不同侧方型者尖对尖颌位时相对力的比较研究

目的比较不同侧方型受检者侧方咬合运动至尖牙尖对尖颌位时的相对力。方法利用T-ScanⅡ咬合分析系统记录85名个别正常者从牙尖交错位侧方咬合运动至尖牙尖对尖颌位时的接触及力分布信息,计算尖对尖颌位相对牙尖交错位时的力值,并就相应数据作多元回归分析。结果所有受检者从牙尖交错位至尖对尖颌位作侧方咬合运动过程中力均逐渐降低。不同侧方型受检者侧方咬合运动至尖对尖颌位时的相对力具有统计学差异(P<0.001),其中以尖牙保护组与仅工作侧第一前磨牙接触组最低。结论尖牙具有"应力缓冲"的能力,提示尖牙保护是对口颌系统最为有利的侧方型。     

老年人动态咬合下的接触特征的初步研究

目的：通过研究老年人多种颌位的咬合观察及前伸咬合运动中前牙的接触模式与牙弓形状的关系,探讨老年人的动态咬合下的接触特征,为临床修复重建提供理论依据。方法：本研究共86例老年患者,通过口内视诊确定牙弓形态。采用厚度为8um的Bausch咬合测试膜检查下颌各个非正中颌位的接触：侧方移动至包括下颌0.5mm、尖对尖接触位置及前伸移动至前牙切对切接触位置。结果：下颌侧方移动至0.5mm时,30.2%受试者为双侧组牙功能,20.1%为混合尖牙保护和组牙功能。下颌侧方移动至尖对尖接触位置时,45.3%的受试者为双侧尖牙保护,17.4%为双侧组牙功能。下颌向前滑动至上、下前牙切对切接触位置时,80.2%的受试者前牙存在接触,后牙分离。前牙的牙合接触模式与牙列形状的关系：71.4%方圆型牙弓受试者是I型前牙接触模式;63.9%尖圆型牙弓受试者为II型前牙接触模式;对于卵圆型牙弓受试者,前牙接触模式I型和II型均占40%。结论：老年患者具有特殊的动态接触特征。前伸咬合运动中前牙的接触模式与牙弓形状关系密切,修复重建需要考虑这种关系。     

侧咬合型及牙齿接触关系的观察

目的 :研究侧咬合型及牙接触关系 ,为临床应用提供基础。材料方法 :活体观察 146名青年人侧咬合型及牙齿接触关系。结果 :侧咬合时 ,型分组牙功能最多 (45 .2 1% ) ,尖牙保护次之 (34 .2 5 % ) ,混合型最少(2 0 .5 4% ) ;组牙功能时 ,上下牙接触关系分为七种类型 ,其中以34 5 634 5 6 最多 (31.0 6 % )。结论 :青年人侧咬合时以组牙功能最多 ,尖牙保护次之 ,混合型最少 ;组牙功能时 ,上下颌牙齿接触关系分为七种类型。     

侧咬合(牙合)型及牙齿接触关系的观察

目的:研究侧咬合型(牙合)及牙接触关系,为临床应用提供(牙合)基础.材料方法:活体观察146名青年人侧咬合(牙合)型及牙齿接触关系.结果:侧咬合时,(牙合)型分组牙功能(牙合)最多(45.21%),尖牙保护次之(34.25%),混合型最少(20.54%);组牙功能(牙合)时,上下牙接触关系分为七种类型,其中以(牙合)最多(31.06%).结论:青年人侧咬合时以组牙功能(牙合)最多,尖牙保护(牙合)次之,混合型最少;组牙功能(牙合)时,上下颌牙齿接触关系分为七种类型.     

