Root fractures in primary and permanent teeth: a review

Dental trauma injuries today account for up to 5% of all dental emergencies in children and young adults (IADT, 2012). A wide range of injuries can be encountered by trauma, which can vary from a simple enamel infraction to complete tooth avulsions (IADT, 2012). While crown fractures are more common, root fractures account for 0.5-7% of all dental traumas to the permanent teeth and 2-4% to the primary (Poi et al., 2002). It was noted that lower percentage of dental trauma in primary dentition is due to the elasticity of the alveolar bone socket which can absorb the impact by acting like cushion (Andreasen et al., 2007). Moreover, with a lower crown to root ratio, such teeth are more susceptible to luxation injuries than to fractures (Glendor, 2008).

In particular, root fractures are fractures that involves dentin, cementum and pulp (Castro et al., 2005). These fractures frequently occur between 2-6 years of age in primary dentition and in 11-20 in permanent dentition (Glendor, 2008) In most cases, the etiology of these fractures ranges from fall accidents including sports and traffic accidents to parafunctional habits, traumatic occlusion or iatrogenic causes (Castro et al., 2005). Additionally, the root fracture in the anterior teeth usually occur from direct impact of trauma and posterior teeth from indirect (Popescu et al., 2017)

Root fractures are classified according to the direction of fracture line of to the axis of the tooth, where we can have either vertical or horizontal root fracture (Andreasen et al., 2007). Horizontal root fractures can be further divided in subclassifications according to position of the fracture line in the root to apical location, middle or cervical (Glendor, 2008). Other classification includes, partial or complete according to the extent and to simple or multiple according to the number of fracture lines (Glendor, 2008). Lastly, the coronal segment of horizontal fracture can be either displaced or present. On the other hand, vertical root fractures are fractures that extend along the length of the axis of the tooth and can be subdivided to complete and incomplete according to the fragment separation and to supra-osseous or intraosseous in relation to the fracture position (Lertchirakarn et al., 2003).

Root fractures are commonly overlooked by the practitioner and discovered on a routine radiograph, therefore, diagnosing root fracture early with extensive clinical and radiographic examination can provide better treatment outcomes and prognosis of the tooth in question (Andreasen et al., 2007). It is important to note that diagnosis can be rendered difficult initially in trauma patients as the practitioner can deal with an anxious child’s first visit to the dental office because of trauma specially in the primary dentition (Prithviraj et al., 2014). Considering this, primarily the first thing to do when a patient present to the clinic is to look for bleeding, facial laceration and hematoma (Cardoso & Rocha, 2004). Then the child and parent must be reassured, medical history and trauma history must be taken, trauma history must involve when the incidence took place with exact time if feasible, location of the incident and how it occurred (IADT, 2020). Obtaining this information can be mandatory for legal purposes to fill in a trauma report (IADT, 2020) and is important to determine if bacterial contamination is apparent, which may necessitate a tetanus vaccine or a systemic antibiotic infusion. (Fuss et al., 2007). Extraoral examination must be done to rule out facial bone fractures, facial asymmetry and condylar fractures which can be presented with limited mouth opening (Cardoso & Rocha, 2004). Additionally, serious neurological consequences may be a result of the trauma so the practitioner should ask about associated symptoms following injury such as loss of conscious, drowsiness, vomiting (IADT, 2012).

Intraoral Examination

After systemic examination extra-orally for hard and soft tissue injuries, intraoral exam is done for the gingiva, frenum and oral mucosa for lacerations, hematoma or embedded tooth fragments (IADT, 2020). A common feature of root fractures can involve bleeding from gingival sulcus or may appear slightly extruded and slightly lingually displaced due to labial position of the impact to the tooth (Andreasen et al., 2007). This displacement and mobility are depended on the extent of impact and position of the fracture line to the crestal bone (Andreasen et al., 2007). Furthermore, patients presenting are most commonly asymptomatic, however, pain to percussion and palpation is noted with root fractures (Lertchirakarn et al., 2003).

In the horizontal root fracture, the position of the line of fracture affects the displacement or degree of mobility, for instances in the apical third there is usually no displacement or mobility. On the other hand, the middle third fractures present with tooth that is slightly extruded and displaced (Kamburoglu et al., 2009). Additionally, in the cervical third there is also displacement and minor to extreme mobility (Kamburoglu et al., 2009).

