口腔頜面醫(yī)學影像診斷學課件：牙片及全口曲斷正常X表現(xiàn)

1、口內(nèi)片正常X片表現(xiàn)1、牙齒及其牙周組織： 牙齒由四種組織構(gòu)成：鈣化的硬組織牙釉質(zhì)、牙本質(zhì)、牙骨質(zhì)和軟組織牙髓 牙周組織即牙齒周圍組織：牙周膜、牙槽骨、牙齦（1）牙釉質(zhì)：機體中鈣化最高和最硬的組織，X片上的影像密度最高，后牙咬牙合面，前牙切緣最厚，似帽狀被覆在牙冠部牙本質(zhì)表面（2）牙本質(zhì)：圍繞牙髓構(gòu)成牙齒的主體，形狀與牙外形一致，牙本質(zhì)中礦物質(zhì)的含量比牙釉質(zhì)少，X線影像密度較牙釉質(zhì)稍低（3）牙骨質(zhì)：被覆于牙根表面，為一層很薄的組織，又因所含礦物質(zhì)量與牙本質(zhì)相差不多，故在x線片上所顯示的影像與牙本質(zhì)不易區(qū)別（4）牙髓腔：冠部的髓室和根部的根管，x線片上顯示為密度低的影像，單根管牙的髓室與根管界限不

2、清，X線片為針形密度低的影像。下頜磨牙一般有一個髓室、兩個根管，髓腔為似H形密度低的影像。上頜磨牙：髓腔多呈圓形或橢圓形，由于投照角度的影響較大。年輕者牙齒，牙髓腔粗大，牙根尚未形成，根尖孔呈喇叭口狀。老年人的牙齒：繼發(fā)牙本質(zhì)增多，髓腔越來越狹窄，髓腔小而細。（5）牙槽骨：是上、下頜骨包圍牙根的部分，又稱牙槽突或牙槽嵴。1）牙槽窩：容納牙根的凹陷。2）牙槽突頂游離端：疾病最早表現(xiàn)此處。3）牙槽間隔：兩牙之間按解剖可分為：固有牙槽骨、骨密質(zhì)、骨松質(zhì)X線片：牙槽骨所顯示的密度較牙齒低。上牙槽骨的骨密度薄，骨松質(zhì)多，骨小梁數(shù)目多，呈交織狀。相交處呈密度高的點狀影像。X線片：上牙槽骨的骨小梁結(jié)構(gòu)呈顆粒

3、狀影像。下牙槽骨骨密質(zhì)厚而骨松質(zhì)少，骨小梁數(shù)目少。牙間骨小梁多呈水平方向排列，而根尖部有時見放射狀排列。X線下牙槽骨骨小梁結(jié)構(gòu)呈網(wǎng)狀結(jié)構(gòu)。骨小梁粗細與多少和牙齒功能有關(guān)。功能大者，骨小梁粗，數(shù)目多。廢用的牙齒，骨小梁較細數(shù)目較少，牙槽骨正常高度為牙頸部。牙槽突頂，前牙呈“”型，后牙其嵴頂較平呈“ ”型。（6）骨硬板：即固有牙槽骨，牙槽窩的內(nèi)壁，圍繞牙根，x線片上：包繞牙根之連續(xù)不斷的密度高的線條狀影像。意義：1)是一些疾病早期表現(xiàn)：牙周病早期，牙合創(chuàng)傷，正畸。2)病變特征性表現(xiàn)，如骨纖、骨硬板消失是典型征像；甲旁亢：骨質(zhì)疏松，骨硬板消失（7）牙周膜：0.150.38mm之間。功能越大的牙齒，牙

4、周膜越厚，反之則比較薄。X線片上顯示為包繞牙根之連續(xù)不斷的密度低的線條狀影像，其寬度均勻一致。牙周膜及骨硬板的連續(xù)性及其均勻?qū)挾仍谠\斷牙齒疾病上有重要意義。 根尖片所見有關(guān)頜骨 正常解剖結(jié)構(gòu)Maxillary Incisor 上頜切牙a = nasal septum（鼻中隔）b = inferior concha （下鼻甲）c = nasal fossa （鼻前庭）d = anterior nasal spine （前鼻棘）e = incisive foramen （切牙孔）f = median palatal suture （腭中縫）g = soft tissue of nose （鼻部的軟

