Normal Anatomy. Concepts of General Anatomy

Transcription

1 Norml Antomy 2 In OPT, the evlution of the mstictory norml ntomy is different for sujects of peditric ge nd dults. Indeed, sujects of peditric ge present rdiogrphic ppernce which cn e de fi ned s mixed dentition, in which deciduous dentl elements nd permnent dentl elements coexist ll together. Therefore, in peditric ge, considertions of ntomic order nd OPT possiilities re completely different from the ones pplicle in the study of n dult suject. We will fi rstly tke into nlysis the dult ntomy, with completed dentl development. In the dult, the study of norml ntomy fi rstly is sed on the de fi nition of some generl concepts, then susequently focused nlysis on the following structures: Generl ntomy of the tooth Antomy of the support pprtus Antomy of the mndile nd the mndiulr cnl Antomy of the surrounding structures (prnsl sinuses, hrd plte, nsl cvities, etc.) Concepts of Generl Antomy The rdiogrphic ntomy of the tooth in the dult, chievle through OPT, does not present the sme detil re fi nement of the rdiogrphic ntomy evluted through endorl rdiogrms. This is due to the technicl peculirity of the methodology which fvours glol vision rther thn detiled evlution. However, even if fcing this limittion, dentl imges chieved through OPT re suf fi cient to fully express the mcroscopicl chrcteristics of the dentl element, in the mjority of the dignostic needs. I. Pndolfo, S. Mzziotti, Orthopntomogrphy, DOI / _2, Springer-Verlg Itli

2 28 2 Norml Antomy On the ntomicl point of view, it is oviously necessry to tke ech of the dentl typologies (incisors, cnines, premolrs nd molrs) into ccount seprtely. In order to esily identify the different dentl elements, clssicl scheme is considered. It visulises the sudivision of the rdiogrm in four qudrnts which re indicted with progressive numers (1, 2, 3, 4), from right to left, from ottom up nd clockwise. Ech numer is ssocited to the reltive dentl element of ech hemirch. Numer 1 indictes the medin incisor, numer 2 indictes the lterl incisor, numer 3 indictes the cnine, etc. According to this method, for exmple, the third inferior right molr is indicted with numer 4.8, the superior left cnine is indicted with numer 2.3, etc. (Fig. 2.1 ). Such methodology, in ddition to fcilitting the detection of speci fi c dentl element (in the OPT report), is lso extremely useful for evluting cses with ltertions regrding the dentl numer, oth in excess nd, more rrely, in defect. Descriptive nd Rdiogrphic Antomy of the Dentl Element From the structurl point of view, the tooth is n rchitectonicl construction which comprises mcroscopicl nd morphofunctionl components. They hve different purposes; therefore, they re constituted y different tissue types. Indeed, the tooth is chrcterised y visile component clled crown nd n introsseous component clled root (Fig. 2.2 ). The dentl crown represents the different functions of the tooth (shredding, stripping, section) through different morphologies (Fig. 2.3, ). The root is involved in the support pprtus nd in the nchorge of the tooth to the jwone. The root end of the tooth is clled tooth pex nd it is chrcterised y very thin hole which gives rise to the vsculr-nervous xis. The dentl element, on its whole complex, is constituted y dentin which is n orgnic sustnce of mesodermic origin. It is covered y n externl sheth clled enmel (of ectoderml origin) in the crown nd y the cementum (of mesodermic origin) in the root. Therefore, the dentin is present oth in the crown nd in the root; it is composed of n orgnic component produced y the odontolsts (out 30 %) nd y minerl component (out 70 %) which is composed of hydroxyptite crystls. Odontolsts produce dentine in dynmic mnner oth during the tooth s physiologicl development ( primry dentine ) nd in pthologicl conditions ( secondry or rective dentine ). The enmel (produced y cells clled melolsts ) covers the crown. Therefore, it turns out to e the set of further mechnicl stress; for this reson, it is composed of hydroxyptite crystls for the 96 %. Finlly, the cementum is lso composed of n orgnic mtrix nd minerl component which determines the formtion of the so-clled mture cementum.

