Playing dentist on my nut - testing dental UV resin

[RJVB]

Ever since reading about redoing nut slots with UV resin on here I've been meaning to try out the stuff that dentists have been putting into our teeth for decades now.

Contrary to the old trick using CA glue with bicarbonate or bone dust or the UV-curing stuff used for creating jewelry and trinkets, this resin is a lot like clay or certain bi-composite fillers (aka "liquid metal"). No risks of spilling onto anything that shouldn't be spilled on.

Plus it has an appropriate tint.

A few weeks ago my dentist gave me a couple of tubes with leftovers that still contain enough for multiple repairs, and a few instructions. I don't particularly like redoing nut slots because I need to repurpose the kitching table for this kind of work and there's always this "better is the enemy of good" mantra in the back of my head. But now I had 2 slots that needed attention so yesterday I redid them. For an optimum 1st experience I decided not to mask with low tack tape this time.

- the stuff is really thick but becomes a lot easier to manipulate when heated. I suppose this happens automatically when applied in a tooth; I just held the open tip next to a lighter flame for 10s.
- I already had a scalpel out for removing the bicarbonate filling from the slots so I used it to take a morcel of resin off the tip of the tube and working it into the slot.
- The nut will of course be "cold" so it's important to really press down such that the resin gets pushed out through the slot ends, etc, making certain the entire slot gets filled.
- The stuff gets really hard (I'd say harder than the bone itself) so it's important but also quite easy to obtain a clean, smooth repair before curing. It's sticky too, but smudges left on e.g. the top of the nut can be removed with a scalpel after curing and some initial sanding.
- Because it's so sticky it will also pick up any dirt so best use a pristine scalpel blade.
- I used a "nail artist" curing lamp with a simple "powerful" UV led and a focusing lens, aiming down from behind both slot ends. 30s from either end proved sufficient.
- I got "tint 3" (or C), the most yellow of the 3 tints existing for the cheap dental resin (<15€ a seringe on A'zon). I like that; makes it possible to see which part is filled.

Getting a smooth result with my usual file and 3-grit nailbuffer was easy enough. Filing a new slot was a lot more work than I expected though: cured it is really hard and the smooth surface I had created made it trick to start the slot in the intended place. Next time I will use a piece of wire of the scalpel to create a "proto slot" where I want it. Creating an imprint with an old piece of a corresponding string might be even better.
NB: I use MusicNomad diamond files ...

The result:
- The E-1 string slot seems to have turned out perfect
- I'll probably be redoing the A-5 slot yet once more. I had noticed after curing and sanding that I had failed to create a perfect join on both sides of the saddle-side slot opening. As a result the opening is probably wider (or more flared) than it should and I still have some occasional sitar'ing going on. Getting all the bicarbonate out was already trickier than I thought, it'll be interesting to see how much a challenge that is with this stuff!