The biomechanics of chewing and suckling in the infant: A potential mechanism for physiologic metopic suture closure.

Craniosynostosis is a condition with neurologic and aesthetic sequelae requiring invasive surgery. Understanding its pathobiology requires familiarity with the processes underlying physiologic suture closure. Animal studies have shown that cyclical strain from chewing and suckling influences the closure of cranial vault sutures, especially the metopic, an important locus of craniosynostosis. However, there are no human data correlating strain patterns during chewing and suckling with the physiologically early closure pattern of the metopic suture. Furthermore, differences in craniofacial morphology make it challenging to directly extrapolate animal findings to humans. Eight finite-element analysis (FEA) models were built from craniofacial computer tomography (CT) scans at varying stages of metopic suture closure, including two with isolated non-syndromic metopic craniosynostosis. Muscle forces acting on the cranium during chewing and suckling were simulated using subject-specific jaw muscle cross-sectional areas. Chewing and suckling induced tension at the metopic and sagittal sutures, and compressed the coronal, lambdoid, and squamous sutures. Relative to other cranial vault sutures, the metopic suture experienced larger magnitudes of axial strain across the suture and a lower magnitude of shear strain. Strain across the metopic suture decreased during suture closure, but other sutures were unaffected. Strain patterns along the metopic suture mirrored the anterior to posterior sequence of closure: strain magnitudes were highest at the glabella and decreased posteriorly, with minima at the nasion and the anterior fontanelle. In models of physiologic suture closure, increased degree of metopic suture closure correlated with higher maximum principal strains across the frontal bone and mid-face, a strain regime not observed in models of severe metopic craniosynostosis. In summary, our work provides human evidence that bone strain patterns from chewing and suckling correlate with the physiologically early closure pattern of the metopic suture, and that deviations from physiologic strain regimes may contribute to clinically observed craniofacial dysmorphism.

Sagittal suture strain in capuchin monkeys (Sapajus and Cebus) during feeding.

OBJECTIVES: Morphological variation in cranial sutures is used to infer aspects of primate feeding behavior, including diet, but strain regimes across sutures are not well documented. Our aim is to test hypotheses about sagittal suture morphology, strain regime, feeding behavior, and muscle activity relationships in robust Sapajus and gracile Cebus capuchin primates. MATERIALS AND METHODS: Morphometrics of sinuosity in three regions of the sagittal suture were compared among museum specimens of Sapajus and Cebus, as well as in robust and gracile lab specimens. In vivo strains and bilateral electromyographic (EMG) activity were recorded from these regions in the temporalis muscles of capuchin primates while they fed on mechanically-varying foods. RESULTS: Sapajus and the anterior suture region exhibited greater sinuosity than Cebus and posterior regions. In vivo data reveal minor differences in strain regime between robust and gracile phenotypes but show higher strain magnitudes in the middle suture region and higher tensile strains anteriorly. After gage location, feeding behavior has the most consistent and strongest impact on strain regime in the sagittal suture. Strain in the anterior suture has a high tension to compression ratio compared to the posterior region, especially during forceful biting in the robust Sapajus-like individual. DISCUSSION: Sagittal suture complexity in robust capuchins likely reflects feeding behaviors associated with mechanically challenging foods. Sutural strain regimes in other anthropoid primates may also be affected by activity in feeding muscles.

Effect of reciprocal headgear forces on the calvarium: A finite element study.

INTRODUCTION: Orthopedic appliances continue to be used for various sagittal, vertical, and transverse corrections of the maxilla. Although cranial growth can continue to adulthood, no study has drawn attention to the effects of headgear forces on the calvarium, in which anchorage is taken. This study focused on the different biomechanical responses on the calvarium of young children wearing a high-pull headgear of varying forces, using a 3-dimensional finite element analysis and the possible implications of such changes on the human skull. METHODS: A 3-dimensional finite element model of a 9-year-old child was designed from the computed tomography scan. The material properties of the juvenile skull were assigned. Varying orthopedic forces (400, 500, and 600 g of force) were applied, and the magnitude of displacement and stresses generated on the cranial bones and sutures were interpreted using ANSYS software (version 12.1; Canonsburg, Pa). RESULTS: Maximum displacement was found for the parietal bone in the inferior direction; parietal and temporal bones in the transverse direction; and frontal, parietal, and temporal bones in the sagittal direction. The least displacement was noted for the occipital bone in all the 3-dimensions. The maximum stresses were concentrated over the region of the lateral margins of the piriform aperture and the medial walls of the orbit. Higher stress values were also found on the parietal bone adjacent to the sagittal suture. The highest value of stresses among the sutures of the craniofacial complex was found to be in the region of the frontonasal, frontomaxillary, and nasomaxillary sutures. CONCLUSIONS: The effects of displacement and stresses obtained from this study suggest a restriction to the growth of the cranial vault and its normal mobility, in turn altering the intracranial tension and causing altered cranial morphology in young, growing children undergoing high-pull headgear therapy. The human cranial system is dynamic throughout life and may be restricted or altered by hereditary or environmental factors.