3 Descriptive nd Rdiogrphic Antomy of the Dentl Element 29 It covers the dentine t the level of the root xis line nd is generted y cementolsts. They re cellulr elements plced in the tooth surfce which re le to produce cementum for the whole life of the tooth. Dentl elements cn e distinguished in monordiculr, irdiculr nd trirdiculr teeth. As generl rule, even if sujected to numerous exceptions, it is possile to estlish tht incisors nd cnines of oth rches turn out to e lwys monordiculr teeth. Moreover, ll the premolrs of the lower rch nd the second premolrs of the upper rch re monordiculr teeth, too. Conversely, the fi rst premolrs of the upper rch generlly hve two roots ( vestiulr one nd pltl one), while the fi rst nd the second molr of the lower rch (which re irdiculr teeth, too) re chrcterised y mesil nd distl root. The fi rst nd the second molrs of the upper rch lwys turn out to e trirdiculr teeth (hving mesil, distl nd pltl root). Finlly, the third molrs present certin vriility. They cn e oth monordiculr nd, more rrely, irdiculr teeth. A trnsition re clled neck of tooth or cementoenmel junction exists etween the crown nd the root. This is the re where the melolstic lyer, represented y enmel, meets the root surfce, which is constituted y the cement. Inside the tooth, which presents high rdiopcity due to its structure, it is possile to recognise rdiolucency re which exist oth in the crown nd the root. Such re is, respectively, the expression of the pulp chmer nd the root cnl (Fig. 2.4 ). The root cnl is chrcterised y very thin horizontl nd olique collterl cnls, clled lterl cnls (however, they re never rdiogrphiclly visile). Vsculr-nervous elements exist oth in the pulp chmer nd in the root cnl. Together with connective support (of mesodermic origin) they constitute the dentl pulp. The dentl pulp hs three purposes: dentine formtion ( dentinogenesis ) nd oth nutritive nd sensoril functions. To conclude this generl nlysis of the dentl ntomy, it must e rememered tht from topogrphic point of view, ech tooth is chrcterised y fce which is oriented towrds the cheek, clled vestiulr surfce, nd nother fce which is oriented towrds the tongue, clled lingul surfce. Another fce ful fi ls the mstiction process nd is prticulrly ugmented in the molrs. It is clled the occlusl surfce s it is in fl uenced, in its morphology, y juxtposition or occlusl rpports with the dentl elements of the opposed rch. Furthermore, two other fces exist. One fce, directed towrds the medin line, is clled mesil surfce nd nother fce, opposed to it, is clled distl surfce. They re interfces etween two dentl elements, therey clled interproximl surfces (Fig. 2.5 ). As forementioned, this distinction is lso vlid for the denomintion of the root xis surfces. Indeed, in trirdiculr element, it is possile to distinguish the mesil root from the distl one, in ddition to the third root, clled pltl. The ltter seems

