Reconstruction of Segmental Bone Defect in Canine Tibia Model Utilizing Bi-Phasic Scaffold: Pilot Study.

The reunion and restoration of large segmental bone defects pose significant clinical challenges. Conventional strategies primarily involve the combination of bone scaffolds with seeded cells and/or growth factors to regulate osteogenesis and angiogenesis. However, these therapies face inherent issues related to immunogenicity, tumorigenesis, bioactivity, and off-the-shelf transplantation. The biogenic micro-environment created by implanted bone grafts plays a crucial role in initiating the bone regeneration cascade. To address this, a highly porous bi-phasic ceramic synthetic bone graft, composed of hydroxyapatite (HA) and alumina (Al), was developed. This graft was employed to repair critical segmental defects, involving the creation of a 2 cm segmental defect in a canine tibia. The assessment of bone regeneration within the synthetic bone graft post-healing was conducted using scintigraphy, micro-CT, histology, and dynamic histomorphometry. The technique yielded pore sizes in the range of 230-430 µm as primary pores, 40-70 µm as secondary inner microchannels, and 200-400 nm as tertiary submicron surface holes. These three components are designed to mimic trabecular bone networks and to provide body fluid adsorption, diffusion, a nutritional supply, communication around the cells, and cell anchorage. The overall porosity was measured at 82.61 ± 1.28%. Both micro-CT imaging and histological analysis provided substantial evidence of robust bone formation and the successful reunion of the critical defect. Furthermore, an histology revealed the presence of vascularization within the newly formed bone area, clearly demonstrating trabecular and cortical bone formation at the 8-week mark post-implantation.

Evaluation of Efficiency of Polymerization, Surface Roughness, Porosity and Adaptation of Flowable and Sculptable Bulk Fill Composite Resins.

A new category of commercial bulk fill composite resins (CRs) enables the placement of 4-mm-thick layers as an alternative to the traditional time-consuming incremental technique. The purpose of the present study was to compare the efficiency of the polymerization, adaptation and porosity of two high-viscosity 'sculptable' bulk fill CRs (Filtek™ Bulk Fill (3M™ ESPE, St. Paul, MN, USA) and Tetric EvoCeram® Bulk Fill (Ivoclar Vivadent AG, Schwan, Liechtenstein)) and two low-viscosity 'flowable' bulk fill CRs (SureFil® SDR™ flow (Dentsply Sirona, Charlotte, NC, USA) and Tetric EvoFlow® Bulk Fill (Ivoclar Vivadent AG, Schaan, Liechtenstein)). Cylindrical samples of the bulk fill CRs (4 mm height × 10 mm diameter) were analyzed by Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Additionally, occlusal cavities were prepared in twelve extracted human molars and restored with the bulk fill CRs (n = 3 for each CR). The adaptation and porosity of the bulk fill CRs were evaluated by X-ray microcomputed tomography (µCT) with a 3D morphometric analysis, and the adaptation was also analyzed by scanning electron microscopy (SEM) on longitudinal vestibulo-oral sections of the restored teeth. The AFM analysis demonstrated that the surface roughness of the SureFil® SDR™ flow was higher than that of the Tetric EvoFlow® Bulk Fill and that the surface roughness of Filtek™ Bulk Fill was higher than that of Tetric EvoCeram® Bulk Fill. µCT and SEM confirmed that the flowable bulk fill CRs had excellent adaptation to the cavity walls. The 3D morphometric analysis showed the highest and lowest degrees of porosity in Filtek™ Bulk Fill and Tetric EvoFlow® Bulk Fill, respectively. In general, the flowable bulk fill CRs exhibited better adaptation, a higher efficiency of polymerization and lower porosity than the sculptable materials.

A Step-by-Step Procedure for Bone Regeneration Using Calcium Phosphate Scaffolds: From Site Preparation to Graft Placement.

Hydroxyapatite (HA) is the main mineral component of bone and teeth. HA is often used as a bone substitute and especially in its granular form it is osteoconductive and osseointegrating as shown by many investigations in animals and humans. HA granules are used for filling bone defects, but they have poor handling qualities and retention at the surgical site, leading to graft voids between the granules and bone tissue and resulting in mechanical instability. Furthermore HA implantation is not constantly followed by favorable results, especially when it is carried out for augmentation of the alveolar ridge. This article offers a protocol for bone reconstruction and predictable implant treatment outcomes. We provide a step-by-step description of both the recipient site and composite graft preparations using coralline HA granules (CHAG) and homologous fibrin glue (HFG). In the present study, 20 randomly selected patients (12 women and 8 men) underwent bone regeneration using CHAG-HFG before a dental implant procedure. Radiographic imaging, physical examination, and histological analysis were performed during a 2-year period. Biopsies were obtained at second-stage surgery before implant insertion using a 2.8-mm trephine bur. A morphological study of 20 bioptic human specimens was performed. Our results demonstrate that this surgical protocol for the preparation of the recipient site associated with a mixture of coralline HA granules with homologous fibrin glue provides reliable bone regeneration, thus reducing failures and minimizing risks of postoperative morbidity.

