Periodontal ligament cells in adolescents and adults: Genetic level responses to orthodontic forces.

Introduction: Periodontal ligament cells (PDLC) respond to the application of mechanical forces by releasing various molecules that participate in bone remodeling. Whether these cellular reactions take place at the same rate in adolescent and adult patients is not known. In this study, we aimed to evaluate differences in genetic expression, if any, between the release of various inflammatory mediators from PDLC in adolescent and adult patients before and after the application of orthodontic forces.

Methods: Forty subjects with bimaxillary dentoalveolar protrusion requiring extraction of first premolars for orthodontic treatment were selected and divided into 2 groups. Group A included 20 adolescents (aged 12-20 years), and group B included 20 adults (aged 35-50 years). Then, 35-50 g of force were applied to the maxillary first premolars, and teeth were extracted at different periods: pretreatment (control group), 7 days, 14 days, and 28 days (experimental group). The periodontal ligament was scraped from the middle third of the root, and the beta-galactosidase assay was performed in the control group. RNA extraction, DNase treatment, quantitative polymerase chain reaction, and complementary DNA synthesis were performed in the experimental group.

Results: Adult PDLC exhibited senescent changes through increased beta-galactosidase activity. The increase in the inflammatory response and bone resorption in adult patients was evident by increased prostaglandin E2, IL1B, and acid phosphatase mRNA expression levels. Controlled bone formation response by adolescent PDLC was evident from increased ALP and BGLAP mRNA levels and a balanced receptor activator of nuclear factor kappa-Β ligand/OPG ratio.

Conclusions: The study could identify the reasons behind the differential response of adolescent and adult PDLC to orthodontic mechanics.