Biomedical subjects

Virginio Quaglini

Publications and source records attributed to Virginio Quaglini.

4 recordsLinked to original sources

PubMed2003

Behavior of the bone-titanium interface after push-in testing: a morphological study.

Fourteen titanium dental implants (Tioblast) were implanted singly in the proximal tibia of New Zealand rabbits for 120 days. A bone defect was surgically produced and filled with Bio-Oss around six of these implants. After the animals were sacrificed and their organs harvested, bone segments were fixed and methacrylate embedded after the push-in test had been performed. Microradiography was performed on longitudinal sections of the implants, whereas scanning electron microscope analysis was performed on the remaining embedded half-implants using secondary electrons only. The results showed that the implants were apically and coronally surrounded by bone, whether Bio-Oss was used or not. Fractures were evident through the newly formed bone and between the pre-existing and newly formed bone. Some fracture lines propagated through the bone and stopped at the implant surface without continuing along the bone-titanium interface. Detachment between the implant and the bone occurred at the coronal extremity of the implants and along its cervical region. These results highlight the fact that the bone-titanium interface has a high resistance to loading. It exhibited greater resistance than the newly formed bone and seems to behave in a manner similar to the cement lines of osteons.

Animals↗

PubMed2002

Experimental procedure for the evaluation of the mechanical properties of the bone surrounding dental implants.

The mechanical stability of the fixture in bone is one of the most important factors for the long-term reliability of dental implants. This paper focuses on an experimental procedure to evaluate the mechanical properties of the bone surrounding dental implants. The procedure is based on a surgical animal model followed by mechanical tests. The experimental mechanical testing has been used for preliminary investigations on the role played by different parameters such as the healing time and the surgical technique (standard or with regenerative material). The procedure has been evaluated in some preliminary tests on a few specimens. Microradiographic analyses have been performed on the bone surrounding the implants in order to give an interpretation of the bone properties on the basis of the bone morphology and to distinguish the newly formed bone from the pre-existing bone. The preliminary results relevant to 10 threaded titanium implants are presented and discussed. Our findings show that the mechanical properties of the bone surrounding the implant improve with the increase in the healing time from 24 to 45 days. The ultimate loads recorded during mechanical tests arise from 395 N to 2665 N in case of coronal defects filled with bone regenerative and from 2200 N to 5700 N in case of standard technique.

Animals↗

PubMed2002

A discrete-time nonlinear Wiener model for the relaxation of soft biological tissues.

The present paper is devoted to introducing discrete-time models for the relaxation function of soft biological tissues. Discrete-time models are suitable for the analysis of sampled data and for digital simulations of continuous systems. Candidate models are searched for within both linear ARX structures and nonlinear Wiener models, consisting of an ARX element followed in cascade by a polynomial function. Both these discrete-time models correspond to sampling continuous-time exponential function series, thus preserving physical interpretation for the proposed relaxation model. The estimation data set consists of normalized stress relaxation curves drawn from experiments performed on samples of bovine pericardium. The normalized relaxation curves are found to be almost insensitive to both the magnitude of strain and the loading direction, and so a single model for the whole relaxation curves is assumed. In order to identify the parameters of the Wiener model an iterative algorithm is purposely designed. Over the ARX one, the nonlinear Wiener model exhibits higher capability of representing the experimental relaxation curves over the whole observation period. The stability of the solution for the iterative algorithm is assessed, and hence physical interpretation as material properties can be attached to the parameters of the nonlinear model. Suitable features of the Wiener model for computational application are also briefly presented.

Algorithms↗

PubMed2002

An in vitro methodology for evaluating the mechanical properties of aortic vascular prostheses.

The main problem in the replacement of pathological segments of the aorta with vascular prostheses consists of matching the fluid admittance of the host artery and the graft. This mismatch results from the different compliance between natural and prosthetic vessels and from the plastic dilatation of the prosthesis diameter that occurs after implantation. An experimental procedure was set up for evaluating the mechanical properties of aortic vascular prostheses. An MTS 858 MiniBionix testing machine was equipped with a purposely designed testing apparatus, which allows loading a ring-shaped prosthesis specimen with forces that can be related easily to the transmural pressure acting on the prostheses in vivo. The reference pressure waveforms are simulated from a lumped parameter model of the cardiovascular system. Preliminary tests on 3 different (woven, warp knitted, and carbon-coated warp knitted fabric) aortic prostheses point out a good reproducibility of the results. The fabric strongly affects the circumferential elasticity and the dimensional stability of the graft. Simulation of hypertension promotes larger diameter dilatation and reduction in compliance. Agreement between in vitro and clinical diameter measurements has been assessed for 8 prosthesis samples and found to be adequate. This method is thus a potentially useful means for preclinical evaluation of compliance of vascular prostheses for the purpose of matching to native vessels.

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