Composite Resin Bond Strength to Zirconia and Base Metal Alloys Using Two Types of Intraoral Porcelain Repair Systems

Objectives: This study aimed to evaluate the shear bond strength (SBS) of two repair composites (Crea.lign vs. PermaFlo) to a base metal alloy and zirconia ceramic. Materials and Methods: Sixty-four discs (12mm diameter, 1mm thickness) were fabricated using Wirobond base metal alloy and zirconia. They were then bonded with their respective composite resins (N=16) in each of the two porcelain chipping repair kit subgroups consisting of PermaFlo and Crea.lign. All specimens were stored in 37°C distilled water for 24 hours. Half of them were subjected to 10,000 thermal cycles (5-55°C, 30s). All specimens were tested for SBS with a universal testing machine. Failure types were analyzed using a digital camera. Analysis of the data was done by two-way ANOVA and Bonferroni post-hoc tests. Results: SBS was significantly affected by the type of composite resin. PermaFlo had a significantly higher SBS than Crea.lign to base metal alloy (P<0.001) and zirconia ceramic (P<0.001). Thermocycling decreased the SBS of both composites to base metal alloy (P<0.001) and zirconia (P<0.001). Conclusion: A universal adhesive could provide higher shear bond strength of zirconia and base metal alloy to composite resin than Crea.lign composite and the MKZ primer supplied by its manufacturer.

The Effect of Colloidal Silica and Glaze Coatings on the Adhesion of Zirconia with Various Ytrria Concentration

PURPOSE

This study evaluated the effect of coating traditional and translucent Y-TZP with an industrial nanometric colloidal silica or glaze before or after sintering on the adhesion of zirconia with various ytrria concentration.

MATERIALS AND METHODS

Specimens of Y-TZP with 3% and 5% yttria were subdivided into 5 groups (n=10), according to the coating applied and moment of application (before or after Y-TZP sintering): Control (no coating), Colloidal Silica/Sintering, Sintering/Colloidal Silica, Glaze/Sintering, Sintering/ Glaze. Lithium disilicate (LD) was used as positive control. Except for Y-TZP controls, groups were conditioned with silane before cementation with a self-adhesive resin cement. After 24 hours, the shear bond strength and failure analysis were performed. Also, analysis of specimens' surface was accomplished with SEM-EDX. Kruskal-Wallis and Dunn tests were applied to analyze differences between groups (p⟨0.05).

RESULTS

Overall, the worst and best values of shear bond strength test were control and glaze after sintering groups. Different morphological and chemical aspects were observed in SEM-EDX analysis.

CONCLUSIONS

Coating Y-TZP with colloidal silica showed unsatisfactory results. In 3Y-TZP, the surface treatment associated with the best adhesion values was the application of glaze after zirconia sintering. However, in 5Y-TZP, glaze application can be performed before or after the zirconia sintering to optimize clinical steps.

Recycling CAD/CAM lithium disilicate ceramic: effect of surface treatment and aging on the bond strength to resin cement

PURPOSE

To investigate the effect of recycling of lithium disilicate (LD), surface treatment and thermocycling (TC) on the bond strength (SBS) to resin cement.

MATERIALS AND METHODS

Blocks of LD were made according to the recycling cycle, with 24 blocks for each strategy: Control-conventional sintering; 1R (1 recycling cycle) and 3R (3 recycling cycles). For the recycling groups, blocks were waxed (10x10x3mm), mounted in a silicone ring, poured with investment material, and then residues of sintered LD blocks were pressed by the lost wax technique. The residual LD was reused as described until reach 3R. Afterwards, the blocks were embedded in acrylic resin, sanded and divided (n=15) according to the factors "surface treatment" (HF20s+Silane and HF120s+Silane and Monobond Etch&Prime- MEP) and TC (with/10.000 cycles and without). After surface treatment, cylinders (Ø:2mm) of resin cement were made and submitted to SBS test (100KgF,1mm/min). Data (MPa) were analyzed by 3-way ANOVA, Tukey's test (5%) and Weibull analysis. Failure analysis was performed with stereomicroscope.

