次氯酸钠和氢氧化钙对牙本质弹性模量和挠曲强度的影响

目的 :评估 5 %次氯酸钠 (NaOCl)溶液和饱和氢氧化钙 [Ca(OH) 2 ]溶液对牙本质弹性模量和挠曲强度的影响 ,以进一步了解根管治疗过程中药物对牙齿机械性能的影响。方法 :取新鲜拔除的完整前磨牙制成标准规格牙本质条 ,经 5 %NaOCl和饱和Ca(OH) 2 溶液处理 ,三点加荷系统测定其弹性模量和挠曲强度。结果 :5 %NaOCl使牙本质弹性模量和挠曲强度显著降低 ;饱和Ca(OH) 2 溶液使牙本质挠曲强度显著降低 ,对弹性模量无显著影响 ;5 %NaOCl处理后再用饱和Ca(OH) 2 溶液处理对牙本质弹性模量和挠曲强度无进一步影响。结论 :5 %NaOCl和饱和Ca(OH) 2 溶液对牙本质的机械性能有一定影响     

Comparison of phosphoprotein isolated from mature and immature human tooth roots

Mature (average patient age = 29.5 yr, closed apical foramen) and immature (average patient age = 17.5 yr, open apical foramen) root shards were placed in dialysis tubing and demineralized to completion using either 10% disodium EDTA plus protease inhibitors or 0.6 N HCl. The demineralized shards were re-extracted (five times) with 0.05 M tris-HCl, 1.0 M NaCl and then collagenase digested. No major differences were observed in chromatograms of extracts, re-extracts or collagenase digests from root shards demineralized in either way. In contrast, chromatograms of immature and mature roots showed qualitative differences. Chromatograms of mature roots demineralized in either way showed broader protein peaks and less organic phosphorus than those from immature tooth roots. A distinct band amid degraded phosphoprotein (150 K) was found in SDS-PAGE gels (7.5%) from EDTA-extracted immature tooth roots but not from mature tooth roots. Electroelution of this band revealed a typical phosphoprotein amino-acid profile containing increased aspartic acid and serine residues. Comparison of the total phosphoprotein and amino acid composition of extracts, re-extracts and collagenase digests revealed that phosphoprotein, serine and to a lesser extent aspartic acid were recovered in greater quantities from immature roots than mature tooth roots. These data suggest that the degree of maturation is crucial to the isolation of an intact phosphoprotein and provides additional evidence that human dentine phosphoprotein undergoes amino acid compositional changes during maturation.     

Structure and properties of methacrylate based dental restorative materials

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.     

Pfeiffer syndrome: oral healthcare management and description of new dental findings in a craniosynostosis

Pfeiffer syndrome is a rare fibroblast growth factor receptor‐related craniosynostosis with variable clinical presentations. We describe new dental findings of hypodontia, microdontia, dilacerations, and radicular dentin dysplasia in a 19‐year‐old girl, and discuss the oral health management.     

Structural Relationship Between the Primary Crystal Formations and the Matrix Macromolecules in Different Hard Tissues. Discussion of a General Principle

For many years we have investigated the earliest crystal formations of different developing hard tissues (matrix vesicle, bone, dentine, enamel, etc.) by different electron microscopic measurements. It was observed that primarily Ca-phosphate (apatite) “chains,” composed of nanometer sized particles (dots, islands), exist, which coalesce rapidly to needles. For the mineralization of collagen (e.g., bone, dentine) the center to center distances between the dots in the mineral chains represent the distances between nucleating sites, so-called “active sites” of collagen which bind primarily Ca for a subsequent nucleation. For the mineralization of noncollagen macromolecules (e.g., enamel) the same principle of mineral nucleation at such “active sites” exists being represented indirectly by corresponding center to center distances between the dots in the mineral chains.