Dentin Matrix Protein-1 and Dentin Phosphophoryn in Saliva as Biomarkers for Root Resorption

Hypothesis: We hypothesize that that concentrations of dentin matrix protein 1 (DMP-1) and dentin phosphophoryn (DPP) will be correlated with the amount of root resorption observed in panoramic radiographs taken before and during orthodontic treatment. Objective: Root resorption (RR) is a common complication of orthodontic treatment. Historically, only radiographic means have been available to detect RR in orthodontic patients. The goals of this study are to compare salivary DMP-1 and DPP levels at various time points during orthodontic treatment to baseline levels and to determine if an association exists between salivary DMP-1 and DPP levels and observed RR. Methods: Patients starting comprehensive orthodontic treatment were recruited to provide saliva samples before beginning treatment and roughly every 2 months until a panoramic radiograph was obtained. Saliva samples were collected, vortexed, and centrifuged with protease inhibitor. The samples were then analyzed using enzyme‐linked immunosorbent assay (ELISA) to detect DPP and DMP1. The incisor crowns and roots were measured on the pre-treatment and progress panoramic radiographs to calculate the amount of RR observed. The amount of root resorption observed was compared to the DMP-1 and DPP levels. Results: N= 50 subjects participated in the study. DMP-1 concentration was higher at 2, 4, 6 and 8 months and DPP absorbance was higher at 2, 6 and 8 months after initiating orthodontic treatment compared to baseline (p<0.05). Maximum DMP-1 concentration was positively correlated to average incisor RR (p<0.05), but no correlation existed between average incisor RR and maximum DPP absorbance (p>0.05). Maximum DMP-1 concentration was higher in the group that experienced at least 10% RR on any tooth than the group that did not (p<0.05), while there was no significant difference in DPP absorbance between the two groups (p>0.05). Conclusions: These results show that DMP-1 and DPP are higher at most time points during orthodontic treatment compared to baseline. An association was found between OIIRR and DMP-1 concentration, but not DPP absorbance. Funding: NIH grant DE 11657 and the Brodie Endowment Fund IRB/ACC protocol: 2012-0767