Bicortical Defects Research Articles

The evaluation of pathologic fracture risk and residual bone height in unicortical and bicortical mandibular corpus defects: A 3D finite analysis

ObjectiveMandibular bone defects are a common problem and difficult to manage. A defected area mostly left to heal spontaneously. It doesn’t have a definite protocol in the literature, when the area will be left to heal spontaneously or when supported with materials such as plates, screws, grafts, especially in intermediate-sized defects. In this study, it was aimed to determine by examining the areas where the stresses due to chewing forces are concentrated on the mandible bone and the risk of fracture in intermediate size unicortical and bicortical defects. Material and MethodsThe all defect models which was the residual bone heights were 6, 8, 10 mm in mandibular corpus region were created. Two different loading scenarios were applied anterior and defected premolar side. Von Mises, Pmax and Pmin stresses in models were evaluated by three-dimensional finite element analysis method. ResultsThe study found higher stress accumulation on the buccal anterior side of defects in both unicortical and bicortical models, with the most stress concentrated at the buccal corners. Under Loading 1, bicortical defects with 10 mm residual bone height showed slightly higher stress accumulations than unicortical defects, while bicortical defects with 8 and 6 mm residual bone height exhibited significantly higher stress values. Under Loading 2, stress accumulations in bicortical defects were higher than in unicortical defects, with bicortical defects at 6 mm residual bone height showing almost double the stress values. Pmax stress values were higher in bicortical defects under both loadings, especially when the residual bone height decreased. Pmin stress values were comparable in unicortical defects but were higher in bicortical defects, particularly at 6 mm residual bone height, under both loading conditions. ConclusionThis study was presented that mandibular resistance decreases significantly when residual bone height is less than 10 mm for bicortical defects and less than 8 mm at unicortical defects. In these conditions it may need supported with materials to prevent fractures. However, in vivo and in vitro studies are necessary for definitive conclusions.

Influence of Screw-Hole Defect Size on the Biomechanical Properties of Feline Femora in an Ex Vivo Model.

The study aims to evaluate the biomechanical properties of feline femora with craniocaudal screw-hole defects of increasing diameter, subjected to three-point bending and torsion to failure at two different loading rates. Eighty femoral pairs were harvested from adult cat cadavers. For each bending and torsional experiment, there were five groups (n = 8 pairs) of increasing craniocaudal screw-hole defects (intact, 1.5 mm, 2.0 mm, 2.4 mm, 2.7mm). Mid-diaphyseal bicortical defects were created with an appropriate pilot drill-hole and tapped accordingly. Left and right femora of each pair were randomly assigned to a destructive loading protocol at low (10 mm/min; 0.5 degrees/s) or high rates (3,000 mm/min; 90 degrees/s) respectively. Stiffness, load/torque-to-failure, energy-to-failure and fracture morphology were recorded. Defect size to bone diameter ratio was significantly different between defect groups within bending and torsional experiments respectively (intact [0%; 0%], 1.5 mm [17.8%; 17.1%], 2.0 mm [22.8%; 23.5%], 2.4 mm [27.8%; 27.6%], 2.7 mm [31.1%; 32.4%]) (p < 0.001). No significant differences in stiffness and load/torque-to-failure were noted with increasing deficit sizes in all loading conditions. Screw-hole (2.7 mm) defects up to 33% bone diameter had a maximum of 20% reduction in bending and torsional strength compared with intact bone at both loading rates. Stiffness and load/torque-to-failure in both bending and torsion were increased in bones subjected to higher loading rates (p < 0.001). Screw-hole defects up to 2.7 mm did not significantly reduce feline bone failure properties in this ex vivo femoral study. These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.

Microcomputed Tomography and Histological Study of Bone Regeneration Using Tooth Biomaterial with BMP-2 in Rabbit Calvarial Defects.

Our study was aimed to analyze the osteoinductive effect of powdered and block type autogenous bone graft along with bone morphogenetic protein (BMP-2) as compared to synthetic bone graft. Three circular bicortical defects were made in the calvaria of each rabbit and randomly divided into three groups as follows: powdered tooth biomaterial+BMP-2, block tooth biomaterial+BMP-2, and control group: synthetic bone+BMP-2. The samples taken from these defects after 4 and 8 weeks were analyzed histologically along with micro CT analysis. In our study, both powered and block type tooth autogenous bone graft successfully stimulated mesenchymal cells leading to endochondral ossification and bone regeneration. We observed that the powered bone graft material which is acid insoluble especially is preferable as a carrier for BMP-2.

