Which one of the following restorative materials is not suitable for use as a temporary filling in a deciduous tooth?

Calcium hydroxide is primarily used as a liner or base in dental procedures, rather than a filling material. Its main function is to promote pulp healing and provide a protective barrier under restorative materials. While it has some temporary sealing properties, it is not designed to withstand the functional pressures associated with chewing and does not have the durability required for a temporary filling in a deciduous tooth.

In contrast, glass ionomer, zinc phosphate, and zinc polycarboxylate are all materials that can be used effectively for temporary fillings. Glass ionomer has good adhesive properties and releases fluoride, which can be beneficial in terms of promoting tooth health. Zinc phosphate is known for its strength and is often used for temporary restorations. Zinc polycarboxylate also offers good adhesion and moderate strength, making it suitable for temporary fillings. Each of these materials provides a level of support and protection that is necessary for a temporary restoration in a primary tooth, while calcium hydroxide is primarily focused on pulp protection rather than providing structural integrity as a filling material.