BACKGROUND: X-linked hypophosphatemia (XLH) is the most common inherited form of rickets. The presence of sequence variations in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene is associated with increased production of fibroblast growth factor 23 (FGF23). This results in renal phosphate wasting and impaired skeletal mineralization. Spontaneous dental abscesses, caused by endodontic infections resulting from hypomineralization of dentin, are a known dental complication of XLH. There is no objective method to evaluate the severity of dentin dysplasia. The purpose of this study was to develop a quantitative method to evaluate dentin dysplasia using orthopantomography that would allow the values in patients with XLH to be compared with the values in healthy participants of the same age.
METHODS: The severity of dentin dysplasia was analyzed by measuring the pulp cavity area of the tooth using orthopantomographic images. The teeth analyzed were mandibular second primary molars and mandibular first permanent molars with complete root formation. Teeth with dental caries, restorations, or root resorption were excluded.
RESULTS: This retrospective observational study included a total of 200 images of healthy participants (aged 2-15 years) divided into five age groups and 42 images of 17 patients with XLH. There was a significant tendency for the pulp cavity area to decrease with increasing age in primary and permanent teeth. The pulp chambers of patients with XLH were larger than those of healthy participants in primary and permanent teeth.
CONCLUSIONS: We have established a method of using orthopantomography for quantitative assessment of dentin dysplasia in XLH from the primary dentition to the permanent dentition. Evaluating the severity of dentin hypomineralization by this method is useful in the diagnosis of the dental manifestations of XLH. Early diagnosis of XLH enables oral management and leads to prevention of dental abscesses.

OBJECTIVE: To provide an evidence-based resource for paleopathologists to consider multiple skeletal indicators of pathology associated with early tooth loss in children to aid in diagnosis.
METHODS: Three databases (Cochrane Library, MedLine, and Scopus) were used for a review.
METHODS: According to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria, a systematic review guideline, 85 articles were selected.
RESULTS: A total of 189 children had a syndrome or disease associated with early tooth loss. Our review, based on 25 diseases, lists the bone and dental lesions observable in archeological remains.
CONCLUSIONS: Based on a review of the literature, a synthesis of 25 diseases and syndromes that may be associated with premature loss of permanent or deciduous teeth in children was developed for paleopathologists. It highlights the importance of a thorough dental examination by paleopathologists to further assess past health conditions.
CONCLUSIONS: This paper provides an extensive resource addressing early tooth loss in childhood to assist researchers with differential diagnosis.
CONCLUSIONS: The articles included in this review are case reports based on living populations.
UNASSIGNED: Further studies into diseases and their association with early tooth loss would complement this work, as would utilizing the differential diagnoses on archeological individuals to clarify its value and limitations.

Dentin dysplasia Type 1 (DD1) is an uncommon inherited condition marked by structural irregularities in dentin, leading to notable dental abnormalities. Clinically, patients typically present with generalized slight yellowish discoloration and tooth mobility, while radiographic examination often reveals a reduced pulp chamber with the absence of pulp stones, a hallmark feature of DD1. Treatment involves a multidisciplinary approach including extraction of affected teeth, direct sinus lift procedure bilaterally, implant placement, and subsequent fixed prosthesis placement. In a recent case, after six months, a patient demonstrated improved oral health-related quality of life with stabilized implant-supported prostheses providing functional and esthetic benefits. This emphasizes the importance of early diagnosis and intervention in managing DD1, underscoring the effectiveness of a multidisciplinary approach in enhancing oral function and esthetics. Further research is warranted to deepen our understanding of the genetic basis of this condition and develop targeted therapies.

OBJECTIVE: 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.
目的: 采用Micro-CT构建Ⅱ型牙本质发育不全（DGI-Ⅱ）和Ⅰ型牙本质发育不良（DD-Ⅰ）离体患牙的三维结构，研究该类患牙的内部结构及硬组织矿化密度的变化。方法: 收集同龄DGI-Ⅱ、DD-Ⅰ患者及健康者的第三磨牙，运用Micro-CT对3份样本逐一扫描并通过Mimics 17.0重建三维结构；截取矢状面和横断面观察患牙的内部结构；分别计算釉质、冠部牙本质以及根部牙本质的灰度值，分析牙齿不同部位的矿化密度。结果: 成功构建包括牙釉质帽、牙本质核和牙髓腔模型在内的DGI-Ⅱ、DD-Ⅰ患者的下颌第三磨牙三维精细模型；矢状面和横断面扫描显示DGI-Ⅱ患牙髓腔未完全钙化、根管狭窄，DD-Ⅰ患牙髓腔及根管闭锁、牙根缺如；灰度值分析发现DGI-Ⅱ、DD-Ⅰ患牙釉质、冠部牙本质及根部牙本质灰度值较正常对照组低（P<0.01）；DGI-Ⅱ、DD-Ⅰ两组相比，釉质、冠部牙本质灰度值差异无统计学意义（P>0.05），根部牙本质的灰度值差异有统计学意义（P<0.01）。结论: Micro-CT技术为遗传性牙本质发育缺陷离体患牙的三维结构重建及其矿化密度定量分析提供了简单而精确的方法。其中DGI-Ⅱ、DD-Ⅰ患牙的牙本质矿化密度均降低，DD-Ⅰ患牙降低更显著，髓腔内均有异常钙化物质，根管狭窄甚至闭塞。.

