3D vector control during alveolar ridge augmentation using distraction osteogenesis and temporary anchorage devices: a new technique

Int. J. Oral Maxillofac. Surg. 2012; 41: 168–170 doi:10.1016/j.ijom.2011.08.003, available online at http://www.sciencedirect.com

Technical Note Dental Implants

3D vector control during alveolar ridge augmentation using distraction osteogenesis and temporary anchorage devices: a new technique

D. Aizenbud1, H. Hazan-Molina1, M. Cohen1, A. Rachmiel2 1 Orthodontic and Craniofacial Department, School of Graduate Dentistry, Rambam Health Care Campus and Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel; 2Oral and Maxillofacial Surgery Department, Rambam Health Care Campus and Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel

D. Aizenbud, H. Hazan-Molina, M. Cohen, A. Rachmiel: 3D vector control during alveolar ridge augmentation using distraction osteogenesis and temporary anchorage devices: a new technique. Int. J. Oral Maxillofac. Surg. 2012; 41: 168–170. # 2011 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. This report describes a combined orthodontic surgical technique involving vertical alveolar distraction using temporary anchorage devices (TADs) in cases of massive alveolar ridge bone and teeth loss. A combined surgical orthodontic protocol included presurgical orthodontic preparation and a preimplantation surgical augmentation stage for insertion of a vertical distractor. During the active vertical alveolar distraction process TADs were inserted. Intraoral orthodontic elastics were attached to the main orthodontic archwire exerting multidirectional forces to control the vertical distraction vector. After 3 months of vector controlling and active bone moulding, the TADs were removed. Anterior alveolar ridge augmentation using distraction osteogenesis was achieved. The application of TADs for better anterior segment curvature enabled dental implant insertion, better positioning and restoration. A combined surgical orthodontic management protocol involving vertical alveolar distraction osteogenesis for augmentation purposes is an efficient treatment method to improve alveolar ridge volume for the preimplantation stage.

During the alveolar distraction process, three dimensional (3D) vector control is a crucial factor in determining the planned movement and in maintaining precise evaluation of the desired distraction direction2,3. Owing to the curved architecture of the maxillary and mandibular alveolar 0901-5027/020168 + 03 $36.00/0

ridge, especially along the intercanine arch span, the distractor is originally angulated appropriately, but the accurate guidance of the vector’s direction is limited. Consequently alveolar ridge augmentation during distraction most often results in a straight and flat alveolar ridge structure

Accepted for publication 19 August 2011 Available online 5 October 2011

rather than a curved one. The delicate distracted bone is also exposed to the moulding forces exerted by the surrounding soft tissue matrix. In this way the transported bone segment is forcefully pushed inward (in a palatal or lingual direction) during regular and normal func-

# 2011 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

3D vector control during alveolar ridge augmentation using distraction osteogenesis and temporary anchorage devices tion of the buccinator mechanism. It is important to identify the direction of the newly regenerated bone early enough to avoid compromising the alveolar ridge augmentation results. Temporary anchorage devices (TADs) are fixed temporarily to the bone to enhance orthodontic anchorage and are removed after use. Their advantages, in addition to their size, include minimal anatomic limitations, minor surgery insertion, increased patient comfort, immediate loading, and low cost1,5,6. As an anchorage device, this type of appliance may be inserted into a regenerated segment enabling the application of orthodontic forces to control the distraction vector, thus moulding its required form for future dental restoration. In this article, the authors present a new technique for 3D vector control during vertical alveolar ridge augmentation using distraction osteogenesis and TADs, for better anterior ridge curvature form.

Fig. 2. Intraoral frontal view of vertical distraction osteogenesis process of the transported alveolar ridge segment resulting in desired bone height augmentation.

After a latency period of 5 days, a vertical distraction of the transported segment begins at a rate of 0.5 mm per day by turning the device twice a day until the desired bone height is achieved (Fig. 2). During the active vertical alveolar distraction process, orthodontic implants (TADs) are inserted into the transported segment according to the desired vector orientation (Fig. 3A). Intraoral orthodontic elastics

Materials and methods

Initially, preliminary orthodontic treatment is carried out to level and align the maxillary and mandibular dental arches until both arches are coordinated (Fig. 1). The preimplantation surgical alveolar bone augmentation stage includes vertical distraction of the residual basal bone using an intraoral distractor (KLS Martin distractor, Tuttlington, Germany). The anterior maxillary or mandibular area is anaesthetized with 2% lidocaine and 1:100,000 epinephrine. A vestibular incision is made in the area of distraction. The incision plane maintains the vascularization of the soft tissues and consequently the bone segment to be distracted. A trapezoid osteotomy is performed using an oscillating microsaw and the distractors are attached by means of 1.5 mm micro screws. The surgical incision is sutured to cover the distractor and the exposed alveolar bone completely. Postoperatively, 500 mg of amoxicillin is prescribed 3 times a day for 7 days.

Fig. 1. Intraoral frontal view after a preliminary phase of orthodontic treatment including levelling and alignment of the maxillary and mandibular dental arches.

