全口义齿不同牙尖斜度对支持组织影响的三维有限元分析
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摘要
全口义齿对于无牙颌患者来说是长期的，甚至是终身性的修复体。牙列缺失患者,戴用修复得当的全口义齿,组织内应力分布均匀,并保持在生理限度内,可延缓牙槽嵴的吸收。反之,义齿作用力大小、方向、分布和传导方式不当,则将加速牙槽嵴的吸收。在全口义齿的修复中，人工牙是很重要的一部分，人工牙的牙合形更是其中的重点，也是多年来最具争议的问题之一，长期以来对于全口义齿选用不同牙尖斜度的义齿，过去有争论，至今仍有不同观点。目前已有百余种总义齿人工牙的设计方案，迄今为止，其中哪些综合评价最高，有利于义齿的稳定，具有较高的咀嚼效能，还不损害口腔支持组织的健康呢？目前尚无统一的结论。
牙列缺失后骨组织的改变主要是牙槽嵴的吸收，牙槽嵴的持续吸收不仅与患者全身健康状态和骨质代谢状况有关，而且与修复义齿与否及修复效果好坏有关。牙槽骨的吸收是一种慢性、渐进性、不可逆的过程，其病因极为复杂，并不是单一的因素决定的，而是多种因素作用的结果。牙槽嵴的骨改建过程与力学因素有直接的联系，骨改建是指机体的骨组织在一生中，不断的进行骨的新生增强和吸收萎缩，从而使骨组织的解剖结构发生变化的现象。骨改建遵从Wolff定律：骨的机械强度取决于骨的结构，正常和异常骨结构随着功能需要而发生变化。机械应力对维持和改变骨的结构很重要。
生理限度内的压力刺激可增强骨的生成,压力过高则使骨生成延缓及骨坏死。没有压力则使其刺激作用丧失，在应力低的区域，骨吸收萎缩而使结构减弱。
本实验利用三维有限元方法进行实验。本实验直接以CT机扫描获取的数据为直接信息来源，由photoshop 7.0专业图像处理软件读取图片，这样获得的数据图像既节省了人力，物力，又更加准确减少了中间环节，降低了误差，再用Solidworks 2001建模软件建成与原解剖模型等大的上下颌的三维数字化图，通过将模型抽壳，牙槽嵴延伸等操作生成骨皮质，粘骨膜，义齿基托，将带有牙尖斜度的义齿，按序排列于义齿基托的主承托区，植入基托内1.5mm，形成全口义齿的后牙区。对于牙槽嵴吸收的模型以增加义齿基托的厚度维持垂直距离，上下颌模型牙槽嵴顶至颌骨底部Ⅰ度吸收为30mm;Ⅱ度吸收为27mm;Ⅲ度吸收为24mm;Ⅳ度吸收为21mm。测得三种牙尖斜度义齿作用下四种不同吸收程度的有限元模型上的应力值及位移大小，并对结果加以计算分析，旨在找出针对不同条件的支持组织应用何种牙尖斜度的义齿，其分布均匀，有利于义齿的稳定和牙槽嵴健康。
结果表明：人工牙牙尖斜度相同的全口义齿，随支持组织吸收程度的增加，牙槽嵴所受的侧方力增加，不利于支持组织健康;支持组织条件相同，戴用人工牙牙尖斜度不同的义齿。随牙尖斜度的增加，牙槽嵴受力不均衡，义齿不稳定因
素增加;人工牙牙尖斜度为0度的义齿，因其产生的水平位移小，适用于本实验中Ⅲ度吸收的患者，对于Ⅳ度吸收的支持组织来说，牙尖斜度为0度的义齿的应力偏大，不利于组织健康，应当考虑采用既有较大的宽容度，又能减轻对牙槽嵴的应力。牙尖斜度为33度的义齿，因其产生的侧向力大，适用于牙槽嵴Ⅰ度吸收的患者。牙尖斜度20度的义齿产生的侧向力和压力介于0度和33度之间，适用于牙槽嵴Ⅰ度或Ⅱ度吸收的患者。
对于全口义齿修复来说，人工牙的牙尖斜度是义齿牙合 形的一项重要因素，对支持组织的应力分布有很大的影响。但我们还应清醒的认识到，牙尖斜度对义齿的稳定和支持组织健康只是一个影响因素，而不是决定因素。本实验只是从人工牙牙尖斜度的角度进行探讨，寻求对支持组织健康有利的方案，以便指导临床对人工牙的选用。
For the edentulous patient, complete denture would be a long-term restoration, it can be used even all one’s life. If the complete denture fit for the edentulous patient, the stress distribution under occlusal force on the supporting tissue is balanced, it may lower the speed of the bone resorption. On the other hand, if the stress’s direction and distribution of complete denture under occlusion force are imbalance. it may cause the alveolar bone resorb quickly. Artificial teeth are important to the complete denture, and they are the most important factor we argued. We have different point of view about choocing the complete denture with different cusp inclination. There have been more than one hundred designs about the artificial teeth, but which one is beneficial for the stabilization of the complete denture; it can improve the mastication efficiency and be good to the supporting tissue? We have not a consistent idea about it.
