Influence of margin design and restorative material on the stress distribution of endocrowns: a 3D finite element analysis

Additively manufactured resin-based endocrowns: Effect of material type, margin configuration, and pulp chamber depth on fabrication trueness and fit

OBJECTIVE

To evaluate the effects of margin configuration and pulp chamber depth on the fabrication trueness and internal fit of resin-based endocrowns fabricated with additive (AM) and subtractive manufacturing (SM).

METHODS

Four mandibular first molar typodonts prepared with butt joint or 1 mm-wide shoulder margins and 2 mm or 4 mm pulp chamber depths were digitized to design reference endocrowns. These designs were used to fabricate endocrowns with AM (Crowntec [AM-CT], FREEPRINT Crown [AM-FP], Tera Harz TC80DP [AM-GR]) or SM (Tetric CAD [SM-TC]) (n = 7). Surface deviations (external, intaglio, and marginal root mean square, RMS) and triple scan protocol (average gap) were used for digital analyses. Data were analyzed with generalized linear models (α = 0.05).

RESULTS

Intaglio RMS was affected by the interaction of all main factors, while all surface deviations were affected by material type-margin configuration interaction. Material type-pulp chamber depth interaction affected intaglio RMS and average gaps, whereas margin configuration-pulp chamber depth interaction affected all outcomes, except intaglio RMS (P ≤ 0.001). AM-GR mostly led to lower intaglio and marginal RMS, while SM-TC mostly led to lower external RMS (P ≤ 0.022). SM-TC endocrowns with 4-mm depth had the highest and AM-GR endocrowns with 4-mm depth mostly had lower average gaps (P ≤ 0.024).

CONCLUSIONS

The interactions among the main factors affected the trueness of the tested endocrowns. However, no clear trend emerged that would highlight any subgroup as having the highest trueness. Most endocrowns demonstrated clinically acceptable internal gaps.

CLINICAL SIGNIFICANCE

Tested additively manufactured resin-based endocrowns had favorable internal adaptation. However, they may require more chairside adjustments on external surfaces compared to tested subtractively manufactured endocrowns.

Impact of Margin Type and Material Choice on Stress Distribution in Endocrown Restorations: A 3D Finite Element Study

BACKGROUND Finite element analysis (FEA) for endocrown restorations (ER) on maxillary molars has rarely been investigated, despite its high incidence in gross decay and being treated endodontically. This study aimed to analyze the influence of various preparation features (margin type, pulp chamber extension, occlusal thickness) and restorative material (zirconia, lithium disilicate, nanoceramic resin) on the stress distribution pattern of maxillary first molar ER using three-dimensional FEA. MATERIAL AND METHODS Six three-dimensional finite element models (models A-F) were created for ER maxillary molars, considering preparation features - margins (flat butt, 20° bevel, shoulder), pulpal extension (2 mm/4 mm), and occlusal thickness (3 mm) - for 3 ER materials (zirconia, lithium disilicate, nanoceramic resin). The closing phase of mastication was loaded with 600 Newtons of functional load from an apple bolus. Von Mises Stress (VMS) was used to calculate tooth component and ER stress distributions. Standard criteria were used to calculate cement layer failure risk. RESULTS Resin nanoceramic shoulder margins with 2- and 4-mm PE (models E and F) had higher stress concentrations on the tooth preparation surface, cervical enamel, buccal roots, and ER intaglio surface. Higher elastic modulus (ME) materials had higher stress concentrations inside ER and less stress in the cement layer, facilitating tooth bonding. Resin nanoceramic distributed stresses more uniformly on ER/tooth tissues. CONCLUSIONS Different margin and pulpal extension preparation features and restorative materials cause varied ER stress distribution. Shoulder margin created considerably larger stresses in dental tissue and ER than flat butt margin, regardless of material type. Increased pulpal extension reduced tooth tissue stresses but increased ER.

