Fracture Resistance Test Research Articles

Fracture Resistance, Failure Mode and Pull-Out Bond Strength of Polymer-Infiltrated Ceramic-Network Post-Core Fabricated using Computer-Aided Design/Computer-Aided Manufacturing

This study compared fracture resistance (FR), failure mode (FM), and pull-out retention in endodontically-treated teeth restored with computer-aided design-and-manufacturing polymer-infiltrated ceramic networks (PICN) to cast post-core. A total of 45 maxillary central incisors were selected, endodontically treated, and were prepared to receive the post-core restorations. The specimens were randomly divided into five groups (n = 9): CG: control (without post-core); NC1, NC2: cast nickel-chromium (Ni-Cr) post-core; and VE1, VE2: PICN post-core. Groups CG, NC1, and VE1 were subjected to the FR test, while Groups NC2 and VE2 were subjected to the pull-out retention test. FR were recorded, and FM were classified as favourable or non-favourable, while the degree of retention in the maximum force was recorded in Newton. A one-way ANOVA was used to assess the FR, and an independent T-test was used for retention of post-core. No significant mean differences of FR between Ni-Cr versus PICN group (p = 0.261). Non-favourable FM was recorded in all samples in the NC group, with 88.9% of the VE group showed favourable FM. No significant mean differences were recorded in retention between NC2 and VE2 (p>0.05). PICN post-core exhibited favourable FR, FM, and retention values, thus having the potential to be used as a substitute post-core in endodontically-treated anterior teeth.

Comparison of Screw Loosening and Fracture Resistance in Different Hybrid Abutment Crown Restorations After Thermomechanical Aging.

To investigate the screw loosening and fracture resistance of different hybrid abutment crown restorations after thermomechanical aging. Restorations were produced from zirconia, lithium disilicate, and hybrid ceramics with a CAD/CAM system (n &#61; 10). Restorations and titanium bases (Ti-bases) were cemented, and the abutment screws were torqued to 30 Ncm. They were retorqued after 10 minutes, and then the removal torque values (RTVs) were measured. After 250,000 and 500,000 cycles of thermomechanical aging were completed, the RTVs were measured again, and removal torque loss (RTL) ratios were calculated. The specimens were subjected to a fracture resistance test after 750,000 cycles of thermomechanical aging, and the load at failure was recorded as the fracture resistance (N). The results were statistically analyzed (α &#61; .05). Aging was effective on the RTVs and RTL ratios (P < .001). The highest RTV was observed before aging; however, the RTVs significantly decreased and RTL ratios significantly increased after aging (P < .05). The fracture resistance values significantly differed among the ceramic materials. All lithium disilicate and hybrid ceramic specimens showed restoration fracture and most of the zirconia specimens showed Ti-base-related failure. Hybrid abutment crowns made of zirconia, lithium disilicate, and hybrid ceramics can withstand the average occlusal forces in the molar region; however, the ceramic type may affect the failure type. Retightening of the abutment screws after 10 minutes following the first tightening and annually may be beneficial to prevent the adverse effects of screw loosening on the integrity of the implant-abutment connection.

A comparative evaluation of fracture resistance of tooth restoration complex restored with PEEK and lithium disilicate endocrowns.

This in vitro study was conducted to compare the fracture resistance of tooth restoration complex restored with polyetheretherketone (PEEK) and lithium disilicate endocrowns. A total of 46 extracted premolars were collected and treated endodontically. The teeth were mounted in cylindrical molds using autopolymerizing resin and were prepared for endocrown restoration. Specimens were divided into two groups (n = 23) to receive endocrowns made with two different materials (polyetheretherketone and lithium disilicate). All the specimens were subjected to thermal cycling. The fracture resistance test was carried out using a Universal Testing Machine. Fractographic analysis was carried out using stereomicroscope and scanning electron microscope after load test. The values obtained were subjected to statistical analysis. Intergroup comparison (two groups) was performed using a t-test. Comparison of frequencies of categories of variables with groups was performed using chi-square test. Fracture resistance tests showed a statistically significant difference in values between the two groups (p<0.01). High fracture resistance values were seen with lithium disilicate endocrowns. Failure mode analysis showed that both groups exhibited mainly catastrophic failure. There were no significant differences in frequencies of the type of fracture between the groups. The fracture resistance of endocrowns fabricated with lithium disilicate material was found to be significantly higher than polyetheretherketone (PEEK) material. Hence, lithium disilicate material is superior for endocrowns.

