Centre for Oral Growth & Development, Barts and The London School of Medicine and Dentistry, London, UK.
Arch Oral Biol. 2009 Dec;54 Suppl 1:S101-6. doi: 10.1016/j.archoralbio.2008.09.013. Epub 2008 Nov 6.
The neonatal line, which is an exaggerated incremental layer line, separates pre- and postnatal enamel. It has been suggested that this layer may be a barrier to the progress of a carious lesions. The objective was to measure the rate of demineralisation in pre- and postnatal enamel and within the neonatal layer using scanning microradiography (SMR). Permanent enamel and compressed permeable hydroxyapatite samples were used as controls.
Enamel specimens from deciduous incisors were cut into mesiodistal blocks of 2mm thickness without altering the labial surface and located within SMR cells. Permanent enamel and hydroxyapatite specimens were similarly prepared. Artificial caries-like lesions were created by exposing the specimens to 0.1 mol l(-1) acetic acid (pH 4.0) 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 20 points across in the control specimens. The rate of demineralisation was almost the same in pre- and postnatal enamel ((6.0-8.0) x 10(-4)gcm(-2)h(-1)), but much lower in the vicinity of the neonatal line (2.0 x 10(-4)gcm(-2)h(-1)). The rate of demineralisation was lower in permanent (5.0 x 10(-4)gcm(-2)h(-1)) than in deciduous enamel, and even lower in the permeable hydroxyapatite specimen (2.5 x 10(-4)gcm(-2)h(-1)).
This study showed no difference in the rate of demineralisation between pre- and postnatal enamel, but a reduced rate within the region that contained the plane of the neonatal line. This supports the hypothesis that the neonatal line may act as a barrier to the propagation of carious lesions.
新生儿线是一条夸张的递增层线，将出生前和出生后的牙釉质分开。有人提出，这一层可能是龋病进展的障碍。本研究目的是使用扫描显微射线照相术（SMR）测量前牙和后牙釉质以及新生儿层内的脱矿速率。使用恒磨牙釉质和压缩可渗透羟磷灰石样本作为对照。
从乳牙切牙切取 2mm 厚的近远中向牙釉质块，不改变唇面，并将其放置在 SMR 细胞内。同样准备恒磨牙釉质和羟磷灰石样本。通过将样本暴露在 SMR 细胞内的 0.1mol l(-1) 乙酸（pH4.0）中来创建类似龋病的人工损伤。使用 SMR 测量在乳牙中，新生儿线两侧和线处的 10 个点以及对照样本中的 20 个点的矿物质损失率。前牙和后牙釉质的脱矿速率几乎相同（（6.0-8.0）x10(-4)gcm(-2)h(-1)），但在新生儿线附近则低得多（2.0x10(-4)gcm(-2)h(-1)）。恒磨牙（5.0x10(-4)gcm(-2)h(-1)）的脱矿速率低于乳牙，而在可渗透的羟磷灰石样本中（2.5x10(-4)gcm(-2)h(-1)）则更低。
本研究表明，前牙和后牙釉质的脱矿速率没有差异，但在包含新生儿线的区域内的脱矿速率降低。这支持了新生儿线可能是龋病进展的障碍的假说。
