Abstract
The aim of the study was to examine the biochemical and structural changes occurring in the periodontal ligament (PDL) during orthodontic-force application using micro-Raman spectroscopy (-RS). Adolescent and young patients who needed orthodontic treatment with first premolar extractions were recruited. Before extractions, orthodontic forces were applied using a closed-coil spring that was positioned between the molar and premolar. Patients were randomly divided into three groups, whose extractions were performed after 2, 7, and 14 days of force application. From the extracted premolars, PDL samples were obtained, and a fixation procedure with paraformaldehyde was adopted. Raman spectra were acquired for each PDL sample in the range of 1000–3200 cm and the more relevant vibrational modes of proteins (Amide I and Amide III bands) and CH and CH modes were shown. Analysis indicated that the protein structure in the PDL samples after different time points of orthodontic-force application was modified. In addition, changes were observed in the CH and CH high wavenumber region due to local hypoxia and mechanical force transduction. The reported results indicated that -RS provides a valuable tool for investigating molecular interchain interactions and conformational modifications in periodontal fibers after orthodontic tooth movement, providing quantitative insight of time occurring for PDL molecular readjustment.
Highlights
The periodontal ligament (PDL) is a membrane-like connective tissue interposed between the tooth root and alveolar bone (Figure 1)
We suggest that the intense and broad peak around 2930 cm−1 observed in the PDL spectra of the sample after 48 h of treatment, correlated with the arachidonic acid (AA) by Toledo et al [47], could be connected to the increase of PGE2, seen by Kang et al [46] after 48 h of a treatment with a compressive force
The present investigation of PDL samples using μ-RS after orthodontic-force application allowed a useful inspection of molecular arrangements and conformational changes in periodontal fibres after different time points of orthodontic-force applications
Summary
The periodontal ligament (PDL) is a membrane-like connective tissue interposed between the tooth root and alveolar bone (Figure 1). If the pressure applied on dental structures is too high there is an interruption of blood circulation in PDL followed by sterile necrosis and disappearance of the cellular component, the tissue remodeling occurs thanks to cells from contiguous areas, which invade the necrosis lacunae causing an indirect resorption These mechanisms of hyalinization and resorption provoke an enforced delay in tooth displacement in the alveolar bone. The initial phase, 24 to 48 h after the orthodontic force application, is characterized by evident immediate tooth movement due to its displacement in the PDL space, and after 48 h the real OTM starts after the alveolar bone remodeling occurring through the combined activity of osteoclasts and osteoblasts. The outcomes revealed that the useful time points for orthodontic tooth movement monitoring should be set, at 2, 7 and 14 days after force application on teeth
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