Repairability of CAD/CAM high-density PMMA- and composite-based polymers

OBJECTIVE

The study aimed to analyse the shear bond strength of computer-aided design and computer-aided manufacturing (CAD/CAM) polymethyl methacrylate (PMMA)- and composite-based polymer materials repaired with a conventional methacrylate-based composite after different surface pretreatments.

METHODS

Each 48 specimens was prepared from six different CAD/CAM polymer materials (Ambarino high-class, artBloc Temp, CAD-Temp, Lava Ultimate, Telio CAD, Everest C-Temp) and a conventional dimethacrylate-based composite (Filtek Supreme XTE, control) and aged by thermal cycling (5000 cycles, 5-55 °C). The surfaces were left untreated or were pretreated by mechanical roughening, aluminium oxide air abrasion or silica coating/silanization (each subgroup n = 12). The surfaces were further conditioned with an etch&rinse adhesive (OptiBond FL) before the repair composite (Filtek Supreme XTE) was adhered to the surface. After further thermal cycling, shear bond strength was tested, and failure modes were assessed. Shear bond strength was statistically analysed by two- and one-way ANOVAs and Weibull statistics, failure mode by chi(2) test (p ≤ 0.05).

RESULTS

Shear bond strength was highest for silica coating/silanization > aluminium oxide air abrasion = mechanical roughening > no surface pretreatment. Independently of the repair pretreatment, highest bond strength values were observed in the control group and for the composite-based Everest C-Temp and Ambarino high-class, while PMMA-based materials (artBloc Temp, CAD-Temp and Telio CAD) presented significantly lowest values. For all materials, repair without any surface pretreatment resulted in adhesive failures only, which mostly were reduced when surface pretreatment was performed.

CONCLUSIONS

Repair of CAD/CAM high-density polymers requires surface pretreatment prior to adhesive and composite application. However, four out of six of the tested CAD/CAM materials did not achieve the repair bond strength of a conventional dimethacrylate-based composite.

CLINICAL RELEVANCE

Repair of PMMA- and composite-based polymers can be achieved by surface pretreatment followed by application of an adhesive and a conventional methacrylate-based composite.

Shear bond strength of resin cement to an acid etched and a laser irradiated ceramic surface

PURPOSE

To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic.

MATERIALS AND METHODS

Fifty-five ceramic blocks (5 mm × 5 mm × 2 mm) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at 37℃ for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (α=0.05).

RESULTS

Adhesion was significantly stronger in Group 2 (3.88 ± 1.94 MPa) and Group 3 (3.65 ± 1.87 MPa) than in Control group (1.95 ± 1.06 MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 (3.59 ± 1.19 MPa) and Control group. Shear bond strength was highest in Group 1 (8.42 ± 1.86 MPa; P<.01).

CONCLUSION

Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique.

Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials

PURPOSE

The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials.

MATERIALS AND METHODS

120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA.

RESULTS

Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05).

CONCLUSION

SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin.

Shear bond strength of veneering porcelain to zirconia and metal cores

STATEMENT OF PROBLEM

Zirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and the veneering porcelain requires investigation in order to facilitate the material's clinical use.

PURPOSE

The purpose of this study was to evaluate the bonding strength of the porcelain veneer to the zirconia core and to other various metal alloys (high noble metal alloy and base metal alloy).

MATERIAL AND METHODS

15 rectangular (4×4×9mm) specimens each of zirconia (Cercon), base metal alloy (Tillite), high noble metal alloy (Degudent H) were fabricated for the shear bond strength test. The veneering porcelain recommended by the manufacturer for each type of material was fired to the core in thickness of 3mm. After firing, the specimens were embedded in the PTFE mold, placed on a mounting jig, and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.5mm/min until fracture. The average shear strength (MPa) was analyzed with the one-way ANOVA and the Tukey's test (α= .05). The fractured specimens were examined using SEM and EDX to determine the failure pattern.

RESULTS

The mean shear strength (± SD) in MPa was 25.43 (± 3.12) in the zirconia group, 35.87 (± 4.23) in the base metal group, 38.00 (± 5.23) in the high noble metal group. The ANOVA showed a significant difference among groups, and the Tukey's test presented a significant difference between the zirconia group and the metal group. Microscopic examination showed that the failure primarily occurred near the interface with the residual veneering porcelain remaining on the core.

CONCLUSION

There was a significant difference between the metal ceramic and zirconia ceramic group in shear bond strength. There was no significant difference between the base metal alloy and the high noble metal alloy.

Repairability of a 3D printed denture base polymer: Effects of surface treatment and artificial aging on the shear bond strength

OBJECTIVES

The present study aimed to evaluate the repairability of a 3D printed denture base material. The effects of surface treatments and artificial aging on the shear bond strength (SBS) were investigated.

