ผลของจำนวนและความยาวเดือยฟันคอมโพสิตเสริมเส้นใยต่อความต้านทานการแตกในฟันกรามน้อยบน / พิราวรรณ จึงพิทักษ์ = Effect of number and dowel length of fiber-reinforced composite posts on fracture resistance in maxillary premolars / Pirawan Chungpituk
The objective of this study was to determined the effect of number and dowel length of fiber-reinforced composite posts on fracture resistance and mode of failure in maxillary premolars. Forty maxillary premolars were sectioned 2 mm above the buccal cemento–enamel junction and then endodontically treated. All teeth were randomly divided into four groups: Group 1 restored with 1 post, 8 mm length at palatal canal. Group 2 restored with 2 posts, 8 mm length at buccal and palatal canal. Group 3 restored with 1 post, 4 mm length at palatal canal. Group 4 restored with 2 posts, 4 mm length at buccal and palatal canal. FibreKleer® posts and full metal crowns were cemented with bonding agent; Excite® DSC and resin cement; Variolink® II . All specimens were tested the fracture resistance using universal testing machine (Instron®). The compressive load was applied at 45 degrees to the long axis of the tooth. The crosshead speed is 0.5 mm/min until tooth fracture occurred. A fracture load and fracture mode were also recorded. Statistical analysis was performed using two-way ANOVA and Tukey multiple comparison (p<0.05). The results showed that the fracture resistance of group 1 was statistically significant different from group 2 (p=0.008) but there was not different from group 3 and 4. No significant differences were identified among group 2, 3 and 4. The oblique root fracture at the end of the posts were found in all groups. The most of fracture line of group 1, 2 and 4 occurred at middle 1/3 whereas that of group 3 occurred at coronal 1/3 more than others. From the result of this study, it can be concluded that fracture resistances of teeth restored with 1 post were more than teeth restored with 2 posts. However, the fracture resistances of teeth restored with post length 4 mm and 8 mm were not different.