Distraction Side Research Articles

Acceleration of Orthodontic Tooth Movement Using Two Different Distraction Techniques

A shortened orthodontic treatment period is the demand of the modern era. Various methods, namely corticotomy, micro-osteoperforation, distraction, etc., have been implored to achieve a quicker tooth movement. Our report presents a comparison of periodontal and dentoalveolar distraction techniques done using a modified HYRAX as distractor in contralateral arches of the same patient. Results showed that the canine was retracted in 13 days on the periodontal distraction side and in 16 days on the side of dentoalveolar distraction. Hence, it can be concluded that the distraction technique significantly reduces the treatment time duration.

Identyfikacja strony szyby, z której doszło do uszkodzenia, jako typ zadań diagnostycznych w ramach badań kryminalistycznych

The peculiarities of the diagnostic tasks of the forensic traces examination in determining the distraction side of the window, depending on the location of the relief drawing on the edges of the cracks and the end surfaces of the fragments are considered in this article. The effects of force on glass have been have been studied in this article. The changes in the lateral force and bending moment affecting the glass plate, which is loaded with force in the middle of the section and at the free end, are analyzed. The sections in which internal force factors have maximum values are established. The order of formation of radial and concentric cracks on the window glass is justified. The relief pattern on the edges of the cracks and the end surfaces of the glass fragments was examined. The mechanism for forming radial and concentric cracks of arcuate shaped lines and serrations on the sides and ribs is justified. The process of formation of the intended radial cracks has been investigated and justified. Recommendations for removing and directing objects from glass for study are made.

Convex Instrumented Hemiepiphysiodesis With Concave Distraction: A Treatment Option for Long Sweeping Congenital Curves.

Convex hemiepiphysiodesis has been reported to have mixed results in the treatment of congenital spine deformities. Multiple modifications of the original technique were suggested to improve the results. The purpose of this study is to report the results and complications of an instrumented convex growth arrest procedure modified with concave distraction. The records of 11 patients with long sweeping congenital curves (involving multiple anomalous vertebrae) who underwent convex instrumented hemiepiphysiodesis with concave distraction were evaluated. Mean age at index operation was 58 months (range, 29 to 101 mo). Lengthening of the concave distraction rod was done every 6 months. The magnitude of coronal/sagittal deformity and T1-T12 height were measured on the preoperative, postoperative, and latest follow-up radiographs. Average follow-up was 44.9 months (range, 24 to 89 mo). In the coronal plane, the convex hemiepiphysiodesis segment was corrected from an average of 60.5 to 40.4 degrees postoperatively and further improved to 35.5 degrees at the latest follow-up. The distracted segment was corrected from 33.4 to 15.2 degrees postoperatively and to 12.7 degrees at the latest follow-up. Sagittal plane alignment was minimally affected. The average T1-T12 height was 157.1 mm in the early postoperative period and 181.1 mm at last follow-up. During follow-up, we identified partial pull-out of screws on the distraction side in 5 of the 11 patients and rod breakages in 3 patients. These were revised during planned lengthenings. There were no unplanned surgeries, deep wound infections, nor neurological complications. Convex instrumented hemiepiphysiodesis with concave distraction resulted in good curve correction while maintaining the growth of thorax. The correction of the anomalous segment improved over time, proving the effectiveness of the hemiepiphysiodesis. Addition of a concave distraction construct appears to enhance spinal growth, thereby augmenting the hemiepiphysiodesis effect.

A Comparative Study of Canine Retraction by Distraction of the Periodontal Ligament and Dentoalveolar Distraction Methods.

Canine distraction was introduced as an alternative treatment to retract the canines in minimum possible period of 3weeks. It involved rapid canine retraction through distraction of the periodontal ligament. Another technique for rapid canine distalization involved osteotomies surrounding the canines to achieve rapid movement of the canines in the dentoalveolar segment known as dentoalveolar distraction. The present study is intended to assess and evaluate canine retraction by the above two mentioned methods of distraction osteogenesis. Eight orthodontic patients who required first premolar extractions were selected and 16 canines were distracted into the extraction space, using a distraction screw. The distraction procedure was completed in 15.38±1.51days on the side of periodontal ligament distraction while it took 14.50±2.45days on the side of dentoalveolar distraction. No significant anchorage loss was seen in both the sides. The distal displacement of the canines was 6.63±0.90mm on the periodontal distraction side at the rate of 0.43±0.05mm/day and 6.91±1.16mm on the side of dentoalveolar distraction at the rate of 0.48±0.08mm/day. An angulation change of 14.94°±7.58° was observed in canine inclination in periodontal distraction side while change of 14.88°±3.15° was seen in the dentoalveolar distraction side. No significant differences in the various parameters were found between both the techniques of canine retraction by distraction osteogenesis, while reducing orthodontic treatment duration by 6-9months without any unfavorable short-term effects on the periodontium.

