Spot-etch technique and other adhesive strategies for provisional veneers.

AIM: The objective of the present study was to evaluate the influence of different adhesive strategies regarding shear bond strength (SBS) of provisional resin--based materials bonded to the enamel surface as well as on the enamel surface roughness. MATERIALS AND METHODS: Bovine incisors were randomly divided into six groups (n = 10) according to the adhesive strategy used: BRControl (bis-acrylic resin); Spot-etch+BR (spot-etch + bis-acrylic resin); Spot--etchSB2+BR (spot-etch + adhesive + bis-acrylic resin); Spot-etchZ350Flow+BR (spot-etch + flowable composite resin + bis-acrylic resin); SBU+BR (universal adhesive + bis-acrylic resin); Spot-etchSBMP+Z350 (spot-etch + adhesive + composite resin). The enamel surface roughness was determined by a surface profil-ometer. An SBS test was performed in a universal testing machine, and failure modes were classified under magnification. The SBS data were analyzed by one-way analysis of variance (ANOVA). A paired t test was used for enamel surface roughness intragroup comparisons, and the Friedman one-way repeated meas-ures analysis of variance by ranks was used for differences in enamel surface roughness between groups, with the Tukey post hoc test (a = 0.05). RESULTS: BRControl had the lowest SBS values (MPa), with a significant difference (P ≤ 0.001) from the other groups. Spot-etch+BR had the highest SBS values but with no significant differences from the other groups in which the spot-etch technique was also used. Adhesive failure mode was predominant for all groups. BRControl had the lowest surface roughness difference, significantly different (P = 0.001) from all the other groups. CONCLUSIONS: Spot-etch and other adhesive strategies could be applied to increase the SBS values of provisional restorations to enamel compared with no surface pretreatment. However, the adhesive strategy may change the enamel surface roughness, revealing the importance of cleaning the tooth surface.

Effect of laser and coating surface treatment on the bond strength of zirconia ceramics.

OBJECTIVES: This study aims to investigate bond strength between zirconia and resin cement through surface treatments with Er: YAG laser, Nd: YAG laser, and Si-Zr coating. METHODS: Seventy-five round pre-sintered zirconia discs with a diameter of 18 mm and a thickness of 1.5 mm were prepared by a powder compactor. Fifty discs were randomly divided into five groups of 10 discs each and were subjected to five surface treatments: no treatment (control group), sandblasting with alumina particles (sandblasting group), Er: YAG laser treatment (Er: YAG laser group), Nd:YAG laser treatment (Nd: YAG laser group), and Si-Zr coating treatment (Si-Zr coating group). The discs were then bonded to composite resin columns with resin cement. The shear bond strength of each group was tested with a universal tester. Roughness tester, scanning electron microscope (SEM), and energy dispersive spectroscopy were used to analyze surface performance. RESULTS: The bond strength of the Si-Zr coating group was higher than that of the remaining groups (P<0.05). The difference in bond strength between the sandblasting group and the Er: YAG laser group was not statistically significant (P>0.05), but both of them had higher bond strength than the Nd: YAG laser group (P<0.05). The Si-Zr coating group had the highest surface roughness (P<0.05). The surface roughness of the sandblasting, Er: YAG laser, and Nd: YAG laser groups was higher than that of the control group (P<0.05), but the difference among the three groups was not statistically significant (P>0.05). SEM observations showed irregular scratches on the surface of the sandblasting group and large pits with holes on the surface of the Er: YAG and Nd: YAG laser groups. In the Er: YAG laser group, the crystal structure was replaced by a smooth surface with a large amount of microcracks due to partial melting. Complex porous structures that comprised "island-like" structures and mass pores among the grains were observed on the surface of the Si-Zr coating. Only Zr, O, and Y were detected on the surfaces of the control, Er: YAG laser, and Nd: YAG laser groups. Al was found on the surface of the sandblasted group, and a higher proportion of Si was detected on the surface of the Si-Zr coating group. CONCLUSIONS: Er: YAG laser and Nd: YAG laser treatment on the zirconia ceramic surface could increase roughness and improve the bond strength to resin cement. Si-Zr coating treatment is an effective alternative for increasing the roughness and bond strength of zirconia surface and is superior to sandblasting and laser treatments.

