Nut Slot Repair with Dental Compound

[pheumiller]

Folks, Ken Jones and I pulled together this video from the repair shop - a neat technique using dental compound to repair a nut slot - hope you enjoy: https://youtu.be/TRkWs4T882w

[Steve Christens]

Awesome technique, especially since I've always had difficulty getting the CA trick to work. But could you provide any links for the required materials? Is this too expensive for a home repair?

Thanks!

[fazool]

seems like one of those great ideas that are so good, they seem obvious (why didnt we think of this earlier).

but.....dental compound and the labor time to use it probably cost more than just making a new bone nut

[srick]

I hope to follow up on this thread in the next few weeks. I'll be doing some experimentation with a local luthier using a wide variety of dental filling materials. The filling material comes in several viscosities. The "flowable" types might be much easier to work with; the "putties" shown in the video are designed to mimic the tooth hardness and needless to say are wear resistant. (We dentists use a lot of diamond burs when working with it). Polishing it takes specialized grits and patience.

Also, there are many priming techniques used when working with teeth. We'll try a few and see if there is any difference. I'll add that the stuff is not cheap, but since this application deals with an inanimate object, you could get cheap Chinese material off of ebay and not compromise the situation.

A bone nut is a lot simpler to work with since there is no nerve to worry about, no saliva and no tongue!

Best,

Rick (DMD West Hartford, CT)

[Silly Moustache]

Fascinating ! I'm having a filling replaced next month. I'll go along with large pockets!

[Hot Vibrato]

Thanks for posting this. I first heard about this technique on this forum a few weeks ago. I've been doing guitar repair professionally for over 20 years, and this is a complete game changer. Sometimes I teach lessons on the side, and one of my students is a dentist who owns and runs a pediatric dental clinic. At his last lesson he told me that he would give me some dental compound, but I haven't heard from him for a few weeks. My friend is the IT guy at the clinic, and he says that Dr. Will has been avoiding me because he hasn't been practicing much. I've been guilty before of avoiding going to the dentist, so would it be hypocritical of me to give him a hard time for avoiding going to his guitar lessons?

[murrmac123]

Originally Posted by Hot Vibrato

Thanks for posting this. I first heard about this technique on this forum a few weeks ago. I've been doing guitar repair professionally for over 20 years, and this is a complete game changer. Sometimes I teach lessons on the side, and one of my students is a dentist who owns and runs a pediatric dental clinic. At his last lesson he told me that he would give me some dental compound, but I haven't heard from him for a few weeks. My friend is the IT guy at the clinic, and he says that Dr. Will has been avoiding me because he hasn't been practicing much. I've been guilty before of avoiding going to the dentist, so would it be hypocritical of me to give him time for avoiding going to his guitar lessons?

HV, the chances are good that he will have some composite which is past its use-by date , and which he will be happy to give you ... it is the primer which is horrendously expensive, and it is unlikely he will have any out-of-date primer, but here's hoping !

[ac]

Originally Posted by srick

. . . . . I'll add that the stuff is not cheap, but since this application deals with an inanimate object, you could get cheap Chinese material off of ebay and not compromise the situation. . . .

Would you point us to what exactly to search for on eBay? Names of materials, terminology, hardware, etc.?

I don't have a clue where to begin other than maybe "dental supplies". I can think of a number of other uses for this type of material for doing various repairs that come along, not just nuts.

Thanks.

[murrmac123]

Originally Posted by ac

Would you point us to what exactly to search for on eBay? Names of materials, terminology, hardware, etc.?

I don't have a clue where to begin other than maybe "dental supplies". I can think of a number of other uses for this type of material for doing various repairs that come along, not just nuts.

Thanks.

I'm not Rick, but the search terms you want are "dental composite" and "dental composite bonding agent".

The only other thing you need is a "cordless ultra violet light".

[srick]

Originally Posted by murrmac123

I'm not Rick, but the search terms you want are "dental composite" and "dental composite bonding agent".

The only other thing you need is a "cordless ultra violet light".

i am looking at e-bay now. i am seeing lots of gray market brands (IOW materials that were packaged for non-US use) and likely some expired material - neither of this is a problem for guitar use!

The "putty" composite comes in several forms - unidose compules which require a special squirt gun and syringes. The syringes are what you want. Also, you will see Flow and flowable products:these are applied with a small syringe and will work perfectly for a nut slot - but I have no idea of the wear characteristics. I'll have to experiment.