METHODS

A total of 224 specimens were printed by digital light processing technology (Rapid Shape D30II) using a 3D printing denture base material (FREEPRINT denture). To evaluate the repairability, the SBS and failure modes were measured after surface treatment and artificial aging. Specifically, half of the specimens were further performed with thermocycling (5-55 °C, 5000 cycles) for artificial aging. The aged and non-aged specimens were further divided into four subgroups (n = 28) to simulate a denture base repair with one of the following treatments: control (without surface treatment), monomer (applying methylmethacrylate for 120 s), P600 (grinding with P600 silicon carbide paper) and sandblasting (blasted with 125 μm aluminum oxide with 2 bar), respectively. Surface roughness was measured (n = 6) and surface topography was observed by scanning electron microscopy (n = 2). A test rod was built on the sample surface using the same 3D printing material. Afterward, all specimens further underwent thermocycling (5-55 °C, 10,000 cycles).

RESULTS

For non-aged groups, no significant differences in SBS could be found (p < 0.05), and bondings failed cohesively in the denture base material. Regarding the aged control and monomer group, adhesive failures at the interface were primarily observed, and SBS values were statistically lower than those of the other groups (p < 0.05).

CONCLUSIONS

The 3D printed denture base material exhibited favorable repairability. For the realignment surface, the SBS at the bonding interface is satisfying and additional surface treatments could be not necessary. In contrast, the aged surface could significantly decrease the SBS; hence subtractive surface treatments are highly recommended.

An in-vitro assessment of the shear bond strength of bulk-fill resin composites to permanent and deciduous teeth

OBJECTIVES

This study aimed to evaluate the shear bond strength (SBS) of bulk-fill resin composites (RCs) to deciduous and permanent teeth.

METHODS

The following parameters were investigated: (1) tooth type (deciduous and permanent), (2) tooth substrate (enamel and dentine), (3) restorative material (a high- and a low-viscosity bulk-fill RC and a regular nanohybrid RC as control), and (4) adhesive (two self-etching adhesives). The combination of those parameters resulted in a total of 24 different groups (n=20). Permanent caries-free human molars (240) and deciduous teeth (240) were selected. The bulk-fill RCs (Tetric Evo Ceram Bulk Fill and SureFil SDR) were applied in one 4-mm increment, whereas the regular RC (Tetric Evo Ceram) was layered in two consecutive 2-mm increments. The SBS was examined after storing the specimens for 24 h at 37 °C in distilled water, followed by thermal ageing (5000 cycles between 5 °C and 55 °C).

RESULTS

Data were statistically analyzed using one- and multiway analyses of variance and an independent-samples t-test (α=0.05). The multivariate analysis (general linear model with partial eta-squared statistics) tested the influence of the parameters tooth type, tooth substrate, restorative material, and adhesive on the SBS. The parameter tooth type showed no significant impact on the SBS (p=0.576). The influence of the other parameters was significant (p<0.05) but low, and the highest influence was exerted by the parameter adhesive (η(P)(2)=0.120, p=0.0001) followed by tooth substrate (η(P)(2)=0.092, p=0.0001) and restorative material (η(P)(2)=0.028, p=0.0001). The fracture pattern was predominantly adhesive (61.9%) or mixed (38.1), and no cohesive or prefailure was registered.

CONCLUSIONS

Bulk-fill materials performed comparable or better than the nanohybrid RC used as control, but the adhesive used was the most relevant factor of influence. This material type might be clinically an option for a faster restoration in both permanent and deciduous teeth.

CLINICAL SIGNIFICANCE

Bulk-fill materials performed comparable or slightly better than the nanohybrid RC used as control. Clinically, flowable bulk-fill RCs might be an advantage in restoring deep, narrow cavities, with difficult access angles, whereas larger cavities might be restored easily and faster using high-viscosity compounds.

Shear bond strength of composite resin to high performance polymer PEKK according to surface treatments and bonding materials

PURPOSE

The object of the present study was to evaluate the shear bonding strength of composite to PEKK by applying several methods of surface treatment associated with various bonding materials.

MATERIALS AND METHODS

One hundred and fifty PEKK specimens were assigned randomly to fifteen groups (n = 10) with the combination of three different surface treatments (95% sulfuric acid etching, airborne abrasion with 50 µm alumina, and airborne abrasion with 110 µm silica-coating alumina) and five different bonding materials (Luxatemp Glaze & Bond, Visio.link, All-Bond Universal, Single Bond Universal, and Monobond Plus with Heliobond). After surface treatment, surface roughness and contact angles were examined. Topography modifications after surface treatment were assessed with scanning electron microscopy. Resin composite was mounted on each specimen and then subjected to shear bond strength (SBS) test. SBS data were analyzed statistically using two-way ANOVA, and post-hoc Tukey's test (P<.05).

