Locator式和球帽式下颌种植覆盖义齿在牙槽嵴应力分布的光弹性研究

目的 分析比较含2个种植体的下颌种植覆盖义齿分别使用球帽附着体和Locator附着体在正中,侧向及前伸(牙合)应力加载时对其种植体和余留牙槽嵴的应力分布差异.方法 应用三维光弹实验的方法,在Atwood 3级无牙颌模型双侧至尖牙区域内各植入1枚种植体后制作环氧树脂光弹模型,进行3种咬合状态下的1kg垂直加载.应力冻结后,比较两者的应力分布差异.结果 正中及前伸(牙合)位加载时,2种附着体均可达到颊舌侧应力分布相近,球帽式牙槽嵴顶应力分布略大;侧向(牙合)加载时,球帽式覆盖义齿较Locator式覆盖义齿工作侧与平衡侧应力差更小;3种(牙合)位加载时,球帽式覆盖义齿种植体周围的应力均小于Locator式覆盖义齿,其中侧向(牙合)尤为明显.结论 (1)在下颌牙槽嵴重度吸收时,使用球帽附着式覆盖义齿较Loctor式覆盖义齿可能对种植体周围的骨质及剩余牙槽嵴有更好的保护作用,建议作为首选(2)在使用Locator附着体时建议选用可减少侧向力的(牙合)型,如舌向集中(牙合)等.

Photoelastic analysis of stress distribution in alveolar ridge under mandibular implanted overdenture with ball-cap attachment and locator attachment

Objective To compare the stress distribution of supporting tissues in serve absorbed alveolar bone under mandible overdentures with ball-cap attachments and locator attachments under the loads of centric, lateral and protrusive occlusion. Methods Photoelastic models of epoxy were fabricated according to the Atwood level 3 edentulous model with two implants in the area of canine. 1 kilogram force was vertically applied in the model under three kinds of biteconditions. After stress frozen, photoelastic model slices in implants and posterior teeth area were observed and the stress was valued. Results Under the loads of centric and protrusive occlusion, the two implant-retained overdenture could provide equal force in buccal-lingual alveolar bone, and the overdenture with ball-cap type attachment could cause a slightly larger stress in residual alveolar ridge; under the load of lateral occlusion, the stress difference between the working side and the balance side in the ball-cap type attachment group was smaller than that in the locator attachment group. Under three kinds of occlusion, the stress surrounding the implant with ball-cap attachments was less than that of Locator attachments especially under the lateral loading. Conclusions (1) When using two-implant-retained overdenture, ball-cap attachments could better protect the bone around the implant from absorption,with regard to this, ball-cap attachments might be considered firstly; (2) Lingualized occlusion was recommended if locator attachment was applied.