Effect of phosphate treatment of Acid-etched implants on mineral apposition rates near implants in a dog model

PURPOSE

This study evaluated the effects of phosphate coating of acid-etched titanium on the mineral apposition rate (MAR) and new bone-to-implant contact (BIC) in a canine model.

MATERIALS AND METHODS

Titanium implants (2.2 3 4 mm) with acid-etched surfaces that were electrolytically phosphated or not were placed in 48 mandibular sites in six foxhounds. Tetracycline and calcein dyes were administered 1 week after implant placement and 1 week before sacrifice. At 12 weeks after implant placement, the animals were sacrificed. MAR and BIC were evaluated using fluorescence microscopy. Light microscopic and histologic evaluations were performed on undecalcified sections.

RESULTS

Microscopic evaluation showed the presence of healthy osteoblasts lining bone surfaces near implants. Similar BIC was observed in phosphated and nonphosphated titanium implant sites. MAR was significantly higher around the nonphosphated titanium implant surfaces than around the phosphated titanium samples. No significant differences were found between dogs or implant sites.

CONCLUSION

Acid-etched implants showed significantly higher MARs compared to acid-etched, phosphate-coated implants. Int J Maxillofac Implants 2010;25:278-286.

Effect of recombinant human bone morphogenetic protein-2 on bone regeneration in large defects of the growing canine skull after dura mater replacement with a dura mater substitute

OBJECT

This study was designed to evaluate the bone regeneration potential of the dura mater and dura mater substitute (Durepair) in the presence of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in a collagen sponge-collagen-ceramic matrix (CCM; MasterGraft Matrix) in a large skull defect in growing canines.

METHODS

Forty immature male beagles were used to create two 2.5 x 4-cm cranial defects on each side of the sagittal suture. The dura mater on the left side was cut to make a 1 x 3-cm defect and replaced with bovine skin collagen (Durepair). The dura mater on the right side remained intact. Different doses of rhBMP-2 (none [8 animals], 0.11 mg/ml [4 animals], 0.21 mg/ml [4 animals], and 0.43 mg/ml [8 animals]) were infused on 2 Type I bovine absorbable collagen sponge (ACS) strips. The strips were layered with the CCM (15% hydroxyapatite [HA]/85% tricalcium phosphate [TCP]) to reconstruct both cranial defects. In a fifth group (8 animals), 0.43 mg/ml rhBMP-2 was directly infused into the CCM. Demineralized canine cancellous freeze-dried demineralized bone matrix (DBM; 8 animals) was used as a control in a sixth group. All materials were fixed under 2 resorbable protective sheets (MacroPore). Skulls were resected 16 weeks after operation. Histological and histomorphometric analyses on the percentage of the defect spanned by bone, and the percentage of residual HA-TCP granules and collagen were analyzed.

RESULTS

Calcified seroma was the only complication observed and only occurred in the 0.43-mg/ml rhBMP-2 groups (Groups 4 and 5). Dura mater repair appeared complete at 4 months in all animals. New bone was formed sporadically throughout the skull defect in the ACS+CCM and DBM groups without rhBMP-2. In all rhBMP-2 groups, mature new bone (compact and trabecular) was uniformly formed across the defect on both the repaired and intact dura mater sides. There was significant new compact bone formation on top of the repaired dura mater, which did not appear in the ACS+CCM and DBM groups lacking rhBMP-2. Greater HA-TCP and collagen scaffold resorption was noted in rhBMP-2 groups compared with non-rhBMP-2 groups. Statistical analysis showed there was a significantly lower percentage of bone spanning the defect in the ACS+CCM group compared with groups with rhBMP-2, with more residual HA-TCP and collagen on the repaired dura mater side than the intact dura mater side (p < 0.05). In all rhBMP-2 groups, there were no significant differences in new bone formation between the repaired and intact dura mater sides (p > 0.05).

CONCLUSIONS

The ACS+CCM combination had an effect similar to demineralized bone-on-bone regeneration in craniofacial reconstruction. The addition of rhBMP-2 to CCM directly or with ACS induces mature new bone formation in large cranial defects both in the presence of intact dura mater and repaired dura mater.