Evaluation of Bond Strength and Fracture Load of Teeth With Flared Root Canals Restored With Prefabricated, Anatomical, and Computer-aided Design and Computer-aided Manufacturing Fiber Posts.

This study compared the use of anatomical glass fiber posts using bulk-fill composite resin with computer-aided design and computer-aided manufacturing (CAD/CAM) milled glass fiber post in oversized root canals, through bond strength (BS) and fracture resistance (FR) tests (fracture load). A total of 48 mandibular premolars were selected, half of them had their crowns removed at the cemento-enamel junction (CEJ) and the other half were sectioned 2 mm above the CEJ. Subsequently, teeth were endodontically treated. After 1 week, the standard preparation of the canals was carried out, and the roots were divided into three groups (n=16), according to the use of different restorative techniques (control: prefabricated glass fiber post [PFP], direct anatomical glass fiber post [AFP], and CAD/CAM milled glass fiber post [MFP]). After luting procedures using Single Bond Universal and RelyX Ultimate (3M ESPE), for eight teeth in each group, six specimens were obtained (two slices from each root third: cervical, middle, and apical). For the remaining eight roots of each group, standardized preparations for metal-free crowns, milling of 5 mol% yttria-stabilized tetragonal zirconia polycrystalline, cementation of the crowns, and periodontal ligament simulation were performed. Then, for each group, the BS was evaluated through the push-out test, and the FR was evaluated in compression. The data obtained from BS were submitted to two-way analysis of variance (ANOVA; group vs root region) and Tukey (α=0.05) and from FR to one-way ANOVA (group) and Tukey (α=0.05). For the BS test, the MFP group was statistically superior to the PFP group in all root regions and was statistically superior to the AFP group only in the cervical region, being statistically similar in the middle and apical root regions. For the FR test, the MFP group was statistically superior to the PFP and AFP groups. The milled fiber post technique can be a legitimate alternative in the restoration of weakened roots with flared root canals.

Performance of direct and indirect onlay restorations for structurally compromised teeth

Research is lacking on the restoration of structurally compromised posterior teeth using direct composite resin or indirect restorations. The purpose of this in vitro study was to measure the fracture resistance and microleakage of different onlay restorations fabricated by using conventional and digital computer-aided design and computer-aided manufacturing (CAD-CAM) to restore structurally compromised teeth. Mandibular molars (n=54) were prepared for onlay restorations. Teeth were allocated to 3 groups (n=18) according to the type of restoration materials, nanohybrid composite resin (Grandio blocs), resin hybrid ceramic (SHOFU Block HC), and fiber-reinforced composite resin (everX Posterior). Onlays were bonded using a dual-polymerized adhesive resin cement. All specimens were thermocycled, followed by cyclic loading. Based on the type of investigation conducted, fracture resistance, and microleakage test, each group was then divided into 2 equal subgroups (n=9). The collected data were statistically analyzed with the chi-square of the Fischer exact test (α=.05). Fracture resistance testing revealed a statistically significant difference between groups (P<.001). The fiber-reinforced composite resin demonstrated the highest fracture resistance, with statistically significantly less microleakage compared with the other groups (P=.013). Direct fiber-reinforced composite resin could be considered a suitable alternative to CAD-CAM composite resin for the restoration of structurally compromised teeth.

Effect of Delayed Endodontic Sealing with Dentin Biomodification on Fracture Resistance of Endodontically Treated Teeth

Aim: Endodontically treated teeth display altered tooth structure pertaining to various chemical irrigants and intracanal medicaments. To prevent the compromised adhesive bond, dentin biomodification is indicated. This study was designed to evaluate the influence of dentin biomodification on the fracture resistance of root canal-treated teeth following Delayed Endodontic Sealing (DES). Materials and Methods: In 50 maxillary central incisors, Class III cavities along with access cavities were prepared. The samples were randomly divided into five groups. Group 1: Intact teeth ( N = 10), Group 2: Immediate Endodontic Sealing (IES) ( N = 10); Group 3: DES after irrigation with 3% NaOCl ( N = 10); Group 4: DES with 2% chlorhexidine (CHX) as a biomodifier ( N = 10) and Group 5: DES with 5% grape seed extract (GSE) as a biomodifier ( N = 10). In Group 2 samples, composite restorations were done prior to irrigation with 3% sodium hypochlorite (NaOCl). Group 3 samples received root canal irrigation with 3% NaOCl for 1 min, etch and rinse procedure and composite restorations. In Groups 4 and 5, dentin biomodification was done prior to composite restorations. Teeth were subjected to fracture resistance tests. Statistical analysis was carried out employing analysis of variance (ANOVA) and Tukey’s post hoc tests ( p &lt; .05). Results: IES group demonstrated the highest fracture resistance, with a significant difference statistically ( p &lt; .05) when compared with the DES groups. DES modified with GSE resulted in significantly superior fracture resistance compared to DES only, but no statistical difference was present between the CHX and grape seed-treated DES groups. Conclusion: DES with the use of dentin biomodifiers such as 5% GSE and 2% CHX increased the fracture resistance of root canal-treated teeth compared to DES only.

