Effect of temporary cement removal methods from human dentin on zirconia-dentin adhesion

This study evaluated the effect of temporary cement residue removal methods from human coronary dentin on the bond strength of adhesively-luted zirconia on dentin. Forty non-carious human molars were embedded in acrylic resin and the dentin surfaces were exposed. Temporary acrylic crowns were provisionally cemented with zinc oxide cement without eugenol and stored in distilled water (37?°C/15?days). After crown removal, the excess temporary cement was removed from dentin according to one of the following cleaning methods: (n?=?8 per group): (a) air-water rinse (AW), (b) pumice paste (PP), (c) air-abrasion with aluminum oxide particles (Al₂O₃) (AA), (d) sodium bicarbonate spray (SB) or (e) glycine powder (CP). Forty zirconia cylinders were made and each cylinder was adhesively luted onto each tooth after adhesive resin (Scotch Bond Universal, 3?M ESPE-SBU) application using resin cement (RelyX Ultimate, 3?M ESPE) and photo-polymerized from each surface for 20?s. The bonded specimens were stored in distilled water (37?°C) for 90?days. The bonded interface was loaded under shear (1?mm/min). Data (MPa) were analyzed using 1-way ANOVA and Tukey's test (α?=?0.05). Mean bond strength was significantly affected by the cleaning method (p?=?0.0289). Cleaning with AA method resulted in significantly higher bond strength than with SB (p?<?0.05) but similar to CP, PP and AW (p?>?0.05). All cleaning methods were effective in removing temporary resin cement from dentin surfaces. Air-abrasion with aluminum oxide particles was more effective than with sodium bicarbonate spray promoting adhesion between zirconia and dentin.     

Effects of surface treatments on the shear bond strength of luting cements to zirconia

Objective: The aim of this in vitro study was to evaluate the effect of surface treatments on the shear bond strength of resin cements to zirconia. Material and methods: Sintered zirconia specimens (n = 192) were divided into four different surface treatment groups: control (no treatment); airborne-particle abrasion; glaze layer and hydrofluoric acid (HF) application, and hot etching solution application. Then, each group was divided into four subgroups (n = 12), and three different resin cements were applied to the zirconia surfaces. The shear bond strength value of each specimen was measured after 5000 thermo cycles. The failure types were examined with a stereomicroscope and the effects of the surface treatments were evaluated with a scanning electron microscope. Results were analyzed using analysis of variance and Tukey’s post hoc tests (α = 0.05). Results: The surface treatment and resin cement type significantly affected the bond strength results (p < 0.05). For all resin cements, the airborne-particle abrasion treatment increased the shear bond strength values (p < 0.05). The glaze layer & HF application increased shear bond strength values for all groups, except the Single Bond Universal-RelyX Unicem Aplicap group (p < 0.05). The surface roughness values of airborne-particle abraded specimens were similar to comparable values for specimens from the control group and the hot etching solution group (p > 0.05). The glaze layer & HF application group produced the highest surface roughness values (p < 0.05). Conclusion: The results of this study recommend using the appropriate combination of surface treatment and adhesive/silane coupling agent to achieve durable zirconia-resin bonding.     

Evaluation of different desensitizing agents effect on shear bond strength of adhesive resin cement to dentin

Desensitizing agents can inhibit the bonding strength between dentin and adhesive resin cement. This study evaluated the effects of different desensitizing agents on the shear bond strength of adhesive resin cement to dentin. Sixty freshly extracted and caries free teeth were classified into five experimental groups, randomly (n?=?12). Each group was treated with a different desensitizing agent (Teethmate, Shield Force Plus, Admira Protect and Ultra-Ez) respectively, except for an untreated control group. After desensitizing agents and adhesive resin cement were applied to each dentin surface, all specimens were stored in incubator at 37?°C for 24?h. The shear bond strength was tested with a Universal testing machine at a 0.5?mm/min crosshead speed. Data were analysed by using a statistical software (SPSS 22). The results of the measurements were analysed by Kruskal Wallis test with Bonferroni correction and multiple comparisons were made by Wilcoxon test (p???.01). Specimens were examined by a scanning electron microscope, additionally. The Shield Force Plus showed significantly the highest shear bond strength compared with other groups (p?<?.01). Ultra-Ez showed the lowest shear bond strength (p?>?.01). There was no significant difference among Teethmate and Admira Protect groups (p?>?.01). Desensitizing agents containing resin monomers increased the bonding strength, however desensitizers containing calcium phosphate, potassium nitrate and fluoride did not effect the bonding strength of resin cement to dentin.     