Effects of recombinant human bone morphogenetic protein-2 on midsagittal sutural bone formation during expansion

INTRODUCTION

The goal of this study was to evaluate whether human recombinant bone morphogenetic protein-2 (rhBMP-2) enhances sutural bone formation or causes premature sutural fusion.

METHODS

Thirty 6-week-old rabbits underwent midsagittal sutural expansion. The animals were randomly assigned to receive 0 (control), 0.1 mg per milliliter, or 0.4 mg per milliliter of rhBMP-2, delivered by an absorbable collagen sponge placed over the suture. A 100-g constant force was delivered for 33 days by using a nickel-titanium spring to expand the suture between 2 miniscrew implants anchored in the frontal bone. At days 10, 20, and 30, sutural separation was evaluated and modeled over time as polynomials by using multilevel statistical procedures. Bone formation and sutural gaps were analyzed histomorphometrically between days 10 and 20 and days 20 and 30.

RESULTS

The control group showed significantly greater overall sutural bone formation than did the 2 rhBMP-2 groups. Over time, bone formation decreased significantly in all groups. Between days 10 and 20, the 0.4 mg per milliliter group produced significantly more (58%) bone than did the 0.1 mg per milliliter group; there were no significant differences in bone formation between the 2 experimental groups between days 20 and 30. Both 0.1 and 0.4 mg per milliliter of rhBMP-2 in the absorbable collagen sponge caused premature fusion by forming a bony bridge connecting the ectocranial aspect of the sutural margins. Premature fusion significantly reduced sutural separation between 10 and 30 days (to 56% and 62% of control values for the 0.1 and 0.4 mg per milliliter groups, respectively). There were no significant differences in sutural separation between the 0.1 and 0.4 mg per milliliter groups.

CONCLUSIONS

Compared with the 0.1 mg per milliliter group, 0.4 mg per milliliter of rhBMP-2 accelerated sutural bone formation between days 10 and 20. After 10 to 20 days, rhBMP-2 in the absorbable collagen sponge caused premature sutural fusion, despite the constant expansion forces.

Biomechanical configurations of mandibular transport distraction osteogenesis devices

Mandibular bone transport (MBT) distraction osteogenesis devices are used for achieving reconstruction of mandibular defects in a predictable way, with few complications, less complexity than other alternative surgical procedures, and minimal tissue morbidity. However, selection of appropriate MBT device characteristics is critical for ensuring both their mechanical soundness and their optimal distraction function for each patient's condition. This article assesses six characteristics of currently available MBT devices to characterize their design and function and to classify them in a way that assists the selection of the best device option for each clinical case. In addition, the present work provides a framework for both the biomechanical conception of new devices and the modification of existing ones.

Tooth movements in foxhounds after one or two alveolar corticotomies

The aim of this split-mouth experimental study was to determine (1) whether corticotomy procedures increase tooth movement and (2) the effects of a second corticotomy procedure after 4 weeks on the rate of tooth movement. The mandibular third and maxillary second premolars of five skeletally mature male foxhounds, approximately 2 years of age, were extracted. One randomly selected mandibular quadrant had buccal and lingual flaps and corticotomies performed around the second premolar; the other quadrant served as the control. Both maxillary quadrants had initial buccal flaps and corticotomies; one randomly selected quadrant had a second buccal flap surgery and corticotomy after 28 days. Coil springs (200 g force), along with a 0.045 mm diameter tube on a 0.040 mm diameter guiding wire, were used to move the mandibular second and maxillary third premolars. Records, including digital calliper measurements and radiographs, were taken on days 0, 10, 14, 28, 42, and 56. Multilevel statistical procedures were used to model longitudinal tooth movements. The radiographic measurements initially showed increasing mandibular tooth movement rates, peaking between 22 and 25 days, and then decelerating. Total mandibular tooth movements were significantly (P < 0.05) greater on the experimental (2.4 mm) than on the control (1.3 mm) side. The rates of maxillary tooth movement slowed over time, with significantly (P < 0.05) more overall tooth movement on the side that had two (2.3 mm) than one (2.0 mm) corticotomy procedure. Alveolar corticotomy significantly increases orthodontic tooth movement. Performing a second corticotomy procedure after 4 weeks maintained higher rates of tooth movement over a longer duration and produced greater overall tooth movement than performing just one initial corticotomy, but the difference was small.

