Compressive Strength of Recycled Dental Plaster Formulated via a Novel Automated Recycling System
Plaster of Paris; Waste Management; Compressive Strength; Automated Calcination; One-Sample tTest; Circular Economy.
AuthorsAbstractObjective: To comparatively evaluate the compressive strength, yield characteristics, and elastic profiles of recycled plaster of Paris synthesized using a novel in-office automated recycling machine versus commercially available virgin dental plaster (Type II). Materials and Methods: Used dental gypsum waste products were reprocessed at source utilizing an innovative automated recycling system (Indian Patent Application No: 202441001326, filed by KMCT Dental College). The machine integrates a vertical hopper feed, a high-torque 10mm grinding blade, a 0.10mm internal sizing mesh screen to filter fine particulate powders (0.06–0.08mm), and an electronically regulated vertical heating unit configured to dehydrate the powder between 120°C and 180°C for a duration of 2 hours. Standard mechanical testing specimens (40mm length × 20mm width × 8mm thickness) were fabricated for both the Original Plaster Control Group (n=1) and the Recycled Plaster Experimental Group (n=5). All specimens were mounted onto a calibrated electronic universal testing machine operating under stroke control mode at a crosshead displacement speed of 0.500 mm/min until catastrophic compressive fracture occurred. Peak failure load (kN), peak ultimate compressive stress (MPa), offset yield strength, and elastic modulus (GPa) were continuously recorded. Inferential statistical evaluation was conducted using a one-sample t-test (α = 0.05) to compare the experimental group means against the fixed control baseline coordinates. Results: The automated processing system successfully synthesized homogeneous hemihydrate powder. Mechanical characterization of the recycled experimental group demonstrated a mean ultimate peak compressive strength of 5.53 ± 1.17 MPa (ranging from 3.61 to 6.36 MPa) and a mean elastic modulus of 0.59 ± 0.13 GPa. The commercial control group specimen exhibited a peak ultimate compressive strength of 4.42 MPa and a corresponding elastic modulus of 0.75 GPa. Statistical analysis revealed no significant differences in ultimate compressive strength (p = 0.102) or elastic modulus (p = 0.051) between the cohorts, thereby failing to reject the true null hypothesis. The experimental recycled group achieved mechanical indices fully compliant with international dental laboratory specifications (ISO 6873 criteria for Type II plaster). Conclusion: The proprietary desk-side automated recycling unit is a viable, eco-friendly, and structurally sound system to reprocess clinical gypsum products, providing a defensible framework for healthcare infrastructure optimization and dental laboratory solid waste management without compromising material quality.
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