牙齿楔状缺损与侧方(牙合)工作侧咬合接触关系的调查

目的研究牙颈部楔状缺损与牙齿咬合接触的关系.方法选取123名中年机关干部.用0.02mm厚的超薄咬合纸,临床检查侧方运动工作侧上颌尖牙、第一、二前磨牙、第一磨牙颊尖各斜面上及咀嚼循环各个时期中的牙齿咬合接触情况;评估接触程度.结果患楔状缺损牙齿咬合接触程度明显高于未患楔状缺损牙.上颌尖牙和前磨牙楔状缺损患牙在远中(上第一磨牙的近、远中)斜面上咬合接触程度高于未患牙,患牙在咀嚼侧方运动循环的中、末(上第一磨牙在初、中或末)期咬合接触程度增加.结论牙颈部楔状缺损的发生与牙齿的咬合接触程度加重有关.     

牙齿楔状缺损与侧方工作侧咬合接触关系的调查

目的　研究牙颈部楔状缺损与牙齿咬合接触的关系。方法　选取 12 3名中年机关干部。用 0 .0 2mm厚的超薄咬合纸 ,临床检查侧方运动工作侧上颌尖牙、第一、二前磨牙、第一磨牙颊尖各斜面上及咀嚼循环各个时期中的牙齿咬合接触情况 ;评估接触程度。结果　患楔状缺损牙齿咬合接触程度明显高于未患楔状缺损牙。上颌尖牙和前磨牙楔状缺损患牙在远中 (上第一磨牙的近、远中 )斜面上咬合接触程度高于未患牙 ,患牙在咀嚼侧方运动循环的中、末 (上第一磨牙在初、中或末 )期咬合接触程度增加。结论　牙颈部楔状缺损的发生与牙齿的咬合接触程度加重有关。     

牙齿楔状缺损与侧方he工作侧咬合接触关系的调查

目的 研究牙颈部楔状缺损与牙齿咬合接触的关系。方法 选取123名中年机关干部。用O．02mm厚的超薄咬合纸，临床检查侧方运动工作侧上颌尖牙、第一、二前磨牙、第一磨牙颊尖各斜面上及咀嚼循环各个时期中的牙齿咬合接触情况；评估接触程度。结果 患楔状缺损牙齿咬合接触程度明显高于未患楔状缺损牙。上颌尖牙和前磨牙楔状缺损患牙在远中(上第一磨牙的近、远中)斜面上咬合接触程度高于未患牙，患牙在咀嚼侧方运动循环的中、末(上第一磨牙在初、中或末)期咬合接触程度增加。结论 牙颈部楔状缺损的发生与牙齿的咬合接触程度加重有关。     

楔状缺损与咬合力关系的研究

目的 临床研究楔状缺损与He力的关系。方法 将123例患不同程度楔状缺损的中老年患者，按楔状缺损的程度分为无、轻、中、重度4组；使用电阻应变式咬合力计测量上颌尖牙、第一、二双尖牙、第一磨牙牙齿咬合力；用光He法测定上颌牙齿最高He接触强度。结果 楔状缺损患牙的咬合力低于无楔状缺损牙。上颌第一双尖牙的楔状缺损患牙的最高He接触强度高于未患牙、楔状缺损组中的第一磨牙和第一双澡牙相对于其邻牙的最高He接触强度增高。结论 He力与楔状缺损的发生有关。     

牙齿楔状缺损与侧方工作侧咬合接触关系的调查

有关因素与楔状缺损关系的临床研究很少。为确定因素与楔状缺损的关系 ,我们对楔状缺损与牙齿咬合接触的关系进行了临床研究。一、材料和方法1 研究对象 :从江西南昌 4 93名做过口腔健康状况普查的 4 0～ 70岁中年机关干部中选出符合纳入标准的 12 3人 ,其中男性 73人 ,女性 5 0人。2 检查方法及标准 :选上颌尖牙、第一、二前磨牙及第一磨牙 ,按徐樱华的咬合接触程度检查方法 ,用 0 0 2mm厚超薄咬合纸 ,对侧方运动工作侧 ,即咀嚼运动循环的初、中、末 3期对应的每个牙尖斜面上的接触点进行检查。接触程度评估标准分为无接触、轻接触…     

