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A molar with decay from bacteria that causes cavities (left) seen in an X-Ray. A portrait of Rodríguez, who died in 1932 (right). Photo: BSIP/Universal Images Group via Getty Images; College of American Dentists

A Puerto Rican dentist was the first to find conclusive evidence of how bacteria cause dental cavities and tooth decay, identifying which types of Lactobacillus were responsible.

Why it matters: The discovery by odontologist and U.S. Army Major Fernando Rodríguez Vargas helped identify how mouth hygiene and diet can influence the “periodic fluctuations” of the caries-causing Lactobacillus bacteria.

  • “His work on the specific bacteriology of dental caries has been the foundation for much of the research in this field,” wrote Willard Camalier, former president of the Medical Service of D.C., in 1940.
  • About 90% of adults aged 20 and older have had at least one cavity. This issue is magnified in people of color, who are twice as likely to have untreated tooth decay, according to the Centers for Disease Control and Prevention.

Details: Rodríguez, born in Adjuntas, Puerto Rico, earned his DDS degree from Georgetown University in Washington, D.C.

  • Rodríguez joined the U.S. Indian Medical Services in 1915, where he studied the mottled enamel of a Native American community in Arizona.
  • In 1917, shortly after the U.S. entered the First World War, Rodríguez was commissioned as a first lieutenant.
  • During his military service, he accepted a commission to the U.S. Army Dental Corps, where he began his research on the bacterial origins of tooth decay.

In 1921, Rodríguez published his principle research on the causes of dental disease, documenting his discovery of the three Lactobacillus species that are believed to cause cavities.

  • At the time of publication, Rodríguez's work was considered one of "the most valuable advances made in the etiology of dental caries."

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Go deeper

Updated 3 mins ago - World

Reports: Up to 17 U.S. missionaries kidnapped in Haiti

Haitian soldiers guard the public prosecutor's office in Port-au-Prince earlier this month. Photo: Richard Pierrin/AFP via Getty Images

Children were among up to 17 American Christian missionaries and their relatives kidnapped by a gang in Haiti on Saturday, the New York Times first reported.

Details: The missionaries had just left an orphanage and were traveling by bus to the airport to "drop off some members" and were due to travel to another destination when the gang struck in Port-au-Prince, Haitian security officials said, per the NYT.

Melbourne, "world's most locked-down city," to lift stay-at-home orders

Victorian Premier Daniel Andrews during a news conference in Melbourne, Australia, on Sunday. Photo: Quinn Rooney/Getty Images

Melbourne's stay-at-home orders will end five days earlier than planned, officials in Australia's second-biggest city announced Sunday.

Why it matters: The capital of the state of Victoria has had six lockdowns totaling 262 days since March last year. That means Melbourne's spent longer under lockdowns than "any other city in the world" during the pandemic, Reuters notes.

Venezuela suspends talks with opposition after Maduro ally extradited to U.S.

Venezuelan President Nicolás Maduro in Caracas, Venezuela, in June. Photo: Gaby Oraa/Bloomberg via Getty Images

A key ally of Venezuela's President Nicolás Maduro was extradited from Cape Verde to the U.S. Saturday to face money laundering charges in Florida, Bloomberg first reported.

Why it matters: Venezuela's government called off negotiations with opposition officials that were scheduled for Sunday in Mexico in response to the extradition of Alex Saab, a Colombian businessman and financial fixer for Maduro. Security forces placed six U.S. oil executives under house arrest later Saturday, per AP.