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Purpose: To evaluate the effects of post length, post material, and substance loss on the fracture resistance of endodontically treated mandibular premolars. Materials and Methods: A total of 96 extracted human mandibular first premolars were endodontically treated and divided into 12 test groups (n = 8 each) based on the number of residual walls (one/two), post material (glass-fiber/titanium), and post length (5 mm, 7.5 mm, and 10 mm). After luting the posts, specimens received a composite resin core and a crown preparation with a 1.5-mm ferrule. Cast cobalt-chromium crowns were cemented using glass-ionomer cement. After 1,200,000 chewing cycles with a load of 49 N and simultaneous thermocycling (5°C to 55°C), specimens were quasi-statically loaded at 30 degrees to the longitudinal axis of the tooth until fracture. Fracture loads were analyzed using three-way, two-way, and one-way ANOVA (a = .05). Fracture modes were examined under a stereomicroscope (×25 magnification) and recorded. Results: The mean ± SD fracture loads ranged from 642 ± 190 N (one wall, glass fiber, 5 mm) to 1,170 ± 130 N (two walls, titanium, 7.5 mm). The mean fracture load of titanium posts was significantly higher than that of glass-fiber posts (P < .001), and the 7.5-mm post length exhibited significantly higher fracture loads than groups with 5-mm and 10-mm post length (P = .008). Conclusions: Teeth restored with titanium posts revealed considerably higher fracture resistance than teeth restored with glass-fiber posts, especially if 7.5-mm-length posts were used. [ABSTRACT FROM AUTHOR]

To incorporate different concentrations of Al2O9Zr3 (1%, 5%, and 10%) nanoparticles (NP) into the ER adhesive and subsequently assess the impact of this addition on the degree of conversion, μTBS, and antimicrobial efficacy. The current research involved a wide‐ranging examination that merged various investigative techniques, including the application of scanning electron microscopy (SEM) for surface characterization of NP coupled with energy‐dispersive x‐ray spectroscopy (EDX), Fourier‐transform infrared (FTIR) spectroscopy, μTBS testing, and microbial analysis. Teeth were divided into four groups based on the application of modified and unmodified three‐step ER adhesive primer. Group 1 (0% Al2O9Zr3 NPs) Control, Group 2 (1% Al2O9Zr3 NPs), Group 3 (5% Al2O9Zr3 NPs), and Group 4 (10% Al2O9Zr3 NPs). EDX analysis of Al2O9Zr3 NPs was performed showing elemental distribution in synthesized NPs. Zirconium (Zr), Aluminum (Al), and Oxides (O2). After primer application, an assessment of the survival rate of Streptococcus mutans was completed. The FTIR spectra were analyzed to observe the characteristic peaks indicating the conversion of double bonds, both before and after the curing process, for the adhesive Etch and rinse containing 1,5,10 wt% Al2O9Zr3 NPs. μTBS and failure mode assessment were performed using a Universal Testing Machine (UTM) and stereomicroscope respectively. The μTBS and S.mutans survival rates comparison among different groups was performed using one‐way ANOVA and Tukey post hoc (p =.05). Group 4 (10 wt% Al2O9Zr3 NPs + ER adhesive) specimens exhibited the minimum survival of S.mutans (0.11 ± 0.02 CFU/mL). Nonetheless, Group 1 (0 wt% Al2O9Zr3 NPs + ER adhesive) displayed the maximum surviving S.mutans (0.52 ± 0.08 CFU/mL). Moreover, Group 2 (1 wt% Al2O9Zr3 NPs + ER adhesive) (21.22 ± 0.73 MPa) samples displayed highest μTBS. However, the bond strength was weakest in Group 1 (0 wt% Al2O9Zr3 NPs + ER adhesive) (14.13 ± 0.32 MPa) study samples. The etch‐and‐rinse adhesive exhibited enhanced antibacterial activity and micro‐tensile bond strength (μTBS) when 1% Al2O9Zr3 NPs was incorporated, as opposed to the control group. Nevertheless, the incorporation of Al2O9Zr3 NPs led to a decrease in DC. Research Highlights: 10 wt% Al2O9Zr3 NPs + ER adhesive specimens exhibited the minimum survival of S.mutans.1 wt% Al2O9Zr3 NPs + ER adhesive samples displayed the most strong composite/CAD bond.The highest DC was observed in Group 1: 0 wt% Al2O9Zr3 NPs + ER adhesive. [ABSTRACT FROM AUTHOR]

