Scientists have found that odontoblasts, the cells that form dentin (the hard tissue of the tooth), contain the TRCP5 protein, which works as a temperature sensor, responding to cold and activating the cells. Therefore, when the temperature drops, odontoblasts send signals to the brain through nerve endings, which leads to the appearance of acute pain. According to the researchers, the appearance of increased sensitivity to cold allows the body to protect damaged teeth from additional injury.