PubMed · 8948181
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F M Blair, J M Thomason, D G Smith. 1996. The flange prosthesis.. https://pubmed.ncbi.nlm.nih.gov/8948181/
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The aim of this study was static and fatigue test investigation of the strength of a tooth fragment reattached with adhesives to the tooth body. Central bovine incisor teeth were used, and standardized fragments were obtained by cutting the incisal edge of the selected teeth. All the fragments were reattached using a multistep dentine adhesive system, and the specimens were randomly divided into two groups (A and B). Group B specimens underwent a further dental treatment: a circumferential double chamfer prepared around the external cut interface was filled with light cured composite restorative resin. Static and fatigue bending tests were performed and linear elastic equations were used to analyze and compare the strength of the treated teeth. The results indicated that the static and fatigue bending properties were improved by using reinforcement with composite restorative resin.
Due to the extended use of acrylic bone cements, its necessary to develop improved formulations in order to resolve their many drawbacks. The present work was conducted to make a physical-chemical characterisation of this kind of acrylic cement in order to introduce future changes in the formulations to: (1) improve or at least maintain their mechanical properties; (2) diminish their toxicity, and (3) control the drug release (rate and amount). From the dissolution method we can conclude that the preparation method (with or without pressure) of specimens is not responsible for the erratic release. The cumulative amount of gentamicin released was fitted to a semi-empirical equation to explain the possible release mechanism. The powder size, shape and distribution that could affect several properties of bone cement were studied with the aid of different techniques such as SEM, laser diffraction spectroscopy, and powder X-ray diffraction. From SEM micrographs, it was possible to observe that the surfaces of the specimens were very irregular with numerous small craters that may serve as conduits for eluting the antibiotic. An 'in vitro' drug diffusion model is proposed to elucidate the drug release mechanism. Finally an 'in vivo' study was performed to evaluate the antibiotic release to the neighbouring bone sites.
A range of poly(acrylic acid)s with different average degrees of polymerisation and cross-linking densities were synthesised using a solution polymerisation process. The rheological characteristics of aqueous dispersions of these materials and those of mixtures with homogenised pigs gastric mucus were investigated using dynamic oscillatory rheology, and compared to the known mucoadhesive Carbopol 934P. From the storage moduli, the rheological synergy and relative rheological synergy were calculated, and the effects of concentration and pH on this considered. Generally, the larger the molecular weight (and degree of cross-linking), the greater the rheological synergy, with Carbopol 934P giving the most pronounced effect. Rheological synergy was seen to be concentration-dependent, and a maximum concentration to produce an optimum effect was evident. Acid pHs were seen to favour synergy, although in marked contrast to previous literature reports, the optimum mucus-polymer interaction was not observed at the half ionised value (pH = pKa) but at pH regimes that were unique to each polymer type. This could be influenced by the structural constrains imposed on potential hydrogen bonded interactions. It was concluded that synthesising poly(acrylic acid)s with better defined physicochemical properties than commercially available polymers will advance the study of the phenomenon of rheological synergy.