Influence of Immediate and Delayed Dentin Sealing on Bonding Strength of Lithium Disilicate Glass Ceramic: An in vitro Study

Abstract

Objective: To investigate the influence of immediate and delayed dentin sealing technique on shear bonding strength (SBS) of the lithium disilicate glass-ceramic on tooth structure with different depths. Methods: The buccal surfaces of 40 maxillary first premolars were prepared with two different depths (1mm and 1.5 mm) and two different timings for bonding (immediate and delayed dentin sealing). G1 (1 mm preparation) and G2 (1.5 mm preparation) were  treated with bonding (Tetric N-Bond Universal, Ivoclar,2021, Schaan/Liechtenstein) two weeks after preparation, before cementation to the ceramic block with delayed dentin sealing (DDS), while G3 (1 mm preparation) and G4 (1.5 mm preparation) were treated immediately after preparation with bonding and immediate dentin sealing (IDS). All specimens were stored in artificial saliva (Biotene dry mouth, GSK goupe, Canada) for two weeks at 24℃. Forty lithium disilicate glass-ceramic rectangular blocks (Rosetta SM) (HASSBIO, Korea) with dimensions of (2 mm height, 2mm width and 3 mm thickness) were prepared. After preparation of the tooth surfaces, all prepared blocks were cemented to the prepared teeth in  groups GI and G2 with phosphoric acid 37% for 15 seconds, and all ceramic fitting surfaces were treated with 10% hydroflouric acid for 20 seconds and coupling agent monobond, then aging was performed for 5000 cycles in artificial saliva from 5-55 °C for all specimens. A universal test machine was used to test the shear bond strength (SBS). The statistical analysis was done using a one-way ANOVA test followed by Tukey's post hoc test (p<0.05). Results: The result revealed that IDS and minimum preparation depth had significantly higher bonding strength than DDS. Bonding strength in sequence was 15.50 ± 3.873 MPa in G3 and G4 8.25 ± 3.344 MPa, while for delayed dentin sealing the bonding strength was 7.75 ± 2.993 in G1 and 6.25 ± 2.125 MPa in G2. Conclusions: Teeth treated with IDS immediately after preparation showed significantly higher bonding strength than those treated with DDS for indirect ceramic restoration. Also, increase in the depth of the preparation toward the dentin led to a decrease in the bonding strength of the restoration.