Comparative Analysis of Wear Resistance in 4D-Printed vs. 3D-Printed Dental Prosthetics

ABSTRACT

Background:

Advancements in additive manufacturing, particularly 3D printing, have revolutionized the field of dental prosthetics. Recently, 4D printing, which incorporates time-responsive materials, has emerged as a potential game-changer. This study aims to compare the wear resistance of 3D-printed and 4D-printed dental prosthetics to evaluate the clinical applicability of these innovative technologies.

Materials and Methods:

Dental prosthetics were fabricated using both 3D printing (polyetheretherketone, PEEK) and 4D printing (shape-memory polymer composites). A total of 40 prosthetics (20 per group) were subjected to wear simulation using a chewing simulator with a load of 50 N at 1 Hz for 100,000 cycles. Surface roughness (Ra) and volumetric loss (mm≥) were measured pre- and post-simulation using 3D laser scanning and confocal microscopy. Statistical analysis was performed using an independent t-test to compare the mean wear resistance between the two groups.

Results:

The 4D-printed prosthetics exhibited significantly lower volumetric loss (mean: 0.34 ± 0.08 mm≥) compared to the 3D-printed prosthetics (mean: 0.76 ± 0.12 mm≥, P < 0.01). Surface roughness analysis revealed a smaller increase in Ra for 4D-printed prosthetics (from 0.22 ± 0.03 μm to 0.28 ± 0.05 μm) compared to 3D-printed prosthetics (from 0.24 ± 0.04 μm to 0.41 ± 0.06 μm, P < 0.01).

Conclusion:

The study demonstrates that 4D-printed dental prosthetics possess superior wear resistance compared to 3D-printed prosthetics, highlighting their potential for enhanced longevity and clinical performance in restorative dentistry. Future studies should focus on long-term in vivo evaluations and material optimization to further validate these findings.

INTRODUCTION

The advent of additive manufacturing technologies, such as three-dimensional (3D) printing, has revolutionized the field of restorative dentistry by enabling the precise and efficient fabrication of dental prosthetics. These technologies allow for the customization of complex geometries, reducing material wastage and production time while improving patient-specific outcomes.[1,2] Among the materials commonly used in 3D printing for dental applications are polymers like polyetheretherketone (PEEK) and resins, which provide adequate mechanical properties and biocompatibility.[3]

Recently, a more advanced innovation—four-dimensional (4D) printing—has emerged, incorporating smart materials that can change their properties over time or in response to external stimuli.[4] This dynamic capability has potential applications in dentistry, particularly in enhancing the functional adaptability of dental prosthetics, such as improved fit and wear resistance.[5] Shape-memory polymers (SMPs), a key component of 4D printing, have shown promise in various medical applications due to their ability to respond to environmental triggers such as temperature, moisture, and stress.[6]

Wear resistance is a critical factor in determining the longevity of dental prosthetics, as these devices endure continuous mastication forces and abrasive interactions in the oral cavity. While the wear properties of 3D-printed dental prosthetics are well-documented,[7] the comparative performance of 4D-printed prosthetics remains relatively unexplored. Given the growing interest in integrating 4D printing into dental practice, it is essential to assess its clinical applicability, particularly in terms of wear resistance.

MATERIALS AND METHODS

Study design and sample preparation

This in vitro experimental study included the fabrication of 40 dental prosthetic specimens, divided into two groups of 20 each: Group 1 (3D-printed prosthetics) and Group 2 (4D-printed prosthetics).

• 3D-Printed Prosthetics: Manufactured using polyetheretherketone (PEEK) through fused deposition modeling (FDM) technology.

• 4D-Printed Prosthetics: Fabricated with shape-memory polymer composites using digital light processing (DLP) technology, incorporating thermoresponsive polymers.

All specimens were standardized to dimensions of 10 mm × 10 mm × 3 mm and polished to a uniform surface finish using a standardized protocol.

Wear simulation

Wear resistance was evaluated using a chewing simulator (CS-4.8; SD Mechatronik GmbH, Germany) under the following conditions:

• Load: 50 N

• Frequency: 1 Hz

• Duration: 100,000 cycles (equivalent to approximately 6 months of clinical use).

The simulator was programmed to mimic physiological mastication movements, including vertical and horizontal motions, in an environment replicating oral conditions (37°C artificial saliva).

Measurements and analysis

1. Volumetric Loss: Measured pre- and post-simulation using a 3D laser scanner (EinScan Pro HD, Shining 3D) to determine material loss in cubic millimeters (mm≥).

