Osteogenic alveolar distraction: A review of the literature

Hybrid Distractor for Continuous Mandibular Distraction Osteogenesis

Distraction osteogenesis (DO) is a reconstruction method for repairing bone deficiencies in the oral and maxillofacial area. Manual DO techniques have shown the functionality of the DO method for bone tissue reconstruction. The DO method can improve treatment conditions, as well as the quality of the reconstructed bone, compared with conventional techniques. Recently, continuous DO devices have been proposed to enable an automatic DO process while using a continuous force for moving the bone segment (BS). Animal studies and clinical trials have shown the successful application of continuous distractors in terms of improving DO factors, including rate and rhythm. The continuous DO technique can shorten the treatment time and enhance the quality of the regenerated tissue. However, the developed continuous distractors are yet to be used in human applications. In this study, by combining motor-driven and hydraulic techniques, a hybrid distractor is proposed. The hybrid distractor is capable of generating a continuous distraction force while controlling the position of the BS in a linear vector, with a high positioning accuracy. Results of modelling and experimental study revealed that the proposed hybrid distractor met all required factors for enabling a continuous DO procedure in humans. The proposed distractor is capable of eliminating the drawbacks of exiting techniques in terms of generating and transferring a controlled distraction force to the BS. The wireless control, as well as the small size of the device, makes this device a suitable solution for use in the reconstruction of bone defects in the maxillofacial area in humans.

Two-Axis Continuous Distractor for Mandibular Reconstruction

The application of Distraction Osteogenesis (DO) techniques in the reconstruction of skeletal deficiencies is a relatively new topic in the fields of oral and maxillofacial surgeries. In many reconstruction applications, using DO is the preferred technique, as opposed to conventional reconstruction techniques, as there are more advantages and fewer side effects when it is used. The first generation of DO devices is made up of manual distractors that can apply an intermittent distraction force to the bone segment during the distraction process. Manual DO techniques have shown the functionality of the DO technique. Further research has recently been performed on the development of automatic devices for generating a controlled continuous force. However, the existing automatic techniques have limitations, and are yet to be used in reconstruction applications in humans. There is still a gap between the developed techniques and an ideal distractor to be used in mandibular reconstruction surgeries. In this research, a two-axis continuous distractor is proposed for use in mandibular reconstruction applications. The proposed distractor can generate two continuous distraction forces that can be applied to two independent distraction vectors. The proposed device can perform the standard distraction process using the predetermined distraction factors. The control system has a high positioning accuracy and resolution in controlling the position of the intra-oral end effectors while applying two continuous forces for moving the bone segment. The proposed two-axis continuous distractor meets the current requirements, and can be used as an ideal continuous DO device for different mandibular reconstruction applications.

Does the Animal Model Influence in Vertical Alveolar Distraction? A Systematic Review of the Literature

Simple Summary

Vertical alveolar osteogenesis distraction (VAOD) technique appears to provide the best results in terms of vertical bone gain. Before its use in humans, most devices are tested on experimental animals. Currently, there is no consensus on which is the ideal biological animal model for VAOD studies. In this review, it has been found that the animal model influences the results. In addition, the most used, easier to handle, and with less complications was the Mongrel dog. The use of pigs and minipigs, given their difficult handling and poor hygiene, is not recommended.

Abstract

This study is aimed at synthesizing all available evidence on vertical alveolar osteogenesis distraction (VAOD) in animal trials to determine whether the animal model used and its handling influence or not, and find which is the most appropriate animal model for this specific technique. This systematic review has been carried out following the PRISMA statements. Bibliographic sources have been consulted manually by two reviewers. Risk of bias was assessed using a version of the Newcastle-Ottawa-Scale (NOS). The selection criteria established by expert researchers were applied in order to decide which studies should be included in the review. Twenty-six studies met the inclusion criteria and were included in the review. Twenty-four of them had a high quality (score between 7 and 9), two medium quality (score between 4 and 6), and none low quality (score between 1 and 3). The highest possible score was 9 (using the NOS). Six studies complied with all NOS criteria. The animal model has been seen to influence the results, leading to failure in some cases. The most used animal model on VAOD, with fewer complications, was the Mongrel dog. The use of the pig and minipig is not recommended, due to the difficulties in handling and complications encountered.

