curing tech- aditi

8/10/2019 Curing Tech- Aditi

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Curing techniques


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INTRODUCTION

Historically, dentists haverestored teeth by usingconventional curing lights to curelayers of composites, typically attime intervals of 40 seconds per

layer.

Over the past few years, theindustry has focused on reducingthe resin curing time by usingstronger curing lights or altering

resin composition.

The goal is to achieverestorations more quickly.

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Curing of dental composites with

blue light was introduced in the

1970s. The source of blue light isnormally a halogen bulb with a filterwhich produces blue light in therange of 410 nm 500 nm of thevisible spectrum.

Although halogen bulb based lightcuring units are most commonlyused to cure dental composites butrecent development in curing lighttechnology has shaken the

compliance of many practitionersand brought to light the aspects ofthe polymerization process whichwere either ignored or not realized.

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One of the major problems with resin compositerestorations is the effect of polymerization shrinkageand the resulting stress at the interface betweenrestoration and tooth tissue.

This leads to poor marginal seal, marginal staining andrecurrent caries.

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Composite polymerization canbe divided into PRE ANDPOST GEL PHASES.

In the pre-gel phase, thereactive species presentenough mobility to rearrangeand compensate for thevolumetric shrinkage withoutgenerating significant amountof internal and interfacialstresses.

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Pre-gel Phase

No Stress, No Translation(Compensation from Free Surface)


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In the post gel phase

When the degree ofconversion approaches 10-20%, the network is extensiveenough to create a gel.

As a consequence, thecontinued polymerization isassociated with elasticmodulus development, stressgeneration within the material,at the tooth/restorationinterface and in the toothstructure.

Beyong the gel point,

polymerization shrinkagecreates strain on the networkand the attachment area to thebonding system.

This facilitates gap formation,affecting the longitivity of therestoration.

Post-gel Phase

DistortionIf bond strength exceeds stress

Gap FormationIf stress exceeds bond strength


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To reduce the shrinkage and thefollowing stress, different kinds ofcuring modes have beenproposed.

A review of standard visible light-curing techniques helps to lay thegroundwork for understandingwhere each type of curing unit fitsinto a dentist's armamentarium.

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Continuous curing techniques

The continuous cure refers to a light cure sequence inwhich the light is on continuously.

There are four types of continuous curing:Uniform continuous cureStep cureRamp cure

High energy pulse

Continuous curing is conducted with halogen, arc, andlaser lamps.

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Uniform continuous cure

In the uniformcontinuous curetechnique, a light of

constant intensity isapplied to acomposite for aspecific period of

time.

This is the mostfamiliar method ofcuring currently used.

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Step cure

In the step curetechnique, thecomposite is first

cured at low energy,then stepped up tohigh energy, each fora set duration.

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The approach allows

for a slow initial rate ofpolymerization and ahigh initial level ofstress relaxation duringthe early stages, and itends at the maximumintensity once the gelpoint has beenreached.

This drives the curingreaction to the highestpossible conversiononly after much of thestress has beenrelieved

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Theoretically, this practice

reduces the overallpolymerization shrinkage atthe margin of the finalrestoration.

The reduction in shrinkage,however, is small andresults in less compositepolymerization because the

lower intensity light yieldslower energy levels.

In addition, this techniqueresults in an uneven cure,

since the top layer is moresaturated with light and thusmore highly cured.

Step curing is possible onlywith halogen lamps; arclamps and lasers cannot beused because they work byapplying large amounts ofenergy over short periods oftime.

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J Can Dent Assoc 2001; 67(10):588-92

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Ramp cure Light is initially applied at low

intensity and graduallyincreased over time to highintensity.

Intensity is increased with time(30 secs) either by bringing the

light toward the tooth from adistance, curing through acusp, or using a curing lightdesigned to increase inintensity.

This sequential curing low tohigh intensity significantlyreduces polymerizationshrinkage withoutcompromising the depth of

cure.

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Ramped curing allows the light-curedmaterial to have a longer gel phase inwhich polymerization contraction stressesare dissipated more readily.

Ramp curing is an attempt to pass throughall of the different intensities in hopes ofoptimizing a composites polymerization.

Ramping consists of either stepwise,linear, or exponential modes.

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Some studies indicate rampcuring causespolymerization with longerchains, resulting in a morestable composite.

In theory, very high energyapplied over a short periodtends to causedimethacrylate monomersto attach to themselves,resulting in shorter polymerchains and a more brittlematerial with higherpolymerization shrinkageand more marginal gaps.

