Introduction
Calcium silicate-based materials, particularly mineral trioxide aggregate (MTA), are widely used in vital pulp therapy and regenerative endodontics for their biocompatibility and ability to promote hard tissue formation. However, MTA is costly and has limitations associated with its radiopacifier, bismuth oxide. Portland cement (PC), with similar calcium silicate chemistry but without bismuth oxide, offers a cost-effective alternative but requires modification to enhance its mechanical and biological performance. Graphene oxide (GO), with high mechanical strength and bioactivity, is a promising additive for dental biomaterials. This study evaluated GO-incorporated Portland cement (GoP) as a novel restorative material.

Methods
GO was incorporated into PC at 1%, 2%, and 3% (w/w). Surface microhardness was assessed using a Through Indenter Viewing tester. Human peri-radicular fibroblast cells viability were assessed using MTT assays under direct, indirect, and eluate exposure. Vimentin expression was analysed by immunofluorescence. Cell attachment and morphology were examined by scanning electron microscopy (SEM), and biomineralisation was quantified by X-ray diffraction (XRD). An exploratory split-mouth in vivo study was conducted in a 1-year-old Labrador dog with traumatic irreversible pulpitis and apical periodontitis affecting all four canine teeth, comparing GoP with MTA.

Results
Microhardness increased with GO concentration, reaching 239.0 ± 33.1 HV at 3% GoP, up to a 5.3-fold increase versus PC. Cell viability was maintained or enhanced across all groups, with 2% GoP showing optimal response and strong vimentin expression. SEM demonstrated superior cell attachment on 2% GoP. XRD showed enhanced biomineralisation, with 3% GoP achieving the highest apatite fraction (11.65%), a 1.61-fold increase relative to MTA. In vivo, 2% GoP showed complete radiographic resolution of periapical lesions at 3 months, while residual radiolucency persisted in MTA-treated sites.

Conclusions
GoP improves mechanical performance, supports favourable cellular responses, and enhances biomineralisation, with promising in vivo healing outcomes. These findings suggest that GO-modified Portland cement, particularly at 2%, may serve as a cost-effective alternative to MTA for dental applications.