Natale und neonatale Zähne

Natal teeth have been defined as teeth which are present at birth, while neonatal teeth erupt during the first 30 days. Their occurrence is rare, the prevalence ranges from 1:2000 to 1:3000 with a higher frequency in the lip and palate clefts and syndroms. In about 85% natal or neonatal teeth are lower central incisors (60% in pairs), rare are upper teeth, molars and multiple teeth. In almost 90% they are part of the deciduous dentition. A lot of possible causes of early eruption are discussed, but only the relation to hereditary factors seems to be evident. An autosomal dominant trait is often described. The appearance of these teeth is dependent on the degree of maturity, but most of the time it is loose, small, discoloured and hypoplastic. Histologically, enamel hypoplasia with normal prism structure is apparent. No significant disturbances of the dentin structures are observed, only cervically dentin becomes atubular with spaces and enclosed cells. A large vascular pulp and failure of root formation are further investigations. Our microhardness measurements showed values from 24.3-32.4 KHN for enamel and 48.3-62.2 KHN for dentin, while normal deciduous teeth have an enamel hardness of 322.0 +/- 17.5 KHN. The thickness of enamel was never more than 280 microm compared to up to 1200 microm in normal teeth. This shows the retarded development of natal and neonatal teeth, because mineralization has not finished at the time of birth. In accordance with developmental age tooth structure and appearence are normal. In consideration of complications as Riga-Fede-disease, feeding problems, possibility of infection and hypermobility most of the time extraction is the treatment of choice, but in the interest of protecting the child this decision should be made carefully.

Pulp and periodontal healing of laterally luxated permanent teeth: results after 4 years

AIM: To evaluate the pulp and periodontal healing of laterally luxated permanent teeth. MATERIAL AND METHODS: Patients presenting with lateral luxation of permanent teeth during 2001-2002 were enrolled in this clinical study. Laterally luxated teeth were repositioned and splinted with a TTS/composite resin splint for 4 weeks. Immediate (prophylactic) root-canal treatment was performed in severely luxated teeth with radiographically closed apices. All patients received tetracycline for 10 days. Re-examinations were performed after 1, 2, 3, 6, 12 and 48 months. RESULTS: All 47 laterally luxated permanent teeth that could be followed over the entire study period survived. In 10 teeth (21.3%), a prophylactic root-canal treatment was performed within 2 weeks following injury. The remaining 37 teeth showed the following characteristics at the 4-year re-examination: 19 teeth (51.4%) had pulp survival (no clinical or radiographic signs or symptoms), nine teeth (24.3%) presented with pulp canal calcification, and pulp necrosis was seen in another nine teeth (24.3%), within the first year after trauma. None of the teeth with a radiographically open apex at the time of lateral luxation showed complications. External root resorption was only seen in one tooth. CONCLUSIONS: Laterally luxated permanent teeth with incomplete root formation have a good prognosis, with all teeth surviving in this study. The most frequent complication was pulp necrosis that was only seen in teeth with closed apices.

[Dens invaginatus. Review of the literature and diagnostic and therapeutic guidelines]

Dens invaginatus is a clinically relevant malformation of teeth resulting from an infolding of enamel and dentine into the dental structure during tooth formation, hence the former denomination "dens in dente". The dens invaginatus shows multiple morphological variations of crown and root formation. This frequently leads to caries, pulpal and periodontal involvement with necrosis and loss of attachment. Therefore, early diagnosis and prevention are of utmost importance. Due to the complexity of the malformation, treatment options in former days were limited. This article presents a profound review of the literature regarding etiology, epidemiology and histology. It discusses clinical appearance and diagnosis and it provides guidelines for decision-making and treatment of invaginated teeth.

Altered expression of the PTR/NRT1 homologue OsPTR9 affects nitrogen utilization efficiency, growth and grain yield in rice

The plant PTR/NRT1 (peptide transporter/nitrate transporter 1) gene family comprises di/tripeptide and low-affinity nitrate transporters; some members also recognize other substrates such as carboxylates, phytohormones (auxin and abscisic acid), or defence compounds (glucosinolates). Little is known about the members of this gene family in rice (Oryza sativa L.). Here, we report the influence of altered OsPTR9 expression on nitrogen utilization efficiency, growth, and grain yield. OsPTR9 expression is regulated by exogenous nitrogen and by the day-night cycle. Elevated expression of OsPTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation and increased grain yield. On the other hand, down-regulation of OsPTR9 in a T-DNA insertion line (osptr9) and in OsPTR9-RNAi rice plants had the opposite effect. These results suggest that OsPTR9 might hold potential for improving nitrogen utilization efficiency and grain yield in rice breeding.

Cell-to-cell communication--periodontal regeneration.

BACKGROUND Although regenerative treatment options are available, periodontal regeneration is still regarded as insufficient and unpredictable. AIM This review article provides scientific background information on the animated 3D film Cell-to-Cell Communication - Periodontal Regeneration. RESULTS Periodontal regeneration is understood as a recapitulation of embryonic mechanisms. Therefore, a thorough understanding of cellular and molecular mechanisms regulating normal tooth root development is imperative to improve existing and develop new periodontal regenerative therapies. However, compared to tooth crown and earlier stages of tooth development, much less is known about the development of the tooth root. The formation of root cementum is considered the critical element in periodontal regeneration. Therefore, much research in recent years has focused on the origin and differentiation of cementoblasts. Evidence is accumulating that the Hertwig's epithelial root sheath (HERS) has a pivotal role in root formation and cementogenesis. Traditionally, ectomesenchymal cells in the dental follicle were thought to differentiate into cementoblasts. According to an alternative theory, however, cementoblasts originate from the HERS. What happens when the periodontal attachment system is traumatically compromised? Minor mechanical insults to the periodontium may spontaneously heal, and the tissues can structurally and functionally be restored. But what happens to the periodontium in case of periodontitis, an infectious disease, after periodontal treatment? A non-regenerative treatment of periodontitis normally results in periodontal repair (i.e., the formation of a long junctional epithelium) rather than regeneration. Thus, a regenerative treatment is indicated to restore the original architecture and function of the periodontium. Guided tissue regeneration or enamel matrix proteins are such regenerative therapies, but further improvement is required. As remnants of HERS persist as epithelial cell rests of Malassez in the periodontal ligament, these epithelial cells are regarded as a stem cell niche that can give rise to new cementoblasts. Enamel matrix proteins and members of the transforming growth factor beta (TGF-ß) superfamily have been implicated in cementoblast differentiation. CONCLUSION A better knowledge of cell-to-cell communication leading to cementoblast differentiation may be used to develop improved regenerative therapies to reconstitute periodontal tissues that were lost due to periodontitis.

