Ossification Defects Research Articles

Growth Charts for Shwachman-Diamond Syndrome at Ages 0 to 18 Years.

Shwachman-Diamond syndrome (SDS) is one of the most common inherited bone marrow failure syndromes. SDS is characterized by hypocellular bone marrow, with a severe impairment of the myeloid lineage, resulting in neutropenia, thrombocytopenia, and, more rarely, anemia. Almost 15% of patients with SDS develop myelodysplastic syndrome or acute myeloid leukemia as early as childhood or young adulthood. Exocrine pancreatic insufficiency is another common feature of SDS. Almost all patients with SDS show failure to thrive, which is associated with skeletal abnormalities due to defective ossification. Considering these observations, it remains unfeasible to use the common growth charts already available for the general population. To address this issue, we report how we drew up growth charts of patients with SDS aged 0 to 18 years. We analyzed height, weight, and body max index (BMI) in 121 Italian patients with SDS. Results indicated that the 50th and 3rd percentiles of weight and height of the pediatric general population correspond to the 97th and 50th percentiles of patients with SDS aged 0-18 years, respectively. In addition, the percentage increment in weight of subjects aged 14-18 years was higher in patients with SDS than in the general population. SDS-specific growth charts, such as those described here, afford a new tool, which is potentially useful for both clinical and research purposes in SDS.

Adams-Oliver Syndrome (OSA)

Introduction: Adams-Oliver's syndrome (SAO) is a rare genetic condition characterized by the association of lumb anomalies and Aplasia cutis congenita in vertex, often accompanied by underlying ossification defect and vascular lesions. The objective through this new observation is to describe the clinical, radiological, therapeutic and evolutionary elements according to what was described up to there in the literature.
 Observation: Female newborn child, stemming from a pregnancy followed with normal obstetric ultrasounds. He presents a scalp agenesis, underlying cranial bone aplasia and toes hypoplasia with syndactyly. The association of these two major criteria allowed making the diagnosis of SAO. Moreover, she presents disjointed and large sagittal suture with left parietal bone borders hypoplasia. The notion of periventricular bleeding. The rest of the balance sheet deformation, namely the abdominal ultrasound and echocardiography was without anomalies. The newborn was sent in neurosurgery for restorative treatment, which will be planned at the age of 3 months.
 Discussion and Conclusion: This observation illustrates sporadic and not complicated SAO. The absence of complete gene mapping in SAO and therefore of any genetic counseling, prenatal morphological ultrasound, is making important in evolutionary terms of subsequent pregnancies.

ANGPTL4 binds to the leptin receptor to regulate ectopic bone formation.

Leptin protein was thought to be unique to leptin receptor (LepR), but the phenotypes of mice with mutation in LepR [db/db (diabetes)] and leptin [ob/ob (obese)] are not identical, and the cause remains unclear. Here, we show that db/db, but not ob/ob, mice had defect in tenotomy-induced heterotopic ossification (HO), implicating alternative ligand(s) for LepR might be involved. Ligand screening revealed that ANGPTL4 (angiopoietin-like protein 4), a stress and fasting-induced factor, was elicited from brown adipose tissue after tenotomy, bound to LepR on PRRX1+ mesenchymal cells at the HO site, thus promotes chondrogenesis and HO development. Disruption of LepR in PRRX1+ cells, or lineage ablation of LepR+ cells, or deletion of ANGPTL4 impeded chondrogenesis and HO in mice. Together, these findings identify ANGPTL4 as a ligand for LepR to regulate the formation of acquired HO.

Characteristics of Scoliosis in Mice Induced by Chondrocyte-specific Inactivation of L-type Amino Acid Transporter 1.