RESULTS

Regardless of bonding materials, mechanical surface treatment groups yielded significantly higher shear bonding strength values than chemical surface treatment groups. Unlike other adhesives, MDP and silane containing self-etching universal adhesive (Single Bond Universal) showed an effective shear bonding strength regardless of surface treatment method.

CONCLUSION

Mechanical surface treatment behaves better in terms of PEKK bonding. In addition, self-etching universal adhesive (Single Bond Universal) can be an alternative bonding material to PEKK irrespective of surface treatment method.

Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

PURPOSE

The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material.

MATERIALS AND METHODS

A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05.

RESULTS

Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001).

CONCLUSION

Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used.

Evaluation of UDMA's potential as a substitute for Bis-GMA in orthodontic adhesives

OBJECTIVES

To investigate the effect of UDMA %, of a range of filled UDMA:TEGDMA resins, on viscosity, degree of conversion and shear bond strength. Furthermore, to compare between model filled and unfilled UDMA adhesives, and clinically used orthodontic adhesives on these properties.

METHODS

Four filled and four unfilled resins with a UDMA to TEGDMA weight ratio 50:50, 60:40, 70:30, 80:20 were formulated, tested and compared to the Bis-GMA control Transbond XT. The properties investigated were: viscosity (rotational viscometry), degree of conversion (DC) (FT-IR) and bond strength (shear bond strength test). One-way ANOVA and Tukey post hoc test was used to statistically analyze the data for viscosity and DC% while the non-parametric Kruskal-Wallis and Mann-Whitney U-test was used for the shear bond strength values.

RESULTS

For SBS a comparable bond strength was obtained between the U80:T20(F) adhesive and the control Transbond XT (27.1 and 30.1 respectively). There was no significant difference between the U70:T30 adhesive and the control. Transbond XT (43.1%) had a significantly lower DC% than all the UDMA based adhesives. Furthermore, there was no significant difference between the DC% means of the various UDMA resins. There was a significant decrease in the viscosity for both filled and unfilled groups, as the TEGDMA concentration was increased.

SIGNIFICANCE

The results indicate that adhesives formulated with UDMA and TEGDMA monomers, could produce resins with comparable viscosities to the Bis-GMA control, Transbond XT. Adhesives formulated with high UDMA %, can be used to produce resins with greater viscosity and increased bond strength, potentially without affecting their degree of conversion.

Antibacterial and protein-repellent orthodontic cement to combat biofilms and white spot lesions

OBJECTIVES

White spot lesions are the most undesired side-effect of fixed orthodontic treatments. The objectives of this study were to combine nanoparticles of silver (NAg) with 2-methacryloyloxyethyl phosphorylcholine (MPC) to develop a modified resin-modified glass ionomer cement (RMGI) as orthodontic cement with double benefits of antibacterial and protein-repellent capabilities for the first time.

METHODS

NAg and MPC were incorporated into a commercial RMGI. Another commercial orthodontic adhesive also served as control. Enamel shear bond strengths (SBS) were determined. Protein adsorption was measured via a micro bicinchoninic acid method. A dental plaque microcosm biofilm model with human saliva as inoculum was tested. Biofilms adherent on the cement samples and planktonic bacteria in the culture medium away from the cement surfaces were both evaluated for bacterial metabolic activity, colony-forming units (CFU), and lactic acid production.

RESULTS

Adding 0.1% NAg and 3% MPC to RMGI, and water-aging for 30 days, did not adversely affect the SBS, compared to the unmodified RMGI control (p>0.1). The modified RMGI containing 0.1% NAg and 3% MPC achieved the greatest reduction in protein adsorption, bacterial adhesion, CFU, metabolic activity and lactic acid production. The RMGI containing 0.1% NAg and 3% MPC inhibited not only the bacteria on its surface, but also the bacteria away from the surface in the culture medium.

CONCLUSIONS

The incorporation of double agents (antibacterial NAg+protein-repellent MPC) into RMGI achieved much stronger inhibition of biofilms than using each agent alone. The novel antibacterial and protein-repellent RMGI with substantially-reduced biofilm acids is promising as an orthodontic cement to combat white spot lesions in enamel.

Influence of surface treatments and repair materials on the shear bond strength of CAD/CAM provisional restorations

PURPOSE

To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials.

MATERIALS AND METHODS

Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA.

RESULTS

The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05).

CONCLUSION

In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.

Comparison of two test designs for evaluating the shear bond strength of resin composite cements

OBJECTIVE

To compare a shear bond strength test for resin composite cements developed in order to better consider the shrinkage stress (here termed "Swiss shear test") with the shear test design according to ISO 29022.

