Are the incremental lines in human cementum laid down annually?

A local Singaporean study of the presence of incremental lines in the cement of extracted teeth of 41 identity card-holding subjects is reported. The undecalcified roots of these teeth were sectioned transversely, some of which were stained with alizarin red. The lines observed were counted by one observer while blind to the actual ages of the subjects. A previous suggestion that these lines are deposited annually could not be supported in this sample, the number of lines tending to produce a lower estimated age than that registered on the identity card. The Pearson correlation coefficient for the line counts between two observers on 26 teeth was 0.73 (r2 = 0.535) which reflected difficulties in visualising the lines.