Introduction:
Maintenance of primary teeth has a special importance for development of occlusion and arc stability. Primary teeth which have lost a lot of tooth structure are restored routinely with stainless steel crowns.Bonded restorations reinforce the remnant structure of tooth and increase the fracture strength.The purpose of this study was to determine the fracture strength of pulpotomized primary molars after restoring with Coremax II and Compoglass.  
Materials & Methods:
In this parallel in vitro interventional study, 60 extracted second primary molars, were selected. After the teeth were mounted in self-curing acrylic resin, the standard pulpotomy was performed. The teeth were divided  into 3 groups of  20. Group A was restored  with Coremax II ,group B with Compoglass and group C(control) with  amalgam. All groups were subdivided into 2 subgroups for load cycling Subgroups A₁, B₁ and C₁ were regarded as baseline without load cycling. Subgroups A₂, B₂ andC₂ were loaded for a period of 5 days load cycling. After that, the specimens were placed in Incubator for 24 hours. Finally all groups were fractured in the Instron Machine. compressive test was performed with the round Cross head speed of 5-mm/min.All specimens were examined for type of fracture(adhesive, cohesive) with use of a steriomicroscope (x16).
Quantitative  data analysis was done using ANOVA and Duncan's test with a 95% significance level. Chi-square test was performed for evaluation of kind of fracture.
Results:
There was an interaction between two factors  of time and material (P<0.05). The time interval had a  significant effect on mean fracture strengths of Coremax II and amalgam(P<0.05). The most fracture strength was observed at  base line. Kind of material had a significant effect on fracture strength. At baseline, Compoglass had the least  mean fracture strength (97.19 kg) and Coremax II had the greatest one (131.39). After 5 years there was  no significant difference in fracture strength between amalgam and Compoglass, but the fracture strength of Coremax was significantly higher than the others. (P<0.05).
There was a correlation between kind of fracture and material. In amalgam, 100% of fracture was of adhesive and in Compoglass, 60% of cohesive type while in Coremax II, 85% of the fracture was of adhesive type.
Conclusion:
According to  this study and because of high fracture strength of teeth  restored with  Core maxII ,this material is an acceptable restoration material just for restoration of  pulpotomized primary molars.