METHOD

Four restorative materials (VITA Enamic (VE), VITA Suprinity (VS), Vitablocs Mark II (VM) and VITA YZ T (YZ)) served as substrate. VE, VS and VM were polished or etched. YZ was polished, sandblasted or etched. Specimens were either bonded according to the Swiss or the ISO shear test. RelyX Unicem 2 Automix, Maxcem Elite and PermaFlo DC were used as cements. Shear bond strength (SBS) was measured. Failure modes (adhesive, cohesive or mixed) were evaluated by means of SEM.

RESULTS

Mean SBS values obtained with the Swiss shear test were significantly lower than those obtained with the ISO shear test. VE and VM exhibited similar SBS, values of VS were significantly higher. On etched surfaces VM and VE exhibited primarily cohesive failures, VS primarily adhesive failures. On polished substrates significantly lower bond strength values and exclusively adhesive failures were observed. YZ exhibited solely adhesive failures. Compared to polished YZ, SBS significantly increased after sandblasting and even more after etching. Only for adhesively failed specimens mean SBS values of Swiss and ISO shear test were strongly correlated.

SIGNIFICANCE

Both test designs showed the same ranking of test results. When adhesive failure occurred test results were strongly correlated. When cohesive failure was involved, both test designs did not provide reliable results.

Evaluating the effect of antioxidant agents on shear bond strength of tooth-colored restorative materials after bleaching: A systematic review

PURPOSE

The main objective of the present study was to make a systematic review of how antioxidant agents affect shear bond strength of tooth-colored restorative materials after bleaching.

DATA SOURCES

Electronic search was used to extract the related articles on the targeted key words such as "antioxidant", "dental bleaching" and "shear bond strength" (SBS) from MeSH, PubMed, Medline, and Cochrane electronic data bases. These articles were all published before 2016.

STUDY SELECTION

Inclusion criteria were restricted to English journal articles concerning humans, clinical trials, cohorts and case-control studies. Therefore, systematic reviews, case reports, letters to editors, editorials and congress abstracts were excluded from the analysis.

CONCLUSIONS

Most studies conducted on the issue have produced experimental data which are rather controversial, and there is no general agreement about the reported outcomes. As an illustration, most studies have not considered the relationship between the type of antioxidant materials and the shear bond strength. In point of fact, some researchers (e.g Kimyai et al.) have concluded that antioxidants like gel and solution leave similar effects on SBS. Alternatively, certain studies (e.g., Kunt et al.) have produced inconclusive data regarding the impact of one week postponement of the restorative process on SBS after the bleaching process. The results of the studies evaluating the role of various adhesive systems used after bleaching have demonstrated that regardless of the type of adhesive system used, applying antioxidants before restorative procedures can adversely affect the bleaching agents utilized for SBS. It has also been suggested that the type of the adhesive system used might be correlated with the magnitude of SBS. The results obtained from the systematic review of the articles under investigation reflected that the use of antioxidant agents, regardless of their type, form, concentration and duration of application, can improve SBS after bleaching.

Influence of different low-pressure plasma process parameters on shear bond strength between veneering composites and PEEK materials

OBJECTIVE

The aim of this study was to evaluate the impact of oxygen and argon/oxygen low-pressure plasma on the shear bond strength (SBS) between dental PEEK compounds and veneering composites as a function of plasma process time.

METHODS

Of an unfilled PEEK ("Juvora") and two pigment powder filled PEEK compounds ("DC4420", "DC4450"), 273 rectangular plates were prepared and polished up to 1200 grit. Afterwards the samples were sandblasted and randomly assigned to five different surface pre-treatment groups (1. No plasma (control); 2. O₂ plasma for 3min; 3. O₂ plasma for 35min; 4. Ar/O₂ plasma for 3min; 5. Ar/O₂ plasma for 35min). Surface roughness and water contact angles were recorded using three samples of each PEEK compound for each of the plasma treatment groups. An adhesive (visio.link, Bredent GmbH & Co KG, Senden, Germany) was applied onto the specimen surfaces and light cured. A mold was used to shape three different veneering composites (a) Vita VM LC, "Vita" (Vita Zahnfabrik, Bad Säckingen, Germany); (b) GC GRADIA, "Gradia" (GC Europe, Leuven, Belgium); (c) GC GRADIA DIRECT Flo, "Gradia Flo" (GC Europe, Leuven, Belgium)) into a cylindrical form on the sample surface before light curing. SBS was measured using a universal testing machine after 24h of incubation in distilled water at 37°C.

RESULTS

The two pigment filled PEEK compounds treated with O₂ plasma and veneered with Gradia Flo showed the highest SBS values (34.92±6.55MPa and 34.2±1.87MPa) followed by the combination of the unfilled PEEK material with Gradia Flo (29.57±3.71MPa). The SBS values of the samples veneered with Gradia were lower, but not significantly so. The SBS values of the specimens with Vita were for the most part associated with significantly lower results.