Effect of storage media on human periodontal ligament cell apoptosis

The ability of storage media to preserve periodontal ligament (PDL) cell vitality has been previously evaluated. However, the mechanisms by which different storage conditions alter the functional status of PDL cells have not been determined. The purpose of the present study was to investigate, in vitro, the level of programed cell death or apoptosis in a population of PDL cells following storage under different conditions. Primary human PDL cells were plated into 24-well-culture plates and allowed to attach for 24 h. Cells were then exposed for 1 h to milk, Hank's balanced salt solution (HBSS), Soft Wear contact lens solution or Gatorade at room temperature or on ice. Culture medium was used as a negative control. Apoptosis was evaluated at 24, 48, and 72 h after treatment on quadruplicate samples by using the ST 160 ApopTag Fluorescein Direct In Situ Detection Kit. The total number of cells and the total number of apoptotic cells were counted. The results indicated that at 24 and 72 h, PDL treated with Gatorade and the contact lens solution displayed the highest percentages of apoptotic cells when compared with the other treatment groups at room temperature. Overall, cells treated on ice showed significantly lower levels of apoptosis when compared with treatments at room temperature. In conclusion, the results indicated that apoptosis plays a major role in cell death in cells treated with Gatorade and contact lens solutions in comparison to other storage solutions and that storage on ice can inhibit programed cell death.

Recombinant human BMP-2 enhances the effects of materials used for reconstruction of large cranial defects

PURPOSE

Cranial defect reconstruction presents 2 challenges: induction of new bone formation, and providing structural support during the healing process. This study compares quantity and quality of new bone formation based on various materials and support frameworks.

MATERIALS AND METHODS

Eighteen dogs underwent surgical removal of a significant portion of their cranial vault. Demineralized bone matrix was used to fill the defect in all animals. In 9 dogs, recombinant human bone morphogenetic protein-2 (rhBMP-2) was added, while the other 9 served as the non-rhBMP-2 group. In each group, 3 animals were fixed with cobalt chrome plates, 3 with adding platelet-rich plasma, and 3 fixed with a Lactosorb (Walter Lorenz Surgical, Inc, Jacksonville, FL) resorbable mesh. Necropsy was done at 12 weeks postoperative. Histomorphometry, density, and mechanical properties of the regenerate were analyzed.

RESULTS

The non-rhBMP-2 groups showed minimal substitution of demineralized bone matrix with new bone, while only sporadic remnants of demineralized bone matrix were present in the rhBMP-2 groups. The defect showed more new bone formation (P < .001) and density (P < .001) in the rhBMP-2 groups by Kruskal-Wallis test. The area of new bone was not significantly different among the rhBMP-2 subgroups. The resorbable mesh struts showed no sign of bone invasion or substitution. In the non-rhBMP-2 resorbable mesh group, demineralized bone matrix almost totally disintegrated without replacement by new bone.

CONCLUSIONS

The addition of rhBMP-2 to demineralized bone matrix accelerated new bone formation in large cranial defects, regardless of the supporting framework or the addition of platelet-rich plasma. The use of a resorbable mesh in such defects is advisable only if rhBMP-2 is added.

Tgf-beta regulation of suture morphogenesis and growth

Premature suture obliteration results in an inability of cranial and facial bones to grow, with resulting craniofacial dysmorphology requiring surgical correction. Understanding the biological signaling associated with suture morphogenesis will enable less invasive treatment of patients with fused sutures, combined with therapy using biological molecules. While a number of advances have been made in identifying the genetic etiologies of various craniosynostotic syndromes, the pathogenesis of this condition is still not completely understood. Recently, it has been shown that differential expression of various transforming growth factor-beta (Tgf-beta) isoforms plays a crucial role in regulating suture patency once the sutures have formed. It has also been shown that differential expression of Tgf-beta isoforms may also play a role in craniosynostosis by altering proliferation, differentiation, and apoptosis within the suture. This chapter focuses on the role of Tgf-beta in suture morphogenesis and growth, exploring Tgf-beta biology, receptors, signaling pathways, animal models, and expression in both normal and pathological sutures.

