Flexural-strength and modulus of hypoallergenic denture base materials

Objectives: Hypoallergenic-denture-base-materials [HDBM] are free from toxic or potential allergic substances. To clinically substitute conventional PMMA-denture-base-resins [PDBR] HDBM should meet the standards in mechanical-physical properties. Fundamental material properties are flexural strength [FS] and flexural modulus [FM]. High FS/FM-values contribute to the preservation of edentulous jaw areas. FS is an indicator of the strength and crack resistance in denture materials. A High FM value specifies rigidity and low ductility and represents denture base material's resistance to elastic deformation. The aim of this in-vitro study was to evaluate mechanical-physical properties of HDBMs and the comparison to established PDBRs. Methods: The 7 tested HDBMs (Acetal, Erkokryl, Luxene, Microbase, Polyan, Sinomer, Versio.com) were free from toxic or potential allergic substances. 3 PDBRs (Paladon65, PalaXpress, SR-Ivocap) represented the standard levels [SL-FS/SL-FM]. Specimens (60x10x4mm) were produced by the respective manufactures. 6 specimens from each product were tested in the three-point-bending-test (ISO178:2006). The automatically recorded force measurement (TestXpert 8.1, Zwick, Germany) was performed until fracturing (v=5mm/min, MPa). FS and FM were calculated and analyzed (T-test, p<0.05). Results: The SL-FS was 85.4MPa. FS of 5 HDBMs were above SL-FS (100.5-136.1MPa). 2 products (Microbase: 65.3MPa, Sinomer: 71,4MPa) were significantly below SL-FS. The SL-FM was 2431MPa. FM of 6 HDBMs was above SL-FSM (2522-3853MPa). FM of 1 product (Sinomer: 2208MPa) was significantly below SL-FM. Conclusions: The flexural strength and –modulus of 5 tested hypoallergenic-denture-base-materials were superior to the standard levels. These products fulfilled the requirements for conventional PMMA denture base resins. Microbase exhibited insufficient flexural strength combined with high flexural modulus which indicates brittle material properties. Sinomer showed deficient values for flexural strength and modulus.