#TL;DR

Key Facts

#Purpose of a Matrix

When a proximal surface of a posterior tooth is prepared (Class II preparation), one or both proximal walls are opened, leaving the prepared cavity with no lateral wall on that side. Without replacing this wall temporarily, placing restorative material into the cavity would result in material flowing into the gingival sulcus and the interproximal space — creating an overhang, an open margin, or a failed proximal contact.

The matrix band serves four functions simultaneously: it confines the restorative material to the cavity, it creates the proximal wall against which material is condensed, it establishes the contact point with the adjacent tooth, and it seals the gingival margin (with wedge assistance) to prevent apical extrusion of material.

A properly placed matrix with a correct wedge produces a restoration with a tight interproximal contact, a well-adapted gingival margin, and no flash. A poorly placed matrix produces one or more of the four classic Class II failures: open contact, flat contact, gingival overhang, or gingival marginal gap.

#Tofflemire Matrix System

The Tofflemire retainer-and-band system has been the dominant posterior matrix system for over a century. Its simplicity, low cost, and compatibility with amalgam condensation pressure make it a practical choice for Class II amalgam restorations. Its key structural limitation — that the band is flat and under no pre-separation tension — is the primary reason it performs poorly for Class II composite.

#Components

• Tofflemire retainer — an L-shaped metal device with a rotating nut mechanism that tightens and releases the band. Available in standard (for posterior) and anterior configurations.
• Matrix band — a thin stainless steel ribbon (~0.04 mm thick), wider at one end, that encircles the tooth. The wide end is the gingival end; the narrow end faces occlusally. Universal bands fit most posterior teeth; narrower premolar bands are available for smaller teeth.
• Wooden or plastic wedge — a triangular wedge placed interproximally below the gingival margin to seal the band at the cervical floor and provide slight gingival tissue retraction.

#Placement Technique

1. Thread and size the band — loop the band through the retainer and tighten it to a diameter slightly larger than the tooth. The band loop should be oriented so the larger (gingival) end is apical and the retainer body is buccal or lingual to the tooth (not occlusal, which would obstruct condensation access).
2. Seat the band — slide the band loop over the occlusal surface and down to the gingival margin. The band must extend 1–1.5 mm below the gingival floor of the preparation.
3. Tighten to the tooth — use the retainer nut to tighten the band snugly against all four axial surfaces. The band should not rotate or rock — if it does, it is too loose.
4. Burnish the contact area — use a ball burnisher to press the band outward against the adjacent tooth at the contact area. This is the most important step for Tofflemire contact creation: manually deforming the flat band outward gives it a slight convexity that may produce a marginal contact.
5. Place the wedge — insert a wooden wedge from the buccal embrasure (or lingual, if easier) to hold the band against the gingival floor. The wedge should be snug but not so tight that it fractures the marginal ridge of the adjacent tooth.
6. Verify the seal — use an explorer at the gingival margin to confirm the band is flush with the cavity floor. No gap should be detectable between band and gingival floor.

#Limitations of the Tofflemire System

The Tofflemire system has three inherent limitations that are relevant to modern composite placement:

• Flat band geometry — the band is flat stainless steel. Even after burnishing, the band cannot be made reliably convex. Composite condensed against a flat surface produces a flat or concave proximal surface — creating a contact area that is a flat plane rather than a convex point, with poor self-cleansing characteristics.
• No pre-separation — the Tofflemire does not separate the adjacent teeth before material placement. Composite polymerisation shrinkage is directed toward the bonded walls, including the proximal wall. Without pre-separation, the restored tooth is slightly tipped away from the adjacent tooth after the band is removed, leaving a detectable open contact.
• Retainer body obstructs access — the retainer body (buccal or lingual) restricts bur access and matrix placement for certain posterior teeth, particularly the second molar.

#Sectional Matrix Systems

Sectional matrix systems were developed specifically to address the limitations of the Tofflemire system for composite restorations. They use a short, pre-curved band segment (rather than a full circumferential band), combined with a separation ring that physically spreads the contact teeth apart before material placement. The ring’s springback after band removal produces a tight, physiological contact.

Well-established commercial systems include Palodent Plus (Dentsply), Composi-Tight 3D Fusion (Garrison), and SuperMat (Kerr). All operate on the same principle.

