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Effects of postwashing with contaminated ethanol solutions on 3D printed materials: Mechanical properties, dimensional trueness, and biocompatibility

Effects of postwashing with contaminated ethanol solutions on 3D printed materials: Mechanical properties, dimensional trueness, and biocompatibility

This in vitro study investigated how postwashing 3D-printed dental resin restorations with contaminated ethanol solutions affects their clinical performance. Two commercial Crown & Bridge resins (NextDent C&B and C&B MFH) were ultrasonically cleaned in ethanol containing 0–30% unpolymerized resin at 60 °C for 30 minutes. Degree of conversion, Vickers hardness, flexural strength, 3D trueness, surface morphology, and biocompatibility were systematically evaluated across contamination levels. Results demonstrated that even low contamination (≥5%) significantly degraded degree of conversion, surface hardness, dimensional accuracy, and cell viability, while flexural strength remained unaffected. Turbidity measurements identified the 5% contamination threshold as a practical compliance indicator for clinical postwashing protocols. These findings underscore the importance of ethanol solution management in dental 3D printing workflows to ensure consistent restoration quality and safety.

This in vitro study investigated how postwashing 3D-printed dental resin restorations with contaminated ethanol solutions affects their clinical performance. Two commercial Crown & Bridge resins (NextDent C&B and C&B MFH) were ultrasonically cleaned in ethanol containing 0–30% unpolymerized resin at 60 °C for 30 minutes. Degree of conversion, Vickers hardness, flexural strength, 3D trueness, surface morphology, and biocompatibility were systematically evaluated across contamination levels. Results demonstrated that even low contamination (≥5%) significantly degraded degree of conversion, surface hardness, dimensional accuracy, and cell viability, while flexural strength remained unaffected. Turbidity measurements identified the 5% contamination threshold as a practical compliance indicator for clinical postwashing protocols. These findings underscore the importance of ethanol solution management in dental 3D printing workflows to ensure consistent restoration quality and safety.

Statement of problem: Whether postwashing treatment with a contaminated ethanol solution adversely affects the biomechanical properties of 3-dimensionally (3D) printed resin restorations is unclear.

Purpose: The aim of this in vitro study was to determine the impact of postwashing treatment using contaminated ethanol solutions on the mechanical properties, degree of conversion (DC) of resin monomers, biocompatibility, 3D trueness of 3D printed products, and ethanol contamination levels.

Material and methods: Specimens were fabricated from 3D models using 2 resins: NextDent C&B resin (C&B) and NextDent C&B MFH resin (MFH). The specimens were ultrasonically cleaned in an ethanol solution containing unpolymerized resin at various concentrations: 0%, 5%, 10%, 15%, 20%, and 30%. Postwashing treatment was conducted at 60 °C for 30 minutes in accordance with the manufacturer's recommendations. The following properties and outcomes were evaluated with their respective sample sizes using appropriate methods: scanning electron microscope (SEM, ×1000, n=3), degree of conversion (DC, n=15), Vickers hardness (VH, n=15), flexural strength (FS, n=15), 3D trueness (n=15), cell viability (n=18), 5-ethynyl-2'-deoxyuridine (EdU) staining (n=3), and the turbidity of the contaminated ethanol solutions (n=15). Statistical analyses were performed using 1-way ANOVA after confirming the normality of the data, with comparisons restricted to contamination groups within the same resin type. Post hoc analysis was conducted using the Tukey HSD or the Games-Howell test, depending on the variance homogeneity (α=.05 or .001).

Results: Surface impurities and particle adsorption were observed via SEM at contamination levels ≥10%. DC decreased significantly from 62.5% to 32.7% (C&B) and from 71.4% to 57.1% (MFH) at contamination ≥5% (P<.001). The Vickers hardness number (VHN) declined significantly at ≥5% for C&B (from 12.97 to 9.01) and at ≥10% for MFH (from 14.76 to 11.52) (P<.001). Flexural strength remained stable across all groups (P>.05). Morphological deviations increased with contamination, with root mean square deviations rising from 51.5 to 105.8 µm (C&B) and from 64.1 to 82.6 µm (MFH) (P<.001); C&B crowns showed expansion, whereas MFH crowns showed shrinkage. Cell viability decreased significantly at ≥10% (C&B) and ≥5% (MFH) contamination (P<.05) but remained above 80% in all groups. EdU-positive cell percentage declined from 23.6% to 16.8% (C&B) and 23.7% to 18.0% (MFH) with increasing contamination (P<.05). Turbidity rose sharply with contamination, exceeding 1000 NTU at 5% (C&B: 1079 NTU; MFH: 1221 NTU), indicating substantial resin-derived particle accumulation.

Conclusions: Postwashing treatment using contaminated ethanol solutions containing unpolymerized resin negatively impacted the surface morphology of resin products, significantly reducing their DC, VH, 3D trueness, and biocompatibility while having no significant effect on FS. Despite the contaminated ethanol solutions exceeding the turbidimeter limit of 1000 NTU, the 5% groups remain near this threshold, yielding more-reliable data and serving as operational indicators for evaluating postwashing compliance.

