Influence of Silane Pretreatment and Warm Air-Drying on Long-Term Composite Adaptation to Lithium Disilicate Ceramic

Background: Repair bonding to lithium disilicate ceramic (LDS) remains an issue. This study examined whether the adaptation of a resin composite to LDS can be improved by a silane pretreatment and warm air-drying. Methods: LDS blocks (IPS e.max CAD) with prefabricated tapered cavities were bonded using a silane-containing universal adhesive (Clearfil Universal Bond Quick ER; UBQ) or the bonding agent of a two-step self-etch adhesive (Clearfil SE Bond 2), with and without a silane pretreatment (Clearfil Ceramic Primer; CP). CP and the adhesives were air-dried with normal air (23 ± 1 °C) or warm air (60 ± 5 °C), light-cured, and the cavities were filled with a flowable composite. Interfacial gap formation was evaluated using swept-source optical coherence tomography immediately after filling, after 24 h, 5000 and 10,000 thermal cycles, and an additional 1 year of water storage. Results: Without the silane pretreatment, all specimens soon detached from the cavities. Warm air-drying significantly decreased gap formation compared to normal air-dried groups (p < 0.001) and improved long-term stability (p < 0.001). The lowest gap formation was observed with UBQ when the silane pretreatment was combined with warm air-drying. Conclusions: Composite adaptation to LDS was insufficient without silanization, but it was stable in the long term if the silane pretreatment and warm air-drying were combined.