Which one of the following materials is not used to cement a molar band to a tooth as part of a fixed orthodontic appliance?

Composite filler is not typically used to cement a molar band to a tooth as part of a fixed orthodontic appliance. The primary reason for this is that composite materials are generally used for bonding or filling purposes rather than for cementing orthodontic bands, which require materials that provide a strong and durable bond capable of withstanding significant forces during orthodontic treatment.

In orthodontics, the materials commonly used for cementing molar bands include glass ionomer, zinc phosphate, and zinc polycarboxylate. Glass ionomer cement bonds chemically to both the tooth structure and the metal band, offering good retention, fluoride release, and ease of handling. Zinc phosphate cement has a long history of use, providing excellent strength and a reliable bond. Zinc polycarboxylate cement, while slightly less strong than zinc phosphate, is still effective and offers a degree of bonding to tooth structure.

Therefore, while composite filler can have its applications in dentistry, particularly for restorative purposes, it is not the material of choice for cementing molar bands in an orthodontic setting.