Atypical radiographic presentation of a horizontal mid-root fracture in a maxillary central incisor tooth.

Prognosis of a horizontal mid-root fracture is favorable, primarily because the dental pulp tends to maintain its vitality and the fracture segments are completely intraalveolar. Healing usually occurs with deposition of calcified tissue. However, if the segment coronal to the fracture becomes nonvital and infected, healing occurs by interposition of granulation tissue. This report describes a case of a horizontal mid-root fracture in a right maxillary central incisor tooth, where the apical fractured segment was significantly displaced in a linear direction. This was attributed to the pressure generated from the expanding granulomatous tissue that was interpositioned between the fractured segments. This resulted in an atypical radiographic presentation. In addition, this report highlights the role of cone-beam computed tomography in the diagnosis, treatment planning, and management of root fractures.

INTRODUCTION

Root Fracture Is a Sequela to Dental Trauma and Constitutes 0.5%–7% of the Total Injuries.[1] They Are Primarily Observed in Permanent Central (68%) and Lateral Incisor Teeth (27%)[2] and Occur in the Age Group of 11–20 years.[1] Horizontal Root Fractures Involve Dentin, Cementum, and Pulp. Based on the Location, They Can Be Classified as Cervical, Middle, or Apical Third Fractures. Healing Depends on the Stage of Root Development, Vascularity of the Dental Pulp, Mobility, Degree of Dislocation, and Diastasis between the Fractured Segments.[1] Andreasen and Hjorting-Hansen Documented the Modalities of Healing After Root Fractures. Accordingly, They Described Healing With Calcified Tissue, Interposition of Connective/bone and Connective Tissue, and Formation of Granulation Tissue.[3] the Latter Type Transpires When the Pulp of the Fractured Coronal Segment Loses Its Vitality and Gets Infected. ingress of Bacteria Can Take Place Either Through a Tear in the Coronal Periodontal Ligament, Exposed Dentinal Tubules or Via the Invading Neovasculature (Anachoresis).[1] This Leads to an Inflammatory Response, Triggering the Release of a Series of Osteoclast-Activating Factors That Are Responsible for Localized Root and Bone Resorption. the Apical Segment Usually Contains Vital Pulp Tissue. Histologic Examination of Tissue Interpositioned between the Fractured Segments Demonstrates Inflamed Granulation Tissue. Fistula on the Buccal Mucosa Is an Occasional Clinical Finding. Widening of the Fracture Line, Loss of Lamina Dura, and Rarefaction of the Adjacent Alveolar Bone Are Typical Radiographic Findings.[1] However, at Times, the Wound Healing Response Can Be Unexpected. This Article Highlights a Case of Horizontal Mid-Root Fracture in a Right Maxillary Central Incisor Tooth Where the Apical Fractured Segment Was Significantly Displaced as a Result of Pressure Generated from Expanding Granulation Tissue.

CASE REPORT

A 24-year-old healthy Asian male reported to the specialty clinic with a primary complaint of pain and swelling in the upper front tooth for the past 1 week. Dental history revealed that the patient had sustained a trauma while riding a bicycle 5 years back. On clinical examination, his right maxillary central incisor (tooth #11) was tender to palpation and percussion and exhibited Grade II mobility. The responses to cold and electric pulp tests were negative. An intraoral periapical radiograph was exposed. It revealed a horizontal root fracture at the junction of middle and apical third of tooth #11. The apical fractured segment was significantly displaced in a linear direction [Figure 1a]. To determine the exact spatial displacement of the apical segment and for appropriate treatment planning, the tooth was subjected to limited field of view (FOV) cone-beam computed tomography (CBCT) scan (3D Imaging Centre, Delhi, India, CS 3D Imaging Software 3.3.11; 5 × 5). The FOV essentially is the scan volume. It can be large, medium, and limited depending on the extent of anatomic structures included. Limitation of large FOV is the irradiated area and reduced resolution. Smaller the scan volume, better is the spatial resolution. Overall scatter is also less in limited FOV. Limited FOV is preferred over large and medium for endodontic applications since the area of interest is limited.[4] CBCT confirmed the diagnosis of horizontal root fracture at the junction of middle and apical third of tooth #11. It revealed a large radiolucent area (gray-scale value 89) between the fractured segments [Figure 1b]. The adjacent labial cortical plate was eroded. In comparison to the contralateral central incisor tooth #21, the apical root segment of tooth #11 was significantly (approximately 8 mm) displaced. It further revealed a periapical radiolucency around the fractured apical segment, indicating pulp necrosis (CBCT Periapical Index Score 1, Estrela et al.).[5] A treatment plan entailing nonsurgical endodontic treatment of coronal segment with orthograde mineral trioxide aggregate (MTA) barrier (ProRoot, Dentsply Tulsa Dental Specialties) and surgical removal of the displaced apical segment was made. The prognosis was explained to the patient and informed consent was taken. Orthograde MTA barrier was established, and obturation was done with thermoplasticized gutta-percha (Calamus Dual A1300, Dentsply Maillefer) [Figure 1c]. Profound anesthesia was achieved with 2% lignocaine (Lignonir 2%, adrenaline 1:200,000, Aculife Healthcare Pvt., Ltd., Gujarat, India). A trapezoidal flap was raised extending from distal surface of the right maxillary lateral incisor tooth to the distal surface of the left maxillary central incisor tooth. The apical root fragment was removed, and 3-0 silk sutures were placed. Postsurgical crown root ratio was optimum (1:1) [Figure 2a]. At 3-year follow-up, the patient was asymptomatic, and the radiograph revealed the re-establishment of the original periapical architecture [Figure 2b].