4 30 2 Norml Antomy to e typiclly present t the level of the fi rst nd the second upper molrs nd it is not lwys demonstrle through OPT, for projective resons. Indeed, the pltl root develops itself in different plne with respect to the other roots. As it is plced frther from the detection plne, it will turn out to e rdiogrphiclly less de fi ned nd rther enlrged (Fig. 2.6, ). It is ovious tht the forementioned expressions of topogrphic nd semntic order re solutely necessry in order to loclise the morid processes. Therefore, they re propedeuticl to correct drft of the rdiologicl report. Descriptive nd Rdiologicl Antomy of the Support Apprtus or Periodontium The ntomicl nd functionl structure is responsile for the stility of the dentl elements, nd in fi nl nlysis, of the whole mstictory pprtus. It is constituted y the following components: the gingiv, the periodontl ligment (PDL) nd the lveolr one, which in turn is constituted y the spongios nd the corticl plte ( lmin dur ). According to some experts, the cementum is prt of the lveolr one, too (Fig. 2.7 ). OPT llows pnormic evlution of the norml ntomy nd, consequently, of the pthologicl ltertions relted only to some of the forementioned components. Indeed, it is well known tht the evlution of the gingivl pprtus is exclusively of clinicl pertinence nd lso direct rdiogrphic visulistion of the periodontl ligment is not possile. As consequence, the stte of the periodontl ligment cn e indirectly evluted ccording to the extent of the periodontl spce which, in norml suject, turns out to e rdiogrphiclly invisile or scrcely detectle. Therefore, the rdiogrphic representtion of the periodontl pprtus is referred only to the nlysis of the lveolr one, which is constituted y interdentl nd intrrdiculr cuspids, with their reltive components (spongios nd lmin dur). Moreover, it is lso referred to the evlution of the periodontl spce extent nd to the stte of the dentl roots (Fig. 2.8 ). The periodontl spce is thin rdiolucent line which hosts the nmeske ligment, constituted y collgen fi res produced y firolsts. Firolsts originte from the emryonic cellulr elements which re contined in the dentl sc. The elements of the forementioned ligment- fi rous pprtus ( Shrpey s fires ) re hooked up to the cementum nd to the corticl plte of the undle one t the level of the lveolr fce. Descriptive nd Rdiogrphic Antomy of the Mndile nd the Mndiulr Cnl The ntomy of the mndile, evlule through OPT, cn e syntheticlly descried s follows.

5 Descriptive nd Rdiogrphic Antomy of the Mndile nd the Mndiulr Cnl 31 Anlogous with the clssic ntomicl literture, it is possile to distinguish the scending rnch or mndiulr rmus. Anteriorly, it gives rise to the coronoid pophysis (insertion re of the temporl muscle ) nd posteriorly to the intercondylr region nd the mndiulr condyle, in which the rticulr reltionships with the glenoid cvity re well rendered. Distlly, the scending rnch continues with the interposition of the mndiulr ngle (ngulr region ), with the mndiulr ody or horizontl rnch. At the level of the medin line, there is the symphysis menti region. In the ngulr region is present superior surfce with tringulr morphology, covered y the gingiv. This ngulr region is set ehind the lst molr nd is clled retromolr trigone. It is the ntomicl re of mjor importnce for oncologicl implictions. Moreover, the mndiulr ngle, in the inferior lterl side, is chrcterised y irregulr slience nd roughness. It represents the insertion re of the msseter muscle (Fig. 2.9, ). In its complex, the mndile is constituted y undle of corticl one tissue which is chrcterised y mjor thickness in the lower prt nd y the sponge tissue which represents the medullry one. The sponge tissue presents different rchitecture nd different grde of opcity, depending on the ge, the nutritionl stte nd the generl skeletl trophism of the ptients. At the level of the horizontl rnch nd of the ngulr region, it is possile, in mny sujects, to detect mjor opcity nd which indictes the ridge (of insertion ) of the mylohyoid muscle. The nd is situted t the level of the vestiulr surfce which is etter evident in edentulous sujects for the hypotrophy of the surrounding one (Fig ). More crnilly, in the scending rnch, it is possile to demonstrte the entry formen of the mndiulr cnl nd little one slience djcent to it, clled Spix spine. The Spix spine is the insertion of the firous pterygomndiulr rphe, which in turn is never demonstrle through the OPT exmintion (Fig ). Conversely, in lmost ll the ptients, it is possile to rdiogrphiclly demonstrte the mndiulr cnl into which the inferior lveolr nerve runs. The inferior lveolr nerve is the medil rmus of the mndiulr nerve, which is the third rnch of the trigeminl nerve. As the mndiulr cnl is one chnnel delimitted y thin corticl side, in OPT, it ssumes the peculir spect of cnliculr structure. This structure hs low density nd dimeter of mm. Its proximl extremity is, in turn, chrcterised y funnel morphology which is the entrnce of the nerve (Fig. 2.12, ). As the mndiulr cnl runs into spongeous one tissue, its visiility in OPT is closely relted to the opcity grde of the surrounding spongios. In the sujects with high level of osteopeni, which cuses the sence of optiml contrst conditions, scrce or sent visulistion of the mndiulr cnl cn occur. In this cse, the medicl report cnnot e considered pthologicl. Conversely, in the presence of high one density, the visiility of the chnnel cn e etter (Fig. 2.13, ).

