Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia

Isolated dentinogenesis imperfecta: Novel DSPP variants and insights on genetic counselling

OBJECTIVE

Dentinogenesis imperfecta (DI) is an inherited dentin defect and may be isolated or associated with disorders such as osteogenesis imperfecta, odontochondrodysplasia Ehler-Danlos and others. Isolated DI is caused mainly by pathogenic variants in DSPP gene and around 50 different variants have been described in this gene. Herein, we report on 19 patients from two unrelated Egyptian families with isolated DI. Additionally, we focused on genetic counselling of the two families.

MATERIALS AND METHODS

The patients were examined clinically and dentally. Panoramic X-rays were done to some patients. Whole exome sequencing (WES) and Sanger sequencing were used.

RESULTS

WES revealed two new nonsense variants in DSPP gene, c.288T > A (p.Tyr96Ter) and c.255G > A (p.Trp85Ter). Segregation analysis by Sanger sequencing confirmed the presence of the first variant in all affected members of Family 1 while the second variant was confirmed to be de novo in the patient of Family 2.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study extends the number of DSPP pathogenic variants and strengthens the fact that DSPP is the most common DI causative gene irrespective of patients' ethnicity. In addition, we provide insights on genetic counseling issues in patients with inherited DSPP variants taking into consideration the variable religion, culture and laws in our society.

Orthodontic treatment of a patient with dentinogenesis imperfecta using a clear aligner system

BACKGROUND

Orthodontic treatment for patients with dentinogenesis imperfecta (DGI) can be risky because of the fragility of their dental hard tissue. Although the Invisalign (Align Technology) clear aligner system should be a suitable orthodontic appliance for patients with DGI, to the authors' knowledge, there has been no related research.

CASE DESCRIPTION

A 28-year-old woman with DGI sought treatment with a 1 mm open bite, edge-to-edge occlusion of the central incisors, and a bilateral Class III cusp-to-cusp molar relationship. Invisalign was applied for her treatment, and after 3 and one-half years of orthodontic therapy, a normal overjet and overbite were achieved, accompanied by retraction of the lower lip as well as a bilateral Class I molar relationship. In addition, there was no iatrogenic injury to the patient's teeth.

PRACTICAL IMPLICATIONS

The Invisalign system may be a suitable orthodontic appliance for patients with DGI because clear aligners lessen the tensile stress to the teeth, decrease the number and area of bonds to the teeth, and offer protective effects through a full wrap of plastic that covers the crowns of the teeth.

Developmental and Acquired Abnormalities of the Teeth

This review aims to present a detailed analysis of the most common developmental and acquired dental abnormalities, including caries, resorptive lesions, and congenital anomalies of teeth number, size, form, and structure. This review highlights how diagnostic imaging can aid in the accurate identification and management of these conditions.

A novel approach to full-mouth rehabilitation of dentinogenesis imperfecta type II: Case series with review of literature

RATIONALE

Dentinogenesis imperfecta (DI) is an autosomal-dominant disorder. The most common clinical manifestations, including obliterated tooth tissues and severe tooth wear, usually lead to tooth extractions. It remains a great challenge for dentists to preserve the residual tooth tissue and establish the esthetics and occlusion of dentitions.

PATIENTS CONCERNS

25-year-old twin sisters, who had suffered from dentinogenesis imperfecta type II for more than 10 years, presented with continuous tooth wear and discomfort from wearing a removable partial denture for more than 3 years.

DIAGNOSIS

Intraoral examination showed extensive tooth wear with enamel exfoliation and typical amber-brown color with an opalescent discoloration. Their panoramic radiographs revealed completely obliterated tooth tissues and severe tooth wear.

INTERVENTIONS AND OUTCOMES

The dentitions were restored with post-and-core crowns and pin lays after preparing root post paths and pin holes guided by computer-aided design/computer-aided manufacturing (CAD/CAM) procedures, resulting in a successful repair.

LESSONS

Severe tooth wear and tooth tissue obliteration are typical clinical manifestations in DI-affected dentitions, increasing the complexity and difficulty in dental restorations. Early diagnosis and appropriate treatments are essential to achieve a favorable prognosis. CAD/CAM procedures, permitting accurate and effective treatment, possess promising potential in the treatment of DI-affected dentitions.

Expert consensus on digital guided therapy for endodontic diseases

Digital guided therapy (DGT) has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades. The concept of DGT for endodontic diseases is categorized into static guided endodontics (SGE), necessitating a meticulously designed template, and dynamic guided endodontics (DGE), which utilizes an optical triangulation tracking system. Based on cone-beam computed tomography (CBCT) images superimposed with or without oral scan (OS) data, a virtual template is crafted through software and subsequently translated into a 3-dimensional (3D) printing for SGE, while the system guides the drilling path with a real-time navigation in DGE. DGT was reported to resolve a series of challenging endodontic cases, including teeth with pulp obliteration, teeth with anatomical abnormalities, teeth requiring retreatment, posterior teeth needing endodontic microsurgery, and tooth autotransplantation. Case reports and basic researches all demonstrate that DGT stand as a precise, time-saving, and minimally invasive approach in contrast to conventional freehand method. This expert consensus mainly introduces the case selection, general workflow, evaluation, and impact factor of DGT, which could provide an alternative working strategy in endodontic treatment.

Atomic force microscopy-mediated mechanobiological profiling of complex human tissues

Tissue mechanobiology is an emerging field with the overarching goal of understanding the interplay between biophysical and biochemical responses affecting development, physiology, and disease. Changes in mechanical properties including stiffness and viscosity have been shown to describe how cells and tissues respond to mechanical cues and modify critical biological functions. To quantitatively characterize the mechanical properties of tissues at physiologically relevant conditions, atomic force microscopy (AFM) has emerged as a highly versatile biomechanical technology. In this review, we describe the fundamental principles of AFM, typical AFM modalities used for tissue mechanics, and commonly used elastic and viscoelastic contact mechanics models to characterize complex human tissues. Furthermore, we discuss the application of AFM-based mechanobiology to characterize the mechanical responses within complex human tissues to track their developmental, physiological/functional, and diseased states, including oral, hearing, and cancer-related tissues. Finally, we discuss the current outlook and challenges to further advance the field of tissue mechanobiology. Altogether, AFM-based tissue mechanobiology provides a mechanistic understanding of biological processes governing the unique functions of tissues.

