Photocuring 2 lots of copypasta sorry

olola's version from 2016-12-11 22:15


Question Answer
factors affecting the extent of cure in a light activated resinThickness of overlying material**, Intensity of curing source, Duration of exposure, Shade of material, Filler type, Distance of light-tip to tooth
optimal clinical curing parametersminimum of 300 mW/cm^2 for 40-60 sec in 2mm increments
what is the most influential factor to resin polymerizationoverlying restorative material thickness (NO MORE THAN 2MM)
optimal distance of light-tip to toothif intensity is 400mW/cm^2- up to 4mm; if intensity is 600mW/cm^2- up to 6mm away
describe the effect shade of material has on extent of cureNo difference b/t shades Universal to Gray; but you have to increase exposure duration for "remarkably darker" shades
Disadvantages of chemical curemust manually mix by hand incorporating air and voids (results in poor clinical stability, internal flaws), setting time not under clinician control, slow setting rx time (wasted chairside time), short shelf life of benzoyl peroxide, still have oxygen inhibited layer
Advantages of chemical curevoids may actually LOWER polymerization shrinkage and stress buildup, slow setting rx time lowers strain at tooth/filling margin b/c the material is permitted to flow, tends to shrink toward its center of mass, fairly uniform cure, can place in bulk and not worry about low cure at innermost portions, can incrementally cure to itself and to light-cured resins
advantages of photo curedone paste no need to mix, fewer voids, greater color stability, greater strength, less wasted material, longer shelf life (components less thermally labile), command cure, less chairside time
describe direction of shrinkage of light cured materialsif placed in a thin layer where is no gradient of cure- NO directed shrinkage (no need to cure from lingual for facial veneers); if placed where there is a gradient in cure- pulling toward the curing source only if the bond b/t restoration and tooth fails. if this bond remains intact, the curing vectors are directed towards the restoration periphery
Clinical implications of shrinkage in light-cured materialsdirected shrinkage can be used to help minimize marginal openings b/t restoration and cavosurface margin: gingival margin class II by using light-transmitting wedges, curing from facial first when inserting a class III from lingual. Important to remember that composite will NOT always be drawn toward the direction of light source placement
describe the effect Filler type has on extent of curelight scattering in microfilled composites tends to DECREASE PENETRATION- but has little affect if you use proper intensity, overlay thickness, and duration of exposure
disadvantages of photo curedfaster rate of cure may present clinical problems- doesn't permit the material to flow, greater chance for building up high stresses at the tooth/resin interface, resulting in tooth sensitivity from biting and pain, attentuation of light intensity through the restoration
state the potential for developing marginal stresses when curing via Ramped photocureThis slow cure is thoug ht to minimize tooth/margin stresses by delaying the time at which the Tq occurs into the exposure cycle. Then, later in the curing cycle, the intensity is purposefully increased to a high level to complete the curing process.
state the potential for developing marginal stresses when curing via High-intensity curing (Pulse-delay technique)~In this method, conventional curing methods are used to place 2 mm increments. The pulse exposure is used ONLY for the last 2 mm increment. This technique involves the application of only a 3 second exposure at 200 mW/cm 2 . The clinician then waits 3 to 5 minutes before delivering the final exposure of 10 seconds at 600 mW/cm 2 . During this waiting time, the top surface is said to be hard enough so that contouring, finishing, and polishing can be accomplished prior to the fi nal exposure. Claims of significantly enhanced marginal adaptation are made at the enamel/restoration surface by using this technique compared to the use of conventional exposure methods as well as those of high output devices: lasers and plasma arc units
state the potential for developing marginal stresses when curing via chemical cure, conventional photo cure,The faster radicals are formed, the quicker the monomers are used up to form polymer, the faster curing shrinkage occurs, and the sooner the Tq is reached. If shrinkage is not allowed to occur slowly, then stress is developed between the tooth and the resin material will be very great, sufficient to break the bond and form a gap. If the rate of cure is slowed, and the Tq is delayed, then polymerization stresses can be dissipated by pulling restorative material inward from the unbonded surface. This method greatly reduces tooth/restorative material stresses and enhancesmarginal integrity. Self-curing composites are now advocated by some manufacturers for use as the first incremental layer when placing Class II composites. Enhanced marginal integrity is obtained at the gingival margin. Although laser curing and plasma - arc light curing have proven to be extremely fast, it is common to see marginal gaps under restorations resulting from the high stresses involved with this mode of polymerization.
influence of rate of polymerization on the potential for stress buildup and marginal gap formation b/t tooth and restoration

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