The Use of Bulk-Fill Flow in the Customization of Glass Fiber Post

Fracture Resistance of Resin Matrix Ceramic Post and Core Compared to Prefabricated Fiber-Reinforced Composite Post and Core in Non-Ferrule Effect Teeth: An In Vitro Study

This research studies the fracture resistance of a non-ferrule endodontically treated tooth restored with two types of resin matrix ceramic (Enamic and Cerasmart) post and core compared with the conventional prefabricated fiber-reinforced composite (FRC) post and core.Thirty single-root-canal premolars were sectioned to 13 mm root length and then all the roots were filled, using a crown-down technique for root canal preparation and one cone technique for root canal obturation, All the roots were randomly divided into three groups (n = 10) according to post and core material; (1) Enamic group (EN), (2) Cerasmart group (CM), and (3) prefabricated fiber post group (FRC). Three groups of specimens were tested using a universal testing machine (EZ Test Series, Shimadzu, Japan). Specimen blocks were fixed into a holder with an inclination of 45 degrees. The force was loaded to a palatal incline of buccal cusp at a crosshead speed of 0.5 mm/minute until there was split or fracture of the tooth. The maximum braking force was recorded in Newton (N), and the mode of failure was observed by a stereomicroscope.The dependent variable was fracture resistance (maximum breaking force) and the data were analyzed using one-way analysis of variance and then multiple comparison Tukey's tests were used, aiming to find means that are significantly different among the groups. Moreover, the failure mode was analyzed using the chi-square test.A significant difference was recorded. Teeth restored with prefabricated FRC had the most fracture resistance 342.19 ± 79.34 N (p = 0.007), followed by the resin matrix ceramic group (265.10 ± 48.58 N: Cerasmart) and Enamic group (260.98 ± 43.96 N: Enamic). No significant difference between the Enamic and Cerasmart groups was noted. Additionally, no significant difference in the mode of failure was recorded among the three groups.The fracture resistance of a non-ferrule endodontically treated tooth restored with the conventional prefabricated FRC post and core is greater than that restored with either type of resin matrix ceramic (Enamic and Cerasmart). This explains the higher failure rate resulting from the use of resin matrix ceramics.

Push-Out Bond Strength of Fiber Posts to Overflared Root Canals in Different Root Regions: Effect of Reinforcement Techniques

Objectives: This study aimed to investigate the effect of different reinforcement techniques on the push-out bond strength of fiber posts to over-flared root canals. Materials and Methods: Forty-eight extracted human single-canal premolars were endodontically treated, over-flared, and randomly divided into four groups (N=12) including SARC: luting with self-adhesive resin cement, DCC: luting with dual-cure core build-up resin composite, CRR: relining root canal walls with bulk-fill resin composite, and DAP: relining fiber post with bulk-fill resin composite. After 24 hours, the roots were sectioned to obtain three cervical, middle, and apical 3mm slices. The push-out test was performed and failure pattern was examined. Kruskal-Wallis and post-hoc Dunn-Bonferroni tests were used for statistical analysis (P<0.05). Results: In all three regions, the lowest and highest bond strength was found in the SARC and DAP groups, respectively. In the middle region, there was a statistically significant difference between the bond strength of the SARC group and that of the DCC (P=0.044), CRR (P=0.021), and DAP (P<0.001) groups. There was no significant difference in the apical region. The lowest bond strength was observed in the apical region, and the highest was related to the cervical region. Adhesive failure was the most common failure pattern in all groups. Conclusion: Based on our results DCC, CRR and DAP methods increased bond strength in the middle and cervical sections of over-flared root regions. Considering that DCC is the easiest and most practical method, we propose that CRR and DAP can be replaced with this method in clinical procedures.

Can the Remaining Coronal Tooth Structure Influence the Mechanical Behavior of Nonpost Full Crowns?

OBJECTIVES

 This study investigated the impact of the remaining coronal tooth structure on the mechanical behavior of nonpost (NP) full crowns on endodontically treated maxillary central incisors.

MATERIALS AND METHODS

 Forty bovine incisors with NP and 2-mm of ferrule were divided into four groups based on the remaining structure: complete 2-mm ferrule (NP-2), absence of mesial and distal ferrule effect (NP-BL), absence of buccal and lingual ferrule effect (NP-MD), and no ferrule (NP-0). The specimens underwent a stepwise stress fatigue test until fracture occurred, and stress distribution was analyzed using in silico finite element analysis (FEA). Additionally, groups with endodontic posts (P) were simulated in the FEA.

RESULTS

 The results showed that the survival rates varied among the different groups under oblique loading. The NP-2 group exhibited the highest survival rate, with all samples enduring loads up to 200 N and some surviving up to 520 N. The NP-MD and NP-BL groups had lower survival rates, while the NP-0 group had the poorest survival rate. The predominant failure mode was a nonrepairable root fracture. FEA results indicated no significant difference between groups with and without posts. NP intraradicular restorations on nonweakened roots with a minimum height of 2mm and partial or total ferrule thickness of 1mm offer a promising treatment option.

CONCLUSION

 A complete 2-mm ferrule was found to be the most favorable configuration for NP full crowns. However, maintaining the remaining tissue is crucial, as both combinations with preserved ferrule effect exhibited superior behavior in terms of fatigue and fracture load compared to the group with no ferrule. These findings contribute to understanding the mechanical considerations for NP full crowns and provide insights into treatment planning and design choices in restorative dentistry.

Fracture resistance of weakened roots restored with relined or milled CAD-CAM glass fiber posts

This in vitro study compared the fracture resistance of weakened roots restored with milled or relined glass fiber post (GFP). Seventy bovine incisors were divided into seven groups, according to the weakening protocol (none: control; medium-weakened: MW; highly-weakened: HW) and post anatomization technique (non-relined, relined with Bulk Fill or Z350 resin; milled GFP: M). Roots were thermomechanical cycled and submitted to compression. Frequencies and groups were compared by the chi-square test and two-factor ANOVA, Tukey's, and t-test (α=5%). The HW-M obtained the lowest values, showing significant differences compared to all groups (p<0.001). The highest value was HW-Bulk fill, with significant difference compared to MW-M (p=0.037) and HW-M (p<0.001). The frequency of repairable fractures was 100% in the control, 87%, and 63% in the MW and HW, respectively. Relined or milled GFPs can be considered to rehabilitate weakened teeth since failure patterns were predominantly repairable in all groups.

The Use of Polyetheretherketone (PEEK) as an Alternative Post and Core Material: Five-Year Follow-Up Report

This clinical report demonstrated the use of polyetheretherketone (PEEK) for manufacturing of custom-made post and core in weakened endodontically treated central incisors. The PEEK structure was manufactured using computer-aided design/computer-aided manufacturing (CAD/CAM). The optimal fit of this custom-made endodontic post allowed a thinner cement layer; and removed the need to manufacture a core build-up. While supplementary clinical trials and in vitro studies are needed to totally elucidate the advantages and limitations of PEEK as an option for post and core manufacturing, this case report showed that it can be promising for a predictable and simplified treatment with five years of success.