SIGNIFICANCE

A low-pressure plasma process using oxygen plasma for a duration of 35min, preceded by sandblasting, seems to be the most effective in increasing shear bond strength between veneering composites and PEEK materials.

A new concept and finite-element study on dental bond strength tests

OBJECTIVE

Numerous bond strength tests have been performed on dental adhesion experiments. Yet, the validity of these bond strength tests is controversial due to the name (e.g., "shear" or "tensile") may not reflect to the true and complete stress situation, i.e., assumed uniform shear or uniaxial tensile conditions. Thus, the aim of this study was to simulate and compare the stress distribution of and between shear bond strength (SBS), tensile bond strength (TBS), mold-enclosed shear bond strength (ME-SBS) and de novo lever-induced mold-enclosed shear bond strength (LIME-SBS) tests.

METHODS

3-Dimensional finite element method (FEM) was used on the dental resin-bonded surfaces (i.e., titanium alloy, dentine and porcelain) interphased with adhesive layer (thickness 5μm) to simulate the mechanical tests. For ME-SBS, both polycarbonate and stainless steel molds were used. For LIME-SBS, stainless steel levers and molds with lengths of 3mm, 6mm, 12mm, 15mm and 18mm were used. The applied loads on these models were 50N, 100N and 200N.

RESULTS

De novo LIME-SBS test was the most optimal configuration to evaluate "shear" bond strength of adhesive in regards to providing significantly high and uniform shear stress as well as eliminating tensile stress at the interface. The conventional SBS test created very high tensile stress at the load area, whereas the TBS created optimal tensile stress but shear stress indeed co-exist. The ME-SBS test could also eliminate some of the tensile stress. Similar stress distributions pattern appeared on the Ti-adhesive models, the dentine-adhesive models and porcelain-adhesive models.

SIGNIFICANCE

None of the bond strength tests could give purely "shear" or "tensile" bond strength, but LIME-SBS seems to be the best model to evaluate the bond strength under true "shear" mode.

Effect of restorative timing on shear bond strength of composite resin/calcium silicate-based cements adhesive interfaces

OBJECTIVES

The aim of this study was to evaluate the shear bond strength inherent to immediate and delayed definitive composite resin restorations, over three different biomaterials.

METHODS

Fifty-four aluminum blocks were randomly assigned to six experimental groups (n = 9) according to the biomaterial (Biodentine, TotalFill BC Putty, or PCM) and restoration timing (immediate or 7 days delayed). Regarding the restorative procedures, a two-step self-etch bonding system (Clearfil SE Bond) was applied and subsequently restored using a flowable composite resin (SDR). After shear bond strength testing, fracture pattern analysis was performed. The significance level was set at α = 0.05.

RESULTS

Within the immediate groups, Biodentine showed the highest mean shear bond strength value, with no statistically significant differences (P > 0.05) being detected when compared with both TotalFill (P = 0.072) and PCM (P = 0.232) groups. Regarding the delayed restoration groups, Biodentine and TotalFill presented the highest mean shear bond strength value, with statistical differences when compared with PCM (P = 0.002 and P = 0.043, respectively). No statistically significant differences (P > 0.05) were verified between both immediate and delayed groups for each tested biomaterial. Also, a statistically significant association was found between the fracture type and the biomaterial (P < 0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings suggest that all tested biomaterials present suitable alternatives which allow to perform restorative procedures immediately after pulp capping biomaterial placement (3 or 12 min, depending on the bioactive cement), therefore requiring one single appointment to complete the procedure. Biodentine and TotalFill BC Putty have shown superior shear bond strength results when compared with PCM, within a delayed timeframe (7 days).

Comparison of shear bond strength and bonding time of a novel flash-free bonding system

OBJECTIVE

To evaluate the bonding time, shear bond strength (SBS), and adhesive residue index (ARI) of APC(TM) Flash-Free bonding system.

MATERIALS AND METHODS

Thirty-six extracted human maxillary premolars were randomly divided into three groups (12 per group) and used for this in vitro study: group 1, APC Flash-Free Adhesive Coated Appliance System; group 2, Clarity ADVANCED Ceramic Bracket pasted manually; group 3 (control group), 3M APC PLUS Adhesive prepasted brackets bonded with the extruded flash removed. Bonding time was measured using a stopwatch. Bond strength was measured using an Instron at a cross-head speed of 1 mm/min. The ARI was graded on a scale from 1 to 5. Repeated-measures analysis of variance and post hoc Tukey tests were used for statistical analysis.

