Mechanical Behaviors of a New Polymer-Based Restorative Material for Immediate Loading: An In Vitro Comparative Study

The aim of the present in vitro comparative study is to validate a novel composite polymer, named “ONLY”, developed to overcome the mechanical drawbacks of conventional, metal-reinforced poly(methyl methacrylate) (PMMA) interim restoration. Ten interim restorations were designed and fabricated (five in the composite “ONLY” group, and five in the metal-reinforced PMMA group). All the samples were screwed into the prototype models, simulating a complete edentulous mandible rehabilitated with six straight implants. Outcome measures were break point (load, N) and displacement (mm) through a static compression test, and material behavior through a dynamic cyclic test method (fatigue test). A total of 20 samples were tested (10 for static and 10 for dynamic). In each group, five samples (test and control) were used. All the specimens completed the mechanical tests, as planned. There was no statistically significant difference between groups for any test. In the test group, the break point was 1953.19 ± 543.73 N, while it was 2031.10 ± 716.68 N in the control group (p = 0.775). The displacement was 1.89 ± 0.34 mm in the test group and 1.98 ± 0.75 mm in the control group (p = 0.763). Using the dynamic cyclic test method, in the control group the mean load was 2504.60 ± 972.15 N, while in the test group the mean load was 3382.00 ± 578.50 N. The difference between groups was 877.40 ± 579.30 N (p value = 0.121). Within the limitations of this in vitro study, the novel composite polymer can be used to immediately load dental implants. Further clinical research is needed to confirm these preliminary results.