In today’s world, it’s easy to ignore information that contradicts our own perceptions and preferences. Take, for example, the topic of climate change. The vast majority of climate scientists (about 97 percent) agree that humans are causing global warming and climate change, yet there are still many educated people who prefer to believe that the science is wrong and that the climate crisis is manufactured. Perhaps this is because the changes that we must make in our lifestyles, if we are to halt or reverse the damage that we are doing to our planet, will be ‘inconvenient’, to borrow from the title of the Al Gore documentary. After TIME magazine announced that climate activist Greta Thunberg, who has publicly and heroically acknowledged that she has been diagnosed as having Asperger’s syndrome (a subtype of autism spectrum disorder was named Person of the Year, a deluge of abuse was hurled at this young woman claiming she was a political prop.
Why do people, including dental professionals, ignore overwhelming scientific evidence? Apparently, we “reason” not only to help us find the most compelling scientific explanations but to help us communicate with others and to fit in with larger groups. We frequently make arguments to convince others which helps us in a social environment, but it doesn’t help when it comes to a search for the most scientifically plausible explanations. There are many instances in dentistry where scientific evidence trumps the opinions of dental professionals but, for whatever reason, we are uncomfortable engaging with opinions that challenge our beliefs. For example, the collective evidence concerning the adjunctive use of the diode laser with SRP demonstrates that the diode laser offers no additional benefit compared to SRP alone1,2. Individuals who are marketing/selling diode lasers or those professionals who are lecturing on diode lasers with industry sponsorship may tell you something different.
Preventing dental caries-various hypotheses and therapeutic claims about etiology
Here’s a message that our patients hear regularly online. This recommendation is from Webmd.com (December 2019) and it reflects what many recommend to prevent dental caries.
To prevent tooth decay:
Let’s travel back to the early part of the twentieth century and review dental caries research and hypotheses and what patients were hearing back then. The focus will be on ads for personal oral hygiene products and their efficacy.
In the 1930s, almost all dentists accepted the hypothesis that dental caries was a disease of dental defects3. Vitamin D was considered an effective remedy against dental caries as a preventive agent and treatment. Defect-free teeth were considered immune to dental caries and clean teeth (brushed and flossed) were viewed as susceptible to decay3. Over time, the dental defect hypothesis was dismissed and the clean tooth hypothesis (brush/floss) was adopted instead and the American Dental Association (ADA) announced in 1945 that Vitamin D did not prevent dental caries3. The clean tooth hypothesis continued to grow even though it was refuted in subsequent clinical trials3.
In 1919, the Pepsodent Company started advertising the benefits of toothpaste and their message was about dental plaque removal to combat decay, control pyorrhea, and prevent serious diseases. (3) The Pepsodent advertising campaign was so successful that a nationwide demand for Pepsodent toothpaste was created in just one year and a worldwide demand resulted after four years3.
This Pepsodent ad appeared in periodicals as early as 1916. The advert warns against film build up on teeth. (Image via Duke University-https://idn.duke.edu/ark:/87924/r4542jx4d).
Leading dentists at that time reported how oral hygiene efforts prevented mouth infections and thus provided vast systemic and economic benefits. Dr. Alfred C. Fones ÂÂ(who is credited with starting the first dental hygiene educational program in 1913) reported in his textbook that defective eyesight was “commonly caused by poisonous products of a mouth infection.” Oral hygiene was linked to the prevention of tuberculosis, the leading cause of death in the early 20th century and an advertisement by a toothpaste company in a trade journal emphasized the “importance of mouth hygiene in tuberculosis.” In addition, brushing teeth thoroughly twice a day became a recognized routine to prevent tuberculosis3. Direct-to-consumer advertising at the time created global memes on the therapeutic benefits of oral hygiene long before scientific regulation existed. The therapeutic claims, like those above and many more, were amplified by dental tradesmen, professional associations, and public health organizations3.
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In 1930, the ADA created the Council on Dental Therapeutics (CDT) in an effort to weigh the scientific evidence regarding therapeutic claims present in dental advertising3. Claims that toothpastes provided any therapeutic benefits were prohibited by the CDT and only claims of mechanical cleansing properties, efficacy, and safety were permitted. This was the first time that therapeutic claims for oral hygiene were subject to scientific rules and the CDT’s rules stated that comparative clinical trials were necessary to support therapeutic claims. The sound tooth hypothesis surfaced again and was considered evidence-based and, as a result, vitamin D products were endorsed by the CDT. It was recognized that caries susceptibility was determined by the structure and density of the tooth and the integrity of enamel. (3) Oral hygiene was viewed as ineffective at removing bacteria from these enamel defects. Therapeutic claims for toothbrushes, another oral hygiene product, were not addressed by the CDT until 1943 when the first nylon toothbrushes were introduced3.
Outside of the purview of the CDT, other powerful forces-bureaus inside and outside the ADA or views expressed in American or European dental textbooks-promoted the clean tooth hypothesis and the message that tooth decay wouldn’t happen if everyone brushed and cleaned interproximal spaces on a daily basis. (3) The origin of this hypothesis was based on histological research which touted that acid-forming bacteria that lived in a thin film were the sole, active cause of dental caries. Therefore, the biological plausibility argument became that antiseptic oral rinses, toothpastes, and brushing teeth prevented dental caries. There was even a recommendation in dental society educational materials in 1930 that teeth should be brushed five times a day3.
