Effect of Down syndrome on the dimensions of dental crowns and tissues

Overexpression of RCAN1, a Gene on Human Chromosome 21, Alters Cell Redox and Mitochondrial Function in Enamel Cells

The regulator of calcineurin (RCAN1) has been implicated in the pathogenesis of Down syndrome (DS). Individuals with DS show dental abnormalities for unknown reasons, and RCAN1 levels have been found to be elevated in several tissues of DS patients. A previous microarray analysis comparing cells of the two main formative stages of dental enamel, secretory and maturation, showed a significant increase in RCAN1 expression in the latter. Because the function of RCAN1 during enamel formation is unknown, there is no mechanistic evidence linking RCAN1 with the dental anomalies in individuals with DS. We investigated the role of RCAN1 in enamel by overexpressing RCAN1 in the ameloblast cell line LS8 (LS8+RCAN1). We first confirmed that RCAN1 is highly expressed in maturation stage ameloblasts by qRT-PCR and used immunofluorescence to show its localization in enamel-forming ameloblasts. We then analyzed cell redox and mitochondrial bioenergetics in LS8+RCAN1 cells because RCAN1 is known to impact these processes. We show that LS8+RCAN1 cells have increased reactive oxygen species (ROS) and decreased mitochondrial bioenergetics without changes in the expression of the complexes of the electron transport chain, or in NADH levels. However, LS8+RCAN1 cells showed elevated mitochondrial Ca2+ uptake and decreased expression of several enamel genes essential for enamel formation. These results provide insight into the role of RCAN1 in enamel and suggest that increased RCAN1 levels in the ameloblasts of individuals with DS may impact enamel formation by altering both the redox environment and mitochondrial function, as well as decreasing the expression of enamel-specific genes.

Dimensions of central incisors, canines, and first molars in subjects with Down syndrome measured on cone-beam computed tomographs

INTRODUCTION

The literature on tooth dimensions in subjects with Down syndrome (DS) is scarce. To our knowledge, no studies have yet been published in which the morphometry of the teeth in DS subjects has been determined using computed tomography.

METHODS

The study group consisted of 40 subjects with DS, aged 10 to 40 years. An age- and sex-matched control group was selected. Cone-beam computed tomography images were retrieved from the archive of the Santiago de Compostela University in Spain. The maxillary central incisors, canines, and first molars were evaluated. The following variables were analyzed: overall tooth length, crown height, root length, mesiodistal diameter, vestibular-palatine diameter, crown-to-root ratio, and cervical circumference.

RESULTS

The teeth of subjects with DS were smaller than those of the controls, although the crown-to-root ratio was maintained. No clear sexual dimorphism was detected, but the root lengths of the incisors were greater in male subjects. Crown height, mesiodistal diameter, and crown-to-root ratio showed progressive reductions with age. There appeared to be a degree of "fluctuating dental asymmetry" with respect to vestibular-palatine diameter and cervical circumference.

CONCLUSIONS

Our findings confirm microdontia of the permanent teeth and progressive reductions in tooth sizes with age in persons with DS. These variations might be relevant to orthodontic treatment planning.

Patterns of tooth agenesis in patients with Down syndrome in relation to hypothyroidism and congenital heart disease: an aid for treatment planning

INTRODUCTION

The purposes of this study were to investigate the patterns of tooth agenesis (oligodontia and nonoligodontia), maxillary canine impaction, and tooth transposition in subjects with Down syndrome and to determine whether congenital heart disease and hypothyroidism are parameters in tooth agenesis.

METHODS

The study included 114 patients with Down syndrome. The data were quantified by using standardized records, clinical examinations, panoramic radiographs, and solo roentgenograms. The subjects were differentiated into oligodontia (6 or more teeth missing) and nonoligodontia (5 or fewer teeth missing).

RESULTS

In these patients with Down syndrome, 59.6% had missing teeth. Those in the nonoligodontia group showed a tendency toward a negative correlation between congenital heart disease and agenesis (P = 0.093; odds ratio = 0.49) but a slight positive correlation between hypothyroidism and agenesis (P = 0.060; odds ratio = 3.71). In the oligodontia group, there was a quantitatively and qualitatively different pattern, indicating another phenotype. When both mandibular central incisors were missing, there was a remarkable chance for oligodontia (P = 0.001; odds ratio = 38.8). In the mandible, symmetrical agenesis of the canines and lateral incisors was more frequent in the nonoligodontia group.

