Yacoub Nidal, Ismail Yahia H, Mao Jeremy J
School of Dental Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
J Prosthet Dent. 2002 Aug;88(2):192-9. doi: 10.1067/mpr.2002.127401.
Little is known about how craniofacial bones that are distant from dental implants are loaded. Whether bone experiences different strain when implants of different diameters are loaded is unknown.
This study was designed to (1) characterize bone strain both adjacent to and distant from dental implants and (2) compare bone strain in response to the same loads on small-diameter and large-diameter implants.
On 4 edentulous, dry adult human skulls, the buccopalatal midpoint of the edentulous occlusal surface was marked unilaterally in the maxillary first molar area with a round bur. A hole for implant placement was prepared, and 2 self-tapping titanium implants (3.75 x 7 mm and 4 x 7 mm) were placed in the same location and at the same orientation, one after the other. A 4-mm-long titanium abutment was connected to the implant. Each implant was loaded 10 degrees lateral to its longitudinal axis, simulating a lateral occlusal force in 3 of the skulls. In skull 2, loading was along the longitudinal axis of the implant and simulated a vertical occlusal force. The magnitude of the ramp forces was 0 to 100 N. Uniaxial strain gages and/or 3-element strain rosettes were implanted in the supramolar cortical bone, the supraincisor cortical bone, the zygomaticomaxillary suture, and the zygomaticotemporal suture. All strain gages/rosettes were excited with 500 mV DC, and the output signals were recorded with a strain conditioner. Tensile strain was expressed as positive values and compressive strain as negative values. Student t tests were used to test for normal distribution of bone strain within each skull; Wilcoxon tests were applied for skewed distribution between small- and large-diameter implants and between 50-N and 100-N loads (P<or=.05).
Bone strain both adjacent to and distant from the implants was complex: compressive strain in the buccal cortical bone superior to the implants; tensile strain in the ipsilateral supraincisor cortical bone but compressive strain in the contralateral supraincisor cortical bone; and tensile strain anterior to the zygomaticotemporal suture but compressive strain posterior to the suture. With the same applied loads, bone strain was higher for large-diameter implants than for small-diameter implants for all the above cortical locations (P<.01 to.001) except posterior to the zygomaticotemporal suture.
Within the limitations of this study, bone strain resulting from dental implant loading was distributed to cortices not only adjacent to but also distant from dental implants. The large-diameter implant was more facilitative of stress transfer to cortical bone than the small-diameter implant tested.
对于远离牙种植体的颅面骨如何受力，人们了解甚少。不同直径种植体受力时，骨是否会经历不同的应变尚不清楚。
本研究旨在（1）描述牙种植体附近和远处的骨应变特征，以及（2）比较小直径和大直径种植体在相同载荷作用下的骨应变情况。
在4个无牙的干燥成人颅骨上，用圆钻在上颌第一磨牙区单侧标记无牙咬合面的颊腭中点。制备种植体植入孔，并将2枚自攻钛种植体（3.75×7mm和4×7mm）先后以相同位置和相同方向植入。将一个4mm长的钛基台连接到种植体上。在3个颅骨中，每个种植体在其纵轴外侧10度方向加载，模拟侧向咬合力。在颅骨2中，加载沿种植体纵轴方向，模拟垂直咬合力。斜坡力大小为0至100N。将单轴应变片和/或三元件应变花植入磨牙上皮质骨、切牙上皮质骨、颧上颌缝和颧颞缝。所有应变片/应变花均用500mV直流电激励，输出信号用应变调节器记录。拉伸应变以正值表示，压缩应变以负值表示。采用学生t检验来检验每个颅骨内骨应变的正态分布；应用Wilcoxon检验来分析小直径和大直径种植体之间以及50N和100N载荷之间的偏态分布（P≤0.05）。
种植体附近和远处的骨应变情况较为复杂：种植体上方颊侧皮质骨出现压缩应变；同侧切牙上皮质骨出现拉伸应变，但对侧切牙上皮质骨出现压缩应变；颧颞缝前方出现拉伸应变，但缝后方出现压缩应变。在相同载荷作用下，除颧颞缝后方外，上述所有皮质部位大直径种植体的骨应变均高于小直径种植体（P＜0.01至0.001）。
在本研究的局限性范围内，牙种植体加载产生的骨应变不仅分布在种植体附近的皮质骨，还分布在远离种植体的皮质骨。与所测试的小直径种植体相比，大直径种植体更有利于应力传递至皮质骨。