These clinical findings are usually similar to luxation injury and it’s not possible to distinguish the type of trauma depending solely on the clinical examination, therefore, diagnosis must be confirmed with radiographic examination (IADT, 2020).

Radiographic Examination

The key component for diagnosis of any trauma injury is considered to be the radiographic examination (IADT, 2020). In case of a root fracture to be detected radiographically, it can only be visible once the beam of the x-ray is in line of the plane of fracture (Andreasen et al., 2007). However, unfortunately some root fractures are misdiagnosed because of the close proximity of the fragments where they will be only later when the diastasis between the fragments is increased (Versiani et al., 2008).

Different approaches can be utilized to capture the root fracture radiographically. First, the multi-directional approach, this comprises of a central periapical x-ray with two extra periapical x-rays at varying angle of plus or minus 15-20 degrees from the conventional beam (Andreasen et al., 2007). Secondly, is utilizing two periapical x-ray exposures at different angles in addition to an occlusal exposure (IADT, 2020).

Lastly, it was mentioned in the literature that Cone-beam computed tomography (CBCT) can be used in trauma patients because of the several advantages such as increased accuracy, high resolution with reduced scan time and elimination of superimposition of surrounding structures (Likubo et al., 2009). On the contrary, the disadvantages such as high cost, the need of special equipment and training and high radiation exposure to the patient, limits its use in the pediatric dentistry (IADT, 2020).

Pulp Testing

This diagnostic modality is usually difficult in a traumatized child due to anxiety and existing pain from trauma therefore if performed can give false-positive (Malhotra et al., 2011). On other instances, immediate pulp testing at the time of trauma can give negative responses which means there is transient pulp damage (Malhotra et al., 2011). However, pulp tests have to be taken at the time of injury to be recorded as a baseline and compared with findings at future follow up visits (IADT, 2020). The normal pulp reaction is expected to be back after 6 weeks from the time of trauma (Fuss et al., 2007).

As in any trauma case in the primary dentition, the priority of the treatment is to avoid any injury to the permanent successor (Andreasen et al., 2007). This is due to the close proximity of the apex of the primary teeth to the developing permanent successor (Ranka, 2013). The choice of treatment therefore is dependent on the child's cooperation and level of maturity, the underlying permanent successor and the exfoliation time of the tooth (Ranka, 2013).

In case of root fracture at the apical third, the tooth may present slightly mobile or with no mobility with minimal or no displacement (Skaare & Jacobsen, 2005). Moreover, the fragment is usually away from the developing tooth germ, therefore, in this case we can only monitor the tooth, and no further treatment is indicated (Skaare & Jacobsen, 2005).

When encountered with a middle or cervical third root fracture, the coronal fragment of the tooth is displaced and loose which can present a high risk of aspiration of the fragment and possible airway complication (IADT, 2020). Hence, extraction of the coronal fragment is indicated, and the apical fragment can be left to resorb physiologically without disrupting the developing tooth germ (Cardoso & Rocha, 2004).

Another option for treatment is repositioning the coronal tooth segment along with a flexible splint for 4 weeks (Welbury et al., 2005). However, splinting is not practical and difficult due to small tooth size and limited patient co-operation in the primary dentition (IADT, 2020).

In conclusion when treating primary teeth with root fracture in an emergency situation, the most appropriate treatment option is observation, unless we encounter an extremely mobile coronal fragment which can pose a risk of aspiration, interference with the occlusion or signs and symptoms of infection then extraction is ideal (IADT, 2020)

In regards of the follow up, it is done is on 1 week, 6-8 weeks, then 1-year intervals until the permanent successor erupt (IADT, 2020) The follow up must thus include clinical and radiographical examination (Prithviraj et al., 2014).

The possible outcome can either be pulp healing and normal physiological resorption or signs of pulp infection, this presents as abscess, gingival swellings and sinus tract with increased mobility and/or dark/grey tooth discoloration (Prithviraj et al., 2014).

Additionally, radiographically the tooth will present with inflammatory root resorption (Fuss et al., 2007).

It is advised that the patient must exercise a soft diet for up to 10-14 days to avoid further trauma to the tooth (Ranka, 2013) with the use of soft toothbrush or gauze soaked with 0.2% chlorhexidine to wipe around the tooth and surrounding area twice daily, this can encourage the gingival healing and reduce plaque (IADT, 2020).