组牙功能(牙合)和尖牙保护(牙合)对提颌肌肌电活动的影响

组牙功能(牙合)和尖牙保护(牙合)是自然牙列侧方运动中工作侧(牙合)接触的两种类型,组牙功能(牙合) 工作侧后牙都有接触,而尖牙保护(牙合)工作侧只有上下尖牙间接触。因为牙周受体对颌肌活动的调节起重要作用,因此(牙合)型对颌肌活动有较大的影响。本文目的是比较组牙功能(牙合)和尖牙保护(牙合)对提颌肌肌电活动的不同影响。选择6名咀嚼系功能正常的成人,4男2女,17～35岁,平均26岁。用表面电极置于颞肌前部和嚼肌表面作双侧肌电记录。     

上下牙尖窝接触关系的生物力特征

咬合接触的生物力特性对于咀嚼功能是否得以正常发挥有非常重要的意义。无论在静态(例如:最大牙尖交错时的咬合接触)还是在动态咬合(例如:咀嚼运动中的咬合接触)时,尖窝关系都是上下牙之间的经典的咬合接触关系。最大牙尖交错位时多向倾斜的牙尖斜面将所承受的咬合力向多个方向分散,从而避免个别牙出现应力集中现象。咀嚼运动中下颌从工作侧运动到最大牙尖交错位、再到非工作侧,该运动的途径以及运动过程中的咬合接触主要由上颌牙的面形态决定。咬合接触的紧密程度与咀嚼肌的收缩活动情况密切相关。为采集可重复性的、由面形态所决定的静态咬合和动态咬合接触信息时,建议对最大紧咬和最大范围咀嚼运动的相关指标进行检测。总之在功能性正常咬合的概念中,除经典的正中关系/正中、组牙功能/尖牙保护等的内容外,还应包括静态/动态咬合中尖窝接触关系的生物力特征等内容。     

学

与咬合都是上下牙发生接触的现象,为下颌静止位时上下牙的接触关系,咬合为下颌运动中上下牙的接触关系。何谓正常历来有两种认识:一是上下牙以一定的尖凹关系相接触为正常,否则为错,例如安格氏错分类;一是全口假牙的平衡验用之于自然牙列,认为前伸及侧的平衡接触有利于功能。近20一30年来,把牙、颌骨、牙周组织、咀嚼肌,颞颌关节及其神     

侧咬合He型及牙齿接触关系的观察

目的：研究侧咬合Ｈｅ型及牙接触关系，为临床应用提供Ｈｅ基础，材料方法：活体观察１４６名青年人侧咬合Ｈｅ型及牙齿接触关系。结果；侧咬合时，Ｈｅ型分组牙功能Ｈｅ最多，尖牙保护次之，沸合型最少。组牙功能Ｈｅ时，上下牙接触关系分为七种类型，其中以３４５６／３４５６最多（３１．０６％）。结论：青年的侧咬合时以组牙功能Ｈｅ最多，尖牙保护Ｈｅ次之，混合型最少；组牙功能Ｈｅ时，上下颌牙齿接触关系分为七种类型。     

天然恒牙列的动态咬合接触形式

目的：在既往研究中．从未停止过关于修复和正畸治疗中进行咬合重建时．应该建立何种形式的咬合接触的讨论。对天然恒牙列的动态咬合的流行病学调查将有助于走出这种持续讨论的困境。本研究的目的就是要通过调查研究．总结年青群体和老年群体天然牙列的特征性动态咬合接触形式,并且分析动态咬合接触形式与性别和年龄之间的相关性。材料和方法：本研究共调查了834人。所有的调查对象都具有天然牙列．并且没有修复体存在。调查对象的年龄范围是20--63岁。在调查对象进行牙诱导的侧方和前伸运动过程中,检查天然牙的动态咬合接触形式。结果：结果发现存在以下的动态咬合接触形式：双侧和单侧的尖牙保护[牙合],组牙功能[牙合]．平衡[牙合]以及“其他[牙合]型”。男性和女性之间不同类型的动态咬合接触形式的出现概率相同。但是．一些咬合接触形式的出现率与年龄有相关性。随着年龄的增加．双侧和单侧尖牙保护耠的出现率出现下降趋势,而组牙功能[牙合]的出现率上升。平衡[牙合]以及“其他[牙合]型”的出现率很低．并且没有呈现与年龄相关的变化趋势。结论：双侧尖牙保护[牙合]和组牙功能[牙合]是年青患者的特征性咬合接触形式．而老年患者中组牙功能[牙合]的接触形式更加普遍。当年青患者接受修复和正畸手段的咬合重建时．尖牙保护[牙合]是一种最适合的咬合接触形式,而对于老年患者来说．组牙功能[牙合]则更加适合。需要进一步的研究来探讨[牙合]型和牙周炎、磨牙症或者颞下颌关节紊乱病之间的关系。     

