Computational fluid dynamics simulation from microCT stacks of commercial biomaterials usable for bone grafting.

Granules of calcium/phosphate biomaterials are used to fill small bone defects in oral and maxilla-facial surgery. Granules of natural (e.g., trabecular bone, coral) or synthetic biomaterials are provided by industry. Small granules can also form of putty. The 3D geometry of granules creates a macroporosity allowing invasion of vascular and bone cells when pores are larger than 300 µm. We analyzed the 3D-porosity of 11 different stacks of biomaterials: Osteopure®, CopiOs®, Bio-Oss®, TCP Dental HP®, KeraOs®, TCH®, Biocoral®, EthOss® and Nanostim®. For each granular biomaterial, two sizes of granules were analyzed: small and large. Microcomputed tomography (microCT) determined porosity and microarchitectural characteristics of the biomaterials stacks. Computational fluid dynamics (CFD), a simulation method, was used on the stacks of microCT images. Stacks of small granules had a much lower permeation and fluid velocity than large granules and the hydraulic tortuosity was increased. Significant correlations were observed between microarchitecture parameters (porosity, mean pore diameter and specific surface) and fluid dynamic parameters. The two putties were associated with low (or absence of) porosity and permeation study revealed a very low (or absence) of flow rate. Stacks of granules represent 3D scaffolds resembling trabecular bone with an interconnected porous microarchitecture. Small granules create pores less than 300 µm in diameter; this induces a low fluid flow rate. CFD simulates the accessibility of body fluids and progenitor cells and confirms that it is depending on the shape and 3D arrangements of granules within a stack. Large granules must be preferred to putties and small granules.

Maxillary sinus floor elevation using Beta-Tricalcium-Phosphate (beta-TCP) or natural bone: same inflammatory response.

Sinus elevation is a common procedure to increase bone volume in the atrophic maxilla to allow placement of dental implants. Autogenous bone is the gold standard but is limited in quantity and causes morbidity at the donor site. ß-TCP is a synthetic biomaterial commonly used in that purpose. It appears to induce a poor inflammatory response. This study aimed to evaluate the degree of edema of the sinus mucosa after sinus lift surgery according to the type of biomaterial. Forty sinuses (20 patients) were included retrospectively and divided into 2 groups according to the biomaterial that was used: synthetic biomaterial (BTCP group), natural bone (BONE group). A control group (CTRL group) was constituted by the non-grafted maxillary sinuses. Twelve measurements per sinus were realized on pre- and post-operative computed tomography and averaged to provide the sinus membrane thickness value (SM.Th). SM.Th was thicker post-operatively in the BTCP and BONE groups in comparison with the CTRL group and in comparison with pre-operative measurements. No difference was found post operatively between the BTCP and BONE groups. We found that a synthetic biomaterial (ß-TCP) induced the same degree of edema, and thus of inflammation, as natural bone. It constitutes therefore an interesting alternative to autogenous bone for maxillary sinus lifts.

Biomaterial granules used for filling bone defects constitute 3D scaffolds: porosity, microarchitecture and molecular composition analyzed by microCT and Raman microspectroscopy.

Biomaterials are used in the granular form to fill small bone defects. Granules can be prepared with a grinder from trabecular bone samples or provided as synthetic biomaterials by industry. Granules occupy the 3D-space and create a macroporosity allowing invasion of vascular and bone cells when the inter-granular pores are larger than 300 µm. We compared the 3D-porosity of granule stacks obtained or prepared with nine biomaterials Osteopure® , Lubboc® , Bio-Oss® , CopiOs® , TCP Dental® , TCP Dental HP® , KeraOs® , and TCH® in comparison with that of human trabecular bone. For each biomaterial, two sizes of granules were analyzed: 250-1000 and 1000-2000 µm. Microcomputed tomography determined porosity and microarchitectural characteristics of granular stacks and Raman microspectroscopy was used to analyze their composition. Stacks of 250-1000 µm granules had a much lower porosity than 1000-2000 µm granules and the maximum frequency of pores was always centered at 200-250 µm. One biomaterial contained substantial amount of cortical bone (Bio-Oss® ). The highest porosity and pore size was obtained with TCP Dental HP. Raman spectroscopy found differences in biomaterials of the same composition. Stacks of granules represent 3D scaffolds resembling trabecular bone with an interconnected porous microarchitecture. Small granules have created pores <300 µm in diameter; this can interfere with vascular colonization. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 415-423, 2019.

