Differential Expression of Long Noncoding RNAs in Normal and Inflamed Human Dental Pulp

Introduction

Dental pulp inflammation is an excellent model for the interaction between tissue inflammation and regenerative processes. It is worthwhile to better understand molecular signaling of repair and regeneration in inflammatory processes. Emerging evidence suggests that long noncoding RNA (lncRNA) participates in immune system inflammatory processes. Here we investigate the expression of lncRNAs in pulpitis, the inflammation of dental pulp tissue, and identify lncRNAs that possibly participate in inflammation responses and odontogenesis.

Enameloid formation in two tetraodontiform fish species with high and low fluoride contents in enameloid

Forming teeth of parrotfish and pufferfish were viewed by transmission electron microscopy to correlate cytological features of the enameloid organ with the species' fluoride (F) content in mature enameloid. Secretory-stage inner dental epithelial cells (IDE) of parrotfish (high F) and pufferfish (low F) secreted procollagen granules into the enameloid collagen matrix. The odontoblasts of both species, less numerous than IDE cells, also contained procollagen granules at the enameloid matrix formation stage. After the full thickness of enameloid matrix collagen had been deposited, enameloid crystallites formed parallel to the long axis of the enameloid collagen fibres. Concurrently, the plasma membranes of the outer dental epithelial cells (ODE) became invaginated in both species, but to a much greater extent in parrotfish. Highly undulating parrotfish ODE cells surrounded numerous fenestrated capillaries. In contrast, pufferfish ODE cells remained straight with few adjacent capillaries. Extensive tight junctions formed between ODE and IDE cells of both species, sealing the extracellular space. With increased mineralization, enameloid collagen fibres were no longer discernible. A thin layer of amorphous material, which subsequently mineralized, was secreted on to the enameloid surface by IDE cells in both species. Pufferfish odontoblasts secreted a mineralizing amorphous layer on the pulpal aspect of the enameloid. The results suggest that at the mineralization stage, a triad of cytostructural features, highly invaginated ODE cells, highly vascularized ODE cells, and extensive tight junctions are strongly correlated with high fluoride content of mature enameloid mineral. Species without any one of these features have lower fluoride in the enameloid.     

Analysis of developmental potentials of dental pulp in vitro using GFP transgenes

BACKGROUND: In recent years there has been increasing progress in identifying stem cells from adult tissues and their potential application for tooth replacement/regeneration. Our previous in vivo studies show that pOBCol3.6GFP and pOBCol2.3GFP transgenic animals provide a unique model to gain insight into progenitor/stem cells in the dental pulp capable of giving rise to odontoblasts. OBJECTIVES: To characterize the behavior of dental pulp cells derived from pOBCol3.6GFP animals in vitro. EXPERIMENTAL DESIGN: Primary cultures were established from the coronal portions of the pulps isolated first molars from 5-day-old pOBCol3.6GFP heterozygous mice and grown for 21 days. In these cultures proliferation, clonogenic capacity, activation of 3.6-GFP and mineralization were examined. RESULTS: Our observations show that dental pulp cells derived from 3.6-GFP contain a population of proliferative, clonogenic cells with the ability to mineralize. We also show the stage specific activation/upregulation of 3.6-GFP in primary cultures derived from dental pulp. In these cultures, expression of Col1a1-3.6-GFP occurs prior to the appearance of mineralized nodules and is unregulated in mineralized nodules. CONCLUSIONS: Col1a1-GFP transgenes appear to fulfill many of the requirements of a marker gene for cell lineage studies in intact tooth and primary cultures derived from dental pulp.     

