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Design of Experiments (DOE) approach for multi-response optimization of experimental self-adhesive flowable resin
Miguel Alves1, Clara Alves1, Diana C Silva2
1Egas Moniz Center for Interdisciplinary Research (CiiEM), Egas Moniz School of Health & Science, 2829-511 Caparica, Almada, Portugal.
Objectives:
To determine how functional monomer type, acidic monomer concentration and powder/liquid ratio affect the multi-response performance of experimental self-adhesive flowable resin composite (SAFRC) formulations, and to identify a favorable formulation window using design of experiments (DOE) modelling.
Methods:
Sixteen SAFRC formulations were prepared from a two-level formulation matrix varying monomer type (HEMA or 10-MDP), acidic monomer concentration (5 or 25 mol%), powder/liquid ratio (2.5 or 3.2) and filler condition. Degree of conversion at 20 and 40 s (DC20 and DC40; n = 3 per formulation/curing time), shear bond strength (SBS; n = 5 per formulation), water sorption/solubility and rheology were measured. Because rheological geometry was linked to formulation consistency, lower-viscosity cone-plate (CP) and higher-viscosity parallel-plate (PP) subsets were analyzed separately. Factorial models were fitted for each response, followed by desirability-based multi-response optimization.
Results:
No formulation simultaneously optimized all responses. HEMA-containing formulations generally showed higher DC20/DC40, whereas 10-MDP-containing formulations favored SBS and lower calculated solubility. In the CP subset, SBS was mainly governed by monomer chemistry and acidic monomer concentration, while DC40 was dominated by monomer type. Sorption was mainly influenced by powder/liquid ratio, and solubility showed the strongest factorial dependence. In the PP subset, DC40 and rheology remained interpretable, whereas SBS, sorption and solubility were not reliably described by the factorial models. CP optimization predicted the best compromise at 10-MDP, 25 mol% and P/L 2.72, with composite desirability of 0.509.
Significance:
DOE-based multi-response modelling revealed how SAFRC formulation variables redistribute performance across bonding, polymerization, handling and hydrolytic responses. This approach identified a rational formulation window for experimental SAFRC development and provides a framework for optimizing self-adhesive restorative materials beyond single-property screening.
