Mechanobiology of craniofacial sutures

Multiscale mechanical characterisation of the craniofacial system under external forces

Premature fusion of craniofacial joints, i.e. sutures, is a major clinical condition. This condition affects children and often requires numerous invasive surgeries to correct. Minimally invasive external loading of the skull has shown some success in achieving therapeutic effects in a mouse model of this condition, promising a new non-invasive treatment approach. However, our fundamental understanding of the level of deformation that such loading has induced across the sutures, leading to the effects observed is severely limited, yet crucial for its scalability. We carried out a series of multiscale characterisations of the loading effects on normal and craniosynostotic mice, in a series of in vivo and ex vivo studies. This involved developing a custom loading setup as well as software for its control and a novel in situ CT strain estimation approach following the principles of digital volume correlation. Our findings highlight that this treatment may disrupt bone formation across the sutures through plastic deformation of the treated suture. The level of permanent deformations observed across the coronal suture after loading corresponded well with the apparent strain that was estimated. This work provides invaluable insight into the level of mechanical forces that may prevent early fusion of cranial joints during the minimally invasive treatment cycle and will help the clinical translation of the treatment approach to humans.

Effect of Different Mini Implant Assisted Rapid Palatal Expansion (MARPE) Designs on Maxillary Protraction in Skeletal Class III malocclusion: An FEM Study

Background

Four different designs of mini-implant-assisted rapid palatal expansion (MARPE) and protraction in nasomaxillary complex and mid-palatal sutures in late adolescent skeletal Class III malocclusion were compared using a three-dimensional finite element analysis.

Methods

A finite element model of skull and related sutures was constructed using the computed tomography scan of a 16-year-old female patient with skeletal Class III and ANB of -2°. Four appliance designs: Type I: MARPE with palatal force, Type II: MARPE with buccal force, Type III: Hybrid hyrax with palatal force, and Type IV: Hybrid hyrax with buccal force. Protraction vectors were and analyzed using Ansys software (ANSYS 2021 R2). The displacement pattern of the nasomaxillary structures and the stress distribution in the sutures were examined in all four appliance designs.

Results

All the appliance designs resulted in a forward movement of the maxilla, while Type I and III, which used palatal protraction force, caused the greatest forward displacement. In Type I, II, and III, along with forward movement, a clockwise rotation of maxilla was observed, while in Type IV, an anticlockwise rotation of maxilla was observed. Type I, II, and III resulted in higher stress distribution around the superior structures, while Type IV resulted in less stress distribution around the superior structures of maxilla.

Conclusion

The forward displacement was enhanced when palatal plates were used to protract the maxilla. The effective appliance design for skeletal class III with open bite case was Type I, II, and III and Type IV for deep bite cases.

Short-term and long-term effects of miniscrew-assisted and conventional rapid palatal expansion on the cranial and circummaxillary sutures

INTRODUCTION

The objective of this study was to analyze the short-term and long-term effects of miniscrew-assisted rapid palatal expansion (MARPE) and conventional rapid palatal expansion (RPE) appliances on cranial and circummaxillary sutures as compared with a matched control group.

METHODS

One hundred and eighty cone-beam computed tomography scans for 60 subjects were evaluated for the 3 groups: (1) MARPE (n = 20; aged 13.7 ± 1.74 years), (2) RPE (n = 21; age 13.9 ± 1.14 years), and (3) control (n = 19; age 13.3 ± 1.49 years) at pretreatment (T1), postexpansion (T2), and posttreatment (T3) (T1 to T3: MARPE, 2 years 8 months; RPE, 2 years 9 months; control, 2 years 7 months). Frontonasal suture, frontomaxillary suture, zygomaticomaxillary suture, zygomaticofrontal suture, intermaxillary suture, pterygomaxillary suture, nasomaxillary suture, and zygomaticotemporal suture were measured on the right and left sides for all 3 time labels. In addition, midpalatal suture was measured at the incisor, canine, and molar levels.

RESULTS

Within-group analysis showed that MARPE and RPE led to a significant increase in the widths of frontonasal, frontomaxillary, intermaxillary, nasomaxillary, and midpalatal suture at incisor, canine, and molar levels at T2 compared with T1. Between-group analysis showed that MARPE and RPE significantly increased the width of the intermaxillary and midpalatal suture at the incisor, canine, and molar compared with controls at T2. In the long term, between-group comparisons showed no significant difference among the 3 groups except that MARPE led to a significant increase in the width of midpalatal suture at incisor, canine, and molar levels compared with RPE and controls at T3.

CONCLUSIONS

MARPE led to a significant increase in the width of the midpalatal suture at incisor, canine, and molar levels compared with RPE and controls in the long term. There was no difference in the width of other cranial and circummaxillary sutures among the 3 groups in the long term.

Orthodontic pain: c-Fos expression in rat brain nuclei after rapid maxillary expansion

BACKGROUND

The aim of this in vivo study was to quantitatively evaluate pain after rapid maxillary expansion (RME) in young rats by analyzing the activation of nociception-related structures, that is, the caudalis, interpolaris, and oralis subnuclei, according to the Fos expression.

METHODS

A total of 65 Wistar rats were assigned to three groups: control group (n = 15) with no treatment, positive control group (n = 25), and experimental group (n = 25) with RME. The experimental animals were euthanized at 6, 12, 24, 48, and 72 hours after RME, and the brain was later carefully collected. Coronal sections through the spinal trigeminal caudalis, spinal trigeminal interpolaris, and spinal trigeminal oralis were cut (thickness of 40 µm) on a cryostat and processed for Fos immunohistochemistry. Images from the sections were captured under light microscopy, and ImageJ software was used to count Fos-like immunoreactive neurons. The Analysis of variance (ANOVA) and Tukey test were used for statistical analysis, and the significance level was set at 5%.

RESULTS

RME induced incisor distalization and opening of the midpalatal suture, as well as neuronal activation of the spinal trigeminal nucleus. The experimental group demonstrated significantly more Fos-positive neurons in subnuclei caudalis and subnuclei interpolaris 6 hours after the maxillary expansion. The Fos immunoreactivity significantly decreased at 12 hours and increased again at 24 and 48 hours (P < 0.001).

CONCLUSIONS

The RME increases the neural activation of brain regions involved in the nociception region, as determined by the Fos expression. The most intense Fos-like immunoreactive expression was detected in the brain 6 hours after the start of the palatal expansion.

Effects of different force directions of intra-oral skeletally anchored maxillary protraction on craniomaxillofacial complex, in Class III malocclusion: a 3D finite element analysis

INTRODUCTION

The intra-oral skeletally anchored maxillary protraction (I-SAMP) has been found to be an effective treatment for skeletal Class III malocclusion.

OBJECTIVE

This in-silico study explored the influence of different force directions of intra-oral skeletally anchored Class III elastics on the changes in craniomaxillofacial complex, using finite element analysis.

METHODS

A 3-dimensional (3D) finite element model of the craniomaxillofacial bones including circummaxillary sutures was constructed with high biological resemblance. A 3D assembly of four miniplates was designed and fixed on the maxilla and mandible of the finite element model. The model was applied with 250g/force at the miniplates at three angulations (10°, 20°, and 30°) from the occlusal plane, to measure stress and displacement by using the ANSYS software.

