Palavras-chave: Enxerto Autólogo; Xenoenxerto; Aloenxerto; Reações Biológicas. Allogenous and xenogenous bone substitutes compared to autogenous bone graft: biologycal reactions AbstractThe implant supported rehabilitation of edentulous patients is hampered by insufficient bone volume, thus, requiring a prior bone reconstruction. Autogenous bone is still the "gold standard" biomaterial, which is effective in bone regeneration process, contains viable cells and doesn't transmit infectious diseases nor triggers immune responses. Moreover, it presents rapid incorporation and consolidation. However, this type of graft has disadvantages such as increased morbidity and limited availability. In view of the constant search for bone substitutes that may have properties similar to autogenous bone, but that do not require a second surgical site, the use of allogeneic (from individuals of the same species, but genetically Substitutos ósseos alógenos e xenógenos comparados... RODOLFO et al. 96 97

To evaluate the bone healing of defects filled with particulate bone graft in combination with platelet-rich plasma (PRP), added with a mixture of calcium chloride and thrombin or just calcium chloride. Two 5-mm bone defects were created in the calvaria of 24 rabbits. Each defect was filled with particulate bone graft and PRP. In one defect the PRP was activated by a mixture of calcium chloride and thrombin; in the other, PRP was activated by calcium chloride only. The animals were euthanized 1, 2, 4, and 8 weeks after the surgeries, and the calvaria was submitted to histologic processing for histomorphometric analysis. The qualitative analysis has shown that both defects presented the same histologic characteristics so that a better organized, more mature, and well-vascularized bone tissue was noticed in the eighth week. A good bone repair was achieved using either the mixture of calcium chloride and thrombin or the calcium chloride alone as a restarting agent of the coagulation process.

Computed tomographic scan is a precise complementary examination of diagnostic imaging and a noninvasive surveying technique that enables the professional to improve precision of implant placement by building a prototype that allows the confection of surgical guides. The authors present a clinical case of mandible rehabilitation based on computed tomography of a patient; the cross sections were reformatted and used to construct a virtual planning of the implants and a guide template in Dental Slice. Immediate loading of 5 titanium implants were placed in the mandible using a Slice Guide System. This technique allows a better surgical planning, makes the procedures more accurate, and reduces surgery time.

O sucesso dos enxertos ósseos autógenos está relacionado à viabilidade das células transportadas para a área receptora. Durante o procedimento cirúrgico, entre a retirada do bloco ósseo da área doadora e sua colocação na área receptora, é comum que o fragmento fique algum tempo em solução fisiológica. O objetivo desse estudo foi realizar avaliação histomorfométrica da preservação de osteócitos em fragmentos de tíbia, mantidos em solução salina por diferentes períodos. Vinte e quatro fragmentos ósseos foram removidos e divididos em quatro grupos iguais. O grupo controle foi fixado em formol 10%, imediatamente após a remoção. Os demais grupos foram mantidos em solução salina por 5, 15 ou 30 minutos, antes da fixação. Em seguida, os espécimes foram descalcificados em EDTA e processados para inclusão em glicol metacrilato. Os cortes com cerca de 3μm de espessura foram corados em azul de toluidina 1%. A análise histológica foi realizada segundo critério que considerou os osteócitos como normais, alterados e lacunas (vazias). Se¬gundo análise estatística (teste de Tuckey) houve redução significativa na quantidade de osteócitos normais em todos os períodos experimentais. O número de lacunas e osteócitos alterados aumentou significativamente em todos os períodos experimentais, exceto em 5 minutos. Segundo os resultados, ocorre redução progressiva da quantidade de osteócitos em fragmentos ósseos de tíbia de coelhos mantidos em solução salina.

Moderate and controlled loading environments support or enhance osteogenesis, and, consequently, a high degree of bone-to-implant contact can be acquired. This is because when osteoprogenitor cells are exposed to limited physical deformation, their differentiation into osteoblasts is enhanced. Then, some range of microstrain is considered advantageous for bone ingrowth and osseointegration. The primary stability has been considered one of the main clinical means of controlling micromotion between the implant and the forming interfacial tissue, which helps to establish the proper mechanical environment for osteogenesis. Based on the biological aspects of immediate loading (IL), the objective of this study is to present a clinical case of maxillary arch rehabilitation using immediate loading with implant-supported fixed restoration after bone graft. Ten dental implants were placed in the maxilla 6 months after the autogenous bone graft, removed from the mandible (bilateral oblique line and chin), followed by the installation of an immediate-load fixed cross-arch implant-supported restoration because primary stability was reached for 8 implants. In addition, instructions about masticatory function and how it is related to interfacial micromotion were addressed and emphasized to the patient. The reasons for the IL were further avoidance of an interim healing phase, a potential reduction in the number of clinical interventions for the patient, and aesthetic reasons. After monitoring the rehabilitation for 8 years, the authors can conclude that maxillary IL can be performed followed by a well-established treatment planning based on computed tomography, providing immediate esthetics and function to the patient even when autogenous bone graft was previously performed in the maxilla.