6 32 2 Norml Antomy If rdiologicl visiility is good, it is esy to visulise the curviliner spect of the cnl in its horizontl portion, s well s the forementioned funnel spect of its proximl extremity. The nterior segment up to the opening of the mentl formen will lso e visile. The mentl formen, most frequently, corresponds to the pex of the second premolr tooth (Fig ). In regrd to this, in the mjority of cses, the missing visulistion of such formen is due to projective resons; therefore, it cnnot e considered pthologicl event. A further considertion is represented y the possile vriility of the mentl formen set. Indeed, if it is not perfectly mtched with the typicl position, it cnnot e considered pthologicl ut norml ntomicl vrition. As mtter of fct, the mentl formen cn e locted oth in correspondence with the pex of the second premolr tooth nd t certin distnce from it. More rrely, it cn e plced t the pex of the fi rst premolr tooth. Errors relted to such vriility re infrequent nd mde only y inexpert oservers who my wrongly interpret the mentl formen rdiolucency s the peripicl lesion of the second premolr tooth (Fig. 2.15, ). This cn e esily voided through comprison with the contrlterl norml side. Oviously, the solute normlity of the dentl element under exm must e evluted. As mentioned erlier, it is sometimes possile to provide evidence of the very thin incisive cnliculus s chrcteristic of norml ntomy. It leds itself from the mentl formen towrds the elements of the inferior incisive undle (Fig ). Moreover, the other dentl cnliculi re rrely nd occsionlly visile in norml ntomy (Fig ). An outstnding ntomicl vrint, to e considered in implntologicl plnning, is represented y the end tht the mndiulr cnl ccomplishes in its more distl portion, efore its opening into the mentl formen. In few words, the cnl, t such level, cn crete curve (lso clled loop of the mndiulr cnl ). This is directed in front nd towrds the medin line. It then folds ck nd returns to the mentl formen (Fig ). It seems to e cler tht, if this ntomicl con fi gurtion is not indicted, it cn negtively revererte during n implntologic intervention in this region. Indeed, it is known tht the second inferior premolr is considered to e the externl ntomicl lndmrk, corresponding to the mentl formen, which identi fi es the distl limit of the lveolr nerve. It is ovious tht the presence of mrked loop of the mndiulr cnl plces the nerve in more mesil set with respect to the second premolr tooth. This con fi gurtion cn determine the itrogenic lesion of the nerve, s consequence of surgicl opertions performed t such level. The rre possiility of mndiulr cnl i fi dity must lwys e rememered with regrd to the ntomicl vritions. It is lso considered to e n importnt ntomicl vrition in the progrmmes of implntologic plnning (Fig ).

