Patrício José de Oliveira Neto

Tomographic, Histological, and Immunohistochemical Evidences on the Use of N-Butyl-2-Cyanoacrilate for Onlay Graft Fixation in Rabbits

BACKGROUND The bone tissue responses to Cyanoacrylate have been described in the literature, but none used N-butyl-2-cyanoacrilate (NB-Cn) for bone graft fixation. PURPOSE The aims of the study were: (a) to analyze the bone grafts volume maintenance fixed either with NB-Cn or titanium screw; (b) to assess the incorporation of onlay grafts on perforated recipient bed; and (c) the differences of expression level of tartrate-resistant acid phosphatase (TRAP) protein involved in bone resorption. MATERIALS AND METHODS Eighteen New Zealand White rabbits were submitted to calvaria onlay grafting on both sides of the mandible. On one side, the graft was fixed with NB-Cn, while on the other hand the bone graft was secured with an osteosynthesis screw. The computed tomography (CT) was performed just after surgery and at animals sacrifice, after 1 (n = 9) and 6 weeks (n = 9), in order to estimate the bone grafts volume along the experiments. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts and to assess the expression of TRAP protein. RESULTS The CT scan showed better volume maintenance of bone grafts fixed with NB-Cn (p ≤ 0.05) compared with those fixed with screws, in both experimental times (analysis of variance). The immunohistochemical evaluation showed that the TRAP expression in a 6-week period was significantly higher compared with the 1-week period, without showing significant difference between the groups (Wilcoxon and Mann-Whitney). Histological analysis revealed that the NB-Cn caused periosteum damage, but provided bone graft stabilization and incorporation similar to the control group. CONCLUSION The perforation provided by screw insertion into the graft during fixation may have triggered early revascularization and remodeling to render increased volume loss compared with the experimental group. These results indicate that the NB-Cn possesses equivalent properties to titanium screw to be used as bone fixation material in osteosynthesis.

Evaluation of Osteoconductive and Osteogenic Potential of a Dentin-Based Bone Substitute Using a Calvarial Defect Model

The aim of this study was to assess the osteoconductive and osteogenic properties of processed bovine dentin using a robust rabbit calvarial defect model. In total, 16 New Zealand White rabbits were operated to create three circular defects in the calvaria. One defect was left unfilled, one filled with collected autogenous bone, and the third defect was filled with the dentin-based bone substitute. Following surgery and after a healing period of either 1 or 6 weeks, a CT scan was obtained. Following sacrificing, the tissues were processed for histological examination. The CT data showed the density in the area grafted with the dentin-based material was higher than the surrounding bone and the areas grafted with autologous bone after 1 week and 6 weeks of healing. The area left unfilled remained an empty defect after 1 week and 6 weeks. Histological examination of the defects filled with the dentin product after 6 weeks showed soft tissue encapsulation around the dentin particles. It can be concluded that the rabbit calvarial model used in this study is a robust model for the assessment of bone materials. Bovine dentin is a biostable material; however, it may not be suitable for repairing large 4-wall defects.

Successful management of malignant hyperthermia during orthognathic surgery: a case report.

Malignant hyperthermia (MH) is a potentially lifethreatening hypermetabolic condition triggered by inhaled halogenated anesthetic agents (eg, halothane, isoflurane, enflurane, desflurane, sevoflurane) or succinylcholine in otherwise normal but genetically susceptible individuals. This disorder was initially de scribed in 1960 by Denborough et al, 2-6 who published the first formal case of MH in an Australian family. MH is inherited as an autosomal dominant disease characterized by uncontrollable skeletal muscle hypermetabolism, rhabdomyolysis, increased oxygen consumption and CO 2 production, tachycardia, hypercapnia, hyperthermia, elevated creatinine kinase, and other features after exposure to a trigger agent. Most MH-susceptible individuals are asymptomatic until they are truly exposed to such an agent. Some genes can counter mutations related to susceptibility to MH; the most widely studied and frequently found of these is the gene for the ryanodine receptor RyR1, located in chromosome 19, which accounts for approximately 50% of the susceptible persons. MH occurs in all ethnic groups, and preva lence varies according to region and age. 2,8 Its exact incidence is unknown but is estimated to be 1:15,000 in children and adolescents and 1:50,000 in adults. The decreased incidence with age may have 2 explanations: a reduced expression of the disease and the death of susceptible individuals before they become adults. 3