Bone Generation in the Reconstruction of a Critical Size Calvarial Defect in an Experimental Model†

Objective: This study was designed to investigate the optimal combination of known osteogenic biomaterials with shape conforming struts to achieve calvarial vault reconstruction, using a canine model. Methods: Eighteen adolescent beagles were divided equally into 6 groups. A critical size defect of 6 x 2 cm traversed the sagittal suture. The biomaterials used for calvarial reconstruction were demineralised perforated bone matrix (DBM), recombinant human bone morphogenetic protein-2 (rhBMP2) and autogenous platelet-rich plasma (PRP). The struts used were cobalt chrome (metal) or resorbable plate. The groupings were as follows: 1) DBM + metal, 2) DBM + PRP + metal, 3) DBM + PRP + resorbable plate, 4) DBM + rhBMP2 + metal, 5) DBM + rhBMP2 + PRP + metal, and 6) DBM + rhBMP2 + resorbable plate. Animals were euthanised at 3 months post-surgery. There was no mortality or major complications. Analysis was performed macroscopically, histologically, and with computed tomography (CT). Results: There was complete bony regeneration in the rhBMP2 groups only. Non-rhBMP2 groups had minimal bony ingrowth from the defect edges and on the dural surface, a finding confirmed by CT scan and histology. PRP did not enhance bone regeneration. Shape conformation was good with both metal and resorbable plate. Conclusion: rhBMP2 but not PRP accelerated calvarial regeneration in 3 months. The DBM in the rhBMP2 groups were substituted by new trabecular bone. Shape molding was good with both metal and resorbable plate. Key words: Critical size calvarial defect, Cranial vault reconstruction, Metal struts, Resorbable plates, rhBMP2

Bone generation in the reconstruction of a critical size calvarial defect in an experimental model

OBJECTIVE

This study was designed to investigate the optimal combination of known osteogenic biomaterials with shape conforming struts to achieve calvarial vault reconstruction, using a canine model.

METHODS

Eighteen adolescent beagles were divided equally into 6 groups. A critical size defect of 6 x 2 cm traversed the sagittal suture. The biomaterials used for calvarial reconstruction were demineralised perforated bone matrix (DBM), recombinant human bone morphogenetic protein-2 (rhBMP2) and autogenous platelet-rich plasma (PRP). The struts used were cobalt chrome (metal) or resorbable plate. The groupings were as follows: 1) DBM + metal, 2) DBM + PRP + metal, 3) DBM + PRP + resorbable plate, 4) DBM + rhBMP2 + metal, 5) DBM + rhBMP2 + PRP + metal, and 6) DBM + rhBMP2 + resorbable plate. Animals were euthanised at 3 months post-surgery. There was no mortality or major complications. Analysis was performed macroscopically, histologically, and with computed tomography (CT).

RESULTS

There was complete bony regeneration in the rhBMP2 groups only. Non-rhBMP2 groups had minimal bony ingrowth from the defect edges and on the dural surface, a finding confirmed by CT scan and histology. PRP did not enhance bone regeneration. Shape conformation was good with both metal and resorbable plate.

CONCLUSION

rhBMP2 but not PRP accelerated calvarial regeneration in 3 months. The DBM in the rhBMP2 groups were substituted by new trabecular bone. Shape molding was good with both metal and resorbable plate.

Effects of phosphated titanium and enamel matrix derivatives on osteoblast behavior in vitro

PURPOSE

The purpose of this study was to evaluate the effects of phosphated titanium and enamel matrix derivatives (EMD) on osteoblast function.

MATERIALS AND METHODS

Primary rat osteoblasts were cultured on disks of either phosphated or nonphosphated titanium. In half of the samples 180 microg of EMD was immediately added. The medium was changed every 2 days for 28 days and then analyzed using transforming growth factor-beta1 (TGF-beta1) and interleukin-1beta (IL-1beta) enzyme-linked immunosorbent assays (ELISAs). Scanning electron microscopy and light microscopy were used to evaluate nodule formation and mineralization.

