Bone regeneration in mandibular distraction osteogenesis combined with compression stimulation

Reverse Dynamization Accelerates Regenerate Bone Formation and Remodeling in a Goat Distraction Osteogenesis Model

UPDATE

This article was updated on December 20, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. Figure 4 has been replaced with a figure that presents different p values. Also, on page 1943, the text that had read: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was much smaller compared with the SF (p = 0.06) and DF (p = 0.007) groups, although it was significantly smaller only compared with the DF group (Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller in the RD group compared with the other groups, but the RD group had values closest to those for the intact tibia. Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p = 0.034; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone. It also had significantly higher vBMD compared with the SF and DF groups (p < 0.0001 for both; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.001 versus SF group, and p = 0.0493 versus DF group)."now reads: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was significantly smaller compared with the SF and DF groups (p < 0.01 for both groups; Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller compared with the SF and DF groups (p < 0.0001 for both). The RD group had values closest to those for the intact tibia, and this difference was not significant (Fig. 4-A). Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p < 0.01; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone, but the intact bone was significantly different compared with all of the other groups (p < 0.0001 for all groups). The RD group had significantly higher vBMD compared with the SF and DF groups (p = 0.042 and p = 0.046, respectively; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.0001 versus SF group, and p = 0.0493 versus DF group). The intact group was significantly different compared with the SF group (p < 0.0001)."

Effect of the accordion technique on bone regeneration during distraction osteogenesis: A computational study

BACKGROUND AND OBJECTIVE

Distraction osteogenesis (DO), a bone lengthening technique, is widely employed to treat congenital and acquired limb length discrepancies and large segmental bone defects. However, a major issue of DO is the prolonged consolidation phase (10-36 months) during which patients must wear a cumbersome external fixator. Attempts have been made to accelerate the healing process of DO by an alternating distraction and compression mode (so-called "accordion" technique or AT). However, it remains unclear how varied AT parameters affect DO outcomes and what the most effective AT mode is.

METHODS

Based on an experimentally-verified mechanobiological model, we performed a parametric analysis via in silico simulation of the bone regeneration process of DO under different AT modes, including combinations of varied application times (AT began at week 1-8 of the consolidation phase), durations (AT was used continuously for 1 week, 2 weeks or 4 weeks) and rates (distraction or compression at 0.25, 0.5, 0.75, and 1 mm/12 h). The control group had no AT applied during the consolidation phase.

RESULTS

Compared with the control group (no AT), AT applied at an early consolidation stage (e.g. week 1 of the consolidation phase) significantly enhanced bone formation and reduced the overall healing time. However, the effect of AT on bone healing was dependent on its duration and rate. Specifically, a moderate rate of AT (e.g. 0.5 mm/12 h) lasting for two weeks promoted blood perfusion recovery and bone regeneration, ultimately shortening the healing time. Conversely, over-high rates (e.g. 1 mm/12 h) and longer durations (e.g. 4 weeks) of AT adversely affected bone regeneration and blood perfusion recovery, thereby delaying bone bridging.

CONCLUSIONS

These results suggest that the therapeutic effects of AT on DO are highly dependent of the AT parameters of choice. Under appropriate durations and rates, the AT applied at an early consolidation phase is beneficial for blood recovery and bone regeneration. These results may provide a basis for selecting effective AT modes to accelerate consolidation and reduce the overall treatment period of DO.

Slight Elongation of the Scaphoid and Cancellous Bone Graft Without Compression for Treatment of Scaphoid Nonunions

In treating scaphoid nonunion, we have developed a technique of bone grafting and elongation of the scaphoid stabilizing the construct with K wires without compression. Bony union was achieved in the large majority of scaphoids as demonstrated on computed tomography (CT) scans. We advocate slight lengthening of the scaphoid with bone graft and K-wire fixation without compression of the grafted bone when treating scaphoid waist nonunion.

Pumping the Periosteum: A Feasibility Study: Periosteal Distraction Osteogenesis in a Rat Model

PURPOSE

Gradual elevation of periosteum from the bone surface is known to promote the adaptation of soft tissues and the formation of hard tissues. The aim of our study was to estimate the benefit of periosteal distraction osteogenesis (PDO) on de novo bone formation in a rat model.

