ABSTRACT
PURPOSE: The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS: Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). RESULTS: The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION: Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.
Subject(s)
Cementation , Dental Cements , Resin CementsABSTRACT
Chlorhexidine solution is one of the widely used mouth antiseptic liquid that prevents teeth tissue damage and also has application as a root canal antiseptic. In this study, cytotoxicity of 2% chlorhexidine solution is compared with another root canal antiseptic, calcium hydroxide powder. Cell cytotoxicity of both chemicals was assessed on cultured L929 fibroblastic cell line for 1, 12, 24, 48 and 72 hours using MTT assay [Methyl tetrazolium bromide assay]. Untreated L929 cells were used as a negative control group. MTT results were recorded by ELISA reader and analyzed using one-way ANOVA statistical tests. Cytotoxicity of studied chemicals showed significant difference in various dilutions and times [1, 12, 24, 48 and 72 h]. The highest cytotoxic effect of 2% chlorhexidine solution was observed in concentration of 0.016% for 72 h. Treatment of cells with 0.016% of 2% chlorhexidine liquid and calcium hydroxide powder for 72 hours showed 80% and 45% cytotoxicity, respectively. Cytotoxicity of calcium hydroxide is significantly less than 2% chlorhexidine liquid and then application of calcium hydroxide powder as root canal antiseptic is recommended