The mechanism of biomineralization: Progress in mineralization from intracellular generation to extracellular deposition

Biomineralization is a highly regulated process that results in the deposition of minerals in a precise manner, ultimately producing skeletal and dental hard tissues. Recent studies have highlighted the crucial role played by intracellular processes in initiating biomineralization. These processes involve various organelles, such as the endoplasmic reticulum(ER), mitochondria, and lysosomes, in the formation, accumulation, maturation, and secretion of calcium phosphate (CaP) particles. Particularly, the recent in-depth study of the dynamic process of the formation of amorphous calcium phosphate(ACP) precursors among organelles has made great progress in the development of the integrity of the biomineralization chain. However, the precise mechanisms underlying these intracellular processes remain unclear, and they cannot be fully integrated with the extracellular mineralization mechanism and the physicochemical structure development of the mineralization particles. In this review, we aim to focus on the recent progress made in understanding intracellular mineralization organelles' processes and their relationship with the physicochemical structure development of CaP and extracellular deposition of CaP particles.

A Fracture From a Physical Exam: A Case Report of Osteogenesis Imperfecta and the Use of Fassier-Duval Rods

Osteogenesis Imperfecta (OI) is a rare hereditary disorder that leads to fragile bone mineralization and is most often due to a genetic defect in type I collagen, the primary collagen subtype that comprises bone. Patients with OI suffer from a significant burden of fractures and bony deformities. It has been recognized in countries throughout the world and has a variable age and severity of presentation depending on the subtype of OI. Recognition of this disorder requires a high index of suspicion on the part of the clinician, as it can easily be mistaken for non-accidental trauma in children. The current approach to care for patients with this disorder comprises surgical care with intramedullary rod fixation, cyclic bisphosphonate therapy, and rehabilitation to maximize the patient's quality of life and function. This case report demonstrates the importance of considering OI in the differential diagnosis of a child presenting with recurrent fractures so that appropriate testing and treatment interventions can be implemented. The case presented here is that of a male patient with osteogenesis imperfecta who suffered from recurrent long bone fractures, including his femurs bilaterally. His index fracture occurred after a visit to the pediatric ER for an unrelated issue, where his mother claimed that the boy demonstrated pain in his affected leg shortly after the visit. There was a delay in his diagnosis, and the patient suffered multiple fractures before undergoing the insertion of Fassier-Duval rods bilaterally into his femurs to prevent further injury.

Morphological and Ultrastructural Collagen Defects: Impact and Implications in Dentinogenesis Imperfecta

Collagen is the building block for the extracellular matrix in bone, teeth and other fibrous tissues. Osteogenesis imperfecta (OI), or brittle bone disease, is a heritable disorder that results from defective collagen synthesis or metabolism, resulting in bone fragility. The dental manifestation of OI is dentinogenesis imperfecta (DI), a genetic disorder that affects dentin structure and clinical appearance, with a characteristic feature of greyish-brown discolouration. The aim of this study was to conduct a systematic review to identify and/or define any ultrastructural changes in dentinal collagen in DI. Established databases were searched: Cochrane Library, OVID Embase, OVID Medline and PubMed/Medline. Search strategies included: Collagen Ultrastructure, DI and OI. Inclusion criteria were studies written in English, published after 1990, that examined human dental collagen of teeth affected by DI. A Cochrane data extraction form was modified and used for data collection. The final dataset included seventeen studies published from 1993 to 2021. The most prevalent findings on collagen in DI teeth were increased coarse collagen fibres and decreased fibre quantity. Additional findings included changes to fibre orientation (i.e., random to parallel) and differences to the fibre organisation (i.e., regular to irregular). Ultrastructural defects and anomalies included uncoiled collagen fibres and increased D-banding periodicity. Studies in collagen structure in DI reported changes to the surface topography, quantity, organisation and orientation of the fibres. Moreover, ultrastructural defects such as the packing/coiling and D-banding of the fibrils, as well as differences in the presence of other collagens are also noted. Taken together, this study provides an understanding of the changes in collagen and its impact on clinical translation, paving the way for innovative treatments in dental treatment.

Dental Anomalies in a Sample of Lebanese Children: a Retrospective Study

Background

Dental anomalies (DAs) represent a significant chapter in pediatric dentistry with a lot of practical relevance. Both primary and permanent dentitions may be affected.

Objective

The main objective of our study was to evaluate, using digital panoramic radiographs, the prevalence, distribution, and patterns of DAs in a sample of Lebanese children aged between 8 and 15 years old.

Methods

112 digital panoramic radiographs of patients aged between 8 and 15 years (60 males and 52 females) from the year 2017 till 2022 attending the department of Pediatric Dentistry and Dental Public Health at the Faculty of Dental Medicine at the Lebanese University were assessed for DAs of number (hypodontia, oligodontia, hyperdontia), of size (microdontia, macrodontia), of shape (fusion, gemination, dilaceration, taurodontism), of position (transposition, ectopia, impaction), and of structure (dentin dysplasia, amelogenesis imperfecta, dentinogenesis imperfecta). The data were analyzed statistically using Chi-square and Fisher's exact tests.

Results

Out of 112 patient radiographs, 84 showed at least one DA, which suggests a very high prevalence (75%). Among them, 36.9% exhibited multiple types of anomalies. These 84 patients showed a total of 274 DAs, distributed equally among males and females.

Conclusion

Dentists should be alerted to the presence of DAs. Their high prevalence requires careful clinical and radiological examinations for early detection. Regular monitoring is mandatory and could guide preventive approaches to minimize associated dental complications.

Hallermann–Streiff syndrome: Case report with abnormal pulp calcifications

Hallermann–Streiff syndrome (HSS) is a disorder of rare occurrence affecting the craniofacial complex, with approximately 200 cases reported in the literature. Nonetheless, its distinctive facial features render it highly recognizable. We present the case of a 5-year-old girl with this syndrome and review the dental manifestations and management in this patient. In addition to the diagnostic facial features of brachycephaly with frontal bossing, beak-shaped nose, microphthalmia, and mandibular retrusion, multiple dental manifestations were noted, including the absence of the mandibular condyle, ghost teeth, and unusual pulpal calcifications in both the primary and the permanent teeth, which have not been previously reported in a case of HSS. There is no consensus on the suitable treatment plan to be given for HSS patients from a young age due to an underreporting of these cases in the literature. In this report, we discuss pediatric dental management options for a patient with HSS and share her perspective of the treatment.

