The scanning electron microscope in craniofacial remodeling research: application of the topographic principle.

Growth and development studies utilizing craniofacial skeletal material are best done by documenting evidence of the bone growth mechanisms responsible for morphogenesis. One primary mechanism is remodeling which involves coordinated bone resorption and deposition in localized areas. Some histological studies have been performed on human facial remodeling, but these studies have been limited in extent because of the destructive nature of the technique. For obvious reasons, large skeletal research collections cannot be utilized in histological work. A new technique is presented which does not damage specimens. This involves making high resolution replicas of subadult craniofacial bone which are then examined with the scanning electron microscope (SEM) for evidence of the characteristic microscopic surface topography of remodeling bone. The Topographic ("T") principle is introduced as a precedent for discriminating remodeling bone activity states with the SEM. These activity states in vivo specify characteristic microscopic surface topographies. The three distinctive surfaces are resorptive, depository, and resting. These surfaces can be mapped on a coordinate representation of the bone replica to obtain results which are similar to those of histological studies. Application of the "T" principle and SEM/replica methodological approach offers great promise to the study of craniofacial morphogenesis.