What was tested

Pacheco, Frigeli, Neculqueo, and colleagues at Pontifícia Universidade Católica do Rio Grande do Sul asked whether stem cells from the apical papilla (SCAP), pre-treated with docosahexaenoic acid (DHA) and combined with a hydroxyapatite/tricalcium phosphate (HATCP) scaffold, could improve pulp repair outcomes. They used human SCAP isolated from third molars of young adults, treated the cells with DHA at 1 µM for 24 h with or without HATCP, and collected conditioned medium after seven days. They then tested the medium on rat incisor pulp cells in vitro and in a rat model of apical periodontitis (Pacheco et al. 2026, Methods).

The in vitro arm used 12 Wistar rats to isolate pulp cells, while the in vivo arm used 48 rats with exposed mandibular first-molar pulps left open for 28 days to establish periapical lesions. After root canal preparation, canals were filled with one of six regimens and sealed for 42 days. Outcomes included cell viability, morphology, alkaline phosphatase activity, alizarin-red mineralization, radiographic lesion area, histological inflammatory score, and aerobic/mesophilic bacterial colony-forming units (CFU) (Pacheco et al. 2026, Methods).

In vitro findings

CM from untreated SCAP had no consistent effect on rat pulp cell viability except at the highest density tested, 10,000 cells per 96-well plate, where it slightly reduced viability compared with control (p < .05). DHA alone or DHA-pretreated SCAP medium did not replicate this reduction (Pacheco et al. 2026, Results, Fig. 1).

DHA exposure did change cell shape. Pulp cells treated with DHA-pretreated SCAP medium showed a larger cell area than controls (p < .01), and DHA alone also increased area (p < .05). Qualitatively, both groups shifted cells from a spindle shape toward a cuboidal morphology (Pacheco et al. 2026, Results, Fig. 2).

After 21 days in osteogenic medium, alkaline phosphatase activity did not differ across groups. However, alizarin-red quantification showed increased mineral deposition with DHA-pretreated SCAP medium (p < .01) and with DHA-pretreated SCAP medium plus HATCP (p < .05), with visible mineralization clusters in both groups (Pacheco et al. 2026, Results, Fig. 3).

Rat model findings

All six canal-filling strategies reduced radiographic periapical lesion area compared with the negative control, in which canals were instrumented but not filled (p < .05). The groups included CM-SCAP, DHA alone, DHA-pretreated SCAP, CM-SCAP plus HATCP, and DHA-pretreated SCAP plus HATCP (Pacheco et al. 2026, Results, Fig. 4).

Histological inflammatory scores dropped only in the DHA-alone group and in the group receiving DHA-pretreated SCAP plus HATCP, both versus the negative control (p < .01). The other treatments did not reach significance on this endpoint (Pacheco et al. 2026, Results, Fig. 5).

Bacterial CFU counts rose sharply after pulp exposure, as expected, but at the end of the 42-day treatment period there was no significant difference among the experimental groups, including the negative control (p > .05). Thus the observed lesion shrinkage was not explained by antibacterial activity of the SCAP or DHA preparations (Pacheco et al. 2026, Results, Fig. 6).

What it means for pulp-dentin repair

For the pulp and dentin repair program, the study adds an immunomodulatory angle to the SCAP story. Rather than requiring living cell transplantation, a cell-free conditioned medium from DHA-exposed SCAP reduced periapical lesion size and inflammatory infiltrate in rats. The mechanism appears to be host-response modulation, because bacterial load was unchanged. If replicated, this would suggest that pro-resolution lipid priming of dental stem-cell secretomes could become part of regenerative endodontic protocols.

What it does not show

The work is in rats, not humans, and the rat pulp cells used for in vitro assays were not human SCAP. The study does not demonstrate functional pulp regeneration with vessels, nerves, or dentin-pulp architecture; it shows periapical bone/lesion reduction and in vitro mineralization. The bacterial assays were aerobic/mesophilic cultures only, so the absence of an antibacterial effect is narrowly defined. The canal-sealing method, 42-day treatment window, and saline irrigation are also study-specific limitations noted by the authors. No trial or clinical data are reported.

Provenance: grounded in the open-access full text of Pacheco ND, Frigeli MP, Neculqueo GW, Estrázulas M, Oliveira SD, Campos MM. Effects of stem cells derived from the apical papilla (SCAP) on dental pulp outcomes: the influence of docosahexaenoic acid (DHA). Regenerative Therapy. 2026;32:101129. doi:10.1016/j.reth.2026.101129, retrieved and verified against the Europe PMC full-text XML (PMC13196467). Method and sourcing standard at /method/.