RESULTS

ANOVA revealed that all factors were significant (P=.000*). The group 3RMEP(105.09±19.49) presented the highest SBS among the experimental groups. 1RHF20sTc(7.50±1.97) group had the lowest SBS, similar to the CHF20sTc(15.69±3.77), 1RHF20s(15.12±3.03), 1RHF120sTc(14.60±3.43) and 3RHF20sTc(15.65±0.97). The Weibull modulus and characteristic strength varied among the experimental groups (P=0.0). Failure analysis revealed adhesive and mixed types.

CONCLUSION

The recycling of DL ceramics increases the SBS to resin cement when the ceramic is treated with HF120s+S or MEP.

Different Dentin Conditioning Protocols on Bond Strength of a Bioceramic Root Canal Filling

Objective

Bioceramic-based sealers, in combination with bioceramic-coated gutta-perchas, have become more commonly used in root canal obturation. The present study aimed to assess the influence of laser-assisted dentin conditioning compared with conventional conditioning protocols on the push-out bond strength (PBS) of a bioceramic-based root canal filling.

Material and Methods

Sixty extracted mandibular premolars with one root canal were instrumented with EndoSequence rotary files up to size 40/0.04. Four types of dentin conditioning protocols were used: 1) 5.25% NaOCl (control), 2) 17% EDTA+5.25% NaOCl, 3) Diode laser-agitated 17% EDTA+5.25% NaOCl, 4) Er,Cr:YSGG laser irradiation+5.25% NaOCl. Teeth were obturated using the single-cone technique with EndoSequence BC sealer+BC points (EBCF). After having obtained 1-mm-thick horizontal slices from the apical, middle and coronal root thirds, push-out test was carried out, and failure modes were determined. The data were analyzed by two-way analysis of variance and Tukey's test with a significance level of p<0.05.

Results

The apical segments showed the highest PBS in all groups (p<0.05). In the apical segments, EDTA+NaOCl and diode laser agitated EDTA increased the PBS compared to the control (p=0.0001) and Er, Cr: YSGG laser (p=0.011 and p=0.027, respectively) groups. Both laser-used groups revealed significantly higher PBS values in the middle and coronal segments than EDTA+NaOCl (p<0.05). The bond failure was predominantly cohesive without any significant difference among the groups (p>0.05).

Conclusions

Laser-assisted dentin conditioning had distinct effects on the PBS of the EBCF at different root segments. Although Er, Cr: YSGG was ineffective in the apical segments, generally, laser-assisted dentin conditioning affected PBS more favorably than conventional irrigation groups, with a more pronounced effect in the diode laser-agitated EDTA group.

Micro-shear bond strength of composite to deep dentin by using mild and ultra-mild universal adhesives

Background

Considering the increasing demand for tooth-colored restorations, this study sought to assess the micro-shear bond strength (μSBS) of composite to deep dentin by using mild and ultra-mild universal adhesives.

Materials and Methods

This in vitro, experimental study evaluated 75 sound third molar teeth randomized into five groups (n = 15) of Clearfil self-etch (SE) Bond (control), Tokuyama Universal Bond (TUB), and All-Bond Universal (ABU) in etch and rinse (E and R) and SE modes. The occlusal surfaces of the teeth were trimmed to expose deep dentin at 0.5 mm distance from the pulp chamber. Adhesives were applied on the dentin surface according to the manufacturers' instructions, and Z350XT composite cylinders were bonded to dentin using Tygon tubes (0.9 mm internal diameter, 2 mm height). After incubation at 37°C and 100% humidity for 24 h, the teeth underwent μSBS test in a universal testing machine. The mode of failure was also determined under a stereomicroscope. Analysis of variance, Bonferroni test, and Fisher's exact test were applied for data analysis (alpha = 0.05).

Results

TUB in E and R mode (13.78 MPa) and ABU in SE mode (7.85 MPa) yielded the maximum and minimum μSBS values, respectively. No significant difference was noted in μSBS of tested universal adhesives in E and R and SE modes to deep dentin (P > 0.05). TUB yielded significantly higher μSBS than ABU (P < 0.05). No significant difference was noted in mode of failure of the groups (P > 0.05).

