In order to clarify the influence of orthodontic therapy on patients with diabetes, the effect of experimental tooth movement on the levels of 3-methoxy-4-hydroxy- phenylglycol (MHPG), blood suger and brain amino acid neurotransmitters, was examined using normal and streptozotocin (STZ)-induced diabetes mice of the male ddY strain, weighing about 30g. On the 18th day after administration of STZ (160mg/kg, i.p.) or vehicle to the mice of each group, a plastic chip, 0.5mm in diameter, was put between the upper incisors and fixed with resin for the purpose of tooth movement. When the fluctuation in their blood sugar levels became stable, a plastic chip, 1.0mm in diameter, was put between the teeth by the same procedure. A blood sugar sample collected from the tail vein was measured, using the glucose oxidase-hexokinase method. On the 2nd day after treatment for tooth movement, MHPG in the corpus striatum and hypothalamus, and amino acid neurotrans mitters (aspartate, glutamate, glutamine, glycine, taurine, gamma-aminobutyric acid) in the corpus striatum, hypothalamus, hippocampus and cerebral cortex of the normal and STZ-induced diabetes mice were measured, using the HPLC-electrochemical detection method. The MHPG levels in the hypothalamus of the STZ-induced diabetes mice, with the treatment for tooth movement, significantly increased, but did not increase in normal mice with the above treatment. The blood sugar levels also showed the same patterns. The treatment for tooth movement exerted an influence on the levels of amino acid neurotransmitters in the hypothalamus and hippocampus but not in the corpus striatum and cerebral cortex of the STZ-induced diabetes mice.

These results indicate that the treatment for tooth movement in the STZ-induced diabetes mice produces an increase in the levels of MHPG, blood sugar and brain amino acid neurotransmitters, and suggest that in patients with diabetes, orthodontic therapy may exert some stress.