In vitro fracture resistance of endodontically treated premolar teeth restored with a direct layered fiber-reinforced composite post and core

Methods for restoring endodontically treated teeth fall short of restoring the physiologic mechanical properties. Fracture of endodontically treated teeth is a common type of clinical failure. New treatment modalities or perfected versions of existing treatment concepts need to be tested to find a biomimetic solution. A novel method of restoring endodontically treated teeth is presented and compared in vitro with currently accepted restorative methods. Seventy-two extracted and endodontically treated maxillary premolar teeth were divided into six groups (n = 12) depending on restorative technique (Groups 1–6). Group 1: fiber-reinforced composite post (FRC), Group 2: direct layered short FRC post and core, Group 3: short fiber-reinforced obliquely layered composite restoration, Group 4: microhybrid composite restoration, Group 5: fiber-reinforced box, Group 6: control. Specimens were submitted to static fracture resistance test. Fracture thresholds and fracture patterns were evaluated. Group 6 exhibited the highest fracture resistance. Group 2 yielded the highest fracture resistance among the restored groups. The fracture resistance of Group 2 did not differ significantly from Group 6. Groups 1, 3, 4, 5 proved to be significantly different from the control group. There was no statistically significant difference among restored groups. Fracture patterns of tested groups were dominantly non repairable opposed to control groups mostly repairable fractures. Application of direct-layered short FRC post and core in endodontically treated premolars performed statistically similarly in the studied conditions as natural teeth. Therefore, it seems a promising alternative to current endo-restorative solutions. However, further testing is required.     

Compressive strength and failure types of cusp replacing direct resin composite restorations in previously amalgam-filled premolars versus sound teeth

This study evaluated the fracture resistance of cusp replacing direct resin composite restorations (DCR) in premolars that had been previously filled with amalgam mesial–occlusal–distal (MOD) restorations and compared their fracture resistance with those made on sound dentin and intact teeth. Recently extracted human premolars with either MOD amalgam restorations or sound/intact ones were selected for the study. Cavities with cusp reduction were made for the following groups: (a) Group 1: DCRs on previously amalgam-affected dentin (n = 11), (b) Group 2: DCRs on sound dentin (n = 10), and (c) Group 3: intact premolars (n = 9). Teeth in Groups 1 and 2 were restored with a 3-step etch and rinse adhesive (Quadrant Unibond) and filled with hybrid composite (Clearfil Photo Posterior). All specimens were thermocycled for 5000 cycles (5–55 °C). The buccal cusps of the teeth were loaded until fracture under compression at 45° to the long axis of the teeth in a universal testing machine (1 mm/min). Data (N) were statistically analyzed using one-way ANOVA and Student’s t-test (α = 0.01). Intact teeth (Group 3) showed significantly higher fracture resistance (893 ± 196) compared to both restored groups (p < 0.01). No significant difference was found between the DCRs made on amalgam-affected dentin (Group 1: 607 ± 166) and sound dentin (Group 2: 588 ± 183) (p > 0.01). More than half of the teeth of Groups 2 and 3 showed unrepairable fractures with pulp exposure.     

The effect of bulk-fill flowable composites on the fracture resistance and cuspal deflection of endodontically treated premolars

The aim of this study was to evaluate the effect of bulk-fill flowable composites on cuspal deflection and fracture resistance of endodontically treated teeth. Forty-two maxillary premolars were subjected to endodontic treatment followed by the preparation of mesioocclusodistal cavities. Teeth were divided into six groups according to restorative materials as follows: Group 1: Clearfil Majesty Flow and Clearfil Majesty Posterior; Group 2: Venus Bulk Fill and Clearfil Majesty Posterior; Group 3: Clearfil Majesty Posterior; Group 4: Vertise Flow and Clearfil Majesty Posterior; Group 5: SDR and Clearfil Majesty Posterior; and Group 6: x-tra base and Clearfil Majesty Posterior. A single-step self-etch adhesive (OptiBond All-in-One) was applied to all groups, except Group 4. The cavities were restored with a centripetal incremental insertion technique and flowable composites using a 2-mm-thick base material, except for Group 3. The distance between cusp tips was measured before and after the cavity preparations, after the restorations, and after thermal cyclus with a digital micrometer. After measuring, each tooth was subjected to compressive loading with a stainless steel ball (4 mm diameter) perpendicular to the occlusal surface with a crosshead speed of 1 mm/min, and mean loads necessary to fracture were recorded in Newtons. The data were statistically analyzed by Kruskal–Wallis test. No statistically significant differences were found between groups in fracture strength or cuspal deflections (p > 0.05). Bulk-fill flowable composite bases did not change the cuspal deflection or fracture resistance of endodontically treated teeth, compared with that of a conventional flowable base and conventional resin composite.     

