Distraction osteogenesis and histogenesis in beagle dogs: the effect of gradual mandibular osteodistraction on bone and gingiva

Periodontal changes following distraction osteogenesis in patients with cleft lip and palate: a clinical trial

Objectives

To evaluate inflammatory mediator levels and periodontal changes following distraction osteogenesis (DO) in patients with cleft lip and palate (CLP) using mid-maxillary distraction (MMD).

Materials and Methods

A total of 20 healthy patients with CLP with Class III malocclusion were included. Segmental forward advancement of the anterior maxilla from the second premolars on both sides using DO was performed. A custom-made, tooth-borne distractor connecting buccal molar segments to the anterior maxilla was used for 7 days with 0.5-mm distraction for the first 2 days and then increased to 1 mm daily until overcorrection. Crevicular interleukin IL-1β and tumor necrosis factor TNF-α levels were measured during distraction. Periodontal clinical parameters and indices were recorded at baseline and 3 and 6 months postoperatively. Soft tissue healing was evaluated histologically at 2 and 4 weeks after distraction.

Results

The periodontal parameters remained stable during the follow-up periods. Insignificant increases in the level of inflammatory cytokines compared with the control were observed. Histological findings revealed mild inflammatory and structural changes in the gingiva immediately after distraction, whereas regeneration was noticed after 4 weeks.

Conclusions

MMD was an effective technique in treating patients with CLP, leading to new bone and soft tissue formation without significant detrimental effect on the periodontium of the adjacent teeth.

Changes in posterior airway space and mandibular plane hyoid distance following mandibular advancement DO

Aim:

To study the changes in posterior airway space (PAS) and mandibular plane hyoid (MPH) distance following mandibular advancement using distraction osteogenesis (DO).

Subjects and Methods:

A prospective study was conducted at a tertiary care dental center from May 2009 to May 2014. Twenty-five consecutively operated patients of mandibular hypoplasia who underwent mandibular advancement using distraction with at least 12 months follow-up were included in the study. The study group comprised 15 males and 10 females with an age range of 15–30 years (mean 22 years). Presurgical and postsurgical cephalometric changes were compared to determine the changes in PAS and MPH distance.

Results:

The mean distraction achieved was 14.50 mm. The mean preoperative MPH was 18.88 mm and mean postoperative MPH was 13.16 mm with a resultant reduction by 32%. Mean preoperative PAS was 6.48 mm and mean postoperative PAS was 11.08 mm. Mean increase in PAS was 75%. Mean preoperative and postoperative SNB values were 75.4° and 79.52°, respectively. The results were statistically analyzed using paired “Student's t-test.”

Conclusion:

From this study, it is concluded that statistically significant changes were achieved in MPH and SNB. Although change in PAS was statistically insignificant, it may have clinical applications, especially in the field of Phase II surgical management of obstructive sleep apnea.

Accelerated Bone Formation in Distracted Alveolar Bone After Injection of Recombinant Human Bone Morphogenetic Protein-2

BACKGROUND

This study evaluates the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on the quality and quantity of regenerated bone when injected into distracted alveolar bone.

METHODS

Sixteen adult beagle dogs were assigned to either the control or rhBMP-2 group. After distraction was completed, an rhBMP-2 dose of 330 μg in 0.33 mL was injected slowly into the distracted alveolar crest of the mesial, middle, and distal parts of the alveolar bone in the experimental group. Histologic and microcomputed tomography analyses of regenerated bone were done after 2 and 6 weeks of consolidation.

RESULTS

After 6 weeks of consolidation, the vertical defect height in the middle of the regenerated bone was significantly lower in the rhBMP-2 group (2.2 mm) than in the control group (3.4 mm) (P <0.05). Additionally, the width of the regenerated bone was significantly greater in the rhBMP-2 group (4.3 mm) than in the control group (2.8 mm) (P <0.05). The bone density and volume of regenerated bone in the rhBMP-2 group were greater than in the control group after 6 weeks of consolidation (P <0.001).

