Fracture Resistance and Stress Distribution Pattern of Different Posts-Core Systems in Immature Teeth: An In Vitro Study and 3D Finite Element Analysis

Stress analysis of horizontal mid-root fracture managed with different intraradicular fixation protocols: A 3D-finite element study

The current study evaluated the stress distribution in a maxillary central incisor with mid-root fracture after splinting with different intra-radicular posts using 3D-finite element analysis (FEA). Five 3D-FEA models were constructed. Model 1 was an intact tooth with no fracture, Model 2: A tooth with a horizontal mid-root fracture, with no treatment. Model 3: Same as model 2, and intraradicular splinting using fiber post. Model 4: Same as model 2 and intra-radicular splinting using Protaper Gold file F3. Model 5: Same as model 2, and with intraradicular splinting with Ribbond. The FEA of all models was done to obtain the maximum Von-Mises stress in the root canal space, the dentin, the periodontal ligament, and the bone. The highest Von Mises stresses for the root canal space and the dentin were found in Model 3, followed by models 4, 5, and 2, and least in Model 1. The Von Mises stress of the periodontal ligament was the least in model 1. The Von Mises stress of bone was higher in all experimental models than in the baseline model. The results suggest that in cases where intra-radicular splinting is indicated, fiber posts and Ribbond are better alternatives to endodontic files due to the lower stresses exerted.

Understanding the Complexities of Cast Post Retention: A Comprehensive Review of Influential Factors

This comprehensive review delves into the intricate landscape of cast post retention in restorative dentistry, encompassing historical perspectives, contemporary techniques, and future directions. Examining factors ranging from tooth-related considerations to prosthesis-related dynamics, the review provides a detailed analysis of clinical techniques, including step-by-step procedures, common challenges, and innovative advancements. Technological breakthroughs, such as digital impressions, computer-aided design and computer-aided manufacturing (CAD/CAM) technology, three-dimensional (3D) printing, and finite element analysis, are explored for their transformative impact on precision and customization. The discussion extends to the promising future of cast post retention, emphasising emerging materials, the integration of artificial intelligence in treatment planning, and patient-specific approaches. Implications for clinical practice underscore the importance of individualised treatment planning and the adoption of advanced technologies. Recommendations for future research advocate for comprehensive long-term clinical studies, investigations into AI-driven treatment planning, and a focus on patient outcomes and satisfaction. This review consolidates existing knowledge and anticipates a future marked by enhanced precision, individualised care, and improved long-term success in cast post-retained restorations.

Comparison of the Fracture Resistance of Root-Canal-Treated Premolars Obturated With Dissimilar Materials: An In Vitro Study

Introduction The utilization of endodontic sealers is of paramount importance in ensuring the sustained efficacy and resilience of endodontic treatment. The primary objective of the research was to appraise and contrast the fracture resistance (FR) of three distinct categories of endodontic sealing materials that are frequently employed in the context of endodontic therapy. Materials and methods This research used an in vitro experimental design. Sixty single-rooted human teeth indicated for extraction were utilized according to established protocols. These teeth were then arbitrarily divided into four piles, one for each of the four possible sealants. All specimens were put through a standardized thermal cycling procedure to simulate clinical conditions after the root canals were obturated. The subsequent step involved testing the FR of each group by utilizing a universal testing machine up until failure. Any statistically significant difference in FR among the three sealing materials was identified through appropriate statistical analysis. Results Group 1, which utilized a particular sealing material, exhibited the highest mean fracture resistance, measuring at an impressive 1198.33 ± 321.4 Newtons (N). A post hoc analysis was done to see the exact differences between each group and statistically significant differences between Groups 1 and 2 (p<0.05), Groups 1 and 4 (p<0.05), and Groups 3 and 4 (p<0.001) were observed. Conclusion The FR of Group 1 specimens were noticeably greater than those of Group 2 and Group 4 while the FR of Group 3 specimens was more than that of the Group 4 specimens. This study provides important insights into the fracture resistance of various endodontic sealing materials.

Measurement of the Dentin Wall Thickness of the Maxillary Central Incisor in Relation to the Stage of Root Development: A Pilot Study

Objective

The aim of this study was to determine the average dentin wall thickness (DWT) of the maxillary central incisor (MCI) required for performing finite element analysis (FEA) models of root development.