Maxillary Sinus Lift with Beta-Tricalcium Phosphate (ß-TCP) in Edentulous Patients: A Nanotomographic and Raman Study.

Sinus lift elevation restores bone mass at the maxilla in edentulate patients before the placement of dental implants. It consists of opening the lateral side of the sinus and grafting beta-tricalcium phosphate granules (ß-TCP) under the olfactory membrane. Bone biopsies were obtained in five patients after 60 weeks. They were embedded undecalcified in poly(methyl methacrylate) (pMMA); blocks were analyzed by nanocomputed tomography (nanoCT); specific areas were studied by Raman microspectroscopy. Remnants of ß-TCP were osseointegrated and covered with mineralized bone; osteoid tissue was also filling the inner porosity. Macrophages having engulfed numerous ß-TCP grains were observed in marrow spaces. ß-TCP was identified by nanoCT as osseointegrated particles and as granules in the cytoplasm of macrophages. Raman microspectroscopy permitted to compare the spectra of ß-TCP and bone in different areas. The ratio of the ~820 cm-1 band of pMMA (-CH2 groups) on the ν1 phosphate band at 960 cm-1 reflected tissue hydration because water was substituted by MMA during histological processing. In bone, the ratio of the ~960 cm-1 phosphate to the amide 1 band and the ratio ν2 phosphate band by the 1240-1250 amide III band reflect the mineralization degree. Specific bands of ß-TCP were found in osseointegrated ß-TCP granules and in the grains phagocytized by the macrophages. The hydration degree was maximal for ß-TCP phagocytized by macrophages. Raman microspectroscopy associated with nanoCT is a powerful tool in the analysis of the biomaterial degradation and osseointegration.

Asymmetric bone remodeling in mandibular and maxillary tori.

OBJECTIVES: Tori are frequent paucisymptomatic bony outgrowths of the oral cavity in three locations: torus palatinus (TP), mandibularis (TM), and maxillaris (TMax). Their usually described histological characteristics are unspecific: normal cortical bone with more or less trabecular bone. The aim of this study was to describe tori's specific morphological and histomorphometric characteristics. MATERIALS AND METHODS: Histological characteristics in a series of 18 tori collected after surgical removal were analyzed. Microcomputed tomography provided a 3D analysis. Mineral apposition rate (MAR) was measured after double tetracycline labeling. Osteoid tissue was identified by Goldner's trichrome and osteoclasts by the tartrate resistant acid phosphatase identification in undecalcified sections. Iron and aluminum were detected by histochemical staining methods. Osteoid thickness and MAR were determined at the outer surface of the torus and in the Haversian canals. RESULTS: Tori appeared made of lamellar Haversian bone in 16/18 cases. Osteoid thickness did not differ between the outer surface and within the canals. An asymmetric bone remodeling was observed in the Haversian canals of 15 tori: osteoid seams were deposited on the side close to the free torus surface, and Howship's lacunae with numerous osteoclasts were observed on the opposite side. A high MAR was found at the surface of the tori and within the canals. There was no iron or aluminum deposit. CONCLUSIONS: Tori may be characterized by a specific asymmetric bone remodeling which seems to determine their shape. CLINICAL RELEVANCE: This finding could constitute a specific histological feature allowing to differentiate tori from exostoses. Graphical abstract.

Clinical performance of a highly porous beta-TCP as the grafting material for maxillary sinus augmentation.

BACKGROUND: Beta-tricalcium phosphate (ß-TCP) is a synthetic bone substitute having high porosity and fast resorption. This retrospective study aimed at evaluating the effectiveness of an highly macroporous ß-TCP for maxillary sinus floor augmentation. METHODS: Twenty-seven consecutive patients (17 woman/10 men, mean age: 59.7 years) in 2 clinics underwent maxillary sinus augmentation by lateral approach using ß-TCP as grafting material. Implant survival, prosthesis success, periimplant bone loss, oral hygiene level, soft tissue condition, complication occurrence, and patient satisfaction were assessed. RESULTS: Thirty-one sinuses were successfully augmented. Sixty implants were placed. No sinus membrane perforations occurred. The mean follow-up after grafting was 39.3 ± 8.7 months (range, 22-52 months), and it was 30.5 ± 8.1 months (range, 15-43 months) after implant loading. No implants were lost. After 1 year of loading, marginal bone loss averaged -0.88 ± 0.46 mm (n = 54 implants). Mean full-mouth plaque and bleeding scores were 11.5% ± 4.8% and 3.5% ± 2.8%, respectively. No biological or mechanical complications were recorded. Patient satisfaction was very high. CONCLUSION: Despite limited sample size and follow-up duration, highly macroporous ß-TCP proved a valuable bone substitute for sinus augmentation, even when used alone.

