What the study is
Qian Wu and Daniel J. Yen, endodontists at Dongyang People’s Hospital affiliated with Wenzhou Medical University in Zhejiang, China, report two cases in Experimental and Therapeutic Medicine (volume 32, article 297, published online September 11, 2026, open access, doi:10.3892/etm.2026.13292). Both cases are teenage boys whose mandibular left second premolar (tooth 20, Universal numbering) was being destroyed by inflammatory root resorption (IRR), the progressive loss of root hard tissue driven by pulp infection. The point of the report is to push regenerative endodontic treatment (RET) into one of its hardest indications: resorption so advanced that in case 1 the apical root segment had already separated completely from the main root at the mid-root level.
The two cases
Case 1, an 11-year-old seen in August 2023, had fractured an anomalous central cusp, leading to pulp necrosis and IRR with full separation of the apical fragment. Treatment followed the standard RET sequence: canal disinfection with 1.5% sodium hypochlorite, a calcium hydroxide medicament for 4 weeks, then at the second visit a 20 ml 17% EDTA rinse, periapical bleeding induced with a size 25 K-file to fill the canal, a 20-minute wait for clot formation, and a 3-mm layer of the bioceramic iRoot BP Plus below the cementoenamel junction. At 1 month the tooth was asymptomatic, the periapical radiolucency had regressed, and the separated fragment had shifted back into contact with the main root. At 12 months the fragment had drifted mesially and resembled a horizontal root fracture on the radiograph; at 24 months it was stable and the tooth symptom-free, with a periodontal ligament space around both fragment and main root and the resorption arrested. The reconnection, however, was positional rather than structural: the authors state plainly that the newly deposited mineral tissue was insufficient to restore root continuity.
Case 2, a 15-year-old seen in June 2022, presented with chronic apical periodontitis and oblique inflammatory resorption that left an open, anomalous apical foramen with thin canal walls; the tooth had been treated at another clinic about a year earlier. The protocol matched case 1 except for the scaffold: periapical bleeding could not fill the canal, so the clinician aspirated blood from the maxillary terminal alveolar bone near the tuberosity with an 18-gauge needle advanced less than 2 mm through the vestibular mucosa and injected it into the canal. At 3 months the tooth was asymptomatic with mineral deposition along the mesial canal wall and apical area, though it did not respond to electric pulp testing, and it still did not respond at 6 months while alveolar bone density increased. At 36 months the patient remained asymptomatic and the periapical lesion had resolved almost completely, with bone density in the lesion area nearly matching normal alveolar bone.
The bone-drawn clot
Case 2 is, by the authors’ own literature check, the first published use of alveolar-derived autologous blood (ADAB) as the RET scaffold for root resorption. Their rationale is practical: when induced periapical bleeding is inadequate, the usual substitutes are platelet-rich plasma or fibrin prepared from peripheral venous blood, which requires someone qualified to perform venipuncture, while alveolar bone blood is harvested by the dentist in the chair. That is a workflow argument, not demonstrated biological superiority; the report contains no comparison showing ADAB clots outperform periapical bleeding or platelet concentrates.
Boundary
This is two cases from one center, with no controls and no histology, so the tissue that mineralized inside the canals cannot be identified as pulp, cementum, or bone. Neither case had cone-beam CT (the guardians declined over radiation concerns), which the authors call a major limitation: without three-dimensional imaging the internal versus external classification of the resorption stays tentative, and in case 1 the exact relationship between the fragment and the main root at 24 months could not be assessed. Case 2’s tooth never regained vitality on electric testing, so that outcome is periapical healing and hard-tissue deposition, not pulp regeneration in the strict sense. The authors’ own table of prior published work lists twelve case reports and case series plus three clinical trials (10, 20, and 92 patients) for RET in resorption; the evidence base remains case-led.
What it changes
For the pulp-dentin repair program, the durable message is about the ceiling of current RET rather than a breakthrough: disinfection plus a blood-derived scaffold can arrest severe resorption and heal large periapical lesions over multi-year follow-up, but it does not rebuild a severed root. The reproducible increment here is procedural, a chairside scaffold source when periapical bleeding fails, and it will matter only if larger, CBCT-documented series adopt it. The field assessment stands at /field/.
Provenance: grounded in the complete open-access text of Wu and Yen (2026) at Spandidos Publications. See /method/.