The effect of different restoration techniques on fracture strength of teeth with flared roots

The aim of this study was to investigate the effect of different restoration techniques on the fracture strength of roots with flared canals. The crowns of 50 extracted single-rooted human teeth were removed and the canals were flared. Five groups were created (n = 10): Group 1: ReforPost (Angelus) was luted using Clearfil SA Cement (Kuraray); Group 2: ReforPost and two accessory posts (Reforpin, Angelus) were luted with Clearfil SA Cement; Group 3: Restored with i-TFC post-core system (Sun Medical); Group 4: The thickness of the root-dentine was increased using composite resin (Clearfil AP-X, Kuraray) and cured with the help of Luminex. ReforPost was then luted; Group 5: Anatomic posts were created by relining ReforPost with Clearfil AP-X and then luted using Clearfil SA Cement. The cores were created with composite resin in all the samples. The crowns of sound teeth were prepared similar to a core (control, n = 10). The specimens were vertically loaded (1 mm/min), the force that was required to fracture each sample was recorded (N) and analyzed (One Way Anova, Tukey tests). No significant difference was found among the groups (p > 0.05). The roots restored by using accessory post and i-TFC post-core (Groups 2 and 3) indicated a 100% favorable fracture pattern. Ten percent of the root fractures were observed in other groups. All techniques saved the root structure and showed 80–100% favorable failure pattern. The use of i-TFC system in flared roots could be an alternative to anatomic, accessory, and prefabricated fiber posts.     

Fatigue and fracture resistance of minimally invasive ceramic and resin composite veneers with different designs bonded adhesively to severely eroded teeth

This study evaluated the load bearing capacity of minimal invasive restoration alternatives on severely worn teeth after cyclic loading. Sound human maxillary incisors (N?=?72, n?=?9 per group) were randomly divided into nine experimental groups to receive one of the following restoration types: Group 1: Intact tooth, Group 2: Direct resin composite, Group 3: Lingual: Indirect resin composite, Labial: Ceramic veneer with lingual overlap, Group 4: Lingual: Indirect resin composite with lingual overlap, Labial: Ceramic, Group 5: Lingual: Direct composite, Labial: Ceramic, Group 6: Lingual: Feldspathic Ceramic, Labial: Feldspathic ceramic, Group 7: Lithium disilicate crown, Group 8: Metal-ceramic crown. Teeth were prepared simulating erosion/wear conditions. Specimens were subjected to cyclic loading (1,200,000 cycles, 5–55?°C) and then loaded to failure from the lingual surface at 105° inclination (1?mm/min). Data (Newton) were analyzed using one-way ANOVA, Tukey`s tests and Weibull moduli were calculated (α?=?0.05). Significant differences were observed between the groups for the initial (p?=?0.006) and maximum fracture load (p?=?0.002). Group 3 (55?±?36) presented significantly lower initial fracture load compared to other groups (79?±?35–134?±?36) (p?<?0.05). When maximum fracture load is considered, control group (1) (602?±?355) and from restored groups 2 (449?±?144) and 4 (495?±?291) showed significantly higher results (p?<?0.05). Weibull modulus for the maximum fracture load was the highest for Group 2 (m?=?3.47) among all groups (m?=?1.61–4.18). Groups 2, 3, 6 presented the highest incidence of repairable failures. Based on the results, severely worn teeth could be restored with lingual direct resin composite and labial veneering with indirect resin with overlap.     