CBCT analysis of bone density in bicortical defects after augmentation with alloplastic and xenogeneic bone substitutes: A study on domestic pigs

Background/Aim. A significant benefit in bicortical defects healing can be achieved by guided tissue and guided bone regeneration. The aim of this study was a cone-beam computed tomography (CBCT) radiographic bone density analysis of bicortical defects healing when treated with guided bone regeneration and two bone substitutes ? bovine xenograft and alloplastic bone substitute. Methods. The research was performed on domestic pigs in two phases. In the first phase, extraction of all teeth in the intercanine sector was performed in the lower jaw and postextraction wounds were sutured. In the second phase, after the period required for healing, bicortical defects were formed ? following the elevation of mucoperiosteal flaps from the vestibular and lingual side in the area of the previously extracted teeth, surgical removal of the cambium layer of periosteum was performed in the area of future defects with sharp surgical scissors and curette. Two defects, 10 mm in diameter, on the left and right side of the medial line were formed and filled with alloplastic bone substitute on the left and xenograft on the right side afterward. After augmentation, the defects were covered by a collagen resorptive membrane on both sides, and the flap was repositioned and sutured. After 12 weeks, experimental animals were sacrificed. The surrounding native bone was used as a control. Results. Analysis of bone tissue density showed a statistically significant difference between the examined bone substitutes (p &lt; 0.01), with a better effect achieved by the use of alloplastic bone substitute. After applying Bonferroni correction, the difference was still statistically significant. Conclusion. Both bone substitutes used in the study showed good osteoconductive properties in the treatment of bicortical defects. Bone tissue density in defects filled with alloplastic bone graft was statistically significantly higher than that in the defects filled with xenograft.

EVALUATION OF BONE TISSUE REGENERATION USING A COMBINATION OF AUTOLOGOUS FIBRIN MATRIX WITH PRE-DIFFERENTIATED MESENCHYMAL STEM CELLS IN AN EXPERIMENTAL MODEL

Introduction. According to domestic and foreign authors, the frequency of damage to the mandible bone is 36-84% of all damage to the bones of the facial skeleton. Since A.Y. Friedenstein made a key contribution to the study of mesenchymal stem cells (MSC), their analysis, types, methods of isolation and use in various combinations with materials, allowed to expand the boundaries of regenerative medicine. Aim of the study. The purpose of the study is to evaluate the regenerative potential of cortical bone tissue in the region of the mandible angle, with the introduction of exogenous pre-differentiated MSC (MSCs) on the autologous fibrin matrix in the experiment. Material and methods. We carried out an experimental study on 27 rabbits of the Soviet Chinchilla breed. Animals were divided into 3 groups: A, B and control. The bone defect diameter of 6mm was formed in the angle of the mandible of all animals with a trepan. Groups A and B mandible defects were injected with autologous fibrin clot with pre-differentiated MSCs in the amount of 300 thousand and 1 million cells, respectively. Defect size was assessed after 8, 10 and 12 weeks. Results. At week 12 after surgery, in the experimental group B the size of the bone tissue defect was significantly reduced and amounted to 0.006022 ± 0.00135 mm3, while in the control group the defect volume was 0.05597 ± 0.00505 mm3, and in group A was 0.02235 ± 0.0056 mm3. In an experimental study, an improvement was obtained in the pathophysiological processes of bone tissue regeneration under conditions of a bicortical defect with minimal presence of spongy substance in the damage zone.

