Segmental Osteotomy in the Correction of an Anterior Open Bite: A Case Report

Ankylosis is the abnormal fusion of alveolar bone to dentin or cementum. It results from severe damage occurring to the periodontal ligament and a healing process that involves osteoclastic cells causing root resorption and, consequently, fusion of the alveolar bone and root surface. The resorption process continues unabated, with an unpredictable time sequence, until the bone totally replaces the root.

Current knowledge of the pathogenesis of ankylosis is based largely on findings from animal and in vitro studies and observations from human studies of replanted teeth. In healthy patients, periodontal ligament fibroblasts block osteogenesis within the periodontium by releasing locally acting regulators, such as cytokines and growth factors, thereby maintaining separation of tooth root and alveolar bone.¹ Necrosis of the periodontal ligament cellular elements by desiccation, crushing, or mechanical damage, as in severe luxation injury, disrupts this normal homeostatic mechanism. Ankylosis is established not only via inflammatory-mediated and mechanical alterations in the periodontal ligament² but also because insufficient functional cellular elements survive to suppress osteogenic activity.³ This disruption allows growth of bone across the periodontal ligament, and ankylosis ensues.

Trauma-induced ankylosis that occurs during the individual's growth period can hamper the vertical growth of alveolar bone. This condition results in an open bite that may pose both esthetic and functional problems.^4,5

A clinical diagnosis of ankylosis can be made only when the affected tooth shows positive evidence of an inability to move either during normal bone growth or when it is subjected to orthodontic movement.⁶ Early detection of ankylosis does not change the inevitable outcome: tooth loss from replacement resorption.⁷ Ankylotic root resorption is a serious complication that is a consequence of traumatic dental injuries. The etiology of root resorption includes acute injury to the cementum and periodontal ligament and subsequent biological processes that propagate the harm.

Infraocclusion and vertical discrepancy of alveolar bone are more severe and progress faster in growing patients than in adults who have stopped growing due to ongoing vertical bone growth and adjacent tooth eruption.⁸ The hopeless prognosis of an ankylosed tooth calls for future replacement planning. A dental implant is a favorable choice if the residual ridge is of adequate dimension. Removal of the ankylosed tooth by extraction could potentially damage the bone and the surrounding tissues,⁹ resulting in vertical ridge deficiency. The situation can be somewhat precarious in growing subjects and become more complex to treat when an implant is indicated.

In 1984 Malmgren et al suggested decoronation as an approach for ridge preservation at an ankylosed tooth site in growing patients as a promising alternative to extraction.¹⁰ In cases of late-onset ankylosis, when no more significant growth is expected, a follow-up is sufficient as long as there is no significant vertical discrepancy between the ankylosed tooth and adjacent teeth.¹¹ If some vertical discrepancy already exists in a late-onset ankylosis case, building up the tooth crown using composite materials or the use of fixed prosthodontics is recommended.¹² Another possible treatment option is surgical luxation of the ankylosed tooth, thereby breaking the bony bridge. An immediate orthodontic force should follow luxation to promote formation of fibrous tissue.^13-15

Segmental osteotomy is a treatment option that may be considered after repeated failure of surgical luxation, or as an alternative treatment option. The alveolar segment of the tooth is sectioned mesially, distally, and subapically. The osteotomized segment may be repositioned with the use of an acrylic splint, which is prepared prior to the surgery. Segment stabilization in most cases is performed using mini-plates and screws, but the osteotomized segment may also be orthodontically stabilized if the inter-osseous gap is limited.¹⁶

Another treatment alternative is distraction osteogenesis. After the latency period, the distraction of newly formed callus is initiated, along with a 1 mm per day separation rate of the two bony parts. Slower rates, such as 0.5 mm per day, may lead to premature consolidation, while faster rates, such as 2 mm per day, could cause poor bone formation.¹⁷

Extraction of the ankylosed tooth can be considered at any stage. Extraction during the patient's growth spurt, when no implant can be immediately placed, will result in severe bone loss due to a possible traumatic extraction and a deficient vertical alveolar height.¹⁸

A 26-year-old male patient with no significant medical history reported a trauma to the anterior maxilla that occurred during his teenaged years. His maxillary right central incisor was avulsed and replanted. An anterior open bite resulted due to normal vertical dental alveolar growth on the adjacent teeth combined with the inability of the right central incisor to move (Figure 1). The patient consulted the authors' clinic for the management of the esthetic deficiency and functional disability.