Conclusion

Type of adhesive affected the μSBS but etching mode of universal adhesives had no significant effect on their μSBS to deep dentin.

Influence of Different Surface Pretreatments of Zirconium Dioxide Reinforced Lithium Disilicate Ceramics on the Shear Bond Strength of Self-Adhesive Resin Cement

Aim

To analyze the influence of different surface pretreatments of zirconium dioxide reinforced lithium disilicate ceramics on the shear bond strength of self-adhesive resin cement.

Materials and methods

Eighty-four zirconium reinforced lithium disilicate disc Vita suprinity (Vita Zahnfabrick, Bad Säckingen, Germany) 14x12x2 mm specimens were fabricated according to the manufacturer's recommendations. The specimens were embedded in acrylic resin blocks and randomly divided in seven groups (n=12/each) accorrding to the treatment: Group 1- 10% hydrofluoric acid; Group 2- silane; Group 3- hydrofluoric and silane; Group 4- sandblasting with silane; Group 5- Er: YAG laser+ silane; Group 6- Nd: YAG laser + silane; and the control group, in which the specimens were not treated. Round shape composite discs (Filtek Bulk fill, 3M ESPE, St.Paul, Minnesota, USA) with 3.5 mm diameter, were made for shear bond strength testing, and then cemented to the ceramic sample surface using composite cement (RelyX U200 Automix, 3M ESPE, Neuss, Germany). After cementing the composite disc on the sample, the samples were subjected to shear bond strength test of 10 N with a “stress rate” of 1 MPa / s. To determine the nature of the fracture (adhesive, cohesive or adhesive-cohesive), the broken samples were examined under a stereomicroscope. The ANOVA test and the Tukey test were used to compare the values ​​of the bond strength characteristics between different types of materials. All tests were performed with a significance level of α = 0.05.

Results

There was a significant difference in the shear bond strength of self-adhesive cement to dental lithium-disilicate ceramics reinforced with zirconium dioxide after different preparation protocols (p<0, 05). The treatment of lithium disilicate ceramics reinforced with zirconium dioxide by silanization, sandblasting + silanization, Nd: YAG + silanization resulted in significantly higher bond strength compared to the control group. There was statistically higher bond strength of self-adhesive cement after pretreatment of lithium disilicate ceramics Nd: YAG + silanization compared to Er: YAG + silanization (p <0.05). Adhesive fracture dominated in the control group, sandblasting + silanization group, and in the laser groups, while mixed fracture dominated in other groups.

Conclusion

Under the limitations of this study, the Nd:YAG irradiation with silanization could be used as pretreatment for providing greater shear bond strength of self-adhesive resin cement to zirconium reinforced lithium disilicate.

Shear bond strength of APC Plus adhesive coated appliance system to enamel in wet and dry conditions: An in vitro study

OBJECTIVE

It is claimed that a hydrophilic primer, called the moisture insensitive primer (MIP), can be used with both dry and wet enamel surfaces. This study sought to assess the shear bond strength (SBS) of APC Plus adhesive coated appliance system to enamel using MIP in wet and dry conditions.

MATERIALS AND METHODS

This in vitro experimental study evaluated 24 extracted maxillary premolars with intact buccal enamel. The teeth were randomly divided into two groups (n=12), and APC Plus premolar brackets were bonded to their buccal surface using moisture insensitive primer (MIP) under wet and dry enamel conditions. The SBS values were measured by a universal testing machine. The adhesive remnant index (ARI) score was also determined under a stereomicroscope. Data were analyzed using t-test and Mann-Whitney test at P<0.05 level of significance.

RESULTS

The SBS in wet condition was significantly lower than that in dry condition (mean value of 18.37MPa versus 25.5MPa, P<0.001). The two groups had no significant difference regarding the ARI scores (P>0.05). However, in both groups, less adhesive was left on the tooth surface. This suggests that bond failure occurred at the adhesive-enamel interface.

CONCLUSIONS

APC Plus adhesive coated appliance system in combination with hydrophilic MIP can be effective in clinical conditions with high risk of moisture contamination.

