Tooth wear is considered a bad thing in the modern era. It can be painful and unsightly. Furthermore, a 2019 analysis of 706 studies involving tooth wear associated it with sleep disorders, oro-facial pain, oral dryness, GERD, and sleep bruxism (tooth grinding). 1  However, several lines of research conclude that tooth wear, even in childhood, may be an evolutionary survival strategy. Especially as it pertains to proper jaw growth. The story is a little complicated, so I want to give you a little background before getting to the tooth wear theory.

The Functional Matrix Theory

In 1962, a former professor of mine, Dr. Melvin Moss, postulated that growth in the craniofacial skeleton was "reactive to, and thus controlled by, the surrounding soft tissues." He claimed that the skull and face grew in response to functional needs and neurotrophic influences mediated by soft tissue. In other words, the forces placed on the bones determined how they grow. Donald Ingber confirmed that parts of interconnected cells are responsible for the changes; specifically, integrins and the cytoskeleton. 2

Open Mouth Posture Study

A 1994 study looked at growing children's arch development. Two groups existed; one had properly closed mouth postures, and the other had improper open mouth postures. They concluded that the children with open mouth postures had significantly narrower upper arches. Their takeaway is that dental arches respond to pressure from the tongue. It is therefore a component of the functional matrix in addition to chewing forces. 3

Native Americans and George Catlin

George Catlin was a famous painter in the mid-19th century. He had always been obsessed with Native Americans and decided to visit them to paint them in their natural surroundings. He painted hundreds of scenes and portraits, many of which are famous. He was keenly interested in their healthy traditional ways and wrote many books on various aspects of their culture. He wrote The Breath of Life Or Mal-respiration: And Its Effects Upon the Enjoyments & Life of Man, and you can read more about it in this post. Amazingly, it was penned in 1864. He wanted the rest of us in the "civilized" world to hear what the native tribes knew for thousands of years: be sure to sleep with your mouth closed, especially make sure your children do.

Weston A. Price

 One of the best-known books describing how ancestral knowledge resulted in superior human physical specimens is Nutrition and Physical Degeneration by Weston A. Price. You can read it for free by clicking on the link. In the 1930's he traveled worldwide to study cultures who practiced ancient traditions and ate the same ancestral diet as their forbears while shunning modern processed foods. He was primarily concerned with tooth decay and crooked teeth being a dentist. He noted their outstanding facial formation, straight teeth, lack of tooth decay, and resistance to diseases like tuberculosis. However, the same locals nearby who had switched to modern ways were much less healthy and had less esthetic faces and teeth. The cultures he studied did not understand the underlying science behind their actions; they knew that following the traditional way of life would produce superior health results. Dr. Price, as a scientist, attributed their health to nutrient-dense foods and the lack of processed foods in their diets. One of the groups he studied were the Inuit, or Eskimos, as they were called back then.

Eskimo (Inuit) Study

Previous studies of traditional Eskimos (Inuits), including Dr. Price’s, have reported that despite immense amounts of tooth wear, they had practically no malocclusion (crooked teeth); yet 82 percent of the modern Inuit children in a study from 1971 had malocclusions. The change from a primitive coarse diet of meat and fat to one which incorporates softer starches and refined sugars has been blamed for the shift. Interestingly, the malocclusions were almost exclusively anterior crowding. The width of the arches and the posterior teeth occlusion was the same in traditional and modern populations, suggesting a genetic component to their facial form. Unfortunately, the research does not mention whether the younger generation had any wear on their teeth. This study contrasts previous studies that concluded that softer diets should also produce narrower arches. 4

Rural Kentucky Study

In 1981, Dr. Corruccinni studied a rural population in Kentucky that had recently switched from many difficult-to-chew foods to modern diets with softer foods. The older inhabitants raised on more traditional diets showed significantly better occlusion. Although not conclusive, Corruccinni thought dietary change to softer foods was the most plausible cause for the shift. 5

 Crossbites and Wear

In 2002 a study of children with extremely narrow upper dental arches that resulted in crossbites was correlated to tooth wear. A crossbite is when the lower arch is closer to the cheeks and lips, which is the reverse of the normal situation. In other words, the lower arch is larger than the upper. In addition, the researchers found less wear when comparing the crossbite group to controls with normal occlusion. When abrasion begins to wear away teeth, it is called attrition. The conclusion is that less attrition represents a softer diet and results in smaller upper arches. So, the connection was one of correlation, not causality. 6

Modern Tooth Wear and Malocclusion 

Researchers used existing dental casts from the orthodontic clinic at the University of Florence for this study. The first group of 100 children was born between 1953 and 1959. Their casts were taken in the '60s. The second group of 100 were born between 1990 and 1998, and their casts were from the mid-90s to 2003. The abrasion was ranked on a scale of 0-3, where zero represents no wear, and three is for severe wear. 

