Conventional denture bases are primarily fabricated using heat-polymerized poly (methyl methacrylate) (PMMA) resins through a multi-step process involving manual mixing, compression molding, and thermal curing [1], [2]. However, this traditional workflow is time-consuming, technique-sensitive, and prone to dimensional inaccuracies [3], Moreover, incomplete polymerization may result in residual monomers, which could compromise mechanical properties and potentially cause mucosal irritation or allergic responses [4], [5]. Additive manufacturing (AM), or 3D printing, has recently gained prominence in dentistry due to its benefits in minimizing material waste, reducing tool wear, and limiting operator-dependent errors [6], [7]. When applied to denture bases, AM offers additional advantages, including reduced fabrication time, improved dimensional accuracy, and consistent reproducibility, while enabling individualized adaptation to the oral mucosa [8], [9]. Among the photopolymerization-based AM techniques, digital light processing (DLP) stands out for its ability to simultaneously cure entire layers via projected light, offering high resolution and printing efficiency. It is particularly well-suited for fabricating customized denture bases [10], [11].

After printing, the fabricated objects remain partially cured and must undergo post-processing to achieve their final mechanical and physicochemical properties [12]. The post-processing workflow typically includes cleaning, support removal, and post-curing steps [13]. Among these, post-curing is a critical phase involving additional light exposure to promote further polymerization of residual photoinitiators and unreacted monomers, thereby enhancing the printed object's final thermal stability and mechanical strength [14]. The effectiveness of the post-curing process is influenced by multiple parameters, including light wavelength [15], light intensity [16], [17], [18], curing duration [19], [20], [21], [22], temperature [22], [23], [24], [25], [26], [27], and the oxygen content in the curing environment [21], [26], [27].

Precise light intensity control is essential for driving polymer crosslinking reactions and significantly enhancing the material's mechanical properties [28]. For vat-photopolymerized denture-base polymers, reported post-curing irradiances range from only a few mW cm-² in enclosed UV chambers [17] to around 100–800 mW cm-² in typical devices [29], and can reach approximately 3200 mW cm-² with high-intensity light units [30]. Significantly, photopolymer resins can only be activated under specific wavelengths of light, and the selection of an appropriate curing wavelength has been shown to substantially impact the final performance of the resin material [31]. For example, camphorquinone (CQ) represents a typical type II photoinitiator with a maximum absorption at approximately 468 nm (effective range 420–500 nm), while type I photoinitiators such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO, ≈380–420 nm) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO, ≈365–420 nm) undergo direct cleavage upon light activation [32]. Kang et al. demonstrated that high light intensity combined with shorter curing times improved flexural strength and Vickers hardness [17]. Li et al. further explored the effects of different post-curing devices on the mechanical behavior of 3D-printed denture base polymers, observing significant differences in flexural strength among devices, potentially attributed to variations in the emission wavelengths of the light sources [33].

Although previous studies have independently evaluated the effects of either light intensity or wavelength on photocurable resins [15], [18], [33], [34], comprehensive investigations into their combined effect remain scarce. These studies mainly compared commercial post-curing units with differing specifications for light intensity and wavelength. However, these devices often vary in irradiation angle, light distribution uniformity, and exposure duration, making it difficult to isolate and quantify the independent contributions of wavelength and intensity. Therefore, a systematic and well-controlled evaluation of their interaction remains lacking.

In this study, a custom-built post-curing device was developed, featuring automatic regulation of both wavelength and light intensity. This platform allowed precise control of irradiation conditions for systematic evaluation of their combined effects on 3D-printed denture base polymers. The selected parameters, comprising three representative wavelengths (365, 385, and 405 nm) and three light intensity levels (200, 800, and 2000 W/m²), were determined based on the characteristics of the photoinitiator contained in the resin and the outcomes of preliminary experiments. The effects on mechanical properties, surface morphology, degree of conversion (DC), and cytotoxicity were assessed. The following null hypothesis was proposed: post-curing with different combinations of light wavelength and intensity exerts no significant influence on the mechanical properties, surface morphology, DC, and cytotoxicity of 3D-printed denture base polymers.