Dental filling and zip: what they have in common
- Step 1. Dental filling — is made of — Silver. Silver in the amalgam.
- Step 2. Silver — is material for — Syringe. Early needles were silver.
- Step 3. Syringe — has part — Needle. A hollow needle.
- Step 4. Needle — is used in — Trousers. Trousers were sewn with a needle.
- Step 5. Trousers — has part — Zip. A fastener.