RESULTS

It took significantly (P < .001) less time to bond in the APC Flash-Free Adhesive group (30.7 ± 3.3 seconds) compared with the control group (41.8 ± 4.0 seconds) and the manual group (39.2 ± 2.8 seconds). The APC Flash-Free Adhesive coated bracket had significantly (P < .001) greater SBS (13.7 ± 2.2 MPa) compared with the control group (10.8 ± 2.0 MPa) and the manual group (10.4 ± 1.4 MPa). The ARI was significantly (P < .001) greater with the APC Flash-Free Adhesive coated bracket compared with that of the other two groups.

CONCLUSIONS

Compared with other methods of bonding, the APC Flash-Free Adhesive Coated System can potentially reduce bonding time while increasing SBS.

Comparative Evaluation of Shear Bond Strength of Various Glass Ionomer Cements to Dentin of Primary Teeth: An in vitro Study

Aim

To evaluate and compare shear bond strength of various glass ionomer cements (GICs) to dentin of primary teeth.

Materials and methods

Sample size taken for the study was 72 deciduous molars with intact buccal or lingual surfaces. Samples were randomly divided into three groups, i.e., groups A, B, and C and were restored with conventional type II GIC, type II light cure (LC) GIC, and type IX GIC respectively. Thermocycling was done to simulate oral conditions. After 24 hours, shear bond strength was determined using Instron Universal testing Machine at crosshead speed of 0.5 mm/ minute until fracture. Results were tabulated and statistically analyzed.

Results

It was found that the shear bond strength was highest in group B (LC GIC) 9.851 ± 1.620 MPa, followed by group C (type IX GIC) 7.226 ± 0.877 MPa, and was lowest in group A (conventional GIC) 4.931 ± 0.9735 MPa.

Conclusion

Light cure GIC was significantly better than type IX GIC and conventional GIC in terms of shear bond strength.

How to cite this article

Somani R, Jaidka S, Singh DJ, Sibal GK. Comparative Evaluation of Shear Bond Strength of Various Glass Ionomer Cements to Dentin of Primary Teeth: An in vitro Study. Int J Clin Pediatr Dent 2016;9(3):192-196.

Influence of surface treatments on bond strength of metal and ceramic brackets to a novel CAD/CAM hybrid ceramic material

This study evaluated the effect of four different surface treatments methods on the shear bond strength (SBS) of ceramic and metal brackets to Vita Enamic (VE) CAD/CAM hybrid ceramic. A total of 240 plates (10 mm × 10 mm × 3 mm) were cut from VE ceramic blocks and divided into two groups. In each group, four subgroups were prepared by hydrofluoric acid (HF); phosphoric acid (H3PO4); diamond ceramic grinding bur; and silica coating using CoJet system (CJ). Maxillary central incisor metal (Victory Series) and ceramic (Clarity) brackets were bonded with light-cure composite and then stored in artificial saliva for 1 week and thermocycled. The SBS test was performed, and the failure types were classified with adhesive remnant index scores. Surface morphology of the ceramic was characterized after treatment using a scanning electron microscope. Data were analyzed using two-way ANOVA, Tukey HSD test, and Weibull analysis. SBS was significantly affected by the type of bracket and by type of treatment (P < 0.001). Specimens treated with CJ presented with significantly higher SBS compared to other groups (P < 0.05). Improvements in SBS values (MPa) were found in the following order: CJ > HF > Bur > H3PO4. Ceramic bracket showed higher SBS compared to metal bracket. Adhesive failures between the ceramic and composite resin were the predominant mode of failure in all groups. Surface treatment of VE CAD/CAM hybrid ceramic with silica coating enhanced the adhesion with ceramic and metal brackets.

Does the bond strength of highly translucent zirconia show a different dependence on the airborne-particle abrasion parameters in comparison to conventional zirconia?

PURPOSE

To compare the effects of airborne-particle abrasion protocols on the surface morphology, the phase transformation and the resin bond strength of highly translucent zirconia (M) and conventional zirconia (Z).

METHODS

Thirteen groups (N = 12) of Z and M specimens were prepared. Except for the control group, the specimens were sandblasted with conditions involving different grit sizes (50 μm or 110 μm), treatment times (10 s or 20 s) and pressures (0.1 MPa, 0.3 MPa or 0.6 MPa). The surface morphology was analyzed using scanning electron microscope (SEM) and the phase analysis was conducted with X-ray diffraction (XRD). The Ra and the shear bond strength (SBS) were measured and statistically analyzed, and the failure mode was determined by optical microscope.

RESULTS

The surface morphologies were strongly dependent on treatment conditions. Larger particle size and higher pressure resulted in higher Ra for both materials. Longer blasting time resulted in higher Ra for Z but not M. Overall, the SBS increased with increasing Ra; the highest average SBS was achieved by M and exceeded 18 MPa. The monoclinic transformation was not found in any treatment for M, but was found in Z.

