Physicochemical properties of dentinogenesis imperfecta with a known DSPP mutation.

AIM: To investigate the chemical and mechanical properties of teeth affected by a 1-bp deletion (c.2688delT) in the DSPP gene. METHODS AND MATERIALS: Maxillary first premolars were extracted from the affected individual at age 9 years due to the orthodontic reason for crowding. A sample was imbedded in epoxy resin and sectioned buccolingually, after micro-computerized tomography (µCT) images were taken. Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS) and Vickers microhardness testing were also performed. RESULTS: µCT reconstruction and analysis showed an irregularly obliterated pulp chamber and an extremely small pulpal volume in the DGI-II sample. The mineral density and microhardness scores were smaller in the dentin of the DGI-II sample compared to the wild-type. Mg content was lower in the dentin of the DGI-II sample compared to the wild-type. CONCLUSION: This study shows that dentin affected by a 1-bp deletion in DSPP has a reduced mineral density, diminished microhardness and reduced Mg content.

A novel hypothesis based on clinical, radiological, and histological data to explain the dentinogenesis imperfecta type II phenotype.

Purpose/Aim: The aim of this study was to explore whether dentinogenesis imperfecta (DGI)-related aberrations are detectable in odontogenic tissues. Materials and Methods: Morphological and histological analyses were carried out on 3 teeth (two maxillary 1st molars, one maxillary central incisor) extracted from a patient with DGI Type II. A maxillary 2nd molar teeth extracted from a healthy patient was used as control. A micro-computed tomographic (µCT) data-acquisition system was used to scan and reconstruct samples. Pentachrome and picrosirius red histologic stains were used to analyze odontogenic tissues and their collagenous matrices. Results: Our findings corroborate DGI effects on molar and incisor root elongation, and the hypo-mineralized state of DGI dentin. In addition to these findings, we discovered changes to the DGI pulp cavity: Reactionary dentin formation, which we theorize is exacerbated by the early loss of enamel, nearly obliterated an acellular but still-vascularized DGI pulp cavity. We also discovered an accumulation of lamellated cellular cementum at the root apices, which we hypothesize compensates for the severe and rapid attrition of the DGI tooth. Conclusions: Based on imaging and histological data, we propose a novel hypothesis to explain the complex dental phenotypes observed in patients with DGI Type II.

Phenotypic Properties of Collagen in Dentinogenesis Imperfecta Associated with Osteogenesis Imperfecta.

INTRODUCTION: Dentinogenesis imperfecta type 1 (OIDI) is considered a relatively rare genetic disorder (1:5000 to 1:45,000) associated with osteogenesis imperfecta. OIDI impacts the formation of collagen fibrils in dentin, leading to morphological and structural changes that affect the strength and appearance of teeth. However, there is still a lack of understanding regarding the nanoscale characterization of the disease, in terms of collagen ultrastructure and mechanical properties. Therefore, this research presents a qualitative and quantitative report into the phenotype and characterization of OIDI in dentin, by using a combination of imaging, nanomechanical approaches. METHODS: For this study, 8 primary molars from OIDI patients and 8 primary control molars were collected, embedded in acrylic resin and cut into longitudinal sections. Sections were then demineralized in 37% phosphoric acid using a protocol developed in-house. Initial experiments demonstrated the effectiveness of the demineralization protocol, as the ATR-FTIR spectral fingerprints showed an increase in the amide bands together with a decrease in phosphate content. Structural and mechanical analyses were performed directly on both the mineralized and demineralized samples using a combination of scanning electron microscopy, atomic force microscopy, and Wallace indentation. RESULTS: Mesoscale imaging showed alterations in dentinal tubule morphology in OIDI patients, with a reduced number of tubules and a decreased tubule diameter compared to healthy controls. Nanoscale collagen ultrastructure presented a similar D-banding periodicity between OIDI and controls. Reduced collagen fibrils diameter was also recorded for the OIDI group. The hardness of the (mineralized) control dentin was found to be significantly higher (p<0.05) than that of the OIDI (mineralized) dentine. Both the exposed peri- and intratubular dentinal collagen presented bimodal elastic behaviors (Young's moduli). The control samples presented a stiffening of the intratubular collagen when compared to the peritubular collagen. In case of the OIDI, this stiffening in the collagen between peri- and intratubular dentinal collagen was not observed and the exposed collagen presented overall a lower elasticity than the control samples. CONCLUSION: This study presents a systematic approach to the characterization of collagen structure and properties in OIDI as diagnosed in dentin. Structural markers for OIDI at the mesoscale and nanoscale were found and correlated with an observed lack of increased elastic moduli of the collagen fibrils in the intratubular OIDI dentin. These findings offer an explanation of how structural changes in the dentin could be responsible for the failure of some adhesive restorative materials as observed in patients affected by OIDI.