Ramp curing, with itsdependence on lowintensity, is possible onlywith halogen lamps; arc andlaser lamps can generateonly large, non-variableamounts of energy.

It is possible to ramp curemanually by holding aconventional curing lamp ata distance from a tooth andslowly bringing it closer toincrease intensity.

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High-energy pulse cure

Uses a brief (10 second) pulse ofextremely high energy {1000-2800 mw per cm), which is threeto six times the normal power

density. High-intensity curing allows for

shorter exposure times for agiven depth of cure.

A depth of 2 mm can be cured in10 secs with a PAC light and 5secs with an Argon laser-curinglight as compared with 40 secsby a OTH lamp.

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A high-intensity curing initiates a multitude of growth centersduring an initial irradiation period along with a final polymer withhigher cross-link density.

Because the relationship between energy density and post-gelshrinkage strain is considered to be linear, high-energy densitiesmay translate into increased stress levels but do not resultnecessarily in high degrees of conversion or superior mechanicalproperties.

Therefore, although high-intensity curing may lead to the same

conversion rate, degree of polymerization shrinkage, andmechanical properties, it likely leads to greater shrinkagestresses.

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Disadvantages:

1. Short exposure times cause accelerated rates ofcuring and insufficient time for stress relaxation.This leads to greater shrinkage stresses and apoorer interface.

2. High-intensity light curing has a narrowedwavelength range for the output. Therefore, thewavelength range of the light source must becoincident with the photoinitiator.

3. Heat is a significant problem.

4. It may not produce the same type of polymernetwork during curing.5. Using a higher intensity of light for shorter exposure

time is reported to result in more cytotoxicity than alonger curing time with lower intensity

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The influence of different light-curing modes onmicroleakage of posterior resin composites

This investigation evaluated the effect of various curing modes on the extent of microleakage of differently resin-based posterior composites.

The cavities were restored by posterior composites (Filtek P90, Filtek Z250, and Filtek P60). The compositewas placed in horizontal layers and irradiated at three modes of continuous intensities (conventional, high intensitypower, and pulse-soft start).

The Kruskal Wallis revealed high significant differences between microleakage medians of the posteriorcomposites examined ( p < 0.05).

However, no significant differences were noted between microleakage medians at different modes of curingintensities occlusally ( p = 0.076) and there were significant differences gingivally ( p = 0.015).

Mann Whitney U-test showed a significant difference in microleakage for cavities restored by Z250 between highpower and pulse modes of cure ( p = 0.006).

The highest microleakage score was identified in the cavities restored with P60, while the lowest microleakagescore was found in cavities restored by P90 specifically at conventional and pulse mode of cure.

The light intensity modes have no significant effect on the microleakage, while the difference in composition ofposterior resin composites investigated was the main factor for such a significant difference.

Journal of Adhesion Science and Technology Volume 28 , Issue 2 , 2014

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Staged Delayed Curing)

The restoration is initiallycured at low intensity tocontour and shape therestoration in occlusion,followed by a secondexposure to completely curethe restoration.

This allows substantialrelaxation of polymerizationstresses.

The longer the periodavailable for relaxation, thelower the generation ofresidual stresses.

This method also aids in thefinishing of compositerestorations a partiallycured composite materialcan be easily finished ascompared with fully curedmaterial.

By filtering the light duringan initial cure, obtaining asoft, easily finished material

is possible. Thereafter, the filter isremoved and the compositeis cured completely.

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Discontinuous curing technique

Also called as soft-cure technique.

A low intensity or soft light is used to initiate a slow polymerization

that allows a composite resin to flow from the free (unbound)restoration surface toward the (bound) tooth structure.

This reduces polymerization stress at the margins and could reduce"white line" or other marginal openings or defects.

To complete the polymerization process, the intensity of the nextcuring cycle is greatly increased, to produce the needed energy foroptimal polymerization.

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Pulse-delay cure

Proposed by Kanca andSuh.

Single pulse of light is

applied to a restoration,followed by a pause andthen by a second pulsecure of greater intensityand longer duration.

It is best thought of as aninterrupted step increase.

An initial exposure of up to 1 j/cm is considered to be mostefficient in reducing shrinkagestresses.

The lower-intensity light slowsthe rate of polymerization, whichallows shrinkage to occur untilthe material becomes rigid, andis reported to result in fewer

problems at the margins.

The second, more intense pulsebrings the composite to the finalstate of polymerization.