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Fig. 4. Postoperative intraoral frontal view of implant supported prosthesis.

are then attached from the TADs to bent loops or prefabricated crimpable hooks on the main orthodontic archwire. These are banded/attached according to the preplanned desired vector for the 3D distraction process controls. The patient continues to wear the elastics after the active distraction period for an 8-week consolidation period. Later, the vertical distraction devices are removed under local anaesthesia. Vector controlling and active bone moulding using the TADs and intraoral elastics continues for 8–10 weeks until the desired curvature of the transported alveolar segment is achieved for ideal implant positioning (Fig. 3B). Finally the TADs are removed and dental implants can be inserted. Good aesthetics, functioning and occlusal relationships can be achieved (Fig. 4). Discussion

Fig. 3. Orthodontic implants (TADs) inserted into the transported segment during the active vertical alveolar distraction process. Vector controlling and active bone moulding using intraoral orthodontic elastics attached from the TADs to the loops on the main orthodontic archwire. (A) During vertical alveolar distraction process with the vertical distractor still in place Fig. 3 will appear in black and white in print and in colour on the web. Based on this, the respective figure caption has been updated. Please check, and correct if necessary.(red circles). (B) Moulding process with intraoral elastics and TADS continues after the removal of the distractors until the desired curvature of the transported alveolar segment is achieved for ideal implant positioning. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)

Atrophic maxillary bony ridge with profound deficiency, in the vertical and sagittal dimensions, may be presented in cases with post-traumatic loss of teeth. The vertical deficient alveolar ridge can, in some cases, be rehabilitated by means of implant-supported prosthesis, but the positioning of dental implants without any surgical augmentation might result in placement of implants of a reduced length which should be rehabilitated by extremely elongated crowns. The sagittal deficient alveolar ridge dictates dental implant inclination that may be inadequate to satisfy the fundamental biomechanical and aesthetic requirements7. For these reasons, a combined surgical orthodontic treatment protocol is presented. Distraction osteogenesis has become a popular surgical modality mainly in cases of trauma and correction of craniomaxillofacial deformities. It has many advantages: it is a relatively safe, effective, and a minimally invasive procedure that can be performed at any age with a low complication rate. Alveolar ridge distraction osteogenesis is one of the available techniques for vertical and transversal restora-

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tion as the origin of the formed bone is the basal bone. Since the generated bone is flat and has no curvature it needs to be moulded by efficient 3D vector control, for the shape of a proper, opposing suitable arch, enabling the application of an implant supported prosthesis. This article presents a combined method for controlling the architecture of the newly restored alveolar bone with the use of TADs and intraoral orthodontic elastics. Different techniques have been described for vector control4,8, but in the present system, preplanned alveolar ridge restoration is accurately achieved by balancing its position against the soft tissue pull by using TADs in addition to orthodontic brackets. The TADs and the orthodontic brackets function as a stable anchoring device during the distraction process, especially during the retention period after the removal of the distractors which heavily support the regenerated bone. This eliminates the dependence on teeth as an anchorage unit as HERFORD & AUDIA4 suggested and allows the use of fewer anchoring units than in the methods described in the literature. Since the distraction process involves a device that needs a precise vector, the direction of bone regeneration can be altered during the distraction process by pressure from the oral musculature and pull from the thick palatal tissue. Consequently, the new alveolar ridge can be reconstructed, but in a far from ideal position that would not allow optimal placement of the implants with respect to the anatomic, functional, and aesthetic outcomes. With the addition of intraoral elastics connected to the TADs and the brackets, the distracted alveolar process is ‘moulded’. The forward traction forces exerted on the regenerated anterior segment opposite the posterior parts, enable its movement to the designated position (Fig. 3) resulting in an improved anterior segment curvature suitable for the accurate preplanned position of the implant (Fig. 4). In this system, the direction of the forces exerted by the elastics can be easily modified during the distraction and

the retention periods. This allows a multidirectional force control of the vertical distraction vector in the three dimensions of space, whilst opposing the soft tissue pull. Bone generation is accompanied by a simultaneous expansion of the surrounding soft tissue envelope (i.e. gingiva, nerves, and vessels), which contributes to the stability of the reconstruction, lessening the risk of relapse10. This technique is expensive and demands more treatment time owing to the need for constant recalls and adjustments during the distraction process, compared with the bone graft procedure, for example. Relapse is considered the second most common complication of distraction surgeries, following insufficient bone formation according to SAULACIC et al.9, who studied the complication rate in alveolar distraction osteogenesis. Less common complications are bleeding, paresthesia, haematoma, infection, wound dehiscence and problems related to the device such as backward rotation, micro bone screw loosening, and fracture of screws9. A slight pain when turning the screw of the distractor is quite common. In conclusion, the presented technique of 3D vector control during vertical alveolar distraction osteogenesis for augmentation purposes is an efficient treatment method to improve alveolar ridge volume and architectural form as a preimplantation stage.

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Funding

None. Competing interests

None declared. Ethical approval

Not required. References 1. Fritz U, Ehmer A, Diedrich P. Clinical suitability of titanium microscrews

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Address: Dror Aizenbud Orthodontic and Craniofacial Department Rambam Health Care Campus P.O. Box 9602 Haifa 31096 Israel Tel: +972 4 8542265; Fax: +972 4 8339889; Mobile: +972 54 4327256 E-mail: [email protected]