Fat tissues can be successfully transplanted into irradiated areas, inducing both aesthetic and functional improvement. The cellular and/or tissular mechanisms underlying these changes need further investigation.

PurposeBeside its efficacy in cancer treatment, radiotherapy induces degeneration of healthy tissues within the irradiated area. The aim of this study was to analyze the variations of proinflammatory (IL-1α, IL-2, IL-6, TNF-α, IFN-γ), profibrotic (TGF-β1), proangiogneic (VEGF) and stem cell mobilizing (GM-CSF) cytokines and growth factors in an animal model of radiation-induced tissue degeneration.Materials and Methods24 rats were irradiated unilaterally on the hindlimb at a monodose of 30 Gy. Six weeks (n = 8), 6 months (n = 8) and 1 year (n = 8) after irradiation the mediators expression in skin and muscle were analyzed using Western blot and the Bio-Plex® protein array (BPA) technology. Additional histological severity for fibrosis, inflammation, vascularity and cellularity alterations scoring was defined from histology and immnunohistochemistry analyses.ResultsA significant increase of histological severity scoring was found in irradiated tissue. Skin tissues were more radio-sensitive than muscle. A high level of TGF-β1 expression was found throughout the study and a significant relation was evidenced between TGF-β1 expression and fibrosis scoring. Irradiated tissue showed a chronic inflammation (IL-2 and TNF-α significantly increased). Moreover a persistent expression of GM-CSF and VEGF was found in all irradiated tissues. The vascular score was related to TGF-β1 expression and the cellular alterations score was significantly related with the level of IL-2, VEGF and GM-CSF.ConclusionThe results achieved in the present study underline the complexity and multiplicity of radio-induced alterations of cytokine network. It offers many perspectives of development, for the comprehension of the mechanisms of late injuries or for the histological and molecular evaluation of the mode of action and the efficacy of rehabilitation techniques.

Although mechanical stress is known as being a significant factor in bone remodeling, most implants are still made using materials that have a higher elastic stiffness than that of bones.Load transfer between the implant and the surrounding bones is much detrimental, and osteoporosis is often a consequence of such mechanical mismatch. The concept of mechanical biocompatibility has now been considered for more than a decade. However, it is limited by the choice of materials, mainly Ti-based alloys whose elastic properties are still too far from cortical bone. We have suggested using a bulk material in relation with the development of a new beta titanium-based alloy. Titanium is a much suitable biocompatible metal, and betatitanium alloys such as metastable TiNb exhibit a very low apparent elastic modulus related to the presence of an orthorhombic martensite. The purpose of the present work has been to investigate the interaction that occurs between the dental implants and the cortical bone. 3D finite element models have been adopted to analyze the behaviour of the bone-implant system depending on the elastic properties of the implant, different types of implant geometry, friction force, and loading condition. The geometry of the bone has been adopted from a mandibular incisor and the surrounding bone. Occlusal static forces have been applied to the implants, and their effects on the bone-metal implant interface region have been assessed and 2 compared with a cortical bone/ bone implant configuration. This work has shown that the low modulus implant induces a stress distribution closer to the actual physiological phenomenon, together with a better stress jump along the bone implant interface, regardless of the implant design.Keywords: Dental biomechanics, Beta titanium alloy, Low modulus implant, Numerical modelling, Bone-implant interface IntroductionOver the last few decades, considerable progress in dental implantology has been made, with success rates exceeding 95% [1]. Implant stability is commonly considered as playing a major role in a successful osseointegration. Obtaining post-operative osseointegration is necessary in order to establish a solid and durable connection between the implant and the osseous structure. In agreement with the Wolff law, a process of osseous remodelling adapted to the stress level occurs after implantation [2][3][4]. This process is controlled by mechanical loads.When the occlusal forces induced on the bone exceed a physiological level, bone resorption can occur, with possible failure [5]. More importantly, the long-term performance of an implant is known to be strongly dependent on the bone tissue interaction [6]. The strain state which takes place at the interface between the bone and implant controls the bone tissue remodelling mechanisms [7]. Bone resorption is associated with a low strain state, and bone necrosis occurs when strain exceeds the maximum level.Evaluation of the risk requires a comprehension of the load transfer along the bone-dental implant interface. T...