Methods: A three-unit bridge master model was fabricated using cold-cure acrylic resin. Four combinations of different viscosities of PVS impression materials - regular body (monophase) alone, light body with regular body, light body with heavy body, and light body with putty - were used to make an impression of the master model. Ten impressions from each group were taken and Type IV gypsum stone was used to generate the dies. The dies were measured at the inter-abutment distance, occlusogingival length, and shoulder width with a measuring microscope and were compared with the master model using one-way analysis of variance and Tukey (honest significant difference) test.
Results: Differences were found for inter-abutment distance between the master model and the light body with regular body and light body with putty dies (both P < 0.02). A difference was found for shoulder width between the master model and the regular body alone die (P = 0.01). No differences were found for occlusogingival distance (all P > 0.08).
Conclusion: Results suggested inter-abutment distance was most accurate when using a PVS light body combination. Occlusogingival length was accurate using any of the studied PVS combinations, and shoulder width was more accurate when using the regular body PVS.
Relevance for patients: These results should be considered when choosing the viscosity of the PVS to use for producing impressions of high accuracy and fabricating a well-fitting fixed prosthesis.
Methods: An experimental study was conducted in our Physics Laboratory during September 2015. A series of syringes sized 1 mL, 3 mL, 5 mL, 10 mL and 20 mL were paired with the original needles, 27G, 27G spinal and 30G. Each combination was tested three times using a compression testing Instron 5940 Series to measure initial and maintenance forces. Statistical analysis was performed using One-way ANOVA.
Results: The lowest initial force was shown by the combination of 1 mL syringe and 27G spinal needle. However, the 1 mL syringe showed no significant difference across the needles [F(3, 8) = 3.545; P < 0.068]. The original and 27G needle showed mean difference 0.28 (95%CI: -0.19, 0.75; P = 0.420). The lowest maintenance force was measured in the combination of 1 mL syringe and its original 26G needle. On the contrary, both the highest initial and maintenance forces were shown by the combination of 10 mL syringe and 30G needle.
Conclusion: The 1 mL syringe with original 26G needle shows the best combination.
MATERIALS AND METHODS: A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05).
RESULTS: SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively.
CONCLUSIONS: Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group.