Distraction Osteogenesis for Augmentation of Anterior Mandibular Segment after Failed Implants Removal: A Case Report

Dental News Volume XVIII, Number III, September, 2011

by Dr. Ali Alajmi

ABSTRACT

One major challenge implant surgeons are often faced with is large edentulous area which has insufficient bone volume for the purpose of implant placement. There are several methods have been used to augment the defected sites most common guided tissue regeneration (GTR), and autogenous bone particulate, or block graft, but these methods have several major disadvantages in GTR has limited ability when it comes to generate adequate bone height predictability, and the complication of membrane exposure, and possibility of infection of the site, or graft loss. In other hand autogenous bone grafting has predictable results, but might cause a major discomfort for the patient at the donor site also has high cost. So, a different method has been developed by using distraction devices, which has acceptable increase in bone volume for the implant surgeon for the correction of severe defect, and possible implant placement in the future.  A case report is presented describing the use of alveolar distraction to augment a vertically deficient of alveolar ridge at the mandible anterior after implants failure at mandible lateral incisors.

Introduction

History of Distraction Osteogenesis

Gravel Ilizarov was a Russian orthopedic surgeon is considered to be the father of distraction osteogenesis (DO) in the 1940s and 1950s.  Professor Ilizarov was able to illustrate that a long bone could be cut and stretched if only the appropriate device and protocol could be established. In 1988, Professor Ilizarov presented his work in US and in 1992 McCarthy reported first cases in mandible. In 1992, McCarthy, Schreiber and Karp applied this concept to treat hemifacial microsomia by distracting the mandible. In 1996, Block, Chang and Crawford described the first alveolar distraction in dogs and in the same year, Chin and Toth applied alveolar distraction to humans.

Ilizarov’s work is based on the well-known law of tension-stress, the principle whereby gradual traction on living tissues can, under certain condition, stimulate the regeneration and active growth of those tissues i.e., tension forces stimulate histogenesis.

Implications of Distraction Osteogenesis

The first advantage of distraction osteogenesis is that it has more potential to regenerate bone compared to bone grafting.

Secondly, distraction osteogenesis does not require a second surgical site for the donor site, which reduces discomfort, treatment time, and the cost of the procedure.

Thirdly, distraction osteogenesis creates a vital bone of excellent quality for the placement of implants, which is not always the case with autogenous or allogeneic bone grafting.

Finally, the greatest advantage of distraction osteogenesis for mandibular augmentation may not be related to bone, but soft tissues which are lengthened together with the bone tissue.

Limitations of Distraction Osteogenesis

The downside of distraction osteogenesis is that there must be a minimum quantity of bone about 5 mm of the transport and anchorage segment is a must to have adequate strength to withstand force of mobilization and transport.

In addition, expansion occurs only in the direction of transport (Vector). The patient must also cooperate with the activation process.

Indication of Distraction Osteogenesis

In alveolar distraction the main indication is the vertical augmentation of the ridge with or without soft-tissue deficiency. DO has an advantage over other techniques such as guided bone regeneration and onlay bone grafting in that it can predictably generate more than 5 mm of alveolar height. ^2,3 In addition, the mucosa also develops with increase of vestibular height. Thus the technique is useful in either optimization of esthetic looks in the anterior or increasing the volume of bone before implant takes place in the posterior. Both distraction osteogenesis and onlay bone grafting are applied in the event that traumatic defects occur in complex multidimensional alveolar and mucosal deficiencies. There may be less bone available to distract in extremely atrophic areas. This requires onlay bone graft to be done first and then the grafted area can be vertically distracted after 16 weeks healing. However, in cases of mild to moderate horizontal atrophy, distraction osteogenesis can be done first, followed by onlay bone grafting, or guided tissue regeneration.

Materials and Method

The purpose of this patient report is to use a clinical case to demonstrate the preoperative planning, surgical technique, treatment protocol, and application of alveolar ridge augmentation with the distraction device in partially edentulous ridges for improvement of esthetic areas, after failed implants. A 47-year-old female patient complained she felt pain because of her lower implants that were done in private clinic about 18 months ago. Her medical history was found to be noncontributory to her present complaint because she has no known drug allergies and neither was she on any kind of medication. The patient drinks only occasionally but has no history of tobacco use. Intra- oral examination revealed severe destruction of soft and hard tissue around the mandible lateral incisors implants (Fig.1and 2).  Radiographic findings showed severe bone lost almost to the apex of the two implants at mandible lateral incisors (Fig. 3 to 5). Based on the clinical examination, it was determined that the patient’s implants had to be removed first, and then reconstructed with alveolar DO to gain vertical height. Clinical features of this case included severe alveolar bone and soft tissue deficiency.

Fig 1: This intra-oral view of the anterior mandibular defect shows significant loss of alveolar ridge height at buccal area.

Fig 2: This intra-oral view of the anterior mandibular defect shows significant loss of alveolar ridge height at lingual area.

Fig 3: Preoperative panoramic radiograph shows significant vertical bone defect is evident in the anterior mandible.

Fig 4: Preoperative panoramic radiograph shows significant vertical bone defect around the mandible implant, left side

Fig 5: Preoperative panoramic radiograph shows significant vertical bone defect around the mandible implant, right side

Failed Implant Removal

Fig 6-7: Full thickness flap was raised to expose the defected site and the implants.