A literature review and hypothesis for the etiologies of cervical and root caries.

The presence of endogenous acids from bacteria acting on a suitable substrate combined with sources of exogenous biocorrosives such as exogenous acids and proteolytic enzymes in areas of stress concentration are hypothesized to lead to the development and progression of cervical and root caries (RC). Quantifying the effects of each of the mechanisms (stress and biocorrosion) is a daunting task to investigate since so many factors are involved at various times in the etiology of noncarious cervical lesions (NCCLs), cervical caries (CC), and RC. Frictional action of the tongue has a cleansing effect and lingual serous saliva, which has a high flow rate buffering capacity from bicarbonates seem to account for the paucity of lingual NCCLs, cervical, and RC in these areas of teeth. Future studies are indicated to determine the effects of stress and biocorrosion and their factors in the etiology of CC and RC. CLINICAL SIGNIFICANCE: This manuscript presents hypothetical and literary information that the combined effects of stress concentration and biocorrosion contribute to the formation as well as progression of cervical and root caries.

Reconstruction of the Maxillary Sinus After Previous Major Sinus Elevation Failure: A Study with a 3-Year Follow-up.

Fourteen maxillary sinuses were reconstructed in 12 patients who presented with a previous sinus elevation failure. In all cases, large perforations of the sinus membrane occurred during removal of the failed graft from the sinus; the perforations were sealed with fibrin glue, then the site was grafted using homologous fibrin glue (HFG) mixed with a calcium phosphate scaffold (CPS). Histologic analyses revealed that the CPS-HFG graft was followed by an ossification process, with the formation of spongy bone similar to that of the normal skeleton. Twenty-four endosseous implants were successfully placed into the newly regenerated bone. All implants were successfully restored with ceramic crowns 6 months after placement. At the 3-year follow-up, no infections or implant failures were reported. The described technique offers several clinical advantages, as the removal of the failed graft, the sinus perforation repair, and the sinus elevation can be achieved in the same surgery without needing to postpone the regenerative surgery phase.

Drug-loaded porous spherical hydroxyapatite granules for bone regeneration.

Porous spherical hydroxyapatite (HAp) granules, which are not only can be used for bone void filler, but also drug delivery systems, were prepared using a liquid nitrogen method. Various pore and channel structures of spherical granules were obtained by adjusting the ratio of water to HAp powder and the amount of sodium chloride (NaCl). By using the water to powder ratio at 2.0 ml/g and the amount of NaCl at 15 wt% by powder, the spherical granules have optimal pore volume, micro-channel structure and strength to handle as well as the ability to work as a drug delivery system. When the NaCl content was 15 wt%, the micro-channel structure was changed, but the pore volume was maintained. For the drug release test, dexamathasone (Dex) was loaded as a model drug on the prepared HAp granules by the immersion method, and the drug release behavior was curved by a UV/vis spectrophotometer. As a result, different drug release behavior was observed according to micro-channel structural differences. Therefore, it was concluded that the NACl could be applied as the pore and micro-channel structure control agent. Porous spherical HAp granules, which were fabricated by a liquid nitrogen method, show potential as bone void filler with the ability of controlled drug release.

A classification of the mechanisms producing pathological tissue changes.

The objectives are to present a classification of mechanisms which can produce pathological changes in body tissues and fluids, as well as to clarify and define the term biocorrosion, which has had a singular use in engineering. Considering the emerging field of biomedical engineering, it is essential to use precise definitions in the lexicons of engineering, bioengineering and related sciences such as medicine, dentistry and veterinary medicine. The mechanisms of stress, friction and biocorrosion and their pathological effects on tissues are described. Biocorrosion refers to the chemical, biochemical and electrochemical changes by degradation or induced growth of living body tissues and fluids. Various agents which can affect living tissues causing biocorrosion are enumerated which support the necessity and justify the use of this encompassing and more precise definition of biocorrosion. A distinction is made between the mechanisms of corrosion and biocorrosion.

Guided bone regeneration in long-bone defects with a structural hydroxyapatite graft and collagen membrane.

