Spontaneous healing response of oblique root fracture: case report with 4-year follow-up

Root fractures can involve the dentin, cementum, and pulp and commonly can occur as oblique fractures with varying orientations. The aim of this study was to demonstrate the maintenance of pulp health in a tooth with a fractured root without any endodontic treatment and to discuss the advantage of cone-bean computed tomography (CBCT) compared with traditional radiographs in the diagnosis of oblique root fractures. Intra-oral radiography of tooth 11 revealed a horizontal root fracture at the level of the apical third, while the sagittal CBCT slice reveals a complete fracture line running obliquely from the apical third on the buccal aspect through the cervical third on the palatal aspect. Four years follow-up, the tooth has kept its pulp vitality, no tooth discoloration or discrepancy in arch position, without endodontic treatment. This result illustrates spontaneous healing of root fracture including preservation of pulp health. In addition, it confirms the importance of exams in 3 dimensions to correctly locate the fracture and assist in the treatment decision.


Introduction
Transverse root fractures can occur as oblique fractures with varied orientations and initial diagnosis must be based on clinical findings and radiographic examination (Abbott et al, 2019). Clinical examination includes pulp testing, evaluation of the degree of mobility, tooth position in the arch and presence of pain on palpation of the soft tissues (Polat-Ozsoy et al. 2008).
In clinical practice, intraoral radiography has been the technique most commonly used to detect root fractures. However, oblique root fractures can be overlooked because of the beam angulation. CBCT imaging offers the advantage over intraoral radiography that the location, extent, and direction of a root fracture can be visualized in all three dimensions (Bornstein et al. 2009, May et al. 2013, Makowiecki et al. 2014. Detection efficiency of the correct location and the type of root fracture are essential aspects in determining appropriate treatments. Immediate treatment with repositioning of the coronal fragment and optimal splinting seem to favor healing (Abbott et al, 2019). The splinting method with a certain flexibility of the splint are appropriate for teeth with luxation injuries and root fractures (Andreasen et al. 2004).
Pulp sensibility testing still represents the most widely used diagnostic procedure for the assessment of pulp status immediately after an acute dental trauma and should be performed initially and at each follow-up appointment in order to determine if changes occur over time, due to the temporary loss of pulpal sensibility after trauma (Cvek et al. 2002, Bastos et al. 2014, Alghaithy & Qualtrough, 2017. Pulp necrosis and infection of the pulp space in the coronal fragment may occurs, leading to granulation tissue in the fracture line while the pulp in the apical fragment of the root remains normal because the blood supply at the apical foramen has not been affected (Ferrari et al. 2006). In this cases, endodontic treatment is limited to the coronal portion only.
Healing of an oblique root fracture may occur by calcified tissue, interposition of fibrous connective tissue and the interposition of bone and periodontal ligament around both fractured segments. Granulation tissue may form in the fracture line as a result of pulp necrosis and infection (Andreasen & Andreasen, 2018).
This case report describes the treatment of oblique root fracture of maxillary central incisor that presented pulp vitality in both coronal and apical segments after 4-years of follow-up, without endodontic therapy recommendation. The location of the fracture and its longitudinal length was detected by CBCT images

Methodology
The case report presented composes an article with demonstrative and descriptive, exploratory purposes, exposing a qualitative approach, made through the direct technique of Pereira et al (2018), in which the researcher is an essential instrument.