RESULTS

The zygomaticotemporal, zygomaticomaxillary, and sphenozygomatic sutures played significant roles in the forward displacement and counterclockwise rotation of maxilla and zygoma, irrespective of the angulation of load application. The displacements and rotations of the zygomatico-maxillary complex decreased gradually with an increase in the angle of load application between miniplates from 10° to 30°. The mandible showed negligible displacement, with clockwise rotation.

CONCLUSIONS

The treatment effects of I-SAMP were corroborated, with insight of displacement patterns and sutures involved, which were lacking in the previously conducted 2D and 3D imaging studies. The prescribed angulation of skeletally anchored Class III elastics should be as low as possible, since the displacement of zygomatico-maxillary complex increases with the decrease in angulation of the elastics.

Response of Gli1+ Suture Stem Cells to Mechanical Force Upon Suture Expansion

Normal development of craniofacial sutures is crucial for cranial and facial growth in all three dimensions. These sutures provide a unique niche for suture stem cells (SuSCs), which are indispensable for homeostasis, damage repair, as well as stress balance. Expansion appliances are now routinely used to treat underdevelopment of the skull and maxilla, stimulating the craniofacial sutures through distraction osteogenesis. However, various treatment challenges exist due to a lack of full understanding of the mechanism through which mechanical forces stimulate suture and bone remodeling. To address this issue, we first identified crucial steps in the cycle of suture and bone remodeling based on the established standard suture expansion model. Observed spatiotemporal morphological changes revealed that the remodeling cycle is approximately 3 to 4 weeks, with collagen restoration proceeding more rapidly. Next, we traced the fate of the Gli1⁺ SuSCs lineage upon application of tensile force in three dimensions. SuSCs were rapidly activated and greatly contributed to bone remodeling within 1 month. Furthermore, we confirmed the presence of Wnt activity within Gli1⁺ SuSCs based on the high co-expression ratio of Gli1⁺ cells and Axin2⁺ cells, which also indicated the homogeneity and heterogeneity of two cell groups. Because Wnt signaling in the sutures is highly upregulated upon tensile force loading, conditional knockout of β-catenin largely restricted the activation of Gli1⁺ SuSCs and suppressed bone remodeling under physiological and expansion conditions. Thus, we concluded that Gli1⁺ SuSCs play essential roles in suture and bone remodeling stimulated by mechanical force and that Wnt signaling is crucial to this process. © 2022 American Society for Bone and Mineral Research (ASBMR).

Success and complication rate of miniscrew assisted non-surgical palatal expansion in adults - a consecutive study using a novel force-controlled polycyclic activation protocol

Introduction

Bone-borne miniscrew assisted palatal expansion (MAPE) is a common technique to improve maxillary transverse deficiency in young adolescents. Adult patients usually present a challenge, as they often require additional surgical assisted maxillary expansion (SARPE). There is still no clear statement about non-surgical expansion in adult patients using this technique. The aim of this study was to evaluate the success and complication rate of non-surgical palatal expansion in adults utilizing MAPE with a novel force-controlled polycyclic expansion protocol (FCPC).

Methods

This consecutive study consisted of 33 adult patients with an average age of 29.1 ± 10.2 years (min. 18 years, max. 58 years), including one dropout patient. First, four miniscrews were inserted and after 12-weeks latency, the expander was placed and the FCPC protocol was applied (MAPE group). In case of missing expansion, a SARPE was performed (SARPE group). After maximum expansion, a cone beam CT was made and widening of the midpalatal suture was measured. The outcome variables were successful non-surgical expansion and, with sample size power above 80%, the odds of failed non-surgical expansion and associated complications were evaluated. The primary predictor variable was age. Statistical analysis was performed using R (Version 3.1) to calculate power, to construct various models for measuring the odds of requiring surgical intervention/complications, and others.

Results

Successful non-surgical expansion was achieved in 27 patients (84.4%), ranging from 18 to 49 years. Mean age differed significantly between both groups (26.8 ± 8.2 years vs. 41.3 ± 9.9 years; p < 0.001). Mean expansion at the anterior and posterior palate for the MAPE group was 5.4 ± 1.5 mm and 2.5 ± 1.1 mm, respectively. Among these subjects’ complications were observed in 18.5%. Age significantly increased the odds of complications (p = 0.019).

Conclusions

1. The success rate of MAPE among individuals aged 18 to 49 years was 84.4%.

2. A V-shaped expansion pattern in the antero-posterior dimension was mostly observed.

3. Complications were significantly associated with age.

4. A careful expansion protocol seems to be beneficial to prevent unfavorable results in adult patients.

Trial registration

Consecutive cohort study, Review Board No. EK-2-2014/0016.

Effect of microimplant assisted rapid palatal expansion on bone-anchored maxillary protraction: A finite element analysis

INTRODUCTION

This study aimed to evaluate the craniofacial effects of microimplant assisted rapid palatal expansion (MARPE) on bone-anchored maxillary protraction (BAMP) through a finite element analysis.

METHODS

A 3-dimensional finite element model of the skull with associated sutures was created from the computed tomography image of a 12-year-old male patient. Two protraction protocols: BAMP without MARPE (protocol 1) and BAMP with MARPE (protocol 2), were analyzed using Ansys software (Ansys, Canonsburg, Pa). Stress distribution in the sutures and displacement pattern of craniofacial structures were analyzed in the 2 protocols using finite element analysis.

RESULTS

Both protocols produced changes in craniofacial structures in all the 3 planes. Displacement of the maxilla was more pronounced in protocol 2 in all directions with mild clockwise rotation. Protocol 1 displayed a translatory movement of the maxilla without any rotation and mild constriction in the anterior region. In protocol 2, an expansion of the maxilla, which increased in the superoinferior direction, was also observed. Von Mises stress in circummaxillary sutures was significantly more in protocol 2, indicating an increased displacement of craniomaxillary structures.

CONCLUSIONS

The use of MARPE during BAMP enhanced maxillary protraction and reduced the counterclockwise rotation tendency of the maxilla. Hence, it may be inferred that incorporation of MARPE during BAMP protocol may prove beneficial in the treatment of patients with skeletal Class III malocclusion with open bite tendency or hyperdivergent growth pattern.

Craniosynostosis: current conceptions and misconceptions

Cranial bones articulate in areas called sutures that must remain patent until skull growth is complete. Craniosynostosis is the condition that results from premature closure of one or more of the cranial vault sutures, generating facial deformities and more importantly, skull growth restrictions with the ability to severely affect brain growth. Typically, craniosynostosis can be expressed as an isolated event, or as part of syndromic phenotypes. Multiple signaling mechanisms interact during developmental stages to ensure proper and timely suture fusion. Clinical outcome is often a product of craniosynostosis subtypes, number of affected sutures and timing of premature suture fusion. The present work aimed to review the different aspects involved in the establishment of craniosynostosis, providing a close view of the cellular, molecular and genetic background of these malformations.

Coronal and lambdoid suture evolution following total vault remodeling for scaphocephaly

OBJECTIVE

Different types of surgical procedures are utilized to treat craniosynostosis. In most procedures, the fused suture is removed. There are only a few reports on the evolution of sutures after surgical correction of craniosynostosis. To date, no published study describes neosuture formation after total cranial vault remodeling. The objective of this study was to understand the evolution of the cranial bones in the area of coronal and lambdoid sutures that were removed for complete vault remodeling in patients with sagittal craniosynostosis. In particular, the investigation aimed to confirm the possibility of neosuture formation.