牙齿功能面磨耗与偏侧咀嚼及侧方咬合的相关性研究

目的:调查研究牙齿功能面磨耗与偏侧咀嚼及侧方咬合的关系。方法:通过问卷调查和临床检查收集数据,t检验分析牙齿功能面磨耗与偏侧咀嚼习惯、侧方咬合之间的关系。结果:在257名受试者中,有133名(52%)受试者有偏侧咀嚼习惯,其中77名(30%)为右侧咀嚼习惯,56名(22%)为左侧咀嚼习惯。偏侧咀嚼习惯与牙齿功能面磨耗相关(P<0.05),进一步分区研究显示主要是习惯侧的磨合面磨耗严重(P=0.038<0.05)。所有的受试者中,在左侧,23名(8.9%)受试者为尖牙保护牙合,213名(82.9%)受试者为组牙功能牙合,21名(8.2%)受试者无法测量;在右侧,22名(8.6%)受试者为尖牙保护牙合,217名(84.4%)受试者为组牙功能牙合,18名(7.0%)受试者无法测量。组牙功能牙合磨牙区牙齿牙合面磨耗要比尖牙保护牙合磨牙区牙齿牙合面磨耗严重(P<0.05)。结论:在偏侧咀嚼侧的牙齿功能面磨耗更严重;组牙功能合磨牙区牙齿牙合面磨耗要比尖牙保护牙合磨牙区牙齿牙合面磨耗严重。     

Effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid EMG activity

This study was conducted to determine the effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid electromyographic (EMG) activity. The study was performed on 20 healthy subjects with natural dentition and bilateral molar support. During laterotrusive occlusal excursion (working side), each individual had to present canine guidance on one side and group function on the opposite side, without balancing-side contacts. Integrated EMG (IEMG) recordings were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. IEMG activity was recorded seated upright with the head unsupported and in the right and the left lateral decubitus body positions (head, neck and body horizontally aligned), under the following experimental conditions: 1. Maximal voluntary clenching in the intercuspal position; 2. Laterotrusive occlusal excursion with canine guidance; 3. Laterotrusive occlusal excursion with group function. Bilateral sternocleidomastoid IEMG activity with canine guidance or group function was significantly lower than the intercuspal position in both body positions. In the seated upright position, significantly lower activity was observed with canine guidance than in group function. In the lateral decubitus position activity was similar with both laterotrusive occlusal schemes and significantly higher than seated upright. Results suggest that both laterotrusive occlusal scheme and body position have significant influence on sternocleidomastoid IEMG activity. The clinical relevance of both factors is discussed.     

The influence of altered occlusal guidance on condylar displacement

This study investigated mandibular displacement and masticatory muscle activity during clenching in lateral occlusal position in relation to the lateral occlusal pattern. Twenty healthy human subjects (mean = 26.5 years) volunteered for this study. Metallic occlusal overlays were fabricated for the lower working side canine to second molar and non-working side second molar in order to simulate a canine protected occlusion, group function occlusion and bilateral balanced occlusion (balancing contact). Three-dimensional displacements of the bilateral condyle and electromyography (EMG) activities in the bilateral masseter, anterior and posterior temporalis were recorded during maximal clenching. The experimental occlusal pattern was revealed to have statistically significant effects on both condylar displacement and EMG activity (P < 0.001 and P < 0.001, respectively). When compared to the simulated group function occlusion, the simulated canine protected occlusion and balancing contact caused statistically significant smaller superior displacements of the non-working side condyle, which suggests that they may result in reduced temporomandibular joint (TMJ) loading. Furthermore, the simulated canine protected occlusion was associated with the lowest EMG activity, which suggests that this occlusal pattern has the capacity to reduce the level of parafunctional activity.     