Osteogenically-induced exosomes stimulate osteogenesis of human adipose-derived stem cells

Exosomes exhibit great therapeutic potential in bone tissue engineering. The study aimed to investigate whether the exosomes derived from human adipose-derived stem cells (hADSCs-Exos) during different time-span of osteogenic differentiation could promote osteogenesis. The appropriate concentrations of hADSCs-Exos to enhance the proliferation, migration and osteogenesis of hADSCs-Exos were also examined. PKH67 labelled hADSCs-Exos was used to detect the internalization ability of hADSCs. The osteogenic differentiation abilities of hADSCs after treatment with hADSCs-Exos was evaluated by Alizarin red staining (ARS). The proliferation and migration of hADSCs was examined by cell counting kit-8 and wound healing assay, respectively. The expression of exosomal surface markers and osteoblast-related protein of hADSCs was assessed by Western blot. PKH67-labelled exosomes were internalized by hADSCs after 4 h incubation. ARS showed that the amount of mineralized nodules in Exo^1−14d group was significantly higher than that in Exo^15−28d group. hADSCs-Exos could promote the proliferation and migration capacity of hADSCs. Western blot analysis showed that after hADSCs-Exos treatment, ALP and RUNX2 were significantly enhanced. Specially, the Exo^1−14d group of 15 μg/mL significantly upregulated the expression of RUNX2 than the other exosomes treated groups. Our findings suggest that exosomes secreted by hADSCs during osteogenic induction for 1–14 days could be efficiently internalized by hADSCs and could induce osteogenic differentiation of hADSCs. Moreover, administration of Exo^1−14d at 15 μg/mL promoted the proliferation and migration of hADSCs. In conclusion, our research confirmed that comprised of hADSCs-Exos and hADSCs may provide a new therapeutic paradigm for bone tissue engineering.

Review of automatic continuous distraction osteogenesis devices for mandibular reconstruction applications

Distraction osteogenesis (DO) is an emerging method for bone tissue reconstruction. In oral and maxillofacial reconstruction applications, DO is playing an important role as a technique without the need of bone graft. In addition, in a DO treatment procedure, a superior outcome could be achieved compared to conventional reconstruction techniques. Recently, a few automatic continuous distraction osteogenesis (ACDO) devices have been designed and developed to be used in human reconstruction applications. Experiments and animal studies have validated the functionality of the developed ACDO devices. It has shown that by using such ACDO devices in a DO procedure, compared to conventional manual DO methods, superior outcomes could be obtained. However, the application of such ACDO devices is still limited. More research and investigation need to be undertaken to study all requirements of ACDO devices to be used in successful human mandibular DO treatment. It is important to determine all requirements and standards that need to be considered and applied in the design and development of ACDO devices. The purpose of this review paper is to highlight the designed and developed ACDO procedures thus far in terms of their working principles, working parameters, and technical aspects for providing a better perspective of the development progress of ACDO devices for oral and maxillofacial reconstruction applications. In this paper, design principles, device specifications, and working parameters of ACDO devices are compared and discussed. Subsequently, current limitations and gaps have been addressed, and future works for enabling an ultimate automatic DO procedure have been suggested.

Continuous distraction osteogenesis device with MAAC controller for mandibular reconstruction applications

Background

Distraction osteogenesis (DO) is a novel technique widely used in human body reconstruction. DO has got a significant role in maxillofacial reconstruction applications (MRA); through this method, bone defects and skeletal deformities in various cranio-maxillofacial areas could be reconstructed with superior results in comparison to conventional methods. Recent studies revealed in a DO solution, using an automatic continuous distractor could significantly improve the results while decreasing the existing issues. This study is aimed at designing and developing a novel automatic continuous distraction osteogenesis (ACDO) device to be used in the MRA.

Methods

The design is comprised of a lead screw translation mechanism and a stepper motor, placed outside of the mouth to generate the desired continuous linear force. This externally generated and controlled distraction force (DF) is transferred into the moving bone segment via a flexible miniature transition system. The system is also equipped with an extra-oral ACDO controller, to generate an accurate, reliable, and stable continuous DF.

Results

Simulation and experimental results have justified the controller outputs and the desired accuracy of the device. Experiments have been conducted on a sheep jaw bone and results have showed that the developed device could offer a continuous DF of 38 N with distraction accuracy of 7.6 nm on the bone segment, while reducing the distraction time span.

Conclusion

Continuous DF with high resolution positioning control, along with the smaller size of the distractor placed in the oral cavity will help in improving the result of the reconstruction operation and leading to a successful DO procedure in a shorter time period. The developed ACDO device has less than 1% positioning error while generating sufficient DF. These features make this device a suitable distractor for an enhanced DO treatment in MRA.

