Analysis of Growth Layers in the Teeth of Tursiops truncatus using Light Microscopy , Microradiography , and SEM

Preliminary results show microradiography and scanning electron microscopy (SEM) to be more accurate methods of accessing growth layer groups (GLGs) in the teeth of Tursiops fmncarus than transmitted light microscopy. Microradiography shoas the rhythmic deposition of mineral as alternating radiopaque and radiolucent layers. I t improves the resolution of CLGs near the pulp cavity in older individuals, better than either SEM or light microscopy. SEM of etched sections show GLGs as ridges and grouves which are easily counted from the micrograph. SEM also shows GLGs to be composed of fine incremental layers of uniform s ~ z e and number which may allow for morc precise age determination. Accessory layers are usually hypomineralized layers within the hypermineralized layer of the GLG and arc' more readily distinguishable as such in SEM of etched sections and microradiographs than in thin sections viewed undcr transmitted lisht. The neonatal line is hypomineralized. appearing translucent under transmitted light, radiolucent in a microradiograph, and as a ridge in SEM.