Effects of different types of laser etching versus phosphoric acid etching on shear bond strength of metal brackets to human enamel: A systematic review and meta-analysis of in vitro studies

INTRODUCTION

This study aimed to assess the effect of different types of laser etching versus phosphoric acid etching on shear bond strength (SBS) of metal brackets to human enamel.

MATERIALS AND METHODS

In this systematic review and meta-analysis, relevant articles published until the end of October 2019 were retrieved from PubMed, ISI Web of Science, Scopus, Embase, and Cochrane Library. The inclusion criteria were in vitro studies on the effect of laser on SBS of metal brackets to the enamel in comparison with acid-etching, and studies published in English to the end of October 2019. After assessing the eligibility criteria and quality, a total of 18 studies were statistically analysed using STATA software.

RESULTS

The SBS of 554 human tooth specimens in the test group (subjected to irradiation of different laser types) was compared with the SBS of 313 tooth specimens in the control group (etched with phosphoric acid). The meta-analysis showed that laser etching decreased the SBS of brackets by 1.39MPa, compared with phosphoric acid etching, and this reduction was statistically significant (P<0.05). The Er:YAG group, however, showed 0.6MPa higher SBS than phosphoric acid etching group, but this increase was not statistically significant.

CONCLUSION

Laser etching yields lower SBS than acid etching; even though different laser types have different effects on SBS. Thus, the conventional acid-etching technique is still recommended for enamel etching prior to the bonding of orthodontic metal brackets.

The Effect of Surface Pretreatment and Water Storage on the Bonding Strength of a Resin Composite Cement to Modified PEEK

The bonding quality of bonding to polyether ether ketone (PEEK) after different surface treatments and adhesive regimens was assessed through shear bond strength.

MATERIALS AND METHODS

Sixty modified PEEK disks were cut out of BioHPP round blanks using CAD-CAM procedures. Disks were subjected to the following surface pretreatments: (A) Sandblasting with alumina (Rocatec) and application of adhesive bonding agent visiolink (control group) (B) Sandblasting with silica-modified alumina (Cojet), application of silane agent Espe Sil, followed by application of adhesive bonding agent Visio-Bond (C) Sandblasting with silica-modified alumina (Cojet), application of silane containing primer-adhesive Clearfil Ceramic Primer, followed by application of adhesive bonding agent visiolink. A dual-curing resin composite cement (combolign) was luted to all treated surfaces. Each group was further divided to subgroups of 10 specimens which were stored in distilled water at 37°C for 150 days without further thermocycling. Specimens were then submitted to shear bond strength testing.

RESULTS

Group (B) was statistically significant different from group (A) (control group). Water storage condition had no significant influence on final bond strength.

CONCLUSIONS

Use of different conditioning protocols had a significant effect on the final bond strength of composite resin cement to PEEK surface. Water storage did not significantly influence bonding.

ELASTOGRAPHIC ANALYSIS OF THE SUPRASPINATUS TENDON IN DIFFERENT AGE GROUPS

OBJECTIVE

To compare the mechanical properties of the supraspinatus tendon in different age groups using Supersonic Shearwave Imaging (SSI) elastography.

METHODS

We evaluated 38 healthy individuals of both genders, 20 being in the range of 20 to 35 years and 18 being over 60 years. The shear modulus of the supraspinatus tendon was measured by SSI elastography, always on the right side. Means between age groups were compared and statistically analyzed using the Shapiro-Wilk normality test followed by the student's t-test and were established as a statistically significant value of p ≤ 0.05.

RESULTS

A statistically significant difference was observed when the mean values of the shear modulus of the supraspinatus tendon of young adults (23.98 ± 9.94 KpA) were compared with those of older adults (17.92 ± 6.17 KpA).

CONCLUSION

We found a difference between the means of the shear modulus measured by the SSI elastography, showing a significant decrease of the shear modulus with the chronological age progression. Level of Evidence III, Diagnostic Studies - Investigating a Diagnostic Test.

Microshear Bond Strength of Different Adhesive Systems to Dentin

Objectives:

The aim of this study was to compare the microshear bond strength (μSBS) of various adhesive systems to dentin.