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Another important parameter is delay time between irradiances.

During the dark period, polymerization reaction occurs at areduced rate.

Thus, longer delays lead to a greater amount of chain relaxation.

Significant reductions in shrinkage stress and microleakage andincreased microhardness have been reported for pulse-delaymethods, with dark periods from 1 min to 5 mins.

For pulse-delay curing, the greatest reduction of polymerization

shrinkage is achieved with a delay of 3 mins to 5 mins.

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Composite depth of cure using fourpolymerization techniques

OBJECTIVE: To evaluate in vitro the effect of four light-curing techniqueson depth of cure of a composite resin.

MATERIAL AND METHODS: Four photoactivation methods wereinvestigated: stepped, ramped, pulse-delay and traditional.

RESULTS: The effect of factors studied (curing method and distancefrom the surface) and the interaction of these factors was statisticallysignificant (p


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INTERMITTENT LIGHT-CURING

The composite is polymerized during shortperiods of light-on and light-off.

Similar to the other techniques, the aim of thisapproach is to reduce the polymerization-induced stress by using light-off periods.

Alonso et al., observed improved marginaladaptation in conjunction with this method.

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TRANS ENAMEL POLYMERIZATION

TECHNIQUE / BULK FILL TECHNIQUE :

There are many methodsof placing and curingcomposite resin thatattempt to control theeffects of polymerizationshrinkage.

One of these techniquesis called trans enamelpolymerization.

Advocated by Belvedere.

Adhesive, a flowablecomposite, and acomposite resin areplaced into the tooth inbulk and thenpolymerized by curingthrough the tooth from thebuccal and lingual

through the enamel.

A final cure is thenapplied from the occlusal.

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3-SIDED LIGHT CURING TECHNIQUE / SLOWPOLYMERIZATION TECHNIQUE :

In this technique, an increment ofcomposite resin is applied at thegingival margin and cured using alight reflecting wedge.

Then an increment is used to fill thefacial two thirds of the box, which iscured from the facial.

Another increment fills the bow andis cured from the lingual.

Other increments complete theocclusal portion of the restoration.

This 3 sided light curing techniquewas evaluated by Losche.

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Extra-Oral Curing

Usually, extra-oral curing is used for the fabrication of indirectRBC (resin based composite) restorations (inlays, veneers,metal-free bridges, etc) that are processed in the laboratory.

These laboratory photocuring units (LPUs) work with variouscombinations of light, heat, pressure, and vacuum to increasethe degree of polymerization and wear resistance of RBCs.

Hardness and depth of cure of an indirect RBC can beinfluenced by the LPUs employed.

It is reported that LPUs, which provide light curing inconjunction with heat and nitrogen pressure, result in asignificant increase in hardness and tensile strength of RBCs.

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LIGHT-CURING UNITS

Various light-curing units belonging to differentgenerations are available commercially.

Usually, they are hand-held devices with a lightsource and light guide of fused optical fibers.

A curing unit with a minimal light output of 550 luxis considered appropriate for dental use

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QTH - QuartzTungstenHalogen

Curing Lights

PAC Plasma ArcCuring Lights

LED LightEmittingDiodes

Curing Light

Laser CuringLights

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Quartz Tungsten Halogen Most widely used light-curing units

Contain a quartz bulb with a tungstenfilament in a halogen environment.

The units irradiate both uv and whitelight that must be filtered to removeheat and transmit light only in theviolet-blue region of the spectrum.

They are available in continuous,step-cure, or ramp-cure modes.

QTH-curing lights work at wavelengths of400 nm to 500 nm with output rangingfrom 400 mW/cm to 800 mW/cm

Less than 0.5% of the total lightproduced in a QTH is suitable forcuring, and most is converted to heat.

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Many halogen curing lamps use a 50- to 100-

watt bulb to produce 500 mw of light that peaks

at 468 nm.

This approach yields an efficiency rate of only0.5%; the other 99.5% of the energy is simplygiven off as heat.

To minimize heating, uv and infrared band-passfilters are inserted just before the fiber opticsystem is used.

Orange filters are widely used because they arecomplementary to blue spectrum and absorbblue radiation.

A small fan is employed to dissipate unwantedheat from the filters and reflector.

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Disadvantages:

They have a slowercure time (about 15

sec to 20 sec).

The units arerelatively large and

cumbersome.

The lights (bulbs)decrease in outputwith time and thus

need frequentreplacement.

They have low-energy

performance andgenerate hightemperatures.

They require a filterand ventilating fan.

