Figure 5

Mosaic of five SXRF montaged images showing Sr concentration (intensity) of three ground sections of SK 835. These are cross-matched to a prominent Sr line in the three separate roots (yellow arrows) that formed at 4.1 years (1505 days) into M3 formation. Tooth formation (initiation) is denoted at zero days (red arrow) in the protocone. The formation times for crown completion (945 days, green arrow) and the stage of tooth root length complete at 2465 days, (RC, purple arrow) are derived from the histological data for daily increments of growth in the crown and root and rates of root extension. Daily rates of dentine formation in the mesiobuccal root apex (2.87 µm/day) were used to estimate the time taken to complete closure of the distobuccal root apex (< 362 days, blue dotted line). Total tooth formation time is estimated to have been ≥ 7 years.