Rabbit Tibial Model Research Articles

Biomechanical and histomorphometric study of dental implants with different surface characteristics

The aim of this study was to investigate the early bone response to the titanium dental implants with different surface characteristics using the rabbit tibia model. Calcium metaphosphate coated, anodic oxidized, hydroxyapatite particle-blasted, and turned (control) surfaces were compared. Surface topography was evaluated by field emission scanning electron microscope and optical interferometer. Eighteen rabbits received 72 implants in the tibia. Resonance frequency was analyzed every week for 6 weeks. Removal torque values were measured 2 and 6 weeks after placement. The implant-bone interfaces were directly observed by light microscope and bone-to-implant contact ratios were measured 2 and 6 weeks after insertion. All the surface-modified implants showed superior initial bone responses to the control. No significant differences were found among the surface-modified groups. Data suggest that various surface modification methods can provide favorable bone responses for early functioning and healing of dental implants.

Revascularization of Diaphyseal Bone Segments by Vascular Bundle Implantation

Vascularized bone transfer is an effective, established treatment for avascular necrosis and atrophic or infected nonunions. However, limited donor sites and technical difficulty limit its application. Vascular bundle transplantation may provide an alternative. However, even if vascular ingrowth is presumed to occur in such situations, its extent in aiding revascularization for ultimate graft incorporation is not well understood. A rabbit tibia model was used to study and compare vascularized, segmental, diaphyseal, nonvascularized conventional, and vascular bundle-implanted grafts with a combination of angiographic, radiographic, histopathologic, and bone scanning techniques. Complete graft incorporation in conventional grafts was observed at 6 months, whereas it was 8 to 12 weeks with either of the vascularized grafts. The pattern of radionuclide uptake and the duration of graft incorporation between vascular segmental bone grafts (with intact endosteal blood supply) and vascular bundle-implanted segmental grafts were similar. A vascular bundle implanted in the recipient bone was found to anastomose extensively with the intraosseous circulation at 6 weeks. Effective revascularization of bone could be seen when a simple vascular bundle was introduced into a segment of bone deprived of its normal blood supply. This simple technique offers promise for improvement of bone graft survival in clinical circumstances.

Distraction osteogenesis for segmental bone defect: Physeal change after acute bone shortening followed by gradual lengthening in a rabbit tibia model

We investigated physeal change after acute bone shortening followed by distraction osteogenesis in a rabbit tibia model. Distraction osteogenesis was performed on acutely shortened right rabbit tibia after removing a diaphyseal segment until distraction reached the length of the excised segment. Sixty animals were divided into three groups (n=20) according to the amount of shortening (20, 30, and 40% of original length) and radiographic, immunohistochemical, and histomorphometric analyses were performed to evaluate the physeal activity. The results showed no differences between groups and all animals could recover the original length without growth retardation. There was no notable venous congestion or lymphatic kinking associated with acute shortening. These results suggest that distraction osteogenesis at the primary site of shortening may have little adverse effects on the growth plate, when the shortening can provide sufficient soft tissue without vascular compromise and the amount of lengthening does not exceed that of shortening.

F2.3 Focal infection in oral cavity of patient with extrasystolic heart arrhythmia

The objective of this study was to demonstrate a successful binding of Doxy hyclate onto a titanium zirconium alloy surface.The coating was done on titanium zirconium coins in a cathodic polarization setup. The surface binding was analyzed by SEM, SIMS, UV–vis, FTIR and XPS. The in vitro biological response was tested with MC3T3-E1 murine pre-osteoblast cells after 14 days of cultivation and analyzed in RT-PCR. A rabbit tibial model was also used to confirm its bioactivity in vivo after 4 and 8 weeks healing by means of microCT.A mean of 141 μg/cm2 of Doxy was found firmly attached and undamaged on the coin. Inclusion of Doxy was documented up to a depth of approximately 0.44 μm by tracing the 12C carbon isotope. The bioactivity of the coating was documented by an in vitro study with murine osteoblasts, which showed significantly increased alkaline phosphatase and osteocalcin gene expression levels after 14 days of cell culture along with low cytotoxicity. Doxy coated surfaces showed increased bone formation markers at 8 weeks of healing in a rabbit tibial model.The present work demonstrates a method of binding the broad spectrum antibiotic doxycycline (Doxy) to an implant surface to improve bone formation and reduce the risk of infection around the implant. We have demonstrated that TiZr implants with electrochemically bound Doxy promote bone formation markers in vitro and in vivo.