In-Vitro Comparison of Fracture Strength of Endocrowns and Overlays in Endodontically Treated Teeth Manufactured with Monolithic Lithium Disilicate and Zirconia.

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann-Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

Evaluation of mechanical properties of different polyetheretherketone endodontic post systems: an in vitro study

BackgroundSurvival of endodontically treated teeth depends on an efficient restoration of the missing tooth structure.ObjectivesThis study aimed to investigate the mechanical properties of different endodontic post systems.Materials and methodsHuman permanent maxillary central incisors (no.=58) were decoronated and root-filled. The specimens with prepared root canals were randomly divided into Group P: Polyether Ether Ketone (PEEK) post and composite core and Group C: custom-made post-core of PEEK. The cementation of the posts was carried out using self-adhesive resin cement. Nano-hybrid composite resin was used for core fabrication. After cementation, the specimens from each group were randomly divided into two subgroups according to the types of tests utilized: 14 from each group were for the fracture strength test, which was restored with IPS e-max CAD crown, and 15 from each group for the pullout resistance test. A universal testing machine was used for the test performance.ResultsThe fracture resistance test showed that the values significantly differed among tested posts (P = 0.013). Group P showed the highest fracture resistance. Group C exhibited higher mean pullout resistance values than the other group (P) (P = 0.059). In the two-piece PEEK post and composite core, the predominant type of failure was a core fracture, while in the one-piece PEEK post-core, most types of failures were either in the crown or in the post.ConclusionsThe prefabricated posts are more resistant to fracture than the custom-made posts, with fracture and displacement mainly of the core. In contrast, both showed similar pullout resistance.

The Influence of Alumina Airborne-Particle Abrasion with Various Sizes of Alumina Particles on the Phase Transformation and Fracture Resistance of Zirconia-Based Dental Ceramics.

The surface of zirconia-based dental ceramic restorations require preparation prior to adhesive cementation. The purpose of this study was to assess the influence of airborne-particle abrasion with different sizes of alumina particles (50 μm, 110 μm, or 250 μm) on the mechanical strength of zirconia-based ceramics' frameworks and on the extent of phase transformations. A fracture resistance test was performed. The central surface of the frameworks was subjected to a load [N]. The identification and quantitative determination of the crystalline phase present in the zirconia specimens was assessed using X-ray diffraction. The Kruskal-Wallis one-way analysis of variance was used to establish significance (α = 0.05). The fracture resistance of zirconia-based frameworks significantly increases with an increase in the size of alumina particles used for air abrasion: 715.5 N for 250 μm alumina particles, 661.1 N for 110 μm, 608.7 N for 50 μm and the lowest for the untreated specimens (364.2 N). The X-ray diffraction analysis showed an increase in the monoclinic phase content after air abrasion: 50 μm alumina particles-26%, 110 μm-40%, 250 μm-56%, and no treatment-none. Air abrasion of the zirconia-based dental ceramics' surface with alumina particles increases the fracture resistance of zirconia copings and the monoclinic phase volume. This increase is strongly related to the alumina particle size.

