Gelatinase A (MMP-2) in developing tooth tissues and amelogenin hydrolysis

Matrix metalloproteinases (MMPs) are thought to play important roles during enamel and dentin biomineralization. Previously, membrane type-1 matrix metalloproteinase (MT1-MMP) was localized to the plasma membranes of ameloblasts and odontoblasts of the developing tooth. The best-characterized function of MT1-MMP is to initiate the activation of gelatinase A (MMP-2). Thus, we hypothesized that gelatinase A may also be expressed by developing tooth tissues. A full-length porcine gelatinase A mRNA was isolated by RT-PCR homology cloning of an enamel-organ-specific cDNA library. Northern blot and in situ hybridization analyses demonstrated gelatinase A expression in developing tooth tissues. Immunohistochemical analysis localized gelatinase A close to the plasma membrane of these tissues. Furthermore, recombinant gelatinase A was demonstrated to cleave recombinant amelogenin into several fragments of differing molecular masses. Thus, gelatinase A is expressed by developing tooth tissues along with its activator MT1-MMP and may, therefore, play an important role during tooth development.     

The distribution of nitric oxide synthetase in Vcx and its relation with the expression of FOS induced by teeth movement in rats]

It was studied the central role of nitric oxide(NO) during experimental teeth movement and the relation between nitric oxide synthetase (NOS) positive neurons and FOS like immunoreactivity (FLN) with the NADPH-diaphorase histochemistry and immunocytochemical reaction method. Results indicated that NOS positive neurons and FLN showed typical distribution in Vcx and there was some overlap between them. It suggests that NO is involved in the central modulation of the stimulating message of teeth movement, and which further explains the central modulation mechanism of experimental teeth movement in rats.     

A point mutation of the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (EDA) is characterized by the hypoplasia or absence of hair, teeth and sweat glands. In this study, the authors investigated the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia. The only affected male fulfils the diagnostic criteria for this disorder. His parents were not consanguineous and both of them were healthy. After informed consent, genomic DNA was isolated from the peripheral blood lymphocytes or oral buccal epithelial cells of all members of the family. A polymerase chain reaction fragment containing exon 9 of the ED1 gene was amplified using primers. The patient's amplified fragment, as well as those from his father, mother and sister, were directly sequenced. The sequence from the patient revealed a point mutation (G1149A) in exon 8 of the ED1 gene, which changes codon 291 from glycine to arginine. Heterozygosity was demonstrated in his mother and sister. This mutation has not been reported previously. The amino acid substitution is predicted to disrupt the transmembrane domain, which strongly implies that this is the disease-causing mutation in the family.     

Type II collagen and aggrecan mRNA expressions in rabbit condyle following disc displacement

The aim of this investigation was to study the remodelling of cartilage in the mandibular condyle following disc displacement (DD) of the temporomandibular joint (TMJ). Forty adult Japanese white rabbits were used in this study. The right joints of 28 of the 40 rabbits had their discs surgically displaced. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and 12 weeks after surgery. The messenger RNA (mRNA) expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results showed that aggrecan mRNA expression reduced in the first week after DD. The expression began to recover after 4 weeks and reached a normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered after 8 weeks. This suggests that the chondrocyte reacting to the displacement of the TMJ disc, alters its matrix gene expression patterns and it is may be the cause of the shape changes of TMJ after DD.     

Cement-retained versus screw-retained implant restorations: a critical review

This article presents a comparison of screw-retained and cement-retained implant prostheses based on the literature. The advantages, disadvantages, and limitations of the 2 different types of restorations are discussed, because it is important to understand the influence of the attachment mechanism on many clinical aspects of implant dentistry. Several factors essential to the long-term success of any implant prosthesis were reviewed with regard to both methods of fixation. These factors include: (1) ease of fabrication and cost, (2) passivity of the framework, (3) retention, (4) occlusion, (5) esthetics, (6) delivery, and (7) retrievability. (More than 50 references).     

