Delayed replantation of an avulsed immature permanent incisor and apexification using a novel fast-setting calcium silicate cement containing fluoride: a 3-year follow-up case report.

BACKGROUND: Traumatic tooth avulsion requires an urgent intervention to replant the tooth. Prolonged post-injury dry extra-oral conditions worsen the prognosis and increase the risk of root resorption. Fluoride has the potential to delay replacement resorption. Calcium silicate cements (CSC) are used to seal the root canal system and to stimulate periapical regeneration in immature open apex teeth (apexification). This report suggests the application of a novel fast-setting CSC with fluoride for apexification in an attempt to hinder root resorption. CASE REPORT: A delayed replantation of an avulsed open apex permanent central incisor after 75 h of storage in a dry condition in a 6-year-old girl. Standard treatment guidelines for avulsed immature permanent teeth were followed. After tooth replantation a novel fast-setting, CSC containing fluoride was used for apexification. FOLLOW-UP: The radiographic and clinical evaluations over a period of 3 years demonstrated periodontal bone healing without root resorption, mobility, and ankylosis and an acceptable periapical tissue tolerance to the novel CSC. However, a longer follow-up period is needed. CONCLUSIONS: Delayed replantation of the avulsed open apex permanent incisor after 75 h of storage under dry conditions and apexification with a novel fast-setting CSC showed a successful outcome after 3 years. Novel CSC with fluoride demonstrated an acceptable biocompatibility and tissue tolerance.

Activation of the Notch signaling pathway in response to pulp capping of rat molars.

Notch signaling is an evolutionarily conserved pathway that controls the developmental choices made by individual cells. Cells communicate via Notch receptors and their ligands, which direct decisions on the fate of stem cells according to the states of their neighbors. In this study we explored Notch signaling after the pulp capping of adult first upper rat molars. The wound was capped with calcium hydroxide. In situ hybridization revealed an increased expression of Notch signaling genes on day 1, which showed a tendency to decrease on day 3. Notch1 increased in the subodontoblast zone and close to the lesion limited to a few cells. Notch2 increased in pulp stroma surrounded by coronal odontoblasts. Notch1 and, especially, Notch3 expression increased, corresponding to perivascular cell groups. A low increase of ligand expression was observed near the injury with Delta1 expression along the dentin wall and Jagged1 in the stroma. Expression of the downstream target, Hes1, was observed along the lesion and adjacent dentin walls. Hes5 expression was not observed. The results indicate that Notch signaling is activated in response to injury and associated with the differentiation of pulp cells into perivascular cells and odontoblasts. The findings are consistent with the concept that the Notch pathway controls stem cell fate during pulp regeneration.

Age-related and site-specific changes in the pulpodentinal morphology of rat molars.

The rat molars are frequently used as experimental models in endodontic research, but there is little systematic information available on the influence of age on the pulpodentinal organ in Wistar rat molars and it is often difficult to evaluate more subtle changes following experimental interventions. The aim here was to describe changes with age in first upper Wistar rat molars with specific reference to the pulpodentinal organ. Animals were perfused with glutaraldehyde at 19 days, 1, 3, 6, 8, 12, 16, or 24 months of age. First upper molars from 56 animals were demineralized in EDTA, embedded in Epon, and processed for light and transmission electron microscopy. Substantial variation in the structure of the dentine and odontoblasts was observed within the root canals and the coronal pulp chamber. In general, odontoblasts changed from a tall, columnar morphology in the coronal pulp chamber to a more cuboidal or flattened shape near the apex, particularly towards the interradicular space. Secondary dentine formation was more pronounced along the mesial aspect of the root chamber and corresponding to the bottom of fissures. Local tertiary dentine formation was layered in the upper pulp chamber, corresponding to occlusal attrition of the cusp. In several molars a local formation of irregular tertiary dentine was observed cervically in the mesial pulp chamber. After 1 year, a distinct protrusion of irregular dentine extended into the mesiocervical pulp, apparently corresponding to a denudation of cervical root dentine. Experimental pulp-capping studies frequently use first upper rat molars with perforations made through the mesial aspect of the crown; such perforations might be close to the irregular dentine in the mesiocervical region. In conclusion, this study identifies age-associated and regional changes of pulpodentinal morphology in first upper rat molars. Therefore, evaluation of morphological alterations following vital-pulp experiments should be done in specific age groups and at specific sites in the pulp.

Formaldehyde cytotoxicity in three human cell types assessed in three different assays.

International standards for preclinical screening of the cytotoxicity of dental materials so far recommend the use of established cell lines. The aim of this study was to assess the relative susceptibility of human dental pulp fibroblasts (HPF), human buccal epithelial cells (HBE) and HeLa cervix cancer cells exposed to identical cytotoxic challenges. Formaldehyde, which may be released from dental materials such as dental composites, glassionomer cements, and endodontic sealers, was used as test chemical. Cytotoxicity data including dose-response relations and TC(50) values were assessed in three different assays: BrdU incorporation, neutral red uptake and MTT assays. HBE and HPF demonstrated statistically significant lower TC(50) values in both the neutral red and the BrdU assay in comparison to HeLa cells. In the MTT assay no statistically significant differences were observed between the cell types. In the two target-tissue cell types (HPF and HBE) the Neutral Red assay revealed lower TC(50) values in comparison to the BrdU assay. In HeLa cells no statistically significant differences were observed between the assays. In conclusion, the present study confirms that cytotoxicity data obtained by cell culture studies are influenced by both cell culture model and choice of assay. Under identical experimental conditions, human target tissue cells appeared to be more sensitive to formaldehyde toxicity than human HeLa cancer cells.

