ABSTRACT
AIM: To compare the resistance to torsion between two implant systems with internal hexagon connection, one using screw-retained abutments (Titanium Fix) and the other using cementable abutments (ITEC) under a tangential load. MATERIALS AND METHODS: An in vitro experimental study was carried out. Fourteen implants, seven implants from each system, were included in this study. The implants were placed at a 45-degree angle into metal blocks to simulate their position in the maxilla. Then, implants were subjected to a resistance test on a CMT5L universal testing machine, and the maximum load was applied to each sample. The maximum force with which the torsion was achieved in each sample was analyzed. The data were tested using the Shapiro-Wilk test and showed normal distribution. Student t-test was used to examine statistical significance between the two groups, and the p-value was set at P < 0.05. RESULTS: There was a statistically significant difference between the two groups (P = 0.001). ITEC implants with a cementable abutment showed greater flexural strength compared to the Titanium fix with a screwed abutment implant system. CONCLUSIONS: The cemented abutment showed more resistance to torsion against a tangential load in comparison with the screwed abutment.
ABSTRACT
OBJECTIVE: To determine the association between genetic factors and molar-incisor hypomineralisation (MIH) and/or hypomineralised second primary molars by means of a systematic review. DESIGN: A search was performed in Medline-PubMed, Scopus, Embase and Web of Science databases; manual search and search in gray literature were also performed. Selection of articles was performed independently by two researchers. A third examiner was involved in cases of disagreement. Data extraction was performed using an Excel® spreadsheet and independent analysis was performed for each outcome. RESULTS: Sixteen studies were included. There was an association between MIH and genetic variants related to amelogenesis, immune response, xenobiotic detoxification and other genes. Moreover, interactions between amelogenesis and immune response genes, and SNPs in the aquaporin gene and vitamin D receptors were associated with MIH. Greater agreement of MIH was found in pairs of monozygotic twins than dizygotic twins. The heritability of MIH was 20 %. Hypomineralised second primary molars was associated with SNPs in the hypoxia-related HIF-1 gene and methylation in genes related to amelogenesis. CONCLUSION: With very low or low certainty of evidence, an association was observed between MIH and SNPs in genes associated with amelogenesis, immune response, xenobiotic detox and ion transport. Interactions between genes related to amelogenesis and immune response as well as aquaporin genes were associated to MIH. With very low certainty of evidence, hypomineralised second primary molars was associated to a hypoxia-related gene and to methylation in genes related to amelogenesis. Moreover, higher agreement of MIH in pairs of monozygotic twins than dizygotic twins was observed.