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Incorporating an Artificially Synthesized Fluoride Complex into Urethane-Acrylate-Based 3D Printing Resin: Effects on Mechanical Properties, Cytotoxicity, Antimicrobial Actions, and its Long-Term Fluoride-Releasing Properties

Journal of Dentistry,

Sep 28, 2024

This study developed a novel urethane acrylate-based 3D printing resin incorporating a custom-synthesized zirconium (IV) fluoride complex designed to confer simultaneous antibacterial activity and sustained fluoride release. The complex was synthesized from 4,4-bis-(4-hydroxyphenyl)-pentanoic acid, characterized by ¹H NMR, and incorporated at 5 and 10 wt% into a DLP-printable resin matrix. Flexural strength, Vickers hardness, surface morphology, antibacterial efficacy against S. mutans, cytotoxicity, and daily fluoride release over 28 days were systematically evaluated. Results demonstrated concentration-dependent fluoride release at clinically relevant low levels, acceptable antibacterial performance, and no detectable cytotoxicity, though mechanical properties were significantly affected by complex addition. These findings establish a compositional foundation for multifunctional 3D-printed dental restorations — including crowns, bridges, and orthodontic appliances — capable of delivering long-term cariostatic and antimicrobial benefits.

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Incorporating an Artificially Synthesized Fluoride Complex into Urethane-Acrylate-Based 3D Printing Resin: Effects on Mechanical Properties, Cytotoxicity, Antimicrobial Actions, and its Long-Term Fluoride-Releasing Properties

Journal of Dentistry,

Sep 28, 2024

This study developed a novel urethane acrylate-based 3D printing resin incorporating a custom-synthesized zirconium (IV) fluoride complex designed to confer simultaneous antibacterial activity and sustained fluoride release. The complex was synthesized from 4,4-bis-(4-hydroxyphenyl)-pentanoic acid, characterized by ¹H NMR, and incorporated at 5 and 10 wt% into a DLP-printable resin matrix. Flexural strength, Vickers hardness, surface morphology, antibacterial efficacy against S. mutans, cytotoxicity, and daily fluoride release over 28 days were systematically evaluated. Results demonstrated concentration-dependent fluoride release at clinically relevant low levels, acceptable antibacterial performance, and no detectable cytotoxicity, though mechanical properties were significantly affected by complex addition. These findings establish a compositional foundation for multifunctional 3D-printed dental restorations — including crowns, bridges, and orthodontic appliances — capable of delivering long-term cariostatic and antimicrobial benefits.

Read article

Incorporating an Artificially Synthesized Fluoride Complex into Urethane-Acrylate-Based 3D Printing Resin: Effects on Mechanical Properties, Cytotoxicity, Antimicrobial Actions, and its Long-Term Fluoride-Releasing Properties

Journal of Dentistry,

Sep 28, 2024

This study developed a novel urethane acrylate-based 3D printing resin incorporating a custom-synthesized zirconium (IV) fluoride complex designed to confer simultaneous antibacterial activity and sustained fluoride release. The complex was synthesized from 4,4-bis-(4-hydroxyphenyl)-pentanoic acid, characterized by ¹H NMR, and incorporated at 5 and 10 wt% into a DLP-printable resin matrix. Flexural strength, Vickers hardness, surface morphology, antibacterial efficacy against S. mutans, cytotoxicity, and daily fluoride release over 28 days were systematically evaluated. Results demonstrated concentration-dependent fluoride release at clinically relevant low levels, acceptable antibacterial performance, and no detectable cytotoxicity, though mechanical properties were significantly affected by complex addition. These findings establish a compositional foundation for multifunctional 3D-printed dental restorations — including crowns, bridges, and orthodontic appliances — capable of delivering long-term cariostatic and antimicrobial benefits.

Read article

Effect of Thermal Aging on a Urethane Acrylate-based 3D Printing Resin Incorporated with Antibacterial Quaternary Ammonium Methacrylate

Journal of the Mechanical Behavior of Biomedical Materials,

May 15, 2025

This study evaluated the effect of incorporating the quaternary ammonium monomer DMAHDM into a urethane acrylate-based 3D printing resin, with particular focus on how thermal aging modifies its performance over simulated clinical service. DMAHDM was added at concentrations of 0.25–1 wt%, and specimens were subjected to up to 5000 thermal cycles to simulate long-term intraoral aging. Degree of conversion, color stability, flexural strength, Vickers hardness, antibacterial effectiveness, and cytotoxicity were systematically assessed. Results revealed concentration- and aging-dependent trade-offs: higher DMAHDM levels and extended aging enhanced hardness and antibacterial activity but progressively compromised flexural strength and biocompatibility, while also inducing notable color shifts. These findings highlight the need to carefully balance DMAHDM concentration against aging-related property changes when designing antimicrobial 3D-printed dental resins for durable clinical use.

