1)Endodontic phase:

Removal of the existing coronal obturation material.Refinement of the access cavity to ensure proper canal desobturation, disinfection and obturation.Orthograde retreatment of tooth #12 (right lateral incisor).Orthograde retreatment of tooth #11 (right central incisor) with placement of an MTA apical plug.

2)Restorative phase:

Placement of a composite resin restoration as a provisional solution, to be replaced after completion of the patient’s orthodontic treatment.

After local anesthesia and rubber dam isolation, the previous filling material was removed using rotary instruments.

Tooth #12: Irrigation was performed with 3% sodium hypochlorite.Tooth #11: Irrigation was performed with 1% sodium hypochlorite.

Retreatment was carried out first on tooth #12, followed by tooth #11. The canals were gently instrumented manually and carefully disinfected. A creamy mix of calcium hydroxide (Prevest Denpro) intracanal dressing was placed in both canals for 2 weeks, until no clinical signs of infection were present (Figure 2Figure 2).

At the second appointment, the canal of tooth #11 was dried. Mineral trioxide aggregate (Trioxident, Vladmiva) was mixed according to the manufacturer’s instructions to a wet-sand consistency and placed incrementally 1 mm short of the working length using pre-measured gutta-percha pluggers. The material was condensed with minimal pressure using inverted absorbent paper points.

This procedure was repeated until a 5-mm apical plug was obtained. The thickness and position of the plug were verified with sequential radiographs.

At the following appointment gutta percha back filling followed by immediate coronal composite obturation.

Tooth #11: gutta-percha backfilling was performed above the MTA apical plug.Tooth #12: the canal was obturated conventionally with gutta-percha.

This was followed by immediate coronal restoration with composite resin (Figure 3Figure 3).

Clinical and radiographic follow-up examinations were performed at 6, 12, and 24 months.

Clinical healing criteria included:

Absence of spontaneous painAbsence of tenderness to percussion or palpationAbsence of swellingAbsence of sinus tractNormal periodontal probing depths and tooth function

The sinus tract resolved within two weeks following intracanal disinfection and did not recur during the follow-up period (Figure 2Figure 2).

Radiographic success was defined by:

Progressive reduction and eventual disappearance of the periapical radiolucencyRe-establishment of normal periapical bone architectureFormation of a mineralized apical barrier at the apex of tooth #11 (Figure 3Figure 3)

No adverse outcomes associated with Mineral Trioxide Aggregate apexification, such as discoloration, reinfection, material extrusion, or need for further intervention, were observed.

MTA Apexification vs. Revascularization (RET)

Systematic reviews report comparable long-term survival and clinical success rates between MTA apexification and RET. However, apexification remains the treatment of choice when revascularization is contraindicated. Successful outcomes in either approach depend primarily on case selection, adequate disinfection, and follow-up [1]-[3].

MTA vs. Long-term Calcium Hydroxide

Historically, calcium hydroxide apexification required prolonged treatment-often over six months-with multiple dressing changes. Beyond the practical limitations, extended Ca(OH)₂ exposure has been shown to alter dentin’s physical properties, decreasing its fracture resistance. In contrast, MTA provides a stable apical barrier within a single or few visits, reducing treatment duration and preserving radicular integrity [4]-[6].

MTA vs. Customized Gutta-percha Cones

An in vitro comparison of obturation techniques in simulated immature anterior teeth demonstrated that MTA apical plugs achieved significantly better marginal adaptation to dentinal walls than single customized gutta-percha cones used with calcium silicate–based sealers. This highlights the material’s superior sealing capability in cases with wide and irregular apices [7].

Sealing and Bioactivity

The chemical composition of MTA makes it bioactive, inducing cementogenesis and hard tissue barrier formation [8]. It provides a reliable seal at the apex, helping to control persistent apical inflammation and promote bone healing. A study compared White MTA (WMTA), Biodentine, and a BC-sealer (bio-ceramic sealer) in terms of their ability to release calcium (Ca) ions, uptake calcium (Ca) and silicon (Si) in the adjacent root dentine demonstrates that MTA (WMTA) has significant bioactivity: it can interact with phosphate in body-like fluid, form mineral precipitates and cause ion exchange/uptake by dentine. These features underlie its sealing ability and ability to promote hard tissue barrier formation [9][10].