MATERIALS AND METHODS

After device placement, animals were allowed for a latency period of 7 days. Animals in the PDO group were subjected to distraction at a rate of 0.1 mm/d for 10 days. In the periosteal pumping (PP) group, the animals were subjected to distraction at a rate of 0.1 mm/d. The direction of distraction was alternated every 2 days. The animals were euthanized at 17, 31, and 45 days after surgery, and the samples were analyzed histologically and by microcomputed tomography.

RESULTS

In both groups, the new bone was characterized as primary woven bone that was located at the leading edge of bone apposition. Bone volumes significantly increased throughout the observation period both in the PP group (P = 0.018) and in the PDO group (P < 0.001). The new bone was denser and more mature in the PP group than in the PDO group, and the difference was significant at the 31-day time point (P = 0.024). However, the volume of the new bone was higher in the PDO at the 45-day time point (P < 0.001).

CONCLUSIONS

We propose that the PP may be applied to enhance the osteogenic capacity of periosteum without plate elevation. Because this is only a proof-of-principle study, the alternated protocol of periosteal distraction warrants evaluation in the future studies.

Distraksiyon ostegenizisi ve maksillofasyal bölge güncel uygulamaları :derleme

Distraksiyon osteogenezisi kallusu gererek yeni kemik oluşturma tekniğidir. Bu teknik ilk olarak Rus bilim adamı ortopedist İlizarov tarafından uzun kemiklerde geliştirilmiştir.Distraksiyon osteogenezisi; osteotomi periyodu, latent periyod, distraksiyon periyodu ve konsolidasyon periyodu olmak üzere 4 safhadan oluşmaktadır. Kolay, etkili ve komplikasyonu az olan bir uygulamadır. Distraksiyon osteogenezisi, maksillofasiyal cerrahide yaygın olarak kullanılabilmesi için modifikasyonlara ve geliştirmelere ihtiyaç duyulan bir tekniktir. Distraksiyon osteogenezisi tekniğinin gelişmesi için materyal ve teknik olarak birçok araştırma yapılmıştır ve birçok gelişme kaydedilmiştir. Ancak bu araştırmalar henüz tam bir kesinlik kazanmamakla beraber olumlu sonuçlar vermektedir

Implant-Supported Hybrid Prosthesis for Severe Mandibular Defects: A Sequence of Treatments From Alveolar Distraction Osteogenesis to Implant Restoration

PURPOSE

Although a variety of treatment methodologies for the physiological reconstruction of mandibular defects exist, the use of these methods has often been fragmented and has focused on partial effects of therapy. This article describes a sequence of treatments for a severe mandibular defect.

PATIENTS AND METHODS

Two patients with severe hard and soft tissue defects had physiological function restored in 4 steps, including alveolar distraction osteogenesis, implant insertion based on a prosthesis, application of dermal matrix membrane in reconstruction of attachment gingiva, and the use of a hybrid prosthesis designed via computer-aided design and computer-aided manufacturing, to produce an adequate bone tissue volume, an adequate amount of attached gingiva, and a reliable prosthesis.

RESULTS

The sequence of treatments successfully achieved physiological reconstruction. Biological complications around the implants and mechanical complications in the implants or prostheses did not occur within a 4-year follow-up period.

CONCLUSIONS

On the basis of the current 4-year follow-up, this study shows that a treatment sequence can be predictable and effective for severe mandibular defects, which suggests that it could be considered a potential protocol for patients with severe mandibular defects.

The effect of biomechanical stimulation on osteoblast differentiation of human jaw periosteum-derived stem cells

Background

This study was to investigate the effect of biomechanical stimulation on osteoblast differentiation of human periosteal-derived stem cell using the newly developed bioreactor.

