[Observation of the roots and root canals of 442 maxillary first premolars].

PURPOSE: To investigate the root and root canal anatomical features of maxillary first premolars in 422 teeth. METHODS: 422 maxillary first premolars were collected to statistically analyze the root types by sex and to observe the root canals by clearing technique; Vertucci's classification was adopted to get the percentage of each root canal type. The data were analyzed with SPSS11.5 software package. RESULTS: (1)Significant gender difference was found in 422 teeth in terms of the percentage of one root(total 57.36%; male 33.58%; female 62.68%), two roots(total 41.47%; male 62.68%; female 33.33%) and three roots(total 1.18%; male 3.73%; female 0%) (P<0.01). (2)In the 422 transparent specimens of the teeth, totally 9 types of root canals were discovered with the percentage of type I(10.12%), II(10.60%), III(6.02%), IV(56.63%), V(12.05%), VI(1.93%), VII(0.72%), VIII(1.45%), IX(0.48%). CONCLUSIONS: Understanding of the various and gender-different morphology of the roots and complex root canals of maxillary first premolars, is of great value for the diagnosis and root canal therapy.

[Culture and characteristics of porcine dental papilla cells (pDPCs) in vitro].

PURPOSE: To culture porcine dental papilla cells (pDPCs) and to study the cytobiological characteristics of the cells in vitro. METHODS: Dental papillae were collected from postnatal (1-3 days) pigs, then the pDPCs were isolated and cultured through the method of enzyme-digestion. Vimentin and cytokeratin (CK) were used to demonstrate the cells' mesenchymal derivation. Collagen I collagen III and dentin sialoprotein (DSP) were detected in pDPCs by immunohistochemistry. RESULTS: The pDPCs were well cultured in the medium of DMEM/F12 containing 10% FBS in vitro. Vimentin was positively expressed in pDPCs but CK was not. Collagen I, collagen III, and DSP were all positive in the plasma of the pDPCs. CONCLUSIONS: The pDPCs were successfully isolated and cultured in vitro. The pDPCs come from mesenchymal tissue and have the capability of synthesizing extracellular matrix (collagen I, collagen III, and DSP) of dentin-pulp complex. This study indicated that the pDPCs may have the potential to be used as seed cell in regeneration of dentin-pulp complex.

[The basic characters and research advancements of odontoblasts].

As the main components of dental pulp cells,the odontoblasts were responsible for the formation and maintenance of dentin during the development and mature age of teeth. Presently the studies were mostly based on the two-dimensional vitro cultured technique,but with the developing research of pulp tissue, three-dimensional vitro cultured technique will be the study hotspot in future. The author retrospected the investigation about the odontoblasts these years and mostly expatiated the morphology,ultrastructure,function and characters of protein expression about the odontoblasts,including the research advancements and research aspects in future.

[Research advances and applications of the methods to repair mandible defect].

Mandible defects can be caused by many diseases, most commonly occurring in cranio-maxillofacial regions. With the development of orthopaedics, biomaterial and cell biology in these years, great improvements have been acquired in repair of mandible defects. This paper systematically reviewed the relevant research advances and applications, and showed the applied prospect of bone tissue engineering in this field.

[Repair of alveolar bone defect with tissue engineered bone: an experimental study of dogs].

OBJECTIVE: To study the feasibility of repairing experimental horizontal alveolar bone defects by tissue engineering based on bone marrow stromal cells (BMSC). METHODS: Dog bone marrow mononuclear cells were isolated from the bone marrow by gradient centrifugation and then cultured in conditional medium to be induced to become osteogenic. Immunohistochemistry was used to examine the expression of core-binding factor alpha subunit 1 (Cbfa1), osteocalcin (OCN), and type I collagen in the cultured BMSCs. Histochemical technique was used to examine the expression of alkaline phosphatase (AKP) in the BMSCs. Inversed phase-contrast microscopy and electron microscopy were used to observe the morphology and proliferation of the BMSCs. Induced BMSCs at passage 3 were harvested and mixed with calcium alginate to form a gelatin form cell-scaffold construct. A horizontal alveolar bone defect (5 mm high) was created surgically in each buccal side of the mandibular premolars 3 and 4 and molar 1 of 11 dogs. The defects was randomly repaired with a cell-scaffold construct (experimental group, 20 teeth), calcium alginate alone (control group A, 15 teeth), or left untreated (control group B, 12 teeth). At four, twelve, and twenty-four weeks after operation, 2, 7, 2 dogs were killed respectively and block sections of mandibular bones at the defects were collected and processed for gross and histological observation as well as X-ray examination. The status of bone repair 12 weeks after operation in the 3 groups was compared. RESULT: In vitro induced BMSCs exhibited an osteogenic phenotype. Since the passage 3 calcium salt sedimentation could be seen in the extracellular stroma of BMSCs. Cbfa1, type I collagen, and AKP were expressed in the BMSCs in every passage. OCN was expressed since the second passage. Histologically, bone nodule structure was observed in the experimental group 4 weeks after operation. The engineered bone became more mature, similar to the normal bone, 12 weeks after operation. Twelve weeks after operation, the alveolar ridge regeneration amounted to a repair height of 2.43 +/- 0.93 mm, 0.98 +/- 0.87 mm, and 0.78 +/- 0.75 mm and reached 48.59%, 19.74%, and 15.76% of the original height in the experimental group, control group A, and control group B respectively, with a significant difference between the experimental and control groups A and B (all P < 0.01). CONCLUSION: BMSCs can be induced to become osteogenic and be used as seed cells to engineer bone tissue and repair experimental alveolar bone defect.

[Experimental study of the inducing BMSCs into osteogenesis].

OBJECTIVE: To study the bone tissue osteogenesis ability of bone marrow stromal cells (BMSCs) in vitro and in vivo. METHODS: The BMSCs were separated by gradient centrifugation on Percoll, culture-expanded and induced with a conditional medium. The cells were examined by transmission electron microscopy and histochemistry or immunochemistry stains technique including AKP,Cbfa1,OCN, OPN, BSP and collagen type I. The mRNA of collagen type I in cultured cell was also examined by in situ hybridization. RESULTS: Histochemical studies showed positive stain of AKP,Cbfa1, OCN, OPN,BSP and collagen type I,and in situ hybridization also showed the positive express of mRNA of collagen type I. The excretion of collagen and deposition of calcium salt were observed under transmission electron microscopy. CONCLUSION: BMSCs cultured in conditional medium shows osteoblast-like functions in vitro, which provides an ideal seed cells for bone tissue engineering.