■带和环空间保持器用于保持早期丢失的落叶磨牙的缺失空间。当第二个落叶磨牙过早丢失时,当第一恒磨牙是基牙时,在不同发育程度上的应力可能会有所不同。空间维护器的设计和使用也可能导致回路的损坏。本文的目的是使用有限元方法研究在有或没有咬合接触的情况下,第一恒磨牙和环上的应力,以四个不同发育程度的第一恒磨牙作为基牙。我们旨在指导空间维持器的临床设计和使用。
■我们开发了下颌第一恒磨牙和带环空间保持器的有限元模型,模拟牙槽骨,牙周膜(PDL),牙釉质和牙本质.四个发育阶段为1/2(I),2/3(II),3/4(III)和全面发展(IV)。AnsysWorkbench用于分析牙根发育和环与对颌之间的咬合接触对基牙和环的影响。基牙以70N的力垂直和倾斜地静态加载。环以14N的力垂直静态加载。计算了所有结构上的应力和环的位移趋势。
■搪瓷上的应力,牙本质,PDL和牙槽骨相似,浓度一致。但是如果有咬合接触,环在与前牙接触的近中间边缘产生最大位移。当环与相对的咬合牙咬合接触时,垂直荷载作用下空间保持者等效应力峰值为:Ⅰ组>Ⅳ组>Ⅲ组>Ⅱ组,最大主应力峰值变化为:Ⅰ组>Ⅲ组>Ⅱ组>Ⅳ组。斜荷载下回路等效应力峰值的变化为:Ⅰ组>Ⅲ组>Ⅳ组>Ⅱ组,最大主应力峰值变化为:III组>I组>II组>IV组。当环不与相对的咬合牙咬合接触时,垂直荷载作用下空间保持者等效应力峰值为:IV组>I组>II组>III组,最大主应力峰值变化为:IV组>I组>II组>III组。斜荷载作用下空间保持器等效应力峰值的变化为:Ⅰ组>Ⅳ组>Ⅱ组>Ⅲ组,最大主应力峰值变化为:Ⅰ组>Ⅳ组>Ⅱ组>Ⅲ组。
■我们的结果表明,只要有可能,建议选择根部发育接近完整的牙齿作为空间保持者的基牙。带和环空间保持器的设计和使用应避免咬合与咬合牙齿接触,以防止环变形。
UNASSIGNED: The band and loop space maintainer is used to maintain the missing space of deciduous molars which are lost early. When the second deciduous molar is lost prematurely, the stress on the first permanent molar during different degrees of development may vary when it is the abutment. The design and use of the space maintainer may also lead to damage of the loop. The purpose of this article is to use the finite element method to study the stress on the first permanent molar and the loop with or without occlusal contact, with the first permanent molar of four different degrees of development serving as the abutment. We aimed to guide the clinical design and use of the space maintainer.
UNASSIGNED: We developed finite element models of the mandibular first permanent molar and the band and loop space maintainer, and simulated alveolar bone, periodontal ligament (PDL), enamel and dentin. The four developmental stages were 1/2 (I), 2/3 (II), 3/4 (III) and full development (IV). Ansys Workbench was used to analyze the effects of root development and occlusal contact between the loop and the opposite jaw on abutment teeth and the loop. Abutment teeth were statically loaded vertically and obliquely with a force of 70 N. The loop was statically loaded vertically with a force of 14 N. The stress on all structures and the displacement trends of the loop were calculated.
UNASSIGNED: The stress on enamel, dentin, PDL and alveolar bone were similar, and the concentration was consistent. But if there was occlusal contact, the loop produced maximum displacement at the near middle edge of contact with the anterior teeth. When the loop was in occlusal contact with the opposing occlusal tooth, the peak value of the equivalent stress on the space maintainer under vertical load was: group I > group IV > group III > group II, and the maximum principal stress peak change was: group I > group III > group II > group IV. The change of the equivalent stress peak value of the loop under oblique load was: group I > group III > group IV > group II, and the maximum principal stress peak change was: group III > group I > group II > group IV. When the loop was not in occlusal contact with the opposing occlusal tooth, the peak value of the equivalent stress on the space maintainer under vertical load was: group IV > group I > group II > group III, and the maximum principal stress peak change was: group IV > group I > group II > group III. The change of the equivalent stress peak value of the space maintainer under oblique load was: group I > group IV > group II > group III, and the maximum principal stress peak change was: group I > group IV > group II > group III.
UNASSIGNED: Our results suggested that whenever possible, choosing the teeth with nearly complete root development as the abutment of the space maintainer is advisable. The design and use of the band and loop space maintainer should avoid occlusal contact with the occlusal teeth to prevent deformation of the loop.