Cuspal deflection and microleakage in pre molar teeth restored with bulk-fill resin-based composites

The aim of this study was to assess the cuspal deflection and cervical microleakage of premolar teeth filled with a bulk-fill composite resin or bulk-fill flowable composite resin base, and comparison between them and a conventional dimethacrylate and a silorane-base composite resin. Forty maxillary premolar teeth were divided into four groups (n?=?10), standardized large mesio-occluso-distal (MOD) cavities were prepared. The distance between cusp tips was measured before and after the cavity preparations with a digital micrometer. In Group 1 Quixfil was used with bulk-fill technique. Teeth in Group 2 were restored to within 2?mm of palatal cusp in a single increment with x-tra base. The remaining occlusal cavity was restored with GrandioSO. In Groups 3 and 4, the teeth were incrementally restored with GrandioSO and Filtek Silorane, respectively. Cuspal deflection was measured 5?min, 24?h, 1 week, and 2 weeks after the completion of restorations. Each restored tooth was subjected to thermocycling regime, and microleakage was assessed. Data were analyzed with Kruskal–Wallis and Mann Whitney U tests (p?<?0.05). Groups restored with bulk-fill composites (Groups 1 and 2) showed similar cuspal deflection with the group restored incrementally with GrandioSO. A significant reduction in cuspal deflection was observed in Filtek Silorane restorations. None of the groups showed complete prevention of dye penetration. Group 2 showed the best marginal sealing. In Conclusion, conventional composite resin applied by incremental technique caused cuspal deflection similar to that of bulk-fill composites used as restorative or base. The flowable bulk-fill composites were superior to others in preventing microleakage.     

Load-bearing capacity and failure types of premolars restored with sonic activated bulk-fill-, nano-hybrid and silorane-based resin restorative materials

This study evaluated the load-bearing capacity of premolars restored with three types of resin composite materials in mesio-occluso-distal (MOD) cavities. Extracted human premolars (N = 30, n = 10 per group) were randomly divided into three groups; MOD cavities were prepared and restored with one of the following resin materials: Group BFC: Bulk-fill composite (SonicFill, Kerr Corporation), Group NC: Nanohybrid resin composite (Filtek Z550, 3M ESPE), Group SC: Silorane-based composite (Filtek Silorane, 3M ESPE). For NC Clearfil SE Bond (Kuraray, Japan) and for SC, Silorane adhesive resin (Filtek Silorane System Adhesive, 3M ESPE) were used. The cavities in NC and SC groups were restored incrementally, while those in BFC groups were restored in bulk. After water storage (24 h, 37 °C), each tooth was subjected to compressive loading with a stainless steel ball (diameter: 4 mm) perpendicular to the occlusal surface (1 mm/min). Failure types were categorized according to being repairable or irrepairable. Data were statistically analysed using Kruskal-Wallis test (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0) values were calculated. Fracture resistance of premolars restored with BFC (829.84), NC (701.35) and SC (807.73) did not show significant difference (p = 0.72). Weibull distribution presented lower shape (0) for SC (m = 2.77) and NC (m = 3.09) compared to BFC (m = 5.01). The incidence of repairable failures was more common in BFC (80%) compared to NC (60%) and SC (50%). Adhesive failures were more often observed in NC (80%) and SC (70%) groups.     

Fracture resistance of endodontically treated molars restored with polyethylene fiber and different posts

