Performance of a novel self-adhesive bulk-fill composite hybrid in endodontically treated maxillary premolars: analysis of fracture resistance and failure mode.

This study evaluated the fracture resistance of endodontically treated maxillary premolars restored with a new self-adhesive composite hybrid material (Surefil one [SO]) using different protocols. A total of 72 maxillary premolars were divided into 6 groups (n = 12). The control group included intact teeth, and the other 5 groups included teeth in which disto-occlusal cavities were prepared and endodontic treatment was performed. The prepared cavities were assigned to groups that were based on the restorative procedures: bulk-fill group, universal adhesive plus conventional bulk-fill composite resin plus a layer of conventional composite resin; SO-SC group, self-cured SO; SO-LC group, light-cured SO; SO-UA group, universal adhesive plus SO; or SO-core group, a 4.0-mm layer of SO covered by a layer of conventional composite resin. Specimens in each group underwent thermocycling and load cycling to test the fracture strength and fracture mode. The results were analyzed using analysis of variance and the Tukey test (α = 0.05). The SO-core group showed the highest mean (SD) fracture resistance, 959.9 (171.8) N, among the restored groups. The SO-core group did not differ significantly from the control group (P > 0.05) but did show significantly higher strength than all other test groups (P < 0.05) except SO-SC (P = 0.364). No significant differences were found between the bulk-fill, SO-SC, SO-LC, and SO-UA groups (P > 0.05). The SO-core group showed the highest number of unrestorable fractures, while the main fracture mode for the other groups was restorable fracture. Although the use of SO as a core material restored the fracture strength of endodontically treated premolars to the level of intact teeth, it also resulted in a higher incidence of unrestorable fractures. The SO-SC group demonstrated a high fracture resistance comparable to that of the SO-core group and had a greater tendency to experience restorable fractures.

Effect of a cross-linking antioxidant agent on the bond strength of adhesive resin to irradiated dentin.

It has been shown that irradiation can cause structural changes in dentin that may reduce the bond strength of adhesives to dentin. Applying cross-linking or antioxidant agents may help reverse this detrimental effect and improve adhesion to dentin. This in vitro study aimed to evaluate the effects of epigallocatechin-3-gallate (EGCG) pretreatment and the time of adhesive bonding (24 hours vs 1 month) on the shear bond strength (SBS) of All-Bond Universal (ABU) to irradiated dentin using etch-and-rinse (ER) and self-etching (SE) modes. Flat dentin surfaces prepared from 96 extracted intact human molars were divided into 8 groups (n = 12) and bonded with ABU. In the control (CO) groups (CO/ER and CO/SE), bonding was performed on nonirradiated dentin; in the irradiated (IR) groups (IR/ER and IR/SE), bonding was performed on irradiated dentin; in the irradiated pretreated groups (IR/EGCG/ER and IR/EGCG/SE), irradiated dentin received a 0.1% EGCG pretreatment before bonding; and in the irradiated delayed bonding (DL) groups (IR/DL/ER and IR/DL/SE), bonding on irradiated dentin was performed 1 month after completion of radiotherapy. The irradiation protocol consisted of a total dose of 60 Gy with 2-Gy exposure applied 5 days per week for a period of 6 weeks. After bonding procedures were completed, the specimens were stored in 100% humidity at 37°C for 24 hours and then the SBS was tested in a universal testing machine. Data were analyzed using 1-way analysis of variance and Tukey tests. There was a statistically significant difference among the 8 groups (P < 0.001). Irradiation diminished the SBS in the IR/ER and IR/SE groups compared with their controls (P < 0.001). Pretreatment with EGCG significantly increased the SBS in the IR/EGCG/ER group only (P < 0.001). The difference between the IR/ER and IR/DL/ER groups was not statistically significant, and the difference between the IR/SE and IR/DL/SE groups was marginally significant (P = 0.056). Pretreatment with EGCG after acid etching restored the SBS of ABU to irradiated dentin, resulting in an adhesive performance equivalent to that observed with nonirradiated dentin. A 1-month delay between irradiation and bonding did not improve the SBS.

Influence of dentin presealing on the fracture strength of endodontically treated maxillary premolars.