Objectives: This laboratory study compared the effects of various post systems on the fracture resistance of endodontically treated mandibular premolars. Method and materials: Thirty-two extracted mandibular first premolars were collected, endodontically treated, and assigned into four test groups (n = 8). The classification was based on the post material as follows: traditional glass-fiber posts (TFP), traditional titanium posts (TTP), coated glass-fiber posts (CFP), and coated titanium posts (CTP). The posts were cemented with a dual-curing luting composite resin. Each specimen, which was prepared with a 2-mm ferrule height, received a composite resin core. All specimens were restored with cast CoCr crowns, which were cemented with glass-ionomer cement. All specimens were submitted to dynamic loading in a dual-axis chewing simulator for 1,200,000 cycles with a nominal load of 5 kg and simultaneous thermal cycling (5 to 55°C). Each specimen was secured in place and loaded at 30 degrees using a universal testing machine until fracture occurred. The results obtained were analyzed using one-way ANOVA and the fracture modes were investigated under stereomagnification (25x). Results: Fracture loads were as follows: 858 ± 216 N for CTP, 953 ±134 N for TFP, 979 ± 219 N for CFP, and 1,130 ± 286 N for TTP group. One-way ANOVA revealed no statistically significant differences among the test groups (P = .112). Conclusions: Under the conditions of the current study, no significant fracture resistance differences were found between teeth with the different prefabricated post systems. [ABSTRACT FROM AUTHOR]

Objective: Restoration of fractured root canal-treated maxillary incisors based on recent advances in adhesive dentistry and minimal invasive principles, which are topics of great importance. In particular, the aim of the present study was to evaluate the fracture resistance of a coronoradicular direct composite restoration compared with fibre post composite restorations and direct conventional composite restorations. Materials and methods: A total of 45 freshly extracted sound maxillary central incisors were used in the study. The teeth were randomly divided into three groups of 15 each. The groups were: group I (CDC), conventional direct composite postendodontic restoration; group II (FPC), fibre post placement and direct composite postendodontic restoration; group III (CRC), coronoradicular composite postendodontic restoration. The fracture resistance was measured using a universal testing machine and a 130 degrees angle of loading. Results: One-way ANOVA depicted a significant difference (P = 0.028) among the three groups with the mean fracture load of group CRC being the highest, at 1045.2 ± 355.7 N. The FPC group had the significantly least fracture resistance load, with 426.7 ± 245.3 N. Conclusions: Within the parameters of this study, the corono-radicular composite restorations had significantly higher fracture resistance than conventional direct composite and fibre post restor- r ations when 50% of the crown structure was lost in fractured root canal-treated maxillary incisors. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the aging effect of thermomechanical cyclic load on fracture resistance of lower premolars obturated with AH Plus and BioRoot RCS root canal sealers. Forty-eight single-rooted premolars teeth were instrumented with REVO-S files up to SU/0.06 taper. The teeth were randomly assigned into 2 main groups (n = 24) according to the selected two root canal sealers (AH Plus or BioRoot RCS). All teeth were obturated using matching gutta-percha. Each main group were further divided into 3 subgroups (A, B and C) (n = 8). Group A acted as the negative control group (non-Thermomechanical aging). Whereas Group B and C were subjected first to thermal variations in a thermal cycling machine (7500 and 15,000 thermal cycles), then two different dynamic loading periods namely 3 × 105 and 6 × 105 in a masticatory simulator with a nominal load of 5 kg at 1.2 Hz which simulate approximately 1 ½ and 3 years of clinical function respectively. The roots were decoronated and fracture resistance were measured using a universal testing machine. After thermal-mechanical aging, BioRoot RCS showed significantly higher fracture resistance (p < 0.05) than AH Plus. As the thermal-mechanical cycles increased both AH Plus and BioRoot RCS exhibited a significant decrease in fracture resistance (p < 0.05). It could be concluded that thermomechanical aging had a significant impact on the outcome of the fracture resistance of AH Plus and BioRoot RCS. [ABSTRACT FROM AUTHOR]