Diagnosis and Management of Suture-Related Concerns of the Infant Skull.

The cranial fontanelles and sutures have several benign variations, including most cases of "early" or "late" closure of the anterior fontanelle, bathrocephaly, overriding sutures, and benign metopic ridging. However, recognizing true craniosynostosis and referring the patient to a craniofacial specialist in a timely fashion are imperative, as minimally invasive options can be offered to most patients younger than 6 months of age. Gaining comfort with the physical examination of an infant with an abnormal head shape is best achieved through experience and pattern recognition and will frequently facilitate an accurate diagnosis without the need for ionizing radiation.

Mathematical modeling of palatal suture pattern formation: morphological differences between sagittal and palatal sutures.

The median palatal suture serves as a growth center for the maxilla; inadequate growth at this site causes malocclusion and dental crowding. However, the pattern formation mechanism of palatal sutures is poorly understood compared with that of calvarial sutures such as the sagittal suture. In the present study, therefore, we compared the morphological characteristics of sagittal and palatal sutures in human bone specimens. We found that palatal suture width was narrower than sagittal suture width, and the interdigitation amplitude of the palatal suture was lower than that of the sagittal suture. These tendencies were also observed in the neonatal stage. However, such differences were not observed in other animals such as chimpanzees and mice. We also used a mathematical model to reproduce the differences between palatal and sagittal sutures. After an extensive parameter search, we found two conditions that could generate the difference in interdigitation amplitude and suture width: bone differentiation threshold [Formula: see text] and growth speed c. We discuss possible biological interpretations of the observed pattern difference and its cause.

Cranial suture biomechanics in Metoposaurus krasiejowensis (Temnospondyli, Stereospondyli) from the upper Triassic of Poland.

Cranial sutures connect adjacent bones of the skull and play an important role in the absorption of stresses that may occur during different activities. The Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis has been extensively studied over the years in terms of skull biomechanics, but without a detailed description of the function of cranial sutures. In the present study, 34 thin sections of cranial sutures were examined in order to determine their histovariability and interpret their biomechanical role in the skull. The histological model was compared with three-dimensional-finite element analysis (FEA) simulations of the skull under bilateral and lateral biting as well as skull-raising loads for maximum and minimum principal stress. Histologically, only two sutural morphologies were recognised in the skull of Metoposaurus: interdigitated sutures (commonly associated with compressive stresses) are dominant along the entire length of the skull roof and palate; tongue-and-groove sutures (commonly associated with tensile stresses) are present across the maxilla. FEA shows a much more complex picture of stress type and distribution than predicted by sutures. Common to both methods is a predominance of compressive stresses which act on the skull during biting. The methods predict different stress regimes during biting in the posterior part of the skull: where histological analysis suggests compression, FEA predicts tension. For lateral biting and skull raising, histological and digital reconstructions show similar general patterns but with some variations.

Stem cells of the suture mesenchyme in craniofacial bone development, repair and regeneration.

Development of the skeleton is mediated through two distinct ossification mechanisms. Craniofacial bones are formed mainly through intramembranous ossification, a mechanism different from endochondral ossification required for development of the body skeleton. The skeletal structures are quite distinct between the two, thus they are likely to have their unique stem cell populations. The sutures serve as the growth center critical for healthy development of the craniofacial skeleton. Defects in suture morphogenesis cause its premature closure, resulting in development of craniosynostosis, a devastating disease affecting 1 in ~2,500 individuals. The suture mesenchyme has been postulated to act as the niche of skeletal stem cells essential for calvarial morphogenesis. However, very limited knowledge is available for suture biology and suture stem cells (SuSCs) have yet to be isolated. Here we report the first evidence for identification and isolation of a stem cell population residing in the suture midline. Genetic labeling of SuSCs shows their ability to self-renew and continually give rise to mature cell types over a 1-year monitoring period. They maintain their localization in the niches constantly produce skeletogenic descendants during calvarial development and homeostastic maintenance. Upon injury, SuSCs expand drastically surrounding the skeletogenic mesenchyme, migrate to the damaged site and contribute directly to skeletal repair in a cell autonomous fashion. The regeneration, pluripotency and frequency of SuSCs are also determined using limiting dilution transplantation. In vivo clonal expansion analysis demonstrates a single SuSC capable of generating bones. Furthermore, SuSC transplantation into injured calvaria facilitates the healing processes through direct engraftments. Our findings demonstrate SuSCs are bona fide skeletal stem cells ideally suited for cell-based craniofacial bone therapy as they possess abilities to engraft, differentiate.(Presented at the 1980th Meeting, April 16, 2019).