Influence of zirconia surface treatments on resin cement bonding and phase transformation

It evaluated the effects of different zirconia surface treatments on the bond strength of a resin cement to Y-TZP (yttria-stabilized tetragonal zirconia) ceramics, as well as their phase-transformations. 75 blocks (5 mm × 5 mm × 4 mm) of Y-TZP were assigned into five groups (n = 15): (tribochemical silica coating - TBS) zirconia surface was abraded by silica coated alumina particles followed by silanization; (GLZ₁) zirconia surface received the application of a thin layer of low-fusing porcelain glaze, followed by hydrofluoric acid (HF) etching for 1 min; (GLZ₅) glaze application + HF etching by 5 min; (GLZ₁₀) glaze application + HF etching by 10 min; (GLZ₁₅) glaze application + HF etching by 15 min. After etching, all the specimens were washed, dried and silanized. Cylinders of composites (diameter: 3.25 mm; height: 3 mm) were cemented to the Y-TZP blocks using a resin cement. All the specimens were subjected to aging (10,000 thermal cycles and 90 days storage), tested under shear conditions, and finally analyzed by a stereomicroscope (failure analysis). In addition, we also performed topographical and phase transformation analyses of the treated zirconia surfaces. The TBS group presented the highest bond strength value (23.34 MPa). The glazed groups presented low bond values and high prevalences of pretest failures. X-ray diffraction analysis showed a phase transformation for the TBS group (13.14%); however, there was no clear phase change observed for the GLZ groups. From our results, we concluded that tribochemical silica coating is the main Y-TZP surface conditioning for resin bond improvements.     

Effect of experimental primers on hydrolytic stability of resin zirconia bonding

This study assessed the effect of experimental silane primers and two adhesive resin cements on resin zirconia adhesion strength. The surfaces of cut Y-TZP zirconia blocks (Lava? Frame), 16 mm × 16 mm × 4.5 mm, were pretreated twice. First, they were grit-blasted with Korox? alumina powder (110 μm) followed by silica-coating with Rocatec? Soft. Next, the blocks were randomly assigned into eighteen sub-groups (n = 6, N = 108) according to three primers (control ESPE Sil?, 1.0 vol.-% 3-acryloxypropyltrimethoxysilane, and 1.0 vol.-% 3-acryloxypropyltrimethoxysilane + 0.5 vol.-% bis-12-(triethoxysilyl)ethane), two in dentistry used resin cement products (Multilink? Speed, and Multilink? N), and three storage conditions (24 h dry, 1 month immersed in distilled water, and 6 months immersed in distilled water at room temperature) used. Onto each pretreated zirconia block, four cylindrical resin composite cement stubs were prepared and light-cured. The surface roughness, contact angle, and adhesion (shear bond) strength (SBS) were measured, and statistically analyzed (ANOVA, the Tukey’s test, p < 0.05). No statistical differences were observed in surface roughness values of different primer-treated zirconia groups. After six months of water aging, the shear bond strength of the groups that employed 1.0 vol.-% 3-acryloxypropyltrimethoxysilane (9.0 MPa ± 0.8 MPa), and the blend of 1 vol.-% 3-acryloxypropyltrimethoxysilane + 0.5 vol.-% bis-12-(triethoxysilyl)ethane (8.9 MPa ± 2.0 MPa) with Multilink? Speed resin composite cement were statistically insignificantly higher compared to using ESPE Sil? (8.7 MPa ± 1.8 MPa). The experimental primers may have potential to be used for long-term resin zirconia adhesion.     