The role of fish scale derived scaffold and platelet rich plasma in healing of rabbit tibial defect: an experimental study

Fish scale is rich in collagen type I and hydroxyapatite, resembling bone structure. It is readily available, cost effective and can compensate for the limitations of grafting methods such as unavailability, zoonotic disease transmission, and high cost. The aim of this study was to evaluate in vivo the fish scale potential and the possible synergistic effect of platelet rich plasma (PRP) with this scaffold in bone regeneration. Fifteen male white New Zealand rabbits were randomly divided into six groups, each involving 5 limbs. Full thickness bicortical defects were created in the proximal tibia of both pelvic limbs of rabbits. The defect was left untreated in the negative control group. In experimental groups the defect was filled with PRP (group 1), cellular fish scale (group 2), combination of cellular fish scale and PRP (group 3), acellular fish scale (group 4), and a combination of acellular fish scale and PRP (group 5). Fresh fish scales were decellularized to increase biocompatibility and reduce immunity reactions. Decellularization was confirmed by DAPI (4',6-diamidino-2-phenylindole) staining. The microstructure and surface characteristics of fish scales were assessed by scanning electron microscopy (SEM). Histopathological evaluation of bone healing was performed on day 56. Although there was no significant difference in the bone union among experimental groups, the union was superior in all experimental groups compared to control. Spongiosa and cortex formation were superior in the acellular groups. Furthermore, PRP promoted bone marrow formation. We concluded that fish scale is a biocompatible scaffold with a high regenerative potential.

Effects of Hypericum perforatum on the healing of xenografts: a histomorphometric study in rabbits

The aim of this study was to investigate effects of the Hypericum perforatum (St John’s Wort) on bone healing in rabbit calvarium. Ten male New Zealand rabbits each had three bicortical defects made in the calvarial bones, which were filled with xenograft, xenograft+H perforatum oil extract, and autogenous graft. Four weeks postoperatively all rabbits were killed and the bony defects examined histomorphometrically. Tissue compartments including new bone (p<0.001), marrow space (p<0.001), and residual bone grafts (p=0.014) differed significantly among groups. The volume of residual graft was significantly decreased in the xenograft/H perforatum group compared with those with xenografts alone (p=0.0147). The differences in microarchitectural variables of de novo bone formation were also significant (trabecular thickness (p<0.001), trabecular width (p<0.001), trabecular separation (p=0.001). There were no significant differences in node:terminus ratio between the xenograft/H perforatum group and the other two groups. However, the difference in node:terminus ratio between the autogenous graft and xenograft group was significant (p=0.001) Oil extracts of H perforatum improved bony healing in defects filled with bovine-derived xenografts.

A novel animal model treated with tooth extraction to repair the full-thickness defects in the mandible of rabbits

BackgroundIt has traditionally been difficult to create full-thickness defects in the mandibles of rodent animals because of dissimilar anatomic structures with humans, interference from teeth of jaws, and limited surgical access. To better mimic the cellular situation and the unique masticatory stresses in maxillofacial regions of humans, we developed an animal model of mandibular defects, in which rabbits were implanted with the beta-tricalcium phosphate/chitosan (β-TCP/CS) scaffolds after a dental extraction and the creation of a full-thickness bone defect. MethodsSeventy-two New Zealand rabbits underwent unilateral mandibular defect surgery in the premolar region and were randomly divided into three groups as follows: (1) The full-thickness bicortical defect with tooth extraction of the mandibular first premolar and implantation of bone marrow stromal cells/β-TCP/CS scaffold graft (group G + E); (2) the bicortical defect, not treated with tooth extraction and implanted with the bone marrow stromal cells/β-TCP/CS grafts (group G); and (3) the bicortical defects created in the same location in the negative control group, not treated with tooth extraction and graft implantation (group C). The defects in all groups were examined at 4 and 12 wk using mechanical tests, x-ray, and histology observation to determine the biomechanical stability, quantity, and quality of the newly formed bone. ResultsGroup G + E displayed the largest amount of new bone formation, with high mechanical forces in compression and three-point bending tests, filled in the mandibular defects at 4 wk, and complete reconstruction of bony contours and bridging by 12 wk after implantation. Although similar mechanical forces and new bone formation were demonstrated by the normal healing specimens, the abnormal cases with periapical diseases of group G demonstrated less amount of new bone formation and smaller mechanical forces when compared with those of group G + E at 4 and 12 wk. In contrast, the defect without graft implantation in the negative control group (group C) failed to bridge itself and displayed fibrous tissue filled in the defects with the lowest mechanical forces at both 4 and 12 wk of implantation. ConclusionsA 10-mm diameter, full-thickness mandibular defect treated with tooth extraction of the first mandibular premolar can mimic the segmental jawbone defects and fulfill the requirements of a critical-size mandibular defect in rabbits. Furthermore, the new bone regeneration and biomechanical stability of the mandible can be promoted by extraction of the teeth located in the defect side, which demonstrated the potential of this model as a test bed for tissue-engineering grafts used in jawbone defects.

