Dental abnormalities associated with familial expansile osteolysis: a clinical and radiographic study

Root resorptions induced by genetic disorders: A systematic review

OBJECTIVES

Root resorption in permanent teeth is a common pathological process that often follows dental trauma or orthodontic treatment. More rarely, root resorption is a feature of genetic disorders and can help with diagnosis. Thus, the present review aims to determine which genetic disorders could induce pathological root resorptions and thus which mutated genes could be associated with them.

METHODS

We conducted a systematic review following the PRISMA guidelines. Articles describing root resorptions in patients with genetic disorders were included from PubMed, Embase, Web of Science, and Google Scholar. We synthesized the genetic disorder, the type, severity, and extent of the resorptions, as well as the other systemic and oral symptoms and histological features.

RESULTS

The synthetic analysis included 25 studies among 937 identified records. We analyzed 21 case reports, three case series, and one cohort study. Overall, we highlighted 14 different pathologies with described root resorptions. Depending on the pathology, the sites of resorption, their extent, and their severity showed differences.

CONCLUSION

With 14 genetic pathologies suspected to induce root resorptions, our findings are significant and enrich a previous classification. Among them, three metabolic disorders, three calcium-phosphorus metabolism disorders, and osteolysis disorders were identified.

Identification of Candidate Genes of Familial Multiple Idiopathic Cervical Root Resorption

INTRODUCTION

Multiple idiopathic cervical root resorption (MICRR) is a disease with an unknown etiology that causes invasive cervical root resorption in multiple teeth. Although previous MICRR genomic studies have identified candidate gene variants, the etiology of the condition remains poorly understood. In the present study, we investigated the genetic causality of MICRR to explore candidate variants.

METHODS

Saliva samples from a family containing 2 affected and two unaffected subjects with the dominant transmission of MICRR were subjected to whole-exome sequencing.

RESULTS

As a result, we identified novel candidate variants of 10 genes. Each variant was confirmed by Sanger sequencing. Among them, the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines classified doublecortin domain containing 1 (c.1099 C > T) and β-defensin 114 (c.189 T > G) as "pathogenic," and solute carrier family 45 member 2 (c.152_153del) as "likely pathogenic."

CONCLUSIONS

These results provide new insight to help clarify the pathogenesis of MICRR, and the variants could be applied for further investigation to understand invasive cervical root resorption.

Multiple Idiopathic Cervical Root Resorption: A Challenge for a Transdisciplinary Medical-Dental Team

The goal of this perspective article is to use multiple idiopathic cervical root resorption (MICRR) as a model to demonstrate the need for transdisciplinary collaborations, from basic science to treatment planning, to improve the quality of health care for all. This is not a review of the literature on the current state of MICRR. Tooth root resorption is a normal physiological process required for resorption and exfoliation of primary teeth; however, root resorption of adult teeth is largely pathological. MICRR is an aggressive form of external root resorption, which occurs near the cemento-enamel junction (CEJ). The cause of MICRR remains elusive, however, it is mediated primarily by osteoclasts/odontoclasts. Accumulating case studies and experiments in animal models have provided insights into defining the etiologies and pathophysiological mechanisms for MICRR, which include: systemic conditions and syndromes, inherited genetic variants affecting osteoclast/odontoclast activity, altered periodontal structures, drug-induced root resorption and rebound effects after cessation of anti-resorptive treatment, chemotherapy, exposure to pets or viral infections, and other factors such as inflammatory conditions or trauma. To determine the causative factors for MICRR, as well as other oral-dental conditions, at minimum, a comprehensive health history should be collected for all patients by dental care providers, discussed with other health care providers and appropriate collaborations established. The examples highlighted in this perspective emphasize the need for transdisciplinary research collaborations coupled with integrated management strategies between medicine and dentistry in order to identify cause(s) early and improve clinical outcomes.

Bone resorption: an actor of dental and periodontal development?