Evaluation of canine retraction following periodontal distraction using NiTi coil spring and implants – A clinical study

ObjectiveTo evaluate the amount of canine retraction with periodontal distraction using miniscrew implants and NiTi coil spring. Material and methodSample comprised of 25 patients who were scheduled for all 1st premolar extraction (13 males and 12 females), in the age range of 16–22 years with mean age 18.8 ± 2.7 years. For each patient left side served as control side (Group I) and right side as experimental side (Group II). At the time of first premolar extraction, periodontal distraction was performed only on the experimental side, followed by retraction of canine from mini-implant by closed NiTi coil spring on both the sides. “Nemotech” software was used to evaluate the amount of canine retraction for a period of 3 months. ResultsSignificantly higher amount of tooth movement was seen from T0–T1 and from T1–T2 in Group II for the maxillary parameters 3C-5C, 6CF-3C, 3C-I/3C-J and for the mandibular parameter 6CF″-3C″. Whereas no significant amount of tooth movement was observed for maxillary and mandibular parameters between T2-T3 except for 6CF″-3C″ (p ≤ 0.01) which was significantly higher for the Group II. ConclusionThere was accelerated canine retraction on the periodontal distraction side as compared to the control side, with negligible anchorage loss.

Morphological Changes in Intervertebral Disks of the Caudal Part of the Rat Spine after Permanent and Temporary Asymmetrical Compression-Distraction

Experiments on 44 rats addressed the histological characteristics of tissue injury and repair in segments of the caudal part of the spine after prolonged permanent and temporary (with subsequent relaxation of the tail) asymmetrical compression-distraction (ASCD). The results showed that permanent ASCD of the tail led to complex structural changes which were very stable and did not disappear after release of ASCD and relaxation. Cell necrosis was seen in the annulus fibrosus (AF), with stretching of the lamellae of the AF and separation from the epiphyses on the side of distraction, and crushing and fiber separation of the collagen lamellae of the AF on the compression side, along with proliferation of chondrocytes around necrotic foci. The nucleus pulposus (NP) showed increases in the number of necrotized chordal cells. Relaxation after temporary ASCD led to decreases in the extent, but not complete elimination, of signs of injury. There were changes in AF thickness, frequency of foci of necrosis, and areas of separation of collagen lamellae, as well as displacement of the NP on the distraction side.

Primary Study of the Use of a Shape-Memory Alloy Distraction Device in the Dog Mandible for Alveolar Ridge Distraction: Determination of Osteotomy Techniques and Evaluation of Osteogenesis Outcome

The titanium-nickel shape-memory alloy distractor is a new kind of alveolar ridge distraction device that can be completely buried and self-activated. To evaluate this new device, the present study compared the effects of 2 osteotomy techniques and investigated the osteogenesis outcome by measuring the bone mineral density and biomechanical properties of newly generated bone tissues. Adult mongrel canines (n = 18) were randomly divided into 3 groups. All the mandibular teeth were extracted. Group I received a complete osteotomy, whereas groups II and III received a partial osteotomy with preservation of the glossal cortical bones. The left mandible served as the experimental site for each group, and the right side served as the internal control. Groups I and II were sacrificed 3 months after the completion of distraction, whereas group III was sacrificed 6 months after the completion of distraction. Radiographs were taken. Dual-energy x-ray absorptiometric results and compressive biomechanics of the distracted and control bone masses were examined for groups II and III (partial osteotomy group). The complete osteotomy group exhibited a larger distraction space initially; however, the distracted area showed a remarkable depression on the buccal-glossal side. In contrast, the partial osteotomy groups exhibited a nearly normal mandibular morphology. The bone mineral density, compressive strength, and elastic modulus were decreased in the distracted side compared with the control side 3 months after distraction. These 3 parameters increased in the distracted side 6 months after distraction, which did not differ significantly from those in the control side. Partial osteotomy with preservation of the glossal cortical bones is more suitable for alveolar ridge augmentation using the shape-memory alloy distraction device. The newly generated bone exhibited adequate strength, which can satisfy the requirements of subsequent implantation.

