Adhesive restoration of anterior endodontically treated teeth: influence of post length on fracture strength

Anterior Endocrowns as An Alternative to Core Crown restorations: A Systematic Review

Restoring extensively damaged endodontically treated teeth presents a challenging task due to the state of biomechanical deterioration affecting long-term prognosis. Therefore, the study aims to assess and compare the biomechanical performance of endocrowns and post core-crown restorations in anterior endodontically treated teeth with severe coronal structure loss. Following PRISMA guidelines, a systematic search was conducted using PubMed, Scopus, Web of Science, and Google Scholar for articles published from January 2014 to March 2024. Two independent reviewers screened and selected studies based on the predefined inclusion and exclusion criteria. The included studies were analyzed using the QUIN tool for risk of bias assessment in in-vitro studies. Additionally, the biomechanical outcomes were collected for qualitative comparative analysis. Twelve studies were included in this systematic review. In most studies, Endocrowns demonstrated comparable fatigue resistance under load to failure to post core-crown restorations. Endocrowns without ferrule exhibited a higher rate of debonding but had significantly more repairable failures. Conversely, post core-crown restorations demonstrated higher fracture resistance with the presence of ferrule, but were associated with more catastrophic failure patterns. Additionally, endocrowns generated lower stress levels in both the restorative material and the luting material compared to post core-crown restorations. Among the tested materials, lithium disilicate ceramics provided the best biomechanical properties. Overall, the studies included provided sufficient information for most evaluation criteria of the QUIN risk of bias assessment tool. Endocrowns are a viable and conservative approach for restoring endodontically treated anterior teeth, offering comparable biomechanical performance to traditional post core-crown restorations and less catastrophic failures. The findings of this systematic review suggest that endocrown restorations, especially with lithium disilicate ceramics and proper ferrule design, can improve fracture resistance and longevity of rehabilitated teeth, enhancing patient outcomes for severely damaged anterior endodontically treated teeth.

Mechanical performance of endocrown restorations in anterior teeth: A systematic review and network meta-analysis

OBJECTIVES

To conduct a systematic review and network meta-analysis (NMA) to answer whether endocrown restorations have similar mechanical behavior than other traditional core-crown systems with or without intracanal posts for the rehabilitation of anterior endodontically treated teeth.

METHODS

The review followed the PRISMA Extension Statement for NMA. Studies were identified by a systematic search to select reports on endocrown restorations in anterior teeth. A search was performed in PubMed (MEDLINE), Scopus, Web of Science, Embase, SciELO, and LILACS databases. Articles evaluating mechanical performance through in vitro and finite element analysis (FEA) studies were selected and the risk of bias was assessed using the RoBDEMAT and ROBFEAD tools, respectively. The data were analyzed qualitatively and quantitatively through NMA using the MetaInsight tool.

RESULTS

Eleven articles were included (eight in vitro and three with FEA design). Six in vitro studies were evaluated using NMA. Composite resin endocrowns showed greater load-to-fracture and lower occurrence of catastrophic failures than traditional restorations. Combining glass fiber post with composite restoration also showed good strength behavior. Regarding FEA studies, two out of three studies showed a more homogeneous distribution of stress for the endocrown group.

SIGNIFICANCE

Endocrowns performed similarly to or better than conventional restorative strategies, with composite resin being the most recommended material of choice. The rehabilitation of endodontically treated anterior teeth with extensive coronal destruction is typically challenging for the dentist, and there is still no consensus in the literature that provides conclusive answers for choosing the appropriate material and restorative strategy. Exploring new techniques and materials that make this procedure easier for the dentist and guarantee good results is paramount.

Fracture Resistance of Anterior Teeth Restored with Post-retained Ceramic Crown vs Ceramic Endocrowns

AIM

To compare the fracture resistance of anterior teeth restored with either glass fiber post (GFP) and conventional lithium disilicate (LDS) crowns or endocrowns made of LDS or hybrid ceramics.

MATERIALS AND METHODS

A total of 21 central incisors with 2-mm ferrule and 1-mm shoulder finish line were applied in this investigation. The teeth were divided into three main groups (n = 7) according to the type of restoration used: PC glass fiber post (GFP) and e-max crown, EE (LDS endocrown), and VE (Vita-Enamic endocrown). Mechanical cyclic loading was conducted in a chewing simulator to simulate 6 months of clinical use. Fracture resistance and failure mode were assessed; further examination of fractured specimens was done with scanning electron microscopy.

RESULTS

Post-hoc Tukey's test was performed to investigate the pairwise differences in fracture resistance among the three groups, and the results were p = 0.0452 between PC and VE groups, which is significant statistically. In contrast, p = 0.0615 between PC and EE groups, which is not significantly different. Chi-square test was made to analyze the results of mode of failure among the three groups, and there was a significant difference; p-value = 0.0289.

CONCLUSION

The LDS endocrowns show fracture resistance similar to that of GFP-supported full coverage LDS crowns, with advantage of more restorable mode of fractures. Vita-Enamic endocrowns, despite having fracture resistance lower than other groups, showed fracture resistance higher than the physiologic load, with restorable fractures more than both LDS endocrowns and GFP LDS crowns.

CLINICAL SIGNIFICANCE

For dental practitioners, endocrowns in damaged anterior endodontically treated teeth provide similar fracture resistance to GFP and full crowns, with the advantage of more restorable fractures if occurred. How to cite this article: Mohamed AA, Badawy MBA, El-Kouedi AMY, et al. Fracture Resistance of Anterior Teeth Restored with Post-retained Ceramic Crown vs Ceramic Endocrowns. J Contemp Dent Pract 2024;25(11):1045-1051.

Clinical performance of polyethylenefiber reinforced resin composite restorations in endodontically treated teeth: (a randomized controlled clinical trial)

AIM

The purpose of this study was to evaluate the performance of polyethylene fiber reinforced resin composite fillings compared to bulk fill resin composite fillings in endodontically treated teeth over a two-year monitoring period.

METHOD

A total of 240 individuals with endodontically treated lower molars and a moderate amount of tooth structure were divided into two equal groups of 120 each. One group received polyethylene fiber reinforced bulk fill resin composite restorations while the other group received only bulk fill resin composite restorations, both applied as per manufacturer guidelines. Two proficient experienced blinded assessors assessed the restorations using modified USPHS criteria at baseline, 6, 12, and 24 months.

