Time-dependent bond strength development and pH dynamics of conventional and self-adhesive resin cements for lithium disilicate restorations

IntroductionThis study investigated shear bond strengths of conventional and self-adhesive resin cements bonded to lithium disilicate at different curing and setting times, and examined pH changes during setting to assess potential pulpal effects. We hypothesized that (1) extended light-curing time would improve bond strength, and (2) adequate light curing would accelerate pH neutralization in self-adhesive cements compared to no light curing, and that (3) conventional cements would achieve higher initial bond strengths compared to self-adhesive systems.MethodsLithium disilicate disks were etched and cemented with Variolink Esthetic DC (VA), DuoLink Universal (DU), Panavia SA Universal (PA), and RelyX UniCem2 (RE) using 20 s or 60 s light curing. Bond strengths were measured at 5 min, 2 h, and 24 h. pH was monitored during initial 4 min curing and up to 60 h in Hank's Balanced Salt Solution. Mixed-effects models with Sidak's test analyzed data (P = 0.05). Ten specimens per group were evaluated (n = 10/group).ResultsBond strength increased significantly over time for all materials (P < 0.0001). During early setting (<5 min), DU and RE showed significantly higher bond strengths regardless of curing time, while VA and PA demonstrated lower initial strengths. Extended curing (60 s) improved final bond strengths. Conventional cements (VA, DU) reached maximum strength within 2 h vs. self-adhesive cements. Conventional cements maintained near-neutral pH during initial curing, while self-adhesive cements exhibited lower initial pH (≈3.5) but neutralized to comparable levels (7.0–7.5) after light curing.DiscussionResin cement bond strength developed significantly over time for all materials, with extended curing improving final bond strengths and adequate light curing accelerating pH neutralization in self-adhesive cements. Early bond strength was governed by individual material characteristics rather than cement category, though conventional cements surpassed self-adhesive systems by 2 h. Clinicians should prioritize extended light curing for thick restorations and advise patients to avoid occlusal loading during the early setting period, particularly with VA and PA.