Impact of restorative materials on biomechanical behavior of endocrown and post-core restorations: A 3-dimensional finite element analysis

PURPOSE

This study evaluated biomechanical behavior of endocrown and post-core restorations produced from computer aided design/computer aided manufacturing (CAD/CAM) and traditional materials in severely damaged teeth that lack a ferrule and assessed the associated failure risk of resin cement.

METHODS

A phantom maxillary central incisor and mandibular second premolar were trimmed 1 mm coronally to the cemento-enamel junction, the root canals were enlarged, and the teeth were scanned. Data were transferred to a solid modeling software. Twenty-two models were constructed, including endocrowns (hybrid ceramic, lithium disilicate, and polyetheretherketone [PEEK]) and post-cores (glass-fiber post/composite core; glass-fiber single-piece post-core; PEEK single-piece post-core; gold single-piece post-core). Hybrid ceramic and lithium disilicate crowns were modeled on the post-cores. Loads of 100 N for the central incisor and 300 N for the premolar were applied in a 45° oblique direction. von Mises stresses were analyzed on both root dentin and restorations, and the failure risks for the resin cement were calculated.

RESULTS

The highest stresses were found at the roots of the PEEK endocrown (37.6 MPa) for the central incisor and of the lithium disilicate endocrown for the premolar (40.0 MPa) among endocrown groups. PEEK endocrowns had the lowest stress within the restoration and presented a higher risk of cement failure. The glass-fiber post/composite core groups demonstrated the highest adhesive and cohesive failure risks for post cement.

CONCLUSIONS

For the central incisor and mandibular premolar, lithium disilicate and PEEK endocrowns, respectively, generated less stress at the root. However, PEEK endocrowns had a higher risk of cement failure.

Compressive Stress in Teeth Restored with Endocrown and Build-up: A Finite Element Analysis

AIM

This study evaluates compressive stress in teeth restored with endocrown (ECW) and build-up (BUP) using finite element analysis (FEA). Understanding stress distribution in dental restorations is crucial for improving treatment outcomes and longevity.

MATERIALS AND METHODS

A second lower molar was modeled using Solidworks® (Version 2017). The ECW was simulated with nanoceramic resin, while the BUP included a core and nanoceramic crown. Mechanical properties, including modulus of elasticity, Poisson's ratio, and tensile strength were assigned to materials. Axial and oblique loads of 900N were applied, and stress was analyzed using Solidworks®.

RESULTS

Results indicated that under axial loading, ECW experienced a maximum stress of 91.9 MPa, significantly higher than BUP's 49 MPa. Under oblique loading, ECW exhibited 132 MPa compared with 116 MPa in BUP. The highest stress concentration was in the cervical area, where ECW showed greater stresses in both the substrate and restored area. Build-up demonstrated better stress distribution and lower fracture risk.

CONCLUSION

Endocrown restoration results in higher compressive stresses, especially in the cervical region, which may increase the risk of fracture. Conversely, the BUP technique, which preserves cervical dentin, offers improved stress distribution and reduced fracture risk, making it a more robust solution for endodontic rehabilitation.

CLINICAL SIGNIFICANCE

This study underscores the importance of selecting appropriate restoration methods to minimize stress and enhance the longevity of dental treatments, ultimately leading to better patient outcomes. How to cite this article: Bardales-Espinoza KA, Mora-Ipince AR, Chávez-Méndez MA, et al. Compressive Stress in Teeth Restored with Endocrown and Build-up: A Finite Element Analysis. J Contemp Dent Pract 2024;25(11):1027-1033.

Optimizing restorative procedure and material selection for pulpotomized primary molars: Mechanical characterization by 3D finite element analysis

Purpose

This study aimed to assess the stress distribution in pulpotomized primary molars with different types of restorative materials using 3D-finite element analysis (FEA), and provide valuable insights into the selection and application of restorative materials, with the ultimate goal of reducing the risk of pulpotomy failure and protecting residual dental tissue.

