Biomedical subjects

Francesco Cavani

Publications and source records attributed to Francesco Cavani.

4 recordsLinked to original sources

PubMed2006

Does static precede dynamic osteogenesis in endochondral ossification as occurs in intramembranous ossification?

Endochondral ossification takes place with calcified cartilage cores providing a rigid scaffold for new bone formation. Intramembranous ossification begins in connective tissue and new bone formed by a process of static ossification (SO) followed by dynamic ossification (DO) as previously described. The aim of the present study was to determine if the process of endochondral ossification is similar to that of intramembranous ossification with both a static and a dynamic phase of osteogenesis. Endochondral ossification centers of the tibiae and humeri of newborn and young growing rabbits were studied by light and transmission electron microscopy. The observations clearly showed that in endochondral ossification, the calcified trabeculae appeared to be lined first by osteoclasts. The osteoclasts were then replaced by flattened cells (likely cells of the reversal phase) and finally by irregularly arranged osteoblastic laminae, typical of DO. This cellular sequence did not include osteoblasts seen in the phase of SO. These findings clearly support our working hypothesis that SO only forms in soft tissues to provide a rigid framework for DO, and that DO requires a rigid mineralized surface. The presence of osteocytes in contact with the calcified cartilage also suggests the existence of stationary osteoblasts in endochondral ossification. Stationary osteoblasts did not appear to be a unique feature of SO. The presence of stationary osteoblasts may appear to provide the initial osteocytes during osteogenesis that may function as mechanosensors throughout the bone tissue. If this is the case, then bone would be capable of sensing mechanical strains from its inception.

Aging↗

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↗

PubMed2003

Effect of trabecular orientation on mechanical resistance and ultrasound propagation in specimens of equine vertebrae.

Osteoporosis involves alterations, not only in density, but also in the architectural organisation of the bone; in particular, trabecular orientation, following the skeletal load directions, lends a high degree of stiffness to the whole bone. We investigated the relationship between trabecular orientation, density, stiffness and ultrasound (US) propagation in two orthogonal directions (par. = parallel to, and ort. = orthogonal to the main orientation of the trabeculae) in cylindrical equine bone specimens (thoracic vertebrae) where a preferential orientation is present. A total of 15 cylinders were progressively decalcified with 0.2 mol/L ethylenediaminetetraacetic acid (EDTA). At different levels of decalcification, we measured the apparent density (g/cm(3)), bone mineral density or BMD (g/cm(2)), stiffness coefficient (MPa) and various US parameters. Before decalcification, stiffness values were the same in all directions. As the decalcification proceeded, the stiffness declined and, at low BMD values, it was significantly different in the two directions, being the highest in the par. one. Different behaviours of US parameters were observed in the two directions: SoS (speed of sound) was closely related to apparent density, BMD and stiffness in the par. direction (r = 0.88, 0.92 and 0.88, respectively, p < 0.0001). In the ort. direction, no significant association has been found between SoS and apparent density, BMD or stiffness. In the same experimental setup, US fast wave amplitude (FWA) was related to apparent density and BMD in the par. direction (r = 0.72 and 0.67, respectively, p < 0.0001) and in the ort. direction (r = 0.83 and r = 0.84 respectively, p < 0.0001). FWA was also correlated to stiffness in both directions (r = 0.61 par.; 0.81 ort., p < 0.0001). These results show that trabecular orientation strongly influences both mechanical properties of bone and US propagation. Furthermore, we found that US parameters can be predictors of mechanical properties of the bone independent of bone density.

Absorptiometry, Photon↗

PubMed2002

The effect of pulsed electromagnetic fields on the osteointegration of hydroxyapatite implants in cancellous bone: a morphologic and microstructural in vivo study.

Effects of pulsed electromagnetic fields (PEMFs, 75 Hz. 1.6 mT) were investigated in 12 rabbits after placing hydroxyapatite (HA) implants in their femoral condyles. Six animals were stimulated with PEMFs for three consecutive weeks, 6 h/day, while the remaining animals were sham-treated (Control Group). Rabbits were sacrificed at 3 and 6 weeks (after a 3-week non-stimulation period) for histomorphometric analysis and microhardness testing (at 200, 500, 1,000, 2,000 microm from the implant) around the implants. Histomorphometric analysis did not highlight any significant changes. On the contrary, there were statistically significant differences between the effects produced by PEMFs and Control Groups (F = 149.70, p < 0.0005) on the Affinity Index results, as well as by the experimental time of 6 and 3 weeks (F = 17.12, p = 0.001) on the same results. In PEMF-stimulated animals the microhardness (HV) values measured in trabecular bone at a distance of 200 and 500 microm from the implants, were significantly higher with respect to controls. At 6 weeks, HV values at the bone-implant interface in PEMF-stimulated animals were not significantly different with respect to normal bone, while they remained significantly lower in control animals. Both morphological and structural results demonstrated a positive therapeutic effect of PEMFs in accelerating HA osteointegration in trabecular bone.

Animals↗