This in vitro study aimed to evaluate the influence of endodontic irrigation solutions and resin sealing of the dentin surfaces of the cavity before irrigation on the fracture strength (FS) of maxillary premolars. Seventy-two human maxillary premolars were randomly assigned to 6 groups (n = 12). Group 1 consisted of intact teeth that served as negative controls. In groups 2 to 6, root canal treatment was performed after mesio-occlusal preparation. In group 6, the dentin surfaces of the mesio-occlusal cavity were sealed with a self-adhesive flowable composite resin before instrumentation and irrigation of the canal. The volume and contact time of the irrigation solutions used during endodontic treatment of groups 2, 4, 5, and 6 were standardized as follows: 2 mL of 5.25% sodium hypochlorite (NaOCl) for 1 minute after each file, 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) for 3 minutes after instrumentation was completed, and 5 mL of 5.25% NaOCl for 1 minute as the final irrigation. In group 3, the irrigation solution was normal saline solution only. After root canal obturation, in group 2, the cavities were left unrestored as a positive control. In groups 3 (saline-rinsed), 4 (conventionally restored), and 6 (presealed), the restorations were carried out with an etch-and-rinse adhesive and composite resin immediately after root canal obturations. In group 5 (delay-restored), the restorations were carried out with an etch-and-rinse adhesive and composite resin after a 1-week delay. After thermomechanical cycling, the teeth were subjected to FS testing under continuous compressive force. Data were analyzed with 1-way analysis of variance and Tukey tests. The unrestored group, which demonstrated the lowest FS, did not differ significantly from the conventionally restored group; the FS of both groups was significantly lower than that in the other groups (P ≤ 0.001). The presealed group exhibited the highest FS (P ≤ 0.02). The FS values of the saline and delay-restored groups were statistically comparable. In the present study, NaOCl/EDTA irrigation had an adverse effect on the FS. Presealing of the dentin surfaces of the cavity with self-adhesive flowable composite resin significantly increased the FS of aged composite resin-restored premolars.

Effect of restorative technique on the fracture strength and fracture mode of premolars after mineral trioxide aggregate pulpotomy.

This study aimed to compare the effects of different combinations of adhesive bases and restorative materials on the fracture strength and mode of maxillary premolars with mesio-occlusodistal (MOD) cavities after mineral trioxide aggregate (MTA) pulpotomy. Ninety-six extracted human maxillary premolars were divided into 8 groups (n = 12). Group 1 (negative control) consisted of intact teeth. In the other teeth, MOD and endodontic access cavities were prepared, and a layer of MTA was placed. Group 2 was left unrestored as the positive control. Group 3 was restored with a glass ionomer cement (GIC) base and amalgam. The remaining groups were restored with a microhybrid composite after application of different bases: 4, resin-modified GIC (RMGIC); 5, zirconia-reinforced GIC (ZRGIC); 6, self-adhesive flowable composite (SAFC); 7, self-adhesive resin cement (SARC); and 8, short fiber-reinforced composite (SFRC). After fracture strength testing via continuous compressive axial loading, the fracture mode was classified as restorable or unrestorable. Data were analyzed using 1-way analysis of variance and post hoc Tamhane tests (P < 0.05). The fracture strength of the negative control group was significantly higher than that of all other groups (P < 0.001). The fracture strengths of groups 2 and 3 were not significantly different (P > 0.05) from each other but were significantly lower (P = 0.002) than those of all composite-restored groups. Group 8 showed a significantly greater fracture strength than group 4 (P < 0.001). Unlike GIC/amalgam, all of the base/composite restoration groups partly restored the strength of pulpotomized premolars. Although their fracture strengths were statistically similar, the fracture modes were more favorable in groups with SAFC or SARC bases than in groups with RMGIC or ZRGIC bases. The SFRC/composite specimens revealed advantages in both fracture strength and fracture mode compared to RMGIC/composite specimens.

Effect of Er:YAG laser etching on topography, microstructure, compressive strength, and bond strength of a universal adhesive to calcium silicate cements.