The parents are asked to observe for any change in color, or if child complains of pain to be referred to the dental practice (IADT, 2020).

Furthermore, the practitioner must explain the possible complications related to trauma to the parent. These complications are seen in permanent successors, it can occur due to pulpal necrosis or followed by trauma of primary teeth (Ranka, 2013). Factors affecting the extent of damage to the permanent successor depends on the age of the patient at the time of injury, stage of development of the permanent tooth and lastly the intensity and type of trauma (Welbury et al., 2005).

The complications can vary from mineralization disturbances to complete tooth and root malformations and disturbances in sequence or pattern of tooth eruption (Arx, 1993).

Common tooth malformation includes enamel hypoplasia, hypocalcification and crown/root dilacerations (Arx, 1993).

In the permanent dentition, when the practitioner encounters a tooth with root fracture the primary aim of treatment is to maintain tooth vitality with encouraging the union of two fragments with hard tissue structure, this is considered the best outcome of root healing (Versiani et al., 2008). In addition, when presented with immature tooth with an open apex, treatment aims for a continued root formation and apex closure (Popescu et al., 2017).

In horizontal root fractures treatment is determined by many factors such as the position of the fracture line, the extent of remaining coronal structure, the location of the fracture in relation to the crest of the bone and pulp vitality (Andreasen et al., 2007)

Apical root fractures

In the apical root fractures, the apical fragment is usually not displaced and therefore it is usually overlooked and detected in routine radiographs (Prithviraj et al., 2014).

In most cases clinically the tooth is asymptomatic and there is no mobility (Popescu et al., 2017). It is suggested that if the pulpal circulation in the apical fragment is not disrupted in most cases, there is a high chance that the fragment remains vital (IADT, 2020).

There are two scenarios in apical third fracture, in the first scenario the tooth has no mobility, no displacement and present with no symptoms, in this case the treatment is just monitoring. It was reported that in most cases spontaneous healing takes place in apical root fractures (Cardoso & Rocha, 2004).

In rare occasions, if the pulp undergoes necrosis surgical removal of apical fragment is indicated and apexification will be done for the coronal segment with a root canal filling (Andreasen et al., 2007). The chances of coronal segment to undergo necrosis is only 25% (Popescu et al., 2017).

The second scenario is when the tooth is displacement and mobile, therefore, the treatment is splinting with a flexible splint for 4 weeks. (IADT, 2020). In this case chances of apical segment necrosis are rare since the pulp circulation is not disrupted (Hovland, 1992).

It was shown that the apical-third horizontal root fracture has the best prognosis for maintaining pulp vitality and root healing (Andreasen et al., 2007).

Middle root fractures

In this type of fracture, the fracture line is positioned at the middle third of the root and therefore the treatment depends on, the degree of diastasis between fragments, displacement and mobility of the coronal fragment and the vitality of apical and coronal fragment (Hovland, 1992).

In cases when there is no mobility or displacement, the diastasis is small between fragments, therefore, only observe and follow up the patient for any future changes (Berman, 2007). However, in case of displacement, repositioning and immobilization is done after application of local anesthesia to avoid eliciting pain (Berman, 2007). Firm but gentle digital manipulation of the coronal fragment into position, then the position must be checked radiographically before splinting (IADT, 2020). Upon repositioning if there was any resistance then axial bone wall fracture must be suspected and surgical reduction must be done before repositioning and splinting (Biner et al., 2011). Repositioning aids in revascularization of the coronal aspect of the pulp if the blood supply was interrupted (Biner et al., 2011). In middle third fractures a flexible splint is applied for 4 weeks (Andreasen et al., 2007).

When considering the vitality of the coronal and apical segment different outcomes may arise after up to 3 months through the follow up, emphasizing the importance of clinical-radiographical vitality assessment after root fracture injury (Brandini et al., 2009).

For instance, after thorough clinical and radiographical analysis, the tooth present with negative response to pulp testing, discoloration of the crown of the tooth and radiographically shows radiolucency surrounding the fracture line (Biner et al., 2011). On the other hand, the apical segment shows normal periodontal space and no inflammatory resorption apically (Biner et al., 2011). Here the radiolucency is compared to the follow up radiographs to make sure it’s an ongoing infection, and then the coronal portion is treated with apexification to create an apical seal, this can be done with either an MTA plug or calcium hydroxide (Cvek et al., 2008). Whereas, the vital apical fragment is then left without instigating any additional treatment. Success rate for this treatment modality was reported up to 94% in the literature (Cvek et al., 2008).

