Gingival margin interfacial microleakage, staining, and push-out strengths of gingival colored composite resins in...

Staining at the gingival margin could impact denture longevity, but the behavior of gingival colored composite resins (GCCs) in this area remains unclear.

This in vitro study evaluated surface staining, microleakage, and push-out bond strength at the gingival margin of artificial teeth, comparing two consistencies of GCCs with two resin base materials.

Specimens included artificial teeth (Ivostar; Ivoclar AG) and two acrylic resin base materials: conventional (Ondacryl; Clássico) and high-impact (Diamond D; Keystone Industries) (n=300). Specimens were divided in three groups: control (acrylic resin) and experimental groups, receiving one of the two GCCs consistencies: paste (SR Nexco; Ivoclar AG) or flowable (Gradia Plus Gum; GC Europe)). Initial artificial aging treatment in distilled water (5 days at 55º C) was performed and the specimens were then immersed in 5% methylene blue dye or coffee for 7 days at 37º C. Staining was visually assessed, and the specimens were sectioned for dye infiltration analysis at the gingival margin using a stereomicroscope. Bond strength was measured with the push-out test in the gingival colored composite resin specimens. Data were analyzed using 2-way and 3-way ANOVA with Bonferroni post hoc test and Kruskal-Wallis test with Dunn post hoc test (α=.05).

A significantly higher surface staining and microleakage was observed in experimental groups compared to the control (acrylic resin) (P<.001). Surface staining revealed that paste consistency GCC was more susceptible to discoloration in coffee, while flowable GCC was more affected by methylene blue. Lower microleakage values were observed in the control (acrylic resin) groups (0.11 ±0.13 mm for the conventional base and 0.08 ±0.11 mm for the high-impact base) in comparison with the experimental groups (P<.05). The flowable GCC showed the highest microleakage with methylene blue (0.98 ±0.21 mm for the conventional base and 0.91 ±0.31 mm for the high-impact base), significantly greater than the paste consistency for both base materials (0.53 ±0.22 mm for the conventional base and 0.66 ±0.34 mm for the high-impact base; P<.001). For coffee immersion, both GCC consistencies displayed similar microleakage values (P>.05). Push-out bond strength was comparable between paste and flowable GCCs (P>.05).

Microleakage at the gingival margin was significantly greater when GCC was applied, regardless of the consistency. However, the GCC consistency seems to not affect push-out bond strength. Further clinical studies are needed to better understand the impact of these findings on prosthesis longevity.