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Light-Emitting Diode Initially, low-power blue LEDs using

silicon carbide (first generationLEDs) having a power output of 7W per LED were introduced.

Blue LEDs, or second-generation

LEDs, were built on gallium nitridetechnology and had a power outputof 3 mW (400-fold increase).

The second generation LEDs areconsidered to be more effective in

curing composites than theirpredecessors.

These units are cordless, small,lightweight, and battery powered.

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A literature review suggests LED

devices and conventional QTH-curinglights have no significant differences.

LED units are considered similar orbetter compared with QTH unitsregarding the degree ofpolymerization, microleakage atenamel and dentin margins, shrinkagestrain behavior, wear rate of RBCs,

flexural properties of cured RBCs, andhardness of cured RBCs.

Also, bond strength values for dual-cure resin cements used incementation of indirect RBC

restorations is found to be equivalentfor LED- and QTH curing lights.

However, depth of curing with LED unitsis higher than QTH devices, and QTH-curing lights tend to show moreyellowing of RBCs than LEDs.

Few authors consider conventionalQTH-curing lights to be better thanLEDs.

LEDs have been shown to take longerfor complete curing of microfilled andhybrid RBCs

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Evaluation of the Influence of Three Types of Light CuringSystems On Temperature Rise, Depth of Cure and Degree of

Conversion of Three Resin Based Composites

Aim of study: The purpose of this study was to evaluate the effectof Quartz tungsten halogen, Light emitted diode & soft start lightcuring units on temperature rise, depth of cure & degree ofconversion of different types of dental composites (Spectrum,Esthet X & Z250).

Result and Conclusion:QTH light curing showed the highest temperature rise value, whilethe soft start gave the lowest values.Soft start light curing revealed the highest depth of cure values,while the QTH showed the lowest values among three curing

modes.Soft start light curing system showed the highest degree ofconversion and QTH had the lowest values.Esthet X dental composite gave the highest results of the degree ofconversion while Z250 showed the lowest values.

J Interdiscipl Med Dent Sci 2:110.

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Effectiveness of light emitting diode and halogenlight curing units for curing microhybrid and

nanocomposites

J Conserv Dent 2013;16:233-7

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Plasma Arc Plasma-arc curing (PAC) lights are high-

intensity light curing units.

Used for pulse energy curing

They have more intense light sources(fluorescent bulb-containing plasma), allowingfor shorter exposure times.

Light is obtained from an electrically conductivegas (xenon) called plasma that forms betweentwo tungsten electrodes under pressure.

The light spectrum provided by plasma is

limited.

The wavelength of high-intensity light emitted isdetermined by the bulb-coating material andfiltered out to minimize transmission of infraredand UV energy and to allow emission of blue

light (400 nm to 500 nm).

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These units have a high energy output and short curing time.

An exposure of 10 secs from a PAC light is equivalent to 40secs from a QTH light.

They yield a power density up to 2500 mW/cm.

These units have been shown to have higher conversion ratesand depths of cure for RBCs as compared with QTH units.

These systems work at wavelengths between 370 nm and450 nm or between 430 nm and 500 nm.

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The heatproduction

must becontrolled.

They areexpensive.

The lamp(bulb)

replacement iscostly.

Most devicesare large,

heavy, and

bulky.

They havelow-energy

performance.

Filters andventilating fanare required.

Disadvantages:

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The results obtained from the QTH

units are better than those acquiredfrom PAC units.

RBCs cured with a PAC unit haveshown more polymerization shrinkagethan with QTH units.

The hardness values of RBCspecimens cured by the PAC unitshave been shown to be significantlylower than LED and QTH units.

The recommended time of 3 secs forPAC units is inadequate and should bedoubled to obtain optimal mechanical

properties of RBCs.

An incremental technique of 2 mm

should be followed.

These units, when used incombination with QTH units, havebeen shown to provide higherbond strength values for dentinbonding agents.

The devices are best suited forcementation of orthodontic bandsand brackets.

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Argon Laser

Laser lamps are high-intensitylamps based on the laserprinciple.

The emitted wavelength dependson the material used (argonproduces blue light).

Argon laser lamps have thehighest intensity.

These lamps work within a limitedrange of wavelengths, do notrequire filters, and require shorterexposure times for curing RBCs.

The devices generate little infraredoutput, so not much heat isproduced.

They work at specific bandwidthsof light in the ranges of 454 nm to466 nm, 472 nm to 497 nm, and514 nm.