Morphological Study of Dental Structure in Dentinogenesis Imperfecta Type I with Scanning Electron Microscopy

Background: Dentinogenesis imperfecta type I (DGI-I) is a hereditary alteration of dentin associated with osteogenesis imperfecta (OI). Aim: To describe and study the morphological characteristics of DGI-I with scanning electron microscopy (SEM). Material and methods: Twenty-five teeth from 17 individuals diagnosed with OI and 30 control samples were studied with SEM at the level of the enamel, dentin–enamel junction (DEJ) and four levels of the dentin, studying its relationship with clinical–radiographic alterations. The variables were analysed using Fisher’s exact test, with a confidence level of 95% and asymptotic significance. Results: OI teeth showed alterations in the prismatic structure in 56%, interruption of the union in the enamel and dentin in 64% and alterations in the tubular structure in all of the cases. There is a relationship between the severity of OI and the morphological alteration of the dentin in the superficial (p = 0.019) and pulpar dentin (p 0.004) regions. Conclusions: Morphological alterations of the tooth structure are found in OI samples in the enamel, DEJ and dentin in all teeth regardless of the presence of clinical–radiographic alterations. Dentin structural anomalies and clinical dental alterations were observed more frequently in samples from subjects with a more severe phenotype of OI.

Anti-Inflammatory and Mineralization Effects of an ASP/PLGA-ASP/ACP/PLLA-PLGA Composite Membrane as a Dental Pulp Capping Agent

Dental pulp is essential for the development and long-term preservation of teeth. Dental trauma and caries often lead to pulp inflammation. Vital pulp therapy using dental pulp-capping materials is an approach to preserving the vitality of injured dental pulp. Most pulp-capping materials used in clinics have good biocompatibility to promote mineralization, but their anti-inflammatory effect is weak. Therefore, the failure rate will increase when dental pulp inflammation is severe. The present study developed an amorphous calcium phosphate/poly (L-lactic acid)-poly (lactic-co-glycolic acid) membrane compounded with aspirin (hereafter known as ASP/PLGA-ASP/ACP/PLLA-PLGA). The composite membrane, used as a pulp-capping material, effectively achieved the rapid release of high concentrations of the anti-inflammatory drug aspirin during the early stages as well as the long-term release of low concentrations of aspirin and calcium/phosphorus ions during the later stages, which could repair inflamed dental pulp and promote mineralization. Meanwhile, the composite membrane promoted the proliferation of inflamed dental pulp stem cells, downregulated the expression of inflammatory markers, upregulated the expression of mineralization-related markers, and induced the formation of stronger reparative dentin in the rat pulpitis model. These findings indicate that this material may be suitable for use as a pulp-capping material in clinical applications.

Interdisciplinary Management of a Patient with Dentinogenesis Imperfecta Type II Using a Combination of CAD-CAM and Analog Techniques: A Clinical Report

Type II dentinogenesis imperfecta is an autosomal dominant condition that affects dentin which increases the complexity of the predictability of restorative treatment. Computer-aided design and computer-aided manufacturing (CAD-CAM) technologies permit the creation of highly accurate devices and dental prostheses that simplify the planning and execution of advanced implant surgery and full-mouth rehabilitation. This clinical report presents the interdisciplinary management of a 20-year-old male with dentinogenesis imperfecta type II. In this article, a combination of analog and CAD-CAM technologies were used to fabricate devices that aided planning, assisted intermaxillary fixation and implant placement, served as interim prostheses, and permitted the accurate establishment of esthetics and occlusion of the definitive full-arch prostheses.

Micro-CT study on isolated teeth with hereditary dentin defects

OBJECTIVES

To construct the three-dimensional structure of the isolated teeth of patients with dentinogenesis imperfecta type Ⅱ (DGI-Ⅱ) and dentin dysplasia type Ⅰ (DD-Ⅰ) by using Micro-CT and explore internal structure and hard tissue mineralization density.

METHODS

The three-dimensional structures of the third molars collected from patients with DGI-Ⅱ and DD-Ⅰ and healthy individuals of the same age were reconstructed by using Micro-CT (Mimics 17.0). The internal structures of the affected teeth along the sagittal and transverse planes were observed. The grayscale values of the enamel, crown dentin, and root dentin were calculated. Then, the mineralization densities of the different parts of the teeth of the three groups were analyzed.

RESULTS

The detailed three-dimensional models of the mandibular third molars with hereditary dentin defects were successfully constructed. The models contained the models of the enamel cap, dentin core, and pulp cavity. Sagittal and transverse section scans revealed that in patients with DGI-Ⅱ, the pulp cavity was incompletely calcified and the root canal was narrow, whereas in those with DD-Ⅰ, the pulp cavity and root canal were obliterated and the root of the tooth was absent. The analysis of the grayscale values showed that compared with those in the healthy group, the grayscale values of the enamel, crown dentin, and root dentin were lower in the DGI-Ⅱ and DD-Ⅰ groups (P<0.01). No significant differences in the grayscale values of the enamel and crown dentin were found between the DGI-Ⅱ and DD-Ⅰ groups (P>0.05), whereas the grayscale value of the root dentin showed statistically significant differences between the two groups (P<0.01).

CONCLUSIONS

The application of Micro-CT provided a simple and accurate method for the three-dimensional structure reconstruction and quantitative analysis of the mineralization density of isolated teeth with hereditary dentin defects. Although the dentin mineralization density of DGI-Ⅱ and DD-Ⅰ teeth decreased, the decrement shown by DD-Ⅰ teeth was more significant than that shown by DGI-Ⅱ teeth. The pulp cavity had abnormal calcifications, and the root canal was narrow or even occluded.

The Human Genetics of Dental Anomalies

The development of tooth is a highly complex procedure and mastered by specific genetic programs. Genetic alterations, environmental factors, and developmental timing can disturb the execution of these programs, and result in various dental anomalies like hypodontia/oligodontia, and supernumerary teeth, which are commonly seen in our clinical practice. Advances in molecular research enabled the identification of various genes involved in the pathogenesis of dental anomalies. In the near future, it will help provide a more accurate diagnosis and biological-based treatment for these anomalies. In this article, we present the molecular phenomenon of tooth development and the genetics of various dental anomalies.

Compendium of causative genes and their encoded proteins for common monogenic disorders

A compendium is presented of inherited monogenic disorders that have a prevalence of >1:20,000 in the human population, along with their causative genes and encoded proteins. "Simple" monogenic diseases are those for which the clinical features are caused by mutations impacting a single gene, usually in a manner that alters the sequence of the encoded protein. Of course, for a given "monogenic disorder", there is sometimes more than one potential disease gene, mutations in any one of which is sufficient to cause phenotypes of that disorder. Disease-causing mutations for monogenic disorders are usually passed on from generation to generation in a Mendelian fashion, and originate from spontaneous (de novo) germline founder mutations. In the past monogenic disorders have often been written off as targets for drug discovery because they sometimes are assumed to be rare disorders, for which the meager projected financial payoff of drug discovery and development has discouraged investment. However, not all monogenic diseases are rare. Here, we report that that currently available data identifies 72 disorders with a prevalence of at least 1 in 20,000 humans. For each, we tabulate the gene(s) for which mutations cause the spectrum of phenotypes associated with that disorder. We also identify the gene and protein that most commonly causes each disease. 34 of these disorders are caused exclusively by mutations in only a single gene and encoded protein.

