Unicoronal Suture Immobilization in the Fetal Rabbit

Pre-clinical evaluation of surgical procedures aimed to correct craniosynostosis is ideally performed in species of small animals characterized by perinatal brain development, early skeletal maturation, and genuine synostosis in all newborns. It would be nearly impossible to breed such a colony to homozygosity, so most researchers have resorted to artificial postnatal suture immobilization. Our aim was to test the hypothesis that artificial immobilization of a unicoronal suture in the fetal rabbit (25 days of gestation) would result in neurocranial growth alterations similar to those seen in the 9-day postnatally immobilized or congenital synostotic rabbit models. The advantages of prenatal immobilization are that rabbits can undergo the tested corrective procedure at postnatal day 9. This age corresponds to a human age of 6 months and allows the deformity and the effects of its correction to be more readily detected. The heads of 25-day-old fetuses of five time-dated pregnant New Zealand white rabbits were exposed by hysterotomy. The left unicoronal suture of 4 fetuses in each litter was immobilized with a polyglactin suture piercing the frontal and parietal bone plates. The remaining two fetuses were sham-operated. Nine days after spontaneous delivery, all rabbits were marked with four titanium screws close to the sagittal and coronal sutures. Growth was recorded with dorsoventral cephalograms at 9 and 90 days. The group with the immobilized suture showed a small increase in growth across the sagittal sutures. However, the decreases in growth at the unicoronal suture in both the immobilized (5.41-mm difference with sham-treated group) and nonimmobilized (1.17-mm difference with sham-treated group) were significant. Fetal immobilization results in growth alterations similar to those observed after postnatal immobilization.

Sutural bone deposition rate and strain magnitude during cranial development

It is widely believed that rapid growth of the human brain generates tensile strain in cranial sutures, and that this strain influences the rate of bone deposition at the sutural margins during development. We developed general theoretical techniques for estimating sutural bone deposition rate and strain magnitude during mammalian cranial development. A geometry-based analysis was developed to estimate sutural bone deposition rate. A quasi-static stress analysis was developed to estimate sutural strain magnitude. We applied these techniques to the special case of normal cranial development in humans. The results of the bone deposition rate analysis indicate that average human sutural bone deposition rate is on the order of 100 microm/day at 1 month of age and decreases in an approximately exponential fashion during the first 4 years of life. The results of the strain analysis indicate that sutural strain magnitude is highly dependent on the assumed stiffness of the sutures, with estimated strain at 1 month of age ranging from approximately 20 to 400 microstrain. Regardless of the assumed stiffness of the sutures, the results indicate that sutural strain magnitude is small and decreases in an approximately exponential fashion during the first 4 years of life. The finding that both sutural bone deposition rate and strain magnitude decrease with increasing age is consistent with quasi-static tensile strain in sutures influencing sutural osteoblast activity in a dose-dependent manner. However, the small magnitude of the predicted strains suggests that tissue level strains in sutures may be too small to directly influence osteoblast biology. In light of these results, we suggest other biomechanical mechanisms, such as a tension-induced angiogenic environment in the sutures or mechanotransduction in the underlying dura mater, through which tension across sutures may regulate the rate of bone deposition in sutures.

New Insight into Progenitor/Stem Cells in Dental Pulp Using Col1a1-GFP Transgenes

In recent years there has been increasing progress in identifying stem cells from adult tissues and their potential application in tissue engineering. These advances provide a promising future for tooth replacement/regeneration. Essential for this approach is the identification of donor stem cells for various components of the teeth. Our studies show that pOBCol3.6GFPtpz and pOBCol2.3GFPemd transgenic animals provide a unique model to gain insight into stem cells in the dental pulp. Our in vivo studies of the developing teeth of these transgenic lines show both Col1a1-GFP transgenes are expressed in functional and fully differentiated odontoblasts. The patterns of expression of Col1a1-GFP transgenes during odontoblast differentiation correlates with the expression of DSPP. In the developing craniofacial bones both Col1a1-GFP transgenes are also expressed in osteoblasts and osteocytes of alveolar and calvarial bones. In the alveolar bones, the expression of Col1a1-GFP in osteocytes correlates with the expression of DMP1. Col1a1-3.6-GFP is expressed in the entire layer of the periosteum and in suture mesenchyme containing osteoprogenitor cells. On the other hand, Col1a1-2.3- GFP expression was limited to the osteoblastic layer of the periosteum and was not detected in the fibroblastic layer of the periosteum or in the suture mesenchyme. These observations indicate that Col1a1-3.6-GFP and Col1a1-2.3-GFP transgenes identify different subpopulations of cells during intramembranous ossification. By using the coronal portion of dental pulps isolated from postnatal transgenic mice our observations also provide direct evidence that the dental pulp contains progenitor/stem cells capable of giving rise to a new generation of odontoblast-like cells, as well as osteoblast-like cells.