RESULTS

Microscopic evaluation revealed no differences in osteoblast attachment between the 4 groups. Osteoblast nodule formation was observed in all groups. In the absence of mineralizing media, nodules on the nonphosphated titanium samples showed no evidence of mineralization. All nodules on the phosphated titanium had evidence of mineralization. ELISA revealed no significant differences in IL-1beta production between any of the groups. The EMD-treated osteoblasts produced significantly more TGF-beta1 than non-EMD-treated cells for up to 8 days, and osteoblasts on phosphated titanium produced significantly more TGF-beta1 at 8 days.

DISCUSSION AND CONCLUSION

Osteoblast attachment appeared unaffected by surface treatment. EMD initiated early TGF-beta1 production, but production decreased to control levels within 10 days. Phosphated titanium increased TGF-beta1 production at 8 days and induced nodule mineralization even in the absence of mineralizing medium.

Biomechanical Strain and Morphologic Changes with Age in Rat Calvarial Bone and Sutures

BACKGROUND

The role of calvarial sutures in transmitting biomechanical forces within the head is unclear.

METHODS

To examine the biomechanical characteristics of sutures, the authors measured bite force changes in rats and tested for alterations in strain across intrafrontal and sagittal sutures and within parietal bone with age. To understand the effects of suture fusion on strain distribution in the head, the authors measured percentage fusion of the intrafrontal sutures with age (n = 6 per age group). The masticatory muscles in anesthetized 9-, 24-, and 70-day-old rats (n = 15 per group) were bilaterally stimulated. Stacked delta rosette gauges were fixed across the intrafrontal sutures and sagittal suture, or on the parietal bone. Strain and bite force were measured with a bite force transducer positioned at the incisors.

RESULTS

Bite force increased significantly (p < 0.05) with age (9-day-old rats, 72.6 +/- 20 gf; 24-day-old rats, 707.3 +/- 150 gf; 70-day-old rats, 2425.6 +/- 255 gf). Some significant differences were found between the volume and direction of strain among sites and age groups. Compressive strains of 230 microepsilon on average were found across the intrafrontal sutures at all ages. In contrast, tensile strains less than 180 microepsilon on average were found across the sagittal sutures of 9- and 24-day-old rats, increasing to 940 microepsilon on average at day 70. Tensile strains in parietal bone tended to be less than 150 microepsilon.

CONCLUSIONS

The timing of sutural closure and patterns of transsutural strain do not suggest that strain patterns contribute to initial fusion in the intrafrontal sutures. Differences in strain are likely related to changes in rat skull kinetics with growth, perhaps resulting from fusion of the intrafrontal sutures.

Anti-TGF-??2 Antibody Therapy Inhibits Postoperative Resynostosis in Craniosynostotic Rabbits

BACKGROUND

Postoperative resynostosis is a common clinical finding. It has been suggested that an overexpression of transforming growth factor (TGF)-beta2 may be related to craniosynostosis and may contribute to postoperative resynostosis. Interference with TGF-beta2 function with the use of neutralizing antibodies may inhibit resynostosis. The present study was designed to test this hypothesis.

METHODS

New Zealand White rabbits with bilateral coronal suture synostosis were used as suturectomy controls (group 1, n = 9) or given suturectomy with nonspecific, control immunoglobulin G antibody (group 2, n = 9) or suturectomy with anti-TGF-beta2 antibody (group 3, n = 11). At 10 days of age, a 3 x 15-mm coronal suturectomy was performed. The sites in groups 2 and 3 were immediately filled with 0.1 cc of a slowly resorbing collagen gel mixed with either immunoglobulin G (100 mug per suture) or anti-TGF-beta2 (100 mug per suture). Three-dimensional computed tomography scan reconstructions of the defects were obtained at 10, 25, 42, and 84 days of age, and the sutures were harvested for histomorphometric analysis.

RESULTS

Computed tomography scan data revealed that the suturectomy sites treated with anti-TGF-beta2 showed significantly (p < 0.05) greater areas through 84 days of age compared with controls. Histomorphometry also showed that suturectomy sites treated with anti-TGF-beta2 had patent suturectomy sites and more fibrous tissue in the defects compared with sites in control rabbits and had significantly (p < 0.001) less new bone area (by approximately 215 percent) in the suturectomy site.