Dental and periodontal tissue development is a complex process involving various cell-types. A finely orchestrated network of communications between these cells is implicated. During early development, communications between cells from the oral epithelium and the underlying mesenchyme govern the dental morphogenesis with successive bud, cap and bell stages. Later, interactions between epithelial and mesenchymal cells occur during dental root elongation. Root elongation and tooth eruption require resorption of surrounding alveolar bone to occur. For years, it was postulated that signaling molecules secreted by dental and periodontal cells control bone resorbing osteoclast precursor recruitment and differentiation. Reverse signaling originating from bone cells (osteoclasts and osteoblasts) toward dental cells was not suspected. Dental defects reported in osteopetrosis were associated with mechanical stress secondary to defective bone resorption. In the last decade, consequences of bone resorption over-activation on dental and periodontal tissue formation have been analyzed with transgenic animals (RANK^Tg and Opg^−∕− mice). Results suggest the existence of signals originating from osteoclasts toward dental and periodontal cells. Meanwhile, experiments consisting in transitory inhibition of bone resorption during root elongation, achieved with bone resorption inhibitors having different mechanisms of action (bisphosphonates and RANKL blocking antibodies), have evidenced dental and periodontal defects that support the presence of signals originating bone cells toward dental cells. The aim of the present manuscript is to present the data we have collected in the last years that support the hypothesis of a role of bone resorption in dental and periodontal development.

Osteoclasts in the dental microenvironment: a delicate balance controls dental histogenesis

The impact of osteoclast activity on dental development has been previously analyzed but in the context of severe osteopetrosis. The present study sought to investigate the effects of osteoclast hypofunction,present in Msx2 gene knockin mutant mice (Msx2-/-), and hyperfunction, in transgenic mice driving RANK over-expression in osteoclast precursors (RANK(Tg)), on tooth development. In Msx2-/- mice, moderate osteopetrosis was observed, occurring exclusively in the periodontal region. Microradiographical and histological analyses revealed an abnormal dental epithelium histogenesis that gave rise to odontogenic tumor-like structures. This led to impaired tooth eruption, especially of the third mandibular molars. In RANK(Tg) mice, root histogenesis showed site-specific upregulation of dental cell proliferation and differentiation rates. This culminated in roots with a reduced diameter and pulp size albeit of normal length. These two reverse experimental systems will enable the investigation of distinctive dental cell and osteoclast communication in normal growth and tumorigenesis.

Bone resorption control of tooth eruption and root morphogenesis: Involvement of the receptor activator of NF-κB (RANK)

Activation of the receptor activator of NF-κB (RANK) is a crucial step in osteoclastogenesis. Loss- and gain-of-function mutations in the Rank gene cause, respectively, osteopetrosis and several forms of extensive osteolysis. Tooth and alveolar bone alterations are associated with these pathologies but remain to be better characterized. The aim of the present study was to establish the tooth and alveolar bone phenotype of a transgenic mouse model of RANK over-expression in osteoclast precursors. Early tooth eruption and accelerated tooth root elongation were observed subsequent to an increase in osteoclast numbers surrounding the tooth. The final root length appeared not to be affected by RANK over-expression, but a significant reduction in root diameter occurred in both control and root-morphogenesis-defective Msx2 null mutant mice. These results indicate that root length is independent of the surrounding bone resorption activity. In contrast, root diameter is sensitive to the activity of alveolar bone osteoclasts. These data suggest that early eruption and thin root are phenotypic features that could be associated with extensive osteolytic pathologies.

