Tooth anatomy Supporting structures Anatomical landmarks Normal Interdental Septa Prichard’s Criteria Other Diagnostic Criterias

Teeth are composed primarily of dentin, with an enamel cap over the coronal portion and a thin layer of cementum over the root surface.

Radiographic Appearance of Enamel ENAMEL appears more radio-opaque than other

tissues.It is 90% mineral ;causes greater attenuation of X-ray photons.

enamel

75% mineral content ;less radiopaque than enamel. Radiopacity similar to bone.

DENTINO ENAMEL JUNCTION appears as a distinctinterface separating these two structures.

Dentin DEJ

50%mineral content and it appears as a very thin layer on the root surface.

It is usually not so apparent radiographically.

CERVICAL BURNOUT

Radiographs sometimes show diffuse radiolucent areas with ill defined borders present on the mesial or distal aspects of the teeth in the cervical region.

These regions appear between the edge of the enamel cap and the crest of the alveolar ridge.

Normal configuration of the affected teeth, results in decreased X-ray absorption in the areas in question.

Perception of these areas is due to contrast with the adjacent ,relatively radiopaque enamel and alveolar –bone.

It should not be confused with root caries which has similar appearance.

It is composed of soft tissues so it appears radiolucent.

Pulp chambers and root canals extend from the interiors of the chamber till the root apices.

It is seen radiographically also as apical foramen.

In some cases, it may exit on the side of the canal.

Lateral canals may end at the apex as a discernible foramen or may exit at the side of the root.

The pulp canals of a developing tooth root diverge and walls of the root taper to a knife edge.

A radiolucent area is seen surrounding it in the trabecular bone. It is surrounded by the hyperostotic bone.

IT IS THE DENTAL PAPILLA WITH ITS BONY CRYPT.

Its radiographic evaluation helps in determining the stage of maturation of the developing tooth.

PULP

Periodontal ligament space

Lamina dura

Alveolar crest

Trabecular bone

It is composed of collagen so appears as a radiolucent space between the root and lamina dura.

It is thinner in the middle of the root and slightly wider near the alveolar crest and the apex ,suggesting that the fulcrum of the physiologic movements is in the region where PDL is thinnest. (hour glass)

It is a thin radiopaque layer of dense bone surrounding the tooth socket.

Its radiographic appearance is due to attenuation of the X-ray beam as it passes tangentially through the thickness of the bone.

It is thicker than the surrounding trabecular bone and thickness increases with increase in amount of occlusal stress.

It is the radiopaque gingival margin of the alveolar process which surrounds the teeth.

It is considered normal if it is 1.5mm or less from the CEJ.

It shows apical recession with the age or periodontal disease.

Also called as the trabecular bone or the spongiosa.

Lies between the cortical plates in both the jaws. It is composed of thin radiopaque plates and rods

surrounding many small radiolucent pockets of marrow.

In posterior maxilla, it is similar to anterior maxilla but marrow spaces are larger.

ANATOMIC LANDMARKS OF MAXILLA

Intermaxillary suture

Anterior nasal spine

Nasal fossa and Nasal septum

Incisive foramen

Superior foramina of nasopalatine canal

Lateral fossa

Nose

Nasolacrimal canal

Maxillary sinus

Zygoma & zygomatic process of maxilla

Nasolabial fold

Pterygoid plates

Also called as median suture. In IOPAR, it appears as a thin radiolucent line in the

midline between the two portions of premaxilla. It extends from the alveolar crest between the

central incisors superiorly through the anterior nasal spine and continues posteriorly between the maxillary palatine process to the posterior aspect of the hard palate.

Mostly seen on IOPAR of maxillary central incisors. Located in midline1.5-2cm above the alveolar crest. It is radiopaque and usually V-shaped.

The nasal cavity shows the hazy shadow of the inferior nasal conchae extending from the right and left lateral walls

Floor of Nasal Fossa

Nasal Septum

Also called as NASOPALATINE or ANTERIOR PALATINE FORAMEN.

It is the oral terminatus of the nasopalatine canal. It transmits the nasopalatine vessels and nerves. Lies in the midline of palate behind the central incisors

at the junction of the median palatine and incisive sutures.

Radiographic image variability is due to:

1.Different angles of the X-ray beam.

2.Variability in its anatomic size.

