Faculty Bibliography

The mandibles of five patients who underwent unilateral or bilateral distraction osteogenesis were analyzed using computed tomography scans. The mandibles were reconstructed in three dimensions using General Electric computed tomography software. The total volume of each hemimandible was determined before and after distraction and compared. The mandibles were then segmented at 1-cm intervals, and the volumes of the segments were determined. The volumes of the mandibular segments before and after distraction were compared to determine the distribution of new bone through the mandible and the quantity of bone generated by distraction. The distracted hemimandibles increased in total volume by an average of 19.9% (statistically significant by the Student paired t test; P < 0.0001), whereas the nondistracted hemimandibles increased in total volume by an average of 5.2%. The segmental volumes of the distracted mandible were of similar or greater volume when compared to the preoperative mandibular segments. In addition, the distribution of regenerate bone mirrored the physiological distribution of the preoperative mandibular bone. This study indicates that distraction not only creates new bone but distributes that bone through the remodeled mandible in an anatomical pattern similar to that of the preoperative bone

Distraction osteogenesis is an innovative technique that has transformed the treatment of craniofacial malformations in young children. Bone generation obviates the need for graft material, which is in short supply in young patients, thus making possible surgical procedures on the craniofacial skeleton in young children. Sufficient mandibular volume is required for the osteotomy and placement of the device screws and/or pins. To have adequate bone stock and to facilitate distraction, the authors preoperatively examined all patients radiographically and selected those with tooth follicles that precluded successful osteotomy and pin placement for planned mandibular distraction. This report is of the first 13 children, aged 9 months to 6 years, who underwent predistraction enucleation. The osteotomy and device placement were performed successfully at least 4 months after enucleation. The described procedure has minimal morbidity and has resulted in successful subsequent distraction. The advantages, disadvantages, and cost-benefit issues are discussed

Objective: The goal of the consolidation phase of mandible distraction is to maintain the improvement in maxillomandibular form and relationship while the generated tissue ossifies. During this period, external deforming forces can act on the healing generated bone. The purpose of this study was to describe the potential cephalometric changes that occur following pediatric bilateral mandibular distraction using external devices. Design: Retrospective lateral superimposition cephalometric analyses. Participants: Thirty-five cases of pediatric mandible distraction were reviewed. Seven of these cases were included in the study after exclusion criteria were applied. These cases represented a group with severe congenital dysmorphology and a mean device activation of 26.5 mm. Main Outcome Measures: Changes in pogonion position, symphyseal plane rotation, mandible length, and mandible length relative to maxillary length during the 18 to 36 days of activation, the eight weeks of consolidation, and the 1-year period following removal of the distraction device were measured. Results: All patients demonstrated variable changes in position of the mandible during the consolidation phase. The most common were retrusion of pogonion, a decrease in mandible length, and a clockwise rotation of the symphyseal plane. In some cases the changes that occurred during consolidation were greater than those that occurred on 1-year follow-up. Conclusions: The consolidation phase of distraction osteogenesis is a dynamic phase and should not be assumed to be static. Multicenter use of this cephalometric technique would help to identify potential risk factors associated with postactivation changes

Mandibular distraction osteogenesis lengthens not only the affected skeleton but also the associated muscles of mastication. The purpose of this study was to determine medial pterygoid volume before and after distraction by using computed tomography. Using computed tomographic scans, the volume of the medial pterygoid muscle was determined before and after mandibular distraction in six pediatric patients. In four unilateral distraction patients (average age, 65 months), the average increase of the medial pterygoid muscle on the distracted side of the mandible was 29 percent, and on the contralateral nondistracted side, 10 percent. The average increase in medial pterygoid muscle volume in two bilateral distraction patients (each aged 8 months) was 75 percent. Results of this study demonstrate that distraction osteogenesis of the human mandible not only lengthens deficient bone, but it also increases the volume of the attached musculature

Initial clinical experience with distraction osteogenesis has demonstrated the risk of developing postdistraction malocclusion that requires secondary orthodontic correction. In addition, optimal mandibular form is not always achieved. Both animal studies and preliminary clinical investigations have suggested that the regenerate can be successfully 'molded' during active mandibular distraction. The authors have applied this concept clinically to obtain a more desirable occlusal relationship in a group of mandibular distraction patients. Eleven patients are described in whom angulation of the distraction device or intermaxillary/interdental elastics were employed to mold the regenerate. Two representative case studies are provided to illustrate the principles. When using elastic traction to close an anterior open bite, care must be taken that extrusion of individual teeth is minimized by distributing the force over the entire dental arch, especially the basilar portions of the jaws. The authors demonstrate that molding of the regenerate can be successfully accomplished not only during device activation but also early in the consolidation period. The outer limit of the time window in which molding is effective remains to be defined

