Correlation between Pain Perception and CGRP Expression during Initial Tooth Alignment Using either a Self-ligating or a Pre-adjusted Bracket System

Abstract

Orthodontic tooth movement (OTM) occurs when the force applied to the tooth stimulates inflammation and alveolar bone remodeling. Less friction is produced by passive self-ligating (PSL) brackets compared to pre-adjusted edgewise (PE) brackets; therefore, PSL bracket use is thought to result in less pain than the use of PE brackets. The neuropeptide calcitonin gene-related peptide (CGRP), isolated from gingival crevicular fluid (GCF), can be used as a pain biomarker for OTM. Pain perception can be subjectively evaluated using the visual analog scale (VAS). This study aimed to analyze pain perception, using the VAS and CGRP levels, and to examine the correlation between VAS scores and CGRP levels. A total of 15 patients were included in this study (a PSL group, a PE group, and a control group). GCF was collected from the lower anterior teeth, at interproximal sites, before bracket insertion and 2 hours, 24 hours, and 168 hours after lower archwire engagement. Pain perception was recorded using the VAS. CGRP concentrations were analyzed using an enzyme-linked immunosorbent assay (ELISA). The VAS scores of the PE and PSL groups increased 2 hours after archwire engagement, peaked after 24 hours, and returned to baseline after 168 hours, and the PE group had high scores than the PSL group, with the highest score being recorded at the 24 hour time point. CGRP concentrations were also the highest at the 24 hour time point compared to the other time points. These results showed that both the VAS score and the CGRP concentration increased during initial orthodontic tooth alignment when using either the PSL or the PE bracket systems. Pain perception scores and CGRP concentrations were weakly positively correlated. The type of bracket system used influenced the patients' pain perception scores and the release of CGRP.