STATISTICAL ANALYSIS USED

Data analysis involved the utilization of Mann-Whitney U, Friedman's test, and Nemenyi post hoc test, with age data being displayed as mean and standard deviation. The significance level was established as p < 0.05, and R software was utilized for statistical analysis.

RESULTS

There were no notable distinctions in any parameters or scores between the intervention and comparator groups at various time points. Alpha scores were present for retention, gross fracture, and secondary caries at all follow up intervals.

CONCLUSION

Both direct resin composite restorations reinforced with polyethylene fibers and direct bulk fill resin composite restorations placed in endodontically treated molars with moderate remaining tooth structure demonstrated satisfactory clinical outcomes during a 24-month follow-up period.

CLINICAL RELEVANCE

Bulk fill resin composites directly placed in endodontically treated molars with moderate remaining tooth structure showed promise as a treatment option over a two-year period.

CLINICAL TRIAL REGISTRATION

(06-01-2022) on https://ClinicalTrials.gov with the ID (NCT05180903).

Clinical and laboratorial performance of rehabilitation of endodontically treated teeth: A systematic review

OBJECTIVE

This systematic review aimed to analyze the clinical (survival rate, failure risk, or fracture) and laboratory performance (fracture mode or failure) of rehabilitations of endodontically treated teeth, with and without posts.

MATERIALS AND METHODS

A systematic search was conducted in the Pubmed, Scopus, Web of Science, Embase, Cochrane Library, and OpenGrey databases up to March 2023, according to PRISMA guidelines. In vitro and clinical studies that compared the clinical and laboratory performance of endodontically treated teeth with and without intraradicular posts were included. Studies selection, data extraction, and risk of bias analysis were performed.

RESULTS

Thirty-one in vitro and 7 clinical studies were included. For in vitro studies, fiberglass post (n = 24) was the most mentioned. The follow-up time of the clinical studies ranged from 1 to 17 years, with the fiber-reinforced composite post (n = 3) being the most evaluated, and only failure risk proved to be more favorable for using intraradicular posts.

CONCLUSION

Rehabilitations of endodontically treated teeth with and without intraradicular retainers showed no difference in fracture resistance and failure mode, evaluated by in vitro studies. Clinical studies showed no difference in survival rate, but failure risk proved to be more favorable for the use of posts.

CLINICAL SIGNIFICANCE

This analysis revealed significant variability between results, however, most laboratory and clinical studies revealed no difference with using the post. Furthermore, it is important to emphasize the need to evaluate the coronary remnant and the general characteristics of the tooth in each situation.

Static Loading of Different Intraradicular Preparation Depths of Trinia Endocrowns in Maxillary Canines

AIM

The aim of this study is to compare the fracture resistance of canine teeth restored using TRINIA Endocrowns with three different types of preparations (2, 3, and 4 intracanal preparations).

MATERIALS AND METHODS

Thirty maxillary-extracted canines were collected. All teeth were fixed in orthodontic acrylic resin and decapitated at the level of the proximal cemento-enamel junction (CEJ). After being endodontically treated, specimens were distributed equally between 3 groups (n = 10) with different preparation depths (GT: 2 mm Intraradicular Preparation, GH: 3 mm Intraradicular Preparation, GF: 4 mm Intraradicular Preparation). Thirty TRINIA endocrowns were dry milled. After surface treatment, all endocrowns were bonded to their corresponding roots using Permaflo a dual-cure resin cement. Each specimen was then fixed in the lower part of a universal testing machine with a load cell of 5 KN, at an angle of 45 degrees to the tooth long-axis at 0.5 mm/min crosshead speed. Failure loads were recorded in Newton's. Data were recorded, organized, and statistically investigated.

RESULTS

Shapiro-Wilk tests revealed that the data were not normally distributed. Descriptive statistics revealed a high mean fracture resistance of GH (647 N), then GT (475.6 N), and finally GF (353.9 N). The Kruskal-Wallis test revealed a significant difference that existed between the groups being studied (p = 0.036).

CONCLUSION

TRINIA endocrowns with intracanal preparations of 2 and 3 mm provide more promising fracture resistance than those with intracanal preparations of 4 mm as a way of treating of root-canal-treated maxillary canines. TRINIA endocrowns (2 and 3 mm intracanal preparations) are as promising as fiber posts and all ceramic crowns in terms of fracture resistance. TRINIA endocrowns with 2 mm intracanal preparations are mostly reparable after failure, but those of 3 and 4 mm are mostly irreparable after failure.

CLINICAL SIGNIFICANCE

Modifying endocrowns to have intraradicular projections, simulating Nayyar core, may improve the success and longevity of endocrowns in anterior teeth. How to cite this article: Alahmad AM, Alenezi AY, Rayyan M, et al. Static Loading of Different Intraradicular Preparation Depths of Trinia Endocrowns in Maxillary Canines. J Contemp Dent Pract 2024;25(6):575-580.

Biomechanical performance of endocrown and core-crown restorations: A systematic review

OBJECTIVE

To assess and compare, through a systematic review of the literature, the biomechanical performance of endocrowns and traditional core-crowns (with and without intracanal post) for the rehabilitation of endodontically treated teeth with severe coronal structure damage.

MATERIALS AND METHODS

A systematic search was performed in MEDLINE/PubMed, Scopus, and Web of Science databases. In-vitro studies comparing endocrowns with (post-)core-crown restorations were selected and screened by two independent reviewers. The included studies were submitted to the risk of bias analysis using the RoBDEMAT tool and the biomechanical outcomes were collected for qualitative analysis. The extracted data were presented based on comparative analyses among the included studies.

RESULTS

Thirty-one studies were included: 9 studies evaluated restorations of molars, 14 for premolars, and 8 studies evaluated anterior restorations. For the majority of the studies, endocrowns showed either similar or greater survival rates under fatigue and monotonic load than (post-)core-crown restorations, irrespectively of the tooth. The endocrowns showed more favorable failure patterns than (post-)core-crowns, irrespectively of the tooth. Endocrowns produced lower stresses in the restorative material for molars and premolars and in the luting material for premolars than (post-)core-crown restorations. The included studies presented adequate information for most items of the RoBDEMAT risk of bias tool.