Comparison of wear and fracture resistance of additively and subtractively manufactured screw-retained, implant-supported crowns

Statement of problemAdditively manufactured resins indicated for fixed definitive prostheses have been recently marketed. However, knowledge on their wear and fracture resistance when fabricated as screw-retained, implant-supported crowns and subjected to artificial aging is limited. PurposeThe purpose of this in vitro study was to evaluate the volume loss, maximum wear depth, and fracture resistance of screw-retained implant-supported crowns after thermomechanical aging when fabricated using additively and subtractively manufactured materials. Material and methodsTwo additively manufactured composite resins (Crowntec [CT] and VarseoSmile Crown Plus [VS]) and 2 subtractively manufactured materials (1 reinforced composite resin, Brilliant Crios [BC] and 1 polymer-infiltrated ceramic network, Vita Enamic [EN]) were used to fabricate standardized screw-retained, implant-supported crowns. After fabrication, the crowns were cemented on titanium base abutments and then tightened to implants embedded in acrylic resin. A laser scanner with a triangular displacement sensor (LAS-20) was used to digitize the pre-aging state of the crowns. Then, all crowns were subjected to thermomechanical aging (1.2 million cycles under 50 N) and rescanned. A metrology-grade analysis software program (Geomagic Control X 2020.1) was used to superimpose post-aging scans over pre-aging scans to calculate the volume loss (mm3) and maximum wear depth (mm). Finally, all crowns were subjected to a fracture resistance test. Fracture resistance and volume loss were evaluated by using 1-way analysis of variance and Tukey Honestly significant difference (HSD) tests, whereas the Kruskal-Wallis and Dunn tests were used to analyze maximum wear depth. Chi-squared tests were used to evaluate the Weibull modulus and characteristic strength data (α=.05). ResultsMaterial type affected the tested parameters (P<.001). CT and VS had higher volume loss and maximum wear depth than BC and EN (P<.001). EN had the highest fracture resistance among tested materials (P<.001), whereas BC had higher fracture resistance than CT (P=.011). The differences among tested materials were not significant when the Weibull modulus was considered (P=.199); however, VE had the highest characteristic strength (P<.001). ConclusionsAdditively manufactured screw-retained, implant-supported crowns had higher volume loss and maximum wear depth. All materials had fracture resistance values higher than the previously reported masticatory forces of the premolar region; however, the higher characteristic strength of the subtractively manufactured polymer-infiltrated ceramic network may indicate its resistance to mechanical complications.

Fracture load of ultrathin occlusal veneers: Effect of thickness and surface conditioning

ObjectiveThis in-vitro study is planned to analyze the effect of different thicknesses of ceramic occlusal veneers and different surface treatments on fracture resistance. Materials and methodsA total of 48 sound mandibular molars are anatomically prepared from the occlusal surface with two different thicknesses (1.0 and 0.5 mm). CAD/CAM zirconia-reinforced glass ceramic blocks (Vita Suprinity) are used for fabricating occlusal veneers. The teeth are randomly divided into two primary groups A and B (n=24) according to occlusal veneer thickness. Each group is subdivided according to surface conditioning into three equal subgroups (n=8)—subgroup HF: etching with hydrofluoric acid and ceramic primer application; subgroup APF: etching with acidulated phosphate fluoride and ceramic primer application; subgroup EP: conditioning with etch and prime only. Dual-cure adhesive resin cement (Multilink Automix) is utilized to adhesively bond the veneers. All specimens are subjected to 240,000 cycles of dynamic load aging prior to the fracture resistance test. The fracture resistance is measured in Newton (N). The Failure mode patterns are analyzed and categorized using a scanning electron microscope (SEM). The results are analyzed using a two-way ANOVA with Bonferroni's Post-Hoc test, followed by a one-way ANOVA for each factor. That is in addition to one-way ANOVA for surface treatment under each thickness, each followed by Bonferroni's Post-Hoc test. Then, a T-test is used to compare the two thicknesses under each surface treatment. All tests are set at 0.05 significance level. ResultsThe two-way ANOVA test revealed that restoration thickness and surface treatment both significantly affect the fracture resistance values (p<0.05). The highest fracture resistance mean (2672±216N) is obtained from HF at 1.0 mm thickness, while the lowest mean (2104±299N) is obtained from APF at 0.5 mm thickness. ConclusionAll test groups, regardless of thickness, demonstrated fracture resistance values that exceeded both normal and parafunctional bite forces. The veneers that bonded after hydrofluoric acid etching followed by ceramic primer application showed more favourable fracture patterns.

Impact of different CAD/CAM materials on internal and marginal adaptations and fracture resistance of endocrown restorations with: 3D finite element analysis

PurposeTo assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis.Material and methodsForty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05.ResultsIn the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively.ConclusionsStatistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.

The assessment of internal adaptation and fracture resistance of glass ionomer and resin-based restorative materials applied after different caries removal techniques in primary teeth: an in-vitro study.