CONCLUSIONS

The oligodontia (with a different phenotype) and nonoligodontia groups had different patterns of agenesis. Maxillary canine impaction was not related to absence of the lateral incisors. Absence of both mandibular central incisors was a high predictor for oligodontia. Congenital heart disease and hypothyroidism are parameters involved in tooth agenesis.

Morphology of dentition in Polish children with trisomy 21 (Down syndrome)

This paper compares the dimensions and non-metric dental traits between Down syndrome patients (DS) and a control group. A total of 1,210 teeth of subjects with Down syndrome (diagnosed as regular trisomy 21 type) were analyzed. The mesiodistal (MD) and labiolingual or buccolingual (BL) diameters of each dental crown were measured, and the selected non-metric dental traits evaluated. The teeth of male and female DS patients were found to have lower values of both measurements compared to controls (excepting for the mesiodistal diameter of the lower mandibular premolar both in males and females). Sexual dimorphism of dental crown dimensions characteristic of contemporary human populations (the highest M-F difference was lower than 6%) was also observed: boys' teeth, particularly canines, are bigger than girls' (2.33 on average). Disorders in maxillary tooth alignment and the faint shoveling of upper central incisors (grade 1 according to ASU scale) were noted significantly more often among Down syndrome patients, but descriptive features correlating with dental crown size were observed more rarely (e.g., the distal accessory ridge on the upper canine and tuberculum Carabelli on the first molar).

Acid resistance of the enamel in primary second molars from children with down syndrome and cerebral palsy

OBJECTIVES

This study was carried out to evaluate the extent of differences in mineralization of inner and outer enamel of the lower primary second molars of children with Down syndrome (DS) and Cerebral Palsy (CP) as revealed by acid treatment of exfoliated teeth. The results were compared to those obtained from a control group of healthy children.

METHODS

The sample included 4 mandibular second molars from each group. On each tooth, a thin section was cut, bisecting the mesial cusps. The analysis was carried out on the mesio-buccal cusps. Atomic force microscopy (AMF) was used to analyze the morphological structure of the dental enamel after 10 sec of 0.1 mol% citric acid treatment. The measurements were performed on 3 points in the enamel close to the outer surface and 3 points in the enamel close to the dentin. The differences between groups were analyzed using Mann Whitney tests.

RESULTS

In controls and CP teeth the outer enamel was more resistant to etching than the inner enamel. In DS teeth both outer and inner enamel showed similar results for all parameters. Between group comparisons showed that roughness values were significantly higher (P<0.01) in DS teeth than in either controls or CP teeth. No significant differences were found between CP and control teeth.

CONCLUSIONS

The higher values obtained for DS enamel reflect increased solubility of the enamel to acid relative to controls and CP teeth together with irregularity of the organic matrix. The practical importance of the results is that DS primary molars needs reduced etching time when prepared for pit and fissure sealants or composite/compomer restorations.

Maxillary Anterior Tooth Size and Arch Dimensions in Unilateral Cleft Lip and Palate

Objective:

To investigate differences in size of the maxillary permanent anterior teeth and arch dimensions between individuals with repaired unilateral cleft lip and palate (UCLP) and a matched control group representing the general population.

Design:

Retrospective study cast review.

Participants:

Study casts of 30 subjects due to commence orthodontic treatment following an alveolar bone graft (ABG) were collected from the Cleft Lip and Palate Units in South Yorkshire. Thirty control subjects were collected from a previously validated control group of white individuals in South Yorkshire.

Main Outcome Measures:

Casts were analyzed with an image analysis system to measure the dimensions of the maxillary permanent anterior teeth, incisor chord lengths, and the intercanine and intermolar widths. The results were analyzed statistically using paired t-tests and two-way univariate analysis of variance (ANOVA).

Results:

The mesiodistal widths of maxillary anterior teeth in the study group were smaller than the noncleft control group (p < .01). The dimensions of the cleft side maxillary incisors and incisor chord length were smaller (p < .05 and p < .01 respectively) compared with the noncleft side. The study group maxillary cleft side incisor chord length and maxillary intercanine width were narrower than the control group (p < .0001).