CONCLUSION

Endocrowns showed similar or greater biomechanical performance than the traditional (post-)core-crown restorations in most of the evaluated studies.

CLINICAL SIGNIFICANCE

This systematic review showed that endocrowns present either similar or greater biomechanical performance than core-crown restorations for anterior and posterior endodontically treated teeth with severe structural damage.

Current Insights on Fiber Posts: A Narrative Review of Laboratory and Clinical Studies

PURPOSE

The aim of this study was to review the literature related to the clinical performance and laboratory findings regarding fiber posts, as well as the cementation technique employed with their use.

MATERIALS AND METHODS

A literature search was performed using an electronic database, PubMed/Medline, between 2010 and 2023. The terms used were "intra coronal post, fiber post, post cementation, and post length". Titles and abstracts were initially screened, and a full-text assessment was conducted for those that fulfilled the inclusion criteria. The reference list of the collected papers was also screened for further relevant citations.

RESULTS

In this work, 135 potentially eligible studies were analyzed. Titles and abstracts of 90 studies followed the inclusion criteria and were selected for a full-text assessment, resulting in 50 studies selected. Moreover, additional studies from relevant citations were included, totaling 57 studies.

CONCLUSION

According to the laboratory and clinical studies revised, the survival rate between fiber and prefabricated and cast metal posts was similar, and failures were mainly related to the loss of retention. The intra-canal post length of less than two-thirds of the root length presented successful results when ferrule was present. Furthermore, the ferrule increased the longevity of teeth restored with fiber posts. Additionally, the use of a surface treatment protocol for fiber posts and the adhesive cementation technique both contributed to the clinical success and longevity of the intra-canal post.

Crack Propagation and Fatigue Performance of Partial Posterior Indirect Restorations: An Extended Finite Element Method Study

Dental ceramics are susceptible to slow, progressive crack growth after cyclic loading. The purpose of this study was to investigate the progressive patterns of cracks in two different types of CAD/CAM ceramic materials used with three different partial posterior indirect restoration (PPIR) designs and to determine the materials' failure risk using a fatigue test. Standard initial cracks were formed in Standard Tessellation Language (STL) files prepared for three different PPIRs. The materials chosen were monolithic lithium disilicate (LS) and polymer-infiltrated ceramic networks (PICNs). The extended finite element method (XFEM) was applied, and the fatigue performance was examined by applying a 600 N axial load. The cracks propagated the most in onlay restorations, where the highest displacement was observed. In contrast, the most successful results were observed in overlay restorations. Overlay restorations also showed better fatigue performance. LS materials exhibited more successful results than PICN materials. LS materials, which can be used in PPIRs, yield better results compared to PICN materials. While inlay restorations demonstrated relatively successful results, overlay and onlay restorations can be specified as the most and the least successful PPIR types, respectively.

Comparison of the pull-out bond strength of endodontically treated anterior teeth with monolithic zirconia endocrown and post-and-core crown restorations

PURPOSE

The purpose of this study was to assess the pull-out bond strength (PBS) of endodontically treated anterior teeth that had been restored with monolithic zirconia endocrowns using different extension depths (EDs) and post-and-core crowns after chewing simulation.

METHODS

Thirty-six maxillary central teeth were used (n = 12). Group I: Glass fiber post-and-core crown, Group II: Endocrown with 3-mm EDs, Group III: Endocrown with 5-mm EDs. Restorations were fabricated from monolithic zirconia blocks using a CAM (computer-aided manufacturing) device. For cementation, conventional resin luting agent (Multilink N) was used. All samples were aged with a chewing simulator and PBS tests were conducted at a speed of 1 mm/min using an electromechanical servo universal testing machine. The values were recorded in MPa by dividing the failure load by the bonding area. One-way ANOVA and the post-hoc Tukey test were used for statistical analysis (P = 0.05).

RESULTS

Group III demonstrated significantly greater PBS values than Groups I and II (P = 0.001). No significant difference was found between Groups I and II (P = 0.072).

CONCLUSION

Increasing the ED of an endocrown influences the PBS of endodontically treated anterior teeth restored with monolithic zirconia endocrowns.

Fracture resistance of root canal-treated molars restored with ceramic overlays with/without different resin composite base materials: an in vitro study

The objective of the study was to evaluate the effect of different restorative protocols on fracture resistance of root canal-treated molars. 48 mandibular first molars were used and divided into six groups (n = 8); G1 (negative control): teeth kept intact. G2 (positive control): teeth had root canal treatment and standard MOD cavity preparations but kept unrestored. G3: prepared as G2 and directly restored with VitaEnamic ceramic overlays (CO). G4: as G3, but the pulp chamber was restored first with smart dental restorative (SureFil SDR flow = SDR) bulk-fill flowable composite base. G5: as G3, but the pulp chamber was restored first with SonicFill (SF) bulk-fill composite base. G6: as G3, but the pulp chamber was restored first with a fiber-reinforced composite (FRC) base. All samples were subjected to thermocycling between 5 °C and 55 °C in a water bath for a total of 2000 cycles with 10 s dwell time. Then specimens were individually mounted on a computer-controlled testing machine with a load cell of 5 kN, and the maximum load to produce fracture (N) was recorded. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test (P = 0.05). There was a significant difference between the groups (P < 0.001). Teeth restored with FRC and ceramic overlays had the highest load-bearing capacity. Pulp chamber restoration with either FRC or SDR before ceramic overlay fabrication provided significantly better tooth reinforcement than ceramic overlay alone (P < 0.001). Fracture modes were analyzed to determine the type of fracture as repairable or catastrophic, where FRC + CO and SDR + CO groups had favorable fracture modes that were mostly repairable. When restoring root canal-treated molars with overlays, the pulp chamber should be sealed with either FRC or SDR to ensure the best possible fracture resistance. The clinical relevance of the study is that a new simple restorative protocol is presented to enhance the survival of root canal-treated molars using ceramic overlays.

Endocrowns versus post-core retained crowns as a restoration of root canal treated molars - A review article

Normally root canal-treated teeth are covered with crowns to prevent fracture, which becomes challenging in cases where the tooth is extensively damaged. In such instances, various restorative methods such as post-core and endocrowns have been in use. The former methodology in recent times is being discouraged owing to impending tooth weakening. Due to this reason, an uncommon type of reconstruction, endocrowns are preferred. We carried out a comparative review of restorations for endodontically treated molars.

