Long-term effect of simulated five years professional mechanical biofilm removal on the luting gap of ceramic restorations

Achieving sufficient professional mechanical biofilm removal (PMPR) can be challenging in supportive periodontal therapy (SPT), particularly in patients with prosthetic restorations. This experimental study aimed to simulate five years of SPT with periodic PMPR near the luting gap of ceramic restorations using a rubber cup with polishing paste (RCP), air polishing with two different low-abrasive powders (LAPA-1: glycine powder, LAPA-2: erythritol powder), and non-professional mechanical cleaning (control group) to measure the extent of volume loss in the luting gap after baseline (∆V = V_baseline-V_1-5; in µm³).

Two operators randomly performed PMPR ten times for thirty seconds on one of four sides of 30 crown replicas fixed with glass-ionomer cement (CGIZ: n = 15) or adhesive bonding (CAB: n = 15). The replicas were separated in a template during PMPR, and afterward, cleaned for five seconds per side with a sonic brush under flowing water. The artificial aging process between two PMPRs simulated a 5-year SPT with two PMPRs per year. Profilometric measurements were performed at baseline and after each second PMPR to obtain the mean change of ∆V. The statistical evaluation of the data was carried out using nonparametric tests with Bonferroni correction applied for multiple tests.

Ninety-six out of 120 sides could be included in the analysis. PMPR methods showed a loss of substance in the luting gap with a ∆V (mean(standard deviation)) of -4.35 × 10⁶(4.8 × 10⁶)µm³ versus 8.79 × 10⁴(1.05 × 10⁶)µm³ for control at V₅ (p ≤ 0.001). No significant differences of ∆V_1-5 values could be identified in the control (p > 0.05), whereat all PMPRs showed a significant increasing loss of substance per simulated year (p ≤ 0.001). Intergroup comparison identified LAPA-1 as having the highest significant loss of substance determined on CAB (∆V: -1.05 × 10⁷ (7,2 × 10⁶) µm³), followed by LAPA-2 on CAB (∆V: -6.29 × 10⁶ (4,24 × 10⁶) µm³), LAPA-1 on CGIZ (∆V: -4.15 × 10⁶ (3,25 × 10⁶) µm³), LAPA-2 on CGIZ (∆V: -3.0 × 10⁶ (2,23 × 10⁶) µm³), RCP on CAB (∆V: -1.86 × 10⁶ (2,23 × 10⁶) µm³) and CGIZ (∆V: -1.2 × 10⁶ (1,31 × 10⁶) µm³; p ≤ 0.001)).

Within study limitations, all PMPRs caused a significantly higher loss of substance in the luting gap versus control without professional intervention, with the highest values in the CAB group for LAPA-1, LAPA-2 and RCP. Similar findings were observed for CGIZ, although the loss values were lower.