The aim of this study was to evaluate the 3-dimensional (3D) internal adaptation (IA) and fracture resistance (FR) of compomer and glass ionomers applied after conventional caries removal to sound dentin (CCRSD) and selective caries removal to firm dentin (SCRFD) in in-vitro. Thirty extracted primary molars were randomly assigned to three main groups (n = 10) as glass hybrid restorative (GHR) (Equia Forte® HT), conventional glass ionomer (CGIR) (Voco Ionofil Molar) and compomer (Dyract XP). Each group was randomly divided into two subgroups according to caries removal technique as CCRSD (n = 5) and SCRFD (n = 5). The restoration procedures were completed after caries removal (CCRSD or SCRFD) in all samples. Then, specimens were subjected to IA and FR tests. Data were analyzed with Student's t, one-way ANOVA, and Kruskal Wallis-H tests. The correlation between IA and FR results was analyzed with a Pearson test. The statistical significance level was considered as 5%. While CCRSD showed superior IA results than SCRFD for all restorative materials (p < 0.05), no statistical difference was found between CCRSD and SCRFD in FR assessment (p > 0.05). In CCRSD, compomer showed superior results for IA and FR than glass ionomers (p < 0.05). In SCRFD, it was found no significant difference between the restoratives for IA (p > 0.05). However, compomer showed superior FR results than glass ionomers (p < 0.05). There was moderate negative correlation between internal voids and FR without statistically significant difference (r = -0.333, p = 0.072). Despite the advantages of SCRFD, it was found to be less superior than CCRSD in IA assessment. Therefore, when SCRFD is preferred, a peripheral seal should be provided for ideal restorative treatment. On the other hand, compomer mostly showed superior results compared to others.

Effect of CAD/CAM Constructed BIOHPP versus Zirconia Frameworks Reinforced Maxillary Complete Denture on Fracture Resistance (In vitro Study)

Aim: this study was to investigate the effect of reinforcing material on the fracture resistances of Computer-aided design/computer-aided manufacturing (CAD-CAM) BIOHPP (Bio High Performance Polymer) and Zirconia-reinforced maxillary complete dentures under fatigue loading. Materials And Methods: BIOHPP and Zirconia framework-reinforced maxillary complete dentures were fabricated using silicone moulds and acrylic resin. A control group was prepared with no reinforcement (n =5 per group). After cyclic loading was applied using a chewing simulator, fracture resistance was measured by a universal testing machine. The fracture resistance was measured for each denture. Results: After cyclic loading, none of the dentures showed cracks or fractures. During fracture resistance testing, all unreinforced dentures experienced complete fracture. The framework-reinforced dentures showed fracture of the acrylic without framework fracture. BIOHPP reinforced maxillary denture showed the highest fracture resistance (1705.70±213.75), followed by the Zirconia reinforced maxillary denture (1690.10±135.40) (p&lt;0.001). Conclusion: CAD/CAM Zirconia and BIOHPP frameworks used as reinforcement for maxillary complete denture shows higher fracture resistance and more retentive dentures under cyclic loading. Maxillary complete denture reinforced by BIOHPP framework show higher fracture resistance than Zirconia. The BIOHPP and Zirconia-reinforced denture exhibits a fracture resistance higher than that of the unreinforced denture, with dentures maintaining their shape even after fracture, indicating the possibility of easier repair.

Investigation of the Effect of Bleaching on Discolored Teeth After Regenerative Treatment on Fracture Resistance of Teeth

Objective: This study aimed to evaluate the effect of bleaching discolored teeth after regenerative endodontic treatment on fracture resistance. Methods: Forty human maxillary incisors were selected for the study and were divided into four study groups (n=10). Group 1 was called the positive control group, and no treatment was applied. In Group 2; root canals were enlarged to size 6 peezo reamer bur to mimic an immature tooth. The disinfection protocol was performed according to the regenerative endodontic treatment protocol of the American Association of Endodontists. 3 mm thick mineral trioxide aggregate (MTA) was placed at the cementoenamel margin and restored with a temporary restorative material. The samples in group 3 were restored with glass ionomer and composite resin. In Group 4 bleaching was applied with 35% hydrogen peroxide bleaching agent to the samples before restoration with glass ionomer and composite resin. Then each group was applied to the cervical fracture resistance test with a universal testing machine. The fracture resistance values were recorded in Newtons (N), and the obtained data were analyzed statistically. Results: While the highest fracture strength was obtained in group 1 (1092 ±9.27N), the lowest fracture resistance was observed in group 2 (493.8 ±7.60N). The difference between all groups was statistically significant (p&amp;lt;0.05). Conclusion: 35% hydrogen peroxide bleaching agent application after regenerative endodontic treatment reduces fracture resistance of the tooth.