Indirect adhesive rehabilitation by cementation under pressure of a case of Dentinogenesis Imperfecta type II: follow-up after 13 years.

AIM: Dentinogenesis imperfecta (DI) is an autosomal dominant genetic disease that affects both deciduous and permanent teeth, with an incidence of 1 out of 6,000 to 1 out of 8,000. Teeth affected with DI type II present bulbous crowns, short and constricted roots, marked cervical constriction, translucent enamel and amber dentin. Also, they present a partial or total obliteration of pulp space, due to continuous dentin production. SEM analysis has shown an undulated dentin-enamel junction (DEJ) with irregularities and locally wide spaces between the two structures instead of a strict junction and a regular linear surface. Treatment options for patients affected by DI-II are intended to protect and restore function and aesthetics of both posterior and anterior teeth. In literature are presented many different therapies, but mainly centered on cemented prosthetic restorations instead of adhesive restorative procedures. We present in this paper a DI-II case successfully treated in 2005 with extensive adhesive rehabilitation. CONCLUSION: The 13 years follow-up proves the reliability of adhesion to dentine and enamel for indirect adhesive restorations even on this kind of anomalous substrates.

Osteogenesis imperfecta with ectopic mineralizations in dentin and cementum and a COL1A2 mutation.

We report a Thai father (patient 1) and his daughter (patient 2) affected with osteogenesis imperfecta type IV and dentinogenesis imperfecta. Both were heterozygous for the c.1451G>A (p.Gly484Glu) mutation in COL1A2. The father, a Thai boxer, had very mild osteogenesis imperfecta with no history of low-trauma bone fractures. Scanning electron micrography of the primary teeth with DI of the patient 2, and the primary teeth with DI of another OI patient with OI showed newly recognized dental manifestations of teeth with DI. Normal dentin and cementum might have small areas of ectopic mineralizations. Teeth affected with DI have well-organized ectopic mineralizations in dentin and cementum. The "French-fries-appearance" of the crystals at the cemento-dentinal junction and abnormal cementum have never been reported to be associated with dentinogenesis imperfecta, either isolated or osteogenesis imperfecta-associated. Our study shows for the first time that abnormal collagen fibers can lead to ectopic mineralization in dentin and cementum and abnormal cementum can be a part of osteogenesis imperfecta.

Alternativa en el tratamiento de la dentinogénesis imperfecta / Alternative treatment for dentinogenesis imperfecta

La dentinogénesis imperfecta es una afección hereditaria autosómica dominante que se origina en la etapa de histodiferenciación durante la odontogénesis. Constituye una forma de displasia mesodérmica localizada, caracterizada por una alteración de las proteínas dentinarias. El propósito de esta presentación es mostrar una alternativa en el tratamiento de esta afección en niños, utilizando coronas de acero inoxidables y resinas adhesivas compuestas. Se describe la forma en que se trató una niña de 8 años de edad que acudió a consulta por presentar dolor al ingerir alimentos fríos y dulces, cambios en la coloración y forma de los dientes, así como, alteraciones psicológicas en cuanto a su apariencia personal. Se corroboró la ausencia de antecedentes de esta afección en su familia. Se realizó examen clínico y radiográfico, donde se observaron las alteraciones en cuanto a forma y coloración de los dientes y pérdida de tejido dentario sobre todo en los primeros molares permanentes, con disminución de la dimensión vertical. Radiográficamente se constató la presencia de los folículos de sucesores permanentes, así como, estructuras óseas normales. Se diagnosticó dentinogénesis imperfecta. Se procedió a la colocación de coronas de acero inoxidable en los primeros molares permanentes y en los segundos molares temporales, para restaurar la dimensión vertical y solucionar las molestias a la ingestión de alimentos. Posteriormente se restauraron los dientes anteriores con resinas adhesivas compuestas. Es de vital importancia el diagnóstico y tratamiento temprano de esta afección para evitar grandes destrucciones de tejido, se muestra que en niños se debe realizar el tratamiento instalando coronas de acero inoxidables y restaurando los dientes con resinas adhesivas compuestas hasta esperar a la adultez donde se puedan realizar otros tipos de restauraciones definitivas(AU)

