Evaluation of Shear Bond Strengths of 3D Printed Materials for Permanent Restorations with Different Surface Treatments

The development of high-filled 3D printing resin necessitates a bonding protocol for dental indirect restorations to achieve optimal bond strength after cementation. This study evaluates shear bond strengths of high-filler 3D printed materials for permanent restorations with various surface treatments. Rodin Sculpture 1.0 (50% lithium disilicate fillers) and 2.0 Ceramic Nanohybrid (>60% zirconia and lithium disilicate fillers) were tested, with Aelite All-Purpose Body composite resin as control. Samples were prepared, post-cured, and sandblasted with alumina (25 µm). Surface roughness was analyzed using an optical profilometer. Two bonding protocols were compared. First, groups were treated with lithium disilicate silane (Porcelain Primer) or zirconia primer (Z-Prime Plus) or left untreated without a bonding agent. Beam-shaped resin cement (DuoLink Universal) specimens were bonded and stored in a 37 °C water bath. Second, additional sets of materials were coated with a bonding agent (All-Bond Universal), either followed by silane application or left untreated. These sets were then similarly stored alongside resin cement specimens. Shear bond tests were performed after 24 h. SEM images were taken after debonding. One-Way ANOVA and post hoc Duncan were performed for the statistical analysis. Rodin 1.0 exhibited increased adhesive failure with silane or zirconia primer coating, but significantly improved bond strengths with bonding agent application. Rodin 2.0 showed consistent bond strengths regardless of bonding agent application, but cohesive failure rates increased with bonding agent and filler coating. In all groups, except for Rodin 1.0 without bonding agent, silane coating increased cohesive failure rate. In conclusion, optimal shear bond strength for high-filler 3D printing materials can be achieved with silane coating and bonding agent application.

Effects of dentin bonding agents and silanization on bond strength between 3D printed resin and composite resin

This study aimed to evaluate the effects of dentin bonding agents and silanization on the bond strength between 3D printed resin and composite resin and compare it with a conventional composite resin. 3D printed resin cylinders (PCB) and composite resin substrates (Z250) were prepared and divided into eight subgroups based on the bonding agents used (n=12). The shear bond strength was measured using a universal testing machine, and the failure modes were evaluated. The bond strength was found to vary significantly among the bonding agents and substrate types. Silane application did not significantly improve the bond strength. Among the bonding agents, the universal adhesives exhibited the highest bond strengths for both substrates. Compared to PCB, Z250 demonstrated stronger bonds and exhibited more cohesive failures. Further research is needed to optimize the surface treatments and resin formulations for enhanced bond strength and durability between 3D printed and composite resins.

Repairability of aged dimethacrylate-free ORMOCER-based dental composite resins with different surface roughening methods and intermediate materials

STATEMENT OF PROBLEM

The repair of damaged composite resin restorations has been recommended as a conservative treatment option. However, a reliable protocol for repairing ORMOCER-based restorations is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the effect of different surface roughening methods, repair composite resins, and intermediate materials on the repair bond strength of a dimethacrylate-free ORMOCER-based composite resin.

MATERIAL AND METHODS

Cylindrical composite resin specimens (Admira Fusion) were roughened by using hydrofluoric acid (HF) or a diamond rotary instrument. In both groups, 4 types of intermediate materials were used (Monobond-S, Clearfil SE bond [second bottle], Clearfil Universal bond, GC Composite Primer), and then half of the specimens were repaired with a similar composite resin, and the other half with dimethacrylate composite resin (Clearfil-APX). The specimens (n=20) were then subjected to repair bond strength and failure mode evaluation. The data were analyzed by using the Weibull test, 3-way and 1-way ANOVA, and the Tukey honestly significant difference (HSD) test (α=.05).

RESULTS

All variables, including the surface roughening method, intermediate material, and repair composite resin, had a significant effect on repair bond strength (P<.001). The lowest repair bond strength values were obtained in the group roughened with HF, prepared with Monobond-S, and repaired with Admira Fusion, and the highest values were obtained in the group roughened with a rotary instrument, prepared with GC Composite Primer, and repaired with Clearfil APX (P<.05). All experimental groups had a lower bond strength than the cohesive and control groups (P<.05). In all experimental groups, the predominant failure modes were adhesive and mixed.

CONCLUSIONS

The use of a diamond rotary instrument was a more reliable method of creating roughness, and different intermediate materials based on the clinical situation can be used to repair dimethacrylate-free ORMOCER-based composite resin with similar or different composite resins. However, in general, the highest repair bond strengths were achieved with Clearfil APX-repaired specimens.

Scoping review: Effect of surface treatments on bond strength of resin composite repair

OBJECTIVE

to evaluate the existing evidence on surface treatment techniques employed in resin composite repair and their effect on the repair short- and long-term bond strength.

DATA AND SOURCE

This scoping review was performed under the PRISMA-ScR guidelines for scoping reviews and registered on the Open Science Framework platform.

STUDY SELECTION

A systematic search was conducted in PubMed, Embase, and Scopus and grey literature up to September 2022 without language or date restriction. In vitro studies comparing mechanical surface and/or chemical treatments on repair bond strength of resin composite were included. Studies evaluating experimental adhesive systems or resin composites were excluded. Selection of studies and data extraction were performed. Data from selected studies was qualitatively analyzed.