Effects of sandblasting distance and angles on resin cement bonding to zirconia and titanium

ObjectivesThe aim of this study was to evaluate effects of sandblasting distance and angles resin to zirconia and titanium bonding.MethodsDensely sintered zirconia and cp2 titanium specimens were prepared and randomly divided into groups, and then sandblasted with various distance (5 mm, 10 mm and 15 mm) and angles (45°, 60°, 75° and 90°). After surface treatment, each specimen surface underwent a silane primer application (RelyX, 3M ESPE), followed by bonding of a resin cement (RelyX Unicem Aplicap, 3M ESPE). Then, each cylindrical resin stub (diameter 3.6 mm×2 mm) underwent a shear adhesive (bond) strength test and surface roughness evaluation. SEM evaluation and EDX analysis were used to observe surface properties of both zirconia and titanium samples. Results were statistically analyzed using analysis of variance (ANOVA) and Turkey test (α=0.05).ResultsSurface roughness showed a significant difference amongst the different distances and angles for both the zirconia and titanium materials and these changes in surface roughness were evident in the SEM imaging photos. As for the adhesive strength, there was a significant difference in the adhesive strength for the titanium and zirconia with different angles. In general, 75° gives the best results although this is not significantly different from 90°. However, no significant difference was observed in changes of sandblasting distance for both materials. EDX analysis at the surface revealed elements carbon, oxygen, silicon, aluminum, and zirconia on the surface.ConclusionsSandblasting at various distance and angles contributes differences in surface roughness when it comes to both zirconia and titanium materials. Despite both 75° or 90° sandblasting angle could yield a sufficiently high adhesive strength for resin to titanium or zirconia bonding, sandblasting at 75° seems to be optimal to increase the adhesive strength.     

Effect of thermal cycling and low pressure sandblasting on the bond strength of a self-adhesive cement to Y-TZP zirconia

The aim of this investigation was to assess the influence of several surface treatments on the shear bond strength (SBS) of a self-adhesive resin cement containing 10-methacryloxydecyl-dihydrogenphosphate monomer to densely sintered zirconia ceramic, before and after thermal cycles. Hundred densely sintered zirconia cylinders were divided into five groups (n = 20). Each of them received a different surface treatment: (1) control [No_T], with the zirconia surface unconditioned, (2) low pressure air abrasion [Sand_S], (50 μm, 1 bar), (3) standardized air abrasion [Sand_H], (50 μm, 2.8 bar), (4) standardized Rocatec? Plus (silica-coated alumina oxide) air abrasion (2.8 bar) and silanization [Roc_H], (5) low pressure Rocatec? Plus (silica-coated alumina oxide) air abrasion (1 bar) and silanization [Roc_S]. Five more surface-treated specimens were addressed to scanning electron microscope for qualitative observations. After specimen fabrication, subgroups of 10 bonded samples were stored in water either for 24 h (T1) or subjected to 5000 thermal cycles (T2); SBSs were determined with a universal testing machine at a crosshead speed of 1 mm/min. At T1, mean SBSs (MPa) obtained for the examined groups were: [Sand_H] 16.24 ± 2.95; [Sand_S] 16.01 ± 2.68; [Roc_H] 17.17 ± 1.64; [Roc_S] 15.92 ± 1.99. All surface treatments positively affected (p < 0.05) the initial self-adhesive cement adhesion to zirconia with respect to No_T (13.29 MPa). Artificial aging decreased the bond strength in all test groups significantly, but no spontaneous debonding was observed in [No_T]: at T2, SBS values ranged from 7.76 ± 2.37 (No_T) to 8.89 ± 1.74 (Sand_S), with no statistically significant difference between groups (p = 0.5293). Both air abrasion with alumina oxide and Rocatec? universal bonding system, used with hard or low air pressure, produced comparable effects on cement–zirconia interface before and after thermal cycles. After artificial aging, minimal differences in bond strength values between sandblasted and control groups were not of statistical significance.     

Effect of ceramic surface treatments on the bond strength of different composite resins

This study was aimed to observe the relationship between the different surface treatments and the bond strength of both composite based adhesive cement and zirconia ceramic. Thirty-two zirconia ceramic discs were fabricated by following the instructions of manufacturer (5 × 5 × 1.5 mm). Four subgroups were obtained from the specimens according to the specified surface treatments respectively: (a) C: control groups: no treatment; (b) SB: sandblasting with 125 μm aluminum oxide particles for 10 s; (c) SC: silica coating for 10 s; (d) Nd :YAG laser . The composite resin specimens Panavia F and Clearfil SA were introduced and polymerized to the treated bonding areas. Afterwards the specimens were stored in distilled water at 37 °C during 24 h, and the shear test was applied. The data were statistically analyzed by ANOVA and Duncan tests. The bond strength was stated significantly higher in silica coating/Panavia F group (23.35 MPa). The lowest bond strength was stated in control groups cemented with Clearfil SA (12.25 MPa). As a result it was determined that the bond strength has affected the both surface treatments and cement types (p < 0.001). The silica coating –treated zirconia ceramic recorded a significant increase in mean bond strength values.     

