Certainly there is a slight change from the uncured and cured state, in terms of translucency. However, shade transition largely depends on the zone of application and layers applied. Shall look into the refernces and update soon.

Dear Priya, thanks for your answer, I would like some references if possible please.  Particularly, if I can reference your statement, "slight change from the uncured and cured state, in terms of translucency".  it will be very helpful. what other factors that can affect such color changes during curing? waiting for references from you; Kind regards

http://www.jopdentonline.org/doi/full/10.2341/06-129

As the double bonds form as the polymer forms from the monomer you should get a denser rein and I assume this accounts for the darkening of the restoration.

Dear Paul, a very interesting and scientific explanation ; could you please provide me the reference for citation purpose for it. A bit more details are highly appreciated, 

Best regards

I made the observation based on my knowledge of the chemical reaction in resin composite. If you go to PubMed and enter "doubler bond dental resins" you should get some scientific articles. These double carbons bonds are famous(infamous) part of resin composite.

Other factor that I observed for many years is the expired date, but there is not nothing publish about it... I'm working right now in one research about... Best regards and good luck.

CAN Method of curing affect on quantitative color changes? for example, if we cure in day light, LED or QTH light?

Generally speaking the color of light cured composite resins do not change upon curing.  The translucency does not change upon curing as translucency is accounted for by the type of filler and the light refractive index of the filler materials and how closely these are matched to the refractive index of the polymer.  The color of the composite can change if the material was to be heated to above 175o C for in excess of 7.5 minutes as in the production of a composite resin inlay/onlay, but the normal time of heat treatment for a composite resin inlay/onlay reaches its best properties at 5-7.5 mins at 125o C.  There should be no reason for expired composites to change color, except when exposed to very high heat conditions over a long period of time and this may effect the composition of the curing materials in the polymer.  There can, however, be a color shift in dual curing or self curing composites and polymer cements over time because of the interaction of the amine and the oral environment. you might want to look at the paper:

Dent Mater. 2013 Apr;29(4):405-12. doi: 10.1016/j.dental.2013.01.005. Epub 2013 Feb 15.Development of a low-color, color stable, dual cure dental resin.

Oei JD1, Mishriky M, Barghi N, Rawls HR, Cardenas HL, Aguirre R, Whang K.

And for more information look on PubMed under the search:

http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=23415498

Lastly, I don't believe there is a corresponding change in color depending on the type of light that you use, but the amount of cure and the quality of cure can affect the color stability in oral fluids over time.  The partially cured material will be degraded to a higher extent over a shorter period of time especially on the surface, especially proximally, at a higher rate than normal by the bacterial products and oral fluids.  That is the reason that I cure proximally ALL composite resin restorations knowing that I can cure up to 7 millimeters through tooth.

Light curing in resin composites occurs through a traditional CQ/amine photo polymerization reaction. It is reported that there can be a yellowing from CQ.  The yellowing effect caused by the CQ photo initiator is related to its concentration in the resin composites. According to Schneider et al., effect of composite yellowing increases in the proportion in which the concentration of photo initiators also increases.1 Although there is evidence that higher concentrations of photo initiators improve the degree of conversion (DC) and mechanical properties of the cured polymer, above a certain concentration, no benefits were observed and may affect aesthetics due to CQ’s yellow color. Although the yellowing might be reduced during the light curing process, part of the photo initiator may remain unreacted due to poor light curing or other physical effects, such as the depth of composite and “inner shielding” effect. Dental resin composites materials (light cure) contain camphorquinone as a photo initiator and can be significantly more yellow prior to irradiation than afterwards.2 If curing is insufficient (i.e., too short or not an appropriate light, or a light that is old or dirty and does not emit/transmit well), the composite may still retain a certain degree of yellow.2 Therefore, the restoration could still be yellowish and non-acceptable esthetically.2

The photo initiator systems include tertiary aromatic or aliphatic amines, which act as so-called synergists or accelerators (The amine is known as a co-initiator, accelerator, or synergist).2  In addition to the concentration of CQ, the amount of tertiary amine can vary by brand and composite formulation.  Some studies have reported that the amine concentration can cause darkening of the composite over the course of time. Some reports state that aliphatic amines are more color-stable than the aromatic amines.3 All amines are known to form byproducts during the photoreaction, which tend to cause yellow to brown discolorations under the influence of light or heat. These discolorations depend on the type and the amount of synergist added to the photo initiator system.2

 Insufficient monomer conversion and the presence of unconverted double carbon bonds can make the resin composite  material more susceptible to degradation,  resulting in color stability reduction, due to the release of by-products such as methacrylic acid, formaldehyde and specific molecules of methacrylate.4

 Reports use in vitro storage in water over time to mimic changes that occur in light cure resin composites through water sorption in the mouth for color stability changes that are from other than extrinsic staining.

1.            Schneider LFJ, Pfeifer CSC, Consani S, Prahl SA, Ferracane JL. Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites. Dental Materials 2008;24(9):1169-77.

2.            Janda R, Roulet JF, Kaminsky M, Steffin G, Latta M. Color stability of resin matrix restorative materials as a function of the method of light activation. Eur J Oral Sci 2004;112(3):280-5.

3.            Asmussen E. Clinical relevance of physical, chemical, and bonding properties of composite resins. Oper Dent 1985;10(2):61-73.

4.            Albuquerque PPAC, Moreira ADL, Moraes RR, Cavalcante LM, Schneider LFJ. Color stability, conversion, water sorption and solubility of dental composites formulated with different photoinitiator systems. Journal of Dentistry 2013;41, Supplement 3:e67-e72.

I think the color will change as the energy absorbed by the composite matrix and fillers through photopolymerizable  materials,,, the absorption of light is a tissue or materials  property like finger print each material absorb light differently,,  we see the color of material  according to their wavelength dependent absorption,, so when they reacted the color will change according to set mixture of material,,,,, to match the exact color one can check small piece of composite (with itching and bonding)  on the tooth that will be used as reference>>>>>>>also storage for a long time if any reaction happen I think the color may change ,,,,,, other thing is time and  the type of light used for curing can also affect the color according to the depth of penetration and complete polymeraization       

Many thanks to all respondents who helped me to understand the subject as beginner 

I mean without acid itching and bonding

You need to use them to obtain a good restoration....

In answer to the first part of your question, "Does the colour change?"

A simple comparison of cured and uncured samples of a variety of composites should give you your answer

In some composites the difference is noticeable between uncured and cured to the point you wonder if you have chosen the right shade when the composite is in the uncured state and then sigh a sigh of relief once the composite has cured.

  " Lighter or less chromatic shades tended to show larger color changes than more chromatic or darker shades. Resin composites become lighter or more translucent on irradiation with light. Polymerisation produced a characteristic chromatic shift toward  the blue region of color space and decrease in chroma. To compensate this, an initial color choice more yellow  or more chromatic than desired final was suggested. "  

The changes in color after polymerisation are shade dependent and vary by brand. The range of color changes in this study was ΔE= 1,1 -7,9, therefore you can`t say that there are correspond uncured shades. In the clinical practice is prudent to polymerize some composite on undried tooth for shade matching.

http://www.ncbi.nlm.nih.gov/pubmed/16924627

b* value from CIE L*a*b system has changed with different curing mode.

You can read this article:

Article The Effect of Different Curing Time Regimens on Immediate Po...