Haug R H, Barber J E, Punjabi A P
Division of Oral and Maxillofacial Surgery, Case Western Reserve University School of Medicine, Cleveland OH, USA.
J Oral Maxillofac Surg. 1999 Mar;57(3):300-8; discussion 308-9. doi: 10.1016/s0278-2391(99)90677-8.
The purpose of this in vitro investigation was to determine whether the number or pattern of placement of positional screws affected their ability to resist vertical loads resembling mastication.
Standardized bone substitutes were secured with varying numbers of 17.0-mm-long, 2.0-mm outer diameter, self-tapping titanium screws (W. Lorenz Surgical, Jacksonville, FL) in various patterns using a positional screw technique. These patterns included one, two, three, four, and five screws in a linear pattern; two screws in a vertical pattern; three screws in an L-pattern, inverted-L pattern, backward-L pattern, inverted-backward-L pattern, and right and left diagonal pattern; four screws in a box pattern; and five screws in a domino pattern. Five models of each group were fabricated along with a control group. The models were secured in a jig and subjected to vertical loads by an Instron 8511.20 Mechanical Testing Unit (Canton, MA) until failure. Common engineering standards, including yield load, yield displacement, stiffness, maximum load, and displacement at maximum load, were measured, and means and standard deviations were derived and compared for statistical significance with an analysis of variance (ANOVA) and Scheffe multiple comparison test.
Screw number and pattern of placement affected the mechanical characteristics in resistance to vertical load. Screw numbers less than three and all linear patterns were the least effective. The three-screw L patterns, as a category, provided greater resistance to vertical loads than either the three-screw linear or three-screw diagonal patterns. The addition of more than three screws in geometric patterns offered no greater benefit than the three-screw L patterns.
In this in vitro study, the three-screw L patterns were the most effective and efficient when using the positional screw technique.
本体外研究的目的是确定定位螺钉的数量或放置方式是否会影响其抵抗类似咀嚼垂直载荷的能力。
使用定位螺钉技术，用不同数量的17.0毫米长、外径2.0毫米的自攻钛螺钉（W. Lorenz Surgical，杰克逊维尔，佛罗里达州）以各种方式固定标准化骨替代物。这些方式包括线性排列的1枚、2枚、3枚、4枚和5枚螺钉；垂直排列的2枚螺钉；L形、倒L形、后L形、倒后L形以及左右对角线形排列的3枚螺钉；方形排列的4枚螺钉；多米诺骨牌形排列的5枚螺钉。每组制作5个模型以及一个对照组。将模型固定在夹具中，通过英斯特朗8511.20机械测试单元（马萨诸塞州坎顿）施加垂直载荷直至失效。测量包括屈服载荷、屈服位移、刚度、最大载荷以及最大载荷时的位移等常用工程标准，并得出均值和标准差，通过方差分析（ANOVA）和谢费多重比较检验进行统计显著性比较。
螺钉数量和放置方式会影响抵抗垂直载荷的力学特性。少于3枚螺钉的情况以及所有线性排列方式效果最差。作为一个类别，3枚螺钉的L形排列比3枚螺钉的线性排列或3枚螺钉的对角线排列对垂直载荷的抵抗力更强。在几何排列中添加超过3枚螺钉并不比3枚螺钉的L形排列更具优势。
在本体外研究中，使用定位螺钉技术时，3枚螺钉的L形排列是最有效且高效的。