CONCLUSION

Injection of rhBMP-2 into regenerated bone after a distraction osteogenesis procedure significantly increased bone volume in the dentoalveolar distraction site and improved both the width and height of the alveolar ridge and increased the bone density.

Distraction histogenesis of the maxillofacial region

The changes in the surrounding soft tissues during long bone distraction in orthopedic surgery have been the subject of several reports, studies on changes in the craniofacial region, in which various tissues, including the skin, muscle, tendon, blood vessel, and gingiva are rare. Therefore, there is a need for studies on the soft tissue aspects of bone lengthening of the craniofacial region. The aim of this review was to address this issue by reviewing the literature about the distraction histogenesis of various tissues, including skin, muscle, blood vessel, nerve, and gingiva.

Biomechanics of the canine mandible during bone transport distraction osteogenesis

This study compared biomechanical patterns between finite element models (FEMs) and a fresh dog mandible tested under molar and incisal physiological loads in order to clarify the effect of the bone transport distraction osteogenesis (BTDO) surgical process. Three FEMs of dog mandibles were built in order to evaluate the effects of BTDO. The first model evaluated the mandibular response under two physiological loads resembling bite processes. In the second model, a 5.0 cm bone defect was bridged with a bone transport reconstruction plate (BTRP). In the third model, new regenerated bony tissue was incorporated within the defect to mimic the surgical process without the presence of the device. Complementarily, a mandible of a male American foxhound dog was mechanically tested in the laboratory both in the presence and absence of a BTRP, and mechanical responses were measured by attaching rosettes to the bone surface of the mandible to validate the FEM predictions. The relationship between real and predicted values indicates that the stress patterns calculated using FEM are a valid predictor of the biomechanics of the BTDO procedures. The present study provides an interesting correlation between the stiffness of the device and the biomechanical response of the mandible affected for bone transport.

Recommendations for optimal distraction protocols for various animal models on the basis of a systematic review of the literature

The principles of orthopaedic distraction osteogenesis (DO) have been successfully applied to the craniofacial skeleton, but the latency time, rate and rhythm of distraction, and length of the consolidation period that are optimal for long-bone distraction may be suboptimal for craniofacial DO. The aim of this study was to provide recommendations for optimal distraction parameters in animal experimental research on craniofacial DO. The data used were from studies, added to the PubMed database between 1 January 1973 and 1 January 2007, on the outcome of DO resulting from variations in a single distraction parameter while standardizing the other distraction parameters. Although experimental animal group sizes were rather small, especially in those studies that used large animals, and both skeletally mature and immature animals were used, the (in most cases quantitative) data provided useful information on the optimal parameters in craniofacial DO. A latency period may not be necessary at all. Distraction should be performed at a rate of 1mm/day (this may be halved when small animals such as rats are used) preferably with a continuous rhythm, followed by a consolidation period of 6-8 weeks. These recommendations can be used as basic guidelines for further animal experimental studies on craniofacial DO.

The effect of mandibular distraction osteogenesis on the histology and immunohistology of keratinized gingiva

OBJECTIVES

We investigated distracted keratinized epithelium to elucidate any proliferative and degenerated changes and to estimate the stability of the gingival tissues in mandibular distraction osteogenesis in a rabbit model.

STUDY DESIGN

Twenty-two rabbits were subjected to unilateral vertical osteotomy. After a latency period of 4 days, devices were activated 3, 6, and 10 days at a rate of 1 mm/day. We additionally investigated the recovery of the distracted gingiva in consolidation periods for 3 weeks. The animals were examined by histologic and immunohistologic methods using proliferating cell nuclear antigen (PCNA), single-stranded DNA (ssDNA), and keratin.