Material and methods

A total of 137 intraoral periapical radiographs of MCI in children aged 7 to 11 years were examined and then classified into 5 groups according to root development stages, which included 1/2 of root development (S1), 3/4 of root development (S2), more than 3/4 of root development (S3), complete development with wide-open apex (S4) and complete development with closed apex (S5). DWT was measured at three reference (horizontal) lines: at a distance of 1 mm from the apex (M), 4 mm from the apex (L) and at the cervical line (K). The distal dentin wall thickness (M1, L1, and K1), the pulp thickness (M2, L2, and K2), the mesial dentin wall thickness (M3, L3, and K3), and the apex thickness (N) were measured using the diagnostic software Soredex Scanora 5.1.2.4. Statistical analysis compared the values of the parameters K, L, and M between developmental stages (multivariate ANOVA) and the linear correlations between the parameters (Pearson's correlation analysis). All analyses were performed at significance level α = 0.05.

Results

There were statistically significant differences between the developmental stages for parameters L and M, while no significant differences were found for parameter K. Most of the correlations between the parameters were statistically significant, with the values of the Pearson correlation coefficient R > 0.6 considered practically significant. All parameters on the same reference line for distal and mesial dentin wall thickness and for pulp thickness correlated well with each other (R = 0.46 - 0.68), but there was no statistically significant correlation with total root thickness on the same reference line (parameters K, L, or M), except for parameter K3 (R = 0.42).

Conclusion

Despite the limitations of this study, the mean values of the selected parameters for the 5 groups of developmental stages of the maxillary central incisor could be used to model dentin wall thickness using finite element analysis.

Compressive Strength and Porosity Evaluation of Innovative Bidirectional Spiral Winding Fiber Reinforced Composites

The aim of this in vitro study was to investigate the compressive strength and the bulk porosity of a bidirectional (bFRC) and an experimental bidirectional spiral winding reinforced fiber composite (bswFRC). Cylindrical-shape specimens were prepared for each material group and processed for the evaluation of compressive strength after different storage conditions (dry, 1 and 3 months) in distilled water at 37 °C. The specimens were also assessed for the degree of bulk porosity through X-ray tomography. A scanning electron microscope (SEM) was used to determine the fracture mode after a compressive strength test. Data were statistically analyzed using Two-Way Analysis of Variance (ANOVA). A significantly lower compressive strength was obtained in dry conditions, and after 1 month of water immersion, with the specimens created with bFRC compared to those made with bswFRC (p < 0.05). No significant difference (p > 0.05) was found between the two groups after 3 months of water immersion. However, the presence of water jeopardized significantly the compressive strength of bswFRC after water storage. The type of fracture was clearly different between the two groups; bswFRC showed a brutal fracture, whilst bFRC demonstrated a shear fracture. The bswFRC demonstrated higher pore volume density than bFRC. In conclusion, bswFRC is characterized by greater compressive strength compared to bFRC in dry conditions, but water-aging can significantly decrease the mechanical properties of such an innovative FRC. Therefore, both the novel bidirectional spiral winding reinforced fiber composites (bswFRC) and the bidirectional fiber reinforced composites (bFRC) might represent suitable materials for the production of post-and-core systems via CAD/CAM technology. These findings suggest that both FRC materials have the potential to strengthen the endodontically treated teeth.

The practicability of different preparation of mandibular molar restored by modified endocrown with intracanal extension: Computational analysis using finite element models

BACKGROUND AND OBJECTIVE

Post-core-crown (PCC) and endocrown are two common restorative methods for severely damaged molars, but exhibit disadvantages. This study aimed to explore the practicability of modified endocrown with a 2 mm intracanal extension (MED) to restore defective teeth using finite element analysis (FEA).

METHODS

Five groups of numerical models of mandibular molars restored by three MEDs, a PCC, and a routine endocrown after root canal treatment were devised by FEA software. We constructed 4 mm, 3 mm, and 2 mm thickness of MED restorations to restore mandibular molars that were prepared to 1 mm, 2 mm, and 3 mm from the cemento-enamel junction (CEJ). Furthermore, PCC and routine endocrown were used to compare the stress distribution with MED. Lithium disilicate glass-ceramics (EMAX) and resin nanoceramics (LU) were considered restorative materials, and a vertical load of 600 N and an oblique load of 200 N were applied to the restorations.

RESULTS

In three MEDs by LU, 2 mm thickness of restoration generated the highest stress on prepared teeth, while the thickness of EMAX did not significantly influence the stress value. MED by LU generated higher stress around the CEJ, and reduced the stress on the middle and lower root compared to MEDs by EMAX, PCC by EMAX, and PCC by LU. MED by EMAX caused lower stress around the CEJ, and generated higher stress in the chamber walls after extended root canals compared with MED by LU, endocrowns by LU, and endocrowns by EMAX. There was an evident stress concentration at the last but one layer, which was a thin area of the tooth root in all restorative models.

CONCLUSIONS

The use of modified endocrown may be considered an effective restorative method to restore defective mandibular molar, but suitable restorative material must be selected based on the tooth preparation method and deficiencies in the tooth structure.