Combined treatment of surgical extrusion and crown lengthening procedure for severe crown-root fracture of a growing patient: a case report
Crown–root fracture (CRF) is a fracture involving the enamel, dentin, and cementum with or without pulp involvement, whereas cervical root fracture involves the cementum, dentin, and pulp extending from the alveolar bone crest up to 5 mm below . The prevalence of CRF is 5% in permanent dentition, while all root fractures affect 0.5–7% of permanent teeth . The fracture line positioned in the gingival connective tissue of crown root and cervical root fractures makes it difficult for clinicians to achieve satisfactory restorations. Restoration margins located in the gingival connective tissue can violate the biological width, resulting in gingival inflammation, clinical attachment loss, and bone loss, clinically manifesting as gingival bleeding, deepening of the periodontal pocket, or gingival recession . In some growing patients with severe crown-root fractures, space maintenance is recommended after extraction or coronectomy to preserve the width of the alveolar bone . Nonetheless, the need for additional bone grafting during implant placement is frequent even after coronectomy. Both the width and height of the alveolar bone are lost during the extraction for implant placement . During implantation in the anterior region, bone grafting is performed in conjunction with extraction and onlay grafting of connective tissue harvested from the palate to compensate for bone volume . The complexity of the implant surgery process and the possibility of failure due to technical sensitivity, and above all, the esthetically unpleasing results of surgery, can impose additional esthetic burdens on patients. Thus, prioritizing the preservation of natural teeth is important when considering the long-term effects of treatment. This case report describes a complicated crown-root fracture of the right maxillary central incisor. Surgical intervention using surgical extrusion with tooth rotation and crown lengthening was performed on the maxillary right central and lateral incisors of a growing patient instead of coronectomy or tooth extraction. Satisfactory esthetic and functional outcomes were observed. During follow-up, clinical and radiographic examinations revealed stable and good periodontal health. 

A 14-year-old male patient was referred to the Department of Pediatric Dentistry at Pusan National University Dental Hospital, Yangsan, South Korea, for treatment of crown-root fractures in the maxillary anterior teeth caused by a baseball bat injury. In the emergency room, a pulpectomy procedure was performed on the affected teeth, and sutures were applied for lower lip laceration. The maxillary right central, lateral, and left central incisors were fractured (Fig. ). Clinical and radiographic examinations were also performed. Examination revealed complicated crown fractures in the right maxillary central and lateral incisors. The margins of the fractures extended apically toward the gingival margin, and periodontal ligament (PDL) space widening on both incisors (Fig. ). Radiographic examination revealed a vertical crown-root fracture of the right maxillary central incisor. The fracture line was located 2 mm subgingivally, at the level of the alveolar crest at the distal aspect. The mobile crown-root fragment was removed and surgical exposure was performed. Temporary root canal therapy using a calcium hydroxide dressing was performed on the affected teeth which were then sealed with Caviton (GC Corporation, Tokyo, Japan) (Fig. ). After local anesthesia, mucoperiosteal flaps were reflected, and the teeth were carefully luxated to prevent damage to the marginal bone or root surface. The luxated teeth were carefully switched and rotated 180-degree atraumatically so that their palatal aspects were buccally turned (Fig. ). Consequently, the fracture margins were positioned at least 2 mm above the bone crests. A semi-rigid splint using 0.016 stainless steel round wire (S3™ SS Trueform, G&H Orthodontics, Franklin, IN, USA) was applied to stabilize the extruded tooth, spanning six teeth from the maxillary right first premolar to the maxillary left lateral incisor, and was bonded to the adjacent teeth with composite resin (CLEARFIL MAJESTY™ Flow, Kuraray Noritake Dental Inc., Okayama, Japan). Antibiotics were prescribed for the first week to prevent infections following surgery. The soft tissue healing proceeded without complications. The sutures were removed 10 days after the procedure, and three weeks later, tooth mobility remained stable. The splint was removed, and the root canal treatment was completed. In this case, despite performing surgical extrusion due to the extension of the fracture line into the alveolar bone, there was insufficient supracrestal dental structure remaining for restoration. Therefore, additional consideration had to be given to crown-lengthening surgery. A clinical crown-lengthening procedure was performed to level the gingival line and expose a sufficiently sound tooth structure for the subsequent prosthesis. During the osteotomy, a surgical stent was fabricated after diagnostic wax-up on a prepared model to minimize bone removal and establish surgical landmarks for the surgeon (Fig. ) . The teeth were simultaneously prepared for the prosthesis. A temporary crown was fabricated using self-curing acrylic resin (Tokuso Curefast, GC Corporation, Tokyo, Japan). Provisional restorations were maintained for six months before the final prosthesis treatment was performed to ensure gingival and bone tissue healing. Additionally, a putty index was made through diagnostic wax-up and adapted for the composite resin build-up of the maxillary left central incisor. The teeth were successfully rehabilitated using porcelain metal-fixed prostheses (Fig. ). The patient was examined at 1, 3, and every 6 months after treatment. A 2-year follow-up is currently being performed. The stability and esthetics of the crowns were maintained. 

