The variation in crown-root morphology of anterior teeth assessed with cone-beam computed tomography

ABSTRACT Objective: To determine the discrepancy of crown-root morphology of anterior teeth, using cone-beam computed tomography (CBCT), and to provide a guidance for proper torque expression. Methods: A total of eligible 200 CBCT were imported into Invivo v. 5.4 software, to obtain the middle labio-lingual sections of anterior teeth. AutoCAD 2007 software was applied to measure the crown-root angulation (Collum angle) and the angle formed by a tangent to the center of the labial surface and the long axis of the crown (labial surface angle). SPSS 18.0 was used for statistical comparisons of the two measurements, at the level of p< 0.05, and the Pearson correlation analysis was applied to investigate the association between the two measurements. Results: The value of Collum angle in maxillary central incisor was close to 0°. Significantly negative Collum angle in lateral incisors and maxillary canine, and positive value in mandibular canine were detected (p < 0.001). The labial surface angle in canine was significantly greater than the intra-arch incisors (p< 0.001), and no significant difference was detected between the central and lateral incisors (p > 0.05). Notably, there was also a significant positive correlation between the two measurements. Conclusions: The crown-root angulations were greatly different among anterior teeth. Accompanying the obvious crown-root angulations, the canines both in maxillary and mandibular arches presented considerable labial surface curvatures. Hence, equivalent deviation during bracket bonding might cause greater torque expression error and increase the risk of alveolar fenestration and dehiscence.

RESUMO Objetivo: Determinar a discrepância na morfologia coroa-raiz de dentes anteriores, utilizando tomografia computadorizada de feixe cônico (TCFC), e fornecer parâmetros para a expressão apropriada do torque. Método: No total, 200 tomografias elegíveis foram importadas para o software Invivo 5.4 para obtenção das secções médias vestibulolinguais dos dentes anteriores. Osoftware AutoCAD 2007 foi usado para medir a angulação coroa-raiz (ângulo Collum) e o ângulo formado por uma tangente ao centro da superfície vestibular da coroa e o longo eixo da coroa (ângulo da superfície vestibular). O software SPSS 18.0 foi utilizado para as comparações estatísticas das duas medições, com nível de significância de p< 0,05, e a análise de correlação de Pearson foi aplicada para investigar a associação entre as duas medições. Resultados: O valor do ângulo Collum do incisivo central superior foi próximo a 0°. Foram detectados valores significativamente negativos para o ângulo Collum nos incisivos laterais e caninos superiores, mas valores positivos nos caninos inferiores (p< 0,001). O ângulo da superfície vestibular no canino foi significativamente maior do que nos incisivos intra-arcada (p< 0,001), e nenhuma diferença significativa foi detectada entre incisivos centrais e laterais (p> 0,05). Também foi observada uma correlação positiva significativa entre as duas medições. Conclusões: As angulações coroa-raiz foram muito diferentes entre os dentes anteriores. Os caninos superiores e inferiores apresentaram considerável curvatura na superfície vestibular, associada a uma evidente angulação coroa-raiz. Consequentemente, desvios durante a colagem de braquetes podem desencadear maior erro na expressão de torque e aumentar o risco de fenestração alveolar e deiscência, sendo necessária uma avaliação antes da colagem.

Effect of miR-21 on the proliferation and osteogenic differentiation of human periodontal ligament stem cells / 口腔疾病防治

Objective @# To explore the effect of miR-21 on human periodontal ligament stem cells (PDLSCs) proliferation and osteogenesis and to provide a theoretical basis for the stem cell treatment of periodontitis.@*Methods@#hPDLSCs were isolated and cultured with the enzymatic tissue block method, and surface molecules (CD34, CD45, CD90 and CD105) were detected by flow cytometry. An miR-21 mimics (pre-miR-21) and inhibitor (anti-miR-21) were transfected into hPDLSCs by Lipofectamine 2000. The experiment groups: mimics-NC group, mimics group, inhibitor group, and inhibitor-NC group. The transfection efficiency of miR-21 was determined by qRT-PCR. Proliferation was detected by CCK-8 and flow cytometry. The osteogenic differentiation ability of hPDLSCs was determined by alizarin red staining. Western blot was used to detect the protein expression of osteogenic related genes: Runx2.@*Results@#The mRNA expression of miR-21in the mimics group was significantly higher than that in the mimics-NC group; additionally, the expression in the inhibitor group was significantly weaker than that in the inhibitor-NC group (P < 0.05). hPDLSCs proliferation and the S phase cell ratio in the mimics group were stronger than those in the mimics-NC group(P < 0.05); those in the inhibitor group were weaker than those in the inhibitor-NC group (P < 0.05). After alizarin red staining, the mimics group was found to have more mineralized modules than mimics-NC group, and the inhibitor group had fewer than that in the inhibitor-NC group. Runx2 protein expression in the mimics group was higher than that in the mimics-NC group (P <0.05), and expression was lower in the inhibitor group than in the inhibitor-NC group (P < 0.05).@*Conclusion@#miR-21can promote the proliferation and osteogenesic differentiation of hPDLSCs.

Mutation breeding of lipase-producing strain Flavobacterium sp. by supercritical CO2 with hydrazine hydrate

This work aimed to obtain an ideal mutant strain with higher lipase yield using hydrazine hydrate (HZH) as a novel additive to treat Flavobacterium sp. strain YY25 by supercritical CO2. The survival rate and the positive mutation rate of the tested strain were strongly dependent on the dose of HZH. The treatment by 0.5% HZH in supercritical CO2 (8 MPa, 35°C) for 30 min provided 58.3% of positive mutation rate and an expected mutant strain with about 76.7% increase in lipase yield compared with the wild strain. Possible mutagenesis mechanisms were further explored. The analysis on pH drop of the treated seed liquid was performed to better understand the interaction. Results proved that the induced mutation with enhanced yield of lipase could be achieved by co-mutagenesis of supercritical CO2 and HZH.