Cavities and Bisphosphonates

Houston dentist Spiker Davis recently wrote that he had seen a lot of cavities (caries) in patients taking oral bisphosphonates. These patients were long-term patients with good dental health:

I am a general dentist and I have noticed lately that I have 3 patients who haven't had a cavity in 20-30 years and all of a sudden they had had a lot of decay. I'm trying to figure out why a common thread of bisphosphonates showed up. I haven't seen or found anything that says that and was just wondering if you had heard of that?

It took me forever to get back to Dr. Davis, and by the time I did, he had this to add:

Since the last email I have had two more patients with bisphosphonates that have shown up with big cavities. What I am finding from other doctors that I have emailed is that after being on these meds for several years or after mixing them with other drugs they might be taking that they start to get a very dry mouth. That is obviously a common side effect of lots of meds but with a very dry mouth they are then very susceptible to rapid decay. So I think that is what is going on. So if you hear of anything else then please let me know, but this is approaching 10 patients in the last 2 years.

First, apologies to Dr. Davis for not answering sooner. I finally got around to looking into the research databases to see if there were any scholarly papers on the topic. The short answer is "No".

Background

The literature is still primarily focussed on intravenous bisphosphonates as used by cancer patients and its connetction to Bisphosphonate- Related Osteonecrosis of the Jaw (BRONJ) or "jaw death". As a reminder: in 2004 Novartis notified healthcare workers about a change in labelling that noted the increased risk of ONJ from intravenous bisphosphonates and in 2005 oral treatments were added to the labelling. The incidence of BRONJ from IV bisphosphonates has been estimated by various studies as being between 0.8% and 12% (800/100,000 to 12,000/100,000). The incidence from oral treatments has been estimated to be much lower, on the order of 0.7 per 100,000 based on manufacturer data for alendronate. A survey of 13,000 Kaiser-Permanente patients on long-term alendronate treatment found an incidence of 0.06% (60/100,000). Large-scale Australian and German surveys came up with even lower numbers. All of these data are according to the American Association of Oral and Maxillofacial Surgeons Position Paper on Bisphosphonate-Related Osteonecrosis of the Jaw—2009 Update.

Cavities and Bisphosphonates

Here the AAOMS has almost nothing to say except:

It is important to understand that patients at risk for or with established BRONJ can also present with other common clinical conditions not to be confused with BRONJ. Commonly misdiagnosed conditions may include, but are not limited to alveolar osteitis, sinusitis, gingivitis/periodontitis, caries, periapical pathology and TMJ disorders.

The misdiagnonsis risk here flows the other way. That is to say, patients are more likely to be misdiagnosed as having BRONJ when in fact they have one of these more common conditions, so it would not be an explanation for a perceived increased in caries. And even were the misdiagnosis to go the other direction, given the rarity of BRONJ from oral bisphosphonates, it's unlikely that any given practitioner would have enough patients presenting with BRONJ to see a statistical rise in the cases of caries due to misdiagnosis.

So then the question remains whether or not there is any evidence of an increase in caries. There are as yet no studies that I could find that address the question. A study of cancer patients on IV bisphosphonates found no difference in the occurrence of caries between patients who had BRONJ and patients who didn't, but this study was trying to identify risk factors for BRONJ and did not compare incidence of dental problems with the general population and did not, in any case, study oral treatments.[1]

There is one study comparing different fluoride treatments in Icelandic children. The three-year, double-blind study of 1,161 Icelandic children ages 11 and 12 tested the efficacy of various fluoride treatments, one of which included a bisphosphonate, tested against the "positive control" monofluorophosphate. In this case they found that sodium fluoride coupled with 1% disodium azacycloheptylidene-2.2-bisphosphonate (AHBP) "was significantly more effective than the positive control." [4] Obviously, the connection between caries prevention in children using a topical treatment that includes a bisphosphonate tells us almost nothing about the effect of long-term use of oral bisphosphonates in an elderly population. So, interesting though that research may be, it doesn't provide any help to dentists on the issue at hand.

The only thing I can do in the absence of focussed studies is propose a possible counter-hypothesis to the hypothesis that oral bisphosphonates like Fosomax cause cavities. Because tooth extractions increase the risk of BRONJ, professional associations frequently recommend that caries be treated early and that care be taken whenever possible to identify problems well before extraction would be necessary.[2,3] So one possibility is that patients who have previously been lax about dental care but who have been put on bisphosphonates, might be motivated to come in for exams and cleanings more often due to fear of BRONJ, and this increased attention might mean that a given dentist would see a lot of patients with cavities who are on bisphosphonates, whereas patients similarly lax about dental health remain so because they aren't being pushed into more frequent dental exams by their other health practitioners. The problem with this is that Dr. Davis said his patients were people with excellent dental health who had not had a cavity in 20–30 years, so this scenario would not apply to them.

Conclusion

For the time being there is no data that I could find to support the hypothesis that oral bisphosphonates contribute to cavities, but there also does not seem to have been any work done on the topic, so it remains an open questions.

Update

Reader Shia Elson has this to add: "I've had two cavities BELOW CAPS for the first time in 30 year after 14 mo of biphosphonates, but what I'm especially suprised at is that I've developed grooving un my upper incisors in the last year. I wonder if the dentine is softer?"

If you know of an article on the subject, please Contact me so I can correct this article. Thanks!

Sources

[1] Daniela Carmagnola. Silvio Celestino and Silvio Abati , "Dental and periodontal history of oncologic patients on parenteral bisphosphonates with or without osteonecrosis of the jaws: A pilot study", Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, Volume 106, Issue 6, December 2008, Pages e10-e15.

[2] American Association of Endodontists, "Bisphosphonate-Associated Osteonecrosis of the Jaw," Endodontics Colleagues for Excellence, Winter 2007. Available online

[3] José Bagán et al., "Recommendations for the prevention, diagnosis, and treatment of osteonecrosis of the jaw (ONJ) in cancer patients treated with bisphosphonates," Medicina Oral, Patología Oral y Cirugía Bucal, v.12, n.4 (August 2007). Available online.

[4] G. Koch, I Bergmann-Arnadottir, S Bjarnason, S Finnbogason, O Höskuldsson, and R Karlsson. "Caries-preventive Effect of Fluoride Dentifrices with and Without Anticalculus Agents: A 3-year Controlled Clinical Trial." Caries Res, 24.1 (1990): 72.