Methods

Human periosteal-derived stem cells were harvested from the mandible during the extraction of an impacted third molar. Using the new bioreactor, 4% cyclic equibiaxial tension force (0.5 Hz) was applied for 2 and 8 h on the stem cells and cultured for 3, 7, and 14 days on the osteogenic medium. Biochemical changes of the osteoblasts after the biomechanical stimulation were investigated. No treatment group was referred to as control group.

Results

Alkaline phosphatase (ALP) activity and ALP messenger RNA (mRNA) expression level were higher in the strain group than those in the control group. The osteocalcin and osteonectin mRNA expressions were higher in the strain group compared to those in the control group on days 7 and 14. The vascular endothelial growth factor (VEGF) mRNA expression was higher in the strain group in comparison to that in the control group. Concentration of alizarin red S corresponding to calcium content was higher in the strain group than in the control group.

Conclusions

The study suggests that cyclic tension force could influence the osteoblast differentiation of periosteal-derived stem cells under optimal stimulation condition and the force could be applicable for tissue engineering.

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.

Sequential treatment for a patient with hemifacial microsomia: 10 year-long term follow up

Hemifacial microsomia (HFM) is the most common craniofacial anomaly after cleft lip and cleft palate; this deformity primarily involves the facial skeleton and ear, with either underdevelopment or absence of both components. In patients with HFM, the management of the asymmetries requires a series of treatment phases that focus on their interception and correction, such as distraction osteogenesis or functional appliance treatment during growth and presurgical orthodontic treatment followed by mandibular and maxillary surgery. Satisfactory results were obtained in a 9-year-old girl with HFM who was treated with distraction osteogenesis. At the age of 19, genioplasty and mandible body augmentation with a porous polyethylene implant (PPE, Medpor®, Porex) was sequentially performed for the functional and esthetic reconstruction of the face. We report a case of HFM with a review of the literature.

The effect of altering the mechanical loading environment on the expression of bone regenerating molecules in cases of distraction osteogenesis

Distraction osteogenesis (DO) is a surgical technique where gradual and controlled separation of two bony fragments following an osteotomy leads to the induction of new bone formation in the distracted gap. DO is used for limb lengthening, correction of bony deformities, and the replacement of bone loss secondary to infection, trauma, and tumors. Although DO gives satisfactory results in most cases, one major drawback of this technique is the prolonged period of time the external fixator has to be kept on until the newly formed bone consolidates thus leading to numerous complications. Numerous attempts at accelerating bone formation during DO have been reported. One specific approach is manipulation of the mechanical environment during DO by applying changes in the standard protocol of distraction. Attempts at changing this mechanical environment led to mixed results. Increasing the rate or applying acute distraction, led to poor bone formation in the distracted zone. On the other hand, the addition of compressive forces (such as weight bearing, alternating distraction with compression or by over-lengthening, and then shortening) has been reported to increase bone formation. It still remains unclear why these alterations may lead to changes in bone formation. While the cellular and molecular changes occurring during the standard DO protocol, specifically increased expression of transforming growth factor-β1, platelet-derived growth factor, insulin-like growth factor, basic fibroblast growth factor, vascular endothelial growth factor, and bone morphogenic proteins have been extensively investigated, the literature is sparse on the changes occurring when this protocol is altered. It is the purpose of this article to review the pertinent literature on the changes in the expression of various proteins and molecules as a result of changes in the mechanical loading technique in DO and try to define potential future research directions.

Quantitative histologic evidence of amifostine-induced cytoprotection in an irradiated murine model of mandibular distraction osteogenesis

BACKGROUND

Head and neck cancer management requires adjuvant radiotherapy. The authors have previously demonstrated the damaging effect of a human equivalent dose of radiation on a murine mandibular model of distraction osteogenesis. Using quantitative histomorphometry, the authors' specific aim was to objectively measure amifostine radioprotection of the cellular integrity and tissue quality of an irradiated and distracted regenerate.

