摘要目的 通过三维有限元方法分析动态载荷下下颌牙列缺失患者前牙区种植体植入位置对种植体及周围骨应力的影响,为种植临床提供参考.方法 利用1例山西医科大学第一医院口腔科拍摄的下颌牙列缺失患者的锥形束CT数据,通过Mimics17.0、UG NX8.5软件构建3种三维实体模型:2枚近中种植体分别垂直分布于下颌骨双侧中切牙、侧切牙和尖牙区(分别命名为中切牙区、侧切牙区和尖牙区模型),3种模型的2枚远中种植体均为30°倾斜植于下颌双侧第二前磨牙区(距颏孔近中5 mm).利用Abaqus6.12软件对模型进行动态加载,设定150 N为工作侧后牙载荷,模拟咀嚼周期为0.875 s,第1阶段:0.000 s至0.130 s,下颌向下、向外(即向工作侧移动),下颌牙与对牙无接触;第2阶段:0.130 s至0.150 s,下颌向上,工作侧同名牙牙尖相对,加载位置为下颌后牙颊尖、舌尖;第3阶段:0.150 s至0.260 s,下颌后牙颊尖颊斜面沿对牙颊尖舌斜面滑行,加载力由颊侧斜向舌侧,与牙体长轴呈45°加载于下颌后牙颊尖颊斜面;第4阶段:0.260 s至0.300 s,下颌后牙颊尖舌斜面沿对牙舌尖颊斜面滑行,约至牙尖一半长度处分离,加载力由舌侧斜向颊侧,与牙体长轴呈45°加载于下颌后牙颊尖舌斜面;第5阶段:0.300 s至0.875 s,卸载阶段,下颌后牙与对牙分离,回归至牙尖交错位.加载位置随咀嚼周期变化.观察3种模型不同加载阶段种植体及周围骨组织应力分布情况.结果 在咀嚼周期的第2~4阶段,3种模型的远中种植体应力均大于近中种植体,且颈部应力最大,向根尖应力逐渐减小;远中种植体周围骨组织应力大于近中种植体周围骨组织,且远中种植体远中骨组织应力大于近中;应力值均表现为逐渐增大,加载第4阶段达峰值.侧切牙区模型远中种植体周围骨组织应力最小,远中骨皮质应力峰值为58.7 MPa,尖牙区模型远中种植体周围骨组织应力组织最大,远中骨皮质应力峰值为135.6 Mpa.结论 下颌牙列缺失患者近中种植体植于侧切牙区时,有利于种植体的应力分散.

abstractsObjective To evaluate the effect of different placement of mesial implants in edentulous jaws on the stress of the implant and the surrounding bone tissue by three-dimensional (3D) finite element analysis. Methods Cone-beam CT data of mandibular edentulous patients was transferred into Mimics 17.0 and UG NX8.5 software, and three groups of 3D solid model were established:two mesial implants were implanted in the anterior region of the mandible (bilateral central incisor, lateral incisor, canine), and two distal oblique implant with 30° were implanted in the mandibular second premolar area(5 mm near the mental foramen). Set mandible 3D model with 4 implant by using UG NX8.5 software, produced 3 groups (mandible Ⅰ-Ⅲ). We took dynamic loading on models with help of software Abaqus 6.12, working side posterior teeth loading was set to 150 N and the simulation cycle was 0.875 s. The first stage:0.000 s to 0.130 s, the lower jaw moves outward (moving toward the side of the work), with no contact between the upper and lower teeth;the second stage:0.130 s to 0.150 s, mandibular upward, the same tooth tip of the working side were relative, the loading position were the posterior buccal tip, tongue tip;the third stage: 0.150 s to 0.260 s, the buccal slopes of buccal tips of mandibular posterior teeth glide along the lingual slopes of buccal tips of maxillary posterior teeth, the loading force was from the buccal side to the lingual side, the long axis of the tooth was 45°, loaded on the buccal slopes of buccal tips of posterior teeth;the fourth stage:0.260 s to 0.300 s, the lingual slopes of buccal tips of mandibular posterior teeth glide along the buccal slopes of the tongue tips of maxillary posterior teeth, separate from the tip of the tooth at half the length, the loading force was from the lingual side to the buccal side, the long axis of the tooth was 45° , loaded on the lingual slopes of buccal tips of posterior teeth; the fifth stage: 0.300 s to 0.875 s, at the unloading stage, mandibular posterior teeth were separated from the maxillary teeth and returned to the intercuspal position. The loading position varied according to the mastication cycle. The stress distribution of implant and surrounding bone tissue at different stages of each model were observed. Results From the early stage to chew occlusal contact to the end of the mastication cycle, three groups of models were displayed:the stress of distal implants was greater than that of mesial implants and the neck stress reached the maximum and gradually decreased to the root tip. The stress of distal implant bone was greater than that of mesial implant bone and the stress of distal bone of distal implant was greater than that of mesial bone of distal implant. All the stress peak showed a gradual increase, and the stress reach the maximum at the fourth stage. In the 3 models, the bone stress around the distal implant of model of the anterior implant located in the lateral incisor region was the lowest. The peak stress of cortical bone of the distal position of implant was 58.7 MPa. The bone stress around the distal implant of model of the anterior implant located in the canine region reached the maximum, and the peak stress of cortical bone of the distal position of implant was 135.6 MPa. Conclusions When mesial implants of edentulous jaws located in the lateral incisor region, it is good for stress dispersion.