dental radiography Flashcards
what are the 3 parts/sections of a tooth
crown
neck
root
describe the structure of a tooth (what makes up a tooth going from exterior to interior)
- enamel
- dentin (underneath enamel)
- pulp cavity (centre of tooth)
- root canals (going from pulp cavity down into gum)
- cementum ( calcified connective tissue covering the outer surface of the root of the tooth and provides a medium for insertion of periodontal ligament fibers)
- nerve and blood vessels (through the bony part of jaw)
which junction of the tooth is found at the neck of the tooth
cementoenamel junction
what alveolar process is found by the tooth of the upper canine and the tooth of the lower pre molar
- near upper canine = maxillary alveolar process
- near lower premolar = mandibular alveolar process
what is an alveolar process
the thickened ridge of bone that contains the tooth sockets on bones that bear teeth
what are the 4 different type of teeth
- incisors
- canines
- pre molars
- molars
how many teeth do children have compared to adults on a singular jaw
kids = 10
adults = 16 (including wisdom)
what are milk teeth also known as
deciduous
what is the most common form of dental notation
palmer dental notation
besides the palmer dental notation, what are 2 other forms of dental notation
- FDI world dental notation
- universal numbering system
what are the 4 dental orientations
- buccal (towards cheeks)
- lingual (towards tongue)
- mesial (towards midline)
- distal (away from midline)
what are the 2 categories of teeth used by dentists
- incisal (incisors +canine)
- occlusal (pre molars +molars)
what are the 4 common positioning planes used in dental radiography
- Frankfort plane
- ala-tragus plane
- midsaggital line
- inter pupillary line
what is the Frankfort plane
horizontal line going from the lower orbital margin across to the EAM/ tragus
what is the ala-tragus plane
diagonal line going from the ala of the nose (bottom side of nose) across through the tragus/EAM of ear
what is the posterior occlusal plane
parallel to the ala-tragus plane, passes through where the upper and low teeth meet, through the mandible backwards
what is the auricle of the ear
outer ear
what is the supraorbital groove
a small groove at superior and medial margin of the orbit in the frontal bone
what is the superciliary ridge
a ridge on the frontal bone above the eye socket.
(eyebrow bone)
what 2 ways can the intra-oral dental xray be mounted on
- the ceiling
- the wall
what are the 3 EXTRA-oral dental xray machines
- OPG (orthopantomagram)
- OPG + lateral cephalogram
- cone beam CT
why should the xray tube be parallel to the metal arm and locator ring of a dental imaging machine
to ensure that the dental receptor is in the middle of the image
digital dental receptor plates are reusable following aseptic technique
state the 6 layers of the digital dental receptor places (back to front)
- back housing + cable
- electronic substrate
- CMOS imaging chip
- fibre-optic face plate
- scintillator screen
- front housing
what are the 3 intra oral dental projections
- peri-apical
- bite wing
- occlusal
what are the 4 main reasons why dental radiographs are taken
- visualisation of hidden caries (dental decay)
- check unerupted teeth + position of emerging wisdom teeth
- bony changes that cant be seen on visual examination
- plan orthodontic treatment
what is a peri-apical xray
shows your entire tooth, from the crown to the root tip
- 1 or 2 teeth screened at a time
why might you take a periodical xray
- detect apical inflammation/ infection
- periodontal problems
- trauma fractures
- post or pre apical surgery
- evaluation of implants
why is the intra-oral parallel technique best to sue
- increased accuracy due to minimal dimensional/geometric distortion (as the beam is parallel to the locator ring, and the film is parallel to the teeth)
- simple to use
- easy to duplicate
the paralleling technique when performed correctly is superior to the bisecting angle technique by producing an image with both linear and dimensional accuracy
when would an intra-oral bisecting angle technique be used
- if the patient has a shallow palette and the xray film cannot get behind the tooth parallel
- when parallel technique is impossible
how do u position a intra-oral bisecting angle technique
- flim is placed as close to the teeth as possible (usually is at an angle)
- imaginary angle formed from the angulation of the back of the tooth and the long axis of the tooth