RESULTS

A total of 76 studies were included in the qualitative analysis. Among the mechanical treatments, alumina blasting was the most frequently used, followed by silica coating and diamond bur. As for chemical treatments, dentin bonding systems were the most frequently evaluated, followed by universal adhesive systems and silane/ceramic primer. The combination of mechanical and chemical pre-treatments increased the repair bond strength of resin composite in both short- and long-term simulated aging scenarios. The evidence obtained from the included studies was classified as moderate quality, mainly due to the medium risk of bias observed across most of the studies.

CONCLUSION

The techniques used to treat the surface of resin composites for repair are diverse. Incorporating a combination of mechanical and chemical pre-treatments resulted in superior repair bond strength of resin composite materials under both short- and long-term simulated aging conditions.

CLINICAL SIGNIFICANCE

The analysis of evidence revealed significant variability among protocols for repairing resin composites. Utilizing both mechanical and chemical pre-treatment methods is important for enhancing the bond strength of resin composites during both short- and long-term simulated aging situations.

Influence of surface treatments and adhesive protocols on repair bond strength of glass-matrix and resin-matrix CAD/CAM ceramics

OBJECTIVE

To specify the effects of self-etching ceramic primer, Monobond Etch and Prime (MEP), and universal adhesive (UA) on repair bond strength between CAD/CAM blocks and resin composite.

MATERIALS AND METHODS

Vita Mark II (VM), IPS e.max CAD (EMAX), Shofu Block HC (SHC), and Tetric CAD (TET) blocks were sliced and thermocycled. They were divided into four groups according to surface treatments (n = 24): control, sandblasting (AL), hydrofluoric acid etching (HF), and MEP application. SEM analysis assessed surface topography. Subdivided, specimens followed distinct adhesive protocols (n = 12): control (silane + adhesive [SA] or adhesive [A] only for MEP group) and UA. Microshear bond strength (μSBS) was measured following resin composite repair. Data were analyzed using two-way ANOVA and Tukey tests (p < 0.05).

RESULTS

The μSBS of CAD/CAM blocks was significantly influenced by surface treatment type and adhesive protocol. The highest μSBS values for each block, considering surface treatment + adhesive protocol, were VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA.

CONCLUSIONS

Except for EMAX, it was not the adhesive protocol that made the significant difference in bond strength for each CAD/CAM block, but the surface treatment. MEP + UA application on glass ceramics lowered μSBS values significantly, so it is not recommended in clinical conditions.

CLINICAL SIGNIFICANCE

Repair is an essential therapeutic option, particularly in esthetic restorations, to swiftly repair the impaired esthetics caused by fracture. Repair protocol is dependent on the restorative material, and to have a reliable repair bond strength, the following surface treatment and adhesive protocol combinations are recommended for each CAD/CAM block: VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA.

Flexural Strength of Conventional or Bulk-fill Resin Composite Repaired with High- or Low-viscosity Restorative Materials

OBJECTIVE

To evaluate the flexural strength of two types of high-viscosity resin composites (conventional or bulk-fill) that were repaired with either high-viscosity composites (conventional or bulk-fill) or low-viscosity composites (conventional or bulk-fill) of the same manufacturer (3M Oral Care, St Paul, MN, USA).

METHODS AND MATERIALS

Specimens (25 mm × 2 mm × 2 mm) of both conventional nanofilled resin (Filtek Z350XT), and bulk-fill nanofilled resin (Filtek One Bulk Fill) were prepared. After fracture of the specimens in the 3-point bending test (initial), half of the specimens were repaired immediately afterwards (24 hours), and the other half were repaired after 6 months of storage in distilled water. Repairs were performed with (n=15) high-viscosity resin composites (Filtek Z350XT, Filtek One Bulk Fill), or their low-viscosity versions (Filtek Supreme XT Flow, Filtek Bulk Fill Flowable Restorative). The repair was performed by roughening the surface and applying phosphoric acid, silane, and adhesive. The bending test (results reported in MPa) was performed in a universal testing machine, and the fracture pattern was determined. Data were evaluated by generalized linear models, chi-square test and the Fisher exact test (α=0.05).

RESULTS

There was no significant difference between the former pair of high-viscosity resins in terms of initial flexural strength (p=0.42). The repairs performed with low-viscosity resin composites after 24 hours or 6 months obtained higher MPa values compared with those using high-viscosity composites (p=0.0006). There was a significant decrease in MPa values when the repair was performed after 24 hours and an increase after 6 months, regardless of the material (p<0.0001). After 6 months, fractures involving the old (conventional) resin were more frequent in the repair performed with bulk-fill resin composites compared with the conventional composites (p=0.02).

CONCLUSIONS

Considering the tested products, the material to be repaired did not influence the flexural strength of the repair composite; however, the use of the low-viscosity resin composites resulted in greater flexural strength of the repaired material. The repair of the aged composite resulted in an increase in its flexural strength, regardless of the material repaired or used to perform the repair.

Comparative analysis of bonding strength between enamel and overlay of varying thicknesses following an aging test

Abstract

Background/purpose: Overlay restorations can be used clinically as a treatment option to preserve natural dentine. However, whether the residual enamel thickness and overlay thickness affect the adhesion between the restoration and tooth is still unknown. This study was to investigate effects of the overlay thickness and residual enamel thickness on bonding strength.

