In Vitro Evaluation of Oral Irrigator–Assisted Mouthrinse Application on Color Stability of Single-Shade Nanohybrid Resin Composites

Summary

This protocol describes an in vitro method to evaluate how different mouthrinse formulations and application methods influence the color stability of single-shade nanohybrid resin composites, demonstrating measurable differences between treatment conditions.

Abstract

Color stability is a key determinant of the long-term esthetic performance of resin-based restorative materials. Single-shade nanohybrid resin composites, developed to simplify shade selection, remain susceptible to extrinsic discoloration and routine oral hygiene procedures. This study aimed to evaluate color stability following coffee staining and subsequent use of different mouthrinse formulations applied with or without an oral irrigator. Disc-shaped specimens were fabricated, stained with coffee, and subjected to mouthrinses using either static immersion or oral irrigator–assisted delivery. Color measurements were obtained at baseline, after staining, and after mouthrinse application, and color changes (ΔE₀₀) were calculated for discoloration after coffee staining (ΔE₁), color change after mouthrinse application (ΔE₂), and total color change (ΔE₃) using the CIEDE2000 formula. Statistical analysis was performed using robust three-way ANOVA with trimmed means. Surface morphology was additionally evaluated using environmental scanning electron microscopy. The results demonstrated that coffee staining resulted in a clinically unacceptable color change in all groups (ΔE₀₀ > 0.8). Composite type significantly influenced color change after coffee staining (ΔE₁) and total color change (ΔE₃) (p < 0.001). Mouthrinse type significantly affected color change after mouthrinse application and total color change (ΔE₂ and ΔE₃) (p = 0.001). Application method significantly affected total color change (ΔE₃) (p < 0.001). Subgroup analysis revealed that within the Charisma Diamond One composite (DO), ΔE₃ values were significantly higher in the oral irrigator group compared to direct immersion (p = 0.001), and within the irrigator group, the DO composite exhibited significantly higher ΔE₃ values than the Vittra APS Unique composite (p = 0.001). These findings demonstrate that composite formulation and mouthrinse application method significantly influence post-staining color stability, with oral irrigator use exacerbating discoloration in certain materials. Clinically, this suggests that restorative material selection and oral hygiene practices should be carefully considered to minimize esthetic degradation.

Introduction

The demand for highly esthetic restorative materials has led to the development of resin composites designed to mimic the optical properties of natural dental tissues. Among these, single-shade nanohybrid resin composites have gained increasing attention due to their chameleon-like blending ability, simplified shade selection, and reduced clinical complexity^1,2,3. Despite these advantages, their long-term esthetic performance remains strongly dependent on resistance to extrinsic discoloration caused by dietary chromogens and routine oral hygiene practices⁴

Protocol

This study was conducted at the Department of Restorative Dentistry, Faculty of Dentistry, Marmara University, Istanbul, Turkey. No human or animal subjects were involved; therefore, institutional ethical approval was not required. The reagents and equipment used in this study are listed in the Table of Materials. Figure 1 illustrates the experimental workflow used in this study. Specimen preparation was first performed to fabricate disc-shaped composite samples (8 mm × 2 mm). Baseline color measurements were then obtained prior to staining. All specimens were subsequently immersed in a coffee solution for 12 days to induce discoloration,....

Results

Specimen Preparation

Color change (ΔE) was evaluated across composite type, group, and different periods (ΔE₁, ΔE₂, and ΔE₃), corresponding to the sequential steps of the experimental protocol (Tables 4 and 5, Figure 2).

Effect	Q	p-value
Composit.......

Discussion

Esthetic outcomes are central to the clinical success of resin composite restorations, as long-term color stability determines their ability to harmonize with surrounding dental tissues. Nanohybrid composites incorporating nanometric and submicron fillers have been developed to improve optical integration, polishability, and resistance to discoloration^22,23. More recently, single-shade resin composites have been introduced as a simplified alternative to conventio.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Aluminum oxide abrasive discs	3M ESPE, USA	Sof-Lex XT	Sequential finishing from coarse to superfine grit
Coffee powder (instant)	Nestlé, Switzerland	Nescafé Classic	Used for preparation of staining solution
Diamond polishing system	3M ESPE, USA	Sof-Lex Diamond Polishing System	Final polishing procedure
Distilled water	Botafarma, Turkey	Distilled Water	Storage and rinsing medium (control solution)
Environmental scanning electron microscope	Carl Zeiss, Germany	EVO MA10	Operated at 10 kV
Glass slide (cement glass)	AmScope, USA	BS-50P-100S-22	Used to flatten specimen surfaces
Light-curing unit	Ultradent, USA	VALO Cordless	Output verified (~1000 mW/cm²)
Microsoft excel spreadsheet	Microsoft Corp., Redmond, WA, USA	Excel	Used for CIEDE2000 calculations
Mouthrinse (Crest 3D White)	Procter & Gamble, USA	Crest 3D White	Hydrogen peroxide–based
Mouthrinse (Listerine Fresh Burst)	Johnson & Johnson, USA	Listerine Fresh Burst	Alcohol-containing
Mouthrinse (Colgate Plax Whitening + Charcoal)	Colgate-Palmolive, USA	Colgate Plax Whitening + Charcoal	Charcoal-containing
Mouthrinse (Sensodyne Pronamel)	Haleon, UK	Sensodyne Pronamel	Fluoride-containing
Oral irrigator	Procter & Gamble, USA	Oral-B Oxyjet MD20	Medium pressure setting (~55–65 psi)
Polyester strip	Extra Dental	Universal Strips	Used to reduce oxygen inhibition
Resin composite (Charisma Diamond One)	Kulzer, Germany	Charisma Diamond One	TCD-DI-HEA-based
Resin composite (Vittra APS Unique)	FGM, Brazil	Vittra APS Unique	APS technology
Silicone mold (prefabricated)	Hagiki, Turkey	Transparent	Disc-shaped (8 mm × 2 mm)
Spectrophotometer	VITA Zahnfabrik, Germany	Easyshade V	Used for color measurement
Stereomicroscope	Leica, Germany	Trinocular stereomicroscope	Used for defect inspection at 20× magnification
Statistical software	R Core Team	R version 4.2.2	Used for data analysis
Statistical software package	R Foundation for Statistical Computing, Austria	WRS2	Robust ANOVA (trimmed means)
Statistical power analysis software	Heinrich Heine University Düsseldorf, Germany	G*Power	Used for sample size calculation