Why tetracycline groups is note given to tthe children below 8 years of ahe?

Tetracycline: The enamel of permanent teeth starts to form during the 3rd trimester in utero. By age 8 the enamel of all permanent teeth, with the exception of of the wisdom teeth, has completed forming. If during those 8+ years the child is exposed to tetra-cyclone the antibiotic can interfere with the matrix that calcifies forming tooth enamel. If so, light refraction becomes altered and the enamel damaged.