Histomorphometric examination of long-term changes in temporomandibular joints after mandibular lengthening by distraction osteogenesis in rabbits

The purpose of this study was to evaluate long-term histomorphometric changes in temporomandibular joints (TMJs) of rabbits after mandibular distraction osteogenesis (DO). Twenty-six rabbits were used in this study. Two of them served as control subjects, and the remaining 24 underwent DO procedures in their left mandibular bodies. After a latency period of 5 days, 5 mm lengthening was performed at a rate of 1 mm/d. The rabbits in the experimental group were randomly divided into 4 subgroups and killed after 1, 2, 4, and 6 months. TMJs from both sides were harvested and prepared with hematoxylin and eosin stain for histomorphometric examination under an optical microscope. Compared with control subjects and nondistracted sides, fibrous articular, proliferative, and hypertrophic areas were significantly increased (P < .05) in the first 2 months in distracted sides. The changes were insignificant in the fourth and sixth postoperative months. Unilateral mandibular distraction of 5 mm was found to be well tolerated and no degenerative changes were observed histologically in the rabbit TMJs in the long-term period.

Condylar cartilaginous changes after mandibular distraction osteogenesis in rabbits

The purpose of this study was to evaluate histologic and immunohistochemical changes in the condylar articular surface in response to distraction osteogenesis (DO) of the mandibular body in rabbits. A unilateral osteotomy of the mandible at the premolar area was performed in 16 rabbits. The animals were divided into 4 groups based on different distraction parameters (rate and rhythm). After a 5-day latency, the mandible was lengthened by 0.5 mm daily for 6 days (group 1); 0.5 mm twice daily for 3 days (group 2); 0.5 mm once daily for 10 days (group 3); or 0.5 mm twice daily for 5 days (group 4). All 4 groups underwent a 14-day consolidation period. Four rabbits were included in the control group. The specimens were stained with hematoxylin-eosin for histologic examination. Immunohistochemical analysis was performed to evaluate the expression of growth factors. None of the groups demonstrated any degenerative changes in the temporomandibular joint (TMJ). On the distraction side in all groups, the histopathological examination revealed a hypertrophic thickening of the cartilage zone. Prominent endochondral ossification and high active osteoblasts were observed in groups 3 and 4. On the nondistraction side, no major changes were observed excluding the appearance of osteoclasts in groups 3 and 4. The immunohistochemical analysis revealed tenascin immunoreactivity in bone marrow mesenchymal cells on the distraction side in group 4. Connexin immunoreactivity did not display a marked change in any of the groups. Osteocalcin was observed on the distraction side in group 2, which suggested that bone formation is increased. Nitric oxide synthase 2 immunoreactivity was observed on the distraction side in group 2, which is associated with stress and inflammation. The results indicated that the hypertrophy of the cartilage zone and endochondral ossification became more pronounced as the extent and rate of distraction increased.

Transport distraction versus costochondral graft for reconstruction of temporomandibular joint ankylosis: which is better?

This study compared the methods of transport distraction and costochondral graft in reconstruction of temporomandibular joint (TMJ) ankylosis. Bilateral bony TMJ ankylosis was induced in 12 adult goats. Transport distraction of the mandibular ramus was performed on one side, whereas costochondral graft was performed on the other side. Jaw movements, TMJ healing, condylar remodeling, and recurrence of ankylosis were assessed by clinical, radiological, and histological examinations. Both transport distraction and costochondral graft established a neo-condyle separating from the pseudo-disc with a joint space. The ankylosis scores were higher in the distraction side in the first 12 weeks. Both techniques showed no significant difference in the calcification scores and recurrence of ankylosis in the long term. The maximal jaw movements in 3 directions returned to the pre-ankylosis stage by both methods. Distraction osteogenesis is an effective reconstruction method for TMJ ankylosis, matching the gold standard of costochondral grafting.

Histomorphometric evaluation of delayed changes in masseter muscle after lengthening the rabbit mandible by distraction osteogenesis

The aim of the study was to evaluate the delayed responses and changes of gradually lengthened masseter muscles of rabbit mandibles. Unilateral lengthening of rabbit mandibles was performed in 18 New Zealand rabbits for 7 days at the rate of 1 mm day(-1). Mandibles of animals were removed at months 3, 4, and 6 after distraction. Biopsy samples of distracted and contralateral side masseter muscles were histopathologically evaluated and mean area of muscle fibers (MAF) was evaluated with histomorphometric methods. Results were statistically analyzed. Mild to moderate atrophy of the fibers, and necrosis and myophagocytosis in some areas were the leading features at month 3 and which were decreased at month 4 in distracted side-muscle specimens, with no statistically significant differences when compared with non-distracted side muscles at the same periods. Almost completely, normal fibers were detected in distracted muscle specimens at month 6. Evidence of myopathic changes was found to disappear at month 6 and no significant difference was found in the MAF of distracted side muscles. This study showed that the masseter muscle could adapt to gradual lengthening of the mandible within 6 months. Regenerative features and some degree of atrophic changes that could be observed at months 3 and 4 disappeared at month 6, with adaptation of the fibers.