After clinical and radiological analysis, which included CBCT images and periapical x-rays, the diagnosis of tooth ankylosis on the maxillary right central incisor (tooth No. 8) and the start of external root resorption were confirmed. Additionally, periapical pathosis due to endodontic origin on tooth No. 7 was evident (Figure 2 and Figure 3). The patient presented with a class II malocclusion, an anterior open bite with a tongue thrust, generalized mild chronic gingivitis, and dental caries aggravated by mouth breathing.

After thorough discussion regarding treatment options, the patient decided to first complete orthodontic treatment to correct the malocclusion and eliminate the anterior open bite by slight intrusion of the maxillary molars. Obviously, tooth No. 8 was not expected to move orthodontically. The ankylosed tooth would be surgically repositioned using segmental osteotomy, and the bone block would be stabilized on arch wire for a period of 5 months.

Eighteen months post-orthodontic treatment, a resolution of the anterior open bite was achieved; teeth were properly aligned in class I occlusion except for ankylosed tooth No. 8 (Figure 4). Under local anesthesia, a full-thickness mucoperiosteal flap was elevated, and distal, apical, and buccal osteotomies were completed around ankylosed tooth No. 8 using a piezoelectric device without harming the palatal mucosa (Figure 5 through Figure 8). Proper detachment of bone block along with the tooth using chisels and a mallet was completed, and, finally, the bone block/tooth was repositioned 3 mm coronally in the arch wire and stabilized with composite material (G-aenial^™ composite, GC Corp., gcamerica.com) and ligature wires.

A thorough curettage of periapical pathosis on tooth No. 7 with a hydrogen peroxide rinse and an apicoectomy without retrograde filling were completed concomitantly. The flaps were sutured (Figure 9) and allowed to heal. The patient was given antibiotics (amoxicillin/clavulanic acid 1 gram, twice per day for 7 days) and anti-inflammatory medication (ibuprofen 600 mg). Sutures were removed at 14 days.

Proper stabilization time is necessary for the success of this procedure; typically 3 months is required for bone healing.¹⁹At 5 months postoperative, orthodontic brackets were removed (Figure 10 through Figure 12). An ideal tridimensional repositioning of the right central incisor was achieved with no necrosis, dehiscence, or recession, and a complete osseous healing was accomplished in the dislodged fragment. Root canal therapy was repeated on tooth No. 8. No signs of internal resorption were observed. The radiolucency and suspected external root resorption were treated with local application of mineral trioxide aggregate cement inside the pulp chamber. Maxillary anterior teeth (Nos. 6 through 11) were prepared, and six lithium-disilicate crowns (e.max^®, Ivoclar Vivadent, ivoclarvivadent.com) were delivered to the patient (Figure 13). Maxillary and mandibular retention wires were bonded to the palatal surfaces of the anterior teeth using hydrofluoric acid-etching and flowable composite (Tetric EvoFlow^®, Ivoclar Vivadent).

At 24 months post-segmental osteotomy the result was stable with mesial and distal papillae present and proper curvature of the facial mucosa achieved. Excellent harmony was attained with regard to pink and white esthetic scores (Figure 14).²⁰ A 24-month x-ray is shown in Figure 15.

The decision in this case to use a segmental osteotomy to reposition the ankylosed maxillary central incisor was made after proper diagnosis. It was clear to the clinician that the tooth had to be either surgically moved in block with the surrounding alveolar bone or extracted. Extraction of such a malpositioned tooth, however, should only be a last resort after surgical luxation has failed or after failure of segmental osteotomy or distraction osteogenesis because of the potential for esthetic damage. Vertical augmentation of the ridge to correct the esthetic deformity would need to be done prior to implant placement. Therefore, the segmental osteotomy was indicated as the best treatment option.

