Objective To investigate fracture resistance and fracture patterns of maxillary anterior endodontically treated teeth restored with two different shapes of glass fiber post systems.Methods Twenty-four human sound maxillary anterior teeth of similar size were collected,and randomly divided into 3 groups,8 teeth each.After endodontical treatment,they were given the following treatments:Group A:parallel glass fiber posts (coltene parapost fiber lux) and composite core;Group B:taper glass fiber posts (coltene parapost taper lux) and composite core; Group C (control group):intact endodontically treated teeth.Teeth in Groups A and B reserved 2 mm dentin ferrule.Then the teeth were prepared and restored with IPS e.max Press all ceramic crowns.All the teeth were embedded in acrylic resin 2 mm below the cementoenamel junction (CEJ),with the silicon impression material stimulating periodontal membrane.All the specimen were loaded under a universal testing machine,at the palatal junction of incisor third and middle third,with an angle of 135 degree to the longitudinal axis of the tooth until fracture occurred,at a cross-head speed of 1.0 mm/min.Fracture loads and patterns were recorded.Statistical analysis was performed using SPSS software.Results The mean fracture loads in the three groups were as follows:(468.8±142.5) N,(440.2±202.7) N,and (459.0±147.6) N,respectively.There was no significant difference in fracture loads among groups (P＞0.05).The incidence of unfavorable fracture in Group A was higher than Groups B and C.Conclusions There is no significant difference in fracture strength between parallel and taper fiber post groups.However,the group with parallel fiber posts demonstrates a higher risk of unfavorable fracture than the group with taper fiber posts,which indicates that taper fiber posts are more favorable to preserve the remaining tooth structure.