# Salivary proteomics in patients with fixed orthodontic appliances and Invisalign treatment

## TL;DR

This study compares salivary protein changes in patients using fixed orthodontic appliances and Invisalign to better understand tooth movement.

## Contribution

Identifies specific salivary proteins (CD19, FAM20C, GNRHR) linked to orthodontic tooth movement and their potential as biomarkers.

## Key findings

- CD19, FAM20C, and GNRHR showed significantly decreased expression during treatment in both groups.
- These proteins are associated with OTM-related proteins like fibronectin and osteopontin.
- PLS-DA revealed distinct salivary proteomic profiles at different treatment stages.

## Abstract

Early detection of biological changes is crucial for effective monitoring of orthodontic tooth movement (OTM). Research that elucidates the connection between OTM and salivary proteomic profiles remains limited. This cross-sectional study aimed to compare salivary protein profiles between fixed orthodontic appliances (FOA) and Invisalign (IN) treatments.

Unstimulated saliva was collected from 17 patients treated with FOA and 6 patients treated with IN before treatment (T0), and at 3 (T1) and 6 (T2) months after therapy initiation. Salivary proteomes were analysed using liquid chromatography-tandem mass spectrometry, followed by label-free protein quantification and identification with MaxQuant. Heatmap visualisation, Partial Least Squares Discriminant Analysis (PLS-DA), and ANOVA were performed using MetaboAnalyst (P ≤ .05) to identify differentially expressed proteins (DEPs). Gene Ontology enrichment analysis and Protein-Protein Interaction (PPI) network analysis were conducted on the identified DEPs. Results: PLS-DA demonstrated clear separation between T0, T1, and T2 in both groups. From 17,603 DEPs, 12 and 50 top proteins were identified between FOA and IN at T1 and T2, respectively. Three DEPs—CD19, FAM20C, and GNRHR—were identified in both groups. Their expression levels significantly decreased (P < .05) at T1 and T2 within each group, with no significant differences in CD19 and FAM20C between the 2 groups at T0, T1, and T2. PPI revealed associations between these proteins and OTM-related proteins, including fibronectin, RANK, osteopontin, dentine sialophosphoprotein, SOX9, alkaline phosphatase, collagen alpha-1, and collagen alpha-2.

CD19, FAM20C, and GNRHR are involved in OTM. Clinical relevance: Monitoring of CD19, FAM20C, and GNRHR expression during OTM may provide valuable biomarkers for predicting progression and outcomes.

Image, graphical abstract