The difference of stress distribution of maxillary expansion using rapid maxillary expander (RME) and maxillary skeletal expander (MSE)-a finite element analysis.

BACKGROUND: Maxillary skeletal expander (MSE) in combination with miniscrews was developed to overcome the drawbacks that may have resulted from the application of conventional rapid maxillary expander (RME). This research was conducted to analyze the difference of stress distribution of maxillary expansion using RME and MSE in the region of interests (ROIs): first molars (M1), palatal alveolar bones of M1, palatine sutures, zygomatic sutures, miniscrews, and their surrounding bones. METHODS: A dry skull was scanned using CBCT and rendered into a three-dimensional (3D) model of craniomaxillary structures. The data analysis was done both visually and numerically. RESULT: The stress distributions in RME group were located at the palatal side of M1, mesial side of palatal alveolar of M1, pulp chamber of M1, and inferior cortex of palatine sutures. The stress distributions in the MSE group were located at the distopalatal cusp of M1, palatal side of palatal alveolar of M1, and inferior and superior cortex of palatine sutures. The stress distributions in zygomatic sutures on both groups were located at the zygomaticotemporal sutures, whereas in the miniscrews, the stress were located at the anterior miniscrews and palatal side of surrounding bones. CONCLUSIONS: There were significant differences of stress distribution of maxillary expansion measured in the ROIs in the craniomaxillary 3D model using RME and MSE.

Midfacial changes in the coronal plane induced by microimplant-supported skeletal expander, studied with cone-beam computed tomography images.

INTRODUCTION: Our objectives were to evaluate midfacial skeletal changes in the coronal plane and the implications of circummaxillary sutures and to localize the center of rotation for the zygomaticomaxillary complex after therapy with a bone-anchored maxillary expander, using high-resolution cone-beam computed tomography. METHODS: Fifteen subjects with a mean age of 17.2 ± 4.2 years were treated with a bone-anchored maxillary expander. Pretreatment and posttreatment cone-beam computed tomography images were superimposed and examined for comparison. RESULTS: Upper interzygomatic distance increased by 0.5 mm, lower interzygomatic distance increased by 4.6 mm, frontozygomatic angles increased by 2.5° and 2.9° (right and left sides), maxillary inclinations increased by 2.0° and 2.5° (right and left sides), and intermolar distance increased by 8.3 mm (P <0.05). Changes in frontoethmoidal, zygomaticomaxillary, and molar basal bone angles were negligible (P >0.05). CONCLUSIONS: A significant lateral displacement of the zygomaticomaxillary complex occurred in late adolescent patients treated with a bone-anchored maxillary expander. The zygomatic bone tended to rotate outward along with the maxilla with a common center of rotation located near the superior aspect of the frontozygomatic suture. Dental tipping of the molars was negligible during treatment.

Evaluation of fontanel size variation and closure time in children followed up from birth to 24 months.

OBJECTIVE Anterior fontanel size and closure time can be useful clinical signs for the early diagnosis of diseases. Knowing age-related normal variations is important to decide on further investigations. The authors of this study aimed to describe fontanel size variation according to age, determine fontanel closure time, and identify the optimal method for assessing fontanel size. METHODS For this prospective cohort study, 321 healthy term babies who fulfilled the inclusion criteria were consecutively recruited. Percentile charts for the mean anterior fontanel size and oblique measurements from birth to 24 months of age were created. RESULTS The mean fontanel closure time was 9.7 ± 5.0 months (girls 10.3 ± 4.7 months, boys 9.2 ± 5.1 months). No differences were observed between the traditional method and oblique measurements. Early fontanel closure was not associated with microcephaly. CONCLUSIONS Oblique measurements can be used because they are as accurate as the traditional method. Children with fontanels measuring above the 95th percentile should be monitored closely and investigated further for potentially associated diseases.

