In vitro Assessment of Open-Access Digital Workflow for Presurgical Nasoalveolar Molding in Unilateral Cleft Lip and Palate

Purpose: To evaluate digitally fabricated nasoalveolar molding (NAM) prostheses using open-source software against conventionally manufactured prostheses using an in vitro assessment of material mechanical properties, and fabrication efficiency. Materials and Methods: Following IRB approval, a retrospective, in vitro comparative study was conducted using previously obtained, deidentified neonatal maxillary gypsum casts from patients with unilateral cleft lip and palate. NAM prostheses were fabricated using either conventional cold-cure acrylic resin or a digital workflow using open-access software (Meshmixer, Autodesk) and stereolithography 3D printing (Formlabs). Surface deviation relative to reference casts, fabrication time, flexural strength, flexural modulus, and microscopic structural analysis of 3D printed resin versus conventional materials were evaluated. Results: Digital NAM prostheses demonstrated significantly (n = 17, p = 0.038) reduced surface cast-based deviation compared to conventional prostheses (mean deviation: 1.53 ± 0.19 mm vs. 1.69 ± 0.25 mm), reflecting nearly 10% improvement in fit relative to the reference cast with the digital method. Materials analysis revealed that 3D-printed resin blocks of standardized testing dimension demonstrated significantly higher flexural strength (n = 7, p < 0.0001) at 67.17 ± 4.8 MPa compared to conventional acrylic blocks at 28.7 ± 3.32 MPa. Flexural modulus was also significantly (n = 7, p < 0.0001) different between groups, with values of 1713 ± 131.6 MPa for 3D printed resin and 797.5 ± 99.0 MPa for conventional acrylic, indicating greater stiffness in the 3D printed resin material. Microscopic analysis revealed a uniform, void-free structure in 3D printed resin blocks in contrast to visible air entrapment in conventional cold-cure acrylic blocks. Conclusion: Within the limitations of this in-vitro study using gypsum casts as a reference standard, this work validates a digital workflow for NAM prosthesis fabrication using freely available open-source software (Meshmixer). By providing a reproducible, cost-free workflow, this study offers a practical guide for clinicians initiating digital NAM design and future sequential treatments, supporting wider accessibility and precision in presurgical NAM therapy, particularly in resource-limited settings.