Fig 8-9: Implants were removed

Fig 10-11: Bone graft (Bio-Oss and DFDBA) and resorb able membrane (Bioguard) were placed to cover the defect after implants removal.

Fig 12: Primary closure of the flap was achieved with continuous locked sutures.

Alveolar Distraction Technique

It is a four steps technique involving

a) Full thickness flap to expose the alveolar defect.

b) Latency period 7 to 10 days. (The latency period is the time from surgery until distraction is     activated).

c) Distraction, during which bone is transported incrementally at the rate close to 1 mm/day.

d) Time for consolidation, typically 2 months, before the device removed.

The entire Alveolar distraction process takes 2-3 months from the time of initial surgery to the time when devices are removed, and possible implants placement.

Fig 13: Morphology of the ridge 3 months after bone grafting although implants could have been placed, the restorations would have been long, unattractive, and difficult to clean. 

Fig 14: Preoperative panoramic radiograph. A significant vertical bone defect is evident in the anterior mandible. 

Fig 15: Preoperative diagnostic cast of the case. 

Fig 16: The appearance of the titanium distraction device before placement. Its components include 2 fixation plates, each with counter-sunk screw holes and a smooth vertical sleeve fixed to the lower member (base plate). The upper (distraction) plate is attached to the threaded adjustment post housed within the sleeve, and its upward movement is governed by the hex-topped post. A longhandled wrench turns it clockwise in order to activate the system. 

Fig 17-18: A horizontal vestibular incision is used to expose the bone without vertical release incision a full thickness flap is elevated on the buccal aspect only, taking care not to reflect the tissue on the alveolar crest or towards the lingual . 

Fig 19: 3 bone cuts are made (2 vertical at the lateral borders of the distractor, and 1 horizontal between the 2 fixation plates) using a saline-cooled, oscillating saw. The forefinger of the surgeon’s other hand is placed firmly against the lingual mucoperiosteum to guide saw-cut depths and to avoid perforation of the mucosa. This lingual flap is the only source of vascular supply, and its sanctity must be preserved 

Fig 20: Placing and twisting an osteotome accomplish the final release of the transport segment of bone. 

Fig 21-22: When the transport segment has been fully mobilized, the distraction device is attached and stabilized with the aid of additional bone screws. 

Fig 23: Primary closure after distractor placement

Discussion

Distraction protocol

The distraction/postoperative protocol typically include the following phases: a latency period, device activation, a consolidation period (Figure. 24).

Latency period

 This latency period is typically 5 to 7 days long. Factors that may affect the duration of the latency period include the age of the patient, the extent of tissue trauma created during surgery, and the healing rate for the patient.

Device activation

Following the latency period, the device is activated; this is done with the ratchet wrench and adapter, screwdriver handle, and straight driver, or with a temporary activation tool. The pitch on the threaded distraction rod is 0.4 mm, so one complete turn equals this vertical distance. Typically, patients are distracted one or two turns (0.4 to 0.8 mm) on a daily basis until the desired amount of vertical distraction has been achieved. Because a clinician can evaluate using only tactile feedback generated by the device, it is recommended that the clinician activate the device in the dental office. Distraction results in vertical elevation of the transport segment, which enlarges the regeneration chamber. Because the chamber is surrounded by vital bone on four sides and by periosteum on two sides.

Consolidation period

 When the desired height of the alveolar crest is achieved, distraction ends and consolidation begins. The threaded rod is left in place for the duration of consolidation, which lasts about 12 weeks; longer consolidation periods may improve results by limiting the amount of relapse. During this time, bony union occurs across osteotomy margins (the vertical osteotomy cut lines and in the distraction zone), and the gingiva expands to the new alveolar bone volume ^3,7.

Fig 24: Alveolar Distraction – Timeline

Table1: HVC ridge classification. Subclassification

Small (s) ≤ 3 mm; medium (m) 4–6 mm; large (l) ≥ 7 mm.

According to this classification in table 1 ⁹, the present case has both horizontal and vertical defects and the defect is larger than 7 mm. Therefore, it is a class III ridge defect.

Conclusion

The key to success in distraction osteogenesis is careful, precise, well planned surgery with care taken to preserve the vitality of the transported segment, educate and follow patients and maintain precise vector control of the regenerating tissue.

References

1. Block M, Chang A, Crawford C, (1996). Mandibular alveolar ridge augmentation in the dog using distraction osteogenesis. Journal of Oral Maxillofacial Surgery. 54; 309-314

2. Chiapasco, M, Romeo E, Vogel G. (2001). Vertical distraction osteogenesis of edentulous ridges for improvement of oral implant positioning: a clinical report of preliminary results. International Journal of Maxillofacial Implants. 16; 43-51

3. Saulacic N, Iizuka T, Martin MS, et al (2008) Alveolar distraction osteogenesis: a systematic review. International Journal of Maxillofacial Implants. 37:1-7

4. Emtiaz S, Noroozi S, Caramês J, Fonseca L (2006) Alveolar vertical distraction osteogenesis:  historical and biologic review and case presentation .  

      International J Periodontics Restorative Dent. 26; 529-41.

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7. Chin M, Toth B. Distraction osteogenesis in maxillofacial surgery using internal devices: review of five cases. J Oral Maxillofac Surg. 1996; 54:45–53.

8. Ilizarov G. The tension stress effects on the genesis and growth of tissues. Part 1. The influence of stability of fixation and soft tissue preservation. Clin Orthop Rel Res. 1989; 238:249–281.

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