Methods

Four 3D models of pulpotomized primary molars with different restorative materials according to the material and its elastic modulus were analysed: resin composite, stainless steel crowns (SSCs), prefabricated zirconia crowns and endocrowns. The food layer was also designed before vertical and bucco-lingual forces were applied to simulate physiological masticatory conditions. The results were obtained by colorimetric graphs of the von Mises stresses (VMS) in the restoration and tooth remnant. The maximum shear stress on the bonding interfaces and pressure stress on the Mineral trioxide aggregate (MTA)-pulp interfaces were recorded.

Results

The results of the 3D-FEA showed that all restorative materials generated stresses and strains on the tooth structure after pulpotomy. In the resin composite group, the marginal enamel exhibited the highest stress peaks. In the zirconia crown and SSC groups, there was a concentration of stress at the dentin-restoration margin. The shear stress concentrations were mainly at the adhesive margins, with lower levels around endocrowns compared to other groups. MTA in the resin composite group experienced more VMS than in the other group. The resin composite group also generated relatively higher pressure stress values at the MTA-pulp interface compared to the other groups.

Significance

In the model of primary teeth following pulpotomy, the three types of restorations covering the occlusal surface can effectively reduce the stress on pulp capping materials under occlusal loads, thereby potentially decreasing the risk of pulpotomy failure. In addition, the group of endocrowns demonstrated reduced stress at the bonding interface and in the stress concentration zone near the dentist-restoration edge, making them more effective at protecting residual dental tissue.

Accuracy and adaptation of one-piece endodontic crowns fabricated through 3D printing and milling

STATEMENT OF PROBLEM

High-level evidence regarding the accuracy and adaptation of 1-piece endodontic crowns fabricated by using 3-dimensional (3D) printing technology is lacking.

PURPOSE

The purpose of this in vitro study was to compare the accuracy and adaptation of 1-piece endodontic crowns produced through 3D printing and computer-numerical-control milling technology and to explore the influence of trueness on 1-piece endodontic crown adaptation.

MATERIAL AND METHODS

One-piece endodontic crowns were prepared for a typodont right mandibular first molar, scanned with a 3Shape E3 scanner, and designed with a computer-aided design software program. Two types of 1-piece endodontic crowns were fabricated: 3D printed by using resin and zirconia slurry and milled from Grandio and zirconia blocks. A reverse engineering software program was used to superimpose 4 groups of crowns with the reference crowns used for accuracy analysis. Microcomputed tomography was used to measure 1-piece endodontic crown adaptation. The correlation between trueness and adaptation was evaluated through the Spearman correlation test (α=.05).

RESULTS

Milled resin-based 1-piece endodontic crowns demonstrated better trueness on marginal and occlusal surfaces compared with 3D printed ones (P<.001). However, no significant difference was observed in the trueness of intaglio surfaces between the 2 groups (P>.05). The milled group exhibited better adaptations than the printed one (P<.05). For zirconia 1-piece endodontic crowns, no significant differences were found in trueness or adaptation between the milled and printed groups (P>.05). Notably, the trueness of the axial wall had the greatest impact on overall crown adaptation, with its adaptation closely linked to the trueness of each area, particularly the axial wall.

CONCLUSIONS

Milled resin-based 1-piece endodontic crowns exhibited higher levels of trueness and adaptation compared with 3D printed ones, while 3D printed zirconia 1-piece endodontic crowns were comparable with milled ones.

How do different intraoral scanners and milling machines affect the fit and fatigue behavior of lithium disilicate and resin composite endocrowns?