RESULTS

Atrophy of distracted gingiva was observed characterized by loss of rete ridges, acanthosis, vacuolation in the prickle cell layer, and cleavage of the keratin layer. Proliferating cell nuclear antigen-positive cells and ssDNA-positive cells were observed in the basal and prickle layers, respectively. During consolidation periods, slight recovery of rete ridges, thinning of the keratin layer, and immature epithelial layer was observed.

CONCLUSIONS

Proliferative and degenerated changes occurred to compensate for cell death and distracted space. Thickness of gingival tissues was maintained by high mitotic activity and delay in the rate of cell maturation. Immature epithelial layer was related to sensitive and weak resistance against various stimulating factors, such as cleavage of the keratin layer among distracted gingival tissues.

Alveolar Distraction Osteogenesis for Bone Augmentation of Severely Atrophic Ridges in 10 Consecutive Cases: A Histologic and Histomorphometric Study

BACKGROUND

This study analyzed bone healing in surgically osteodistracted maxillary and mandibular ridges histologically and histomorphometrically at two different times to determine the best time to insert dental implants.

METHODS

Ten consecutive patients with severe maxillary (two patients) or mandibular (eight patients) atrophy underwent surgical osteodistraction with an extraosseous distractor. Seven days after the surgery, the distractor was activated at a rate of 1 mm/day until achieving the planned bone lengthening. The distractor was removed after a consolidation period of 70 days. Bone biopsies were obtained at implant insertion: 70 days after the end of distraction on the day of distractor removal in six patients (group A) or 180 days afterwards in four patients (group B). The biopsies were evaluated histologically and histomorphometrically to measure the osteocyte lacunar area (OLA).

RESULTS

The histologic and histomorphometrical analysis of the distracted bone 70 days after the end of distraction showed well-organized lamellar bone. At 180 days, the bone was more compact and mature; the mineralization of the matrix was greater; and an increased, but small, amount of marrow space was evident (35% versus 45%). The mean OLA was 80.11 +/- 27.59 microm2 in group A and 70.4 +/- 33.58 microm2 in group B. The difference between the two biopsy groups was not significant (P = 0.315).

CONCLUSION

The results of this study showed that there was definitely similar bone formation in the distracted area for both healing periods, and placing implants clinically worked in both of these time periods in the limited number of cases observed.

Osteoclastogenic activity during mandibular distraction osteogenesis

Mandibular distraction osteogenesis is a well-developed clinical modality for the treatment of craniofacial deformities and dental arch discrepancies, in combination with orthodontic treatment. However, in our previous study, orthodontic tooth movement into the distraction gap caused severe root resorption. The present study aimed to clarify the osteoclastogenic activity of cells in the distraction gap. We hypothesized that the gene expression of osteoclastogenic- and osteoclast-supporting molecules in osteoblasts and stromal cells would increase at distraction sites during the consolidation period. An animal model experiment involving rabbits was designed for mandibular distraction osteogenesis and subjected to in situ hybridization analysis. The number of osteoclasts was larger in the distraction gap during the early consolidation period than in normal controls, due to an increase of gene expression for osteoclastogenic cytokines in osteoblasts. It was concluded that osteoclastogenic and osteoclastic activities are stimulated at distraction sites during the early consolidation period.

Microstructural and Strength Evaluation of Regenerate Tissue during the Consolidation Period after Vertical Mandibular Ramus Distraction

Mandibular ramus height restoration by distraction osteogenesis (DO) is a key procedure in mandibular hypoplasia reconstruction. The objective of this study was to evaluate short-term skeletal changes in the regenerated bone after vertical mandibular ramus DO using a buried distraction device. Eight subadult beagle dogs underwent bilateral vertical mandibular ramus DO. After a 7-day latency period, distraction was performed at a rate of 0.5 mm twice a day for 12 days. Four dogs were killed at 1 month and four dogs at 2 months after the end of distraction. One intact beagle was included as an unoperated control. After sacrifice, micro computed tomography (muCT) and mechanical testing of distracted sites were used to measure bone volume (BV), total volume (TV), and mechanical peak load strength, respectively. The muCT images showed wide variation in the response, with some animals demonstrating considerable bone formation and reconstitution of the canal for the inferior alveolar nerve. Quantitatively, BV was no more than 67% and BV/TV was less than 25% of the intact control, and strength was approximately 33% of the intact control value. The 1 and 2 month values were similar. These results suggest that internal distractors can successfully reconstitute bone but that the regenerated tissue did not regain structural and mechanical characteristics of native bone within the 2 month study period.