Mandibular Reconstruction by Osteogenic Distraction Due to Two Different Injuries

Varied factors, whether intrinsic or extrinsic, may lead to a decrease in the bone volume of the jaws. Trauma and pathology can be listed as examples of such factors. The aim of this study is to present the osteogenic distraction technique as alternative to augmentation of low mandibular bone volume caused by different etiologies. The first case reports a mandibular marginal resection of ameloblastoma and the second one reports a male patient presenting mandibular fracture sequelae. Both cases were treated according to the osteogenic distraction technique. Several factors have influence on the decision of treatment management of these conditions. Although autogenous bonegraft is considered criterion standard for alveolar reconstruction, its high rates of resorption and the morbidity associated to donor sites lead surgeons to seek for other surgical alternatives such as osteogenic distraction. Therefore, it also aims to expose the advantages and benefits of this technique as well as the satisfactory results achieved.

Vertical augmentation of the posterior atrophic mandible by interpositional grafts in a split-mouth design: a human tomography evaluation pilot study

OBJECTIVE

Using computed tomography, to compare vertical and volumetric bone augmentation after interposition grafting with bovine bone mineral matrix (GEISTLICH BIO-OSS^® ) or hydroxyapatite/tricalcium phosphate (STRAUMANN^® BONECERAMIC) for atrophic posterior mandible reconstruction through segmental osteotomy.

MATERIAL AND METHODS

Seven patients received interposition grafts in the posterior mandible for implant rehabilitation. The computed tomography cone beam images were analysed with OsiriX Imaging Software 6.5 (Pixmeo Geneva, Switzerland) in the pre-surgical period (T0), at 15 days post-surgery (T1) and at 180 days post-surgery (T2). The tomographic analysis was performed by a single trained and calibrated radiologist. Descriptive statistics and nonparametric methods were used to analyse the data.

RESULTS

There was a significant difference in vertical and volume augmentation with both biomaterials using the technique (P < 0.05). There were no significant differences (P > 0.05) in volume change of the graft, bone volume augmentation, or augmentation of the maximum linear vertical distance between the two analysed biomaterials.

CONCLUSIONS

The GEISTLICH BIO-OSS^® and STRAUMANN^® BONECERAMIC interposition grafts exhibited similar and sufficient dimensional stability and volume gain for short implants in the atrophic posterior mandible.

Custom-made titanium devices as membranes for bone augmentation in implant treatment: Clinical application and the comparison with conventional titanium mesh

OBJECTIVE

Development of new custom-made devices to reconstruct alveolar bone for implantation, and comparison with conventional methods were the goals of this study.

MATERIALS AND METHODS

Using a computer-aided design technique, three-dimensional images were constructed. From these data, custom-made devices were produced by a selective laser melting method with pure titanium. Clinical trials also have been conducted with 26 participants who needed bone reconstruction before implantation; they were divided into 2 groups with 13 patients each. The first group uses custom-made devices; the other uses commercial titanium meshes that need to bend during operation. Some clinical aspects are evaluated after the trial.

RESULTS

The custom-made devices can be produced closely by following the data precisely. Devices are fit for bone defect site. Moreover, the operation time of the custom-made group (75.4 ± 11.6 min) was significantly shorter than that of the conventional group (111.9 ± 17.8 min) (p < 0.01). Mucosal rupture occurs, without significant difference (p = 0.27), in a patient in the custom-made without severe infection (7.7%), and 3 in conventional (23.1%), respectively. The retaining screw is significantly fewer in the custom-made group than commercial mesh group (p < 0.01).

CONCLUSION

These results indicate that our novel protocol could be simple and safe for providing powerful support for guided bone regeneration.

Complications in the treatment with alveolar extraosseous distractors. Literature review

Background

To review the literature that analyses the types and frequency of complications associated with the use of extraosseous alveolar distraction from 2007 to 2013.

Material and Methods

Review of the literature in PubMed, using these keywords; alveolar ridge, alveolar distraction osteogenesis, complication, literature review. Inclusion criteria were: articles published between 2007 and 2013 that included the distraction protocol, the complications encountered and the time when they occurred.

Results

According to the above criteria, 12 articles were included in this review, where 334 extraosseous distractors were placed and 395 complications were encountered, of which 19 (4.81%) were intraoperative, 261 (66.07%) postoperative and 115 (29.11 %) were postdistraction. The most common complication was the incorrect distraction vector found in 105 cases (26.58%), in 23 cases (5.82%) there were severe complications, of which 14 (3.54%) were mandibular fracture and 9 (2.27%) were fractures of the distractor elements.

Conclusions

According to this review, although alveolar distraction is a safe and predictable technique, it can cause complications; however, they are usually minor and easily resolved without affecting the treatment outcome.

Key words: Alveolar ridge, alveolar distraction osteogenesis, complication, literature review.