Effects of hydroxyapatite coating on Ti‐6 Al‐4V implant‐site infection in a rabbit tibial model

To investigate the effect of implant type after direct contamination, a hydroxyapatite-coated or noncoated Ti-6A1-4V implant was inserted into both tibiae of 32 New Zealand White rabbits. Prior to implantation, the left tibia was contaminated with increasing concentrations of Staphylococcus aureus (10(2)-10(5) colony-forming units), ranging from very low (10(2)) to relatively high (10(5)). Four weeks after implantation, half of the tibial bone adjacent to the implant was harvested for bacteriological examination. Bacterial counts were quantified by plating serial dilutions. For the histological evaluation, sections of the implant with the remaining tibia were examined by semiquantitative scoring of infection parameters. The bacteriological data showed the inoculum dose and implant type to have a significant effect on the culture outcome: more bacteria were retrieved from the hydroxyapatite-coated implants than from the noncoated titanium implants. Histological evaluation showed an increased score for the infected left tibiae compared with their contralateral control. In addition, with increasing inoculum dosage, the difference between the two types of implant increased. We demonstrated that infections can occur with biocompatible, noncemented implants and that they are related to the dose of the original inoculum. Bacteria were more likely to grow onto or next to the hydroxyapatite implants than on titanium implants and resulted in a more severe histopathological characterization of infection.

Effect of prosthetic superstructure accuracy on the osteointegrated implant bone interface

Objective. This study evaluated the biologic result of forces induced by a misfitting prosthetic superstructure on implants placed in a New Zealand white rabbit tibia model. Study design. Nine rabbits had two dental implants placed in both right and left proximal tibias. After 6 weeks, one animal was sacrificed for baseline integration data, and the remaining animals had fitting or misfitting prosthetic superstructures attached to the implants for 12 weeks. Implants were evaluted clinically, radiographically, and histomorphometrically at the scanning electron microscopic level. Results. No clinical, radiographic, or histomorphometric evidence exists of integration failure with implants subjected to superstructure strain, although bone remodeling is noted. Conclusions. Given the limitations of sample size, animal model used, duration of prosthetic superstructure attachment, and loading confounders possible, the study of prosthetic framework misfit must be evaluated with another animal model, such as an intraoral primate model, to determine the relationship between clinical performance and histologic findings.

Neuromuscular injury during limb lengthening: A longitudinal follow-up by rabbit tibial model

Limb lengthening has been used for many years to correct congenital anomalies and unequal leg length. Some surgeons focus on bone genesis and anatomical alignment, and pay less attention to potential damage to muscles, nerves, and vessels during the gradual stretching. In an attempt to identify the presence and extent of neuromuscular abnormalities during leg elongation, a rabbit tibial osteotomy model was used for 17 male rabbits, and fixation-distraction apparatuses were applied at a rate of 1 mm lengthening per day. Electrophysiological test was used to investigate both hindlegs every 2 weeks for 8 weeks after surgery. Needle electromyography (EMG) showed denervation in the elongated legs with 14 limbs having peroneal nerve damage and 12 limbs having damage to the posterior tibial nerve. Nerve regeneration signs were found in ankle extensors and flexors beginning 2 weeks postoperatively. The results of nerve conduction studies revealed significant differences ( P < .05) in CMAP amplitude (mV) and area (mV.mS) in ankle extensors and flexors between elongated and nonelongated legs. There was no significant side-to-side difference with respect to distal latency. The incidence of neuromuscular injury was common in these rabbits. These findings suggest that early detection of neuromuscular involvement by electrophysiological test is a practical way to assess neuromuscular function during limb lengthening.

