Nanosuperfície de Titânio como uma nova realidade na implantodontia: Revisão de Literatura / Nano-surface Titanium a new reality in implant dentistry: Literature Review

Resumo: A odontologia vem buscando cada vez mais métodos de reabilitação dentária que sejam menos traumáticos e eficazes estética e visualmente falando. Sob esse aspecto, os implantes dentários têm se desenvolvido cada vez no intuito de garantir a satisfação dos pacientes, através de avanços tecnológicos como o da Nanosuperfície de Titânio. Assim, o presente estudo objetiva abordar a questão das superfícies de implantes de titânio no que se refere à sua capacidade de estímulo na formação óssea, por ser uma técnica que diminui o tempo de osseointegração e, consequentemente, a duração do processo e recuperação do paciente. Para tanto, foi realizada uma revisão bibliográfica em bases de dados eletrônicas acerca do tema, que comprovassem a diminuição de tempo do trabalho do profissional da Odontologia e uma melhor qualidade no que se refere aos implantes dentários, através da análise de três marcas nacionais a fim de comprovar sua eficácia. Palavras-chave: Implante dentário. Nanosuperfície de Titânio. Osseointegração. ---Abstract: Dentistry is increasingly seeking dental rehabilitation methods that are less traumatic and effective aesthetically and visually. In this regard, dental implants have been increasingly developed to ensure patient satisfaction, through technological advances such as the Titanium Nano-surface. Thus, this study aims to address the issue of titanium implant surfaces in terms of their ability to stimulate bone formation, as it is a technique that reduces the time of osseointegration and, consequently, the duration of the process and patient recovery. To this end, a bibliographic review was carried out in electronic databases on the subject, which could prove the reduction of time in the work of the dentistry professional and a better quality regarding dental implants, through the analysis of three national brands to prove its effectiveness. Keywords: Dental implant. Titanium Nano-surface. Osseointegration.

Osteoporosis: From Molecular Mechanisms to Therapies

Osteoporosis is a common skeletal disorder, occurring as a result of an imbalance between bone resorption and bone formation, with bone breakdown exceeding bone building. Bone resorption inhibitors, e.g., bisphosphonates, have been designed to treat osteoporosis, while anabolic agents such as teriparatide stimulate bone formation and correct the characteristic changes in the trabecular microarchitecture. However, all of these drugs are associated with significant side effects. It is therefore crucial that we continue to research the pathogenesis of osteoporosis and seek novel modes of therapy. This editorial summarizes and discusses the themes of the fifteen articles published in the Special Issue, Osteoporosis: From Molecular Mechanisms to Therapies 2019, as part of the global picture of the current understanding of osteoporosis.

Anabolic Therapies in Osteoporosis and Bone Regeneration

Osteoporosis represents the most common bone disease worldwide and results in a significantly increased fracture risk. Extrinsic and intrinsic factors implicated in the development of osteoporosis are also associated with delayed fracture healing and impaired bone regeneration. Based on a steadily increasing life expectancy in modern societies, the global implications of osteoporosis and impaired bone healing are substantial. Research in the last decades has revealed several molecular pathways that stimulate bone formation and could be targeted to treat both osteoporosis and impaired fracture healing. The identification and development of therapeutic approaches modulating bone formation, rather than bone resorption, fulfils an essential clinical need, as treatment options for reversing bone loss and promoting bone regeneration are limited. This review focuses on currently available and future approaches that may have the potential to achieve these aims.

Binding Selectivity of Abaloparatide for PTH-Type-1-Receptor Conformations and Effects on Downstream Signaling

The PTH receptor type 1 (PTHR1) mediates the actions of two endogenous polypeptide ligands, PTH and PTHrP, and thereby plays key roles in bone biology. Based on its capacity to stimulate bone formation, the peptide fragment PTH (1–34) is currently in use as therapy for osteoporosis. Abaloparatide (ABL) is a novel synthetic analog of human PTHrP (1–34) that holds promise as a new osteoporosis therapy, as studies in animals suggest that it can stimulate bone formation with less of the accompanying bone resorption and hypercalcemic effects that can occur with PTH (1–34). Recent studies in vitro suggest that certain PTH or PTHrP ligand analogs can distinguish between two high-affinity PTHR1 conformations, R0 and RG, and that efficient binding to R0 results in prolonged signaling responses in cells and prolonged calcemic responses in animals, whereas selective binding to RG results in more transient responses. As intermittent PTH ligand action is known to favor the bone-formation response, whereas continuous ligand action favors the net bone-resorption/calcemic response, we hypothesized that ABL binds more selectively to the RG vs the R0 PTHR1 conformation than does PTH (1–34), and thus induces more transient signaling responses in cells. We show that ABL indeed binds with greater selectivity to the RG conformation than does PTH (1–34), and as a result of this RG bias, ABL mediates more transient cAMP responses in PTHR1-expressing cells. The findings provide a plausible mechanism (ie, transient signaling via RG-selective binding) that can help account for the favorable anabolic effects that ABL has on bone.

New Insights Into the Physiology of Bone Regulation: the Role of Neurohormones

Bone metabolism is regulated by interaction between two skeletal cells – osteoclasts and osteoblasts. Function of these cells is controlled by a number of humoral factors, including neurohormones, which ensure equilibrium between bone resorption and bone formation. Influence of neurohormones on bone metabolism is often bimodal and depends on the tissue, in which the hormone is expressed. While hypothalamic beta-1 and beta-2-adrenergic systems stimulate bone formation, beta-2 receptors in bone tissue activate osteoclatogenesis and increases bone resorption. Chronic stimulation of peripheral beta-2 receptors is known to quicken bone loss and alter the mechanical quality of the skeleton. This is supported by the observation of a low incidence of hip fractures in patients treated with betablockers. A bimodal osteo-tropic effect has also been observed with serotonin. While serotonin synthetized in brain has osteo-anabolic effects, serotonin released from the duodenum inhibits osteoblast activity and decreases bone formation. On the other hand, both cannabinoid systems (CB1 receptors in the brain and CB2 in bone tissue) are unambiguously osteo-protective, especially with regard to the aging skeleton. Positive (protective) effects on bone have also been shown by some hypophyseal hormones, such as thyrotropin (which inhibits bone resorption) and adrenocorticotropic hormone and oxytocin, both of which stimulate bone formation. Low oxytocin levels have been shown to potentiate bone loss induced by hypoestrinism in postmenopausal women, as well as in girls with mental anorexia. In addition to reviewing neurohormones with anabolic effects, this article also reviews neurohormones with unambiguously catabolic effects on the skeleton, such as neuropeptide Y and neuromedin U. An important aim of research in this field is the synthesis of new molecules that can stimulate osteo-anabolic or inhibiting osteo-catabolic processes.