A mouse study of the Slc7a5 gene using conditional knockout to assess the effects of its inactivation on spinal deformity. This study aimed to investigate whether the mice with scoliosis [induced by chondrocyte-specific inactivation of L-type amino acid transporter 1 (LAT1)] show a developmental process similar to that of pediatric scoliosis and to examine the relationship between reduced bone mineral density (BMD) and scoliosis. Furthermore, we aimed to obtain insights into elucidating the etiology and pathophysiology of scoliosis. The etiology and pathogenesis of scoliosis are not fully understood despite substantial investigative efforts. LAT1 is an amino acid transporter that mediates the cellular uptake of large neutral amino acids. A recent study revealed that chondrocyte-specific inactivation of LAT1 in mice results in scoliosis (Col2a1-Cre;Slc7a5fl/fl mice: "Sko mice"). Body length, body weight, Cobb angle, vertebral body rotation angle, and BMD at 1, 2, 4, 6, and 8 weeks of age were examined and statistically compared with those of normal control mice. Pathologic and morphologic evaluation was performed on specimens from 10-week-old euthanized mice. The Sko mice developed thoracic scoliosis in infancy without congenital malformations. This spinal deformity progressed rapidly during growth, with diverse curve patterns and hypoplastic vertebral bodies. Pathologic examination revealed thickening of the growth plates and decreased osteoblasts, suggesting that impaired endochondral ossification was the cause of the scoliosis. Sko mice were also observed to have decreased BMD and degraded bone microstructure. Reduced BMD and bone quality may not be the causes of the onset and progression of scoliosis in the Sko mice. In Sko mice, the characteristics of scoliosis and vertebral pathology showed many similarities with syndromic scoliosis in humans. Endochondral ossification defects may impair growth, leading to scoliosis and decreased BMD.

α-parvin controls chondrocyte column formation and regulates long bone development

Endochondral ossification requires proper control of chondrocyte proliferation, differentiation, survival, and organization. Here we show that knockout of α-parvin, an integrin-associated focal adhesion protein, from murine limbs causes defects in endochondral ossification and dwarfism. The mutant long bones were shorter but wider, and the growth plates became disorganized, especially in the proliferative zone. With two-photon time-lapse imaging of bone explant culture, we provide direct evidence showing that α-parvin regulates chondrocyte rotation, a process essential for chondrocytes to form columnar structure. Furthermore, loss of α-parvin increased binucleation, elevated cell death, and caused dilation of the resting zones of mature growth plates. Single-cell RNA-seq analyses revealed alterations of transcriptome in all three zones (i.e., resting, proliferative, and hypertrophic zones) of the growth plates. Our results demonstrate a crucial role of α-parvin in long bone development and shed light on the cellular mechanism through which α-parvin regulates the longitudinal growth of long bones.

Osteochondrosis in the central and third tarsal bones of young horses.

Recently, the central and third tarsal bones of 23 equine fetuses and foals were examined using micro-computed tomography. Radiological changes, including incomplete ossification and focal ossification defects interpreted as osteochondrosis, were detected in 16 of 23 cases. The geometry of the osteochondrosis defects suggested they were the result of vascular failure, but this requires histological confirmation. The study aim was to examine central and third tarsal bones from the 16 cases and to describe the tissues present, cartilage canals, and lesions, including suspected osteochondrosis lesions. Cases included 9 males and 7 females from 0 to 150 days of age, comprising 11 Icelandic horses, 2 standardbred horses, 2 warmblood riding horses, and 1 coldblooded trotting horse. Until 4 days of age, all aspects of the bones were covered by growth cartilage, but from 105 days, the dorsal and plantar aspects were covered by fibrous tissue undergoing intramembranous ossification. Cartilage canal vessels gradually decreased but were present in most cases up to 122 days and were absent in the next available case at 150 days. Radiological osteochondrosis defects were confirmed in histological sections from 3 cases and consisted of necrotic vessels surrounded by ischemic chondronecrosis (articular osteochondrosis) and areas of retained, morphologically viable hypertrophic chondrocytes (physeal osteochondrosis). The central and third tarsal bones formed by both endochondral and intramembranous ossification. The blood supply to the growth cartilage of the central and third tarsal bones regressed between 122 and 150 days of age. Radiological osteochondrosis defects represented vascular failure, with chondrocyte necrosis and retention, or a combination of articular and physeal osteochondrosis.

Evaluation of the appearance of osteochondrosis lesions by two radiographic examinations in sport horses aged from 12 to 36 months.