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Effect of Thermal Aging on a Urethane Acrylate-based 3D Printing Resin Incorporated with Antibacterial Quaternary Ammonium Methacrylate

Journal of the Mechanical Behavior of Biomedical Materials,

May 15, 2025

This study evaluated the effect of incorporating the quaternary ammonium monomer DMAHDM into a urethane acrylate-based 3D printing resin, with particular focus on how thermal aging modifies its performance over simulated clinical service. DMAHDM was added at concentrations of 0.25–1 wt%, and specimens were subjected to up to 5000 thermal cycles to simulate long-term intraoral aging. Degree of conversion, color stability, flexural strength, Vickers hardness, antibacterial effectiveness, and cytotoxicity were systematically assessed. Results revealed concentration- and aging-dependent trade-offs: higher DMAHDM levels and extended aging enhanced hardness and antibacterial activity but progressively compromised flexural strength and biocompatibility, while also inducing notable color shifts. These findings highlight the need to carefully balance DMAHDM concentration against aging-related property changes when designing antimicrobial 3D-printed dental resins for durable clinical use.

Read article

Effect of Thermal Aging on a Urethane Acrylate-based 3D Printing Resin Incorporated with Antibacterial Quaternary Ammonium Methacrylate

Journal of the Mechanical Behavior of Biomedical Materials,

May 15, 2025

This study evaluated the effect of incorporating the quaternary ammonium monomer DMAHDM into a urethane acrylate-based 3D printing resin, with particular focus on how thermal aging modifies its performance over simulated clinical service. DMAHDM was added at concentrations of 0.25–1 wt%, and specimens were subjected to up to 5000 thermal cycles to simulate long-term intraoral aging. Degree of conversion, color stability, flexural strength, Vickers hardness, antibacterial effectiveness, and cytotoxicity were systematically assessed. Results revealed concentration- and aging-dependent trade-offs: higher DMAHDM levels and extended aging enhanced hardness and antibacterial activity but progressively compromised flexural strength and biocompatibility, while also inducing notable color shifts. These findings highlight the need to carefully balance DMAHDM concentration against aging-related property changes when designing antimicrobial 3D-printed dental resins for durable clinical use.

Read article

Influence of postwashing process on the elution of residual monomers, degree of conversion, and mechanical properties of a 3D printed crown and bridge materials

Dental Materials,

Oct 1, 2022

This study investigated how postwashing method and duration affect the mechanical performance and biocompatibility of DLP-printed crown and bridge resins. Specimens were washed using either an ultrasonic bath or a rotary washer with TPM solvent across five time points (3, 6, 10, 20, and 60 minutes), followed by standardized postcuring. Flexural strength, Vickers hardness, degree of conversion, water sorption and solubility, residual monomer elution, and cytotoxicity were comprehensively evaluated. The ultrasonic bath demonstrated superior monomer removal efficacy, reducing residual HEMA and TEGDMA to near-negligible levels. However, extended washing progressively compromised mechanical properties and degree of conversion, while cytotoxicity decreased with longer washing times. These findings highlight the importance of optimizing both washing method and duration to balance structural integrity and biological safety in clinical 3D printing workflows.

Read article

Influence of postwashing process on the elution of residual monomers, degree of conversion, and mechanical properties of a 3D printed crown and bridge materials

Dental Materials,

Oct 1, 2022

This study investigated how postwashing method and duration affect the mechanical performance and biocompatibility of DLP-printed crown and bridge resins. Specimens were washed using either an ultrasonic bath or a rotary washer with TPM solvent across five time points (3, 6, 10, 20, and 60 minutes), followed by standardized postcuring. Flexural strength, Vickers hardness, degree of conversion, water sorption and solubility, residual monomer elution, and cytotoxicity were comprehensively evaluated. The ultrasonic bath demonstrated superior monomer removal efficacy, reducing residual HEMA and TEGDMA to near-negligible levels. However, extended washing progressively compromised mechanical properties and degree of conversion, while cytotoxicity decreased with longer washing times. These findings highlight the importance of optimizing both washing method and duration to balance structural integrity and biological safety in clinical 3D printing workflows.

Read article

Influence of postwashing process on the elution of residual monomers, degree of conversion, and mechanical properties of a 3D printed crown and bridge materials

Dental Materials,

Oct 1, 2022

This study investigated how postwashing method and duration affect the mechanical performance and biocompatibility of DLP-printed crown and bridge resins. Specimens were washed using either an ultrasonic bath or a rotary washer with TPM solvent across five time points (3, 6, 10, 20, and 60 minutes), followed by standardized postcuring. Flexural strength, Vickers hardness, degree of conversion, water sorption and solubility, residual monomer elution, and cytotoxicity were comprehensively evaluated. The ultrasonic bath demonstrated superior monomer removal efficacy, reducing residual HEMA and TEGDMA to near-negligible levels. However, extended washing progressively compromised mechanical properties and degree of conversion, while cytotoxicity decreased with longer washing times. These findings highlight the importance of optimizing both washing method and duration to balance structural integrity and biological safety in clinical 3D printing workflows.

Read article