Open Apex and its Management: Review Article

ABSTRACT

During root development, the teeth are subjected to a variety of assaults. Due to this, the root stops forming and the closure of the apex does not take place. Root canal treatment becomes a major challenge in these cases because of the width of the canal and wide-open apices. Management of open apices includes apexogenesis in vital young permanent teeth and apexification, which is a method to induce a calcified barrier in the root. Newer concepts include regeneration and revascularization procedures, which still need to be experimented with further.

INTRODUCTION

Post-eruption of the tooth, root development and apex closure are completed within three years. The tooth is susceptible to various accidents and aggressions throughout this period. When immature teeth are faced with accidents such as these, the root stops forming, and root canal treatment is a major challenge because of the width of the canal and wide-open apices.

According to Frances M. Andreasen et al., 30% of pulp necrosis on immature permanent teeth is a consequence of dental trauma.[1]

Due to anatomical complexities, the treatment of immature necrotic teeth remains a challenge for the clinician.[2]

Endodontic treatment of teeth with immature root development has always been difficult for several reasons:

1. Due to the anatomical features of the developing tooth, mechanical instrumentation of the root canal is challenging.

2. It is difficult to seal the root canal using traditional filling methods because of the absence of an apical stop.

3. Teeth that are still developing have thin root canal walls that are prone to fracturing.[3]

Etiology of open apex

Trauma is one of the major causes of teeth, leading to open apices.

Significant alterations in pulpal microcirculation brought on by irritation of pulp tissue may also cause pulpal necrosis and halt or stop root formation.[4] Thermal injuries and chemical injuries can also affect the pulpal tissue and therefore lead to incomplete root development.

Iatrogenic root end enlargement can result from improper working length management and subsequent enlargement with both hand and rotary files.[5]

Other causes include dental anomalies dens evaginatus and dens invaginatus.

Classification of open apex

Classically, there are two types of open apices: the blunderbuss and non-blunderbuss apices.

In the blunderbuss apex, the walls are divergent and the flaring of the apex is funnel-shaped. The walls of the canals may be parallel or slightly convergent in the non-blunderbuss apex; hence, the apex may be broad-shaped or convergent.

Funnel-Shaped Apex - In inverted root canal conicity, the apical opening may be larger than the coronal orifice.

Non-Blunderbuss - The walls of the canal may be parallel to slightly convergent as the canal exits the root apex.

The treatment of an immature permanent tooth with a blunderbuss canal, one of the two types of open apex, can be difficult in terms of mechanical preparation, canal disinfection, the absence of a tapered root canal apical seal, and the presence of existing thin radicular walls that are brittle.[6]

Diagnosis of open apex

A detailed history and documentation of any injury are of prime importance from both a diagnostic and treatment points of view.[7]

Cautious case assessment and precise pulpal diagnosis are significant in the treatment of immature teeth with pulpal injury. A full history of subjective symptoms, a complete clinical and radiographic examination, and the administration of diagnostic tests are all necessary for the clinical assessment of the pulpal state. A precise pain history must be obtained. The duration, nature of the pain, and aggravating and relieving factors must be considered.

Confirmation from objective tests is necessary. These include visual examination, percussion testing, and thermal and electric pulp testing.[2]

By identifying the pulp’s blood supply, the most recent noninvasive pulp testing tools, such as laser Doppler flowmetry, dual-wavelength spectrophotometry, pulse oximetry, and light photoplethysmography, have produced more accurate results.[8]

Radiographic interpretation can be difficult. An immature tooth with a healthy pulp is typically surrounded by a radiolucent region where the open apex is still forming. It may be difficult to differentiate between this finding and a pathologic radiolucency resulting from a necrotic pulp. Comparison with the periapex of the contralateral tooth may be helpful.[2]

Cone-beam computed tomography (CBCT) or digital volume tomography overcomes the drawbacks of two-dimensional radiography but at the expense of more radiation and higher cost.

Apexogenesis procedures can be used if the pulp is deemed to be important.[9,10]

Apexification

Apexification is a technique for inducing root end closure in an immature nonvital permanent tooth by removing the coronal and radicular tissue and placing a suitable biocompatible agent.

