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Medical Forum / General / Dentistry / August 2006Distal cusp broke on back molar
Short version of my question: When repairing a backmost molar, is it REALLY essential to restore a broken distal cusp? If so, why? 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@richw.org http://www.richw.org *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. > Short version of my question: When repairing a backmost molar, > is it REALLY essential to restore a broken distal cusp? If so, [quoted text clipped - 41 lines] > *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. Steve > Another acceptable type of restoration would be an onlay-- > made of gold, ceramic or perhaps lab-cured resin. The > exposed dentin should be covered. . . . 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. OK. Thanks for mentioning this. How would an onlay typically compare, in terms of cost, with a full crown? (I want to be cost-conscious if possible, and I'm sure my insurance will also be interested in the cost issues. :-}) > 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. Hmmm. So, omitting the broken cusp in a restoration of #18 might not really reduce the stresses, then, as I had imagined it would? > I generally will recommend a crown though for patients with > significant caries activity. And something I didn't mention in my initial posting is that I had a sizable amalgam (covering most of the mesial-occlusal-lingual quadrant) put on #18 when I was in high school. This amalgam lasted over 20 years until it started to have problems and was replaced with another amalgam about a dozen years ago; the second amalgam, in turn, started breaking down recently, and my current dentist replaced it with resin a couple of months ago. It's been suggested to me that having such a sizable restoration on this molar, so long ago, means the molar has been subjected to significant additional stresses for decades, and that eventual breakage of the distal-lingual cusp was probably inevitable sooner or later. I haven't really had a lot of cavities since high school, though; I've brushed and flossed regularly for many years now. Rich Wales richw@richw.org http://www.richw.org *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 [quoted text clipped - 7 lines] > cost-conscious if possible, and I'm sure my insurance will also > be interested in the cost issues. :-}) Generally the fees should be pretty close. > > In a high-stress area like a second molar, resin would not > > likely hold up well even if a full cusp weren't constructed. [quoted text clipped - 3 lines] > Hmmm. So, omitting the broken cusp in a restoration of #18 might > not really reduce the stresses, then, as I had imagined it would? Including a cusp will definitely increase the chances of the restoration breaking IF the cusp is in function. Often the lingual cusps of lower second molars aren't in heavy function. This depends on the particular way your teeth come together. > > I generally will recommend a crown though for patients with > > significant caries activity. [quoted text clipped - 12 lines] > breakage of the distal-lingual cusp was probably inevitable sooner > or later. Certainly having a large restoration weakens the remaining tooth structure. If the restoration is wide it particularly predisposes the cusps to fracture (this has to do with the anatomy of the enamel and direction of the enamel rods). Amalgam also expands slightly when setting. Some people maintain that this leads to fracture, and would favor composite resin for this reason. However, composite resins contract when setting (and by a considerably higher magnitude than the expansion of amalgam) so I don't think resin would be any less likely to encourage fracture. In any case, if the restoration is wide, the cusps should be covered--whether by an onlay or a crown. It really doesn't matter in this context whether you have a full contoured cusp in function or not. Steve > I haven't really had a lot of cavities since high school, though; > I've brushed and flossed regularly for many years now. > > Rich Wales richw@richw.org http://www.richw.org > *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.  SignatureMark & Steven Bornfeld DDS http://www.dentaltwins.com Brooklyn, NY 718-258-5001 Steven Bornfeld wrote: > Including a cusp will definitely increase the chances of the > restoration breaking IF the cusp is in function. Often the > lingual cusps of lower second molars aren't in heavy function. > This depends on the particular way your teeth come together. My mandibular second molars are slightly lingual in relation to their maxillary counterparts. The lingual cusps of my maxillary second molars are lined up with the occlusal basins of the corresponding mandibular second molars. When I close my jaw slowly and carefully, the first points of contact between upper and lower teeth involve the second premolars (#4 touching #29, and #13 touching #20). Rich Wales richw@richw.org http://www.richw.org *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. > Steven Bornfeld wrote: > [quoted text clipped - 11 lines] > contact between upper and lower teeth involve the second premolars > (#4 touching #29, and #13 touching #20). I've rarely had a patient as in touch with their occlusal scheme. Seriously, if you are contacting your second premolars first when biting normally (what we call centric occlusion), they are in hyperocclusion and I'd expect them to be tender. When you bite down normally, all the back teeth and often the front teeth should pretty much meet simultaneously. I've seen situations where this is not the case--including severe ones where the only contacting teeth were the second and third molars. But these people have significant skeletal deformities. Have your dentist check for centric prematurities. If what you say is true, they are likely easy to correct. Steve > Rich Wales richw@richw.org http://www.richw.org > *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. > if you are contacting your second premolars first when biting > normally (what we call centric occlusion), they are in hyper- > occlusion and I'd expect them to be tender. . . . Have your > dentist check for centric prematurities. If what you say is > true, they are likely easy to correct. Thanks. I'll ask about that after the current problem with my #18 has been taken care of. Given what I've described, though, does it sound like it would be that crucial to restore a fully functional distal-lingual cusp on my #18? (Assuming, of course, that I don't end up needing a root canal and a full crown.) Rich Wales richw@richw.org http://www.richw.org *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. > > if you are contacting your second premolars first when biting > > normally (what we call centric occlusion), they are in hyper- [quoted text clipped - 9 lines] > my #18? (Assuming, of course, that I don't end up needing a root > canal and a full crown.) With the caveat that I haven't examined you, and your dentist will definitely know more by examining you, no. The buccal cusps of the lower molars ideally sit in the fossae of the upper; the palatal cusps of the upper molars sit in the fossae of the lower molars (in centric relation). The actual movement in function of the various surfaces against each other can be numbingly arcane, and it's altogether possible another dentist with a specific idea of how teeth contact in function could disagree. However, if you have centric holding cusps your bite should be stable even if the lingual cusps are out of contact. Steve > Rich Wales richw@richw.org http://www.richw.org > *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. Unless you are having symptoms on the tooth, the endodontist should not recommend a root canal. Endodontists can perform root canals on anything...however, if the tooth is asymptomatic, and the referring dentist isn't even sure if he/she is going to put a crown on it, what more can the endodontist really tell you? > Short version of my question: When repairing a backmost molar, > is it REALLY essential to restore a broken distal cusp? If so, [quoted text clipped - 41 lines] > *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. > Unless you are having symptoms on the tooth, the endodontist > should not recommend a root canal. Endodontists can perform > root canals on anything...however, if the tooth is asymptomatic, > and the referring dentist isn't even sure if he/she is going to > put a crown on it, what more can the endodontist really tell you? The reason I was referred to the endodontist is that I've started having intermittent pain in my lower jaw near the tooth in question (#18) -- especially if I've been chewing or if I eat something cold (I don't drink coffee or tea, so I'm not sure about heat sensitivity). I'm taking ibuprofen (Advil / Motrin) for the time being to manage the pain, plus topical Orajel (benzocaine) as needed. I'm not afraid of having a root canal if necessary, but I don't intend to agree to RCT unless it really is necessary (i.e., unless there really is pulp infection). The referral to the endodontist is to determine if RCT is really required in my case or not. My primary dentist actually recommended a gold crown at the start, but when I hesitated to have such an invasive and expensive procedure done right away, he opted for a more conservative route (which, however, appears not to be feasible after all). I understand that if I do have a root canal, this will definitely make the tooth weaker, and I'll really have no option at that point but to have a full crown. I had a large (mesial-occlusal-lingual) amalgam filling put on #18 when I was in high school. This amalgam lasted over 20 years until it started to break down and was replaced with another amalgam about a dozen years ago. My current dentist recently replaced this large amalgam again, a couple of months ago, with a composite resin filling because it was starting to break down again. It's been suggested to me that one reason #18's distal-lingual cusp broke off recently may be because replacement of such a large amount of the tooth with a filling, decades ago, has subjected the tooth to extra stresses over time (which were bound to cause further problems eventually). Rich Wales richw@richw.org http://www.richw.org *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. |
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