Effect of cyclic loading on fracture strength of endodontically treated teeth restored with conventional and esthetic posts

Abstract

Introduction:Esthetic post and core systems were recently introduced. There are few reports regarding their behavior under cyclic loading.Objectives:This study compared the effect of cyclic loading on survival rate, residual strength and mode of fracture of endodontically treated teeth restored with esthetic and direct metallic post systems subjected to mechanical cyclic loading.Materials and Methods:Thirty canines were endodontically treated, decoronated and prepared for metal free ceramic crowns, leaving 1.5 mm of dentin for ferrule effect. They were distributed in 3 groups and restored as follows: group 1 with zirconia posts (Cosmopost) and glass-ceramic cores (IPS Empress Cosmopost); group 2 with fiber reinforced composite posts (FibreKor) and group 3 with titanium posts (AZthec Anchor). Direct resin composite (Build It FR Resin Composite) was used as core in groups 2 and 3. All specimens were restored with all ceramic crowns (IPS Empress 2). A resin cement/adhesive system (Cement It/Bond It Primer A+B) was used to lute the posts to root canals and metal free porcelain crowns to the teeth preparation. Specimens were subjected to mechanical load of 250 N for 500,000x at a frequency of 1.7 Hz and then to static load until failure in a universal testing machine. Data were analyzed using One-way ANOVA and Fischer Exact tests α=0.05.Results:All groups had 100% survival rate after cyclic loading; fracture strength values (SD) in N were: group 1 = 886.5(170.6), group 2 = 762.2(113.6) and group 3 = 768.9(72.9); there was no difference among groups (p=0.08); the percentage of mode of favorable fracture found was: group 1 = 60%, group 2 = 90% and group 3 = 50%; there was no correlation between the mode of failure and post and core system used (P=0.142).Conclusions:Esthetic post and core systems showed statistically equivalent fracture strength values, mode of failure and survival rate compared to conventional direct metallic post and resin composite core system after cyclic loading.

Zirconia ceramic post systems: a literature review and a case report

“…Fracture strength The fracture strength of zirconia posts was evaluated using natural teeth in 15 studies 12,14,33,39,[41][42][43]48,49,51,55,58,[60][61][62] ( Table 1) and artificial roots in three studies 29,53,59) , and according to core material (composite resin core versus ceramic core) in nine studies 35,40,[44][45][46][47]52,54,57) (Table 2). Table 1 shows that the fracture strengths of teeth with zirconia posts and composite cores ranged between 300 N and 700 N. However, when ceramic cores were used, these values ranged between 800 N and 1500 N. These results concurred with studies which evaluated the fracture strength of zirconia posts according to core material 35,40,44,45,54) .…”

Ferrule Effect: A Literature Review

“…After subjecting the specimens only to mechanical loading, there was no difference in the survival rate (100%) among teeth with a 1.5-mm ferrule restored with zirconia, FRC, or titanium post (47). After cycling loading, specimens were exposed to an oblique, static load until failure, and, likewise, all systems showed statistically equivalent fracture strength values and modes of failure.…”

“…Type of Post and Core System and Final Restoration. The effectiveness of different procedures for restoring the function of endodontically treated teeth subjected to static (13,30,32,(40)(41)(42)(43)(44)(45)(46) or fatigue loading (47)(48)(49)(50)(51)(52) has been widely investigated. Combinations of different ferrule designs and various post and core systems and final restorations were tested in an attempt to find the best treatment option that would provide the highest fracture resistance and the most favorable fracture pattern of severely compromised teeth.…”

“…However, the results were controversial. Some research reported that changes in stiffness and design associated with post and core material did not significantly influence fracture resistance as long as sufficient dentine structure remained (13,41,47,49,52), whereas other studies pointed out that post type may have an impact (32,(42)(43)(44)(45)50).…”

Durability of fiber-post and resin core build-up systems

“…FRC posts offer a number of advantages over metal posts due to their modulus of elasticity being closer to that of dentin and superior esthetic quality. Teeth restored with FRC posts show better resistance to fracture propagation than teeth restored with prefabricated or cast metal posts 2) . Endodontically treated teeth reinforced with a prefabricated fiber post have shown lower incidences of root fracture 3,4) .…”