#Components

• Sectional band — a short, curved stainless steel or titanium-nitride coated segment, pre-contoured to follow the natural convexity of the proximal surface. Available in narrow, medium, and wide to match tooth height. The curved geometry means composite condensed against it produces an anatomically convex proximal surface.
• Separation ring — a stainless steel spring ring with two tines that slide over the contact area buccally and lingually. When the tines engage the tooth structure at the buccal and lingual of the proximal area, the ring separates the teeth by 50–150 µm. This pre-separation is the mechanism that ultimately produces a tight contact after ring removal.
• Wedge — a small anatomical or round wedge placed from the buccal embrasure to stabilise the band at the gingival margin and prevent flash at the cervical seal.

#Placement Technique

1. Select the correct band size — the band height should match the distance from the gingival floor to the marginal ridge. A band that is too tall will be unstable; too short will not seal the gingival margin.
2. Place the wedge first — insert the wedge from the buccal embrasure to the level of the gingival floor. The wedge stabilises the band during ring placement.
3. Place the band — using band placement forceps, seat the curved band against the prepared proximal surface. The concave side of the band faces the cavity; the convex side faces the adjacent tooth.
4. Apply the separation ring — using ring-placing forceps, spread the ring tines and position them over the band at the buccal and lingual embrasures. Release the forceps — the ring engages and pre-separates the teeth. The band is now held firmly in position by both the ring and the wedge.
5. Verify the gingival seal — probe the junction between band and gingival floor with an explorer. No gap should be felt. If a gap exists, reposition the wedge deeper or change to a wider wedge size.
6. Place the restoration — apply bonding agent, then place composite incrementally against the proximal band first. After curing, remove the ring and band, then complete the occlusal increments.

#Wedge Selection and Placement

Correct wedging is as important as matrix selection. An under-sized or poorly positioned wedge allows composite or amalgam to flow apically past the gingival margin, creating a subgingival flash or overhang that is difficult or impossible to remove and that perpetuates gingival inflammation.

The wedge should be placed from the buccal embrasure as the primary insertion point in most cases — the buccal embrasure is wider and allows larger wedges to be inserted, providing better gingival adaptation. For MOD preparations, place wedges from both buccal embrasures (one mesial, one distal). Ensure the wedge tip reaches to or slightly past the gingival margin of the preparation floor.

#Anterior Matrix Systems (Class III & IV)

Anterior restorations (Class III and IV) require different matrix solutions because circumferential bands cannot be applied to incisors without blocking access to the labial surface. Several options exist:

• Transparent (Mylar) strip matrix — a thin polyester (PET) strip that is held against the proximal surface manually or with a finger during composite placement. Light-cured through the strip. Produces smooth, finished proximal surfaces. Used for small Class III restorations.
• Pre-contoured cervical matrices — shaped plastic or metal forms designed to wrap the cervical region of anterior teeth for Class V or cervical composite restorations.
• Silicone index (putty key) — for Class IV restorations, a silicone impression of the adjacent intact incisor (or a waxed-up study model) creates a template that supports the palatal composite increment and guides incisal contour during layering. Not a matrix in the traditional sense, but fulfils the same templating function.

#Matrix Systems Compared

#Related Topics

#References

1. Loomans BAC, Opdam NJM, Roeters FJM, Bronkhorst EM, Burgersdijk RCW. Restoration techniques and marginal overhang in Class II composite resin restorations. J Dent. 2007;35(4):342–349.
2. Wirsching E, Lohbauer U, Schmitt J, Munz I, Petschelt A, Ebert J. Proximal contact tightness of Class II resin composite restorations in vitro. Oper Dent. 2011;36(4):399–406.
3. Peumans M, Politano G, Van Meerbeek B. Treatment of non-carious cervical lesions: when, why, and how. Int J Esthet Dent. 2020;15(1):16–42.
4. Sturdevant CM, Roberson TM, Heymann HO, Sturdevant JR. The Art and Science of Operative Dentistry. 6th ed. St. Louis: Mosby; 2011.

#Summary

About the Author

Dr. Andries Smith

BChD, FRCS — Restorative & Operative Dentistry

Dr. Smith is a restorative dentist and clinical educator with a focus on evidence-based operative techniques. He writes for Dental Panda to make complex clinical science accessible to students and practising clinicians alike.