[Comparative study of root canal morphology of mandibular incisors by cone-beam CT and canal staining and clearing technique].

PURPOSE: To compare the root canal morphology of mandibular incisors by using cone-beam CT (CBCT) and canal staining and clearing technique. METHODS: Sixty-one extracted mandibular incisors with complete dental root and apex which received no endodontic treatment and no post crown restoration were selected. Each tooth was radiographed with CBCT, and the root canal system was stained by canal staining and clearing technique. The consistency of the number of root canal, root canal Vertucci type of mandibular permanent incisors between the two methods were compared, and the differences of the detection rate on root canal branch structure between the two methods were analyzed. The results were statistically analyzed with SPSS 17.0 software package. RESULTS: The Kappa value of single and double root canal types between CBCT and canal staining and clearing technique was 0.847 (P<0.001). The Kappa value of Vertucci root canal types between CBCT and canal staining and clearing technique was 0.861 (P<0.001). The detection rates of root canal branch structure were 8.19% and 22.95%, respectively, with significant difference between the two methods (P=0.025). The canal staining and clearing technique was significantly better than CBCT in detection of root canal branch structure. CONCLUSIONS: CBCT can reflect the root canal types nearly perfectly, but inferior to canal staining and clearing technique in detection of root canal branch structure, CBCT is a relatively accurate clinical diagnosis tool of root canal morphology.

Analysis of Mtwo rotary instrument separation during endodontic therapy: a retrospective clinical study.

To analyze the incidence of instrument separation (IS) and the factors influencing it, when associated with Mtwo rotary system (VDW, Munich, Germany) during endodontic therapy. A retrospective study involving a total of 24,108 root canals (11,036 endodontic treated teeth) was conducted at Nanjing Stomatology Hospital between January 2011 and March 2013. The information included were tooth type, root canal curvature, number of fractured instruments, length of the separated fragments, and the distance from broken tip to apex. The incidence of IS was observed to be 2.2 % according to the number of teeth and 1.0 % according to the number of root canals. Many of the separated fragments were 2-4 mm in length and the mean length was 3.07 ± 1.46 mm, and 78.4 % of fractures occurred in the apex. The mean length of separated fragments in severely curved canals was maximum, while ultra-severe curved canals was observed to be minimum. Mtwo instruments demonstrated an extremely low fracture rate during endodontic therapy. Molar teeth (especially lower molars) and the degree of canal curvature had a significant effect on the incidence of IS.

[A comparative study of the cytotoxicity of five dental bonding agents to human periodontal ligament cells].

PURPOSE: To compare the cytotoxicity of 5 different dental bonding agents to human periodontal ligament cells(HPDLCs). METHODS: Primary cultured HPDLCs were exposed to different concentrations (100%,50% and 25%) of Super Bond, Clearfil SE Bond, G-Bond, Single Bond2, and Adper Easy One for different times (24 h, 48 h and 72 h). Cytotoxicity of 5 different agents to HPDLCs were observed by MTT method. The data was analyzed using SPSS 19.0 software package. RESULTS: Cytotoxicity of 5 dentin bonding agents to HPDLCs were Super Bond0.05). CONCLUSIONS: Cytotoxicity of 5 dentin bonding agents are different. Cytotoxicity of Super-bond C&B,G-Bond and Clearfil SE Bond are weak, while cytotoxicity of Single Bond2 is the strongest among the 5 agents. Supported by Medical Leading Talents and Innovation Team Project of Jiangsu Province (LJ201110) and Natural Science Foundation of Jiangsu Province (SBK201340904).

[Analysis of mandibular bone mineral density of senile osteoporosis patients].

OBJECTIVE: To investigate the mandibular bone mineral density (BMD) change of senile osteoporosis patients and the relationship between the mandible bone loss and systemic bone loss. METHODS: Forty senile osteoporotic patients (group A), 40 non-osteoporosis control elders (group B) and 40 healthy youths (group C) were included in this study. Standard digital panoramic tomography (SDPTG) was taken for each participant. Cortical width (CW), panoramic mandibular index (PMI), alveolar bone density and alveolar bone height were measured on the SDPTG. Lumbar and hip BMD were measured with dual energy X-ray absorptiometry (DXA). RESULTS: Close relationship was found between CW (3.57 +/- 0.82) and systemic BMD for osteoporosis patients (P < 0.05). All the SDPTG indices including CW, PMI, alveolar bone density and alveolar bone height were different for osteoporosis patients from the healthy youths (P < 0.05). The osteoporosis patients had thinner CW (3.57 +/- 0.82) and smaller PMI (0.29 +/- 0.06) than non-osteoporosis control elders (CW: 4.07 +/- 0.75, PMI: 0.32 +/- 0.07, P < 0.05). The alveolar bone density (105.40 +/- 20.48) and alveolar bone height (10.42 +/- 1.82) of the non-osteoporosis control elders reduced compared with the healthy youths (alveolar bone density: 117.10 +/- 22.23, alveolar bone height: 11.69 +/- 1.63, P < 0.05). CONCLUSIONS: The senile osteoporotic patients had significant mandibular cortical bone loss.

[Evaluation of mandibule bone loss of periodontitis with standard digital panoramic tomogram].

OBJECTIVE: To compare the mandibular indices differences between periodontitis and non-periodontitis subjects by digital panoramic tomograms in order to find a simple and effective method to evaluate the density of alveolar bone and study the relativity between local bone loss and systemic bone loss. METHODS: Standard digital panoramic tomograms of sixty periodontitis subjects and sixty non-periodontitis subjects were taken. Density and height cortical width (CW) and panoramic mandibular index (PMI) of alveolar bone were measured on the digital panoramic tomograms. SPSS 12.0 was used for statistics analyses. RESULTS: The periodontitis subjects had lower height of alveolar bone (8.76 mm vs. 11.85 mm, P=0.000), lower density of alveolar bone (106.08 vs. 113.33, P=0.034), thinner cortical width (3.80 mm vs. 4.27 mm, P=0.008), while the difference of PMI between the two groups was not significant (P>0.05). The relativity between both density and height of alveolar bone with CW was significant (P<0.05), but not significant with PMI (P>0.05). CONCLUSION: The optical method is a simple and effective method to measure the density of the alveolar bone. Compared with the non-periodontitis subjects, the periodontitis subjects not only have alveolar bone changed significantly but also have thinner cortical width.