Efficacy of Photobiomodulation and Vitamin D on Odontogenic Activity of Human Dental Pulp Stem Cells

Introduction: The regeneration of dental pulp tissue using human dental pulp stem cells (HDPSCs) has attracted increasing attention in recent years. Recent studies have suggested that several factors such as photobiomodulation (PBM) and vitamin D affect the proliferation and differentiation of HDPSCs. Therefore, the present study evaluated the effects of PBM and vitamin D on odontogenic differentiation of HDPSCs for dentin -like tissue formation. Methods: HDPSCs were collected, isolated, and characterized and then divided into six groups: group I, control; group II, vitamin D (10^-7 Mol); group III, irradiation at 1 J/cm² of 810 nm diode laser; group IV, irradiation at 1 J/cm² and culture with vitamin D; group V, irradiation at 2 J/cm², and group VI, irradiation at 2 J/cm² and culture with vitamin D, cell viability assay was measured through MTT. Alkaline phosphatase (ALP) enzyme activity and mRNA levels of vascular endothelial growth factor (VEGF), bone morphogenic protein-2 (BMP-2), and dentin sialophosphoprotein (DSPP) were also assessed. Results: PBM at 1 and 2 J/cm² combined with vitamin D significantly promoted HDPSCs proliferation through MTT assay and odontogenic differentiation through gene expression of VEGF, BMP-2, and DSPP levels (P < 0.0001). Conclusion: PBM at 2 J/cm² combined with vitamin D enhanced the HDPSCs proliferation and odontogenic differentiation and thus could be a novel strategy for dentin regeneration in dentistry.

Missing and unerupted teeth in osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility and craniofacial and dental abnormalities such as congenitally missing teeth and teeth that failed to erupt which are believed to be doubled in OI patients than normal populations and were associated with low oral health quality of life. However, the etiology of these abnormalities remains unclear. To understand the factors influencing missing and unerupted teeth, we investigated their prevalence in a cohort of OI patients as a function of the clinical phenotype (OI type), the genetic variant type, the tooth type and the onset of bisphosphonate treatment.

METHOD

A total of 144 OI patients were recruited from The Shriners Hospital, Montreal, Canada, between 2016 and 2017. Patients were evaluated using intraoral photographs and panoramic radiographs. Missing teeth were evaluated in all patients, and unerupted teeth were assessed only in patients ≥15 years old (n = 82).

RESULTS

On average, each OI patient had 2.4 missing teeth and 0.8 unerupted teeth, and the most common missing and unerupted teeth were the premolars and the upper second molars, respectively. These phenomena were more prominent in OI type III and IV than in OI type I, and were not sex or age-related. Missing teeth were significantly more common in patients with C-propeptide variants than all other variants (p-value <0.05). Unerupted teeth were significantly more common in patients with α1 and α2 glycine variants or substitutions than in those with haploinsufficiency variants. Early-onset of bisphosphonate treatment would significantly increase the risk of unerupted teeth in patients with OI types III and IV (OR = 1.68, 95% CI (1.15-1.53)).

CONCLUSION

The prevalence of missing and unerupted teeth at the tooth type level in OI patients varies according to the nature of the collagen variants and the OI type. These findings highlight the role of collagen in tooth development and eruption.

Non-Syndromic Dentinogenesis Imperfecta Caused by Mild Mutations in COL1A2

Hereditary dentin defects can be categorized as a syndromic form predominantly related to osteogenesis imperfecta (OI) or isolated forms without other non-oral phenotypes. Mutations in the gene encoding dentin sialophosphoprotein (DSPP) have been identified to cause dentinogenesis imperfecta (DGI) Types II and III and dentin dysplasia (DD) Type II. While DGI Type I is an OI-related syndromic phenotype caused mostly by monoallelic mutations in the genes encoding collagen type I alpha 1 chain (COL1A1) and collagen type I alpha 2 chain (COL1A2). In this study, we recruited families with non-syndromic dentin defects and performed candidate gene sequencing for DSPP exons and exon/intron boundaries. Three unrelated Korean families were further analyzed by whole-exome sequencing due to the lack of the DSPP mutation, and heterozygous COL1A2 mutations were identified: c.3233G>A, p.(Gly1078Asp) in Family 1 and c.1171G>A, p.(Gly391Ser) in Family 2 and 3. Haplotype analysis revealed different disease alleles in Families 2 and 3, suggesting a mutational hotspot. We suggest expanding the molecular genetic etiology to include COL1A2 for isolated dentin defects in addition to DSPP.

Osteogenesis imperfecta tooth level phenotype analysis: Cross-sectional study

INTRODUCTION

Dental anomalies in Osteogenesis imperfecta (OI), such as tooth discoloration, pulp obliteration (calcified dental pulp space), and taurodontism (enlarged dental pulp space) vary between and within patients. To better understand the associations and variations in these anomalies, a cross-sectional study was designed to analyze the dental phenotype in OI patients at the individual tooth type.

METHOD

A cohort of 171 individuals with OI type I, III and IV, aged 3-55 years, were recruited and evaluated for tooth discoloration, pulp obliteration, and taurodontism at the individual tooth level, using intraoral photographs and panoramic radiographs.

RESULTS

Genetic variants were identified in 154 of the participants. Patients with Helical α1 and α2 glycine substitutions presented the highest prevalence of tooth discoloration, while those with α1 Haploinsufficiency had the lowest (<10%). C-propeptide variants did not cause discoloration but resulted in the highest pulp obliteration prevalence (~%20). The prevalence of tooth discoloration and pulp obliteration was higher in OI types III and IV and increased with age. Tooth discoloration was mainly observed in teeth known to have thinner enamel (i.e. lower anterior), while pulp obliteration was most prevalent in the first molars. A significant association was observed between pulp obliteration and tooth discoloration, and both were associated with a lack of occlusal contact. Taurodontism was only found in permanent teeth and affected mostly first molars, and its prevalence decreased with age.

