Dental Caries, Developmental Defects of Enamel and Enamel Microhardness Associated with Genetic Polymorphisms in the RANK/RANKL/OPG System.

Purpose: Recent studies have suggested that disruptions in the RANKL/RANK/OPG system might be involved in enamel conditions. The aim of this study was to test whether genetic polymorphisms in RANK, RANKL and OPG are associated with dental caries, developmental defects of enamel (DDE) and enamel microhardness. Study design: Saliva samples were collected from two subsets for the purpose of genomic DNA extraction. In the first subset, composed of 248 children, dental caries and DDE were evaluated during their clinical examination. In the second subset, composed of 72 children, enamel samples from the buccal surface of primary teeth were used for enamel microhardness analysis. Genetic polymorphisms in RANK, RANKL and OPG were genotyped by real-time polymerase chain reactions in all samples from both populations. The chi-square test was used for dental caries and DDE analysis while, one-way ANOVA with Tukey's post-test was used for microhardness analysis. Hardy-Weinberg equilibrium was also calculated. The established alpha was 5%. Results: Caries experience analysis demonstrated a statistically-significant difference for OPG allele distribution in primary dentition (p=0.033). The studied polymorphisms in RANK, RANKL and OPG were not associated with DDE or enamel microhardness (p>0.05). Conclusion: The genetic polymorphism rs2073618 in OPG is associated with dental caries experience in primary dentition.

Histochemical changes of substance P, FRAP, serotonin and succinic dehydrogenase in the spinal cord of rats with adjuvant arthritis.

Various histochemical changes were found in spinal segments L4-L5 of rats with adjuvant arthritis, predominantly 30 days after inoculation. A slight to marked increase of substance P immunoreactivity occurred in laminae I, II and X. FRAP activity was enhanced in lamina II. Serotonin immunoreactivity was heavier in laminae I, VIII and IX in a few animals. The intensity of the histoenzymological reaction for succinic dehydrogenase increased in certain laminae VIII and X neurons. At day 15 of the disease the increase of substance P and FRAP activities was chiefly restricted to the medial portion of the superficial dorsal horn. There was a significant positive correlation between the scratching behaviour of arthritic rats and the substance P immunoreactivity in laminae X and I. If one accepts that scratching is pain-related, the data are consistent with a possible role of substance P in the chronic pain associated with adjuvant arthritis. They leave undetermined the significance of the other histochemical changes.