5、組織）bagfedcefa = nasal septum （鼻中隔）b = inferior concha （下鼻甲）c = nasal fossa （鼻前庭）d = anterior nasal spine （前鼻棘）e = incisive foramen （切牙孔） f = median palatal suture （腭中縫）badcfacial viewpalatal view鼻腔(Nasal cavity)與鼻中隔Nasal septum 鼻腔位于上切牙牙根尖的上方，顯示為對稱性半圓形密度低的影像，其中間被一密度高的骨隔分開，為鼻中隔；需與囊腫鑒別。Nasal septum （鼻中

6、隔）facial viewaInferior conchafacial viewaInferior concha （下鼻甲）facial view Nasal fossafacial viewNasal fossa （鼻前庭）facial view Anterior nasal spine （前鼻棘）facial view 切牙孔（Incisive foramen ） 兩上中切牙之間或稍上方，多呈橢圓形密度低的影像，有時頗似棗核形。切牙孔影像可重疊在一側(cè)中切牙根尖處，易誤為根尖周病變?？梢曆乐苣ず凸怯舶迨欠裢暾澡b別。Incisive foramen （切牙孔）palatal view 腭中縫

7、（Median palatal suture ） 位于兩側(cè)上中切牙牙根之間，由牙槽突頂向上，呈直線狀密度低的影像；直線狀密度低的影像兩側(cè)為密度高的影像是兩側(cè)上頜骨腭突的致密骨層。兒童時期，因頜骨尚未發(fā)育完全，腭中縫影像顯示較寬，且從牙槽嵴頂直至鼻中隔。Median palatal suture（腭中縫）palatal viewSoft tissue of the nose （鼻部的軟組織）Red arrow points to periapical lesion （根尖損害）abeadbRed arrows = lip line（唇線）gRed arrow = mesiodens (super

8、numerary tooth) （額外牙）dfBlue arrow = chronic periapical periodontitis.（根尖周炎） Superior foramina （孔）of the nasopalatine canals (鼻腭管red arrows). These foramina lie in the floor of the nasal fossa （鼻前庭）. The nasopalatine canals (鼻腭管）travel downward to join in the incisive foramen(切牙孔）.The red arrows poin

9、t to the soft tissue of the nose. The green arrows identify the lip line.a = floor of nasal fossa （鼻前庭底部）b = maxillary sinus（上頜竇）c = lateral fossa（外側(cè)的窩）d = nose（鼻）Maxillary Cuspid 上頜尖牙dcbaa = floor of nasal fossa （鼻前庭底部）b = maxillary sinus （上頜竇）c = lateral fossa （外側(cè)的窩或側(cè)窩）(a & b form inverted Y)acbac

10、bfacial view Floor of nasal fossa （鼻前庭底部）(red arrows)and anterior border(前邊)of maxillary sinus (blue arrows), forming the inverted(倒） (upside down) Y.Yfacial viewLateral fossa(側(cè)窩）. The radiolucency （射線投射性）results from a depression（窩） above and posterior to the lateral incisor（側(cè)切牙）. To help rule out（

11、排除) pathology（病變）, look for an intact lamina dura（硬骨板 ） surrounding the adjacent teeth.facial viewSoft tissue of the noseRed arrows point to nasolabial fold（鼻唇溝）. Also note the inverted Y.The maxillary sinus surrounds the root of the canine（尖牙）, which may be misinterpreted as pathology.The white arr

12、ows indicate the floor of the nasal fossa （鼻前庭底部）. The maxillary sinus (red arrows) has pneumatized（含有氣腔)between the 2nd premolar and first molar The red arrow identifies the lateral fossa（側(cè)窩）. The pink arrow points to CPP (chronic periapical periodontitis （根尖周炎） = abscess, granuloma（肉芽腫） , etc.).a

