A study published in The Journal of Evidence-Based Dental Practice recently examined how dentin bonds degrade over time. This was the first in vivo human study on bond degradation. It showed expected results. Over a 3 year time period, the bind between dentin and resin. After 3 years, bond strength decreased almost 60%.  The study did indicate some clinical steps that dentists can easily do to maximize bind strength. These included using a 4th generation three step dentin bonding system, improving impregnation of the hybrid layer by using multiple applications of resin primer, and ensuring adequate polymerization of the adhesive system.

Of course there is much in vivo human work to do studying bonding. This study goes a long way but there are still some questions. After the dentin bond has deteriorated, does the enamel bond that is theoretically there keep the restoration viable?  Certainly in traditional amalgam restorations there is no dentin bond yet they seem to last for years with no problem. Does the resin’s affinity for water absorption cause problems long term after the dentin bond has deteriorated. These are all questions we should be pondering when placing resin composite restorations.

Study citation:  In vivo degradation of resin-dentin bonds in humans over 1 to 3 years. Hashimoto M, Ohno H, Kaga M, Endo K, Sano H, Oguchi H. J Dent Res 2000;79(6):1385-91

The fine folks over at J. Morita make more than the Root ZX apex locator we know and love.  They have been producing some very nice consumable products recently as well.  I had a chance to demo their provisional cement, PowerTemp and I have nothing but good things to say about it.  Provisional cement is one of those things that you never think about until you have a problem.  There are lots of different options on the market.  For me, there are certain hall marks I am looking for in a provisional cement.  Those hallmarks are:
1- The dispensing system should be easy.  I hate having to mix things.  Syringe-mixed provisional cement is easy, neat and quick.
2- It needs to be non-eugenol.  I use strictly resin cements.  Eugenol based provisional cements can interfere with the set of of resin or resin modified glass ionomer cements.
3- It needs to hold tightly.  I hate having to waste time with recementing provisionals.
4- It needs to hold tightly but come off when I want it to.  I also hate having to cut of provisionals because I can’t remove them.

PowerTemp passed all these tests with flying colors.  It is easy and neat to dispense and load a provisional crown.  It sets relatively quickly and cleans up easily as well.  In every case we have used it, no provisional has came loose.  I also never had to cut a provisional off.  PowerTemp is non-eugenol so there is no chemical inhibition of resin curing.  Like most provisional cements there were some areas of the preparation where the PowerTemp was a bit difficult to remove.  This was mainly on resin buildup materials.  I used a cotton pellet with chlorhexidine to get those areas clean.

PowerTemp is competitively priced with other provisional cements.  I would highly recommend it if you are looking for a provisional cement that is easy to use and does it’s job well.

http://www.morita.com/usa/cms/website.php?id=/en/products/dental/partner/auxiliaries/powertemp.htm