Rip2 mRNA and IL-6. The up-regulation of Nods and Rip2 mRNA started after P. gingivalis infection, reached maximal level at 2 h, and then decreased at 6 h; whereas elevated IL-6 was found when P. gingivalis infected. CONCLUSION: P. gingivalis activate host innate immune responses in HDPC, and induce IL-6 production through Nod/Rip2-mediated signaling pathway.

[Establishment of a model of intracellular infection on human dental pulp fibroblast by Porphyromonas gingivalisin vitro].

OBJECTIVE: To establish a model of intracellular infection of human dental pulp fibroblast (HDPF) by Porphyromonas gingivalis in vitro. METHODS: HDPF was incubated with live Porphyromonas gingivalis with a multiplicitas of infection (MOI) from 100 for 0.5, 1.0, 2.0 hours. HDPF infected with live Porphyromonas gingivalis were observed by inverted microscope. Metronidazole, Penicillin, Streptomycin were added to the medium to kill any extracellular bacteria. Then the cells were lysed by sterile distilled water, dilutions of the lysates of cells were cultured anaerobically. Colony of invasive bacteria were then observed. HDPF exposed live Porphyromonas gingivalis with a MOI 50 and 100 for 1.0 hour, then cells survival rate were detected by MTT assay. RESULTS: After infected with Porphyromonas gingivalis 2.0 hours, cells were eumorphism. Porphyromonas gingivalis of incubation for 1.0, 2.0 hours was invasive cells. MTT assays indicated 99.07% cells survival rate with a MOI from 50 and 74.43% cells survival rate with a MOI from 100. CONCLUSION: A model of HDPF intracellular infection with Porphyromonas gingivalis was successfully established in vitro.

[Radiographic anatomy of pulp chamber of Chinese permanent anterior teeth].

OBJECTIVE: The aim of this study was to measure and analyze the anatomic characteristics of the pulp chamber of Chinese permanent anterior teeth radiographically. METHODS: There were 137 human permanent anterior teeth to be used. The crown length, crown width and crown thickness were measured by vernier caliper. Labial-lingual and mesial-distal radiographs were obtained by parallel technique and Photoshop 8.0 was adopted for measuring the largest labial-lingual length, the largest mesial-distal length, the pulp chamber height and the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber; the ratios of the largest labial-lingual length to the crown thickness, the largest mesial-distal length to the crown width and the pulp chamber height to the crown length were calculated. Finally the coefficients of variance were caculated. RESULTS: (1) The ratios of the largest mesial-distal length to the crown width of maxillary and mandibular canines were statistically different from those of the other anterior teeth. There was not statistically significant difference for those ratios either between maxillary and mandibular canines or among incisors. (2) Indexes of the pulp chamber had higher variance than those of the external morphology. (3) The distance between the lingual surface of the crown and the corresponding wall of the pulp chamber had the smallest coefficient of variance. (4) The largest mesial-distal length of the pulp chamber had the largest coefficient of variance, except for the mandibular canines. CONCLUSION: This study provided anatomical basis for clinical work; the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber could be used as a depth reference for the endodontic access, and the access should not be extended excessively in mesial-distal direction.

[Shaping ability of multi-taper nickel-titanium files in simulated resin curved root canal].

OBJECTIVE: To compare the shaping ability of ISO standard stainless steel K files and multi-taper ProTaper nickel-titanium files in simulated resin curved root canals. METHODS Thirty simulated resin root canals were randomly divided into three groups and prepared by stainless steel K files, hand ProTaper, rotary ProTaper, respectively. The amount of material removed from inner and outer wall and canal width after canal preparation was measured, while the canal curvature before and after canal preparation and canals aberrations were recorded. RESULTS: The stainless steel K files removed more material than hand ProTaper and rotary ProTaper at the outer side of apex and inner side of curvature (P < 0.05). The mean degree of straightening in stainless steel K files group was significantly bigger than in ProTaper group (P < 0.05). The canals prepared by ProTaper had no evident aberration. CONCLUSION: The shaping ability of ProTaper is better than stainless steel K files.