13、= malar process （顴突）b = sinus septum （上頜竇間隔）c = sinus recess (上頜竇隱窩）d = maxillary sinus （上頜竇）abcdMaxillary Premolar 上頜前磨牙a = malar process（顴突）b = sinus recess(上頜竇隱窩）c = sinus septum （上頜竇間隔） d = maxillary sinus（上頜竇）bacdbdcafacial viewMalar (zygomatic) process. U or j-shaped radiopacity, often superim

14、posed over the roots of the molars, especially when using the bisecting-angle technique. The red arrows define the lower border of the zygomatic bone. （顴骨）facial view malar process（顴突） zygomatic bone (顴骨）Sinus septum（上頜竇間隔）This septum is composed of folds of cortical bone（皮質(zhì)骨） that arise from the fl

15、oor and walls of the maxillary sinus, extending several millimeters into the sinus. In rare cases, the septum completely divides the sinus into separate compartments.facial view Sinus septum （上頜竇間隔）Sinus recess. Increased area of radiolucency caused by outpocketing 外包縫合法(localized expansion局限擴大) of

16、sinus wall. If superimposed（重疊) over roots, may mimic (酷似）pathology.facial view sinus recess(上頜竇隱窩）Maxillary Sinus. An air-filled cavity lined with mucous membrane（粘膜）. Communicates with nasal cavity through 3-6 mm opening below middle concha. Red arrows point to neurovascular （神經(jīng)血管的）canal containin

17、g superior alveolar（牙槽的） vessels and nerves.facial view maxillary sinus（上頜竇）Blue arrows identify radiopacity which is a mucous retention cyst. （粘膜潴留囊腫）Note relatively recent premolar extraction sites. Green arrow points to neurovascular canal. The red arrows point to the nasolabial fold （鼻唇溝）. The t

18、hicker cheek tissue makes the area more radiopaque posterior to the line.Pneumatization.（氣腔形成） Expansion of sinus wall into surrounding bone, usually in areas where teeth have been lost prematurely（早期）. Increases with age. Maxillary Molar上頜磨牙a = maxillary tuberosity （上頜結(jié)節(jié)）b = coronoid process （喙突）c

19、= hamular process （翼鉤）d = pterygoid plates （翼板）e = zygoma （顴骨）f = maxillary sinus （上頜竇）fedcbagdaef a = maxillary tuberosity* e = zygoma (dotted lines) （上頜結(jié)節(jié)) （顴骨 ） b = coronoid process f = maxillary sinus （喙突） （上頜竇） c = hamular process （翼鉤） g = sinus recess (上頜竇隱窩） d = pterygoid plates（翼板） * image o

20、f impacted third molar superimposed疊加 cbfacial viewdbaecfg 上頜結(jié)節(jié)（Maxillary Tuberosity） 在最后一個磨牙遠中區(qū)域，其邊緣向后上，此區(qū)域骨小梁數(shù)目較少。X線片上常呈稀疏的網(wǎng)狀結(jié)構(gòu)，此為正常骨疏松區(qū)，不要誤為骨質(zhì)病變。Maxillary Tuberosity. The rounded elevation located at the posterior aspect of both sides of the maxilla. Aids in the retention of dentures（假牙）.facial v

21、iew Maxillary Tuberosity（上頜結(jié)節(jié)） 喙突（Coronoid process ） 患者開口較大或投照水平角向近中方向傾斜，則常在上頜7、8牙冠區(qū)域有一較牙齒密度稍低，由后伸向前方的三角形影像。因受投照技術(shù)的影響，其影像可與第二、三磨牙冠部相重疊或在其下方或下后方。Coronoid process（喙突）. A mandibular structure sometimes seen on the maxillary molar periapical film when using the bisecting angle technique with finger rete

