Stimulation of intradentinal dye penetration by feeding in the rat

Dentinal fluid movement, as measured by intradentinal dye penetration (IDDP), may be under the control of an endocrine system that includes the parotid glands. It was earlier demonstrated that parotid hormone stimulates IDDP when infused into rats, and in the pig the onset of feeding signals the release into the circulation of immunoreactive parotid hormone (iPH), the titre of which remains elevated for more than 1 h after feeding. As, for technical reasons, it is impossible to measure iPH and IDDP activity in the same animal, the hypothesis that feeding causes IDDP stimulation in the rat was now tested. Feeding rats for 15 min stimulated IDDP to a level significantly higher than when fasting (0.418 +/- 0.040 versus 0.106 +/- 0.022, p < 0.001). Within the experimental conditions, IDDP stimulation lasted longer than 15 min. Sialoadenectomy before the feeding experiment did not change the feeding-stimulated IDDP response unless the parotid glands were removed. In parotidectomized and totally sialoadenectomized rats fed for 15 min, the level of IDDP was not different from that of sham-operated fasting animals. It is postulated that, in addition to the existence of possible local regulatory factors in the pulp, dentinal permeation may be under a physiological control mechanism involving a parotid endocrine function. It is also suggested that a hormonally controlled mechanism of dentinal fluid movement may play a systemic, protective role against the bacterial acidogenic challenge to teeth.