Fracture resistance of endodontically treated maxillary premolars restored by silorane-based composite with or without fiber or nano-ionomer

Influence of cusp reduction and fiber reinforcement on cusp deflection and fracture strength of restored endodontically treated molar teeth

OBJECTIVE

This study aimed to investigate the influence of various cusp reduction amounts, localization, and the use of coronal polyethylene fiber on cusp deflection in endodontically treated molar teeth.

MATERIAL AND METHODS

The 120 intact molar teeth observed in the study were divided into 12 groups, and standard MOD cavities were prepared after the root canal treatment was completed. Groups 1 and 2 were determined as positive and negative control groups, respectively. Two cusp reductions were applied to Groups 3, 4, 5, and 6, and functional cusps reduction were applied to Groups 7, 8, 9, and 10. The cusp reductions were either 1.5 mm or 3 mm. After preparation, Groups 3, 5, 7, 9, and 11 were restored with Filtek One Bulk-Fill, while Groups 4, 6, 8, 10, and 12 were restored with Filtek One Bulk-Fill + Ribbond. As the teeth were restored, the amount of cusp deflection was measured with a twin channel deflection gauge device. The fracture strength of the teeth was measured using a universal test machine. The experimental results were statistically evaluated with two-way and one-way ANOVA tests.

RESULTS

The reinforcement of the coronal structure with fiber reduced cusp deflection and increased fracture strength. The statistically significantly less cusp deflection was obtained in the groups with the same cavity design of having fiber placed than in the groups without fiber placed (p < 0.001). The statistically significantly lower fracture strength was obtained in Group 11 than all the reduced groups except Groups 5 and 7 (p < 0.05). The statistically lower fracture strength was obtained in Group 12, than in Group 4 (p < 0.05). Experimental groups with cusp reduction showed less cusp deflection (p < 0.001) and higher fracture strength (p < 0.05) than experimental groups without cusp reduction.

CONCLUSIONS

Fiber application and cusp reduction may have positive effects in terms of reducing cusp deflection and increasing fracture strength in direct restoration cases involving excessive substance loss in endodontically treated teeth.

CLINICAL RELEVANCE

Incorporating cusp reduction and coronal fiber applications in treatment plans for endodontically treated teeth ensures that restorations are both functional and durable.

Fracture Resistance of Maxillary Premolars With Class II MOD Cavities Restored With Direct and Indirect Resin Composite Restorative Systems

OBJECTIVE

To assess the fracture resistance of maxillary premolars with mesio-occluso-distal (MOD) Class II cavities restored with lab composite and microhybrid resin composite, with or without a short fiber-reinforced composite (SFRC) base.

METHODS

Fifty sound maxillary premolars were divided randomly into 5 groups (n = 10); G1: Intact teeth (negative control), G2: Unrestored MOD cavities (positive control), G3: MOD inlay cavities restored with indirect lab composite, G4: MOD cavities restored with an SFRC base and microhybrid composite, and G5: MOD cavities restored with microhybrid composite. All specimens were thermocycled for 5000 cycles, then subjected to an axial static compressive load until fracture occurred. Failure modes were inspected.

RESULTS

Negative control group exhibited maximum fracture resistance, whereas positive control revealed the lowest (p < 0.05). Microhybrid composite restorations with an SFRC base demonstrated fracture thresholds not significantly different from indirect lab composite (p = 0.22); however, those without an SFRC base presented the least resistance to fracture among restored groups (p < 0.05). Cohesive failure of restorative material was mainly noted in the microhybrid composite group without an SFRC base, whereas adhesive failures were observed in all groups.

CONCLUSIONS

The resistance of teeth to fracture is significantly influenced by the restorative material. Under compressive loads, the teeth restored with microhybrid composite restorations incorporating a short fiber-reinforced composite base exhibited comparable fracture resistance to laboratory composite restorations.

CLINICAL SIGNIFICANCE

Considering that short fiber-reinforced composites revealed experimental outcomes comparable to those of indirect lab composites, along with the added benefits of shorter treatment time and cost-effectiveness, the direct approach becomes an ideal option for restoring teeth with Class II MOD cavities.