Case Report
As a result of a traffic accident, a 19-year-old male presented with root fractures of the right maxillary central incisor with complete root formation. The patient sought dental care 2 days after trauma. No periodontal injury, signs of soft tissue damage or subjective symptoms were observed. There was no sensitivity to palpation, but the traumatized tooth was sensitive to percussion. The radiographic examination of the upper anterior region revealed a horizontal root fracture at the level of the apical third in the upper right central incisor. (Figure 1A). However, the sagittal CBCT slice of tooth 11 reveals a complete fracture line running obliquely from the apical third on the buccal aspect through the cervical third on the palatal aspect ( Figure   1B). The upper left central and lateral incisors responded normally to the pulp testing with cold spray (Endo Frost, Roeko, Germany). The upper right central incisor did not respond. The immediate treatment consisted of the reduction of the root fragments and splinting with an orthodontic wire and photopolymerizable composite resin extended from canine to canine, which remained for 2 months ( Figure 1C). After 60 days the splint was removed and the tooth responded positively to the pulp test and presented physiological mobility.
After 4 months, the tooth is still positive to sensitive tests. From then on, semiannual controls were performed for up to 2 years. Thereafter, assessments became annual to assess fracture healing and maintenance of pulp vitality.
After 16 months, obliteration of the pulp space was observed in the radiographic images, although the tooth is still positive to pulp testing (Figure 2). Three years later, a clinical and radiographic examination was performed and no signs or symptoms were observed. A new tomographic examination was requested and mineralized tissue interposition was observed in the fracture region, without any resorptive alterations, periradicular lesion or ligament thickening (Figure 3). Four years later, the tooth is well positioned in the maxillary arch and has kept its pulp vitality, despite pulp space obliteration, no tooth discoloration or discrepancy in arch position. (Figure 4).

Discussion
In the present study, the sagittal CBCT slice of tooth 11 reveals a complete fracture line running obliquely from the middle third on the facial aspect through the cervical third on the palatal aspect, rather than the horizontal fracture that was diagnosed on periapical radiographs. The location of horizontal root fractures seen on conventional radiographs and CBCT may be different and the application of CBCT can aid in the accurate diagnosis of root fracture (May et al. 2013, Wang et al, 2011, Rothom & Chuveera, 2017. Although, higher image resolution in digital intraoral radiography seem to enhance the accuracy of horizontal root fractures diagnostic imaging, root fractures might not be visible radiographically if the X-ray beam doesn't pass directly through the fracture line (Bornstein et al. 2009, Likubo et al. 2009, Nejaim et al. 2016. In this case the root fracture was diagnosed at the time of injury (after two days) and was splinted with orthodontic appliance for two months. However, root fracture may heal spontaneously without any treatment. It appears that there is no significant relation between the treatment delay and type of healing (Andreasen et al. 2004, Chala et al. 2009). Rapid healing of a periodontal ligament wound doesn't require a longer splinting period. However, stabilization for 2 months was needed because a part the fracture was located cervically.
The International Association of Dental Traumatology (IADT) guidelines recommend endodontic treatment only after pulp necrosis (Bourguignon et al. 2020). An initial negative response to the sensitivity tests does not indicate the further development of pulp necrosis, because the tooth may remain vital even though it does not respond to sensibility tests 18. In the present study, the absence of a response to pulp sensibility tests in the initial visit confirm that transition from a negative to a positive response to sensibility tests, and it can be explained by the transient damage to pulpal nerve fibers. For this reason, the immediate pulp test should not be used to indicate root canal treatment at this early stage (Abbott et al, 2019, Bastos et al. 2014).
Healing with dental hard tissue, in this case, may have occurred because there was only a minimal displacement of the coronal fragment with immediate repositioning. Therefore, the pulp tissue was not damaged or suffered minimal displacement, becoming slightly elongated, but maintaining its blood supply. If the blood supply to the coronal fragment was cut off at some point, revascularization may have occurred, since once the coronal fragment was repositioned (Abbott et al, 2019).
Pulp space obliteration is a common root fractures post healing complication and usually indicates the presence of viable tissue within the root canal (Jacobsen & Kerekes 1980, Heithersay & Kahler, 2013. Apposition of hard tissue on the dentinal walls was observed, leaving only a tiny pulpal lumen. However, pulp necrosis and periradicular inflammation has so far not been observed. Pulp space obliteration had no adverse effect on the survival of the tooth and this is in accordance with previous reports (Cvek et al. 2008).

Conclusion
The present study reports a clinical case worthy of discussion around of differential diagnosis, decision making and management based on clinical guidelines. The follow-up with CBCT and pulp testing showed it to have been the best choice to follow the healing process avoiding unnecessary radical endodontic treatment. Four years later, the tooth has kept its pulp vitality despite the obliteration of the root conduct.