7 Antomy of the Surrounding Structures 33 Finlly, the duplicity of the mndiulr cnl represents more signi fi cnt nd rre condition from the clinicl point of view, s it is linked (demonstrted only in few cses in literture) to the presence of neoformtions of vsculr origin (rteriovenous fi stul). One of the two cnls represents the course of the nerve; the other cnl represents the pth of the fferent vsculr structures to the forementioned lesions (Fig ). Antomicl vrints re often deprived of ny pthologicl signi fi cnce, ut sometimes they re the cuse of clinicl sintomthology nd/or of complictions fter tooth extrction. Considering those vrints, the mndiulr cnl nd the third molr tooth cn interfce etween them in numerous wys. Indeed, ccording to this vriility, some risks cn occur. These include the trnsference of pthologicl events from the dentl element to the cnl nd itrogenic dmges relted to tooth extrction. It is ovious tht the relevnce of the security distnce etween the tooth nd the cnl involves minor risks (Fig ). Conversely, close djcency etween the dentl element nd the cnl determines mjor risk conditions (Fig c ). In regrd to this, disppernce of one of the cnl corticl, in djcency to the tooth is n importnt semeiologicl finding. Such disppernce could indicte the rel contct etween the two structures. Conversely, where the corticl is visile, even in correspondence with the tooth, it must e considered tht the structures re not in contct ut only superimposed projectively. Brie fl y, such semeiologicl sign is n extension of the silhouette sign, very well known in generl rdiogrphic semeiotics (Fig. 2.23, ). Finlly, the forementioned itrogenic risks ecome more relevnt in cse of nomlies of position nd orienttion of the third molr tooth. In prticulr, the inclusion of the third molr tooth, incresing the proximity of the tooth to the cnl, represents signi fi cnt risk condition, long with its frequency (Fig c ). Furthermore, it hs to e to e considered tht CT cn exhustively de fi ne the rel spce reltions etween the tooth nd the cnl, thnks to its tridimensionl pproch. This is not possile using OPT s it is only le to de fi ne the forementioned reltions idimensionlly. Antomy of the Surrounding Structures Therefore, the surrounding structures of the dentl rches which re visile in OPT minly include mxillry sinuses, nsl cvities, hrd plte, pterygoid pophysis, pterygopltine fosse, temporomndiulr joints nd zygomtic rches (Fig. 2.25, ). It is ovious tht the nlyticl evlution of the forementioned structures (except the temporomndiulr joints, whose nlysis does not elong to the ims

8 34 2 Norml Antomy of the following text) is not the fundmentl im of OPT, s the imging of such res lwys pertin to other techniques of mjor ef fi ciency such s CT nd MR. However, it is evident tht the rdiologist must e le to recognise such ntomicl structures nd their more common vrints (Fig ); in ddition, he must e le to detect ny possile nomlies, indicting the most suitle imging techniques. From this viewpoint, some ltertions of the skeletl components of the fcil ones seem to e prdigmtic, such s those relted to fi rous dysplsi, osteolytic lesions, pltoschisis nd osteomtous formtions (Figs. 2.27, 2.28, nd 2.29 ). The content of the mxillry sinuses cn lso e the set of pthologicl events which genericlly occur s endoluminl opcity. Most of the times they re considered innocuous retentive pseudocysts, ut they cn e in differentil dignosis oth with other pthologicl events (polyposis, neoplsi) nd with prticulr ntomicl vritions (Fig. 2.30, ). Finlly, the possiility of nomlies of odontogenic origin must not e ignored. These nomlies re chrcterised y n endosinusl development nd will e discussed susequently in the text. Rdiogrphic Antomy in Peditric Age As previously explined, the spect of the mstictory pprtus in peditric ge turns out to e very different to tht of the dult. As consequence, oth ge groups hve entirely distinct rdiogrphic cses nd descriptive terminology. However, for oth ge groups, the sme scheme is used for the function of identifying nd enumerting the dentl elements. The study sector cn e sudivided into four qudrnts: considering s numer 5 the superior right hemirch, numer 6 the superior left hemirch, numer 7 the inferior left hemirch nd numer 8 the inferior right hemirch. As the deciduous dentl elements re 5 for ech hemirch, they re detected (similrly to the dults) with the following numers: 5.1 refers to the superior medin right incisor, 6.1 refers to its corresponding left tooth nd so on (see Fig ). This clcultion must oviously consider the fct tht the development of molr teeth does not precede the ppernce of deciduous dentl elements. Also from the morphologicl point of view, there is sustntil difference etween the deciduous dentl elements nd the permnent ones. The deciduous dentl elements present minor dimensions; they hve somewht squt spect nd some distinct morphologicl connottions: for exmple, chrcteristic of the deciduous premolr teeth is irdiculted spect. In ddition, the deciduous elements, under the push of the underlying permnent elements, present vrile grde of rdiculr resorption, which is clled rhizolysis or physiologicl picolysis (it hs to e distinguished from the pthologicl

