# The effect of different surface treatment on shear bond strength of soft and hard liners to CAD-CAM and conventional denture base resins: in vitro comparative study

## TL;DR

This study compares how different surface treatments affect the bond strength of dental liners to various denture base materials.

## Contribution

The study identifies optimal surface treatments for improving bond strength of hard and soft liners to CAD-CAM and conventional resins.

## Key findings

- Sandblasting significantly increases shear bond strength of hard liners to most denture base resins.
- Bur roughening improves soft liner bond strength for certain resins but not others.
- FormLabs resins show limited improvement with sandblasting compared to other materials.

## Abstract

To evaluate the impact of different surface treatments on shear bond strength (SBS) of hard and soft denture liners bonded to CAD-CAM and conventional denture base resins.

A total of 300 acrylic denture base specimens were fabricated with dimensions of 10 × 10 × 3 mm, with five different denture base materials: two milled (AvaDent and IvoCad), two printed (NexDent and FormLabs), and one heat-processed acrylic resin. The specimens underwent 5,000 thermal cycles both before and after the reline procedures, and each specimen was treated using one of three surface treatment methods: sandblasting, bur roughening, or no treatment (control). The reline procedure was performed with either a soft liner or a hard liner (n = 10). Shear bond strength was tested using a universal testing machine with a crosshead speed of 1 mm/min until failure. Data were analyzed by two-way ANOVA (α = 0.05).

Sandblasting significantly increases the SBS of hard liners to AvaDent, IvoCad, NextDent, and conventional resins compared to both the control and bur roughening groups (p ≤ 0.0001). For FormLabs, sandblasting significantly improved SBS compared to the control group only (p ≤ 0.01). In the case of soft liners, bur roughening significantly enhanced SBS for AvaDent, IvoCad, and conventional resins, while no significant improvement was observed for NextDent and FormLabs.

Sandblasting is recommended to enhance the shear bond strength of hard liners across various denture base resins, whereas bur roughening is more effective when using soft liners.