正常接触位、下颌后退接触位咬合接触的计算机图像分析

目的 :研究正常牙合肌接触位及下颌后退接触位咬合接触的基本规律。方法 :采集 35名正常牙合肌接触位及下颌后退接触位的硅橡胶牙合记录 ,进行计算机图像分析。结果 :肌接触位 33人前牙无接触 ,单颌后牙区接触数为 16 .6± 7.2 ,所有受试者均为双侧接触。肌接触位咬合接触均在牙尖交错位重复出现。接触频率超过 5 0 %的部位位于上颌磨牙颊尖和舌尖的远中斜面 ,下颌磨牙颊尖和舌尖的近中斜面。下颌后退接触位所有受试者均为双侧接触 ,有接触的牙齿数目单颌单侧 2 .7± 0 .8,接触点数目单颌 8.0± 2 .3,前牙无接触 ,接触数目及比率从第二磨牙到第一前磨牙依次减少。接触频率超过 40 %以上的斜面上颌为前磨牙舌尖、磨牙远中舌尖及第二磨牙近舌尖的近中颊斜面 ,下颌为前磨牙及第二磨牙颊尖的远中舌斜面。结论 :以硅橡胶为记录材料准确采集到肌接触位及下颌后退接触位牙合记录 ,经计算机图像分析 ,得出其咬合接触的基本特征。     

正常He肌接触位,下颌后退接触位咬合接触的计算机图像分析

目的研究正常肌接触位及下颌后退接触位咬合接触的基本规律。方法采集35名正常肌接触位及下颌后退接触位的硅橡胶记录，进行计算机图像分析。结果肌接触位33人前牙无接触，单颌后牙区接触数为16．6±7．2，所有受试者均为双侧接触。肌接触位咬合接触均在牙尖交错位重复出现。接触频率超过50％的部位位于上颌磨牙颊尖和舌尖的远中斜面，下颌磨牙颊尖和舌尖的近中斜面。下颌后退接触位所有受试者均为双侧接触，有接触的牙齿数目单颌单侧2．7士0．8，接触点数目单颌8．0±2．3，前牙无接触，接触数目及比率从第二磨牙到第一前磨牙依次减少。接触频率超过40％以上的斜面上颌为前磨牙舌尖、磨牙远中舌尖及第二磨牙近舌尖的近中颊斜面，下颌为前磨牙及第二磨牙颊尖的远中舌斜面。结论以硅橡胶为记录材料准确采集到肌接触位及下颌后退接触位记录，经计算机图像分析，得出其咬合接触的基本特征。     

自然牙牙裂综合征患者咬合类型调查

目的调查自然牙牙裂综合征(CTS)的牙合型特点。方法79例自然牙CTS患者及268名大学生,取研究模比较咬合类型。结果CTS组患牙分布:上颌第一磨牙23例,下颌第一磨牙14例,上颌第二磨牙12例,下颌第二磨牙11例,上颌第一前磨牙8例,上颌第二前磨牙7例,下颌第一前磨牙、下颌第二前磨牙、上颌第三磨牙、下颌第三磨各1例。与对照组相比,CTS组远中牙合、深覆牙合、深覆盖以及第三磨牙反牙合的比例增高,后牙锁牙合比例降低(P<0.05)。结论自然牙CTS患者远中牙合、深覆牙合、深覆盖以及第三磨牙反牙合的比例明显增高。     

人工楔状缺损对牙颈部硬组织应力分布的影响

目的 分析楔状缺损患牙颈部硬组织的应力分布.方法 在下颌前磨牙沿釉牙本质界建立三角形缺损,设计楔状缺损模型,模拟侧方运动中牙齿的受力情况,对下颌前磨牙颈部硬组织行非线性接触分析.结果 斜向载荷下,釉牙本质界缺损的下颌前磨牙缺损区尖端存在明显的拉应力集中.随缺损高度的增加,应力值增大,应力集中程度也增加:应力集中区沿釉牙...     

