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

A Review of Dentinogenesis Imperfecta and Primary Dentin Disorders in Dogs

This review describes the clinical, radiographic and histologic characteristics of dentinogenesis imperfecta diagnosed in two unrelated young dogs without evidence of concurrent osteogenesis imperfecta. The dentition was noted to have generalized coronal discoloration ranging from grey-blue to golden brown. Clinical pulp exposure, coronal wear and fractures were observed as was radiographic evidence of endodontic disease, thin dentin walls or dystrophic obliteration of the pulp canal. The enamel was severely affected by attrition and abrasion despite histologically normal areas; loss was most likely due to poor adherence or support by the underlying abnormal dentin. Histologically, permanent and deciduous teeth examined showed thin, amorphous dentin without organized dentin tubules and odontoblasts had dysplastic cell morphology. Primary dentin disorders, including dentinogenesis imperfecta and dentin dysplasia, have been extensively studied and genetically characterized in humans but infrequently reported in dogs. Treatment in human patients is aimed at early recognition and multi-disciplinary intervention to restore and maintain normal occlusion, aesthetics, mastication and speech. Treatment in both humans and canine patients is discussed as is the documented genetic heritability of primary dentin disorders in humans.

Manifestation and Mechanisms of Abnormal Mineralization in Teeth

Tooth biomineralization is a dynamic and complicated process influenced by local and systemic factors. Abnormal mineralization in teeth occurs when factors related to physiologic mineralization are altered during tooth formation and after tooth maturation, resulting in microscopic and macroscopic manifestations. The present Review provides timely information on the mechanisms and structural alterations of different forms of pathological tooth mineralization. A comprehensive study of these alterations benefits diagnosis and biomimetic treatment of abnormal mineralization in patients.

Nanoscopic wear behavior of dentinogenesis imperfecta type II tooth dentin

OBJECTIVES

The aim of this study was to investigate the wear behavior of Dentinogenesis imperfecta type II (DGI-II) dentin and elucidate the correlation between its tribological properties and components.

METHODS

The mid-coronal dentin of normal and DGI-II teeth were divided into two groups: perpendicular and parallel to the dentin tubules. The microstructure of dentin was detected using atomic force microscopy (AFM). The wear behavior of dentin was evaluated by nanoscratch tests and scanning electron microscopy (SEM). Meanwhile, changes in molecular groups and chemical composition were analyzed by Raman and Energy-Dispersive X-ray (EDX) tests, respectively. Nanohardness was also evaluated.

RESULTS

AFM images of DGI-II dentin illustrated a decrease in the number of tubules and the tubule diameter. Nanoscratch test showed a higher friction coefficient and a greater depth-of-scratch in DGI-II dentin. The wear resistance of DGI-II dentin was reduced independent of tubule orientation. EDX results indicated that DGI-II dentin mineral content decreased and Raman spectra results showed DGI-II dentin had a decreased collagen matrix structure stability coupled with hypomineralization. Furthermore, a significant reduction in nanohardness and elastic modulus of DGI-II dentin was observed. Regression analysis revealed a close correlation between dentin components and inferior wear resistance.

CONCLUSIONS

All results indicated the wear behavior of DGI-II dentin was significantly deteriorated, presumably caused by the disorder in microstructures and the reduction of chemical composition.

Human dentin characteristics of patients with osteogenesis imperfecta: insights into collagen-based biomaterials

Osteogenesis imperfecta (OI), also known as "brittle bone disease", is a rare genetic disorder of the skeleton, whose most benign form I corresponds to autosomal dominant mutations in the genes encoding type I collagen (COLA1, COLA2). Several associated skeletal manifestations are often observed but, surprisingly, while dentin defects often reflect genetic bone disorders, about half of OI patients have no obvious oral manifestations. Here, we investigated the collagen, mineral and mechanical properties of dentin from deciduous teeth collected from patients with mild form of OI and displaying no obvious clinical signs of dentinogenesis imperfecta. For the first time, an increase in the hardness of OI dentin associated with an increase in mineral content compared to healthy patients was reported. In addition, OI altered the tissue characteristics of the dentin-enamel junction but the interfacial gradient was preserved. The impact of changes in molecular structure due to mutations in OI was assessed by Raman microspectroscopy. Our results highlighted a change in the hydroxyproline-proline ratio in direct association with collagen mineralization. Our findings suggest that the evaluation of teeth could be an important aid for mild types of OI that are often difficult to diagnose clinically and provide experimental evidence that hydroxyproline content should be considered in future studies on collagen-based biomaterials.

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 1^st molars, one maxillary central incisor) extracted from a patient with DGI Type II. A maxillary 2^nd 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.

