Objectives: This study aimed to measure the microtensile bond strength (μTBS) of a new universal adhesive (UA) bonded to dentin following a quick bonding mode.
Materials and methods: The experimental UA 'SKB-100,' now commercialized as Clearfil Universal Bond Quick ('C-UBq'; Kuraray Noritake), was investigated, with Scotchbond Universal ('SBU'; 3M Oral Care) and the two-step self-etch (SE) adhesive Clearfil SE Bond 2 ('C-SE2'; Kuraray Noritake) serving as references. The adhesives were employed separately in etch&rinse (E&R) and SE modes on each tooth half following a split-tooth design and following their respective instructions for use, except for C-UBq that besides the manufacturer's instructed quick bonding mode was also applied and left untouched for 20 s prior to light curing ('C-UBq_20s') and for C-SE2 that was also applied in the E&R mode. μTBS of half of the specimens was measured upon 1 week (1w), with the other half tested after 6-month (6m) storage in distilled water at 37 °C. Data were statistically analyzed using linear mixed-effects modeling and three-way ANOVA (p < 0.05). The adhesive-dentin interfaces were ultrastructurally characterized by TEM.
Results: C-UBq revealed a significantly lower μTBS than C-SE2. The highest μTBS was recorded for C-UBq_20s_1w and C-SE2_1w, both when applied in E&R mode. However, μTBS of C-UBq_20s significantly decreased upon aging in both modes. C-SE2 presented the significantly highest 'aged' μTBS.
Conclusion: C-UBq applied in the quick bonding mode did not underperform to the UAs applied for 20 s. Superior bonding effectiveness was achieved by C-SE2 in SE and E&R bonding modes.
Clinical relevance: Extended application time of C-UBq improved solely its immediate but not aged bonding effectiveness.
Keywords: Bond strength; Durability; Interface; Linear mixed-effects model (LME); TEM.