CONCLUSIONS

Z and M showed different dependence on the airborne-particle abrasion parameters in terms of Ra, SBS and phase transformation. The conditions for maximizing SBS included a 110 μm particle size and 20 s treatment for both, with pressures of 0.3 MPa and 0.6 MPa for the M and Z, respectively.

Promoting porcelain-zirconia bonding using different atmospheric pressure gas plasmas

OBJECTIVES

To evaluate the effects of different atmospheric-pressure plasma (APP) on the physicochemical properties of yttria-stabilized zirconia, and promoting the adhesion of veneering porcelain.

METHODS

Cercon base zirconia disks were prepared to receive different treatments: as-polished, three APPs (oxygen, OP; argon, AP; and CF₄, CP), and grit-blasted (GB). Their surface roughness and hydrophilicity were measured, and surface morphology was examined either after treatments, after simulated porcelain firing, or additional thermal etching. X-ray photoelectron spectroscopy (XPS) analysis characterized the surface chemical compositions. Shear bond strength (SBS) tests examined the adhesion between veneering porcelain and zirconia either before or after thermocycling. The layered ceramic disks were also sectioned to inspect the porcelain-zirconia interfaces. Statistical analysis was performed with one-way ANOVA and post hoc Duncan's test.

RESULTS

Grit-blasting caused surface damage and increased roughness. All APP-treated disks exhibited deeper grain boundaries and enlarged grain sizes after thermal etching, while CP disks revealed additional particle dispersions. Three APPs rendered the zirconia surface superhydrophilic. XPS spectra of three APP groups revealed increased hydroxyl groups and reduced C-C contents, and CP group especially showed the existence of Z-F bonds. CP exhibited the highest SBS both before and after thermocycling, while AP and GB also showed improved SBSs compared to the as-polished. OP presented reduced SBS, and its cross-sections showed increased microporosities in the veneering porcelain.

SIGNIFICANCE

APP did not change surface morphology but enhanced wettability. CP and AP improved porcelain-zirconia SBSs, primarily through surface hydroxylation. OP induced the microporosities in porcelain and adversely affected the adhesion.

Effects of surface treatment and artificial aging on the shear bond strength of orthodontic brackets bonded to four different provisional restorations

OBJECTIVE

To evaluate the combined effects of material type, surface treatment, and thermocycling on the bond strength of orthodontic brackets to materials used for the fabrication of provisional crowns.

MATERIALS AND METHODS

Four materials were included in this study (ProTemp, Trim Plus, Trim II, and Superpont C+B). Sixty cylindrical specimens (1 × 3 cm) were prepared from each material and equally divided into three groups. The first group was ground with silica carbide paper, the second was polished with pumice, and the last group was sandblasted with 50-µm aluminum oxide particles. Stainless-steel maxillary central incisor brackets (Victory Series, 3M) were bonded to the provisional material specimens with Transbond XT light-cured composite resin, and half of the specimens from each group were thermocycled 500 times in 5°C and 55°C water baths. Then the brackets were debonded with shear testing, and the results were statistically analyzed by three-way analysis of variance and Tukey's multiple-comparison tests at α  =  0.05. Adhesive Remnant Index (ARI) was also identified.

RESULTS

Before and after thermocycling, ProTemp materials showed the highest shear bond strength with orthodontic brackets (10.3 and 13.1 MPa, respectively). The statistical analysis indicated an interaction among the three independent variables (P < .05) and statistically significant differences in bond strength among provisional materials (P < .001), surface treatments (P < .001), and thermocycling (P < .05). According to the ARI, most groups demonstrated adhesive failure.

CONCLUSIONS

The provisional material type, surface treatment, and artificial aging have a significant effect on bond strength. Sandblasting treatment exerts a beneficial effect on shear bond strength.

Influence of methylene blue, Riboflavin, and indocyanine green on the bond strength of caries affected dentin when bonded to resin-modified glass ionomer cement

AIM

The present study aimed to assess the influence of methylene blue (MBP), Riboflavin, and indocyanine green (ICG) on the bond strength of caries affected dentin (CAD) when bonded to resin-modified glass ionomer cement (RMGIC).