An investigation of atomic force microscopy,surface topography and adhesion of luting cements to zirconia: effect of silica coating,zirconia primer and laser

This study evaluated the effect various surface conditioning methods on the surface topography and adhesion of luting cements to zirconia. Zirconia blocks (N?=?25) were randomly assigned to five groups according to the surface conditioning methods: (a) No conditioning, control (CON), (b) tribochemical silica coating (TSC), (c) MDP-based zirconia primer (ZRP), (d) coating with nano aluminum nitride (ALN) (e) etching with Er: YAG laser (LAS). The conditioned zirconia blocks were further divided into five subgroups to receive the luting cements: (a) MDP-based resin cement (Panavia F2.0) (PAN), (b) 4-META-based cement (Super Bond) (SUB), (c) UDMA-based (GCem) (GCE), (d) bis-GMA based (Bifix QM) (BIF) and (e) polycarboxylate cement (Poly-F) (POL). Cements were applied in polyethylene moulds (diameter: 3?mm; height: 2?mm). The bonded specimens were first thermocycled for 5500 cycles (5–55?°C) and then adhesive interface was loaded under shear (0.5?mm/min). The data (MPa) were analyzed using 2-way ANOVA, Tukey’s and Bonneferroni tests (alpha?=?0.05). Regardless of the cement type, TSC resulted in significantly higher bond strength (p???0.05) (13.3?±?4.35–25.3?±?6.3) compared to other conditioning methods (2.96?±?1.5–5.4?±?5.47). Regardless of the surface conditioning method, no significant difference was found between MDP, 4-META and UDMA based cements (p?>?0.05) being significantly higher than those of bis-GMA and polycarboxylate cements (p???0.05). Failure types were frequently adhesive in all groups. Tribochemical silica coating provided superior bond results compared to other conditioning methods tested on zirconia especially in conjunction with UDMA- and 4-META-based resin cements.     

Effect of different surface shapes formed by femtosecond laser on zirconia-resin cement shear bond strength

Objective: The purpose of this study was to evaluate the effect of different surface shapes formed by femtosecond (FS) laser on zirconia (Y-TZP)-resin cement shear bond strength (SBS). Background data: All ceramic restoration is used as an alternative to metal-ceramic restorations, due to its better aesthetics, strength, and toughness properties. However, bond strength of restoration to tooth and other materials is effective to long term success of the restoration, and to achieve it surface treatment is required on ceramic surface. Materials and methods: Forty square-shaped zirconia samples were prepared and assigned to four groups of 10. The details of the groups are as follows: Group A, square-shaped recessed surface; Group B, square-shaped projection surface; Group C, circular-shaped recessed surface; Group D, circular-shaped projection surface. The SBSs values were performed with a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed statistically using analysis of variance (ANOVA) and Tukey HSD multiple comparisons tests. Results: The one-way ANOVA results on SBSs of the zirconia material bonded with resin cement revealed significant differences among the groups (p < 0.05). The Tukey HSD test results revealed that Group B and D had significantly higher SBS values than other groups (p < 0.05), but there were no significant differences between each other (p > 0.05). Additionally, Group A and C had significantly lower values than other groups (p < 0.05). Conclusions: Different surface shapes formed by FS laser provided a significant increase in SBSs. The SBS values of projection surfaces of circular and square-shapes are greater than that of recessed surfaces of circular and square-shapes.     

Efficacy of novel cleansing agent for the decontamination of lithium disilicate ceramics: a shear bond strength study

Purpose: To investigate the efficacy of Ivoclean as a ceramic cleansing agent, by assessing shear bond strength of pre-etched lithium disilicate (LD) ceramic to resin cement.