Osteochondrosis is a developmental orthopedic disease characterized by a defect of enchondral ossification. This pathological condition develops and evolves during growth and is influenced by various factors, in particular genetic and environmental. However, little research has been conducted on the dynamic of this condition in horses after the age of 12 months. The retrospective study presented here investigates changes in osteochondrosis lesions through two standardized radiographic examinations carried out on young Walloon sport horses after one year of age (mean age at first and second examination was 407 (±41) and 680 (±117) days respectively). Each examination, analyzed independently by three veterinarians, included latero-medial views of the fetlocks, hocks, stifles, plantarolateral-dorsomedial hocks view and additional radiograph if the operator deemed it necessary. Each joint site was graded as healthy, osteochondrosis (OC) or osteochondrosis dissecans (OCD) affected. A group of 58 horses was studied, among them 20 presented one or more osteochondrosis lesions for a total of 36 lesions present during at least one examination. In this population, 4 animals (6.9%) presented osteochondrosis during only one examination (2 at the first examination and 2 at the second one). Moreover, it was possible to demonstrate the appearance, disappearance and more generally the evolution of 9/36 lesions (25%) within the different joints. The results of the study suggest that, although substantial main limitations, osteochondrosis lesions can evolve after the age of 12 months in sport horses. Knowing this is useful in helping to decide the appropriate radiographic diagnosis timing and management.

Effect of chlorpyrifos and its metabolites on skeletal system development of chick embryo.

Chlorpyrifos is an organophosphate insecticide used primarily to control pests on a variety of food and feed crops. Humans are directly or indirectly exposed to this pesticide through food, air, and occupation. The ill effects of chlorpyrifos on various organ systems of human has been widely documented, but less is known about its influence on human bones. To analyze the effect of chlorpyrifos and its metabolites 3,5,6-trichloro-2-pyridinol (TCPy) on the skeletal system of the chick embryo. Fertilized chick eggs were exposed to different concentrations of chlorpyrifos and its metabolite 3,5,6-TCPy on 1.5 days of incubation. The proximal phalanx of 18-day-old embryos was analyzed for defects in growth and ossification through histopathology, immunohistochemistry, angiogenesis assay, and gene expression study. Dose-dependent variations in developing bone of chick embryo were observed. Histochemical and histomorphometry studies of proximal phalanx showed increased in the growth plate length (F(9, 59)=228.9509, p=.00001) with a reduction in the total length of the phalanx (F(9, 59)=109.9905, p=.00001), decreased mineralization (F(9, 59)=224.6872, p=.00001), decreased blood islands in the bone marrow (F(9, 59)=7.7083, p=.0001) of chlorpyrifos, and 3,5,6-TCPy-exposed group. Significant downregulations in the expression patterns of the transcription factors, such as SOX9, RUNX2, and ALP, were also observed. Chlorpyrifos and its metabolite 3,5,6-TCPy exposure alters the chondrogenesis in the growth plate cartilage of long bone in chick embryo. The pesticide and its metabolite also interfere in ossification.

Autologous Cranioplasty Using a Dental SafeScraper Device.

Conventional methods to reconstruct cortical bone defects introduced by pediatric cranial vault remodeling (CVR) procedures have shortcomings. Use of bone burr shavings as graft material leads to variable ossification, and harvesting split-thickness cortical grafts is time-intensive and often not possible in thin infant calvaria. Since 2013, the authors' team has used the SafeScraper, originally developed as a dental instrument, to harvest cortical and cancellous bone grafts during CVR. The authors assessed the effectiveness of this technique by analyzing postoperative ossification using computed tomography scans of 52 patients, comparing cohorts treated with the SafeScraper versus those who received conventional methods of cranioplasty during fronto-orbital advancement. The SafeScraper cohort had a greater reduction in total surface area of all defects (-83.1% ± 14.9 versus -68.9% ± 29.8; P = 0.034), demonstrating a greater and more consistent degree of cranial defect ossification compared with conventional methods of cranioplasty, suggesting potential adaptability of this tool. This is the first study that describes the technique and efficacy of the SafeScraper in reducing cranial defects in CVR. Therapeutic, III.

