中华桥（四）     

杨国华 《上海集邮》2009,(7):15-16

三、飞索高悬的索桥 索桥又称吊桥、绳桥或悬索桥。是一种以绳索为桥身主要承重构件的桥梁，有竹索桥、藤索桥、铁索桥。桥梁两端建有石屋，安有柱桩、铁山、铁牛、石狮等，以固定桥索，或将桥索直接系在山岩上，并用木棍或绞车将桥索绞紧，然后在桥绳匕安置木板即成。有的还在桥面两侧安置绳索，作扶栏。索桥多建于沟深水急的峡谷中，现在四川、云南、贵州、西藏等地较常见。  相似文献   

探秘“第三副牙齿”——访种植牙专家王艺教授     

北门 《科学生活》2009,(9):28-29

23岁的小陈,在一次车祸中折断了2颗门牙,为此他苦恼不已。在多方查询如何修复牙齿之后,他决定舍弃传统烤瓷桥的做法,多花些钱做了2颗种植牙,术后他觉得做种植牙一点也不痛苦,新做的牙齿不仅美观,而且非常逼真。  相似文献   

Stabilization of an abutment under a rigidly fixed bridge by holographical-speckle interferometry     

Zhang YZ  Zhou YC  Liu L  Lu Y  Hirofumi Y 《Journal of Zhejiang University. Science. B》2007,8(6):416-421

Objective： There are no detailed reports of three-dimensional measurement of abutment teeth in mastication, because it is knotty to observe the rotation in chewing directly, and inexact to estimate indirectly. This work studies the three-dimensional stability of rigidly fixed bridge under the stresses of distributed loads and concentrated loads by optical method that gives the tip angle and rotation angle calculated directly based on measurement data. Methods： The specimen, taken from a 25-year-old male, was a left mandible without the second premolars and the first molars. As abutments, first premolar and second molar have complete periodontium. The specimen was soaked in formaldehyde solution. The bridge was fixed between two abutment teeth （first premolars and second molars）, and the mandible was cemented in a steel box. The load was increased from 0 kg to 23 kg. Laser holographic technique was used to measure the three-dimensional bit shift of the dens, both buccolingual bit shift and mesiodistal bit shift, and determine tip angle and rotation angle. Results： The effects of stress distribution on the rigidly fixed bridge were evaluated, and stabilization of the bridge under the stresses of distributed loads and concentrated loads, respectively, were analyzed. The results showed that the tips of two abutments were very similar, and no distinct difference was observed between the distributed load and the concentrated load. However, the maximum rotation angle for the distributed load was two to four times as large as that for the concentrated load. In the experiment, the tip angle of the abutment teeth was no more than 0.65 degree, and the rotation angle was no more than 0.60 degree. All maximum angles occurred in the second molar. Conclusion： The fixed bridge is considered to be safe. In addition, a method for measuring the rotation angle was provided effectively.  相似文献   

牙齿保健问答     

《科学生活》2010,(12):73-73

一般什么情况下应该镶假牙,如果不及时镶假牙会有何影响?Q:我有一颗牙齿已经掉了一个月了,因为不影响美观,所以一直没去镶牙,不知道不及时镶牙会有什么坏处?A:对于成年人来说除了智齿和多生牙以外,口腔牙齿缺失后都应该及时镶假牙。有些人在牙齿缺失后,没有重视,认为只要对美观和进食没太大影响就凑合着用。这种做法其实是非常错误的。因为功能牙齿的缺失会在不知不觉中影响口腔健康,改变口腔的生理状况,从而在一段时间之后给你带来更多口腔问题。  相似文献