Virtual bracket removal: a comparative assessment of different software packages.

BACKGROUND: High precision intra-oral scans, coupled with advanced software, enable virtual bracket removal (VBR) from digital models. VBR allows the delivery of retainers and clear aligners promptly following debonding, thus reducing the patients' appointments and minimizing the likelihood of tooth movement. The objective of this study was to compare the enamel surface before bonding and after VBR using three different Computer-aided design (CAD) software and to compare their accuracy. METHODS: Maxillary scans of 20 participants starting orthodontic treatment were selected for inclusion in the study, who exhibited mild to moderate crowding and required bonding of brackets on the labial surface of permanent maxillary teeth (from the maxillary left first molar to the maxillary right first molar). Two intra-oral scans were conducted on the same day, before bonding and immediately after bonding using CEREC Omnicam (Sirona Dental Systems, Bensheim, Germany). The virtual removal of the brackets from the post-bonding models was performed using OrthoAnalyzer (3Shape, Copenhagen, Denmark), Meshmixer (Autodesk, San Rafael, Calif, USA), and EasyRx (LLC, Atlanta, GA, USA) software. The models that underwent VBR were superimposed on the pre-bonding models by Medit Link App (Medit, Seoul, South Korea) using surface-based registration. The changes in the enamel surface following VBR using the three software packages were quantified using the Medit Link App. RESULTS: There was a significant difference among the 3Shape, Meshmixer, and EasyRx software in tooth surface change following VBR. Specifically, EasyRx exhibited lower levels of accuracy compared to the other two VBR software programs (p<.001, p<.001). A significant difference in enamel surface change was observed between tooth segments across all software groups, in both incisors and molars, with VBR of the molars exhibiting the lowest level of accuracy (3Shape p=.002, Meshmixer p<.001, EasyRx p<.001). Regarding the direction of tooth surface changes following VBR, it was observed that all three groups exhibited a significant increase in the percentage of inadequate bracket removal across all teeth segments. CONCLUSIONS: 3Shape and Meshmixer manual VBR software were found to be more accurate than EasyRx automated software, however, the differences were minimal and clinically insignificant.

Comparison of the accuracy of two techniques for three-dimensional digital indirect bonding of orthodontic brackets: A randomized controlled trial.

OBJECTIVE: This study aimed to clinically compare the accuracy of bracket positioning between three-dimensionally (3D) printed indirect bonding trays and vacuum-formed trays made over 3D-printed models. MATERIAL AND METHODS: Fourteen patients, planned for fixed orthodontic therapy, were randomly divided into two equal groups. For both groups, both dental arches were scanned, to acquire virtual models, brackets were virtually positioned from central incisors to second premolars, and scans for the final bracket positions were performed. In the first group, transfer trays were 3D-printed. In the second group, virtual models were 3D-printed, and vacuum-formed soft sheets were thermoformed on the printed model. Teeth were indirectly bonded and then scanned. Superimposition of the virtual and the final bracket positioning scans was performed to measure linear and angular deviations in brackets positions. RESULTS: The first group showed significantly less occlusogingival and buccolingual linear errors than the second group. No significant differences in angular deviations were found between both groups. The frequencies of clinically acceptable linear errors within 0.5 mm and angular errors within 2° showed no statistically significant difference between both groups (p> 0.05 for all measurements). The transfer errors in both groups showed linear directional biases toward the mesial, gingival and labial directions. There was no statistically significant difference in the rate of immediate debonding between both groups (10.7% and 7.1% for the first and the second groups, respectively, p=0.295). CONCLUSIONS: 3D-printed indirect bonding trays were more accurate than vacuum-formed trays, in terms of linear deviations. Both types of trays showed similar angular control.

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.

Nanostructured ZnO thin film to enhance gutta-percha's adhesion to endodontic sealers.

