Toronto: Our susceptibility to oral infection parallels those of ancient reptiles that evolved to eat a diet incorporating plants in addition to meat, a study says.
Robert Reisz from the University of Toronto and his colleagues have found evidence of bone damage due to oral infection in Paleozoic reptiles as they adapted to living on land.
The researchers investigated the jaws of several well-preserved specimens of Labidosaurus hamatus, a 275-million-year-old terrestrial reptile from North America, reports the journal Naturwissenschaften - The Science of Nature.
One specimen stood out because of missing teeth and associated erosion of the jaw bone. With the aid of CT-scanning, Reisz and colleagues found evidence of a massive infection, according to a Toronto statement.
This resulted in the loss of several teeth, as well as bone destruction in the jaw in the form of an abscess and internal loss of bone tissue.
The primitive dental pattern in which teeth were loosely attached to the jaws and continuously replaced, changed in some lineages to be strongly attached to the jaw, with little or no tooth replacement.
This was clearly advantageous to some early reptiles, allowing them to chew their food and thus improve nutrient absorption. The abundance and global distribution of Labidosaurus and its kin attest to the evolutionary success of this strategy.
However, Reisz and his colleagues suggest that as this reptile lost the ability to replace teeth, the likelihood of infections of the jaw resulting from damage to the teeth increased substantially.
This is because prolonged exposure of the dental pulp cavity of heavily worn or damaged teeth to oral bacteria was much greater than in other animals that quickly replaced their teeth.
The study authors conclude: "Our findings allow us to speculate that our own human system of having just two sets of teeth, baby and permanent... is more susceptible to infection than that of our distant ancestors that had a continuous cycle of tooth replacement."