Which instrument is used to enlarge the coronal portion of the canal?

• A. Gates Glidden drill
• B. Cresophene
• C. Tapered diamond bur
• D. Paper points

Answer: (A)

Enlarging the coronal portion to create straight-line access is a key step before cleaning and shaping the canal. Gates Glidden drills are designed for this purpose; they are thin, flame-shaped cutting instruments used in the coronal third to progressively widen the canal walls with short, brushing motions. Using these drills in increasing sizes helps remove dentin and flare the canal without venturing into the apical region, making subsequent file progression smoother. The other items here don’t serve this purpose: Cresophene is an antiseptic canal irrigant, paper points are for drying the canal, and a tapered diamond bur is primarily used for general hard tissue removal in restorative work rather than controlled coronal canal enlargement.