OBJECTIVE: To evaluate the effect of Er:YAG etching on topography, microstructure, compressive strength, and shear bond strength (SBS) of All-Bond Universal adhesive to mineral trioxide aggregate-Angelus (AMTA) and Biodentine (BD). METHODS AND MATERIALS: Sixty cylindrical specimens of each cement (AMTA and BD) in five groups were prepared and stored for 72 h. The control groups were non-etched, and four other groups were acid-etched and laser-etched with a pulse energy of 60, 80, or 100 mJ, followed by compressive strength testing. Surface micromorphology and topography were evaluated. Similar groups were bonded using All-Bond Universal with self-etch and etch-and-rinse (acid-etch) approaches, and laser-etch 60, 80, and 100 mJ, and SBS was tested. Data were analyzed using two-way and one-way ANOVA and the Bonferroni post hoc tests (α = 0.05). RESULTS: BD had a significantly higher compressive strength and SBS (except for laser-etch 100) compared to AMTA, regardless of the etching method (p < 0.001). Acid etching and laser etching 100 of both cements and laser etching 80 of BD alone produced a significantly lower compressive strength than that for the other groups. Contrary to BD, for AMTA, all the treatments significantly increased SBS compared to that of the self-etch group. CONCLUSIONS: Etching of AMTA was needed for stronger bonding; laser etching with 60 or 80 mJ without compromising compressive strength was recommended. Etching not only did not improve bonding ability of BD, but it also negatively affected the strength of BD. CLINICAL RELEVANCE: To achieve successful combined calcium silicate cement-resin material restoration, an adequate bond between the materials is mandatory. This might be provided with the ultramild adhesive through laser etching without compromising compressive strength, depending on cement composition and laser energy level used.

Effect of Simulated Pulpal Pressure on Knoop Hardness of Two Self-etch Adhesives with Different Aggressiveness.

AIM: Simulated pulpal pressure (PP) has been shown to affect the bond strength and nanoleakage of different adhesives at dentin interfaces but the effect of simulated PP on polymerization of adhesives has not been studied yet. Furthermore, it has been proposed that strong and mild self-etch adhesives have different polymerization behaviors. This study aimed to evaluate the effect of simulated PP on polymerization of two self-etch adhesives, Adper Prompt L-Pop (APLP) and Adper Easy Bond (AEB), by means of the Knoop hardness test. MATERIALS AND METHODS: Sixty caries-free human molars were used to prepare deep dentin specimens with a mean remaining dentin thickness of 0.9 mm. The specimens were bonded in the absence or presence of PP. The specimens were assigned to four equal groups (n = 15) as follows: AEB/-PP, APLP/-PP, AEB/+PP, and APLP/+PP. Bonding procedures were completed; then the specimens' hardness was measured with the Knoop test. Data were analyzed with two-way ANOVA and the t test. RESULTS: In the absence of PP, the hardness of AEB was significantly higher than that of APLP (p < 0.001). In contrast, when PP was simulated, the hardness of APLP was higher than that of AEB (p = 0.002). The hardness of AEB was not influenced by the presence of PP (p = 0.153). Simulation of PP resulted in a significant improvement in the hardness of APLP (p < 0.001). CONCLUSION: The polymerization degree of strong self-etch adhesive was lower compared to mild self-etch adhesive. In the presence of hydrostatic PP, the polymerization degree of strong self-etch adhesive was higher than mild self-etch adhesive. CLINICAL SIGNIFICANCE: Dentin moisture caused by positive PP might improve polymerization of strong self-etch adhesives.

Correction to: Effect of Er:YAG laser etching on topography, microstructure, compressive strength, and bond strength of a universal adhesive to calcium silicate cements.

Figure 2 was incorrect in the original published version of this article. Correct figure in presented here. The original article has been corrected.

Effect of hydroxyapatite nanoparticles on enamel remineralization and estimation of fissure sealant bond strength to remineralized tooth surfaces: an in vitro study.