The shades can be very tricky - A shades have a bit of red and yellow in them (A2 is considered standard tooth color); B shades have more yellow; C shades have grey and D shades have a little brown. The lower numbers ( i.e.) C1, A1, B1 vs. C4, A4, B4)have a higher color value and appear whiter. The bone nut on my Bourgeois looks to be B1 or what we call bleach shades, but I have to take it to the office and examine it in the dental chair to make sure!

The curing could likely be done in the sun or with a projector bulb - it need not be UV. There are some very cheap ones available from Hong Kong and while not suitable for humans, may work very well for guitars; with these POS (pardon my acronyms)lights you may have to cure for a minute or so, but shouldn't be an issue for your nut.

There are also very inexpensive priming/bonding agents available - again; no issues on nuts. i would recommend preparing the nut slot with either some 400 grit sandpaper or a little bit of naval jelly applied for 45 seconds then thoroughly rinsed and dried. Naval jelly is phosphoric acid and almost identical to what is used in the mouth.

The protocol would go like this:

1) lightly sand the slot (scuff it) OR apply naval jelly for 30-45 seconds
2) rinse and dry
3) apply primer/bonding agent to the slots with a fine brush. let sit for 20 seconds; blow dry; cure for 20 seconds with the light
4) squirt in flowable composite or push in putty; remove as much excess as you can in advance! then cure for 30-45 seconds.

You are then ready to re-cut the slot.

Now you might also think that you are qualified to do your own dentistry too... (please don't do that!)

Rick

PS: I overcut the nut slots on my Bourgeois last month. Rather than go to the trouble of filling in the slots, I went to Frets.com and Frank Ford had the simple, but elegant answer. He recommends applying a computer mailing label to the underside of the nut and then removing the excess with an X-acto knife.

If you really butchered the nut, you might have to use two. WORKS LIKE A CHARM! And no difference in tone!

[cattzap]

I wonder if the powder for acrylic nails will work. My wife used to do those and that stuff is like steel yet easily shaped and filed. Easily obtainable

[mirwa]

The idea sounds good.

I am curious as to how resistant it is long term to separation from the nut, considering that the final end result is a bonded graft of growth in the range of possibly 5 thou.

I would personally recommend the use of gloves and not exposed skin, whilst blue light is becoming more prevalent for curing, the real true dangers are still unknown.

Most people are aware now that UV light can be dangerous and care should be exercised with the use of it, years ago, scientists and health advisers, said it was not that bad for us.

Many years ago, X-rays were apparently not that bad for us, but over the years the legal allowed exposure to those people that use it daily have been steadily dropping as we become more aware of the long term issues that are arising.

Long story short, I would wear gloves.

Steve

[Frank Ford]

I have had some adhesion "issues" with the dental fill compound, although not when using it on ivory nuts. One trick that's helped is to use a bit of cyanoacrylate as a bonding agent, and before it hardens, follow with the dental compound. Most of the time, I do the work "in situ."

Here's another view of the process, written just after Dan Erlewine introduced me to it some time ago:

http://www.frets.com/FretsPages/Luth...htcurenut.html

[srick]

Originally Posted by Frank Ford

I have had some adhesion "issues" with the dental fill compound, although not when using it on ivory nuts.

and of course, ivory is essentially tooth structure! The microstructure of bone as compared with tooth is very different and bonding to it is a whole different animal (so to speak).

Nail Acrylic (methyl methacrylate) is mentioned earlier in the thread and of course that will work. I wouldn't trust its long term stability however, it tends to outgas and breakdown over time. Not unlike the Gibson tuner buttons from the 30s and 40s. In thin sections (like a nut repair), I would think it would chip easily.

Best,

Rick

[srick]

Originally Posted by mirwa

The idea sounds good.

I am curious as to how resistant it is long term to separation from the nut

> me too, especially comparing bonded vs. unbonded material. Bone has an entirely different microstructure than tooth; the dental materials are optimized for tooth and the formulas have been honed over many years.

I would personally recommend the use of gloves and not exposed skin, whilst blue light is becoming more prevalent for curing, the real true dangers are still unknown.

> the monomers in these products (the liquid portions) can be very irritating. the fumes can also irritate your eyes. Gloves and glasses are a good idea. Once the material is cured, there is often still a layer of monomer on the top that is uncured (oxygen inhibited layer) and this can be removed with some alcohol. However, it is used millions of times daily in the mouth and over the last 30-40 years of experience, my guess is that this is as safe as it gets (nothing is 100% however!)

>And don't look at the light... Agreed!

Also, the materials set in white light. When youre working with them, it should be in subdued light or with an orange filter!

Long story short, I would wear gloves.

Steve

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