Dentin Matrix Protein 1 in Saliva as a Biomarker for Root Resorption

Objectives: Root resorption (RR) is a common complication of orthodontic treatment. Historically, only radiographic means have been available to detect RR in orthodontic patients. Recent studies have shown that increased levels of specific biomarkers can be found in the gingival crevicular fluid of orthodontic patients displaying RR relative to control. The goal of this study is to detect the levels of dentin matrix protein 1 (DMP-1) in saliva samples from orthodontic patients.
Methods: Patients starting comprehensive orthodontic treatment were recruited to provide saliva samples before beginning treatment and roughly every 2 months until a panoramic radiograph is obtained. Saliva samples were collected, vortexed, and centrifuged with protease inhibitor. The samples were then analyzed using enzyme-linked immunosorbent assay (ELISA) to detect our target protein.
Results: N=25 saliva samples were analyzed from 6 study subjects at various stages in treatment. DMP-1 was detected in the pretreatment saliva samples tested with a mean absorbance of 0.369. The mean absorbance was 1.137 at 2 months, 0.382 at 4 months, 0.175 at 6 months, and 0.200 at 8 months. Paired student T-test showed a significant difference between pretreatment and 2 months (p<.05) and pretreatment and 8 months (p<.05), but no significant difference between pretreatment and 4 months and pretreatment and 6 months.
Conclusions: These results show that DMP-1 can be reliably detected in saliva. There were significant changes in the 2 and 8 month time points, while there were much higher variations at 4 and 6 months. As more samples are analyzed this variation may decrease. Our goal is to demonstrate that DMP-1 in saliva can be directly correlated with RR seen in panoramic radiographs. The eventual clinical application would be to develop a non-invasive, chair-side test to aid in early detection of root resorption resulting from orthodontic treatment.