下颌第一磨牙在不同咬合接触受力下的有限元分析

Finite element analysis of mandibular first molar under different conditions of occlusal contact

目的通过有限元法,建立Ⅰ类磨牙关系不同的咬合接触类型的下颌第一磨牙,分析咬合接触类型对牙体、牙周组织受力及牙位移的影响。方法选取下颌第一磨牙为中性磨牙关系的患者,通过CBCT扫描,获得DICOM数据,建立有限元模型,分别构造出不同咬合接触类型的各个工况,通过垂直加载300N载荷作用力,获取在不同工况下下颌第一磨牙牙体应力、应变及位移极值,分析不同咬合接触类型对牙体及牙周组织的影响。结果仅有C区(下颌第一磨牙舌尖颊斜面)受力时应力峰值最大,仅有A、B区(A区:下颌第一磨牙颊尖颊斜面;B区:下颌第一磨牙颊尖舌斜面)受力时次之,应力峰值大小随着受力区的增多呈减小趋势。应力集中的部位除1、4工况外,其余大多集中在牙体牙合面的中央窝侧壁。牙体受到应力位置不同,牙体位移也不同,其中,仅C区接触时牙体移动值达最高,仅A区接触时其次,后依次为BC、AB、B区接触,而牙体移动值最小的是AC和ABC区接触。结论仅有C或A区接触时对牙齿稳定性不利,应尽量避免,在咬合调整时,多点接触式咬合可有利分散咬合应力。

ObjectiveTo establish a finite element model of the mandibular first molar and analyze the effects of different conditions of occlusal contact on stress distribution in the tooth and periodontal tissue and on tooth displacement. MethodsThe DICOM data of conebeam computed tomography （CBCT） were obtained from a patient with neutral occlusion of the mandibular first molar to establish the finite element model of the mandibular first molar and the periodontal tissue. Three occlusal contact areas were defined on the occlusal surface of the first molar, namely the buccal slope at the buccal cusp （A）, lingual slope at the buccal cusp （B）, and buccal slope at the lingual cusp （C）. The extreme values of stress, strain and displacement of the mandibular first molar were determined under a vertical loading of 300 N, and the impact of different conditions of occlusal contact on the dental and periodontal tissues was analyzed. ResultsForce loading at the occlusal contact area C resulted in the greatest peak stress, followed by simultaneous loading at A and B, and then by loading at all the 3 contacts. The stress was concentrated mostly on the lateral walls of the central fossa of the occusal surface. The variation of stress distribution in the tooth with strain loading caused displacements of the tooth, which was the greatest with force loading at C, followed sequentially by loading at A, BC, AB, and B, and was the smallest with loading at AC and ABC. ConclusionOcclusal contact at A or C exclusively can be detrimental to maintaining the tooth contact stability and should be avoided, and occlusal adjustment to allow multiple occlusal contacts helps to disperse the occlusal stress.