METHODS

CT images of the skulls of children who underwent operations for scaphocephaly at the Hôpital Femme Mère Enfant, Lyon University Hospital, Lyon, France, from 2004 to 2014 were retrospectively reviewed. Inclusion criteria were diagnosis of isolated sagittal synostosis, age between 4 and 18 months at surgery, and availability of reliable postoperative CT images obtained at a minimum of 1 year after surgical correction. Twenty-six boys and 11 girls were included, with a mean age at surgery of 231.6 days (range 126-449 days). The mean interval between total vault reconstruction and CT scanning was 5.3 years (range 1.1-12.2 years).

RESULTS

Despite the removal of both the coronal and lambdoid sutures, neosutures were detected on the 3D reconstructions. All combinations of neosuture formation were seen: visible lambdoid and coronal neosutures (n = 20); visible lambdoid neosutures with frontoparietal bony fusion (n = 12); frontoparietal and parietooccipital bony fusion (n = 3); and visible coronal neosutures with parietooccipital bony fusion (n = 2).

CONCLUSIONS

This is the first study to report the postoperative skull response after the removal of normal patent sutures following total vault remodeling in patients with isolated sagittal synostosis. The reappearance of a neosuture is rather common, but its incidence depends on the type of suture. The outcome of the suture differs with the incidence of neosuture formation between these transverse sutures. This might imply genetic and functional differences among cranial sutures, which still have to be elucidated.

Skeletal Changes in Growing Cleft Patients with Class III Malocclusion Treated with Bone Anchored Maxillary Protraction-A 3.5-Year Follow-Up

This prospective controlled trial aimed to evaluate the skeletal effect of 3.5-years bone anchored maxillary protraction (BAMP) in growing cleft subjects with a Class III malocclusion. Subjects and Method: Nineteen cleft patients (11.4 ± 0.7-years) were included from whom cone beam computed tomography (CBCT) scans were taken before the start of BAMP (T0), 1.5-years after (T1) and 3.5 y after (T2). Seventeen age- and malocclusion-matched, untreated cleft subjects with cephalograms available at T0 and T2 served as the control group. Three dimensional skeletal changes were measured qualitatively and quantitatively on CBCT scans. Two dimensional measurements were made on cephalograms. Results: Significant positive effects have been observed on the zygomaticomaxillary complex. Specifically, the A-point showed a displacement of 2.7 mm ± 0.9 mm from T0 to T2 (p < 0.05). A displacement of 3.8 mm ± 1.2 mm was observed in the zygoma regions (p < 0.05). On the cephalograms significant differences at T2 were observed between the BAMP and the control subjects in Wits, gonial angle, and overjet (p < 0.05), all in favor of the treatment of Class III malocclusion. The changes taking place in the two consecutive periods (ΔT1-T0, ΔT2-T1) did not differ, indicating that not only were the positive results from the first 1.5-years maintained, but continuous orthopedic effects were also achieved in the following 2-years. Conclusions: In conclusion, findings from the present prospective study with a 3.5-years follow-up provide the first evidence to support BAMP as an effective and reliable treatment option for growing cleft subjects with mild to moderate Class III malocclusion up to 15-years old.

A multicenter, prospective, randomized trial of pain and discomfort during maxillary expansion: Leaf expander versus hyrax expander

BACKGROUND

Pain suffered by the young patient is the most frequent symptom during orthodontic treatment and is the one that most frightens children and causes worry in their families.

AIM

To investigate pain perception and function impairment during the first week of activation of two palatal expansion screws.

DESIGN

A total of 101 subjects were randomly divided into two groups: RME group included patients treated with the standard hyrax expansion screw and LEAF group included patients treated with Leaf Expander appliance. Pain intensity was assessed via the Wong-Baker scale. A questionnaire on oral function impairments was also compiled by the patients.

RESULTS

The Pain Scale analysis showed that patients in the RME group suffered from a significantly higher level of pain than those in the LEAF group (88.6% vs 25%, P < .01). RME group showed highest pain indexes from day 1 to day 4 (51.4% RME vs 9.7% LEAF suffered at least once from strong pain in the first 4 days, P < .01). Furthermore, oral functions were similarly affected in both groups.

CONCLUSIONS

Pain reported during maxillary arch expansion is influenced by clinical activation protocol and by the screw type. Patients treated with Leaf Expander reported significantly lower pain level in the first 7 days of treatment.

Three-dimensional finite element analysis of the dural folds and the human skull under head acceleration

Bone and collagen fiber architecture adapt to external mechanical loads. In humans, due to the low insertion of the temporal muscle, mastication does not lead to a physiological loading of the calvaria. Forces applied to the skull by the dural folds can lead to compressive stresses in the calvaria. To investigate the relationship between mechanical loads and form in the skull and its membranes, in a finite element three-dimensional model of the human skull, loads due to head acceleration in daily activities are applied to the falx cerebri and the tentorium cerebelli. The dural folds are modeled as membranes. The stress paths in the dural folds correlate with anatomical fiber direction. Head accelerations of 9 g lead to compressive stress in the calvaria. Finite element analysis of the falx cerebri and the tentorium cerebelli can be used to study the influence of mechanical stresses on the ossification of the dural folds and their impact on calvarial growth. This study presents an example of functional loading of bone by fibrous membranes and describes a possible mechanism by which Wolff's law works on the bone of the calvaria creating evolutionarily beneficial lightweight constructions.

Computed tomography analysis of the cranium of Champsosaurus lindoei and implications for the choristoderan neomorphic ossification

Choristoderes are extinct neodiapsid reptiles that are well known for their unusual cranial anatomy, possessing an elongated snout and expanded temporal arches. Although choristodere skulls are well described externally, their internal anatomy remains unknown. An internal description was needed to shed light on peculiarities of the choristodere skull, such as paired gaps on the ventral surface of the skull that may pertain to the fenestra ovalis, and a putative neomorphic ossification in the lateral wall of the braincase. Our goals were: (i) to describe the cranial elements of Champsosaurus lindoei in three dimensions; (ii) to describe paired gaps on the ventral surface of the skull to determine if these are indeed the fenestrae ovales; (iii) to illustrate the morphology of the putative neomorphic bone; and (iv) to consider the possible developmental and functional origins of the neomorph. We examined the cranial anatomy of the choristodere Champsosaurus lindoei (CMN 8920) using high‐resolution micro‐computed tomography scanning. We found that the paired gaps on the ventral surface of the skull do pertain to the fenestrae ovales, an unusual arrangement that may be convergent with some plesiosaurs, some aistopods, and some urodeles. The implications of this morphology in Champsosaurus are unknown and will be the subject of future work. We found that the neomorphic bone is a distinct ossification, but is not part of the wall of the brain cavity or the auditory capsule. Variation in the developmental pathways of cranial bones in living amniotes was surveyed to determine how the neomorphic bone may have developed. We found that the chondrocranium and splanchnocranium show little to no variation across amniotes, and the neomorphic bone is therefore most likely to have developed from the dermatocranium; however, the stapes is a pre‐existing cranial element that is undescribed in choristoderes and may be homologous with the neomorphic bone. If the neomorphic bone is not homologous with the stapes, the neomorph likely developed from the dermatocranium through incomplete fusion of ossification centres from a pre‐existing bone, most likely the parietal. Based on the apparent morphology of the neomorph in Coeruleodraco, the neomorph was probably too small to play a significant structural role in the skull of early choristoderes and it may have arisen through non‐adaptive means. In neochoristoderes, such as Champsosaurus, the neomorph was likely recruited to support the expanded temporal arches.

