Background: Short-fiber-reinforced resin composite (SFRC) is a direct bulk fill resin composite specially indicated in large complex cavities. It is characterized by having high fracture toughness and load bearing capacity to decrease the incidence of fracture of the restoration.
Materials and methods: In two parallel groups (n = 38 restorations), 76 participants having complex proximal cavities with asymptomatic vital pulp were randomly enrolled in this trial and received either SFRC (Ever X Posterior, GC, Japan) covered by Gaenial posterior (GC, Japan) or chairside indirect restorations (Grandioso inlay system; VOCO, Germany) fabricated on a silicon die. Materials were applied according to the manufacturer instructions with the corresponding adhesive system. Only 67 participants completed the trial, which was assessed using the modified United States Public Health Service (USPHS) criteria by two independent blinded assessors at 6 months and 1 year follow-up visits.
Statistical analysis: Fisher\'s exact and Cochran\'s Q tests were used to analyze inter- and intragroup comparisons, respectively. The significance level was set at p = 0.05.
Results: No statistically significant difference was observed between both tested groups for all USPHS criteria at different follow-up periods except for marginal integrity favoring the SFRC at 12 months when the difference became significant (p < 0.001), and color match favoring the nanohybrid indirect resin composite restorations with significant difference in scores at all follow-up intervals (p < 0.001) was found. Cochran\'s Q test showed significant differences within the same technique during the follow-up period for some criteria.
Conclusion: Direct SFRC and indirect nanohybrid resin composite complex proximal restorations showed an acceptable clinical performance along the 1 year follow-up period.
Clinical relevance: Direct SFRC restorations could be a viable treatment option for complex restorative cases.