Materials and Methods: Seventy LD discs (10 × 10 × 4 mm) were fabricated and etched using 5% hydrofluoric acid (HF) for 20 s. Ten specimens were not exposed to saliva and silicone disclosing medium (negative control). The other 60 specimens, divided into six groups (n = 10), were exposed to saliva for 20 s and silicone disclosing medium for 3 min. Following contamination, 10 specimens were not cleansed (positive control). The remaining five groups were exposed to one of the five different cleansing agents: 96% isopropanol, 37% phosphoric acid-30 s, 5% HF acid- 20 s, 5% HF acid- 120 s, and Ivoclean paste-20 s. All specimens were treated with primer and bonded to a self-curing resin cement. Before shear bond strength testing, all specimens were thermocycled (3000 cycles; 5–55°).

Results: Contamination of pre-etched LD ceramic specimens significantly reduced the shear bond strength values from 22.39 ± 0.38 MPa (negative control) to 6.54 ± 0.90 MPa (positive control) (p < 0.05). Cleansing of contaminated ceramic specimens with 5% HF acid [20 s (19.28 ± 1.06 MPa) and 120 s (20.04 ± 1.09 MPa)] and Ivoclean (18.30 ± 0.97) provided significantly higher bond strength values than other cleansing methods with 37% phosphoric acid and 96% isopropanol (p < 0.05).

Conclusion: Ivoclean and 5% HF acid were found to be effective in cleansing of LD ceramic surface by demonstrating maximum increase in shear bond strength values as compared to contaminated LD ceramics.     

Fracture strength and fractographic analysis of zirconia copings treated with four experimental silane primers

This study evaluated and compared the effect of new four experimental silane coupling agents on the fracture strength of zirconia copings. The findings were supported with fractographic and finite element analyses. All together 125 zirconia copings with a ?wall thickness of 0.6?mm were fabricated on identical nickel-chromium master dies and then divided randomly into five groups (n?=?25). Four test groups were prepared according the experimental silane primer (labeled: OIWA1, OIWA2, OIWA3 and OIWA4) ?and one control group without silanization. The silane monomers used were: ?3-methacryloxypropyltrimethoxysilane (in OIWA1), ?3-acryloxypropyltrimethoxysilane (in OIWA2), ?3-?isocyanatopropyltriethoxysilane (in OIWA3) and styrylethyltrimethoxysilane (in OIWA4). Tribochemical sandblasting (silica-coating) treatment was performed to the inner surface of the copings in the ?test groups. All the specimens were silanized at the inner surfaces of the zirconia copings. Self-?adhesive universal resin cement was used to cement the copings to ?the underlying master die. Zirconia copings were vertically loaded on the ?cusp ?area until the first crack failure was occurred using Precision Universal Tester ?at a ?constant crosshead speed of 1?mm/min. Then, the machine ?was manually controlled to cause more failure ?to further determine the texture of fracture. Three dimensional finite element analysis and fractography were performed to support the fracture strength findings. Based on the finite element analysis results, zirconia silanized with ?3-acryloyloxypropyltrimethoxysilane showed the highest fracture strength with a mean of ?963.75??N (SD 4.5?N), while zirconia copings silanized with ?3-methacryloyloxypropyltrimethoxysilane showed a mean fracture strength value of ?925.65?N (SD 2.4?N). Styrylethyltrimethoxysilane-silanised zirconia showed mean fracture strength of 895.95?N (SD 3.5?N). Adding silane coupling agents to the resin-zirconia interface increased the fracture strengths significantly (ANOVA, p?<?0.05). Silanization with four new experimental silane primers in vitro produced significantly ?greater fracture strength than the control group not treated with the test silane.?     

Effect of nonthermal plasma treatment on surface roughness and bond strength between veneer ceramic and zirconia core

This in vitro study evaluated the effect of nonthermal plasma (NTP) treatment on the surface roughness (Ra) of the zirconia and the shear bond strength (SBS) between the veneer ceramic and the zirconia. Ninety zirconia specimens were divided into six groups according to the surface treatments applied: control with no treatment; sandblasting with 50-μm Al₂O₃ particles; oxygen plasma treated for 5 min; oxygen plasma treated for 10 min; argon plasma treated for 5 min; and argon plasma treated for 10 min. Ra values were measured using a profilometer. Specimens (n = 12) were then veneered with a nano-fluorapatite ceramic, and the SBS test was performed. Scanning electron microscopy, atomic force microscopy, and X-ray diffraction analyses were performed. The sandblasting procedure significantly increased the surface roughness; however, the plasma groups showed similar Ra values compared to the control group. NTP and sandblasting treatment significantly increased the bond strength and led to higher SBS values than the control. Plasma application did not induce phase transformation; however, sandblasting caused monoclinic phase transformation of the zirconia. NTP application (either oxygen or argon) can enhance the bond strength between the veneer ceramic and the zirconia core without altering the surface morphology or causing zirconia phase transformation.     

