【作者】 吕正辉；

【导师】 张少锋；

【作者基本信息】 第四军医大学 ， 口腔临床医学， 2007， 硕士

【摘要】 在牙列缺损的修复中,固定桥因其方便、舒适、美观、咀嚼效率高、价格适中和制作周期短等优点,在临床应用广泛。但是,对于游离端缺牙进行固定修复时,固定桥为单端固定桥,其结构属于悬臂梁结构形式,在桥体受力时有可能使基牙负担过重,进而造成损害,如何合理地设计单端固定桥一直以来是口腔医学工作者关注的课题。本研究通过制作单端固定桥修复D区7游离端缺失时的基牙及其牙周支持组织的光弹模型,对增加基牙数目和桥体减径两种减负措施,设计出不同组合的单端固定桥,对桥体进行模拟加载,分析基牙牙周支持组织的应力状况,筛选最佳的设计方案,为游离端缺牙的单端固定桥修复设计提供实验依据。实验首先根据物理和几何相似性原理,按实验设计制作出10组实验所需的光弹模型。即为基牙为D区6时,桥体在不减径、减径1/3、减径1/2时分别为1、2、3组,基牙为D区5、6时,桥体在不减径、减径1/3、减径1/2时分别为4、5、6组,基牙为D区4、5、6时,桥体在不减径、减径1/3、减径1/2时分别为7、8、9组,正常D区4、5、6的下颌光弹模型为对照组即第10组;其次,对所使用的光弹性模型材料进行条纹值标定实验,根据条纹级数N推算出材料条纹值f;然后,模拟在牙周支持组织健康情况下,对不同基牙数目和桥体长度组合设计的单端固定桥进行模拟加载,加载部位选择在桥体远中边缘嵴处,使基牙处于最大承载状态,测量出承载后基牙支持组织光弹模型上的条纹级数,根据公式δ=Nf/h换算成压强;最后,通过统计分析方法,比较不同修复设计的单端固定桥基牙的应力分布情况,筛选出最佳设计方案。本研究实验结果如下:1.制作出了几何形态、物理参数和边界条件与牙齿、牙周膜和牙槽骨接近的健康D区4、5、6牙齿及牙周支持组织的光弹模型;2.通过材料条纹值的标定实验测得了实验所用光弹性材料的条纹值:f =11.48N/mm;3.在桥体加载的情况下,距桥体最近的基牙远中根尖处有最大的应力集中区,且其根尖区应力明显大于牙颈部应力;4.基牙数目对近桥体基牙远中根尖部及牙颈部的应力大小有影响,基牙由一个增加到两个时较基牙由两个增加到三个时应力减少明显;5.桥体近远中径长短对近桥体基牙远中根尖部及牙颈部的应力大小有影响;6.对照组正常D区6的牙周支持组织应力平均值为2.2MPa,1、2组的最大应力平均值分别为5.73 MPa和4.97 MPa,根据牙周储备力理论,都大于对照组应力的两倍,因此为不合理修复设计,说明单基牙单端固定桥在桥体近远中不减径和减径1/3时的修复设计是不合理的。7. 3组、4组应力平均值分别为4.37 MPa、4.57 MPa,与对照组应力平均值2倍接近,因此说明单基牙单端固定桥桥体近远中减径1/2时和两基牙单端固定桥桥体近远中不减径时,这两种修复设计要慎用。8. 5、6、7、8、9组最大应力平均值分别3.83 MPa、3.07 MPa、4.03 MPa、3.27 MPa、2.33 MPa,均小于对照组的2倍,所以,采用双基牙,桥体近远中减径1/3和1/2,以及三基牙,桥体近远中不减径、减径1/3和减径1/2,这些单端固定桥修复设计都是可行的。根据上述实验结果,结合临床实际综合考虑,一方面要减少对健康基牙的磨切,另一方面基牙所受应力不能超过基牙牙周储备力的两倍,因此,选用双基牙减径的单端固定桥设计最为理想。更多还原

