Great question! Let me review the science before I give you the answer.
An interesting paper published in the Journal of Periodontology in 2009 described a study of 10 individuals.1 These people had to eat a Paleo-type diet, which strictly avoided refined sugars and all processed foods. For 30 days, they could not brush or floss their teeth. At the beginning of the study, their teeth were examined for any signs of gum disease, and the bacteria around their teeth were identified. At the end of the 30 day period, the bacteria around their teeth as well as any gum bleeding or gum pockets were reexamined. The results at the end of this study showed that bleeding from their gum tissues decreased, the depth of their gum pockets decreased, and unhealthy types of bacteria around their teeth decreased. They did have quite a bit of bacteria around their teeth, but they were not the unhealthy types that caused gum disease or tooth decay. As a reminder, they did not brush or floss for the entire 30 day study.
Let’s go back in time and look at our primal ancestors. They rarely had gum disease or tooth decay. We know that from skeletal remains.
Skeletal remains from 20,000 to 10,000 years ago showed minimal signs of tooth decay or gum disease.2 And, through DNA testing today, the amount of bacteria around the teeth from those skeletons were significant, but these bacteria were not the virulent types that would cause dental disease. However, the skeletal remains from 10,000 years ago until modern days progressively showed tooth decay and bone destruction surrounding the teeth. The DNA tests from these jaw samples identified increasing numbers of disease-producing bacteria.
I don’t have to tell you that our primal ancestors did not see a dentist every 6 months and did not brush or floss their teeth. (Although some societies did use sticks to clean around their teeth.) So, what was going on?
Other researchers have reported that the prevalence of dental decay and gum disease were the results of a change in the human diet – specifically the introduction of processed grains and sugars. 3 It appears that grains and sugars change the ratios of bacteria in the gut as well as the mouth to favor unhealthy types. These fermentable carbohydrates feed the unhealthy bacteria as well as damage the delicate gut lining. Undigested food particles and bacterial remnants pass through the damaged gut lining into our bloodstream causing chronic inflammatory reactions throughout the body. A common term for this is leaky gut. Cellular damage leads to organ damage that leads to body damage.
But there was an anomaly. A group of primal people, about 5,000 years before agriculture farming, had serious dental decay.4 Remains from a society in Morocco around 13,000 BC actually showed that they lived with severe tooth decay. It turned out that they were unique in that they were a relatively sedentary society and regularly ate acorns that they mashed and cooked.
Raw acorns have a carbohydrate density of 41%. The processing of these acorns probably increased the carbohydrate density to greater than 41%. The cooked acorns were sticky and clung to their teeth. In contrast, the diet of most Paleo peoples consisted of foods that contained 23% carbohydrate density or less.5 The concentrated fermentable carbohydrates from the mashed acorns changed the bacteria in the mouth to become more virulent, which initiated tooth decay.
To sum up, here is what the research suggests. Processed foods, grains and sugars replaced the nutrient-dense Paleo-type diet. As a result, there also was a decrease in the necessary dietary nutrients that provided a natural method for the saliva to remineralize teeth. These dietary changes increased the levels of harmful bacteria and damaged the gut lining. Chronic cellular inflammation became the rule rather than the exception. This change in diet was the culprit leading to tooth decay and gum disease. Returning to a strict Paleo diet should protect the health of the mouth. But there is more to the story.
Today there are at least three other considerations that generally were not a concern for our primal ancestors: inadequate levels of Vitamin D,6 chronic stress,7 and environmental toxins.8 These factors affect the biochemistry of the body. They affect the gut, the microbiome, and the immune system. Unhealthy bacteria in our gut increase unhealthy bacteria in our mouth. When fermentable carbohydrates come into contact with these nasty bugs, which congregate around the teeth as dental plaque, they set the stage for tooth decay and gum disease.
So, the answer to the original question is a little more complex than just a simple yes or a simple no. If you were strictly eating a Paleo diet and (1) maintained healthy levels of Vitamin D and (2) did not include foods that had a carbohydrate density greater than 23% and (3) had minimal chronic stress and environmental toxins in your life, then you probably would do OK without brushing and flossing most of the time. However, if you live in the modern world as I do, and there are toxins and stresses that you must endure, then I would recommend that you brush and floss on a Paleo diet at least once a day.
Dr. Danenberg is a periodontist in South Carolina who has been in practice for 40 years. Within the last 4 years, he has included Laser Periodontal Therapy as his primary treatment for periodontal disease. The procedure is called “Laser Assisted New Attachment Procedure” or “LANAP”. The last two years he has incorporated a lifestyle program for all his periodontal patients including an ancestral diet to enhance their overall body’s health and function. In July of this year he was awarded the designation, “Certified Functional Medicine Practitioner.” For more information, please visit www.DrDanenberg.com.
 Adler CJ, Dobney K, Weyrich LS, Kaidonis J, Walker AW, Haak W, et al. Sequencing ancient calcified dental plaque shows changes in oral microbiota with dietary shifts of the Neolithic and Industrial revolutions.Nat Genet. 2013;45(4):450–455. doi: 10.1038/ng.2536. [PMC free article]
 Humphrey LT, De Groote I, Morales J, Barton N, Collcutt S, et al. (2014) Earliest evidence for caries and exploitation of starchy plant foods in Pleistocene hunter-gatherers from Morocco. Proc Natl Acad Sci USA 111: 954–959doi:10.1073/pnas.1318176111 [PMC free article]
 Spreadbury I. Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity. Diabetes Metab Syndr Obes. 2012;5:175–89. [PMC free article]
 Martelli FS, Martelli M, Rosati C, Fanti E. Vitamin D: relevance in dental practice. Clinical Cases in Mineral and Bone Metabolism. 2014;11(1):15-19.
 Rodiño-Janeiro BK, Alonso-Cotoner C, Pigrau M, Lobo B, Vicario M, Santos J. Role of Corticotropin-releasing Factor in Gastrointestinal Permeability. Journal of Neurogastroenterology and Motility. 2015;21(1):33-50. doi:10.5056/jnm14084.
 Bischoff SC, Barbara G, Buurman W, et al. Intestinal permeability – a new target for disease prevention and therapy. BMC Gastroenterology. 2014;14:189. doi:10.1186/s12876-014-0189-7.