Upon hydration, MTA releases Ca²⁺ ions, leading to the formation of Ca(OH)₂, which reacts with phosphate ions from tissue fluids to produce hydroxyapatite. This reaction accounts for its progressive increase in alkaline pH-from approximately 10.2 immediately after mixing to 12.5 within 3 hours-creating an environment that is antibacterial, bio inductive, and conducive to cell adhesion and mineralization [8][11].

Cellular and Molecular Effects

At the biological level, MTA modulates inflammatory mediators and stimulates osteoblastic and odontoblastic activity. It downregulates pro-inflammatory cytokines (IL-1β, TNF-α) and upregulates anti-inflammatory pathways that favor healing. Moreover, it enhances the differentiation and migration of hard tissue–forming cells, contributing to osteogenesis, and periodontal reformation [8][11].

Irrigation and Disinfection

Effective chemomechanical disinfection is fundamental to the success of apexification. The absence of a natural apical constriction increases the risk of irrigant extrusion and periapical injury. Therefore, irrigation must balance antibacterial efficacy with tissue compatibility [12].

In the present case, a conservative protocol using 1.25% NaOCl, 17% EDTA, and 2% CHX, interspersed with saline rinses, was employed to maximize disinfection while minimizing cytotoxicity. Studies confirm that lower NaOCl concentrations, when used in sufficient volumes and for extended contact times, can achieve effective microbial reduction with lower extrusion risk [12][13].

Irrigant Activation and Delivery

Activation improves irrigant penetration and biofilm disruption. However, in teeth with thin dentinal walls or open apices, ultrasonic or laser activation may jeopardize the fragile radicular structure. Safer alternatives include manual agitation using a fitted gutta-percha cone and apical negative pressure systems (e.g., EndoVac^TM), which enable irrigants to reach the apical third without extrusion. The use of double-vented needles and frequent irrigant exchange further enhances cleaning efficacy [14].

For high-risk cases, a collagen apical barrier (CAB) can be temporarily placed beyond the apex to prevent extrusion and allow safe irrigant activation [15].

Intracanal Medication:Role of Calcium Hydroxide

Short-term placement (1 - 4 weeks) of a creamy calcium hydroxide dressing can elevate periapical pH, reduce inflammation, and improve the subsequent marginal adaptation of MTA (3, 4). Since MTA’s setting and sealing ability are negatively affected by acidic environments, this preconditioning step enhances treatment predictability [16].

Micro-CT analyses reveal that access cavity design and placement technique significantly influence MTA plug density and void formation. Conservative accesses, though structurally conservative, may increase porosity within the plug. Therefore, a traditional access cavity was selected in this case to enhance apical visibility and compaction [17].

A 5-mm MTA plug, placed with a calibrated carrier and pluggers under a “reverse tamponade” technique, provided an optimal barrier. Evidence supports a minimum thickness of 4 mm to resist bacterial penetration and mechanical stresses. Delivery systems such as the MAP System or micro-carriers allow precise placement without the need for a matrix [18].

Material Selection: MTA, Biodentine, or Bioceramic Putties

Recent comparative studies indicate that MTA, Biodentine, and premixed bioceramic putties all demonstrate high clinical success and favorable biocompatibility [19][20].

Biodentine offers advantages in handling and setting time, while MTA retains the longest clinical track record for apical barrier formation. However, MTA may cause coronal discoloration, exhibit porosity under acidic conditions, and has a longer setting time. Despite these drawbacks, the material’s apatite layer formation subsequently seals surface voids, ensuring a durable chemical bond with dentin [8].

Prognosis and Clinical Relevance

Apexification with MTA had demonstrated favorable clinical and radiographic outcomes and appears to be a good and reliable treatment option in the open apex teeth [21].

In a case series of 5 - 15 years, MTA as an apical barrier achieved a healing rate of 96%.

The apexification failure rate of an MTA apical plug with a single placement of calcium hydroxide for immature permanent teeth was 7.1% over 2 years [22].