The resorption of residual ridge is the main change after
the teeth get off from the alveolar bone. The bone resorption have relation to not only the health of the patient and the metabolism of bone, but also have relation to the effect of the restoration .It is chronically、gradually 、unreversible for the the resorption of residual ridge. The residual ridge resorption has direct relation with the stress, the rebuilding of bone is the bone of the body has metabolism all life, the bone’s structure may be get stronger or weaker. The bone’s rebuild defering to Wolff's law： The mechanical strength of bone is decided by the bone’s structure. The stress is very important for bone to keep or change it’s structure. If the intensity of stress inner the physiology limit, the stimulate will get the bone stronger, If the intensity of stress is higher or lower the physiology limit, it will weaken the bone .
This study based on the biomechanical considerations. We used Solidworks 2001 computer-acided design system to establish four kinds of models with different resorption degrees(by Kent’s) ,Ⅰdegree of the alveolar bone from it’s top to it’s bottom is 30mm; Ⅱ degree of the alveolar bone
from it’s top to it’s bottom is 27mm; Ⅲ degree of the alveolar bone from it’s top to it’s bottom is 24mm; Ⅳ degree of the alveolar bone from it’s top to it’s bottom is 21mm. then we build complete denture with cusp inclination. In this way we built 24 models, we use the method of three-dimentional finite element analysis to investigate the influence of the strees’s distribution under the complete denture with cusp inclination, so that we can find out which kind of denture is beneficial for the residual ridge with different degree of resorption .
Experimental results demostrate that: The side-stress which is on the alveolar bone under the complete denture with same cusp inclination is increased with the aggravation of residual ridge resorption, it is harm for the alveolar bone; If the alveolar bone is in the same condition, when the cusp inclination increased, the factors of unsteadiness will increase. The complete denture with cusp inclination of 0 degree fit for the patient whose alveolar bone’s resorption is Ⅲ degree ; the complete denture with cusp inclination of 33 degree fit for
the patient whose alveolar bone’s resorption is Ⅰ degree . the tress under the complete denture with cusp inclination of 20 degree is between that of 0 degree and 33 degree, the complete denture with cusp inclination of 20 degree fit for the patient whose alveolar bone’s resorption isⅠor Ⅱ degree.
For the complete denture, the cusp inclination of artificial teeth is a important factor, it will do much influence to the stress distribution of supporting tissue. But we should have good cognizance about that the cusp inclination of artificial teeth is only a factor to influence the stabilization of the complete denture and the health of the alveolar bone. The study is investigating the cusp inclination of artificial teeth to find out which is beneficial for the health of the
牙列缺失后骨组织的改变主要是牙槽嵴的吸收，牙槽嵴的持续吸收不仅与患者全身健康状态和骨质代谢状况有关，而且与修复义齿与否及修复效果好坏有关。牙槽骨的吸收是一种慢性、渐进性、不可逆的过程，其病因极为复杂，并不是单一的因素决定的，而是多种因素作用的结果。牙槽嵴的骨改建过程与力学因素有直接的联系，骨改建是指机体的骨组织在一生中，不断的进行骨的新生增强和吸收萎缩，从而使骨组织的解剖结构发生变化的现象。骨改建遵从Wolff定律：骨的机械强度取决于骨的结构，正常和异常骨结构随着功能需要而发生变化。机械应力对维持和改变骨的结构很重要。
生理限度内的压力刺激可增强骨的生成,压力过高则使骨生成延缓及骨坏死。没有压力则使其刺激作用丧失，在应力低的区域，骨吸收萎缩而使结构减弱。
