What type of cement is considered the worst for deep restorations?

Zinc phosphate cement is regarded as the least suitable option for deep restorations due to several inherent properties. This type of cement can be relatively abrasive and may not provide the necessary adhesion to dentin that is crucial in deep restorations involving a significant amount of tooth structure. Furthermore, zinc phosphate cement is less able to accommodate the thermal expansion discrepancies that may occur in deeper cavities, potentially leading to failure or debonding over time.

Additionally, zinc phosphate has a lower fluoride release compared to glass ionomer cements, which can be a disadvantage when protecting against secondary caries—a common concern in deep restorations. In contrast, glass ionomer cements, composite resins, and resin-modified glass ionomers (RMGIs) are generally preferred for their adhesive properties, lower solubility, and ability to release fluoride, which provides additional protection and enhances long-term outcomes in restorative dentistry.