Texture analysis of computed tomographic images in osteoporotic patients with sinus lift bone graft reconstruction.

OBJECTIVE: Bone implants are now widely used to replace missing teeth. Bone grafting (sinus lift) is a very useful way to increase the bone volume of the maxilla in patients with bone atrophy. There is a 6- to 9-month delay for the receiver grafted site to heal before the implants can be placed. Computed tomography is a useful method to measure the amount of remaining bone before implantation and to evaluate the quality of the receiver bone at the end of the healing period. Texture analysis is a non-invasive method useful to characterize bone microarchitecture on X-ray images. PATIENTS AND METHODS: Ten patients in which a sinus lift surgery was necessary before implantation were analyzed in the present study. All had a bone reconstruction with a combination of a biomaterial (beta tricalcium phosphate) and autograft bone harvested at the chin. Computed tomographic images were obtained before grafting (t0), at mid-interval (t1, 4.2 ± 0.7 months) and before implant placement (t2, 9.2 ± 0.6 months). Texture analysis was done with the run-length method. RESULTS: A significant increase of texture parameters at t1 reflected a gain of homogeneity due to the graft and the beginning of bone remodeling. At t2, some parameters remained high and corresponded to the persistence of bone trabeculae while the resorption of biomaterials was identified by other parameters which tended to return to pregraft values. CONCLUSION: Texture analysis identified changes during the healing of the receiver site. CLINICAL RELEVANCE: The method is known to correlate with microarchitectural changes in bone and could be a useful approach to characterized osseointegrated grafts.

Sinus lift augmentation and beta-TCP: a microCT and histologic analysis on human bone biopsies.

Sinus lift elevation is an interesting method to restore bone mass at the maxilla in edentulated patients. We have investigated the histological effects of beta tricalcium phosphate (beta-TCP) combined with autograft bone for sinus lift elevation. A series of 14 patients who were candidate for dental implantation were grafted with beta-TCP granules and morcellized autograft bone harvested at the chin. beta-TCP was characterized by scanning electron microscopy and optical profilometry. Before implant placement, a small bone biopsy (2mm in diameter) was done. The amount of residual material and newly formed bone were determined by microcomputed tomography. Histological analysis was done on undecalcified sections stained by Goldner's trichrome and osteoclast identification (TRAcP). beta-TCP served as a template for bone apposition by osteoblasts onto the granules' surface. The material was simultaneously resorbed by TRAcP positive osteoclasts and macrophages. Fragments of the material remained buried in bone trabeculae as long as 12 months post-graft but the formed bone onto the granules surface had a lamellar texture. beta-TCP combined with autograft bone appears a suitable biomaterial for sinus lift augmentation before the placement of bone implants. The material favors the apposition of lamellar bone by osteoblasts and is simultaneous resorbed by two types of cells.

Viability of osteocytes in bone autografts harvested for dental implantology.

Bone autograft remains a very useful and popular way for filling bone defects. In maxillofacial surgery or implantology, it is used to increase the volume of the maxilla or mandible before placing dental implants. Because there is a noticeable delay between harvesting the graft and its insertion in the receiver site, we evaluated the morphologic changes at the light and transmission electron microscopy levels. Five patients having an autograft (bone harvested from the chin) were enrolled in the study. A small fragment of the graft was immediately fixed after harvesting and a second one was similarly processed at the end of the grafting period when bone has been stored at room temperature for a 20 min +/- 33 s period in saline. A net increase in the number of osteocyte lacunae filled with cellular debris was observed (+41.5%). However no cytologic alteration could be observed in the remaining osteocytes. The viability of these cells is known to contribute to the success of autograft in association with other less well-identified factors.

Dibarium zirconium tetraoxalate trihydrate.

A new mixed barium zirconium oxalate, triaquatetra-mu-oxalato-dibarium(II)zirconium(IV), Ba(2)Zr(C(2)O(4))(4).3H(2)O or [Ba(2)Zr(C(2)O(4))(4)(H(2)O)(3)](n), has been synthesized. The complex is built from eightfold-coordinated Zr atoms and eleven- and sixfold-coordinated Ba atoms, linked by oxalate groups. The Zr atom, the two Ba atoms and one water O atom lie on crystallographic twofold axes, so that each coordination polyhedron has imposed C2 symmetry. Packing in the crystal is also assumed through hydrogen bonds.