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This page describes products and general use; it is not medical advice.
A sectional matrix system is a set of single-tooth parts used when a dental cavity involving the side of a tooth is restored: a pre-contoured thin matrix band, a separating ring and a wedge. This page is for clinic staff, buyers and students who need to know what is in the system, how one manufacturer sizes it, and what randomised trials found when it was compared with the older circumferential band.
What it is
A sectional matrix system (SMB) holds a contoured band against one tooth while a ring and wedge hold it in place. A 2025 systematic review of six randomised controlled trials describes it as a relatively recent innovation that is technique-sensitive and reported to create tight proximal contact points and to separate teeth faster. Who uses it: dentists, dental assistants and dental students working on class II cavities (cavities that involve the side of a back tooth).
How it is built
The parts, as listed in one manufacturer’s instructions for use (Premier X5, ref 0421066 Rev0):
- Matrix: a pre-contoured band supplied in several heights.
- Ring: its tines close near the gingival margin, straddling the wedge. Rings can be stacked for a tooth with cavities on both sides (MOD).
- Wedge: colour-coded by size.
The ring is not the band: it is the separate part that provides the separating force. A flat circumferential band, by contrast, is held by a retainer around the whole tooth; see the Tofflemire circumferential matrix and dental matrix bands for that system and dental wedges for wedges in general.
Sectional vs circumferential: what the trials found
The table below reports the trial-level findings in the Kamble et al. review (1,720 class II cavities across six RCTs, searched January 1990 to April 2024). Each row is attributed to its trial.
| Question | Finding | Trial cited in the review |
|---|---|---|
| Contact tightness | Pre-contoured sectional matrices with a separation ring significantly increased contact tightness; the flat circumferential band produced a significant decrease, attributed to the ring’s stronger separating effect | Loomans 2006 |
| Two-surface vs three-surface cavities | Sectional tighter in two-surface cavities; no significant difference in three-surface cavities | Wirsching 2011 |
| Patient sex | Sectional superior in men; no significant difference in women | Asif 2023 |
| Operator satisfaction | No significant difference; sectional easier to use | Almushayti 2022 |
| Operator experience | Optimum contacts closer with sectional regardless of experience | Shaalan 2021 |
| Overhangs and defective contacts | Circumferential gave more overhanging borders and defective contacts, yet students often preferred it for ease of use | Durr-E-Sadaf 2018 |
In the student survey reported there, 48.6% said extra placement time was the difficulty with circumferential, and 57.1% said lack of training was the difficulty with sectional. The review gives 0.038 to 0.05 mm for traditional steel circumferential bands.
Sizes in one manufacturer’s kit
These sizes belong to one product, not to a standard. The Premier X5 Essential Kit (REF 9061155) contains:
| Component | Sizes or colour in the kit (quantity per the IFU contents list) |
|---|---|
| Matrices | 3.5 mm, 4.5 mm, 5.5 mm, 6.5 mm; 25 of each |
| Wedges | Small (yellow), medium (green), large (blue); 25 of each |
| Matrix ring | Gray; 10 in the kit |
How to choose
In that IFU the matrices are sized by the approximate occlusogingival height, that is, the height of the tooth from biting surface toward the gum, which is why the kit offers four matrix heights.
Handling and regulatory basics
- The same IFU states the matrices and wedges are single use only and must not be autoclaved or reused.
- Regulatory status: openFDA lists product code JEP (Retainer, Matrix) and EKF (Instrument, Contouring, Matrix, Operative), both Class 1 under 21 CFR 872.4565, the dental hand instrument regulation. The regulation names matrix bands and matrix retainers; FDA does not list “sectional matrix systems” as a named category.
Common mistakes
- Treating the ring as the band. They are different parts with different roles.
- Assuming every component is reusable. For the X5 system the IFU says single use; check the IFU of whatever product you hold.
- Reading “sectional is always better”. The trials show subgroup differences, and operator satisfaction did not differ significantly.
FAQ
Does a sectional matrix give tighter contacts than a circumferential band?
In the trials reviewed, often yes for two-surface cavities, but not significantly for three-surface cavities (Wirsching 2011).
Can sectional matrices be reused?
The Premier X5 IFU states its matrices and wedges are designed for single use only and are not to be autoclaved or reused.
Is a sectional matrix system an FDA-regulated device?
Matrix retainers and contouring matrix instruments are Class 1 devices under 21 CFR 872.4565.
Sources
- Kamble S et al. Cureus 2025;17(5):e84967, PMC12204051 (PROSPERO CRD42024556368), checked 2026-10-31.
- Premier Dental, X5 Sectional Matrix System Instructions for Use, checked 2026-10-31.
- openFDA device classification, product codes JEP and EKF, checked 2026-10-31.
- 21 CFR 872.4565 Dental hand instrument, checked 2026-10-31.
- Related: dental hygiene instruments.