楔状缺损与干扰关系的研究

的分析楔状缺损患者咬合接触的特征,探讨干扰与楔状缺损的关系。方法从46例楔状缺损患者中选取157颗楔状缺损患牙和毗邻的157颗未患楔状缺损牙分别作为实验组和对照组,应用T- ScanⅡ咬合分析仪对患者进行正中、前伸及侧方咬合检查,观察实验组和对照组的干扰和早接触情况。结果实验组存在干扰的牙数所占比例（23.57%）高于对照组（10.19%）,且有统计学意义（P<0.05）。实验组患牙中,存在侧方工作侧干扰的牙数所占比例高于对照组（P<0.05）;存在干扰患牙的楔状缺损的缺损程度高于无干扰患牙。结论楔状缺损的发生及缺损程度与牙齿所受的过大力有关。     

老年人楔状缺损的患病情况及相关因素调研

目的 调查老年人楔状缺损发病情况及其相关因素。方法 使用Ｓｍｉｔｈ磨损指数调查分析４０７例老年知识分子齿楔状损发病情况及用问卷方式调查与病损发生发展可能相关的因素。结果 该组老年人楔状缺损扫病率为９７．３％,且随年龄递增;楔状缺损的好发部位和缺损程度第一双尖牙列首位,其次为第二双尖牙,第一磨牙;其中第一麻牙比以往人们认为的尖牙更好发楔状缺损。另外,发现该组人有６９例１７１颗患牙舌 不同程度的楔状缺     

A clinical study of the functional significance of the occlusal contacts on chewing movements

The study was aimed to investigate the effects of the occlusal contacts on chewing movements according to the changes of the mandibular first molar crown surfaces in 32 young adults. The study includes three components of the experiments as the control, various types of occlusal contact defects and the excessive conditions of occlusal surface contacts on the tooth. The chewing movement consistency was tested in the control study. The effects of the occlusal contact defects to the chewing movements, i.e., a periodontal mechanoreceptive defect (sensory block), a complete defect of coronal contact, partial defects (buccal or lingual cusp and inclination) of coronal surface, were then examined. Third, the effects of the occlusal deflective interference provided for the subjected tooth to the chewing movement was examined as the experiment in the excessive condition. The results obtained were as follows: 1. The consistency of segmental single tooth chewing movements was tested in the control study and revealed highly reliable among parameters of intra-day variance, but not enough for the inter-day variance in each subject. 2. The effects of occlusal contact defects were significant to the path and the rhythm of chewing movements in a poriodontal mechanoreceptive defect, complete coronal defect, cusp and inclination defects. 3. The effects of deflective occlusal interference were significant in the parameters, such as posterior deviation during closing path and inferior deviation of occluding point, prolonged duration in the closing phase, and shortening of duration in the occluding phase. It is suggested that either the occlusal defects or the interference conditions on one side of the first mandibular molar tooth may provide some effects to the chewing movements, and that appropriate occlusal contacts for the tooth may serve to maintain stabilized the path and the rhythm during chewing movements.     

Masticatory Tooth Contact Patterns: Predicted and Observed Cuspid and First Molar Contacts in Cuspid and Group Function

Using the mouth as an “in vivo articulator,” the bilateral nonmasticatory (“empty”) contact patterns of opposing cuspid and first molar teeth were determined in two healthy subjects with well-defined cuspid function and two healthy subjects with well-defined group function. The electronically recorded “empty” contact patterns pertained to the static intercuspal position and dynamic laterotrusion to the right and the left. On the basis of the “empty” tooth contact patterns and the number of electronically recorded masticatory cycles of one masticatory sequence, we postulated two simple models that attempted to predict the masticatory (“functional”) tooth contacts of one sequence of unilateral mastication of apple and banana. Statistical comparisons between the predictions of the two models and the actual (“functional”) contacts of in vivo mastication showed that the models predicted fairly well the observed tooth contacts on the nonchewing-side of the mouth, but not the observed tooth contacts on the chewing-side of the mouth. In consequence, “empty” (nonmasticatory) tooth contact patterns should not be equated with “functional” (masticatory) tooth contact patterns.     

Effect of long-lasting clenching on dental occlusion

Durable clenching on a particular occlusal area may affect the masticatory muscle activity and induce transitional deformation of the dentoalveolar, mandibular and temporomandibular tissues. These effects may provide detectable alterations in the occlusal contact pattern. The aim of this study was to evaluate the subsequent effect of clenching on the number and location of occlusal contacts. This study was carried out on 16 volunteers with correct occlusion and sharply demarcated occlusal contact pattern. The patient closed to intercuspal position with maximal biting force and the occlusal contacts were revealed with a 12 microns thick occlusal foil. Then a gnathometer was placed between the upper and lower incisors and the mouth was closed for two minutes with about 50 N closing force. After that the occlusal contacts were evaluated again. Paired t-test was used to evaluate the data. Both before and after clenching the highest average number of contacts was recorded on the surface of first molars. They were followed in decreasing order by the second molars, second premolars, first premolars, and finally the canines. When the number of contacts was compared in tooth groups, the first molars and the second premolars had more contacts than the second molars and the first premolars. On the surfaces of molars more occlusal contacts were registered after clenching than before. Significant differences were found in case of the left second molar only. It was concluded that durable clenching on a particular occlusal area might change transitionally the distribution of occlusal contacts.     

