Restorative Functions: Isolation, Matrix/Wedge, Amalgam and Composite Placement, Finishing
The Restorative Functions domain of the DANB CRFDA exam tests the chairside skills an expanded-function dental assistant uses during direct restorative procedures: field isolation, matrix and wedge placement, amalgam and composite handling, carving and contouring, finishing/polishing, and occlusal verification. The published outline for this domain could not be independently verified here, so the content below reflects standard, widely taught restorative-assistant practice. Your state's scope of practice and your dentist's written protocol always govern what you may perform.
Field isolation and moisture control
- The rubber dam remains the reference standard for operative isolation; verify the seal with an explorer and floss ligatures, and confirm no leakage before the dentist begins.
- High-volume evacuation is positioned by the assistant to control water spray and retract tissue without obscuring the operating field.
- For cervical and Class V lesions, a retraction cord (with or without a hemostatic agent) controls sulcular fluid and improves access.
- Once dentin is etched and bonded, blood or saliva contamination degrades the bond; the surface must be re-etched and re-bonded if contamination occurs.
Matrix and wedge fundamentals
- Posterior Class II amalgam typically uses a Tofflemire-type retainer; the band must adapt to the gingival margin without impinging on tissue. Probe both proximal margins for gaps before condensation.
- The wedge seats from the embrasure where the band is least adapted (usually buccal), with the smaller diameter toward the gingiva. It stabilizes the band, prevents overhang, and slightly separates teeth to compensate for band thickness so the contact is restored.
- Class II composite often uses a sectional matrix with a separating ring; Class III/IV composite uses a Mylar strip with a wedge.
Amalgam versus composite rules
- Amalgam: condense in small increments, overbuild, remove the matrix, then carve anatomy and margins; pass floss to confirm a contact that snaps through.
- Composite: select shade before dehydration; place increments no thicker than about 2 mm and cure each for the manufacturer's time (commonly 20 seconds); do not air-dry the bonded surface; finish with fine diamonds and polish with aluminum oxide discs.
Worked example: Class II amalgam on tooth #19 (mandibular left first molar)
The lesion is mesio-occlusal. The assistant seats the wedge first from the buccal, then places the band so its contoured edge follows the gingival margin, tightens the retainer, and probes both margins. Amalgam is condensed in increments, overfilled slightly, the band and wedge are removed, and the assistant passes a Hollenback carver. Floss is passed through the mesial contact and should snap through with resistance; shredding signals an overhang. Articulating paper is used in centric and excursions before the patient is dismissed.
Traps that cost marks
- Leaving a proximal overhang or a flash the floss shreds.
- Seating the wedge from the wrong embrasure or with the large end gingivally.
- A band impinging on gingiva, which produces a poor gingival margin.
- Failing to check occlusion in excursions, leaving a high spot.
- Allowing saliva contact after bonding, then not re-etching.
- Placing composite in one bulk increment, causing incomplete cure and marginal failure.