Comparison of fracture resistance between immediate and delayed composite restorations with or without fiber after root canal treatment: a field-emission-gun scanning electron microscope study

Background

This study aimed to evaluate the fracture resistance of immediate and delayed restorations after root canal treatment (RCT).

Methods

Sixty human intact premolar teeth were used. Teeth were prepared disto-occlusally. After RCT, teeth were randomly divided into two groups according to restoration times (immediate or 3 months delayed). The three month delay was imitated by thermomechanical aging. Then, samples were divided into six subgroups (n = 10). While I (Composite resin), II (Flowable bulk-fill) and III (Ribbond+Flowable bulk-fill) were restored immediately, Groups IV, V and VI were restored with temporary filling material and stored in distilled. After subjected to thermo-cycling (2,500 cycles, 5-55 °C) and exposed to 60,000 cycles in a chewing simulator, Group IV (Composite resin), V (Flowable bulk-fill) and VI (Ribbond+Flowable bulk-fill) were restored. All of the teeth were fractured on the universal testing machine. Failure modes were analyzed using scanning electron microscope. Data were analyzed using the Shapiro-Wilk and two-way ANOVA tests (p < 0.05).

Results

The highest fracture resistance was recorded in Group III while the lowest in Group VI. No statistically significant difference was observed among groups (p > 0.05). Most of the repairable fractures were seen in Groups I and II.

Conclusion

Delaying the permanent restorations of teeth for 3 months did not affect fracture resistance. However, it was suggested to avoid delaying restorations for obtaining repairable surfaces.

Optimizing fracture resistance of endodontically treated maxillary premolars restored with preheated thermos-viscous composite post-thermocycling, a comparative study. Part I

PURPOSE

This research aimed to investigate fracture resistance of endodontically treated maxillary premolars restored using preheated thermo-viscous and fiber-reinforced bulk fill resin composite, in vitro.

METHODOLOGY

Sixty sound human maxillary premolars were selected and divided randomly into 6 groups of ten teeth each (n = 10). Group 1; is the positive control with sound unprepared teeth (P), Group 2; is the negative control in which Mesio-occluso-distal (MOD) cavities were left unrestored (N), Group 3; includes the teeth restored by incremental packing with conventional nanohybrid composite (ChP), Group 4; includes teeth restored with short fiber reinforced bulk fill composite (EF), Group 5; includes teeth restored with preheated thermo-viscous bulk fill composite (VB), and Group 6; includes teeth restored using packable bulk fill composite (XF) Tested restorative materials were bonded with a universal adhesive in self-etch mode. Teeth were kept in distilled water for 24 h at 37 °C proceeded by thermocycling (5- 55 °C, 1200×). Teeth were then exposed to compressive load till fracture at a crosshead speed of 1 mm/min. One-way ANOVA followed by Tukey post-hoc test was implemented to compare between more than two groups in non-related samples. The significance level was established at α = 0.05 for both tests.

RESULTS

Intact teeth significantly recorded the highest fracture resistance values among all groups. A significant difference was recorded among all the tested groups, with the EF recording the highest values, followed by the VB group then the XF group and ChP that recorded the lowest data. Negative control premolars significantly recorded the lowest fracture.

CONCLUSIONS

After thermocycling, endodontically treated maxillary premolars restored with pre-heated thermos-viscous composite did not exhibit an increase in fracture resistance. Notably, our findings indicate that short fiber-reinforced composite demonstrated significantly higher fracture resistance compared to other types of composites assessed in this study. This suggests the potential superiority of short fiber-reinforced composite in enhancing the overall structural integrity of endodontically treated teeth subjected to occlusal forces.