MATERIALS AND METHODS

Human third molars with caries lesions were isolated and collected scrutinized based on ICDAS criteria. The teeth were cleaned using a periodontal scaler and disinfected. All samples were positioned in polyvinyl up to the cementoenamel junction. The samples were randomly distributed into five groups based on the pretreatment regime. Samples in group 1, were pretreated with MBP; group 2, polyacrylic acid (PAA) group 3, ICG, group 4, Riboflavin photosensitizer, and group 5, 37% phosphoric acid (PA). All samples were bonded with RMGIC. 10 samples were subjected to the universal testing machine for shear bond strength (SBS) testing. Five samples from each group were placed in fuchsine dye for the microleakage assessment. Comparison of means and standard deviations (SD) of SBS and microleakage in investigated groups was performed using analysis of variance (ANOVA) and Tukey's post hoc test at a significance level (p=0.05) RESULTS: : The highest micro shear bond values were observed in group 2 (CAD conditioned with PAA) (14.26±1.67 MPa). Whereas, the lowest bond values were found in group 1 (treated with MBP) (8.82±1.08 MPa). CAD conditioned with different photosensitizers i.e., MBP, ICG, and Riboflavin before bonding to RMGIC displayed comparable bond values (8.82±1.08 MPa), (9.47±0.21 MPa), and (11.23±0.47 MPa) respectively (p>0.05). Samples conditioned with 37% PA showed significantly higher microleakage scores compared to other surface-treated groups (p<0.05).

CONCLUSION

Caries-affected dentin conditioned with polyacrylic acid demonstrated low microleakage and high bond strength.

Shear bond strength and interface analysis between a resin composite and a recent high-viscous glass ionomer cement bonded with various adhesive systems

OBJECTIVE

This study investigated the shear bond strength (SBS) and interface between a resin composite and a new high-viscous glass ionomer cement (HV-GIC), a HV-GIC, a resin-modified glass ionomer cement (RM-GIC), a bulk-fill flowable composite, and a regular flowable composite bonded with various adhesive systems.

METHODS AND MATERIALS

A resin composite (Filtek Z350) was bonded to a new HV-GIC (EQUIA Forte Fil) using various adhesive systems, including a universal adhesive in self-etch and etch-and-rinse mode (Scotchbond Universal), a two-step etch-and-rinse adhesive (Scotchbond 1-XT), a one-step self-etch adhesive (Optibond All-in-one) tested also after silane application (Monobond Plus), and a coating material (EQUIA Forte Coat). The resin composite was also bonded to a HV-GIC (Fuji IX GP), a RM-GIC (Fuji II LC), a bulk-fill flowable composite (SDR), and a regular flowable composite (Tetric Evo Flow) with the universal adhesive in self-etch mode (Scotchbond Universal). Two-way ANOVA followed by Dunnett's post hoc test was used to investigate the difference in SBS. Failures were analyzed by chi-square test. Bonding interfaces were examined by environmental scanning electron microscopy (E-SEM).

RESULTS

SBS to EQUIA Forte Fil was significantly lower with Scotchbond 1-XT than with all other adhesive systems. By using Scotchbond Universal with the self-etch technique, the SBS to EQUIA Forte Fil was significantly higher than the SBS to Fuji IX GP and significantly lower than the SBS to Fuji II LC, SDR, and Tetric Evo Flow. E-SEM images showed an intimate contact at all interfaces examined.

CONCLUSION

EQUIA Forte Fil showed satisfactory SBS and interfaces with all adhesives tested.

CLINICAL RELEVANCE

Bonding between the resin composite and HV-GIC can be achieved using a universal adhesive in self-etch mode, an easy-to-use adhesive system.

Effect of laser groove treatment on shear bond strength of resin-based luting agent to polyetheretherketone (PEEK)

PURPOSE

The mechanical properties of polyetheretherketone (PEEK) are ideally suited for fixed dental prostheses. However, PEEK typically has low adhesion strength to resin-based luting agent. This study assessed the shear bond strength between laser groove treated PEEK and resin-based luting agent.

METHODS

A total of 230 specimens were randomly divided into five groups (n=46): no-treatment, air abrasion treatment, 100μm-deep, 150μm-deep, and 200μm-deep laser groove treatments. The surface roughness was measured, scanning electron microscopy was used to observe the specimen surfaces, and X-ray photoelectron spectroscopy (XPS) was used to analyze the surfaces. Each group was divided into four resin-based luting agent subgroups: Panavia V5, RelyX Ultimate Resin Cement, G-CEM Link Force, and Super-Bond C&B. After the resin-based luting agent was bonded to the specimens, the bond strength was measured using shear tests and the failure modes were assessed by stereomicroscopy. The surfaces were also observed by scanning electron microscopy (SEM) after the shear bond strength measurements. The data were statistically analyzed using a two-way analysis of variance and Tukey's honest significant difference test (α=0.05).

RESULTS

The PEEK surface after laser groove treatment groups exhibited the highest mean Ra values. In the XPS analysis, the laser treated PEEK surface exhibited an effective surface composition for bonding with resin-based luting agent. The shear bond strengths for the laser groove treated samples were significantly higher (p<0.05) than those of the no-treatment and air abrasion treatment groups.

CONCLUSIONS

The shear bond strength between PEEK and resin-based luting agent was substantially improved by laser groove treatment.