Fracture Resistance of Molars With Simulated Strip Perforation Repaired With Different Calcium Silicate-Based Cements.

Background and aims A root perforation is a connection between the root canal system and the external supportive tissues. Strip perforation (SP), occurring within root canals in a strip, can worsen the prognosis of a treated tooth, reduce its mechanical resistance, and impair the tooth structure. One of the suggested methods to treat SP is to seal it with a bio-material such as calcium silicate cement. Therefore, this in vitro study aimed to assess the molar structure impairment due to SP, which requires studying the fracture resistance, and the ability of mineral trioxide aggregate (MTA), bioceramic, and calcium-enriched mixture (CEM) to repair this perforation. Materials and methods Seventy-five molars were instrumented to size #25 and taper 4%, irrigated with sodium hypochlorite and ethylenediaminetetraacetic acid (EDTA), dried, and then divided randomly into five groups (G1-G5): in G1, root canals were filled with gutta-percha and sealer (negative control sample), whereas the rest of the groups (G2-G5) had a manual simulated SP made with Gates Glidden drill at the mesial root of the extracted molar, and filled with gutta-percha and sealer up to their perforation area; in G2, SP was filled with gutta-percha and sealer (positive control sample); G3 used MTA to repair the SP; G4 used bioceramic putty; and G5 used CEM. Fracture resistance tests of the molars were conducted in the crown-apical direction using a universal testing machine. One-way ANOVA test and Bonferroni test were used to study the significance of the differences in the mean values of the tooth fracture resistance, where statistical significance was set at 0.05. Results The ANOVA test showed that there were statistically significant differences between the fracture resistance (in newtons) values among groups (p = 0.000). The Bonferroni test showed that G2 had a smaller fracture resistance mean than the other four study groups (656.53 N; p = 0.000), and that of G5 was smaller than G1, G3, and G4 (794.40 N, 1083.73 N, 1025.20 N, and 1034.20 N, respectively; p = 0.000 in each pairwise comparison). Conclusion SP reduced the fracture resistance of endodontically treated molars. SP restored using MTA and bioceramic putty was better than that treated with CEM and similar to molars without SP. Moreover, MTA and bioceramic putty enhanced the fracture resistance of endodontically treated teeth to levels similar to molars without SP.

Impact of different intraorifice barriers on fracture resistance of non-vital bleached teeth.

This study aimed to evaluate the effects of bleaching agents on the fracture resistance of endodontically treated teeth using different intraorifice barrier (IOB) materials. The endodontic treatment was performed for 160 mandibular premolars, and then, the teeth were divided into four groups according to the IOB: Ionoseal, Biodentine, ProRoot MTA, and TheraBase. Then, these teeth were subdivided into four subgroups (n = 10) based on the bleaching agents as distilled water (control), hydrogen peroxide 35% (HP), sodium perborate (SP), and carbamide peroxide 37% (CP). The access cavities were restored with composite resin after applying the bleaching agents for 7 days. The fracture resistance test was performed using a universal testing machine. Data were statistically analyzed, and the significance level was set at 5%. A scanning electron microscope was used to evaluate the effect of bleaching agents on the surfaces of IOBs. The highest fracture resistance values were observed in Biodentine groups with significant differences compared to Ionoseal and ProRoot MTA (P <.05). The distilled water groups showed significantly the highest fracture resistance compared to SP and HP groups (P <.05). There was no significant difference between SP, HP, and CP groups (P >.05). It was demonstrated that the morphological surface of the intact IOBs (control) was different from the surface of IOBs treated with bleaching agents. The intracoronal bleaching procedures affected negatively the fracture resistance of the endodontically treated teeth.

Impact of access cavities on root canal preparation, restorative protocol quality, and fracture resistance of teeth.