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores

Objectives

The aim of this in vitro study was to investigate the fatigue survival and fracture behavior of endodontically treated (ET) premolars restored with different types of post-core and cuspal coverage restorations.

Materials and methods

MOD cavities were prepared on 108 extracted maxillary premolars. During the endodontic treatment, all teeth were instrumented with rotary files (ProTaper Universal) to the same apical enlargement (F2) and were obturated with a matched single cone obturation. After the endodontic procedure, the cavities were restored with different post-core and overlay restorations (n = 12/group). Three groups (A1–A3) were restored with either conventional composite core (PFC; control) or flowable short-fiber-reinforced composite (SFRC) core with/without custom-made fiber posts and without overlays. Six groups had similar post-core foundations as described above but with either direct PFC (B1–B3) or indirect CAD/CAM (C1–C3) overlays. Fatigue survival was tested for all restorations using a cyclic loading machine until fracture occurred or 50,000 cycles were completed. Kaplan-Meyer survival analysis was conducted, followed by pairwise post hoc comparisons.

Results

None of the restored teeth survived all 50,000. Application of flowable SFRC as luting-core material with fiber post and CAD/CAD overlays (Group C3) showed superior performance regarding fatigue survival (p < 0.05) to all the other groups. Flowable SFRC with fiber post and direct overlay (Group B3) showed superior survival compared to all other direct techniques (p < 0.05), except for the same post-core foundation but without cuspal coverage (Group A3).

Conclusions

Custom-made fiber post and SFRC as post luting core material with or without cuspal coverage performed well in terms of fatigue resistance and survival when used for the restoration of ET premolars.

Clinical relevance

The fatigue survival of direct and indirect cuspal coverage restorations in ET MOD premolars is highly dependent on whether the core build-up is fiber-reinforced or not. The combination of short and long fibers in the form of individualized post-cores seems to offer a favorable solution in this situation.

Restoration of Severely Damaged Endodontically Treated Premolars: Influence of the Ferrule Effect on Marginal Integrity and Fracture Load of Resin Nano-ceramic CAD-CAM Endocrowns

OBJECTIVES

To explore the ferrule effect on Resin Nano-Ceramic (RNC) premolar endocrown marginal integrity and fracture resistance.

METHODS

Thirty-six root-canal-treated premolars were cut 2 mm above the cemento-enamel junction (CEJ). They were restored with standardized RNC computer-aided design/computer-aided manufacturing (CAD/CAM) restorations (Lava Ultimate, 3M Oral Care, St. Paul, MN, USA) and divided into three groups (n=12): endocrowns with a 3-mm endo-core (Group 1), endocrowns with a 3-mm endo-core and a 2-mm ferrule (Group 2), and conventional post-and-core crowns with a 2-mm ferrule (Group 3). All specimens were submitted to thermo-mechanical cycling loading (TMCL) (1.7 Hz, 49 N, 600 000 cycles, 1500 thermocycles). Margins were analyzed before and after the TMCL. In the second part of the experiment, the surviving specimens were submitted to unidirectional monotonic loading until fracture. Fragments were then analyzed using scanning electron microscopy (SEM) and the fracture mode was established.

RESULTS

Endocrowns of Groups 1 and 2 performed better than conventional crowns (Group 3) in terms of marginal continuity. Differences in fracture load values within all groups were not statistically significant. Most of the specimens fractured in a non-repairable way.

CONCLUSIONS

The present test failed to provide evidence of any kind of difference between endocrowns with and without a ferrule in terms of load-bearing capacity and marginal integrity after fatigue. Further studies are needed to confirm the role of the ferrule in adhesive restorations of endodontically treated teeth.

Comparison of the fracture strength of endodontically treated teeth restored with polyether ether ketone, zirconia and glass-fibre post-core systems

PURPOSE

This study aimed to compare the fracture resistance and fracture mode of maxillary central incisors restored with four different sizes and three different post-core systems.

MATERIALS AND METHODS

One hundred and twenty maxillary incisors were endodontically treated and randomly divided into three groups (12 subgroups). Post cavities for the narrow subgroups were prepared with 1.4-mm-diameter drills in lengths of 7.5 mm (SN) and 10 mm (LN). Post cavities for the wide subgroups were prepared with 1.6-mm-diameter drills in lengths of 7.5 mm (SW) and 10 mm (LW) (n = 10). Group F was restored with glass-fibre post and composite resin core, Group P was restored with custom PEEK post-core and Group Z was restored with custom zirconia post-core. All posts were cemented with a dual-cure resin cement. Zirconia copings were cemented. Specimens were loaded on the palatal surface with a universal testing machine, and the fracture strengths of the teeth were statistically analysed using ANOVA and post hoc Tukey tests.

RESULTS

Statistically significant differences existed between the fracture strengths of the post materials. The highest fracture strength was in Group F, and the lowest was in Group P. Evaluation of the fracture strengths of the post lengths and diameters demonstrated that the short-narrow group of Group Z had the lowest fracture strength (P < .05). The long-wide group of Group F showed the highest fracture resistance. In Group P, no statistically significant difference existed between the post-cores of different dimensions (P > .05). Irreparable fractures were observed mostly in Group Z, and decementation was more common in Group P.

CONCLUSIONS

PEEK post-cores showed sufficient fracture strength for the anterior region, similar to the other two post-core materials. PEEK post-cores showed more decementation and repairable fractures at lower forces, while restoration failure was mostly catastrophic for glass-fibre and zirconia posts.

Retention of different CAD/CAM endocrowns bonded to severely damaged endodontically treated teeth: An in vitro study

Aim:

Assess the retention of endocrowns fabricated of different CAD/CAM materials.

Settings and Design:

In vitro - comparative study.

Material and Methods:

Root canal treated mandibular first molars were prepared in a standardized method. Standardized endocrowns were manufactured using four CAD-CAM blocks: resin infiltrated ceramic (Vita Enamic), partially stabilized tetragonal zirconia (Katana), lithium disilicate ceramic (IPS e.max CAD), and polyether-ether-keton (PEEK, BioHPP). After proper surface treatment, the restorations were cemented using a resin cement (Panavia F2.0) and were connected to a special attachment unit and secured to a universal testing machine. The amount of axial load required to dislodge the restoration from the tooth structure was measured (n = 12, α = 0.05). Failures were classified as adhesive debonding from the tooth structure without damaging the supporting tooth structure and cohesive fracture of the supporting tooth structure

Statistical Analysis Used:

One-way analysis of variance,Tukey's post hoc test.

