# Interfacial Bond Strength of CAD/CAM Resin Composites on Dentin vs. Composite Substrates: Influence of Dual-Cure and Self-Adhesive Resin Cements

## TL;DR

This study compared how well different dental materials bond to dentin and composite substrates, finding that bonding is stronger on composites due to better compatibility.

## Contribution

The study introduces new insights into the influence of substrate type and cement chemistry on bond strength in dental restorations.

## Key findings

- Bond strength was significantly higher on composite substrates than on dentin due to polymer-polymer compatibility.
- Tescera ATL and Ceramage showed superior adhesion with dual-cure cement, while Lava Ultimate had the lowest values.
- Dual-cure adhesive systems provided stronger bonding than self-adhesive systems across all substrates.

## Abstract

This in vitro study evaluated the shear bond strength (SBS) of four CAD/CAM (Computer aided design/Computer aided manufacturing) polymer-based indirect composites bonded to dentin and microhybrid composite substrates using two resin cements. Gradia Plus (GP), Ceramage (Ce), Tescera ATL (TA), and Lava Ultimate (LA) were fabricated into cylindrical specimens (3 × 3 mm). Dentin substrates were obtained from extracted molars, while composite substrates were prepared from Filtek Z250 (4 mm × 2 mm). Bonding was performed using either a self-adhesive resin cement (RelyX U200; RU200) or a dual-cure adhesive resin cement (RelyX Ultimate; RU), resulting in 16 experimental groups (n = 12 per group). SBS was measured using a universal testing machine (1 mm/min), and failure modes were assessed under stereomicroscopy. Bond strength was significantly higher on composite substrates than on dentin (p < 0.001), primarily due to favorable polymer–polymer compatibility and matrix interdiffusion, which improved stress accommodation at the adhesive interface. TA and Ce showed superior adhesion when combined with RU, while LA exhibited the lowest values, particularly on dentin bonded with RU200. Overall, the dual-cure adhesive system provided stronger bonding than the self-adhesive system (p < 0.05). These findings highlight the influence of substrate type, composite architecture, and cement chemistry on interfacial performance in indirect polymer-based restorations.