Reassessment of fluctuating dental asymmetry in Down syndrome

Relating metric crown dimensions to underlying internal daily secretion rates in antimeric premolars

OBJECTIVES

The underlying cause for metric differences in antimeric tooth pairs is an important question for understanding dental variation. We hypothesize that localized variation in crown dimensions will be reflected in localized variation in daily enamel secretion rate.

DESIGN

Casts of pairs of human premolars from a tissue bank were 3D scanned using an optical scanning system (n = 32). Histological slides were created, and daily secretion rates (DSRs) were recorded in two areas of enamel that corresponded to scanner measurements. Antimeres were compared for both metric measurements and DSRs. Outliers for scanner measures were compared to significant differences in DSRs measurements in right and left teeth in corresponding areas.

RESULTS

Thirteen of the 16 individuals differed significantly in antimeric metric measurements, but only ten of those also differed in the underlying DSR. Fifteen of the 16 total individuals differed significantly in at least one DSR area.

DISCUSSION

While some individuals were outliers for metric measurements and had multiple areas of DSR differences, the majority of individuals had antimeric DSR differences regardless of metric differences. While there was no conclusive correlation between 3D metric analysis and underlying DSR differences, the most important result of this study is that DSR differences between antimeres are common.

Cranial-Vertebral-Maxillary Morphological Integration in Down Syndrome

Background: Morphological integration refers to the tendency of anatomical structures to show correlated variations because they develop in response to shared developmental processes or function in concert with other structures. The objective of this study was to determine the relationships between the dimensions of different cranial-cervical-facial structures in patients with Down syndrome (DS). Methodology: The study group consisted of 41 individuals with DS who had undergone cone-beam computed tomography (CBCT) at the Dental Radiology Unit of the University of Santiago de Compostela (Spain). In the historical archive of this same unit, 41 CBCTs belonging to individuals with no known systemic disorders or severe malformations of the maxillofacial region were selected, forming an age and sex-matched control group. Twenty-nine measurements were performed on each participant’s CBCT images, which were grouped into three blocks: atlantoaxial dimensions, craniovertebral dimensions and cephalometric dimensions. To determine whether there were significant differences between the dimensions obtained in the DS and control groups, we applied multiple analysis of variance and linear discriminant analysis tests. The analysis of the association between blocks (in pairs) was performed with the canonical correlation analysis test. Results: The dimensions evaluated in the three blocks of variables of individuals with DS differ significantly from those of nonsyndromic controls (p < 0.001). The highest discriminative capacity to identify controls and patients with DS was obtained with the cephalometric dimensions (87.5%). With regard to the association between blocks (two-by-two measurements), we found no significant relationship in the DS group. However, we confirmed a statistically significant correlation between all pairs of blocks of variables in the controls, especially between the atlantoaxial and cephalometric dimensions (p < 0.001) and between the craniovertebral and cephalometric dimensions (p < 0.001). Conclusions: Our results confirm a very poor morphological integration of the cranial-cervical-maxillary complex in individuals with DS. This finding reinforces the proposal that gene overload enhances the channeling process.

Oro-dental characteristics in patients with hypermobile Ehlers-Danlos Syndrome compared to a healthy control group

BACKGROUND

Ehlers-Danlos syndrome (EDS) is a hereditary disorder that affects the connective tissue and collagen structures in the body characterised by joint hypermobility, skin hyperextensibility and tissue fragility.

OBJECTIVE

The aim of the study was to investigate the oro-dental characteristics including measurements of tooth size of 26 patients with hypermobile EDS (hEDS), differentiated by a genetic test, compared to 39 healthy controls.

METHODS

Interview, clinical and radiological examination on panoramic radiograph and cone-beam computed tomographic (CBCT) scan were performed. Statistical analyses included Fisher's exact test, paired t test and multiple logistic and linear models adjusted for age and gender.

RESULTS

The experience of xerostomia (P = 0.039), local anaesthetic insufficiency (P < 0.001) and tooth extraction complications (P < 0.003) were significantly higher in hEDS compared to controls. The debris index was significantly higher in hEDS (P < 0.001), and the distance between the cement-enamel junction (CEJ) and the bone level on the upper left first incisor and molar and the lower right first molar was significantly larger in hEDS compared to controls (P = 0.021, P = 0.024, P = 0.021, respectively). The crown heights of the upper and lower first incisors were significantly smaller (P = 0.001, P = 0.003, P = 0.002, P < 0.001, respectively) in hEDS compared to controls. When adjusting for debris index, only the distance between CEJ and the marginal bone level on the upper left and lower right molar was associated with hEDS.

CONCLUSION

The results indicate that xerostomia, resistance to local anaesthesia, tooth extraction complications, poor oral hygiene, larger distance between CEJ and marginal bone level and small crown heights can be found in patients with hEDS.

Determination of mandibular morphology in a TURKISH population with Down syndrome using panoramic radiography

Background

Down syndrome (DS) is by far the most common known chromosomal disorder. Some characteristic features of DS are generalised growth deficiency, craniofacial abnormalities such as mandibular prognathism and underdevelopment of the midfacial region, dental abnormalities such as taurodontism and hypodontia. Individuals with DS have an increased prevalence of periodontal disease compared with age-matched control patients. The aim of the present study is to determine the morphologic features of the mandible among individuals with DS.

Methods

Thirty-four DS patients and thirty four age- and gender-matched control subjects underwent panoramic radiography, which included measurement of the mandibular canal (MC), the mandibular foramen (MF), the mandibular ramus (MR), the distance from the MC to the mandibular lower border (C-MLB), and the distance between the MC and the alveolar crest upper limit (C-AUL). Patients were separated into two groups based on age: < 15 (n = 15) and ≥ 15 (n = 19). In order to determine whether the MF, MR, MC, C-AUL, and C-MLB scores differed according to the groups (DS and control), one-way multivariate analysis of covariance (MANCOVA) was applied in which gender and age were taken as covariates.

Results

When the main effect according to the group was examined separately according to each measurement, the MF in the DS group was high with a moderate effect (F = 9207; p = 0.003). MR (F = 40,518; p < 0.001), MC (F = 23,747; p < 0.001), and C-AUL (F = 58,571; p < 0.001) in the DS group were lower with a larger effect. C-MLB did not significantly differ between the groups, and the effect size was quite low (p > 0.05).

Conclusions

Mandibular canal morphology may exhibit anatomical variations in DS. The alveolar bone level may differ from non-DS due to growth development retardation and/or periodontal diseases.