The purpose of this study was to compare the fracture strength and mode of teeth restored with fiber/titanium post, polyethylene fiber, and adhesive composite. The mesial, distal, and palatal walls of human maxillary molar teeth were removed, so that only the buccal wall remained. Group 1, with caries-free maxillary molars, was used as a positive control group and the remaining groups were restored as follows: group 2, with only adhesive composite; group 3, with polyethylene fiber and adhesive composite; group 4, with fiber post and adhesive composite; group 5, with fiber post, polyethylene fiber, and adhesive composite; group 6, with titanium post and adhesive composite; and group 7, with titanium post, polyethylene fiber, and adhesive composite. A universal testing machine was used for fracture tests. Compressive loads were applied at an angle of 90 degrees on the occlusal surface of the specimens at crosshead speed of 1?mm/min until fracture occurred. Kruskal–Wallis and Mann–Whitney U tests were adopted for statistical analysis. The study shows that, based on the fracture strength, the group of teeth that were restored with glass fiber post, polyethylene fiber, and adhesive composite has the most significant improvement over all the other teeth groups. Based on the fracture mode, the teeth groups restored with only glass fiber post, adhesive composite, polyethylene fiber, and adhesive composite have relatively more restorable fractures observed.     

Fracture resistance of mechanically compromised premolars restored with polyethylene fiber and adhesive materials

No previous study has tested the strength of teeth restored with a fiber post inside the root canal combined with a ribbon fiber in the crown surrounding the post. The aim of this study was to compare a new adhesive technique to other conventional techniques in the fracture resistance of endodontically treated premolars. Fifty superior premolars were divided into 5 groups (n=10), prepared as follows: intact teeth used in G1 as control; in the other experimental groups (G2, G3, G4 and G5), mesio-occlusal-distal cavities were prepared, extending toward the palatal cups (MODP), and root canal treatments were performed. Groups were restored by varying the restorative technique: G2 – only with composite resin (CR); G3 fiber post+CR; G4 – polyethylene fiber (Ribbond)+CR; and G5, fiber post+Ribbond+CR. The teeth were thermocycled 1000 times. After 24 h, the specimens were loaded in a universal testing machine until fracture, and the failure mode was checked. ANOVA and Tukey–Krammer tests were used for statistical analysis (α=0.05). Results: The fracture strength (N) of control (G1 – 410.7±106.9) was not significantly different (P>0.05) from Ribbond+CR (G4 – 300.7±80.2) and fiber post+Ribbond+CR (G5 – 377.5±107.7). Specimens restored only with CR (G2 – 177.7±52.1) and fiber post+CR (G3 – 264.6±88.5) were statistically similar (P>0.05), but both had their mean values differed from the control (P<0.05). Longitudinal and oblique crown fractures were predominant in all groups. Ribbon–fiber reinforced resin restorations provided superior fracture resistance of premolars with MODP and endodontic access cavities when compared to conventional direct techniques.     

Load bearing capacity of minimal invasive direct and indirect veneers bonded to maxillary incisors with severe wear: effect of preparation design and material type

This study evaluated the load bearing capacity of direct and indirect veneers vs. full-coverage crowns and classified the failure types after fracture load. Sound human maxillary incisors (N = 108, n = 12 per group) were randomly divided into nine groups to receive one of the following restoration types: Group 1: Intact tooth, Group 2: Direct resin composite, Group 3: Lingual: Indirect composite veneer, Labial: Ceramic veneer, Lingual overlap: Ceramic, Group 4: Lingual: Indirect composite, Labial: Ceramic, Lingual overlap: Indirect composite, Group 5: Lingual: Direct composite, Labial: Ceramic, Group 6: Lingual: Ceramic, Labial: Ceramic, Group 7: Feldspathic ceramic crown, Group 8: Metal-ceramic Crown, Group 9: Lithium disilicate crown. Teeth were prepared simulating the erosion/wear conditions in each group. After cementing, the specimens were stored in distilled water at 37 °C for 2 months and then loaded to failure from the lingual surface at 105° inclination in the Universal Testing Machine (1 mm/min). Failure types were classified as irreparable or repairable. Data were analyzed using one-way ANOVA, Sheffe and Bonneferroni tests (α = 0.05). Mean fracture strength (N) of Groups 1, 4, 8, and 9 (558 ± 278 – 880 ± 319) were significantly higher than those of other groups (348 ± 101–421 ± 162) (p < 0.05). Lingual veneering with direct/indirect resin composite or ceramic did not significantly affect the results (p > 0.05) but lingual overlap with indirect composite increased the results (p < 0.05). Group 1, 2, 4 and 5 presented more repairable failures. Restoration of eroded teeth could best be achieved with direct composite veneer at the lingual and ceramic veneer on the labial surface.     