BACKGROUND: Gutta-percha (GP) combined with an endodontic sealer is still the core material most widely used for tridimensional obturation. The sealer acts as a bonding agent between the GP and the root dentinal walls. However, one of the main drawbacks of GP core material is the lack of adhesiveness to the sealer. ZnO thin films have many remarkable features due to their considerable bond strength, good optical quality, and excellent piezoelectric, antibacterial, and antifungal properties, offering many potential applications in various fields. This study aimed to explore the influence of GP surface's functionalization with a nanostructured ZnO thin film on its adhesiveness to endodontic sealers. METHODS: Conventional GP samples were divided randomly into three groups: (a) Untreated GP (control); (b) GP treated with argon plasma (PT); (c) Functionalized GP (PT followed by ZnO thin film deposition). GP's surface functionalization encompassed a multi-step process. First, a low-pressure argon PT was applied to modify the GP surface, followed by a ZnO thin film deposition via magnetron sputtering. The surface morphology was assessed using SEM and water contact angle analysis. Further comprehensive testing included tensile bond strength assessment evaluating Endoresin and AH Plus Bioceramic sealers' adhesion to GP. ANOVA procedures were used for data statistical analysis. RESULTS: The ZnO thin film reproduced the underlying surface topography produced by PT. ZnO thin film deposition decreased the water contact angle compared to the control (p < 0.001). Endoresin showed a statistically higher mean bond strength value than AH Plus Bioceramic (p < 0.001). There was a statistically significant difference between the control and the ZnO-functionalized GP (p = 0.006), with the latter presenting the highest mean bond strength value. CONCLUSIONS: The deposition of a nanostructured ZnO thin film on GP surface induced a shift towards hydrophilicity and an increased GP's adhesion to Endoresin and AH Bioceramic sealers.

The effect of antimicrobial peptide-added adhesive resins on shear bond strength and the adhesive remnant index of orthodontic brackets.

OBJECTIVES: The aim of this study was to evaluate the effect of in-vivo produced Nisin which is an antimicrobial peptide (AMP) added to adhesive resin on shear bond strength (SBS) and the adhesive remnant index (ARI) of orthodontic brackets. METHODS: Bacterial AMP was produced by fermentation and the ideal AMP/Bond concentration and antimicrobial efficacy of the mixture were tested. To evaluate the SBS and ARI scores of AMP-added adhesive resins, 80 maxillary premolar teeth extracted for orthodontic purposes were used and randomly assigned into 2 groups (n = 40). Group 1: Control Group (teeth bonded with standard adhesive resin); Group 2: Experimental Group (teeth bonded with AMP-added adhesive resin). Statistical analysis was performed using the SPSS package program and applying the Mann-Whitney U and Fisher's exact tests. P < 0.05 was considered as statistically significant. RESULTS: Nisin synthesized in-vivo from Lactococcus lactis (L. lactis) (ATCC 7962) bacteria was provided to form a homogenous solution at an ideal concentration To find the minimum AMP/Bond mixture ratio that showed maximum antimicrobial activity, AMP and Bond mixtures were tested at various concentration levels between 1/160 and 1/2 (AMP/Bond). As a result, the optimum ratio was determined as 1/40. The antimicrobial efficacy of Nisin-added adhesive resin was tested against Streptococcus mutans (S. mutans) (ATCC 35,688) and Lactobacillus strains (cariogenic microorganisms). AMP formed a 2.7 cm diameter zone alone, while 1/40 AMP-bond mixture formed a 1.2 cm diameter zone. SBS values of the teeth bonded with Nisin added adhesive (17.49 ± 5.31) were significantly higher than the control group (14.54 ± 4.96) (P = 0.004). According to the four point scale, Nisin added adhesive provided a higher ARI score in favour of the adhesive and tooth compared to the control group (ARI = 3, n = 20). CONCLUSIONS: Nisin produced from L. lactis (ATCC 7962) had greater antimicrobial effects after mixing with adhesive bond against cariogenic microorganisms S. mutans (ATCC 35,688) and Lactobacillus strains. Nisin added adhesive increased shear bond strength (SBS) of orthodontic brackets and ARI scores in favor of adhesive & teeth. CLINICAL RELEVANCE: Clinicians should take into account that using Nisin-added adhesive resin in orthodontic treatments can provide prophylaxis against tooth decay, especially in patients with poor oral hygiene.

Comparative in-vivo bond failure rate of orthodontic brackets when bracket base is treated with micro-abrasive blasting vs. acid etching: eighteen month randomized control trial and scanning electron microscope study.

