Placed on the mesial or distal buccal cusp of lower first and second molars to anchor the rubber dam during root canal therapy. The 12A jaw design grips bulbous molar crowns securely without crushing enamel, isolating the pulp chamber from salivary contamination. Endodontists select this clamp when treating mandibular molars with intact clinical crowns and adequate ferrule height.

Selected for isolation of mandibular molars that present with shorter clinical crowns or altered cusp anatomy where the 12A pattern does not achieve stable retention. The 13A bow engages the buccal groove of lower molars during endodontic retreatment and post-and-core preparation. It maintains a dry field while the clinician negotiates curved mesial canals under the dental operating microscope.

Stretches medium-weight rubber dam sheet over the 6-inch frame to create a taut isolation barrier during multi-visit endodontic cases. The 15 cm span accommodates quadrant isolation when treating two adjacent posterior teeth under rubber dam. Assistants position the frame wings outside the oral cavity so the dam does not collapse onto the access cavity during file negotiation.

Used as an endodontic measuring guide to estimate working length and canal curvature before inserting files into anterior and premolar teeth. The U of Washington markings on the Palmer instrument help clinicians compare canal depth against radiographic landmarks during initial access preparation. It supports consistent reference measurements when transitioning from #10 to #15 K-files in calcified canals.