Amyloid-mediated remineralization for tooth hypoplasia of cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is an autosomal-dominant, heritable skeletal and dental disease, involving hypoplastic clavicles, defective ossification of the anterior fontanelle, dentin and enamel hypoplasia, and supernumerary teeth, which can seriously affect the oral and mental health of patients. Amyloid-like protein aggregation, which is established by lysozyme conjugated with polyethylene glycol (Lyso-PEG), forms a mineralized nanofilm layer on a healthy enamel surface. However, whether it can form a remineralization layer in dental tissues from CCD remains unclear. This study evaluated deciduous teeth from healthy individuals and a patient with CCD. Because pulp and dentin are functionally closely related, stem cells from human exfoliated deciduous teeth (SHED) from CCD patients and healthy individuals were collected to compare their biological properties. The results found that deciduous teeth from patients with CCD exhibited dentin hypoplasia. In addition, the proliferative ability and osteogenic potential of SHED from patients with CCD were lower than those of control individuals. Finally, Lyso-PEG was applied to dentin from the CCD and control groups, showing a similar remineralization-induced effect on the dentin surfaces of the two groups. These results extend our understanding of the dentin and SHED of patients with CCD, exhibiting good caries-preventive capacity and good biocompatibility of Lyso-PEG, thus providing a novel dental therapy for CCD and patients with tooth hypoplasia.

Behavioural disorder in a dog with congenital agenesis of the vomeronasal organ and the septum pellucidum

ABSTRACTA 1.5‐year‐old, entire male mongrel dog with a bifid nose and primary cleft palate showed aggressiveness towards unknown dogs despite having adequate canine socialisation and the absence of previous traumatic experiences; furthermore, he does not exhibit sexual behaviour towards females in heat. He was previously treated for fear‐related aggression towards unknown people and environmental phobia due to poor human socialisation. Pharmacological treatment with fluoxetine and trazodone, together with behaviour modification, was started without success. Therefore, it was decided to repeat medical tests. CT and MRI revealed a rostral middle raphe ossification defect incompatible with the presence of the vomeronasal organ (VNO) and the absence of the septum pellucidum (SP). The dog was presumptively diagnosed with aggressiveness towards unknown dogs due to an organic cause, a congenital anomaly with agenesis of the VNO and SP. This case shows the importance of both structures in the regular intraspecific interactions of dogs.

LP-52 Leaf ethanolic extract of Etlingera hemesphaerica Blume mitigates defects in fetal anatomy and endochondral ossification due to mercuric chloride during the post-implantation period in Mus musculus

LP-52 Leaf ethanolic extract of Etlingera hemesphaerica Blume mitigates defects in fetal anatomy and endochondral ossification due to mercuric chloride during the post-implantation period in Mus musculus

Unilateral Anophthalmia and Congenital Frontal Cranioschisis Associated with Extradural Neuroglial Heterotopia: new Insights into a Possible New Malformative Spectrum

Background: Neuroglial heterotopia, characterized by mature ­neuroglial tissue outside the central nervous system, has not been previously associated with cranioschisis. Case Report: A 4-year-old female patient, with left congenital anophthalmia, had a nasofrontal neuroglial heterotopia protruding through an ossification defect. Discussion: Nasofrontal cranioschisis may be associated with neuroglial heterotopias. The combination of anophthalmia and neuroglial heterotopia, previously described only once in the literature, may be part of a broader malformation spectrum that has not been properly characterized to date.

Morbid Constellation of Osseous and Vascular Abnormalities in a Female Patient with Congenital Central Hypoventilation/Overgrowth Syndrome