Restoration of Oral Function for Adult Edentulous Patients with Ectodermal Dysplasia: A Prospective Preliminary Clinical Study

BACKGROUND

Therapy with zygomatic implants (ZIs) or conventional implants (CIs) has proven to be an effective method to restore oral function for systemically healthy patients. However, it is still a major challenge to fully restore oral function to edentulous adult patients with ectodermal dysplasia (ED).

PURPOSE

The aim of this study was to determine an effective treatment protocol for restoring oral function using ZIs and CIs to edentulous adult ED patients.

MATERIALS AND METHODS

Ten edentulous adult ED patients were treated in this study. The treatment protocol involved the following: (1) bone augmentation in the region of the anterior teeth; (2) placement of two ZIs and four CIs in the maxilla, and four CIs in the mandible; (3) fabrication of dental prosthesis; and (4) psychological and oral education. Following treatment of these patients, implant success rates, biological complications, patient satisfaction, and psychological changes were recorded.

RESULTS

Although there was evidence of bone graft resorption in the maxilla, bone augmentation of the mandible was successful in all patients. Nine CIs in the maxilla failed and were removed. All ZIs were successful, and the CIs success rates were 77.50% in the maxilla and 100% in the mandible, with a mean of 88.75%. The mean peri-implant bone resorption for the CIs ranged from 1.3 ± 0.4 mm to 1.8 ± 0.6 mm, and four cases exhibited gingival hyperplasia in the maxilla and mandible. One hundred percent of the patients were satisfied with the restoration of their oral function, and >50% of the patients exhibited enhanced self-confidence and self-esteem.

CONCLUSIONS

This study demonstrates that oral function can be restored in edentulous adult ED patients using a comprehensive and systematic treatment protocol involving psychological and oral education, bone augmentation, implant placement, and denture fabrication. Despite these positive outcomes, bone augmentation remains challenging in the anterior region of the maxilla for edentulous adult ED patients.

Clinical study comparing alveolar distraction using the lead system and MODUS MDO 1.5/2.0

This article compares 2 different alveolar distractors: Lead System (LS) and MODUS MDO 1.5/2.0 (M-MDO). This is a clinical retrospective study; 32 distractions were performed. We used the LS distractor (intraosseous) on 24 patients and the M-MDO (extraosseous) on the other 8. The variables included bone alveolar ridge height, alterations of the oral mucosa, number of distractors, implant survival, and complications. We also developed descriptive and univariate statistical analysis. The mean increase of bone height after performing the alveolar distraction was 6.15 mm, 5.74 mm with LS, and 8.36 mm with M-MDO (P < 0.0001). The survival rates of the implants in the intraosseous and extraosseous groups reached 100%. However, the use of M-MDO resulted in a significant defect in the alveolar mucosa during implant insertion (100%), an event that did not occur when using LS (P < 0.001). The most common complication in the intraosseous group was the tilting of the segment (25%), whereas, in the extraosseous group, the main difficulty was the rod interference with the opposing arch (75%). Bone defects after alveolar distraction appeared both in the intraosseous group (66.7%) and in the extraosseous group (50%). Both the LS and the M-MDO distractors are effective for alveolar bone distraction. The choice of one distractor over another depends on the clinical characteristics of each case, such as the size and shape of the defect, the patient's tolerance, the distance to the opposing arch, and the surgeon's experience.

Influence of periosteal coverage on distraction osteogenesis with dental implant distractors

PURPOSE

The continuity and integrity of the enveloping nutritive periosteum can be compromised during installation of a dental implant distractor (DID) device. This novel animal experiment investigated the influence of the periosteum on the bony regenerate in 3 scenarios of periosteal coverage: whole periosteum (WP), half periosteum (HP), and no periosteum (NP).

MATERIALS AND METHODS

Twelve goat tibias were vertically osteotomized into 2 segments each and divided into 3 groups (WP, HP, and NP). A DID device was surgically installed onto each segment, followed by 10 days of distraction at a rate of 0.35 mm twice daily. Fluorescence labeling and trabecula count per high-power field (TBC/HPF) measurements were performed and statistically compared across groups. Implant stability quotients (ISQs) of all fixtures were performed.

RESULTS

New bone formation occurred sooner in the WP and HP groups than in the NP group under fluoroscopy. The TBC/HPF values showed an obvious but not statistically significant decrease between the WP and HP groups (P = .500), WP and NP groups (P = .157), and HP and NP (P = .077). And the WP group showed no significantly higher ISQ values compared with the HP (P = .712) and NP (P = .958) groups, also between the HP and NP (P = .751) groups.