Prenatal Organization and Morphogenesis of the Sphenofrontal Suture in Humans

OBJECTIVE

The aim of this study was to describe the prenatal structure and morphogenesis of the sphenofrontal suture.

METHODS

Eleven human specimens, two embryos and nine fetuses, were prepared for light microscopy study of the sphenofrontal suture. Ten-micrometer sections were made with the microtome in the sagittal plane from the midline to the sphenoidal fontanelle.

RESULTS

At the end of the fetal period, the sphenofrontal suture had a five-layer structure like the cranial sutures, and was formed by two different morphogenetic unities. The orbitosphenofrontal suture was formed between the membranous ossification of the orbital part of the frontal bone and the endochondral ossification of the lesser wing of the sphenoid bone, i.e. the ala orbitalis. In the early stage, a transient sphenoethmoidal cartilage was inserted between these two ossifications. The second unit, the lateral sphenofrontal suture, was formed between the frontal bone and the greater wing of the sphenoid, and the ossification was membranous in this portion. It is formed like the cranial suture, directly from the mesenchyme.

CONCLUSION

The sphenofrontal suture is a typical fibrous suture arising from two morphogenetic unities.

Age-Dependent Changes in Material Properties of the Brain and Braincase of the Rat

Clinical and biomechanical evidence indicates that mechanisms and pathology of head injury in infants and young children may be different from those in adults. Biomechanical computer-based modeling, which can be used to provide insight into the thresholds for traumatic tissue injury, requires data on material properties of the brain, skull, and sutures that are specific for the pediatric population. In this study, brain material properties were determined for rats at postnatal days (PND) 13, 17, 43, and 90, and skull/suture composite (braincase) properties were determined at PND 13, 17, and 43. Controlled 1 mm indentation of a force probe into the brain was used to measure naive, non-preconditioned (NPC) and preconditioned (PC) instantaneous (G(i)) and long-term (G( infinity )) shear moduli of brain tissue both in situ and in vitro. Brains at 13 and 17 PND exhibited statistically indistinguishable shear moduli, as did brains at 43 and 90 PND. However, the immature (average of 13 and 17 PND) rat brain (G(i) = 3336 Pa NPC, 1754 Pa PC; G( infinity )= 786 Pa NPC, 626 Pa PC) was significantly stiffer (p < 0.05) than the mature (average of 43 and 90 PND) brains (G(i) = 1721 Pa NPC, 1232 Pa PC; G( infinity ) = 508 Pa NPC, 398 Pa PC). A "reverse engineering" finite element model approach, which simulated the indentation of the force probe into the intact braincase, was used to estimate the effective elastic moduli of the braincase. Although the skull of older rats was significantly thicker than that of the younger rats, there was no significant age-dependent change in the effective elastic modulus of the braincase (average value = 6.3 MPa). Thus, the increase in structural rigidity of the braincase with age (up to 43 PND) was due to an increase in skull thickness rather than stiffening of the tissue. These observations of a stiffer brain and more compliant braincase in the immature rat compared with the adult rat will aid in the development of age-specific experimental models and in computational head injury simulations. Specifically, these results will assist in the selection of forces to induce comparable mechanical stresses, strains and consequent injury profiles in brain tissues of immature and adult animals.

