Background: The diagnosis of dentin hypersensitivity is done by exclusion. Yet no universally accepted gold-standard treatment, which reliably relieves the pain of dental hypersensitivity in the long term and satisfy both the dentist and the patient, was found. Objective: to compare the effect of photo polymerized versus chemical cured glass ionomer based desensitizing agents in respect to: a) Their ability to occlude the dentinal tubules. b)Their depth of penetration inside the dentinal tubules. Materials and Methods: A total of 20 permenant molars were selected, promximal enamel was removed, EDTA gel (17%) was applied for three min. The prepared fourty surfaces were divided into two groups. Half of both surfaces received different desensitizing agent while the other half was left untreated as a control. Each group was divided into four subgroups, the first subgroup faced abrasion challenge, the second faced thermocycling, third faced both abrasion and thermocycling and the last was left as a control group. An ESEM at 2000 magnification was used to observe the patent dentinal tubules, and a digital Analysis program was used to evaluate the patency. Results: showed that the percent of obliteration of dentinal tubules when the samples faced abrasion only was higher in CGI than RMGI, same result when the samples face termocycling only it was still higher in CGI than RMGI. Whereas there was no statistical significance when the samples received both abrasion and thermocycling. Conclusion: 1-The abrasion resistance and the ability of CGI to withstand thermocycling makes it better in occluding dentinal tubules rather than RMGI. 2-Although the resinous component of RMGI allows better penetration inside the tubules, yet the lower abrasion resistance and poor resistance to thermocycling made the material inferior in maintaining an efficient dentinal tubules seal.