Re: Distal cusp broke on back molar

Rich Wales wrote:
Short version of my question: When repairing a backmost molar,
is it REALLY essential to restore a broken distal cusp? If so,

Longer story:

A few months ago, the distal-lingual cusp on my mandibular left
second molar (#18 in the US; #37 in Canada and elsewhere) broke
off without any warning (and without any pain) while I was eating.
FWIW, since my wisdom teeth were removed when I was in my teens,
my second molars are my backmost teeth.

My dentist has attempted to repair the tooth twice, by building
a new cusp using composite resin. The first time, the new cusp
seemed just fine at first, but it broke off after about a month
(just like the original cusp). The second repair attempt also
seemed OK initially, but it too broke off, this time after only
about a week.

Assuming a root canal is not needed (I'm seeing an endodontist
next week to have the tooth evaluated for possible RCT), I'm
wondering what my options might be for further restoration. I
realize one (maybe the best, or even the only) approach is a
crown -- but I want to know if anything else makes sense (again,
assuming I end up not needing RCT, in which case I understand
there would definitely be no alternative to a crown).

In particular, I want to understand if it might make any sense
to put another filling over the broken area of the molar, but
WITHOUT attempting to construct a full-fledged cusp where the
original cusp had been. (Sort of like a permanent version of
the temporary "sedative" filling which was put on the tooth
right after the original breakage, before my regular dentist
could do his first repair attempt.) I realize the result of
this sort of permanent repair would, at the least, involve a
slight reduction in chewing function -- owing to the one missing
cusp -- but I'm not sure I understand how much of an issue this
is. Is there some specific anatomical reason why this kind of
repair wouldn't work? Or is this just something so completely
out of the question that a reputable dentist would simply never
even consider it?

Rich Wales richw@xxxxxxxxx
*DISCLAIMER: I am not a doctor. My comments are for discussion pur-
poses only and are not intended to be relied upon as medical advice.

Another acceptable type of restoration would be an onlay--made of gold, ceramic or perhaps lab-cured resin. The exposed dentin should be covered. In a high-stress area like a second molar, resin would not likely hold up well even if a full cusp weren't constructed. I have seen large amalgams hold up in this area, but even here they usually break down eventually. The advantage of a lab-fabricated onlay (or alternatively a CAD-CAM restoration such as Cerec) is that it requires less sacrifice of tooth structure. I generally will recommend a crown though for patients with significant caries activity.