fracture resistance of structurally compromised premolar roots restored with single and accessory glass or quartz fiber posts

background: glass and quartz fiber posts are used in restoration of structurally compromised roots. accessory fiber posts are recently introduced to enhance the fiber post adaptation. this study evaluated the effectiveness of glass versus quartz accessory fiber posts. materials and methods: in this experimental study, 40 mandibular premolar roots with similar dimension (radius of 3.5 ± 0.2 mm and length of 13 ± 0.5 mm) were selected and their root canals were flared until 1.5 mm of dentin wall remained. they were randomly assigned to four groups ( n = 10) and restored as follows: exacto glass fiber post (ex), exacto glass fiber post + 2 reforpin accessories (exr), d. t. light quartz fiber post (dt), and d. t. light quartz fiber post + 2 fibercone accessories (dtf). all posts were cemented with duo-link resin cement and the cores were built with the particulate filler composite. following 1-week water storage, specimens were subjected to fracture loads in a universal testing machine. the maximum loads and failure modes were recorded and analyzed with the two-way analysis of variance (anova) and fisher’s exact tests (a = 0.05). results: the mean fracture resistance values ( n ) were 402.8 (ex), 378.4 (exr), 400.1 (dt), and 348.5 (dtf). two-way anova test showed neither reinforcing method ( p = 0.094), nor post composition ( p = 0.462) had statistically significant differences on fracture resistance of the structurally compromised premolar teeth. fisher’s exact test also demonstrated no statistically significant difference regarding two variables ( p = 0.695). core fracture was the most common failure mode (62.5%). conclusion: glass and quartz fiber posts with or without accessories restored the weakened premolar roots equally. key words: accessory fiber post, compromised roots, fracture resistance, glass, quartz