BACKGROUND: The management of noncavitated caries lesions before sealant therapy is a clinical challenge when the tooth needs sealant application. Sealing noncavitated carious lesions in pits and fissures may lead to failure of the fissure sealant (FS) due to incomplete sealing. Therefore the use of remineralizing agents such as nanoparticles has been suggested. This study investigated the ability of hydroxyapatite nanoparticles (nano-HA) to remineralize enamel, and their effect on sealant microleakage and shear bond strength (SBS). METHODS: A total of 192 third molars were demineralized and pretreated with two concentrations of nano-HA with and without sodium hexametaphosphate (SHMP), followed by phosphoric acid etching and resin FS application. The study groups were 1) etching + FS, 2) etching + nano-HA 0.15% + FS, 3) etching + nano-HA 0.03% + FS, 4) etching + mixture of nano-HA 0.15% and SHMP 0.05% + FS, 5) etching + mixture of nano-HA 0.03% + SHMP 0.01% + FS. The laboratory tests included microleakage in 50 teeth, scanning electron microscopy (SEM) evaluation in 10 samples, and SBS in 100 samples. Enamel remineralization changes were evaluated in 32 teeth with energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscope (FESEM). RESULTS: Nano-HA enhanced the SBS to remineralized enamel in a large percentage of nanoparticles. Mean SBS in group 2 was significantly greater than in groups 1, 3 and 4 (all P < 0.05). SBS was related to nano-HA concentration: nano-HA 0.15% yielded greater SBS (16.8 ± 2.7) than the 0.03% concentration (14.2 ± 2.1). However, its effect on microleakage was not significant. Nano-HA with or without SHMP led to enhanced enamel remineralization; however, the Calcium (Ca)/Phosphate (P) weight percent values did not differ significantly between the groups (P > 0.05). SEM images showed that SHMP did not affect sealant penetration into the deeper parts of fissures. FESEM images showed that adding SHMP led to increased nanoparticle dispersal on the tooth surface and less cluster formation. CONCLUSIONS: The ultraconservative approach (combining nano-HA 0.15% and SHMP) and FS may be considered a minimal intervention in dentistry to seal demineralized enamel pits and fissures.

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.

Influence of Primers and Additional Resin Layer on Zirconia Repair Bond Strength.

PURPOSE: To evaluate the influence of alloy/zirconia primer and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin layer treatments on the shear bond strength (SBS) of composite resin to zirconia after aging. MATERIALS AND METHODS: Sixty zirconia (Y-TZP) blocks were air-abraded (35-µm Al2 O3 ) and divided into 6 experimental groups (n = 10) in terms of primer/resin layer as follows: (1) control, without any primer or resin; (2) AP, Alloy Primer; (3) ZPP, Z-Prime Plus; (4) PL/ZPP, Z-Prime Plus with light polymerization; (5) AP+SEB, Alloy Primer along with light-cured bonding resin of a self-etch adhesive system (SE Bond); and (6) ZPP+SEB, Z-Prime Plus with SE Bond. After composite resin placement and light polymerization, the specimens were stored in distilled water (37°C for 4 months) and thermal-cycled for 6000 cycles. The SBS was tested with a universal testing machine. Statistical analysis of the SBS data was performed with one-way ANOVA, followed by HSD Tukey test (α = 0.05). RESULTS: There were significant differences between the groups (p < 0.001, F = 116.5). All the groups revealed significantly higher SBS than the control (p < 0.001). ZPP+SEB group exhibited the highest SBS (16.14 ± 2.52 MPa) and AP group the lowest SBS (7.00 ± 1.97 MPa) among experimental groups; both had significant differences with the other groups (p < 0.001). There were no significant differences between ZPP, PL/ZPP, and AP+SEB groups (p > 0.05). CONCLUSIONS: The bond strength between zirconia ceramic and composite resin was affected by different primers/resin layer. Applying an MDP-containing resin layer along with both primers resulted in significant enhancement of SBS. This improvement for Z-Prime Plus was significantly higher than that of Alloy Primer.

The Effect of the Application Sequence of Casein Phosphopeptide-Amorphous Calcium Phosphate Paste on the Shear Bond Strength of Etch-and-Rinse Resin Cements to Dentin.