Background: The aim of this study was threefold. Firstly, it aimed to introduce and detail a novel method for chemically etching the bases of stainless-steel orthodontic brackets. Secondly, the study sought to investigate the structural alterations within the brackets' microstructure following chemical etching compared to those with sandblasted bases, using electron microscopy analysis. Lastly, the study aimed to evaluate and compare the long-term durability and survivability of orthodontic brackets with chemically etched bases versus those with sandblasted bases, both bonded using the conventional acid etch technique with Transbond XT adhesive, over an 18-month follow-up period. Methods: The study was a randomized clinical control trial with triple blinding and split-mouth study design and consisted of two groups. The brackets in the sandblasted group were prepared by sandblasting the intaglio surface of the base of the bracket with 50 µm SiO2 particles. Hydrofluoric acid was used to roughen the base in the acid-etched group. The bases of the brackets were viewed under an electron microscope to analyze the topographical changes. Results: A total of 5,803 brackets (3,006 acid-etch, 2,797 sandblasted) in 310 patients were bonded, in a split-mouth design by the same operator. The patients were followed for 18 months. The failure rate of 2.59% and 2.7% was noted in an acid-etched and sandblasted group, respectively. There was a close approximation of curves in the Kaplan-Meier plot, and the survival distribution of the two groups in the log-rank (Mantel-Cox) test was insignificant; x2 = 0.062 (P value = 0.804). Conclusion: Acid etching if the bases of the brackets can be used as an alternative to sandblasting furthermore acid etching can be performed on the chair side.

Evaluation of Monomer-containing Isocyanate Groups on Stabilizing Demineralized Dentin Matrix Against Bond Interface Degradation.

PURPOSE: To evaluate the effect of urethane methacrylate precursor (UMP) on the enzymatic resistance of demineralized dentin (DD) matrices. MATERIALS AND METHODS: Experimental treatments containing 0 (control), 1, and 5 mmol/L UMP dissolved in an acetone (Ace) solution were formulated. Dentin matrix specimens were demineralized in vitro and immersed in the experimental treatments for 1 h. The treated specimens were then stored in 0.1 mg/mL collagenase solution for 24 h, after which their dry mass loss and hydroxyproline (HYP) release were assessed. The swelling ratios of specimens in each group were also evaluated. The interaction between UMP and the dentin matrix was observed using field-emission scanning electron microscopy (FE-SEM). Endogenous enzyme activity in dentin was evaluated using confocal laser scanning microscopy (CLSM). RESULTS: Compared with the other treatment groups, treatment with 1 mM and 5 mM UMP-Ace significantly decreased the dry mass loss, HYP release and swelling ratio of the DD matrix (p < 0.05). FE-SEM and CLSM observations showed that treatment with UMP-Ace protected the structure of the dentin matrix and decreased porosity within the dentin-collagen network. CONCLUSION: Treatment with 1 mM and 5 mM UMP-Ace protects DD matrix against collagenase degradation and may be clinically useful for improving the durability of the hybrid layer.

Effect of Different Adhesive Resin and Composite Veneering Materials on Adhesion to Polyetheretherketone.

OBJECTIVE: To evaluate the effect of different adhesives and veneering resins on the shear bond strength (SBS) of polyetheretherketone (PEEK). METHODS: A total of 138 PEEK specimens were randomly divided into 6 groups according to adhesive material application: Control (C, no application), Adhese Universal (A) (Ivoclar Vivadent, Schaan, Liechtenstein), Gluma Bond Universal (G) (Heraeus Kulzer, South Bend, IN, USA), G-PremioBOND (P) (GC Corporation, Tokyo, Japan), Single Bond Universal (S) (3M, Saint Paul, MN, USA) and visio.link (V) (Bredent, Senden, Germany). Each adhesive group was divided into two subgroups according to the type of veneering material: Estenia direct composite (D) and Gradia Plus indirect composite (IN) (both GC Corporation). After the veneering process, the specimens were aged by thermal cycling. Kruskal-Wallis and Mann-Whitney U tests were used for SBS analysis (P < 0.05). RESULTS: The highest SBS results were obtained in the VIN group, followed by the VD, PD, GIN, AIN, AD, SIN, SD, PIN, GD, CIN and CD groups, respectively (P = 0.001). There were no significant differences in terms of the type of veneering composite when the same adhesive was applied (P > 0.05), except for Gluma Bond Universal (P = 0.009). All the adhesives tested showed clinically acceptable SBS results. CONCLUSION: Visio.link offered the highest adhesion to PEEK, whereas the tested universal adhesives may be used as an alternative to visio.link in clinical settings. It was determined that changing the veneer type has no statistical difference when the same adhesive material is used.

