口解 整理

牙体形态及髓腔

解剖牙冠anatomical crown ：the portion which is coverd by enamel, the anatomical crown and dental root is separated by dental cervix.

临床牙冠clinical crown：the portion which expose in the oral cavity，the clinical crown and dental root is separated by gingiva.

舌面隆凸cingulum：Semi-sphere elevation which makes up the bulk of the cervical third of the lingual surface of anterior teeth.

嵴：Liner elevation of the enamel of the tooth.

切缘结节Mamelon –small and rounded projections of enamel found at the incisal ridges of newly erupted incisor teeth.

三角嵴triangular ridge: Composed of mesial and distal incline of the cusp.

牙尖嵴cusp ridge: The liner elevation of enamel goes from the top of cusp to the mesial or distal direction.

横嵴Transverse ridges- a combination of two triangular ridges which transversely cross the occlusal surface on a posterior tooth to merge with each other. (Mandibular first premolar)

斜嵴Oblique ridge ---a ridge obliquely crossing the occlusal surfaces of maxillary molars and formed by the triangular ridges of the distobuccal cusp and the distal cusp ridge of mesiolingual cusp, (Maxillary first molar)

点隙pit：The convergence of three (or more) developmental grooves.

线角：The angle formed by the intersection of two surface of the teeth

height of contour*2：The most protruding part of the axial surface of the teeth

髓角2 Pulp horn：The angle part of the pulp chamber which protrude towards the dental cusp.

根管侧支lateral branch of root canal：The small branch arises perpendicularly from the root canal and goes through the dentin and cementum to the periodontal ligament.

apical ramification根尖分歧：Small branches arise at the apical part of root canal, the root canal still exists.

根尖分叉apical furcation：Two or more branches arise at the apical part of root canal, the root canal do not exists.

管间吻合intercanal anastomoses：The anastomoses of two adjacent toor canals, usually can be seen in bicanal type root canal.

牙演化的特点

1.由同形牙向异形牙演化：isodont becomes heterodont

2.牙数由多变少Number of teeth decreases

3.牙替换次数由多牙列向双牙列演化：polyphyodont diphyodont

4.牙根从无到有no dental root

5.牙的分布由广泛至集中于上下颌骨concentrate in maxilla or mandible

6.牙附着于颌骨的方式由端生牙到侧生牙到槽生牙。Acrodont, pleurodont, thecodont

7.

1。牙冠形态的生理意义

2试述三个牙的命名系统

1.Quadrant coding method（符号+数字+罗马数字）

2.Plammer notation system(符号+数字+字母)

Using a simply symbol differing for each of the four quadrants, plus the numbers 1 through 8

to identify central incisor though third molar in the specified quadrant. Letters A through E, with the quadrant symbol, are used for the deciduous dentition.

3.Universal numbering system（数字，1到32，字母，A到T）

4.FDI numbering system（双位数，十位表象限，个位表牙）

It identifies both the permanent and deciduous teeth using two number, the 1st digit represents which dentition and which quadrant, the 2nd digit represents the individual tooth in one quadrant.

Demonstrate the components of root canal system

乳牙的特点：

1.体积小，牙冠宽而短，乳白色。

2.乳牙的牙颈缩窄，唇颈嵴、颊颈嵴突出，合面缩窄，冠根分明。

3.乳前牙宽冠窄根，但上颌乳中切牙宽冠宽根，根尖弯向唇侧。

4.上颌乳尖牙的牙尖偏向远中。

5.下颌第二乳磨牙的近中颊尖、远中颊尖、远中尖等大。

乳牙的髓腔特点

1.乳牙髓腔按比例算，比恒牙的髓室大，表现为髓室大，髓壁薄，髓角高，根管粗，根管

方向斜度大，根尖孔大。

2.髓室顶和髓室角多位于牙冠中部。

3.乳前牙髓腔与牙冠外形相似，多为单根管，偶见下颌乳切牙根管分为唇舌向2个根管。

4.乳磨牙髓室大，通常有3个根管，上颌乳磨牙有2个颊侧根管，1个舌侧根管；下颌乳

磨牙有2个近中根管，1个远中根管。

牙冠突度的生理意义

切端与合面的生理意义：

切嵴具有切割（cut）的作用，尖牙的牙尖具有穿透(penetrate)和撕裂(lacerate)食物的作用。后牙的凸与凸结构接触具有压碎（crush）的作用，凸与凹结构接触具有研磨（grind）的作用。三角嵴的斜面使牙齿容易进入牙尖交错合（intercusping occlusion）。边缘嵴使食物局限于窝内。发育沟将食物流向固有口腔或口腔前庭。

牙冠唇、颊、舌面突度的生理意义：前牙唇面舌面及后牙的颊面的突度在颈1/3，后牙舌面的突度在中1/3，牙冠的正常突度，可以使部分咀嚼过的食物擦过牙龈表面，起按摩massage 作用，促进血液循环，有利牙龈健康。颈1/3突度还可以扩展龈缘，使其紧张有力。

The prominence of axial surface can let food debris flow over the gingiva, which can massage the gingiva , facilitate the blood circulation of the gingiva. The prominence of cervical third also can extend the gingival margin, make it more tensive.

邻面突度的生理意义：在正常接触点的旁边均有V字形的空隙，称为外展隙(embrasure)。