Extraction of an ankylosed tooth is a common scenario orthodontists face in daily practice. The extraction of an ankylosed tooth is often traumatic, leaving behind a defective alveolar ridge. A common approach to correct alveolar bony defects is bone grafting periodontal surgeries. This article shows a less invasive biological method by bodily horizontal tooth movement into the edentulous defect to build a wide bony ridge.
Restoring esthetics, comfort and function when teeth are missing is one of the most common problems dental teams face in daily practice. Teeth may be missing for several reasons; including trauma, caries, periodontal disease, ankylosed teeth which fail to erupt, orthodontic extractions and congenitally missing teeth. Treatment options were enhanced when implants became more accessible. The dimensions of the alveolar ridge are critically significant for implant outcome. The importance of the vertical ridge height is intuitive in that vertical confers implant stability needed for initial rigid fixation and primary stability needed for osseointegration. The importance of the horizontal dimensions are less obvious, but have been well elucidated in the literature. Greater than 2 mm of bone buccal to the planned implant confers long term confidence in the stability of the gingival margin such that the margin would remain intact rather than recede from the implant, abutment, and crown interface.
Unfortunately it is common that the alveolar ridge presents with deformities. stemming from tooth extraction, or extracted teeth that are not promptly replaced. The stages of ridge resorption after tooth extraction have been well described in the literature. When alveolar bone is deficient site development is indicated prior to implant therapy. Bone augmentation for its correction can be achieved using various surgical techniques including guided bone regeneration, block grafts, and ridge expansion techniques. Horizontal bone augmentation continues to be more predictable, especially with the technologic developments in tissue engineering. In spite of the multiple surgical methods, gaining vertical bone height remains a surgical challenge.
The burgeoning role for orthodontics in sophisticated cases in need of implant site development started with forced eruption as more predictable option for vertical bone augmentation. The bone adaptive response was elucidated when forced eruption was identified by multidisciplinary teams as a means to address the problems with vertical ridge defects.
On the other hand, moving a tooth mesiodistally along the ridge is a much more novel means for implant site development. Hom and Turley in the mid 80’s, while closing spaces of missing permanent molars, noticed an increase in the alveolar ridge width. They mention how there is little information regarding orthodontic closure in remodeled or edentulous areas, and the periodontal benefits that orthodontic movement may bring to such a case. 
Classically, such horizontal tooth movement was cumbersome as compared to forced eruption. However, with the advent of TADs horizontal tooth movement can be explored for implant site development using the same adaptive bone response as a strategy to target defects.
The following clinical case shows an adolescent patient who had a severe alveolar ridge defect after traumatic extraction of an ankylosed maxillary second premolar. An orthodontic approach, enhanced with TADs, was used to create more ideal ridge architecture by moving the first premolar distally to the second premolar position. As a result, a more appropriate alveolar ridge is available for the dental implant.
A 17.5 year-old girl was referred to the Case Western Reserve University orthodontic department for comprehensive orthodontic treatment. Patient and parents chief complaint was the impacted right maxillary second premolar. Intraoral examination revealed a missing maxillary right second premolar. The panoramic radiograph constructed from cone beam computed tomography (CBCT) showed a retained but submerged maxillary right deciduous second molar, impacted maxillary right second premolar, mesially tipped maxillary right first molar and distally tipped maxillary right first premolar ( Fig 1 ). At initial presentation, complete periodontal evaluation was completed. The first molar and the erupted premolar probed 2–3 mm and there was no bleeding on probing or any clinical signs of inflammation to the area. The gingiva presented with thick biotype, and the area was deemed healthy for further treatment.
In consideration of the patient’s age and goals, initial treatment objectives were to create space for guided eruption of the impacted premolar and establish proper occlusion on both sides. Patient was referred for extraction of the retained maxillary primary second molar and placement of a gold chain attachment on the impacted premolar to start bringing it into occlusion using a closed eruption technique ( Fig. 2 ). Sliding mechanics were used to open a space between first molar and premolar. Once space was opened, power thread was attached to the gold chain to start guided eruption of the impacted second premolar. After 6 months of orthodontic traction, a progress panoramic radiograph was taken to assess the position of the impacted premolar which did not show any movement towards the occlusal plane. The tooth was deemed ankylosed and it was decided that further attempts to move it could lead to reciprocal, undesired intrusion of the adjacent maxillary teeth. The patient was sent to her oral surgeon for extraction and possible implant replacement. Five weeks after the extraction, the patient presented to her orthodontic appointment with a large combination ridge defect, both vertical and horizontal in dimension, in the area of the second premolar. Although the biotype remained thick, the interdental col had an overly exaggerated saddle shape ( Fig. 3 ). Furthermore, just to address the significant vertical and horizontal ridge deficiencies multiple surgical bone augmentation procedures would be necessary. And even with such intensive surgery, obtaining significant gains specifically the vertical component of the deficiency has a poor surgical prognosis. This left little promise of ever having an esthetic papilla mesial to the molar.
Given that information, alternative treatment options for implant site development were presented to the patient that included, multiple bone augmentation surgical procedures, and orthodontic tooth movement through the defective ridge. The orthodontic option was chosen. with the plan of retracting the first premolar in place of the extracted second premolar, such that the predictable biologic bone response would be to “bring” the alveolar housing round the first premolar into the deficient second premolar site. This would leave behind a morphologically compatible alveolar for a first premolar dental implant and create bone in the along the ridge to the newly distalized first premolar in the second premolar site. In order to prevent any anchorage loss, a temporary anchorage device (TAD) was placed in the palatal alveolar process, connected to the first molar using a stainless steel wire to provide indirect anchorage, locking-in the first molar while retracting the first premolar. Palatal buttons were bonded to both the first molar and first premolar to control for rotation during retraction ( Fig. 4 ). Light continious force (50 g) was used for retraction for 10 months. Retraction was performed on a rectangular stainless steel wire (0.017 × 0.025 ss). The rate of tooth movement was approximately 0.8 mm per month. After 8 months of retraction, a progress small field of view CBCT was taken to visualize bone formed in three dimensions. Periodontal health continued to be excellent, with no bleeding on probing or other signs of inflammation in the quadrant. Plaque control continued to be excellent. All six sites around the molar and premolar probed 3 mm or less. Greater than 2 mm keratinized tissue was identified on all sites. Recession was present, <2 mm on the mesial of the molar, conferring a stage I periodontitis classification. Clinically healthy periodontal presentation of area allowed for mucoperiosteal flap elevation. The vitally important dimensions of the regenerated alveolar ridge was confirmed when the flap was elevated. With ridge morphology such that two mm are available buccal to the planned implant, confers confidence in stability buccal bone scalloped architecture, interdental festooning, and the long term soft tissue margin. Complete retraction of the first premolar was achieved 2 months after the progress CBCT ( Fig. 5 ). Furthermore, distal root movement of the retracted premolar was attempted, but the dilacerations of the roots have interfered. The resulting space showed a broad alveolar ridge, suitable for dental implant placement. Fig. 6 shows radiographically the subsequently inserted implant and Fig. 7 shows from an occlusal view, the retraction from initial to implant placement.