PURPOSE: To evaluate the effect of the application sequence of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (MI paste) on shear bond strength (SBS) of 2 etch-and-rinse resin cements to dentin. MATERIALS AND METHODS: Sixty extracted human maxillary premolars were cut to expose the mid-coronal dentin surfaces. The teeth were randomly divided into 6 groups (n = 10), based on the resin cement used and CPP-ACP application. In groups 1-3, Excite DSC/Variolink II and in groups 2-4, One-Step Plus/Duolink was bonded to dentin. There were 3 groups for each cement as follows: with no treatment as a control; 3-minute application of CPP-ACP before acid etching (CPP-ACP/Etching); 3-minute application of CPP-ACP after acid etching (Etching/CPP-ACP). After storage in distilled water at 37°C for 24 hours, SBS test was performed. Data were analyzed with 2-way ANOVA and post-hoc Tukey test (α = 0.05). RESULTS: CPP-ACP application on the dentin before and after acid etching significantly decreased the SBS of OS/Duolink (13.60 and 14.71 MPa, respectively vs. control; 21.21 MPa, p < 0.001); however, it did not influence the SBS of Excite DSC/Variolink II (25.14 MPa) before acid etching (27.37 MPa) or after acid etching (26.41 MPa, p > 0.388). The application sequence of CPP-ACP did not influence the SBS of etch-and-rinse resin cements evaluated. CONCLUSION: CPP-ACP applications may lower the SBS in some etch-and-rinse resin cements, and timing of applications makes no difference.

Effect of operator skill on the dentin bonding ability of a self-adhesive resin cement after different adhesive treatments.

This study evaluated the influence of operator skill on the shear bond strength of a self-adhesive resin cement to dentin after different adhesive treatments. Flat dentin surfaces were prepared on 160 extracted molars. The teeth were distributed evenly (n = 80) to 2 groups based on the operator's skill (undergraduate dental student vs operative dentistry specialist). The teeth in each operator group were distributed into 5 groups based on pretreatments used before they were cemented to indirect composite resin cylinders with Panavia SA Luting Plus resin cement. The operators prepared the dentin surfaces for bonding according to the following pretreatment groups: 1, no treatment; 2, phosphoric acid etching; 3, Clearfil Universal Bond in etch-and-rinse mode; 4, Clearfil Universal Bond in self-etching mode; and 5, Clearfil SE Bond 2-step adhesive. After cementation was performed by the 2 operator groups, shear bond strength testing was performed, and data were analyzed with 2-way analysis of variance. The effects of operator skill and surface pretreatment and their cumulative effect were statistically significant (P < 0.05). The shear bond strength of the control group in the student group was significantly greater than that of the specialist group (P = 0.02). In group 5 (2-step adhesive), the shear bond strength of the specialist group was significantly greater than that of the student group (P < 0.001). The use of acid etching and the 3 adhesive treatments improved the bonding ability of resin cement for the expert group. This positive effect was observed only in the etch-and-rinse and self-etching modes for the student group. Extensive clinical experience did not have a positive effect on the bonding effectiveness of resin cement with no pretreatment, while the expert group showed better results in applying this cement with a 2-step adhesive pretreatment.

Influence of Cavity Pretreatments on the Fracture Resistance of Premolars with Self-adhesive Cemented Composite Inlay.

AIM: The aim of this study is to investigate whether different cavity pretreatment approaches affect the strength of premolars restored with self-adhesive (SA) resin cemented-composite resin inlays after mechanical and water aging. MATERIALS AND METHODS: A total of 120 intact maxillary premolars were divided into 10 groups (n = 12). Mesio-occluso-distal (MOD) cavities were prepared in the teeth of nine groups, except group I in which the teeth remained intact. In group II, cavities were unrestored. Following fabrication of composite resin inlays for groups III-X, in group III, the inlays were cemented using the etch-and-rinse (E and R) adhesive/conventional resin cement. In other groups, cementation was performed using a SA cement with or without cavity pretreatments as follows: group IV: SA cement alone, group V: acid etching of enamel and dentin, group VI: acid etching of enamel, group VII: universal adhesive in the selective enamel-etching mode, group VIII: universal adhesive in the E and R mode, group IX: ethylenediaminetetraacetic acid (EDTA) conditioning, and group X: 20% polyacrylic acid conditioning. After aging processes, static fracture resistance was tested. Data were analyzed using one-way ANOVA and Dunn tests (α = 0.05). RESULTS: Fracture resistance of the 10 groups yielded a significant difference (p < 0.001). The median fracture resistances in Newton were the following: Gr I = 1025A, Gr II = 311BC, Gr III = 785A, Gr IV = 500B, Gr V = 435B, Gr VI = 775A, Gr VII = 805A, Gr VIII = 411BC, Gr IX = 397BC, and Gr X = 312C. CONCLUSION: Unlike the conventional method, SA cementation could not restore the strength of inlay-cemented premolars. Selective enamel acid etching with or without universal adhesive significantly increased the fracture resistance. CLINICAL SIGNIFICANCE: Selective enamel acid etching is recommended for increasing the fracture resistance of the SA cemented composite inlay to the level of intact teeth.

