8 Anatomy of the maxillofacial skeleton and introduction to radiological interpretation

dental radiographic images are 2D representations of the 3D teeth and bones of the skull 

• soft tissue shadowing, is for the most part, not relevant

• it is important that you are aware of the whole skull but particularly the maxilla and the mandible 

the upper jaw - the maxilla - what is circled in red?

the nasal cavity

what is seen here?

the nasal septum and the inferior nasal concha 

what is the bottom arrow showing?

the floor of the nose - just above the apices of the upper anterior teeth 

what can you say about the surface anatomy of the maxilla around the teeth themselves?

very undulating - prominences over roots

bony spike of the anterior nasal spine 

becomes visible at the side view 

posteriorly, the maxilla….

widens as it articulates with the zygoma or cheekbone

The zygomatic buttress is a key vertical support structure of the midface, formed by the junction of the zygomatic process of the maxilla and the zygomatic bone

underneath the surface layer of the maxilla 

large cavity - maxillary air sinuses /antrum -can extend anteriorly almost to the midline or posteriorly, to hollow out the zygoma 

maxillary sinus is evident radiographically when the upper posterior teeth are shown

internally, the maxillary sinus is not smooth ….

there are small ridges and bumps- thin in cross sections - can appear as dense white opaque lines radiographically

bulk/prominence of the zygomatic cheekbone - radiographically this can overly the apical tissues of the upper molar teeth - solid, dense, white shadow

if its hollowed out by the maxillary sinus, it casts a white, radiopaque U shaped shadow - radiolucent centre

what is the canine prominence?

• bony undulation over the canine root that is especially prominent 

the end of the maxilla can be described as,  

smooth, rounded end - called the tuberosity 

when the thin, surface bone of the maxilla is removed …

can see the roots of the teeth as they are positioned in the alveolar part of the maxilla

the alveolar bone has an internal trabecular, honeycomb appearance - wide enough to envelope all the roots of the posterior teeth

what is this thin line over the palate?

mid-palatal suture 

what is this large hole?

naso-palatine foramen 

• resultant radiographs are always 2d demonstrations of a 3d object - all structures, internal and external will be superimposed on one another 

• how the anatomy is presented geometrically is dependent on the relative positions of the patient, image receptor and the X ray beam

what does this anterior periapical graph show?

oval radiolucent area between the central incisors - is it Infront of the teeth (buccally?) or is it behind them? - you can’t tell radiographically

 but its shape and position is compatible with the palatally positioned with the nasopalatine formaina 

more posteriorly - radiopacities indicate the nasal septum and floor of the nose 

dense, thin , white line in the middle of the image is the nasal septum 

less dense opacity is caused by the 

inferior nasal concha 

radiolucency - nasal septum 

lateral wall of the nose 

maxillary air sinus

mid-palatal suture

this increased radiopacity is caused by the soft tissues at the tip of the nose - shadow - dense tissue 

occlusal view shows how maxillary air sinus varies in size 

density of the maxillary sinus varies 

blacker in some parts than in others 

shape varies and the density of the overlying bone varies 

radiolucent, antral air cavity and the radiopaque white line of the anterior wall and floor 

faint lines in the maxillary air sinus represents the irregularities in the wall 

periapical radiograph → posterior maxilla

radiolucent maxillary sinus and radiopaque floor

radiopaque shadow cast by zygoma, hollowed out by maxillary sinus 

lower end of the dense, zygomatic bone 

posterior aspect of the maxilla - smooth round tuberosity 

• 1st image taken using the bisected angle technique 

• 2nd was taken using the geometrically accurate, paralleling technique

• upper image is geometrically distorted  

• shadow caused by zygoma

• this was taken using the bisected angle technique 

x ray beam was directed below the zygoma

very lower of the zygoma is seen - projected above the apices 

• pterygoid hammulus - supports the muscles of the soft palate 

• coronoid process of the mandible 

edentulous patient 

can see u shaped edge of hollowed out zygomatic bone 

mandible - the lower jaw

mental prominence 

body 

mental foramina 

dense bony prominence of the external oblique ridge

angle

coronoid process - and ascending rami on both sides????

anterior lingual/inner aspect of the mandible

bony spurs 

genial tubercules - muscles of the tongue and neck attach here 

lingual pit 

mylohyoid ridge - mylohyoid attaches to form the floor of mouth 

mandible varies in cross sectional thickness 

left hand side of the mandible buccal surface has been removed 

roots of the teeth protrude in the underlying trabecular bone 

inferior dental nerve

mental nerve - coming out of the mental foramen 

reveals honeycombed pattern of trabecular bone 

• dense outline of the individual sockets of the teeth

• cortical bone which forms the lower border 

periapical region 

can see honeycombed pattern 

mental foramen - black radiolucency - near 1st and 2nd premolars

sockets of the teeth are represented by thin, white, opaque lines → ‘ lamina dura’ 

dense, white, radiopaque line → dense bone of mylohyoid ridge

underneath mylohyoid ridge - looks more radiolucent → this is due to the lingual indentation of submandibular fossa

dense cortical bone of the lower border

radiolucent shadow created by the lingual pit 

lower occlusal

small bony spurs of the genial tubercles

oblique lateral technique allows you to take extraoral radiographs 

• image receptor is placed outside the mouth and against the side of the face

• resultant radiographs are larger and show anatomical structures in both jaws

• direction of Xray beam on this skull

for right hand side - tube head left and receptor opposite - passes between the cervical spine and the left ascending ramus of the mandible - viewed like you are looking at the patient’s right cheek

posterior edge of left side 

radiolucent band around the posterior part of the body of the mandible

• created by inferior dental nerve and blood vessel, created by the inferior dental canal

• the edges of the canal can be seen as thin, white radiopaque lines → ‘tram lines’

inferior dental canal can easily be seen in cross sectional dental images

to see both jaws, a panoramic radiograph can be taken 

this creates a complicated radiograph with several types of shadows superimposed on top of each other - image shows why the cervical spine appears on both sides of the image - anatomical structures are severely distorted 

real hard tissue shadows 

real hard tissue shadows of nasal septum, hard palate, maxilla, zygoma, mandible and the hyoid 

real soft tissue shadows

real soft tissue shadows of the soft palate, ear lobe and the dorsum of the tongue 

real equipment shadows 

bite peg and the plastic head support 

ghost hard tissue shadows

• mandible from the opposite side

• cervical spine 

• shadows of the air space - between the tongue and the roof of the mouth