Materials and methods

Overlays of different thicknesses were prepared with natural teeth which had 2, 4, and 6 mm of occlusal reduction (n = 10). Specimens were subjected to 10,000 cycles in water at 5-55 °C, and finally compressive strength tests were used to evaluate the bonding strength.

Results

All groups showed good bond strength (P > 0.05). The overlay restorations of different thicknesses reduced the preparation amount by 30.3%-7.2% and significantly preserved more of the tooth structure (P < 0.005). Compared to the control group, the overlay restoration increased the marginal fitness by about 0.67-0.88 times. The thermal cycling indicated that the decrease in the maximum bearing stress was due to the aging of the ceramic itself. Therefore, the thickness of the overlay had a greater influence on the compressive strength than the bond strength.

Conclusion

Based on the above this study recommends an overlay thickness of at least 2 mm in clinical practice. The aging test confirmed that adhesion between the overlay and teeth was quite firm and stable. This shows that a stable adhesive effect of the overlay can be used as a treatment option for preserving a greater amount of a tooth's structure.

Effects of Different Primers on the Bond Strength to Properly and Excessively Etched Ceramic-coated Zirconia

PURPOSE

To determine the effects of various primers on the immediate and long-term bond strength of ceramic-coated ultratranslucent zirconia that is properly or excessively etched.

METHODS AND MATERIALS

Ceramic-coated zirconia plates were etched with 9.5% hydrofluoric acid (HF) for 2 or 5 minutes, after which the surface morphology and elemental composition were examined. The etched specimens were treated with different primers including methacryloyloxydecyl dihydrogen phosphate (MDP)-only containing primer, silane-only containing primer, MDP and silane-containing ceramic primer as well as MDP and silane-containing adhesive system. For surface contact angle and shear bond strength (SBS) data, the difference between groups was evaluated by one-way analysis of variance (ANOVA) and three-way ANOVA factorial analysis, respectively. The statistical significance level of 0.05 was set and the Tukey test and the Dunnett-T3 test were used for post-hoc multiple comparisons.

RESULTS

Excessive etching (9.5% HF for 5 minutes) led to overconsumption of the glass layer and exposure of zirconia substrate compared to proper etching (9.5% HF for 2 minutes). Among different primers, the surface contact angle of the silane-only containing primer group was the lowest. The silane-only containing primer and MDP and silane-containing ceramic primer produced higher shear bond strength of properly and excessively etched ceramic-coated zirconia, respectively, both before and after thermal aging.

CONCLUSIONS

The silane-only containing primer and MDP and silane-containing primer can obtain better immediate and long-term shear bond strength for properly and excessively etched ceramic-coated zirconia, respectively.

Chemical Surface Modification Methods of Resin Composite Repaired with Resin-Modified Glass-Ionomer Cement

OBJECTIVE

 This study examined the chemical surface modification methods of resin composite repaired with resin-modified glass-ionomer cement (RMGIC).

MATERIALS AND METHODS

 Ninety aged resin composite rods were produced and sorted into 9 groups of 10 specimens and surface modified with silane agent and/or bonding agent as follows: group 1, no surface modified; group 2, etch + single bond 2 (SB2); group 3, SB2; group 4, etch + RelyX ceramic primer (RXP) + SB2; group 5, RXP + SB2; group 6, etch + single bond universal (SU); group 7, SU; group 8, etch + RXP + SU; and group 9, RXP + SU. A clear silicone mold was placed on the top of specimen center, and then filled with RMGIC. The specimens' shear bond strengths (SBSs) were examined in mechanical testing equipment. To determine failure types, the fractured specimen surfaces were inspected using a stereomicroscope.

STATISTICAL ANALYSIS

 The data collected were analyzed using one-way analysis of variance, and significance level was operated using Tukey's test (p < 0.05).

RESULTS

 Group 8 had the greatest SBS, but it was statistically indistinguishable from groups 4, 5, and 9. The most frequent fracture mode was adhesive failure. High SBS was commonly associated with mixed failure.

CONCLUSION

 The use of bonding agents enhances the resin composite's wettability and allows it to bond to RMGIC. Moreover, the use of the silane coupling agent before applying bonding agent showed significantly higher bonding ability of resin composite and RMGIC interface.

Surface characterization of alkane viral anchoring films prepared by titanate-assisted organosilanization

Studies of virus adsorption on surfaces with optimized properties have attracted a lot of interest, mainly due to the influence of the surface in the retention, orientation and stability of the viral capsids. Besides, viruses in whole or in parts can be used as cages or vectors in different areas, such as biomedicine and materials science. A key requirement for virus nanocage application is their physical properties, i.e. their mechanical response and the distribution of surface charge, which determine virus-substrate interactions and stability. In the present work we show two examples of viruses exhibiting strong surface interactions on homogeneous hydrophobic surfaces. The surfaces were prepared by titanate assisted organosilanization, a sol-gel spin coating process, followed by a mild annealing step. We show by surface and interface spectroscopies that the process allows trapping triethoxy-octylsilane (OCTS) molecules, exhibiting a hydrophobic alkane rich surface finishing. Furthermore, the surfaces remain flat and behave as more efficient sorptive surfaces for virus particles than mica or graphite (HOPG). Also, we determine by atomic force microscopy (AFM) the mechanical properties of two types of viruses (human adenovirus and reovirus) and compare the results obtained on the OCTS functionalized surfaces with those obtained on mica and HOPG. Finally, the TIPT+OCTS surfaces were validated as platforms for the morphological and mechanical characterization of virus particles by using adenovirus as initial model and using HOPG and mica as standard control surfaces. Then, the same characteristics were determined on reovirus using TIPT+OCTS and HOPG, as an original contribution to the catalogue of physical properties of viral particles.