22、ntion (The mouth is opened wide, moving the coronoid down and forward). Note the supernumerary （額外）molar. facial view Coronoid process（喙突） 翼鉤（Hamular process） 如果翼鉤發(fā)育較大，則在上頜結(jié)節(jié)后方，呈長條狀邊緣整齊、寬約0.2cm、長1cm直的或下端略向后彎曲的密度稍高的影像。Hamular process （翼鉤） (white arrows) and pterygoid plates （翼板） (purple arrows). The

23、hamular process is an extension of the medial pterygoid plate of the sphenoid bone（蝶骨） , positioned just posterior to the maxillary tuberosity（上頜結(jié)節(jié)）. facial view Hamular process（翼鉤） 顴骨(zygoma) 若顴骨較大或投照垂直角大，可在第一、二磨牙根尖上方或重疊在牙根上，為近似三角形或半圓形密度高的影像，應注意與埋伏牙鑒別。 在有上頜竇顯示時，其影像可以與上頜竇影像重疊，勿誤為含牙囊腫。顴骨與上頜骨顴突相連接，如果上

24、頜竇發(fā)育較大，其上頜骨顴突充以氣體，此時可顯示為“v”形致密線條影。Zygomatic (malar) bone/process/arch. The zygomatic bone (white/black arrows) starts in the anterior aspect with the zygomatic process (blue arrow), which has a U-shape. The zygomatic bone extends posteriorly into the zygomatic arch 顴弓 (green arrow).facial view malar

25、（顴骨) 上頜竇(Maxillary sinus) 上頜磨牙根尖片時，牙根上方有一密度低的影像。大的上頜竇向后可擴展到上頜結(jié)節(jié)，向前可延伸到尖牙區(qū)。長期無牙頜或磨牙有缺失的患者，因牙槽突吸收致高度減低，竇底可緊貼牙槽突稍上（咬合力可限制上頜竇生長） 形態(tài)：上頜竇底有時可突入牙根之間的牙槽間隔環(huán)繞數(shù)個牙根而使其竇底呈波浪狀，有時可見自竇底向上有一、二個致密線條狀影像，使竇底顯示為“w”形，此為上頜竇的分隔。磨牙腭側(cè)根，可依據(jù)牙周膜及骨硬板連續(xù)不斷，判斷牙根并非位于上頜竇內(nèi)。Maxillary sinus. As seen in the above film, the floor of the m

26、axillary sinus flows around the roots of the maxillary molars and premolars. The walls of the sinus may become very thin. As a result, sinusitis may put pressure on the superior alveolar nerves resulting in apparent tooth pain, even though the tooth is perfectly healthy. Note coronoid process (green

27、 arrow), zygomatic bone (blue arrow), sinus septum (yellow arrow) and neurovascular canal (orange arrows).facial view Maxillary sinus(上頜竇）The maxillary sinus is evident anterior to the second molar (black arrows) but it disappears posteriorly due to the superimposition of the zygomatic bone. The ora

28、nge arrows identify a mucous retention cyst (retention pseudocyst) within the sinus. This film shows the coronoid process (green arrow) and a distomolar (blue arrow) that has erupted ahead of the third molar (red arrow). A distomolar is a supernumerary tooth that erupts distal (posterior) to the oth

29、er molars.The zygomatic process (green arrows) is a prominent U-shaped radiopacity. Normally the zygomatic bone posterior to this is very dense and radiopaque. In this patient, however, the maxillary sinus has expanded into the zygomatic bone and makes the area more radiolucent (red arrows). The cor

30、onoid process (orange arrow), the pterygoid plates (blue arrows) and the maxillary tuberosity (pink arrows) are also identified.This film shows the expansion of the borders of the maxillary sinus through pneumatization (red arrows). This expansion increases with age and it may be accelerated as a re

31、sult of chronic sinus infections. It is most commonly seen when the first molar is extracted prematurely, as in the film at right (the second and third molars have migrated anteriorly to close the space). The coronoid process is seen in the lower left-hand corner of each film. The green arrow identi

