The aim of the study was to asses the resistance to vertical root fracture of endodontically treated teeth with two types of resin - based sealers (AH Plus and Endorez) when matched taper single cone technique is used, and to measure the maximum depth of dentinal tubule sealer penetration in teeth obturated with (Gutta - Percha /AH Plus) and (Resin - coated Gutta - Percha / Endorez).Materials and methods: Eighty single rooted teeth were used in this study. Teeth were sectioned leaving a root length of 13 mm. Sixty roots were used for fracture resistance test, and were divided into four groups (n=15); group I: (negative control) received no instrumentation nor obturation; groupII: (positive control) instrumented but not obturated; group III:obturated with AH Plus /Gutta -Percha points ; group IV obturated with Endorez / Endorez points. For scanning electron microscopic evaluation (SEM), the remaining twenty roots were divided into two groups (n=10) group A: obturated with AH Plus /Gutta - Percha points; group B: obturated with Endorez / Endorez points.All the instrumented teeth were prepared using Revo-S Ni-Ti rotary system and irrigated using 5 % NaOCl during instrumentation, then received a final flush of 17 %EDTA, followed by a final rinse of distilled water. Obturation was carried using single cone technique. For fracture resistance test, roots were mounted in acrylic blocks then, the blocks were mounted on the lower fixed compartment of Lloyd testing machine. The upper plate of the machine including a metal rod was then mounted directly over the canal opening of each root, which was subjected to a slowly increasing vertical load until the fracture occurred. The load at failure was recorded in newtons. Specimens for (SEM) evaluation were transversely sectioned at the apical, middle, and coronal thirds at 2, 5, and 9 mm from the apex respectively. Samples were then prepared for (SEM) evaluation to detect the maximum depth of dentinal tubule sealer penetration. Statistical analysis was performed.Results:A) For fracture resistance test:.There was statistically significant difference between the four groups;the negative control group (no instrumentation or obturation) showed the highest fracture resistance.AH Plus group showed higher fracture resistance than Endorez group. The positive control group (instrumented but not obturated ) showed the least fracture resistance B) For scanning electron microscopic evaluation:At the coronal as well as the middle segments, Endorez showed statistically significantly higher mean sealer penetration than AH Plus. No penetration was seen apically for both sealers. With AH Plus and Endorez sealers; coronal segments showed statistically significantly higher mean sealer penetration than middle segments.Conclusions:Instrumentation of the root canal significantly weakened the tooth structure to fracture. When used with matched-taper single cone technique, AH Plus and Endorez have the potential to reinforce endodontically treated teeth. Filling the canal with AH Plus sealer increased the in vitro resistance to fracture of endodontically treated teeth when compared with Endorez sealer. The depth of dentinal tubule penetration of sealer cements was influenced by the chemical composition of the material. Endorez sealer displayed significantly greater dentinal tubule penetration than AH Plus.