臼齿

The results show that the frequencies of both the agenesis and impaction of third molar are much higher in East Asian populations than all other populations around the world.

这一特征在居住于不同的地理区域的人类始发的时间及增加的速率不尽一致。结果造成了种族群体之间的差异。而第三臼齿阻生则是退化的另一种表现形式，但影响第三臼齿阻生的因素更为复杂。

Results: When the slide segment was retained 1 mm width,the fifth cheek tooth and anterior edge midpoint of condyle process anterior slope and coracoid process showed negative displacement and the angle of mandible and the posterior edge midpoint of condyle process posterior slope showed positive displacement on x axes.

结果：在牵张过程中牵张侧下颌骨标志点位移趋势为在内外方向上第五臼齿、喙突、髁状突前斜面前缘中点的运动趋势是向外的，而下颌角、髁状突后斜面后缘中点的运动趋势是向内的；在前后方向上第五臼齿、喙突的运动趋势是向后的，而下颌角的运动趋势是向前的；在上下方向上第五臼齿的运动趋势是向上的。

For an orthodontic case with the discrepancy of the discoordination between the length of palate bone and tooth size or for a case with skeletal discrepancy of the unsymmetry upper and lower jaw in their size and position, the most common treatment i

摘要一般矫正治疗，对于齿槽骨和牙齿大小长度总和的不调和或上下颚骨骨骼性大小、位置不对称，其处置原则通常都以上下颚第一小臼齿或第二小臼齿等4齿做为拔除对象来进行矫正治疗。

Both upper and lower dental study models were collected from 30 boys (12 years old) and 30 girls (12 years old) with acceptable normal occlusion to understand the characteristics of the crown size, dental arch width and length such as (1) mesiodistal diameters of crown size from central incisor to first molar,(2) the width and length of dental arch and basal arch and (3) the morphology of dental arch form. After statistical analysis, data were compared with Japanese, Central and South American Indians and North American Caucasians from papers. The results were:(1) There was no statistical difference in teeth size between males and females, except the upper first molar of males was larger than that of females, lower central incisor of males was smaller than that of females.(2) The dimensions of dental arch of males were larger than that of females in general, especially such items as width and length of basal arch.(3) The crown size of Chinese male was in generally smaller than that of four other races, especially the upper canine, lower central incisor and first molar.

为了解住在台湾的中国人其牙齿的大小，齿列弓幅径及形态，为齿科人类学上的特微，以期能对儿童牙科，齿颚矫正科之临床及齿科基础医学能有所贡献，抽取12岁学童男女各30名共60名，可接受为正常咬合之上下颚齿列模型，测量其上下颚(1)左侧正中门牙到第一大臼齿共计12颗恒牙之牙冠近远心径，(2)齿列弓宽径、长径及齿槽基底宽径、长径，(3)齿列弓之形态，以上资料经统计分析作t-test检定，并与诸学者对日本人、北美白人、中美及南美印第安人人种的研究结果作检讨得知；(1)男女性恒牙的近远心径无明显差异，但男性上颚第大臼齿比女性者大，下颚正中门牙比女性者小；(2)男性的齿列弓幅径比女性者为大，尤以齿槽基底宽径及长径最显著；(3)国人男子的牙齿近远心径比其他四人种者为小，特别是国人的上颚犬齿，下颚正中门牙及第一大臼齿最小。

One of many factors contributory to development of periodontitis is an unerupted or abnormally erupted third molar and it may cause deep pocket formation and bony resorption at the distal side of adjacent second molar. It is also prone to result in periodontitis due to interdental food impaction and uneasy cleaning between the third molar and second molar.

在形成牙周炎的众多贡献因子中，其中因第三大臼齿萌发方向异常或萌发不全，可能造成第二大臼齿远心侧形成牙周囊袋和周围牙周骨头吸收；或第二及第三大臼齿间因缝隙口腔清洁不良而好犯牙周病。

The core issue is how to construct a reasonable physical, chemical and microbial condition for early rapid precipitation and filling of molar tooth cracks in the subtidal shallow marine.

在综述臼齿碳酸盐岩成因研究历程和国内外最新研究成果的基础上，总结评述了6种主要的臼齿构造成因模式，其核心问题是在元古代正常潮下浅海环境中构建成岩作用早期臼齿构造裂缝形成及等粒微亮晶方解石快速沉淀充填的物理、化学及微生物条件。

Upper premolars and molars lie outside those of the lower jaw.

上前臼齿和臼齿位于下领前臼齿和臼齿的外侧。

The first group is the6 incisors, the next group is the four premolars on the bottom and top of each side, and the final group is the three top molars and two molars on the bottom of each side.

第一组是6颗门齿，第二组是每边的底部和顶端上的四个小臼齿，最后的一组是两边顶端三颗臼齿和底部的二颗臼齿。

Their characters include (1) the particular configuration of the MT structures;(2) the obvious interface with rich organic matter and pyrite between the MT ribbon cracks and the host rock;(3) the host rocks are characterized by nonstromatolitic micrite limestones with few liminites;(4) the special macroscopic fossils of algae which were simultaneously developed with the MT structures.

这些特征包括：(1)臼齿状构造特别的形态学特征，(2)由微亮晶所充填的臼齿状裂缝具有明显的边界（以富集残余有机质和黄铁矿为特点），(3)臼齿状构造的宿主岩石是不发育叠层石和纹理化构造的隐晶质泥晶灰岩，(4)与臼齿状构造常常共生的极为特别的宏观藻类化石等。

In the treatment of impacted third molar, dental practioner and oral surgeon more often think about how to extract the third molar completely, but rarely consider to add some procedures such as distal wedge, alveoloplasty, guided tissue regeneration, and apically repositioned flap etc., to prevent 2nd molar from developing periodontitis. The latter procedures can reduce its accompanying deep pocket, to remove plaque and calculus on its diseased root surface.

在治疗阻生第三大臼齿，诊所执业医师和一般口腔外科医师较常会考虑怎样把阻生第三大臼齿完全拔除，但却较少考虑在拔除阻生第三大臼齿的同时做一些措施，像远心楔形手术，齿槽骨整形术，引导组织再生术和牙周办膜根向移动术等来预防第二大臼齿远心端形成牙周炎，或同时替第二大臼齿治疗深的牙周囊袋和去除其牙根表面的牙结石和牙菌斑。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。