Mechanical properties of provisional crown and bridge materials: chemical-curing versus dual-curing systems.

Objectives: This study aimed to investigate the flexural strength (FS) and flexural modulus (FM) of provisional crown and bridge materials at different storage times after mixing using materials with different curing mechanisms (dual-curing vs. self-curing).

Methods: FS and FM of four proprietary materials (Trim, Luxatemp AM Plus, Luxatemp AM Plus Solar and Cool Temp Natural) were tested in a 3-point bending test according to EN ISO 4049:2000 at various times after mixing (37 degrees C dry/water) including thermocycling (5000x, 5-55 degrees C). Mean values of all measurements were calculated and subjected to the Games-Howell test (p=0.05) as well as a regression analysis (p=0.05). A two-way ANOVA (p=0.05) was used to identify the influence of the curing mechanism and chemical nature of the materials used.

Results: FS ranged between 11.1 and 24.0 MPa and FM between 82.5 and 548.2 MPa for all tested materials except for the dual-curing material (FS: 82.4 MPa; FM: 2060 MPa) 10 min after mixing. The r2-values, describing the goodness-of-fit of the regression curve for the relation between the mechanical properties and storage time, ranged from 0.701 to 0.979 for the composite based materials and 0.671 to 0.685 for the methacrylate resin. The chemical nature and curing mechanism significantly influenced (p<0.001) the mechanical properties, however, the influence of the curing mechanism disappeared at progressive points in time after mixing comparing Luxatemp AM Plus versus Luxatemp AM Plus Solar.

Conclusions: FS and FM significantly depend on the time after mixing. Composite resin based materials are preferred versus methacrylate resins due to more favourable mechanical properties. If a high mechanical strength is indispensable directly after fabrication, a dual-curing provisional material is recommended.