Bonding of novel self-glazed zirconia dental ceramics

ABSTRACT

Bonding behaviours of a novel self-glazed zirconia dental material were investigated. The effect of a preformed porous nanoceramic bonding surface and the different cleansing methods on saliva-contaminated bonding surfaces was assessed in this in vitro study. Cleaning procedures commonly used in dental offices were tested. All specimens demonstrated adhesive fracture patterns except for airborne particle abrasion group, which resulted in mixed-type fracture pattern and the highest bonding force values. No statistically significant differences in bonding force values were found between self-glazed zirconia with and without a preformed porous nanoceramic bonding surface when bonded with the self-adhesive resin cement (RelyX? Unicem 2). Scanning electron micrographs revealed no interaction between the bonding surface and the resin cement after priming. Mechanical retention is the predominant bonding mechanism between the bonding surface and the luting resin cement.     

Influence of different surface treatments on zirconia/resin shear bond strength using one-bottle universal adhesive

ABSTRACT

This study was designed to evaluate the effect of different treatments on the zirconia/resin shear bond strength (SBS) using commercial one-bottle universal adhesive. Zirconia discs with different surface treatments (blank control; airborne-particle-abrasion; glazing) were bonded to the bovine enamel surfaces using one-bottle universal adhesive. All specimens were tested for SBS (MPa) before and after 10000 thermocycles. Statistically analysis were conducted by using one-way analysis of variance and multiple-comparison least significant difference tests (α = 0.05). Airborne-particle-abrasion group showed higher SBS (36.19 ± 11.86) than control group (14.98 ± 5.90) and glazing group (10.63 ± 5.39) (p < 0.05). After thermocycling test, the SBS significantly decreased for control group (8.84 ± 2.55) and glazing group (6.18 ± 2.78) while not for airborne-particle-abrasion group (41.5 ± 7.95). One-bottle universal adhesives combined with airborne-particle-abrasion showed quite high SBS of zirconia/resin, which was appropriate for bonding of zirconia restoration.     

The effect of MDP-based primer on shear bond strength of various cements to two different ceramic materials

The aim of this study was to determine the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer on the shear bond strengths of thermally aged self-adhesive and conventional adhesive resin cements and zinc phosphate cement to zirconia and lithium disilicate substructures. Sixty zirconia (Z) and 60 lithium disilicate (L) disk specimens were cut from ceramic blocks. Each group was divided into six subgroups (n = 10). Half of the specimens of each ceramic group were treated with primer (P) and the other half was remained untreated. Three types of cement were applied: zinc phosphate cement [(ZPC) (Hoffmann Harmonic Shades)]; self-adhesive resin cement [(SAC) (RelyX U200)]; conventional adhesive resin cement [(CAC) (C&B)]. The specimens were subjected to thermal aging procedure for 1 week under 37 °C water bath. Shear bond strength (SBS) was determined using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with three-way (ANOVA). Pairwise comparisons and interactions between groups were analyzed by using Tukey’s simultaneous confidence intervals. There was no significant difference between the SBS values of SAC-Z (11,47 ± 0,47) and SAC-ZP (11,39 ± 0,42) (p > 0.05). However, the SBS values of SAC-L (12.34 ± 0,55) and SAC-LP (12,50 ± 0,49) were significantly higher than those of SAC-Z and SAC-ZP (p < 0.00). The use of primer significantly increased the SBS value of CAC-ZP (8,05 ± 0,55) when compared to the SBS value of CAC-Z (3,53 ± 0,41) (p < 0.00). Resin cement that contains methacrylate monomers with phosphoric ester functional groups exhibited reliable bond to zirconia. However, the use of an MDP-based primer may not further improve its bond strength.     