Effect of fiber inserts on gingival margin microleakage of Class II bulk-fill composite resin restorations.

This study evaluated the effect of fiber inserts combined with composite resins on enamel and dentin margin microleakage. The fiber inserts were used with high- (x-tra fil) and low-viscosity (x-tra base) bulk-fill composite resins and as well as conventional composite resins (Grandio and Grandio Flow). In 96 sound, recently extracted molars, 2 standardized Class II cavities were prepared. The teeth were randomly divided into 8 groups of 12 teeth each, based on composite resin type and presence or absence of fiber inserts: groups 1 and 2, x-tra fil with and without fiber inserts, respectively; groups 3 and 4, x-tra base with and without fiber inserts; groups 5 and 6, Grandio with and without fiber inserts; and groups 7 and 8, Grandio Flow liner (gingival floor)/Grandio (remainder of cavity) with and without fiber inserts. In all the groups, a 2-step etch-and-rinse adhesive was used. The specimens were processed in a dye penetration technique to determine microleakage percentages. Data were analyzed with analysis of variance, Tukey, and t tests. There was significantly less leakage at the enamel margins than the dentin margins. Fiber reinforcement significantly decreased enamel microleakage in all the groups, with no significant differences among the groups. Concerning dentin microleakage, there were no significant differences among the 4 groups without fiber inserts, while a significant difference was detected in groups 2 (x-tra fil plus fiber) and 8 (Grandio Flow plus fiber/Grandio). Fibers significantly improved dentin sealing in groups 2 and 8. These findings suggest that a fiber insert reinforcing bulk-fill and conventional composite resins might improve enamel sealing in shallow Class II cavi-ties. The effect of fiber reinforcement on the dentin margins of deep cavities depended on the viscosity of the composite resins; fiber reinforcement was effective for flowable bulk-fill and conventional composite resin restorations.

Effect of Silver Nanoparticles, Zinc Oxide Nanoparticles and Titanium Dioxide Nanoparticles on Microshear Bond Strength to Enamel and Dentin.

AIM: This study was aimed to evaluate whether antibacterial pretreatment of enamel and dentin with silver nanoparticles (SNPs), zinc oxide nanoparticles (ZNPs) and titanium dioxide nanoparticles (TNPs) has any effect on the microshear bond strength of an etch-and-rinse adhesive system. MATERIALS AND METHODS: Eighty human third molars were randomly assigned to eight subgroups (n = 10). Enamel groups included no pretreatment (E), pretreatments with SNPs (ESNP), ZNPs (EZNP) and TNPs (ETNP) before acid etching and adhesive application. Dentinal groups included no pretreat-ment (D), pretreatments with SNPs (DSNP), ZNPs (DZNP) and TNPs (DTNP). The specimens were bonded by Adper Single Bond and polyvinyl chloride microtubes and were restored with Z250 composite. The bonded surfaces underwent microshear bond strength (uSBS) test. Data in megapascal (MPa) were analyzed with the Kruskal-Wallis test and the Mann-Whitney test (p = 0.05). RESULTS: There was not a significant difference among the groups in enamel (p > 0.05). There was no significant difference between the application of three nanoparticles and the control group in dentin. However, DSNPs had a higher uSBS (25.60 ± 14.61) than that of the DZNPs and DTNPs groups (p = 0.03 and p = 0.001, respectively). Also, the mean uSBS value was lower in dentin groups compared to the respective enamel groups (p < 0.05) except for groups DSNPs and ESNPs in which no significant difference was found (p > 0.05). CONCLUSION: Pretreatment with SNPs, TNPs, and ZNPs can be suggested to achieve potent antibacterial activities without compromising the bond strength. The best result was obtained for pretreatment with SNPs compared to pretreatment with TNPs or ZNPs in dentin and enamel, albeit the differences were not significant in the enamel groups. CLINICAL SIGNIFICANCE: Effective antibacterial treatment prior to adhesive bonding application is desirable to provide successful restoration if it would not adversely affect the bond strength of the adhesive system. Nanoparticles can be applied to meet this goal.

