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.

The Reparative Function of MMP13 in Tertiary Reactionary Dentinogenesis after Tooth Injury.

MMP13 gene expression increases up to 2000-fold in mineralizing dental pulp cells (DPCs), with research previously demonstrating that global MMP13 deletion resulted in critical alterations in the dentine phenotype, affecting dentine-tubule regularity, the odontoblast palisade, and significantly reducing the dentine volume. Global MMP13-KO and wild-type mice of a range of ages had their molar teeth injured to stimulate reactionary tertiary dentinogenesis. The response was measured qualitatively and quantitatively using histology, immunohistochemistry, micro-CT, and qRT-PCR in order to assess changes in the nature and volume of dentine deposited as well as mechanistic links. MMP13 loss affected the reactionary tertiary dentine quality and volume after cuspal injury and reduced Nestin expression in a non-exposure injury model, as well as mechanistic links between MMP13 and the Wnt-responsive gene Axin2. Acute pulpal injury and pulp exposure to oral fluids in mice teeth showed upregulation of the MMP13 in vivo, with an increase in the gene expression of Mmp8, Mmp9, and Mmp13 evident. These results indicate that MMP13 is involved in tertiary reactionary dentine formation after tooth injury in vivo, potentially acting as a key molecule in the dental pulp during dentine-pulp repair processes.

Dynamic Alterations in Acetylation and Modulation of Histone Deacetylase Expression Evident in the Dentine-Pulp Complex during Dentinogenesis.

Epigenetic modulation, including histone modification, alters gene expression and controls cell fate. Histone deacetylases (HDACs) are identified as important regulators of dental pulp cell (DPC) mineralisation processes. Currently, there is a paucity of information regarding the nature of histone modification and HDAC expression in the dentine-pulp complex during dentinogenesis. The aim of this study was to investigate post-translational histone modulation and HDAC expression during DPC mineralisation and the expression of Class I/II HDACs during tooth development and in adult teeth. HDAC expression (isoforms -1 to -6) was analysed in mineralising primary rat DPCs using qRT-PCR and Western blot with mass spectrometry being used to analyse post-translational histone modifications. Maxillary molar teeth from postnatal and adult rats were analysed using immunohistochemical (IHC) staining for HDACs (1-6). HDAC-1, -2, and -4 protein expression increased until days 7 and 11, but decreased at days 14 and 21, while other HDAC expression increased continuously for 21 days. The Class II mineralisation-associated HDAC-4 was strongly expressed in postnatal sample odontoblasts and DPCs, but weakly in adult teeth, while other Class II HDACs (-5, -6) were relatively strongly expressed in postnatal DPCs and adult odontoblasts. Among Class I HDACs, HDAC-1 showed high expression in postnatal teeth, notably in ameloblasts and odontoblasts. HDAC-2 and -3 had extremely low expression in the rat dentine-pulp complex. Significant increases in acetylation were noted during DPC mineralisation processes, while trimethylation H3K9 and H3K27 marks decreased, and the HDAC-inhibitor suberoylanilide hydroxamic acid (SAHA) enhanced H3K27me3. These results highlight a dynamic alteration in histone acetylation during mineralisation and indicate the relevance of Class II HDAC expression in tooth development and regenerative processes.

Dentinogenesis imperfecta: case report with nanoceramic resin crowns restorative treatment.

Children with dentinogenesis imperfecta require restorative or prosthodontic treatment to minimize the aesthetic and functional impact of the condition. This clinical case report describes the oral rehabilitation procedure in a 12-year-old patient with dentinogenesis imperfecta type II using nanoceramic resin crowns fabricated with Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) technology and the patient's progression over eight years. This minimal intervention approach enabled functional and aesthetic reestablishment along with tooth wear prevention. The result simplified an extensive prosthetic procedure and facilitated an affordable rehabilitation for the young patient while providing excellent long-term outcomes.

LPS-induced inflammation potentiates dental pulp stem cell odontogenic differentiation through C5aR and p38.