Background: Congenital Central Hypoventilation Syndrome (CCHS), is a condition characterized by ventilatory impairment that results in arterial hypoxemia. Studies revealed that the vast majority of patients with CCHS are free from any associated pulmonary, cardiac or brainstem pathologies. Material and Methods: F.R is a 20 -year-old- Austrian-girl presented in my consultation seeking advice for her unpleasant clinical history. In her early life, seizures were the first serious clinical presentation. Followed later on with hypertension, bouts of respiratory dysfunction and impairment of consciousness. In 2019 she underwent surgical intervention to remove a 2 cm hamartoma (posterior upper aspect of the right thigh). Few years later, another hamartoma on the ventral side of the tongue has been identified as well. Early on, she received the diagnosis of Mediterranean fever syndrome and the geneticist encountered homozygosity to the MEFV M694V mutation as the reason behind the constellation of the current unpleasant symptomatology. Later on a presumptive diagnosis of Ehlers-Danlos syndrome-hypermobile type has been suggested in other Medical Institutions. We proceeded with our documentation via clinical and radiological phenotypic characterizations. Results: Clinical examination showed growth above the 97th percentile (overgrowth) with no specific facial dysmorphic features. She manifested generalized ligamentous hyper laxity. Her ligamentous hyperlaxity was compatible with 6 points out of 9 in correlation with Beighton scoring test. On the bases of skeletal survey; lateral skull radiograph showed features of mastoid and temporal bone characterized with extensive-pneumatization. Axial CT scan shows bilateral hyper-pneumatization of the temporal bones, demonstrating expansion of aerial spaces with loss of the bony trabeculae and thinning of the mastoid bone. Mastoid cells appear to be in communication with a large intracranial epidural air cavity in the temporal and parietal regions. Reformatted CT scan of temporal bone, through coronal and axial images, at the level of the cavum tympani and the mastoid, showed a defect in the right tegmen appeared as cloudy/ opaque lesions around the cavum and the surrounding air cells. Contrast- enhanced computed CT angiography of the cervical and cerebral vasculature showed unusual malalignment and spiral twisting along several vascular segments resulted in the mal-development of basilar artery stenosis without atherosclerosis. The current patient manifested overgrowth syndromic entity with a constellation of osseous and vascular abnormalities resulted in a clinical course of congenital central hypoventilation syndrome. Conclusion: The etiology behind the extension of pneumatization has most likely occurred because of defective ossification of the occipito-mastoid synchondrosis . The reason behind the extension of pneumatization into the occipital and parietal bone is probably due to incomplete closure of the occipito-mastoid synchondrosis, lambdoid and sagittal sutures, which usually close in early adulthood and later, even at the age of thirties. In our patient, we postulate that the history of multiple hamartomas and abnormal vascular phenotype in conjunction with extensive hyper-pneumatization of the skull were the main etiology behind her unpleasant course of her devastating ailment regardless the genetic results. Our impression is neither Mediterranean fever syndrome nor Ehlers-Danlos syndrome seem compatible with her current constellation of osseous and vascular abnormalities. The overall clinical and imaging findings are highly likely in connection with either one of the different types of overgrowth syndromes or might be a novel syndromic association. We believe that congenital central hypoventilation is a symptom complex rather than a diagnostic entity.

Multiplanar imaging in a familial case of cleidocranial dysplasia and various orthodontic-surgical protocols approved for its treatment

Introduction: Cleidocranial dysplasia (CCD) is a rare autosomal-dominant disorder that results in defective ossification. The gene responsible for pathogenesis has been mapped to the short arm of chromosome 6p21 core-binding factor alpha-1 or runt-related transcription factor-2. The condition being a complex congenital disorder with numerous skeletal and dental anomalies, its management depends considerably on the patient's ambitions, age, economic status and permanent dentition status, endodontic and periodontal health. Case Report: A 17-year-old female reported with complaint of misaligned teeth and desired orthodontic treatment. The patient had been diagnosed with CCD during childhood but, seemingly, with no previous management. Family wise patient's mother presented with features of CCD but no previous health records. A familial case report of CCD is presented with a brief explanation of various orthodontic-surgical methods carried out for its treatment Conclusion: CCD is a rare disorder, with no universally acknowledged treatment plan; hence, it is appropriate to involve a multidisciplinary team for its management.

Proteus Syndrome: Case Report with Anatomopathological Correlation

Background Proteus syndrome is characterized by a progressive segmental or patchy growth of bone, skin, adipose tissue, and central nervous system, associated with a wide range of neoplasms, pulmonary pathology, and thrombotic risk. The main histological findings are diffuse patchy overgrowth of skin and subcutaneous tissue, plantar cerebriform connective tissue nevus, and ossification defects. Case report: We present a patient that met the clinical and histological criteria necessary for the diagnosis of the disease. He required multiple surgical interventions, including amputation of the right foot. Genetic evaluation confirmed an AKT1 mutation. Discussion: CLOVES syndrome, neurofibromatosis 1 or PTEN hamartoma tumor syndrome are partially superimposable entities to Proteus syndrome and may generate diagnostic doubt. Although the clinical criteria and histologic findings are indicative, the diagnostic confirmation of this entity is genetic.

Decompressive Surgery for Craniovertebral Foramen Magnum Stenosis with Medullary Compression in Paediatric Skeletal Dysplasia Syndromes

More than 450 skeletal dysplasias have been described including Achondroplasia. Due to defective ossification of the occipital bone and upper cervical spine, neural structures may be compressed, causing increased morbidity/mortality during childhood, mainly from sleep apnoea and other respiration abnormalities, myelopathy, syringomyelia, hydrocephalus, and even sudden infant death. This highlights the importance of early and effective treatment of craniovertebral stenosis in infants with skeletal dysplasias.