本实验利用三维有限元方法进行实验。本实验直接以CT机扫描获取的数据为直接信息来源，由photoshop 7.0专业图像处理软件读取图片，这样获得的数据图像既节省了人力，物力，又更加准确减少了中间环节，降低了误差，再用Solidworks 2001建模软件建成与原解剖模型等大的上下颌的三维数字化图，通过将模型抽壳，牙槽嵴延伸等操作生成骨皮质，粘骨膜，义齿基托，将带有牙尖斜度的义齿，按序排列于义齿基托的主承托区，植入基托内1.5mm，形成全口义齿的后牙区。对于牙槽嵴吸收的模型以增加义齿基托的厚度维持垂直距离，上下颌模型牙槽嵴顶至颌骨底部Ⅰ度吸收为30mm;Ⅱ度吸收为27mm;Ⅲ度吸收为24mm;Ⅳ度吸收为21mm。测得三种牙尖斜度义齿作用下四种不同吸收程度的有限元模型上的应力值及位移大小，并对结果加以计算分析，旨在找出针对不同条件的支持组织应用何种牙尖斜度的义齿，其分布均匀，有利于义齿的稳定和牙槽嵴健康。
结果表明：人工牙牙尖斜度相同的全口义齿，随支持组织吸收程度的增加，牙槽嵴所受的侧方力增加，不利于支持组织健康;支持组织条件相同，戴用人工牙牙尖斜度不同的义齿。随牙尖斜度的增加，牙槽嵴受力不均衡，义齿不稳定因
素增加;人工牙牙尖斜度为0度的义齿，因其产生的水平位移小，适用于本实验中Ⅲ度吸收的患者，对于Ⅳ度吸收的支持组织来说，牙尖斜度为0度的义齿的应力偏大，不利于组织健康，应当考虑采用既有较大的宽容度，又能减轻对牙槽嵴的应力。牙尖斜度为33度的义齿，因其产生的侧向力大，适用于牙槽嵴Ⅰ度吸收的患者。牙尖斜度20度的义齿产生的侧向力和压力介于0度和33度之间，适用于牙槽嵴Ⅰ度或Ⅱ度吸收的患者。
对于全口义齿修复来说，人工牙的牙尖斜度是义齿牙合 形的一项重要因素，对支持组织的应力分布有很大的影响。但我们还应清醒的认识到，牙尖斜度对义齿的稳定和支持组织健康只是一个影响因素，而不是决定因素。本实验只是从人工牙牙尖斜度的角度进行探讨，寻求对支持组织健康有利的方案，以便指导临床对人工牙的选用。
For the edentulous patient, complete denture would be a long-term restoration, it can be used even all one’s life. If the complete denture fit for the edentulous patient, the stress distribution under occlusal force on the supporting tissue is balanced, it may lower the speed of the bone resorption. On the other hand, if the stress’s direction and distribution of complete denture under occlusion force are imbalance. it may cause the alveolar bone resorb quickly. Artificial teeth are important to the complete denture, and they are the most important factor we argued. We have different point of view about choocing the complete denture with different cusp inclination. There have been more than one hundred designs about the artificial teeth, but which one is beneficial for the stabilization of the complete denture; it can improve the mastication efficiency and be good to the supporting tissue? We have not a consistent idea about it.
The resorption of residual ridge is the main change after
the teeth get off from the alveolar bone. The bone resorption have relation to not only the health of the patient and the metabolism of bone, but also have relation to the effect of the restoration .It is chronically、gradually 、unreversible for the the resorption of residual ridge. The residual ridge resorption has direct relation with the stress, the rebuilding of bone is the bone of the body has metabolism all life, the bone’s structure may be get stronger or weaker. The bone’s rebuild defering to Wolff's law： The mechanical strength of bone is decided by the bone’s structure. The stress is very important for bone to keep or change it’s structure. If the intensity of stress inner the physiology limit, the stimulate will get the bone stronger, If the intensity of stress is higher or lower the physiology limit, it will weaken the bone .
This study based on the biomechanical considerations. We used Solidworks 2001 computer-acided design system to establish four kinds of models with different resorption degrees(by Kent’s) ,Ⅰdegree of the alveolar bone from it’s top to it’s bottom is 30mm; Ⅱ degree of the alveolar bone
from it’s top to it’s bottom is 27mm; Ⅲ degree of the alveolar bone from it’s top to it’s bottom is 24mm; Ⅳ degree of the alveolar bone from it’s top to it’s bottom is 21mm. then we build complete denture with cusp inclination. In this way we built 24 models, we use the method of three-dimentional finite element analysis to investigate the influence of the strees’s distribution under the complete denture with cusp inclination, so that we can find out which kind of denture is beneficial for the residual ridge with different degree of resorption .
