Graeme,
I have found that when I dissect cracks, very often they will spark. Is this from mercury that has leached into the crack, or is it something else?
Robert

Just so others understand what I am going on about.
In the first image, a force in the direction of arrow 1 places the dentin in the bottom corner of the cavity under tension and a crack begins to slowly propogate from the base of the cavity, obliquely through the dentin

Constant cycling creates micromovement in the direction of arrow 2 and creates a cleavage plane.  The dentin is no longer connected, so when the patient creates micro-movement by chewing, that creates a load in the direction of Arrow 1, and the gap opens slightly.  Release of the pressure then causes a hydraulic pressure on the dentin tubules and causes PAIN.  The common complatin is pain on chewing hard things and cold sensitivity, sometimes hot sensitivity (just like a debond under a composite.  The solution is the same. Get rid of the microgap!!!)

If you restore the tooth in this state, the crack is still there and continues to cause problems.  Also, if you restore then prep for a crown, the section that is cracked is still dissociated from the underlying tooth, even if it is held in palce by some composite and will most likey still cause problems

Here is how I control the microgap and get rid of it.  Most of these are done as in teh example below and I don’t bother crowning them. They remain functional and stable for years.
I have had 100% success in restoring these teeth by dissecting out the fracture using a fine bur or Air-abrasion.  Often these cracks stop short of the enamel.  If they make it all the way, the cusp falls off.

In teh next image, I have dissected out the “crack” and reduced the cusp height and created a nearly full thickness bevel onto the buccal enamel

Then it is a simple matter of restoring the tooth either using a GIC composite co-cure restoration or a bonded composite.  The advantages of this technique are that the margin – arrow 3- are ealy to finish and make very aesthetic and they are well above the gingival margin so there is little chance of microleakage and recurrent caries because it is finished on enamel, not dentin.

THe remaining cusp is now stable, there is no microgap still present that can continue moving creating thehydraulic decompression/compression cycle that causes all the pain.

.

The chance of exposure exists it the tip of arrow 4 and is totally dependent on the angle the fracture runs out at.  If it exposes, so be it, but about 99% don’t and teh patient gets to avoid an endo.  Occcasionally ther is an incredibly high pulp horn and you are doomed on these.  Just have a really close look once you have dissected out the crack.  I never remove dentin from the pulpal side of the crack, only the cuspal side, to avoid getting any closer to the pulp

Here is a case using this concept. (not good photos, I captured these with an intraoral camera several years ago)

Works on any number of fractured cusps.  You can crown thesetat any point, as long as you can establish a 2mm ferrule.

Cheers

(Edited by Graeme Milicich at 6:04 pm on May 26, 2005)

Have you ever tried a pulsed Nd:YAG for selective dissection of fracture lines?

I have found they are more precise and selective for these sorts of defects.

Bob

anyone know a price?

Allen I have some photos of you and your entourage that I MUST post this weekend. Thanks for the GREAT laughs and its awesome seeing all my net friends.

I will post the photos…..

By the way , I didnt fall for the kiss on the cheek of Rusty……the oldest trick in the book. SHeesh , next thing he will be showing up in a speedo on his ten speed……to sell me a laser.

Finally, Bob was showing how big a pocket he used the periolase on in his office last week……actually that might be the size of the Canadian wad of bills that I will need to buy one by the time he actually gets approval in Canada.

David is travelling so much these days, I hardly think he has anytime for posting these days. What I wonder is how he got such a nice wife…….

Grin

Cya and thanks again Allen , it really was great sharing a laugh or a dozen.

Glenn

6 months or so have passed since the last post – Has Elexxion yet provided copies of their published studies?