IT IS FREQUENTLY THE POTENTIAL SITE

OF CYST FORMATION.

The nasopalatine canal originates at two foramina in floor of the nasal cavity.

Radiographically, it can be recognized as two radiolucent areas above the apices of the central incisors in floor of the nasal cavity near its anterior border and both the sides of the septum.

Lateral wall of nasopalatine canalSuperior

foramina

Also called as INCISIVE FOSSA. Appears as depression in the maxilla near

the apex of the lateral incisor . Appears diffusely radiolucent in the IOPA.

The nasal and maxillary bones form the nasolacrimal canal.

It runs from the medial aspect of the antero inferior border of the orbit inferiorly, to drain under the inferior conchae into the nasal cavity.

The soft tissue of the nose is frequently seen in the projections of the maxillary central and lateral incisors ,superimposed over the roots of these teeth.

Image appears uniformly opaque with a sharp border.

An oblique line demarcating a region thatappears to be covered by a slight radio

opacityfrequently traverses periapical

radiographs ofthe premolar region.

MAXILLARY SINUS is an air containing cavity lined by mucous membrane.

Appears as the three sided pyramid .Base -formed by mesial wall adjacent

to nasal cavity.Apex –extending laterally into the

zygomatic process of maxilla.

On the IOPAR, maxillary sinus appears as a thin delicate radiopaque line.

It extends from the distal aspect of the canine to the posterior wall of the maxilla above the tuberosity.

Around the age of puberty, its floor coincides with the floor of the nasal cavity.

In response to the loss of function (associated with loss of posterior teeth) the sinus may expand further into the alveolar bone , occasionally extending to the alveolar ridge.

Thin radiolucent lines of the uniform width are found within the image of the maxillary sinus.

These are shadows of the neuro -vascular canals that accommodate the posterior superior vessels and nerves.

The zygomatic process of the maxilla is an extension of the lateral maxillary surface that arises in the region of the apices of the first and the second molars and serves as the articulation for the zygomatic bone.

Appears as a U-shaped radiopaque line with rounded ends projected in the apical region of the first and second molars.

The medial and lateral pterygoid plates lie immediately posterior to the tuberosity of maxilla.

They cast a single radiopaque shadow without any

evidence of trabeculation.

Extending inferiorly from the medial pterygoid plate, the hamular process may be seen.

Symphysis Genial tubercles Lingual foramen Mental ridge Mental fossa Mental foramen Mandibular canal Nutrient canals Mylohyoid ridge Submandibular gland fossa External oblique ridge Inferior border of mandible Coronoid process

The region of mandibular symphysis in infants demonstrate a radiolucent line through the midline of the jaw between the images of the forming deciduous central incisors.

The suture usually fuses by the end of 1st year of life and is no longer radiographically apparent.

These are tiny bumps of bone that serve as attachment for the genioglossus and geniohyoid muscles.

Present on lingual side.

On IOPAR, appears as ring shaped radiopacity below the apices of mandibular incisors.

It is a hole or tiny opening located on the internal surface of mandible and surrounded by the genial tubercles.

Radiographically, appears as a radiolucent dot inferior to the apices of the mandibular incisors.

It is a linear prominence of cortical bone located on the external surface extending from the premolar region to the midline and slopes upward.

Radiographically, appears as a radiopaque band that extends from the premolar region to the incisor region.

Located above the mental ridge.

On peri apical radiograph, appears as a radiolucent area above the mental ridge.

Located on the external surface of the mandible as an opening in the region of the mandibular premolars.

Mental nerves and blood vessels exit through it.

Radiogarphically, it appears as a small ovoid radiolucent area located below the apices of the premolars.

Tube like passage extending from the mandibular foramen to the mental foramen and contains inf.alv. Nerves and blood vessels.

Appears as a radiolucent band outlined by two radiopaque lines of cortical plate.

Nutrient canals are tube like passage-ways through bone that contains nerves and blood vessels that supply the teeth.

Radiographically seen as vertical radiolucent lines.

More prominent in anterior mandible where bone is thin.

Linear prominence of bone located on the internal surface of mandible.

Extends from the molar region downward and forward towards the lower border of mandibular symphysis.

On IOPAR, appears as radiopaque band extending downward from molars.

Linear prominence of bone located on external surface of mandible extending downwards and is a continuation of anterior border of ramus.