Distraction osteogenesis has evolved as a mainstream surgical technique for lengthening and augmentation of the hypoplastic mandible. As clinical experience accumulated, there developed the need to 'mold' the bony regenerate to avoid the development of postdistraction malocclusion and to achieve the desired craniofacial form. Although the potential to mold the regenerate has important clinical implications, the safety and efficacy of such an acute manipulation of the bony regenerate form have not yet been investigated in the laboratory. The purpose of this study was to determine if the distraction regenerate could be molded and result in a bony union. Four adult female dogs underwent bilateral mandibular distraction with an external multiplanar device (Stryker, Osteonics). After a latency period of 5 days, the mandibles underwent linear (anteroposterior) and angular (superoinferior) distraction to produce an anterior open bite of approximately 30 degrees. At the conclusion of the distraction procedure, the distraction sites were molded to close the open bite. In two dogs, the maneuver was performed over 3 days by changing the angulation of the devices (gradual molding), and in the other two dogs, molding was achieved with a single movement (acute molding). In the latter, the distraction devices were adjusted and reapplied to allow for anatomical fixation during the consolidation period of 49 days. According to the research protocol, the mandibles were assessed serially by cephalograms and computed tomography (CT) scans. All dogs survived the study without complications. The bony regenerate was easily molded in both groups to close the surgically created open bite. After molding, all the regenerates showed CT scan evidence of solid bone (consolidation), which was classified as 'extended' on the Hamanishi scale. After the dogs were killed and soft tissue was removed, the regenerate seemed to be robust on gross examination without any evidence of fibrous nonunion. In addition, histological study of the regenerate confirmed the bony union. The study demonstrates that the mandible can be successfully molded into a desired anatomical position immediately after distraction without producing a fibrous union. Furthermore, it has been demonstrated that the bony regenerate is sufficiently malleable before consolidation to undergo either acute or gradual angular molding without disturbing osteogenic potential. The ability to mold the regenerate without the fear of creating a fibrous union or destroying bony potential provides the surgeon the capability to optimize the dental occlusion and mandibular form as part of the distraction treatment process

OBJECTIVE: The purpose of this study was to compare the financial impact of two treatment approaches to the unilateral cleft alveolus. The recently advocated nasoalveolar molding (NAM; and gingivoperiosteoplasty (GPP; at the time of lip repair were compared with the traditional approach of secondary alveolar bone graft. DESIGN: The records of all patients (n = 30) with unilateral cleft lip and alveolus treated by a single surgeon during 1985 through 1988 were examined retrospectively. The patients were divided into two groups: group 1 patients (n = 14) were treated by lip repair, primary nasal repair, and secondary alveolar bone graft prior to eruption of permanent dentition; group 2 patients (n = 16) were treated by NAM, GPP, lip repair, and primary nasal repair. Patients who required secondary alveolar bone graft after GPP were noted. The cost of treatment by each protocol was calculated in 1998 dollars. RESULTS: The average cost of treatment for a patient treated by lip repair, primary nasal repair, and secondary alveolar bone graft prior to eruption of permanent dentition was $22,744. Of the 16 patients treated by NAM, GPP, lip repair, and primary nasal repair, 10 required no further treatment of the unilateral cleft alveolus; six patients required secondary alveolar bone graft. The average per-patient treatment cost in this group was $19,745. The average cost savings of NAM and GPP, compared with alveolar bone graft is $2999. CONCLUSIONS: The treatment of unilateral cleft alveolus by nasoalveolar molding and gingivoperiosteoplasty results in substantial cost savings, compared with treatment by secondary alveolar bone graft

Distraction osteogenesis of the craniofacial skeleton has become a widely accepted, safe, and effective means of craniofacial reconstructive surgery. Despite excellent results in general, there are still some uncertainties related to the procedure, such as development of an anterior open bite (AOB) during mandibular distraction. The aim of this study was to examine whether 'moulding of the generate', i.e. use of intermaxillary elastics during the active distraction phase is possible to close the mandibular plane angle and open bite. Three subjects, 13- and 15-year-old males and a 7-year-old female, underwent mandibular linear and angular bilateral distraction osteogenesis with moulding of the generate. Lateral cephalograms were obtained before the introduction of elastics and following distraction, once the activation was stopped and the patients were ready for the consolidation phase. Conventional cephalometric measurements were used to assess possible changes in the mandibular plane angle and incisor position. Three different anchorage systems (dental, orthopaedic, and skeletal) were used for placement of the intermaxillary elastics. Cephalometric examination showed that the mandibular plane angle was decreased during active distraction osteogenesis with the introduction of elastics and angulation of the distraction device. Depending on the type of elastic anchorage system, smaller or greater amounts of extrusion of the incisors were noted. Moulding of the generate during active distraction can be performed to reduce the mandibular plane angle and open bite. To prevent unwanted dentoalveolar changes from occurring during elastic traction, skeletal rather than dental fixation of the elastics is recommended. Intrusive mechanics may be incorporated into the orthodontic appliances to balance extrusive force by the moulding elastics