Non-viral-mediated gene therapy approaches for bone repair

OBJECTIVES: Bone repair strategies continue to be developed for alternatives to autografting, allogeneic implants of banked bone, and other bone substitutes. Efforts have included the delivery of potent growth and/or differentiation factors and the use of gene therapy. For bone regeneration, gene therapy is the delivery, uptake and expression of DNA that has been localized to a wound bed. The objective of the current study is to investigate methods to enhance non-viral-mediated means of gene uptake and expression for use in bone regeneration. METHODS: Several types of DNA-polymer complexes, either applied directly to baby hamster kidney (BHK) cells, or released from a porous, resorbable gene-activated matrix (GAM), were evaluated in vitro for their ability to transfect cells with a circular plasmid DNA construct expressing green fluorescent protein. Complexes included conjugates containing a lipophilic reagent, liposomes, poly-ethyl-oxazoline, and poly-ethyleneimine (PEI). Data were subjected to analysis of variance and Fisher's protected least significant difference for multiple comparisons with significance established at p < 0.05. RESULTS: Transfection efficiencies of the liposome and PEI complexes improved in vitro when released from resorbable GAMs. The lipophilic reagent FuGene 6 demonstrated abundant uptake and expression in the initial 1- and 2-day evaluation periods. In contrast, the DNA-liposome and PEI GAM complexes demonstrated a sustained release, uptake and expression by the BHK cells at the 2-, 4-, and 7-day, and 4- and 7-day evaluation intervals, respectively. CONCLUSION: GAM technology appears to improve the functional stability and release duration of incorporated DNA-polymer complexes in the present in vitro studies. The ongoing objective of our research is to develop a localized treatment to improve the uptake and expression of plasmid DNA by non-viral-mediated gene therapy.     

A simple method of making an implant-level impression when presented with limited space,unfavorable implant positions,or problematic implant angulations

Making an implant-level impression for the purpose of abutment selection when implants are placed in limited space, unfavorable positions, or compromising angulations can be a time-consuming procedure. An impression procedure is presented that makes use of either prefabricated screw-retained titanium implant index copings or plastic snap-on implant index copings to help resolve problematic implant placement. Both the titanium and plastic implant index copings are easy to modify and therefore make impression procedures more predictable.     

上颌半口义齿金属基托的计算机辅助设计

目的 :在自行重建无牙颌三维数据模型的基础上设计上颌半口义齿金属基托数字模型。方法 :采用数控铣床及新型层析数据采集系统 ,通过对标准无牙颌模型的层切 ,二维轮廓数据获取及计算 ,重建无牙颌模型 ,在此数据基础上 ,通过SURFACER软件 ,设计上颌半口义齿金属基托。结果 :获得无牙颌三维数据及上颌金属基托的数据文件。结论 :通过新型层析系统可以实现对无牙颌三维建模 ;在此基础上设计的三维数字基托可为进一步激光立体成形制作奠定基础。     

Pellicle precursor protein crosslinking characterization of an adduct between acidic proline-rich protein (PRP-1) and statherin generated by transglutaminase

Recent work with oral transglutaminase indicated that this enzyme, derived from oral epithelial cells, crosslinked pellicle precursor proteins which may be important in the formation of the acquired enamel pellicle. The purpose of this study was to investigate whether purified acidic PRP-1 can form crosslinks with statherin, and whether such a crosslink is derived from a transglutaminase-catalyzed reaction between glutaminyl and lysyl side-chains, leading to a covalent bond formation. Enzymatic reaction products were analyzed by SDS-PAGE and reverse-phase HPLC. The SDS electrophoretogram revealed a protein band with an apparent molecular weight of 32 kDa, which is consistent with the combined apparent molecular weight of acidic PRP-1 (24 kDa) and statherin (8 kDa). A reaction product isolated by HPLC was characterized by amino acid analysis, which showed a stoichiometry consistent with being an adduct composed of one molecule of acidic PRP-1 and one molecule of statherin. In negative control experiments, it could be shown that this adduct was not detected when the lysines of both substrates were modified by reductive methylation prior to the enzymatic reaction. In addition, amino acid analysis and mass spectrometry confirmed the presence of a gamma-glutamyl-epsilon-lysine dipeptide after enzymatic hydrolysis and the absence of this dipeptide after acid hydrolysis. Analysis of the data obtained indicates that oral transglutaminase is capable of crosslinking acidic PRP-1 and statherin in vitro. In addition, this finding exemplifies the potential of post-secretory processing of salivary proteins, which may represent an additional mechanism to generate new protein species.