Journal of Dental Medicine

Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins have an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS) between targis (a ceromer) and two alloys (noble and base metal) was studied and the effect of thermocycling on the bond investigated.

Materials and Methods: In this experimental study, alloys samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the alloys. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance.

Result: The studied alloys did not differ significantly, when the samples were not thermocycled (P=0.136) but after thermocycling a significant difference was observed in SBS of resin to different alloys (P=000.1). Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003). There was a significant difference in SBS before and after thermocycling in noble alloys (P=0.009), but this was not true in base metals (P=0.29). Maximum SBS (19.09 Mpa) belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa) was seen in Degubond 4 after thermocycling.

Conclusion: The effect of thermocycling in reducing bond strength of resin to metal depends on the type of alloy. The noble metal studied is significantly affected by thermal tensions.