Application of Reactive Oxygen Species in Dental Treatment

Reactive oxygen species (ROS) and free radicals, which have been implicated in inflammation, pain, carcinogenesis, and aging, are actually used in dental treatments such as tooth bleaching and composite resin polymerization. Recently, numerous studies have investigated the application of ROS in the medical and dental fields. In previous studies, ROS were generated intentionally through pathways such as photolysis, photocatalytic methods, and photodynamic therapy, which are used in the medical field to target cancer. In the field of dentistry, generated ROS are applied mainly for periodontal treatment and sterilization of the root canal, and its effectiveness as an antibacterial photodynamic therapy has been widely reported.. Given this background, the present article aimed to review the basic effects of ROS in dental medicine, especially endodontic therapy, and to discuss future applications of ROS

A Single Neonatal Injection of Ethinyl Estradiol Impairs Passive Avoidance Learning and Reduces Expression of Estrogen Receptor α in the Hippocampus and Cortex of Adult Female Rats.

Although perinatal exposure of female rats to estrogenic compounds produces irreversible changes in brain function, it is still unclear how the amount and timing of exposure to those substances affect learning function, or if exposure alters estrogen receptor α (ERα) expression in the hippocampus and cortex. In adult female rats, we investigated the effects of neonatal exposure to a model estrogenic compound, ethinyl estradiol (EE), on passive avoidance learning and ERα expression. Female Wistar-Imamichi rats were subcutaneously injected with oil, 0.02 mg/kg EE, 2 mg/kg EE, or 20 mg/kg 17β-estradiol within 24 h after birth. All females were tested for passive avoidance learning at the age of 6 weeks. Neonatal 0.02 mg/kg EE administration significantly disrupted passive avoidance compared with oil treatment in gonadally intact females. In a second experiment, another set of experimental females, treated as described above, was ovariectomized under pentobarbital anesthesia at 10 weeks of age. At 15-17 weeks of age, half of each group received a subcutaneous injection of 5 μg estradiol benzoate a day before the passive avoidance learning test. Passive avoidance learning behavior was impaired by the 0.02 mg/kg EE dose, but notably only in the estradiol benzoate-injected group. At 17-19 weeks of age, hippocampal and cortical samples were collected from rats with or without the 5 μg estradiol benzoate injection, and western blots used to determine ERα expression. A significant decrease in ERα expression was observed in the hippocampus of the estradiol-injected, neonatal EE-treated females. The results demonstrated that exposure to EE immediately after birth decreased learning ability in adult female rats, and that this may be at least partly mediated by the decreased expression of ERα in the hippocampus

Neonatal exposure to ethinyl estradiol (EE) decreases the expression level of estrogen receptor alpha (ERα) in the hippocampus of adult female rats.

<p>A. Representative western blot images showing ERα expression in the hippocampus of EE-treated ovariectomized OVX rats injected with (+) estradiol benzoate or without injection (-) EB. B. Levels of ERα expression in the hippocampus. *<i>P</i> < 0.05, Tukey-Kramer test; n = 6/group.</p

Impairment of avoidance learning in ovariectomized (OVX) low dose ethinyl estradiol (LEE)-treated female rats.

<p>The line plots show the effect of LEE (0.02 mg/kg), HEE (2 mg/kg), and 17β-estradiol (E2; 20 mg/kg) treatment within 24 h after birth on the cumulative percentage of rats that displayed a transfer response in the passive avoidance test. All rats were OVX at 10 weeks of age; at 15–17 weeks, the animals were either not injected (A) or injected with EB (B) 1 day before the session. Numerals in parentheses indicate the number of rats in each group. †<i>P</i> < 0.1, log-rank comparison.</p

Neonatal exposure to ethinyl estradiol (EE) decreased the expression level of estrogen receptor alpha (ERα) in the female rat cortex.

<p>A. Representative western blot images showing the ERα expression in the cortex of EE-treated 15–18-week-old ovariectomized (OVX) rats injected with estradiol benzoate (+) or without injection (-). B. The levels of ERα in the cortex. *<i>P</i> < 0.05, Tukey-Kramer test; n = 6/group.</p