Alternatively, in case of complete pulp necrosis of both apical and coronal segment with clinical signs and radiographic findings on apical and coronal segment (Westphalen et al., 2008). Initially RCT through the apical and coronal segment was practiced, however, this treatment was rendered difficult and shown to have a low success rate due to further separation of the fragments (Berman, 2007). Thus, apicectomy which is the surgical excision of the apical segment is considered with endodontic treatment of the coronal segment (Westphalen et al., 2008).

Cervical root fracture

Treatment of cervical third root fracture is considered the most challenging and carries the lowest prognosis (Canoglu et al., 2007). Whereas this treatment depends on whether the fracture line is exposed to oral cavity, the remaining root length and coronal segment presence or absence (Malmgren et al., 1991).

In case if the coronal portion is present and the fracture is below the crestal bone the treatment is reduction and splinting from 4 weeks and up to 4 months, to ensure stability of the coronal fragment (IADT, 2020). On the other hand, when the coronal portion is not present and the fracture is above the alveolar crest and root is of sufficient length, the practitioner can perform an endodontic treatment followed by post and crown (Parolia et al., 2010). If exposure of coronal margin is required, then gingivoplasty or apical flap can be performed for aesthetics and function (Parolia et al., 2010). Conversely, if the fracture line is below the alveolar crest, to ensure proper seating of the coronal restoration and clearance of the biological width, we can perform the following:

• Crown lengthening (1-2 mm of bone removed around the root) (Hempton & Dominici, 2010).
• Orthodontic extrusion, this is considered the best and most predictable treatment option and is relatively easy to be performed (Malmgren et al., 1991).
• Surgical extrusion, this is not usually recommended as it can lead to excessive bone loss (Hempton & Dominici, 2010).

If the fracture line is in an unfavourable position and the root length is insufficient for a proper a crown-to-root ratio. Therefore, the treatment is extraction of the tooth when conservative treatment is not possible. Decoronation was also suggested as an alternative approach which is preserving the apical segment of the root to maintain the alveolar bone for future implant placement (Malmgren, 2000)

The prognosis for spontaneous healing of the cervical root fractures is 2-9% (Berman, 2008). This is due to the lack of hard tissue union, bacterial contamination from the oral cavity and mobile short coronal segment (Prithviraj et al., 2014).

Splinting

The rationale behind splinting teeth is to reposition the tooth from its displaced position and to prevent further injury to the periodontal ligament or pulp during healing (Andreasen et al., 2007). This procedure is regarded as the ideal practice to maintain teeth in position with the advantage of the provided comfort for the patient and sustained function (IADT, 2020). Although there is controversy regarding the effect of the duration or the type of splint on the healing outcome of root fractured teeth (IADT, 2012). However, the current evidence suggests that the use of short-term flexible splint is recommended in most trauma cases including root fractures (Di-Angelis et al., 2012). Many types of splints were used in root fractures such as: 0.4 mm Stainless steel wire with composite resin, titanium splints, fiber splints and orthodontic bracket splints (Brown & Mackie, 2003). The ideal properties of a splint are easy fabrication, attachment and cleaning with the advantage of allowing pulp testing and endodontic access (Kahler et al., 2016). In addition, the splint shouldn’t interfere with the occlusion or irritate soft tissues (Kahler et al., 2016).

Healing of the root fracture depend highly on the interaction between the pulp and periodontal ligament at the fracture site, which is in turn influenced by the bacterial presence or absence (Andreasen et al., 2007). Suggested factors that contribute to the healing of the root fractures include the mobility and position of the coronal segment in relation to the apical fragment, the vitality of the pulp, diastasis between the fracture segments, tooth maturity and communication with oral environment (Herweijer et al., 1992).

Andreasen et al. (1967) suggested four scenarios for the healing for root fractures, the first type is called the calcific union, here the root fragments heal in the most desirable way by forming a hard tissue connection, radiographically the fracture line would still be visible but with no accompanied radiolucency. Only 30% of the cases heal with this type (Versiani et al., 2008).