CONCLUSION

The dental phenotype evaluation at the tooth level revealed that different genetic variants and associated clinical phenotypes affect each tooth type differently, and genetic variants are better predictors of the dental phenotype than the type of OI. Our results also suggest that tooth discoloration is most likely an optical phenomenon inversely proportional to enamel thickness, and highly associated with pulp obliteration. In turn, pulp obliteration is proportional to patient age, it is associated with malocclusion and likely related to immature progressive dentin deposition. Taurodontism is an isolated phenomenon that is probably associated with delayed pulpal maturation.

Radiographic Diagnosis of Systemic Diseases Manifested in Jaws

Radiographic changes of the oral and maxillofacial hard tissues can be an indication of an underlying systemic disease. In this article, the range of individual disease entities that have both systemic and dental manifestations are reviewed. Images for many conditions are provided to illustrate the radiographic changes. A summary of the most common jaw affected, radiographic and pathognomonic findings, and management aspects is listed in a table format within this article for quick reference.

Reduced mesiodistal tooth dimension in individuals with osteogenesis imperfecta: a cross-sectional study

OBJECTIVE

Osteogenesis imperfecta (OI) is a rare, hereditary disease affecting collagen type-1 in connective tissue. Collagen type-1 is a substantial component of dentine, and it is speculated, whether affected dentine could cause altered mesiodistal tooth dimension possibly affecting restorative treatment regimen. Therefore, the aim of the present study was to measure mesiodistal tooth dimensions in individuals with OI and compare them with healthy controls.

MATERIALS AND METHODS

Fifty-seven individuals aged 20-77 years with OI type 1-4 were included and 70 control patients aged 11-34 years were drawn from an orthodontic database. Mesiodistal tooth dimensions of all tooth types, except third molars, were measured in mm (two decimals) on digital 3 D-models of the tooth-bearing arches.

RESULTS

Multilevel mixed-effects linear regression analysis showed that mesiodistal tooth dimension on average was 0.17 mm (95% CI = (-0.33; -0.01)) reduced for the OI group compared to controls. The analysis revealed variation between tooth types; incisors and first premolars were most affected and molars minimally affected.

CONCLUSIONS

The mesiodistal tooth dimension in individuals diagnosed with OI is significantly smaller compared to healthy controls, which should be taken into consideration in the restorative treatment planning of individuals with OI, although the magnitude of the deviation is relatively small. The results on mesiodistal tooth dimensions of the present controls may be used as a standard for comparisons in future studies on tooth dimensions.

Dentinogenesis Imperfecta and Caries in Osteogenesis Imperfecta among Vietnamese Children

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility and low bone mass, caused mainly by mutations in collagen type I encoding genes. The current study aimed to evaluate dentinogenesis imperfecta (DI), oral manifestations and caries status of OI children. Sixty-eight children (41 males, 27 females) aged from 3 to 17 years old (mean 9 ± 4.13) participated in the study. Participants were classified into three OI type groups (I—2 cases, III—31 cases and IV—35 cases). Clinical examination and an orthopantomogram were used to obtain prevalences and associations of DI, caries status, malocclusion, crossbite, open bite, eruption, impaction and missing teeth with OI. The prevalence of DI among OI patients was 47.1%, more common in OI type III than type IV. The yellow-brown discoloration type was more vulnerable to attrition than the opalescent-grey one in the primary dentition. OI seemed not to have a high risk of caries; the prevalence of caries was 69.1%. A high incidence of malocclusion, crossbite and open bite was observed. In-depth oral information would provide valuable data for better dental management in OI patients. Parents and general doctors should pay more attention to dental care to prevent caries and premature tooth loss.

Phenotypic features of dentinogenesis imperfecta associated with osteogenesis imperfecta and COL1A2 mutations

OBJECTIVE

Dentinogenesis imperfecta (DI) requires dental treatment. This study investigated the characteristics of DI teeth associated with osteogenesis imperfecta (OI) and COL1A2 mutations.

STUDY DESIGN

Whole exome and Sanger sequencing were performed. Three primary teeth (called "OIDI teeth") obtained from 3 unrelated COL1A2 patients were investigated and compared with 9 control teeth from age-matched healthy individuals using colorimetry, micro-computed tomography, Knoop microhardness, energy dispersive X-ray spectroscopy, scanning electron microscopy, and histology.

RESULTS

All patients were identified with heterozygous glycine substitutions in COL1A2. The COL1A2 mutations, c.1531G>T and c.2027G>T, were de novo, whereas c.3106G>C was inherited. OIDI1, 2, and 3 teeth had a substantial decrease in dentin microhardness and lightness. OIDI2 enamel microhardness was significantly reduced, whereas OIDI1 and 3 had enamel microhardness comparable to that of control individuals. The OIDI1 pulp cavity was large; OIDI2 was narrow; and OIDI3 was obliterated. OIDI1 and 3 had significantly higher carbon levels than those in control individuals. Numerous ectopic calcified masses, sparse and obstructed dentinal tubules, dentin holes, and collagen disorientation were observed.

CONCLUSIONS

OIDI teeth had reduced lightness and variable pulp morphology. Weak dentin, mineral disproportion, and abnormal ultrastructure could contribute to the brittleness of OIDI teeth and adhesive restoration failure. Here, we expand the phenotypic spectrum of COL1A2 mutations and raise awareness among dentists seeing patients with OI.

Hypoxia-Responsive Oxygen Nanobubbles for Tissues-Targeted Delivery in Developing Tooth Germs

Hypoxia is a state of inadequate supply of oxygen. Increasing evidence indicates that a hypoxic environment is strongly associated with abnormal organ development. Oxygen nanobubbles (ONBs) are newly developed nanomaterials that can deliver oxygen to developing tissues, including hypoxic cells. However, the mechanisms through which nanobubbles recover hypoxic tissues, such as developing tooth germs remain to be identified. In this study, tooth germs were cultured in various conditions: CO₂ chamber, hypoxic chamber, and with 20% ONBs for 3 h. The target stages were at the cap stage (all soft tissue) and bell stage (hard tissue starts to form). Hypoxic tooth germs were recovered with 20% ONBs in the media, similar to the tooth germs incubated in a CO₂ chamber (normoxic condition). The tooth germs under hypoxic conditions underwent apoptosis both at the cap and bell stages, and ONBs rescued the damaged tooth germs in both the cap and bell stages. Using kidney transplantation for hard tissue formation in vivo, amelogenesis and dentinogenesis imperfecta in hypoxic conditions at the bell stage were rescued with ONBs. Furthermore, glucose uptake by tooth germs was highly upregulated under hypoxic conditions, and was restored with ONBs to normoxia levels. Our findings indicate that the strategies to make use of ONBs for efficient oxygen targeted delivery can restore cellular processes, such as cell proliferation and apoptosis, glucose uptake, and hypomineralization in hypoxic environments.