CONCLUSION

Vertical distraction osteogenesis can be performed successfully with the DID to obtain bone of adequate stock and density. However, the enveloping periosteum should be preserved as much as possible during installation of the DID device.

Partially Biodegradable Distraction Implant to Replace Conventional Implants in Alveolar Bone of Insufficient Height: A Preliminary Study in Dogs

BACKGROUND

Dental implants have been widely used in the last few decades. However, patients with insufficient bone height need reconstructive surgeries before implant insertion. The distraction implant (DI) has been invented to simplify the treatment procedure, but the shortcomings of DIs have limited their clinical use. We incorporated biodegradable polyester into a novel DI called the partially biodegradable distraction implant (PBDI).

PURPOSE

The purpose of this study was to assess the radiological, histological, and biomechanical properties of the PBDI in animal models.

MATERIAL AND METHODS

PBDIs were manufactured and inserted into the atrophied mandibles of nine dogs. Box-shaped alveolar bones were segmented and distracted. The dogs were randomly divided into three groups that were sacrificed 1, 2, and 3 months after the implant insertion. Actual augmentation height (AAH) of the bone segments was measured to evaluate the effect of distraction. X-ray examination and micro-CT reconstruction and analysis were used to evaluate the regenerated bone in the distraction gap and bone around the functional element. Histological sections were used to evaluate the osseointegration and absorption of the PBDI. Fatigue tests were used to evaluate the biomechanical properties of the PBDI.

RESULTS

Little change was found in AAH among the three groups. X-ray examination and micro-CT reconstruction showed good growth of regenerated bone in the distraction gap. Alveolar bone volume around the functional element increased steadily. No obvious bone absorption occurred in the alveolar crest around PBDI. Three months after distraction, the functional element achieved osseointegration, and the support element began to be absorbed. All PBDIs survived the fatigue test.

CONCLUSIONS

The PBDI is a novel and reliable dental implant. It becomes a conventional implant after the absorption of the support element and the removal of the distraction screw. It is a promising replacement for conventional implants in patients with insufficient alveolar bone height.

Evaluation of Vertical Bone Gain Following Alveolar Distraction Osteogenesis in the Anterior Edentulous Mandible: A Clinical Study

AIM AND OBJECTIVES

To calculate the gain in bony height and volume of the distracted upper segment using an extraosseous unidirectional device to improve the retention of the future prosthesis.

MATERIALS AND METHODS

Ten cases with completely or partially edentulous but severely or considerably resorbed anterior mandibles were managed by vertical alveolar distraction osteogenesis. All the patients were evaluated preoperatively, intraoperatively and post-operatively for various parameters clinically and radiographically i.e. on OPG, lateral cephalogram and on CT scan, at different time intervals. In all cases there was increase in vertical bone height.

RESULTS

The study showed mean vertical bone gain (VBG) on OPG as 8.2 mm. The mean VBG on lateral cephalogram was 8.1 mm. The mean VBG on CT scan at right canine was 8.35 mm, at left canine was 8.2 mm and at midline was 8.27 mm.

CONCLUSION

Alveolar distraction osteogenesis is a predictable method for restoring alveolar ridges prior to implant placement or prosthesis. Distraction osteogenesis is ideally suited for recreating missing tissue in the anterior esthetic zone by increasing vertical bone height as well as good width and soft tissue growth.

Alveolar distraction osteogenesis in the human mandible: a clinical and histomorphometric study

PURPOSE

To identify the quality of newly formed bone in the distraction region and to determine the percentage of mineralized bone formed in the distraction area.

METHODS

Ten patients with vertically deficient mandibular alveolar ridges were treated by means of distraction osteogenesis. Four months after consolidation of distracted segments, a total of 40 dental implants were inserted in native bone and distracted bone. Bone biopsies were taken at the implant sites with trephine burrs for histological and histometric analyses. Four months after implant placement, abutments were connected, and prosthetic loading of the implants was started.

RESULTS

The mean bone gain at the end of distraction was 7.2 ± 0.8 mm. The cumulative success rate of implants 3 years after the onset of prosthetic loading was 100%. The newly formed bone consisted of woven bone reinforced by parallel-fibered bone with bone marrow spaces and the percentage of mineralized bone ranged from 50.56% to 76.88%.

CONCLUSIONS

Alveolar distraction osteogenesis is able to produce adequate mature bone for the correction of mandibular bone deficits before dental implant insertion.

Alveolar ridge augmentation using distraction osteogenesis: a clinical trial

BACKGROUND

Severely resorbed ridges present a great challenge to prosthodontic rehabilitation. Available reconstructive options include autologous/alloplastic augmentation with questionable results, or regeneration of new bone under gradual and controlled tension using distraction osteogenesis. This study focused on use of distraction osteogenesis for the treatment of vertically deficient alveolar ridges to assess its feasibility and outcome.