In vitroEvaluation of the Torsional Strength Reduction of Neonate Calf Metatarsal Bones with Bicortical Defects Resulting from the Removal of External Fixation Implants

ObjectiveTo compare the torsional strength of calf metatarsal bones with defects produced by removal of 2 different implants.Study DesignIn vitromechanical comparison of paired bones with bicortical defects resulting from the implantation of 2 different external fixation systems: the transfixation pin (TP) and the pin sleeve system (PS).Sample PopulationNeonatal calf metatarsal bones (n = 6 pairs).MethodsFrom each pair, 1 bone was surgically instrumented with 2 PS implants and the contralateral bone with 2 TP implants. Implants were removed immediately leaving bicortical defects at identical locations between paired metatarsi. Each bone was tested in torque until failure. The mechanical variables statistically compared were the torsional stiffness, the torque and angle at failure, and work to failure.ResultsFor TP and PS constructs, respectively, there were no significant differences between construct types for any of the variables tested. Mean ± SD torsional stiffness: 5.50 ± 2.68 and 5.35 ± 1.79 (Nm/°),P= .75; torque: 57.42 ± 14.84 and 53.43 ± 10.16 (Nm);P= .34; angle at failure: 14.76 ± 4.33 and 15.45 ± 4.84 (°),P= .69; and work to failure 7.45 ± 3.19 and 8.89 ± 3.79 (J),P= .17).ConclusionsBicortical defects resulting from the removal of PS and TP implants equally affect the investigated mechanical properties of neonate calf metatarsal bones.

In vivo behaviour of a biodegradable poly(trimethylene carbonate) barrier membrane: a histological study in rats

The aim of the present study was to evaluate the response of surrounding tissues to newly developed poly(trimethylene carbonate) (PTMC) membranes. Furthermore, the tissue formation beneath and the space maintaining properties of the PTMC membrane were evaluated. Results were compared with a collagen membrane (Geistlich BioGide), which served as control. Single-sided standardized 5.0 mm circular bicortical defects were created in the mandibular angle of rats. Defects were covered with either the PTMC membrane or a collagen membrane. After 2, 4 and 12 weeks rats were sacrificed and histology was performed. The PTMC membranes induced a mild tissue reaction corresponding to a normal foreign body reaction. The PTMC membranes showed minimal cellular capsule formation and showed signs of a surface erosion process. Bone tissue formed beneath the PTMC membranes comparable to that beneath the collagen membranes. The space maintaining properties of the PTMC membranes were superior to those of the collagen membrane. Newly developed PTMC membranes can be used with success as barrier membranes in critical size rat mandibular defects.

Surface Characteristics of Biomaterials Used for Space Maintenance in a Mandibular Defect: A Pilot Animal Study

The purpose of the present study was to evaluate the effect of implant porosity on wound healing between solid and porous implants placed within a bony mandibular defect with intraoral exposure. Solid poly(methyl methacrylate) (PMMA) implants similar to those used currently in clinical space maintenance applications in maxillofacial surgery were compared with poly(propylene fumarate) implants that contained a porous outer surface surrounding a solid core. A 10-mm diameter nonhealing bicortical defect with open communication into the oral cavity was created in the molar mandibular region of 12 adult male New Zealand white rabbits. Of the 12 rabbits, 6 received the hybrid poly(propylene fumarate) implants and 6 received the solid PMMA implants. At 12 weeks, the rabbit mandibles were harvested and sent for histologic staining and sectioning. Gross inspection and histologic examination showed all 6 poly(propylene fumarate) implants to be intact within the defect site at the termination of the study period, with 3 of the 6 specimens exhibiting a continuous circumferential soft tissue margin. In contrast, 5 of the 6 PMMA-implanted specimens were exposed intraorally with an incomplete cuff of soft tissue around the implant. One of the PMMA-implanted specimens exhibited complete extrusion and subsequent loss of the implant. Fisher's exact test was used to compare the occurrence of oral cavity wound healing between the 2 groups (P = .09). Although statistically significant differences between the 2 groups were not seen, our results have indicated that advantages might exist to using porous implants for space maintenance. Additional study is needed to evaluate these findings.

