week six - I/O BW radiographs, adv probing techniques Flashcards
list 5 indications of taking I/O BWs
- routine exam
- detection of caries - approximal
- monitoring caries progression
- assessment of eisting restos -recurrent caries and overhangs
- evaluation of periodontal status - incl bone height and calculus detection
describe five ideal outcomes for BWs
- adequate image quality - no artefacts
- 2mm of root apical to CEJ must be visible
- minimal crown overlapping
- centered occ plane and no overlapping interproximal areas
- may be minor faults but still clinically acceptable and of diagnostic quality
describe the film positioning of BWs
- horizontal for posterior BW
- vertical for anterior BW
- bite platform positioned on middle of film and parallel to upper/lower film edges
- post. teeth + film should be in contact or as close tgt as possible
- in vert plane = 5-8 degrees w xray tube head to ensure adequate vertical angulation [minimises overlap of opposing cusps onto occlusal surface , helps detect caries at DEJ
- in horz plane = xray tube head should be aimed so beam meets film at right angles and passes through contact areas
outline THREE advantages and disadvantages of BWs
adv
- simple/inexpensive
- tab/foam = disposable and holders = autoclavable/disposable
- using holder decreases chance of cone cutting, and enable technique replication
disadv
- tongue can displace film
- holders usually not suitable for children
- positioning can be uncomfortable
define radiation doses:
exposure
absorbed dose
equivalent dose
effective dose
exposure = measure of radiation quantity [capacity of radiation to ionise air]
absorbed dose [Gv] =measure of energy absorbed by any type of ionising radiation per unit of mass of any type of matter
equivalent dose = used to compare biological effects of diff types of radiation on tissue/organ
effective dose = used to estimate risk in human
describe the linear non-threshold [LNT] hypothesis
in this hypothesis = no threshold or safe dose of radiation –> with every exposure = risk of cancer ^
- linear relationship between eadiation dose and risk of inducing a new cancer
define scatter radiation and distinguish the THREE types
scatter radiation = occ when radiation beam hits an object –> some rays come apart and bounce of the substance [eg walls, tissue, equipment]
- the pt creates the most scatter radiation
types
1. backscatter
- created by remnant radiation that exists in pt body and bounces off the film –> heading back toward xray tube
- side scatter
- created by objects in room [chairs, tables etc] - scatter radiation
- xray directly bouncing off pt body
describe the lethal and sublethal effects of radiation
lethal = direct cell death
- resulting from high/large radiation dosage
- eg mucositis assoc w radiation tx for head/neck cancer
sublethal = damage to cells that result in mutation or cancer formation
- frequency of effect proportional to dose [LNT hypothesis]
- radiosensitive structuresin head/neck = thyroid glands, salivary glands, bone marrow and brain
- cells can repair in most situations [low radiation amt and sufficient time between exposures]
define the ALARA principle
as low as reasonably achievable
- lowest dose that will accomplish diagnostic task
- responsibility of clinician to assure that each exposure is justified
considerations
1. justify clinical need for exam
2. selection of most approriate method of exam [eg BW vs OPG]
3. optimising radigraphic tehcniques [eg film holders]
4. use of optimal film or electronic image processing techniques
outline THREE factors of protection during radiation therapy and considerations for the operator and patient
- time
- minimise time exposed to radiation
- use of digital techniques
- gigicounter to detect exposure - distance
- clinician at least 2m away from xray tube head - behind shielding or wall of adequate thickness - shielding
- eg thyroid collars, lead apron
- depends on radiation eg digital v conventional
considerations
- operator must be able to observe pt during all radiographic process
- neither operator or fam mem must hold pt during radiographic exposure - if needed to assist = must be > 18 yo, not pregnant, wear protective apron and positioned to avoid primary xray beam
outline the film sizes
0 = children w prim dentition
1 = mixed dentition + ant view of adult dentition
2 = both vert + horz positions
3 = longer verson of 2 - used for interproximal BWs
4 = occlusal film
outline how the gingival margin is documented and how it relates to calculating the CAL
0 = margin at normal lvl
[-] negative number = margin significantly covers CEJ
[+] positive number = gingival recession
CAL calc using gingival margin lvl readings + probind depth reading
- if ging.margin = 0 –> CAL and probing depth = same
- if ging.margin [-] above CEJ –> CAL = subtract ging.marg reading from probing depth
- if ging.margin [+] recessed –> CAL = add ging.marg reading to probing depth