Assessment of the Efficacy and Bond Strength of Different Dentin-bonding Agents with Adhesives on Primary Teeth: An In Vitro Study.

AIM: The purpose of this study was to evaluate the effectiveness and strength of three various dentin-bonding agents used with adhesives on primary teeth. MATERIALS AND METHODS: The study used 80 recently extracted, healthy human maxillary anterior primary teeth that had undergone physiologic resorption, or over-retention. Teeth were cut to expose a flat dentin surface at a depth of 1.5 mm. All samples were divided into four groups (20 samples in each group) as follows: Group I-Control group, Group II-Primary teeth bonding with 6th-generation bonding agent, Group III-Primary teeth bonding with 7th-generation bonding agent, Group IV-Primary teeth bonding with 8th-generation bonding agent. All of the samples' dentinal surfaces were covered with composite resin using a Teflon mold after adhesive had been applied. A universal testing machine (INSTRON) was used to assess the shear bond strength. Data were collected and statistically analyzed. RESULTS: The maximum mean shear bond strength was found in 8th-generation bonding agent (30.76 ± 0.16), followed by 7th-generation bonding agent (26.08 ± 0.21), 6th-generation bonding agent (25.32 ± 0.06), and control group (6.18 ± 0.09). Statistically significant difference was found between the three different bonding agents (p < 0.001). CONCLUSION: On conclusion, the 8th-generation bonding agent demonstrated a greater shear bond strength to dentin than the 7th and 6th-generation bonding agent. CLINICAL SIGNIFICANCE: The emergence of different bonding techniques to the market improves the durability and quality of restorations. An effective bonding to the tooth would also reduce bacterial penetration, marginal microleakage, possibility of pulpal inflammation preserve tooth structure, and postoperative sensitivity by allowing less cavity preparation. How to cite this article: Alqarni AS, Al Ghwainem A. Assessment of the Efficacy and Bond Strength of Different Dentin-bonding Agents with Adhesives on Primary Teeth: An In Vitro Study. J Contemp Dent Pract 2024;25(4):342-345.

Comparative evaluation of bond strength and color stability of polyetheretherketone and zirconia layered with indirect composite before and after thermocycling: An in vitro study.

AIM: This study investigates the interaction of zirconia and polyetheretherketone (PEEK) with indirect composite in fixed dental prostheses. This investigation aimed to assess the shear bond strength (SBS) and color stability of zirconia and PEEK before and after aging, addressing critical concerns in dental restorative applications. SETTINGS AND DESIGN: The current in vitro study used 96 samples, 48 of which were divided into two groups, zirconia and PEEK, before and after thermocycling. A dual-axis chewing simulator was used for thermocycling. SBS was measured using a universal testing machine, and color stability was checked using a reflective spectrophotometer. MATERIALS AND METHODS: Ninety-six samples were categorized into zirconia and PEEK groups, each with subgroups undergoing thermocycling. Samples were prepared using computer-aided design/computer-aided manufacturing milling and veneered with composite resin. Thermocycling involved 10,000 cycles, simulating stress levels equivalent to approximately 1 year of clinical use. SBS was assessed using standardized tests. Stereomicroscopic analysis was performed to evaluate the type of failure. Color stability of the core materials with indirect composite was done using a spectrophotometer before and after aging. STATISTICAL ANALYSIS USED: Statistical analysis included paired t-tests and independent t-tests in SPSS software. RESULTS: The results revealed that SBS values for composite on PEEK decreased from 13.86 ± 0.164 MPa before thermocycling to 13.46 ± 0.185 MPa after thermocycling, with a significant difference (P < 0.005). However, both pre- and postthermocycling values for PEEK were higher than zirconia. The t-test confirmed the lower bond strength of composite to zirconia, with a noteworthy improvement after aging. Stereomicroscopic images revealed adhesive failure for the zirconia group and mixed (adhesive and cohesive) failure for the PEEK group. ΔE values were 3.21 ± 0.127 and 2.93 ± 0.142 for zirconia and PEEK groups, respectively (P < 0.005). CONCLUSION: Within the limitations of this study, it can be deduced that PEEK is a feasible substitute for zirconia when used in conjunction with indirect composite for the fabrication of dental prostheses.

