Age estimation based on aspartic acid racemization in dentine: what about caries-affected teeth?

Age estimation based on aspartic acid racemization (AAR) in dentine is one of the most precise methods in adult age. Caries induces protein degradation and may have an impact on the kinetics of AAR in dentine. We systematically examined standardized prepared dentine samples from caries-affected teeth to clarify the question, if caries-affected teeth should not be used for age estimation based on AAR at all, or if the analysis of dentine samples from such teeth may be useful after removal of the caries-affected tissue according to clinical standards. Our results suggest that caries may lead to an extensive protein degradation even in macroscopically healthy-appearing dentine samples from caries-affected teeth and may significantly affect the precision of age estimation. To ensure the quality of age estimation based on AAR in forensic practice, we recommend using dentine samples from healthy teeth. If only caries-affected teeth are available, dentine samples from at least two teeth from the same individual should be analyzed as it seems unlikely that caries-induced protein degradation occurred with identical kinetics in two different teeth. In any case, results of the analysis of caries-affected teeth must be interpreted with caution.

Post-treatment of coking industry wastewater by the electro-Fenton process.

Effluents of the coking industry cannot be effectively treated in biological treatment units because of non-biodegradable organic matters and phenolic compounds present in the wastewater. In this study, post-treatment of biologically treated coking wastewater via the electro-Fenton process was investigated to minimize the effects of discharge of this kind of wastewater on the environment. The electro-Fenton experiments were performed using cast iron electrodes. Chemical oxygen demand (COD) and phenol were selected as the target parameters. The optimum operating conditions were as follows: reaction time = 10 minutes, pH = 3.0, electrical current = 1.0 A, and [H2O2] = 2000 mg/L. Under these conditions, COD and phenol removal efficiencies were 67.8% and 98.0%, respectively. In addition, it was determined that COD removal followed first-order reaction kinetics. Consequently, the electro-Fenton process was determined as an effective alternative post-treatment method for coking industry effluents.