AIM: Inflammation is a complex host response to harmful infection or injury, and it seems to play a crucial role in tissue regeneration both positively and negatively. We have previously demonstrated that the activation of the complement C5a pathway affects dentin-pulp regeneration. However, limited information is available to understand the role of the complement C5a system related to inflammation-mediated dentinogenesis. The aim of this study was to determine the role of complement C5a receptor (C5aR) in regulating lipopolysaccharide (LPS)-induced odontogenic differentiation of dental pulp stem cells (DPSCs). MATERIAL AND METHODS: Human DPSCs were subjected to LPS-stimulated odontogenic differentiation in dentinogenic media treated with the C5aR agonist and antagonist. A putative downstream pathway of the C5aR was examined using a p38 mitogen-activated protein kinase (p38) inhibitor (SB203580). RESULTS: Our data demonstrated that inflammation induced by the LPS treatment potentiated DPSC odontogenic differentiation and that this is C5aR dependent. C5aR signaling controlled the LPS-stimulated dentinogenesis by regulating the expression of odontogenic lineage markers like dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1). Moreover, the LPS treatment increased the total p38, and the active form of p38 expression, and treatment with SB203580 abolished the LPS-induced DSPP and DMP-1 increase. CONCLUSIONS: These data suggest a significant role of C5aR and its putative downstream molecule p38 in the LPS-induced odontogenic DPSCs differentiation. This study highlights the regulatory pathway of complement C5aR/p38 and a possible therapeutic approach for improving the efficiency of dentin regeneration during inflammation.

Role of alpha smooth muscle actin in odontogenic differentiation of dental pulp stem cells.

Pulpotomy is an effective treatment for retaining vital pulp after pulp exposure caused by caries removal and/or trauma. The expression of alpha smooth muscle actin (α-SMA) is increased during the wound-healing process, and α-SMA-positive fibroblasts accelerate tissue repair. However, it remains largely unknown whether α-SMA-positive fibroblasts influence pulpal repair. In this study, we established an experimental rat pulpotomy model and found that the expression of α-SMA was increased in dental pulp after pulpotomy relative to that in normal dental pulp. In vitro results showed that the expression of α-SMA was increased during the induction of odontogenic differentiation in dental pulp stem cells (DPSCs) compared with untreated DPSCs. Moreover, α-SMA overexpression promoted the odontogenic differentiation of DPSCs via increasing mitochondrial function. Mechanistically, α-SMA overexpression activated the mammalian target of rapamycin (mTOR) signaling pathway. Inhibition of the mTOR signaling pathway by rapamycin decreased the mitochondrial function in α-SMA-overexpressing DPSCs and suppressed the odontogenic differentiation of DPSCs. Furthermore, we found that α-SMA overexpression increased the secretion of transforming growth factor beta-1 (TGF-ß1). In sum, our present study demonstrates a novel mechanism by which α-SMA promotes odontogenic differentiation of DPSCs by increasing mitochondrial respiratory activity via the mTOR signaling pathway.

Tubular dentin formation by TGF-ß/BMP signaling in dental epithelial cells.

OBJECTIVES: This study aimed to identify formation of tubular dentin induced by transforming growth factor-ß (TGF-ß) and bone morphogenic protein (BMP) signaling pathway in dental epithelial cells. METHODS: We collected conditioned medium (CM) of rTGF-ß1/rBMP-2-treated HAT-7 and treated to MDPC-23 cells. The expression levels of odontoblast differentiation markers, KLF4, DMP1, and DSP were evaluated by real-time PCR and Western blot analysis. To evaluate whether CM of rTGF-ß1/rBMP-2 induces tubular dentin formation, we made a beagle dog tooth defect model. RESULTS: Here, we show that Cpne7 is regulated by Smad4-dependent TGF-ß1/BMP2 signaling pathway in dental epithelial cells. CM of rTGF-ß1/rBMP-2 treated HAT-7 or rCPNE7 raises the expression levels of KLF4, DMP1, and DSP in MDPC-23 cells. When rTGF-ß1 or rBMP-2 is directly treated to MDPC-23 cells, however, expression levels of Cpne7-regulated genes remain unchanged. In a beagle dog defect model, application of rTGF-ß1/BMP2-treated CM resulted in tubular tertiary dentin mixed with osteodentin at cavity-prepared sites, while rTGF-ß1 group exhibited homogenous osteodentin. CONCLUSIONS: Taken together, Smad4-dependent TGF-ß1/BMP2 signaling regulates Cpne7 in dental epithelial cells, and CPNE7 protein secreted from pre-ameloblasts mediates odontoblast differentiation via epithelial-mesenchymal interaction.

