Objectives: Intraoral try-in of ceramic restorations before adhesive cementation is frequently accompanied by saliva-contamination of the to-be-bonded surface. Decontamination with phosphoric acid gel (PAG) is effective for silica-based ceramics, but severely reduces bond strength/longevity to zirconia surfaces. This study compares cleaning efficacy of a universal cleaning agent (IVC; Ivoclean, Ivoclar-Vivadent) to PAG on lithium-disilicate (LD2; E.maxCAD, Ivoclar-Vivadent) and zirconia (ZIR; ZirCAD, Ivoclar-Vivadent).
Methods: Cleaning efficacy was investigated via shear-bond-strength (SBS; N=5) on HF-etched LD2 or sandblasted ZIR using a universal primer-formulation (MBP; Monobond Plus, Ivoclar-Vivadent) and resin cement (MLM, Multilink Automix, Ivoclar-Vivadent). The following contamination-scenarios were studied: uncontaminated reference (REF), saliva+water (WAT), saliva+PAG+water, saliva+IVC+water. Contamination consisted of 60sec saliva-contact , 20sec rinsing with water-spray, 20sec unagitated PAG-/IVC-contact and rinsing with 10sec water-spray. Air-dried specimens were then primed with MBP according to manufacturer's instructions and MLM applied in single increment using an Ultradent-SBS-jig. Samples were light-cured for 20sec (Bluephase Style, 1200mW/cm2, Ivoclar-Vivadent) and stored in water for 24h@37°C or thermo-cycled 5000-times at 5-55°C with 45sec dwell-time (TC).
Results:
| REF | WAT (saliva+water) | PAG (saliva+PAG+water) | IVC (saliva+IVC+water) | |
TBS | |||||
LD2 | 24h@37°C | 32.4±6.7(a,A) | 20.8±5.0(b,A) | 28.7±11.8(d,A) | 34.8±9.6(e,A) |
5000 TC | 27.0±9.1(a,B) | 0.0±0.0(c,C) | 14.9±5.0(d,B) | 28.9±10.2(e,B) | |
ZIR | 24h@37°C | 22.1±5.0(a‘,A‘) | 9.1±1.3(b‘,B‘) | 12.8±2.5(d‘,B‘) | 20.0±3.7(f‘,A‘) |
5000 TC | 20.7±8.3(a‘,C‘) | 0.0±0.0(c‘,D‘) | 0.0±0.0(e‘,D‘) | 23.4±8.4(f‘,C‘) | |
Same letters/capital letters denominate statistical equivalence in columns-per-ceramic/rows (ANOVA, Tukey, p<0.05)
Conclusion: Saliva-contamination proved highly detrimental for primer-mediated adhesion between ceramics and resin cement. SBS of WAT (24h/TC) was significantly lower than in REF and TC of WAT was accompanied by spontaneous debonding. Though PAG proved effective on LD2, ZIR-passivation to phosphate-functional primer-components due to contact with phosphate-ions is evident from low 24h/TC values. Use of PAG should therefore be limited to silicate surfaces. Only IVC proved an effective cleaning agent and decontaminated either surface to provide SBS comparable to REF.