The effect of 4 mm bicortical drill hole defect on bone strength in a pig femur model

In orthopaedic surgery, small bicortical circular bone defects are often produced as a result of internal fixation of fractures. The aim of this study was to determine the amount of torsional strength reduction in animal bone with a bicortical bone defect and how much residual strength remains if the bicortical bone defect was occluded. Forty pig femurs were divided into four groups. Group 1 femurs were left intact. Group 2 femurs were given a 4 mm bicortical bone defect. Group 3 were prepared as in Group 2, but occluded with a 4.5 mm cortical screw. Group 4 were prepared as in Group 2, but occluded with plaster of paris. Measurements including the length of the bone, working length of the bone, mid-diaphyseal diameter and cortical thickness were recorded. All specimens were tested until failure under torsional loading. Peak torque at failure and angular deformation were recorded. One-way analysis of variance was used to test the sample groups, with a value of P < 0.05 considered to be statistically significant. When compared with Group 1, all of the other groups showed a reduction in peak torque at failure point. Only the difference in peak torque between Groups 1 and 2 was statistically significant (P = 0.007). Group 2 showed the most reduction with 23.11% reduction in peak torque and 38.19% reduction in total energy absorption. No significant difference was found comparing the bone length, bone diameter and the cortical thickness. The presence of the defect remains the major contributing factor in long bone strength reduction. It has been shown that a 10% bicortical defect was sufficient to produce a reduction in peak torque and energy absorption under torsional loading. By occluding this defect using a screw or plaster of paris, an improvement in bone strength was achieved. These results may translate clinically to an increased vulnerability to functional loads immediately following screw removal and prior to the residual screw holes healing.

Comparison of ready-made and self-setting alginate membranes used as a barrier membrane for guided bone regeneration

In order to understand the requirements of guided bone regeneration (GBR) involving alginate base self-setting barrier membranes, GBR was performed in the case of bicortical bone defects formed at the tibiae of experimental animals employing self-setting and ready-made alginate membranes. Connective tissue ingress into the bone defects at the skin side of the tibia was observed when GBR was generated utilizing ready-made alginate membrane. In contrast, bone defects were reconstructed with bone tissue when GBR was generated with self-setting alginate membrane formed from aqueous 3% sodium alginate and 3% CaCl(2) solutions. The unreacted aqueous sodium alginate solution inherent to self-setting alginate membrane did not inhibit bone tissue regeneration. Rather, callus bone was formed using sodium alginate as the nucleus. However, when GBR was effected with self-setting alginate membrane formed from aqueous 10% CaCl(2) solution, membrane was too thick and thus regeneration of bone tissue in the bone cavity was prevented. Therefore, we concluded that self-setting alginate membrane is very useful as a barrier membrane for GBR upon appropriate adjustment of conditions with respect to preparation of alginate membrane.

Basic studies on the bone formation ability by platelet rich plasma in rabbits.

Platelets, which contain many growth factors, such as platelet-derived growth factor (PDGF) and transforming growth factor-beta(TGF-beta), can be obtained in high concentrations by centrifugal separation and are being used as platelet-rich plasma (PRP) in clinical applications. The authors evaluated the bone formation ability by PRP in rabbits. In experiment 1, the authors made platelet precipitations from the whole blood obtained from rabbits. Each precipitated platelet was resuspended in fibrin glue. The glue was applied to a 1-mm wide slit defect of the same rabbit mandible. After 1 week, the authors observed the histologic appearances. In experiment 2, the fibrin glue containing the precipitated platelet was applied to a bicortical defect of a rabbit cranium with beta-tricalcium phosphate (beta-TCP) granules as artificial bone material. After 1 week, 1 month, and 2 months, the authors observed the radiologic and histologic appearances. In both experiments, a prosperous bone formation was observed from the beginning more in the group treated with PRP than in the group untreated. In experiment 2, gradual appearances of the bone formation were observed in the bubble of beta-TCP. In application with artificial bone materials, bone formations by PRP were suitably observed.