The effect of different energy levels of the Er: YAG laser on the repair bond strength of a nanohybrid composite resin

This study evaluates the durability of repair microshear bond strength (µSBS) of nanohybrid composite resins which surfaces are treated with different laser parameters and bur. A total of 240 nanohybrid composite resin disk shaped specimens were prepared. Then, specimens were divided into eight test groups as regards to surface treatment types (Erbium (Er:YAG) laser with seven different parameters and bur). Half of the specimens in each group were subjected to 5000 thermal cycling (TC) and the other half to 20,000 TC. Universal testing machine was used for µSBS test. The data were analyzed with a two-way analysis of variance and Tukey test. Among the specimens treated with ER:YAG laser+5000 TC, we detected the highest mean µSBS test values in the subgroups L200 and L250. Among the specimens treated with ER:YAG laser+20,000 TC, the highest mean µSBS test values were seen in the L200 subgroup. The µSBS values after the 20,000 TC were significantly lower than those after 5000 TC for all different treatment types. Thermal cycling and laser energy levels have effects on repair µSBS. Considering the bond strength and durability it seems more effective to use Er:YAG laser at 200 mJ. To repair an aged nanohybrid composite resin, Er:YAG laser surface treatments may provide some benefits by acquiring a reliable bond strength with durability. This study may give information on which parameters are more suitable to use Er:YAG laser for the repair of nanohybrid composite resins.

Silanizing Effectiveness on the Bond Strength of Aged Bulk-Fill Composite Repaired After Sandblasting or Bur Abrasion Treatments: An in vitro Study

Objective

To measure the repair shear bond strength (SBS) of an aged bulk-fill composite after different mechanical (diamond bur vs sandblasting) and chemical (universal adhesive with or without a previous silanization) surface treatments.

Materials and Methods

Bulk-fill composite (Filtek One Bulk Fill, 3M ESPE) was used to construct seventy-two specimens aged through 10,000 thermal cycles. The specimens were allocated into two groups (n = 36 each) according to the mechanical roughening: Db, treated with a diamond bur, and Sb, treated by sandblasting. Each group was further subdivided into three subgroups (n = 12 each) according to the chemical conditioning: Db-only and Sb-only, unconditioned specimens; Db-U and Sb-U, specimens were conditioned with silane-containing universal adhesive (Scotchbond Universal adhesive, 3M ESPE); and Db-S-U and Sb-S-U, specimens were conditioned with a silane agent (Prosil, FGM) before employing the universal adhesive. The same composite material was used for repair. An additional reference group was constructed to measure the cohesive strengths of the bulk-fill composite. SBS testing was performed using a universal testing machine at a crosshead speed of 1 mm/min, and the failure modes were evaluated by stereomicroscope. The surface topography of resin composite after roughening was assessed by scanning electron microscopy. SBS data were statistically analyzed by ANOVA, Tukey’s test and independent t-test.

Results

The significantly highest SBS was recorded in the reference group (P ≤ 0.05). Sb-only obtained significantly higher SBS than Db-only (P < 0.001). No significant difference in SBS was noted between Db-U and Sb-U or Db-S-U and Sb-S-U. Likewise, no significant difference was observed between the subgroups treated with or without silane (P > 0.05).

Conclusion

The sandblasted specimens demonstrated a higher repair SBS than the diamond bur-treated specimens. The use of an additional silanizing step before applying silane-containing universal adhesive did not enhance the SBS of the repaired composite.

Repair of Bulk-Fill and Nanohybrid Resin Composites: Effect of Surface Conditioning, Adhesive Promoters, and Long-Term Aging

The aim of the study was to investigate the effect of different repair procedures on the repair bond strength of bulk-fill and nanohybrid resin composites after different aging periods. The resin composite blocks (8 × 8 × 4 mm3) were prepared from a bulk-fill (reliaFIL Bulk) and a nanohybrid (reliaFIL LC) resin composite and grouped according to aging duration (6 months, 1 year, and 2 years). Following aging, the blocks were assigned to different surface treatments; air-abrasion with aluminum oxide powder, roughening with a diamond bur, and no treatment. After cleansing with phosphoric acid, a silane layer (Porcelain Primer) was applied on the surface of half of the specimens in each group. The specimens were subdivided into two groups (n = 5): Scotchbond Universal (3M Oral Care) and All-Bond Universal (Bisco). The blocks were repaired with the nanohybrid composite (8 × 8 × 8 mm 3). The repaired specimens were stored in distilled water (37 °C/24 h) and segmented into beams. Half of the beams were immediately subjected to microtensile μTBS testing (1 mm/min), while the other half was stored in distilled water (37 °C) for 6 months before testing. Failure modes were analyzed using stereomicroscope and SEM. Statistical analyses were performed with ANOVA and least significant difference tests (LSD) tests (p = 0.05). The extension of aging periods (6 months, 1 year, and 2 years) reduced the repair bond strength in some groups for both resin composites (p < 0.05). The air-abrasion and bur roughening improved the repair bond strength (p < 0.05). The silane application did not influence the repair bond strength and durability (p > 0.05). There was no difference among the universal adhesives in the same surface treatment groups (p > 0.05). The mechanical roughening treatments are necessary for the repair of resin composite. The universal adhesives might be used for the repair of resin composites regardless of silane content without prior silane application.