Benign fibro-osseous lesions of the craniofacial complex. A review

Benign fibro-osseous lesions of the craniofacial complex are represented by a variety of disease processes that are characterized by pathologic ossifications and calcifications in association with a hypercellular fibroblastic marrow element. The current classification includes neoplasms, developmental dysplastic lesions and inflammatory/reactive processes. The definitive diagnosis can rarely be rendered on the basis of histopathologic features alone; rather, procurement of a final diagnosis is usually dependent upon assessment of microscopic, clinical and imaging features together. Fibrous dysplasia and osteitis deformans constitute two dysplastic lesions in which mutations have been uncovered. Other dysplastic bone diseases of the craniofacial complex include florid osseous dysplasia, focal cemento-osseous dysplasia and periapical cemental dysplasia, all showing a predilection for African descent individuals; although no specific genetic alterations in DNA coding have yet to be uncovered and most studies have been derived from predominant high African descent populations. Ossifying fibromas are neoplastic lesions with four subtypes varying with regard to behavior and propensity for recurrence after surgical excision. The clinicopathologic and molecular features of this unique yet heterogeneous group of diseases are reviewed.

Sporadic hyperphosphatasia syndrome featuring periostitis and accelerated skeletal turnover without receptor activator of nuclear factor-kappaB, osteoprotegerin, or sequestosome-1 gene defects

CONTEXT

A middle-aged woman with recent-onset painful swollen fingers and widespread periostitis, elevated serum alkaline phosphatase (ALP) activity and erythrocyte sedimentation rate, and accelerated skeletal turnover was found not to have mutations in the gene sequences for exon 1 of receptor activator of nuclear factor-kappaB (RANK), osteoprotegerin (OPG), or sequestosome-1.

INTRODUCTION

Hyperphosphatasia refers to disorders that feature elevated serum ALP activity (hyperphosphatasemia) usually from excesses of the bone isoform of ALP. Such conditions include familial expansile osteolysis, expansile skeletal hyperphosphatasia, and a familial form of early-onset Paget's disease of bone (PDB2), all from constitutive activation of RANK, and juvenile Paget's disease from OPG deficiency.

PATIENT AND METHODS

A 38-yr-old woman developed painful swollen fingers and achy bones after an episode of unexplained pericarditis and restrictive lung disease. Sequence analysis of exon 1 of TNFRSF11A encoding RANK, TNFRSF11B encoding OPG, and SQSTM1 encoding sequestosome-1 searched for mutations responsible for familial expansile osteolysis, expansile skeletal hyperphosphatasia, or PDB2, juvenile Paget's disease, or Paget's disease of bone (PDB), respectively.

RESULTS

Serum ALP and osteocalcin and urinary hydroxyproline were increased. Radiographs showed widespread, symmetric hyperostosis in the limbs where bone scintigraphy demonstrated enhanced radionuclide uptake. Iliac crest histology revealed accelerated skeletal turnover. No mutations were detected in the three genes examined. Three years of therapy with 70 mg alendronate orally once weekly improved symptoms, radiographic abnormalities, and biochemical markers.

CONCLUSIONS

Our patient manifested a unique, sporadic hyperphosphatasia syndrome. Unexplained, transient inflammation seemed to cause her pericarditis, restrictive lung disease, and periostitis with accelerated skeletal turnover that responded well to antiinflammatory drugs and alendronate therapy.

Paget's Disease of Bone and Genetic Disorders of RANKL/OPG/RANK/NF- B Signaling

Identification of the RANKL/OPG/RANK/NF-kB (receptor activator of nuclear factor kappa-B ligand / osteoprotegerin) signaling pathway as the major regulatory system for osteoclastogenesis began with discovery of these ligands and receptors in the tumor necrosis factor (TNF) superfamily. Subsequently, genetically altered mice revealed physiologic roles for these proteins in bone biology. However, full appreciation of their significance for the human skeleton came from clinical characterization of several extremely rare, heritable disorders followed by discovery of their genetic bases. Familial expansile osteolysis (FEO) is an autosomal dominant disorder featuring constitutive activation of RANK due to an 18-bp tandem duplication in its gene (TNFRSF11A). A similar, 27-bp duplication causes what has been called a familial form of early-onset Paget's disease of bone (PDB2). Expansile skeletal hyperphosphatasia (ESH) is allelic to FEO and PDB2 and involves a 15-bp tandem duplication in TNFRSF11A. Autosomal recessive inheritance of deactivating mutations of the gene encoding OPG (TNFRSF11B) causes most cases of juvenile Paget disease. These disorders feature high bone turnover, deafness during early childhood, "idiopathic external lysis" of adult teeth, and sometimes focal lesions in appendicular bones that mimic active PDB. Biochemical markers indicate rapid skeletal remodeling. In FEO, osteolysis progresses to fat-filled bone rather than to osteosclerosis. Antiresorptive therapy with bisphosphonates can be effective for each disorder.