CONCLUSIONS

These data support the initial hypothesis that interference with TGF-beta2 function inhibited postoperative resynostosis in this rabbit model. They also suggest that this biologically based therapy may be a potential surgical adjunct to retard postoperative resynostosis in infants with craniosynostosis.

Impaired posterior frontal sutural fusion in the biglycan/decorin double deficient mice

Biglycan (Bgn) and decorin (Dcn) are highly expressed in numerous tissues in the craniofacial complex. However, their expression and function in the cranial sutures are unknown. In order to study this, we first examined the expression of biglycan and decorin in the posterior frontal suture (PFS), which predictably fuses between 21 and 45 days post-natal and in the non-fusing sagittal (S) suture from wild-type (Wt) mice. Our data showed that Bgn and Dcn were expressed in both cranial sutures. We then characterized the cranial suture phenotype in Bgn deficient, Dcn deficient, Bgn/Dcn double deficient, and Wt mice. At embryonic day 18.5, alizarin red/alcian blue staining showed that the Bgn/Dcn double deficient mice had hypomineralization of the frontal and parietal craniofacial bones. Histological analysis of adult mice (45-60 days post-natal) showed that the Bgn or Dcn deficient mice had no cranial suture abnormalities and immunohistochemistry staining showed increased production of Dcn in the PFS from Bgn deficient mice. To test possible compensation of Dcn in the Bgn deficient sutures, we examined the Bgn/Dcn double deficient mice and found that they had impaired fusion of the PFS. Semi-quantitative RT-PCR analysis of RNA from 35 day-old mice revealed increased expression of Bmp-4 and Dlx-5 in the PFS compared to their non-fusing S suture in Wt tissues and decreased expression of Dlx-5 in both PF and S sutures in the Bgn/Dcn double deficient mice compared to the Wt mice. Failure of PFS fusion and hypomineralization of the calvaria in the Bgn/Dcn double deficient mice demonstrates that these extracellular matrix proteoglycans could have a role in controlling the formation and growth of the cranial vault.

Postoperative Anti-Tgf-β2 Antibody Therapy Improves Intracranial Volume and Craniofacial Growth in Craniosynostotic Rabbits

Postoperative resynostosis and secondary craniofacial growth abnormalities are common sequelae after craniofacial surgery. It has been suggested that an overexpression of transforming growth factor-beta2 (Tgf-beta2) may be related to craniosynostosis and contribute to postoperative resynostosis. Interference with Tgf-beta2 function using neutralizing antibodies may inhibit resynostosis and improve postoperative craniofacial growth; the present study was designed to test this hypothesis. Twenty-nine New Zealand white rabbits with bilateral coronal suture synostosis were used: 1) suturectomy controls (n=9); 2) suturectomy with nonspecific, control IgG antibody (n=9); and 3) suturectomy with anti-Tgf-beta2 antibody (n=11). At 10 days of age, a 3 mm x 15-mm coronal suturectomy was performed. The sites in groups 2 and 3 were immediately filled with 0.1 cc of a slow resorbing collagen gel mixed with either IgG (100 microg/suture) or anti-Tgf-beta2 (100 microg/suture). Three-dimensional computed tomography scan reconstructions of the skulls and cephalographs were obtained at 10, 25, 42, and 84 days of age. Computed tomography scan data revealed patent suturectomy sites and significantly (P<0.05) greater intracranial volumes by 84 days of age in rabbits treated with anti-Tgf-beta2 compared with controls. Cephalometric analysis revealed significant (P<0.05) differences in craniofacial, cranial vault, and cranial base growth by 84 days of age in rabbits treated with anti-Tgf-beta2 compared with controls. These data support the initial hypothesis that interference with Tgf-beta2 function inhibited postoperative resynostosis and improved cranial vault growth in this rabbit model. Thus, this biologically based therapy may be a potential surgical adjunct in the treatment of infants with craniosynostosis.