METHODS

Sprague-Dawley rats were assigned randomly into two groups: radiotherapy/distraction osteogenesis and amifostine/radiotherapy/distraction osteogenesis, which received amifostine before radiotherapy. Both groups received a fractionated human equivalent dose of radiation prior to left mandibular osteotomy with fixator placement. Distraction to 5.1 mm was followed by a 28-day consolidation period. Quantitative histomorphometry was performed on left hemimandibles for osteocytes, empty lacunae, bone volume-to-tissue volume ratio, and osteoid volume-to-tissue volume ratio.

RESULTS

Amifostine/radiotherapy/distraction osteogenesis exhibited bony bridging as opposed to radiotherapy/distraction osteogenesis fibrous unions. Quantitative histomorphometry analysis revealed statistically significant higher osteocyte count and bone volume-to-tissue volume ratio in amifostine-treated mandibles compared with irradiated mandibles. There was a corresponding decrease in empty lacunae and the ratio of osteoid volume-to-tissue volume between both groups.

CONCLUSIONS

The authors have successfully established the significant osseous cytoprotective and histoprotective capacity of amifostine for distraction osteogenesis in the face of radiotherapy. The amifostine-sparing effect on bone cellularity correlated with increased bony unions and elimination of fibrous union. The authors posit that the demonstration of similar efficacy of amifostine in the clinic may allow the successful implementation of distraction osteogenesis as a viable reconstructive option for head and neck cancer in the future.

The effect of 2 different distraction-compression models on new bone generation

PURPOSE

To compare the stimulating effect of distraction and 2 different distraction-compression models on maturation of new bone during healing.

MATERIALS AND METHODS

Thirty adult Sprague-Dawley rats underwent unilateral mandibular osteotomy. The animals were divided into 3 groups. A unidirectional external distraction device was fixed to the mandible. A total of 4 mm of distraction was planned in all groups. After a latency period of 3 days, 0.2 mm of distraction was performed twice a day for 10 days in the distraction group. In the intermittent distraction-compression group, 0.2 mm of distraction was performed twice a day for 3 days, followed by 0.2 mm of compression twice a day for 1 day. In the overdistraction-compression group, 0.2 mm of distraction was performed twice a day for 14 days, followed by 0.2 mm of compression twice a day for 4 days. After a consolidation period of 6 weeks in all groups, animals were killed for macroscopic, microscopic, and radiologic evaluation.

RESULTS

Radiologic evaluation proved that more mature bone generation occurred in the groups in which compression was added to distraction. The number of osteoblasts in the intermittent distraction-compression group was significantly higher than that in the distraction group and overdistraction-compression group (P < .001). The highest number of vessels was found in the intermittent distraction-compression group (17.7 ± 6.4) (P < .001).

CONCLUSIONS

The intermittent distraction-compression model was found to generate greater new bone compared with distraction alone. In clinical applications, to increase the quality of the bone and to shorten the consolidation period, compression can be applied during distraction.

Experimental model of distraction osteogenesis in edentulous rats

Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin.

STUDY PROTOCOL

latency: 6 days, distraction: ¼ turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.

Analysis of the biomechanical properties of the mandible after unilateral distraction osteogenesis

BACKGROUND

The purpose of this study was to establish biomechanical outcomes measures to evaluate how mandibular distraction osteogenesis affects the overall quality of bone healing. Strength and functional integrity of the regenerate were determined quantitatively after unilateral mandibular distraction osteogenesis in comparison with the contralateral mandible and a partially reduced fracture. The authors hypothesized that the breaking load, yield, and stiffness of mandibular distraction osteogenesis would be significantly reduced in comparison with both the contralateral mandible and a partially reduced fracture.

METHODS

Sprague-Dawley rats underwent mandibular distraction osteogenesis (n = 8) or a partially reduced fracture (n = 6). Distraction was performed using 4 days' latency and then 0.3 mm every 12 hours for 8 days (5.1 mm). Partially reduced fractures had gaps fixed postoperatively at 2.1 mm. Both groups underwent 4 weeks of consolidation. The contralateral mandibles were used as controls (n = 14). Mandibles were tension tested at 0.5 mm/second to failure, and then breaking load, yield, and stiffness were determined.

