Expert: Mark Bornfeld DDS - 7/26/2007

Question
Dr. Bornfeld,

Am 50 years old, with #18 molar that is severely worn, presumably from grinding. Did not start wearing a night guard until a year ago, but believe most wear likely occured before then.

Dentist originally suggested need for a crown lengthening followed by gold crown/onlay. Visited periodontist who took an xray, studied the tooth and advised against doing a crown lengthening - felt tooth was too worn down to be able to perform without a) exposing furcation, and b)cited need to taper bone removal to next tooth (#19) with concern that would only risk that tooth later.

Dentist suggested next step was root canal followed by post and core restoration - on looking at tooth again subsequently indicated would not have sufficient tooth to get impressions and manage crown build up properly - might end up with temporary crown and not be able to proceed with permanent.

With nothing to lose, followed suggestion for 2nd opinion on crown lengthening; 2nd perio. assessed and sees no problem - feels roots are long enough to provide stability, no risk to adjacent tooth.

Followup discussion with dentist has not produced much clearer direction, needed to repair composite filling on #19 and during the visit, dentist proceeded to also do composite build up on #18 - no issue with that, even if I grind that away it provides protection for some length of time.

Dentist then took impressions for crown prep for #18 and #19 (also has "cracks" in it though tooth is solid), which am scheduled for in couple of weeks. No crown lengthening or root canal...In principle, I'm ok with not doing the crown lengthening - would seem that once the bone is gone, it's permanent. Would seem that composite restoration provides some build up on which to place the crown, but (I imagine) not as solid as the tooth itself would be. If crown can't be solidly attached to #18, options would be to re-assess and subsequently do crown lengthening, root canal, or splint the two crowns.

1. Aside from the obvious difficulty of cleaning between two teeth which are conjoined with a splinted crown, are there any other reasons for avoiding splinting - eg. risk of having to touch both if either tooth needed to be treated.

2. Assuming the crown/onlay on #18 is placed, the margins above the gum have got to turn out absolutely minimal, especially on the back of the tooth - does this present any significant concerns other than hygiene?

3. Significantly greater tendancy towards crown failure of placing over a tooth that has at least been partially restored with composite?

4. Dentist hasn't done a stellar job of communicating options and articulating the risks/benefits of alternative treatments...not sure this reflects negatively on him or is more the nature of what is an apparently challenging restoration and a desire to proceed slowly to see what works. General thoughts?

Understand this is all in the context of having not seen the tooth or any x-rays...none-the-less, have read many of your responses and appreciate any input you might have. Thank you.

Answer
Dear Carl,

1. Aside from the obvious difficulty of cleaning between two teeth which are conjoined with a splinted crown, are there any other reasons for avoiding splinting - eg. risk of having to touch both if either tooth needed to be treated.
A: You've pretty much delineated the scope of the problem. Not being able to floss between two teeth is a significant disadvantage; depending on the distance between the two splinted teeth, it may or may not be possible to substitute some other means of interproximal cleaning. And you're right on the second count-- splinting two teeth compels them to more or less share a common fate-- a problem with one of the crowns means a problem with both.

2. Assuming the crown/onlay on #18 is placed, the margins above the gum have got to turn out absolutely minimal, especially on the back of the tooth - does this present any significant concerns other than hygiene?
A:The biggest problem derives from the conflicting need for both retention (the reliability of the cement bond between restoration and tooth) and occlusal clearance (available vertical height between the tooth being crowned and the opposing tooth). In order to create room for covering the tooth with a crown or onlay, the chewing surface must be ground down-- otherwise, the thickness of the restoration would cause it to interfere with the closure of the mouth. However, the tooth is already short, as evidenced by your dentist's desire to expose more of it by doing a crown lengthening. This situation tends to favor the making of crowns that are either so thin on their chewing surfaces that they wear through and perforate, or are so short that they repeatedly fall off the tooth and require re-cementation.

3. Significantly greater tendancy towards crown failure of placing over a tooth that has at least been partially restored with composite?
A: Not necessarily, provided that the dentist can realistically assess the amount of remaining tooth structure available to support and retain the crown or onlay. Whatever resin is on the tooth will not appreciably add to support or retention. In fact, your dentist may need to drill the resin off the tooth to provide enough room for the thickness of the crown on its occluding surface.

4. Dentist hasn't done a stellar job of communicating options and articulating the risks/benefits of alternative treatments...not sure this reflects negatively on him or is more the nature of what is an apparently challenging restoration and a desire to proceed slowly to see what works. General thoughts?
A: Maybe he's not a great communicator, or maybe there's something more insidious-- he may not have enough experience to anticipate the potential pitfalls of his treatment options. I suppose every dentist has to learn through experience, but his knowledge should not come at your expense.

The restoration of worn teeth is a particularly difficult task, and is often more complex than appreciated when looking at one tooth at a time. The scope of the problem may be wider, involving more teeth, and may have actually caused a reduction in vertical facial height. If so, optimal management may require more extensive treatment, including the opening of the bite. You may wish to seek a second opinion just to assure you're getting the whole picture.

Good luck!

Mark Bornfeld DDS
www.dentaltwins.com
Brooklyn, NY