Dentin is a unique material with the ability to provide not only sensation to the pulp but protection of this soft tissue. The jury is still out concerning the practice of etching dentin with caustic substances in order to remove the smear layer and to open dentinal tubules prior to restorative procedures. Additional research is required to evaluate the long-term vitality of teeth that have been treated in this fashion. The dentinal tubule is truly a window through which the clinician and the researcher may find answers to a variety of clinical problems. Furthermore, dentinal tubules may provide a noninvasive path by which the difficulty of accurately assessing pulpal health may be overcome.