【Abstract】 In repairing defect of dentition the fixed bridge has many advantages for example comfort, beautiful outlook,low-price,convenience and shot period of manufacture.but in repairing unilateral distal-extension edentulous the fixed bridge is the cantilever fixed bridge.The structure of cantilever fixed bridge is remained with the structure of cantilever beam.Loading on the bridge pontic,there is any possibility to make too much loading on abutment and hurt the abument then proceeding to the next step.How to manufacture and design the cantilever fixed bridge is always focused on by dental researchers..In this study, to manufact and design the Photoelastic model of the abutment and periodontal tissue of mandibular unilateral distal-extension edentulous restored by cantilever fixed bridge.Using two measures that adding the number of the abutment and reducing the mesial and distal length of the bridge pontic to design vairous cantilever fixed bridge .To load on the the bridge pontic and study the stress and the factors of effecting the stress distribution.We can make out a better design for providing a experimental base of the application of the cantilever fixed bridge in clinic.The way apllied in this study is a experimental mechanics method.Fist, according to principles of physical and chemical similarity , different materials have been used to manufacture the photoelastic model used in this experiment .The models are setting off ten groups.The abutment is the sixth, the mesial and distal length of the bridge pontic is invariability ,reducing 1/3 and 1/2.The group is the 1th,2nd and 3ird. The abutment is the fifth and sixth, the mesial and distal length of the bridge pontic is invariability ,reducing 1/3 and 1/2. The group is the 4th,5th and 6th. The abutment is the sixth, the mesial and distal length of the bridge pontic is invariability ,reducing 1/3 and 1/2.The group is the 7th,8th and 9th. The tenth group is the fourth,the fifth,the sixth in D zone which includes healthy teeth,alveolar bone and pericementum membrane.Second , it is to do the experiment of measuring the material streak value for the same photoelastic material.According streak numbers,N,calculates the f value that is the material streak value.Third, finished the photoelastic models simulate healthy periodontal tissue.The cantilever fixed bridge that is designed by the difference number of the abutment and the difference mesial and distal length of bridge pontic is loaded on the part distal marginal ridge of the bridge pontic that can made abutment on maximum loading. The streak numbers of photoelastic models can be measured after loaded.According the f value and the formula (δ=Nf/h) the streak numbers convert pressure.At last,it is to select the best design after comparing the stress distribution of the abutment of vairous designing cantilever fixed bridges with the method of statistics analysis.Result of experiment:1. The photoelastic model that the fourth,the fifth and the sixth tooth in D zone are health,which includes teeth,alveolar bone and pericementum membrane is builded.the photoelastic model finished is similar to actual teeth,alveolar bone and pericementum membrane in the geometrical appearance,the physical parameter and the borderline condition.2. It is to measure the material streak value for the photoelastic material of experiment in the experiment of measuring the material streak value.The material streak value is 11.48N/mm(f =11.48N/mm).3. In the condition of loading on the bridge pontic,there is the maximum stress in the abutment which closest to the bridge pontic.The stess is localized in the zone of the distal root tip. The stess in the zone of the distal root tip is bigger than it in the distal dental cervix.4. The stress in the zone of the distal root tip and distal dental cervix is influenced by numbers of abutment.The diminishing of the stress in the condistion of the number of the abutment from one to two is more obvious than it in the condition of the number of the abutment from two to three.5. The stress in the zone of the distal root tip and distal dental cervix is influenced by treciprocationl and distal length of the bridge pontic.6. The average stress in the sixth in D zone of the10th group is 2.2MPa.The max average stress of the 1st and 2nd group is 5.73MPa and 4.97MPa.From the reserve of periodontium,the stess of 1st and 2nd is bigger than the one of the 10th group.So the design of the 1st and 2nd group is unreasonable.That descript the design of one abumtment and reducing 1/3 the mesial and distal length of the bridge pontic is unreasonable.7. The max average stress of the 3th and 4nd group is 4.37MPa and 4.57MPa.That is nearest two times to the 10th group. That descript to apply the design of one abumtment and reducing 1/2 the mesial and distal length of the bridge pontic or two abumtments must be careful.8. The max average stress from the 9th to 10th group is 3.83 MPa,3.07 MPa,4.03 MPa,3.27 MPa,2.33 MPa.that tress is more little than two times the 10th group.these designs are all reasonable.Thinking about clinic, diminishing the treciprocationl and distal length of the bridge pontic is more practical than adding the number of the abutment.The most ideal design is diminished the treciprocationl and distal length of the bridge pontic and two abumtments.更多还原