Use of light cure in dentistry Flashcards
discuss materials that require light curing in density
name different types of phot activated dental materials
describe the composite chemistry and photo polymerisation process
- composite is made out of resin and coupling agent, glass and photoiniator
- apply light at certain wavelength- the photoinaitor gets activated and absorbs light
- free radicals bring components together
- get fully polymerised state
- don’t want it to break and want ti to full potential
- prevents it from staining and leaching out from chemicals
- resin composite materials are hardened in situ by the process and procedures of phot polymerisation or photo curing
what are the consequences of incomplete polymerisation
- creme brûlée effect
- reduction in mechanical properties resulting in marginal breakdown, increased wear and decreased strength, fractures and staining
- increased elution of non reacted monomers
- ultimately affecting long term longevity
- don’t want soggy bottom
composites are toxic when not cured - safe to use when fully cured
-last minimum 7 years - recurrent caires
- fractures or leakage
describe the evolution of light curing units in dentistry
- discoloured quickly
- introduce light activated materials
- started with a UV light
- Halogen lights lasts couple hours
- 2nd gen battery lasts longer
describe the spectral wavelength requirements of resin based materials in dentistry?
- photoiniators
- makes campsites
- camphor-quinone- makes it Leith activated and brings everything together
- light needs to be at 470nm
- limited to add camphor-quinone due to aesthetics
- absorb a lot more light
- more active photoinaitors, curing will be quicker
name two photoiniators and their wavelengths
- CQ- 470nm
- PPD - 390-410nm
what are the materials wavelength requirements?
- majority of light cured dental materials contain CQ as a photoiniator
- some contain alternative photo inaction requiring a polywave LED light
- Bulk fill - STR require POLYWAVE
- normal CQ
flowable
resin based cements - some more bleached shade materials contains traces of Lucinrin -TPO ignitor
- this bulk fill composite material is example where different photo ignitors are used requiring a poly wave LED light
describe second and third generation LED lights
what light factors affect curing process
- wavelength, irradiance, homogeneity, effective tip size
what are clinical factors affecting curing process
- distance (further the less powerful the light)
- handling technique
- damage contamination
- protective sleeves, restoration size, matrix bands
how long do we cure composites
20 seconds
why do we cure composites for 20 seconds?
- energy requirement to cure 2mm composite increment is 16 J/cm2
- energy = irradiance x times
therefore to cure composite increment in 20 seconds, a minimum irradiance of 800 mW/cm2 is required from the light source - mot manufactures states 500m W/cm is the minimum required irradiance
how can we check irradiance of light?
- integrating sphere
- commercial dental radiometers
- check MARK resin calibrator
what is beam light homogeneity?
- some beams can be narrow or flared out
- how much energy is coming out from light
- not homogenous
- ## big filling and whole tip is hot and powerful but looking at that maps its only the centre part
what does a contaminated, chipped or damage of fibreotpic tip do?
contaminated- blocks beam
internal damaged tip need to cure over 1 minute
how do we decide which light to go for?
- reputable company
- check the irradiance ideally above 1000mW/cm^2
- investigate beam homogeneity
- investigate the light irradiance with distance
- select an appropriately sized tip with fibre optic bundle
- match your material and light
Ask the questions and do your research!
what are wavelength requirement fir bleached shade materials and different photinaitors
describe the homogeneity of beam and how it effects light curing of large restorations
what is avaega distance form cusp tip to depth of cavity box
6mm which decreases irradiance by 22%