It appears as a radiopaque band extending downwards and forwards from ant. border of mandible & ends in 3rd molar region.

Depressed area of bone located on the internal surface of mandible.

Submandibular salivary gland lies in this fossa.

It appears as a radiolucent area in the molar region below the mylohyoid ridge.

Linear prominence of bone located on internal surface of mandible extending downwards and forwards from ramus.

It appears as a radiopaque band extending downwards from ramus and forward from coronoid process, in a horizontal position, stop at the third molar area or become cotinuous with the mylohyoid line.Its placed below the external Oblique ridge.

Occasionally, seen as a dense broad radiopaque band of bone.

It is a marked prominence of bone on the ant. ramus of the mandible.

Not seen on a mandibular IOPAR but appears on a maxillary molars IOPAR.

It is seen as a triangular radiopacity superimposed over or inferior to maxillary tuberosity.

Vary in their radiographic appearance. Depend primarily on their thickness,

density and atomic number. A variety of restorative materials may be

recognized on intra oral radiographs. RO- silver amalgam,gold crown &

inlay,stainless steel pins,GP cones,silver points,composites,orthodontic appliances.

CaOH- RL but mostly RO RL- mainly silicates. 

Radiographic evaluation of bone changes in periodontal disease is based mainly on the appearance of the interdental septa because the ralatively dense root structure obscures the facial and lingual bony plates.

The IDS normally presents a thin,radiopaque border adjacent to PDL and at the alveolar crest known an LAMINA DURA.

It appears radiographically as continous white line,but is relatively perforated by numerous small foramina and traversed by blood vessel,lymphatic and nerve.

Because LD represents the bone surface lining the tooth socket,the shape and position of root and changes in the angulation of the X-ray beam produce considerable variation in its appearance.

Variations in technique produce artifacts that limit the diagnostic value of the RG.

Bone level Pattern of bone destruction Width of PDL space Radiodensity Trabecular pattern Marginal contour of IDS

Long cone paralleling technique : projects most realistic image of the level of the alveolar bone.

Bisecting angle technique : increase the projection and make the bone margin appear closer to the crown.

Shifting the cone mesially or distally without changing horizontal plane projects the X-ray obliquely and changes the :

a)Shape of interdental bone on RGb)RG width of PDL spacec) Appearance of LDd)It also distorts the extent of furcation

involvement.

Prichard established following 4 criterias to determine adequate angulation of PA RG:

i. The RG should show the tips of molar cusps with little or none of the occlusal surface showing

ii. Enamel caps and pulp chambers should be distinct

iii.Interproximal spaces should be open iv.Proximal contacts should not overlap

unless teeth are out of line anatomically.

An additional IO projection that can be used for evaluation of alveolar crest is the bitewing projection

For bitewing the film is placed behind the crowns of upper and lower teeth parallel to long axis of teeth

The X-ray beam is directed through contact area of teeth and perpendicular to film

Thus projection geometry of bitewing allows the evaluation of the relationship between interproximal alveolar crest and CEJ without distortion

If bone loss is severe and bone level cannot be visualised on regular bitewing ; film can be placed vertically to cover larger areas of jaw.

Enamel caps and pulp chamber distinct

Tip of molar cusp seen with little or no occlusal surface

Open interproximal spaces

Interproximal areas should not overlap

Radiopaque horizontal line across the roots:this line demarcates the portion of root

where labaial or lingual bony plate has been partially or completely destroyed from the remaining bone supported portion.

Vessel canals in alveolar bone : HIRSCHFELD described linear and circular

radiolucent areas produced by interdental canals and their foramina. The RG image of canals is often so prominent in mandibular anterior region that they might be confused with radiolucency resulting from periodontal disease.

Differentiation between treated and untreated periodontal disease:

Its sometimes necessary to determine whether the reduced bone level is the result of periodontal disease that is no longer destructive or whether destructive periodontal disease is present .

The RG is an indirect method for determinig the amount of bone loss in periodontal disease; it shows the amount of bone remaining rather than the amount of bone lost and it does not reveal minor destructive changes in bone . Therefore ,slight RG changes in periodontal tissues mean that disease has progressed beyond its earliest stages.

Clinical periodontology – Carranzas 10th edition.

Oral radiology – principles and interpretations : White and Pharoah 6th edition.

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