Conclusions:

(1) Anterior teeth are smaller mesiodistally in individuals with UCLP. (2) Maxillary incisors are smaller on the cleft side than the noncleft side. (3) UCLP subjects had smaller maxillary cleft side incisor chord lengths and intercanine widths than the control group despite pre-ABG expansion.

Prenatal growth acceleration in maxillary deciduous canines of children with Down syndrome: Histological and chemical composition study

Previous studies have reported that the abnormal development of the second deciduous molar in Down syndrome and cerebral palsy begins before birth. In view of these results we have turned our attention to the earlier stages of dental development in utero, represented by the primary canine, in order to see if we can identify more precisely the origin and timing of developmental insults in these conditions. The study was carried out on exfoliated or extracted maxillary primary canines of children with Down syndrome (DS) and cerebral palsy (CP) and they were compared to a control group of children with no adverse medical history. Thin sections were made through the mid-sagittal bucco-palatinal axis. Using a light microscope, the width of prenatal enamel and postnatal enamel, defined by the neonatal line was measured on each section at a standardized location. The chemical composition of the enamel was then measured at three different locations using an energy dispersive spectrophotometer (ESR) in a high vacuum mode. The total enamel width in DS and controls was similar and greater than that of CP canines. Significantly more enamel was laid down prenatally in DS teeth than in controls or CP and it was more highly mineralized. These results for DS canines differ from those previously published for the later developing second primary molars. They support the hypothesis of accelerated growth in the early stages of intra-uterine development, prior to the establishment of reduced growth trajectories in the later stages. The results for CP teeth showed that more prenatal enamel was laid down prenatally than in controls. Mineralization in CP was poor during the first two trimesters and improved significantly during the last trimester. While this approach is retrospective, we propose that it may aid in identifying the onset of developmental anomalies of unknown etiology that are expressed in later life.

Microstructure and chemical composition of primary teeth in children with Down syndrome and cerebral palsy

This study was designed to test the hypothesis that prenatal growth insults leave permanent signs in the developing primary teeth that can be identified in later life. To test this hypothesis we examined exfoliated and extracted lower second primary molars of children with Down syndrome (DS) and cerebral palsy (CP). Teeth of children with no adverse medical history were used as a control group. Informed consent of parents and children was obtained in all cases. On each tooth two thin sections were cut, one bisecting the mesial cusps and one bisecting the distal cusps. Using a light microscope, the width of prenatal enamel and postnatal enamel was measured on each section at standardized locations from the dentin-enamel junction (DEJ) with the neonatal line used to distinguish between prenatal and postnatal enamel. Chemical analysis of each section was carried out using an energy dispersive spectrophotometer (ESR). The Ca/P ratios of enamel and dentin for each cusp were calculated and intercusp and intergroup differences analysed using non-parametric statistical tests. The results showed that significantly less enamel was laid down prenatally in DS and CP teeth than in the control group and that the enamel of the mesial cusps in these groups was less highly mineralised than that of the controls. The results also showed that in DS teeth growth and mineralisation of all cusps was affected. Based on these findings we propose that analysis of exfoliated deciduous teeth in developmentally challenged children may help in identifying the onset and severity of growth insults in utero and its impact on later development.

The effect of hereditary disorders on tooth components: a radiographic morphometric study of two syndromes

OBJECTIVE

The purpose of this study was to compare tooth components (enamel and dentin) in Familial Dysautonomia (FD) and Down syndrome (DS) in order to assess the extent to which each was affected.

DESIGN

The design was cross-sectional. The sample consisted of 20 FD patients and 45 DS patients. The control group comprised 250 healthy subjects. Mesio-distal crown width (CW), enamel and dentin thickness and pulp chamber dimensions were measured on standardized bitewing radiographs of mandibular second primary and first permanent molars. Statistical analyses were performed between groups using SAS programs.

RESULTS

CW was reduced in both hereditary disorders. In the DS group enamel height (EH) and dentin thickness were reduced. In FD enamel thickness in the primary and permanent molars as well as dentin height (DH) in permanent molars was increased.

