Adhesive 101

Hey all,

I had a really rough weekend. I don't know when I have been more disappointed by sports in my life. I don't know if you watched the college basketball games this weekend or not, but the Gators lost in a heart-breaker. We were winning by 13 with 8 minutes to play when we had a total collapse. I thought we were the better team (at least we were for 32 minutes of the game). I am telling you, I think I need a sports therapist.

Now every time I hear someone talking about the Final Four I turn the station (radio or TV).If I hear the word Louisville, I get physically sick. I had to kick a Louisville fan off this blog for good after she made a comment about it. I am looking into how to get her dental license revoked. She messed with the wrong blogger.

It has been a tough week for me. Saturday night, I woke up in a cold sweat (it could have been from the alcohol) at 2:30 a.m. and I couldn't go back to sleep. It gave me an opportunity to watch a movie I had, The Girl with the Dragon Tattoo. Wow, was this movie graphic. Very explicit in a lot of ways. Good movie, but very graphic. I told you I read the book and that was really good.

Speaking of books and movies, I had to take my son to see The Hunger Games because he and I both read the book. I thought it was okay. The book was so good that I thought the movie was going to have trouble living up to it. It did, but I thought it was a pretty good movie. It was a 2 and a half hour movie and when it was done I was like, "That was it? It was too short.”

Okay, topic. I told you that from time to time I am going to test-run my lecture on you guys. I have been spending a lot of time reading up on bonding agents, trying to learn the science behind them. Not to act all "la dee da," but more so I can answer questions if they arrive. If I am going to go up there and speak, I kind of have to know this stuff, even if I am not going to talk much about it.

I don't really want to spend much time on it and I don't want people to be bogged down in the details of stuff they don't really need to know. Clinicians Report says, "If you like your material and it is close to the top of the list, just keep doing what you are doing." That means that people don’t want to be bothered with the details, they just want to know the stuff they are using is okay.

But I thought the stuff I am reading is interesting enough to let you guys know about it. I will do my best to not screw up the science. And if you are a dental geek and get into this stuff, let me know and I will try to do more of it. I think I will tell you what I know today and then have a counterpoint tomorrow.

Adhesives are a big thing in posterior composites. Fourth generation adhesives were the gold standard of bonding strength. Now, 6th generations are giving the 4th generations a run for their money. The bond strength is there at the time of the filling placement (we know this), but the issue is becoming that dentin bond strength is diminishing over time. So what is going on?

Have you heard of things called MMPs - matrix metalloproteinases? Me neither. These are "a family of zinc-dependent structural and functional related endopeptidases that are capable of degrading extracellular matrix proteins." [Did I make your eyes just glaze over? stay with me.] In Gammichia speak, MMPs = bad.

Let me back up. The goal of manufacturers is to develop bonding adhesives that completely encapsulate the conditioned collagen fibrils through total infiltration of resin. Collagen fibrils that are completely surrounded by resin are protected from degradation. These are not my words. I am quoting a lot from an article written by Gregg Helvey, DDS. (By the way, this guy is in private practice. How do you dentistry all day and know this much about adhesives? Boggles my mind.)

If the adhesive does its job right, it is supposed to protect the collagen from degradation. But none of the adhesives are doing it completely. They are also saying studies have shown that host-derived proteinases also contribute to the breakdown of collagen matrices. This means there is going to be breakdown in a filling at the adhesive level. But the host of the filling has something to do with it. You and I see this every day. One filling you do starts to look like crap in 5 years and others you did 14 years ago, look awesome. In Gammichia speak, certain people you put a filling in will break down a filling faster.

Turns out, MMPs are bound to the collagen matrix in a mineralized state where they are covered with extrafibrillar and intrafibrillar apatite crystallites. While the MMPs remain in this mineralized state, they are inactive. So we are having the unprotected collagen being degraded by MMPs because the adhesive is not doing its job. In Gammichia speak, crystallized collagen = good.

Cool so far, isn't it?

Naturally, once scientists know this, they are going to try to create a bonding agent to fully crystallize the collagen, protecting it from degradation. So, scientists have found that acid-etched collagen matrixes don't degrade if in an aqueous solution of 0.2% chlorhexidine (CHX), like Consepsis. They do degrade over time, but this is definitely a step in the right direction. They are finding that the degradation doesn't start until 9-18 months after bonding. In Gammichia speak, Consepsis before the acid etch stage = good.

But 0.2% chlorhexidine (CHX) is not the only MMP inhibition. There are a ton of other things, bromide being one of them. Can you imagine if they had a bonding agent with bromide in it? That would be smart.

In fact, the people at Kuraray are way ahead of us. This is something else that boggles my mind. I am hearing about this MMP stuff for the first time, yet they already have a product for that. That means the research has been done on MMPs. That means all the research and development has been done on a product. That means the product has been made and is available all before I hear about MMPs.

There is a product that is called Clearfil SE Protect that incorporates bromide. That means there is a product that is Clearfil SE plus an aqueous solution of bromide that fully crystallizes the collagen, protecting it from breakdown.

How can we do more? How about releasing fluoride in an adhesive? Well, guess what. They have thought about that, too. There is a product called Clearfil Tri-S Plus. That is, Clearfil SE+bromide+fluoride. Incredible right?

Okay, let’s stop there for today. My head hurts.

Have a great Thursday.
john