What does a dental assistant use to prevent build-up of tartar on teeth?

A scaler is a dental instrument specifically designed for the removal of plaque and tartar that accumulate on teeth. It is used during dental cleanings to scrape off deposits that can lead to gingivitis and other periodontal diseases if not addressed. The effective use of a scaler helps maintain oral health by preventing the build-up of harmful substances on the teeth.

In contrast, a polisher is employed to smooth and shine the surfaces of teeth after they have been cleaned and scaled. While polishing can help remove surface stains and give the teeth a clean appearance, it does not prevent tartar build-up as effectively as scaling does.

An explorer is primarily used for detecting cavities or other surface irregularities on the teeth. It helps the dentist or dental hygienist assess the condition of the teeth but does not serve any function in preventing the formation of tartar.

An excavator is a tool used to remove decayed material from a tooth during restorative procedures. While it's essential in caries management, it does not play a role in preventing tartar formation, which is a preventative concern addressed by scaling.

Hence, the scaler is crucial in preventing the accumulation of tartar on teeth, making it the correct answer.