Hereditary dentin defects with systemic diseases.

OBJECTIVE: This review aimed to summarize recent progress on syndromic dentin defects, promoting a better understanding of systemic diseases with dentin malformations, the molecules involved, and related mechanisms. SUBJECTS AND METHODS: References on genetic diseases with dentin malformations were obtained from various sources, including PubMed, OMIM, NCBI, and other websites. The clinical phenotypes and genetic backgrounds of these diseases were then summarized, analyzed, and compared. RESULTS: Over 10 systemic diseases, including osteogenesis imperfecta, hypophosphatemic rickets, vitamin D-dependent rickets, familial tumoral calcinosis, Ehlers-Danlos syndrome, Schimke immuno-osseous dysplasia, hypophosphatasia, Elsahy-Waters syndrome, Singleton-Merten syndrome, odontochondrodysplasia, and microcephalic osteodysplastic primordial dwarfism type II were examined. Most of these are bone disorders, and their pathogenic genes may regulate both dentin and bone development, involving extracellular matrix, cell differentiation, and metabolism of calcium, phosphorus, and vitamin D. The phenotypes of these syndromic dentin defects various with the involved genes, part of them are similar to dentinogenesis imperfecta or dentin dysplasia, while others only present one or two types of dentin abnormalities such as discoloration, irregular enlarged or obliterated pulp and canal, or root malformation. CONCLUSION: Some specific dentin defects associated with systemic diseases may serve as important phenotypes for dentists to diagnose. Furthermore, mechanistic studies on syndromic dentin defects may provide valuable insights into isolated dentin defects and general dentin development or mineralization.

METTL3 enhances dentinogenesis differentiation of dental pulp stem cells via increasing GDF6 and STC1 mRNA stability.

BACKGROUND: The dentinogenesis differentiation of dental pulp stem cells (DPSCs) is controlled by the spatio-temporal expression of differentiation related genes. RNA N6-methyladenosine (m6A) methylation, one of the most abundant internal epigenetic modification in mRNA, influences various events in RNA processing, stem cell pluripotency and differentiation. Methyltransferase like 3 (METTL3), one of the essential regulators, involves in the process of dentin formation and root development, while mechanism of METTL3-mediated RNA m6A methylation in DPSC dentinogenesis differentiation is still unclear. METHODS: Immunofluorescence staining and MeRIP-seq were performed to establish m6A modification profile in dentinogenesis differentiation. Lentivirus were used to knockdown or overexpression of METTL3. The dentinogenesis differentiation was analyzed by alkaline phosphatase, alizarin red staining and real time RT-PCR. RNA stability assay was determined by actinomycin D. A direct pulp capping model was established with rat molars to reveal the role of METTL3 in tertiary dentin formation. RESULTS: Dynamic characteristics of RNA m6A methylation in dentinogenesis differentiation were demonstrated by MeRIP-seq. Methyltransferases (METTL3 and METTL14) and demethylases (FTO and ALKBH5) were gradually up-regulated during dentinogenesis process. Methyltransferase METTL3 was selected for further study. Knockdown of METTL3 impaired the DPSCs dentinogenesis differentiation, and overexpression of METTL3 promoted the differentiation. METTL3-mediated m6A regulated the mRNA stabiliy of GDF6 and STC1. Furthermore, overexpression of METTL3 promoted tertiary dentin formation in direct pulp capping model. CONCLUSION: The modification of m6A showed dynamic characteristics during DPSCs dentinogenesis differentiation. METTL3-mediated m6A regulated in dentinogenesis differentiation through affecting the mRNA stability of GDF6 and STC1. METTL3 overexpression promoted tertiary dentin formation in vitro, suggesting its promising application in vital pulp therapy (VPT).

Expression and localization of CD63 in the intracellular vesicles of odontoblasts.