Comparison of microtensile bond strength of prepared teeth treated with proanthocyanidin, Camellia sinensis - Polyphenols, and metal crowns luted with resin-modified glass ionomer cement: An in vitro study.

AIM: The aim of this study was to evaluate the effect of proanthocyanidin and C. sinensis-polyphenols on microtensile bonding properties of prepared teeth with resin-modified glass ionomer cement (GIC). SETTING AND DESIGN: This was an in vitro study. MATERIALS AND METHODS: Seventy-eight maxillary premolars were selected and mounted into auto-polymerizing acrylic resin blocks. The samples were prepared and metal crowns were fabricated. The samples were randomly divided into three groups. Samples under Group 1 were not treated with any of the extracts and followed conventional bonding protocol. Samples under Group 2 and Group 3 were treated with proanthocyanidin and C. sinensis-polyphenols, respectively. After dentin treatment, these samples were luted to metal crowns using resin-modified GIC. Universal testing machine was used to measure the load at which the crowns were debonded and microtensile bond strength in MPa was calculated. STATISTICAL ANALYSIS: The results were statistically analyzed using one-way ANOVA and post hoc Tukey HSD. RESULTS: Samples treated with C. sinensis polyphenols (Group 3) had maximum bond strength followed by Group 2, where the samples were treated with proanthocyanidin. CONCLUSION: C. sinensis polyphenols due to their anti-proteolytic and antioxidant properties showed improved bond strength compared to proanthocyanidin, a cross-linking agent, followed by conventional bonding protocol.

Antibacterial and preventive effects of newly developed modified nano-chitosan/glass-ionomer restoration on simulated initial enamel caries lesions: An in vitro study.

BACKGROUND: Despite the superiority of glass-ionomer cements (GICs) over composites in treating white spot lesions (WSLs), there is still a concern about their preventive and antibacterial properties. Efforts have been made to improve the strength of their bond to demineralized enamel, fluoride release and antibacterial properties by adding nanoparticles of chitosan, which seems to be a promising method. OBJECTIVES: The aim of the present study was to assess the antibacterial effect, the microshear bond strength (µSBS) to enamel at the WSL area, and the fluoride and nano-chitosan release after modifying the polyacrylic acid liquid phase of a traditional GIC with different nano-chitosan volumes. MATERIAL AND METHODS: A total of 120 samples were prepared, and then divided into 4 groups (n = 30): G1 - non-modified GIC, which served as a control group, while G2, G3 and G4 were modified with different nano-chitosan volumes (50%, 100% and 150%, respectively). Microshear bond strength was assessed using a universal testing machine (UTM) after storage in distilled water for 24 h. Fluoride and nanochitosan release was measured with the use of spectrophotometers at different time points (initially, and at 1 h, 24 h, 48 h, 72 h, 1 week, 2 weeks, 3 weeks, and 6 weeks) after storage in distilled water. The antibacterial effect against the Streptococcus aureus strain was assessed with the agar diffusion test. The data was statistically analyzed. RESULTS: After 24-hour storage, G2 recorded a slight, yet non-significant, increase in the µSBS values (4.1 ±0.94 MPa) as compared to G1 (3.9 ±1.30 MPa). With regard to fluoride release, the amount recorded for G1 was significantly greater at the end of the 24-hour storage period (0.70 ±0.30 µmf/cm2) than modified nano-chitosan GIC groups; G1 was followed by G4 (0.54 ±0.34 µmf/cm2). The highest amount of nano-chitosan release after 24-hour storage was noted for G3 (0.85 ±0.00 µmf/cm2). The highest inhibition zone value was recorded for G2. CONCLUSIONS: Glass-ionomer cement modified with 50% nano-chitosan was shown to positively affect µSBS and the antibacterial effect, while modification with 150% nano-chitosan significantly increased fluoride release.

