A vertical alveolar defect is one of the most challenging conditions faced in oral reconstructive surgery. Over the course of time, several techniques have been introduced in an attempt to solve the esthetic and functional concerns of alveolar bone loss, including guided bone regeneration, onlay grafting, and alveolar distraction. The choice of which technique is the most ideal for future implant placement remains controversial. The ultimate goal of any reconstruction is to achieve a soft tissue profile similar to that of the natural dentition, with absence of fibrous tissue at the site, and the presence of adequate bone for implant placement.
The physiologic challenges in alveolar reconstruction involve soft tissue, bone, and blood supply. As noted by Dr. David Garber, “The tissue is the issue, but the bone sets the tone.” This is clearly illustrated in many cases in which the final result of a procedure is compromised because of lack of adequate bone at the site. Frequently, the patient judges the final result on the soft tissue contours and profile and lack of symmetry with respect to the adjacent teeth. Blood supply to the site can be compromised by multiple previous surgeries, scarring, and host factors. When dealing with an alveolar defect, all of these issues must be taken into consideration in choosing which technique will give the best result.
Horizontal defects in both the maxilla and mandible lend themselves well to be treated with traditional grafting techniques, with predictable results. Vertical defects, however, tend to have a higher risk for complications with traditional grafting. Soft tissue defects, infection, inadequate bone volume, and loss of the graft are just some of the issues that frustrate our efforts.
This chapter looks at the uses, techniques, advantages, and disadvantages of alveolar distraction osteogenesis for vertical defects in the maxilla and mandible. It should be remembered, though, that no one technique is perfect and that there will always be alternatives that work better for some clinicians. As Dennis Tarnow is often quoted, “We need to achieve one miracle at a time.”
Historical Perspective
As early as 1905, the Italian surgeon Alessandro Codivilla was attempting to distract long bones with various techniques. In 1927, L. C. Abbott reported using distraction to elongate tibial defects. All modern distraction is based on the revolutionary work of the Russian orthopedic surgeon Dr. Gavril Ilizarov. Over a period of 30 years, Ilizarov explored the basic science, defined parameters for clinical application, and improved the instrumentation for the distraction osteogenesis process. Restricted communication between Soviet and Western medical communities limited dissemination of the work outside Russia. Once relations between the former Soviet Union and the West improved, this invaluable work was made widely available. Distraction osteogenesis is the biologic process of new bone formation between the surfaces of bone segments that are gradually separated by incremental traction. Specifically, this process is initiated when distraction forces are applied to the callus tissues that connect the divided bone segments, and it continues as long as these tissues are stretched. The traction generates tension that stimulates new bone formation parallel to the vector of distraction. A mechanical apparatus, the distraction device, is used to provide gradual, controlled transport of a mobilized bone segment. When the desired repositioning of the bone segment is achieved, the distraction device is left in a static mode to act as a fixation device. Displacement of the osseous segment results in positioning of a healthy portion of bone into a previously deficient site. Because the soft tissue is left attached to the transport segment, movement of the bone also results in expansion of the soft tissue adjacent to the bone segment. At the original location of the segment remains a regeneration chamber that has a natural capacity to heal by filling with bone. This propensity of the regeneration chamber to heal by filling with bone instead of fibrous tissue is a function of the surrounding, healthy cancellous bone walls and location within the skeletal functional matrix. As a result of the gradual distraction, the entire housing, including the osseous and soft tissue components, are enlarged in a single, simultaneous process.
Alveolar Distraction
The techniques of distraction apply no matter what bone is being considered for the procedure. Distraction osteogenesis techniques for the craniofacial skeleton have been pioneered by Chin and McCarthy. Alveolar distraction devices have now been developed by multiple manufacturers, and all have similar characteristics for application. The advantages of alveolar distraction over other bone-grafting techniques center around several factors, including the movement of vital bone, minimal risk for infection, short treatment times, little or no resorption of bone, and predictable results in which soft tissue is generated along with bone.
Movement of Vital Bone
This technique is the only approach in which the blood supply to the graft is maintained and, therefore, is a vital graft as opposed to a free graft. This greatly reduces the risk for failure or sloughing of the bone. This concept is debated by some since the small segments of bone being moved in alveolar distraction are sometimes stripped of their blood supply when the segment is mobilized. Several authors have reported that these small segments are vulnerable to resorption. However, with careful manipulation of the site, the blood supply can be maintained and the vital segment moved to the desired position.
Minimal Risk for Infection
In a study by Block, Chang, and Crawford, no infections developed in patients undergoing alveolar distraction. However, in 2002, Klesper and colleagues reported two instances of infected devices. Obviously, any time that a foreign body is placed, there is a risk for infection, but this author as well has seen no cases of infection in 12 years of performing the alveolar distraction process and indeed has had several cases in which the titanium plate and segment became partially exposed but were not lost.
Shorter Treatment Times
The overall treatment time for alveolar distraction is 3 to 4 months, as opposed to 6 months with traditional grafting techniques. This allows more rapid entry into the implant phase of treatment. Multiple studies have documented that the distracted bone is solid and will accept and undergo successful integration of implants. This shorter treatment time is an advantage in today’s era of greater patient expectation and pressure to get to the final result.
Alveolar Distraction
The techniques of distraction apply no matter what bone is being considered for the procedure. Distraction osteogenesis techniques for the craniofacial skeleton have been pioneered by Chin and McCarthy. Alveolar distraction devices have now been developed by multiple manufacturers, and all have similar characteristics for application. The advantages of alveolar distraction over other bone-grafting techniques center around several factors, including the movement of vital bone, minimal risk for infection, short treatment times, little or no resorption of bone, and predictable results in which soft tissue is generated along with bone.
Movement of Vital Bone
This technique is the only approach in which the blood supply to the graft is maintained and, therefore, is a vital graft as opposed to a free graft. This greatly reduces the risk for failure or sloughing of the bone. This concept is debated by some since the small segments of bone being moved in alveolar distraction are sometimes stripped of their blood supply when the segment is mobilized. Several authors have reported that these small segments are vulnerable to resorption. However, with careful manipulation of the site, the blood supply can be maintained and the vital segment moved to the desired position.
Minimal Risk for Infection
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