Cusp fracture resistance of maxillary premolars restored with the bonded amalgam technique using various luting agents.

Objective. This in vitro study uses measurements of fracture resistance to compare maxillary premolars restored with the bonded amalgam technique using a new resin luting cement, glass ionomer, and resin-modified glass ionomer as the bonding agents. Materials. Eighty-five sound maxillary premolars were selected and randomly assigned to one of five test groups of 17 teeth each. One group of intact teeth served as the control. The remaining groups were prepared to a standard cavity form relative to the dimensions of the overall tooth and restored with amalgam alone or a bonded amalgam using one of three luting agents: RelyX Arc (a new resin luting cement), RelyX luting (a resin-modified glass ionomer), or Ketac-Cem æ (a glass ionomer) as the bonding agents. Each tooth was then subjected to compressive testing until catastrophic failure occurred. The mean loads at failure of each group were statistically compared using ANOVA with a post hoc Bonferroni test. Results. It was found that regardless of the luting cement used for the amalgam bonding technique, there was little effect on the fracture resistance of teeth. Conclusion. Cusp fracture resistance of premolars prepared with conservative MOD cavity preparations is not improved by using an amalgam-bonding technique compared to similar cavities restored with amalgam alone.

In vitro evaluation of the retention of zirconia-based ceramic posts luted with glass ionomer and resin cements

The retention of zirconia-based ceramic posts (CosmoPost system) luted with glass ionomer and resin cements was evaluated. Thirty two extracted, caries-free, unrestored teeth were selected and stored in chlorhexidine and water solution. The teeth were endodontically treated and randomly assigned to two groups (n=16). Each tooth was decoronated and prepared to a depth of 10.0 mm from root surfaceto receive a 1.4 mm diameter zirconium dioxide post. Each group had posts cemented with either glass ionomer cement (Fuji I) or resin cement (Variolink II). The post/teeth specimens were embedded in resin blocks and subjected to tensile testing. The tensile force required to dislodge the cemented posts in a tensile testing machine was recorded. The mean stress values of both groups were analyzed for statistical differences using ANOVA and Student’s t-test. Significance level was set at 5 percent. Mean peak forces at failure (N) and standard deviation for the tested cements were the following: Fuji I = 121.8 (plus or minus 17.4) and Variolink II = 228.1 (plus or minus 36.8). Posts luted with the resin cement presented statistically significant higher tensile bond strength than those retained with glass ionomer (p<0.05). It may be concluded that zirconia posts cemented with resin-based cement (Variolink II) failed at statistically significant higher valuescompared to those cemented with glass ionomer cement (Fuji I). Regardless of the cement type, the posts failed adhesively at the cement/post interface when subjected to a tensile force.

An in vitro evaluation of shear bond strengths of glass ionomer/amalgam combinations

Purpose: The purpose of this study was to assess the shear bond strength of amalgam when bonded to dentine with various cements. Materials and Methods: Eighty human molars were divided into five groups and ground dentine surfaces treated, with one of five cements (Fuji I, Vitrebond, Rely X, Fuji II and Panavia F). Spherical amalgam (Tytin) was condensed onto the unset cement and shear bond strengths were measured after one week. Results: The mean shear bond strength of Panavia F (25.3 MPa) was significantly higher compared with Fuji I (16.8 MPa), Fuji II (10.3 MPa) and Vitrebond (5.1 MPa) however there was no significant difference with Rely X (19.0 MPa). Conclusion: The combination of a resin modified glass ionomer luting cement with a spherical alloy may enhance bonding of amalgam to dentine.