Dental adhesion with resin composites: a review and clinical tips for best practice

Modern restorative dentistry would not be possible without the ability to bond to tooth structure. The development of dental adhesives has a lengthy gestation, from the beginnings around 1950, to the latest generation: modern universal adhesives, which were introduced during the 2010s. The foundation for these developments was a deeper understanding of the mechanisms of adhesion to the tooth structure, and to restoration materials. Typically, the performance of an adhesive does not depend on the use of a single ingredient, but on an overall balanced and optimised formulation that contains various components with different roles, such as functional adhesive monomers.While a wealth of literature exists on adhesives that have a long and successful clinical history ('gold standards'), some universal adhesives have also accumulated a lot of scientific evidence while offering benefits like ease of use, low technique sensitivity and versatility.To achieve reliable results with a modern adhesive, several tips should be kept in mind regardless of the product, which result in a homogeneous adhesive layer, proper cure and ultimately high bond strength. Although high performance is already achieved with the adhesives currently available, this is still an exciting area of ongoing research.

Composite repair: On the fatigue strength of universal adhesives

OBJECTIVES

To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.

METHODS

Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).

RESULTS

Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p < 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface.

SIGNIFICANCE

Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

Do universal adhesives provide the benefits from double-application or an extra bonding layer in composite repair?

This study aimed to determine whether the application of extra hydrophobic resin (EHR) or double layer (DL) improves microtensile bond strength (μTBS) of two universal adhesives to composite resin. Composite blocks were fabricated and exposed to thermal cycles. The specimens were horizontally sectioned into two halves. Scotch Bond Universal (SBU) and Clearfil S3 Bond Universal (CSBU) were applied to the ground composite surface according to the manufacturers' instructions, or with DL application or EHR application. The repair composite was incrementally placed to bonded planes. Composite sticks were achieved and tensed with a universal testing machine, followed by examining the fracture surfaces by a scanning electron microscope. Data were evaluated by Weibull analysis (shape and scale [σ_θ and σ_0.10 ] parameters) using the maximum likelihood method. The σ_θ and σ_0.10 , respectively, estimate strength at 63.2 and 10% probability of failure. Shape parameter values showed significant differences among treatments. DL application of CSBU did not affect μTBS values at σ_θ of failure but caused to decrease μTBS values at σ_0.10 of failure. DL application of SBU reduced μTBS values at σ_θ of failure. DL or EHR coating did not improve μTBS of SBU. EHR application increased μTBS of CSBU, whereas DL application did not benefit.

Effect of adhesive application method on repair bond strength of composite

Objectives

This study aimed to evaluate the effect of the application method of universal adhesives on the shear bond strength (SBS) of repaired composites, applied with different thicknesses.

Materials and Methods

The 84 specimens (Filtek Z350 XT) were prepared, stored in distilled water for a week and thermocycled (5,000 cycles, 5°C to 55°C). They were roughened using 400-grit sandpapers and etched with phosphoric acid. Then, specimens were equally divided into 2 groups; Single Bond Universal (SU) and Prime&Bond Universal (PB). Each group was subdivided into 3 subgroups according to application methods (n = 14); UC: 1 coat + uncuring, 1C: 1 coat + curing, 3C: 3 coats + curing. After storage of the repaired composite for 24 hours, specimens were subjected to the SBS test and the data were statistically analyzed by 2-way analysis of variance and independent t-tests. Specimens were examined with a stereomicroscope to analyze fracture mode and a scanning electron microscope to observe the interface.

Results

Adhesive material was a significant factor (p = 0.001). Bond strengths with SU were higher than PB. The highest strength was obtained from the 1C group with SU. Bonding in multiple layers increased adhesive thicknesses, but there was no significant difference in SBS values (p = 0.255). Failure mode was predominantly cohesive in old composites.

Conclusions

The application of an adequate bonding system plays an important role in repairing composite resin. SU showed higher SBS than PB and the additional layers increased the adhesive thickness without affecting SBS.

Repair potential of a bulk-fill resin composite: Effect of different surface-treatment protocols

This study evaluated the effect of different surface-treatment protocols on the repair bond strength of a bulk-fill resin composite. One-hundred and forty specimens (Filtek Bulk-fill) were created (5 mm diameter, 4 mm depth) and allocated to one of 14 groups according to surface treatment (no treatment, tribochemical silica coating, sandblasting with aluminum oxide), adhesive application (no adhesive, total-etch, self-etch), and type of repair resin (bulk-fill, universal resin) (n = 10 per group). Twenty specimens were selected for measuring the cohesive strengths of non-aged resin composites and used as reference. Other specimens were thermocycled. Shear bond-strength testing was performed. Data were analyzed using linear regression of bond strength as a function of the surface treatment, type of adhesive and whether or not adhesive was applied, and type of repair resin. The failure modes were analyzed using logistic regression of failure mode (cohesive failure vs. other types, or adhesive failure vs. other types) on the type of surface treatment, adhesive application, and repair resin used. Surface treatment, regardless of whether this was tribochemical silica coating (mean difference = 5.44 MPa; 95% CI = 4.77-6.11) or sandblasting with aluminum oxide (mean difference = 4.22 MPa; 95% CI = 3.55-4.88), resulted in higher shear bond strength than no treatment. Application of adhesive resulted in a substantial and statistically significant decrease of shear bond strength (by 8.77 MPa, for self-etch and by 7.26 MPa for total-etch) relative to no adhesive. Conversely, the type of repair resin did not influence the shear bond strength to any appreciable extent.

