Methods: Deciduous enamel specimens were cut into mesiodistal blocks of 2 mm thickness, without altering the labial surface and located within SMR cells. Permanent enamel and HAP specimens were similarly prepared. Artificial caries-like lesions were created by exposing the specimens 0.1 mol/l of 98% acetic acid (pH 4) within the SMR cells. SMR was used to measure the rate of mineral loss at 10 points either side of and at the neonatal line in the deciduous enamel, and in the control specimens.
Results: The rate of demineralisation was almost the same in pre- and postnatal enamel (6-8x10-4 g cm-2h-1). The rate of demineralisation was lower in the vicinity of the neonatal line (1-2x10-4 g cm-2h-1). The rate of demineralisation was lower in permanent (4x10-4 g cm-2h-1) than in deciduous enamel, and even lower in the hydroxyapatite specimen (2x10-4 g cm-2h-1).
Conclusion: This study supports the hypothesis that the neonatal line may act as a barrier to the propagation of carious lesions.