The biomechanical role of the chondrocranium and sutures in a lizard cranium.

The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the role of both the sutures and the chondrocranium in the South American tegu lizard Salvator merianae We use multi-body dynamics analysis (MDA) to provide realistic loading conditions for anterior and posterior unilateral biting and a detailed finite element model to examine strain magnitude and distribution. We find that strains within the chondrocranium are greatest during anterior biting and are primarily tensile; also that strain within the cranium is not greatly reduced by the presence of the chondrocranium unless it is given the same material properties as bone. This result contradicts previous suggestions that the anterior portion (the nasal septum) acts as a supporting structure. Inclusion of sutures to the cranium model not only increases overall strain magnitudes but also leads to a more complex distribution of tension and compression rather than that of a beam under sagittal bending.

Biomechanical behaviour of craniofacial sutures during distraction: An evaluation all over the entire craniofacial skeleton.

OBJECTIVE: Sutures are fibrous joints connecting the bones of the head. Despite the fundamental role played by sutures in dentofacial orthopaedics, their biomechanical properties are not completely understood. This study evaluated anatomy, biomechanics, and acoustic emission (AE) during distraction of the sutural ligament (SL). METHODS: Seventy-two suture samples were removed from a twelve-months-old swine (Sus scrofa) head. Each volume was acquired using micro-computed tomography (µCT), and the linear interdigitation index was calculated on both planes (LIICOR and LIISAG). Mechanical testing till failure was carried at 1mm/min, and four piezoelectric sensors were used for recording of amplitude (A), duration (D), and energy (E) of AE. The relationships between interdigitation, fracture types, tensile stress (σ0), and AE were statistically analysed with non-parametric tests (α=0.05). RESULTS: σ0 of the SL had median values of 4.0MPa, and AE were characterised by A of 49.3dB (IQR=2.2), D of 826.3µs (IQR=533.4), and E of 57,715.8 eu (IQR=439,613.5). Most of the fractures happened in the SL (46%), some within the bone (34%), and fewer were combined (19%). LIICOR had correlation with A (0.383, p=0.028), D (0.348, p=0.048), and E (0.437, p=0.011) of the AE, and σ0 had similar relationship with A (0.500, p=0.003), D (0.495, p=0.003), and E (0.579, p<0.001). Maximum energy values were different between fractures within the bone and within the SL (p=0.021). SIGNIFICANCE: Biomechanical properties under tension of most of the sutures of the craniofacial skeleton were reported. AE provided information about the sequence of events during SL distraction, and had significant relationship with its mechanical properties. Further studies are necessary to confirm these preliminary findings, and to identify their relationship with biological processes and dentofacial treatments.

Histomorphometric Comparison of Bone Regeneration in Critical-Sized Bone Defects Using Demineralized Bone Matrix, Platelet-Rich Fibrin, and Hyaluronic Acid as Bone Substitutes.

AIM: To compare bone regeneration in the critical-sized bone defects grafted with demineralized bone matrix, platelet-rich fibrin, and hyaluronic acid in rats. MATERIALS AND METHODS: Forty Wistar Albino rats allocated into 4 experimental groups: platelet-rich fibrin (PRF) group, noncross-linked hyaluronic acid gel (HA) group, demineralized bone matrix in putty form (DBM) group, and control group. A critical-sized defect of 8 mm was formed involving the sagittal suture for each rat under anesthetic induction. All animals were sacrificed at 21st day after surgery and histomorphometric parameters of total horizontal length (THL) and total vertical length (TVL) of newly produced bone and longest bone trabecula (LBT) were measured in the histologic slides. The difference between experimental groups for these parameters was analyzed. RESULTS: There was statistically significant difference in THL and LBT but not in TVL. Total horizontal length was significantly increased in DBM group compared with control and HA groups (P < 0.05). There was also statistically significant increase in THL in PRF group compared with control group (P < 0.05). Longest bone trabecula significantly increased in DBM group compared with HA group (P < 0.05). There was also statistically significant increase in HA group compared with control group (P < 0.05) and LBT significantly increased in PRF group compared with HA group (P < 0.05). CONCLUSION: The sole usage of HA does not effectively increase bone regeneration when compared with DBM and PRF. The DBM and PRF do not have superiority to each other in the bone regeneration while they are superior to HA.