Sagittal suture maturation: Morphological reorganization, relation to aging, and reliability as an age-at-death indicator

OBJECTIVES

The sagittal suture (SS) is assumed to be an initial site for the commencement of cranial suture closure as well as the most frequent spot of isolated craniosynostosis. The present study aimed to inspect the reorganization of the SS at the microlevel to assess the relation between its closure and aging and to establish whether it could be used as a reliable indicator in age-at-death prediction.

MATERIALS AND METHODS

The SS was investigated in 68 dry contemporary adult male skulls of known age-at-death. An additional series of 20 skulls was used for verification. The skulls were scanned using a micro-computed tomography system. The SS closure degree was assessed along the three bone layers on cross-sectional tomograms by using a scoring scale.

RESULTS

In the entirely open SS, the bone edges consist of compact bone and are widely separated. With SS maturation, the bone edges come into contact, and the remodeling process leads to a decrease in the sutural area and bone homogenization across all three layers. SS closure is an irregular process roughly related to aging, beginning in the early 20s, reaching its peak at about 30 years of age and abating in the late 40s.

DISCUSSION

Although related to aging, SS closure is not a simple function of it. Rather, the underlying factors inducing and managing this process are multifaceted and complex. Although the etiology of SS maturation remains unclear, it is reasonable to use SS closure cautiously and only as a supportive method for age prediction.

Characterizing and Modeling Bone Formation during Mouse Calvarial Development

The newborn mammalian cranial vault consists of five flat bones that are joined together along their edges by soft fibrous tissues called sutures. Early fusion of these sutures leads to a medical condition known as craniosynostosis. The mechanobiology of normal and craniosynostotic skull growth is not well understood. In a series of previous studies, we characterized and modeled radial expansion of normal and craniosynostotic (Crouzon) mice. Here, we describe a new modeling algorithm to simulate bone formation at the sutures in normal and craniosynostotic mice. Our results demonstrate that our modeling approach is capable of predicting the observed ex vivo pattern of bone formation at the sutures in the aforementioned mice. The same approach can be used to model different calvarial reconstruction in children with craniosynostosis to assist in the management of this complex condition.

Effects of equibiaxial mechanical stretch on extracellular matrix-related gene expression in human calvarial osteoblasts

Mechanical stretch commonly promotes craniofacial suture remodeling during interceptive orthodontics. The mechanical responses of osteoblasts in craniofacial sutures play a role in suture remodeling. Moreover, the extracellular matrix (ECM) produced by osteoblasts is crucial for the transduction of mechanical signals that promote cell differentiation. Therefore, we aimed to investigate the effect of mechanical stretch on cell viability and ECM-related gene-expression changes in human osteoblasts. Human calvarial osteoblasts (HCObs) were subjected to 2% deformation. Caspase activity, MTT, and cell viability assays were used to estimate osteoblast apoptosis, proliferation, and viability, respectively. Real-time RT-PCR (RT² -PCR) arrays were used to assess expression of cytoskeletal-, apoptosis-, osteogenesis-, and ECM-related genes. We found that mechanical stretch significantly increased osteoblast viability and cell proliferation, and decreased the activities of caspases 3 and 7. Moreover, the expression of 18 genes related to osteoblast differentiation, apoptosis, and ECM remodeling changed by more than two-fold in a time-dependent manner. Therefore, mechanical stretch promotes HCOb viability and alters expression of genes that are closely related to suture remodeling under mechanical stretch.

Dietary material properties shape cranial suture morphology in the mouse calvarium

Cranial sutures are fibrous connective tissue articulations found between intramembranous bones of the vertebrate cranium. Growth and remodeling of these tissues is partially regulated by biomechanical loading patterns that include stresses related to chewing. Advances in oral processing structure and function of the cranium that enabled mammalian-style chewing is commonly tied to the origins and evolution of this group. To what degree masticatory overuse or underuse shapes the complexity and ossification around these articulations can be predicted based on prior experimental and comparative work. Here, we report on a mouse model system that has been used to experimentally manipulate dietary material properties in order to investigate cranial suture morphology. Experimental groups were fed diets of contrasting material properties. A masticatory overuse group was fed pelleted rodent chow, nuts with shells, and given access to cotton bedding squares. An underuse group was deprived of cotton bedding as well as diverse textured food, and instead received gelatinized food continuously. Animals were raised from weaning to adulthood on these diets, and sagittal, coronal and lambdoid suture morphology was compared between groups. Predicted intergroup variation was observed in mandibular corpus size and calvarial suture morphology, suggesting that masticatory overuse is associated with jaw and suture growth. The anterior region of the sagittal suture where it intersects with the coronal suture (bregma) showed no effect from the experiment. The posterior sagittal suture where it intersects with the lambdoid sutures (lambda) was more complex in the overuse group. In other words, the posterior calvarium was responsive to dietary material property demands while the anterior calvarium was not. This probably resulted from the different strain magnitudes and/or strain frequencies that occurred during overuse diets with diverse material properties as compared with underuse diets deprived of such enrichment. This work highlights the contrasting pattern of the sutural response to loading differences within the calvarium as a result of diet.

Anatomical and mechanical properties of swine midpalatal suture in the premaxillary, maxillary, and palatine region

The mechanical properties of the midpalatal suture and their relationship with anatomical parameters are relevant for both tissue engineering and clinical treatments, such as in sutural distraction osteogenesis. Soft tissues were dissected from ten swine heads and the hard palate was sliced perpendicularly to the midpalatal suture. Thirteen specimens were collected from each animal and analysed with micro-computed tomography and 4-point-bending for sutural width (Sw), interdigitation (LII), obliteration (LOI), failure stress (σ _f ), elastic modulus (E), and bone mineral density (BMD). Values of the premaxillary, maxillary, and palatine region were compared with Kruskal-Wallis one-way ANOVA and Spearman's rank coefficient was used to analyse the correlation between parameters and their position along the suture (α = 0.05). LII had values of 1.0, 2.9, and 4.3, LOI had values of 0.0%, 2.5%, and 4.5%, and E had values of 12.5 MPa, 31.3 MPa, and 98.5 MPa, in the premaxillary, maxillary, and palatine region, respectively (p < 0.05). Failure stress and rigidity of the midpalatal suture increased from rostral to caudal, due to greater interdigitation and obliteration. These anatomical and mechanical findings contribute to characterise maxillary growth, and may help to understand its mechanical reaction during loading, and in virtual simulations.

Stress and displacement patterns in the craniofacial skeleton with rapid maxillary expansion-a finite element method study

Background

Rapid maxillary expansion (RME), indicated in the treatment of maxillary deficiency directs high forces to maxillary basal bone and to other adjacent skeletal bones. The aim of this study is to (i) evaluate stress distribution along craniofacial sutures and (ii) study the displacement of various craniofacial structures with rapid maxillary expansion therapy by using a Finite Element model.