Effect of timing of repair on repair bond strength of methacrylate- and silorane-based composite resins.

Successful repair of defective composite resin restorations is considered a conservative treatment. The aim of this study was to compare the repair bond strengths of a methacrylate composite (MC) and a silorane composite (SC) repaired after 5 different intervals. Seventy-two test specimens of each material (MC and SC) were prepared. The specimens of each material were divided into 6 groups (n = 12): 1, control (additional composite bonded immediately after polymerization of the substrate composite resin); 2, repaired after 20 minutes; 3, repaired after 24 hours; 4, repaired after 1 week; 5, repaired after 1 month; and 6, repaired after 6 months. Repair consisted of placement of a layer of adhesive bonding agent and then new composite using a plastic mold. Each repair was made with the same material as the original specimen but in a different shade to facilitate fracture assessment. The repaired specimens were stored in distilled water at 37°C for 24 hours before they were submitted to a shear test. There was no statistically significant difference between group MC1 and the other MC groups, except for group MC4, which had lower shear bond strength (SBS) values than groups MC1, MC2, and MC3. Among the SC specimens, all the groups had significantly lower SBS values than group SC1. The mean SBS values of groups SC4, SC5, and SC6 were significantly lower than the SBS of group SC2. All the SC repair time groups presented significantly lower SBS values compared to their corresponding MC groups (P ≤ 0.004). The results showed that the repair bond strength of SC was adversely affected at all time periods, while this effect was not detected for MC groups except for group MC4. The SC material exhibited less repairability than the MC material.

Microleakage of Class II composite resin restorations with self-adhesive composite resin liners.

This study investigated the microleakage of Class II composite restorations with composite resin liners. Standardized box cavities were prepared on the mesial and distal surfaces of 84 extracted intact human molars. Proximal margins were located in enamel (occlusal) and 1.0 mm apical to the cementoenamel junction (gingival). The teeth were randomly divided into 6 groups (n = 28 cavities) and restored with Filtek Z350 nanohybrid composite resin (FZ). The test groups were lined with a conventional flowable composite resin, Premise Flowable (PF), or 1 of 2 self-adhesive composites (SACs): Vertise Flow (VF) or Clearfil SA luting cement (CSA) with or without their respective self-etching adhesives: Optibond All-in-One (OB) or Clearfil SE Bond (CSE). The adhesive/lining procedure was performed as follows: OB/FZ (control), OB/PF/FZ, VF/FZ, OB/VF/FZ, CSA/FZ, or CSE/CSA/FZ. Microleakage was evaluated at the occlusal and gingival margins using a dye penetration technique and quantitative assessment. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data at the significance level of α = 0.05. None of the restorative techniques was capable of preventing microleakage completely. The greatest amount of microleakage was detected in the VF/FZ and CSA/FZ groups at both margins (P < 0.02). Among the groups placed with a bonding agent, OB/VF/FZ showed significantly greater values of microleakage at the occlusal margins than did OB/FZ, OB/PF/FZ, and CSE/CSA/FZ (P < 0.05). At the gingival margins, the OB/PF/FZ group exhibited the least leakage compared with the OB/VF/FZ and CSE/CSA/FZ groups (P < 0.001). The results indicated that the additional application of bonding agents improved the marginal sealing of SACs in Class II composite restorations.

The effect of antibacterial agents on fissure sealant microleakage: a 6-month in vitro study.