CONCLUSIONS

In both syndromes the reduction in CW suggests reduced proliferation during tooth germ formation. However, the differences in enamel and dentin thickness suggest that ameloblasts and odontoblasts were affected differently in the later phases of cell function. In FD cell function is stimulated resulting in thicker enamel and dentin. In DS cell function is reduced resulting in thin enamel and dentin.

Integrating the genotype and phenotype in hominid paleontology

Competing interpretations of human origins and evolution have recently proliferated despite the accelerated pace of fossil discovery. These controversies parallel those involving other vertebrate families and result from the difficulty of studying evolution among closely related species. Recent advances in developmental and quantitative genetics show that some conventions routinely used by hominid and other mammalian paleontologists are unwarranted. These same advances provide ways to integrate knowledge of the genotype into the study of the phenotype. The result is an approach that promises to yield a fuller understanding of evolution below the family level.

Genetics and the evolution of primate enamel thickness: A baboon model

The thickness of mammalian tooth enamel plays a prominent role in paleontology because it correlates with diet, and thicker enamel protects against tooth breakage and wear. Hominid evolutionary studies have stressed the importance of this character for over 30 years, from the identification of "Ramapithecus" as an early Miocene hominid, to the recent discovery that the earliest hominids display molar enamel intermediate in thickness between extant chimpanzees and Australopithecus. Enamel thickness remains largely unexplored for nonhominoid primate fossils, though there is significant variation across modern species. Despite the importance of enamel thickness variation to primate evolution, the mechanisms underlying variation in this trait have not yet been elucidated. We report here on the first quantitative genetic analysis of primate enamel thickness, an analysis based on 506 pedigreed baboons from a captive breeding colony. Computed tomography analysis of 44 Papio mandibular molars shows a zone of sufficiently uniform enamel thickness on the lateral surface of the protoconid. With this knowledge, we developed a caliper metric measurement protocol for use on baboon molars worn to within this zone, enabling the collection of a data set large enough for genetic analyses. Quantitative genetic analyses show that a significant portion of the phenotypic variance in enamel thickness is due to the additive effects of genes and is independent of sex and tooth size. Our models predict that enamel thickness could rapidly track dietary adaptive shifts through geological time, thus increasing the potential for homoplasy in this character. These results have implications for analyses of hominoid enamel thickness variation, and provide a foundation from which to explore the evolution of this phenotype in the papionin fossil record.

Structure and microstructure of coronary dentin in non-erupted human deciduous incisor teeth

The dentin structure of non-erupted human deciduous mandibular and maxillary central and lateral incisor teeth was studied employing light and scanning electron microscopy. For light microscopy, nitric-acid-demineralized and ground sections were used. The sections were stained by hematoxylin-eosin, picrosirius and azo-carmine methods, and ground specimens were prepared using a carborundum disk mounted in a handpiece. For SEM study, teeth were frozen in liquid nitrogen and fractured at longitudinal and transversal directions. Structurally, demineralization and ground methods revealed tubules with primary and secondary curvatures, canaliculi, giant tubules, interglobular dentin, predentin, and intertubular dentin. Scanning electron microscopy showed three-dimensional aspects of dentinal tubules, canaliculi, peritubular dentin, intertubular dentin, and predentin. This study contributes to knowledge about dentin morphology showing characteristics of teeth not yet submitted to mastication stress.

Use of dental implants in patients with Down syndrome: a case report

Down syndrome is caused by trisomy of the 21st chromosome and is associated with well-described physical and systemic problems. Most people with Down syndrome have some degree of mental retardation as well as malformation of head and neck. Oral structures that are commonly affected include the tongue (macroglossia), abnormalities in the number and shape of teeth, and poor quality (osteoporotic-like) of alveolar bone and jaw. These oral malformations as well as a tendency toward poor cooperation in the dental office contribute to the belief among dentists that people with Down syndrome are not good candidates for oral rehabilitation with dental implants. This article describes the use of dental implants in the oral rehabilitation of a 16-year-old boy with Down syndrome. Although more experience is needed before dental implants can be considered a suitable option during oral rehabilitation in people with Down syndrome, this case report shows a promising beginning.