Results:

The retention of Vita Enamic (61 ± 11 N) and IPS e.max CAD (58 ± 9 N) was significantly higher (F = 123, P < 0.01) than Katana (33 ± 13) and Peek restorations (23 ± 11). Vita Enamic and IPS e.max CAD were associated with fractured tooth segments during debonding while Katana and PEEK specimens were adhesively debonded from the remaining tooth structure.

Conclusions:

Within the limitations of this study, using lithium disilicate ceramics and resin infiltrated ceramics as restorative materials to fabricate endocrowns to restore severely damaged endodontically treated teeth, recorded significantly higher retention values. Meanwhile, using yttrium partially stabilized zirconia and polyether ether ketones for the same purpose recorded a favorable mode failure which avoided the possibility of tooth fracture.

Fracture resistance of maxillary premolars restored with different endocrown designs and materials after artificial ageing

PURPOSE

To evaluate the effect of three different designs and two monolithic ceramic materials on the durability and fracture resistance of endocrowns on maxillary first premolars, in comparison to post-and-core crowns.

METHODS

Fifty-six maxillary premolars were endodontically treated and shortened to a level of 2 mm from the cervical line, and randomly categorized into six endocrown groups and post-and-core crown control group (n=8); E1; endocrowns with flat occlusal table (without ferrule), E2; endocrowns with 1.5 mm circumferential ferrule, E3; endocrowns with 1.5 mm buccal ferrule preparation. Two materials were used for endocrowns: zirconia (4YSZ; Z), and lithium disilicate (L). The control group was restored with zirconia posts, and lithium disilicate crowns. All restorations were bonded using Panavia V5 and its respective primers and underwent thermo-mechanical fatigue with a 10 kg dynamic load for 1,200,000 cycles and thermocycling between 5 and 55 °C. Thereafter all survived specimens were loaded to fracture. The results were statistically analyzed using ANOVA and T-Test.

RESULTS

None of the specimens showed any signs of debonding or fracture caused by the fatigue test. The PC control group showed no statistically significant difference in comparison to groups ZE1, ZE2 and LE2 ( p > 0.05 ). However, it was significantly different from groups LE1, LE3, and ZE3 ( p ≤ 0.05 ).

CONCLUSIONS

Preparation designs and materials affected the fracture resistance of endocrowns. The results showed a superiority of the post-and-core crowns,zirconia/lithium disilicate endocrowns with 1.5 mm circumferential ferrule, and zirconia endocrowns with the flat occlusal table.

The Influence of Dentin Wall Thickness and Adhesive Surface in Post and Core Crown and Endocrown Restorations on Central and Lateral Incisors

CLINICAL RELEVANCE

Post and core crowns and endocrowns perform similarly on fracture strength, but endocrowns have more repairable fractures.

SUMMARY

Influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors

The aim is to evaluate the influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors. 150 maxillary central incisors were divided into three groups, Group 0, intact teeth; Group 1, removal of distal wall; Group 2, removal of mesial and distal walls, and further into two subgroups A₀,A₁,A₂ and B₀,B₁,B₂ according to post-endodontic restoration (post/no-post), then loaded to fracture. Interactions among variables and intergroup significance were tested with two-way ANOVA and Kruskal Wallis's tests (p≤0.05). Tukey's test was applied for multiple comparisons. Statistically significant differences were found between groups B₁-A₁, and B₂-A₂, but they were not found between B₀-A₀. Intragroup analysis showed statistically significant differences in both groups post/no-post with decreasing dental substance. Fiber post placement causes an increase in fracture strength and a reduction of irreparable fractures in endodontically treated maxillary central incisors that lost at least one wall.

Fatigue failure of anterior teeth without ferrule restored with individualized fiber-reinforced post-core foundations

OBJECTIVES

The aim was to explore the survival of extensively damaged anterior teeth without ferrule restored with different fiber-reinforced composite (FRC) post-core foundations and composite crowns.

MATERIALS AND METHODS

Sixty extracted upper central incisors were decoronated and randomly divided into four groups (n = 15). After endodontic treatment, the specimens were restored with different individualized fiber-reinforced post-core foundations as follows: control group (CTRL): multiple unidirectional FRC-post + dual-cure composite-core, PFC: multiple unidirectional FRC-post + packable short fiber-reinforced composite (SFRC), BPFC: Bioblock technique with only packable SFRC, BFFC: Bioblock technique with only flowable SFRC. After core build-up, the teeth were finalized with adhesively luted CAD/CAM composite crowns. Cyclic isometric loading (5 Hz) was applied at 100 N for 5000 cycles, and then 200 N and 300 N for 15,000 cycles each in a fluid chamber. The specimens were loaded until fracture occurred or when a total of 35,000 cycles were reached. Kaplan-Meyer survival analysis was conducted, followed by pairwise log-rank post hoc comparisons (Mantel-Cox).

RESULTS

The survival rates of the control (8279 cycles) and PFC (6161 cycles) were significantly higher compared to BPFC (3223 cycles) and BFFC (2271 cycles) (p < 0.05). Regarding fracture pattern, nearly all specimens fractured in a restorable manner.

CONCLUSIONS

For restoring extensively damaged anterior teeth, multiple unidirectional FRC posts are recommended.

CLINICAL RELEVANCE

Although different FRC post/core systems are available for the restoration of damaged root canal treated anterior teeth, multiple unidirectional FRC posts tend to be a good option when the ferrule is missing.