Industry and product endorsement wins over science
In 1930, the CDT declared that toothpastes should join soaps in cosmetic aisles of stores but the ADA was sued by a manufacturer of oral hygiene products for $500,000.00 ($7.5 million inflation-adjusted) because they informed the public that oral hygiene products had no therapeutic benefits. (3) As a result, the ADA started to lose advertising revenue. Industry and their advertising budgets abandoned the dental profession for the most part and engaged in direct-to-consumer marketing instead. (3) After a lot of rankling in the dental profession, discussions were initiated to suspend the activities of the CDT. This didn’t happen but the CDT’s authority to determine therapeutic claims was taken away3.
Preventing dental caries: How memes on dental plaque influenced patient experience and ignored the role of diet in dental caries etiology
Direct-to-consumer advertising started to show that dental plaque was the formidable cause of disease. Personal and professional oral hygiene intervention was promoted for dental caries prevention. The CDT now watched toothpaste companies enlist the help of dentists to increase sales in the oral hygiene industry and the “see your dentist twice a year” message began to appear in consumer advertising. Here’s an example of a 1931 direct-to-consumer advertisement at the time:
No dentifrice (i.e., toothpaste) can effectively clean the hidden areas of the teeth-the interproximal surfaces, the tiny pits, and crevices and the parts beneath the gum margins. These are the real danger spots where the toothbrush cannot reach. These are the places that tartar collects and where germs are apt to cause decay spots. If allowed to go unattended, these conditions frequently lead to a vast train of serious ailments.
These surfaces require frequent, thorough inspection and cleansing by a Dentist. At least once in three months, everyone should receive this treatment called Dental Prophylaxis to keep the teeth really clean, the mouth healthy, and the body reasonably safe from diseases emanating from the mouth.
…A good dentifrice can retard the development and activity of decay germs….It can retard the formation of tartar-thereby giving some protection against gum infection and pyorrhea-but it cannot prevent or completely correct this condition. Only your Dentist can safeguard you from these grave dangers3.
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The global memes on the therapeutic effectiveness of toothpastes were bombarding consumers at the time by radio. Pepsodent promoted its toothpaste nightly, six days a week to twenty million listeners and Iodent toothpaste promoted the “valuable lesson of oral hygiene” to three-quarters of the US population via the NBC network. In 1944, the ADA distributed an educational movie showing how improved oral hygiene and visits to the dentist were two of the three keys to prevent dental and systemic diseases and the movie was funded by a toothbrush manufacturer with a script stating to “use the best toothbrush obtainable.” According to this review, consumers had developed a false sense of security in accepting the message of effectiveness of oral hygiene products. (3) In accepting false therapeutic claims about oral hygiene products, consumers discounted the harms of sugar and there was no attempt to diagnose and treat dental or medical causes of dental caries. (3) Oral hygiene companies with ADA-accepted toothpastes printed ads in the ADA Journal which further perpetuated the value of oral hygiene and prophylaxis in dental caries prevention.
This ad promoting Dr. West's Toothpaste appeared in The Saturday Evening Post on May 6, 1933. (Image via Duke University-https://idn.duke.edu/ark:/87924/r4gb1z432).
The oral hygiene companies selling nonâADA accepted toothpastes, who were likely engaged in directâtoâconsumer advertising, had greater liberty in explicitly enforcing the memes that are now common wisdom, that toothpaste (without fluoride) removed dental plaque and thus prevented dental caries. The Sugar Association similarly inferred that sugar did not cause dental caries as long as teeth were clean3.
Who’s winning the dental caries prevention battle?
Results of controlled trials and the scientific community make it clear: Oral hygiene without fluoride should be last as a priority for dental caries prevention. The CDT was correct in 1930 in their assertion that oral hygiene products fail to control dental caries3. The moderate restriction of added sugars has been shown (in controlled trials) to prevent 70 percent of dental caries. In addition, clinical trials suggest that vitamin D prophylaxis and fluoride toothpaste can prevent 50 percent and 30 percent of dental caries, respectively3.
Advertising memes throughout the last century have pounded the global message of therapeutic benefits of oral hygiene into the heads of consumers and dental professionals and these messages are inconsistent with evidence3. According to Hujoel:
Directâtoâconsumer advertising can indeed turn ineffective and potentially harmful drugs into blockbusters, advertising to health professionals can indeed create a 100 percent to 400 percent return on investment for the advertiser, and advertising revenues can indeed lead professional organisations to adopt conflicted editorial policies and conflicted standards of care3.
Following the science, objectively, just like in climate science, is difficult because reasoning is often clouded by our social environment, our personal preferences, and bias. There are many forces at work which collectively distort our reasoning and we tend to block out information we disagree with. Dental professionals can overcome deep-seated flaws and we can open ourselves up to compelling evidence, and become more objective, even when it means going against the status quo. Advertised health claims for oral hygiene products are even going beyond dental therapeutic claims. For example, The National Healthy Mothers, Healthy Babies Coalition, funded by a toothbrush manufacturer, advised expectant mothers “to make sure to brush teeth twice a day,” because periodontitis contributes to more adverse pregnancy outcomes than alcohol and tobacco combined. (3) Company and speaker/writer claims about improving overall systemic health with improved or vigilant oral hygiene need to be consistent with pivotal trials funded by the National Institute of Health3.
Professional organizations are slowly adopting an evidence-based approach to health recommendations but bias, self-interest, and competitive forces remain a threat to objectivity.