Evaluating Chairside Composite Crown Approximal Contact Points: Comparing Two Workflows

Objectives: A direct and an indirect workflow have been developed by 3M™ to adapt a new chairside composite crown (CC). The objective of this clinical study was to compare the quality of the approximal contact point (AC) produced by the two workflows. The null hypothesis is that there would be no difference in the ACs produced.
Methods: Participants (n=20) requiring a full-coverage crown were recruited from Newcastle Dental Hospital. Subject teeth were required to have at least one opposing and one approximal contact point.

Following crown preparation (CP), and single cord retraction, participants were randomly allocated into either Direct (n=10) or Indirect (n=10) workflows. CCs were selected, adapted by hand, then tack cured on the CP. Following removal, CCs were fully polymerised, shaped with polishing discs and then relined with a flowable composite (Filtek™ Supreme, 3M™) either

a) On the CP (Direct)

or

b) On a trimmed chairside die (Mach 2,Parkell), poured from a sectional impression (Imprint™4, 3M™)(Indirect).

All CCs were fabricated and cemented with a self-adhesive resin cement (RelyX™ Unicem2) by a single operator.

At a baseline review (T+7-28 days), the ACs were measured by recording the thickest of 3 matrix strips (Deppeler) that could pass through them. ACs were categorised: Unsatisfactory (100mm), Satisfactory (50 mm) or Good (25 mm).

Results were analysed using the Fischer Exact test.
Results: 27 of the 33 ACs tested were rated satisfactory or good (table 1). While only Indirect CCs had unsatisfactory ACs the results did not confirm that you are statistically more likely to get an unsatisfactory AC with an Indirect CC (P=0.07).
Conclusions: This study suggests that CCs produced using an Indirect workflow are more likely to have an Unsatisfactory AC than the Direct workflow.