Primary Teeth Stains and Discoloration: A Review

The current review assesses the literature concerning the etiology of primary teeth staining and discoloration. The appearance of the dentition is of concern to many children and their caregivers seeking dental treatment as the color of the teeth is of aesthetic importance. The correct diagnosis of the cause of the discoloration is important as, invariably, it has a profound effect on treatment outcomes. It would seem reasonable, therefore, that dental practitioners understand the etiology of tooth discoloration to make a diagnosis and enable appropriate treatment to be conducted. Knowledge of the etiology of tooth staining is of importance to the dental practitioner to explain the patient the exact nature of the condition. In some instances, the mechanism of staining affects the outcome of the treatment and influences the options the dentist will be able to offer. Many of these contributing factors are preventable if parents are educated, managed by professional interventions, or provide a multidisciplinary approach. In this review, we highlight the importance of children smiles and the difference between primary and permanent teeth. We discuss the different types of primary teeth staining and discoloration and whether it is intrinsic or extrinsic, as well as the different impacts of some conditions on primary teeth compared with permanent teeth.

Mother's sense of coherence and dental characteristics in children and adolescents with osteogenesis imperfecta: A paired study

BACKGROUND

The relevance of sense of coherence (SOC) is important to the wellbeing of parents, especially mothers of children and adolescents with osteogenesis imperfecta (OI).

OBJECTIVE

Determine whether the oral health status of children/adolescents with OI is associated with mother's SOC.

MATERIALS AND METHOD

A paired cross-sectional study was conducted with 37 children/adolescents with OI, 37 without OI, and their respective mothers. The children/adolescents were between two and 19 years of age, mean age 7.2 years, being 47 male and 27 female. The mothers completed Antonovsky's SOC questionnaire (SOC-13), and the oral status of the children/adolescents was investigated. The following clinical conditions were evaluated: dentinogenesis imperfecta, malocclusion, gingivitis, and dental caries experience.

RESULTS

The genetic condition of the children was significantly associated with mother's SOC (P < .001). Mothers of children with OI had lower SOC scores (mean: 35.6 [± 4.9]) than mothers of children without OI (mean: 38.5 [± 4.3]). In the group with OI, a low socioeconomic status was associated with lower mother's SOC scores (P = .004). In both groups, dental caries experience was associated with lower mother's SOC scores (P = .007). Most individuals with OI presented malocclusion (78.3%) and experience of dental caries (59.4%).

CONCLUSION

Having a child with OI influenced the sense of coherence of the mothers. Socioeconomic status and dental caries experience in children and adolescents with OI were associated with mother's SOC.

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.

Oral health-related quality of life in X-linked hypophosphataemia and osteogenesis imperfecta

X‐linked hypophosphataemia (XLH) and osteogenesis imperfecta (OI) are rare congenital disorders characterised by skeletal dysplasia. The two disorders may include dental anomalies potentially affecting individual well‐being. The aims of study were (a) to assess the oral health‐related quality of life (OHRQoL) in Danish adults with XLH or OI, and (b) to compare the results of the groups. A cross‐sectional study including 35 adults with XLH, 56 adults with OI type I and 17 adults with OI types III‐IV was conducted. The OHRQoL was assessed by the 49‐item version of the questionnaire Oral Health Impact Profile (OHIP). Summed domain scores (seven) were compared between XLH and OI groups. Prevalence of severe impact on OHRQoL (scores 3‐4) was compared between groups. The median scores in XLH group exceeded the medians in OI (P < .05) in the domains functional limitation (XLH:6.5; OI:4.0), pain (XLH:9.5; OI:5.0), psychological discomfort (XLH:5.5; OI:2.0), psychological disability (XLH:2.0; OI:0.0), handicap (XLH:2.0; OI:0.0) and total OHIP (XLH:35.0; OI:14.0). Differences in domains physical disability (XLH: 4.0; OI: 1.0) and social disability (XLH: 0.0; OI: 0.0) were not significant. Prevalence of severe impact on OHRQoL in the XLH group significantly exceeded the level in OI group in the domains functional limitation (XLH: 59%; OI: 35%), psychological discomfort (XLH: 38%; OI: 20%) and physical disability (XLH: 32%; OI: 13%). In conclusion, adults with XLH experience a higher negative impact on their OHRQoL than adults with OI. Only to a minor degree, individuals with OI types III‐IV experience a higher impact on OHRQoL than individuals with OI type I.

Guided endodontic treatment of multiple teeth with dentin dysplasia: a case report

Background

To report the outcome of guided endodontic treatment (GET) of a case of dentin dysplasia with pulp canal calcification (PCC) and apical periodontitis based on the use of a 3D-printed template designed by merging cone-beam computed tomography (CBCT) and surface scan data.

Case presentation

A 12-year old female with radicular dentin dysplasia type I (DD-1) presented for endodontic treatment. Radiography revealed PCC in all teeth and apical radiolucency in seven teeth (12, 15, 26, 31, 32, 36 and 46). Tooth 36 had the most acute symptoms and was thus treated first by conventional access cavity preparation and root canal detection. Despite meticulous technique, the distal and mesiolingual canals were perforated. The perforations were immediately repaired with mineral trioxide aggregate, and the decision was made to switch to guided endodontic treatment for the remaining 6 teeth. CBCT and intraoral surface scans were acquired and matched using coDiagnostix planning software (Dental Wings Inc.), the respective drill positions for root canal location were determined, and templates were virtually designed and 3D-printed. The template was positioned on the respective tooth, and a customized drill was used to penetrate the calcified part of the root canal and perform minimally invasive access cavity preparation up to the apical region. All root canals were rapidly and successfully located with the templates. At 1-year follow-up, clear signs of apical healing were present in all treated teeth.

Conclusions

In patients with dentin dysplasia, conventional endodontic therapy is challenging. GET considerably facilitates the root canal treatment of teeth affected by dentin dysplasia.

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.

A Digital Esthetic Rehabilitation of a Patient with Dentinogenesis Imperfecta Type II: A Clinical Report

A 19‐year‐old female affected by dentinogenesis imperfecta type II (DI‐II), a genetic disease that affects the structural integrity of the dentin, presented with a chief complaint of discolored teeth. For this patient, digital techniques, including digital smile design (DSD), the ARCUSdigma axiograph and computer‐aided design/computer‐aided manufacturing (CAD/CAM), were extensively used in all phases of the rehabilitation process. Compared to traditional analog methods, these digital techniques could reduce the constant confirmation of occlusion, promote communication between clinicians and dental technicians, achieve accurate occlusion with relatively high efficiency, and improve the efficacy of esthetic rehabilitation in the treatment of this patient with DI‐II.