The group from the sixties had much more wear than the more modern group. The researchers stated, "The decrease in masticatory performance caused by the widespread use of processed food could be responsible for inadequate wear of deciduous teeth and underdeveloped jaws." Importantly, the more recent group had significantly narrower arches measured between the canines and the distance between the molars. The measurements are called the intercanine and intermolar distances, respectively. The researchers explain the difference, "Occlusal abrasion allows an adequate sliding between the dental arches, which is necessary to achieve a functionally correct development of the masticatory system." In other words, lack of dental wear is a cause of crowded teeth. The researchers concluded that the wear was causing better occlusion; it was not just a simple correlation. 7

Aboriginal Child Study

A 1961 examination of Aboriginal children in Australia found they had two phases of wear-one for the deciduous teeth and another for the permanent dentition. Their diet consisted of very course natural foods. Perfect occlusion had been the norm for previous generations eating their ancestral diet, as noted by Weston Price and others. They found that some children had so much wear in their baby teeth by the time they were five that their jaws had shifted so that their front teeth met edge-to-edge. Once the permanent molars started erupting behind the primary teeth, the anterior teeth began to overlap. However, by maturity, they achieve a second edge-to-edge occlusion of the incisors. It should be noted that modern dentists try to correct edge-to-edge occlusions. However, when the lower jaw is in a more forward position, sleep apnea and restricted airways are less likely.

Mesial Migration

Teeth tend to drift toward the anterior of the mouth with time; a phenomenon called mesial drift or mesial migration. As a result, many people notice their own lower front teeth become more crowded as they age. Dr. Lombardi described this phenomenon as having an "adaptive value" in 1981. Dr. Lombardi knew that dental crowding is endemic among technologically advanced populations and uncommon in primitive groups. He noticed that the anterior drift of teeth was normally coupled with interproximal attrition, which is the loss of width of teeth over time. So, if teeth become thinner in the posterior-to-anterior plane, their ability to drift forward and close the spaces makes sense. As Dan Leiberman noted, bones seldom participate only in one functional matrix and are influenced by many overlapping factors. So, if a factor like wear is removed, it makes sense that the bones will respond differently. 8 

Genetics

A 2009 study of ancient Egyptian skeletons from Amarna, Egypt, reveals extensive tooth wear but very little dental crowding, unlike in modern Americans. The analyses by Rose and Roblee suggest it was not the reduction in tooth wear that increased crowding and malocclusion, but rather the tremendous reduction in the forces of mastication which produced this extreme tooth wear and the subsequently reduced jaw involvement. This view is shared by my colleague Dr. Mike Mew. They noted that the jaws and teeth were reduced in size resulting in good occlusion, suggesting a genetic or epigenetic component. Whether they were aware of Dr. Lombardi’s theory is not stated in their paper. But suddenly, as modern food preparation techniques spread throughout the 19th century, so did dental crowding. 9 

Conclusion

I believe that the shape of the jaws depends on various factors. Genetics is one. The forces we place on our facial bones also factor in heavily. The consistency of our food, how hard we chew, our tongue posture, the pressure from our lips, and the nutritional value of our food all matter. Could tooth wear aid in keeping our teeth in good occlusion when coupled with forward drift? I think so. The problem arises in modern times when tooth wear is caused by tooth grinding and gum chewing. I see so many tooth and facial discomfort complaints in my practice that I try to eliminate the grinding and soft gum-chewing causing them. I recommend mastic gum for those who chew gum, as it is very hard.

Remember this: developing perfect teeth and faces start in the womb.

For a comprehensive guide to all the major components involved in forming good occlusion and perfect jaws, click here.