Technological advances and improvements have enabled the integration of additive manufacturing into digital dentistry. Additive manufacturing, also called three-dimensional (3D) printing, is an emerging technology widely used in the dental area, contributing to significant progress in clinical practice, especially in the production of prostheses, indirect temporary restorations, and orthodontics [[1], [2], [3], [4]]. The light-curing resins used for 3D printing, which are compatible with Digital Light Processing (DLP) or Liquid Crystal Display (LCD) technology printers, are generally composed of monomers and oligomers that polymerize when exposed to light, allowing the creation of complex geometries through the consecutive deposition of layers [[4], [5], [6], [7]].

The advances in 3D printers and printing techniques have enabled the development of 3D printing resins for indirect restorations for long-term use. Nano-hybrid and micro-hybrid filler particles were added to these resins to increase the mechanical strength, stability, biocompatibility and aesthetics required in long-term dental applications [[8], [9], [10]]. Nevertheless, the properties of printed materials can be significantly affected by various factors, including intrinsic factors related to the material composition and extrinsic factors associated with the parameters used in printing and post-curing methods [[11], [12], [13], [14]].

Previous studies have emphasized the impact of post-processing on the dimensional accuracy and mechanical and optical properties of devices produced by additive manufacturing [[15], [16], [17], [18], [19]]. Post-processing involves residual monomers removal in alcohol, preferably isopropyl, followed by complementary polymerization in a post-curing unit (PCU). Post-curing refers to the process of additional polymerization of 3D printed materials in chambers that emit light at the appropriate wavelength for each resin [15,20]. A previous study showed a significant impact of post-curing on mechanical properties and degree of conversion of 3D printed resins [21]. It was found improved mechanical properties and degree of conversion with increased post-curing times (PCU) but poor polymerization in the inner portions of a 3D-printed resin [17]. This is because the post-curing chamber emits violet light, which has a low penetration depth into the resin [22].

To overcome this problem, post-curing methods complementary to violet light were evaluated to optimize the properties of 3D printed resins [23]. Ovens and autoclaves were proposed as heat sources for the additional polymerization of indirect restorations, as these devices are readily available in dental clinics [24,25]. They showed a significant increase in the degree of conversion and improved the properties of these materials. Nevertheless, high temperatures can volatilize residual monomers and distort the 3D printed resin. In addition, little is known about the effect of heat on the depth of cure of 3D printed resin, as well as its effect on the physicochemical properties of 3D printed resins [[26], [27], [28]]. These limitations have not been thoroughly investigated in previous studies, highlighting the need for further research to investigate the influence of combined post-curing methods, incorporating both light and heat, on critical factors such as filler content, depth of cure, and the overall physicochemical properties of 3D printed resins.

The aim of this study was to evaluate the effect of different post-curing methods on the degree of conversion, optical, and mechanical properties of a 3D printed resin for indirect restorations. The tested hypotheses were as follows: 1) The association of post-curing methods using light and heat sources provides significantly higher 3D printing accuracy compared to using each method alone; 2) The association of post-curing methods using light and heat sources provides significantly greater polymerization depth compared to the use of each method alone; 3) The association of post-curing methods using light and heat sources results in a significantly lower percentage reduction in hardness compared to the use of each method alone, according to the softening test; 4) The association of post-curing methods using light and heat sources results in significantly enhanced mechanical properties, surface roughness and gloss, and optical properties compared to the use of each method alone.