# Perspectives on Matrix Metalloproteinase-8 and Salivary Osteoprotegerin in Orthodontic Strategy in Children with Chronic Kidney Disease

## TL;DR

This study examines how levels of MMP-8 and OPG in saliva differ among children with chronic kidney disease and how these levels relate to orthodontic needs.

## Contribution

The study introduces saliva-based MMP-8 and OPG as potential non-invasive markers for bone metabolism disorders in children with CKD.

## Key findings

- MMP-8 and OPG levels in saliva were significantly higher in children with CKD compared to healthy controls.
- The highest MMP-8 levels were observed in children receiving hemodialysis.
- OPG levels increased in children with early and post-transplant CKD stages.

## Abstract

Background/Objectives: This study aimed to establish the regularities of changes in the content of matrix metalloproteinase 8 (MMP-8) and osteoprotegerin (OPG), the most well-known indicators of bone metabolism disorders, in the saliva of children with different severities of chronic kidney disease (CKD) who need orthodontic treatment. Methods: The study of MMP-8 and OPG content in saliva was carried out in 76 children in need of orthodontic treatment, who were divided into equal groups (G) of 19 people: G1—children with congenital malformations of the urinary tract, acquired renal pathology, and CKD stage 1 and 2, receiving medical therapy, as well as more having a deep distal bite formed by mandibular micrognathia; G2—children with a terminal stage of CKD, receiving renal replacement therapy in the volume of hemodialysis, with a characteristic distal bite of different etiology; G3—children one year after kidney transplantation, with a tendency to form an open distal bite, associated to a greater extent with maxillary macrognathia. G4—practically healthy children without renal pathology stratified by sex and age. Results: It was found that the content of MMP-8 and OPG in the saliva of children with different CKD stages who needed orthodontic treatment was significantly higher than the G4. The maximum values of MMP-8 were registered in G2. An increase in OPG content in saliva was observed in the G1 and G3. Conclusions: The identified changes in markers of mineral and bone disorders in the saliva of children with different stages of CKD show the possibility of their use as non-invasive predictive and prognostic markers for the diagnosis of preclinical stages of bone metabolic disorders.