Pulp-capping with recombinant human insulin-like growth factor I (rhIGF-I) in rat molars.

The aim of this study was to explore pulp healing and reparative dentinogenesis following pulp-capping by using recombinant human insulin-like growth factor I (rhIGF-I). Exposures were made through the mesial pulp horn in first upper molars in two-month-old Wistar rats. The pulp was covered with one dose of sterile 4% methylcellulose gel containing either 400 ng rhIGF-I or saline in contralateral controls. The exposure site was closed with sterile Teflon membrane, and the cavity was filled with IRM cement. Additional molars were capped with Dycal as controls. After 3, 7, or 28 days, animals were anesthetized and fixed by intravascular glutaraldehyde perfusion. Molars were decalcified and processed for histological analysis and cut with membrane and residual methacrylate from IRM in situ. Only specimens with acceptable pulp sealing according to blinded microscopy control were included. On day 3, identical inflammatory responses in the upper pulp were observed in molars with rhIGF-I gel or control gel. On day 7, granulation tissue ingrowth had partly replaced inflammatory infiltration in both groups. After 28 days, complete dentin bridging and tubular dentin formation were observed more frequently and closer to the test substance containing rhIGF-I. The reparative dentin response to capping with rhIGF-I was similar to that after the use of Dycal. In conclusion, microscopic control of membrane sealing in situ gives valid information on the more subtle pulp effects of growth factors. The observations suggest that pulp-capping of rat molars by means of rhIGF-I enhances reparative dentinogenesis in comparison with vehicle controls.

[Apoptosis: molecular aspects]. / Apoptosis: molekylaere aspekter.

Many signals and external stimuli regulate the apoptosis activity by interaction with the genome. These stimuli include morphogenetic signals, physiological factors, and environmental influence. The signals mediate their effect on cells with suitable receptors, relevant signalling pathways, and competence to execute the apoptosis cascade. Apoptosis is triggered indirectly by deprivation of survival factors, or directly by intercellular cell death signalling factors, and also by unbalanced intracellular messenger molecules, which are, more or less, involved in regulation of both programmed cell death and survival. Several genes are involved in regulation of cell survival and apoptosis: bcl-2/bax, p53, c-myc and transcription factors such as cdk, c-myc, c-fos and c-jun. Apparently, apoptosis could be triggered by increased or inhibited gene expression as well as biochemical reactions without changed gene expression. The morphological changes during apoptosis reflect a cascade of genetic and biochemical reactions in the cell. In the signal transduction pathway both secondary messenger Ca2+, different kinases, and polyamines are involved. Cysteine proteases cleave cytoskeletal proteins, endonucleases divide DNA into fragments, and transglutaminases cross-link macromolecules. Degradative enzymes such as proteases, endonucleases and transglutaminases are activated during apoptosis, leading to cellular collapse and formation of vesicular apoptotic bodies. Both increased and inhibited apoptosis activity may have pathological consequences. New therapeutic strategies aim to counteract dysregulation of apoptosis in specific tissues by pharmacological intervention. Thus there is a need for identification of molecules and gene products involved in regulation of apoptosis activity and clarification of the conditions where this knowledge may be used.

[Apoptosis: cellular and clinical aspects]. / Apoptosis: cellulaere og kliniske aspekter.

Removal of damaged cells is essential for the maintenance of life in multicellular organisms. The process of self destruction, apoptosis, eliminates surplus or damaged cells as part of the pathophysiological defence system. Apoptosis is essential in structural and functional organogenesis during embryological development. The physiological regulation of tissue kinetics is a product of both cell proliferation and cell death. Internal and external regulatory stimuli regulate the balance between apoptosis and mitosis by genetic interaction. Apoptosis is characterized by condensation of chromatine as a result of DNA degradation, formation of blebs in the plasma and nuclear membranes, condensation of cytoplasma, formation of vesicular apoptotic bodies, and phagocytosis by neighbouring cells without inflammatory response. A number of observations indicate that programmed cell death plays an important role in the regulation of cytofunctional homeostasis and defense against accumulation of damaged cells, eg with DNA alterations. Dysregulation of the apoptotic gene program, eg by mutations, may not only lead to loss or degeneration of tissue, but also to hyperproliferative and tumorigenic disorders. New evidence indicates that apoptosis regulation is important both in aging processes and diseases such as: neuropathies, immunopathies, viral infections, cancer, etc. Pharmacological intervention designed to modulate apoptosis seems to raise new possibilities in the treatment of disease.