How much evidence is enough?

by Richard H. Nagelberg, DDS

The debate about the mouth-body connection is hurtling down the same pathway that many health-care revelations have travelled in the past. Examples include the dangers of smoking, the bacterial etiology of ulcers, and the inflammatory nature of periodontal tissue destruction, among many others. In some instances, researchers who proposed alternative explanations or novel ideas were ridiculed before their theories were proven and accepted.

Is there sufficient evidence currently to reach some conclusions about the mouth and the body? If not, will there ever be enough? This question is posed in a 2013 journal article (Periodontol 2000. 2013 Jun;62(1):271-86). The authors state "the weight of evidence from numerous studies conducted over this period, together with several systematic reviews and meta-analyses, supports an association between periodontitis and cardiovascular disease, and between periodontitis and diabetes. The association has also been supported by a number of biologically plausible mechanisms, including direct infection, systemic inflammation, and molecular mimicry."

Other studies are focusing on different links including periodontal disease and rheumatoid arthritis. One such 2013 study demonstrated the presence of DNA of the periodontal pathogens Aa and Pg in the synovial fluid of patients with RA. Another 2013 study states that apart from the link between RA and periodontal disease based on an enzyme present in the periodontal pathogen P. gingivalis, the two diseases have "similarities in immune response and tissue degradation and that the two diseases share the same environmental and genetic risk factors" (Curr Opin Rheumatol. 2013 Mar;25(2):241-7). The authors also stated, "treatment studies have revealed that nonsurgical periodontal treatment, that is removal of subgingival calculus and biofilm deposits, is accompanied by a reduction in the severity of RA."

About 60 years ago, smoking was thought to protect one's health and many physicians smoked. The Australian physician who postulated a bacterial cause of stomach ulcers rather than the prevailing opinion that ulcers were the result of stress, was ridiculed until he induced an ulcer in himself and successfully treated it with antibiotics. It is now a medical fact that the vast majority of peptic ulcers are caused by the bacterium Helicobacter pylori and that antibiotics are used to treat the condition.

Research into various aspects of mouth-body connections is not slowing down. Many studies conclude by stating that more research needs to be conducted to affirm their findings. So how much is enough, and who decides? Is it valid to consider the overall weight of all the studies in addition to the study protocols? No one is going to announce that the debate is over and the oral-systemic links are now proven. There are researchers and clinicians for whom enough studies have been done at this point to conclude that certain links exist and have modified their approach to diseases accordingly. For others, more work needs to be done before they are sufficiently convinced to act in the interest of their patients.

Discussion and debate among health-care professionals is healthy and to be encouraged, as long as it is focused on the ultimate goal of benefitting patients. Acting on research findings without adequate evidence is to be avoided for obvious reasons, as is ignoring adequate evidence and denying patients the benefit of the knowledge. Unfortunately it is not that simple, although it should be. Many confounders are in play including competitiveness, agendas, reputations, and many other personal factors as well as commercial interests, all of which provide barriers to the primary goal of benefitting patients. Responsible practitioners will not overstate evidence nor deny the existence of adequate evidence before acting, for any reason that does not involve the patients' best interests.

The evolving nature of accepting research findings over a number of years is a good thing. It takes a considerable amount of time and effort to amass a body of knowledge sufficient for the profession as a whole to accept and modify patient care. The infectious and inflammatory properties of periodontal disease are in this category. Only 30 years ago, these ideas were not widely known or accepted. Operating outside this knowledge in terms of patient care would be difficult to defend if the need to do so occurred. So it seems as if the answer to the question "How much evidence is enough?" is when the majority of the profession modifies the manner in which disease is addressed.

Richard Nagelberg, DDS, has practiced general dentistry in suburban Philadelphia for more than 30 years. He is a speaker, advisory board member, consultant, and key opinion leader for several dental companies and organizations, and he lectures on a variety of topics centered on understanding the impact dental professionals have beyond the oral cavity. Contact him at [email protected]