Effects of plasma surface treatment on the bond strength of zirconia with an adhesive resin luting agent.

The purpose of this study was to evaluate the effect of the atmospheric pressure plasma treatment as a surface treatment method on the contact angle and shear bond strength (SBS) of zirconia ceramics and the failure mode between the self-adhesive resin luting agent and zirconia. The zirconia specimens were divided into eight groups based on the surface treatment method: alumina blasting, air plasma, argon plasma (AP), Katana cleaner, ozonated water, ozonated water+AP, Katana cleaner+AP, and tap water+AP. The contact angles, SBS, and fracture modes were tested. AP treatment significantly reduced the contact angle (p<0.0001). The combination of AP and other cleaning methods showed a higher bond strength and more mixed fractures. Our findings indicate that using atmospheric pressure plasma with argon gas, combined with other cleaning methods, results in a stronger bond than when using alumina blasting alone.

Performance of Bonded Lithium Disilicate Partial-coverage Crowns in the Restoration of Endodontically Treated Posterior Teeth: An Up to Seven-Year Retrospective Study.

OBJECTIVES: To evaluate the clinical performance of adhesively bonded lithium disilicate glass-ceramic (LDG) partial-coverage crowns in restoring posterior endodontically treated teeth (ETT). METHODS AND MATERIALS: A total of 121 morphologically compromised posterior ETT were restored with LDG partial-coverage crowns between October 2015 and January 2018. The restorations were fabricated in the laboratory or at the chairside. Two adhesive systems and resin cements were used to cement the restorations. Tooth and restoration survival rates were calculated. The restorations were evaluated clinically using the modified United States Public Health Service (USPHS) criteria for an observation period of 5-7 years. The Cox proportional hazards model was used to estimate relative failure risks such as tooth type, resin cements, gender, and sleep bruxism. The standard chi-squared test was used to compare the survival of different tooth types for significant differences (α=0.05). In addition, survival probability was calculated using the Kaplan-Meier algorithm. RESULTS: Among seven failed cases, one was a tooth fracture, and six were restoration fractures. According to the Kaplan-Meier analysis, the estimated survival rate of the teeth was 99% for seven years, while the estimated survival rate of the restorations was 94.8% for 5 years and 92.8% for 7 years. Tooth type and resin cements did not influence restoration survival rates (p>0.05), while sleep bruxism and male patients might increase the risk of failure (p<0.05). CONCLUSIONS: The indirect adhesively bonded LDG partial-coverage crowns of posterior ETT exhibited favorable clinical outcomes. Ceramic fracture was the most common failure pattern.

Effect of Blood Decontamination Procedures on the Microshear Bond Strength of Resin-modified Glass Ionomer Cement to Resin Composite.

OBJECTIVE: To investigate the effect of decontamination procedures on the microshear bond strength (µSBS) of blood-contaminated resin-modified glass ionomer cement (RMGIC) bonded to resin composite (RC). METHODS: Eighty RMGIC disc specimens were allocated into 5 groups (n=16). All groups except Group 2 were contaminated with blood. Group 1 had no decontamination procedure, Group 3 was decontaminated by rinsing, Group 4 was decontaminated by 34% phosphoric acid etching, and Group 5 was decontaminated by 5% sodium hypochlorite application. RMGIC specimens were subsequently bonded with RC using a universal adhesive in self-etch mode. µSBS tests were conducted using a universal testing machine at a crosshead speed of 1 mm/min. Failure mode analysis was conducted on RMGIC fracture surfaces under a scanning electron microscope. RESULTS: µSBS results indicated that Group 4 had the highest mean µSBS value of 6.22 ± 2.14 MPa, while Group 1 had the lowest mean µSBS value of 3.53 ±1.67 MPa. Significant differences were observed in the µSBS of Group 2 with no contamination (p=0.023) and Group 4 with decontamination by phosphoric acid-etching (p=0.003) when compared to Group 1 with blood contamination. No statistically significant differences (p>0.05) were observed between all other groups' µSBS. For all groups, the predominant mode of failure was adhesive failure between the RMGIC-RC interface, with a few mixed failures in RMGIC for Groups 2-5. CONCLUSIONS: Blood contamination before adhesive application significantly reduced the µSBS between RMGIC and RC. Phosphoric acid etching was the most effective blood decontamination procedure to improve the µSBS.

