New Findings Relevant to Our Practices and Our Patients
These are uncertain times. But today’s uncertainty is different from what humanity has historically faced. Our species is much less uncertain about premature death, enslavement, poverty, illiteracy, war, or violent crime than ever before (Pinker, S., The Better Angels of Our Nature, 2012). Instead, we are faced with epistemic uncertainty; that is, in the modern era we increasingly doubt what we thought was true. Traditions, institutions, and belief systems are challenged with unprecedented levels of skepticism. This extends to medicine and to our niche as dental professionals. To constrain uncertainty, it is possible to find clarity by distinguishing among three conditions: what we have evidence for, what we have evidence against, and what is currently lacking evidence either way; and to knowing when the conditions change. Being uncritically and unalterably sure of ourselves is easy and natural, and often a path toward error.
An example is the recent media takedown of flossing. We have previously written an entire newsletter analyzing this event, concluding that the lack of extensive evidence for the benefits of flossing did not necessarily prove its ineffectiveness. Absence of evidence is not evidence of absence. There are myriad questions that science has not answered. Sometimes there is no answer, but more often, there has not been enough research done to allow a conclusion. In these cases, we must rely on guidance from experts and experience. These are less reliable than science, and may be refuted by future findings. But in the absence of conclusive evidence, this is the best we have. With regard to flossing or equivalent substitutes, the experience of experts overwhelmingly supports its use. In addition, research has shown that electric toothbrushes, Waterflossers, and interdental aids such as proxabrushes, stimudents, and rubber tip stimulators, can achieve most or all of the benefit of flossing. So when floss is not used, or used incorrectly, other options can suffice. The fact is not that flossing is a waste of time, but that there are reasonable alternatives, and that doing something the wrong way can be just as bad as not doing it at all. But that is not the same as not doing anything at all.
A second example concerns blood pressure screening in our offices. For decades we have believed that patients should not be treated if their BP exceeds a certain limit – typically 160/100 for routine treatment and 180/110 for urgent treatment. But these guidelines have never been verified by research, and they were recently revisited by a panel of expert physicians and dentists using protocols developed for anesthesiologists by the American Heart Association and the American College of Cardiology (Yarows, S et al, JADA 151(4): 239, April 2020). The panel concluded that a BP less than 180 /110 could reasonably be considered safe for dental procedures. Above these limits, the recommendation is to assess the patient’s risk based on two criteria. The first includes 3 questions:
Is the patient taking antihypertensive medication, and was it taken today?
Has the patient been seen and managed by a physician in the past 6 months?
Is the patient anxious or exhibiting a heart rate >100 beats per minute?
The second criterion also asks 3 questions:
Was the patient able to drive or take public transportation, and then walk into our office?
Does the patient take care of their own house or apartment?
Can the patient walk up a flight of stairs?
If one of the questions in category one and one of the questions in category two are answered yes, then the patient should be considered safe to proceed with treatment. This seems like a pretty lax screening process, but it is based on the reality that a huge number of actively hypertensive patients have been treated with extremely few cardiovascular incidents. With this extremely low incidence, controlled studies are impossible to design. And in the absence of controlled studies, expert guidance is the best we have.
A final example centers on implants. For the first decades of implant use, multiple studies found very high success rates. But success was defined as the implant surviving in the mouth. Once the distinction was made between survival and health, it became clear that a significant proportion of implants were surviving but losing bone. Our belief that implants could replace conventional treatment such as root canal, post and core, and crown lengthening therapy, was naive. So our profession has swung back toward assessing the feasibility of saving teeth rather than reflexively extracting and replacing them. Similarly, we once thought that the widest, longest implants should be used since they provided maximal surface area for osseointegration. But the relatively recent finding that 2 mm of bone should be preserved around implants has driven us to use narrower implants, even in central incisor, canine and molar sites. And now, an argument is emerging to use shorter implants, since they are often equally successful to longer fixtures, require less bone grafting, and are easier to remove in the event of long-term failure.
And during the pandemic, understanding and updating what we know and what we don’t know can make all the difference.
Amy and David
P.S. As we were completing this, a study was published showing that elderly people who flossed their teeth had lower rates of caries and periodontal disease and lost fewer teeth over a five-year period (J Dent Res 2020(9):1047). So in this case, our conclusions in the absence of research have now been validated in the presence of research.