# Biological mediators involved in tooth resorption following avulsion and delayed replantation: an experimental in vivo study

## TL;DR

This study explores how tooth resorption occurs after tooth avulsion and delayed replantation in dogs, focusing on biological mediators involved in the process.

## Contribution

The study identifies specific biological mediators and their roles in inflammatory and replacement resorption following delayed replantation of avulsed teeth.

## Key findings

- TRAP+ osteoclasts were observed in inflammatory resorption regardless of extra-alveolar time.
- RANKL synthesis was more intense after 90 minutes of dry storage compared to shorter durations.
- Replacement resorption showed higher alkaline phosphatase and reduced periostin synthesis.

## Abstract

This study aimed to investigate the biological mediators involved in tooth resorption following permanent tooth avulsion and late replantation at various periods. Premolars of healthy dogs were extracted and divided into: Control Group (CG): negative control, sound teeth (n= 5 teeth / 10 roots); or kept dry and replanted after 20 min (G20): the teeth were replanted after 20 minutes of extraoral time in a dry environment (n= 5 teeth / 10 roots); 60 min (G60): the teeth were replanted after 60 minutes of extraoral time in a dry environment (n= 5); or 90 min (G90): the teeth were replanted after 90 minutes of extraoral time in a dry environment (n= 5 teeth / 10 roots). After this, the teeth were replanted and splinted with 0.4 mm nickel-titanium (Ni-Ti) archwire. After 120 days, the animals were sacrificed, and the tissues were removed for histological processing. The slides were stained for microscopic analysis, submitted to tartrate-resistant acid phosphatase (TRAP) histoenzymology, and immunostained for RANK, RANKL, OPG, alkaline phosphatase, and periostin. Data obtained were submitted to statistical analysis at a 5% significance level. In areas of inflammatory resorption, TRAP + osteoclasts around the replanted teeth were identified, regardless of the duration of extra-alveolar time. RANKL synthesis in this region was more intense after keeping the tooth dry for 90 minutes when compared with other periods (p < 0.05). In areas of replacement resorption, there was less periostin synthesis and a higher level of alkaline phosphatase production (p < 0.05). Late replantation of avulsed teeth resulted in tooth resorption. Inflammatory resorption was characterized by osteoclast recruitment and RANKL synthesis and replacement resorption by alkaline phosphatase synthesis and inhibition of periostin.