Taurodontism: A minor diagnostic criterion in Laurence-Moon/Bardet-Biedl syndromes

Prevalence of taurodontism in individuals in Northwest China determined by cone-beam computed tomography images

Objective

The aim of this retrospective study was to evaluate the prevalence of taurodontism in a group of adult dental patients in Northwest China with the aid of cone-beam computed tomography (CBCT).

Methods

This study used Shifman and Chanannel's criteria to statistically analyze the prevalence of taurodontism in the premolars and molars of the Chinese population. CBCT images of 5488 teeth from 580 subjects of Chinese origin were evaluated. The measured data were statistically analyzed and the chi-square test was also used to compare the prevalence of taurodontism between male and female subjects and between the upper and lower jaws (P < 0.05).

Results

Taurodontism was detected in 169 patients, with a prevalence of 29.14%, of which 27.24% were males and 30.65% were females. The chi-square test showed that there was no significant difference between males and females (P > 0.05). Taurodontism was found in 7.45% of all teeth examined. Taurodonts were significantly more common in the maxilla (9.06%) than in the mandible (5.15%) (P < 0.001), and the maxillary second molar (25.18%) was the most common tooth affected. According to morphology, hypotaurodonts were the most common (60.39%) among taurodontic teeth.

Conclusions

Taurodontism was relatively common in the Chinese population and was almost equally distributed between males and females. The maxillary second molar was the most common tooth of all taurodonts measured, and taurodonts were significantly more common in the maxilla than in the mandible. Hypotaurodontism was the most common form of taurodontism. Our study provides a reference for dental deformities in the Chinese population and the diagnosis and treatment of taurodontism.

High prevalence of taurodontism in North China and its relevant factors: a retrospective cohort study

OBJECTIVE

The purpose of this study was to investigate the prevalence and relevant factors of taurodontism in North China.

METHODS

We retrospectively analysed the cone beam computed tomography (CBCT) of 1025 patients (496 male and 529 female) aged between 10 and 59 years. The crown-body/root (CB/R) ratios of the maxillary and mandibular molars were measured. The prevalence of hypotaurodontism, mesotaurodontism, and hypertaurodontism was then calculated and the incidence of taurodontism along with its relevant factors, was evaluated.

RESULTS

The overall rate of taurodontism in North China was as high as 78.9%. If the third molars (opsigenes) were excluded, which have a big morphological variation from each other, the rate was 52.4%. The mean CB/R ratio of taurodontism differs from tooth position: maxillary mandibular third molars > maxillary third molars > maxillary second molars > maxillary first molars > mandibular second molars > mandibular first molars (P < 0.05). In addition, the 1025 patients were divided into different age groups, and it was found that the mean CB/R ratio decreased with age (P < 0.05). Moreover, the CB/R ratio of the mandibular first and second molars in female patients was higher than males (P < 0.05).

CONCLUSION

This study revealed that taurodontism is widely prevalent in North China. The incidence of taurodontism increases the closer the tooth is to the back end of the dental arch, and quite a few of the maxillary and mandibular third molars teeth have tapered roots. And the taurodontism is decreased by age, as there were more affected female than male patients.

Dental Anomalies in Ciliopathies: Lessons from Patients with BBS2, BBS7, and EVC2 Mutations

Objective: To investigate dental anomalies and the molecular etiology of a patient with Ellis−van Creveld syndrome and two patients with Bardet−Biedl syndrome, two examples of ciliopathies. Patients and Methods: Clinical examination, radiographic evaluation, whole exome sequencing, and Sanger direct sequencing were performed. Results: Patient 1 had Ellis−van Creveld syndrome with delayed dental development or tooth agenesis, and multiple frenula, the feature found only in patients with mutations in ciliary genes. A novel homozygous mutation in EVC2 (c.703G>C; p.Ala235Pro) was identified. Patient 2 had Bardet−Biedl syndrome with a homozygous frameshift mutation (c.389_390delAC; p.Asn130ThrfsTer4) in BBS7. Patient 3 had Bardet−Biedl syndrome and carried a heterozygous mutation (c.389_390delAC; p.Asn130ThrfsTer4) in BBS7 and a homozygous mutation in BBS2 (c.209G>A; p.Ser70Asn). Her clinical findings included global developmental delay, disproportionate short stature, myopia, retinitis pigmentosa, obesity, pyometra with vaginal atresia, bilateral hydronephrosis with ureteropelvic junction obstruction, bilateral genu valgus, post-axial polydactyly feet, and small and thin fingernails and toenails, tooth agenesis, microdontia, taurodontism, and impaired dentin formation. Conclusions: EVC2, BBS2, and BBS7 mutations found in our patients were implicated in malformation syndromes with dental anomalies including tooth agenesis, microdontia, taurodontism, and impaired dentin formation.

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.

