The effect of two different types of forces on possible root resorption in relation to dentin phosphoprotein levels: a single-blind, split-mouth, randomized controlled trial

BACKGROUND: The purpose of this 2-arm-parallel split-mouth trial was to evaluate and compare the extent of possible root resorption using dentin phosphoprotein levels in gingival crevicular fluid between controlled continuous and intermittent orthodontic force groups. MATERIALS AND METHODS: A sample of 16 maxillary first premolars from 8 patients requiring bilateral extractions of the upper first premolars as part of their orthodontic treatment were recruited. A buccally directed continuous force of 150 g, reactivated after 28 days, was applied to the upper first premolar on one side for 8 weeks. On the contralateral first premolar, a buccally directed intermittent force (21 days on, 7 days off) of the same magnitude was applied for the same period. Gingival crevicular fluid samples were collected at the beginning of the study, 1st, 3rd, 4th and 5th week, and at the end of the study to quantify and compare dentin phosphoprotein levels in both groups. RESULTS: Dentin phosphoprotein levels showed a higher concentration in the continuous force group than the intermittent force group in week 4 and 8 of sample collection; where the differences were statistically significant (95% CI 0.007-0.14; P < .04) and (95% CI 0.02-0.17; P < .04) respectively. No harm was observed. CONCLUSIONS: Dentin phosphoprotein was found to be a useful early biomarker to detect and monitor root resorption, showing that the application of an intermittent orthodontic force caused less root resorption than a continuous force. TRIAL REGISTRATION: NCT04825665 ClinicalTrials.gov. Registered 1 April 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04825665 .