Full Mouth Rehabilitation of Two Siblings with Dentinogenesis Imperfecta Type II Using Different Treatment Modalities

Background: Dentinogenesis imperfecta (DGI) is a complex anomaly, not only by its structure but by treatment approach. The treatment protocol depends on the severity, behavior, and the age of the patient. Case Description: This paper presents two siblings’ cases of DGI type II (DGI-II) with different treatment based on the patient’s clinical severity, behavior, and age (mixed versus primary dentition). The first case involves a patient in the primary dentition with severe attrition leading to a reduction in the vertical dimension of occlusion (VDO) treated by the fabrication of complete overlay dentures. The second case involves a patient in the early mixed dentition treated with restorations and extractions. Conclusion: Full mouth rehabilitation in the two patients dramatically improves function, aesthetics, and proved to be a significant psychological boost to the patient’s well-being. Practical Implications: Early diagnosis and a multidisciplinary approach for patients with DGI to preserve the remaining teeth and rehabilitation for their function and aesthetics are essential for obtaining a favorable prognosis.

VPS4B mutation impairs the osteogenic differentiation of dental follicle cells derived from a patient with dentin dysplasia type I

A splicing mutation in VPS4B can cause dentin dysplasia type I (DD-I), a hereditary autosomal-dominant disorder characterized by rootless teeth, the etiology of which is genetically heterogeneous. In our study, dental follicle cells (DFCs) were isolated and cultured from a patient with DD-I and compared with those from an age-matched, healthy control. In a previous study, this DD-I patient was confirmed to have a loss-of-function splicing mutation in VPS4B (IVS7 + 46C > G). The results from this study showed that the isolated DFCs were vimentin-positive and CK14-negative, indicating that the isolated cells were derived from the mesenchyme. DFCs harboring the VPS4B mutation had a significantly higher proliferation rate from day 3 to day 8 than control DFCs, indicating that VPS4B is involved in cell proliferation. The cells were then replenished with osteogenic medium to investigate how the VPS4B mutation affected osteogenic differentiation. Induction of osteogenesis, detected by alizarin red and alkaline phosphatase staining in vitro, was decreased in the DFCs from the DD-I patient compared to the control DFCs. Furthermore, we also found that the VPS4B mutation in the DD-I patient downregulated the expression of osteoblast-related genes, such as ALP, BSP, OCN, RUNX2, and their encoded proteins. These outcomes confirmed that the DD-I-associated VPS4B mutation could decrease the capacity of DFCs to differentiate during the mineralization process and may also impair physiological root formation and bone remodeling. This might provide valuable insights and implications for exploring the pathological mechanisms underlying DD-I root development.

Bobby sox homolog regulates tooth root formation through modulation of dentin sialophosphoprotein

Tooth root development occurs through the interaction of multiple growth factors and transcription factors expressed in Hertwig's epithelial root sheath (HERS) and dental mesenchyme. Previously, we demonstrated that bobby sox homolog (Bbx) regulates odontoblast differentiation of human dental pulp stem cells. Here, we generated Bbx knockout (Bbx^-/- ) mice to address the functional role of Bbx in tooth formation. During tooth development, Bbx was expressed in both dental epithelium and mesenchyme. However, molar and incisor morphology in Bbx^-/- mice at postnatal Day 0 (P0) exhibited no prominent abnormalities compared with their wild-type (Bbx^+/+ ) littermates. Until P28, the crown morphology in Bbx^-/- mice was not distinctively different from Bbx^+/+ littermates. Meanwhile, the length of the mandibular base in Bbx^-/- mice was notably less at P28. Compared with Bbx^+/+ mice, the mesial and distal root lengths of the first molar were reduced by 21.33% and 16.28% at P14 and 16.28% and 16.24% at P28, respectively, in Bbx^-/- mice. The second molar of Bbx^-/- mice also showed 10.16% and 6.4% reductions at P28 in the mesial and distal lengths, compared with Bbx^+/+ mice, respectively. The gene expression analysis during early tooth root formation (P13) showed that the expression of dentin sialophosphoprotein (Dspp) was significantly decreased in Bbx^-/- mice. Collectively, our data suggest that Bbx participates in tooth root formation and might be associated with the regulation of Dspp expression.

Tooth Formation: Are the Hardest Tissues of Human Body Hard to Regenerate?

With increasing life expectancy, demands for dental tissue and whole-tooth regeneration are becoming more significant. Despite great progress in medicine, including regenerative therapies, the complex structure of dental tissues introduces several challenges to the field of regenerative dentistry. Interdisciplinary efforts from cellular biologists, material scientists, and clinical odontologists are being made to establish strategies and find the solutions for dental tissue regeneration and/or whole-tooth regeneration. In recent years, many significant discoveries were done regarding signaling pathways and factors shaping calcified tissue genesis, including those of tooth. Novel biocompatible scaffolds and polymer-based drug release systems are under development and may soon result in clinically applicable biomaterials with the potential to modulate signaling cascades involved in dental tissue genesis and regeneration. Approaches for whole-tooth regeneration utilizing adult stem cells, induced pluripotent stem cells, or tooth germ cells transplantation are emerging as promising alternatives to overcome existing in vitro tissue generation hurdles. In this interdisciplinary review, most recent advances in cellular signaling guiding dental tissue genesis, novel functionalized scaffolds and drug release material, various odontogenic cell sources, and methods for tooth regeneration are discussed thus providing a multi-faceted, up-to-date, and illustrative overview on the tooth regeneration matter, alongside hints for future directions in the challenging field of regenerative dentistry.

Pathogenic variants in the TRIP11 gene cause a skeletal dysplasia spectrum from odontochondrodysplasia to achondrogenesis 1A

The thyroid hormone receptor interactor 11 (TRIP11) gene encodes the Golgi microtubule-associated protein 210 (GMAP-210), a protein essential for the operation of the Golgi apparatus. It is known that null mutations in TRIP11 disrupt Golgi function and cause a lethal skeletal dysplasia known as achondrogenesis type 1A (ACG1A), however recently, hypomorphic mutations in that gene have been linked to odontochondrodysplasia (ODCD), a nonlethal skeletal dysplasia characterized by skeletal changes in the spine and in the metaphyseal regions, associated with dentinogenesis imperfecta. Here we present two patients reflecting the phenotypic spectrum related to different TRIP11 variants. The first is a female child with ODCD, for whom a homozygous in-frame splicing mutation in intron 9 of TRIP11 was identified. The mutation appears to lead to the expression of an alternative TRIP11 transcript, that may explain the less severe radiological alterations in ODCD. The second is a fetus with classical form of ACG1A, associated with typical molecular findings (frameshift) in exon 11 of TRIP11, both novel mutations. The two patients reported here represent the TRIP11 spectrum of skeletal dysplasia ranging from mild to lethal phenotypes, thereby enabling one to suggest a genotype-phenotype correlation in these diseases.

