Biocompatibility assessment of spark plasma-sintered alumina-titanium cermets.

Alumina-titanium materials (cermets) of enhanced mechanical properties have been lately developed. In this work, physical properties such as electrical conductivity and the crystalline phases in the bulk material are evaluated. As these new cermets manufactured by spark plasma sintering may have potential application for hard tissue replacements, their biocompatibility needs to be evaluated. Thus, this research aims to study the cytocompatibility of a novel alumina-titanium (25 vol. % Ti) cermet compared to its pure counterpart, the spark plasma sintered alumina. The influence of the particular surface properties (chemical composition, roughness and wettability) on the pre-osteoblastic cell response is also analyzed. The material electrical resistance revealed that this cermet may be machined to any shape by electroerosion. The investigated specimens had a slightly undulated topography, with a roughness pattern that had similar morphology in all orientations (isotropic roughness) and a sub-micrometric average roughness. Differences in skewness that implied valley-like structures in the cermet and predominance of peaks in alumina were found. The cermet presented a higher surface hydrophilicity than alumina. Any cytotoxicity risk associated with the new materials or with the innovative manufacturing methodology was rejected. Proliferation and early-differentiation stages of osteoblasts were statistically improved on the composite. Thus, our results suggest that this new multifunctional cermet could improve current alumina-based biomedical devices for applications such as hip joint replacements.

Bacterial and dye penetration through interim restorations used during endodontic treatment of molar teeth.

INTRODUCTION: The purpose of this study was to investigate the association between dye and bacterial penetration through interim restorations used during endodontic treatment. METHODS: Sixty-four extracted human teeth were used, with 2 teeth each as positive and negative controls. Endodontic access with a mesio-occluso-distal cavity was prepared. Palatal cusps of maxillary molars and buccal cusps of mandibular molars were removed. Cotton was placed over the canals and covered with Cavit. Thirty teeth were restored with Ketac Silver (KS) and 30 with KS reinforced with a stainless steel band (KSSB). Samples were submersed in India ink mixed with brain heart infusion broth containing Streptococcus gordonii. After 3 months of simulated chewing, structural integrity and dye and bacterial penetration were assessed. RESULTS: Positive controls had both dye and bacterial penetration. Negative controls had no dye or bacterial penetration. All KS restorations debonded, whereas 18 KSSB restorations (60%) debonded. KS restorations were 1.67 times more likely to debond than KSSB restorations (Fisher exact test). KS was 1.3 times more likely to have dye penetration than KSSB (Fisher exact test) and 3 times more likely to have bacterial penetration, although not statistically significant (chi(2) test). Overall, 88.3% of specimens had dye penetration, and 20% had bacterial penetration. This 68.3% difference indicated no association between dye and bacterial penetration (exact McNemar test). CONCLUSIONS: Stainless steel bands helped maintain structural integrity of KS restorations under masticatory function. Bands helped prevent dye penetration but not bacterial penetration. There was no association between dye and bacterial penetration.

Experimental model: dye penetration of extensive interim restorations used during endodontic treatment while under load in a multiple axis chewing simulator.

The purpose of this study was to design an experimental model that allowed extensive endodontic interim restorations to be tested for dye penetration while under simulated masticatory load. Extracted premolar teeth had standardized mesio-occluso-distal cavities prepared, and the root canals were instrumented. A cotton wool pellet was placed in the pulp chamber, and the cavities were restored with Cavit, IRM, Ketac-Fil Plus, Ketac-Silver, or composite resin (Z100). They were subjected to the equivalent of 3 months of clinical load while exposed to methylene blue dye. Results of this study could not support IRM as a suitable interim endodontic restorative material to use in extensive cavities. The dye penetration in the Ketac-Fil Plus and Ketac-Silver specimens was not predictable, and the results suggested Cavit and Z100 composite resin require further investigations as potentially useful materials for this purpose.