2. Surface Roughness (Ra): Measured before and after wear simulation using confocal microscopy (LEXT OLS5000, Olympus), with results expressed in micrometers (μm).

Statistical analysis

Data were analyzed using SPSS software (version 26.0, IBM Corp). The mean volumetric loss and surface roughness were compared between groups using an independent t-test. Statistical significance was set at P < 0.05.

This methodology ensured a standardized and reproducible approach to evaluating the wear resistance of 3D- and 4D-printed dental prosthetics under simulated oral conditions.

RESULTS

The results of the wear simulation demonstrated significant differences between the 3D-printed and 4D-printed prosthetics in terms of volumetric loss and surface roughness. Detailed findings are summarized in the tables below.

The volumetric loss was significantly lower in the 4D-printed prosthetics group compared to the 3D-printed group (P < 0.01), indicating superior wear resistance of 4D-printed materials [Table 1].

Table 1.

Volumetric loss comparison between groups

Group	Mean Volumetric Loss (mm3)	Standard Deviation (mm3)	P
3D-Printed Prosthetics	0.76	0.12	<0.01
4D-Printed Prosthetics	0.34	0.08

The increase in surface roughness was significantly greater for the 3D-printed prosthetics compared to the 4D-printed prosthetics, with a P value < 0.01. This further highlights the enhanced performance of 4D-printed materials under simulated mastication conditions [Table 2].

Table 2.

Surface roughness (Ra) comparison between groups

Group	Pre-Simulation Ra (µm)	Post-Simulation Ra (µm)	Difference (µm)	P
3D-Printed Prosthetics	0.24±0.04	0.41±0.06	0.17±0.02	<0.01
4D-Printed Prosthetics	0.22±0.03	0.28±0.05	0.06±0.01

Summary of results

• Volumetric Loss: The 4D-printed prosthetics exhibited a 55% reduction in volumetric loss compared to the 3D-printed group.

• Surface Roughness: Post-simulation surface roughness increased by 70.8% for the 3D-printed group, compared to only 27.3% for the 4D-printed group.

These results demonstrate the superior wear resistance and surface stability of 4D-printed prosthetics, suggesting their potential for improved longevity in clinical applications.

DISCUSSION

The results of this study indicate that 4D-printed dental prosthetics exhibit superior wear resistance compared to 3D-printed prosthetics, as evidenced by significantly lower volumetric loss and a smaller increase in surface roughness after simulated mastication. These findings highlight the potential clinical advantages of integrating 4D printing technologies in restorative dentistry.

The enhanced wear resistance of 4D-printed prosthetics can be attributed to the unique properties of shape-memory polymers (SMPs) used in their fabrication. SMPs possess the ability to recover their original shape under specific stimuli, such as temperature or stress, which likely contributes to their durability under repetitive mastication forces.[1,2] Additionally, the cross-linked molecular structure of SMPs provides superior mechanical properties compared to traditional 3D-printed materials, such as PEEK.[3]

Previous studies have established the wear properties of 3D-printed dental materials, including PEEK, which are known for their biocompatibility and moderate mechanical strength.[4] However, their wear performance has been shown to degrade over time, particularly under high masticatory loads, as evidenced by increased surface roughness and material loss.[5] The current findings align with these observations, as 3D-printed prosthetics exhibited greater volumetric loss and roughness changes compared to their 4D-printed counterparts.

The superior performance of 4D-printed prosthetics also underscores the potential for these materials to enhance patient outcomes by reducing the frequency of repairs or replacements. Reduced surface roughness post-wear simulation is particularly important, as smoother surfaces minimize plaque accumulation and reduce the risk of secondary caries and periodontal disease.[6,7] The ability of 4D-printed prosthetics to maintain their structural and surface integrity over time could significantly improve the long-term success of restorative treatments.

Despite these promising findings, there are limitations to consider. The study was conducted in vitro, and the wear conditions may not fully replicate the complex oral environment. Factors such as variable chewing patterns, temperature fluctuations, and enzymatic activity were not accounted for. Future studies should include in vivo assessments to validate these results and explore the long-term clinical implications of 4D printing in dentistry.

CONCLUSION

In conclusion, this study demonstrates that 4D-printed dental prosthetics exhibit superior wear resistance and surface stability compared to 3D-printed prosthetics, making them a promising option for restorative applications. Continued research into material optimization and clinical trials is warranted to further explore the potential of 4D printing in advancing dental care.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.