RESULTS

Mandibular distraction osteogenesis had significantly lower breaking load, yield, and stiffness than contralateral mandible, by 40, 30, and 60 percent, respectively. Breaking load was reduced in partially reduced mandibular fractures by 40 percent when compared with distraction osteogenesis.

CONCLUSIONS

Using a standard Ilizarov protocol, the biomechanical properties of breaking load, yield, and stiffness in mandibular distraction osteogenesis were significantly lower than those in contralateral mandibles. Surprisingly, the breaking load of mandibular distraction osteogenesis was significantly greater than that of partially reduced mandibular fracture. These verifiable metrics of regenerate integrity can be used to discern optimal outcomes of mandibular distraction osteogenesis, potentially enhancing the clinical applications of this powerful technique.

Regenerate healing outcomes in unilateral mandibular distraction osteogenesis using quantitative histomorphometry

BACKGROUND

The authors' goal was to ascertain regenerate bone-healing metrics using quantitative histomorphometry at a single consolidation period.

METHODS

Rats underwent either mandibular distraction osteogenesis (n = 7) or partially reduced fractures (n = 7); their contralateral mandibles were used as controls (n = 11). External fixators were secured and unilateral osteotomies performed, followed by either mandibular distraction osteogenesis (4 days' latency, then 0.3 mm every 12 hours for 8 days; 5.1 mm) or partially reduced fractures (fixed immediately postoperatively; 2.1 mm); both groups underwent 4 weeks of consolidation. After tissue processing, bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, and osteocyte count per high-power field were analyzed by means of quantitative histomorphometry.

RESULTS

Contralateral mandibles had statistically greater bone volume/tissue volume ratio and osteocyte count per high-power field compared with both mandibular distraction osteogenesis and partially reduced fractures by almost 50 percent, whereas osteoid volume/tissue volume ratio was statistically greater in both mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles. No statistical difference in bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, or osteocyte count per high-power field was found between mandibular distraction osteogenesis specimens and partially reduced fractures.

CONCLUSIONS

The authors' findings demonstrate significantly decreased bone quantity and maturity in mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles using the clinically analogous protocols. If these results are extrapolated clinically, treatment strategies may require modification to ensure reliable, predictable, and improved outcomes.

Expression of TGF-beta1, osteonectin, and BMP-4 in mandibular distraction osteogenesis with compression stimulation: reverse transcriptase-polymerase chain reaction study and biomechanical test

PURPOSE

This study compared the levels of transforming growth factor-beta1 (TGF-beta1), osteonectin, and bone morphogenetic protein-4 (BMP-4) expression in regenerated bone in a rabbit mandible that had undergone conventional distraction osteogenesis (DO) with those in regenerated bone from a modified DO technique with compression stimulation.

MATERIALS AND METHODS

A total of 42 rabbits were used in this reverse transcriptase-polymerase chain reaction study. In the control group, distraction was performed at 1 mm/day for 8 days. In the experimental group, overdistraction was performed for 10 days, followed by a 3-day latency period and 2 days of compression to achieve the same amount of DO. Three rabbits per subgroup were killed at 0, 5, 13, 20, 27, 34, and 41 days after the initial osteotomy. The levels of TGF-beta1, osteonectin, and BMP-4 in the bone regenerates were measured by reverse transcriptase-polymerase chain reaction. A biomechanical microhardness test was also performed in 8 rabbits as a separate experiment.

RESULTS

Reverse transcriptase-polymerase chain reaction revealed a greater level of TGF-beta1 in the experimental group immediately after applying the compression force that continued for 2 weeks. The level then decreased to that of the control group at 3 weeks. The greater level of osteonectin in the experimental group after compression than that in the control group continued for 3 weeks. In the experimental group, the level of BMP-4 increased immediately after compression. However, the level in the control group decreased. The microhardness ratio of distracted bone to normal bone on the cortex was statistically different at 0.47 in the control group and 0.80 in the experimental group (P = .049) at 55 days after osteotomy.

CONCLUSION

The effectiveness of the new DO technique with compression stimulation was confirmed by the gene expression study and the biomechanical test findings.

