Okay - I spent a few more minutes with this today and here's what I came up with. I'm using Photoshop CS4 and Noiseware Professional but these techniques would work in CS3 as well.
Open the image.
Before doing any adjustment work, I ran it through Noiseware using default settings.
The next step involves creating a density mask that we'll use to apply our changes. Open the "Channels" tab, hold the CMD key (cntrl on PC) and click on the word RGB. You should see a selection appear on the bright parts of the image.
http://images.hopdog.com/step1.png
Next, we need to invert that selection. (Select/Inverse)
Now go back to the layers tab. Click Layer/Duplicate Layer and click OK.
http://images.hopdog.com/step2.png
This is where the magic starts to happen. With the "background copy" layer selected, click the mask icon below the layers palette:
http://images.hopdog.com/step3.png
Change the layer blend mode to Screen.
http://images.hopdog.com/step4.png
It's brigher, but not bright enough. Effectively, we've just brightened just the dark areas 1 full stop. With the background copy layer selected, hit CMD J (cntrl on PC) or do Layer/New/Layer via copy.
That looks pretty good now so let's focus on sharpening those teeth.
Go back to the Channels tab and make do the same selection that we started with.
( Open the "Channels" tab, hold the CMD key (cntrl on PC) and click on the word RGB. You should see a selection appear on the bright parts of the image.)
Go back to the Layers palette, click the original background layer. Go to Filter/Convert for Smart Filters.
Next click on Filters/Sharpen/Smart Sharpen.
http://images.hopdog.com/step5.png
I'm using some pretty aggressive values but that's okay because we're going to mask them to just the teeth. Once you've entered the values, click okay.
Photoshop used our selection and created a mask for the sharpening. It's a start but we're not done.
http://images.hopdog.com/step6.png
Hold down the Option key (alt on PC) and click on the mask. You should see the image turn to grayscale. What you're actually looking at is the mask that we created. We need to refine it.
Click filter/Stylize/Find Edges.
http://images.hopdog.com/step7.png
Click CMD i (cntrl on PC) to invert the mask.
Select Filter/Other/Maximum and set it to 1 pixel.
http://images.hopdog.com/step8.png
Almost done. Now we need to smooth out the mask.
Select Filter/Blur/Gaussian Blur and select 1 pixel.
Hold down the Option key (alt on PC) and click on the mask. You should see the image turn back to full color. If I were going to save this for the web I'd flatten the image (Layer/Flatten image) and then do a "Save for web"
Cheers
