What was proposed
Ruchi Singhal, Akshita Bansal, Shiwani Chawla and Ritu Namdev, at the Post Graduate Institute of Dental Sciences in Rohtak, India, published a two-phase retrospective study in Biomaterial Investigations in Dentistry on 8 October 2026 (DOI 10.2340/biid.v13.46956) proposing a six-class radiographic framework for reporting outcomes of regenerative endodontic procedures (REPs) in immature necrotic permanent teeth. The framework, which the authors call the Singhal and Bansal classification, modifies and extends response patterns described by Chen et al. in 2012 by treating apical closure, root lengthening and dentinal-wall thickening as separable components rather than lumped patterns.
The classes run from Class 1, apical closure with increased root length and dentin thickness, down to Class 6, no dimensional change but radiographic healing of a documented pretreatment periapical lesion, with Classes 2 through 5 covering closure with only one dimension gained, closure with neither, and intracanal barrier formation. Two scope rules matter for reading the results. First, classification was restricted to teeth that were already clinically asymptomatic with no persistent periapical disease, so the classes describe radiographic response after the American Association of Endodontists primary goal of symptom elimination and bony healing has been met. Second, partial or complete intracanal calcification is recorded as a modifier on any class, not as a class of its own.
The cohort
In Phase I, radiographs of 20 cases treated between 2015 and 2018 were analyzed to identify recurring outcome patterns. In Phase II, the framework was applied to an independent cohort: 54 immature single-rooted permanent teeth in 44 patients aged 8 to 13 years (23 boys, 21 girls), treated between 2019 and 2023 with a minimum follow-up of 24 months (range 24 to 53). The teeth were 46 maxillary central incisors, 5 maxillary laterals, 1 mandibular central incisor and 2 mandibular premolars; 52 of 54 became non-vital from trauma and 2 from caries. By Cvek’s staging, 16 teeth were stage 2 and 38 were stage 3 at treatment.
The protocol followed AAE clinical considerations: 1.5% sodium hypochlorite irrigation (20 mL per canal over 5 min), triple antibiotic paste (ciprofloxacin, metronidazole, minocycline, each at 1 mg/mL) as intracanal medicament, a 17% EDTA rinse at the second visit one to four weeks later, an induced bleeding clot as scaffold, and a calcium silicate barrier of MTA or Biodentine. Cases that needed platelet-rich plasma or platelet-rich fibrin because bleeding could not be induced were excluded, which removes most scaffold variability from the cohort.
What the classes showed
Class 1 was the single largest outcome: 18 of 54 teeth (33.3%). Class 2 had 3 teeth, Class 3 had 10, Class 4 had 9, Class 5 had 5 and Class 6 had 9. Pooling the classes, root lengthening occurred in 21 of 54 teeth (38.9%, Classes 1 and 2) and dentinal-wall thickening in 28 of 54 (51.85%, Classes 1 and 3). Partial intracanal calcification appeared in 19 of 54 teeth (35.18%); no case showed complete canal obliteration.
Pretreatment periapical radiolucency was documented in 14 of 54 teeth (25.9%). It resolved completely in 11 of those 14 (78.6%): nine Class 6 teeth and two Class 3 teeth. The remaining three lesions were shrinking without progression at the latest radiograph. Every Class 6 tooth in the cohort carried a pretreatment lesion, which is a definitional consequence of the class rather than a finding.
Neither patient age group (under 10 versus 10 to 13) nor pre-treatment root stage was significantly associated with the outcome class (Fisher’s exact test, p = 0.215 and p = 0.872). Class 1 did occur numerically more often in the younger group (38.9% versus 22.2%) and in stage 2 teeth (37.5% versus 31.6%), but the study is explicit that these trends did not reach significance. Reliability was the framework’s strongest result: Cohen’s kappa was 0.82 between two blinded calibrated examiners and 0.86 within examiner on repeat assessment after 15 days.
What it does not show
The classes measure radiographic dimensions, not tissue type. A tooth in Class 1 has gained length and wall thickness on a periapical film; the framework cannot say whether the canal contains regenerated pulp, fibrous repair or osseous ingrowth, and no histology or pulp sensibility testing was reported. The imaging basis is two-dimensional periapical radiography with no software calibration and no CBCT, so projection error is unaccounted for, and the fixed 6.5 mm measurement point below the cemento-enamel junction is a pragmatic mid-root proxy that does not scale with baseline root length. The class assigned at latest follow-up is a snapshot, not an endpoint: the authors note teeth can transition between classes with longer observation. There is no control group and no comparison against apexification, so the distribution says nothing about whether REPs outperform conventional care. Finally, this is one center’s internal validation; the authors themselves state that prospective multicenter validation is required before the framework can support inter-study comparison.
Where we differ from the framing
We found no press or popular coverage of this study to differ from. Against the paper’s own framing, we would hold back the title’s implication: the study redefines outcome reporting for a procedure, not regeneration itself. And because classification was limited to already clinically successful cases, the 33.3% Class 1 share is not a success rate for REPs. It is the share of successfully treated teeth that also showed the full radiographic maturation pattern at the last film.
Where it sits in the field
For the pulp and dentin repair program, the piece addresses a measurement problem this record keeps running into. Recent clinical analyses on this site, including the 148-tooth regenerative-versus-apexification comparison and the 12-month i-PRF adjunct trial, each had to define radiographic success on their own terms, because the field still lacks a shared outcome language; the Chen patterns this study builds on have been adapted in different ways by the groups that used them, for example with Schei’s ruler or periapical index scores layered on top. A component-based classification with demonstrated examiner agreement is a reasonable candidate for that common language, and the calcification modifier is worth keeping, since 35 percent of cases here developed partial intracanal calcification without complete obliteration. Whether the classes predict tooth survival or fracture resistance is exactly what the framework has not yet tested. The current field assessment stands at /field/.
Provenance: grounded in the open-access full text (Biomaterial Investigations in Dentistry 13:744-755, published 8 October 2026, CC-BY), retrieved and cross-checked for this piece; every number above was verified against the published text and tables by two independent reviewers. Method and sourcing standard at /method/.