Biomechanical behavior of endocrowns vs fiber post-core-crown vs cast post-core-crown for the restoration of maxillary central incisors with 1 mm and 2 mm ferrule height: A 3D static linear finite element analysis

To analyze the stress distribution of the maxillary central incisor with oblique fracture, repaired by different methods, using 3-dimensional finite element analysis. From the biomechanical point of view, it is expected to provide a reference for clinical selection of restoration method which is more conducive to stress distribution and preservation of dental tissue as much as possible.Use cone beam CT and finite element software to establish the finite element models of the maxillary central incisor with oblique fracture, and then create models according to 5 repairing methods(A. fiber post-core-crown group; B. cast post-core-crown group; C.3 mm deep endocrown; D.4 mm deep endocrown; E.5 mm deep endocrown)after root canal treatment, and analyze the Von Mises equivalent stress and maximum principal stress distribution and peak value of each model.When the height of dentin ferrule was fixed, the value of the Von Mises equivalent stress and the maximum principal stress in residual tooth tissue: group A was the highest, and there was no significant difference in group B, C, D and E. And the stress distribution area of 5 groups were the same. In prosthodontic layer: group B was the highest, while group A was the lowest, and the stress peak slightly increased with the increase of depth in group C, D and E. And the 5 groups were with the same stress distribution area as well. In adhesive layer: group A was the highest, while group B was the lowest, and there was little difference among group C, D and E. Group A was concentrated in 1/3 of the post tip, while group B,C,D and E were concentrated in 1/3 of the post and the post tips.Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 3 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown.

Influence of glass fiber posts on the fracture susceptibility of endodontically treated maxillary anterior teeth with direct veneers: Preliminary results of a randomized clinical trial

OBJECTIVE

The purpose of this randomized clinical trial was to evaluate the influence of glass fiber posts on fracture susceptibility of endodontically treated maxillary anterior teeth with direct veneers.

MATERIALS AND METHODS

Fifty participants had 1 maxillary anterior tooth restored with a direct veneer. They were divided into 2 groups (n = 25) according to the use of intraradicular glass fiber posts. Clinical evaluation was performed at baseline, 6 and 12 months. The treatment success was determined by the absence of tooth fracture. If there was fracture, it was classified according to its extent. Fischer exact test was performed to analyze the criteria among the groups at each evaluation time. Friedman repeated analysis of variance assessed the difference in the performance of each group at three recall times (α = 0.5).

RESULTS

For control group, at the 6-month follow-up, one tooth had suffered a catastrophic failure, which resulted in tooth extraction. Fisher statistical analysis showed no significant difference between the cumulative success rate of the groups for the 6 (P > .999) and the 12-month (P > .999) period. Friedman test showed no significant difference among the periods of evaluation (P > .999).

CONCLUSIONS

Both groups had a similar success rate for maxillary anterior endodontically treated teeth with direct veneers after 12 months.

CLINICAL IMPLICATIONS

Glass fiber post use does not influence the fracture susceptibility of maxillary anterior endodontically treated teeth with direct veneers in the short term.

Marginal adaptation and fracture strength of endocrowns manufactured with different restorative materials: SEM and mechanical evaluation

Endocrowns were manufactured using different restorative materials to evaluate the marginal adaptation and fracture strength. Fifty endodontically treated mandibular first molar teeth were divided into five groups (n = 10). Endocrowns were obtained from lithium disilicate glass ceramic ingots by heat-press technique (Group e.max Press: GEP), and from feldspathic blocks (Group Cerec: GC), polymer infiltrated ceramic network blocks (Group Enamic: GE), lithium disilicate glass ceramic blocks (Group e.max CAD: GEC), and zirconia-reinforced glass ceramic blocks (Group Suprinity: GS) by CAD/CAM technique. After thermocycling, marginal adaptation was evaluated under scanning electron microscope at ×200 magnification. The specimens' fracture strengths were tested in universal test machine, and fracture types were evaluated. Statistical analyses were performed with Kruskal-Wallis test. The highest marginal gap value was found in GEP, but no significant differences were determined among the other four groups (p > .05). Significant differences were observed among the groups in terms of fracture strength (p = .019). The fracture strength values of GEC were significantly higher than GE, GC, and GS (p < .05). Values were not significantly different between the GEC and GEP groups (p > .05). CAD/CAM endocrowns showed better marginal adaptation than heat-pressed endocrowns. Clinically acceptable marginal gaps were seen in both endocrown types. Both CAD/CAM and heat-pressed lithium disilicate glass ceramic endocrowns showed higher fracture strength.

Effect of restorative treatment with endocrown and ferrule on the mechanical behavior of anterior endodontically treated teeth: An in vitro analysis

This study evaluated the effect of endocrown and ferrule restorative treatment on the mechanical behavior of anterior endodontically treated teeth. Human canines were treated endodontically and distributed in five groups (n = 10): sound teeth (S), crown associated with glass fiber post (GFP) and ferrule (GFP_f+) and that without ferrule (GFP_f-), and endocrown with ferrule (E_f+) and that without ferrule (E_f-). The crowns were obtained in lithium disilicate-based glass ceramic and cemented with resin. Thermomechanical loading (TL) was performed with progressive load of 80, 120, 160, 200, 240, 280, and 320 N with 20,000 cycles each, 140,000 cycles in total, frequency of 5 Hz, and temperature variation of 5°C-55 °C, followed by fracture resistance testing with load cell of 1000 Kgf and crosshead speed of 0.5 mm/min in a universal testing machine. Failure mode has been evaluated. Data were compared by Kaplan-Meier survival analysis (p < 0.05) for TL and one-way ANOVA and Tukey's test (p < 0.05) for fracture resistance. TL showed higher number of fractures for groups without ferrule (GFP_f- = 7, GFP_f+ = 3, E_f- = 10, and E_f+ = 2) and lower mean fracture load probability (GFP_f+ = 300 N, GFP_f- = 280 N, E_f+ = 320 N, E_f- = 188 N) than those with ferrule. Regarding fracture, teeth rehabilitated with GFP were more resistant to endocrowns with ferrule (p < 0.05). A higher percentage of type III failures after fatigue and type II failures after fracture were found. In conclusion, rehabilitation using GFP with ferrule is more favorable for anterior teeth, but the use of endocrown with ferrule proved feasible.

The fracture strength of endocrowns manufactured from different hybrid blocks under axial and lateral forces

AIM

This in vitro study was conducted to compare the fracture strength of endocrowns manufactured from different hybrid blocks under axial and lateral forces.