Because a laser is a narrow beamof coherent light, no loss of powerover distance occurs as in seen inQTH units.

Therefore, argon laser curing lightsare the units of choice forinaccessible areas.

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The curing depthis limited to 1.5mm to 2 mm.

The curing tipis small, so

more time isneeded to cure

the RBCs.

They areexpensive.

They have a

narrow lightguide {or spotsize)

Disadvantages:

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Studies have reported similar results for both laser andQTH units.

No difference in bond strength is seen between theargon laser and standard QTH units.

Laser devices have been shown to produce anincreased degree and depth of cure for RBCs.

The laser systems have also demonstrated greatermaterial wear, more polymerization shrinkage, andincreased marginal leakage.

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Factors That Affect Light-

Curing1. Exposure time,

2. Intensity,3. Temperature,4. Light distance,

5. Resinthickness,

6. Air inhibition,

7. Tooth structure,8. Composite

shade,9. Filler type,10. Accelerator

11.Quantity,12.Heat,13.Room light

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Exposure time

Light-cured composites polymerizeboth during and after visible lightactivation.

These two curing reactions are knownas the light and dark reactions .

The Light reaction occurs while lightfrom the curing unit penetrates thecomposite.

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The Dark reaction , also called Post-irradiationpolymerization , begins immediately after thecuring light goes off and continues for upto 24hours, even in total darkness, but most of itoccurs within 10 to 15 minutes post cure.

The minimum curing time for a light reaction formost composites under a continuous curing

mode is 20 to 40 seconds (using curing unitswith the normal 400 mW/cm 2 output).

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Intensity

The curing intensity of a 468 20 nm blue light has beenabout 400 mW/cm 2 .

This is the output of mostcuring units and is referredto as the Power Density.

Problems occur when theminimum intensity is notachieved.

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There are four common causes ofdecreased intensity:

I. As the bulbs in curing lamps age, the intensityof blue light can decrease

II. Voltage drops can affect blue light productionIII. Sterilization of curing tips can reduce light

transmissionIV. Filters to increase blue light transmission can

degrade

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Temperature Light-cured composites cure less effectively if they are cold

during application (e.g., just taken out of the refrigerator).

Composites at room temperature cure more completely andrapidly.

Composites should be held at room temperature at least 1hour prior to use.

Most curing lamps produce heat, which speeds the curingprocess.

However, excess heat can result in pulpitis and pulp death.

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Distance and angle betweenlight and resin

The ideal distance of the light source from the compositeis 1 mm, with the light source positioned 90 degreesfrom the composite surface.

Light intensity drops off rapidly as the distance from thelight rod to the composite increases.

Distance can still be a problem if the lamp is placedagainst the tooth, since a deep box increases thedistance the light must penetrate.

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With many curing lamps, a higher power density (ofabout 600 mW/cm 2) is required to ensure that 400mW/cm 2 reaches the first increment of composite ina posterior box.

To compensate for the loss of intensity, cure forlonger periods of time the layers of composite thatare at a greater distance from the light rod.

Further polymerization can be achieved by curingfrom the proximal surfaces after finishing.

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Fig. In deep restorations and those with poor access, the distance between the light guide and the composite can increase, which generallyreduces the power density at the surface by over 70%.

Fig. Schematic representation of a 50% reduction in light intensity in deeper areas of a preparation60

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Angle and path of the light

As the angle diverges from 90 degrees to thecomposite surface, the light energy is reflectedaway and penetration is greatly reduced.

This can be demonstrated by angling the lightrod against a radiometer and watching theintensity values shown on the meter drop.

In molar preparations, the marginal ridge of theadjacent tooth blocks light when placed at anangle.

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Thickness of resin Resin thickness greatly affects resin curing.

Optimum polymerization occurs at depths of just 0.5 to1.0 mm, because of the inhibition of air at the surface

and the difficulty with which light penetrates a resin.

One classic study showed that 7 days after a 40- second

curing cycle, a 1-mm deep composite (of light shade) iscured to 68 to 84% of optimum hardness, as measuredby surface hardness.

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At 2 mm, this same composite has only 40to 60% of the desired hardness.

At 3 mm, it has only 34% of the hardness.

Thus, composites should be cured inincrements of not more than 1 to 2 mm.

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Air inhibition

Oxygen in the air competes with polymerizationand inhibits setting of the resin.

The extent of surface inhibition is inversely relatedto filler loading.

The under-cured layer can vary from 50 to 500 m(or more), depending on the reactivity of thephotoinitiators used.