Rescue of coronal suture fusion using transforming growth factor-beta 3 (Tgf-beta 3) in rabbits with delayed-onset craniosynostosis

Craniosynostosis results in cranial deformities and increased intracranial pressure, which pose extensive and recurrent surgical management problems. Developmental studies in rodents have shown that low levels of transforming growth factor-beta 3 (Tgf-beta 3) are associated with normal fusion of the interfrontal (IF) suture, and that Tgf-beta 3 prevents IF suture fusion in a dose-dependent fashion. The present study was designed to test the hypothesis that Tgf-beta 3 can also prevent or "rescue" fusing sutures in a rabbit model with familial craniosynostosis. One hundred coronal sutures from 50 rabbits with delayed-onset, coronal suture synostosis were examined in the present study. The rabbits were divided into five groups of 10 rabbits each: 1) sham controls, 2) bovine serum albumin (BSA, 500 ng) low-dose protein controls, 3) low-dose Tgf-beta 3 (500 ng), 4) high-dose BSA (1,000 ng) controls, and 5) high-dose Tgf-beta 3 (1,000 ng). At 10 days of age, radiopaque amalgam markers were implanted in all of the rabbits on either side of the coronal suture to monitor sutural growth. At 25 days of age, the BSA or Tgf-beta 3 was combined with a slow-absorbing collagen vehicle and injected subperiosteally above the coronal suture. Radiographic results revealed that high-dose Tgf-beta 3 rabbits had significantly greater (P < 0.05) coronal suture marker separation than the other groups. Histomorphometric analysis revealed that high-dose Tgf-beta 3 rabbits also had patent coronal sutures and significantly (P < 0.01) greater sutural widths and areas than the other groups. The results suggest that there is a dose-dependent effect of TGF-beta 3 on suture morphology and area in these rabbits, and that the manipulation of such growth factors may have clinical applications in the treatment of craniosynostosis.

Osteopontin expression in osteoblasts and osteocytes during bone formation under mechanical stress in the calvarial suture in vivo

To clarify the role of OPN in bone formation under mechanical stress, we examined the expression and the function of OPN in bone using an expansion force-induced osteogenesis model. Our results indicated that OPN expression was enhanced during the bone formation and that OPN would be one of the positive factors for the bone formation under mechanical stress.

INTRODUCTION

Bone formation is known to be stimulated by mechanical stress; however, molecules involved in stress-dependent regulation of bone formation have not yet been fully characterized. Extracellular matrix proteins such as osteopontin (OPN) could play a role in mediation of the mechanical stress signal to osteoblasts. However, the function of OPN in bone formation under mechanical force is not known. Therefore, we examined the expression and the role of OPN in bone formation in vivo under tensile mechanical stress.

MATERIALS AND METHODS

Sagittal sutures of mice were subjected to expansion mechanical stress by setting orthodontic spring wires, and OPN expression during bone formation within the suture gap was examined.

RESULTS

Expansion of the sutures resulted in bone formation at the edges of the parietal bones within the sagittal suture. Immunohistochemical analysis revealed abundant accumulation of OPN protein in the matrix of newly formed bone on the inner edge of the parietal bone within the mechanically expanded sutures. Osteoblasts forming bone within the suture subjected to tensile stress also exhibited high levels of OPN protein expression. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicated that OPN mRNA expression was enhanced in wild-type calvariae subjected to expansion force compared with the control calvariae where dead spring wires were set without expansion stress. In addition, type I collagen mRNA was also expressed in the calvariae under the mechanical stimuli. To understand the function of OPN, sagittal sutures in OPN-deficient mice were subjected the expansion stress, and bone formation within the suture to fill the expanded gap was compared with that observed in wild-type mice. OPN deficiency reduced bone formation at the edge of the parietal bone in contact with the expanded suture gap.

CONCLUSIONS

These observations revealed that OPN plays a pivotal role in bone formation under tensile mechanical stress.

Gross growth and regrowth of sutures: reflections on some personal research

A series of experiments was performed on young monkeys, rabbits, and turtles to study gross sutural growth of bones. Radiopaque implants in conjunction with serial, direct gross, and indirect radiographic measurements were employed. Differences in growth were observed in the monkey among five facial sutures and also the same suture at different times. Growth was greatest at the zygomaticotemporal suture and least at the premaxillomaxillary suture. In the rabbit, the nasal bone side of the frontonasal suture grew about twice as fast as the frontal bone side. In the turtle shell, the midsagittal suture grew faster than the transverse suture. In all of the animals, the rate of sutural growth decreased with an increase in age. No gross regional growth disturbance was noted after resection of the frontonasal, midpalatine, or transpalatine sutures. The frontonasal suture reformed presumably because of the underlying nasomucoperiosteum, as in a cranial suture, presumably because of the underlying dura. After extirpation of the midpalatine suture with the formation of a complete cleft and despite no underlying membrane, a new suture reformed in an eccentric position in a number of instances. Bone growth at sutures is secondary or compensatory to some other factors.