Evaluation of Street Food Safety and Hygiene Practices of Food Vendors in Can Tho City of Vietnam

The objective of this study was to investigate the food safety status of street foods in the city of Can Tho, Vietnam. A total of 410 consumers was interviewed to get an insight into the popular street foods in the studied area. Vietnamese sandwich (34.63%) and sugarcane juice (24.51%) were consumed popularly according to the survey. A total of 263 street food samples (i.e.Vietnamese sandwich, n = 131 and sugarcane juice, n = 132) were collected from different locations such as schools, hospitals, markets, and other locations in four districts (i.e. Ninh Kieu, Cai Rang, Phong Dien and O Mon) of Can Tho city for microbiological analysis. Total aerobic mesophilic counts (TMC), yeast and mold, coliform, E. coli, and Staphylococcus aureus were assessed. Microbial contamination of Vietnamese sandwich was 5.7-9.2 log CFU/g (TMC), 2.0-7.4 log CFU/g (yeast and mold), 2.5-7.9 log CFU/g (coliform), 1.0-5.9 log CFU/g (E. coli), and 1.7-6.6 log CFU/g (Staphylococcus aureus). There was a significant difference in Vietnamese sandwich sampling among districts (p<0.05). In contrast, the contamination of sugarcane juice samples with regards to total aerobic mesophilic counts, yeast and mold, coliform, E. coli, and Staphylococcus aureus were 7.53±0.74, 5.56±0.71, 6.02±1.21, 2.26±1.31, 1.47±0.77 log CFU/mL, respectively. No statistically significant difference (p>0.05) was observed in sugarcane juice samples among districts and locations. The observation of the handling practices of street food vendors showed inadequate hygiene practices, assessment of the street foods safety showed that they do not satisfy the Vietnam hygiene standard of specific foods. These findings give an insight into the safety status of sampled street foods and may provide needed information for Vietnam’s authorities to further improve the safety of street food and create food safety awareness among consumers and handlers, thereby preventing risk to public health.

Effect of universal adhesive and silane pretreatment on bond durability of metal brackets to dental glass ceramics

This study aimed to investigate the effect of universal adhesive and silane pretreatment on the bond durability of metal brackets to dental glass ceramics. Eighty lithium disilicate glass ceramic specimens were randomly assigned to one of four groups (n = 20) defined by the pretreatment and adhesive used: (i) Adper Single Bond 2; (ii) silane + Adper Single Bond 2; (iii) Single Bond Universal; and (iv) silane +Single Bond Universal. Maxillary central incisor metal brackets were bonded on the ceramic surfaces with resin composite. A shear bond strength test was conducted after 24 h of water storage and after 10,000 thermocycles. Adhesive remnant index scoring and field-emission scanning electron microscopy were performed to determine adhesives remaining on the ceramic surfaces and the ceramic ultrastructure following bracket debonding, respectively. After 10,000 thermocycles, specimens treated with Single Bond Universal preserved an appropriate bond strength between brackets and glass ceramics and showed minimum ceramic surface damage following bracket debonding, which was not the case in the other three groups. The application of a silane-containing universal adhesive without silane pretreatment achieves adequate durability of the bond of metal brackets to dental glass ceramics and allows safe debonding, which may aid in optimizing the effectiveness for orthodontic treatment.

Effect of argon plasma on repair bond strength using nanofilled and microhybrid composites

OBJECTIVES

To evaluate the effect of atmospheric pressure plasma (PLA), sandblasting (SAN), silanization (SIL) and hydrophobic bonding resin (HBR) on the micro-shear bond strength (MSBS) of fresh nanofilled (NF) or microhybrid (MH) composites to water-aged nanofilled composite.

MATERIALS AND METHODS

NF plates were fabricated and stored in distilled water for 4 months. The aged plates were assigned to the groups (n = 6): 1- untreated; 2- SAN + SIL + HBR; 3- HBR; 4- PLA + HBR; 5- SAN + HBR; 6- SAN + PLA + HBR; and 7- PLA. Two fresh composite cylinders were constructed on each plate with NF or MH composites and tested after 24 h or 1 year of water-storage, using the MSBS testing. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05).

RESULTS

NF yielded better outcomes than MH at 24 h, which was not observed at 1 year. HBR showed the highest MSBS results, while untreated and PLA groups yielded the lowest one. MSBS reduced for all groups after 1 year.

CONCLUSIONS

Only HBR can obtain good MSBS results, while PLA alone was not beneficial. After 1 year, a reduction in repair MSBS was observed and the type of composite did not influence the results.

CLINICAL RELEVANCE

The repair technique can be simplified with the use of only an adhesive and macromechanical retentions in the old composite, regardless the type of fresh composite.

Adhesive strength of bioactive resin for endodontic tooth build up to dentin treated with conventional and contemporary treatments

AIM

The aim of present ex-vivo study was to assess and evaluate the influence of alternative dentinal conditioning methods- Er,Cr:YSGG (ECL) and Photodynamic therapy (PDT) in comparison to traditional etching regimes- Self Etch Resin (SER) and total etch and rinse (TER) on the bond values of Bioactive restorative material (BA) and Multicore (MC) bulk filled resin composite restorations.