Posterior Mandibular Alveolar Distraction Osteogenesis Utilizing an Extraosseous Distractor: A Prospective Study

BACKGROUND

The aim of this clinical study was to evaluate bone elongation and the effectiveness of distraction osteogenesis when utilizing an extraosseous distractor to treat cases of atrophic posterior mandible.

METHODS

Fourteen surgical sites were evaluated in 10 healthy, non-smoking, female patients, with varying degrees of atrophic posterior mandible, who underwent surgery by alveolar bone distraction. The patients presented between 6 and 10 mm above the mandibular, inferior alveolar nerve. Panoramic radiographs were taken before surgery and at the beginning and end of the consolidation period. The extraosseous distractor was fixed to both the basal and the osteotomized bone. After a 7-day latency period, the patients rotated the distractor rod three times a day for 3 to 10 days (1 mm per day). The mobile segment was held in place for 8 to 12 weeks for bone consolidation.

RESULTS

The results revealed a distraction range of 2.32 to 8.11 mm (mean distraction +/- standard deviation, 5.12 +/- 1.67 mm), which was less than the real, measured distance between the upper and lower miniplates of the distractor (5.58 +/- 1.62 mm). The bone segments showed between 0.03 and 2.53 mm (mean, 0.88 +/- 0.59 mm) resorption above the upper miniplate. The efficacy of the extraosseous distractor was calculated as between 30.41% and 94.58% (73.45% +/- 20.32%).

CONCLUSIONS

Bone regeneration was obtained in all cases; however, when planning alveolar bone distraction using the extraosseous distractor, greater distraction should be performed to compensate for the inclination of the distractor rod and possible bone loss. This adjustment should increase the efficacy of distraction osteogenesis.

Healing of maxillary alveolus in transport distraction osteogenesis for partial maxillectomy

PURPOSE

This study aims to evaluate histologic healing of the new bone and soft tissue in the distraction gap of maxillary alveolus after transport distraction at different consolidation intervals.

MATERIALS AND METHODS

In a monkey model, dentoalveolar segment was distracted backward to a surgical defect in the posterior maxilla with an internal distractor at a rate of 1 mm/day for 2 weeks. The distracted dentoalveolar processes were harvested at 1, 2, and 3 months of consolidation after the completion of distraction. Histologic examination included the new bone, gingiva of the distraction gap, and teeth carrying the transport segments. Tartrate-resistant acid phosphatase was used to assess the presence of osteoclasts in the new bone. The collagen type and expression of bone morphogenetic proteins (BMPs) in the new bone were assessed by immunohistochemistry.

RESULTS

The histology confirmed new bone bridging the distraction gap at 1 month of consolidation. Woven bone was progressively replaced by mature lamellar bone at the second and third months. The gingiva covering the distraction gap was of normal appearance. There were no pathologic pulpal changes noted in the transport segment. Tartrate-resistant acid phosphatase-positive osteoclasts were minimal in the new bone. The mode of ossification was confirmed as intramembranous, and the fibrous stroma consisted mainly of collagen type I. At 1 month of consolidation, the BMPs were expressed profusely in the fibrous matrix and also inside the fibroblasts and osteoblasts. At 2 and 3 months of consolidation, the BMP expression intensity was reduced significantly in the fibrous stroma.

CONCLUSIONS

The study confirmed that the bone regenerate in maxillary transport distraction was formed by intramembranous ossification and teeth in the transport segment remain viable after maxillary transport distraction osteogenesis.