The effectiveness of the stress-breaking system of the superstructure on the hydroxylapatite-coated implants.

本研究的目的是评估羟基磷灰石（HA）涂层牙种植体上部结构安装应力断裂系统的有效性。高弹性聚氨酯弹性体（Biotron R）被选择作为该应力破坏系统的材料，因为这些特性如容易的模型成形和弹性常数的控制。在体外研究中，在Biotron R-M25中观察到材料的弹性常数和体积变化很小，而在Biotron R-M8、M12和M17中观察到一些显著变化。在体内研究中，使用了四只猴子。将四个HA涂层种植体插入每只动物的无牙下颌骨中。分别在种植体上设置两个带有Biotron R-M25应力断裂系统的上部结构（应力断裂组）和两个不带应力断裂系统的上部结构（非应力断裂组）。在12个月的随访期内，所有种植体均临床稳定。在少数种植体的种植体周围牙龈周围观察到一些肿胀，但在种植体周围未观察到其他剧烈变化。在组织学评价中，周围骨直接与两种种植体表面对合。组织形态计量学分析显示，应力断裂组种植体的骨接触率和骨体积均高于非应力断裂组，表明应力断裂组种植体的骨锚定效果优于非应力断裂组。

The purpose of this study was to evaluate the effectiveness of the stress-breaking system installed with the superstructure of the hydroxylapatite(HA)-coated dental implant. High resilient polyurethane elastmer(Biotron R) was selected as the material of this stress-breaking system because of these characteristics as the easiness of model shaping and control of elastic constant. In vitro study, little change of elastic constant and volume of the material was seen in Biotron R-M25, whereas some significant changes were seen in Biotron R-M8, M12 and M17. In vivo study, four monkeys were used. Four HA-coated implants were inserted into the edentulous mandible of each animal. Two superstructures with stress-breaking system by Biotron R-M25(stress-breaking group) and two superstructure without stress-breaking system (non-stress-breaking group) were set on the respectively implants. During 12-month follow-up period, all implants were clinically stable. Some swelling was observed around the periimplant gingiva of a few implants, but no other drastic change was seen around the implant. In the histological evaluation, the surrounding bone was apposed directly to the surface of both implants. Histomorphometric ally, implants in stress-breaking group showed higher bone contact ratio and bone volume than implants in non-stress-breaking group.These results show that the implants set on the superstructure with the stress-breaking system can obtain more stable bone anchorage than the implants set on the superstructure without the stress-breaking system.