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Unfilled resins should be cured, then covered

with an air-inhibiting gel, such as a thin layer ofpetroleum jelly, glycerin, or commercial products,such as Oxyguard, and then re-cured.

In addition, curing through a matrix increasessurface polymerization because the matrix

reduces air inhibition.

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Curing through tooth structure

It is possible to light-cure resin through enamel,but this technique is just one- to two-thirds aseffective as direct curing and is appropriate onlywhen there is no alternative.

Such curing is possible through up to 3 mm ofenamel or 0.5 mm of dentin, but the clinicianshould double or triple exposure times.

When light-curing through tooth structure,porcelain veneers, and other barriers, it isadvisable to use a high-intensity light.

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Shade of resin

Darker composite shades cure more slowlyand less deeply than lighter shades.

At a depth of 1 mm, a dark composite shadeachieves just two- thirds of optimum depth ofcure achieved in translucent shades.

A brighter light reduces the amount of time ittakes to cure darker shades.

Hence, when esthetics is not critical, thelightest shade should be used.

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Amount of Photoinitiators

All photoinitiators deteriorate over time.

However, light-cured composites are more stable thanchemically cured composites.

Some light- cured composites lose about 10% of theirphysical properties when stored for 2 years at roomtemperature.

The maximum usable life span of a light- cured composite is

generally 3 to 4 years or more from the date of manufacture, ifstored at room temperature.

If contained in a sealed tube, they last much longer.

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The major cause of decreased shelf life for light-curedcomposite is evaporation of critical monomers fromunidose containers.

Auto- cured materials have shelf life of 6 to 36 months.

There are large variations in the shelf life of variousauto- and dual-cured composites.

Most autocured composites have an extended shelflife if kept under refrigeration.

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Room-light polymerization

The working time of light-cured composites depends on theoperatory light and the ambient room light to which thecomposites are exposed.

Differences in these light sources can dramatically affect workingtime. Newer, faster-setting composites are even more sensitive.

1. Operatory lighting:

Most operatory lights operate at high temperature thatproduce spectrums in the blue range.

This spectrum is included to improve the color selection ofdental restoratives, but it initiates curing.

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2. Incandescent lighting:

Incandescent lights are low in blue light andprovide the longest composite working time.

3. Fluorescent lighting:

In general, fluorescent lighting has the shortestworking time for light-cured composites,because it emits a large amount of blue light.

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Related studies

Clinical Evaluation of the Soft-Start Pulse-delay)

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y)Polymerization Technique in Class I and II Composite

Restorations

A double blind, randomized clinical trial was carried out to comparetwo curing techniques Soft-Start (SS) and the plasma arc curinglight (PAC).

The hypothesis that, delaying the gel point (with SS) improves

marginal seal, was tested.

Protocols: PAC (Control) incremental curing


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pof light-curing techniques on microleakage

Purpose: To evaluate the effect of light-curing techniques on in vitromicroleakage of class I and class V composite restorations.

A resin composite (TPH 3 Dentsply) was inserted in two layers andlight-cured using two protocols (n=15 each): conventional curing (500mW/cm2, 30 s each increment) and pulse delay technique (firstincrement similar to the conventional technique and the last incrementinitially cured with 200 mW/cm2 for 3 s and after 5 min light-cured againwith 500 mW/cm2 for 30 s)

Results: In class I cavities the pulse delay light-curing technique showedstatistically significant better sealing than the conventional technique. Inclass V restorations no difference was detected between the twotechniques in enamel and dentin.

Conclusion: Light-curing technique affected the microleakage in class Icomposite restorations but not in class V.

Rev. odonto cinc. 2009;24(3):299-304


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The cytotoxicity of resin composites cured with78


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three light curing units at different curingdistances

Objective: The purpose of this study was to compare the effect of lightcuring distance on the cytotoxicity of five resin composites cured withthree high-power light curing units.

For curing, soft-up mode of quartz-tungsten-halogen, exponential modeof light emitting diode for 20 s, and ramp-curing mode of plasma arc lightcuring units for 6 s were used.

The curing tip distances were determined as 2 and 9 mm.

Conclusions: The results of this study suggest that the light curing unitsand resin composites should be harmonized to one another and thecuring distance between the tip of the light curing unit and therestoration surface should be as close as possible in order to achievemaximal biocompatibility.

Med Oral Patol Oral Cir Bucal. 2011 Mar 1;16 (2):e252-9.

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Conclusion

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References

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