Comparison of Processed Nerve Allograft and Laminin Derived Peptide Incorporated Nerve Conduit for Peripheral Nerve Regeneration / 대한정형외과학회잡지

PURPOSE: To compare a processed nerve allograft, laminin derived peptide incorporated nerve conduit, and autograft in terms of electrodiagnostic testing and nerve histomorphometry for peripheral nerve regeneration in a rabbit sciatic nerve defect model. MATERIALS AND METHODS: Thirty New Zealand white rabbits were divided into three groups, and a unilateral 15 mm sciatic nerve defect was made. Group I, II and III was repaired with a reversed autograft, a processed acellular nerve allograft, and a laminin derived peptide incorporated nerve conduit, respectively. At twelve weeks, the animals were evaluated with the compound muscle action potential, wet muscle weight, and nerve histomorphometric parameters such as nerve area, number of axons, and myelin thickness. RESULTS: At twelve weeks, the compound muscle action potential for group I, II and III was 54.1%, 38.2% and 26.4%, respectively. Significant differences were found between the three groups (p<0.001, group I vs II; p<0.001, group I vs III; p<0.001, group II vs III). The wet muscle weight for group I, II and III was 57.8%, 54.4% and 43.9%, respectively. Group I had significantly more muscle weight than group III (p<0.001), but the difference was not significant with group II (p=0.256). Group II and III showed a significant difference (p=0.002). The number of axons in group III decreased and the shape of the axon was irregular, even though the nerve area and myelin thickness were similar in the three groups. CONCLUSION: An autograft remains the gold standard to repair a segmental nerve defect. Processed allograft demonstrated superior nerve recovery compared to the laminin derived peptide incorporated nerve conduit.

Development of New Coronary Stent-Grafts using Surface-Modified Polymers

BACKGROUND AND OBJECTIVE: The purpose of this study was to develop a new type of coronary stent-graft, using surface modification of polymeric synthetic graft materials, to improve biocompatibility. MATERIALS AND METHODS: Three different polymers, Dacron, GoreTex and Teflon were tested. During the surface-modification process, hydroxybutyl acrylate (HBA) choline, an excellent blood-compatible phospholipid, was stably grafted onto the polymer surface. The optimal conditions for maximizing the amount of HBA choline grafted onto the polymeric surface were determined by quantitative analysis. The surface-modified polymers were then tested for their biocompatibility using an in vitro platelet adhesion test. Thereafter, stent-grafts were constructed with each of three different types of surface-modified polymer and implanted in porcine coronary arteries to compare their biocompatibility in vivo. RESULTS: In the platelet adhesion test, all the surface-modified polymers showed better biocompatibility than the control polymers. The in vitro biocompatibility correlated positively with the increasing quantity of grafted HBA choline. In the animal experiment, the surface-modified Teflon stent-graft showed the best biocompatibility. Whereas, all pigs implanted with the modified Dacron and GoreTex stent-grafts died within 48 hours of the implantation, five out of the six pigs with the Teflon stent-grafts remained alive at after the 4th week. In four of the five surviving pigs, angiography, intravascular ultrasound (IVUS) and histological evaluations demonstrated the patency of the stent-grafts, with a uniform neointima formation covering the entire stent-graft, without stent thrombosis or chronic inflammatory cells. CONCLUSION: The surface-modified Teflon coronary stent-grafts showed good in vitro and in vivo biocompatibility. Further animal and clinical studies will be required to validate the efficacy of the surface-modified polymer stent-grafts.

Effect Of Surface Treatments On The Bond Strength Of Denture Base Resins To Dental Alloy / 대한치과보철학회지

The purpose of this study is to compare tensile bond strength between Cr-Co alloy and three denture base resins after surface treatment. Following the manufacturer's instructions, 180 bonded specimens were made from three denture base resins (Lucitone 199, Paladent 20, POSS resin) and three surface treatment methods(sandblasting, metal primer, silicoating). 20 samples were made in each group and a half was thermocycled 1000 times between 5 celsius degrees and 55 celsius degrees. The tensile bond strength was measured using an Instron with 5mm/min crosshead speed. Data was analyzed with one-way ANOVA, T-test and Duncan test. The results were as follows: 1. Samples with metal primer coating had significantly high tensile bond strength than the other surface treated groups (p.05). 3. Tensile bond strength was decreased in silicoated samples after thermocycling (p<.05). 4. Of the surface treated groups with metal primer,Lucitone 199 had the greatest bond strength and POSS resin and Paladent 20 were followed (p<.05). 5. Of the surface treated groups with silicoating, POSS resin and Lucitone 199 had greater bond strength than Paladent 20 (p<.05).

Developement of the reinforced acrylic-based hybrid denture composite resin with vinyloligosilsesquioxane(POSS) / 대한치과보철학회지

The mainly used polymeric material for the denture is PMMA because of its cost and easiness to handle. So it was widely used material among dentists for past decades. But the acrylic-based denture materials have several common weak points such as shrinkage after curing and lack of strength. In order to solve these problems, we adapted one of hybrid system using acrylic polymer and vinyloligosilsesquioxane(POSS). POSS, which is a well known expandable monomer during polymerization process, may eventually suppress volumetric shrinkage. And the hybrid system makes it possible for the polymer to be stable in various severe conditions. Eight different kinds of samples were designed and synthesized. Each samples were characterized with dynamic mechanical analyser(DMA) to confirm their thermodynamic properties, fractured to analyze the cross-sectional morphology of the samples. And elongation, flexural and impact tests were also executed to evaluate the mechanical properties of the samples. From the results, hybrid composites had well defined crosslinked network structure compared to the widely used denture materials, and the mechanical strength improved without changing any surface condition as increment with POSS ratio in hybrid system. Fractured morphology showed homogeneous surfaces in spite of mutli component system, therefore we can conclude that the adoption of the POSS brought the reinforcement of the denture resin.