32、fies a sinus recess. Note the two distomolars in film at right (blue arrows).a. lingual foramen(舌孔）b. genial tubercles（頦棘） c. mental ridge（頦嵴） d. mental fossa（頦窩 ）Mandibular Incisor 下頜切牙 abcd 頦棘genial tubercles 位于兩下中切牙根尖下方，下頜骨正中聯(lián)合處，顯示為小圓形密度高影像。在中心有點狀密度減低區(qū)，其周圍骨小梁稀少，為正常骨疏松區(qū)。b = genial tubercles （頦棘） a

33、 = lingual foramen (舌孔）c = mental ridge （頦嵴） d = mental fossa （頦窩 ）abcdfacial viewlingual viewLingual foramen (舌孔）. Radiolucent “hole” in center of genial tubercles （頦棘）. Lingual nutrient vessels pass through this foramen. lingual view Lingual foramen (舌孔）Genial tubercles. Radiopaque area in the mid

34、line, midway between the inferior border of the mandible and the apices of the incisors. Serve as attachments for the genioglossus（頦舌肌 ） and geniohyoid（頦舌骨肌 ） muscles. May have radiolucent hole in center (lingual foramen), but not on this film. Note double rooted canine（尖牙） (red arrows).lingual view

35、 genial tubercles （頦棘）Mental ridge （頦嵴）. These represent the raised portions of the mental protuberance（頦隆凸） on either side of the midline. More commonly seen when using the bisecting angle technique, when the x-ray beam is directed at an upward angle through the ridges.facial view Mental ridge （頦嵴）

36、Mental fossa（頦窩 ）. This represents a depression on the labial aspect of the mandible overlying the roots of the incisors. The resulting radiolucency may be mistaken for pathology. facial view Mental fossa（頦窩 ） 營養(yǎng)管（ nutrient canals） 常位于下頜前牙區(qū)，在牙根之間的牙槽骨區(qū)并與牙齒長軸平行的密度低的條狀影像，其數(shù)目、長短和粗細可不同，此為小血管進入牙槽突的影像。有外傷史

37、者應注意和牙槽突骨折線區(qū)別。營養(yǎng)管的影像較柔和，不象骨折線那樣僵硬，影像密度較折斷線稍高。The radiolucent area above corresponds to the location of the mental fossa （頦窩 ）. However, this slide represents chronic periapical periodontitis; these teeth are non-vital, due to trauma.The orange arrows above identify nutrient canals. They are most oft

38、en seen in older persons with thin bone, and in those with high blood pressure or advanced periodontitis.Mandibular Canine 下頜尖牙aba = mental ridge（頦嵴 )b = genial tubercles(頦棘 ）/ lingual foramen（舌孔）c = mental foramen（頦孔） cb2a = mental ridge （頦嵴 )c = mental foramen （頦孔） b2 = lingual foramen （舌孔）b1 = ge

39、nial tubercles (頦棘 ）facial viewlingual viewdcdadb1db2Mental ridge（頦嵴 )。The raised portions of the mental protuberance（頦隆凸）， sloping（傾斜的 ） downward and backward from the midline. facial viewmental ridge （頦嵴 ) Lingual foramen/genial tubercles. (See description under mandibular incisor above). lingual

40、view genial tubercles (頦棘 ）The red arrows identify the mandibular canal（下頜管 ）and the blue arrow points to the mental foramen （頦孔）.facial viewMandibular Premolar 下頜前磨牙a = mylohyoid ridge（頜舌骨嵴 ）b = mandibular canal（下頜管）c = submandibular gland fossa（下頜下腺窩）d = mental foramen （頦孔）cb = mandibular canal （下

41、頜管）d = mental foramen （頦孔）a = mylohyoid ridge （頜舌骨嵴 ） (internal oblique內(nèi)斜線)c = submandibular gland fossa （下頜下腺窩）facial viewlingual viewcaddbMylohyoid (internal oblique) ridge. This radiopaque ridge is the attachment for the mylohyoid（下頜舌骨的 ） muscle. The ridge runs downward and forward from the third