9 Rdiogrphic Antomy in Peditric Age 35 rhizolysis which cn pper in the dult in presence of peripicl- fl ogistic lesions) (Fig ). Also the permnent dentl elements, while still in the phse of dehiscence, present signi fi cnt morphologicl nd dimensionl differences, with respect to the sme elements lredy developed. They present more or less incomplete development of the rdiculr xes, which pper to e short or not present, when compred to their fully developed stte. For the sme reson, the picl formen is very wide (Fig ). In order to etter understnd the min morphologicl chrcteristics of the permnent tooth still in phse of dehiscence, some preliminry remrks re essentil in regrd to the emryogenetic development. The dentl germ (oth the deciduous nd permnent one) origintes from n intro fl exion of the dentl ridge. It turns out to e entirely surrounded y thin memrne clled dentl sc (or lveolr sc ). Its primry function is protection. In its interior, the dentl germ ppers further lined y memrne composed of n internl lyer ttched to the crown germ. This is the set of melolsts (cells of ectodermic origin, responsile for the formtion of the enmel). The dentl germ is lso covered y n externl lyer in contct with the dentl sc. Between the forementioned memrnes, there is certin mount of mesenchyml tissue which siclly hs trophic function, clled stellte reticulum. The forementioned ntomicl-functionl structure tkes the nme of orgn of the enmel nd it is responsile for the whole tooth development. In prticulr it is responsile for the construction of the norml enmel shell of the crown dentine. Even if it vries in reltion to the evolutionry stte, it is nerly lwys rdiogrphiclly detectle (Fig ). The orgn of the enmel represents criticl structure. This is due to the cystic degenertion of the mesenchyml component, which constitutes the stellte reticulum, nd is the sis for odontogenic folliculr cyst formtion.

10 36 2 Norml Antomy Imge Gllery Fig. 2.1 Scheme showing the topogrphic detection of the dentl elements Dentine Pulp chmer Root cnl Enmel Crown Cementoenmel junction Cementum Fig. 2.2 Schemtic digrm which illustrtes the different morphologicl nd structurl components of the tooth Root

11 Imge Gllery 37 Fig. 2.3 ( ) Crown morphology of the medin nd lterl incisors nd of the left cnine (2.1, 2.2 e 2.3) iming t stripping. ( ) Crown morphology of the premolrs 2.4 nd 2.5 nd of the fi rst left molr (2.6) iming t shredding Fig. 2.4 The long red rrow indictes the enmel chrcterised y mximum opcity. The short red rrow indictes the cementoenmel junction. The long yellow rrow indictes the pulp chmer. The short yellow rrows indicte the rdiculr cnls Fig Vestiulr surfce. 2 Lingul (or pltl) surfce. 3 Occlusl surfce. 4 Distl surfce. 5 Mesil surfce

12 38 2 Norml Antomy Fig. 2.6 ( ) The imge shows the irdiculr tooth; letter d indictes the distl root; letter m indictes the mesil root. ( ) The imge shows the trirdiculr tooth. The pltl root (indicted y rrows ) seems to e enlrged with lurred outlines Fig. 2.7 Schemtic digrm which represents the periodontium Gingiv Periodontl Ligment Spongeous one Lmin dur Vsculrnervous xis Fig. 2.8 Rdiogrphic representtion of the periodontl pprtus. The rrowhed indictes the periodontl spce; the yellow rrow indictes the lmin dur; the green str indictes the spongios of the interdiculr cuspid; the sterisk indictes the spongios of the interdentl cuspid