The aim of this in vitro study was to evaluate the effect of the combinations of two different intraoral scanners (IOS), two milling machines, and two restorative materials on the marginal/internal fit and fatigue behavior of endocrowns produced by CAD-CAM. Eight groups (n= 10) were considered through the combination of TRIOS 3 (TR) or Primescan (PS) IOS; 4-axes (CR; CEREC MC XL) or 5-axes (PM; PrograMill PM7) milling machines; and lithium disilicate (LD; IPS e.max CAD) or resin composite (RC; Tetric CAD) restorative materials. Specific surface treatments were applied to each material, and the bonding to its corresponding Endocrown-shaped fiberglass-reinforced epoxy resin preparations was performed (Variolink Esthetic DC). Computed microtomography (μCT) was performed to assess the marginal/internal fit, as well as a mechanical fatigue test (20 Hz, initial load = 100 N/5000 cycles; step-size = 50 N/10,000 cycles until a threshold of 1500 N, then, the step-size was increased if needed to 100 N/10,000 cycles until failure or a threshold of 2800 N) to evaluate the restorations long-term behavior. Complementary analysis of the fracture features and surface topography in scanning electron microscopy was performed. Three-way ANOVA and Kaplan-Meier test (α = 0.05) were performed for marginal/internal fit, and fatigue behavior data, respectively. PS scanner, CR milling machine, and RC endocrowns resulted in a better marginal fit compared to their counterparts. Still, the PM machine resulted in a better pulpal space fit compared to the CR milling machine. Regardless of the scanner and milling machine, RC endocrowns exhibited superior fatigue behavior than LD ones. LD endocrowns presented margin chipping regardless of the milling machine used. Despite minor differences in terms of fit, the 'IOS' and 'milling machine' factors did not impair the fatigue behavior of endocrowns. Resin-composite restorations resulted in a higher survival rate compared to glass-ceramic ones, independently of the digital devices used in the workflow.

Effect of margin designs and loading conditions on the stress distribution of endocrowns: a finite element analysis

BACKGROUND

Margin designs and loading conditions can impact the mechanical characteristics and survival of endocrowns. Analyzing the stress distribution of endocrowns with various margin designs and loading conditions can provide evidence for their clinical application.

METHODS

Three finite element analysis models were established based on the margin designs: endocrown with a butt-joint type margin (E0), endocrown with a 90° shoulder (E90), and endocrown with a 135° shoulder (E135). The E0 group involved lowering the occlusal surface and preparing the pulp chamber. The E90 group created a 90° shoulder on the margin of model E0, measuring 1.5 mm high and 1 mm wide. The E135 group featured a 135° shoulder. The solids of the models were in fixed contact with each other, and the materials of tooth tissue and restoration were uniform, continuous, isotropic linear elasticity. Nine static loads were applied, with a total load of 225 N, and the maximum von Mises stresses and stress distribution were calculated for teeth and endocrowns with different margin designs.

RESULTS

Compared the stresses of different models under the same loading condition. In endocrowns, when the loading points were concentrated on the buccal side, the maximum von Mises stresses were E0 = E90 = E135, and when there was a lingual loading, they were E0 < E90 = E135. In enamel, the maximum von Mises stresses under all loading conditions were E0 > E90 > E135. In dentin, the maximum von Mises stresses of the three models were basically similar except for load2, load5 and load9. Compare the stresses of the same model under different loading conditions. In endocrowns, stresses were higher when lingual loading was present. In enamel and dentin, stresses were higher when loaded obliquely or unevenly. The stresses in the endocrowns were concentrated in the loading area. In enamel, stress concentration occurred at the cementoenamel junction. In particular, E90 and E135 also experienced stress concentration at the shoulder. In dentin, the stresses were mainly concentrated in the upper section of the tooth root.

CONCLUSION

Stress distribution is similar among the three margin designs of endocrowns, but the shoulder-type designs, especially the 135° shoulder, exhibit reduced stress concentration.

