This in press article needs final revision Sharafeddin F, et al. J Dent Shiraz Univ Med Scien. 1 Original Article Comparison of Shear Bond Strength of Three Types of Glass Ionomer Cements Containing Hydroxyapatite Nanoparticles to Deep and Superficial Dentin Farahnaz Sharafeddin, DMD, MScD 1 ; Ali Asghar Alavi, DMD, MScD 1 ; Saba Siabani, DMD, MScD 2 ; Mina Safar 2 , DMD, MScD; 1 Dept. of Operative Dentistry, Biomaterials Research Center, School of Dentistry, Shiraz University of Medial Sciences, Shiraz, Iran. 2 Postgraduate Student, Dept. of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. KEY WORDS Glass ionomer cements; Hydroxyapatites; Nanoparticles; Shear strength; Received: Revised: Accepted: ABSTRACT Statement of the Problem: The clinical success of glass ionomer cement (GIC) restora- tions depends on the strength of its bonding to dentin, yet the bond strength of nanohy- droxyapatite (nHAp) added GIC to dentin needs to be investigated. Purpose: This study aimed to assess if the type of GIC containing nHAp and dentin depth can affect the shear bond strength (SBS). Materials and Method: In this experimental study, 60 freshly extract intact third molars were randomly divided into two main groups of flat occlusal dentin with different cuts as superficial (S): just below the dentinoenamel junction (DEJ) and deep (D): 2mm be- low DEJ. After conditioning with 20% polyacrylic acid, each group randomly assigned to the tested GIC (n=10) subgroups as 1: Fuji IX Extra+nHAp, 2: Fuji II LC+nHAp and 3: Zirconomer+nHAp. Plastic tubes were placed on the pre-treated surfaces and filled with one of the GIC, then stored in an incubator at 37 o C under 100% humidity for 24hr. The specimens were thermocycled at5/55 o C for 500 cycles and subjected to shear bond strength (SBS) test using a universal testing machine (1 mm/min). The data analyzed by Mann-Whitney and Kruskal-Wallis test (p< 0.05). Results: The means of SBS of Fuji II LC+nHAp was significantly higher than Fuji IX+nHAp and Zirconomer+nHAp both in superficial and deep dentin ( p< 0.05). The means of SBS of Fuji IX Extra+nHAp and Zirconomer+nHAp subgroups in superficial dentin were higher than deep dentin, this differences was statistically significant (p= 0.0001 and p= 0.009, respectively). Conclusion: It can conclude that SBS was influenced by type of GIC, and depth of den- tin. Corresponding Author: Siabani S, Postgraduate Student, Dept. of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. Tel: +98-83-38361512, +98-918-3894170 Email: sabasiabani@yahoo.com Cite this article as: Introduction Glass ionomer cement (GIC) is widely used in clinical dentistry due to its unique properties which include low coefficient of thermal expansion, fluoride release, good biocompatibility and chemical adhesion [1-2]. Despite these attractive features, GICs have some dis- advantages such as poor mechanical properties that limited their use in stress-bearing areas [1, 3-4]. Since GICs were introduced, in order to improve its physical and mechanical properties and to make it more suitable for clinical use, GIC has undergone several formula changes, that led to produced resin modified glass ion- omer (RMGI) and zirconia reinforced glass ionomer (Zirconomer), but sufficient enhancements in mechan- ical and chemical properties have not yet been achieved [4-6]. The research for more biocompatible material led to the use of hydroxyapatite (HAp) as a biocompatible