Mechanical properties of flared root canals restored with fiber post and chemically activated resin: study using push-out bond strength and fracture load tests

This study aimed to evaluate the fracture load and push-out bond strength of flared root canals restored with different procedures, including a technique with a fiber post and a chemically activated resin composite. Eighty human canines were selected and treated endodontically. Two methodologies were used: push-out and fracture load. The teeth were divided into four groups: Cast metal core (CMC); PAN (direct anatomic post); PAC (fiber post and accessory posts); and PE (fiber post with chemically activated resin composite). For the fracture load test, the samples were submitted to load application in a universal testing machine. The fracture mode was evaluated visually. Forty other samples were submitted to the push-out test. The fracture load (n = 10) and the bond strength (n = 10) were analyzed by analysis of variance and Tukey tests (α < 0.05). CMC presented the highest fracture load (p < 0.05), and no significant differences were observed in the fracture load values for Groups PAN, PAC, and PE. CMC presented 90% of unfavorable failures; PAN and PAC, the remaining 10% of these failures. PE presented only favorable failures. PAC presented lower push-out bond strength values. The fracture load for CMC procedure was higher than that of the others, but presented 90% unfavorable fractures, indicating the use of any of the glass fiber post techniques evaluated for restoring flared root canals due to favorable fracture modes.     

The bonding effect of adhesive systems and bulk-fill composites to sound and caries-affected dentine

Purpose: To investigate the influence of adhesive type and increment thickness on shear bond strength of flowable bulk-fill resin composites compared with a flowable conventional resin composite, in both sound and caries-affected dentine.

Methods: Shear bond strength was tested in 100 extracted human molars with coronal dentine caries. Half of the teeth were restored with Adper? Easy Bond and the other half with Adper? Single Bond Plus. Bonded surfaces were restored with Filtek? Ultimate Flow and two bulk-fill composites (SDR and X-tra base) (n = 10 teeth for each subgroup). Restorations of 4 mm were performed with incremental or bulk-fill technique. The shear bond was determined and statistically analysed using three-way ANOVA and Bonferroni multiple comparison post hoc tests (p ≤ 0.05). Dentine–resin interfaces were evaluated by scanning electron microscopy.

Results: For both adhesives, the highest shear bond strength values were obtained for sound dentine. In sound dentine, the highest bond strength observed with Easy Bond when used in 2-mm increments of SDR. In caries-affected dentine, Single Bond in combination with SDR displayed significantly lower bond strength.

Conclusion: There was no significant difference in shear bond strength between the incremental and bulk-fill groups for molars with sound dentine when the etch-and-rinse adhesive system was used; however, for the self-etch adhesive system, incremental application caused higher bond strength than bulk application.     

Effects of sodium ascorbate and delayed bonding after bleaching on shear bond strengts of orthodontic brackets

Introduction: The aim of the study was to determine the effects of sodium ascorbate and delaying bonding for 4 weeks after bleaching on SBS of orthodontic brackets.

Methods: Sixty freshly extracted, noncarious, premolars were randomly assigned to 4 groups of 15 each. Orthodontic brackets were bonded with a composite resin and cured with a halogen light. After bonding, the shear bond strengths of the brackets were tested with a universal testing machine. Group I served as the control. In groups II, III, and IV, teeth were bleached with an office bleaching method. In group II, brackets bonded immediately after bleaching. In group III, teeth were immersed in artificial saliva of 4 weeks after bleaching before bonding brackets. In group IV, teeth were treated with 10% sodium ascorbate after bleaching before bonding brackets.

Results: One-way analysis of variance indicated a significant difference between groups (P < .001). The highest values for SBS were measured in group I (11.92 ± 0.81 MPa). The SBS was significantly lower in groups II, III, and IV than in group I (P < .001). There was no statistically significant difference between groups III and IV.

