[Considerations of the classification and treatment for fused teeth].

Fused teeth were a phenomena of teeth anomalies in shape, which can affect the dental teeth both in primary and permanent dentition. Fused teeth do not only cause problems on crowding of dentition, abnormal occlusion and aesthetic, but also increase risks of dental caries, endodontics diseases, periapical diseases and periodontal diseases. Fusion of deciduous teeth may lead to abnormality of subsequent permanent teeth. Treatment of fused teeth may require multidisciplinary approach in endodontics, periodontics, oral and maxillofacial surgery, prosthodontics and orthodontics. The aim of the present article is to review the etiology, classification, clinical manifestations and treatment of fused teeth in order to provide dental clinicians with a reference of clinical management for fused teeth.

[Etiology and pathogenesis of internal root resorption].

Internal root resorption is a pathologic phenomenon with a characterization of the intraradicular dentin destruction due to the abnormal activities of odontoclasts. With its insidious pathology, internal root resorption can progress to a great extent before its clinical detection. The etiology and natural history of internal root resorption are uncertain and the associated key molecular pathogenesis have not been understood completely. The resorption is usually initiated by a stimulus with the loss of the protective predentin and progressed by the continuous stimuli of pulp infection. Various factors including trauma, chronic inflammation of the pulp, pulpotomy and tooth transplantation have been proposed for the occurrence of internal root resorption. The present paper reviews the etiology and pathogenesis of internal root resorption and provides guidance for the early intervention in the clinical practice.

[Prevention and treatment of root surface caries].

With the acceleration of population aging in China, the incidence of root surface caries is increasing year by year. Different from coronal caries, lesions of root surface caries mostly occur on the exposed root surfaces after gingival recession in elderly patients, mainly involving cementum and dentin. Root surface caries shows specificity in the pathogenic characteristics, clinical manifestations, diagnosis, treatment, and prevention. This review mainly summarizes the etiology and prevalence, pathology and clinical manifestations, classification, as well as three-level-prevention of root caries, in order to provide relevant guidance for the clinical prevention and treatment of root caries.

[Effects of Porphyromonas endodontalis lipopolysaccharides on the expression of matrix metalloproteinase-9 in mouse osteoblasts].

Objective: To evaluate the effects of lipopolysaccharides (LPS) extracted from Porphyromonas endodontalis (Pe) on the expression of matrix metalloproteinase-9 (MMP-9) mRNA and protein as well as enzyme activity in MC3T3-E1 cells and the role of nuclear factor-κB (NF-κB) in the process, so as to investigate the expression of MMP-9 dependent signaling pathways in mouse osteoblasts induced by Pe LPS. Methods: The experiment was conducted in 3 sessions: MC3T3-E1 cells were treated with various concentrations of Pe LPS (0-20 mg/L) and 10 mg/L Pe LPS for different time intervals (0-48 h). The expression of MMP-9 mRNA and protein were detected by real-time reverse transcription-PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), while the enzyme activity was detected by gelatin zymography method. The expression of MMP-9 mRNA was also detected in 10 mg/L Pe LPS treated MC3T3-El cells after pretreated with specific NF-κB inhibitor BAY 11-7082 for l h. Statistical analysis was performed using one-way ANOVA and Dunnett t test with SPSS 13.0 software package. Results: The levels of MMP-9 mRNA and protein increased significantly after the treatment with various concentrations of Pe LPS (0-20 mg/L), which indicated that Pe LPS induced osteoblasts to express MMP-9 in dose dependent manners. The expression of MMP-9 protein increased from (5 395±362) ng/L (blank control group) to (12 684±375) ng/L (20 mg/L group). Maximal induction of MMP-9 mRNA expression was found in the MC3T3-E1 cells treated with 10 mg/L Pe LPS for 24 h. The expression of MMP-9 mRNA in the 20 mg/L group was about 7 times than that in the blank control group. After 24 h, the expression of MMP-9 mRNA decreased. Maximal expression of MMP-9 protein was found in the MC3T3-E1 cells treated with 10 mg/L Pe LPS for 48 h ([35 055±2 346] ng/L) showing the highest enzyme activity. The mRNA of MMP-9 decreased significantly after pretreatment with 10 µmol/L BAY 11-7082 for 1 h. Conclusions: Pe LPS might induce the expression of MMP-9 in MC3T3-E1 cells through the signaling of NF-κB.