13 Imge Gllery 39 Fig. 2.9 ( ) Antomicl digrm which shows the insertion of the msseter muscle ( m ) into the ngulr region of the mndile. The temporl muscle ( t ) inserts itself into the coronoid pophysis. ( ) Rdiogrm which shows the min elements of the mndile: Letter c stnds for condyle; letters c stnds for coronoid pophysis; the short rrows indicte the mndiulr cnl; the long rrow indictes the corticl roughness which is due to the insertion of the msseter muscle Fig The mylohyoid muscle ridge (indicted y rrows ) is clerly visile Fig Antomicl photo which shows the entry formen of the mndiulr cnl (indicted y long rrow ). The short rrow indictes the Spix spine. The rrow heds indicte the sulcus of the mylohyoid nerve. The sterisk indictes the insertion re of the internl pterygoid muscle. TR retromolr trigone. The lck line indictes the mylohyoid ony ridge

14 40 2 Norml Antomy Fig ( ) Good visiility of the mndiulr cnl (indicted y short rrows ). () Funnel spect of the mndiulr cnl in its proximl extremity (indicted y long rrows ) Fig ( ) Scrce visiility of the mndiulr cnl in () ptient with hypotrophy of the spongios. ( ) Optiml visiility of the mndiulr cnl due to the sclerosis of the surrounding spongios

15 Imge Gllery 41 Fig Mentl formen (indicted y rrow ) in its typicl colloction which is in proximity to the pex of the second premolr (3.5) Fig (, ) Vriility of the mentl formen set (indicted y rrows ). In () the mentl formen is t certin distnce from the pex of the second inferior right premolr (4.5). In () the formen is djcent to the second inferior left premolr (3.5) nd it must not e interpreted s peripicl re of one resorption

16 42 2 Norml Antomy Fig It is possile to provide evidence of the incisive cnliculus (indicted y rrows ) which leds itself from the mentl formen towrds the inferior centrl elements Fig Occsionl visiility of dentl cnliculus (represented y rrow ) in norml ntomy Fig Bend of the mndiulr cnl (indicted y rrows ). This con fi gurtion determines the mndiulr cnl s pproch to the region corresponding to the fi rst premolr on ech side (3.4 e 4.4)

17 Imge Gllery 43 Fig Bifidity of the right mndiulr cnl (indicted y short rrow ) following fi stulous pth towrds the pex (indicted y long rrow ) of the mesil root of the 4.6 Fig Rel duplicity of the mndiulr cnl (indicted y rrows ). The superior cnl gives wy to the pth of vsculr structures nd widens into lcunr imge ( F ), which is the expression of the rteriovenous fistul Fig Wide security distnce etween the pex of the 3.8 nd the mndiulr cnl doule side rrow

18 44 2 Norml Antomy c Fig ( c) Different criticl situtions of the rpports etween the third molr (3.8) nd the mndiulr cnl

19 Imge Gllery 45 Fig In () the corticl of the mndiulr cnl (indicted y rrows ) is detectle, even if projectively superimposed to the dentl element. In ( ) the corticl turns out to e foclly deleted in correspondence to the rdiculr xis of 3.8 (indicted y rrow ) c Fig ( c) Criticl reltions etween the inclusive elements nd the mndiulr cnl. In c 3.8 turns out to e trirdiculr tooth. In ll three cses disppernce of the mndiulr cnl s corticl occurs, which is indictive of the djcency etween the ltter nd the inclusive teeth