Hydroxyapatite cement (BoneSource TM) for repair of critical sized calvarian defects—an experimental study

Aim: In an experimental study the hydroxyapatite cement BoneSource TM was tested for the ability in relation to the defect size and for its resorption properties. Material and methods: In an animal study, BoneSource TM was applied to repair bicortical defects of different sizes in frontal bones of six Goettingen minipigs. The area was evaluated radiographically and histologically 12, 18 and 40 weeks postoperatively. Results: After 40 weeks approximately 90% of the hydroxyapatite cement had been resorbed and replaced with bone. After 12 weeks, approximately 30% had been degraded, and 40% after 18 weeks. In small bone defects, the mucosa of the frontal sinus lined the bone substitute (BoneSource TM). In the reconstruction of large areas, a membrane was used to stabilize the material. Despite this membranous support, BoneSource TM material prolapsed into the frontal sinus. Discussion: Hydroxyapatite cement is for the repair of bone defects. It can be moulded to shape the reconstruction. Its use is limited by the defect size and the need for a dry bed. Conclusion: BoneSource TM is well suited to repair small defects with proven high biocompatibility. However, in large defects, the material is not sufficiently stable.

SUBSTITUTES FOR AUTOLOGOUS BONE GRAFT IN ORTHOPAEDIC TRAUMA

SUBSTITUTES FOR AUTOLOGOUS BONE GRAFT IN ORTHOPAEDIC TRAUMA

Opposite Effects of Recombinant Human Transforming Growth Factor-β1 on Bone Regeneration In Vivo: Effects of Exclusion of Periosteal Cells by Microporous Membrane

The efficacy of local delivery of recombinant human transforming growth factor-β1 (rhTGF-β1) to promote bone regeneration, with or without cellular contribution from the periosteum, was evaluated in transosseous defects. Implantation of rhTGF-β1 into 5 mm in diameter “critical size defects” in the rat mandible resulted in a dose-dependent (0.1–20 μg/defect) bone bridging at both 12 and 24 days, independent of the type of delivery system [3% methyl cellulose gel, porous CaCO 3 particles, or poly(lactide- co-glycolide) beads]. The bridging, however, never exceeded 24% at 12 days or 34% after 24 days. In contrast, when access of cells from the periosteum to the defect was prevented by means of microporous expanded polytetrafluoroethylene barrier membranes (GORE-TEX® membrane), rhTGF-β1 caused a dose-dependent inhibition of bone regeneration. The bioactivity of the growth factor was confirmed by implantation of 5 or 10 μg rhTGF-β1 in 12 mm in diameter bicortical defects in rabbit calvaria, which resulted in complete bone healing within 28 days, whereas control defects displayed a bridging of 40%–50%. The findings support the concept, based on in vitro experiments by others, that TGF-β1 primarily has a proliferative effect on cells already committed to the osteoblastic lineage, but also imply that TGF-β1 may be inhibitory to induction of osteogenic cells in vivo.

The relationship among CD 4, CD 8, and MRC OX-12 antigen expression in 4NQO induced premalignant lesion of rat

The relationship among CD 4, CD 8, and MRC OX-12 antigen expression in 4NQO induced premalignant lesion of rat

Surgical management of the osteoradionecrotic mandible with free vascularised composite flaps

Osteoradionecrosis (ORN) of the mandible is a serious sequel to radiotherapy administered for malignant neoplasms of the head and neck. In a retrospective/prospective study, 28 patients with mandibular defects due to ORN were reviewed. Monocortical and bicortical defects as well as pathological fractures were reconstructed by means of a free serratus anterior/rib (n = 8) or a vascularised iliac crest flap (n = 25). All the former survived; a pathological fracture, however, occurred postoperatively in 2 of the patients (25%). Five iliac crests were lost (20%). The remaining bone struts healed well. The donor site morbidity was very low. Clinical and radiological longterm follow-up showed that a very acceptable functional and cosmetic result was achieved in all cases. Progress of ORN was prevented in ca. 90% of all patients. The radiological follow-up was facilitated with the use of high-resolution CT-scans.