Dentinogenesis imperfecta is an inherited dominant autosomal condition originating during the histodifferentiation stage of odontogenesis. It is a form of localized mesodermal dysplasia characterized by an alteration in dentin proteins. The purpose of the study was to present an alternative treatment for dentinogenesis imperfecta in children, using stainless steel crowns and adhesive composite resins. A case is presented of an eight-year-old girl attending consultation for pain when eating cold or sweet food, changes in the color and shape of teeth, and psychological disorders related to her personal appearance. No history of the disease was found in the family. Clinical and radiographic examination revealed alterations in the shape and color of teeth as well as the loss of dental tissue, particularly in the first permanent molars, with a reduction in the vertical dimension. Radiographic examination confirmed the presence of permanent successor follicles as well as normal bone structures. Dentinogenesis imperfecta was diagnosed. Stainless steel crowns were placed over the first permanent molars and the second temporary molars with the purpose of restoring the vertical dimension and eliminating the discomfort when eating. Anterior teeth were then restored with adhesive composite resins. Early diagnosis and treatment of this condition is crucial to prevent large tissue destruction. As is shown in the study, treatment in children should consist in placing stainless steel crowns and restoring the teeth with adhesive composite resins until adult age, when other definitive restorations may be performed(AU)

Microscopic study of dental hard tissues in primary teeth with Dentinogenesis Imperfecta Type II: Correlation of 3D imaging using X-ray microtomography and polarising microscopy.

OBJECTIVES: The aim of this study was to examine the histological appearance of dental hard tissues in primary teeth from children with DI using conventional polarised light microscopy and correlate that with 3D imaging using X-ray microtomograpy (XMT) to gain a further understanding of the dentine structure of teeth diagnosed with dentinogenesis imperfecta. DESIGN: Undecalcified sections of primary teeth from patients diagnosed with Dentinogenesis Imperfecta Type II were examined using polarised light microscopy. XMT was employed for 3D-imaging and analysis of the dentine. RESULTS: The polarised light microscopy and XMT revealed tubular structures in the dentine seen as vacuoles coinciding with the path of normal dentinal tubules but not continuous tubules. The size of the tubules was close to that of capillaries. The largest tubular structures had a direction corresponding to where the pulp tissue would have been located during primary dentine formation. The dysfunctional mineralisation of the dentine and obliteration of the pulp evidently leaves blood vessels in the dentine which have in the main been tied off and, in the undecalcified sections, appear as vacuoles. CONCLUSIONS: Although from radiographs, the pulp in teeth affected by Dentinogenesis Imperfect type II appears to be completely obliterated, a network of interconnected vessels may remain. The presence of large dentinal tubules and blood vessels, or the remnants of blood vessels, could provide a pathway for bacteria from the oral cavity. This might account for why some of these teeth develop periapical abscesses in spite of apparently having no pulp.

Novel PAX9 and COL1A2 missense mutations causing tooth agenesis and OI/DGI without skeletal abnormalities.

Inherited dentin defects are classified into three types of dentinogenesis imperfecta (DGI) and two types of dentin dysplasia (DD). The genetic etiology of DD-I is unknown. Defects in dentin sialophosphoprotein (DSPP) cause DD type II and DGI types II and III. DGI type I is the oral manifestation of osteogenesis imperfecta (OI), a systemic disease typically caused by defects in COL1A1 or COL1A2. Mutations in MSX1, PAX9, AXIN2, EDA and WNT10A can cause non-syndromic familial tooth agenesis. In this study a simplex pattern of clinical dentinogenesis imperfecta juxtaposed with a dominant pattern of hypodontia (mild tooth agenesis) was evaluated, and available family members were recruited. Mutational analyses of the candidate genes for DGI and hypodontia were performed and the results validated. A spontaneous novel mutation in COL1A2 (c.1171G>A; p.Gly391Ser) causing only dentin defects and a novel mutation in PAX9 (c.43T>A; p.Phe15Ile) causing hypodontia were identified and correlated with the phenotypic presentations in the family. Bone radiographs of the proband's dominant leg and foot were within normal limits. We conclude that when no DSPP mutation is identified in clinically determined isolated DGI cases, COL1A1 and COL1A2 should be considered as candidate genes. PAX9 mutation p.Phe15Ile within the N-terminal ß-hairpin structure of the PAX9 paired domain causes tooth agenesis.

Frameshift mutations in dentin phosphoprotein and dependence of dentin disease phenotype on mutation location.