The second type of union is by connective tissue formation, in this type of union there will be a thin radiolucent line between the fragments with the edges rounded, this type of healing is the most common one and it’s seen in 43% of cases (Andreasen et al., 2004; Berman, 2007).

The third type of healing is by bone and connective tissue, it is rarely seen, only 5% of the cases. Radiographically it appears as a separate lamina dura surrounding each fragment (Versiani et al., 2008; Berman, 2007). Lastly is healing with a granulation tissue or non-union which occurs by formation of granulation tissue that resulted from persistent inflammation, the granulation tissue either originates from the gingival sulcus or from the necrotic pulpal tissue, this is seen in 22% of the cases (Andreasen et al., 2004; Berman, 2007).

Vertical fractures are rare accounting for 2-5% of root fractures. This type of fracture is considered very challenging to treat and diagnose. (REF) Most reported cases are seen in older patients and in posterior teeth with non-vital pulp and are endodontically treated. There are two types, complete and incomplete vertical fracture.

The etiology of vertical fracture is usually iatrogenic, by over preparation of the canal where most of these teeth have excessive restoration and post and core (Kawai & Masaka, 2002). The most susceptible teeth for vertical root fractures are the premolars followed by molar teeth, vertical fractures are rarely seen in anterior teeth, the orientation of the fracture line in posterior teeth is in the buccolingual direction and is noted in individual roots. (REF)

Treatment of anterior teeth is ideally extraction, however, in the posterior teeth, other options are considered such as root hemisection or complete root amputation (Mokbel et al., 2019).

Follow up

The treatment outcomes can only be confirmed by regular follow up, as late complications may frequently but not always occur (Davidovich et al., 2005). It is important to note that the follow up intervals must be done at 4 weeks, 6-8 weeks, 6 months, 1-year intervals (IADT, 2020). This follow up is comprised of clinical and radiographic examination (IADT, 2020).

Sequelae of root fractures

The commonly seen changes in the injured tooth are pulp canal obliteration, pulp necrosis and root resorptions, root resorption include external, internal and replacement resorption (Berman, 2007).

Pulp canal obliteration

Pulp canal obliteration is the most commonly seen sequelae of root fractures, it occurs in 69-73% of cases (Welbury et al., 2002). Clinically, it is identified when the crown becomes yellowish in color and radiographically it appears as an opacification of the canal space (McCabe & Dummer, 2012).

It should be noted that the pulp is vital in most cases, that’s why if no additional pathology exists, no further treatment is indicated (McCabe & Dummer, 2012).

Pulp necrosis

Pulp necrosis is a sequela of persistent inflammation and or contamination of the fracture site, this is apparent in 22% of the cases (Andreasen et al., 2004). Signs of pulpal necrosis that are commonly seen in follow up visits are the development of clinical symptoms, radiolucency in the periapical area and/or at the fracture site. In addition, in later stages discoloration of the crown can be apparent (Andreasen et al., 2004). Moreover, immature teeth with incomplete root formation can present with arrested root development and open apices, which indicate necrotic pulp change (Berman, 2007).

Root resorption

Inflammatory response can result in various types of root resorption such as external and internal resorption, external resorption was observed in 60% of root fractured teeth (Andreasen et al., 2007), it is usually self-limiting and can resolve within 1-2 years. Another type of external root resorption is replacement resorption also known as ankylosis, in this case there is no effective treatment possible to resolve this, literature suggest that Decoronation can be considered in order to maintain the alveolar bone for future implant placement (Malmgren, 2000). On the other hand, internal resorption is coincident with chronic pulp inflammation (Andreasen et al., 2007). Although it is not common in root fractures, but it can be detected clinically, when pink discoloration is seen in the crown (Ranka et al., 2012). Pulp extirpation and root canal therapy must be done readily when discovered to avoid root perforation (Berman, 2007).

Conclusion

Management of root fractures in pediatric dentistry can be a challenging procedure, where applying knowledge and understanding of recent treatment modalities can lead to the best outcome possible. In the primary dentition, the goal is to prevent further injury to the permanent successor. On the other hand, in the permanent, we aim to retain the tooth by allowing root healing with calcific union, in addition to maintaining the pulp vitality. Diagnosis and regular follow up are emphasized to initiate the proper treatment timeously and encountering any future complications.