Stress Analysis on Mesiolingual Cavity of Endodontically Treated Molar Restored Using Bidirectional Fiber-Reinforced Composite (Wallpapering Technique)

Introduction

Endodontically treated teeth (ETT) undergo extensive structure change and experience high stress during biomechanical function. Stress distribution is influenced by the restoration material and the type of bond between material and tooth structure. The selection of materials that can distribute stress will affect the resistance and retention of ETT to mastication forces, thus biomechanical functions were achieved. Composite has mechanical properties similar to dentin, it can transmit and distribute stresses throughout the tooth surface. The disadvantage of composites in large cavities is their lack of toughness. The addition of fiber to composites can increase their toughness.

Purpose

This research is to determine the stress distribution of a fiber-reinforced composite made of polyethylene and e-glass on the mesiolingual cavity of ETT.

Materials and Methods

A three-dimensional model of the mandibular molar was prepared for cavity preparation and the formation of restorations using SolidWorks 2021. The models were analyzed with Abaqus 2020 to determine stress concentrations after given vertical and oblique loading.

Results

The maximum and minimum principal stress data were obtained to assess material resistance and interfacial damage criterion. Polyethylene fiber shows a more homogeneous stress distribution because the modulus of elasticity is close to the dentin and has a thickness that can reduce the volume of the composite. The E-glass shows the stress concentration on the circumferential fiber and cavity floor.

Conclusion

The stress distribution of fiber-reinforced composite on the buccolingual cavity of ETT using the finite element method did not show structural failure in the polyethylene group because the maximum and minimum principal stresses were lower than the strength of the material. Interfacial bond failure occurs at the enamel portion. The maximum and minimum principal values of e-glass indicate structural failure in the circumferential fiber and the base fiber because the stress exceeds the strength of the material. Interfacial bond failure occurred on the circumferential and the cavity floor.

Yousief S, Tammam R, M. Galal R, Brakat A, Mohamed El Sayed H, Kamal A, Noushad M, Nassani MZ. Biomechanics of Central Incisor Endocrowns with Different Lengths and Milled Materials after Static and Vertical Loading: A Finite Element Study

Purpose

The aim of this study was to compare and assess the stress distribution and failure possibility of endodontically treated central incisor protected with endocrowns with different heights, with various CAD-CAM blocks such as IPS e.max CAD, Katana Zirconia, and Zolid Fx Zirconia.

Materials and Methods

A root canal-treated central incisor (plastic model) restored with an endocrown was scanned with a laser scanner to prepare a control model with a CAD software and then transferred to an FEA software. Proposed crown heights were 2, 4, and 6 mm. The model that was duplicated and restored with CAD-CAM blocks, IPS e.max CAD, Katana Zirconia, and Zolid Fx Zirconia were tested as endocrown materials. Bone geometry was simplified to be two coaxial cylinders in all models. Stress distributions under 50 N axial and oblique (with 135° angle from the vertical plane) loading were analyzed. Each model was then subjected to two occlusal loading conditions-the lingual slope of the incisal edge and the junction between incisal and middle thirds. Eighteen runs and calculations were performed to determine the endocrown height and material effect.

Results

The results showed a minor or negligible effect of changing the endocrown material. Increasing endocrown height was shown to reduce stresses and deformations on most of the model components (bone, gutta-percha, periodontal ligament, and endocrown), except root and cement. Differences in deformations and stresses between the two models of 4 and 6 mm were relatively smaller (ranged between 1% and 30%) compared to those between the 2 and 4 mm models (ranged between 10% and 400%).

Conclusions

The material used to fabricate endocrowns did not show considerable effect on the underlying structures. However, the endocrown design (2, 4, and 6 mm height) was shown to affect all components of the studied systems. Increasing endocrown height is recommended for bone, periodontal ligaments, and endocrown body, as it reduces stresses and deformations. On the other hand, it dramatically increases stresses on the root and cement layer. Smaller endocrown sizes represent an acceptable treatment option when there is a healthy periodontal state, while using larger sizes will be more suitable when there is a periodontal compromise with bone loss.