Methods

An analytical model was developed from a dried human skull of a 12 year old male. CT scan images of the skull were taken in axial direction parallel to the F-H plane at 1 mm interval, processed using Mimics software, required portion of the skull was exported into stereo-lithography model. ANSYS software was used to solve the mathematical equation. Contour plots of the displacement and stresses were obtained from the results of the analysis performed.

Results

At Node 47005, maximum X-displacement was 5.073 mm corresponding to the incisal edge of the upper central incisor. At Node 3971, maximum negative Y-displacement was -0.86 mm which corresponds to the anterior zygomatic arch, indicating posterior movement of craniofacial complex. At Node 32324, maximum negative Z-displacement was -0.92 mm representing the anterior and deepest convex portion of the nasal septum; indicating downward displacement of structures medial to the area of force application.

Conclusions

Pyramidal displacement of maxilla was evident. Apex of pyramid faced the nasal bone and base was located on the oral side. Posterosuperior part of nasal cavity moved minimally in lateral direction and width of nasal cavity at the floor of the nose increased, there was downward and forward movement of maxilla with a tendency toward posterior rotation. Maximum von Mises stresses were found along midpalatal, pterygomaxillary, nasomaxillary and frontomaxillary sutures.

Stretch force guides finger-like pattern of bone formation in suture

Mechanical tension is widely applied on the suture to modulate the growth of craniofacial bones. Deeply understanding the features of bone formation in expanding sutures could help us to improve the outcomes of clinical treatment and avoid some side effects. Although there are reports that have uncovered some biological characteristics, the regular pattern of sutural bone formation in response to expansion forces is still unknown. Our study was to investigate the shape, arrangement and orientation of new bone formation in expanding sutures and explore related clinical implications. The premaxillary sutures of rat, which histologically resembles the sutures of human beings, became wider progressively under stretch force. Micro-CT detected new bones at day 3. Morphologically, these bones were forming in a finger-like pattern, projecting from the maxillae into the expanded sutures. There were about 4 finger-like bones appearing on the selected micro-CT sections at day 3 and this number increased to about 18 at day 7. The average length of these projections increased from 0.14 mm at day 3 to 0.81 mm at day 7. The volume of these bony protuberances increased to the highest level of 0.12 mm³ at day 7. HE staining demonstrated that these finger-like bones had thick bases connecting with the maxillae and thin fronts stretching into the expanded suture. Nasal sections had a higher frequency of finger-like bones occuring than the oral sections at day 3 and day 5. Masson-stained sections showed stretched fibers embedding into maxillary margins. Osteocalcin-positive osteoblasts changed their shapes from cuboidal to spindle and covered the surfaces of finger-like bones continuously. Alizarin red S and calcein deposited in the inner and outer layers of finger-like bones respectively, which showed that longer and larger bones formed on the nasal side of expanded sutures compared with the oral side. Interestingly, these finger-like bones were almost paralleling with the direction of stretch force. Inclined force led to inclined finger-like bones formation and deflection of bilateral maxillae. Additionally, heavily compressive force caused fracture of finger-like bones in the sutures. These data together proposed the special finger-like pattern of bone formation in sutures guided by stretch force, providing important implications for maxillary expansion.

Comparison and evaluation of stresses generated by rapid maxillary expansion and the implant-supported rapid maxillary expansion on the craniofacial structures using finite element method of stress analysis

Background

The study aimed to evaluate and compare the stress distribution and 3-dimensional displacements along the craniofacial sutures in between the Rapid maxillary Expansion (RME) and Implant supported RME (I-RME).

Methods

Finite element model of the skull and the implants were created using ANSYS software. The finite element model thus built composed of 537692 elements and 115694 nodes in RME model & 543078 elements and 117948 nodes with implants model. The forces were applied on the palatal surface of the posterior teeth to cause 5mm of transverse displacement on either side of the palatal halves, making it a total of 10mm. The stresses and the displacement values were obtained and interpreted.

Results

Varying pattern of stress and the displacements with both positive and negative values were seen. The maximum displacement was seen in the case of plain RME model and that too at Pterygomaxillary suture and Mid-palatal suture in descending order. In the case of I-RME maximum displacement was seen at Zygomaticomaxillary suture followed by Pterygomaxillary suture. The displacements produced in all the three planes of space for the plain RME model were greater in comparison to the Implant Supported RME model. And the stresses remained high for all the sutures in case of an I-RME.

Conclusions

There is a definite difference in the stress and the displacement pattern produced by RME and I-RME model and each can be used according to the need of the patient. The stresses generated in case of conventional RME were considerably less than that of the I-RME for all the sutures.

Signaling networks in joint development

Here we review studies identifying regulatory networks responsible for synovial, cartilaginous, and fibrous joint development. Synovial joints, characterized by the fluid-filled synovial space between the bones, are found in high-mobility regions and are the most common type of joint. Cartilaginous joints such as the intervertebral disc unite adjacent bones through either a hyaline cartilage or a fibrocartilage intermediate. Fibrous joints, which include the cranial sutures, form a direct union between bones through fibrous connective tissue. We describe how the distinct morphologic and histogenic characteristics of these joint classes are established during embryonic development. Collectively, these studies reveal that despite the heterogeneity of joint strength and mobility, joint development throughout the skeleton utilizes common signaling networks via long-range morphogen gradients and direct cell-cell contact. This suggests that different joint types represent specialized variants of homologous developmental modules. Identifying the unifying aspects of the signaling networks between joint classes allows a more complete understanding of the signaling code for joint formation, which is critical to improving strategies for joint regeneration and repair. Developmental Dynamics 246:262-274, 2017. © 2016 Wiley Periodicals, Inc.

Novel use of cranial epidural space in rabbits as an animal model to investigate bone volume augmentation potential of different bone graft substitutes

Background

The success of bone augmentation to a major degree depends on the biomechanics and biological conditions of the surrounding tissues. Therefore, an animal model is needed providing anatomical sites with similar mechanical pressures for comparing its influence on different biomaterials for bone regeneration. The present report describes the new bone formation associated to biomaterial in a bursa created in the epidural space, between dura mater and cranial calvaria, under the constant pressure of cerebrospinal fluid.

Methods

Five adult California rabbits were used for the trial. In each animal, two bursae were created in the epidural spaces, in the anterior part of the skull, below both sides of the interfrontal suture. The spaces between dura mater and cranial calvaria were filled with in-situ hardening biphasic calcium phosphate containing hydroxyapatite and beta tricalcium-phosphate (BCP), in-situ hardening phase-pure beta-tricalcium phosphate (β-TCP) or without any biomaterials (sham). After 90 days, the animals were sacrificed, and the defect sites were extracted and processed for histomorphometric analysis by optical and backscattered electron microscopy.

Results

The cranial epidural spaces created (n = 10) could be preserved by the application both BCP (n = 3) and β-TCP biomaterials (n = 3) in all experimental sites. The sites augmented with BCP showed less new bone formation but a trend to better volume preservation than the sites augmented with β-TCP. However, the bone in the BCP sites seemed to be more mature as indicated by the higher percentage of lamellar bone in the sites. In contrast, the created space could not be preserved, and new bone formation was scarce in the sham-operated sites (n = 4).

