# Residuals of Chemical Cleaning Agents Impair Peri-Implant Cell Viability: An in Vitro Study

## TL;DR

This study shows that leftover chemical cleaning agents used on dental implants can harm nearby cells, especially at high concentrations and over time.

## Contribution

The study reveals dose- and time-dependent effects of chemical debridement agents on peri-implant cell viability and resistance differences among cell types.

## Key findings

- High concentrations of H2O2 and NaClO reduced LDH activity and cell viability in a dose- and time-dependent manner.
- hBMSCs showed greater resistance to H2O2 compared to other cell types.
- Chemical agents suppressed anti-apoptotic genes BCL2 and MCL1 in MC3T3-E1 and HGF cells but not in hBMSCs.

## Abstract

Background: Chemical
debridement agents are commonly
used during
the cleaning of implants for peri-implantitis treatment; however,
how these agents affect lesion healing remains unclear. In addition,
the dose- and time-dependent effects of these residuals on implant
biocompatibility remain poorly understood. Materials and methods:
We evaluated the effects of active compounds in commercial products-3%
hydrogen peroxide (H2O2), 0.43% sodium hypochlorite
(NaClO), and 0.12% chlorhexidine with 0.05% cetylpyridinium chloride
(CHX-CPC) at graded dilutions on murine osteoblastic cells (MC3T3-E1),
human gingival fibroblasts (HGFs), and human bone marrow mesenchymal
stromal cells (hBMSCs). Cells were cultured for 24 h, then exposed
to the agents for 2, 12, or 24 h. Cytotoxicity and viability were
assessed using lactate dehydrogenase (LDH) release and CCK-8 assays,
while cell morphology was examined by scanning electron microscopy
(SEM). Apoptotic gene expression (BCL2, MCL1, BAX) was analyzed after 2 h using quantitative
PCR. Results: At high concentrations, H2O2 and
NaClO significantly reduced LDH activity in supernatant, likely due
to oxidant-induced enzyme inactivation. All three agents inhibited
cell viability in a dose- and time-dependent manner, accompanied by
cell shrinkage and deformation. Among the tested cell types, hBMSCs
displayed greater resistance to H2O2, maintaining
proliferative viability at 0.15% (1:20 dilution). Gene expression
analysis revealed that concentrated H2O2 and
CHX-CPC downregulated BCL2 and MCL1 expression in MC3T3-E1 cells, with broader suppression of these
genes observed in HGFs across all agents. In hBMSCs, high concentrations
of the agents did not significantly reduce BCL2 and MCL1 levels. Conclusion: Residual chemical debridement agents,
when inadequately removed, compromise the viability of cells in peri-implant
tissues in a dose- and time-dependent manner. hBMSCs exhibited greater
resistance to apoptosis than MC3T3-E1 cells and HGFs. Thorough removal
of residual chemical cleaning agents after peri-implant debridement
is therefore crucial to preserve the biocompatibility of the implant
and the healing potential of peri-implant tissues.