Relationship between vitamin D receptor gene polymorphism and periodontitis

Recent studies have shown that vitamin D receptor (VDR) gene polymorphism had regulatory effects on bone mineral density (BMD) and bone turnover. The VDR gene has also been indicated as a candidate gene for the susceptibility of osteoporosis. However, it is unclear whether VDR genotypes could be associated with alveolar bone loss of patients with periodontitis, or whether vitamin D receptor gene could be a candidate gene for susceptibility to periodontitis. The purpose of this study was to answer these two questions. METHODS: Twenty-four cases of adult periodontitis (AP), 37 cases of early onset periodontitis (EOP) and 39 healthy controls were recruited for the study. Individual samples of venous blood and DNA were obtained from each subject. Genotypes of the TaqI VDR gene were determined by PCR and TaqI restriction endonuclease digestion. RESULTS: One out of 24 AP patients, nine out of 37 EOP patients and two out of 39 healthy controls were detected with Tt genotype, while the rest had the TT genotype. The detected frequency of Tt genotype was significantly higher in EOP patients (24.3%) than in AP patients (4.2%) and healthy controls (5.1%). The frequency of t allele was also significantly higher in EOP patients. There was no statistical difference in the distribution of TaqI VDR genotypes between AP patients and healthy controls. The study suggests that Tt genotype might be a risk indicator for the susceptibility to EOP. Carriage of the allele (t) of the TaqI VDR gene may increase the risk of developing EOP.     

Cell and tissue behavior on micro-grooved surfaces

In this review, we discuss substrates and implant surfaces provided with micrometer-sized groove and ridge patterns. Such "microgrooves" influence cell behavior: the cells align themselves, and migrate guided by the surface grooves. This phenomenon is known as "contact guid-ance". First, cell structure and cell attachment behavior are described. Then techniques for the production of microgrooves are addressed, and a summary is given of a number of previous in-vitro and in-vivo experiments on this subject. Based on the knowledge of cell movement, we suggest a theory involving the dynamics of fibrous cellular components in the filopodium. Finally, future directions for this type of research, and implications for medical and dental implantology, are addressed. Received: September 27, 2000 / Accepted: June 7, 2001     

The multiple roles of major histocompatibility complex class-I-like molecules in mucosal immune function

The human major histocompatibility complex (MHC) on chromosome 6 encodes three classical class-I genes: human leukocyte antigens (HLA) A, B, and C. These polymorphic genes encode a 43- to 45-kDa cell surface glycoprotein that, in association with the 12-kDa beta2-microglobulin molecule, functions in the presentation of nine amino acid peptides to the T-cell receptor of CD8-bearing T lymphocytes and killer inhibitory receptors on natural killer cells. In addition to these ubiquitously expressed, polymorphic proteins, the human genome also encodes several nonclassical MHC class-I-like, or class Ib, genes that, in general, encode nonpolymorphic molecules involved in various specific immunological functions. Many of these genes, including CD1, the neonatal Fc receptor for IgG, HLA-G, HLA-E, the MHC class-I chain-related gene A, and Hfe, are prominently displayed on epithelial cells, suggesting an important role in epithelial cell biology.     

Novel identification of a four-base-pair deletion mutation in PITX2 in a Rieger syndrome family

Rieger syndrome is one of the most serious causes of tooth agenesis. Mutations in the PITX2, FOXC1, and PAX6 genes have been associated with Rieger syndrome. We have studied a three-generation Chinese family affected with Rieger syndrome and showing prominent dental abnormalities. Mutational screening and sequence analysis of the PITX2 gene revealed a previously unidentified four-base-pair deletion of nucleotides 717-720 in exon 5 in all affected members. The mutation causes a frame shift after Thr44, the 7th amino acid of the homeo-domain, and introduces a premature stop codon in the gene sequence. This deletion is the first unquestionable loss-of-function mutation, deleting all the functionally important parts of the protein. Our novel discovery indicates that the oligodontia and other phenotypes of Rieger syndrome observed in this family are due to this PITX2 mutation, and these data further support the critical role of PIXT2 in tooth morphogenesis.     

Quantitatively study of voice onset time-Glottal stop]

To quantitatively evaluate the acoustic characteristics of glottal stop, pronunciation of/ka/in 10 normal subjects and 14 patients with cleft palates were analyzed by sound spectrography and 20 msec in all normal articulation of /ka/ with an average time of 44.6 msec.In the test group of /ka/ demonstrated an average time of 20.8 msec.The inverse correlation ship between VOT and the psyco-acoustical judgment for the degree of distortion was demonstrated to be significant.     

Clinical study on wedge-shape ditch restoration with several restorative materials]

There appeared difficulties in either cavity preparation of restoration retention when wedge-shaped ditch was restored.In order to choose an ideal material and method restored wedge-shaped ditch,we used three kinds of restorative materials (glass ionomer,light curing glass ionomer,light curing composite resin)and four restorative methods (glass ionomer,light curing glass ionomer,light curing composite resin,glass ionomer mixed with light curing composite resin).carried on clinical observation.According to the results of six months follow-up,four methods have no significant differences in abrasion,fracture,shedding and failing incidence(including of abrasion,fracture,and shedding) through statistical test(chi-square test).According to the results of one year follow-up,there were significant differences in abrasion and failing incidence,but fracture and shedding have no significant differences.Results showed that light curing composite resin was better than glass ionomer in wedge-shaped ditch restoration.     

Remineralization of incipient caries studied by high-resolution electron microscopy

The present study presents a study on the remineralization of enamel incipient caries by HREM (high-resolution electron microscopy). The electron-transparent specimens (200-100 A) were prepared with argon ion thinning technique. The result showed some special crystallites, single or conglomerate (mostly on both sides of sheath), their shape, size and degree of electron-transparency indicated that they might be remineralized crystallites. They were distributed in the centre and edge of the carious lesions. Two patterns of remineralization had been observed. One was formation of new crystallites, and the remineralized crystal nuclear during development were found under HREM. The other was growth of the original crystals. The HREM images directly showed that the remineralized crystallites' chemical structure was mainly apatite, but its characteristics should be further studied.     

固齿健周煎剂对老年小鼠的抗氧化作用

目的探讨中药固齿健周煎剂对老年小鼠的抗氧化作用。方法实验组为固齿健周煎剂灌胃的老年小鼠，对照组为灌胃等量自来水的青、老年小鼠。检测过氧化脂质、超氧化物歧化酶及过氧化氢酶。结果实验组与青、老年小鼠对照组比较差异均有显著性。结论固齿健周煎剂具有抗脂质过氧化的作用，可能对调节机体代谢功能、抗自由基损伤及恢复牙周组织健康有益