We hypothesized that odontoblasts release exosomes as well as dental pulp cells and focused on the exosome membrane marker CD63. Odontoblasts are well-differentiated mesenchymal cells that produce dentin. Dental pulp, a tissue complex formed with odontoblasts, releases exosomes to epithelial cells and stimulates their differentiation to ameloblasts. However, the localization of CD63 in differentiated odontoblasts is poorly understood. Therefore, herein, we aimed to reveal the expression of CD63 in odontoblasts during tooth development. We first investigated the localization of CD63 in mouse incisors and molars using immunofluorescence. In adult mouse incisors, the anti-CD63 antibody was positive in mature odontoblasts and dental pulp cells but not in pre-odontoblasts along the ameloblasts in the apical bud. Additionally, the anti-CD63 antibody was observed as a vesicular shape in the apical area of odontoblast cytosol and inside Tomes' fibers. The anti-CD63 antibody-positive vesicles were also observed using immunoelectron microscopy. Moreover, during mouse mandibular molar tooth morphogenesis (E16 to postnatal 6 weeks), labeling of anti-CD63 antibody was positive in the odontoblasts at E18. In contrast, the anti-CD63 antibody was positive in the dental pulp after postnatal day 10. Furthermore, anti-CD63 antibody was merged with the multivesicular body marker Rab7 in dental pulp tissues but not with the lysosome marker Lamp1. Finally, we determined the effect of a ceramide-generation inhibitor GW4869 on the mouse organ culture of tooth germ in vitro. After 28 days of GW4869 treatment, both CD63 and Rab7 were negative in Tomes' fibers, but were positive in control odontoblasts. These results suggest that CD63-positive vesicular organelles are important for mouse tooth morphogenesis.

Sclerostin is a promising therapeutic target for oral inflammation and regenerative dentistry.

Sclerostin is the protein product of the SOST gene and is known for its inhibitory effects on bone formation. The monoclonal antibody against sclerostin has been approved as a novel treatment method for osteoporosis. Oral health is one of the essential aspects of general human health. Hereditary bone dysplasia syndrome caused by sclerostin deficiency is often accompanied by some dental malformations, inspiring the therapeutic exploration of sclerostin in the oral and dental fields. Recent studies have found that sclerostin is expressed in several functional cell types in oral tissues, and the expression level of sclerostin is altered in pathological conditions. Sclerostin not only exerts similar negative outcomes on the formation of alveolar bone and bone-like tissues, including dentin and cementum, but also participates in the development of oral inflammatory diseases such as periodontitis, pulpitis, and peri-implantitis. This review aims to highlight related research progress of sclerostin in oral cavity, propose necessary further research in this field, and discuss its potential as a therapeutic target for dental indications and regenerative dentistry.

mTORC1 promotes mineralization via p53 pathway.

The objectives of our study were to investigate the roles of mTORC1 in odontoblast proliferation and mineralization and to determine the mechanism by which mTORC1 regulates odontoblast mineralization. In vitro, MDPC23 cells were treated with rapamycin (10 nmol/L) and transfected with a lentivirus for short hairpin (shRNA)-mediated silencing of the tuberous sclerosis complex (shTSC1) to inhibit and activate mTORC1, respectively. CCK8 assays, flow cytometry, Alizarin red S staining, ALP staining, qRT-PCR, and western blot analysis were performed. TSC1-conditional knockout (DMP1-Cre+ ; TSC1f/f , hereafter CKO) mice and littermate control (DMP1-Cre- ; TSC1f/f , hereafter WT) mice were generated. H&E staining, immunofluorescence, and micro-CT analysis were performed. Transcriptome sequencing analysis was used to screen the mechanism of this process. mTORC1 inactivation decreased the cell proliferation. The qRT-PCR and western blot results showed that mineralization-related genes and proteins were downregulated in mTORC1-inactivated cells. Moreover, mTORC1 overactivation promoted cell proliferation and mineralization-related gene and protein expression. In vivo, the micro-CT results showed that DV/TV and dentin thickness were higher in CKO mice than in controls and H&E staining showed the same results. Mineralization-related proteins expression was upregulated. Transcriptome sequencing analysis revealed that p53 pathway-associated genes were differentially expressed in TSC1-deficient cells. By inhibiting p53 alone or both mTORC1 and p53 with rapamycin and a p53 inhibitor, we elucidated that p53 acts downstream of mTORC1 and that mTORC1 thereby promotes odontoblast mineralization. Taken together, our findings demonstrate that the role of mTORC1 in odontoblast proliferation and mineralization, and confirm that mTORC1 upregulates odontoblast mineralization via the p53 pathway.