Primary cilia in hard tissue development and diseases

Bone and teeth are hard tissues. Hard tissue diseases have a serious effect on human survival and quality of life. Primary cilia are protrusions on the surfaces of cells. As antennas, they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis. Mutations in cilium-related genes result in a variety of developmental and even lethal diseases. Patients with multiple ciliary gene mutations present overt changes in the skeletal system, suggesting that primary cilia are involved in hard tissue development and reconstruction. Furthermore, primary cilia act as sensors of external stimuli and regulate bone homeostasis. Specifically, substances are trafficked through primary cilia by intraflagellar transport, which affects key signaling pathways during hard tissue development. In this review, we summarize the roles of primary cilia in long bone development and remodeling from two perspectives: primary cilia signaling and sensory mechanisms. In addition, the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described. We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

Oral and Craniofacial Anomalies of Bardet-Biedl Syndrome: Dental Management in the Context of a Rare Disease

Standardized guidelines for the oral health management of patients with rare diseases exhibiting morphologic anomalies are currently lacking. This review considers Bardet-Biedl syndrome (BBS), a monogenic autosomal recessive nonmotile ciliopathy, as an archetypal condition. Dental anomalies are present in a majority of individuals affected by BBS due to abnormal embryonic orofacial and tooth development. Genetically encoded intrinsic oral structural anomalies and heterogeneous BBS clinical phenotypes and consequent oral comorbidities confound oral health management. Since the comorbid spectrum of BBS phenotypes spans diabetes, renal disease, obesity, sleep apnea, cardiovascular disease, and cognitive disorders, a broad spectrum of collateral oral disease may be encountered. The genetic impact of BBS on the anatomic development of oral components and oral pathology encountered in the context of various BBS phenotypes and their associated comorbidities are reviewed herein. Challenges encountered in managing patients with BBS are highlighted, emphasizing the spectrum of oral pathology associated with heterogeneous clinical phenotypic expression. Guidelines for provision of care across the spectrum of BBS clinical phenotypes are considered. Establishment of integrated medical-dental delivery models of oral care in the context of rare diseases is emphasized, including involvement of caregivers in the context of managing these patients with special needs.

Role of Primary Cilia in Odontogenesis

Primary cilium is a solitary organelle that emanates from the surface of most postmitotic mammalian cells and serves as a sensory organelle, transmitting the mechanical and chemical cues to the cell. Primary cilia are key coordinators of various signaling pathways during development and maintenance of tissue homeostasis. The emerging evidence implicates primary cilia function in tooth development. Primary cilia are located in the dental epithelium and mesenchyme at early stages of tooth development and later during cell differentiation and production of hard tissues. The cilia are present when interactions between both the epithelium and mesenchyme are required for normal morphogenesis. As the primary cilium coordinates several signaling pathways essential for odontogenesis, ciliary defects can interrupt the latter process. Genetic or experimental alterations of cilia function lead to various developmental defects, including supernumerary or missing teeth, enamel and dentin hypoplasia, or teeth crowding. Moreover, dental phenotypes are observed in ciliopathies, including Bardet-Biedl syndrome, Ellis-van Creveld syndrome, Weyers acrofacial dysostosis, cranioectodermal dysplasia, and oral-facial-digital syndrome, altogether demonstrating that primary cilia play a critical role in regulation of both the early odontogenesis and later differentiation of hard tissue-producing cells. Here, we summarize the current evidence for the localization of primary cilia in dental tissues and the impact of disrupted cilia signaling on tooth development in ciliopathies.

Oral healthcare management in Bardet Biedl syndrome

Bardet Biedl syndrome is a rare autosomal recessive disorder with variable clinical presentation and challenging diagnosis. Recognition of orofacial features might help in the diagnosis. Dental management of affected patients might be complicated by renal, cardiac, metabolic, neurosensory, and cognitive defects.

Taurodontism, Root Dilaceration, and Tooth Transposition: A Radiographic Study of a Population With Nonsyndromic Cleft Lip and/or Palate

OBJECTIVES

In an effort to contribute to proper dental planning and define possible dental phenotypes of nonsyndromic cleft lip and/or palate (CL/P), this study aimed to investigate the occurrence of taurodontism, root dilaceration, and tooth transposition in persons with nonsyndromic CL/P, specifically analyzing the differences among gender, cleft types, and the most affected teeth.

DESIGN

This retrospective study analyzed 974 panoramic x-rays from nonsyndromic Brazilians older than 16 years and categorized into the following four groups: group 1, 250 persons with unilateral cleft lip and palate; group 2, 250 persons with unilateral cleft lip; group 3, 224 persons with cleft palate; and a control group of 250 persons without clefts. Radiographs were digitalized with a scanner and analyzed.

RESULTS

In the Brazilian population studied, the prevalence of taurodontism was 60.4% in group 1, 62.4% in group 2, 67.0% in group 3, and 42.8% in the control group. Root dilacerations had a prevalence of 31.2% in group 1, 29.6% in group 2, 26.3% in group 3, and 27.2% in the control group. The teeth most affected by taurodontism were 17 and 27; whereas root dilacerations were most common in teeth 38 and 48. No tooth transpositions were found in any radiograph analyzed.

CONCLUSIONS

Taurodontism is significantly more prevalent in Brazilians with nonsyndromic CL/P than in persons without clefts; whereas the prevalence of root dilaceration no different from that in the control group. However, root dilacerations in anterior teeth were increased in groups 1 and 2 when compared to the control group.

Developmental disorders of the dentition: an update

Dental anomalies are common congenital malformations that can occur either as isolated findings or as part of a syndrome. This review focuses on genetic causes of abnormal tooth development and the implications of these abnormalities for clinical care. As an introduction, we describe general insights into the genetics of tooth development obtained from mouse and zebrafish models. This is followed by a discussion of isolated as well as syndromic tooth agenesis, including Van der Woude syndrome (VWS), ectodermal dysplasias (EDs), oral-facial-digital (OFD) syndrome type I, Rieger syndrome, holoprosencephaly, and tooth anomalies associated with cleft lip and palate. Next, we review delayed formation and eruption of teeth, as well as abnormalities in tooth size, shape, and form. Finally, isolated and syndromic causes of supernumerary teeth are considered, including cleidocranial dysplasia and Gardner syndrome.