Tooth formation is a process tightly regulated by reciprocal interactions between epithelial and mesenchymal tissues. These epithelial-mesenchyme interactions regulate the expression of target genes via transcription factors. Among the regulatory elements governing this process, Epiprofin/Sp6 is a zinc finger transcription factor which is expressed in the embryonic dental epithelium and in differentiating pre-odontoblasts. Epiprofin knockout (Epfn-/-) mice present severe dental abnormalities, such as supernumerary teeth and enamel hypoplasia. Here, we describe dentin defects in molars and incisors of Epfn-/- mice. We observed that in the absence of Epfn, markers of early odontoblast differentiation, such as alkaline phosphatase activity, Dsp/Dpp expression, and Collagen Type I deposition, are downregulated. In addition, the expression of tight and gap junction proteins was severely impaired in the predontoblastic cell layer of developing Epfn-/- molars. Altogether, our data shows that Epfn is crucial for the proper differentiation of dental mesenchymal cells towards functional odontoblasts and subsequent dentin-matrix deposition.

Ⅰ型牙本质发育不良（DD-Ⅰ）是一种口腔罕见的常染色体显性遗传性牙本质异常疾病，本文报告一例替牙期DD-Ⅰ病例，通过相关临床检查和锥形束CT检查明确诊断，并分析其影像学特点，结合相关文献探讨DD-Ⅰ的病因、临床表现、诊断及治疗方法。旨在提高临床医师对DD-Ⅰ的认识，为制订更合理的诊疗方案及深入探究其致病机制提供帮助。.

Background and Objectives: Type I dentin dysplasia (DD-I) is a rare genetic disorder with autosomal dominant or recessive inheritance at risk of late or long-misunderstood diagnosis because the teeth, compared to other degenerative dentin diseases, do not have coronal defects and/or alterations but only at the root level (absent, conical, pointed roots, and obliterated pulp canals). The first radiographic suspicion often occurs only in case of sudden mobility and/or abscesses of the permanent teeth. Genetic tests confirm the diagnosis. Case Presentation: This case report describes the oral and radiographic characteristics of two siblings, 12 and 10 years old, a male and a female, at an early age affected by DD-I, whose diagnosis was made for a first orthodontic visit. The father and the older child had already undergone dental and orthodontic treatments, respectively, without the disease being suspected by the dentist. Results: Genetic tests support the diagnosis of DD-I. Following the diagnosis, the patients began a process of close periodic checks every 3-4 months to monitor their situation. The male child lost upper lateral incisors, which were then replaced with a light nylon removable prosthesis. Conclusions: The ability to recognize the radiographic features characteristic of DD-I is very important to avoid prejudicial diagnostic delays and to be able to plan the long-term treatment of these patients better, especially when the pathology was primarily misrecognized in the family.

Dentin dysplasia type Ⅱ (DD-Ⅱ) is a subtype of hereditary dentin disorders. The dentin sialophosphoprotein (DSPP) gene has been revealed to be the causative gene, whose mutations could affect the normal tooth development process. The lesions involve both deciduous and permanent dentition, mainly manifested as tooth discoloration, attrition and even the subsequent malocclusion. If not treated in time, it will significantly affect the physical and psychological health of patients. The disease is difficult to be diagnosed in clinic accurately as its low incidence and hidden manifestations. The present article aims to discuss the clinical and radiographic characteristics, diagnosis, treatment of DD-Ⅱ, in order to improve the overall understanding on DD-Ⅱ for clinicians.
Ⅱ型牙本质发育不良是遗传性牙本质发育异常的一个亚型，致病基因为牙本质涎磷蛋白基因，其突变导致牙齿正常发育过程受到影响。病变可累及乳牙列和恒牙列，主要表现为牙齿变色、磨耗，甚至继发咬合关系异常，如未及时治疗将显著影响患者的身心健康。该疾病在人群中患病率低，表型隐匿，临床诊断困难。本文主要对Ⅱ型牙本质发育不良的临床和影像学特征、诊断、鉴别诊断及治疗等方面进行阐述，以期提高临床医师对Ⅱ型牙本质发育不良的全面认识。.

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.
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.
CONCLUSIONS: 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.

The present study aims to investigate the mutation in a Chinese family with dentin dysplasia type II (DD-II) and to summarize mutation hotspots, clinical manifestations, and disease management strategies. Phenotype analysis, clinical intervention, mutation screening, and cosegregation analysis within the enrolled family were performed. A summary of the reported mutations in the dentin phosphoprotein (DPP) region of dentin sialophosphoprotein (DSPP) was analyzed. Pathogenicity prediction analysis of the physical properties and function of DSPP variants was performed by bioinformatic processing. Clinical management strategies are discussed. A novel pathogenic mutation (c.2035delA) in the DPP region of DSPP was identified, which was cosegregated in the family. The immature permanent teeth of patients with DD-II presented with X-shaped root canal phenotypes. Most of the identified mutations for DD-II were clustered in the DPP region between nucleotides 1686-2134. Points of differential diagnosis, clinical interventions, and management strategies are proposed. This study revealed a novel DSPP frameshift mutation and presented new clinical features of DD-II. The locus involving nucleotides 1686-2134 of DSPP may represent a mutational hotspot for the disease. Appropriate management of DD-II at different stages is important to avoid the development of secondary dental lesions.