Substrate stiffness promotes dentinogenesis via LAMB1-FAK-MEK1/2 signaling axis.

OBJECTIVES: In vivo, the principal function of mechanosensitive odontoblasts is to synthesize and secrete the matrix which then calcifies and forms reactive dentin after exposure to appropriate stimuli. This study aims to develop the influence of mechanical factors on dentinogenesis based on odontoblasts, which contribute to reparative dentin formation. METHODS: We fabricated polydimethylsiloxane with different stiffnesses and seeded 17IIA11 odontoblast-like cells on the substrates in different stiffnesses. Cell morphology was detected by scanning electron microscope, and the mineralization phenotype was detected by alkaline phosphatase staining and alizarin red staining, while expression levels of dentinogenesis-related genes (including Runx2, Osx, and Alp) were assayed by qPCR. To explore mechanism, protein distribution and expression levels were detected by immunofluorescent staining, Western blotting, and immunoprecipitation. RESULTS: In our results, during dentinogenesis, 17IIA11 odontoblast-like cells appeared better extension on stiffer substrates. The binding between LAMB1 and FAK contributed to converting mechanical stimuli into biochemical signaling, thereby controlling mitogen-activated protein kinase kinase 1/2 activity in stiffness-driven dentinogenesis. CONCLUSION: The present study suggests odontoblast behaviors can be directly regulated by mechanical factors at cell-material interfaces, which offers fundamental mechanism in remodeling cell microenvironment, thereby contributing to physiological phenomena explanation and tissue engineering progress.

Dentin Particulate for Bone Regeneration: An In Vitro Study.

The aim of this in vitro study was to investigate the commitment and behavior of dental pulp stem cells (DPSCs) seeded onto two different grafting materials, human dentin particulate (DP) and deproteinized bovine bone matrix (BG), with those cultured in the absence of supplements. Gene expression analyses along with epigenetic and morphological tests were carried out to examine odontogenic and osteogenic differentiation and cell proliferation. Compressive testing of the grafting materials seeded with DPSCs was performed as well. DPSC differentiation into odontoblast-like cells was identified from the upregulation of odontogenic markers (DSPP and MSX) and osteogenic markers (RUNX2, alkaline phosphatase, osteonectin, osteocalcin, collagen type I, bmp2, smad5/8). Epigenetic tests confirmed the presence of miRNAs involved in odontogenic or osteogenic commitment of DPSCs cultured for up to 21 days on DP. Compressive strength values obtained from extracellular matrix (ECM) synthesized by DPSCs showed a trend of being higher when seeded onto DP than onto BG. High expression of VEGF factor, which is related to angiogenesis, and of dentin sialoprotein was observed only in the presence of DP. Morphological analyses confirmed the typical phenotype of adult odontoblasts. In conclusion, the odontogenic and osteogenic commitment of DPSCs and their respective functions can be achieved on DP, which enables exceptional dentin and bone regeneration.

Transcriptome Analysis Reveals Modulation of Human Stem Cells from the Apical Papilla by Species Associated with Dental Root Canal Infection.

Interaction of oral bacteria with stem cells from the apical papilla (SCAP) can negatively affect the success of regenerative endodontic treatment (RET). Through RNA-seq transcriptomic analysis, we studied the effect of the oral bacteria Fusobacterium nucleatum and Enterococcus faecalis, as well as their supernatants enriched by bacterial metabolites, on the osteo- and dentinogenic potential of SCAPs in vitro. We performed bulk RNA-seq, on the basis of which differential expression analysis (DEG) and gene ontology enrichment analysis (GO) were performed. DEG analysis showed that E. faecalis supernatant had the greatest effect on SCAPs, whereas F. nucleatum supernatant had the least effect (Tanimoto coefficient = 0.05). GO term enrichment analysis indicated that F. nucleatum upregulates the immune and inflammatory response of SCAPs, and E. faecalis suppresses cell proliferation and cell division processes. SCAP transcriptome profiles showed that under the influence of E. faecalis the upregulation of VEGFA, Runx2, and TBX3 genes occurred, which may negatively affect the SCAP's osteo- and odontogenic differentiation. F. nucleatum downregulates the expression of WDR5 and TBX2 and upregulates the expression of TBX3 and NFIL3 in SCAPs, the upregulation of which may be detrimental for SCAPs' differentiation potential. In conclusion, the present study shows that in vitro, F. nucleatum, E. faecalis, and their metabolites are capable of up- or downregulating the expression of genes that are necessary for dentinogenic and osteogenic processes to varying degrees, which eventually may result in unsuccessful RET outcomes. Transposition to the clinical context merits some reservations, which should be approached with caution.