Inheritance of sutural pattern at the pterion in rhesus monkey skulls

Five of the bones that characteristically comprise the cranial vault articulate on the lateral aspect of the skull at or near the cephalometric landmark referred to as the pterion. The pattern of articulation in the sutures associated with these bones varies among and within primate species and has been used as a criterion for classification in taxonomic studies, as well as in archeological and forensic studies. Within species, the sutural patterns found within the region of the pterion have remarkable consistency, which lead to the hypothesis that these patterns have a genetic basis. Sutural pattern variations were investigated at the pterion in 422 skulls from 66 rhesus monkey families with known genealogies from the long-standing colony on Cayo Santiago. Four specific types of articulation patterns were recorded. The results demonstrated that the most common suture pattern at the pterion of Cayo Santiago rhesus monkeys (86%; similar to that seen in some other anthropoid species but not humans and some apes) was characterized by an articulation between the temporal bone and parietal bone. Articulation between the sphenoid and parietal bones (type SP) accounted for 14% of the specimens and was concentrated in a dozen families. Mothers with the SP phenotype had a high incidence of offspring with SP phenotypes. Most non-SP mothers having SP offspring had siblings or family members from previous generations with the SP type. This is the first study to examine variation in sutural patterns at the pterion in pedigrees. Variation of sutural patterns shows familial aggregation, suggesting that this variation is heritable. Future work will be focused on defining the inheritance patterns of variation at the pterion, with the ultimate objective of identifying the specific genes involved and their mechanism of action.

Cellular response to force application at craniofacial sutures

OBJECTIVES

To provide a comprehensive review of the literature describing research done on the responses of suture cells to force application in vitro and in vivo.

DESIGN AND RESULTS

This review outlines the types of forces that can be applied, methods of applying the forces, the sutures used in experiments, and the changes in morphology, molecular biology (gene and protein expression), and cell biology (proliferation, differentiation, apoptosis) in response to these forces.

CONCLUSION

The molecular response of sutures to force needs to be further investigated as these molecules can be used to enhance the way in which craniofacial sutures respond to mechanical force during orthopedic-orthodontic treatment.

The extracellular matrix environment in suture morphogenesis and growth

Sutures are the major bone growth sites of the craniofacial skeleton and form in response to developmental approximation of and interaction between two opposing osteogenic fronts. Premature obliteration of these craniofacial bone growth sites or craniosynostosis results in compensatory growth at other bone growth sites, with concomitant craniofacial dysmorphology. While much is now known about the growth and transcriptional factor regulation of suture formation and maintenance, little about the nature of the extracellular environment within sutures and their surrounding bones has been described. This review elucidates the nature of the sutural extracellular matrix and its role in mediating suture maintenance and growth through the regulation of cellular and biomechanical signaling.

Distraction osteogenesis versus autogenous onlay grafting. Part II: biology of regenerate and onlay bone

PURPOSE

Few studies have directly compared the quality of bone generated by distraction osteogenesis with that generated by autogenous onlay grafting. The purpose of this study was to compare rates of bone turnover at 5 months in bone produced by distraction osteogenesis and onlay grafting.

MATERIALS AND METHODS

Alveolar defects created in jaws of American foxhounds were augmented with distraction osteogenesis or onlay grafting and allowed to heal for 5 months. The animals were then sacrificed and the jaws were resected and prepared for decalcified and undecalcified histologic examination.

RESULTS

Both procedures produced bone containing a mixture of haversian systems and trabecular bone. A significantly greater ratio of osteoblast-covered bone surface to total trabecular bone surface (mean +/- SEM) was noted in distraction bone (0.124 +/- 0.049) compared to onlay bone (0.081 +/- 0.048) or control host bone (0.085 +/- 0.042 microm) (P < .05). In addition, significantly (P <.05) greater numbers of osteoclasts per microm of bone surface were noted in distraction bone (0.939 +/- 0.07) compared to onlay bone (0.605 +/- 0.06) or control host bone (0.725 +/- 0.08). No differences in rates of mineralization were noted between the groups.

DISCUSSION

While bone from both experimental groups appeared adequate for implant placement, distraction bone appeared to be remodeling at a higher rate than either onlay or control bone.

CONCLUSION

Given that the state of healing of the bone in each of these comparative groups was examined at a static point in time, it is premature to draw conclusions about the efficacy of one procedure over the other.