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.     

Effects of erbium,chromium:YSGG laser irradiation on canine mandibular bone

BACKGROUND: Only relatively few reports have described the morphological effects on bone produced by erbium,chromium: yttrium,scandium,gallium,garnet (Er,Cr:YSGG) laser irradiation, and none has investigated the atomic changes or estimated the temperature increases involved. The objectives of this study were to investigate the morphological, atomic, and temperature changes in irradiated areas during and after laser irradiation, and to evaluate the cutting effect on canine mandibular bone in vitro. METHODS: Two canine mandibular bones were cut into 3 to 5 cm pieces and irradiated by an Er,Cr:YSGG laser utilizing a water-air spray at 5 W and 8 Hz for 10 or 30 seconds. During and after laser irradiation, temperature increases in the irradiated areas were measured by thermography. The samples were then observed by stereoscopy and scanning electron microscopy to determine morphological changes and by energy dispersive x-ray spectroscopy to evaluate atomic alterations. RESULTS: Regular holes or grooves having sharp edges and smooth walls were produced, but no melting or carbonization was observed. The maximum temperature increase was an average 12.6 degrees C for 30-second irradiation. The continuous time of a temperature increase of more than 10 degrees C was consistently less than 10 seconds. An atomic analytical examination revealed that the calcium:phosphorus ratio was not significantly changed between the lased and unlased areas (P>0.0 1). CONCLUSION: These results showed that the Er,Cr:YSGG laser cuts canine mandibular bone effectively without burning, melting, or altering the calcium:phosphorus ratio of the irradiated bone.     

23例恒牙根管机械预备断针的原因分析和处理

目的：近年来，临床上通过镍钛机用根管器械，采用逐步深入法进行患牙根管预备的病例越来越多，导致根管内断针的病例也在逐渐增多，对这类断针原因进行分析以减少并发症的发生。方法：针对23例近两年来采用Step-down或Crown-down技术进行机械根管预备后所出现的根管内断针进行分析和根管再处理。结果：断针位于根管上、中、下的比率为4：12：7，原因包括：①未按操作规程。②操作的方法不当。③忽视手动器械的作用。④根管冲洗不到位。⑤使用的器械不当。经过处理后，大部分病例通过取出断针或建立旁路的方法完成治疗。结论：不当操作还可导致根管内产生台阶、穿孔或折裂，同时，金属疲劳和扭矩是影响器械寿命的重要因素。通过合理操作，综合运用机械法、手动法甚至超声法的根管预备技术，大多数并发症均可避免。     

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.     

Microleakage Evaluation in Amalgam Restorations Used with Bases

Marginal leakage in amalgam restorations often precedes the development of secondary caries. One potential way to improve the marginal seal of such restorations, and thus minimize the risk of carles development, is to apply a glassionomer base prior to amalgam placement.
This study compared microleakage resistance among amalgam restorations placed with and without light-cured glass-ionomer base materials. Preparations were made in extracted human molar teeth. Four groups were studied, including copal varnish, which was used as a control. All specimens were restored with amalgam. Results indicated significantly greater leakage at the cavity wall/base interface for restorations with a copal varnish cavity liner than for those with a glass-ionomer base. Leakage differences among bases were also found at the amalgam/base interface. Best results were obtained with a dual-cure resin-based system. These samples showed minimal leakage at both the cavity wall/base and the base/amalgam interfaces. These findings suggest that light-cured glass-ionomer bases can be effective in the prevention of microleakage in amalgam restorations.