MATERIALS AND METHODS

Alveolar distraction osteogenesis (ADO) was studied at 10 different intra-oral, partial or complete edentulous sites. After a latency period of 5 days, distraction was carried out for 6-7 days at the rate of 0.5 mm every 12 hours (1 mm/day). Distractor was removed after a consolidation period of 12 weeks.

RESULTS

The mean height gained at the 10 intra-oral sites was 4.8 mm with standard deviation of ± 0.056. The mean follow-up period was 2 years. Complications of therapy included hardware failure, wound gape and extra-oral scar. The overall complication rate was 10%.

CONCLUSION

Distraction osteogenesis is a promising option to aid uneventful prosthodontic rehabilitation of severe vertically resorbed alveolar ridges.

Bone regeneration and docking site healing after bone transport distraction osteogenesis in the canine mandible

PURPOSE

Bone transport distraction osteogenesis provides a promising alternative to traditional grafting techniques. However, existing bone transport distraction osteogenesis devices have many limitations. The purpose of this research was to test a new device, the mandibular bone transport reconstruction plate, in an animal model with comparable mandible size to humans and to histologically and mechanically examine the regenerate bone.

MATERIALS AND METHODS

Eleven adult foxhounds were divided into an unreconstructed control group of 5 animals and an experimental group of 6 animals. In each animal, a 34-mm segmental defect was created in the mandible. The defect was reconstructed with a bone transport reconstruction plate. Histologic and biomechanical characteristics of the regenerate and unrepaired defect were analyzed and compared with bone on the contralateral side of the mandible after 4 weeks of consolidation.

RESULTS

The reconstructed defect was bridged with new bone, with little bone in the control defect. Regenerate density and microhardness were 22.3% and 42.6%, respectively, lower than the contralateral normal bone. Likewise, the anisotropy of the experimental group was statistically lower than in the contralateral bone. Half the experimental animals showed nonunion at the docking site.

CONCLUSION

The device was very stable and easy to install and activate. After 1 month of consolidation, the defect was bridged with new bone, with evidence of active bone formation. Regenerate bone was less mature than the control bone. Studies are underway to identify when the regenerate properties compare with normal bone and to identify methods to augment bone union at the docking site.

Alveolar regions of the mandible for the installation of immediate-implant fixtures and bone screws of alveolar distractors

The purposes of this study were to elucidate the anatomic relationship between the dental roots and surrounding tissues and to identify the optimal sites at which to install dental surgical devices including immediate-implant fixtures and alveolar distractors. We made 5 types of measurements on horizontal cross sections obtained at 1-mm intervals from 20 Korean mandibles. The following results were obtained: (1) the mandibular facial plate was thinnest at the canine (0.5-0.7 mm) and became thicker toward the molar region; (2) the thicknesses of the facial and lingual cortical bone in the interdental region increased from anterior to posterior and from coronal to apical aspects; (3) in each section, the buccolingual root was narrower than 4 mm at depths greater than 8 and 9 mm in the central and lateral incisors, respectively, and the maximum mesiodistal root widths were 3.0 and 3.3 mm; (4) the interroot distance increased from anterior to posterior and from coronal to apical aspects; and (5) on the sections of the first and second molars, the diameter of the septal bone ranged from 4.2 to 7.9 mm buccolingually and from 1.3 to 3.3 mm mesiodistally. Achieving successful placements of implant fixtures and bone screws requires an accurate understanding of the anatomic structure at the installation site. The reported anatomic data might facilitate successful treatments and provide crucial information for use when planning and performing placements of dental surgical devices.

RANK/RANKL/OPG role in distraction osteogenesis

Distraction osteogenesis is a fundamental pillar for craniomaxillofacial reconstruction processes. Nonetheless, although the clinical, biomechanical, and histologic changes associated with distraction osteogenesis have been widely described, this is not the case with the molecular mechanisms that regulate bone synthesis in the interfragmentary gap resulting from the gradual separation of bone segments. Recent studies have attributed a decisive role to the RANK/RANKL/OPG system in regulating bone metabolism and osteoclastogenesis. Receptor activator of nuclear factor kappa beta (RANK), belonging to the tumor necrosis factor superfamily, is present in the osteoclasts. It promotes osteoclastogenesis when it binds to RANK ligand (RANKL), which is produced by the osteoblasts and other stromal cells. Osteoprotegerin (OPG) acts as a decoy receptor by binding to RANKL and preventing RANK signaling. Osteoclast activation is thus blocked and apoptosis induced. The aim of this review is to analyze the influence of the RANK/RANKL/OPG system on the bone healing and remodeling processes that occur in distraction osteogenesis, with a view to possibly developing molecular mechanisms that stimulate bone regeneration and inhibit resorption, thereby improving the clinical outcome for distraction osteogenesis.