For growing patients, saving severely fractured teeth is valuable not only for the restoration of function and esthetics, but also for the prevention of psychological trauma associated with tooth extraction. Moreover, it can reduce time and opportunity costs. Dental professionals must consider the psychological burden and social inconvenience that adolescents endure during implant surgery after reaching adulthood. The concept of the biological width derives from the histological description of the dentogingival complex by Gargiulo et al. The mean sulcus depth was 0.69 mm, epithelial attachment was 0.97 mm, and connective tissue was 1.07 mm . Therefore, the total length of the dentogingival complex was 2.73 mm. Gingival inflammation occurs when the restorative margins invade the biological width. Several authors have recommended that a crown-lengthening procedure should aim to obtain a minimum supracrestal tooth structure of 3 mm according to these criteria . Sorensen and Engelman defined the ferrule as “a 360-degree metal collar of the crown surrounding the parallel walls of the dentine extending coronal to the shoulder of the preparation.”  (Fig. ). It offers a form of resistance to the crown and serves a protective function by minimizing stress, which is known as the 'ferrule effect.’ Libman and Nicholls suggested a ferrule of no less than 1.5 mm . Therefore, dentists need to remove both hard and soft tissue to allow for the establishment of a 3 mm biological width and a 1.5 mm ferrule length during the crown-lengthening procedure . Different treatments are available to maintain the biological width and ferrule effect, depending on the location of the fracture line. These treatments include orthodontic extrusion, surgical extrusion, and crown-lengthening procedures . Orthodontic extrusion has been described as a treatment option for crown-root fracture. The whole attachment apparatus moves with the fractured tooth when it is repositioned coronally to prevent elongation of the clinical crown or the loss of supportive tissues . In cases of severe crown-root fractures, if a crown is fabricated to match the fractured margin, the margin must be set deeper toward the root compared to the current clinical crown height. This may result in the clinical crown appearing longer. In most cases, additional surgical correction of both the gingival and bone margins is necessary to complete the treatment. The treatment usually takes four to eight months to complete . A period of stabilization is also required to prevent a relapse . Surgical extrusion is defined as the ‘procedure in which the remaining tooth structure is repositioned at a more coronal/supragingival position in the same socket in which the tooth was located originally’ . Before replantation, the tooth may be completely extracted from the socket to assess the integrity of the root structure and to identify any additional fractures. Minimally invasive extraction with minimal damage to the cementoblast layer on the root surface is key to successful surgical extrusion . Surgical extrusion treatment outcome is considered successful when periodontal healing is present, without root resorption or ankylosis. Age did not appear to have an impact on these results . Previous studies, including most clinical studies that evaluated the success rates of surgical extrusion over the last four decades, have concluded that this treatment should be considered an important technique for managing teeth with subgingival fractures or caries . Although surgical extrusion is considered a feasible treatment approach for non-restorable teeth, a balanced risk–benefit analysis, including other alternatives such as surgical crown lengthening or orthodontic extrusion (forced eruption), is recommended . The crown-lengthening procedure is utilized to adjust the gingival and osseous tissue, allowing more of the tooth structure to be accessible for restorative purposes. In cases where additional apical tooth structure is required for retention or to prevent encroachment on the biologic width, the crown-lengthening procedure allows for the extension of the tooth preparation by 1–2 mm. The crown-lengthening procedure creates sufficient clearance between the restoration and the biologic width by exposing more of the tooth which helps avoid chronic