Heidemann W, Gerlach K L, Gröbel K H, Köllner H G
Department of Maxillofacial Surgery, Otto-von-Guericke University, Magdeburg, Germany.
J Craniomaxillofac Surg. 1998 Feb;26(1):50-5. doi: 10.1016/s1010-5182(98)80035-8.
When screws are inserted in thick cortical bone, a small pilot hole size, corresponding to the core diameter of the screw, can result in high torsional stress, leading to screw fracture. The aim of this study was to enlarge the drill size up to a critical pilot hole size (CPHS) which, if exceeded, means a rapid decrease in the screw holding power. 1.5 and 2 mm titanium screws were inserted in discs of polyvinylchloride (PVC), wood and porcine mandibular bone with thicknesses differing between 2 to 4 mm, using an increasing pilot hole size between 66% and 95% of the screw external diameter. Torque measurements and pullout tests were performed and the CPHS was calculated. In torque measurements, the CPHS of microscrews ranged between 83% and 85% of the screw external diameter (SED). The CPHS of miniscrews lay between 80% and 90% of SED. In pullout analysis, the CPHS of microscrews ranged between 83% and 89% of SED; the CPHS of miniscrews lay between 79% and 91% of SED. The mean of the CPHS was calculated to be approximately 85% of the SED. Up to this critical point, the pilot hole size may be increased without affecting the holding power of the screws.
当螺钉拧入较厚的皮质骨时，与螺钉芯直径对应的较小的引导孔尺寸会导致高扭转应力，从而导致螺钉断裂。本研究的目的是将钻头尺寸扩大到临界引导孔尺寸（CPHS），如果超过该尺寸，则意味着螺钉固位力会迅速下降。使用外径介于螺钉外径66%至95%之间且不断增大的引导孔尺寸，将1.5毫米和2毫米的钛螺钉拧入厚度在2至4毫米之间的聚氯乙烯（PVC）、木材和猪下颌骨圆盘。进行了扭矩测量和拔出试验，并计算了临界引导孔尺寸。在扭矩测量中，微型螺钉的临界引导孔尺寸介于螺钉外径（SED）的83%至85%之间。小型螺钉的临界引导孔尺寸介于SED的80%至90%之间。在拔出分析中，微型螺钉的临界引导孔尺寸介于SED的83%至89%之间；小型螺钉的临界引导孔尺寸介于SED的79%至91%之间。临界引导孔尺寸的平均值经计算约为SED的85%。在达到这个临界点之前，可以增大引导孔尺寸而不影响螺钉的固位力。