Biomechanics of anterior endocrowns with different designs and depths: Study of finite elements

Background

To date, there is no clear consensus in the literature on which endocrown design and depth is the most effective treatment option for restoring endodontically treated maxillary central incisors. Aim: To determine the stress distribution of the anterior endocrowns by means of finite element analysis.

Material and Methods

Nine 3D finite element models (groups A - I) were made, each one representing a restoration system of endodontically treated upper central incisors. The models were endocrowns with and without ferrules at 0, 1, 3, and 5 mm depth and a post-core stump control group. A static load of 100N of force was applied to the palatal face at 45º from the long axis of the tooth. The Von Mise values and the maximum stress in the crown, dentin and resin cementum were evaluated separately.

Results

The maximum stress distribution was C < B < A < D < H < F < E < G < I and the Von Mises stresses were in the upper 1/3 of the retainer of endocrowns A, B, C and D. ; in the vestibular neck in endocrowns E and F; in the final 1/3 of the retainer in the endocrown G; in the middle 1/3 of the retainer in the H endocrown; and at the level of the vestibular neck of the crown in model I.

Conclusions

The smallest distribution of maximum and Von Mises stresses was observed in model C. Key words:Finite element analysis, Biomechanics, upper central incisor, endodontically treated teeth, dental restoration.

Recent Advances in 3D Printing of Polymers for Application in Prosthodontics

Contemporary mass media frequently depict 3D printing as a technology with widespread utilization in the creation of dental prosthetics. This paper endeavors to provide an evidence-based assessment of the current scope of 3D printing's integration within dental laboratories and practices. Its primary objective is to offer a systematic evaluation of the existing applications of 3D-printing technology within the realm of dental prosthetic restorations. Furthermore, this article delves into potential prospects, while also critically examining the sustained relevance of conventional dental laboratory services and manufacturing procedures. The central focus of this article is to expound upon the extent to which 3D printing is presently harnessed for crafting dental prosthetic appliances. By presenting verifiable data and factual insights, this article aspires to elucidate the actual implementation of 3D printing in prosthetic dentistry and its seamless integration into dental practices. The aim of this narrative review is twofold: firstly, to provide an informed and unbiased evaluation of the role that 3D printing currently plays within dental laboratories and practices; and secondly, to instigate contemplation on the transformative potential of this technology, both in terms of its contemporary impact and its future implications, while maintaining a balanced consideration of traditional dental approaches.

Comparative Finite Element Analysis of Endocrowns and Traditional Restorations for Endodontically Treated Mandibular First Molars

BACKGROUND This study evaluated 2 endocrown designs and traditional restoration with a conventional crown using post and core to find the best restoration design for endodontically treated mandibular first molars. MATERIAL AND METHODS Three 3D finite element models were constructed: (1) post and core restoration, (2) endocrown butt joint margin design, and (3) endocrown with shoulder finish line. The intact tooth geometry was extracted with computed tomography, then modified to the selected restoration designs. Bone and mucosa geometry was simplified and represented as 3 cylinders. Two loading cases were examined on E-max crowns as 400N and 200N vertically and 45º oblique, respectively, that were located at buccal cusp tips and central fossa by nodal force distributed on circular areas with 0.5-mm diameter in each location. RESULTS Traditional restoration kept crown deformation and stresses at lower levels than did endocrowns. Results of the butt joint margin design were comparable to that of shoulder finish line design. Cement had the lowest stress values under shoulder finish line design, while the remaining tooth indicated the superiority of butt joint margin design, with less stresses by 20% and 24%, compared with traditional and shoulder finish line restorations, respectively. CONCLUSIONS The 3 tested restoration designs worked well. Although the differences were small, according to stress analysis results, conventional restoration by post and core achieved the best performance, followed by butt joint margin, which ensures lowest level of stresses on dentine. Finally, the shoulder finish line endocrown can replace the other designs but with higher stress levels.

