3D Modeling of Enamel Formation

Normal development and disturbances caused by disease can be represented by changes in five biological parameters that characterize enamel formation. “Fossilized” in tooth structure, there is a detailed record of development traced by incremental growth lines. Enamel growth lines represent the configuration of deposited enamel at a succession of stages in its history of apposition.  We hypothesize that we can use them to estimate enamel growth parameters and thus model crown development. 

Objectives: To measure the distances between incremental lines and use the obtained values to construct 2D and 3D models of daily enamel formation. To reveal the importance of each biological parameter in determining crown shape and quantify the extent to which regulatory mechanisms alter these parameters during human crown formation. 

Methods: Enamel incremental features include daily cross-striations (CS) and long-period (~7-day) striae of Retzius (SR), and surface perikymata.  SEM was used to measure perikymata along the outer enamel surface of intact human crowns.  Ground sections of teeth were analyzed with confocal and polarized light microscopy (the latter facilitated by use of a universal stage) to visualize SR and CS.  Measurements were done using Image-J and 2D modeling using R.  

Results: Preparation techniques including staining, etching, ultrasonic cleaning, varying section thickness and polishing techniques, and varying orientation of sections relative to transmitted light were evaluated to obtain optimal images for measurement. Measurements were used to generate 2D models of daily enamel formation. 3D modeling and incorporation of regulatory pathways are also being integrated in our analyses.  

Conclusion: This research will yield significant insights into the parameters governing enamel formation and crown morphogenesis. A systems biology approach is critical to unraveling the biological clock mechanisms that regulate enamel formation and is necessary for understanding how biological parameters and gene expression vary during development, disease and evolution of crown form.