Fracture resistance and failure pattern of endodontically treated maxillary premolars restored with transfixed glass fiber post: an in vitro and finite element analysis

The aims of the study were to determine the effect of different types of endodontic sealers and the presence of a horizontal glass fiber post (HGFP) on the fracture resistance and fracture pattern of mesio-occluso-distal (MOD) restored upper premolars and to analyze the stress distribution. Sixty extracted upper premolars received root canal treatment (RCT) and a MOD cavity preparation. All MOD cavities were restored with the same composite resin (CR). The 60 teeth were divided randomly into 6 groups (n = 10); Group1= AH Plus sealer; Group 2= TotalFill BC sealer; Group 3= BioRoot RCS sealer; Group 4= AH plus sealer + HGFP; Group 5= TotalFill BC sealer + HGFP; and, Group 6= Bio Root RCS sealer + HGFP. All specimens were thermocycled and subjected to cyclic loading. Next, the specimens were subjected to a static load using a universal testing machine. Data were analyzed using two-way ANOVA. Two micro-CTs of the same upper premolar, one without the HGFP and later one with HGFP inserted were made and used to create two finite element (FE) models. For the fracture resistance, two-way ANOVA revealed significant differences for the effect of HGFP (p = 0.029), but no differences for the effect of root canal sealer type (p = 0.561). The HGFP groups showed higher restorable fracture compared to groups without HGFP (p = 0.013). Finite element analysis showed that the inclusion of HGFP reduces stress concentration at the occlusal interface and cervical region. Therefore, it can be concluded that HGFP significantly increased the fracture resistance of endodontically treated upper premolars with MOD cavities and reduced the risk for non-restorable fractures. The FE analysis supports the mechanical test results.

Fracture Resistance of Endodontically Treated Premolars Using Nanohybrid Composite, Fiber-Reinforced Composite, Horizontal Glass Fiber Posts, and Ceramic Inlays: An In Vitro Study

INTRODUCTION

This study evaluated the resistance to fracture of endodontically treated premolars (ETPs) with mesio-occluso-distal (MOD) cavities filled with nanohybrid composite (NHC), fiber-reinforced composite (FRC), horizontal glass fiber posts (HFP), and ceramic inlays (CI).

METHODS

Eighty-four intact maxillary premolars were taken, and endodontic treatment was performed followed by MOD cavity preparations (except in the control group). They were distributed into 7 groups based on type of restoration: intact teeth (control group), ETP + MOD (not restored), NHC, FRC + NHC, HFP + NHC, FRC + HFP + NHC, and CI groups. Samples were subjected to universal testing machine until the fracture occurred and failure mode was visually inspected.

RESULTS

Mean and standard deviation of fracture resistance of the 7 groups ranged from 265.6 ± 68.0 N to 1023.7 ± 76.5 N. The highest reading was noted for intact teeth followed by FRC + HFP + NHC group and then the CI group, with no significant difference among the 3 groups. The lowest reading was noted for the ETP + MOD group. Maximum unrepairable fractures were seen in the ETP + MOD and CI groups.

CONCLUSION

FRC + HFP + NHC combination and CIs increased the resistance to fracture of ETPs significantly.

Assessing Fracture Resistance of Restored Premolars with Novel Composite Materials: An In Vitro Study

During restorative treatment, premolars restored with resin filling materials using the conventional incremental-fill technique take longer restoration time and undermine the integrity of the tooth. The aim of this study was to assess fracture resistance of premolars restored by various types of novel bulk-fill composite resin materials. Forty-eight (n = 48) freshly extracted sound maxillary first premolars were used in this in vitro study. The teeth were divided into six groups, each having 8 specimens. Group A (positive control) was allocated for the intact teeth. For specimens in Groups B to F, a large cavity (Class-II MOD) was prepared with a standardized dimension of cavity (3 mm depth on the pulpal floor, 4 mm at the gingival seat, and 3 mm cavity width). Group B represented prepared teeth without any restoration. Group C, Group D, Group E, and Group F were restored with Tetric EvoCeram^® incremental-fill (conventional), Beautifil bulk-fill, Filtek posterior bulk-fill, and SonicFill 2 bulk-fill restorative materials, respectively. All samples were finished and polished with an enhanced finishing kit and stored in distilled water for a month before the fracture resistance testing. All the samples were exposed to the axial loading (the speed of crosshead was 1 mm/min) in a computer-controlled universal testing machine (LARYEE, China) via a steel bar (6 mm in diameter) and the maximum applied force in Newton was recorded as the fracture resistance. One-way analysis of variance (SPSS 21) was used to compare the fracture resistance within the groups, and Tukey's post hoc test was used to determine the difference between the groups. The lowest value of fracture resistance was recorded for Group B, and the highest value was recorded for Group A followed by the values of Group D, Group C, Group F, and Group E. One-way ANOVA revealed a statistically significant difference between the groups (P < 0.05). Nonsignificant difference was found between the premolars restored by bulk-fill and conventional composites. Among the bulk-fill restored specimens, Beautifil restorative demonstrated significantly higher fracture resistance in comparison with the other two bulk-fill restored specimen groups (SonicFill 2 and Filtek). Bulk-fill composite such as Beautifil could be an alternative option to conventional incremental-fill composite for premolar restoration.

