The Effect of Different Framework Fabrication Techniques on Marginal Adaptation in All-on-4 Implant-Supported Fixed Prostheses

Background The durability of implant-supported prosthetic structures is closely related to the attainment of precise marginal sealing at the connection among the prosthesis, implant fixture, and abutment. Traditionally, implant-supported metal frameworks have been produced using conventional wax patterning and casting approaches; nevertheless, these procedures can result in variable manufacturing outcomes and are susceptible to a range of process-dependent inaccuracies. To overcome these limitations, digital manufacturing approaches such as Selective Laser Melting (SLM) and three-dimensional (3D) printing technologies have been introduced for framework fabrication. Materials and methods Frameworks for 12-unit maxillary fixed prostheses planned according to the All-on-4 concept were designed using digital data obtained from a clinical case. Four different fabrication techniques were evaluated: conventionally cast Co-Cr frameworks, Co-Cr frameworks produced by Selective Laser Melting (SLM), 3D-printed resin frameworks, and Co-Cr frameworks obtained by casting the 3D-printed resin patterns (n = 6 per group). Marginal fit was assessed under a stereomicroscope using the Sheffield single-screw test. The obtained data were statistically analyzed. Results Marginal gap measurements differed across the evaluated groups. The 3D-printed resin frameworks exhibited the greatest marginal gap values; however, a marked improvement in marginal fit was observed following their conversion into Co–Cr frameworks through the casting process. Variability in marginal fit was observed among Co-Cr frameworks fabricated using the SLM technique, Co-Cr frameworks obtained by casting resin patterns, and Co-Cr frameworks produced by conventional casting methods, depending on the measurement regions. In certain regions, SLM-fabricated Co-Cr frameworks exhibited lower marginal gap values, whereas in other regions, Co-Cr frameworks obtained through resin pattern casting or those produced by conventional casting demonstrated lower marginal discrepancies. Conclusions Considering the methodological boundaries of the present investigation, the framework fabrication technique was found to affect the marginal fit of All-on-4 implant-supported fixed prostheses. However, clear superiority could not be established among the fabrication techniques, and marginal adaptation varied according to both fabrication technique and measurement region.