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.

Mesenchymal stem cells: A comprehensive methods for odontoblastic induction.

BACKGROUND: In the area of oral and maxillofacial surgery, regenerative endodontics aims to present alternative options to conventional treatment strategies. With continuous advances in regenerative medicine, the source of cells used for pulp tissue regeneration is not only limited to mesenchymal stem cells as the non-mesenchymal stem cells have shown capabilities too. In this review, we are systematically assessing the recent findings on odontoblastic differentiation induction with scaffold and non-scaffold approaches. METHODS: A comprehensive search was conducted in Pubmed, and Scopus, and relevant studies published between 2015 and 2020 were selected following the PRISMA guideline. The main inclusion criteria were that articles must be revolving on method for osteoblast differentiation in vitro study. Therefore, in vivo and human or animal clinical studies were excluded. The search outcomes identified all articles containing the word "odontoblast", "differentiation", and "mesenchymal stem cell". RESULTS: The literature search identified 99 related studies, but only 11 articles met the inclusion criteria. These include 5 odontoblastic differentiation induction with scaffold, 6 inductions without scaffolds. The data collected were characterised into two main categories: type of cells undergo odontoblastic differentiation, and odontoblastic differentiation techniques using scaffolds or non-scaffold. CONCLUSION: Based on the data analysis, the scaffold-based odontoblastic induction method seems to be a better option compared to the non-scaffold method. In addition of that, the combination of growth factors in scaffold-based methods could possibly enhance the differentiation. Thus, further detailed studies are still required to understand the mechanism and the way to enhance odontoblastic differentiation.

Tooth ultrastructure of a novel COL1A2 mutation expanding its genotypic and phenotypic spectra.

OBJECTIVES: To investigate tooth ultrastructure and mutation of two patients in a family affected with osteogenesis imperfecta (OI) type IV and dentinogenesis imperfecta (DGI). METHODS: Mutations were detected by whole exome and Sanger sequencing. The permanent second molar obtained from the proband (DGI1) and the primary first molar from his affected son (DGI2) were studied for their color, roughness, mineral density, hardness, elastic modulus, mineral content, and ultrastructure, compared to the controls. RESULTS: Two novel missense COL1A2 variants, c.752C > T (p.Ser251Phe) and c.758G > T (p.Gly253Val), were identified in both patients. The c.758G > T was predicted to be the causative mutation. Pulp cavities of DGI1 (permanent teeth) were obliterated while those of DGI2 (primary teeth) were wide. The patients' teeth had darker and redder colors; reduced dentin hardness; decreased, disorganized, and scattered dentinal tubules and collagen fibers; and irregular dentinoenamel junction (DEJ), compared to controls. Lacunae-like structures were present in DGI2. CONCLUSIONS: We reported the novel causative mutation, c.758G > T (p.Gly253Val), in COL1A2 for OI type IV and DGI. The DGI dentin demonstrated inferior mechanical property and ultrastructure, suggesting severe disturbances of dentin formation. These could contribute to fragility and prone to infection of DGI teeth. This study expands phenotypic and genotypic spectra of COL1A2 mutations.

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.

Unexpected formation of root-like structures subsequent to the avulsion of immature permanent teeth: Case report.

This report describes the unexpected formation of root-like structures following the avulsion of immature permanent teeth without replantation. A 6-year-old female patient had avulsed the four permanent mandibular incisors and the two deciduous mandibular canines. The patient was seen in an emergency healthcare unit but did not receive specialized treatment for tooth replantation. As follow-up treatment, she received a removable prosthesis. After 4 years of follow-up, an image obtained by panoramic radiography showed formations similar to four root structures in the alveolus of the previously avulsed permanent teeth. This finding was confirmed by periapical radiography and computed tomography. This case report demonstrates that in teeth with incomplete root development, even after avulsion without replantation, cells from the pulp stump may have the capacity to form mineralized structures that appear radiographically comparable to root dentin.