Formation of caries-like lesions in vitro on the root surfaces of human teeth in solutions simulating plaque fluid

Lesion formation on root surfaces of human posterior teeth was studied in acetate/lactate buffers with a background electrolyte composition based on plaque fluid analyses. Lesion depth after 28 days at 37 degrees C was measured in relation to: the presence or absence of cementum; the concentration of undissociated buffer; the presence or absence of magnesium ions at plaque fluid concentration. Each factor was evaluated at several values of -log(ion activity product for hydroxyapatite): pI(HA). Solutions were formulated to minimize variation in pH, which varied by < or =0.03 for a given comparison (individual pI(HA)) and by 0.42-0.82 over the range of pI(HA) within experiments. Lesions on surfaces from which cementum had been ground were significantly deeper than on intact surfaces, but this is considered to be due to subsurface mechanical damage and not to a solubility difference. Neither the concentration of undissociated buffer nor the presence of magnesium ions significantly affected lesion depth. Lesion depth was strongly influenced by the correlated variations in pI(HA) and pH. At pI(HA) 54 and 55, only extremely shallow lesions formed. From pI(HA) 56, lesion depth increased with increasing pI(HA). The results confirm that the solubility of the mineral of root tissues is higher than that of hydroxyapatite, but indicate that it is probably lower than suggested by Hoppenbrouwers et al. [Arch Oral Biol 1987;32:319-322]. For calcium concentrations of 3-12 mM, the critical pH for root tissue mineral was calculated as 5.22-5.66 assuming solubility equivalent to pI(HA) 54 and 5.08-5.51 assuming pI(HA) 55.

Intraneuronal angiotensinergic system in rat and human dorsal root ganglia

To elucidate the local formation of angiotensin II (Ang II) in the neurons of sensory dorsal root ganglia (DRG), we studied the expression of angiotensinogen (Ang-N)-, renin-, angiotensin converting enzyme (ACE)- and cathepsin D-mRNA, and the presence of protein renin, Ang II, Substance P and calcitonin gene-related peptide (CGRP) in the rat and human thoracic DRG. Quantitative real time PCR (qRT-PCR) studies revealed that rat DRG expressed substantial amounts of Ang-N- and ACE mRNA, while renin mRNA as well as the protein renin were untraceable. Cathepsin D-mRNA and cathepsin D-protein were detected in the rat DRG indicating the possibility of existence of pathways alternative to renin for Ang I formation. Angiotensin peptides were successfully detected with high performance liquid chromatography and radioimmunoassay in human DRG extracts. In situ hybridization in rat DRG confirmed additionally expression of Ang-N mRNA in the cytoplasm of numerous neurons. Intracellular Ang II staining could be shown in number of neurons and their processes in both the rat and human DRG. Interestingly we observed neuronal processes with angiotensinergic synapses en passant, colocalized with synaptophysin, within the DRG. In the DRG, we also identified by qRT-PCR, expression of Ang II receptor AT(1A) and AT(2)-mRNA while AT(1B)-mRNA was not traceable. In some neurons Substance P and CGRP were found colocalized with Ang II. The intracellular localization and colocalization of Ang II with Substance P and CGRP in the DRG neurons may indicate a participation and function of Ang II in the regulation of nociception. In conclusion, these results suggest that Ang II may be produced locally in the neurons of rat and human DRG and act as a neurotransmitter.

Enamel matrix protein adsorption to root surfaces in the presence or absence of human blood

Background: The clinical use of an enamel matrix derivative (EMD) has been shown to promote formation of new cementum, periodontal ligament (PDL), and bone and to significantly enhance the clinical outcomes after regenerative periodontal surgery. It is currently unknown to what extent the bleeding during periodontal surgery may compete with EMD adsorption to root surfaces. The aim of this study is to evaluate the effect of blood interactions on EMD adsorption to root surfaces mimicking various clinical settings and to test their ability to influence human PDL cell attachment and proliferation. Methods: Teeth extracted for orthodontic reasons were subjected to ex vivo scaling and root planing and treated with 24% EDTA, EMD, and/or human blood in six clinically related settings to determine the ability of EMD to adsorb to root surfaces. Surfaces were analyzed for protein adsorption via scanning electron microscopy and immunohistochemical staining with an anti-EMD antibody. Primary human PDL cells were seeded on root surfaces and quantified for cell attachment and cell proliferation. Results: Plasma proteins from blood samples altered the ability of EMD to adsorb to root surfaces on human teeth. Samples coated with EMD lacking blood demonstrated a consistent even layer of EMD adsorption to the root surface. In vitro experiments with PDL cells demonstrated improved cell attachment and proliferation in all samples coated with EMD (irrespective of EDTA) when compared to samples containing human blood. Conclusion: Based on these findings, it is advised to minimize blood interactions during periodontal surgeries to allow better adsorption of EMD to root surfaces.