Conclusions: Bleaching significantly reduced the SBS of orthodontic brackets on human enamel. If bleaching is mandatory, teeth should be treated with sodium ascorbate before bonding.     

Microleakage in class V cavities prepared using conventional method versus Er:YAG laser restored with glass ionomer cement or resin composite

This study evaluated the effect of tooth preparation method (diamond bur vs. Er:YAG laser) on the microleakage levels of glass ionomers and resin composite. Human permanent premolars (N = 80) were randomly divided into two groups (n = 40). Cavities on half of the teeth were prepared using diamond bur for enamel and carbide bur for dentin and the other half using Er:YAG laser. The teeth were randomly divided into four groups according to the restoration materials, namely (a) ChemFil Rock (CFR), (b) IonoluxAC (IAC), (c) EQUIA system (EQA) and one resin composite (d) AeliteLS (ALS) (n = 10 per group). Microleakage (μm) was assessed at the occlusal and gingival margins after dye penetration (0.5% basic fuchsine for 24 h). On the occlusal aspect, while the cavity preparation types significantly affected the microleakage for CFR (p = 0.015), IAC (p = 0.001) glass ionomer restorations, it did not show significant effect for glass ionomer EQA (p = 0.09) and resin composite ALS (p = 0.2). Er:YAG laser presented less microleakage compared to bur preparation in all groups except for EQA. On the gingival aspect, microleakage decreased significantly for CFR (p = 0.02), IAC (p = 0.001), except for EQA where significant increase was observed (p = 0.001) with the use of Er:YAG laser. Microleakage decrease was not significant at the gingival region between diamond bur and Er:YAG laser for ALS (p = 0.663). At the occlusal and gingival sites in all groups within each preparation method, microleakage level was not significant.     

Influence of desensitizing procedures on adhesion of resin cements to dentin

This study evaluated the effect of two desensitizer agents with different contents and Nd:YAG laser irradiation on the shear bond strength (SBS) of adhesive resin cements to dentin. New treatment options of Nd:YAG laser irradiation and tetracalcium phosphate-containing agent applications were compared with routinely used glutaraldehyde-containing agents. One hundred and twenty human, caries-free premolars were embedded in acrylic resin blocks 2 mm below the cementoenamel junction. Buccal surfaces of the teeth were ground to expose dentin. The specimens were randomly assigned into three different surface treatments (desensitizing agents, Nd:YAG laser) and the control, then into three different adhesive resin cement applications (n = 10). Resin cements (Panavia SA cement (PA), Panavia SA cement with Clearfil Universal Bond (PACU), and Multilink N (MN)) were applied to the conditioned teeth surfaces using Teflon tubes. The specimens were thermocycled (5000 cycles, 5–55 ± 1 °C, dwell time 30 s). The SBS test was performed in all groups. The results were submitted to two-way ANOVA and Tukey HSD tests (p < .05). Further, SEM analysis was performed on the dentin surfaces. SBS values were significantly difference among the surface treatment groups and also among adhesive resin cement groups (p < .05). The specimen cemented with PA showed lower SBS values than PACU- and MN-applied specimens. The highest SBS value was obtained in the Nd:YAG laser group which was cemented with PACU cement. The lowest SBS value was obtained in the control group which was cemented with PA cement. In addition, SEM evaluation revealed that desensitizing agents and Nd:YAG laser occluded dentin tubules.     

Fracture resistance of roots obturated with a novel calcium silicate-based endodontic sealer (BioRoot RCS)