MATERIAL AND METHODS

Eighty caries free mandibular molars were disinfected and embedded in acrylic resin up to Cemento enamel junction (CEJ). Buccal surfaces of all samples were grounded to depth of 2 mm. Specimens were divided into eight groups (n = 20) based on surface treatment received. Samples in group 1 and 2 conditioned with ECYL, group 3 and 4 pre-treated with methylene blue photosensitizer (MBP), group 5 and 6 surfaces conditioned with TER and samples in group 7 and 8 conditioned with SER. Dentin bonding agent was applied and samples of group 1, 3, 5 and 7 were bonded with BA and 2,4,6,8 bonded to MC. Samples were placed in universal testing machine for SBS testing. Data was assessed using analysis of variance (ANOVA) and Tukey multiple comparisons test.

RESULTS

Specimens in group 6 treated with TER and bonded with MC demonstrated maximum SBS (19.61 ± 0.587 MPa). Whereas, group 3 dentin conditioned to MBP and bonded to BA displayed lowest bond values (12.01 ± 0.892 MPa). Samples in group 3 and group 4 dentin treated with MBP bonded to MC (13.68 ± 0.221 MPa) and BA (12.01 ± 0.892 MPa) displayed comparable bond integrity (p > 0.05) CONCLUSION: Dentin pre-treated with TER still remains the gold standard. ECYL as an alternative approach to condition dentin has shown potential and can be recommended in clinical settings. MC as bulk fill composite is recommended over BA irrespective of dentine conditioning technique. MBP as dentin conditioner needs further investigation.

Does use of silane-containing universal adhesive eliminate the need for silane application in direct composite repair?

This in vitro study aimed to evaluate the effect of a silane-containing universal adhesive used with or without a silane agent on the repair bond strength between aged and new composites. Forty nanohybrid composite resin blocks were stored in distilled water for 14 d and thermo-cycled. Sandpaper ground, etched, and rinsed speciments were randomly assigned into four experimental groups: silane + two-step etch-and-rinse adhesive system, two-step etch-and-rinse adhesive system, silane + silane-containing universal adhesive system, and silane-containing universal adhesive system. Blocks were repaired using the same composite. After 24 h of water storage, the blocks were sectioned and bonded sticks were submitted to microtensile testing. Ten unaged, non-repaired composite blocks were used as a reference group to evaluate the cohesive strength of the composite. Two-way ANOVA and Tukey's tests were used to analyze average µTBS. One-way ANOVA and Dunnet post-hoc tests were used to compare the cohesive strength values and bond strength obtained in the repaired groups (α = 0.05). The µTBS values were higher for the silane-containing universal adhesive compared to the two-step etch-and-rinse adhesive system (p = 0.002). Silane application improved the repair bond strength (p = 0.03). The repair bond strength ranged from 39.3 to 65.8% of the cohesive strength of the reference group. Using universal silane-containing adhesive improved the repair bond strength of composite resin compared to two-step etch-and-rinse adhesive. However, it still required prior application of a silane agent for best direct composite resin repair outcomes.

Silane Effect of Universal Adhesive on the Composite-Composite Repair Bond Strength after Different Surface Pretreatments

This study investigated the impact of a separate silanization step on the repair bond strength of composite substrates using a universal adhesive after various mechanical surface treatments. Composite specimens were aged and exposed to the following mechanical roughening treatments: diamond bur abrasion, aluminum oxide sandblasting, or silica coating. The specimens were then either left untreated or conditioned with universal adhesive (Scotchbond Universal), or a silane coupling agent was applied before the use of the universal adhesive or a conventional adhesive (Optibond FL). The conditioned surfaces and fresh substrate (positive control group) were covered with repair composite, and microtensile bond strength testing was performed. The significantly highest bond strength was obtained in the positive control group. Repair bond strength of the universal adhesive applied after a separate silanization step was similar to that without prior silanization, independent of the mechanical surface treatment. Moreover, after silica coating, no significant differences in the repair bond strength were detected among the different adhesive treatments. In conclusion, a separate silanization step before surface conditioning with the universal adhesive does not enhance the repair bond strength. On silica-coated composite substrates, repair bond strength values of the universal adhesive were similar to those of the conventional adhesive.

Bonding Strength of Universal Adhesives to Indirect Substrates: A Meta-Analysis of in Vitro Studies

PURPOSE

To evaluate the in vitro bond strength of universal adhesive systems to indirect substrates.

MATERIAL AND METHODS

Two reviewers performed a literature search up to March 2018 in seven databases: PubMed, Web of Science, SciELO, Scopus, LILACS, IBECS, and BBO. The review included studies that compared the bond strength of universal adhesives and well-established material-specific primers to indirect substrates: lithium disilicate ceramic, yttrium-stabilized zirconium dioxide ceramic, leucite-reinforced ceramic, feldspathic porcelain, polymer infiltrated ceramic material, resin composite or metal alloys. Analyses were carried out using RevMan 5.3.5. A global comparison was performed with the standardized mean difference using a random-effects models at a significance level of p < 0.05.