Figure 1

(a) Intraoral periapical radiograph of tooth #11 revealed a horizontal root fracture at the junction of middle and apical third, blunting and loss of lamina dura of the root segment coronal to the fracture, widening of the fractured line, and substantial linear displacement of the apical segment. (b) Cone-beam computed tomography image (sagittal section) of tooth #11 confirmed the diagnosis. A large radiolucent area (gray-scale value 89) between the fractured segments, suggestive of granulation tissue. (c) Intraoral periapical radiograph of tooth #11. Orthograde mineral trioxide aggregate barrier and obturation with thermoplasticized gutta-percha

Figure 2

(a) Intraoral periapical radiograph of tooth #11. Postsurgical crown root ratio of (1:1) was achieved. (b) Intraoral periapical radiograph of tooth #11. Three-year follow-up revealed uneventful healing and re-establishment of the original periapical architecture

DISCUSSION

Frontal traumatic impact invariably results in root fracture. As a consequence, shearing compression zones develop labially and lingually, dictating the plane of fracture.[1] Histology studies have demonstrated periodontal ligament injury and laceration of pulp at the level of fracture. This is the site where fracture healing is initiated. The response of the pulp depends on its integrity. When it is intact, odontoblast progenitor cells are recruited, creating a hard tissue dentin bridge between the fractured segments. This forms the callus which stabilizes the fracture. It is followed by deposition of cementum. This type of healing is predominantly seen in cases with little or no dislocation of the coronal fragment and occurs most often in teeth with immature root formation. In case the pulp is severed or stretched at the fracture site, revascularization of the coronal pulp is initiated. Simultaneously at the site of fracture, there is ingress of periodontally derived cells that result in union of the coronal and apical root fragments by interposition of connective tissue. When root fracture occurs before complete growth of the alveolar process, healing proceeds with interposition of connective tissue and bone. These healing modalities are considered as favorable outcome.

In the case under consideration, the tooth did not respond to pulp sensibility test. The radiograph revealed blunting and loss of lamina dura of the root segment coronal to the fracture. Widening of the fractured line, rarefaction of the alveolar bone, and substantial displacement of the apical segment were evident. This could be attributed to healing and pressure generated from the expanding granulomatous tissue that was interpositioned between the fractured segments. This resulted in an atypical radiographic presentation. A similar radiographic picture may be apparent in cases where trauma occurs before the complete growth of the alveolar process. Here, the coronal fragment continues to erupt, while the apical fractured segment remains stationary.[6] However, in the case under consideration, the subject was 19 years old when he sustained the injury, and the growth of the alveolar process would have been completed. In addition, a concomitant intrusive luxation and root fracture injury could also have resulted in a similar radiographic appearance. However, this injury is characterized by the axial displacement of the teeth into the alveolar bone, reduced clinical crown length, and expansion of the labial alveolar bone.[6] A case under discussion did not exhibit these features.

Meister et al. reported two cases that exhibited displacement of apical portions of the root. This spreading apart or movement occurred long after obturation of the canal. It was postulated that the pressure from the proliferating chronic inflammatory granulation tissue was instrumental in causing the migration of apical portions of the root.[7] Dua et al. reported a case of an endodontically treated mandibular second premolar. The periapical radiograph gave an impression of an additional distal root. Examination of the extracted tooth revealed a complete vertical root fracture extending from the mesial to distal surfaces across the pulp chamber and extending up to the apical foramen. The smaller buccal fragment had got displaced, giving a radiographic appearance of a distinct second root. The unusual gross displacement of the fractured segment was ascribed to the formation of granulation tissue between and around the fractured segments, gradually pushing them apart.[8] Hirschfeld (1932) reported seven illustrious cases of teeth drifting from their original position and location. The expanding pressure of growing granulomatous tissue in a pyorrheal pocket was deemed as the cause. They concluded that there was a dynamic relationship between pathologic migration of teeth and inflammatory tissue in periodontal pockets.[9]

