Hyaluronic Acid Stimulates Osseointegration of β-TCP in Young and Old Ewes

Hyaluronic acid in Dentoalveolar regeneration: Biological rationale and clinical applications

Background

Hyaluronic acid (HA) is found in different locations in the periodontium, including mineralized tissues (i.e., cementum and alveolar bone) and non-mineralized tissues (i.e., gingiva and periodontal ligament). In addition, it seems to play an essential part in regulating the underlying mechanisms involved in tissue inflammatory reactions and wound healing. HA has the potential to regulate periodontal tissue regeneration and treat periodontal disease.

Aim

The current review of the literature was conducted to assess how HA plays its part in periodontal therapy and examine the contemporary literature's viewpoint on its use in periodontal regeneration.

Conclusion

HA has a multifunctional character in periodontal regeneration, and healing and appears to provide promising outcomes in different periodontal regenerative applications.

Rheological properties and decomposition rates of Gellan gum/hyaluronic acid/β-tricalcium phosphate mixtures

The effects of β-tricalcium phosphate (TCP) on the mixture of low acyl gellan gum (LA-GAGR) and hyaluronic acid (HA) were investigated for the rheological properties and decomposition rates. All the tested mixture samples exhibited shear-thinning and typical viscoelastic behaviors. The sample made with 1.0% TCP and 0.30% LA-GAGR had the highest viscosity and loss and storage moduli and displayed gel-like behavior with the highest swelling capacity. The same mixture also exhibited the lowest average cumulative decomposition rate. High concentrations of LA-GAGR and TCP increased the degree of cross-linking of the polysaccharides, and as a result, the mixture was more elastic and less fluidic and decomposed slower. The samples prepared by gradual mixing of LA-GAGR and TCP decomposed slower than the sample prepared by sudden mixing, which indicates the well-dispersed TCP enhanced cross-linking of the polymers. This study demonstrates the possible applicability of natural polysaccharide-based shear-thinning gels for biomedical applications.

Osseointegration of two types of titanium cylinders with geometric or trabecular microarchitecture: A nanotomographic and histomorphometric study

Porous biomaterials promote osseointegration. We have prepared porous titanium cylinders by additive manufacturing from titanium beads. Two types of morphology were tested: cylinders with geometric pores or mimicking trabecular microarchitecture. Cylinders were decontaminated and cleaned by HF/HNO₃ to remove unmelted balls. Surgical implantation in ewes was performed under general anesthesia and the animals were housed for 90 and 270days. The femoral condyles were collected and analyzed by nanoCT, embedded in pMMA and analyzed by histomorphometry. No significant difference was found in terms of bone volume or bone/titanium interface between the two types of cylinders. There was no evolution over time except for the mineralization rates which decreased, reflecting the effect of the aging of the animals. The influence of the pores (geometrical or "natural") did not influence osseointegration. HF/HNO₃ etching treatments are effective on the outermost surfaces but do not seem to reach the central cavities of the samples. Finally, osseointegration seems to occur only in the few millimeters around the periphery of the implants and does not extend in the center. This is explained by the absence of stress transmission within the very rigid metal cylinders, preventing bone modeling and remodeling.

Microarchitecture of titanium cylinders obtained by additive manufacturing does not influence osseointegration in the sheep

Large bone defects are a challenge for orthopedic surgery. Natural (bone grafts) and synthetic biomaterials have been proposed but several problems arise such as biomechanical resistance or viral/bacterial safety. The use of metallic foams could be a solution to improve mechanical resistance and promote osseointegration of large porous metal devices. Titanium cylinders have been prepared by additive manufacturing (3D printing/rapid prototyping) with a geometric or trabecular microarchitecture. They were implanted in the femoral condyles of aged ewes; the animals were left in stabling for 90 and 270 days. A double calcein labeling was done before sacrifice; bones were analyzed by histomorphometry. Neither bone volume, bone/titanium interface nor mineralization rate were influenced by the cylinder's microarchitecture; the morphometric parameters did not significantly increase over time. Bone anchoring occurred on the margins of the cylinders and some trabeculae extended in the core of the cylinders but the amount of bone inside the cylinders remained low. The rigid titanium cylinders preserved bone cells from strains in the core of the cylinders. Additive manufacturing is an interesting tool to prepare 3D metallic scaffolds, but microarchitecture does not seem as crucial as expected and anchoring seems limited to the first millimeters of the graft.

In vivo osseointegration and erosion of nacre screws in an animal model

The use of resorbable devices for osteosynthesis has become a subject of interest. Nacre has been proposed as a resorbable and osteoconductive material favoring bone apposition without triggering an inflammatory reaction. We compared the in vivo osseointegration and erosion of nacre screws in an animal model with titanium screws. Implantation of similar nacre and titanium screws was performed in the femoral condyles of adult rats. Animals (n = 41) were randomized in four groups sacrificed at day one, 1, 6, and 12 months. Microcomputed tomography (microCT) allowed 3D morphometry of erosion of nacre. Osseointegration was measured as the volume of trabecular bone bone volume/tissue volume (BV/TV) in a standardized volume of interest around each screw. Undecalcified bone histology was also done. Gross examination revealed a similar clinical osseointegration for titanium and nacre screws. A progressive erosion of nacre screws, but no erosion of titanium screws, was observed in microCT. The volume of nacre screws progressively decreased over time whereas no modification occurred for titanium. For titanium screws, BV/TV remained stable throughout the study. For nacre screws, the BV/TV decrease was not statistically different. A significant difference was found between nacre and titanium screws at 6 months but not at 12 months. The screw heads, outside the bone shaft, were not eroded even after 12 months. Erosion of nacre occurred during the entire study period, only within the bone shaft in direct contact with bone marrow. Bone apposition was observed on nacre surfaces without signs of erosion. Nacre is a promising biomaterial in maxillofacial surgery.