Why Glutaraldehyde Is Not Just for Desensitization

I’m going to make a case for using glutaraldehyde as the second step in all of your total-etch adhesive techniques. That is, any time you use a fourth or fifth generation bonding system. As much as I’ve tried to strip most of the heavy science jargon out of this article, it’s a still a heavy one. If you want the goods without the investment, here’s my protocol:

1. Acid-etch
2. Place Glutaraldehyde/HEMA
3. Primer
4. Adhesive
5. Resin

Why? The long and short of it is that glutaraldehyde not only desensitizes, but it disinfects; it also strengthens the bonding agent’s ability to penetrate, and therefore makes your bond last longer.

Let’s get to it.

​Gluma by Heraeus Kulzer has been used as a desensitizing agent since 1991 and is a combination of 5% glutaraldehyde and 35% hydroxyethylmethacrylate (HEMA). One of my favorite tips from Frank Spear at one of his seminars was that Gluma's patent has run out, and there are currently less-expensive options available with the same chemical composition. I use G5 by Clinician’s Choice in my practice, and MicroPrime from Danville is another less-expensive alternative.

Densensitization

Current bonding techniques are known to cause post-operative sensitivity through the hydrodynamic theory of pain. When Gluma is used, the glutaraldehyde creates a plug inside of the dentin tubules that eliminates the hydrodynamic mechanism of dentin hypersensitivity. Basically, it clogs the dentin pores so fluid can’t seep out, and post-op discomfort is significantly reduced.

Inactivation

While the desensitizing effect of glutaraldehyde is a good reason to use it in and of itself, there’s a second compelling reason that has gained attention in recent literature. Glutaraldehyde has been shown to affect the longevity of the dentin-resin interface. That’s right, it not only makes your patients feel better, it makes your restorations last longer, too!

Without getting too scientific, our bodies make enzymes that break down proteins, called MMPs, that get trapped in the demineralized dentin layer. It’s the MMPs that result in reduced bond strength and debonding over time. Those MMPs are activated by our acid etchant during the adhesion process.

​MMPs, which degrade Type I collagen, can slowly degrade the collagen fibrils at the interface of the dentin with the resin. Glutaraldehyde cross-links MMPs, inactivating their enzymatic activity. If you use glutaraldehyde on acid-etched dentin, you can effectively inactivate most MMP activity.

It is the water-loving monomers, like acetone or ethanol in the primer, that allow bonding to moist, etched dentin. Although our bonding techniques have improved significantly, we still aren’t able to completely replace the water in the collagen matrix of dentin with monomer in our primer. Since this isn’t possible, we get the hybrid layer containing some voids.

So now we have MMPs activated by etching that want to break down collagen if they can get in there, and we have voids left during the adhesion process. These voids at the dentin-adhesive interface make the bond more susceptible to degradation by enzymes like MMPs over time.

(Click this link for two steps to better bonding in dental restorations.)

Re-wetting

If you’re still with me (virtual applause), there’s another bonus we should get into. If we air-dry the dentin after acid-etching, the air removes water from the collagen matrix. When you remove water, this causes the collagen to collapse and condense. When there are less spaces between the collagen fibers, there’s decreased ability of our monomer to get into the collagen. So not only do we have voids in the hybrid layer, now we’ve desiccated the collagen and made it even harder to penetrate.

When we re-wet the dentin after air-drying from the etchant, the collapsed collagen network expands again and our bond strength is increased. We can use glutaraldehyde for this re-wetting!

To recap, if you don’t use glutaraldehyde when you acid-etch and dry the tooth, you stimulate MMPs and make it harder for the primer to effectively penetrate the dentin. If you re-wet with glutaraldehyde, you decrease the MMPs and allow more monomer penetration, which equals greater bond strength.

Anti-bacterial

Glutaraldehyde has several benefits to its use as an anti-bacterial agent. It has a broad spectrum of action, a fast kill rate, and can destroy not only bacteria, but fungal spores, tubercle bacilli and viruses as well. Mechanical debridement alone doesn’t effectively remove bacteria from a carious lesion. Acid etching kills S. mutans, but doesn’t kill acid-loving (acidophilic) and acid-producing (acidogenic) bacteria. In fact, it may even stimulate them.

So why are we going to use glutaraldehyde after acid-etching teeth?

• It desensitizes the tooth by blocking fluid flow
• It inactivates harmful enzymes that break down bond strength like MMPs
• It serves as a re-wetting agent to plump up the collagen fibers for monomer penetration
• It is anti-bacterial

(Click this link for more articles by Dr. Courtney Lavigne.)

Courtney Lavigne, DMD, Contributing Author - http://www.courtneylavigne.com

Resources

Bedran-Russo AK, Pashley DH, Agee K, et al. Changes in stiffness of demineralized dentin following application of collagen crosslinkers. J Biomed Mater Res B Appl Biomater. 2008;86B:330-334.

Cilli R, Prakki A, de Araujo PA, et al. Influence of glutaraldehyde priming on bond strength of an experimental adhesive system applied to wet and dry dentine. J Dent. 2009;37:212-218.

Felton D, Bergenholtz G, Cox CF. Inhibition of bacterial growth under composite restorations following GLUMA pretreatment. J Dent Res. 1989;68:491-495.

Gorman SP, Scott EM, Russell AD. Antimicrobial activity, uses and mechanism of action of glutaraldehyde. J Appl Bacteriol. 1980;48:161-190.

Perdigao J, Reis A, Loguercio A. Dentin Adhesion and MMPs: A Comprehensive Review. JERD. 2013; 219-241.

Sabatini C, Scheffel D, Scheffel R, Agee K, Rouch K, Takahashi M, Breschi L, Mazzoni A, Tjaderhane, Tay F, Pashley D. Inhibition of endogenous human dentin MMPs by Gluma. Dent Mater. 2014; 30(7):752-8.