Skeptical Thoughts From The Dental Chair: Part 2, Are Routine Dental Cleanings Beneficial?

In Part I of this series we listened to the skeptical cardiologist’s seemingly paranoid thoughts questioning the risk/benefit ratio and value of things that dentists do.
One such thing is the routine 3, 6, or 12 month visit for teeth cleaning that has been recommended by every dentist I’ve ever seen, and was vigorously defended by my current dentist (actually, he deferred the defense to his assistant). Exactly what is done at these sessions apparently varies widely and has widely varying names.
A 2015 review of the topic in The Journal of Clinical Periodontology likes to use the term  professional mechanical plaque removal for the various processes involved:

“This may include scaling or polishing teeth (or both) at supragingival locations, subgingival sites or a combination of each. Oral hygiene instructions (OHI) for personally performed mechanical plaque control may be an integral aspect of this intervention. Thus, the term PMPR covers a heterogeneous group of procedures but excludes deliberate root planning or root surface debridement.”

The lead author, one Ian Needleman, works at the Unit of Periodontology, UCL Eastman Dental Institute, UCL, London, UK.
After reviewing the best evidence available (from randomized controlled trials, RCTs), the authors concluded:

The strongest findings from this review are that professional mechanical plaque removal (PMPR) when combined with oral hygiene instructions (OHI) results in a greater reduction in plaque and gingival bleeding than no treatment. However, there is no evidence of a difference in the effect on plaque and gingival bleeding comparing PMPR combined with OHI versus OHI alone when OHI is both thorough and repeated, that is there is no additional effect of PMPR on plaque and gingival bleeding above that gained from OHI where PMPR has initially been provided.

Yep, you heard that right. The dental cleaning you’ve been suffering through all your life adds nothing to the oral hygiene instructions (brush your teeth twice a day, floss once a day) and presumably the home daily oral hygiene that results from those instructions.
Furthermore :

A striking further key finding for these comparisons remains the lack of data investigating prevention of periodontitis.

Correct. There are no studies that PMPR prevents periodontitis.
A brief discussion from the NIH website on gum disease is helpful here:

When gingivitis is not treated, it can advance to “periodontitis” (which means “inflammation around the tooth”). In periodontitis, gums pull away from the teeth and form spaces (called “pockets”) that become infected. The body’s immune system fights the bacteria as the plaque spreads and grows below the gum line. Bacterial toxins and the body’s natural response to infection start to break down the bone and connective tissue that hold teeth in place. If not treated, the bones, gums, and tissue that support the teeth are destroyed. The teeth may eventually become loose and have to be removed.

The periodontal review paper concludes:

• There is most likely no value in providing PMPR without oral hygiene instruction. Repeated, thorough oral hygiene instructions for personally applied plaque control appear as influential as PMPR on periodontal health.

• PMPR might achieve greater patient satisfaction with treatment. The impact on adherence to care might be important.

• Although more frequent PMPR favours greater health gains for surrogate outcomes of prevention, there is little to guide the frequency of PMPR applications. This should therefore be judged by a needs and risk assessment although such an approach should be tested in a rigorously designed study.

A 2013 review by the Cochrane Collaboration came to similar conclusions (Cochrane review periodontal PDF), finding only one acceptable study comparing “scale and polish” of the teeth to no “scale and polish” and concluding:

This study showed no evidence to claim or refute benefit for scale and polish treatments for the outcomes of gingivitis, calculus and plaque.

A search of the website of the American Dental Hygienist Association, including the section entitled “evidence-based practice recommendations,” fails to find any support for routine dental cleaning.
To be clear, the question asked is: is there any benefit to performing the PMPR on patients with no evidence of gum disease?  If you have chronic periodontitis, then a  2015 review from the American Dental Association (ADA ) concludes that there is moderate evidence that scaling and polishing is helpful, improving the amount of clinical attachment of gum to teeth by 0.35 mm. There are no studies showing that it prevents tooth loss.
If your gums are fine and you want to start skipping the “scale and polish” two Cochrane reviews suggest that powered toothbrushes do better than manual toothbrushes at plaque removal.  I promise, that is all the oral hygiene instruction I am providing.

Finally, the theory my dentist put forth that gingivitis or periodontitis causes heart disease or coronary artery disease has not been proven. Check out this NPR story or this statement from the American Heart Association for more discussion on this topic.
Stay tuned for Parts III and IV of the skeptical questions about dentistry in which we examine the risks of disease transmission and the role of dental radiography.
Gingerly Yours,
-ACP