Animal experimental study on repairing alveolar clefts by using rectilinear distraction osteogenesis

The aim of this study was to evaluate the clinical applicability of rectilinear distraction osteogenesis for repairing alveolar cleft models. Alveolar process distraction surgery to produce bilateral clefts was performed on six adult cats. In our study, the left side with the distraction device was the experimental side, and the other side without a distraction device was the control side. After a 6-day latent period, animals underwent gradual distraction at a rate of 0.6mm per day (distraction was performed twice each day, at a rate of 0.3mm each time), until the tissue on the two sides of the cleft touched, then the distraction strength was maintained for 2 days. Two cats were sacrificed at 2 weeks, 6 weeks and 10 weeks postoperatively. Gross anatomical, histological and radiographical analyses were performed after the animals were sacrificed. In addition, the arch width was measured both before setting the distraction device and after distraction was complete. Two weeks after the distraction was complete, the soft tissue of the two sides of the cleft region on the experimental side touched, and it began to coalesce. The extremities of the two sides of the cleft region on all the experimental sides drew close to each other, but there was no bony conjunction. New bone formation appeared in the distraction region. The arch width at the front of the maxillary bone on the distraction side after distraction was smaller than before distraction. The alveolar cleft could be closed by rectilinear distraction osteogenesis. Two sides of the cleft touched each other and only soft tissue coalesced, but we did not observe bone coalescing. This phenomenon suggested that it might be difficult to achieve complete bony repair by rectilinear distraction osteogenesis. However, rectilinear distraction osteogenesis can minimise the size of the alveolar cleft and make bone grafting advisable for those patients who are not suitable for bone grafting before distraction osteogenesis.

Growth of the Mandible after Condylar Reconstruction Using Transport Distraction Osteogenesis: An Experimental Investigation in Goats

Mandibular condyle damage during childhood disturbs mandibular growth and facial skeletal development. Transport distraction osteogenesis provides a new treatment for condyle reconstruction, but there are no data available on mandibular growth in growing individuals following surgery. The authors investigated the effect of condylar reconstruction by transport distraction osteogenesis on mandibular growth in goats. A condylar defect was created unilaterally in 44 growing goats. The animals were divided randomly into group A (n = 22) and group B (n = 22). Transport distraction was used to reconstruct the condyles in group A, whereas group B served as sham controls. Three-dimensional computed tomographic imaging was performed at different intervals. Ten animals from each group were used for mandibular growth measurements at 48 weeks after the end of distraction. Four animals from each group were euthanized at 12, 24, and 48 weeks after surgery. Their transport disks were harvested and processed for histologic evaluation. In group A, the hemimandible of the distracted side exhibited similarities to the contralateral side except for the larger neocondyles. In group B, ramus height and width were significantly shorter on the undistracted side than on the contralateral side; concomitantly, there was mandibular deviation to the operated side. Well-organized fibrocartilage was seen at the neocondylar surface over time in group A but not in group B. This study suggests that a neocondyle reconstructed by means of transport distraction has the potential to grow under functional stimuli of the temporomandibular joint. Therefore, this technique may serve as an alternative method for condylar reconstruction in growing individuals.

Torus Mandibularis and Maxillary Exostoses following Distraction Osteogenesis

The aetiology of torus and exostoses is still an uncertain issue, although there are several hypotheses explaining the development thereof. The present case reports an unfavourable outcome following mandibular distraction for the treatment of unilateral temporomandibularjoint ankylosis in a patient and describes the possible causes of its occurrence. A 30-year-old female patient with monolateral ankylosis of the temporomandibular joint and serious deformity of the maxillomandibular complex secondary to functional limitation was treated with mandibular distraction osteogenesis in order to lengthen the mandible. The patient showed recovery both injunction and symmetry. In the first year of postoperative follow-up, the occurrence of mandibular torus and maxillary exostoses were observed on the distraction side. Follow-up of the lesions was opted as the lesions were small in size and not causing the patient any problems.

