The mechanical behavior of bone is a critical factor in the attainment and maintenance of osseointegration. Current procedures and classifications in assessing bone quality have limitations. Micro-computed tomography (microCT) is a new method to image and quantify bone with very high resolution. This study was aimed to analyze cadaveric maxillary and mandibular trabecular bone with 3-D morphometric data acquired through microCT and correlate with conventional bone assessment methods. Moderately resorbed edentulous maxilla and mandible from a human cadaver were scanned in the conventional CT unit with opaque markers indicating specific anterior and posterior sites. These sites were then sectioned and standard periapical radiographs were obtained. Bone cores were harvested from the sectioned sites and scanned in the microCT unit. Bone density values based on the Hounsfield scale ranged from 51 to 529 in the mandible and 186 to 389 in the maxilla, anterior sites being higher in both. Periapical images did not yield distinct differences. 3-D morphometric analysis in microCT produced a range of values with anterior specimens being favorable: bone volume density (0.12-0.291), trabecular thickness (0.12-0.16 mm), trabecular separation (0.46-0.82 mm), trabecular number (1.08-2.071/mm) and structural model index (0.29-1.27). General agreement between bone density and microCT indices was noted; however, subtle differences have to be studied with larger samples. This preliminary study suggests that the understanding of mechanical competence of trabecular bone might reveal further information about the prognosis of implant therapy, advancements in implant design, surgical techniques and grafting.

Bone micro-morphology has a prevailing effect over implant design on intraosseus initial implant stability, and ITV is more sensitive in terms of revealing biomechanical properties at the bone-implant interface in comparison with ISQ.

No abstract

BackgroundOsteoporosis may present a risk factor in achievement of osseointegration because of its impact on bone remodeling properties of skeletal phsiology. The purpose of this study was to evaluate micro-morphological changes in bone around titanium implants exposed to mechanical and electrical-energy in osteoporotic rats.MethodsFifteen 12-week old sprague-dowley rats were ovariectomized to develop osteoporosis. After 8 weeks of healing period, two titanium implants were bilaterally placed in the proximal metaphyses of tibia. The animals were randomly divided into a control group and biophysically-stimulated two test groups with five animals in each group. In the first test group, a pulsed electromagnetic field (PEMF) stimulation was administrated at a 0.2 mT 4 h/day, whereas the second group received low-magnitude high-frequency mechanical vibration (MECHVIB) at 50 Hz 14 min/day. Following completion of two week treatment period, all animals were sacrificed. Bone sites including implants were sectioned, removed en bloc and analyzed using a microCT unit. Relative bone volume and bone micro-structural parameters were evaluated for 144 μm wide peri-implant volume of interest (VOI).ResultsMean relative bone volume in the peri-implant VOI around implants PEMF and MECHVIB was significantly higher than of those in control (P < .05). Differences in trabecular-thickness and -separation around implants in all groups were similar (P > .05) while the difference in trabecular-number among test and control groups was significant in all VOIs (P < .05).ConclusionBiophysical stimulation remarkably enhances bone volume around titanium implants placed in osteoporotic rats. Low-magnitude high-frequency MECHVIB is more effective than PEMF on bone healing in terms of relative bone volume.

This in vitro study investigated the stress distribution in the bone surrounding an implant that is placed in a posterior edentulous maxilla with a sinus graft. The standard threaded implant and anatomy of the crestal cortical bone, cancellous bone, sinus floor cortical bone, and grafted bone were represented in the 3-dimensional finite element models. The thickness of the crestal cortical bone and stiffness of the graft were varied in the models to simulate different clinical scenarios, representing variation in the anatomy and graft quality. Axial and lateral loads were considered and the stresses developed in the supporting structures were analyzed. The finite element models showed different stress patterns associated with helical threads. The von Mises stress distribution indicated that stress was maximal around the top of the implant with varying intensities in both loading cases. The stress was highest in the cortical bone, lower in the grafted bone, and lowest in the cancellous bone. When the stiffness of the grafted bone approximated the cortical bone, axial loading resulted in stress reduction in all the native bone layers; however, lateral loading produced stress reduction in only the cancellous bone. When the stiffness of the graft was less than that of the cancellous bone, the graft assumed a lesser proportion of axial loads. Thus, it caused a concomitant stress increase in all the native bones, whereas this phenomenon was observed in only the cancellous bone with lateral loading. The crestal cortical bone, though receiving the highest intensity stresses, affected the overall stress distribution less than the grafted bone. The stress from the lateral load was up to 11 times higher than that of the axial load around the implant. These findings suggest that the type of loading affects the load distribution more than the variations in bone, and native bone is the primary supporting structure.