Method: Four groups of specimens were prepared for the study. The first group contained specimens prepared from Palacosâ R PMMA mixed with 50 wt% of BAG S53P4 (BonAlive®) particulate. The second group Palapress® vario PMMA mixed with 50 wt% of BAG S53P4 (BonAlive®) particulate Ø~315 – 1000 µm fraction. Two control groups contained specimens of unmodified PMMA, Palacosâ R and Palapress® vario respectively. Rectangular molds (3.3×10×65mm3) were used to prepare the specimens. The specimens were left to autopolymerize in the molds for 30min under 500N compression strength. The specimens in all four groups were subdivided into two categories. Specimens in the first category were stored in ambient conditions, specimens in the second category were stored in wet conditions (Milli-Q water (15ml) at +37◦C 1 week). A destructive three-point bending test was performed to assess the flexural properties of the specimens. A universal testing machine (model LRX, Lloyd Instruments) was used the span of supports was 50mm. The load was applied at the speed of 5 mm/min.
Result: : The storage in wet condition affected the flexural properties of the BAG-modified PMMA specimens irrespective of the PMMA type. The flexural strength was decreased by ca. 50% and the flexural modulus by >70 %, whereas for the control PMMA specimens the decrement were 30-50% and 20-50%, respectively. The addition of BAG granules to PMMA was responsible for the decrease in the flexural strength. Development of a macroporous outermost surface was observed for the BAG-modified PMMA specimens stored in wet conditions. The obtained information is beneficial, when BAG-implants are designed for applications in dental or craniofacial implantology.
Conclusion: The flexural properties of BAG-modified PMMA specimens decreased considerably upon storage in wet conditions.