This study compared the flexural strength of various 3D printed resins fabricated at different building angles (0°, 45°, and 90°). Four groups of resins were tested: Varseo Smile Teeth (Bego GmbH & Co., Bremen, Germany), V-print C&B Temp (Voco GmbH, Cuxhaven, Germany), Bego Triniq (Bego GmbH & Co. KG, Bremen, Germany), and Sprintray Crown (SprintRay, Los Angeles, CA, USA). A digital light processing 3D printer (Asiga MAX UV, NSW, Sydney, Australia) was used to fabricate the samples at the specified build angles (0°, 45°, and 90°) in accordance with the ISO 4049:2019 standard. Flexural strength was measured using a universal testing machine (Instron 5567; Instron Ltd., Norwood, MA, USA), and fracture analysis was performed using a scanning electron microscope (Jeol JSM-6060LV, Tokyo, Japan). Statistical analysis was carried out using the Statistical Package for the Social Sciences (SPSS, version 26; IBM Corp., Chicago, IL, USA). Means and standard deviations were calculated for each group, and statistical differences were assessed using one-way ANOVA followed by the Bonferroni post hoc test (p < 0.05). All tested resins exhibited high flexural strength values. The maximum flexural strength was observed in the 0° printed samples (137.18 ± 18.92 MPa), while the lowest values were recorded for the 90° printed samples (116.75 ± 24.74 MPa). For V-print C&B Temp, the flexural strength at 90° (116.97 ± 34.87 MPa) was significantly lower compared to the 0° (156.56 ± 25.58 MPa) and 45° (130.46 ± 12.33 MPa) orientations. In contrast, Bego Triniq samples printed at 45° (148.91 ± 21.23 MPa) demonstrated significantly higher flexural strength than those printed at 0° (113.37 ± 31.93 MPa) or 90° (100.96 ± 16.66 MPa). Overall, the results indicate that the printing angle has a significant impact on the flexural strength of the materials, with some resins showing lower strength values at the 90° build angle.

Bioceramic sealers have gained widespread acceptance in contemporary endodontics due to their favorable biological properties, dimensional stability, and bioactivity. However, their strong adhesion to dentinal walls and penetration into dentinal tubules may complicate removal during endodontic retreatment procedures. Additionally, the obturation technique may influence both the retreatability of root canal filling materials and the bond strength of sealers and resins to radicular dentin. Methods: One hundred extracted human single-rooted teeth were instrumented using the WaveOne Gold system and obturated with a bioceramic sealer using two techniques: single-cone (Group A, n = 50) and warm vertical compaction (Group B, n = 50). After sealer setting, retreatment procedures were performed using ProTaper Universal Retreatment files combined with passive ultrasonic irrigation. Scanning electron microscopy was used to evaluate smear layer removal and dentinal tubule obstruction. Eighty specimens were subsequently re-obturated with a bioceramic sealer and divided into four subgroups according to the obturation technique used before and after retreatment. A push-out bond strength test was performed on coronal, middle, and apical root sections. Statistical analysis was conducted using SPSS software with a significance level set at p ≤ 0.05. Results: No statistically significant differences were observed between the groups regarding the working time required for root filling removal (p > 0.05). However, significant differences were found in push-out bond strength values among the experimental groups (p < 0.05). Specimens obturated using warm vertical compaction showed significantly higher bond strength compared with the single-cone technique. Scanning electron microscopy observations revealed less residual bioceramic sealer on dentinal walls in the warm vertical compaction group. Conclusions: Within the limitations of this in vitro study, the warm vertical compaction technique demonstrated superior bonding performance and resulted in less residual bioceramic sealer after retreatment compared with the single-cone technique.

Background: The aim of this study was to find out a combination between the endodontic treatment and the restorative procedure to be performed in one step. For that, the validity of a combined warm vertical condensation technique, an immediate washout of the bi-oceramic sealer (Bioceramic Immediate Wash Out, BIWO), and an immediate build-up (IBU) of the endodontically treated tooth was evaluated. Methods: One hundred ten single-root human teeth were selected. Then, the sample roots were divided into 3 Groups according to the used the endodontic sealer and the wash out technique: Group 1. CeraSeal root canal sealer with the continuous wave of condensation technique (CWC), BIWO and IBU; Group 2. Ceraseal with a week delayed BDWO (Bioceramic Delayed Wash Out, BDWO) and a delayed build-up (DBI); Group 3. Pulp Canal Sealer EWT (PCS) with the BIWO and IBU; Restorations were made with a fiber post or using a fiber re-inforced flowable resin composite. The samples were tested by push out and SEM ob-servation to evaluate the cleanliness of root canal walls. Also, apical leakage test was performed to evaluate if BIWO might negatively affect the apical seal. Results: Group 1 post scored the highest values (15.23 ± 4.2 MPa), followed closely by Group 1 composite (14.51 ± 3.1 MPa), and then Group 2 post (12.83 ± 3.1 MPa), and Group 2 composite (12.52 ± 2.1 MPa). The lowest values were recorded for Group 3 post (9.55±1.32) and Group 3 composite (9.12±1.67). Statistically significant differences were detected among these Groups (p > 0.05). Regarding the influence of sealer type, the groups obturated with BES (Group 1 and 2) demonstrated significantly higher bond strength values than those obturated with Pulp Canal Sealer (p < 0.05). From the SEM observation was evident that the BIWO technique obtained a better cleaned dentin surface from the smear layer. The apical leakage test did not show any differences among BIWO and BDWO, and BES and PCS. Conclusions: From the findings of this in vitro study, the following conclusions can be drawn: 1. The BIWO is more effective than BDWO. 2. The BIWO achieved clean dentinal wall surfaces, available for bonding. 3. The BIWO dos not affect the apical seal of the endodontic obturation.