There are few synthetic graft alternatives to treat large long-bone defects resulting from trauma or disease that do not incorporate osteogenic or osteoinductive factors. The aim of this study was to test the additional benefit of including a permeable collagen membrane guide in conjunction with a preformed porous hydroxyapatite bone graft to serve as an improved osteoconductive scaffold for bone regeneration. A 10-mm-segmental long-bone defect model in the rabbit radius was used. The hydroxyapatite scaffolds alone or with a collagen wrap were compared as experimental treatment groups to an empty untreated defect as a negative control or a defect filled with autologous bone grafts as a positive control. All groups were evaluated after 4 and 8 weeks of in vivo implantation using microcomputed tomography, mechanical testing in flexure, and histomorphometry. It was observed that the use of the wrap resulted in an increased bone volume regenerated when compared to the scaffold-only group (59% greater at 4 weeks and 27% greater after 8 weeks). Additionally, the increase in density of the regenerated bone from 4 to 8 weeks in the wrap group was threefold than that in the scaffold group. The use of the collagen wrap showed significant benefits of increased interfacial bone in-growth (149% greater) and periosteal remodeling (49%) after 4 weeks compared to the scaffold-alone with the two groups being comparable after 8 weeks, by when the collagen membrane showed close-to-complete resorption. While the autograft and wrap groups showed significantly greater flexural strength than the defect group after 8 weeks, the scaffold-alone group was not significantly different from the other three groups. It is most likely that the wrap shows improvement of function by acting like a scaffold for periosteal callus ossification, maintaining the local bone-healing environment while reducing fibrous infiltration (15% less than scaffold only at 4 weeks). This study indicates that the use of a collagen membrane with a hydroxyapatite structural graft provides benefits for bone tissue regeneration in terms of early interfacial integration.

Porous hydroxyapatite scaffold with three-dimensional localized drug delivery system using biodegradable microspheres.

In this study, ionic immobilization of dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres was performed on the hydroxyapatite (HAp) scaffold surfaces. It was hypothesized that in vivo bone regeneration could be enhanced with HAp scaffolds containing DEX-loaded PLGA microspheres compared to the use of HAp scaffolds alone. In vitro drug release from the encapsulated microspheres was measured prior to the implantation in the femur defects of beagle dogs. It was observed that porous, interconnected HAp scaffolds as well as DEX-loaded PLGA microspheres were successfully fabricated in this study. Additionally, PEI was successfully coated on PLGA microsphere surfaces, resulting in a net positive-charged surface. With such modification of the PLGA microsphere surfaces, DEX-loaded PLGA microspheres were immobilized on the negatively charged HAp scaffold surfaces. Release profile of DEX over a 4week immersion study indicated an initial burst release followed by a sustained release. In vivo evaluation of the defects filled with DEX-loaded HAp scaffolds indicated enhanced volume and quality of new bone formation when compared to defects that were either unfilled or filled with HAp scaffolds alone. This innovative platform for bioactive molecule delivery more potently induced osteogenesis in vivo, which may be exploited in implantable bone graft substitutes for stem cell therapy or improved in vivo performance. It was thus concluded that various bioactive molecules for bone regeneration might be efficiently incorporated with calcium phosphate-based bioceramics using biodegradable polymeric microspheres.

Repair of full-thickness defects in alimentary tract wall with patches of expanded polytetrafluoroethylene.

OBJECTIVES: To test the efficacy of patches of expanded polytetrafluoroethylene (ePTFE) for the repair of full-thickness defects in alimentary tract wall. SUMMARY BACKGROUND DATA: A recent report of successful replacement of duodenal wall with patches of ePTFE was met with skepticism and clearly warranted confirmation as well as evaluation in repair of other segments of the abdominal intestinal tract. METHODS: Defects of 4 cm2 were created in various segments of canine abdominal alimentary tract (stomach, duodenum, small bowel, and colon) as well as in bladder dome. For the duodenum in 13 dogs, three different ePTFE fabrications were used: CVX (cardiovascular), PDX (preclude dura membrane), and DLM (dual mesh plus). In repair of the other areas in six dogs, the PDX patch was used. When the animals were killed, both gross inspection of the parietes and tissue for histologic study became the basis for evaluation. Peritoneal and intraluminal cultures of the specific study viscera were also taken. RESULTS: There were no patch failures. Only six significant adhesions were noted in 3 of the 19 dogs. Serosal surface healing was complete without exception by 1 week in all animals. Patches of CVX and PDX had heaping mucosa at the margin of well-sealed patch edges in the study involving duodenum. However, the DLM patch had an undergrowth of mucosa with partial patch separation by 1 week, beginning patch extrusion into gut lumen at 3 weeks, and total separation of patch with complete mucosal repair at 6 weeks. The fate of the PDX patches at 6 weeks in stomach, small bowel, colon, and bladder was identical to what had been observed for the PDX patch in the duodenum. All peritoneal and bladder cultures had no growth, whereas the contents of the alimentary tract grew expected flora. CONCLUSIONS: These observations suggest that ePTFE may well be an acceptable membrane for at least temporary replacement of full-thickness hollow viscus defects, even in the face of heavy bacterial contamination, and that certain structural configurations of ePTFE may provide a base for increasing absorptive mucosal surface area.