Poster 125: Mandibular Lengthening by Distraction Osteogenesis (DO) in a Porcine Model: Changes in Anterior Digastric Muscle

The effects of mandibular lengthening by distraction osteogenesis on the muscles of mastication are not well understood. The purpose of this investigation was to document the changes, over time, in the digastric muscle in response to unilateral mandibular lengthening. In this experiment, 17 mixed dentition Yucatan minipigs were used: Osteotomy and unilateral (right side) mandibular distraction osteogenesis using a protocol of 0-day latency, 1 mm/day rate of distraction for 12 days, followed by 24 days of fixation (n=14 minipigs); osteotomy and acute lengthening of 12 mm (n=2); and sham control with dissection and 0 mm advancement (n=1). Anterior digastric muscles were harvested from the distraction and contralateral sides at mid-DO, end-DO, mid-fixation, and end-fixation. The same muscle samples were harvested from the acute lengthening and sham control groups 24 days after operation. All muscle samples were fixed, embedded in paraffin, and sectioned transversely and longitudinally. Specimens were stained with Hematoxylin & Eosin (H&E) or immunostained against PCNA. To evaluate histologic changes, a blinded pathologist examined all the H&E slides under light microscopy for the presence of inflammation, hematoma, necrosis, fibrosis, edema and for the size of muscle fibers. Histologic images (400X) from H&E slides were used for computer histomorphometric analysis. The cross-sectional surface area of the muscle fibers was measured by histomorphometric software (Image J, NIH) and the data were analyzed for statistical significance (two sample T-test). Proliferation activity was evaluated by calculating the percentage of PCNA positive nuclei in six randomly chosen fields in each sample. Statistical significance of the means was evaluated using the Wilcoxon’s matched pairs test. In two of 4 pigs, at mid-DO, there was a mild and scattered inflammatory infiltrate in the experimental side muscle. There were no inflammatory changes observed in specimens at end-DO (n=4), mid-fixation (n=4) and end-fixation (n=2). Muscles from the sham control group also demonstrated no inflammatory changes. In the acute lengthening group (n=2), inflammatory infiltrate, fibrosis, edema, and hematoma were present in the digastric on the experimental side. Histomorphometric analysis showed that cross-sectional surface area of the anterior digastric myocyte fibers on the distracted side were significantly (10%) larger than controls at end-fixation. In the acute lengthening group there was a 23% reduction in myocyte fiber cross-sectional surface area 24 days postoperative. The size of myocyte fiber nuclei was increased on the distracted side at all time points. Data from PCNA immunohistochemistry revealed that the anterior digastric muscle, which is parallel to the distraction vector, had a 3.6-fold (mid-DO group), 7.1-fold (end-DO group), 10.4-fold (mid-fixation group), 10.3-fold (end-fixation group) increase in PCNA-positive myocytes compared with the contralateral samples. Anterior digastric muscle in the acute lengthening group had a 2.9-fold increase in PCNA-positive myocytes when compared to the contralateral muscle. The results of this study indicate that the anterior digastric muscle, whose fibers are parallel to the distraction vector, undergoes hypertrophy and proliferation in response to DO.

The influence of callus distraction on the growth plate

This study was designed to investigate the morphology, thickness and cellularity of the growth plate during callus distraction performed in the immediate vicinity of the growth plate. Lengthening of the right tibia by 25% was carried out on 24 beagle dogs by callus distraction. Distraction was started at the fifth postoperative day with a distraction rate of 0.5 mm twice a day. A control group of six dogs underwent tibial osteotomy and external fixation without distraction. Half of the dogs of both groups were sacrificed at the end of the distraction phase of 25 days (Group A) and the remaining 15 dogs after an additional consolidation period of 25 days (Group B). The tibia and femur was removed from the distracted right leg and from the left control side of each animal and longitudinal sections were cut and stained with Pentachrome. The thickness and cellularity of the regeneration zone, the proliferation zone and the hypertrophic zone were determined for the proximal tibial and the distal femoral epiphysis. During the distraction phase the thickness of the proximal tibial growth plate and its cellularity were reduced on the distraction side. During the consolidation phase there was a slight recovery in the proximal tibial growth plate. Callus distraction leads to a temporary reduction in growth of the affected physis.

Changes in growth and morphology of the condyle following mandibular distraction in minipigs: Overloading or underloading?

