Haack J E, Sakaguchi R L, Sun T, Coffey J P
Department of Oral Sciences, Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, Minneapolis, USA.
Int J Oral Maxillofac Implants. 1995 Sep-Oct;10(5):529-36.
A common problem associated with dental implant restorations is loosening of screws that retain the prosthesis to the implant. A method was developed to determine initial preload on UCLA-type abutment screws by measuring elongation after applying known tightening torques with a digital torque gauge. Loosening torque was also measured after tightening to 32 N-cm torque for gold alloy abutment screws and 20 N-cm for titanium abutment screws. Gold alloy and titanium abutment screws were each used to secure a gold UCLA hexed abutment to a titanium implant. Stresses and forces were calculated from the elongation measurements for three regions of each screw. Elongation of the screws after applying the manufacturer's recommended tightening torques were within the elastic range. Induced stresses were 57.5% and 56% of the yield strengths for gold alloy and titanium, respectively. Tightening of screws beyond recommended levels may be possible without producing plastic deformation. At manufacturer's recommended torques, mean preload was 468.2 (+/- 57.9) N using gold alloy screws and 381.5 (+/- 72.9) N with titanium screws.
与牙种植体修复相关的一个常见问题是将假体固定在种植体上的螺钉松动。开发了一种方法，通过使用数字扭矩计施加已知拧紧扭矩后测量伸长量来确定加州大学洛杉矶分校（UCLA）型基台螺钉的初始预紧力。对于金合金基台螺钉，拧紧至32 N·cm扭矩后测量松动扭矩，对于钛基台螺钉，拧紧至20 N·cm扭矩后测量松动扭矩。金合金和钛基台螺钉分别用于将金制UCLA带六角形的基台固定到钛种植体上。根据每个螺钉三个区域的伸长量测量值计算应力和力。施加制造商推荐的拧紧扭矩后，螺钉的伸长量在弹性范围内。金合金和钛的诱导应力分别为屈服强度的57.5%和56%。在不产生塑性变形的情况下，可能可以将螺钉拧紧到超过推荐水平。在制造商推荐的扭矩下，使用金合金螺钉时平均预紧力为468.2（±57.9）N，使用钛螺钉时为381.5（±72.9）N。
