Implications of Vertebrate Craniodental Evo‐Devo for Human Oral Health

Abstract

Highly processed diets eaten by postindustrial modern human populations coincide with higher frequencies of third molar impaction, malocclusion, and temporomandibular joint disorders that affect millions of people worldwide each year. Current treatments address symptoms, not causes, because the multifactorial etiologies of these three concerns mask which factors incline certain people to malocclusion, impaction, and/or joint issues. Deep scientific curiosity about the origins of jaws and dentitions continues to yield rich insights about the developmental genetic mechanisms that underpin healthy craniodental morphogenesis and integration. Mounting evidence from evolution and development (Evo-Devo) studies suggests that function is another mechanism important to healthy craniodental integration and fit. Starting as early as weaning, softer diets and thus lower bite forces appear to relax or disrupt integration of oral tissues, alter development and growth, and catalyze impaction, malocclusion, and jaw joint disorders. How developing oral tissues respond to bite forces remains poorly understood, but biomechanical feedback seems to alter balances of local bone resorption and deposition at the tooth-bone interface as well as affect tempos and amounts of facial outgrowth. Also, behavioral changes in jaw function and parafunction contribute to degeneration and pain in joint articular cartilages and masticatory muscles. The developmental genetic contribution to craniodental misfits and disorders is undeniable but still unclear; however, at present, human diet and jaw function remain important and much more actionable clinical targets. New Evo-Devo studies are needed to explain how function interfaces with craniodental phenotypic plasticity, variation, and evolvability to yield a spectrum of healthy and mismatched dentitions and jaws.

Changes in Dietary Consistency and the Epidemiological Occlusal Transition

“…Sengupta and colleagues (1999) conducted a study looking at occlusal macrowear, third molar presence, and COS. The modern dentition is associated with a greater frequency of third molar impaction and agenesis, as well as modest wear rates when compared with typical pre-Industrialized dentitions (Boughner 2017;Kaifu et al 2003;von Cramon-Taubadel 2011). Owing to this, the authors hypothesize that increased rates of wear in the past, due to abrasive diets, maintained a flattened COS. Their rationale that any modern wear is caused by prolonged use-life rather than abrasive diets is most likely a robust assumption (Kaifu et al 2003).…”

“…The ability to efficiently process tough food is greatly influenced by the diet consumed during development (Boughner 2017;Lieberman et al 2004;Limme 2010). Permanent dentition is almost fully erupted by late adolescence, with the variable exception of third molars.…”

“…Boughner (2017) examined the biomechanical relevance of this concept in relation to the epidemiological occlusal transition. She investigated the effects of mastication on orofacial development, concluding that modern children who consume more processed diets go on to experience higher rates of malocclusion, temporomandibular joint disorders, and tooth impaction (Boughner 2017). The stimulation from bite force that begins soon after weaning plays a large role in the eventual morphology and functional capacity of the mouth as a whole, which is why diet at this young age is so pivotal.…”

“…Functional integration is the idea that human jaws are evolved to masticate to a certain level, and that by not using them for this function from a young age, we are causing an interruption in tissue development. While the effects of biomechanical forces on growing musculoskeletal tissues of the face are not well understood, it is suggested that introducing hard foodssuch as raw vegetables, nuts, and fruitscould minimize malocclusion and joint disorders (Boughner 2017). This has important implications for determining health policies and parenting advice, because altering dietary consistency could possibly lessen the need for orthodontic treatment.…”

“…Mandibular morphological characteristics, including COS, prognathism, and gonial angle, are determining factors in the etiology of malocclusion (Boughner 2017). Tooth macrowear has often also been included in the suite of traits that facilitate proper occlusion (Kaifu et al 2003).…”