Analysis of transdentinal cytotoxicity of HEMA-free universal adhesive systems

• Grant number: 24/17561-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2025
• End date: December 31, 2025
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Carlos Alberto de Souza Costa
• Grantee: Adrielly de Moraes da Costa Sousa
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

Different monomers present in resinous materials cause cytotoxic effects of varying intensities. It has already been demonstrated that the monomer 2-hydroxyethyl methacrylate (HEMA), which is present in the composition of most adhesive systems, is a hydrophilic molecule with low molecular weight. Therefore, unpolymerized HEMA, which is released from adhesive systems applied to the floor of very deep cavities, can diffuse in large quantities through dentinal tubules, causing damage to the dental pulp. Recently, the introduction of universal adhesives (UAs) containing the functional monomer 10-MDP has brought advances in the chemical adhesion of these resinous materials to dental tissues, but the presence of HEMA continues to be a biological challenge for pulp cells. Therefore, the main objective of this study is to comparatively evaluate the transdentinal cytotoxicity of HEMA-free UAs on MDPC-23 odontoblast-like cells and a primary culture of human dental pulp cells (HDPCs). To simulate a clinical condition of a very deep cavity, dentin discs with a standardized thickness of 0.4 mm will be adapted in artificial pulp chambers (APCs), and MDPC-23 cells will be seeded on their pulpal surface. Then, the occlusal surface of the discs will receive the following treatments: NC - negative control (no treatment); PC - positive control (Scotchbond Universal Adhesive); GLUMA - Gluma Bond Universal adhesive; ZIPBOND - Zipbond Universal adhesive; and SOLARE - Solare Universal Bond adhesive. All adhesive systems will be applied according to the manufacturers' recommendations. At 24 hours after completing the treatments, the viability (AlamarBlue; n=8) and morphology (SEM; n=4) of the MDPC-23 cells that remain adhered to the pulpal surface of the discs will be analyzed. The extracts (culture medium + components of adhesive systems diffused through the discs) will be collected and then applied to HDPCs previously cultured in 96-well plates. After 24 hours of exposure to the extracts, cell viability (AlamarBlue; n=8) and alkaline phosphatase activity (ALP; n=8) will be analyzed. Gene expression (RT-qPCR; n=8) of HDPCs for markers involved in the inflammatory response (Tumor Necrosis Factor Alpha - TNF¿; Cyclooxygenase 2 - PTGS2; and Interleukin 1 beta - IL1¿) and oxidative stress (Hemeoxygenase 1 - HMOX1) will also be evaluated. Seven days after the treatments, it will also be possible to quantify (RT-qPCR; n=8) the mineralization markers (ALPL) and odontogenic differentiation markers (Dentin Sialophosphoprotein - DSPP and Dentin Matrix Protein 1 - DMP1). The numerical data obtained will be subjected to specific statistical analysis.