Correlation of dentin bond durability with water absorption of bonding layer.
(17/1113)
In order to understand the relationship between the durability of adhesive strength in the oral cavity and water absorption, a series of O-methacryloyl-N-acyl tyrosines (MAATY)-2-hydroxyethyl methacrylate (HEMA) bond system samples was prepared and their bonding strength to unetched human dentin was measured as a function of immersion period in water. Also, bulk polymerization was carried out to measure the amount of water absorption as a function of time. All specimens absorbed water suddenly when they were immersed into water. The amount of absorbed water was large when the carbon number in the acyl group was small or the number of carboxylic groups was large. The adhesive strength of the MAATY-HEMA system to unetched dentin decreased significantly when the MAATY-HEMA absorbed a larger amount of water. We concluded, therefore, that preparation of MAATY which absorbs less water may improve durability even when immersed in water. (+info)
Effect of functional monomer in commercial dentin bonding agents use of an experimental dentin bonding system.
(18/1113)
The objective of the present study was to understand the role of the functional monomers in dentin bonding agents of an experimental dentin bonding system by measuring the wall-to-wall contraction gap and tensile bond strength measurement. The efficacy of three commercial dentin bonding agents after using EDTA for conditioning and GM for priming was evaluated by measuring the contraction gap of the resin composite in a cylindrical dentin cavity, and by measuring the tensile bond strength of the composite to a flat dentin surface. The effect of the functional monomers was demonstrated by the contraction gap measurement alone. The value of the contraction gap was significantly different between the commercial dentin bonding agents and these agents without functional monomers (p < 0.05). It was concluded that the functional monomers were essential to obtaining the marginal integrity of the resin composite in the dentin cavities. (+info)
Adhesion of a new commercial self-etching/self-priming bonding resin to human caries-infected dentin.
(19/1113)
We have examined the adhesive properties of a new commercial self-etching/self-priming bonding resin (Unifil Bond, UB) to normal and caries-infected dentin of human extracted molars using scanning electron microscopy (SEM) and a micto-tensile bonding strength (MTBS) test. In this study, 7 human extracted molars with moderate occlusal caries were used, and flat surfaces including occlusal dentin caries were prepared from the teeth. After the application of UB to the surfaces, a composite resin was built up, and subjected to the measurement of MTBS and SEM observation of the interfacial morphology between UB and dentin. The MTBS of UB to normal dentin was 33.4 MPa, but that to caries-infected dentin was 11.0 MPa. There was a significant difference between the MTBS to normal and carious dentin. SEM observation revealed that the typical hybrid layer was not formed in caries-infected dentin. These results suggested that resin infiltration into caries-infected dentin was not sufficient to allow perfect sealing of the restoration. (+info)
Caries-detector dyes--how accurate and useful are they?
(20/1113)
Commercially available caries-detector dyes are purported to aid the dentist in differentiation of infected dentin, yet research has established that these dyes are not specific for infected dentin. They are non-specific protein dyes that stain the organic matrix of less mineralized dentin, including normal circumpulpal dentin and sound dentin in the area of the amelo-dentinal junction. A considerable body of evidence indicates that conventional tactile and optical criteria provide satisfactory assessment of caries status during cavity preparation. There is reason for concern that subsequent use of a caries-detector dye would result in unnecessary removal of sound tooth structure. The use of caries-detector dyes has also been suggested as a diagnostic aid for occlusal caries. Although diagnosis of carious dentin beneath apparently sound enamel can be challenging, there is a lack of substantive evidence supporting the use of dyes for this purpose and false positives are a significant concern. Careful visual inspection combined with bitewing radiographic diagnosis has been shown to be the most reliable diagnostic method for the presence of infected dentin requiring operative treatment. (+info)
Bone induction in implants of decalcified bone and dentine.
(21/1113)
The fate of decalcified bone and dentine implanted in muscle and beneath the kidney capsule has been studied in young rats. Quantitatively speaking there was a great deal of variation, but in general the implants became surrounded and invaded by young vascular connective tissue; then tunnels were eroded and cavities enlarged by multi-nucleated giant cells; then the matrix around erosion chambers became recalcified; and finally new bone was induced on the eroded recalcified surfaces. Erosion was much more extensive, and bone was much more readily induced in the intramuscular than in the subcapsular implants. It is concluded that the presence of an eroded, recalcified surface is a pre-requisite for bone induction under these conditions. (+info)
Structure-based design of an osteoclast-selective, nonpeptide src homology 2 inhibitor with in vivo antiresorptive activity.