Computed tomographic assisted study of morphological changes in the sutural areas as resulting from obliteration

The authors have studied the morphological differences of sutural areas in human skulls at distinct stages of obliteration. A computed tomography aided with computer algorithm of tonal correction was applied to visualise structural changes in the sutural areas that are correlated with sutural ossification. The results of our study suggest that obliteration of cranial sutures is accompanied by local fluctuations of bony density in sutural areas, gradual unification of structural density towards ectocranium. When the obliteration proceeds, the sutural gap ceases. The laminas and diploic layers of the two opposing bones become a single structure of increased integrity.

The role of fibroblast growth factor (FGF) and type beta transforming growth factor (TGF-beta 1-beta 2-beta 3) during rat craniofacial development

Growth factors seem to be part of a complex cellular signalling language, in which individual growth factors are the equivalents of the letters that compose words. According to this analogy, informational content lies, not in an individual growth factor, but in the entire set of growth factors and others signals to which a cell is exposed. The ways in which growth factors exert their combinatorial effects are becoming clearer as the molecular mechanisms of growth factors actions are being investigated. A number of related extracellular signalling molecules that play widespread roles in regulating development in both invertebrates and vertebrates constitute the Fibroblast Growth Factor (FGF) and type beta Transforming Growth Factor (TGF beta). The latest research literature about the role and fate of these Growth factors and their influence in the craniofacial bone growth ad development is reviewed.

Regional dura mater differentially regulates osteoblast gene expression

Recent studies have suggested that regionally differentiated dura mater regulates murine cranial suture fate by providing growth factors to the osteoblasts in the overlying suture complex. To determine if regionally differentiated dura mater is capable of effecting changes in osteoblast gene expression, an in vitro coculture system was established in which osteoblast-enriched cell cultures derived from neonatal rat calvaria were grown in serum-free media in the presence of dural cells derived from posterior frontal (PF) or sagittal (SAG) dural tissues, recapitulating the in situ relation between the underlying dura mater and the osteoblasts in the overlying cranial suture. In this study, the changes in osteoblast gene expression induced by signaling from regional dura mater were examined by analyzing total cellular RNA isolated from osteoblasts cocultured with PF or SAG dural cells. The expression of extracellular matrix molecules (alkaline phosphatase, bone sialoprotein, osteopontin, and osteocalcin) and the transcription factor Msx2 was assessed. Consistent with previous data, the findings demonstrate that osteoblasts cocultured with dural cells undergo changes in gene expression indicative of a more differentiated osteoblast. Additionally, the data suggest that regionally differentiated dura mater isolated from the PF suture enhances the expression of osteogenic genes to a greater extent than SAG suture-derived dural cells. These data support an osteoinductive role for suture-derived dural cells in vitro that may have implications for suture biology in vivo.

Unicoronal suture autotransplantation in the rabbit

INTRODUCTION

Our hypothesis was that a neurocranial suture autograft will, when shielded from dura, grow and be incorporated into the calvarium.

METHODS

Growth was monitored by marker separation in three isohistogenic groups of rabbits, between postnatal days 9 and 90. In order to simulate increased neurocapsular expansion force, the left-sided coronal suture of a group of 20 rabbits was immobilised with a resorbable suture on gestational day 25. The other group of 10 rabbits was sham-operated. On postnatal day 9, 10 of the experimental rabbits underwent transplantation of the suture contralateral to the defect resulting from extirpation of the immobilised suture. The transplant was shielded from dural influence by a platinum foil.

RESULTS

The growth of the immobilised coronal sutures was severely impaired, and also that of the contralateral unicoronal sutures to a lesser extent. A significant catch-up of growth occurred in the transplanted unicoronal sutures. Overgrowth occurred at the donor sites.

CONCLUSION

The results allow us to consider suture transplantation combined with endosteal dura stripping in craniosynostosis surgery.