The aim of this ex vivo study was to evaluate the vertical-fracture resistance of roots obturated with a newly developed tricalcium silicate cement (BioRoot RCS; Septodont, Saint Maur Des Fosses, France) using cold lateral compaction technique (LC) or matched-taper single-cone gutta-percha technique (SC). Decoronated 82 single-rooted mandibular premolars were chemo-mechanically prepared and then randomly divided into 6 experimental groups (n = 12) and 2 control groups (n = 5): Group 1 iRoot SP-LC; Group 2 iRoot SP-SC; Group 3 MTA Fillapex-LC; Group 4 MTA Fillapex-SC; Group 5 BioRoot RCS-LC and Group 6 BioRoot RCS-SC. In the positive-control group, roots were instrumented but not filled, and in the negative-control group, roots were neither instrumented nor filled. All samples were incubated for two weeks and then subjected to vertical loading force (1 mm/min) until fracture. The force required to fracture each specimen were determined, and the data were statistically analyzed. The highest significant fracture resistance was recorded for the iRoot SP-LC, iRoot SP-SC, BioRoot RCS-LC, and BioRoot RCS-SC groups, with no significant difference among them (p > 0.05) when compared with the positive-control group (p < 0.05), whereas the lowest significant values were observed in the MTA Fillapex-LC and MTA Fillapex-SC groups (p < 0.05). The vertical fracture resistance of roots obturated with BioRoot RCS and iRoot SP sealers using either LC or SC technique was found to be similar to that of intact teeth. BioRoot RCS, newly developed tricalcium silicate cement, might have the potential to reinforce the instrumented teeth against vertical root fracture.     

Long-term microleakage trends in access cavities conditioned with phosphoric acid and deproteinizing agent for root-canal-treated teeth: an investigation of fluid filtration and microscopy analysis

This study evaluated the long-term microleakage of access cavities conditioned with phosphoric acid and deproteinizing agents for root-canal-treated teeth using fluid filtration and microscopical analysis. Occlusal surfaces of extracted human mandibular premolars (N = 90) were removed leaving a 4 mm coronal length from the cemento-enamel junction. After root canal treatment, the specimens were randomly divided into four experimental groups (n = 21) and the remaining teeth were used for positive control group (n = 6): SB: 35% H₃PO₄ + Adper Single Bond 2; SSB: 35% H₃PO₄ + 5.25% NaOCl + 10% Sodium ascorbate (C₆H₇NaO₆) + Adper Single Bond 2; XP: 35% H₃PO₄₊XP Bond; SXP: 35% H₃PO₄₊5.25% NaOCl + 10% Sodium ascorbate + XP Bond. All cavities were restored with a resin composite (Filtek Z250). After removing the root filling from the apical side, teeth were subjected to fluid filtration test for 1 week, 6 and 12 months followed by ×2500 thermocycling after 1st week and 6th months each. Data were analyzed using one-way ANOVA and Dunnet T3 tests (α = 0.05). SEM analyses were carried out after each microleakage evaluation in two random teeth from all groups. Microleakage values in groups SB and XP presented no significant difference in any of the evaluated period (p > 0.05). Microleakage results of SXP (0.01665) group showed significant difference compared to XP (0.03377) and SB (0.03049) groups after 12 months. SSB group (0.00901) showed significantly less microleakage among all other groups (0.01665–0.03377) (p < 0.05). Prior to endodontic treatment, in access cavities, acid etching with 35% H₃PO₄ followed by the application of NaOCl and sodium ascorbate completely destroyed the collagen layer, reducing the microleakage and resin–dentin interface degradation up to 12 months.     

Influence of Dynamic Loading and Different Adhesive Systems on the Microleakage in Root Canals

Abstract

The objective of this study was to evaluate the influence of dynamic loading and different adhesive systems on the microleakage in root canals.

80 human premolars were used in this study. The crowns of the teeth were sectioned at the cemento-enamel junction using a low speed diamond saw. After post space preparation, the roots were randomly assigned to 4 groups (n = 20) and restored with different adhesive systems. Group 1: Rely X ARC (RA) + Single Bond (SA), Group 2: Clearfil SA Cement (CL), Group 3: Panavia F 2.0 (PAN), Group 4: Rely X Unicem (RU). All the teeth were restored with the same type of glass fiber post and coronal cores built up with light-polymerizing hybrid composite resin. Half of the specimens of each group (n = 10) were subjected to additional dynamic loading in a universal testing machine. Apical parts of the roots were attached to computerized fluid filtration device for leakage measurement.

