Introduction

Horizontal root fracture (HRF) is a combined injury of the pulp, dentin, cementum and periodontal ligament. It is a relatively uncommon type of dental trauma with the frequency of 5-7% of all dental traumatic injuries. The location of the fracture line may vary from coronal and middle third to the apical third. The type of healing at the fracture line depends on a number of determining factors including the patient’s age, closeness of the fragments after fixation, absence of infection and stage of root development (1-8). Based on the interposition of different kinds of tissues, there are four types of histological reaction at fracture line; type I: calcified tissue; type II: connective tissue; type III: bone and connective tissue and type IV: granulation tissue. Type IV is considered as a non-healing pattern since an infected or necrotic pulp in the coronal fragment causes it (1, 2).

HRF generally has a good prognosis of healing at fracture line after repositioning and flexible splinting, as documented by many studies (1, 2, 8-21). However, various factors such as sever dislocation and/or delayed initiation of the treatment seem to have an unfavorable influence on close reduction of the displaced coronal fragment, which locked firmly and subsequently on the long-term prognosis.

The aim of this report is to illustrate clinical and radiologic outcomes of two cases with HRF with displaced coronal fragments firmed in place.

Case Report

Case 1: A 25-year old woman with HRF and displaced coronal fragments in her maxillary central incisors referred to Dental Trauma Clinic, ACECR, Mashhad, Iran, 1 week after trauma. Her medical history was noncontributory and no injuries were observed in the adjacent teeth or soft tissues except for a prominent swelling in the buccal area, possibly arising from an alveolar fracture. Fighting was the etiology of root fractures. She presented Class I occlusion with competent lips.

Both coronal fragments had been displaced palatally and had firmed in place, resulting in serious interference with occlusion (Fig. 1). The periapical radiograph showed severe displacement of the coronal fragments in both teeth (Fig. 2). While the right upper central incisor was replaced to its original position correctly, repositioning with digital maneuver was not successful for the left one. Despite questionable prognosis for this case, close reduction and flexible splinting were performed following its coronal fragment removal, minor curettage in alveolar socket and immediate replantation. Calcium hydroxide (Densply/Caulk, Tulsa, OK) dressing and mineral trioxide aggregate (MTA; ProRoot; Dentsply Dental, Tulsa, OK) plug placement for coronal fragment were carried out after 1 and 3 weeks, respectively (Fig. 3). The crown was restored with composite resin (3M Unitek, Monrovia, CA) and a minor permanent splint was applied after removal of the flexible splint (8 weeks). At 4-year follow-up, complete healing at fracture lines was revealed in the periapical radiograph and the teeth were clinically functional and the patient was asymptomatic (Figs. 4 and 5). The CBCT image also showed the proximity of fractured parts (Fig. 6). The healing pattern of the fracture lines seemed to be interposition of connective tissue in both teeth.

Case 2: A 17-year-old boy was referred to Dental Trauma Clinic, ACECR, Mashhad, Iran, 3 weeks after trauma. HRF was observed in his left maxillary central incisor and the displaced coronal fragment had been firmed and locked in place (Fig. 7). The patient history was non-contributory and there were no injuries in the adjacent teeth or soft tissues. Fighting was the etiology of root fractures. Occlusion of the patient was Class I relationship with competent lips.

Close reduction with digital pressure was impossible because of sever dislocation and delayed referral. Therefore, the above-mentioned protocol for case 1 was applied for this case. First, the coronal fragment was loosened by forceps (Dena, Tehran, Iran), then repositioned gently and finally fixed with flexible splint for 8 weeks. Pulpal removal and calcium hydroxide (Densply/Caulk, Tulsa, OK) dressing for coronal fragment were carried out after 1 week and then MTA (ProRoot; Dentsply Dental, Tulsa, OK) plug was placed in the coronal fragment after 3 weeks (Fig. 8). The crown was restored with composite resin (3M Unitek, Monrovia, CA) and a minor permanent splint was applied after removal of flexible splint.

As evidenced by the periapical radiograph, complete healing at fracture line was obvious at 4-year follow-up and the tooth was clinically functional and the patient was asymptomatic (Figs. 9 and 10). The healing pattern of the fracture line seemed to be the interposition of bone and connective tissue.

 Figure 1: Initial photograph indicating the palatally displacement of maxillary central incisors

 Figure 2: Initial radiograph indicating the fracture lines in both maxillary central incisors

Figure 3: Final radiograph indicating placement of MTA plug

 Figure 4. Radiographic view after 4-years follow-up indicates healing in fracture lines

Figure 5. Clinical view after 4-years follow-up

    Figure 6. The CBCT image showed proximity of fractured parts in both incisors

Figure 7. Initial radiograph indicating the fracture line in the left maxillary central incisor, 3 weeks after trauma

Figure 8. Final radiograph indicating placement of MTA plug

Figure 9. Radiographic view after 4-years follow-up indicates healing in fracture line

Figure 10: Clinical view after 4-years follow-up

Discussion

HRF most commonly occurs in the maxillary anterior region. The coronal fragment of a root-fractured tooth frequently shows extrusion and displacement to the palatal/lingual region (1, 2). According to the guideline released by International Association of Dental Traumatology (6) and the American Association of Endodontists (7), the emergency treatment for HRF is optimal repositioning as soon as possible, flexible splinting (4 weeks or longer) and follow-up of the healing process at fracture line. In 75% of cases, healing will happen and it will not be necessary to remove the coronal pulp. Whenever there are signs or symptoms of a non-healing process at fracture line (25%), the coronal pulp must be extirpated (1, 2).

Different types of healing may depend on proximity of the fragments, fixation of the fragments as soon as possible and absence of infection (18-21). Success rate for midroot fractures has been estimated to be 80% (1, 2).

In many cases with tooth displacement, the patient requires medical care for concomitant head trauma prior to dental care; also, some patients spend a great deal of time to find a dentist who provides them definitive dental treatment. When the time interval between trauma and treatment is extended, the treatment of tooth displacement becomes more complicated. This may be a major concern in planning the treatment for these patients and therefore the general protocol may be non-indicative in some of these complicated cases. Since there is considerable swelling and fluid accumulation around the displaced tooth, it is very difficult, if not impossible, to reposition it without additional luxation or extraction/reimplantation. In addition, in sever dental injuries,  trauma breaks the facial plate of bone or disturbs the alveolar socket wall to the point that it is impossible to replace the tooth in its original position. In both mentioned cases, repositioning with digital pressure was not successful because of delayed referral and the severity of trauma. In these types of situations, the clinician may wish to consider orthodontic treatment as an option to reposition the displaced tooth into the correct position (22). However, since occlusal interference was too severe, a rather faster approach seemed necessary. Therefore, after loosening the displaced coronal fragment in case 2, and removal with forceps followed by minor curettage of alveolar socket in case 1, close reduction was performed successfully.

For the replanted fragments, pulpal necrosis was an inevitable consequence. To prevent non-healing pattern at fracture lines which compromise the long-term prognosis, endodontic treatment including pulpal removal and intracanal dressing for coronal fragment were carried out 1 week after repositioning.

As this treatment protocol was successful in the reported cases, it seems that in some instances, some modifications in the general protocol may be helpful.

Conclusion

A promising finding from the present cases is that healing at fracture line is very likely to happen even in cases of HRF with delayed referral and sever dislocation, which has been replanted after extraction of coronal fragments.