Autoimmune amelogenesis imperfecta in patients with APS-1 and coeliac disease.

Ameloblasts are specialized epithelial cells in the jaw that have an indispensable role in tooth enamel formation-amelogenesis1. Amelogenesis depends on multiple ameloblast-derived proteins that function as a scaffold for hydroxyapatite crystals. The loss of function of ameloblast-derived proteins results in a group of rare congenital disorders called amelogenesis imperfecta2. Defects in enamel formation are also found in patients with autoimmune polyglandular syndrome type-1 (APS-1), caused by AIRE deficiency3,4, and in patients diagnosed with coeliac disease5-7. However, the underlying mechanisms remain unclear. Here we show that the vast majority of patients with APS-1 and coeliac disease develop autoantibodies (mostly of the IgA isotype) against ameloblast-specific proteins, the expression of which is induced by AIRE in the thymus. This in turn results in a breakdown of central tolerance, and subsequent generation of corresponding autoantibodies that interfere with enamel formation. However, in coeliac disease, the generation of such autoantibodies seems to be driven by a breakdown of peripheral tolerance to intestinal antigens that are also expressed in enamel tissue. Both conditions are examples of a previously unidentified type of IgA-dependent autoimmune disorder that we collectively name autoimmune amelogenesis imperfecta.

Investigation of silver nanoparticles on titanium surface created by ion implantation technology.

Objectives: Using dental Ti implants has become a well-accepted and used method for replacing missing dentition. It has become evident that in many cases peri-implant inflammation develops. The objective was to create and evaluate the antibacterial effect of silver nanoparticle (Ag-NP) coated Ti surfaces that can help to prevent such processes if applied on the surface of dental implants. Methods: Annealing I, Ag ion implantation by the beam of an Electron Cyclotron Resonance Ion Source (ECRIS), Ag Physical Vapor Deposition (PVD), Annealing II procedures were used, respectively, to create a safely anchored Ag-NP layer on 1x1 cm2 Grade 2 titanium samples. The antibacterial effect was evaluated by culturing Staphylococcus aureus (ATCC 29213) on the surfaces of the samples for 8 hours, and comparing the results to that of glass as control and of pure titanium samples. Alamar Blue assay was carried out to check cytotoxicity. Results: It was proved that silver nanoparticles were present on the treated surfaces. The average diameter of the particles was 58 nm, with a 25 nm deviation and Gaussian distribution, the the filling factor was 25%. Antibacterial evaluation revealed that the nanoparticle covered samples had an antibacterial effect of 64.6% that was statistically significant. Tests also proved that the nanoparticles are safely anchored to the titanium surface and are not cytotoxic. Conclusion: Creating a silver nanoparticle layer can be an option to add antibacterial features to the implant surface and to help in the prevention of peri-implant inflammatory processes. Recent studies demonstrated that silver nanoparticles can induce pathology in mammal cells, thus safe fixation of the particles is essential to prevent them from getting into the circulation.

Effect of mixing technique on shrinkage rate of one polyether and two polyvinyl siloxane impression materials.

