Highly alkaline mineral trioxide aggregate (MTA) affects restorative materials

Mineral trioxide aggregate (MTA) is widely used as an effective pulp-capping material. However, limited scientific evidence is available regarding the optimal restorative material to be placed over MTA. Additionally, the influence of MTA's highly alkaline environment on adjacent restorative materials remains unclear. This study aimed to evaluate the endurance of various restorative materials, namely a conventional glass-ionomer (GI), a resin-modified glass-ionomer (RMGI), and a UDMA- and BisGMA-based composite, under water and alkaline conditions, and to examine the interfacial characteristics between these materials and hardened MTA.

The endurance of the selected restorative materials was assessed after immersion in distilled water or an alkaline solution. Mechanical strength was evaluated, and material degradation, including turbidity and visible degradation products, was monitored. The interfacial characteristics between hardened MTA and each restorative material were analyzed to determine the stability and bonding behavior at the material interface.

In the alkaline solution, turbidity and visible degradation products were observed. Both the RMGI and the UDMA-based composite exhibited significant reductions in mechanical strength. At the interface with hardened MTA, GI demonstrated notable detachment, whereas the composite bonded to MTA by an adhesive exhibited a closely adapted interface with MTA.

These findings indicate that material selection following MTA placement is critical for maintaining stability and interfacial integrity, particularly under alkaline conditions. Composite resin used in combination with an adhesive may offer superior interfacial performance compared with GI-based materials when placed over MTA.