Adhesive procedures have changed the way to restore endodontically treated teeth (ETT). It started with the shift from cast post-and-core to fiber post. The original focus on strength also shifted towards failure modes, revealing that catastrophic failures are still a concern when restoring endodontically-treated teeth even with fiber posts. As an alternative, postless approaches have been proposed in order to improve the chances of repair. The goal of this critical review is to present a survey of the current knowledge on adhesive approaches to restore endodontically treated teeth with and without extensive coronal tissue loss. The preservation of tooth structure of endodontically treated teeth is paramount. Partial versus full coverage of ETT, the role of the ferrule, the post type effect on catastrophic failures and postless alternatives as endocrowns and postless build-ups are reviewed. There is a consensus that the remaining tooth structure plays an important role in ETT survival, although the current literature still is contradictory on the influence of post type on root fractures as well as the benefits of avoiding a post or partially restoring a tooth. More clinical studies should be carried out with the modern postless adhesive alternatives to conventional approaches.

Multiphase resin composite materials have been advocated as an alternative to reinforced ceramics but limited information is available to date on their stability. This in vitro study evaluated the effect of axial and lateral forces on the strength of endocrowns made of Li2Si2O5 and multiphase resin composite. Sound human molars (N=60, n=10 per group) were randomly divided into 6 groups: Group C: Control, no preparation or restoration; Group LI: Endocrown made of Li2Si2O5 (IPS e.max CAD) and Group LA: Endocrown made of multiphase resin composite material (Lava Ultimate). After decapitation and endodontic preparation, immediate dentin sealing was performed. Following CAD/CAM fabrication, their cementation surfaces were silica coated (CoJet System) and silanized (ESPE-Sil). Endocrowns were then adhesively cemented (Variolink II). All specimens were thermocycled (×10,000 cycles). While half of the specimens in each group were subjected to axial (C(A), LI(A), LA(A)), the other half was subjected to lateral static (C(L), LI(L), LA(L)) loading (1mm/min). Failure type and location after debonding/fracture were classified. Data were analyzed using ANOVA and Tukey's post hoc test (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated. Under axial loading, mean fracture strength (N) did not show significant difference between groups: LAA (2675±588)(a), LIA (2428±566)(a), CA (2151±672)(a) (p>0.05) and under lateral loading, LAL (838±169)(A) presented significantly lower mean values than those of other groups: CL (1499±418)(B), LIL (1118±173)(B) (p<0.05). Both endocrown materials and the control group were more vulnerable to lateral loading than axial loading. Under axial loading, Weibull distribution presented higher shape (0) for Groups LIA (5.35) and LAA (5.08) than that of the control (3.97) and under lateral loading LIL (7.5) showed higher shape (0) than those of other groups (4.69-6.46). After axial loading, failure types were mainly cohesive in the material and after lateral loading primarily adhesive between the material and dentin for both LI and LA, most of which were repairable. Under axial loading, molars restored with endocrowns performed similar with both Li2Si2O5 and multiphase resin composite but the latter was less durable under lateral loading.