- the xray tube is angled so it is perpendicular between the imaginary angle formed
what is the difference between the holding of the film for the bisecting and parallel technique
- bisecting technique, patient holds the film behind tooth
- parallel technique, film holder mandatory holds behind tooth
what is the bite wing xray
small tabs upon which a patient bites to hold the x-ray film or sensor in place
why would you take a bitewing xray
- show dental caries between teeth not visible during oral examination
- show recurrent caries under existing restorations
- detect changes to jawbone caused by gum disease
what does the bitewing xray allow a clear projection of
- depicts maxillary and mandibular crowns of teeth
- providing clear image on inter proximal surfaces of teeth and detection of inter proximal caries
what is an occlusal xray
- not primarily taken, supplement for unsatisfactory panoramic radiograph
- occlusal plane parallel to floor
- tube above patient angled 65-70 degree down through nose into mouth
- IR placed flat in mouth (barrier wrapped) and bitten gently (horizontally in adults, vertically in kids)
- thyroid Shield supported below face by patient
why would you take an occlusal xray
- show roof or floor of mouth
- find extra teeth
- show unerupted teeth
- demonstrate jaw fractures
- identify cleft palate, system, accesses or growths
what is a cleft palate
a congenital split in the roof of the mouth.
how is a standard lower occlusal projection taken
- receptor placed in mouth flat, in the occlusal plane
- patient seated with head tilted back in head rest
- central ray directed perpendicular to the receptor in the midline, 3cm below chin
what is an orthopantomogram / OPG
- most common extra oral scan
- panoramic single image radiograph of the mandible, maxilla and teeth
reasons for taking an orthopantomogram?
- general dental evaluation
- trauma assessment for fractures
- infection evaluation
- assessment of wisdom teeth
how do you position a patient for an orthopantomogram
- patient sits or stands with the Frankfort plane horizontal
- patient bites block so incisors are in correct position
- tongue pressed to roof of mouth
- lips closed
- machine rotates around head for 10-15 seconds
reasons for taking a lateral cephalogram?
- orthodontic diagnosis of malocclusion (teeth not aligned properly)
- treatment planning and progression
why is cephalometric radiography a standardised and reproducible form of skull radiography
- it is used to assess relationship of teeth to jaw and jaws to rest of facial skeleton
how do you position a patient for a lateral cephalogram
- patient sits or stands
- Frankfort plane is horizontal
- inter pupillary line parallel to floor
- midsagittal line is perpendicular to IR
- head positions placed in EAM
- measurement ruler placed over naison/nasal bone
- aluminium filter placed over soft tissue of face
lateral cephlametry can show maxillary or mandibular recursion (under and over bite)
what is the cone beam CT
- uses xray and computer processed xray info to make 3D cross-sectional images of jaws and teeth
- moves around head in circular motion
reasons for performing cone beam CT
- visualisation of bone structure
- tooth structure and orientation
- localising pathology
- assessment of nerve canals
- assessment and treatment of dental trauma
- planning for dental implants
- TMJ diagnosis
- locate pain source not detected on 2D scans
how is the cone beam CT adapted to have lower radiation dosage
- using cone shaped beam, the radiation dose is lower and the time needed for scanner is reduced
why is cone beam CT scans superior to other extra-oral scans
- provides anatomical accuracy fo diagnosis, treatment planning, surgical execution and followup for implant procedures
- high resolution
which 3 equipment rotates around the patients head during xray
OPG
CBCT
occlusal
During an OPG, why is it important for the patients to close their lips and press their tongue against the roof of their mouth
- reduced air shadow that can be mistaken for caries where it overlies the dentition in the premolar region
which plane/line during an OPG should be parallel to the floor?
as a result of that, which plane is now 5 degrees caudally angled
- Frankfort line
if the Frankfort line is parallel to the floor, the ala-tragus line would now be 5 degrees caudal
where should the anterior-posterior light be entered on an orthopantomogram
distal to the upper lateral incisor (canine inter proximal space)