Effect of hydrofluoric acid concentration and aging on the bond strength ceramics to a resin cement.

This study evaluated the influence of hydrofluoric acid (HF) concentration and thermal cycling on the microshear bond strength (µSBS) of a resin luting agent to IPS e.max® CAD and Rosetta® SM. Ceramic specimens (12.0 x 14.0 x 1.5mm) were randomized into 8 groups (n=10) according to HF concentration, commercial brand, and aging. Immediately after polishing, and etching, all specimens were silanized and a layer of adhesive was applied. A PVS mold of 3 mm thickness and 10mm diameter with (four) 1.0mm holes was fabricated, placed on each specimen, and then filled with a resin luting agent. Half of the specimens were subjected to the µSBS test using an Instron at a speed of 1.0 mm/min, following a 24-hour storage in deionized water at 37ºC. The remaining specimens were subjected to thermal cycling (5ºC-55ºC, 30 seconds per bath) and µSBS. The data were evaluated utilizing a three-way ANOVA and Tukey's post-hoc test (α=0.05). Significant differences were found for HF concentration and aging (p<0.0001). No significant difference in µSBS was found for commercial brands (p=0.085). The interaction between brand and HF concentration (p=0.358), brand and aging (p=0.135), and HF concentration and aging (p=0.138) were not statistically significant. The triple interaction among these factors was not statistically significant (p=0.610). In conclusion, the bond strength is affected by the HF concentration. No statistical difference was observed between the two ceramics. Thermal cycling significantly reduced µSBS.

Relined fiberglass posts: influence of resin opacity on the bond strength to intraradicular dentin.

This study aimed to evaluate the bond strength between relined fiberglass posts with different composite resin opacities in different thirds of the intraradicular dentin. Thirty single-rooted premolars were endodontically treated and divided into three groups (n=10): fiberglass posts relined with translucent composite resin, fiberglass posts relined with opaque composite resin, and fiberglass posts without relining. After cementation of the posts, the specimens were cut perpendicular to the long axis of the tooth in slices of approximately 1.3 mm of each third to be analyzed (cervical, middle, and apical) and then subjected to the push-out test. The bond strength (MPa) data were subjected to Shapiro-Wilk normality tests and two-way repeated measures analysis of variance, considering the experimental groups and different regions as study factors. Tukey's post-hoc test (p<.05) was applied for comparisons between the groups. In the cervical third, higher values of bond strength were found for the group relined with translucent resin, with a statistically significant difference for the other groups. In the other regions, both opaque and translucent resins showed similar results, but both showed higher values of bond strength compared to fiberglass posts without relining. The bond strength of fiberglass posts to different thirds of intraradicular dentin is influenced by composite resin relining as well as the opacity of the resin. The use of translucent composite resin is a more effective alternative for fiberglass posts relining.

Effects of blood and root-dentin cleaning on the porosity and bond strength of a collagen bioceramic material.

To assess the effect of cleaning protocols on dentin contaminated with blood in reparative endodontic materials, bovine root samples were divided: no contamination (N); contamination (P); contamination and cleaning with saline (S), 2.5% NaOCl+saline (Na) or 2.5% NaOCl+17% EDTA+saline (NaE) and filled with: mineral trioxide aggregate (MTA), calcium-aluminate-cement (C), or C+collagen (Ccol) (n=13). The samples were evaluated for porosity, chemical composition, and bond strength. MTA porosity was lower than C (p=0.02) and higher than Ccol (p<0.001). P and NaE were similar (p=1.00), but higher than the other groups (p<0.001). MTA bond strength was similar to Ccol (p=0.777) and lower than C (p=0.028). P presented lower bond strength than the N (p<0.001); S and Na were similar to each other (p=0.969), but higher than P and lower than N (p<0.001). It was observed a predominance of mixed and cohesive failures. None of the samples showed Ca/P ratio values similar to human hydroxyapatite. This study showed that contamination with blood increased the materials porosity, but dentin cleaning with 2.5% NaOCl reduced this effect, and the collagen additive reduced the material porosity. Furthermore, blood contamination reduced the materials bond strength, and cleaning with saline or 2.5% NaOCl diminished this effect.