inflammation and potential periodontal issues . The goal of the procedure is to improve the retention of restorations and esthetics in patients with an uneven gingival margin or excessive gingival display, thereby facilitating a more predictable prosthetic outcome . A conventional crown-lengthening procedure involves resective osseous surgery and the removal of a large amount of supportive periodontal tissue, including the gingiva and underlying bone, around the injured teeth to obtain a biologic width. When osseous surgery is performed to reconstruct the positive architecture around a single-rooted anterior tooth, the stability of the treated dentition may be affected, and the interdental papillae are likely lost . On the other hand, a hyperplastic excess gingival contour can occur when the crown-lengthening procedure is delayed after a severe crown-root fracture. This condition is particularly noticeable in patients with medium or high lip lines. If the patient desires a normal tooth length, resection to expose the anatomical crowns may be indicated . This patient initially presented with a square-shaped anterior tooth form, thick biotype, and deep bite. Therefore, the reductive osseous surgery was needed rather than orthodontic extrusion for a more aesthetically satisfactory crown shape. In these procedures, the dentist may require a surgical stent as a guide to determine the position of the new crown margins. An altered morphology of the interdental papillae of the anterior teeth after surgery can cause esthetic concerns. Black triangles can occur if the distance between the contact area and the interdental osseous crest after resection exceeds 5 mm . Dentists can correct the widened embrasure spaces that may result after healing from the surgical procedure by adjusting the crown contact areas to be longer and wider, thereby accommodating the new shape of the interproximal papillae . Accordingly, two stages of provisional restoration were used to adjust the contact point and emergence profile aiming to prevent black triangles and to aesthetically position the gingival zenith. Researchers have noted that when the flap margin is positioned at the level of the osseous crest, there is an average postoperative vertical gain or rebound of approximately 3 mm in the supracrestal soft tissues . Lanning et al. demonstrated that the coronal advancement of healing tissues from the osseous crest averages 3 mm by three months post-surgery. Additionally, they found that six months after the procedure, there were no significant changes in the vertical position of the free gingival margin . Brägger et al. also observed that during the six-month healing period following crown-lengthening, periodontal tissues remained stable, with only slight changes in the gingival margin level. These findings suggest that a six-month waiting period is advisable before proceeding with final prosthetic treatment in the esthetic zone after a crown-lengthening procedure . Therefore, temporary restorations were placed for six months before the final prosthetic restoration treatment for this patient, aiming to promote the stability of the periodontal tissues. Morrow et al. investigated the relationship between age, sex, and clinical crown height in a longitudinal . This study indicate that passive eruptions continue at least until the age of 18–19 years in both male and female. Evian et al. compared anterior and posterior teeth and discovered that gingival stability in the anterior teeth was achieved by the age of 20, whereas in the posterior teeth, gingival maturation could continue into the 30 s. . Therefore, regular examinations are necessary in the future to monitor the potential exposure of the margins of porcelain-fused-to-metal restorations owing to the increased length of the anterior crown. Additionally, after growth completion, reassessment is required to determine the need for crown retreatment. 

Surgical extrusion and crown lengthening may be considered effective treatments to save teeth instead of coronectomy or extraction for severely fractured teeth. The key factors in the successful functional and esthetic rehabilitation of complicated crown and crown-root fractures are multidisciplinary approaches, which involve surgery, endodontics, periodontics, orthodontics, and prosthodontics. 

