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

本研究的目的是评估安装羟基磷灰石（HA）涂层牙种植体上部结构的应力断裂系统的有效性。高弹性聚氨酯弹性体（Biotron R）具有易于建模和弹性常数控制的特点，因此选择高弹性聚氨酯弹性体作为断裂系统的材料。体外实验中，百创R-M25对材料的弹性常数和体积变化不大，而百创R-M8、M12和M17对材料的弹性常数和体积变化较大。在体内研究中，使用了四只猴子。在无牙动物的下颌骨内植入4个ha涂层种植体。在植入体上分别设置2个具有Biotron R-M25破应力系统的上部结构（破应力组）和2个不具有破应力系统的上部结构（非破应力组）。在12个月的随访期间，所有种植体临床稳定。少数种植体周围牙龈出现肿胀，但种植体周围未见明显变化。在组织学评估中，周围的骨直接与两个种植体的表面相对。在组织形态学上，应力破坏组种植体的骨接触率和骨体积均高于非应力破坏组。结果表明，有应力破坏系统的种植体比没有应力破坏系统的种植体获得更稳定的骨锚定。

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.