Endosseous alveolar distractor (LEAD™) in the management of residual alveolar ridge resorption

BACKGROUND

Lack of sufficient alveolar bone height or width is one of the most frequent problems in the dental rehabilitation of the edentulous patient.

METHODS

A prospective study to evaluate the efficacy of an endosseous alveolar distractor (LEADTM) in managing residual alveolar ridge resorption was carried out. The complications related to the surgical procedure and the quantitative changes in the regenerate over a 6 month period following distraction were studied in 13 cases with alveolar ridge atrophy.

RESULT

Desired ridge augmentation was achieved in 11 cases. In 2 cases the distraction failed. Some unusual complications were encountered.

CONCLUSION

The LEAD™ alveolar distractor produces consistent augmentation of the alveolar bone but is confronted with stability issues.

Bone resorption and complications in alveolar distraction osteogenesis

Distraction osteogenesis presents an alternative procedure for augmentation of atrophic alveolar bone prior to inserting dental implants. The aim of this retrospective study was to evaluate complications of this method with specific focus on bone resorption during the consolidation period and the follow-up period after dental implant insertion into distracted bone. Thirty partially edentulous patients underwent a total of 36 vertical alveolar distractions with an extraosseous distraction system. Eleven devices were placed in the maxilla and 25 in the mandible. Eighty-two dental implants were inserted after a mean consolidation period of 4.5 months. Treatment results were evaluated by means of panoramic radiographs for distraction follow-up and periapical radiographs for implant follow-up. The mean length of the transport segment was 19 mm. The average alveolar height achieved was 6.4 mm with a mean resorption of 1.8 mm (21.1%) at the time of dental implant insertion. Main problems comprised oral displacement of the transport segment (n = 15) and inadequate soft tissue extension (n = 13). Eighty-two dental implants were inserted with an overall survival rate of 95.1% after 45.8 months. For periimplant marginal bone, an average resorption of 3.5 mm was recorded 50.4 months after implant insertion. Although alveolar distraction osteogenesis seems to be an effective tool to treat vertical defects of the alveolar ridge, it is not an uncomplicated procedure. A combination with vestibular augmentation of autogenous bone grafts should be considered. Overcorrection of 20% may compensate bone relapse during the consolidation period of the distracted alveolar bone. Further bone resorption after dental implantation is common.

Vertical distraction osteogenesis using a titanium nitride-coated distractor

OBJECTIVES

The purpose of this study was to examine the effect of using a titanium nitride (TiN)-coated vertical distractor on osseointegration after implantation.

STUDY DESIGN

Four adult mongrel dogs, weighing 9-10 kg, were used in this study. The lower premolars were extracted, and vertical distraction was performed after 10 weeks using 8 distraction devices (left, 4 titanium; right, 4 nitrified). A 7-day latency period was allowed before distraction began. The distraction device was activated at a rate of 0.5 mm twice a day for 5 days. After completing distraction, the device was removed after a consolidation period of 6 weeks and 24 implants were installed. The dogs were killed after 4 or 8 weeks. Histologic examinations were performed.

RESULTS

The implant success rate was 100% in all of the study groups. Direct bone contact was achieved, and there were no significant differences between the control and experimental groups in the implantation area.

CONCLUSION

The results suggested that the nitrified distraction device does not negatively affect osseointegration in the vertical distraction osteogenesis; therefore, it has the advantageous potential to substitute for the conventional distractor.

Osteogenesis distraction and platelet-rich plasma: combined use in restoration of severe atrophic mandible. Long-term results

OBJECTIVES

The purpose of this paper is to report long-term results on the use of autologous bone graft and platelet-rich plasma in alveolar distraction osteogenesis (DO) for restoration of severe atrophic mandible. We tested the efficacy as to reabsorption of bone volume, peri-implant reabsorption, implant survival and success rate.

MATERIALS AND METHODS

Twelve patients were treated. The surgical procedure consisted in mixing autologous bone, harvested from the iliac crest, with autologous platelet concentrate (APC) and in filling the distraction gap with this graft. After a latency of 15 days, a distraction rate of 0.5 mm/day was followed. After a 60-day period of consolidation, the distraction device was removed and implants were placed simultaneously. The abutment connection was accomplished after 6 months. In addition, every patient was evaluated clinically and radiographically annually for 5 years.

