Parts of a Matrix Retainer – Labeled Retainer and Band

All 11 parts on the diagram

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The retainer 8

Matrix band A thin strip of metal. Its two ends are held in the retainer.
Outer knob It turns the spindle, tightening its point against the band.
Inner knob It moves the vise to make the loop larger or smaller.
Spindle A pointed screw whose tip holds the band in the slot.
Vise (locking vise) The sliding block that holds the ends of the band.
Diagonal slot The slanted slot in the vise. The ends of the band sit in it.
Guide channels (guide slots) Openings at the end that lead the loop straight, left or right.
Frame The body of the retainer. The vise slides along it.

The band 3

Loop The ring made by bringing the two ends of the band together.
Occlusal edge The longer edge of the band, toward the biting surface.
Gingival edge The shorter edge of the band, toward the gum.

How this list was compiled: Every name checked on 2026-10-01 and kept only where two of these use it. (1) Dental Assistant, Health Occupations Education, a 1981 state curriculum on ERIC, https://archive.org/details/micro_IA41153340_0706 : a labeled figure of the retainer (outer nut, inner nut, spindle, guide channels, diagonal slot vise) with what each is used for, and the band's gingival edge, occlusal edge and loop. (2) Dental Assistant Test Development Project, final report, 1986, ERIC ED287987, https://archive.org/details/ERIC_ED287987 : outer nut, inner nut, spindle, diagonal slot, guide channels, the band's loop, gingival and occlusal edges. (3) Illinois Occupational Skill Standards: Dental Assistant, 2002, ERIC ED473346, https://archive.org/details/ERIC_ED473346 : guide channels, the diagonal slot on the vise, inner knob, outer knob, the pointed end of the spindle, gingival edge, occlusal edge, loop. (4) Dental assisting textbooks read as snippets through archive.org's full-text search: a 2002 handbook of essential skills (guide channels, vise, diagonal slot, spindle, inner knob, outer knob and frame), https://archive.org/details/delmarshandbooko0000phin ; a 1996 essentials text (vise, frame, inner knob, spindle, outer knob, guide slots), https://archive.org/details/chasteensessenti0000miya ; a 1995 text (outer knob, frame, diagonal slot, guide slots, inner knob), https://archive.org/details/dentalassistant0000ande_6thedi ; a dental materials text (locking vise; the retainer named for the dentist who developed it), https://archive.org/details/dentalmaterialsc0000hatr_l6e6 . Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work

How it works

A matrix retainer holds the thin metal band a dentist fits round a tooth that is being filled. Dental assistants know this universal kind as the Tofflemire, after the dentist who developed it. Names only, with what each part is for.

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The retainer

The frame is the body. The vise slides along it and has a diagonal slot that takes the two ends of the band. The spindle is a pointed screw: the outer knob turns it until its tip holds the band in the slot. The inner knob moves the vise, which makes the loop larger or smaller. The guide channels at the end lead the loop straight out or to either side.

The band

Laid flat, the band is a curved strip. Its longer curve is the occlusal edge and its shorter curve the gingival edge. Bringing the two ends together makes the loop.

The quiz takes outer nut and inner nut for the two knobs, and guide slots for guide channels.

Questions and answers

What are the parts of a matrix retainer?

The frame, the vise with its diagonal slot, the spindle, the inner knob, the outer knob and the guide channels. The matrix band it holds has a loop, an occlusal edge and a gingival edge.

What does the outer knob of the retainer do?

It turns the spindle. Turned one way, the pointed tip of the spindle moves into the diagonal slot and holds the ends of the band; turned the other way, it lets them go.

What does the inner knob do?

It moves the vise along the frame. Because the ends of the band are held in the vise, moving it makes the loop of the band larger or smaller.

Which edge of a matrix band is the occlusal edge?

The longer one. A band laid flat is a curved strip: the longer, outer curve is the occlusal edge, toward the biting surface, and the shorter, inner curve is the gingival edge, toward the gum.