Condicionamento de superfície cerâmica aluminizada: estudo em microscopia eletrônica de varredura e análise EDS / Alumina ceramic surface treatment: scanning electron microscopy study and EDS analysis

Este estudo avaliou, por meio de microscopia eletrônica de varredura (MEV) e análise de composição EDS, o padrão morfológico e a deposição de sílica da superfície de uma cerâmica aluminizada (In-Ceram Alumina) sob quatro condições de tratamento de superfície: 1) sem tratamento; 2) jateamento com óxido de alumínio; 3) Sistema Rocatec; 4) Sistema CoJet. Analisando as imagens obtidas pelo MEV, foi possível constatar que o padrão de irregularidades da superfície dos grupos 2, 3 e 4 foi semelhante. Entretanto, nos grupos 3 e 4 foi observado pelo EDS aumento no conteúdo de sílica na superfície cerâmica, em comparação ao grupo 1 e 2. Esses resultados sugerem que os tratamentos com os sistemas Rocatec e CoJet podem contribuir para a união com cimentos resinosos, pois a sílica interage com o silano (Rocatec-Sil e ESPE-Sil) e este com os cimentos resinosos, por meio de uniões siloxanas.

Alternatives to silver amalgam and resin composite in pediatric dentistry.

Silver amalgam has become a less attractive dental restorative material for restoration of primary teeth. After many decades of scientific and nonscientific controversy, use of silver amalgam for primary teeth is waning, not because of its mercury content but because dentistry has come up with more suitable materials. This article reviews the development and use of glass-ionomer silver-cermet cements, resin-modified glass-ionomer cements, and polyacid-modified resin composites (compomers) for restoration of primary teeth.

Sealing ability of three materials used to repair lateral root perforations.

Thirty-five extracted single-rooted human teeth were decoronalized, root filled with AH-26 and gutta-percha, and perforated at the apical one third level. Repairs of the lateral perforations were carried out with three materials: amalgam plus cavity varnish, EBA cement, and silver glass-ionomer cement. Negative controls were not perforated and positive controls had unrepaired perforations. The roots were then implanted subcutaneously in rats for 5 days to place the materials in a surgical environment. Following retrieval, the roots were placed in a solution containing 20 microCi/ml of calcium-45 for 7 days to measure microleakage. They were rinsed, sectioned, and autoradiographs of the repaired perforations were made. The autoradiographs were projected onto a screen and the extent of penetration of the radioisotope measured. Statistical analysis showed that the EBA cement group exhibited significantly less leakage than the silver glass-ionomer cement group (p < 0.05). No differences were found between the other groups. It was concluded that EBA cement provides a superior seal in lateral root perforations to silver glass-ionomer cement while amalgam was intermediate between the two.

Effect of different glass ionomers on the acid production and electrolyte metabolism of Streptococcus mutans Ingbritt.

In order to study the effects of different glass ionomers on the metabolism of Streptococcus mutans, test slabs of freshly mixed conventional glass ionomer (Fuji), silver glass ionomer (Ketac-Silver), composite (Silux), and 2-week-old Fuji were fitted into the bottom of a test tube. A plaque-like layer of S. mutans strain Ingbritt was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% (w/v) sucrose solution. For freshly mixed Fuji and Ketac-Silver, the pH fall was significantly smaller than for old Fuji and composite. These materials also released the largest amount of fluoride into the fluid phase. Incubation with glass ionomer materials led to an increase in the cellular concentration of fluoride in bacteria, but intracellular fluoride did not correlate with the fall in pH. The lowest pH was associated with the lowest cellular magnesium content. Ketac-Silver released large amounts of calcium in the fluid phase, and the cellular calcium content was doubled in this group. The results show that freshly mixed glass ionomers affect acid production and electrolyte metabolism of S. mutans in vitro. The effect of conventional glass ionomer, however, seems to disappear after a few weeks. The effects of calcium and silver released by cermet glass ionomer deserve further study.