Effect of different surface treatments on bond strength of recycled brackets to feldspathic porcelain

Aim: The aim of the study was to compare the shear bond strength of three different types of recycled brackets on porcelain facets following different surface treatments. Materials and Methods: Eighty-four porcelain facets were produced by duplication of the labial surface of a maxillary right first premolar. Each porcelain facet was individually embedded in autopolymerizing acrylic resin. A thin coat of sealant was also painted on the bracket base and cured for 15 s before applying the paste. The bracket was then positioned on the porcelain facet, pressed lightly and light-cured. Each specimen was loaded into a universal testing machine using Nexjen software for testing, with the long axis of the specimen perpendicular to the direction of the applied force. Then, the brackets were rebonded following different surface treatments (Laser, hydrofluoric acid, sandblasting with Al₂O₃, and silane treatment). Kruskal–Wallis analysis of variance and post hoc Wilcoxon signed-rank tests were performed to test the differences in shear bond strength values (p < 0.05). The significance of differences in the ARI scores was analyzed with chi-square test (p < 0.05). Results: Statistical analysis indicated significant differences among surface treatment procedures (p < 0.0001). In addition, the effect of the first and second bonding factors on shear bond strength behaviors was shown to be significant for the brackets (p < 0.001). Conclusion: The use of sandblasting, HF treatment and silanization procedure could be used for improving the rebond shear bond strength of zirconia brackets to porcelain surface. However, rebonding the brackets to porcelain surfaces may not be recommended due to the dramatic decrease in bonding values.     

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

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

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

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

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

Shear bond strength of PEEK and PEEK-30GF cemented to zirconia or titanium substrates

Objectives: The aim of this study was to evaluate the use of dual-cure resin cement to promote the bonding between a veneering PEEK and zirconia or titanium surfaces.

Materials and methods: The surface of titanium and sintered zirconia disks were gritblasted, ultra-sonically cleaned in distilled water, and dryed by oil-free air. Then, a adhesive system was applied on the clean and dry surfaces. Disks of PEEK or 30% glass-reinforced PEEK were cut from a rod and their surface were acid etched and therefore the PEEK roughness was analysed using a contact profilometer. A resin cement was then applied between the substrates and the veneering PEEK and light cured for 4 Shear bond strength tests were performed on PEEK-cement to zirconia or titanium interfaces. Scanning electron microscopy (SEM) analyses were performed to evaluate the samples surface, interface and failure mode.

Results: Surface treatment with acid etching decreased the average roughness of PEEK-based surfaces. oMicroscopic analyses by SEM revealed morphological aspects of a poor bonding between the resin-based cement and PEEK. Those aspects could be confirmed by the low mean values in shear bond strength. The fracture analysis showed that the main failure mode was adhesive, which explain the low values of shear bond strength.

Conclusion: PEEK is a promising material for dental applications. However, significant improvements on surface modifications and in chemical composition of the cement are still required for dental applications involving cementation of PEEK or PEEK-30GF to zirconia or titanium concerning a desirable long-term clinical performance of prosthetic structures.     

Effect of different surface treatments on the shear bond strength of resin cement to zirconia ceramic and metal alloy*

The bonding of resin cement to ceramic materials plays an important role in dentistry. The purpose of this study is to evaluate the effects of various surface treatments on the shear bond strength (SBS) of zirconia ceramic and metal alloy. A total of 60 specimens were prepared from Y-TZP ceramic and metal alloy. The specimens were divided into three subgroups (n = 10) that received different surface treatments for each material. An Er:YAG laser (ER), a femtosecond laser (FS), and air-borne particle abrasion (A) were employed as surface treatments. One specimen from each group was analyzed using a scanning electron microscope (SEM) at 500 x magnification after surface treatments. The self-adhesive resin cement was then bonded to the treated surfaces using a Teflon mold. The specimens were thermocycled for 5,000 cycles at 5–55 °C, and then the SBS test was performed. Kruskal–Wallis and Mann–Whitney U tests were used to determine the differences between the groups (p = 0.05), and failure modes were evaluated for each specimen. Statistical analyses revealed significant differences between the surface treatment methods. The mean SBS values of the air-borne particle-abraded groups were higher than those of the other groups. The femtosecond-irradiated groups of each material showed significantly higher SBS values than the Er:YAG-irradiated groups (p < 0.05). Within the limitations of this study, air-borne particle abrasion and the femtosecond laser were more effective than Er:YAG laser treatment.