Biomechanics of craniofacial sutures: orthopedic implications

Sutures are soft connective tissue articulations between craniofacial bones. Suture mechanics deals with patterns of mechanical stress experienced in sutures resulting from natural activities such as mastication and exogenous forces such as orthopedic loading. Patterns of sutural mechanical stress can be delineated readily as sutural strain using strain gages attached over the suture. In mastication, complex sutural strain patterns have been elucidated in a few species. Mechanical stresses are not transmitted in the skull as a continuing gradient, for different sutures are capable of redefining a propagating mechanical force as predominately tensile or compressive strain. Exogenous mechanical forces with engineering waveforms such as static and sine wave at different frequencies induce corresponding waveforms and rates of sutural strain, providing the basis for applying novel mechanical stimuli to engineer sutural growth. The available data on suture mechanics converge to a hypothetical theme that mechanical forces regulate sutural growth by inducing sutural mechanical strain. Various orthopedic therapies, including headgear, facemask, and functional appliances may induce sutural strain, leading to modification of otherwise natural suture growth.

Incidence of metopism in the Lebanese population

This study was carried out on 968 skull X-rays to determine the incidence of the metopic suture in the Lebanese population. Complete and incomplete metopism was present in 0.82% and 0.93% of cases, respectively, leading to an overall incidence of 1.75%. In both categories, the incidence was relatively higher in males (1.84%) than in females (1.62%). Persons living in rural areas had a higher incidence of complete and incomplete metopism compared to persons living in urban areas, with ratios of 4:1 and 4:2, respectively. Other findings included an absence of frontal sinuses in all but one skull with complete metopism, accessory ossicles in the majority of cases of complete metopism (7/8), and hydrocephalus in one case. Medical records did not reveal any other associated diseases or abnormalities. Despite the low incidence of metopic suture in the Lebanese population, in X-ray diagnosis of fractures of the frontal bone, metopic suture must not be ruled out.

Strain induced osteogenesis of the craniofacial suture upon controlled delivery of low-frequency cyclic forces

Static forces have been used for more than a century to modulate osteogenesis of craniofacial sutures in not only laboratory research, but also clinical practice. Whether cyclic forces more effectively stimulate sutural osteogenesis than static forces is unknown. Here, the premaxillomaxillary sutures of growing rabbits received in vivo exogenous static forces with peak magnitude of 2 Newtons, or cyclic forces also at 2 Newtons but with frequencies of 0.2 Hz and 1 Hz. The static force and two cyclic forces did not evoke significant differences in the peak magnitude of static bone strain (506 microstrain 182; mean S.D.), 0.2-Hz cyclic strain (436 microstrain 191) or 1-Hz cyclic strain (461 microstrain 229). However, cyclic forces at 0.2 Hz delivered to the premaxillomaxillary suture for 10 min/d over 12 days (120 cyclic per day) induced significantly more craniofacial growth (p< 0.01), marked sutural separation, and islands of newly formed bone, in comparison with both sham controls and static force of matching peak magnitude. The bone strain threshold of approximately 500 microstrain for inducing sutural osteogenesis is lower than the minimum effective strain capable of inducing bone apposition in long bones. These data demonstrate, for the first time, that application of brief doses of cyclic forces induces sutural osteogenesis more effectively than static forces with matching peak magnitude.

Mechanobiology of craniofacial sutures

Craniofacial sutures are soft connective-tissue joints between mineralized skull bones. Suture mechanobiology refers to the understanding of how mechanical stimuli modulate sutural growth. This review's hypothesis is that novel mechanical stimuli can effectively modulate sutural growth. Exogenous forces with static, sinusoidal, and square waveforms induce corresponding waveforms of sutural strain. Sutural growth is accelerated upon small doses of oscillatory strain, as few as 600 cycles delivered 10 min/day over 12 days. Interestingly, both oscillatory tensile and compressive strains induce anabolic sutural responses beyond natural growth. Mechanistically, oscillatory strain likely turns on genes and transcription factors that activate cellular machinery via mechanotransduction pathways. Thus, sutural growth is determined by hereditary and mechanical signals via the common pathway of genes. It is concluded that small doses of oscillatory mechanical stimuli have the potential to modulate sutural growth effectively: either accelerating it or initiating net sutural bone resorption for various therapeutic objectives.