This procedure should induce an apical barrier, which can be confirmed by clinical and radiographic assessment. There should be no evidence of posttreatment adverse clinical signs or symptoms of pain, sensitivity, or swelling. Root fracture, lateral root pathosis, or external root resorption should not be evident during or following therapy.[9]

The purpose of apexification is to create an apical barrier that will stop root canal toxins and germs from entering the periapical tissues.[11]

The major problem in cases of a wide-open apex is the need to limit the material, thus avoiding the extrusion of a large amount of material into the periodontal tissue. Using a matrix avoids the extrusion of the material into the periodontal tissues, reduces leakage in the sealing material, and allows a favorable response of the periodontal tissues.[12]

Mineral trioxide aggregate (MTA)

MTA is biocompatible, induces hard tissue formation, and is slightly more radio-opaque than dentine. It allows for shorter treatment duration (two to three appointments) and better patient compliance.[13]

Procedure

It involves disinfection of the root canals with chemo-mechanical preparation and short-term dressing of the canals with calcium hydroxide for at least a week. At a subsequent appointment, the calcium hydroxide paste is irrigated from the canals with sodium hypochlorite and 17% ethylenediaminetetraacetic acid, followed by drying of the canals and placement of a thick paste of MTA into the apical portion of the root canal.

The MTA is condensed such that a 3–4 mm apical plug is created, which is confirmed radiographically. The MTA is then moistened and the tooth is temporarily restored for at least 3–4 h, while the MTA is allowed to set. The canals are later filled with gutta-percha and cement, and a bonded composite coronal restoration is placed.[13]

One-visit apexification procedure can also be performed with MTA, which offers major advantages over the traditional calcium hydroxide methods.

Biodentine and other bioceramic materials can also be used for apexification procedures.

Apexogenesis

The continuing physiological development and creation of the root’s apex are referred to as apexogenesis in histology. Formation of the apex in vital young permanent teeth can be accomplished by implementing the appropriate vital pulp.

The treatment of vital pulp in an immature tooth to permit continued root growth and apical closure is called apexogenesis.

Vital pulp therapy (VPT) aims to retain healthy pulp tissue that has been damaged by trauma, caries, or restorative techniques. This is crucial for young adults with teeth that lack fully developed root systems. This tooth’s retention of radicular pulp tissue enables ongoing apical maturation.

Direct pulp capping and partial and complete pulpotomy are important treatment options for the immature permanent tooth. Whether the coronal pulp tissue is preserved in toto, partially removed, or removed to the base of the pulpal floor, the preservation of the radicular pulp tissue allows continuing development and apical maturation (apexogenesis) of teeth with open apices.

Calcium hydroxide can be used for apical closure, but due to its various limitations and the amount of time it takes for apexogenesis, MTA, biodentine, and other bioceramic materials are now being used.

Determination of working length in teeth with open apices

Radiographic methods known for their inherent interpretation difficulties are even more challenging in open apices where dentinal walls frequently end at different levels and have irregular margins. As a result, the radiographic working length is overestimated because the apical end of the canal, which is circumferentially enclosed by dentine, is a few millimeters away from the radiographic apex.

It has been demonstrated that apex locators are quite effective at locating the apical foramen and constriction.[14]

Unfortunately, in open apices, they give incorrect measurements because wide root canals (e.g., >size 60), associated with open apices, adversely influence the function of apex locators. In wide canals, the electronic working length is shorter than the actual canal length.

The European Society of Endodontology recommends the use of an electronic apex locator (EAL) followed by confirmation of canal length with an undistorted radiograph during root canal treatment. The working length needs to be changed if the instrument in the canal appears to be farther than 3 mm from the radiography apex.

Obturation of blunderbuss canals

The thermoplasticized gutta-percha master cone obturation method is primarily used in teeth with open apices. The use of this technique does not require any special preparation of the root canal, and therefore, shaping the root canal using well-established methods, for example, step back and step down, is considered adequate.[13]

Tailor-made gutta-percha can be prepared of the size and shape of canal. This method is especially suggested for restoring the function and esthetics of anterior teeth in an otherwise healthy arch. Multiple gutta-percha cones are joined from butt to tip to create a roll to create a custom tailor-made gutta-percha. Then, ethyl chloride spray is used to soften this roll.[14,15]

This method is no longer used, and the thermoplasticized gutta-percha technique is preferred.

Newer concepts

The concept of regeneration and revascularization is overtaking traditional methods.

A revascularization procedure is performed to reestablish the vitality of a nonvital, immature tooth with a wide-open often blunderbuss apical opening. This enables tissue repair and regeneration, which thickens the delicate dentinal walls and lengthens the undeveloped root.[15]

In addition, MTA rather than glass ionomer cement was used as an intracanal barrier. This protocol has been broadly adopted in many subsequent studies in the literature and the Clinical Considerations for a Regenerative Procedure (AAE 2016).

CONCLUSION

Even though calcium hydroxide and MTA are tried-and-true apexification materials, a wealth of literature indicates that the prognosis is occasionally in doubt for teeth that receive a thin and frail root after successful apexification, making these teeth prone to fracture. Therefore, recent advances in regenerative dentistry may help clinicians to choose a conservative approach for the generation of an apical barrier.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.