Hereditary Bilateral Conductive Hearing Loss Caused by Total Loss of Ossicles: a Report of Familial Expansile Osteolysis

OBJECTIVE

The objective of this study was to report on three members of a family with familial expansile osteolysis; the important point about these patients was that none of them had middle-ear ossicles.

STUDY DESIGN AND SUBJECTS

A retrospective case review including three cases with familial expansile osteolysis.

SETTING

Department of Otolaryngology in a tertiary referral center.

INTERVENTIONS

Each patient underwent computerized tomography of the temporal bone in the coronal view, audiometric and tympanometric evaluations, biochemical investigation, whole body isotope scans by Tc-99 mMDP and X-ray. Also the patients' pedigree was studied. Two of the patients had exploratory middle-ear surgery as well.

RESULTS

The temporal-bone computed-tomography scan in the coronal view of all three patients and also exploratory middle-ear surgery, which was done on two of the patients, showed no ossicles in the middle ear of either ear in all three cases. This feature hadn't been reported in previous studies. Hearing loss was revealed in the medical histories since childhood. Audiometry indicated mild to moderate conductive and mixed hearing loss and also an AD-type tympanogram pattern along with an absence of acoustic reflexes in both ears of the cases. Both serum alkaline phosphatase and hydroxyproline levels were elevated. There was an increase in uptake and activity at multiple foci of the whole skeleton. No improvement in hearing thresholds was obtained after reconstruction of the middle ear.

CONCLUSION

The total absence of middle-ear ossicles can probably be regarded as a new symptom in some patients with familial expansile osteolysis. Common ossiculoplasty for improving the hearing thresholds in this condition may be unsuccessful; therefore, both surgeons and patients must be completely aware of the contingent undesirable results.

[Familial expansive osteolysis otological and dental manifestations of genetic origin]

OBJECTIVES

Familial Expansive Osteolysis (FEO) ist a rare autosomal dominant bone dysplasia. The disease can show general and focal skeletal alterations, the latter having a predominantly peripheral distribution. Onset occurs after the second decade of life.

PATIENTS AND METHODS

We present the study, of 30 years, of a family consisting of 49 members covering five generations.

RESULTS

Among the 35 members studied, 18 have familial expansive osteolysis (FEO). The first clinical sign of the condition is transmission deafness at an early age. The features of the teeth has a unique and characteristic appearance. Thinning of the cortical bone leads to severe, painful, disabling deformities. Serum alkaline phosphatase, and urinary hydroxyproline and deoxipyridinoline are elevated. Calcium and parathyroid hormone are normal. Treatment with diphosphonates, calcitonin and vitamin D has been unsuccessful. We present the surgical technology and the results to short and long term of 13 interventions on 8 patients.

CONCLUSION

Progressive osteoclastic reabsorption accompanied by weak osteoblastic activity results in medullary expansion characterized by rarefaction of the bone marrow, which is replaced by fibrous tissue and fat. FEO is histologically similar to Paget disease, but the age of onset, the distribution of the bone lesions, the dental and middle ear alterations, and the clinical progression are different. These features also differentiate FEO from fibrous dysplasia, fibrocystic osteitis and imperfect osteogenesis. The gene responsible for FEO is located in the 18q21-22 chromosome region. Mutations in TNFRSF11A, the gene encoding receptor activator of nuclear factor-kappa-B (RANK), has been recently identified as the cause of FEO. A duplication of 18 base pairs in exon 1 of the TNFRSF11A gene suggests that this corresponds to the site of the anomaly and can be considered a "hot spot" for mutations.