42、 molar region to the area of the premolars.lingual view mylohyoid ridge （頜舌骨嵴 ） facial view mandibular canal（下頜管）Mandibular canal （下頜管）. (Inferior alveolar canal). Runs downward from the mandibular foramen to the mental foramen, passing close to the roots of the molars. More easily seen in the molar

43、 periapical.lingual view submandibular gland fossa（下頜下腺窩）Submandibular gland fossa（下頜下腺窩）. The depression below the mylohyoid ridge （頜舌骨嵴 ） where the submandibular gland is located. More obvious in the molar periapical film. 頦孔 mental foramen 下頜4、5根尖區(qū)域為一大致圓形密度低的影像Mental foramen （頦孔）. Usually located

44、 midway between the upper and lower borders of the body of the mandible, in the area of the premolars. May mimic pathology if superimposed（重疊） over the apex（根尖） of one of the premolars.facial view mental foramen （頦孔）The mental foramen （頦孔）(blue arrow) is adjacent to a periapical lesion associated wi

45、th tooth # 21 (red arrow). There is slight external resorption on # 21.The green arrow points to the mental foramen. The yellow arrow identifies a periapical lesion on # 30. Note the overextension（伸展過度 ） of the silver point in the distal root, the perforation of the mesial root and the amalgam（汞合金）

46、protruding（伸出的 ） through the perforation from the pulp chamber（髓室） .Mandibular Molar a = external oblique ridge(外斜線）b = mylohyoid ridge（頜舌骨嵴） c = mandibular canal （下頜管）d = submandibular gland fossa （下頜下腺窩）facial viewlingual viewbcaba = external oblique ridge (外斜線）c = mandibular canal （下頜管）b = mylohy

47、oid ridge （頜舌骨嵴） d = submandibular gland fossa （下頜下腺窩）ddabcdda = external oblique ridge (外斜線）b = mylohyoid ridge （頜舌骨嵴） c = mandibular canal（下頜管）d = submandibular gland fossa （下頜下腺窩） 外斜線external oblique ridge 由升支前緣下部斜向前下，為一密度高的帶狀影像，重疊在第二、三磨牙牙冠部、頸部或根部，使牙髓室或根管不能清晰地顯示。外斜線重疊在牙齒的部位與投照時垂直角度的大小有關(guān)。External

48、oblique ridge(外斜線）A continuation of the anterior border of the ramus（分支）， passing downward and forward on the buccal side of the mandible. It appears as a distinct radiopaque line which usually ends anteriorly in the area of the first molar. Serves as an attachment of the buccinator（頰?。?muscle. (The

49、 red arrows point to the mylohyoid ridge （頜舌骨嵴） ).facial view external oblique ridge (外斜線）Mylohyoid ridge （頜舌骨嵴） (internal oblique). Located on the lingual surface of the mandible, extending from the third molar area to the premolar region. Serves as the attachment of the mylohyoid muscle（下頜舌骨?。?lin

50、gual view mylohyoid ridge （頜舌骨嵴） 下頜管mandibular canal 位于磨牙牙根尖下方，呈寬約0.4cm凹面向上邊緣整齊的帶狀密度低的影像，其兩側(cè)有密度高的線條狀影像，為下頜管致密骨層。facial view mandibular canal（下頜管）Mandibular (inferior alveolar下齒槽) canal （下頜管）. Arises at the mandibular foramen （下頜孔） on the lingual side of the ramus and passes downward and forward, mov

51、ing from the lingual side of the mandible in the third molar region to the buccal side of the mandible in the premolar region. Contains the inferior alveolar nerve and vessels.lingual view submandibular gland fossa （下頜下腺窩）Submandibular gland fossa （下頜下腺窩）. A depression(凹陷 ) on the lingual side of th

52、e mandible below the mylohyoid ridge （頜舌骨嵴）. The submandibular gland（頜下腺）is located in this region. Due to the thinness of bone, the trabecular（有小梁的） pattern of the bone is very sparse（稀少） and results in the area being very radiolucent. The fact that it occurs bilaterally(兩側(cè)地 )helps to differentiate