Conclusion

The experimental bursae created bilaterally in the epidural space allows comparing objectively bone formation in relation to biomaterials for bone regeneration under permanent physiological forces from cerebrospinal fluid pressure.

Signaling mechanisms implicated in cranial sutures pathophysiology: Craniosynostosis

Normal extension and skull expansion is a synchronized process that prevails along the osteogenic intersections of the cranial sutures. Cranial sutures operate as bone growth sites allowing swift bone generation at the edges of the bone fronts while they remain patent. Premature fusion of one or more cranial sutures can trigger craniosynostosis, a birth defect characterized by dramatic manifestations in appearance and functional impairment. Up until today, surgical correction is the only restorative measure for craniosynostosis associated with considerable mortality. Clinical studies have identified several genes implicated in the pathogenesis of craniosynostosis syndromes with useful insights into the underlying molecular signaling events that determine suture fate. In this review, we exploit the intracellular signal transduction pathways implicated in suture pathobiology, in an attempt to identify key signaling molecules for therapeutic targeting.

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Cranial sutures operate as bone growth sites.

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Premature fusion of one or more cranial sutures can trigger craniosynostosis.

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Several genes are involved in the pathogenesis of craniosynostosis syndromes.

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An array of molecular signaling events determine suture fate.

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Herein, the signal transduction pathways implicated in suture pathobiology are discussed.

Variation in the Developmental and Morphological Interaction Between the Nasal Septum and Facial Skeleton

While the nasal septum exerts a morphogenetic influence on the facial skeleton, there is evidence that this relationship is highly variable. To better appreciate the precise role of the septum, it is important understand the variable interaction between the septum and surrounding skeleton during ontogeny. Here we analyzed nasal septal and facial skeletal postnatal phenotypic variation using cross-sectional samples of C3H/HeJ and C57BL/6J mice. Initial observations indicated between-strain variation in the magnitude of septal deviation, suggesting differences in septal and facial skeletal interaction. We examined whether variation in septal deviation is due to ontogenetic differences in septal size, or whether variation in facial skeletal growth imposes spatial constraints on the septum. Using microCT we quantified septal size and deviation, and collected coordinate landmark data, which we analyzed using geometric morphometrics. C3H/HeJ mice were significantly more deviated than C57BL/6J during development. We found no differences in septal size between the two strains. However, while both strains exhibited an ontogenetic increase in snout length, C3H/HeJ mice exhibited a non-allometric reduction in nasal bone length. This appears to be influenced by between-strain variation in the spatial relationship between the nasal septum and nasofrontal suture. Unlike C57BL/6J mice, the C3H/HeJ nasal septum is positioned anterior to the nasofrontal suture potentially limiting an early direct influence of septal growth (e.g., through interstitial expansion) on sutural growth. Ultimately, our results underscore that while the septum is a key facial growth center, its precise influence on facial growth varies even in narrow morphological and taxonomic ranges. Anat Rec, 299:730-740, 2016. © 2016 Wiley Periodicals, Inc.

Fusion Patterns in the Skulls of Modern Archosaurs Reveal That Sutures Are Ambiguous Maturity Indicators for the Dinosauria

The sutures of the skulls of vertebrates are generally open early in life and slowly close as maturity is attained. The assumption that all vertebrates follow this pattern of progressive sutural closure has been used to assess maturity in the fossil remains of non-avian dinosaurs. Here, we test this assumption in two members of the Extant Phylogenetic Bracket of the Dinosauria, the emu, Dromaius novaehollandiae and the American alligator, Alligator mississippiensis, by investigating the sequence and timing of sutural fusion in their skulls. As expected, almost all the sutures in the emu skull progressively close (i.e., they get narrower) and then obliterate during ontogeny. However, in the American alligator, only two sutures out of 36 obliterate completely and they do so during embryonic development. Surprisingly, as maturity progresses, many sutures of alligators become wider in large individuals compared to younger, smaller individuals. Histological and histomorphometric analyses on two sutures and one synchondrosis in an ontogenetic series of American alligator confirmed our morphological observations. This pattern of sutural widening might reflect feeding biomechanics and dietary changes through ontogeny. Our findings show that progressive sutural closure is not always observed in extant archosaurs, and therefore suggest that cranial sutural fusion is an ambiguous proxy for assessing maturity in non-avian dinosaurs.

Short-term effects of strain produced on a split palatal screw-type hyrax appliance after rapid maxillary expansion: A clinical trial

INTRODUCTION

The aim of this study was to establish an accumulated strain pattern in different parts of rapid maxillary expansion appliances and relate them to different vertical growth patterns. A clinical study was conducted of 40 patients with posterior crossbite who required rapid palatal expansion.

METHODS

Patients (mean age, 8.48 years) were recruited and treated at the Dental Hospital of Bellvitge, Hospitalet de Llobregat, Barcelona, Spain. Strain gauges were placed on the arms of the RME hyrax screw appliance to record deformation (strain) during the expansion and the retention phases for 75 days. A finite element model was used to place the gauge at the point where the strain was most expressed. The vertical coefficient of variation was used to classify the patients by their vertical growth pattern. P = 0.05 was considered to be statistically significant.

RESULTS

During the expansion phase, the highest values of accumulated strain were measured in the posterior part of the appliance for all facial biotypes, but these values passed to the anterior area at the end of the retention phase of the mesocephalic and brachycephalic patients. There was statistically significant difference in the strain of the posterior arms in accordance with the vertical growth pattern (P = 0.05) during the retention phase. At 75 days of retention, 61.25% of the arms had already begun to have strain dissipation.

CONCLUSIONS

The accumulated strain pattern in the rapid maxillary expansion appliance can vary depending on the facial biotype. In the future, orthodontists should try to tailor the activation and retention protocol based on each patient's characteristics.

Three-dimensional finite element analysis of maxillary protraction with labiolingual arches and implants

INTRODUCTION

In this study, we aimed to evaluate the effects of maxillary protraction using traditional labiolingual arches and implant-type protraction devices before orthopedic treatment of patients with skeletal Class III malocclusion.

METHODS

A 3-dimensional finite element model of the maxillofacial bones with high biologic similarity and including the sutures was constructed. Through stress and displacement calculations, a biomechanical study was performed for the maxillofacial bones, mandible, and sutures.

RESULTS

We quantified detailed changes in the sutures with 2 protraction methods to analyze their effects on the growth of the maxillofacial bones.

CONCLUSIONS

(1) The labiolingual arch is suitable for skeletal Class III patients with crossbite and deep overbite. The frontomaxillary and zygomaticomaxillary sutures played major roles in the forward displacement and counterclockwise rotation of the maxilla. The temporozygomatic and pterygopalatine sutures did not change significantly. (2) The implant type of protraction device is suitable for skeletal Class III patients with crossbite and open bite. Both the frontomaxillary and zygomaticomaxillary sutures played decisive roles in the forward displacement and clockwise rotation of maxilla. The temporozygomatic and pterygopalatine sutures showed small changes. (3) The labiolingual arch caused less stimulatory growth on the maxilla, whereas the implant caused greater stimulatory growth on the maxilla. Protraction with the labiolingual arch is more suitable for early skeletal Class III patients at a younger age; protraction with an implant is applicable to skeletal Class III patients in the late mixed dentition or early permanent dentition.

