# Effect of Chlorhexidine Solution on the Tensile Bond Strength and Hardness of Two Soft Liners With Denture Base Resin: An In-Vitro Comparative Study

## TL;DR

This study found that using chlorhexidine solution to clean dentures can weaken the bond and make soft liners harder, affecting their performance.

## Contribution

The study empirically evaluates the impact of chlorhexidine on two common denture liner materials' mechanical properties.

## Key findings

- Permasoft showed higher tensile bond strength and hardness than Ufi Gel P.
- Chlorhexidine immersion reduced tensile bond strength and increased hardness in both liners.
- Ufi Gel P was more compatible with chlorhexidine than Permasoft.

## Abstract

Background

Edentulism presents significant functional, nutritional, and psychological challenges, often requiring complete denture rehabilitation. Soft denture liners are used to enhance comfort and fit, and functionality of existing dentures, especially in patients with compromised oral tissues. However, the longevity of their performance is hindered by the deterioration of tensile bond strength and material softness. Chlorhexidine gluconate solution, recommended as a denture cleanser, may alter these properties.

Objective

To evaluate the effect of 0.2% chlorhexidine gluconate solution (HEXIDINE -ICPA Health Products Ltd, Mumbai, India) on the tensile bond strength and Shore A hardness values of two types of denture liners: acrylic-based, Permasoft (Perma Laboratories, Broadview Heights, OH, USA), and silicone-based Ufi Gel P (VOCO GmbH, Cuxhaven, Germany), bonded to heat-cured polymethyl methacrylate (PMMA) denture base resin (AcryPol R, Ruthinium, Dental Manufacturing S.P.A., Badia Polesine, Italy). This study investigated whether the daily use of chlorhexidine solution alters the mechanical properties of these commonly used denture liners.

Materials and methods

Seventy-eight specimens were prepared to assess the effect of 0.2% chlorhexidine gluconate on the tensile bond strength and Shore A hardness of two soft denture liners: acrylic-based, Permasoft, and silicone-based, Ufi Gel P, bonded to heat-cured PMMA resin. For tensile strength testing, fifty-two specimens were fabricated by bonding two PMMA blocks (40 × 10 × 10 mm) with a 3 mm thick liner. For hardness testing, twenty-six cylindrical specimens (6 mm height, 10 mm diameter) were prepared. Specimens were divided into two groups for immersion in distilled water as a control and in 0.2% chlorhexidine gluconate solution. Tensile bond strength was measured using a universal testing machine. Failure modes were classified as adhesive, cohesive, or mixed. Hardness was evaluated using a Shore A digital durometer, with five readings per specimen.

Results

Permasoft exhibited significantly higher tensile bond strength (mean: 0.72 MPa) compared to Ufi Gel P (mean: 0.60 MPa). Shore A hardness values were also greater for Permasoft (mean: 45.5) than Ufi Gel P (mean: 36.1). Specimens immersed in distilled water showed higher tensile bond strength than those treated with 0.2% chlorhexidine gluconate (P = 0.001). Conversely, Shore A hardness increased following chlorhexidine immersion for both liners, with Permasoft reaching the highest value (49.3). Two-way analysis of variance (ANOVA) revealed significant main effects of material type and solution on both tensile bond strength and hardness (P = 0.001).

Conclusions

Both Permasoft and Ufi Gel P demonstrated clinically acceptable tensile bond strength with PMMA denture base resin. However, daily immersion in 0.2% chlorhexidine gluconate solution significantly reduced tensile bond strength and increased Shore A hardness in both materials compared to distilled water. Ufi Gel P showed better compatibility with chlorhexidine solution than Permasoft, under disinfectant exposure. While chemical denture cleansers are effective for oral hygiene, their impact on material properties should be carefully considered in clinical practice.