Effect of condensation methods on mechanical and physical properties of restorative composites
Hassan, Nisreen Nabiel
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OBJECTIVE: To evaluate the effect of different condensation techniques on their flexural strength (FS) and compressive strength (CS) of different composite-resin restoration, to evaluate the effect of different condensation techniques and different curing durations on the level of cure of different composite resins at different depths. METHODS: Three manipulation instruments were tested: SonicFill (Kavo), ET 3000 (Brasseler) and Hand Condenser. Two different composite-resins were tested: Filtek Supreme Ultra (3M ESPE), SonicFill (Kerr). For compressive strength (CS), Cylinder-shaped specimens (N=10/group) measuring 4×6 mm were prepared. For flexural strength (FS), rectangular bars measuring 2×2×25 mm (N=10/group) were prepared. For level of cure, Cylinder-shaped specimens (N=27/ each composite) measuring 4×6 mm formed in Teflon molds and cured for three light curing durations (10, 20, 40 seconds) photocured with Bluephase 16i (ivoclar vivadent) that generate light intensity of 1350 mW/cm2 were prepared. All specimens were stored in water at 37 C° for 24 hours prior to testing. Specimens were tested for the flexural and compressive strength in an Instron machine. Vickers microhardness Test (Micromet 2003, Buehler) for the level of cure. Measurements were taken at 6 different depth levels from the top: 0.1, 2, 3, 4, 5 and 6 mm. Four indentations were recorded at each level. A total of 24 measurements for the level of cure were taken for each specimen. Data were analyzed using ANOVA and multiple comparison tests. RESULTS: Two-way ANOVA indicated a significant difference in the compressive strength between the two types of composites and the three different condensation techniques (P<0.0001). The (3M) composite recorded significantly higher compressive strength by approximately 39% vs. SonicFill composite (P<0.0001). By using the SonicFill Handpiece it increases the compressive strength of the (SonicFill) composite by 20%. Also, there is significant difference in the flexural strength between the two types of composites as the SonicFill composite recorded higher flexural strength by 34% vs. (3M) composite (P<0.0001). But there is no significant difference in the flexural strength between the three condensation techniques at (P>0.05). Moreover, this study investigated the effect of different condensation techniques and curing duration on the increase in the microhardness of composites and significance was recorded at different depth levels of the composite specimens (p value<0.05). CONCLUSIONS: The following were drawn: • The type of composite can increase significantly the material’s compressive strength and flexural strength. While the condensation techniques significantly increases only the compressive strength. • Curing time had significant effects on the microhardness of both composites (P< 0.0001). The condensing method had significant effects on the microhardness of SonicFillTM composite (P= 0.0001), but had no significant effects on the microhardness of Filtek Supreme Ultra composite (P= 0.1111).