In Vitro Resistance of Natural Molars vs. Additive-Manufactured Simulators Treated with Pulpotomy and Endocrown

Endocrowns are designed to restore endodontically treated teeth with root canal treatment (Rct). Recently, endocrowns were proposed for teeth treated with full pulpotomy (FP). No data exist on in vitro evaluations for this combination. This study aimed to evaluate the mechanical behavior of pulpotomy-treated teeth with endocrowns according to different protocols for preparation design and materials and to assess whether 3D-printed resin simulators could be a reliable alternative for human teeth during in vitro strength tests. One hundred and ten extracted natural molars were randomized into 11 groups according to the type of endodontic treatment, the material used, and the design of peripheric preparation. One hundred and ten resin simulators were separated similarly. The samples were embedded in epoxy resin blocks before being subjected to oblique compressive load until failure. For natural teeth, the variance analysis separated two homogeneous groups, one regrouping the endodontically treated or pulpotomy-treated teeth without coronal restoration and the other one regrouping all the other samples, i.e., the untreated teeth (positive controls) and the treated and restored teeth. The strength resistance was lower for the resin simulators than for natural teeth in all groups. Within the limit of this study, strength resistance is not the most important criterion for choosing the type of material, preparation, or endodontic treatment for endocrowns. Resin simulators are not efficient for in vitro strength studies.

Effect of various preparation designs on pull-out bond strength of endocrown

Background

The endocrown is described as monobloc ceramic component. The pull-out bond strength acts as a real-life scenario of failure that occurs in endocrown. The different preparation designs have been included to assess the type of preparation that resists the least failure.

Aim

To evaluate the effect of three different types of preparation designs on the pull-out bond strength (PBS) of computer-aided design/computer-aided manufacturing (CAD/CAM) monolithic endocrowns.

Methods and Materials

Thirty extracted mandibular first molars were used for this study. Root canal treatment was done. Samples were divided into three groups of 10 samples each. Group A consists of traditional endocrown preparation with a butt joint preparation. The group B consists of a modified preparation with 50-60 degree inward slope. The group C consists of preparation with a 50-60 degree outward slope. Endocrowns were fabricated using CAD/CAM lithium disilicate glass-ceramics. The endocrowns were adhesively bonded to the respective preparations. Pull-out bond strength was calculated using the universal testing machine at a crosshead speed of 1 mm/min.

Statistical Analysis

The results were statistically evaluated by one-way ANOVA and Tukey's post hoc analysis.

Results

Group B had higher pull-out bond strength compared to the other two types of preparation designs and showed a statistically significant value with a mean significant difference at 0.05 level (P < 0.05).

Conclusion

The 50-60 degree inward bevel in endocrown preparation increased the pull-out bond strength in lithium disilicate endocrowns.

Post-fatigue fracture load, stress concentration and mechanical properties of feldspathic, leucite- and lithium disilicate-reinforced glass ceramics

Objective

To evaluate the mechanical properties of different CAD/CAM ceramic systems and the post-fatigue fracture and stress distribution when used as cemented crowns.

Materials and methods

Sixty (60) CAD/CAM monolithic crowns were milled using three different ceramic materials (FD - Feldspathic [Vita Mark II]), LE - Leucite-based ceramic [IPS Empress CAD] and LD - Lithium Disilicate [IPS e.max CAD]) and adhesively cemented on resin composite dyes. Specimens were stored in distillated water (37 °C) for 7 days. After, half of the crowns were submitted to immediate fracture load test while the other half was submitted to fatigue cycling. The average cement layer of approximately 80 μm was assessed using scanning electron microscopy (SEM). The average thickness was used in the three-dimensional (3D) Finite Element Analysis (FEA). For each ceramic material, the density, Poisson ratio, shear modulus, Young modulus, fracture toughness, and true hardness were assessed (n = 3). The data was used to assess the Maximum Principal Stress throughout 3D-FEA according to each material during load to fail and post-fatigue. Data were submitted to two-way ANOVA and Tukey test (α = 0.05).