20 46 2 Norml Antomy Fig ( ) Schemtic digrm which illustrtes the min ntomicl structures of the fcil ones which re visile in OPT: M mlr one, MS mxillry sinus, NC nsl cvity, S nsl septum, HP hrd plte. ( ) Rdiologic representtion of the min ntomicl structures visile in OPT: 1 nsl septum, 2 nsl cvity, 3 mxillry sinus, 4 hrd plte, 5 pterygopltine fosse, 6 pterygoid pophysis, 7 zygomtic rch, 8 mndiulr condyle, 9 styloid pophysis Fig Antomicl vrition due to norml downwrd expnsion of the mxillry sinuses (indicted y rrows ). This sitution cn sometimes simulte the presence of rdiculr cysts

21 Imge Gllery 47 Fig The imge shows pltoschisis. The rrows indicte the schisis mrgin ffecting the hrd plte Fig Dysmorphic nd rudimentl dentl element (indicted y rrow ) which is inclusive in the left mxillry sinus

22 48 2 Norml Antomy Fig rrows ) (, ) The imge shows two cses of osteom in the mxillry sinus (indicted y Fig ( ) Mucous retentive cyst (indicted y rrows ) of the right mxillry sinus. ( ) Opcity, projecting itself into the mxillry sinus, due to the trnsport shdow of the inferior turinte one (indicted y rrows ), which must not e confused with n endosinusl cystic lesion

23 Imge Gllery 49 Fig Scheme showing the detection nd the denomintion of the deciduous elements Fig ( ) Physiologicl picolysis (indicted y rrows ) of the deciduous superior cnines. ( ) Pthologicl picolysis in peditric ge due to fl ogistic peripicl re of one resorption (indicted y rrows ) of deciduous element Fig Chrcteristic deciduous spect of the inferior right deciduous second premolr (8.5). The correspondent permnent element (4.5) is in phse of dehiscence nd it is possile to detect the lveolr or dentl sc (indicted y short rrows ). Both 4.4 nd 4.5 typiclly present incomplete rdiculr xis with wide picl formen (indicted y long rrow )

24 50 2 Norml Antomy Fig The imge shows 4.3 nd 4.4 in phse of dehiscence. The long rrows indicte the rdiolucency which identi fi es the remins of the enmel orgn Suggested Reding Brr JH, Stephen RG (1980) Dentl rdiology. Sunders, Phildelphi Buchnn LS (2012) Everything s chnged except the ntomy! Dent Tody 31(9):100, 102, Dhrmr S (1997) Locting the mndiulr cnl in pnormic rdiogrphs. Int J Orl Mxillofc Implnts 12: Kim MS, Yoon SJ, Prk HW, Kng JH, Yng SY, Moon YH, Jung NR, Yoo HI, Oh WM, Kim SH (2011) A flse presence of i fi d mndiulr cnls in pnormic rdiogrphs. Dentomxillofc Rdiol 40(7): Lnglis RP, Lnglnd E, Nortje CJ (1995) Dignostic imging of the jws. Willims & Wilkins, Bltimore/Phildelphi Lnglnd OE, Lnglis R, Mc Dvid W, Del Bso A (1989) Pnormic rdiology, 2nd edn. Au fl, Le & Feiger, Phildelphi Mestre-Ferrín L, Crrillo-Grcí C, Glán-Gil S, Peñrroch-Digo M, Peñrroch-Digo M (2011) Prevlence, loction, nd size of mxillry sinus sept: pnormic rdiogrph versus computed tomogrphy scn. J Orl Mxillofc Surg 69(2): Prk JH, Srisurpol T, Ti K (2012) Impcted mxillry cnines: dignosis nd mngement. Dent Tody 31:62, 64 66; quiz Pri CM, Msood F, Beckerley JM, Crson RE (2011) Study of the inferior lveolr cnl nd mentl formen on digitl pnormic imges. J Contemp Dent Prct 12(4): von Arx T, Hänni A, Sendi P, Buser D, Bornstein MM (2011) Rdiogrphic study of the mndiulr retromolr cnl: n ntomic structure with clinicl importnce. J Endod 37(12): Epu 2011 Oct 26 White SC, Phroh MJ (2000) Orl rdiology: principles nd interprettion. Mosy, St Louis

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