CGRP1 and NK1 receptors in postnatal, developing rat dental tissues

There is little evidence that neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP) participate in the regulation of tooth development. The aim of this study was to analyse the expression of their respective receptors, neurokinin (NK) 1 and CGRP1 receptor, in postnatal developing rat molars and supporting tissues, thereby localizing the target areas for neuropeptide activity. Mol:WIST rats were killed at 7, 14 and 21 d after birth and upper and lower jaws were processed for immunohistochemistry. At early crown stage (P7), only a few individual cells in the dental follicle were receptor positive. At the onset of root formation (P14), post-secretory ameloblasts, cells in the stratum intermedium, the reduced enamel epithelium and the developing alveolar bone demonstrated both NK1 and CGRP1 receptor immunoreactivity. The CGRP1 receptor sites were occasionally evident on cells in the odontoblast layer. At advanced root development (P21), neuropeptide receptor expression was evident on cells close to the developing dentin, cementum and alveolar bone. These data demonstrate dynamic changes in the localization of NK1 and CGRP1 receptors in developing rat dental tissues and indicate an active role for their ligands in the regulation of crown and root development.     

Response to Intracanal Medication in Immature Teeth with Pulp Necrosis: An Experimental Model in Rat Molars

Introduction

The present study aimed at developing an experimental model in rat molars for evaluating treatment strategies in necrotic immature teeth.

Methods

To define the periods to be adopted in the experimental procedures and to confirm induction of periapical lesions and interruption of root embryogenesis, the left lower first molars of 4-weeks-old Wistar rats underwent pulpectomy and were left open to the oral environment. Comparisons with the right lower first molars (vital teeth) were performed in animals with ages of 7, 10, 13, and 16 weeks. In another group of animals the teeth were left open for 3 weeks, and then interventions for disinfection including the use of an antibiotic paste were carried out. Root formation was then assessed after 3 and 6 weeks on the basis of radiographic and histologic evaluation.

Results

Vital teeth showed increase of root length and hard tissue thickness throughout the experimental periods. On the other hand, induction of necrosis arrested root formation. Teeth subjected to disinfection with sodium hypochlorite associated with the triple antibiotic paste showed significant reduction of periapical lesions, gain in root length, and increased wall thickness compared with the control (P < .05).

Conclusions

The root canal disinfection protocol used was able to reduce periapical lesion size and improve root development. The experimental model presented should contribute to studies that aim at improving therapeutic strategies for necrotic immature teeth by using a rat model.     

Microdontia after chemotherapy in a child treated for neuroblastoma

OBJECTIVE: Chemotherapy used on paediatric oncology patients often causes disturbances in dental development. Aim of this case report is to present the late effects of chemotherapy on dental development in a patient treated for neuroblastoma at early age. DESIGN: Case report. RESULTS: This paper presents a female patient treated at early age with surgery and chemotherapy for a neuroblastoma (stage IVS) in the right thorax and massive liver metastases. The examination of the patient at age 11.7 years showed microdontia of six teeth. In three of them size and form of the crown were affected, while in the other three the size was reduced but the form was not affected. CONCLUSIONS: Chemotherapy on children treated for neuroblastoma can adversely influence tooth development. This has to be taken into consideration by the dentist when monitoring the development of the dentition and occlusion.     

Mechanisms of Mineralization in the Enameloid of Elasmobranchs and Teleosts

Ultrastructural and cytochemical studies on the mineralization of enameloid were performed using Heterodontus japonicus, an elasmobranch, and Tilapia buttikoferi, a teleost as materials. The mineralization of the enameloid in the Heterodontus was divided into the following two steps: (1) initial crystallization in the tubular vesicles that originated from the odontoblasts, and (2) crystal growth that was accompanied by the degeneration and removal of the organic matrix around the crystals. In the Tilapia, the mineralization of the cap enameloid followed three steps: (1) initial crystallization at the matrix vesicles, (2) aggregation of fine slender crystals along collagen fibrils, and (3) crystal growth with the degeneration and removal of the organic matrix. The pattern of early mineralization and the composition of organic matrix in enameloid were considerably different between the two species examined, while in both species the odontoblasts were mainly involved in the formation of the organic matrix of enameloid and in the initial mineralization. In the next step, remarkable crystal growth associated with the degeneration and removal of the organic matrix occurred in both the elasmobranch and the teleost species. The absorptive functions of the dental epithelial cells in the later stages of enameloid formation is probably similar in the two types of enameloid, and is essential for the production of well-mineralized enameloid.