# Pulpectomy in Primary Teeth > Pulpectomy in primary teeth — BDS Pedodontics notes on ribbon-shaped canals, working length, ZOE versus iodoform pastes, obturation and recall criteria. - Canonical URL: https://prepelephant.com/topics/bds/pedodontics/pulpectomy-primary-bds - Exam / course: BDS · Subject: Pedodontics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Pulpectomy in Primary Teeth", PrepElephant, https://prepelephant.com/topics/bds/pedodontics/pulpectomy-primary-bds ## Direct answer Pulpectomy in a primary tooth removes necrotic or irreversibly inflamed radicular pulp from ribbon-shaped, tortuous canals and seals them with a paste that resorbs in step with the root — which is why gutta-percha is never used. The indications are spontaneous unprovoked pain, a sinus tract, furcation radiolucency or pathologic resorption in a tooth that is restorable and far enough from exfoliation; the contraindications are non-restorable crowns, internal resorption communicating with the exterior, external resorption involving most of the root, and medically fragile children in whom infection is better removed than managed. Working length stays short of the radiographic apex — roughly two millimetres short or about two-thirds of root length — because thin curved roots curl around the permanent follicle, and the furcation, not the apex, is where primary molars drain. ## What you must remember - **Canal anatomy dictates everything:** narrow ribbon-shaped canals with fine lateral communications, accessory canals emptying into the furcation, roots thin, curved and divergent around the successor follicle — filing is circumferential, gentle and never apically patrolled. - **Contraindications:** non-restorable crown, internal resorption perforating the root, external resorption beyond roughly the coronal two-thirds, periapical or furcation involvement extending into the successor crypt, and systemic conditions where operative infection control is unsafe. - **Working length:** short of the radiographic apex — commonly quoted as 1-2 mm short, or about two-thirds of the root length — respecting physiologic resorption and the follicle below. - **Instrumentation and irrigation:** small K-files (commonly size 15-30) with light filing, irrigated with normal saline (safest) or cautiously with dilute sodium hypochlorite, avoiding forceful extrusion through furcation canals; dry with paper points. - **Obturation pastes:** zinc oxide eugenol (sets hard, resorbs slowly), iodoform-calcium hydroxide pastes such as Vitapex (resorb rapidly if pushed past the apex), and Endoflas FS combining ZOE, calcium hydroxide and iodoform — chosen by resorption behaviour and departmental preference; filled via syringe or lentulo, deliberately avoiding overfill. - **The stainless steel crown finishes the job:** a pulpectomised primary molar is a crowned primary molar; amalgam or composite on a root-treated primary molar is a known failure pattern. - **Recall criteria:** comfortable tooth, no fistula or pathologic mobility, furcation radiolucency resolving, physiologic resorption proceeding, and successor follicle intact at six- to twelve-month films. ## A necrotic second primary molar, step by step A five-year-old presents with a buccal sinus beside a grossly carious mandibular second primary molar and night pain the mother measures in lost sleep. The radiograph shows furcation radiolucency, intact roots with better than two-thirds of root length remaining, and a healthy second premolar crypt below — pulpectomy territory, with extraction and a space maintainer held in reserve. Rubber dam on, access opened through the caries, the chamber roof removed, and the ribbon-like orifices located with an explorer and a size 15 file. Files work circumferentially at short working length, enlarging gently to perhaps a 25 or 30; saline irrigates quietly, paper points dry. Vitapex is spun in with a lentulo until it backs out of the access — the aim is a paste-filled canal, not a paste-filled furcation, though a small puff past the apex is tolerated because the material resorbs. Zinc oxide eugenol bases the chamber, and the tooth is prepared for a stainless steel crown the same visit. Six months later the film tells the verdict: furcation clearing, roots resorbing physiologically, premolar follicle undisturbed. Had the film shown internal resorption or half-length roots, the appointment ends with forceps and a space maintainer. ## What examiners keep asking The guaranteed two-mark question is why gutta-percha is excluded — the filling must resorb with the root, or the successor erupts through a wall of rubber. The paste comparison is asked with one discriminator each: ZOE for hardness with slow resorption, iodoform-calcium hydroxide for rapid resorption of overfill, Endoflas for the combination. Working length numbers are MCQ fodder, alongside furcation radiolucency as the radiographic sign of necrosis (accessory canals, not apical drainage). Indian practicals grade pulpectomy among the most common exercises; the external's script runs access, length, irrigant, paste, coronal restoration. ## Frequently asked questions ### Why must primary root canals never be filled with gutta-percha? Gutta-percha does not resorb, so it would obstruct physiologic root resorption and complicate successor eruption; only resorbable pastes belong in primary canals. ### Which pastes are used for primary tooth obturation? Zinc oxide eugenol, iodoform-calcium hydroxide pastes such as Vitapex, and combination pastes such as Endoflas FS — all resorbable at rates compatible with root resorption. ### How far short of the apex is the working length kept? Roughly 1-2 mm short of the apex, with many departments teaching about two-thirds of root length. ### When should a necrotic primary molar be extracted rather than pulpectomised? When the crown is non-restorable, internal resorption communicates externally, external resorption involves most of the root, or the successor's crypt is involved — extraction with a space maintainer then serves the arch better. ### What defines success at the recall visit? An asymptomatic tooth without fistula or abnormal mobility, resolving furcation radiolucency, continuing physiologic resorption, and an undisturbed permanent successor.