Advanced Endodontics

Classic Endo Lit: The Birth of the “Zip”

Ever wonder where terms like apical transportation, zip, and elbow came from?

In 1975, Weine et al. used resin block models to show exactly what happens when we don’t respect canal curvature during instrumentation. When stiff files are forced down a curved canal, they straighten—cutting the outer wall and shifting the apex 😬

This study didn’t just identify the problem. It gave us the vocabulary, the visual evidence, and the impetus for safer shaping techniques like anti-curvature filing, balanced force, and eventually NiTi rotary systems.

Without Weine, we’d still be zipping canals blind.

📚 Weine FS, Kelly RF, Lio PJ. J Endod. 1975;1(8):255–262.

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