Tgf-beta1, Tgf-beta2, Tgf-beta3 and Msx2 expression is elevated during frontonasal suture morphogenesis and during active postnatal facial growth

OBJECTIVES

It is hypothesized that regulation of facial suture morphogenesis is similar to that of cranial sutures, with expression of similar regulatory molecules, governing suture formation and patency. The present study was designed to characterize the morphology of the frontonasal (FN) suture of the rat at different developmental stages and to investigate the presence and temporal-spatial expression of transforming growth factor-beta 1 (Tgf-beta1), Tgf-beta2, Tgf-beta3 and Msx2 mRNA within these structures.

SETTING AND SAMPLE POPULATION

The Department of Biomedical Sciences at Texas A&M University System Health Science Center, Baylor College of Dentistry, Dallas, TX USA. Histological sections and RNA isolated from FN suture tissues of Sprague-Dawley rats, aged embryonic day 16 through postnatal day 20.

METHOD

Sections were examined after immunohistochemical staining. Gene expression was determined by densitometric analysis of RT-PCR products run on agarose gels.

RESULTS

FN sutures develop slightly later than cranial sutures and show increased complexity over time when compared to cranial sutures. FN sutures were closely associated with the nasal capsular cartilage, with intervening layers of perichondrium and periosteum. The pattern of expression of Tgf-betas within the FN suture tissues was similar to that seen in the cranial sutures. However, mRNA and protein of the Tgf-betas were differentially expressed over time compared to cranial sutures. In FN sutures, Tgf-beta mRNA levels were elevated both during the period of suture morphogenesis and during active bone growth from the suture in the early postnatal period. Msx2 mRNA expression was elevated in both the prenatal and postnatal periods, similar to Tgf-beta mRNA expression.

CONCLUSION

Tgf-beta and Msx2 are present in facial sutures similar to cranial sutures, but are differentially expressed over time, perhaps reflecting different bone growth rates from these sutures.

The anatomic basis for palatal implants in orthodontics

Orthodontic anchorage without negative reciprocal influences on tooth position can be achieved by the use of immobile implants. An existing dentition permits placement of endosseous implants in only a few regions. These are the edentulous parts of the ridge due to previous extractions, the ascending ramus of the mandible, and the os palatinum. A precondition for successful implant osseointegration is a satisfactory bone base. The midline of the os palatinum is of particular anatomic interest due to the increasing use of anchorage implants in this area. Even though most implants are incorporated uneventfully, in some cases, the osseointegration of these implants fails. Therefore, anatomic data characterizing the palatal midline region are of clinical importance. In this study, trephine bur biopsies provided the material for histologic facings. The donor age covered a span from 12 to 53 years and illustrated that complete ossification of the suture palatina mediana (SPM) is rare before the age of 23 years. Therefore, especially in adult orthodontic treatment, the use of palatal implants should be considered. The anterior SPM is less often ossified than the posterior region. Implant placement should take this into account and consider that a bone bed more favorable to osseointegration might be found posterior to the interconnecting line of the first premolars.

Persistent open anterior fontanelle in a healthy 32-month-old boy

Delayed closure of the anterior fontanelle is often associated with significant disease entities. Range of normal closure of the anterior fontanelle is 4 to 26 months. Increased intracranial pressure, hypothyroidism, and skeletal anomalies are common etiologic factors. History, physical examination, and diagnostic testing rule out most disorders. Once these disorders have been ruled out, it is important for the physician to realize that a persistent open anterior fontanelle beyond the accepted ranges of closure can be a normal outlier.

Transforming growth factor-beta 3(Tgf-beta3) in a collagen gel delays fusion of the rat posterior interfrontal suture in vivo

Postnatal expansion of the intramembranous bones of the craniofacial skeleton occurs as bone growth at sutures. Loss of the bone growth site occurs when the suture fails to form, or when the newly formed sutures become ossified, resulting in premature obliteration. Previous experiments demonstrated that removal of dura mater from fetal rat coronal sutures, or neutralizing transforming growth factor-beta 2 (Tgf-beta2) activity using antibodies resulted in premature obliteration of the suture in vitro. Conversely, addition of Tgf-beta3 to coronal sutures in vitro rescued them from osseous obliteration. To examine whether Tgf-beta3 rescues sutures from obliteration in vivo, a collagen gel was used as a vehicle to deliver Tgf-beta3 to the normally fusing rat posterior interfrontal (IF) suture. Surgery was done on postnatal day 9 (P9) rats, in which collagen gels containing 0, 3, or 30 ng Tgf-beta3 were placed above the IF suture, underneath the periosteum for 2 weeks. By P24, 75-100% of animals in control unoperated, sham-operated, and collagen gel-only groups had fused IF sutures. In contrast, 40% of sutures exposed to 3 ng Tgf-beta3 remained open, while sutures exposed to 30 ng Tgf-beta were similar to controls. By immunohistochemistry, sutures rescued from obliteration by Tgf-beta3 had the same Tgf-beta receptor type II (Tbetar-II) distribution as controls. However, Tgf-beta3-treated sutures had altered Tgf-beta2 and Tbetar-I distribution compared to controls.