Expansile skeletal hyperphosphatasia: a new familial metabolic bone disease

We describe a new familial metabolic bone disease characterized by expanding hyperostotic long bones, early onset deafness, premature tooth loss, and episodic hypercalcemia. The condition affects a mother and daughter studied at the age of 36 years and 11 years, respectively. Both individuals lost all hearing in early childhood and suffered premature shedding of teeth. Skeletal pains began just before puberty. Swelling and aching of most middle phalanges in the hands is an especially troublesome manifestation. The mother also had episodes of symptomatic hypercalcemia first documented in late childhood and subsequently during intercurrent illness and postpartum lactation. Radiographs show hyperostosis and/or osteosclerosis predominantly in the skull and appendicular skeleton. Long bones also are expanded considerably, especially the middle phalanges in the fingers. The mother's skeletal abnormalities are more severe. Biochemical parameters of bone turnover, including serum alkaline phosphatase (ALP) activity, are elevated substantially. In the proposita, dynamic histomorphometry of nondecalcified sections of iliac crest revealed rapid skeletal remodeling. In the mother, who had been treated with bisphosphonates, electron microscopy (EM) showed disorganized collagen bundles as well as necrotic and apoptotic bone cells but no osteocytic osteolysis. Measles virus gene transcripts were not detected in peripheral blood monocytes. Karyotyping was normal, 46,XX. Hyperphosphatasia with bone disease previously has been reported as either a sporadic or autosomal recessive condition. Expansile skeletal hyperphosphatasia (ESH) is probably inherited as an autosomal dominant trait with a high degree of penetrance.

A heritable component for external apical root resorption in patients treated orthodontically

External apical root resorption (EARR) is a common and occasionally critical problem in orthodontic patients. Mechanical forces compress the periodontium, leading to localized resorption of cementum that exposes dentin to destruction by clastic activity. Factors controlling occurrence and extent of EARR are poorly understood, but there may be a familial (genetic) factor in susceptibility. A sample of full siblings (103 pairs) was studied, all of whom were treated with the same technique by one orthodontist. Crown and root lengths were measured on cephalograms and panoral films before and after treatment. Six roots were scored on each patient, and decrease in root length was the dependent variable. Generalized linear models were used to quantify within and among sibship variances while controlling for sex, age, and severity of malocclusion (FMA, ANB, AOBO, overjet, NAP) as covariates. Results showed significantly greater among-than within-sibship variances, meaning there is a substantive genetic factor in susceptibility to EARR. Heritability estimates were fairly high, averaging 70% for three roots, although low for the mandibular incisor, probably because of little variation. No evidence was found for a sex or age difference in susceptibility. Quantification of a transmissible component suggests it would be useful to search for the biochemical factors controlling the familial differences in susceptibility.

Repair processes in the periodontium following dentoalveolar ankylosis: the effect of masticatory function

It has recently been shown that administration of the drug 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) perturbs the homeostasis in the periodontal ligament resulting in an osteoid-mediated ankylosis between the alveolar wall and the root surface. In the present study, the events after discontinuing HEBP administration were investigated and the effect of function on repair of the periodontal ligament was evaluated. In mice, the maxillary left molars were extracted. They then received a daily subcutaneous injection of HEBP (10 mg P/kg b.w.) for a period of 50 days, were killed 24 h, 14, 28, 56 and 112 days after the last injection and their mandibles processed for light microscopy. HEBP administration caused a significant decrease of the width of the periodontal ligament space with localized ankylosis. In the period after discontinuing HEBP treatment, the newly-formed bone did first mineralize and was then partly resorbed resulting in the disappearance of the ankylotic areas. Furthermore, root resorption was seen. Finally, the periodontal ligament regained its normal architecture and width and a new layer of cementum was formed. Functional teeth showed more root resorption than hypofunctional ones and a more rapid repair of the periodontal ligament. It is concluded that in the period after HEBP treatment the periodontal ligament regains its normal width by a repair process including extensive root resorption, that seems to accelerate this process.