We describe results from a mutational analysis of the region of the dentin sialophosphoprotein (DSPP) gene encoding dentin phosphoprotein (DPP) in 12 families with dominantly inherited dentin diseases. In eight families (five mutations in the N-terminal third of DPP), the clinical and radiologic features were uniform and compatible with dentin dysplasia type II (DD-II) with major clinical signs in the deciduous dentition. In the other families (four mutations in the more C-terminal part), the permanent teeth also were affected, and the diseases could be classified as variants of dentinogenesis imperfecta. Attrition was not prominent, but periapical infections were common. Discoloring with varying intensity was evident, and pulps and root canals were obliterated in the permanent dentition. All mutations caused a frameshift that replaced the Ser-Ser-Asx repeat by a code for a hydrophobic downstream sequence of approximately original length. We conclude that frameshift mutations in DSPP explain a significant part of dentin diseases. Furthermore, we propose that the location of the mutation is reflected in the phenotypic features as a gradient from DD-II to more severe disease that does not conform to the classic definitions of DI-II.

Dentinogenesis imperfecta associated with short stature, hearing loss and mental retardation: a new syndrome with autosomal recessive inheritance?

The follow-up history and oral findings in two brothers from consanguineous parents suggest that the association of dentinogenesis imperfecta (DI), delayed tooth eruption, mild mental retardation, proportionate short stature, sensorineural hearing loss and dysmorphic facies may represent a new syndrome with autosomal recessive inheritance. Histological examination of the dentin matrix of a permanent molar from one of the siblings reveals morphological similarities with defective dentinogenesis as presenting in patients affected with Osteogenesis Imperfecta (OI), a condition caused by deficiency of type I collagen. A number of radiographic and histological characteristics, however, are inconsistent with classical features of DI. These findings suggest that DI may imply greater genetical heterogeneity than currently assumed.

Intrafibrillar mineral may be absent in dentinogenesis imperfecta type II (DI-II).

High-resolution synchrotron radiation computed tomography (SRCT) and small-angle x-ray scattering (SAXS) were performed on normal and dentinogenesis imperfecta type II (DI-II) teeth. The SRCT showed that the mineral concentration was 33% lower on average in the DI-II dentin with respect to normal dentin. The SAXS spectra from normal dentin exhibited low-angle diffraction peaks at harmonics of 67.6 nm, consistent with nucleation and growth of the apatite phase within gaps in the collagen fibrils (intrafibrillar mineralization). In contrast, the low-angle peaks were almost non-existent in the DI-II dentin. Crystallite thickness was independent of location in both DI-II and normal dentin, although the crystallites were significantly thicker in DI-II dentin (6.8 nm [SD = 0.5] vs. 5.1 nm [SD = 0.6]). The shape factor of the crystallites, as determined by SAXS, showed a continuous progression in normal dentin from roughly one-dimensional (needle-like) near the pulp to two-dimensional (plate-like) near the dentin-enamel junction. The crystallites in DI-II dentin, on the other hand, remained needle-like throughout. The above observations are consistent with an absence of intrafibrillar mineral in DI-II dentin.

Radiological features of hereditary opalescent dentin.

A case of hereditary opalescent dentin is described, which showed the same clinical and radiological features as those reported previously. However, there was no evidence of osteogenesis imperfecta. While a diagnosis of type II dentinogenesis imperfecta was therefore made, this case also had features characteristic of type III dentinogenesis imperfecta. Treatment by means of an overdenture is described.

Dental manifestations of osteogenesis imperfecta and abnormalities of collagen I metabolism.

The in vitro protein-chemical features and the molecular background of osteogenesis imperfecta (OI), a heritable disorder of collagen I metabolism, have been elucidated in recent years. The aim of our study was to find the prevalence of dentinogenesis imperfecta (DI) and other dental anomalies in 88 patients with OI, to compare clinical with radiologic abnormalities, and to correlate these clinical/radiologic findings with the results of gel electrophoresis and molecular studies of collagen I. Twenty-eight percent of OI patients had DI. Most patients with DI had radiologic abnormalities, but some patients had radiologic signs compatible with DI, but no clinical signs of DI. OI type I patients with DI were more severely affected by OI than those without DI. In OI type III and IV, in contrast, there was no difference in overall severity between patients with and without DI. DI was not associated with any particular molecular aberration in any OI type. If defining DI from the presence of both clinical and radiologic signs, collagen I produced by cultured fibroblasts was qualitatively abnormal from all OI patients with DI. Some OI patients had dental abnormalities not resembling DI. A qualitative collagen abnormality could not be found in any of these patients. Denticles, i.e., calcifications within the pulpal cavity, were found more frequently in OI patients than in control subjects.

Presence of dentin phosphoprotein in molars of a patient with dentinogenesis imperfecta type II.