PURPOSE: Different mixing techniques may affect the quality of set impression materials. Therefore, dimensional accuracy is the most important factor when constructing a passive and accurate prosthesis. In this study, observation of the shrinkage rate of one polyether and two polyvinyl siloxane impression materials, which are both commercially available for cartridge- and hand-mix techniques, was used for comparative analysis. The hypothesis was that the cartridgemix technique would produce a more precise impression. The authors also sought to confirm the hypothesis that the studied materials would remain stable after setting. MATERIALS AND METHODS: The low-viscosity polyether material was Permadyne Garant 2:1, type 3 (ESPE). The polyvinyl siloxane materials were: (1) medium-viscosity Provil Novo Medium, cartridge- and hand-mix type 2 (Heraeus Kulzer); and (2) low-viscosity President, hand- and cartridge-mix type 3 (Coltène). Measurements were made according to American Dental Association specification No. 19. Ten specimens were made of each impression material; the same examiner measured each specimen 10 times. Shrinkage rates of the same materials mixed using different techniques were compared 30 minutes, 24 hours, and 72 hours after mixing. Dimensional changes at the different measuring times were also compared. The results were statistically analyzed and compared with the SPSS for Windows program package, version 11.0 (SPSS); a two-sample t test was applied to compare the mixing techniques at every measuring time; and a Friedman test was used to analyze the changes in shrinkage rate during the evaluation period (P > .05). RESULTS: Figure 1 shows the shrinkage rate data for all materials. Statistical analysis showed no significant difference at any measuring point when the mixing techniques of the polyvinyl siloxane materials were compared. However, analysis showed significant differences for both hand- and cartridge-mixed materials when measurements at 30 minutes, 24 hours, and 72 hours were compared; the shrinkage rate increased significantly as time passed. Statistical analysis of the results of the polyether material showed no significant difference at 30 minutes, but at 24 and 72 hours, the cartridge-mixed material produced a statistically higher shrinkage rate. Analysis also showed significant differences for both hand- and cartridge-mixed materials when measurements at 30 minutes, 24 hours, and 72 hours were compared; shrinkage rate also increased significantly as time passed. CONCLUSION: We could not detect significant differences in dimensional changes when hand- and cartridge-mix techniques were compared at the same measuring time for the tested polyvinyl siloxane materials. The cartridge-mix technique for the polyether material showed significantly higher shrinkage at 24 and 72 hours, while the mean shrinkage rate of all six materials showed a significant time-dependent increase.

[Applicability of titanium in preparing dental prostheses for allergic patients]. / A titán, es alkalmazhatóságának sajátosságai fémallergiás betegek fogpótlásának készítésénél.

Owing to its excellent biocompatibility, titanium has been used in health care, including dental care, for a long time. The unalloyed light metal is a non-allergic one, it resists corrosion, has low heat conducting ability, it tastes neutral and is relatively cheap to apply. Titanium's biocompatibility may be associated with its fast oxidizing capacity, which can inhibit its binding with proteins. Due to titanium's oxidizing capacity, its applicability in dentistry is difficult, because such prostheses are not easy to cover with ceramics, which is essential for aesthetic reasons. The bond between the ceramic, developed specially for titanium, and the metal surface is weaker than in the case of NiCr alloys or alloys of noble alloys. The strength of the bond, however, meets ISO requirements, and, according to the latest literature, it can be further strengthened by surface treatment techniques and new bond systems. These solutions are aimed at stopping cavity formation on the titanium surface and in the oxide phase (which would lead to the disjunction of the oxide phase at the interface). Comparative studies have mentioned problems with right marginal closure and precision of fitting, still they have found titanium-based prostheses acceptable. According to data in the literature the ceramic fused to titanium, and removed partial dentures are artificial dental structures which may offer an inexpensive, still aesthetically and functionally acceptable solution for certain patients suffering from metal allergy.

[Comparative evaluation of the shrinkage of addition-type silicone impression material using hand-mix and cartridge-mix technique]. / Addíciós szilikon lenyomatanyag zsugorodásának összehasonlító vizsgálata pisztolyos és kézi keverés esetén.

Impression materials show shrink during polymerisation. The average shrinkage of C-silicon impression materials is 0.6-1% after 24 hours. The A-silicons show 0.15-0.2% shrinkage after 24 hours. Like in other chemical reactions, the ratio of the ingredients and the mixing can strongly effect the final properties of the polymerised material. In their study the authors compared the shrinkage of Promodent ASK low-viscosity A-type silicon impression material using hand mix and cartridge mix technique. The measurements were carried out according to ADA 19 specifications. The statistical analysis of the results did not show significant differences in the shrinkage between the two mix techniques after 30 minutes, 24 hours and 72 hours.