Additive manufacturing has revolutionized the fabrication of complete dentures. However, this process involves support structure, which is a construction part that holds the specimen during printing, and may prove to be disadvantageous. Therefore, this in vitro study compared the effect of support structure reduction on various volume and area distributions of a 3D-printed denture base to determine optimal parameters based on accuracy. Methods: A complete maxillary denture base construction file was used as reference. Twenty denture bases were 3D printed under four conditions (total n=80): no support structure reduction (control), palatal support structure reduction (Condition P), border support structure reduction (Condition B), and palatal and border support structure reduction (Condition PB). Printing time and resin consumption were also recorded. The intaglio surface trueness and precision of all acquired data were exported to a 3D analysis software, and the dimensional changes to the denture base were analyzed using the root-mean-square estimate (RMSE) to assess geometric accuracy and generate color map patterns. Nonparametric Kruskal-Wallis and Steel-Dwass tests (α=0.05) analyzed the accumulated data. Results: Control had the lowest RMSE values for trueness and precision. Nevertheless, it demonstrated a significantly lower RMSE than that of Condition B (P=0.02) in precision. Owing to negative deviation at the palatal region, Conditions P and PB had higher retention than Control and Condition B regarding the color map pattern. Conclusions: Within the limitations of this study, the reduction of palatal and border support structures showed optimal accuracy with resource and cost savings.

Implant overdentures have become a reliable treatment option for edentulous patients because of their enhanced retention, stability, masticatory performance, and higher patient satisfaction compared to conventional complete dentures [1,2]. Mini-implants have a reduced diameter of <3.0 mm and are manufactured using biocompatible materials used for manufacturing standard-sized implants [3]. Mini-implant overdentures are beneficial alternatives for elderly patients with severely resorbed mandibles or physical conditions that hinder advanced surgeries such as bone reshaping or grafting when using standard-sized implants [4]. They are also associated with a reduced cost, as the relatively high cost of standard-sized implant overdentures could limit patients' willingness to accept treatment [5]. In addition, they require minimal intervention and lower operative time compared to standard-sized implants[6] and demonstrate adequate survival rates [7]. Despite these advantages, mini-implants reportedly have lower mechanical strength and increased risks of implant fractures and peri-implant bone damage [4,8]. Clinical studies have highlighted the threat of fatigue fractures in implants with diameters <3.5 mm. In addition, mini-implants showed considerably low strength in in vitro monotonic loading tests, indicating a risk of fracture [9,10]. Therefore, while determining the applications of implants with a diameter ≤3 mm, practitioners should exercise extreme caution, particularly in selecting implant designs that have been proven to affect the mechanical response of implants. The optimal mini-implant J Prosthodont Res. 2022; **(**):