Miniscrew-assisted slow expansion of mature rabbit sutures.

INTRODUCTION: In this study, we experimentally evaluated whether complex, mature sutures can be separated using skeletal anchorage and light, continuous forces. METHODS: Twelve adult, 8- to 9-month-old female New Zealand white rabbits were randomly assigned to 1 control group and 2 experimental groups. Open-coil nickel-titanium springs delivered constant forces of 100 g across the sagittal suture to miniscrew implants placed bilaterally in the frontal bone. Sutural separation was measured biweekly. Separation was also measured with microcomputed tomography. Bone formation (mineral apposition) was measured with fluorescent labels. Qualitative histologic analyses of the suture tissues were performed using hematoxylin and eosin staining; osteoclasts were evaluated with tartrate resistant acid phosphatase staining. RESULTS: All 24 miniscrew implants remained stable throughout the experiment. There was no statistically significant sutural separation in the control group. In the experimental groups, sutural separation was significant (P <0.05) at all time points after the initial records were taken. The rate of separation was linear during the first 42 days. There were moderate correlations (R = 0.59-0.89; P <0.05) between miniscrew implant separation and bone marker separation. Mineral apposition rate, which was not measureable in the control group, was significant in the experimental group. The mineral apposition rate was greater between 14 and 28 days than between 28 and 38 days, and it was greater on the ectocranial than on the endocranial surface. Based on the microcomputed tomography analysis, 3-dimensional sutural volume of the experimental group increased significantly (P = 0.02), but surface area did not (P = 0.26). CONCLUSIONS: It is possible to separate the sagittal suture of mature rabbits. Sutural separation is limited, indicating involvement of other articulations.

A comparison of three-dimensional stress distribution and displacement of naso-maxillary complex on application of forces using quad-helix and nickel titanium palatal expander 2 (NPE2): a FEM study.

BACKGROUND: Our objectives are to analyse and to compare the stress distribution and displacement of the craniofacial structures, following the application of forces from quad-helix and Nickel Titanium Palatal Expander-2 (NPE2) using finite element analysis. METHODS: Three-dimensional finite element models of young dried human skull, quad-helix appliance and NPE2 were constructed, and the initial activation of the expanders was stimulated to carry out the analysis and to evaluate the Von Misses stresses and displacement. RESULTS: Both the models demonstrated the highest stresses at the mid-palatal suture, with maximum posterior dislocation. The second highest stress was recorded at the fronto-zygomatic suture. The pattern of stress distribution was almost similar in both the groups, but NPE2 revealed lower magnitude stresses than quad-helix. The only exception being quad-helix model showed high stress levels around pterygo-maxillary suture whereas minimal stress around pterygo-maxillary suture was noticed after NPE2 activation. The cusp of the erupting canine and the erupting mesiobuccal cusp of the second molar showed outward, backward and downward displacement signifying increase in their eruption pattern following maxillary expansion. CONCLUSIONS: Maxillary expansion using quad-helix and NPE2 can be used in posterior crossbite correction in cases where maximum skeletal changes are desirable at a younger age; it is furthermore effective in treating young patients with impacted or displaced teeth. Quad-helix and NPE2 produced acceptable forces for orthopaedic treatment even after being orthodontic appliances; their clinical application should be correctly planned as the effects of these appliances are largely age dependent.

Brief Communication: Skeletal and dental development in a sub-adult western lowland gorilla (Gorilla gorilla gorilla).

OBJECTIVES: Non-human primate growth trajectories are often used to estimate the age and life history traits of fossil taxa. The exclusive use of chimpanzee growth patterns to estimate developmental stages for the earliest hominins is problematic because incomplete lineage sorting in the hominoid clade has produced a mosaic human genome that contains different regions shared with any one of the great apes. The accidental death of a sub-adult male western lowland gorilla (Gorilla gorilla gorilla) provides not only an opportunity to compare the degree of dentoskeletal maturation in this individual with published data from conspecifics, but also insight into gorilla growth and development as it applies to modeling that of early hominins. MATERIALS AND METHODS: Dental stage was assessed for a sub-adult male western lowland gorilla by comparing dental eruption and calcification to established relative age categories. Ectocranial suture fusion, epiphyseal union, and long bone dimensions were compared to growth standards for wild male gorillas of a similar dental stage to determine developmental timing variability. RESULTS: Results suggest that greater variability exists in developmental rates and patterns and in morphological parameters than is often acknowledged. DISCUSSION: These results have implications for selecting appropriate models for studying extinct taxa. Ecological and physical characteristics shared between humans and gorillas may make gorilla life history equally valid in a comparative framework and encourage non-exclusive use of chimpanzee life history for paleoanthropological models.