Results

LD showed the highest compression load, density, shear modulus, Young modulus, fracture toughness and true hardness values. While LE presented the lowest mechanical properties values. There is no difference in the Poisson ratio between the evaluated ceramics.

Conclusion

LD was susceptible to aging process but presented stronger physicomechanical properties, showing the highest post-fatigue fracture load and highest stress magnitude.

Unlocking Endocrown Restoration Expertise Among Dentists: Insights from a Multi-Center Cross-Sectional Study

BACKGROUND This study, employing an online questionnaire, aimed to assess and contrast the awareness, knowledge, and perceptions of dentists in Saudi Arabia (SA) regarding endocrowns (EC) as post-endodontic restorations with those of dentists educated in various other countries. MATERIAL AND METHODS We conducted a cross-sectional survey among dental interns and practicing dentists in government facilities, private dental centers, and dental colleges in SA, including participants of diverse nationalities. We disseminated validated, closed-ended questionnaires through WhatsApp via Google Forms. The Chi-square test was applied to assess associations between categorical variables, with a P-value of ≤0.05 indicating statistical significance. RESULTS The majority of participants (61.2%) indicated that EC restorations are best suited for molar teeth. Furthermore, 69.6% asserted that the primary objective of employing EC is to accomplish minimally invasive preparations while preserving the existing tooth structure. Among the responses, 68.3% pinpointed debonding of ECs as a significant cause of failure. Notably, substantial differences were observed in responses concerning the knowledge or practice of EC across various factors such as gender, educational attainment, country of graduation, and workplace. CONCLUSIONS The findings reveal a comparatively low adoption of ECs among the participants, irrespective of experience or country of education. This underscores the need for incorporating ECs into dental curricula through theoretical and clinical discussions or considering them as a subject for post-graduate continuing education programs.

Dental Fiber-Post Systems: An In-Depth Review of Their Evolution, Current Practice and Future Directions

The field of dental medicine is constantly evolving and advancing toward minimally invasive techniques. Several studies have demonstrated that bonding to the tooth structure, particularly enamel, yields the most predictable results. In some instances, however, significant tooth loss, pulpal necrosis, or irreversible pulpitis may limit the options available to the restorative dentist. In these cases, placement of a post and core followed by a crown is the preferred treatment option, provided all requirements are met. This literature review provides an overview of the historical development of dental FRC post systems as well as a comprehensive examination of the currently available posts and their bonding requirements. In addition, it offers valuable insights for dental professionals seeking to understand the current state of the field and the prospects of dental FRC post systems.

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.

Present status and future directions: The restoration of root filled teeth

This narrative review will focus on a number of contemporary considerations relating to the restoration of root filled teeth and future directions for research. Clinicians are now more than ever, aware of the interdependence of the endodontic and restorative aspects of managing root filled teeth, and how these aspects of treatment are fundamental to obtaining the best long-term survival. To obtain the optimal outcomes for patients, clinicians carrying out endodontic treatment should have a vested interest in the restorative phase of the treatment process, as well as an appreciation for the structural and biomechanical effects of endodontic-restorative procedures on restoration and tooth longevity. Furthermore, the currently available research, largely lacks appreciation of occlusal factors in the longevity of root filled teeth, despite surrogate outcomes demonstrating the considerable influence this variable has. Controversies regarding the clinical relevance of minimally invasive endodontic and restorative concepts are largely unanswered with respect to clinical data, and it is therefore, all too easy to dismiss these ideas due to the lack of scientific evidence. However, conceptually, minimally invasive endodontic-restorative philosophies appear to be valid, and therefore, in the pursuit of improved clinical outcomes, it is important that the efficacies of these treatment protocols are determined. Alongside an increased awareness of the preservation of tooth structure, developments in adhesive bonding, ceramic materials and the inevitable integration of digital dentistry, there is also a need to evaluate the efficacy of new treatment philosophies and techniques with well-designed prospective clinical studies.