MATERIAL AND METHODS

Following root-canal treatment, 100 permanent mandibular first molars were randomly distributed among 5 groups according to restoration material. Endocrown restorations were produced from IPS e.max CAD (IPS), Vita Enamic (VE), GC Cerasmart (GC), Shofu (SH), and Brilliant Crios (BC) using CAD/CAM technology. Specimens were cemented, subjected to artificial aging, and further divided into 2 subgroups (n = 10) per group for fracture testing. Each specimen was placed on a universal testing machine and subjected to axial or lateral forces applied at a crosshead speed of 1 mm/min. Fracture data were analyzed using one-way ANOVA, Tukey, Tamhane T2, and Weibull tests.

RESULTS

Statistically significant differences in fracture-strength (FS) values under axial and lateral forces were observed among the groups (P < 0.05). Group BC had the highest FS value under axial forces, whereas group IPS had the highest FS value under lateral forces. According to Weibull analysis, VE exhibited the highest reliability under axial forces (7.62), whereas IPS exhibited the highest reliability under lateral forces (4.68). No statistically significant differences were detected in the distribution of failure types under either axial or lateral forces among the groups (P > 0.05).

CONCLUSION

All of the hybrid blocks tested showed sufficient fracture strength for use as CAD/CAM-fabricated endocrowns.

CLINICAL RELEVANCE

Hybrid blocks can be used as an alternative to lithium disilicate blocks in endocrown restorations.

Influence of restoration thickness on the stress distribution of ultrathin ceramic onlay rehabilitating canine guidance: a 3D-finite element analysis

BACKGROUND

The rehabilitation of canine guidance can be performed with adhesive indirect materials, but can the restoration thickness be reduced without mechanical disadvantages? Thus the goal of this study was to analyze the stress of upper canines which received different thicknesses of ceramic fragments for the rehabilitation of the canine guidance using finite element analysis.

METHODS

A superior canine was modeled using a computer aided design software. The dental tissues were individually shaped containing enamel, dentin and periodontal ligament. The following three different ceramic fragment thicknesses were then implemented: 0.3, 0.7 and 1.5 mm. Lithium disilicate was chosen as the ceramic material. The solid geometries were exported to the analysis software. The materials were considered isotropic, homogeneous and linear. The set was submitted to efforts in the incisal third in the palatine face to analyze maximal principal stress, mimicking mandibular lateral movement. The applied load was 100N, and the fixation region was on the medullary bone.

RESULTS

For restoration, the thinner the ceramic, the higher the stress concentration was; while for the adhesive surface of teeth, the thicker the ceramic, the higher the stress concentration.

CONCLUSIONS

The smaller the ceramic thickness was, the lower stress concentration showed at the adhesive interface, while the stress concentration was higher on the restoration intaglio surface.

Direct restoration of endodontically treated maxillary central incisors: post or no post at all?

OBJECTIVES

The aim of this ex-vivo study was to evaluate the impact of cavity size and glass-fiber post (GFP) placement on the load capability of endodontically treated maxillary incisors directly restored with resin composite.

MATERIALS AND METHODS

Ninety-six extracted human maxillary central incisors were endodontically treated and distributed to four groups (n = 24): access cavity (A), access cavity and uni-proximal class III cavity (U), access cavity and bi-proximal class III cavity (B), and decoronated tooth (D). Specimens were restored with resin composite, and 12 specimen of each group received an adhesively placed glass-fiber post (P). Prior to linear loading, specimens were exposed to thermo-mechanical loading (TCML). Statistical analysis was performed using log-rank test after TCML, Kruskall-Wallis and Mann-Whitney U test to compare load capabilities (F_max).

RESULTS

Significantly more failures occurred in group D for specimens without GFP during TCML (p = 0.001). F_max (mean (SD) in N was (A) 513 (124), (AP) 554 (201), (U) 438 (171), (UP) 537 (232) (B) 483 (219), (BP) 536 (281), D 143 (181), and DP 500 (331), and differed significantly among groups (p = 0.003). Pair-wise comparison revealed lower F_max values for group D compared to all other groups (p < 0.034) except group DP.

CONCLUSIONS

Endodontically treated maxillary central incisors with cavity sizes up to bi-proximal class III may be successfully directly restored with resin composite. Post placement shows no additional effect except for decoronated endodontically treated incisors.

CLINICAL RELEVANCE

Endodontically treated incisors with access cavities to class III cavities can be successfully restored with resin composite. Post placement for decoronated ETT is recommended.

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials

The objectives of this study were to compare the fracture strength of endocrown restorations fabricated with different preparation depth and various CAD/CAM ceramics, and to assess the fracture types. Endodontically treated 100 extracted human permanent maxillary centrals were divided into two preparation depth groups as short (S: 3-mm-deep) and long (L: 6-mm-deep), then five ceramic subgroups, namely: feldspathic-ceramic (Vita Mark II-VM2), lithium-disilicate glass-ceramic (IPS e.max CAD-E.max), resin-ceramic (LAVA Ultimate-LU), polymer infiltrated ceramic (Vita Enamic-VE) and monoblock zirconia (inCoris TZI-TZI) (n=10/subgroup). The endocrowns were fabricated by CAD/CAM and were cemented with resin cement (RelyX U200). The teeth were thermally cycled (5,000cycles) and fracture tests were performed at 45º angle to the teeth. The data were statistically analyzed (Kruskal-Wallis, Mann Whitney U), failure modes were evaluated with stereomicroscopy. Zirconia group provided the statistically highest fracture strength, but also exhibited non-repairable failures. Preparation depth has an effect on the fracture strength only for feldspathic ceramic.

Comparison of resistance to fracture between three types of permanent restorations subjected to shear force: An in vitro study

Introduction:

Our study's objective was to compare resistance to fracture between endocrown and conventional post and core restorations when subjected to shear force.

Materials and Methods:

Thirty human mandibular premolars were extracted for orthodontic reasons, endodontically treated, and restored using three different methods: endocrown, glass fiber post and composite resin core, and metal post. All the crowns were made from IPS e.max ceramic. Shear forces were applied to these restorations using a test machine until breakage. Load and displacement were recorded every 0.1 s.

Results:

No significant difference was observed in resistance to fracture between glass fiber post and metal post. No relationship between the displacement of prosthetic dental system and type of material used was uncovered and by comparing the type of fracture with the restoration material used. However, a greater number of favorable fractures were observed in the glass fiber group whereas most of the fractures in the endocrown and metal post groups were unfavorable.

