A dental curing light search usually finds the kind of equipment used to fix or cure composite resins or composite resin cements for different dental restorative applications.  I'm not familiar with any other applications of this equipment since dentistry is my background.
There are a number of different types of dental curing lights.  Plasma, Halogen and LED. 
The most common is the halogen light.  Classically seen with a cord attached light with a base (transformer) and a hand held light with usually a cooling fan. These are very common and generally reliable even used.  Replacement parts are available for most newer models but I have noticed that some older (7-10+ years) models are not supported for parts.  Well, they just made 'em too good and they have to create functional obsolescence somehow.
Next and usually more expensive and not as common are plasma lights.  These perform faster and for this reason 'better' than the halogen light but they are bulkier and not as user friendly.  If they don't work you have to have them sent off for repair or refurbishing.  I have not had to do this personally but I will bet it is not cheap, but you could get a great unit for less if you are careful.  In some auctions, I have seen older and clearly obsolete units.  They show yellowed cases and unfamiliar ergonomics and when I google the brand I don't get any info.
As with any auction, you will do much better to know particular product or model numbers and verify with the seller prior to bidding what exactly you are buying and confirm that they have tested or can assure you (guarantee is better) that it is functional.  For example in copiers, I like to buy a unit with an actual warranty.
Now, the third type, and this is the punch-line, is LED.  This category is fraught with peril.  There are a LOT of these offered lately and most are not name brand and most are from overseas but some are continental, but all are poorly made.
There are wonderful name brand LED units that you can buy.  Know the exact model and product code for what you are seeking to buy.  To buy a unit that looks like it might perform the way you expect will only lead to disappointment.  Read the feedback.  Overseas return shipping is never as cheap as you hope and you could spend the cost of your item to return it.
This is also the same as 'If it looks too good to be true, It probably is.'
The glut of cheap poorly made LED lights is not good for dentistry or the manufacturers.  Thanks for reading.

Update:  I recently viewed a light for sale which looked like a great deal.  It was new, had a radiometer and was an off brand but seemed to look like the right stuff.
When I asked about a return policy or warranty or shipping insurance because there was nothing about this in the description, the seller wrote back that there was none, zero, zilch, nadda.  I prefer to know that I'm covered even for smaller items like these that cost less. So watch what you're buying because you might actually get it.  Best wishes.