An In Vitro Study On The Fracture Resistance Of Teeth Restored With Casting Posts With Bonding Surfaces Treatment Before Cementation

Objective: This study is aimed at analyzing the effects of bonding surface treatments including sandblasting on the posts' surfaces and acid etching on root canal walls on the fracture resistance of teeth restored with casting posts and cores. Methods: Sixty-four recently extracted human mandibular single root first premolars were endodontically treated and randomly divided into eight groups of eight each. About 1.5mm ferrule was prepared for each of the teeth. The groups were divided into the following categories: Group A: no treatment on the bonding surfaces(control group); Group B: no treatment on the posts' surfaces and acid etching for 10 s on the root canal walls; Group C: no treatment on the posts' surfaces and acid etching for 30 s on the root canal walls; Group D: no treatment on the posts' surfaces and acid etching for 60 s on the root canal walls; Group E: sandblasting on the posts' surfaces and no treatment on root canal walls; Group F: sandblasting on the posts' surfaces and acid etching for 10 s on root canal walls; Group G: sandblasting on the posts' surfaces and acid etching for 30 s on root canal walls; Group H: sandblasting on the posts' surfaces and acid etching for 60 s on root canal walls. All the posts were cemented with zinc phosphate cement after treatment and all the specimens received casting metal crowns. Each specimen was embedded in acrylic resin and tested in a universal material testing machine. Statistical analysis of the data was carried out to show whether there was any significant correlation between the groups. One-way ANOVA and a LSD test were used to determine the significance of the failure resistance loads between groups. A nonparametric chi-square test was conducted for statistical evaluation of the mode of fracture. Results:1. The fracture resistance load in group B was compared with that in group A using the t-test, there was significant statistical difference between the two groups (p<0.01).2. The fracture resistance load in group C was compared with that in group A using the t-test, there is significant statistical difference between the two groups (p<0.01).3. The fracture resistance load in group D was compared with that in group A using the t-test, there is significant statistical difference between the two groups (p<0.01).4. The fracture resistance load in group E was compared with that in group A using the t-test, there is significant statistical difference between the two groups (p<0.01).5. The fracture resistance load in group B was compared with that in group F using the t-test, there is significant statistical difference between the two groups (p<0.01).6. The fracture resistance load in group C was compared with that in group G using the t-test, there is significant statistical difference between the two groups (p<0.01).7. The fracture resistance load in group D was compared with that in group H using the t-test, there is significant statistical difference between the two groups (p<0.01).8. One-way ANOVA was used to determine significant difference of the fracture resistance loads among groups B, C, D. Between-group differences in the fracture resistance load of teeth were significant (p<0.01). Then a LSD test was used to compare the fracture resistance loads between groups. Differences were significant between group B and group C (p<0.01). There were also significant differences between group B and group D (p<0.01). But differences were not evident between group C and group D (p>0.05).9. One-way ANOVA was used to determine significant difference of the fracture resistance loads among groups F, G, H. Between-group differences in the fracture resistance load of teeth were significant (p<0.01). Then a LSD test was used to compare the fracture resistance loads between groups. Differences were significant between group F and group G (p<0.01). There were also significant differences between group F and group H (p<0.01). But differences were not evident between group G and group H (p>0.05).10. Mode of fracture: nonparametric chi-square test was conducted for statistical evaluation of the mode of fracture. The result showed that there were significant differences between the control group and the test groups, while there were no significant differences among the test groups.Conclusions:1. Surface sandblasting to the casting posts resulted in significant higher fracture resistance than that without treatment.2. For the acid etching time, the effect of acid etching on the root canal wall for thirty seconds and sixty seconds is higher than that for ten seconds; while there is no significant statistical difference between 30 s and 60 s.3. Fracture resistance is higher if the sandblasting and acid etching were used in combination rather than the use of sandblasting or acid etching alone.4. Surface sandblasting to the casting posts and acid etching on the root canal wall could change the load distribution on roots.