The effect of different concentrations of topical ozone administration on bone formation in orthopedically expanded suture in rats.

BACKGROUND/OBJECTIVE: The aim of this study was to investigate the effects of different concentrations of ozone (O3) therapy on bone regeneration in response to an expansion of the inter-premaxillary suture in rats. MATERIALS AND METHODS: Forty-eight Wistar rats were randomly divided into four groups (n = 12). In groups I, II, and III, 1ml of O3 at 10, 25, and 40 µg/ml was injected at the premaxillary suture, respectively. In group IV (control group), 1ml of saline solution was injected at the same point during the expansion procedure for 5 days. Bone regeneration in the suture was evaluated histomorphometrically. The area of new bone and fibrotic area, the number of osteoblasts and osteoclasts, and the amount of vascularity were measured and compared. The density of the newly formed bone in the expansion area was measured by using cone beam computed tomography. Data were analyzed using the Kruskal-Wallis one-way analysis of variance and post hoc Student-Newman-Keuls tests. RESULTS: New bone area, fibrotic area, osteoblast and osteoclast numbers, and the amount of vascularity were significantly higher in experimental groups compared with the control group (P < 0.001). The density of newly formed bone (P < 0.001), new bone formation (P = 0.009), number of capillaries (P < 0.001), number of osteoclasts (P = 0.016), and number of osteoblasts (P < 0.001) in the maxillary sutures were highest in the 25 µg/ml O3 group compared with the other experimental groups and control group. CONCLUSIONS/IMPLICATIONS: The application of O3 therapy can stimulate bone regeneration in an orthopedically expanded inter-premaxillary suture during both the expansion and retention periods.

Utilization of bone impedance for age estimation in postmortem cases.

In the field of Forensic Medicine the number of unidentified cadavers has increased due to natural disasters and international terrorism. The age estimation is very important for identification of the victims. The degree of sagittal closure is one of such age estimation methods. However it is not widely accepted as a reliable method for age estimation. In this study, we have examined whether measuring impedance value (z-values) of the sagittal suture of the skull is related to the age in men and women and discussed the possibility to use bone impedance for age estimation. Bone impedance values increased with aging and decreased after the age of 64.5. Then we compared age estimation through the conventional visual method and the proposed bone impedance measurement technique. It is suggested that the bone impedance measuring technique may be of value to forensic science as a method of age estimation.

Peroxisome proliferator-activated receptor gamma regulates bone remodeling after midpalatal suture expansion in mice.

PURPOSE: The effectiveness of rapid maxillary expansion is adversely affected by failure and relapse. It is important to identify key factors that increase new bone formation and improve bone remodeling of midpalatal sutures to improve the stability and effectiveness of this commonly used orthodontic procedure. Peroxisome proliferator-activated receptor gamma (PPARγ) plays an important role in modulating osteogenesis and bone resorption in long bones. This study was designed to explore the function of PPARγ in bone remodeling and tissue engineering of midpalatal sutures. MATERIALS AND METHODS: Pioglitazone, a PPARγ agonist, and osteoclast PPARγ knockout mice were used to explore the impact of PPARγ activation and inactivation, respectively, on bone remodeling in a mouse model of midpalatal suture expansion (MSE). Histologic analysis including staining with hematoxylin-eosin, tartrate-resistant acid phosphatase, and alkaline phosphatase was used to evaluate tissue remodeling. Reverse-transcriptase quantitative polymerase chain reaction was used to measure gene expression. RESULTS: Pioglitazone decreased new bone formation after MSE. This was accompanied by an increased amount of osteoclasts and expression of genes promoting osteoclastogenesis, as well as a decreased amount of osteoblasts and expression of genes promoting osteoblastogenesis in midpalatal sutures. Conversely, osteoclast PPARγ knockout mice increased new bone formation and decreased the amount of osteoclasts and expression of genes promoting osteoclastogenesis. CONCLUSION: In the process of bone remodeling after MSE, PPARγ, particularly in osteoclasts, is an important regulator of osteoblast and osteoclast homeostasis and bone remodeling in midpalatal sutures. Blockade of PPARγ might be an effective strategy to improve stability and decrease relapse in the practice of rapid maxillary expansion.