Objective Loading of temporomandibular tissues during mandibular distraction may cause changes in condylar growth and cartilage thickness. This study examines the effects of distraction on the condyle in a large animal model by explicitly measuring growth and in vivo loading. Design Unilateral mandibular distraction was carried out on 20 growing minipigs divided into three groups. One group underwent distraction but not consolidation, whereas the other two groups were allowed a period of consolidation of either 1 or 2 weeks. Animals received fluorochrome and 5-bromo-2′-deoxyuridine (BrdU) labelling and masticatory strain was measured from the condylar neck. Condylar strain was also recorded in an age-matched sample of eight animals that received no distraction surgery. Immunohistochemical procedures were used to identify dividing prechondroblasts and histological analysis was used to measure mineral apposition rate, count dividing cells, and measure the thickness of condylar cartilage. Results Strain magnitude, particularly compressive strain, was much larger on the non-distraction side compared to the distraction side condyle. Compared to normal loading levels, the distraction side condyle was underloaded whereas the condyle on the intact side was overloaded. Mineral apposition and cartilage thickness were greater on the distraction side condyle compared to the opposite side. Differences between the sides were most pronounced in the group with no consolidation and became progressively reduced with consolidation time. Conclusions Increased mineralisation and cartilage thickness on the distraction side condyle are associated with reduced, not increased loading, perhaps because of disruption of the distraction side masseter muscle.

Distraction Osteogenesis Promotes Angiogenesis in the Surrounding Muscles

Distraction osteogenesis is used to treat atrophic nonunion and focal osteomyelitis. It enhances blood vessel formation in the distracted callus and in the surrounding soft tissues. Long-term angiogenesis, however, is not well described. We hypothesized newly formed blood vessels persist in the surrounding muscles until the late consolidation period. We performed unilateral tibial lengthening in eight adult Beagles. Seven days after tibial osteotomy, we began lengthening for 30 days, following which consolidation was allowed to proceed for another 60 days. We took bilateral microangiograms of the bilateral tibialis anterior, extensor digitorum longus, and gastrocnemius muscles. We determined the blood vessel volume density and the longitudinal and transverse microangiographic scores. The number of blood vessels in specified diameter ranges was determined histologically. The blood vessel volume density of the distracted limb was higher in all three muscles. The longitudinal microangiographic score was higher for the tibialis anterior and extensor digitorum longus muscles on the distracted side, whereas the transverse microangiographic score was not higher. Histologically, the number of blood vessels less than 100 mum in diameter on the distracted side was higher in the tibialis anterior and extensor digitorum longus muscles. Our data suggest distraction osteogenesis activates angiogenesis and maintains increased vascularity until the late consolidation period.

O.362 Bimaxillary distraction in hemifacial microsomia: A retrospective study of 6 patients

Seven children with facial asymmetry, mean age 12 years (range 11–14.5) were treated by intraoral distraction osteogenesis to lengthen the hypoplastic ramus.We achieved a mean increase in length of the ramus of 13 mm (range 10–16). In only one patient did we achieve a posterior open bite on the distraction side. All patients ended with a symmetrical chin.It was helpful to place an orthodontic bite block on the opposite side either preoperatively or postoperatively to cant the plane of occlusion. The duration of follow-up was too short to allow conclusions to be drawn about the future requirement for bimaxillary osteotomies.

Condylar Mineralization Following Mandibular Distraction in Rats

The impact of mandibular distraction on condyles is poorly understood. To examine how condylar mineralization is affected, we performed distraction in 128 one-month-old rapidly and 126 three-month-old slowly growing rats. The rate of distraction was 0.0 mm (sham), 0.2 mm (slow), 0.4 mm (moderate), or 0.6 mm (rapid). From 7 to 9 rats from each rate (n = 29-32) were killed at 4 time periods (D6, D10, D24, and D38) following osteotomy. Calcein and alizarin were injected 6 and 3 days, respectively, prior to death. Methacrylate-embedded sagittal condylar sections were examined under epifluorescence, and mineral apposition rates were measured. Results indicated that: (1) rapidly growing rats showed higher mineral apposition rates (p < 0.01-0.001) than did slowly growing rats; (2) mineral apposition rates were lower in distracted sides at all times in rapidly growing rats (p < 0.05-0.01), while this side-dependency was seen only at D24 in slowly growing rats (p < 0.05); and (3) distraction rates had little effect on mineral apposition rates. Thus, mandibular distraction decreases condylar mineral apposition rates, but only in rapidly growing rats, which is related to surgery and its functional consequences, not to the distraction rate.