radiology

2 types of extra oral radiographic images

• OPG (orthopantomogram)

• lateral cephalometric radiogram (for ortho)

what is an OPG?

• panoramic image of lower face, displaying all upper and lower teeth

• reveals maxilla, mandible and TMJ

• no. position and growth of mixed dentition (monitor eruption pattern)

why would you take an OPG?

• general screening

• can reveal pathological tumours and cysts

• can assess status of wisdom teeth, sinus, TMJ articulation

what is a lat ceph radiograph?

• shows pt profile

• standardised, reproducible radiograph used for ortho diagnosis and tx planning

advantage of extraoral radiographs

• simple to take and has value when explaining tx to patients

• accuracy, sensitivity and specificity of images is generally inferior in imaging of dental diseases

indications for OPG

• impacted wisdom teeth diagnosis and tx

• perio bone loss + periapical involvement

• dental pain source

• dental implant assessment

• ortho assessment

• developmental anomalies diagnosis

• benign/malignant jaw lesions

• TMJ dysfunction/ankylosis (arthritis, inflamm, bone resorp)

• salivary stones

selection criteria for OPG

• pt new to practice/no comp exam done (generalised screeening)

• ortho tx assist

• prior to oral surgery

• after facial trauma

• pathology/post op bony healing follow up

• TMJ dysfunction investigation

radiographic lesions of the jaw

• inflammatory lesions (periapical lesions)

• odontogenic cysts

• radicular/residual cysts

• nasopalatine cyst

• nasolabial cyst (soft tissue lesion)

types of images on panoramic

SINGLE REAL IMAGE

• only one image results from a given anatomical structure

DOUBLE REAL IMAGE

• produced by structures located in midline (hard and soft palate, hyoid bone, cervical spine)

GHOST IMAGE

• dense objects between tube head and rotation centre (eg earrings, mandible, glasses)

advantage of panoramic images

• broad coverage of facial bones and teeth

• low pt radio dose

• convenience of exam for pt

• can be used if you cant open mouth/opening is restricted

• less time needed

• for education and case presentation

what are some uses of CBCT scans?

• orthodontics

• complex tx planning

• trauma and sinus airway imaging

• implants

• endo

• facial reconstruction

CBCT and implants

• plans posterior implant with long axis and resto space

• measurement to plan sinus augmentation using 1:1 ratio

CBCT and endo/perio

• can see where endo needs to be done

• or fractures (more detail than OPG)

CBCT and oral and maxillofacial surgery

• artefact is low in CBCT (good thing)

• high artefact in normal CT w metal (beam hardening - flares up and you can’t see what it is)

what is an artefact?

anything that can impact the quality of the study

CBCT and cone beam reconstructions

• shows differences in density

what is effective dose?

• measured in Sieverts (Sv)

• allows doses from different investigations of different body parts to be compared by converting all doses to an equivalent whole body dose

• anyone under 40 yrs gets covered (especially for gonads and thyroid and eyes)

give details about multislice detector CT

DENTASCAN similarities

• provides 3D imaging of anatomy

• axial/coronal/sagittal/parasagittal and panoseries

• raw data DICOM

differences

• higher radiation dose

• fan shaped detector array

• pt supine

why should you do a cone beam as opposed to an OPG?

• lower dose of radiation, more info (eg parasagittal, panoseries, 3D)

does the pt have to stand for the CBCT exam? if you can’t stand, then what?

• yes

• if you can’t, improvise!

• eg stack chairs

what is the break glass code?

• pt ID