What is the major component by weight of gutta-percha points?

Correct answer: D. Zinc oxide

• A. The gutta-percha polymer is the matrix that gives the material its name and its thermoplastic behaviour, but at around 20% it is a minority component by weight.
• B. Waxes and resins are plasticisers present in very small amounts, giving the points their pliability.
• C. Barium and bismuth sulphate are the radiopacifiers, a small percentage of the total.
• D. CORRECT. Despite the name, gutta-percha points are mostly ZINC OXIDE — roughly 60–75% by weight — which acts as filler and provides the antimicrobial and radiopaque properties. The actual gutta-percha polymer (trans-1,4-polyisoprene) makes up only about 20%, with radiopacifiers such as barium or bismuth salts at 1–17% and plasticisers (waxes and resins) at 1–4%.

Note: The high zinc oxide content explains a common exam point: gutta-percha itself has mild antibacterial activity, and beta-phase gutta-percha converts to alpha phase on heating, which is the basis of warm vertical compaction.