Mandibular Carnassial Tooth Malformations in 6 Dogs-Micro-Computed Tomography and Histology Findings

Objective: To document the clinical, radiographic, and histological characteristics of mandibular first molar teeth with developmental abnormalities previously attributed to dens invaginatus and enamel pearls in dogs. Materials and Methods: Affected mandibular first molar teeth from dogs were evaluated grossly and via intraoral radiography. Endodontically and/or periodontally compromised teeth were extracted and subjected to some combination of micro-computed tomography, histopathology, and immunohistochemistry with anti-amelogenin antibody. Results: Six dogs with developmental abnormalities of mandibular first molar teeth were identified, representing 11 affected teeth. The condition was bilateral in 5 dogs, while in 1 dog, only one mandibular first molar tooth was present. Patient weight ranged from 1.7 to 6 kg (median = 4.09 kg). On intraoral radiographs, root convergence or parallelism was noted in 6 of 11 teeth, and root dilaceration was noted in 3 of 11 teeth. Eight teeth required extraction due to periapical lucencies or periodontitis. On micro-CT, the abnormal teeth were characterized by the presence of abnormal, heterogenous hard tissue with beam attenuation characteristics midway between that of enamel and dentin. Enamel fissures were identified in 4 of 8 teeth, while ectopic radicular enamel was identified in 2 of 8 teeth. The abnormal tissue was traversed by channels measuring 20-40 μm in diameter. Channels communicated with the enamel fissures in 2/8 teeth, the furcation in 2/8 teeth and the pulp in 4/8 teeth. The abnormal tissue was frequently surrounded by disorganized dentin. Histologic features of enamel and dentin were absent from the abnormal tissue and immunohistochemistry to detect amelogenin in the abnormal tissue was negative in all samples. Conclusion: The dental abnormalities described here correspond to a previously unrecognized developmental abnormality involving the mandibular first molar teeth in dogs. The developmental origin of the abnormal tissue could not be ascertained, and further investigations are required to determine the mode of formation, origin of the abnormal tissue, and factors associated with development. These developmental abnormalities more closely resemble molar-incisor malformation, rather than dens invaginatus or enamel pearls as described in humans. The authors propose that affected mandibular first molar teeth simply be referred to as having carnassial tooth malformations.

X-ray microanalysis of dentine in primary teeth diagnosed Dentinogenesis Imperfecta type II

Aim

To analyse the elemental composition of dentine in primary teeth from children diagnosed with Dentinogenesis Imperfecta type II (DI) and from normal sound primary teeth using X-ray microanalysis.

Materials and methods

X-ray microanalysis of the elements C, O, Na, Mg, P, Cl, K and Ca were performed in the dentine of five normal primary teeth and in seven primary teeth diagnosed DI. The analysis was made in a low magnification in 10 points from the enamel-dentine junction/root surface toward the pulp. The data was also evaluated with an inductive analysis.

Results

Lower values for C were found in DI-dentine compared with normal dentine. Na had significantly higher values in DI-dentine while Mg had significantly lower values. The inductive analysis revealed that Na and Mg were the most important elements for discriminating DI-dentine from normal dentine.

Conclusions

Dentine in primary teeth from patients diagnosed with Dentinogenesis Imperfecta type II analysed with XRMA have lower values of C and Mg and higher values of O and Na compared with normal primary dentine.

Electronic supplementary material

The online version of this article (10.1007/s40368-018-0392-2) contains supplementary material, which is available to authorized users.

Pulp Chamber Analysis of Primary Molars Using Micro-Computed Tomography: Preliminary Findings

Purpose: To determine the three-dimensional (3D) tooth morphology of all primary molars and to identify and consolidate positional factors that could potentially have an effect on tooth preparation. Study design: Thirty-one non-carious primary molars were scanned using micro-CT and reconstructed using 3D analysis software. Each pulp horn to its respective cusp tip distance (PHCD) was measured as well as the distances from the pulp chamber to the mesial, distal, lingual and buccal surfaces. One-way ANOVA and post-hoc t-tests were used for data analysis. Results: The mesio-buccal and disto-buccal PHCD was significantly shorter than the mesio-lingual and disto-lingual PHCDs in maxillary second primary molars (P < 0.05). Mesial, distal and lingual walls were thinner than the buccal walls of mandibular molars while in maxillary molars; the mesial and distal walls were thinner than the palatal and buccal walls (P < 0.05). Conclusions: First primary molars have thinner tooth structure surrounding the pulp than second primary molars in the same arch with the exception of the buccal walls of all molars and lingual walls of maxillary molars. The mesial and distal walls are thinner than the buccal walls of all molars and lingual walls in maxillary molars.

Structure and collagen crimp patterns of functionally distinct equine tendons, revealed by quantitative polarised light microscopy (qPLM)

Structure-function relationships in tendons are directly influenced by the arrangement of collagen fibres. However, the details of such arrangements in functionally distinct tendons remain obscure. This study demonstrates the use of quantitative polarised light microscopy (qPLM) to identify structural differences in two major tendon compartments at the mesoscale: fascicles and interfascicular matrix (IFM). It contrasts functionally distinct positional and energy storing tendons, and considers changes with age. Of particular note, the technique facilitates the analysis of crimp parameters, in which cutting direction artefact can be accounted for and eliminated, enabling the first detailed analysis of crimp parameters across functionally distinct tendons.

IFM shows lower birefringence (0.0013 ± 0.0001 [−]), as compared to fascicles (0.0044 ± 0.0005 [−]), indicating that the volume fraction of fibres must be substantially lower in the IFM. Interestingly, no evidence of distinct fibre directional dispersions between equine energy storing superficial digital flexor tendons (SDFTs) and positional common digital extensor tendons (CDETs) were noted, suggesting either more subtle structural differences between tendon types or changes focused in the non-collagenous components.