Root fractures are not readily discernible on periapical radiographs. The central X-ray beam must pass within a maximum range of 15°–20° of the fracture plane for them to be visible.[10] Hence, there is a possibility of missing the horizontal fracture on two-dimensional (2D) radiographs. CBCT imaging has made diagnosis of root fractures predictable.[11] Kamburoǧlu et al. (2009) demonstrated the effectiveness of this imaging modality in the detection of simulated horizontal root fracture and concluded that limited CBCT outperformed the 2D intraoral conventional as well as digital radiographic methods.[12] Costa et al. conducted a study with the aim to test the accuracy of small-volume (0.2 mm voxel resolution) CBCT in detection of horizontal root fracture with the presence and absence of intracanal metallic post. It was concluded that small-volume CBCT showed high accuracy in detecting horizontal root fractures. However, the presence of a metallic post significantly reduced the specificity and sensitivity.[10] May et al. concluded from a database research that CBCT was useful to rule out false negatives, i.e., a suspected root fracture not visualized with conventional radiography. Furthermore, for a root fracture in the middle third, CBCT may eliminate or confirm an oblique course of fracture involving the cervical third in the labiolingual dimension.[2] American Association of Endodontists (AAE) and the American Academy of Oral and Maxillofacial Radiology (AAOMR) Joint Position Statement (2015) for the use of CBCT in endodontics recommend the use of this imaging modality for diagnosis and management of dentoalveolar trauma, especially root fractures.[4] Microcomputed tomography (micro-CT) is a non-destructive technique that provides quantitative and qualitative information of the root canal anatomy with higher resolution and accuracy as compared to CBCT. However, its application is limited to ex vivo use. Moreover, micro-CT devices allow higher degree of rotation of the specimen (360°) as compared to CBCT (200°). While CBCT is used as a diagnostic aid in a clinical scenario, micro-CT is used in laboratory studies, notwithstanding the fact that it allows for future improvements in CBCT scanners.[13]

In the context of the present case, CBCT aided both in the diagnosis and in the treatment planning. When the traumatized tooth was subjected to CBCT imaging, it revealed periapical pathology (CBCT Periapical Index Score 1, Estrela et al.) associated with the segment apical to the fracture.[5] This confirmed that the segment had become nonvital, necessitating its removal. Hence, a surgical approach was undertaken. In a scenario, if the apical segment would have maintained its vitality (in mid-root fractures, the apical segment tends to remain vital and can be left in situ), nonsurgical endodontic therapy followed by MTA barrier in the segment coronal to the fracture would have sufficed. Furthermore, based on the gray-scale values (89) obtained on the CBCT scan, it could be conjectured that the tissue interpositioned between the fractured segments was granulation tissue. Simon et al. compared the differential diagnosis of large periapical lesions (granuloma versus cyst) to traditional biopsy using CBCT. Large lesions were scanned, and a preoperative diagnosis based on gray-value measurements of the imaged lesion area was made. After surgery, a biopsy was done. In 13 out of 17 cases, the diagnosis coincided. Hence, it was concluded that CBCT may provide an accurate diagnosis without invasive surgery.[14] Shekhar and Shashikala used CBCT for diagnosis, treatment planning, and long-term follow-up of large periapical lesions treated by endodontic surgery. They highlighted that CBCT was found to be an accurate diagnostic method to identify large periapical lesions based on the gray-scale value.[15]

CONCLUSION

Diagnosis in dental trauma can be a challenge for even the most astute clinician. This is primarily because of the variability in the clinical and radiographic presentation. “The eyes only see what the mind knows;” hence, it is prudent to understand the underlying pathophysiology of root fracture healing. This would help us to encompass the spectrum of typical and atypical healing patterns. In the present case, the uncharacteristic radiographic finding could be attributed to the pressure generated from the expanding granulation tissue. Advancements in imaging modalities in the form of CBCT have come as a boon for the clinicians. AAE and AAOMR recommend the use of limited FOV CBCT in endodontics Primarily for diagnosis of cases that present with non specific signs and symptoms, for detection of vertical root fractures, for non-surgical/surgical re-treatment and in understanding complex morphological variations.[4] It, however, comes with its own demerits in the form of possible higher radiation dose, potential for artifact generation, high levels of noise and scatter, and variations in dose distribution.[4] Limited FOV CBCT has overcome most of the limitations encountered with 2D radiography. It can be an important aid for diagnosis and treatment planning in dental trauma when used cautiously and judiciously.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.