Acceleration of spinal fusion using syngeneic and allogeneic adult adipose derived stem cells in a rat model

Posterolateral spinal fusion is the standard treatment for lumbar compression fractures. Adult adipose tissue-derived stem cells (ASCs) promote osteogenesis in vivo and in vitro. The hypothesis tested in this study was that syngeneic and allogeneic ASCs on a biomaterial scaffold composed of tricalcium phosphate and collagen I will accelerate spinal fusion in a rat model. ASCs from male Fischer or ACI rats were loaded onto scaffolds (53,571 cells/mm(3)) and cultured in stromal media for 48 h. Male Fisher rats were assigned to 4 cohorts (n = 14/cohort) after bilateral decortication of the L4 and L5 transverse processes: (1) No treatment; (2) scaffold only; (3) scaffold + syngeneic ASCs; or (4) scaffold + allogeneic ASCs. Half of each cohort was harvested 4 or 8 weeks after surgery. Spinal fusion was evaluated with radiographs, microcomputed tomography, and light microscopy. Callus did not form in spines without scaffolds. There were no significant differences in callus formation among scaffold cohorts 4 weeks after surgery. Callus formation was more mature in both ASC cohorts versus scaffold alone 8 weeks after surgery based on microstructure as well as radiographic and microcomputed tomographic evidence of active bone formation. Inflammatory cell infiltrate was significantly lower in both ASC cohorts (syngeneic = 18.3 +/- 0.85%; allogeneic = 23.5 +/- 2.33%) versus scaffold alone (46.8 +/- 11.8%) 4 weeks after surgery. Results of this study support syngeneic and allogeneic ASC acceleration of posterior lumbar spinal fusion in a rat model.

Histologic study of the cellular events during rat mandibular distraction osteogenesis

OBJECTIVE

The cellular events, underlying bone regeneration through rat mandibular distraction osteogenesis (DO) was examined using micro computerized tomography (microCT), histology, and histochemistry.

STUDY DESIGN

After 5-day latency, mandibles were distracted at 0.2 mm/12 h for 10 days, and fixed at latency 5 days (L5D), distraction 3, 6, 10 days (D3D, D6D, D10D), and consolidation 1, 3, 6, 10 weeks (C1W, C3W, C6W, C10W).

RESULTS

The microCT demonstrated radiopacity at the distraction gap (DG) during C1W, which was filled with new bone at C6W and C10W. At D3D, collagen fibers were aligned along the axis of the distraction vector. At D6D, alkaline phosphatase-positive osteoblasts and intramembranous ossification was observed. Collagen bundles became thicker with new bony trabeculae at D10D. Type II collagen-immunopositive areas first appeared at C1W. At C3W, cartilage tissue and endochondral ossification were found. By C6W, the entire DG had been bridged by new bone. The C10W specimens showed mature lamellar bone.

CONCLUSION

Mandibular DO produces bone through both intramembranous and endochondral ossification.

Nicotine impairs distraction osteogenesis in the rat mandible

Distraction osteogenesis (DO) has gained clinical acceptance as a surgical technique for treatment of congenital craniomaxillofacial deficiencies requiring skeletal expansion. The use of this technique elsewhere requires more information on overcoming difficult clinical settings, for which new animal models will be needed. The aim of this study was to develop and validate a model of impaired DO of the rat mandible with nicotine. Twenty rats underwent a right vertical mandibular body osteotomy, after which distraction began with custom-made percutaneous devices and a 3-day latency period, 6-day distraction (0.25 mm twice daily) and 30 days of neutral fixation. Rats received either nicotine or placebo slow-release pellets. Specimens were analysed after removal of the devices for quantitative radiographic bone fill, amount of bone advancement and histological features. The mean radiographic bone-fill score with nicotine treatment was 75% of that with placebo (P=0.0036). The nicotine-treated rats had less (49%) elongation than the placebo-treated controls (P=0.0008). Histological analysis demonstrated less bone, vascularity and cellular activity in nicotine-treated rats. This study shows that nicotine reproducibly inhibits osteogenesis, vascularity and bone lengthening in mandibular DO.