53、 it from pathology.The external oblique ridge (外斜線） (red arrows) and the mylohyoid ridge （頜舌骨嵴） (blue arrows) usually run parallel with each other, with the external oblique ridge (外斜線） always being higher on the film.The mandibular canal (red arrows identify inferior border of canal) usually runs v

54、ery close to the roots of the molars, especially the third molar. This can be a problem when extracting these teeth. Note the extreme dilaceration (curving) of the roots of the third molar (green arrow) in the film at left. The film at right shows “kissing” impactions located at the superior border

55、of the canal. 下頜骨下緣：膠片在口內(nèi)放的位置較低，加之投照時垂直角度過大，則在牙根尖下方X線片顯示為帶狀密度很高的影像。下頜角區(qū)：在下頜管的后下區(qū)域，骨小梁很少或根本不顯示，這是正常骨疏松區(qū)，易誤為病變。內(nèi)斜線：亦稱頜舌線或下頜舌骨線，為自頦棘斜向上后的致密線條狀影像，至升支前緣即消失位于外斜線之下，走行方向一致。Identify the anatomical structures on the following eight slides. The answers are on the last slide. Slide # 1A. The red arrows identif

56、y the ?Slide # 2A. The red arrow points to the ?B. The white arrows identify the ?C. The blue arrow points to the ?D. The yellow arrow identifies the ?Slide # 3The small radioluceny identified by the green arrow is the ?Slide # 4The radiopacity identified by the blue arrows is the ?B. The orange arr

57、ow identifies the ?Slide # 5The yellow arrows point to the ?The red arrows identify the ?Slide # 6The red arrow points to the ?The orange arrow points to the ?The blue arrows point to the radiolucent line known as the ?Slide # 7A. The red arrows point to the ?Slide # 8The red arrows identify the ?Wh

58、at is the name of the radiolucent area surrounding the canal? KEYSlide # 1: A. Floor of the nasal fossaSlide # 2: A. Coronoid process B. Maxillary sinus (pneumatized into maxillary tuberosity) C. Sinus septum D. Zygomatic processSlide # 3: A. Lingual foramenSlide # 4: A. Mylohyoid ridge B. Submandib

59、ular gland fossaSlide # 5: A. Zygomatic process B. Maxillary sinusSlide # 6: A. Inferior concha B. Nasal septum C. Median palatal sutureSlide # 7: A. Mental ridgeSlide # 8: A. Mandibular canal B. Submandibular gland fossa 3、兒童牙齒與頜骨乳牙從胚胎第二個月開始發(fā)生，3歲后牙根才完全形成，恒牙則從胚胎第4-5個月發(fā)生，直到20歲左右第三磨牙的牙根才完全形成。 牙齒的全部發(fā)育過

60、程：可分為三個階段：（1）牙胚的發(fā)生（2）牙體組織的形成（3）牙齒的萌出。造牙齒組織叫牙胚，一個發(fā)育完全的牙胚由造釉器、牙乳頭和牙囊所組成，牙齒及牙周組織均由牙胚形成，造釉器形成牙釉質(zhì)，牙乳頭形成牙本質(zhì)及牙髓，牙囊形成牙骨質(zhì)、牙周膜及牙槽骨的內(nèi)壁。牙胚在頜骨內(nèi)其X線片上的影像，隨其發(fā)育各個時期不同而有所不同。牙胚早期顯示在頜骨為一邊緣清晰的圓形的密度低的影像，外圍有一致密線條影，此為其周圍的骨密度邊緣，這時牙胚內(nèi)雖有牙釉質(zhì)及牙本質(zhì)基質(zhì)形成，但尚無鈣質(zhì)沉著，故呈密度低的影像，應注意不要誤為囊腫，隨著牙胚的發(fā)育，可見圓形的透影內(nèi)有小三角形密度高的影像出現(xiàn)，此為開始鈣化的牙尖，鈣質(zhì)沉著逐漸增多，則逐