RESULTS

A total of 45 studies were included in the qualitative analysis, and the meta-analysis was performed with 42 studies. Bond strength to glass-based ceramics and alloys was improved with the use of a specific-primer as separate step before the bonding procedures (lithium disilicate, p < 0.001; alloys, p < 0.001). The bond strength to zirconium substrates was improved with the use of universal adhesives (p < 0.001). For bond strength to composite resin as indirect substrate, universal adhesives performed in a manner similar to that of the material-specific primer (p = 0.11).

CONCLUSIONS

The clinical procedure of luting zirconia and resin composite restorations could be simplified by using single-bottle universal adhesives. However, the ability of universal adhesives to achieve an adequate and durable bond to glass-based ceramics and alloys appears to be limited.

Universal dental adhesives: Current status, laboratory testing, and clinical performance

Increasing demand for simplified and user-friendly adhesive systems has led to the development of a new class of adhesives termed as Universal Adhesives (UAs). The term "Universal" reflects manufacturers' claims that these adhesives can be applied with any adhesion strategy and offer the versatility of use with a variety of direct and indirect restorative materials. The aim of this review was to synthesize the literature regarding the current status of UAs, their adhesion potential to various substrates and their performance in different restorative situations. In vitro studies, clinical trials and systematic reviews were identified utilizing controlled vocabulary and keyword searches in Medline and EMBASE databases. About 282 studies (272 in vitro studies; 11 clinical studies) were included. Available laboratory and clinical evidence does not support the claim that UAs can be used with any adhesive strategy. Although, they can chemically bond to various tooth and direct/indirect restorative substrates, the stability of this bond is material-dependent and subject to hydrolytic degradation. Hence, additional measures are still needed to ensure long-term durability. which undermines the versatility of UAs. The lack of long-term data regarding the clinical performance of UAs further complicates clinical decision-making. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2121-2131, 2019.

Original and Repair Bulk Fracture Resistance of Particle Filler and Short Fiber-Reinforced Composites

OBJECTIVE

This study aimed to evaluate the original (OR) and repair (RR) fracture resistance of a semi-interpenetrating polymer network (semi-IPN)-based short fiber-reinforced composite compared to dimethacrylate-based composite materials by means of the V-notch test.

METHODS AND MATERIALS

Circular specimens (5×2 mm) with a centrally machined 90° V-shaped notch were prepared. Four bulk fill (Filtek Bulk Fill, Venus Bulk Fill, TetricEvo Ceram Bulk Fill, SDR), three microfilled hybrid (GC-Anterior, GC-Posterior, Z250), one nanofilled (SupremeXTE), and two short fiber-reinforced (Alert, everX Posterior) composites were selected. EverX Posterior was the semi-IPN material. Specimens (n=12/group) were either dry or water stored for 7 and 30 days, respectively, at 37°C and then loaded in two-point load until fracture. One-half of each tested specimen was used for the repair procedure. Repairing surfaces were diamond-bur ground, etched, and treated with silane containing universal adhesive (Scotchbond Universal) before repair.

RESULTS

Three-way analysis of variance revealed a significant statistical difference between the groups ( p<0.05). The fracture resistance of dry-stored groups was greater than that of water-stored groups. The highest OR was observed for dry-stored Alert (23.4 N/mm), which significantly deteriorated in water (17.4 N/mm) ( p<0.05). The highest RR was observed for everX Posterior (20.0 N/mm), which did not deteriorate in water significantly (19.0 N/mm) ( p>0.05). The everX Posterior preserved the specimens' integrity at the final fracture load (ductile fracture), whereas all other materials fractured into two halves at the interface (adhesive failure).

CONCLUSIONS

The only material that provided enhanced repair strength that was close to the original cohesive strength of the material was everX Posterior. The endurance of repaired restorations can be improved by using semi-IPN-based filling material.

Repair bond strength of nanohybrid composite resins with a universal adhesive

Objective: To investigate the repair bond strength of fresh and aged nanohybrid and hybrid composite resins using a universal adhesive (UA).

Materials and methods: Fresh and aged substrates were prepared using two nanohybrid (Venus Pearl, Heraus Kulzer; Filtek Supreme XTE, 3 M ESPE) and one hybrid (Z100, 3 M ESPE) composite resin, and randomly assigned to different surface treatments: (1) no treatment (control), (2) surface roughening with 320-grit (SR), (3) SR + UA (iBOND, Heraus Kulzer), (4) SR + Silane (Signum, Ceramic Bond I, Heraeus Kulzer) + UA, (5) SR + Sandblasting (CoJet, 3 M ESPE) + Silane + UA. After surface treatment, fresh composite resin was added to the substrates at 2 mm layer increments to a height of 5 mm, and light cured. Restored specimens were water-stored for 24 h and sectioned to obtain 1.0 × 1.0 mm beams (n = 12), and were either water-stored for 24 h at 37 °C, or water-stored for 24 h, and then thermocycled for 6000 cycles before microtensile bond strength (µTBS) testing. Data were analyzed with ANOVA and Tukey’s HSD tests (p = .05).

Results: Combined treatment of SR, sandblasting, silane and UA provided repair bond strength values comparable to the cohesive strength of each tested resin material (p < .05). Thermocycling significantly reduced the cohesive strength of the composite resins upto 65% (p < .05). Repair bond strengths of UA-treated groups were more stable under thermocycling.

Conclusions: Universal adhesive application is a reliable method for composite repair. Sandblasting and silane application slightly increases the repair strength for all substrate types.