A piezoelectric system uses ultrasonic vibration to cut hard tissue only, not soft tissue. Piezoelectric surgical devices do not cause soft-tissue lacerations or burns during an osteotomy and make micrometric bone cuts resulting in precise, highly controllable osteotomies.²¹ Precise mesial subapical and distal osteotomies were completed in this case cutting from buccal to palatal plates without reflection and laceration of the palatal mucosa. A small luxation of the block was performed using chisels to ensure its mobility; this step was done with extreme care to avoid perforation of the palatal mucosa, which is essential to the nourishment of the segmented block. A disadvantage of this technique is the possible side effects that may occur, such as loss of tooth vitality, avascular necrosis of the bone segment, gingival recession, loss of crestal bone and pocket formation,delay in movement of the segment due to bone interferences, and traumatic occlusion.^22,23 Additionally, there is potential for injury to teeth adjacent to the osteotomy from the piezoelectric surgical unit.

Isaacson et al demonstrated in a case report a similar technique for moving an ankylosed central incisor in a 12-year-old patient using orthodontics, surgery, and distraction osteogenesis.⁶Kang et al exhibited a single-tooth dento-osseous osteotomy with a CAD/CAM surgical guide in a similar approach⁵; the guide facilitated the osteotomy by shortening the duration of surgery and reducing the risk of trauma. Iskenderoglu et al found on an animal model that single-tooth osteotomy is an effective surgical method for an ankylosed or ectopically erupted tooth in orthodontic treatment.²⁴ It can reduce the total orthodontic treatment time and root resorption, which is a common complication. Significant improved bone formation was seen with the addition of platelet-rich fibrin. Harshitha et al found that an anterior segmental osteotomy applied on 10 patients aged 18 to 30 years resulted in good functional and esthetic correction with a high success rate and minimal complications 6 months postoperative.²⁵

In the present case, because the inter-osseous gap was small (2 mm to 3 mm), the osteotomized segment could be properly repositioned in the arch wire, and it was stabilized using ligature wire and composites buccally and palatally and left out of occlusion for 5 months. The external resorption of the root is a direct consequence of the trauma to the tooth and is an irreversible process.²⁶ Presently, the patient is aware that this tooth might need to be extracted in the future due to the external resorption; the repositioned osteotomized segment, however, is in an adequate tridimensional position to withstand proper implant placement. An implant may be immediately loaded if primary stability were to be achieved.

The satisfying esthetic and functional result at 24 months may be attributed to proper diagnosis, excellent execution of the surgery, allowance of sufficient stabilization and healing time, good patient compliance, and, finally, proper completion of the prosthetic rehabilitation. It should be noted that although there is a chance of a relapse in this case, which utilized individual non-splinted anterior crowns, the patient is wearing an orthodontic retainer at night and has changed his form of deglutition (with lingual interposition between the maxillae) with the help of a psychometrist.

The patient in this case required management of an esthetic and functional disability stemming from an anterior open bite due to ankylosed tooth No. 8 as a result of trauma. A resolution of the anterior open bite was achieved after 18 months of orthodontic treatment, as teeth were properly aligned in class I occlusion except for ankylosed tooth No. 8. A segmental osteotomy was completed to reposition the ankylosed tooth, and stabilization of the segmented block was completed after 5 months. Six maxillary anterior teeth were then prepared and lithium-disilicate crowns delivered to the patient. At 24 months post-segmental osteotomy, the result was stable with regard to pink and white esthetic scores. The case demonstrates the challenge that treatment of an anterior open bite can pose and the use of a segmental osteotomy to correct it.

Peter Tawil, DDS, MS
Diplomate, American Board of Periodontology; Private Practice limited to Periodontology, Oral Surgery, and Implant Dentistry, Beirut, Lebanon, and United Arab Emirates

Mehand Boufassa, DDS
Private Practice limited to Orthodontics, United Arab Emirates