Effect of optical impression, timing of dentin sealing application and cavity design optimization on microleakage of ceramic onlays: an in vitro study

Immediate dentin sealing (IDS) is used to improve bonding of indirect restoration. However, interaction between polyether impressions may affect the future bonding of indirect restoration. So, digital impressions with IDS may have a better impact on microleakage. The current in vitro study aimed to investigate the effect of using digital impression versus polyether impression and different dentin sealing techniques on the microleakage of lithium disilicate onlays. A total of 60 identically sized human mandibular molars were allocated into two groups (n = 30): group DI, which uses a digital impression, and group CI, which uses a polyether impression. After preparation of all teeth for onlay, based on the dentin sealing technique, these groups were further divided into three subgroups (n = 10): subgroups I, II, and III. Dentin sealing was postponed in subgroup I prior to cementation. Immediate dentin sealing was applied prior to impression processes in subgroups II and III, plus cavity design optimization (CDO) for subgroup III. All teeth received e.max CAD onlay restoration (Ivoclar Vivadent, Schaan, Liechtenstein). The specimens were exposed to thermocycling with bath temperatures of 5 °C and 55 °C for a total of 5000 cycles. The specimens were then submerged in 0.5% aqueous Rhodamine B dye for 48 h. Buccolingual sections were examined under confocal microscopy. Microleakage was scored (0–3). Data were analyzed using the Scheirer–Ray–Hare test (α = 0.05). Microleakage was significantly lower in DI than CI (P=.0046). Delayed dentin sealing (subgroup I) showed significantly higher microleakage than IDS (subgroup II) and IDS + CDO (subgroup III) (P<.001), with no significant difference between IDS and IDS + CDO. Digital impressions were associated with significantly lower microleakage compared to polyether impressions. IDS, with or without CDO, significantly reduced microleakage compared to delayed sealing. Combining digital impressions with IDS may enhance the marginal seal and longevity of ceramic onlays.