The occlusal contact mode during lateral excursion

The purpose of this study is to clarify the occlusal contact mode between the upper and lower molars on the working side of group function occlusion during lateral excursion. After the intercuspal position (IP) and two lateral positions (L1, the middle point between IP and L2; L2, the edge-to-edge occlusal position of the molars) on the Gothic arch were defined, occlusal contact relations in these three occlusal positions were recorded, using black silicone. Digital data of real occlusal contacts and visualized data of close (less than 30 microns) occlusal areas, by computer image processing, were analyzed. The conclusions are as follows: 1. Although the numbers of real occlusal contacts and the visualized occlusal area tend to decrease toward L2 during lateral excursion, the former, in some cases, goes up and down. 2. Functional cusps play an important part in occlusal contact at the intercuspal position. 3. Occlusal contact points are on the functional cusps of the upper and lower molars, which can be clinically regarded as certain points, and these points slide on the inclining non-functional cusps of antagonistic teeth during lateral excursion. 4. Each upper and lower molar has 2 to 6 occlusal contact points near the top functional cusps at the intercuspal position, and some of them contact continuously during lateral excursion.     

A possible biomechanical role of occlusal cusp–fossa contact relationships

Summary Biomechanical features of occlusal contacts are important in understanding the role of the occlusion contributing to masticatory function. Cusp–fossa contact is the typical pattern of occlusion between upper and lower teeth. This includes static relations, such as that during clenching, and dynamic relations when mandibular teeth contact in function along the maxillary occlusal pathways, as during mastication. During clenching in the maximum intercuspal position (ICP), cuspal inclines may take the role of distributing the occlusal forces in multi‐directions thus preventing excessive point pressures on the individual tooth involved. During chewing movement on the functional side, the mandible moves slightly from buccal through the maximum ICP to the contralateral side. The part of the chewing cycle where occlusal contacts occur and the pathways taken by the mandible with teeth in occlusal contacts are determined by the morphology of the teeth. The degree of contact is associated with the activity of the jaw muscles. To obtain repeatable static and dynamic occlusal contact information provided by the morphology of the teeth, maximum voluntary clenching and chewing movements with maximum range are needed. In conclusion, in addition to the standard occlusal concepts of centric relation/centric occlusion and group function/cuspid protection relation, biomechanics in static and dynamic cusp–fossa relationships should be included to develop an understanding of occlusal harmony which includes no interfering or deflective contacts in functional occlusal contact.     

Effect of bilateral asymmetric tooth clenching on load distribution at the mandibular condyles

The effects of balancing-side tooth contacts on temporomandibular joint loads are unclear. We used a 3-D computer model to calculate the magnitude and direction of temporomandibular reaction forces during simulated clenching on interocclusal acrylic resin shims and between natural teeth. Muscle tensions were proportioned according to the task modeled. Working-side tooth contacts included the canine alone, as well as group function, and occlusal loads were progressively shifted toward a posterior contralateral simple balancing contact. In the acrylic resin shim experiments, group function with simple balancing contact yielded the highest forces at the load point and at both temporomandibular joints. Movement of the occlusal load toward the balancing side produced greater, anteriorly oriented forces on the working condyle. For natural teeth, changes in the angle of resultant tooth force (simulating facet angulation) greatly influenced condylar forces. As the occlusal load moved toward the balancing side, greater and more laterally oriented forces were produced on the balancing condyle. Unilateral clenching on the canine produced the least condylar and bite forces. The simulation involving natural teeth offers a possible explanation for deviations in form and osteoarthrosis at the temporomandibular joints.