Conclusion:

Endocrown displays better resistance to fracture compared to conventional post and core restorations. In addition, endocrown did not show more displacement or cause more unfavorable fractures than the conventional restorations. This restoration may represent a reliable alternative for restoring a damaged, endodontically treated tooth.

Strength comparison of anterior teeth restored with ceramic endocrowns vs custom-made post and cores

PURPOSE

The aim of the study was to compare strength of the anterior teeth restored with ceramic endocrowns versus custom-made post and core.

METHODS

The investigation used the finite element analysis. Three 3-D models of maxillary central incisor were created: model A-tooth restored with metal post and core with ceramic crown; model B-tooth with leucite ceramic endocrown; model C-tooth with lithium disilicate ceramic endocrown. Each model was subjected to a 100N force applied at a distance of 5mm from the incisal edge, at the angle of 130° to the long axis of the tooth. The modified von Mises failure criterion was used to evaluate the strength of the dentin, ceramic and resin cement, and Huber-Mises-Hencky failure criterion for cast alloy. Contact stresses in the cement-tissue adhesive interface were calculated.

RESULTS

The lowest stresses occurred in the anterior tooth restored with custom post and core (model A). The mvM stress of 47.5MPa concentrated in leucite ceramic endocrown (model B) and its value was close to the tensile strength of this material. The maximal mvM stresses in the lithium disilicate ceramic endocrown (model C) were 4 times lower than tensile strength of this material. In all cases contact stresses in the adhesive interface under restorations did not exceed the resin cement bond strength to dentin.

CONCLUSIONS

Leucite ceramic endocrowns in incisors may fracture during physiological loading. Endocrowns made of lithium disilicate ceramic are resistant to failure. Posts and prosthetic crowns are still recommended for anterior teeth restorations.

Biomechanical behavior of endodontically treated premolars using different preparation designs and CAD/CAM materials

OBJECTIVES

To evaluate the effect of restoration design ('2.5-mm deep endocrown', '5-mm deep endocrown' or '5-mm deep post&crown') and CAD/CAM material type (composite or lithium disilicate glass-ceramic) on the load-to-failure of endodontically treated premolars in absence of any ferrule.

METHODS

The crowns of 48 single-rooted premolars were cut and the roots were endodontically treated. Teeth were randomly divided into six groups (n=8); teeth in each group were restored using one of the two tested materials with standardized CAD/CAM fabricated endocrowns (with either 2.5-mm or 5-mm deep intra-radicular extension) or conventional crowns (5-mm deep post&crown). After cementation using luting composite, the specimens were immersed in distilled water and subjected to 1,200,000 chewing cycles with a load of 50N applied parallel to the long axis of the tooth (0°). After cyclic loading, a compressive load was applied at 45° to the tooth's long axis using a universal testing machine until failure. Load-to-failure was recorded (N) and the specimens were examined under a stereomicroscope with 3.5x magnification to determine the mode of failure.

RESULTS

All specimens survived the 1,200,000 chewing cycles. A significant interaction between restoration design and CAD/CAM material was found using two-way ANOVA. In the '2.5-mm deep endocrown' groups, the composite achieved a significantly higher load-to-failure than the lithium disilicate glass-ceramic, while no differences between materials were found in the '5-mm deep endocrown' and '5-mm deep post&crown' groups. More unfavorable failures (root fractures) were observed for higher load-to-failure values.

CONCLUSIONS

Only following a '2.5-mm deep endocrown' design, composite appeared more favorable than lithium disilicate glass-ceramic as crown material; this may be explained by their difference in elastic modulus.

CLINICAL SIGNIFICANCE

Shallow endocrown preparations on premolars present less surface for adhesive luting and a difference in crown material becomes apparent in terms of load-to-failure. The use of a more flexible composite crown material appeared then a better option.

Autogenous Tooth Fragment Adhesive Reattachment for a Complicated Crown Root Fracture: Two Interdisciplinary Case Reports

Trauma of anterior teeth is quite a common occurrence in both children and adults. Various degrees of trauma leading to fracture may affect teeth in different ways depending on the age of the patient and extent of fracture and other factors that will be discussed. Guidelines have been given as to how each of these situations should be treated. In the past, often more aggressive restorations were performed to restore fractured teeth. However improved and more efficient adhesion may affect the type of treatment we decide to carry out, leading to more conservative therapies through an increased preservation of tooth structures.

Evaluation of Temperature and Stress Distribution on 2 Different Post Systems Using 3-Dimensional Finite Element Analysis

BACKGROUND The mouth is exposed to thermal irritation from hot and cold food and drinks. Thermal changes in the oral cavity produce expansions and contractions in tooth structures and restorative materials. The aim of this study was to investigate the effect of temperature and stress distribution on 2 different post systems using the 3-dimensional (3D) finite element method. MATERIAL AND METHODS The 3D finite element model shows a labio-lingual cross-sectional view of the endodontically treated upper right central incisor and supporting periodontal ligament with bone structures. Stainless steel and glass fiber post systems with different physical and thermal properties were modelled in the tooth restored with composite core and ceramic crown. We placed 100 N static vertical occlusal loading onto the center of the incisal surface of the tooth. Thermal loads of 0°C and 65°C were applied on the model for 5 s. Temperature and thermal stresses were determined on the labio-lingual section of the model at 6 different points. RESULTS The distribution of stress, including thermal stress values, was calculated using 3D finite element analysis. The stainless steel post system produced more temperature and thermal stresses on the restorative materials, tooth structures, and posts than did the glass fiber reinforced composite posts. CONCLUSIONS Thermal changes generated stresses in the restorative materials, tooth, and supporting structures.

Endocrowns: review

The ideal restoration of endodontically treated teeth (ETT) has been widely and controversially discussed in the literature. Prevention of healthy dental structure is essential to help mechanical stabilization of tooth-restoration integrity, increase the amount of suitable surfaces for adhesion and thus positively affect the long-term success. ETT are affected by a higher risk of biomechanical failure than vital teeth. With the development of adhesive systems, the need for post-core restorations is also reduced. Especially for restoration of excessively damaged ETT, endocrowns have been used as an alternative to the conventional post-core and fixed partial dentures. Compared to conventional methods, good aesthetics, better mechanical performance, and less cost and clinic time are the advantages of endocrowns.