PURPOSE: To evaluate microleakage from an antibacterial adhesive and bonding agent added to the ssure sealant on intact enamel. MATERIALS AND METHODS: One hundred twenty sound third mandibular molars were randomly divided into 6 groups of 20 teeth each. Occlusal pits and ssures were sealed with un lled sealant material (Clinpro, 3M) after pretreatment with 1. phosphoric acid etching (control); 2. acid etching + Adper Single Bond 2 (SB, 3M); 3. chlorhexidine digluconate (CHX, Ultradent) + acid etching; 4. CHX + acid etching + SB; 5. acid etching + Clear l Protect Bond (CPB, Kuraray) 6. CPB alone. After 6-month water storage and thermocycling, the specimens were placed in 0.5% fuschin, sectioned and evaluated under a digital microscope. The data were compared between groups with Kruskal-Wallis and Mann-Whitney tests. RESULTS: Differences between groups were statistically signi cant at P < 0.05. Acid etching alone and with SB showed the lowest microleakage, followed by acid etching + CPB. Chlorhexidine with and without bonding agent showed the greatest microleakage. CONCLUSION: Conventional acid etching alone or with a one-bottle adhesive were the two most effective methods of reducing microleakage from ssures. Acid etching together with a self-etching adhesive showed better results than self-etching alone. Appling CHX increased microleakage in sealed teeth.

Cytotoxic effect of silorane and methacrylate based composites on the human dental pulp stem cells and fibroblasts.

OBJECTIVES: The aim of this study was to compare the cytotoxic effect of a methacrylate-based and a silorane-based composite on the human dental pulp stem cells (DPSCs) versus human dental pulp fibroblasts (DPFs). STUDY DESIGN: Samples of the Filtek Z250 and P90 were polymerized and immersed in the culture medium to obtain extracts after incubation for one, seven and 14 days. Magnetic cell sorting based on the CD146 expression was performed to purify DPSCs and DPFs. After incubation of both cells with the extracts, cytotoxicity was determined using the MTT test. RESULTS: For the extracts of first and seventh day, both composites showed significantly lower cytotoxicity on DPSCs than DPFs (p=0.003). In addition, there was a significant difference in the time-group interaction of both materials indicating different cytotoxic behaviours (p=0.014). In contrast to Z250, exposure to the 14th day extract of P90 resulted in higher cell viability compared to that of day seven. CONCLUSIONS: DPSCs are less susceptible to the cytotoxic effect of the composites than DPFs. Compared to Z250, the cytotoxic effect of silorane-based composite decreases as the time passes on. This difference should be considered, particularly in deep cavities, in order to preserve the regenerative capacity of the pulp.

Pre-Sealing of Endodontic Access Cavities for the Preservation of Anterior Teeth Fracture Resistance.

OBJECTIVE: Sodium hypochlorite solution (NaOCl) is an effective canal irrigant but interferes with the mechanical features of dentin and the bonding capability of adhesives when restoring endodontically treated teeth. This study evaluated whether access cavity resin sealing before using canal irrigant would augment the resistance of endodontically treated anterior teeth against fracture. METHODS: Sixty maxillary incisors underwent endodontic treatment in five groups (n = 12). Irrigation with 5.25% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA) was performed in all groups except for Group 5. After root canal obturation, in Group 1, the access cavity was kept unrestored. In Group 2, immediate restoration after obturation was achieved. For Group 3, delayed restoration after 1 week was provided. In Group 4 (pre-sealed), before canal irrigation, the dentin surface of access cavities was sealed using self-adhesive composite resin (Vertise Flow) and then restored after obturation. In Group 5, which was saline irrigated, immediate restoration was performed. After storage and thermal cycling for 5000 cycles at 5°C-55°C with a dwell time of 15 s and a transfer time of 5 s, teeth were statically loaded by a universal testing machine until a fracture occurred. Data were collected as the fracture resistance (FR) and analyzed using the one-way analysis of variance and Tukey's tests. RESULTS: FR significantly differed between all groups (p < 0.001). The lowest FR was recorded in the unrestored group (284 ± 86 N), which was not statistically different from the immediately restored group (p = 0.065). The pre-sealed group exhibited the highest FR value (810 ± 127 N, p ≤ 0.02 vs. other groups). The FR of the saline-irrigated and delayed restored groups was almost similar (p = 0.13). CONCLUSIONS: NaOCl/EDTA irrigation resulted in an adverse effect on FR. Delayed restoration could reduce this adverse effect. Access cavity pre-sealing with flowable composites led to a higher FR than conventional methods and may be considered an effective step during treatment procedures.