The Effect of Wnt Family Member 5a Gene Silencing on the Proliferation of Achondroplasia Using a DNAzymes-CoOOH Nanocomposite.

Achondroplasia is a kind of congenital dysplasia due to the defect of endochondral ossification. Achondroplasia is considered to be a protein folding disease leading to endoplasmic reticulum stress. Endoplasmic reticulum stress may lead to disease by affecting the function and survival state of chondrocytes, but the specific mechanism requires further study. In this study, bioinformatics methods, online database mining, screening of differentially expressed genes for pathway enrichment, and interaction analysis were conducted to detect the Wnt family member 5a (Wnt5a) gene. Additionally, we designed a novel DNAzymes-based nanocomposite that can simultaneously silence Wnt5a genes in chondrocytes. The nanocomposite was composed of amino-functionalized cobalt oxyhydroxide nanoflakes modified by DNAzymes that target the Wnt5a gene. Further, we conducted in vitro experiments to verify that Wnt5a can mediate the mitogen-activated protein kinase signaling pathway through the endoplasmic reticulum stress pathway to affect the proliferation of chondrocytes.

Foramen Magnum Stenosis in Achondroplasia

Achondroplasia is the most common hereditary skeletal dysplasia and is characterized by disproportionately short stature with rhizomelic short extremities [1]. The skull features include a narrowed foramen magnum, short skull base, and clivus [2]. Foramen magnum stenosis is a characteristic funding, secondary to an abnormal placement and premature fusion of the posterior synchondroses [1]. The second factor responsible for stenosis is a defect in endochondral ossification in the basiocciput that may result in an extension of the squamous occipital bone [2]. It can cause hydrocephalus and prominent emissary and meningeal veins (Figure 1). Figure 1: Sagittal T1WI revealing a narrowed stenosis of the foramen magnum and compression of the cervicomedullary junction. The most severe complication is the compression of the cervicomedullary junction, associated with severe morbidity and sudden death in younger children [1].

Characterization of Wolf‐Hirschhorn Syndrome Candidate 1 ( Whsc1 ) in Pitx2 ‐ miR‐23/24 ‐mediated Tooth Development

Objective Wolf-Hirschhorn syndrome (WHS) is a developmental disorder attributed to a partial deletion on the short arm of chromosome 4. WHS patients suffer from oral manifestations including cleft lip and palate (CLP), hypodontia and taurodontism. However, the causative factors and underlying mechanisms of these oral anomalies are relatively unknown. Wolf-Hirschhorn syndrome candidate 1 (WHSC1) is a H3K36-specific methyltransferase that is frequently deleted in WHS. This gene has been associated with craniofacial defects including CLP and defects in occipital ossification. In our study, we aim to understand the role of WHSC1 in tooth development. Methods To characterize the role of Whsc1 in tooth development, we profiled the Whsc1 expression pattern during mouse tooth development by immunofluorescence staining (IF). To investigate the regulatory effects between Whsc1 and Pitx2, we overexpressed either Whsc1 or Pitx2 in oral epithelial cell line LS8 and detected their expression. Then, ChIP-PCR and luciferase assays were performed to confirm the binding on the promoter regions. To determine the negative regulation of Whsc1 by miR-23-3p and miR-24-3p, miRs were inhibited by our Plasmid-based microRNA inhibition system in PMIS-miR-23-27-24 embryos and LS8 cells followed by detecting the mRNA and protein level of Whsc1. Luciferase assays were also conducted to confirm the direct binding between miRs and Whsc1 3’UTR. Results Whsc1 expresses from early stage of tooth development and restricts to stem cell niches in homeostatic tooth germ. Whsc1 and Pitx2 reciprocally activate each other's expression through chromosomal and transcriptional regulation. miR-23-3p and miR-24-3p, two miRs that regulated by Pitx2, directly inhibit Whsc1. Conclusion Whsc1 expresses in the developing tooth germ and participates the Whsc1-Pitx2-miR23/24 regulatory network in oral epithelium cells. Our observations provide new insights into the potential role of Whsc1 in regulating tooth development and a possible causer of the dental defects in WHS.