Bone and suture regeneration in calvarial defects by e-PTFE-membranes and demineralized bone matrix and the impact on calvarial growth: an experimental study in the rat

The aim of this study was to evaluate the effect of: guided tissue regeneration (GTR) alone, implantation of demineralized bone matrix (DBM) alone, and of the combined treatment on the healing of craniectomy defects involving the sagittal cranial suture, and to examine subsequent calvarial growth. Sixty four-week-old rats were used in the study. These animals were randomly assigned to five groups (A-E) of 12 animals. In four groups (A-D), a calvarial defect (5.0 mm) involving the sagittal suture was produced in each animal. Group A: The defect was left untreated. Group B: DBM was implanted into the defect. Group C: The cerebral and the galeal aspect of the defect was covered with an e-PTFE membrane. Group D: The defect was treated with the double membrane technique combined with implantation of DBM. Group E: The animals were sham-operated, no defect was created. In all groups, two gutta-percha points were placed to indicate the lateral borders of the parietal bones. Histological analysis 4 months following surgery showed that the untreated cranial defects (A) had healed with fibrous connective tissue in the midportion of the defect. The DBM grafted defects (B) healed either completely with bone containing DBM particles or partially with bone and connective tissue. The defects (D) treated with DBM combined with GTR healed completely with bone, while the defects (C) treated with membranes alone healed with bone but a suture-like tissue similar to the normal sagittal suture of the sham-operated controls (E) was always present in the midportion of the defect. Cephalometric radiography demonstrated that the membrane-treated (C) and the sham-operated animals (E) exhibited similar coronal growth of the cranial vault following treatment. Craniometric measurements on chemically defleshed specimens showed that sham-operated and membrane-treated animals presented significantly more biparietal width than the animals treated with DBM alone or DBM combined with GTR (P < 0.05). The results demonstrated that predictable osseous healing including the formation of a sagittal suture can be accomplished in craniectomy defects by GTR, and undisturbed cranial growth reestablished. The treatment of the defects with DBM alone or DBM combined with GTR resulted in craniosynostosis and reduced cranial growth.

Experimental study of the frontal sinus development on Goettingen miniature pigs

According to the literature, the development of the frontal sinus cavity is a result of the active immigration of cells from the ethmoidal complex into the os frontale. This migration theory is in contrast to the operative outcome of Apert's syndrome patients, after fronto-orbital advancement. When a fronto-orbital advancement at the age of a few months is performed in these patients while the frontal suture is yet closed, a sinus developed even the distance between nasal root and frontal bone bing up to 2 cm. In order to study the development of the frontal sinus, an animal study on 12 five-week-old infant Goettingen minipigs (GMP) was conducted, which did not have any clinical or histological signs of a frontal sinus development to investigate the development of the frontal sinus in "orthotopically" transplanted frontal bone with an open frontal suture. A comparison was made to a control group. The macro- and microscopical comparison with a control group revealed that the orthotopical transplants in the occipital bone developed epithelium-lined sinus, beginning from the thirty-fifth week. Based on these histomorphological results, a development scheme for the genesis of the sinus frontalis as a model were drawn.

[Growth and morphogenesis of the craniofacial bones. Applications in orthodontics. The concepts of J. Delaire]

The present report about J. Delaire's lecture summarizes his approach to: the nature and physiology of the membranous sutures, the "neural" and "adaptive" growth of the cranial base, the "central" and "cortical" development of the maxillary, the role of the premaxillary "skeletal entity" in the development of the anterior part of the face, the "bifocal" development of the mandible, the architectural balance of the craniofacial set (leading to the author's cephalometric analysis).