Influence of Air Polishing and Ultrasonics on Veneer Margins in Vitro: An Optical Coherence Tomography Pilot Study

In vitro evaluation of substance loss at the restoration margin of veneers was conducted as a function of prophylaxis procedures, air polishing, or ultrasonic instrumentation.

Forty-eight extracted premolars were restored with CAD/CAM materials after veneer preparation (t₀): lithium disilicate, zirconia-reinforced lithium silicate ceramics, and resin-based composite. Five cycles of prophylaxis treatment (air polishing or ultrasonic scaling) and thermocycling (t_E) were conducted. The substance loss of the luting material at the restoration margin was evaluated regarding width, depth, and the veneer inclination angle using optical coherence tomography and contour analysis. Group differences were determined using two-factor analysis of variance, Tukey tests, and linear regression models.

Both prophylaxis procedures lead to substance loss at the restoration margin. The material choice had a significant effect on width and depth at the veneer margin (p < 0.002), this was not observed for the prophylaxis procedures (p ≥ 0.445). Air polishing resulted in the largest reduction in width and depth in zirconia-reinforced lithium silicate. A cross-group influence of inclination angle on substance loss was not detected.

Both prophylactic procedures cause substance loss at the margins of the investigated CAD/CAM ceramic as well as composite veneers in the area of adhesive bonding.

The choice of luting and veneer material seems to have a more significant influence on the extent of substance loss than the type of instrumentation of the prophylaxis procedure.