LED-UV lamps now come in several variants:
- those that cure at 405nm UV wavelength - these were the original LED-UV lamps designed for gel polish
- dual band LEV lamps, that cure at both 365nm and 405nm. These have been on the market for around 1 year (although we tested one 3 years ago) and claim to have the advantage they can cure hard gels designed for UV bulb lamps, and the newer 405nm UV compatible hard gels and gel polishes.
However, as others have said it is so simple. UV wavelength is important, but so too is the "brightness" of the UV - how much UV energy falls on the fingernail - this is called UV Illuminance.
Different UV and LED-UV lamps generate different levels of UV Illuminance and that affects effectiveness of curing. This is because lamps have different designs.
In addition, there are hundreds of different gels and gel polishes on the market, and they use different photoinitiators that require 365nm or 405nm UV light, but also a specific amount of UV Illuminance.
A simple analogy would be trying to cure hundreds of different cake recipes each with different yeasts and amounts of yeast, in an oven whose temperature you can't control.
So the UV or LED-UV lamp has to be matched to the brands gels. This has to be tested in a scientific laboratory. If the brand decides to change their UV / LED-UV lamp, they may have to adjust the formula of their products to make sure they cure correctly. Or if they have mega bucks, have a lamp designed for their gels. This is why serous companies only offer one type of UV / LED-UV lamp. Its too costly to support more.
If the lamp and gels aren't matched, you can get heat spikes, nails that lift or fall off, or developed an allergy due to under cured gel dust.