Fracture resistance of endodontically treated premolars restored with bulk-fill composite resins: The effect of fiber reinforcement

BACKGROUND

Coronal restoration of endodontically treated teeth (ETT) with mesio-occluso-distal (MOD) cavities is of a great importance in long-term success of the treatment. This study evaluated the effect of fiber reinforcement on the fracture resistance (FR) of ETT restored with flowable or paste bulk (PB)-fill composite resin compared to conventional composite (CC) resin.

MATERIALS AND METHODS

In this in vitro experimental study, eighty maxillary premolars were divided into eight groups (n = 10). The first group was left intact (G₁) and the other groups received MOD cavities along with endodontic treatment. G₂: Remained unrestored while the other experimental groups were restored with three types of composite resin with or without fiber insertion. G₃: CC resin, G₄: PB fill, G₅: Flowable bulk fill (FB). G₆: Fiber + CC, G₇: Fiber + PB, and G₈: Fiber + FB. FR was tested at crosshead speed of 1 mm/min and recorded in Newton. Data were analyzed using one-way analysis of variance and Tukey's tests at significance level of P < 0.05.

RESULTS

G₁ and G2 revealed the highest and the lowest FR, respectively. The mean FR of the testing groups in Newton was as follows: G₁ = 1204.8 ^A, G₂ = 352.1 ^C, G₃ = 579.6 ^BD, G₄ = 596.7 ^BD, G₅ = 624.9 ^BDE, G₆ = 858.3 ^E, G₇ = 529.6 ^CB, and G₈ = 802.5^DE. Different uppercase letters indicate the significant difference between the groups.

CONCLUSION

The effect of fiber insertion on FR depended on the type of composite resin; the highest reinforcing effect was obtained in the CC resin + fiber, followed by bulk-fill flowable + fiber, and flowable bulk (FB)-fill composite resin. The strength of the former was significantly higher than the conventional and PB fill with and without fiber.

Fracture Resistance of Endodontically Treated Maxillary Premolars Restored With Different Methods

Purpose:

The purpose of this in vitro study was to evaluate the resistance and patterns of fracture of endodontically treated maxillary premolars (ETPs) restored with different methods.

Methods and Materials:

Mesio-occluso-distal cavities were prepared in 50 extracted caries-free human maxillary premolars after endodontic treatment. The teeth were divided into five groups (n=10), according to the restorative method. G1: intact teeth (control group); G2: conventional composite resin; G3: conventional composite resin with a horizontal glass fiber post inserted between buccal and palatal walls; G4: bulk-fill flowable and bulk-fill restorative composites; and G5: ceramic inlay. For direct restorations, Filtek Z350 XT, Filtek Bulk Fill Flowable Restorative, and Filtek Bulk Fill Posterior Restorative were used. Indirect restorations were fabricated from a pressable lithium disilicate glass-ceramic (IPS e-max Press) and adhesively cemented (RelyX Ultimate). All specimens were subjected to thermocycling (5°C to 55°C/5000 cycles) and additionally submitted to cyclic loading 50,000 times in an Electro-Mechanical Fatigue Machine. Next, the specimens were subjected to a compressive load at a crosshead speed of 1 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern using a stereomicroscope, and then representative specimens were carbon coated to allow for the studying of the fracture surface under scanning electron microscopy. One-way analysis of variance (ANOVA) was used to compare fracture resistance of the groups. The results of fracture patterns were submitted to the Fisher exact test (α=0.05).