RESULTS

Planned alveolar height was reached in 11 out of 12 patients. The total number of implants positioned was 47. At the time of implant positioning, the mean decrease of total bone volume was 2.3%. The mean peri-implant resorption was 0.40 mm at the time of abutment connection, 0.61 mm 1 year after implant loading and 1.51 mm after 5 years. After 5 years of follow-up, the mean rate of vertical bone loss was 18.7%. Instead, the implant survival and success rates were 97.9% and 91.5%, respectively.

CONCLUSIONS

Long-term results allow us to confirm the combination of autologous bone-platelet gel with alveolar DO as an effective and predictable procedure in restoration of severe atrophic mandible.

Complications and relapse in alveolar distraction osteogenesis in partially dentulous patients

Vertical distraction of the alveolar process is an efficient method for augmentation prior to inserting dental implants. In this study, complications of this procedure and relapse of the transport segment were evaluated in partially dentulous patients. Twenty patients underwent distraction by means of extraosseous distractors. The location of the defects was the anterior mandible (4), posterior mandible (4), anterior maxilla (10) and posterior maxilla (2). Bone height was measured on panoramic radiographs preoperatively, after distraction and after implant placement at the mesial and distal point of the implant(s). Mean alveolar distraction was 6.5mm at the mesial point (P<0.001) and 6.1mm at the distal point (P<0.001). The mean relapse at the mesial point was 20% and at the distal point 17% (P<0.05). The intraoperative and postoperative problems encountered were fracture (1) and lingual (4) and palatal (6) displacement of the transport segment. Overall complication rate was 55%. Of all implants placed (n=63) one was lost. Implant success rate was 98%. Distraction seems to be a suitable treatment for vertically deficient alveolar bone, but a relatively high although manageable complication rate must be confronted, including considerable relapse.

Implant treatment without bone grafting in edentulous severely resorbed maxillas: a long-term follow-up study

PURPOSE

To evaluate retrospectively the surgical outcome of tilted implants in severely resorbed edentulous maxillas as an alternative to bone grafting and the prosthodontic outcome of posterior extension bridges on tilted implants.

PATIENTS AND METHODS

A total of 33 consecutive patients with severely resorbed edentulous maxillas participated in the study. In these patients, the maxillary bone volumes were insufficient for conventional placement of implants to support a fixed prosthesis. As an alternative to bone transplantation, a surgical technique with fenestration of the maxillary sinus to visualize the total amount of maxillary bone was used, followed by implant placement in a tilted manner along the anterior maxillary sinus wall. Thus, 4 to 6 implants of optimal length could be installed in each patient. Nineteen patients were included in this long-term follow-up study and were eligible for clinical evaluation at 8 to 12 years (mean, 10 years) after second-stage surgery. Each patient was examined clinically and radiographically.

RESULTS

The 19 patients had a total of 103 implants. In 2 of these patients, 3 fixtures were lost during the first year after second-stage surgery. All other patients had all implants intact with functionally fixed dental prostheses, corresponding to a success rate of 97%. Radiographic examination showed bone resorption in 10% of the implants (10 implants in 5 patients with a total number of 27 implants), with a mean bone loss of 1.2 mm. Mucositis was seen in 47% of the patients.

CONCLUSIONS

This long-term follow-up study (mean time, 10 years) demonstrates that patients with a severely resorbed maxilla can be treated successfully with conventional implant treatment. This simplified surgical technique can be an alternative to the more resource-demanding technique with bone grafting.

[Bidirectional and unidirectional distraction of defects of the alveolar process comparative clinical study]

AIM

The purpose of the retrospective study was to compare bidirectional distraction osteogenesis with the currently used unidirectional method of alveolar ridge distraction with regard to bone height attained and complications.

PATIENTS AND METHODS

Overall 21 patients were treated by distraction osteogenesis for localized defects of the alveolar ridge. Vertical augmentation of the mandible and maxilla was performed using 10 unidirectional (group A) and 12 bidirectional (group B) devices. The effect of therapy was evaluated by height of bone gain and observed complications.

RESULTS

The average gain of vertical bone height was approximately 6 mm. No statistically significant differences occurred between the two treatment groups (p=0.09). For the entire study two complications were observed: beside breakage of a distractor device (unidirectional distraction) an infection during the retention time (bidirectional distraction) developed.

CONCLUSIONS

It could be shown that osteodistraction is a potentially valuable therapy for the correction of alveolar defects. We observed complications in both groups. No statistical differences were noted in regard to gained bone height and complications between the two groups.