Dentin phosphoprotein (DPP) is the major noncollagenous protein component of the dentin extracellular matrix. This highly acidic phosphorylated protein is solely expressed by the ectomesenchymal-derived odontoblast cells of the tooth organ. Several biochemical studies have suggested diminished levels of, or even the absence of, this protein, which is associated with the human genetic disease dentinogenesis imperfecta (DGI) type II. However, more recent molecular studies have established that the DPP gene locus is not localized to the region of human chromosome 4 (4q13-q21), where several previous linkage analysis studies have mapped DGI types II and III. The purpose of this study was to determine the presence or absence of DPP in the dentition of a patient affected with DGI type II using a sensitive and specific immunodetection method with a polyclonal antibody against mouse DPP. Our results indicate that a 95-kDa protein, immunologically crossreactive with the DPP antibody, was detected within the dentin extracellular matrix of molars isolated from both a proband affected with DGI-II and from an age-matched normal individual. In addition, both DGI-II and normal individuals showed comparable DPP in situ degradation associated with dentin extracellular matrix maturation. These results strongly support the hypothesis that the DPP structural gene does not produce the gene product primarily responsible for the human genetic disease DGI type II.

Dentinogenesis imperfecta: a case report.

Dentinogenesis imperfecta is a localized form of mesodermal dysplasia of the dentin affecting both the primary and permanent dentitions. Most previous reports on dentinogenesis imperfecta describe treatment with overdentures, which have several disadvantages. The present report describes a case of dentinogenesis imperfecta in an 11-year-old girl. A combination of restorative, prosthetic, and surgical treatment was used to resolve the condition.

[The radiology of osteogenesis imperfecta]. / La radiologia dell'osteogenesi imperfetta.

The term "osteogenesis imperfecta" refers to a heterogeneous group of hereditary diseases characterized by osteopenia, increased bone fragility, blue sclerae and dentinogenesis imperfecta. The abnormal synthesis of type-I collagen is responsible for the pathologic changes occurring not only in bone, but also in skin, tendons and ligaments, sclerae and teeth. The clinical and radiographic features of 5 cases (2 males and 3 females; age range: 1 month to 29 years) were analyzed. The patients were unrelated with each other. The diagnosis of the different types of osteogenesis imperfecta is as difficult as the identification of the various genotypes which are responsible for the different clinical pictures. The most characteristic radiographic pattern--which is observed in any type of the disease--consists in osteopenia associated, in most cases, with multiple fractures and deformities--e.g., micromelia, large metaphysis, archon long bones. Typically, "pop corn" calcifications are observed in both epiphysis and metaphysis of long bones. Dentinogenesis imperfecta is one of the most significant clinical patterns, and it can be the only bone abnormality. The prognosis of osteogenesis imperfecta is as varied as its genetics--i.e., the fractures discovered at birth are not necessarily a negative prognostic sign.

[A microradiographic and histological study of a case of dentinogenesis imperfecta type I]. / Etude microradiographique et histologique d'un cas de dentinogenèse imparfaite de type I.

Four temporary teeth, extracted for periodontal infection reasons, from a 53-months-old child with osteogenesis imperfecta, have been coated in methyl metacrylate and prepared for microradiographic analysis and light microscopic study. The enamel and dentin of three teeth (51, 65 and 85) don't show any particularity, some how the cementum is remarkably thin. Pulp chambers was large and contain a great number of calcifications. Some of them present a radial striation around a radio-transparent center, and when coloured with blue of methylen, they revealed inflammatory or fibroblastic cells. The fourth tooth (55) shows a dentinogenetic overproduction which closed the major part of the pulp chamber. The dentin presents two rows of different aspect, separated with a calcified bond. The mantle dentin contains sinuous tubules with a type I arrangement of SIAR classification (1986). But, in the deepest dentin, they are very little size and joined together while approaching the center of the tooth and coast along cellular inclusions, pathognomonic sign of dentinogenesis imperfecta. The pulpal space not obliterated contains a calcification with radial and microlacunary aspect.

Hereditary opalescent dentine: variation in expression.

A family is described in which two females are more severely affected by hereditary opalescent dentine than the males. The genealogy of this family does not provide an accepted pattern of inheritance for this dentine anomaly. This may indicate that there is considerable variation in inheritance patterns for hereditary opalescent dentine and that this trait does not always exhibit 100 percent penetrance.

Dentinogenesis imperfecta in a six-generation family. A clinical, radiographic and histologic comparison of two branches through three generations.

Dentinogenesis imperfecta type II through 2 branches of a 6-generation family was presented focusing on individual differences in clinical, radiographic and histological appearances. These differences lead to different treatment approaches emphasizing prevention of attrition in order to avoid loss of vertical height and development of periapical lesions.