The survival of endodontically treated teeth depends on the remaining tooth structure. The aim of this study was to evaluate the impact of different access cavities on root canal preparation, restorative protocol, and fracture resistance of endodontically treated teeth. Fifty-six mandibular molars were divided into control (n=8) and experimental (n=16) groups according to access cavity: Traditional, Conservative, and Truss; and redistributed (n=8) according to instrumentation protocols: Reciproc Blue and R-motion. After, teeth were scanned in micro-CT and then filled and redistributed according to composite resin restoration (n=8): Filtek One BulkFill and Filtek Z350. A new micro-CT scan was performed to analyze the restorative material. Then, samples were submitted to fracture resistance testing and the failure pattern was determined. Data were analyzed using paired T-test, ANOVA, Tukey, and chi-square tests (α=0.05). In Truss, R-Motion promoted less transportation in different thirds of root canals. Higher percentages of voids (5.05%) and filling material (11.7%) were observed in Truss. Fracture resistance values were higher for the control group, followed by Truss, Conservative, and Traditional. The predominant failure pattern was type-II. In Truss, reciprocating instruments with smaller taper showed less canal transportation. Also, Truss provided higher values of fracture resistance, although it presented a higher percentage of voids and remaining filling material. Thus, in Truss, reciprocating files with smaller taper showed less canal transportation, and these cavities provided higher values of fracture resistance, although it presented a higher percentage of voids and remaining filling material.

Effect of deep margin elevation on fracture resistance of premolars restored with ceramic onlay: In vitro comparative study.

This in vitro comparative study aimed to compare the influence of two levels of deep margin elevation (2 and 3 mm) with either bulk-fill flowable composite or short fiber-reinforced flowable composite on the fracture resistance of maxillary first premolars restored with ceramic onlays. Fifty sound-extracted maxillary first premolar teeth were selected to prepare mesio-occluso-distal cavities with standardized dimensions. The cervical margins were extended 2 mm below the cemento-enamel junction on both mesial and distal sides. These teeth were randomly divided into five groups: Group I: no box elevation (control group). Group II: 2 mm marginal elevation with bulk-fill flowable composite. Group III: 2 mm marginal elevation with short fiber-reinforced flowable composite. Group IV: 3 mm marginal elevation with bulk-fill flowable composite. Group V: 3 mm marginal elevation with short fiber-reinforced flowable composite. After cementation, all teeth were subjected to a fracture resistance test using the universal testing machine, and the mode of failure was analyzed using a digital microscope at 20x magnification. The result showed a non-significant difference in the fracture resistance between 2 and 3 mm marginal elevation (p>0.05) with respect to each restorative material used for deep margin elevation. However, the fracture resistance of teeth elevated with short fiber-reinforced flowable composite was significantly higher than those elevated with bulk-fill flowable composite at both levels 2 and 3 mm, p=0.041 and 0.038 respectively. The fracture resistance of premolars restored with a ceramic onlay was not influenced by the levels of deep margin elevation (2 or 3 mm). However, marginal elevation with short fiber-reinforced flowable composites provided higher fracture resistance than those elevated with bulk-fill flowable composites, and those without marginal elevation. Key words:Fracture Resistance, Short fiber reinforced flowable composite, Bulk-fill flowable composite, Ceramic onlay, Cervical margin elevation.

The effect of intraorifice barriers (TheraCal LC, Lime-Lite and Ionoseal) on the fracture resistance and failure patterns of endodontically treated teeth submitted to intracoronal bleaching

The aim of the study was to compare the root reinforcement potential of different light cured intraorifice barriers (TheraCal, lime-lite, Ionoseal and resin-modified glass-ionomer [RMGI] [Fuji II LC]) with or without bonding agent placed in the orifice of endodontically treated and bleached teeth. In this experimental in vitro study, single-rooted bovine teeth were instrumented and obturated with gutta-percha. Except the control group, in other specimens, gutta-percha was removed 3 mm under cementoenamel junction. Then, the specimens were divided into seven groups according to the bases was applied: TheraCal LC, TheraCal LC with bonding agent, Lime-Lite, Lime-Lite with bonding agent, Ionoseal, Ionoseal with bonding agent, and RMGI (Fuji II LC). After internal bleaching, the teeth were decoronated. Then, all the groups were subjected to fracture resistance testing using Universal Testing Machine. For evaluating fracture resistance, analysis of variance and Tukey's test were used and for comparing the mode of fracture fisher test was applied in SPSS software. The significance was determined at (α = 0.05) confidence interval. The group of TheraCal LC with bonding agent showed better fracture resistance as compared to the control group (P = 0.004). Although there was no statistically significant difference in the pairwise comparison between the other groups. TheraCal LC with bonding agent can be used as intraorifice barriers with good fracture resistance in endodontically treated and bleached teeth.