Managing Medicare and Health Reform Survival

In ten healthy subjects, bilateral contacts between opposing cuspid and first molar teeth were recorded during one sequence of unilateral chewing of apple, peanuts, and banana. Unknown magnitudes of mechanophysical (masticatory) forces were inferred to act directly on the chewing-side cuspid teeth in 71% of all masticatory cycles and on the nonchewing-side cuspid teeth in 68% of all masticatory cycles. In addition, unknown magnitudes of mechanophysical forces were inferred to act directly on the chewing-side first molar teeth in 74% of all masticatory cycles and on the nonchewingside first molar teeth in 86% of all masticatory cycles. During the chewing of peanuts, the total number of chewing-side cuspid contacts exceeded significantly the total number of nonchewing-side cuspid contacts, suggesting more repetitive direct mechanophysical loading of the chewing-side cuspid teeth. During the chewing of apple, the total number of nonchewing-side first molar contacts exceeded significantly the total number of chewing-side first molar contacts, suggesting more repetitive direct mechanophysical loading of the nonchewing-side first molar teeth. The variable contact patterns were, to a large extent, explained by rotational movements of the entire mandible resulting in translational movements of the hemimandible.     

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.     

Influence of clenching intensity on bite force balance, occlusal contact area, and average bite pressure.

It has been difficult for investigators to simultaneously and reliably evaluate bite force in the intercuspal position with the area and location of occlusal contacts. This study was designed to investigate the variations in these parameters with respect to two factors: three levels of clenching and the preferred chewing side. Human subjects with normal occlusion were examined with a recently developed system (Dental Prescale Occluzer, Fuji Film, Tokyo, Japan). The three levels of clenching intensity were assessed by masseteric EMG activity and included the maximum voluntary contraction, and 30% and 60% of the maximum. The results indicated that the bite force and occlusal contact area on the whole dental arch increased with clenching intensity. In contrast, the average bite pressure, obtained by dividing the bite force by the contact area, remained unchanged regardless of the clenching intensity. As the clenching intensity increased, the medio-lateral position of the bite force balancing point shifted significantly (P<0.01) from the preferred chewing side toward the midline. The antero-posterior position remained stable in a range between the distal third of the first molar and the mesial third of the second molar. The bite force and occlusal contact area, which were mainly on the molars, increased with the clenching intensity, whereas the proportions of these two variables on each upper tooth usually did not change significantly. The exception was the second molar on the non-preferred chewing side. When comparisons were made between pairs of specific upper teeth of same name, usually no significant difference was found in bite force or occlusal contact area, regardless of the clenching level. Again, the exception to this observation was the second molar on the preferred chewing side, which had a larger area at the 30% clenching level. The results in normal subjects suggest that as the clenching intensity increases in the intercuspal position, the bite force adjusts to a position where it is well-balanced. This adjustment may prevent damage and overload to the teeth and temporomandibular joints.     

Anatomical studies on a supernumerary tooth considered to be a successional tooth of the lower first molar

The purpose of this study is to investigate features of the successional tooth of the lower first molar. Materials investigated in this study deal with a supernumerary tooth formed at the distolingual deep part to the lower right first molar of a male patient aged twenty-four. It was observed with binocular microscopy and under X-ray. The occlusal surface of it was observed with scanning electron microscopy. Horizontal ground sections of it were prepared and observed with polarizing microscopy, fluorescent microscopy, and scanning electron microscopy. It is thought that this supernumerary tooth is a true successional tooth of the lower first molar because it was formed at the distolingual deep part to the lower first molar and the fissure of it is Y-shaped and it has five cusps. It is considered that two impressions at buccal and distal surfaces of it isn't original hereditary features but was accidentally formed by pressures of mesial and distal roots of the lower first molar. The rough form of it has most resemblance to the lower second premolar and distal and lingual parts of it are smaller than that of the lower first molar. But fundamental features of the lower first molar are preserved in it. It is thought that the center of the molarization field of human lower successional teeth lies at the successional tooth of the lower first molar because the form of the occlusal surface of it is more complex and functional than those of the lower first and second premolars.