By contrast, collagen crimp characteristics are strongly tendon type specific, indicating crimp specialisation is crucial in the respective mechanical function. SDFTs showed much finer crimp (21.1 ± 5.5 µm) than positional CDETs (135.4 ± 20.1 µm). Further, tendon crimp was finer in injured tendon, as compared to its healthy equivalents. Crimp angle differed strongly between tendon types as well, with average of 6.5 ± 1.4° in SDFTs and 13.1 ± 2.0° in CDETs, highlighting a substantially tighter crimp in the SDFT, likely contributing to its effective recoil capacity.

Statement of Significance

This is the first study to quantify birefringence in fascicles and interfascicular matrix of functionally distinct energy storing and positional tendons. It adopts a novel method – quantitative polarised light microscopy (qPLM) to measure collagen crimp angle, avoiding artefacts related to the direction of histological sectioning, and provides the first direct comparison of crimp characteristics of functionally distinct tendons of various ages.

A comparison of matched picrosirius red stained and unstained tendons sections identified non-homogenous staining effects, and leads us to recommend that only unstained sections are analysed in the quantitative manner.

qPLM is successfully used to assess birefringence in soft tissue sections, offering a promising tool for investigating the structural arrangements of fibres in (soft) tissues and other composite materials.

Dentinogenesis imperfecta type II- genotype and phenotype analyses in three Danish families

BACKGROUND

Dentinogenesis imperfecta (DI) is a rare debilitating hereditary disorder affecting dentin formation and causing loss of the overlying enamel. Clinically, DI sufferers have a discolored and weakened dentition with an increased risk of fracture. The aims of this study were to assess genotype-phenotype findings in three families with DI-II with special reference to mutations in the DSPP gene and clinical, histological, and imaging manifestations.

METHODS

Nine patients participated in the study (two from family A, four from family B, and three from family C). Buccal swab samples were collected from all participants and extracted for genomic DNA. Clinical and radiographic examinations had been performed longitudinally, and the dental status was documented using photographic images. Four extracted and decalcified tooth samples were prepared for histological analysis to assess dysplastic manifestations in the dentin. Optical coherence tomography (OCT) was applied to study the health of enamel tissue from in vivo images and the effect of the mutation on the function and structure of the DSPP gene was analyzed using bioinformatics software programs.

RESULTS

The direct DNA sequence analysis revealed three distinct mutations, one of which was a novel finding. The mutations caused dominant phenotypes presumably by interference with signal peptide processing and protein secretion. The clinical and radiographic disturbances in the permanent dentition indicated interfamilial variability in DI-II manifestations, however, no significant intrafamilial variability was observed.

CONCLUSION

The different mutations in the DSPP gene were accompanied by distinct phenotypes. Enamel defects suggested deficit in preameloblast function during the early stages of amelogenesis.

Dentinogenesis imperfecta type II: A case report with 17 years of follow-up

Dentinogenesis imperfecta is a dominant autosomal hereditary disorder of dentin formation that affects the deciduous and permanent teeth. Its etiology is characterized by inadequate cell differentiation during odontogenesis. The clinical characteristics of dentinogenesis imperfecta are discolored teeth with a translucency that varies from gray to brown or amber. Radiographically, the teeth exhibit pulp obliteration, thin and short roots, bell-shaped crowns, and periapical bone rarefaction. The aim of this report was to present a case of dentinogenesis imperfecta type II that was followed up over a 17-year period. This report also presents scanning electron microscopy images of the enamel and dentin, showing that both were altered in the affected teeth. The disease characteristics and the treatments that were administered are reported in this study to guide dentists with respect to the need for early diagnosis and adequate follow-up to avoid major sequelae.

Minimally invasive orthodontics: elastodontic therapy in a growing patient affected by Dentinogenesis Imperfecta

AIM

The aim of the study was to report the use of an elastodontic therapy in a growing patient affected by Dentinogenesis Imperfecta, second class malocclusion, deep bite and lower arch crowding from the deciduous dentition to permanent one.

CASE REPORT

At first, the 5-year-old patient was treated with an elastodontic device known as "Nite-Guide". When the patient was 7 years old, during her first permanent molars and incisors eruption and after optimal house-practices, an Occlus-o-Guide Series G was placed at night and on daylight (two hours a day) performing exercises aimed to activate facial muscles and facilitate the deep bite reopening. At 9 years of age, with totally deep bite resolution, she used the Occluso-Guide only at night to hold down previous results and follow patient's dental growth. At 11 years of age, after successful teeth switching, we prescribed an Occlus-o-Guide Series N, which is functional for permanent dentition and guaranteed an eruptive guide for last dental elements.

CONCLUSIONS

This clinic case could be considered an example of approach for all those patients with systemic and/or dental diseases that do not allow adequate dental retention, which is necessary for most orthodontic appliances; elastodontic devices do not require adequate dental retention and define a minimum intervention on the surfaces of the teeth.