Statistical analysis of biomechanical properties of the adult sagittal suture using a bending method in a Japanese forensic sample

This study examined the mechanical properties of the adult sagittal suture compared with surrounding parietal bones using bending tests and investigated the association between the mechanical properties of the suture and age. We used the heads of 116 Japanese cadavers (76 male cadavers and 40 female cadavers) of known age and sex. A total of 1160 cranial samples, 10 from each skull, were collected. The samples were imaged using multidetector computed tomography, and the sample thickness at the center of each sample (ST) was measured. The failure stress of each sample (FS) was measured by a bending test, and the ratio of failure stress to the square of sample thickness (FS/ST(2)) was calculated. Statistical analyses revealed that the FS and FS/ST(2) values were significantly lower at all suture sites than at all bone sites regardless of sex. There were not significant but slight positive correlations between age and FS and FS/ST(2) values at any suture site in male samples. In female samples, age had significant positive correlations with FS and FS/ST(2) values at the middle suture sites, whereas there were not significant but slight positive correlations between age and FS and FS/ST(2) values at the edges of the suture. Statistical analyses also demonstrated that FS and FS/ST(2) values were significantly greater in male samples than in female samples at the middle suture sites. These findings suggest that the bending strength of the adult sagittal suture is significantly lower than that of surrounding parietal bones. Therefore, avoiding direct impact on cranial sutures may be important for preventing skull fractures and severe complications that can cause death. The results of this study also revealed that the bending strength of the middle sagittal suture significantly increases with age in only female samples, whereas the bending strength is significantly higher in male samples than in female samples at the middle suture sites, indicating the possibility of sex difference in the bony interdigitation of the sutures during childhood.

Cranial sutures work collectively to distribute strain throughout the reptile skull

The skull is composed of many bones that come together at sutures. These sutures are important sites of growth, and as growth ceases some become fused while others remain patent. Their mechanical behaviour and how they interact with changing form and loadings to ensure balanced craniofacial development is still poorly understood. Early suture fusion often leads to disfiguring syndromes, thus is it imperative that we understand the function of sutures more clearly. By applying advanced engineering modelling techniques, we reveal for the first time that patent sutures generate a more widely distributed, high level of strain throughout the reptile skull. Without patent sutures, large regions of the skull are only subjected to infrequent low-level strains that could weaken the bone and result in abnormal development. Sutures are therefore not only sites of bone growth, but could also be essential for the modulation of strains necessary for normal growth and development in reptiles.

A sensitivity analysis to the role of the fronto-parietal suture in Lacerta bilineata: a preliminary finite element study

Cranial sutures are sites of bone growth and development but micromovements at these sites may distribute the load across the skull more evenly. Computational studies have incorporated sutures into finite element (FE) models to assess various hypotheses related to their function. However, less attention has been paid to the sensitivity of the FE results to the shape, size, and stiffness of the modeled sutures. Here, we assessed the sensitivity of the strain predictions to the aforementioned parameters in several models of fronto-parietal (FP) suture in Lacerta bilineata. For the purpose of this study, simplifications were made in relation to modeling the bone properties and the skull loading. Results highlighted that modeling the FP as either an interdigitated suture or a simplified butt suture, did not reduce the strain distribution in the FP region. Sensitivity tests showed that similar patterns of strain distribution can be obtained regardless of the size of the suture, or assigned stiffness, yet the exact magnitudes of strains are highly sensitive to these parameters. This study raises the question whether the morphogenesis of epidermic scales in the FP region in the Lacertidae is related to high strain fields in this region, because of micromovement in the FP suture.

Evidence of interlinks between bioelectromagnetics and biomechanics: from biophysics to medical physics

A vast literature on electromagnetic and mechanical bioeffects at the bone and soft tissue level, as well as at the cellular level (osteoblasts, osteoclasts, keratinocytes, fibroblasts, chondrocytes, nerve cells, endothelial and muscle cells) has been reviewed and analysed in order to show the evident connections between both types of physical energies. Moreover, an intimate link between the two is suggested by transduction phenomena (electromagnetic-acoustic transduction and its reverse) occurring in living matter, as a sound biophysical literature has demonstrated. However, electromagnetic and mechanical signals are not always interchangeable, depending on their respective intensity. Calculations are reported in order to show in which cases (read: for which values of electric field in V/m and of mechanical pressure in Pa) a given electromagnetic or mechanical bioeffect is only due to the directly impinging energy or even to the indirect transductional energy. The relevance of the treated item for the applications of medical physics to regenerative medicine is stressed.

Reciprocal influence of masticatory apparatus, craniofacial structure and whole body homeostasis

There are evidences that the evolution into Homo erectus was partially induced by masticatory muscular dystrophy caused by a gene mutation, which in turn increased brain capacity and led to bipedalism. It is generally accepted that the morphology and function of mammalian skull are partially controlled by epigenetic mechanisms. Archeologic evidences support that the masticatory apparatus have influenced the mechanical stress distribution in hominin skull, and consequently changed craniofacial morphology and function. Even after evolution into H. erectus, alterations in food properties by civilization and cultural preferences have caused modification of human masticatory pattern and accordingly craniofacial structure. Since there are evidences that prehuman and human masticatory apparatus has been influenced the craniofacial and whole body morphology and function, this apparatus in turn might influence whole body homeostasis. Plausible reciprocal influencing mechanisms of the masticatory apparatus on the whole body homeostasis might be (1) direct mechanical influence on the craniofacial structure, (2) distortion of cerebrospinal fluid circulation, and/or (3) several neural/humoral routes. Based on these backgrounds, the hypothesis of the present study is that the morphology and function of masticatory apparatus influence the whole body homeostasis and these interactions are reciprocal. Therefore, human masticatory apparatus, at the present time, should be kept in its physiological status to maintain the whole body homeostasis. We recommend basic and clinical approaches to confirm this hypothesis.

Changes in biomechanical strain and morphology of rat calvarial sutures and bone after Tgf-β3 inhibition of posterior interfrontal suture fusion

Craniofacial sutures are bone growth fronts that respond and adapt to biomechanical environments. Little is known of the role sutures play in regulating the skull biomechanical environment during patency and fusion conditions, especially how delayed or premature suture fusion will impact skull biomechanics. Tgf-β3 has been shown to prevent or delay suture fusion over the short term in rat skulls, yet the long-term patency or its consequences in treated sutures is not known. It was therefore hypothesized that Tgf-β3 had a long-term impact to prevent suture fusion and thus alter the skull biomechanics. In this study, collagen gels containing 3 ng Tgf-β3 were surgically placed superficial to the posterior interfrontal suture (IFS) and deep to the periosteum in postnatal day 9 (P9) rats. At P9, P24, and P70, biting forces and strains over left parietal bone, posterior IFS, and sagittal suture were measured with masticatory muscles bilaterally stimulated, after which the rats were sacrificed and suture patency analyzed histologically. Results demonstrated that Tgf-β3 treated sutures showed less fusion over time than control groups, and strain patterns in the skulls of the Tgf-β3-treated group were different from that of the control group. Although bite force increased with age, no alterations in bite force were attributable to Tgf-β3 treatment. These findings suggest that the continued presence of patent sutures can affect strain patterns, perhaps when higher bite forces are present as in adult animals.

