Gingival fibroblasts behavior on bioactive zirconia and titanium dental implant surfaces produced by a functionally graded technique

Abstract Adding a biological apatite layer to the implant surface enhances bone healing around the implant. Objective This study aimed to characterize the mechanical properties and test human gingival fibroblasts behavior in contact with Zirconia and Titanium bioactive-modified implant materials. Methodology 6 groups were considered: Titanium (Ti6Al4V), Ti6Al4V with 5% HA and 5% ßTCP, Zirconia (YTZP), YTZP with 5% HA and 5% ßTCP. For each group, we produced discs using a novel fabrication method for functionally graded materials, under adequate conditions for etching and grit-blasting to achieve equivalent surface microroughness among the samples. Surface roughness (Ra, Rz), water contact angle, shear bond strength, and Vickers hardness were performed. Human gingival fibroblasts immortalized by hTERT gene from the fourth passage, were seeded on discs for 14 days. Cell viability and proliferation were assessed using a resazurin-based method, and cellular adhesion and morphology using field emission gun scanning electron microscopy (FEG-SEM). After 3 days of culture, images of fluorescent nucleic acid stain were collected by confocal laser scanning microscopy (CLSM). Results Results were presented as mean ± standard deviation (SD). We compared groups using one-way ANOVA with Tukey's post-hoc test, and significance level was set at p<0.05. After 14 days of culture, cell viability and proliferation were significantly higher in YTZP group than in other groups (p<0.05). Samples of YTZP-ßTCP presented significantly higher wettability (p<0.05); yet, we observed no improvement in cell behavior on this group. Fibroblast spreading and surface density were more evident on YTZP specimens. Adding calcium-phosphate bioactive did not alter the tested mechanical properties; however, Ti6Al4V material shear bond strength was statistically higher than other groups (p<0.05). Conclusion Adding bioactive materials did not improve soft-tissue cell behavior. When compared to other zirconia and titanium groups, pure zirconia surface improved adhesion, viability and proliferation of fibroblasts. Cell behavior seems to depend on surface chemical composition rather than on surface roughness.

Porphyria Cutanea Tarda and HFE Gene Mutations in Argentina.

Aims: Porphyria Cutanea Tarda (PCT), the most common of porphyrias is triggered by several factors, including iron overload. Type I Hereditary Hemochromatosis is inherited as an autosomal recessive trait of the mutation p.C282Y or as a compound heterozygous form p.C282Y/p.H63D in HFE gene. Our aim was to study the frequency of HFE mutations in Argentinean PCT patients and in control subjects. Place and Duration of Study: CIPYP, CONICET, Hospital de Clínicas José de San Martín: Av. Córdoba 2351, 1º subsuelo, Buenos Aires, Argentina (1120). Between March 2008 and March 2010. Methodology: We analyzed HFE mutations in 103 PCT patients (67 males, 36 females) and in 93 control subjects (63 males and 30 females). PCT patients were classified as familial, sporadic or Type III PCT measuring URO-D activity in red blood cells. HFE mutations were detected by amplification and automatic sequencing of exons 2 and 4 in the HFE gene. In some cases p.H63D and p.C282Y mutations were also detected by digestion with restriction enzymes (Mbo I for p.H63D and Rsa I for p.C282Y), followed by 3% polyacrilamide gel electrophoresis. Results: In PCT group, 34.9% carried mutation p.H63D (26.2% heterozygous, 5.8% homozygous and 2.9% as p.C282Y/p.H63D) and 7.8% carried mutation p.C282Y (2.9% in heterozygocity, 1.9% in homozygocity and 2.9% as p.C282Y/p.H63D). In the control group, 30.1% carried p.H63D (28% in heterozygous and 2.1% in homozygous), and 5.4% had p.C282Y in heterozygosity. There were no significant differences between sporadic and familial PCT and neither between PCT and control groups. Our findings are in agreement with the prevalence of the Mediterranean origin of our patients, where p.C282Y mutation is less common than p.H63D mutation. Conclusion: We conclude that mutations in HFE gene do not play a relevant role in the triggering of PCT in our country.