Contemporary Ortho Appliances Practice Test

The important point is the inside of the bracket slot. In plastic brackets, the slot walls are made of polymer, which can wear, deform, or abrade during archwire sliding and ligation. That leads to loss of precise slot dimensions and increased friction, making tooth movement slower and less predictable. Lining the slot with metal creates a hard, smooth inner surface that resists wear and maintains consistent slot width, so the archwire can slide more freely and torque control stays more accurate. This addresses both common complaints with plastic brackets: slot wear/deformation and high friction. The other options wouldn’t provide the same durability or friction reduction—the rubber slot would wear quickly, the titanium base affects adhesion to the tooth rather than the slot mechanics, and a ceramic slot would be brittle and prone to fractures.