[Research on the microhardness and microstructure of permanent tooth enamel in childhood].

Objectives: Through the investigation of the microhardness and microstructure of permanent tooth enamel at various eruption stages during childhood, this research offers references for the early prevention of childhood dental caries.

Methods: Forty-five premolars extracted due to orthodontic reasons were collected and screened. These premolars were divided into three experimental groups according to the time since eruption: Group A (erupted for 0-1 year), Group B (erupted for 1-3 years), and Group C (erupted for 3-5 years). Additionally, the third molars that were extracted due to impaction and had not erupted were selected as the control group, with 15 teeth in each group. Samples were prepared, and the surface microhardness, microstructure, and elemental composition of the enamel were measured using Vickers microhardness tester, scanning electron microscope, and electron probe, respectively.

Results: Compared with that in the control group, the microhardness of enamel in groups A, B, and C increased with prolonged eruption time, the surface porosity structure decreased considerably, the contents of Na and Mg on the surface decreased, and that of F increased (P<0.05).

Conclusions: The microhardness and microstructure of enamel in permanent teeth at different stages vary. Permanent teeth are at a substantially higher risk of caries within one year after eruption, and early prevention should be emphasized.