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.

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.

A histological continuum between dentinogenesis imperfecta and dentin dysplasia: A case report with literature review

Dentinogenesis Imperfecta and dentin dysplasia are genetic oral diseases inherited in a simple autosomal dominant mode, with high penetrance and a low mutation rate. Both of them are present with bulbous crowns, marked cervical constrictions, severe attritions, few periapical radiolucencies, and premature tooth loss. The diagnosis is based on family history, and detailed clinical examination, while genetic diagnosis may become useful in the future once sufficient disease-causing mutations have been discovered. Here, we present a case with overlapping features of both dentinogenesis imperfecta and dentin dysplasia asserting both the anomalies to be part of the same continuum of the genetic event.

Dentin dysplasia Type I: A rare case report

Dentin dysplasia (DD) is an uncommon developmental disturbance affecting dentin, resulting in enamel with atypical dentin formation and abnormal pulpal morphology. Type I (radicular) and Type II (coronal) are the two types of DD. Type I is more common, and both types include single or multiple teeth in primary and permanent dentition. Combinations of both types have also been described in literature. Four distinct forms of Type I and one form of Type II were identified. This case report documents one such rarity of DD in an 11-year-old female with clinical and radiographical findings and management aspects.

Dentinogenesis imperfecta in Osteogenesis imperfecta type XI in South Africa: a genotype-phenotype correlation

Background

The maxillofacial and dental manifestations of Osteogenesis imperfecta (OI) have significant implications in terms of management. Although the occurrence of abnormal dentine in some forms of OI is well documented, there is scant information on the association of abnormal dentine in the Black African persons with phenotypic OI III and genotypic OI XI in South Africa.

Methods

This was a cross-sectional analytic study. A series of 64 Black South African individuals with a confirmed phenotypic diagnosis of OI III, ages ranging from 3 months to 29 years, were assessed clinically, radiographically, and at a molecular level.

Results

A total number of 64 saliva samples were analyzed and 3 DNA variations were identified in exon 5 of the FKBP10 gene. The homozygous mutation, c.[831dupC]; [831dupC], was identified in 23 affected persons who had no clinically obvious features of DI in their primary and secondary teeth. Radiologically, mild features of DI were evident in 10 persons in whom radiographic images were obtained and were given a Clinical–radiological score of 2. A compound heterozygous mutation, c. [831delC]; [831dupC], was identified in three siblings. An intraoral examination of these affected persons revealed no clinically apparent features of DI in their primary and secondary teeth. Due to the lack of radiological facilities, the presence or absence of DI could not be confirmed or negated. A second compound heterozygous mutation, c.[831dupC]; [1400-4C>G], was identified in a female of 29 years belonging to the Xhosa linguistic group. Her teeth appeared clinically normal but it was not possible to obtain radiographs. In 37 affected individuals, no disease-causing mutations were identified.

Conclusion

Black African individuals in SA with the homozygous mutation in the FKBP10 gene have clinically unaffected teeth yet exhibited radiographic features of DI to varying degrees. This characterization is suggestive of a relationship between the genetic abnormality and the clinical manifestations of DI. The authors suggest that this diagnosis must include teeth that are clinically and/or radiologically aberrant, and should not exclude the presence of other, milder, dentinal aberrations associated with OI. There was no correlation between severity of OI and DI in this cohort of individuals.

Regional Odontodysplasia Affecting the Maxilla

Regional odontodysplasia (RO) is a rare dental anomaly of unknown etiology that can affect both deciduous and permanent dentition. RO is characterized by severe hypoplasia of enamel and dentin, and teeth affected are friable and more susceptible to caries and fractures. Most of the lesions occur in the anterior maxilla and correlation with clinical and radiographic features is essential to provide a correct diagnosis. The major criteria for diagnosis are predominantly based on radiography, which shows presence of large pulp chambers and a marked reduction in the radiopacity of enamel and dentin, making the distinction between these mineralized structures difficult. Early diagnosis is important to minimize future sequels and allow preventive or conservative treatment. The therapeutic approach of the RO should be based on the degree of severity of the anomaly and in the individual functional and aesthetic needs of each case. A classic case of RO affecting the maxilla is exemplified in this Sine Qua Non Radiology-Pathology article.

Wnt Production in Dental Epithelium Is Crucial for Tooth Differentiation

The Wnt ligands display varied spatiotemporal expression in the epithelium and mesenchyme in the developing tooth. Thus far, the actions of these differentially expressed Wnt ligands on tooth development are not clear. Shh expression specifies the odontogenic epithelium during initiation and is consistently restricted to the dental epithelium during tooth development. In this study, we inactivate Wntless ( Wls), the key regulator for Wnt trafficking, by Shh-Cre to investigate how the Wnt ligands produced in the dental epithelium lineage act on tooth development. We find that conditional knockout of Wls by Shh-Cre leads to defective ameloblast and odontoblast differentiation. Wls^Shh-Cre teeth display reduced canonical Wnt signaling activity in the inner enamel epithelium and the underlying mesenchyme at the early bell stage, as exhibited by target gene expression and BAT-gal staining. The expression of Wnt5a and Wnt10b is not changed in Wls^Shh-Cre teeth. By contrast, Wnt10a expression is significantly increased in response to epithelial Wls deficiency. In addition, the expression of Hedgehog signaling pathway components Shh, Gli1, and Patched1 was greatly decreased in Wls^Shh-Cre teeth. Epithelial Wls loss of function in Shh lineage also leads to aberrant cell proliferation in dental epithelium and mesenchyme at embryonic day 16.5; however, the cell apoptosis is unaffected. Moreover, we find that Decorin and Col1a1, the key markers for odontoblast differentiation that are downregulated in Wls^Shh-Cre teeth, act as direct downstream targets of the canonical Wnt signaling pathway by chromatin immunoprecipitation analysis. Additionally, Decorin and Col1a1 expression can be increased by lithium chloride (LiCl) treatment in the in vitro tooth explants. Taken together, our results suggest that the spatial expression of Wnt ligands within the dental epithelial lineage regulates the differentiation of tooth structures in later stages.