The two-way ANOVA test was used first to detect overall significance, followed by two-sample t-test to identify which pairs of groups had significant differences. For each outcome statistical significance was set at p < 0.05. Dynamic loading significantly increased the microleakage values for Rely X ARC (p = 0.005), Clearfil SA Cement (p = 0.002) and Rely X Unicem groups (p = 0.001) but Panavia F 2.0 group was not affected by the dynamic loading (p = 0.111). One-way ANOVA test was applied to detect any significant differences in microleakage values for the adhesive systems. In the unloaded groups, there is no difference between the adhesive systems (p = 0.13). For the dynamically loaded groups, there is only significant difference between PAN and RA groups (p = 0.010). Post-hoc pairwise comparisons were done using Tukey’s multiple comparisons. Differences between Rely X ARC-Clearfil SA Cement and Rely X ARC-Panavia F 2.0 are statistically significant (p = 0.009, 0.013).     

Effect of Different Restorative Materials on Microleakage of Ozone Gas and Traditional Cavity Disinfectant Applied Teeth

The aim of this in vitro study is to investigate the effects of ozone and conventional cavity disinfectant on microleakage at the cavities which are restorated with different restorative materials. Ninety human molar teeth were used in this study. Black V cavities are prepared on buccal surfaces of teeth. Teeth are divided to 3 groups which contains 30 teeth. Group 1: ozone applied; Group 2: 2% chlorhexidine applied; Group 3: any disinfectant is not applied. And then all groups are divided to three subgroups. All subgroups are restored with silorane, ormocer, and traditional composite according to the manufacturer’s directions. Sections were examined under a microscope. Occlusal and gingival microleakage values by a separate researcher and scores were recorded. Statistically results were reviewed with ANOVA and Kruskal–Wallis Tests. Statistically significant difference of microleakage between cavity disinfectant and control groups’ occlusal and gingival lines was not found (p > 0.05). There was no differences at occlusal lines of composite subgroups (p > 0.05) but also significant difference at gingival lines was found (p < 0.05). Statistically significant difference was found among the composite materials, between chlorhexidine and control groups’ gingival lines. The most successful results at gingival lines were found with silorane.     

Effect of material and fabrication technique on marginal fit and fracture resistance of adhesively luted inlays made of CAD/CAM ceramics and hybrid materials

This study evaluated the fracture resistance and marginal fit of CAD/CAM ceramic and composite inlays. Molars (N = 80) were prepared to receive Mesio-occlusal-distal (MOD) inlays and randomly divided into four groups to be restored depending on the materials: (a) HLD: heat-pressed lithium disilicate ceramic (IPS e.max Press), (b) CLD: CAD/CAM-fabricated lithium disilicate ceramic (IPS e.max CAD), (c) NC: CAD/CAM nano-ceramic resin (Lava Ultimate), (d) RC: Indirect resin composite (Filtek P60). Each group was randomly divided into two subgroups regarding the resin cement: (a) High-viscosity resin cement (Syntac, Variolink II), (b) Self-adhesive low-viscosity cement (RelyX Ultimate). After marginal gap and cement thickness measurements, specimens were loaded to fracture in a Universal Testing Machine (1 mm/min). Intact molars acted as the control group (n = 10). Data were analyzed using one-way and two-way ANOVA, Tukey’s tests (α = 0.05). Before cementation, CLD group showed significantly lower mean marginal gap (65 ± 22.4 μm) and after cementation, cement thickness was again the lowest with CLD (82.6 ± 24.6 μm) and the highest with HLD (108.4 ± 21.3 μm) (p < 0.001). The mean marginal gaps of inlays at the gingival margin were significantly higher than at the occlusal and the axial margins (p < 0.05). While material type significantly affected the mean fracture resistance (p < 0.001), the cement type had no effect on the results (p = 0.083). NC group (2486 ± 40 N) showed significantly higher mean fracture load compared to those of other three groups (1997.5 ± 60–2007 ± 30) (p < 0.05). The mean fracture resistance of control group with the intact teeth was significantly higher than those of all groups (p < 0.05) except for NC (p > 0.05).