An international team of scientists has come together to understand, once and for all, cold-induced toothaches. "It's a unique kind of pain," says David Clapham, vice president, and chief scientific officer of the Howard Hughes Medical Institute (HHMI), who co-wrote the paper.
Through collaboration with the Friedrich-Alexander University (FAU) in Erlangen-Nuremberg, Germany, and the Massachusetts General Hospital, the team uncovered a specific notion in the tooth which causes the pain. "We found that odontoblasts, which support the shape of the tooth, are largely responsible for sensing cold," says pathologist Jochen Lennerz, one of the paper's senior authors. "This research contributes a new function to this cell, which is exciting from a basic science standpoint. But we now also know how to interfere with this cold-sensing function to inhibit dental pain."
Dental aches have been notoriously difficult to study in the past. The main reason for this is the enamel, or the hard part of the tooth, making it a challenging tissue to survey as it essentially requires opening the tooth. But Clapham's wanted to take a different, more interesting approach by looking at their past. In previous toothache research attempts, the scientists had discovered a protein encoded by the TRCP5 gene, which acts as a receptor of pain found in many nerves across the human body. These earlier findings helped the researchers to focus on TRCP5 as a mediator of pain from cold.
So in this new study, they used genetically altered mice that did not have the TRCP5 gene. Then, they drilled the rodent's molars under anesthesia to induce toothache. Weirdly enough, they found that the mice with the injured teeth behaved just like the ones without denticle damage. "We now have definitive proof that the temperature sensor TRCP5 transmits cold via the odontoblast and triggers nerves to fire, creating pain and cold hypersensitivity," wrote co-author Dr. Jochen Lennerz. "This cold sensitivity may be the body's way to protect a damaged tooth from additional injury." The researchers also unveiled that TRCP5 reacts to cold specifically by opening "channels" in the odontoblasts, allowing other molecules to enter and interact with the membrane.
Along with uncovering the culprit responsible for cold toothaches, the team provided a treatment solution: oil of cloves. The active agent in the oil is a chemical called eugenol, which happens to block TRCP5. Even though eugenol-infused toothpaste is available on the market, this study may help find even better solutions to the hypersensitive teeth dilemma. "I'm excited to see how other researchers will apply our findings," says Lennerz in the study, which can be found here.