Experimental results demostrate that: The side-stress which is on the alveolar bone under the complete denture with same cusp inclination is increased with the aggravation of residual ridge resorption, it is harm for the alveolar bone; If the alveolar bone is in the same condition, when the cusp inclination increased, the factors of unsteadiness will increase. The complete denture with cusp inclination of 0 degree fit for the patient whose alveolar bone’s resorption is Ⅲ degree ; the complete denture with cusp inclination of 33 degree fit for
the patient whose alveolar bone’s resorption is Ⅰ degree . the tress under the complete denture with cusp inclination of 20 degree is between that of 0 degree and 33 degree, the complete denture with cusp inclination of 20 degree fit for the patient whose alveolar bone’s resorption isⅠor Ⅱ degree.
For the complete denture, the cusp inclination of artificial teeth is a important factor, it will do much influence to the stress distribution of supporting tissue. But we should have good cognizance about that the cusp inclination of artificial teeth is only a factor to influence the stabilization of the complete denture and the health of the alveolar bone. The study is investigating the cusp inclination of artificial teeth to find out which is beneficial for the health of the
引文
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2.Van Waas MAJ.Determinants of dissatisfaction with dentures:amultiple regression analysis.J Prosthet Dent,1990.64(5):569-572
3.Kydd WL. The comminuting efficiency of varied occlusal tooth from and the associated deformation of the complete dentures base. J.A.D.A. 1960;6(10):465-471
4.Sauser CW. Posterior occlusion in complete denture construction. J Prosthet Dent.1957;7(4):456-464
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7.Sears V.H.Channel type posterior tooth forms. J.A.D.A. 1928;15(6):1111
8.Hall R.E. The inverted cusp tooth. J.A.D.A. 1931;18(12):2366
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11.Payne SH. A posterior set-up to meet individual requirements. Dent Dig.1941;47:20-22
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2.Van Waas MAJ.Determinants of dissatisfaction with dentures:amultiple regression analysis.J Prosthet Dent,1990.64(5):569-572
3.Kydd WL. The comminuting efficiency of varied occlusal tooth from and the associated deformation of the complete dentures base. J.A.D.A. 1960;6(10):465-471
4.Sauser CW. Posterior occlusion in complete denture construction. J Prosthet Dent.1957;7(4):456-464
5.Frush J P. Lineal occlusion. Illinois Dental Journal. 1966;35:788-794
6.Becker CM,Charles C.Swoop, Albert D.Guckes. Lingualized occlusion for removable prosthodontics. J Prosthet Dent. 1977;38(6):601-608
7.Sears V.H.Channel type posterior tooth forms. J.A.D.A. 1928;15(6):1111
8.Hall R.E. The inverted cusp tooth. J.A.D.A. 1931;18(12):2366
9.徐君伍，主编.口腔修复学，第三版，北京人民卫生出版社.1994.4
10.Sosin M.B. Re-evaluation of posterior tooth forms for complete denture.J Prothet Dent.1961;11:55-61
11.Payne SH. A posterior set-up to meet individual requirements. Dent Dig.1941;47:20-22
12.Payne SH. Fallacy of balanced articulation. NYJ Dent.1944;14:151-154
13.Pound E. Personalized denture procedures. Dentist's Manual,Anaheim.1973;Denar Corp. 80
14.Jones PM. An efficient, nontraumatic posterior occlusion. J.A.D.A.1962;64(5):345-350
15.徐君伍主编，第四军医大学口腔修复学讲义，P36
16.朱希涛主编 ，口腔修复学（二版），人民卫生出版社，1988，278
17.小材义典，齿科展望，1979，53（5）：757
18.徐君伍主编，口腔修复学（四版），人民卫生出版社，2001，146-147
19.Rieger MR, Mayberry M,Brose MO. Finite element analysis of six endosseous implants. J Prosthet Dent, 1990, 63:671
20.巢永烈，梁星主编。种植义齿学，第一版，北京：北京
医科大学中国协和医科大学联合出版社。1999，41。
21.Krajicek, DD, et al.Observations on the histologic features of the human edentulous ridge PartⅢ:Bone. J Prosthet Dent,1984,52:836
22.Brehm TW,Abadhi BJ.Patient response to variations in complete denture technique.Jprosthet Dent, 1980, 44:491.
23.Cambell RL.A comparative study of the resorption of the alveolar ridges in denture wearers and non-denture wearers.J Am Dent Assoc,1970,60:143.
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