An evaluation of the Effect of Surface Treatment On Amalgam Repair


The purpose of this in vitro study was to evaluate the effect of different surface treatments on shear bond strength of repaired amalgam using two types of amalgam. 120 acrylic blocks (2.7cm diameter by 2.0cm high) were constructed from cold cure resin, each one contained cylindrical hole (7mm diameter by 2mm high) on its circular face that filled with amalgam. The samples were divided into immediate repair group and delayed repair group, which was stored and incubated at 37C0 for one month. After aging the amalgam surface of delayed repair was finished with carbide bur and polished with abrasive rubber cup then divided into three groups according to the surface treatment that include group with out surface treatment, group roughened with diamond bur and the last group was abraded with aluminum oxide (50m) particles size, both immediate and delayed repair were further subdivided according to the type of amalgam used into three subgroups. The repair procedure was done by using a Teflon split mold which containing an opening (3mm diameter by 5mm high) then all the samples were storage and incubated at 37C0 for one week prior to testing.Testing was done by applying shear force at the interface between the initial and repair amalgam with special designed chisel shape rod by using Zwick testing machine at across head speed of 5mm/min.Analysis of the results showed that the shear bond strength in immediate repair were significant higher than of delayed repair and the group roughened with diamond bur is higher than group treated with aluminum oxide and untreated group.The shear bond strength of delayed repair of amalgam is less than that of immediate repair, the surface produced by roughening the samples with a diamond bur will give best strength than the surface treated by aluminum oxide and untreated surface (smooth surface) and the same types of amalgam restorations used in amalgam repair gave better result than different type of amalgam.