Results:

All specimens survived fatigue. Mean (standard deviation) failure loads (N) for groups were as follows: G1: 949.6 (331.5); G2: 999.6 (352.5); G3: 934.5 (233.6); G4: 771.0 (147.4); and G5: 856.7 (237.5). The lowest fracture resistance was recorded for G4, and the highest ones were recorded for G2, followed by that of G1 and G3. One-way ANOVA did not reveal significant differences between groups (p&gt;0.05). The highest repairable fracture rates were observed in G1 (100%) and G3 (80%).

Conclusions:

ETPs restored with conventional composite resin with or without horizontal fiber post, bulk-fill composite, and ceramic inlay showed fracture resistance similar to that of sound teeth. Conventional composite resin restorations exhibited the highest prevalence of unrepairable fractures, and the insertion of a horizontal fiber post decreased this prevalence. Intact teeth showed 100% of repairable fractures. It is difficult to extrapolate the results directly to a clinical situation due to the limitations of this study.

The Silorane-based Resin Composites: A Review

This article aims to review the research done on the silorane-based resin composites (SBRC) regarding polymerization shrinkage and contraction stresses and their ability to improve the shortcomings of the methacrylate-based resin composites (MRBC). Special attention is given to their physical and mechanical properties, bond strength, marginal adaptation, and cusp deflection. The clinical significance of this material is critically appraised with a focus on the ability of SBRC to strengthen the tooth structure as a direct restorative material. A search of English peer-reviewed dental literature (2003-2015) from PubMed and MEDLINE databases was conducted with the terms "low shrinkage" and "silorane composites." The list was screened, and 70 articles that were relevant to the objectives of this work were included.

Nanomaterials in dentistry: a cornerstone or a black box?

Aim: The studies on tooth structure provided basis for nanotechnology-based dental treatment approaches known as nanodentistry which aims at detection and treatment of oral pathologies, such as dental caries and periodontal diseases, insufficiently being treated by conventional materials or drugs. This review aims at defining the role of nanodentistry in the medical area, its potential and hazards. Materials & methods: To validate these issues, current literature on nanomaterials for dental applications was critically reviewed. Results: Nanomaterials for teeth restoration, bone regeneration and oral implantology exhibit better mechanical properties and provide more efficient esthetic outcome. However, still little is known about influence of long-term function of such biomaterials in the living organism. Conclusion: As application of nanomaterials in industry and medical-related sciences is still expanding, more information is needed on how such nano-dental materials may interfere with oral cavity, GI tract and general health.

Effect of Different Liners on Fracture Resistance of Premolars Restored with Conventional and Short Fiber-Reinforced Composite Resins

PURPOSE

To see whether applying four different liners under short fiber-reinforced composite (SFRC), everX Posterior, compared to conventional composite resin, Z250, affected their strengthening property in premolar MOD cavities.

MATERIALS AND METHODS

Mesio-occluso-distal (MOD) cavities were prepared in 120 sound maxillary premolars divided into 10 groups (n = 12) in terms of two composite resin types and 4 liners or no liner. For each composite resin, in 5 groups no liner, resin-modified glass ionomer (RMGI), conventional flowable composite (COFL), self-adhesive flowable composite resin (SAFL), and self-adhesive resin cement (SARC) were applied prior to restoring incrementally. After water storage and thermocycling, static fracture resistance was tested. Data (in Newtons) were analyzed using two-way ANOVA (α = 0.05).

RESULTS

Fracture resistance was significantly affected by composite resin type (p = 0.02), but not by the liner (p > 0.05). The interaction of the two factors was not statistically significant (p > 0.05). SFRC exhibited higher fracture strength (1470 ± 200 N) compared to conventional composite resin (1350 ± 290), irrespective of the application of liners. Application of SARC and SAFL liners led to a higher number of restorable fractures for both composite resins.

CONCLUSIONS

The four liners can be used without interfering with the higher efficacy of SFRC, compared to conventional composite resins, to improve the fracture strength of premolar MOD cavities.