Effects of rapid maxillary expansion on the cranial and circummaxillary sutures

INTRODUCTION

The aim of this study was to determine whether the orthopedic forces of rapid maxillary expansion cause significant quantitative changes in the cranial and the circummaxillary sutures.

METHODS

Twenty patients (mean age, 12.3 ± 1.9 years) who required rapid maxillary expansion as a part of their comprehensive orthodontic treatment had preexpansion and postexpansion computed tomography scans. Ten cranial and circummaxillary sutures were located and measured on one of the axial, coronal, or sagittal sections of each patient's preexpansion and postexpansion computed tomography scans. Quantitative variables between the 2 measurements were compared by using the Wilcoxon signed rank test. A P value less than 0.05 was considered statistically significant.

RESULTS

Rapid maxillary expansion produced significant width increases in the intermaxillary, internasal, maxillonasal, frontomaxillary, and frontonasal sutures, whereas the frontozygomatic, zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures showed nonsignificant changes. The greatest increase in width was recorded for the intermaxillary suture (1.7 ± 0.9 mm), followed by the internasal suture (0.6 ± 0.3 mm), and the maxillonasal suture (0.4 ± 0.2 mm). The midpalatal suture showed the greatest increase in width at the central incisor level (1.6 ± 0.8 mm) followed by the increases in width at the canine level (1.5 ± 0.8 mm) and the first molar level (1.2 ± 0.6 mm).

CONCLUSIONS

Forces elicited by rapid maxillary expansion affect primarily the anterior sutures (intermaxillary and maxillary frontal nasal interfaces) compared with the posterior (zygomatic interface) craniofacial structures.

A radiographic analysis of tooth morphology following the use of a novel cyclical force device in orthodontics

Background

The purpose was to determine whether or not a novel device used in conjunction with orthodontic treatment produced root resorption shown on 3D images generated from a new cone beam computerized tomography.

Methods

Subjects were actively recruited and those who received braces for the first time were invited to participate. Patients were assigned to receive a functioning device and used the devices for 20 min daily for a six month study period. CBCT images were taken of the dentition at the start of treatment and at the end of the study period.

Results

14 subjects out of a possible 17 subjects completed using the device during the study period. The mean age of the subjects was 20.3 years. Measurements of all teeth present were made from the mesial buccal roots of the first molar on one side of the dental arch to the mesial buccal roots of the first molar on the opposing side of the same arch. These measurements were recorded as linear lengths in mm. A paired t-test was used to determine if significant differences occurred for root lengths at the end of treatment compared to the start of treatment for each of the individual tooth groups. No statistical differences were noted for root length changes above 0.5 mm and 1 mm.

Conclusions

No statistically significant findings were noted for root length change at the end of treatment compared to the start of treatment when using this novel robotic device. No significant differences were noted between roots of anterior and posterior teeth. No clinically significant changes between root lengths were noted above 0.5 mm.

A bidirectional interface growth model for cranial interosseous suture morphogenesis

Interosseous sutures exhibit highly variable patterns of interdigitation and corrugation. Recent research has identified fundamental molecular mechanisms of suture formation, and computer models have been used to simulate suture morphogenesis. However, the role of bone strain in the development of complex sutures is largely unknown, and measuring suture morphologies beyond the evaluation of fractal dimensions remains a challenge. Here we propose a morphogenetic model of suture formation, which is based on the paradigm of Laplacian interface growth. Computer simulations of suture morphogenesis under various boundary conditions generate a wide variety of synthetic sutural forms. Their morphologies are quantified with a combination of Fourier analysis and principal components analysis, and compared with natural morphological variation in an ontogenetic sample of human interparietal suture lines. Morphometric analyses indicate that natural sutural shapes exhibit a complex distribution in morphospace. The distribution of synthetic sutures closely matches the natural distribution. In both natural and synthetic systems, sutural complexity increases during morphogenesis. Exploration of the parameter space of the simulation system indicates that variation in strain and/or morphogen sensitivity and viscosity of sutural tissue may be key factors in generating the large variability of natural suture complexity.

Timing of ectocranial suture activity in Gorilla gorilla as related to cranial volume and dental eruption

Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns and a similar suture ontogeny (relative timing of suture fusion during the species ontogeny). This ontogeny includes patency during and after neurocranial expansion with a delayed bony response associated with adaptation to biomechanical forces generated by mastication. Here we investigate these relationships for Gorilla by examining the association among ectocranial suture morphology, cranial volume (as a proxy for neurocranial expansion) and dental development (as a proxy for the length of time that it has been masticating hard foods and exerting such strains on the cranial vault) in a large sample of Gorilla gorilla skulls. Two-hundred and fifty-five Gorilla gorilla skulls were examined for ectocranial suture closure status, cranial volume and dental eruption. Regression models were calculated for cranial volumes by suture activity, and Kendall's tau (a non-parametric measure of association) was calculated for dental eruption status by suture activity. Results suggest that, as reported for Pan and Homo, neurocranial expansion precedes suture synostosis activity. Here, Gorilla was shown to have a strong relationship between dental development and suture activity (synostosis). These data are suggestive of suture fusion extending further into ontogeny than brain expansion, similar to Homo and Pan. This finding allows for the possibility that masticatory forces influence ectocranial suture morphology.

Effect of aging on cellular mechanotransduction

Aging is becoming a critical heath care issue and a burgeoning economic burden on society. Mechanotransduction is the ability of the cell to sense, process, and respond to mechanical stimuli and is an important regulator of physiologic function that has been found to play a role in regulating gene expression, protein synthesis, cell differentiation, tissue growth, and most recently, the pathophysiology of disease. Here we will review some of the recent findings of this field and attempt, where possible, to present changes in mechanotransduction that are associated with the aging process in several selected physiological systems, including musculoskeletal, cardiovascular, neuronal, respiratory systems and skin.

Nasal septal and premaxillary developmental integration: implications for facial reduction in Homo

The influence of the chondrocranium in craniofacial development and its role in the reduction of facial size and projection in the genus Homo is incompletely understood. As one component of the chondrocranium, the nasal septum has been argued to play a significant role in human midfacial growth, particularly with respect to its interaction with the premaxilla during prenatal and early postnatal development. Thus, understanding the precise role of nasal septal growth on the facial skeleton is potentially informative with respect to the evolutionary change in craniofacial form. In this study, we assessed the integrative effects of the nasal septum and premaxilla by experimentally reducing facial length in Sus scrofa via circummaxillary suture fixation. Following from the nasal septal-traction model, we tested the following hypotheses: (1) facial growth restriction produces no change in nasal septum length; and (2) restriction of facial length produces compensatory premaxillary growth due to continued nasal septal growth. With respect to hypothesis 1, we found no significant differences in septum length (using the vomer as a proxy) in our experimental (n = 10), control (n = 9) and surgical sham (n = 9) trial groups. With respect to hypothesis 2, the experimental group exhibited a significant increase in premaxilla length. Our hypotheses were further supported by multivariate geometric morphometric analysis and support an integrative relationship between the nasal septum and premaxilla. Thus, continued assessment of the growth and integration of the nasal septum and premaxilla is potentially informative regarding the complex developmental mechanisms that underlie facial reduction in genus Homo evolution.