Direct powder extrusion 3D printing of a polyhydroxybutyrate-based dual-release drug delivery device for dental therapy

: This study investigates the processability of polyhydroxybutyrate (PHB) in different physical forms (i.e., powder, pellets, and granules) using direct powder extrusion (DPE) 3D printing (3DP), a technique that enables the direct use of raw materials without prior filament fabrication. The raw materials were thoroughly characterized with respect to their thermal properties to evaluate their suitability for additive manufacturing application. Two DPE 3D printers employing distinct extrusion-driven mechanisms were used to enable a comparative evaluation under identical material conditions. Following printing, the resulting scaffolds were assessed in terms of their thermal, chemical and morphological characteristics to determine the feasibility and performance of each material form within the DPE 3D-printing process. In the second phase of the work, the potential of DPE to fabricate a functional PHB-based dental device enabling dual drug release (i.e., immediate and extended) was investigated. This was achieved by optimizing the printed geometry to incorporate a hydrophilic gel reservoir for burst release. Benzydamine hydrochloride, a non-steroidal anti-inflammatory drug with anti-inflammatory and antimicrobial properties, was selected as the model drug due to its compatibility with PHB processing temperatures (∼160 °C). The drug-loaded devices were successfully printed and evaluated through in vitro release studies and antimicrobial testing, confirming both controlled release and biological activity. The findings support the use of PHB and DPE 3DP for the development of customizable, biodegradable drug delivery systems, with promising applications in oral and dental care.