(22/1113)
Targeted disruption of the pp60(src) (Src) gene has implicated this tyrosine kinase in osteoclast-mediated bone resorption and as a therapeutic target for the treatment of osteoporosis and other bone-related diseases. Herein we describe the discovery of a nonpeptide inhibitor (AP22408) of Src that demonstrates in vivo antiresorptive activity. Based on a cocrystal structure of the noncatalytic Src homology 2 (SH2) domain of Src complexed with citrate [in the phosphotyrosine (pTyr) binding pocket], we designed 3',4'-diphosphonophenylalanine (Dpp) as a pTyr mimic. In addition to its design to bind Src SH2, the Dpp moiety exhibits bone-targeting properties that confer osteoclast selectivity, hence minimizing possible undesired effects on other cells that have Src-dependent activities. The chemical structure AP22408 also illustrates a bicyclic template to replace the post-pTyr sequence of cognate Src SH2 phosphopeptides such as Ac-pTyr-Glu-Glu-Ile (1). An x-ray structure of AP22408 complexed with Lck (S164C) SH2 confirmed molecular interactions of both the Dpp and bicyclic template of AP22408 as predicted from molecular modeling. Relative to the cognate phosphopeptide, AP22408 exhibits significantly increased Src SH2 binding affinity (IC(50) = 0.30 microM for AP22408 and 5.5 microM for 1). Furthermore, AP22408 inhibits rabbit osteoclast-mediated resorption of dentine in a cellular assay, exhibits bone-targeting properties based on a hydroxyapatite adsorption assay, and demonstrates in vivo antiresorptive activity in a parathyroid hormone-induced rat model. (+info)
The presence of multiple rat DSP-PP transcripts.
(23/1113)
Phosphoproteins or phosphophoryns (PPs) are the most abundant (>50%) non-collagenous proteins (NCPs) in dentin. PPs bind to calcium and hydroxyapatite and are believed to play a crucial role in dentin mineralization. Dentin sialoprotein (DSP), a highly glycosylated protein, comprised 5-8% of NCPs in dentin. The coding sequences for these two major NCPs are known to be contiguously located (i.e. DSP-PP) at the cDNA and genomic DNA levels in both rat and mouse. Previous studies have demonstrated the presence of multiple DSP-PP transcripts in the total RNA of adult rat incisors. To further understand the nature of these multiple transcripts, we performed reverse transcription-PCR and obtained a PP cDNA variant which encoded a 171 amino acid peptide (PP(171)) that shares many of the same characteristics as that of the published rat PP(240) sequence [Ritchie, H.H. and Wang, L.-H., J. Biol. Chem. 271 (1996) 21695-21698]. Due to its reduced size, as compared to PP(240), this cDNA encodes a phosphorylated protein with a reduced negative charge that may differentially affect mineralization processes. We provide evidence that there are multiple DSP-PP transcripts with various sizes of PP sequences in rat. (+info)
Identification and characterization of the carboxyl-terminal region of rat dentin sialoprotein.
(24/1113)
Two acidic proteins, dentin sialoprotein (DSP) and dentin phosphoprotein (DPP), are present in the extracellular matrix of dentin but not in bone. These two proteins are expressed in odontoblasts and preameloblasts as a single cDNA transcript coding a large precursor protein termed dentin sialophosphoprotein (DSPP). DSPP is specifically cleaved into two unique proteins, DSP and DPP. However, the cleavage site(s) of DSPP and the mechanisms for regulating the cleavages are unknown. To identify the specific site(s) of DSPP that are cleaved when the initial translation product is converted to DSP and DPP, we performed a detailed analysis (Edman degradation and mass spectrometry) on selected tryptic peptides of a size originating from the COOH-terminal region of rat DSP. After cleavage with trypsin, the DSP fragments were separated by a two-dimensional method (size-exclusion chromatography followed by reversed phase high performance liquid chromatography). We characterized 13 peptides from various regions of DSP. The analyses showed that peptide Ile(409)-Tyr(421) was the major COOH-terminal fragment, ending at Tyr(421) only 9 residues from the NH(2) terminus of DPP. Peptide Gln(385)-His(406) represented a second, minor COOH-terminal peptide that terminated at His(406). Both of these residues are well beyond the COOH terminus predicted previously by two independent studies estimating that rat DSP contained 360-370 amino acids. Careful studies on two peptides showed that, among 9 potential casein kinase II phosphorylation sites, 2 serines were phosphorylated. We found that rat DSP was heterogeneous with respect to phosphorylation, because this same peptide sequence eluted in two discrete peaks, one with 2 phosphoserines and the other having 1. The finding that 3 lysines just preceding the COOH termini were modified by a 43-Da substituent (possibly a carbamoyl substituent) suggests that the lysines in this region were particularly susceptible to attachment of this substituent. (+info)