Histological response to cylinders of a low modulus titanium alloy (Ti‐13Nb‐13Zr) and a wear resistant zirconium alloy (Zr‐2.5Nb) implanted in the rabbit tibia

AbstractTo assess new and existing materials for total joint arthroplasty, the authors performed a comprehensive histomorphologic and morphometric analysis of bone to cylinders implanted transversely in the proximal tibia of mature New Zealand white rabbits. Four sterile, cylindrical implants measuring 6.1 × 3.8mm were manually inserted through drill holes in both tibiae with a „line‐to‐line fit.”︁ The materials tested included: ASTM F‐75 cast cobalt‐chrome‐molybdenum alloy, commercially pure titanium wrought zirconium‐2.5 niobium alloy, zirconium oxide coated zirconium‐2.5 niobium alloy, wrought titanium‐13 niobium‐13 zirconium alloy, and nitrogen diffusion hardened titanium‐6 aluminum‐4 vanadium alloy. Control animals with or without drill holes were included. The animals were killed by barbiturate overdose 6 months postoperatively. The upper tibiae were harvested and processed for undecalcified histologic sections that were stained with toluidine blue. The sections were examined by an investigator blind to the identity of the implanted materials. A full necropsy was also performed.A collar of lamellar bone, of variable length and thickness, continuous with the original cortex formed a buttress around the implants. There was no evidence of foreign body or inflammatory reaction. The marrow was slightly fatty, but cells of allthree hematopoietic lines were identifiable. The materials investigated had the following ranking in decreasing order of bone contact: Ti‐13Nb‐13Zr &gt; nitrogen hardened Ti‐6Al‐4V &gt; C.P. titanium &gt; Zr 2.5Nb &gt;ZrO2 coated Zr‐2.5Nb &gt; cast CoCr alloy. The difference between the groups was statistically significant (p = 0.05). For the variable „average bone layer thickness”︁ the ranking in decreasing order was: nitrogen hardened Ti‐6Al‐4V alloy = C.P. titanium &gt; Ti‐13Nb‐13Zr &gt; ZrO2/Zr‐2.5Nb &gt; Zr‐2.5Nb &gt; cast CoCr alloy (p = 0.19). For the variable „average bone layer thickness in bone contact regions,”︁ the ranking of the values, in decreasing order were: nitrogen hardened Ti‐6Al‐4V &gt; C.P. titanium &gt; ZrO2 coated Zr‐2.5Nb &gt; Ti‐13Nb‐13Zr &gt;Zr‐2.5 Nb &gt; cast CoCr alloy (p = 0.02). The final necropsy reports of the animals identified no adverse findings that were concentrated to any particular implant group. The new, lower modulus materials Ti‐13Nb‐13Zr and Zr‐2.5 Nb, and nitrogen hardened Ti‐6Al‐4V appear to have a similar or superior bone response to CoCr alloy when implanted in the rabbit tibia model. © 1993 John Wiley &amp; Sons, Inc.

Cell wall alterations in staphylococci growing in situ in experimental osteomyelitis.

When cells of both Staphylococcus aureus and Staphylococcus epidermidis are grown in batch culture in nutrient-rich media, their cell walls are regular in thickness, their cell size is within the normal range for each species, and their septation patterns are orderly. When cells of each of these species are examined directly in infected tissue in the rabbit tibia model infection, their cell wall thickness is often much increased and very irregular around the circumference of the cell, their cell size is often increased, and their septation patterns are often severely deranged. All of these alterations in cell wall structure occur in the absence of antibiotics, and we suggest that they may be an expression of phenotypic plasticity in response to altered environmental conditions such as specific nutrient limitations, the presence of antibacterial factors, and growth of the cells on hard surfaces such as rabbit bone or plastic catheters. Some of these specific cell wall alterations are also seen when staphylococcal cells are exposed, in vitro or in vivo, to antibiotics such as clindamycin, but we emphasize that growth in tissue alone is sufficient for their induction.