Materials and Methods:

In this in vitro experimental study, 60 sound human third molars were divided into four groups. Dentin discs were prepared of middle-third dentin measuring 4 mm in diameter and 2 mm in thickness. Dentin surfaces were bonded with one of the four types of adhesives: (A) Single Bond (3M ESPE), Scotchbond Universal (3M ESPE) in etch and rinse (B) and self-etch (C) modes and (D) Clearfil SE Bond (Kuraray Noritake Dental). After the application of adhesive systems according to the manufacturers’ instructions, composite cylinders (Vit-l-escence) were bonded to dentin surfaces. The μSBS test was performed using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with one-way ANOVA and Tukey’s test (α=0.05).

Results:

The μSBS was the highest in self-etch Scotchbond Universal (15.8±6.08 MPa) followed by Clearfil SE Bond (15.24±4.6 MPa), etch and rinse Scotchbond Universal (11.68±4.07MPa) and Single Bond (11.24±3.74 MPa). A significant difference was only found between Single Bond and etch and rinse Scotchbond Universal groups (P=0.04).

Conclusion:

Based on the results of this study, application of Scotchbond Universal in self-etch mode provides a reliable bond to dentin.

Shear Bond Strength of Molar Tubes to Enamel Using an Orthodontic Resin-Modified Glass Ionomer Cement Modified with Amorphous Calcium Phosphate

Objectives:

This study aimed to assess the shear bond strength (SBS) of molar tubes to the enamel surface of molar teeth using a resin-modified glass ionomer (RMGI) cement modified with amorphous calcium phosphate (ACP).

Materials and Methods:

In this in-vitro study, 60 extracted human third molars were randomly divided into four groups for bonding of molar tubes to the enamel surface. Fuji Ortho LC and Fuji Ortho LC modified with ACP (1.55 wt%) were used in groups 1 and 2, respectively. In group 3, the enamel surface was sandblasted, and bonding was then performed using Fuji Ortho LC glass ionomer modified with ACP. In group 4, molar tubes were conventionally bonded using Transbond XT composite. The SBS was measured using a universal testing machine.

Results:

The mean SBS of groups 1 to 4 was 10.22, 6.88, 9.4, and 13.68 MPa, respectively. Only the SBS of group 1 was not significantly different from that of groups 3 and 4 (P>0.05). Comparison of adhesive remnant index (ARI) scores of the groups revealed significant differences only between groups 1 and 4 (P<0.001) and between groups 1 and 2 (P=0.002).

Conclusion:

The results revealed that the addition of ACP to Fuji Ortho LC significantly decreased the SBS of molar tubes bonded to enamel compared to the conventional resin bonding system. Sandblasting of the enamel surface significantly increased the bond strength. Fuji Ortho LC modified with ACP is recommended for bonding of molar tubes to posterior teeth considering its cariostatic property.

Repair Bond Strength of Composite to Zirconia Ceramic Using Two Types of Zirconia Primers

Objectives

This study aimed to assess the effect of application of two types of zirconia primers on repair bond strength of composite to zirconia ceramic.

Materials and Methods

In this in vitro, experimental study, 60 zirconia blocks were divided into five groups and subjected to the application of Z-Prime Plus (ZPP), Monobond Plus (MBP), Porcelain Bonding Resin (PBR), ZPP followed by PBR (ZPP+PBR) and MBP followed by PBR (MBP+PBR). They were then bonded to Z100 composite. The samples were then immersed in water at 37°C for 24 hours, thermocycled for 1000 cycles between 5-55°C and subjected to shear bond strength (SBS) test. The mode of failure was determined under a stereomicroscope and a scanning electron microscope (SEM).

Results

The mean bond strength was the highest in ZPP+PBR group followed by MBP+PBR, ZPP, PBR and MBP group (22.29±8.86, 15.75±2.81, 12.02±3.24, 3.60±2.92 and 2.92±1.78 MPa, respectively). The effects of type of zirconia primer and use/no use of PBR on SBS were significant (P<0.05). The frequency of adhesive failure in MBP and PBR groups was significantly higher than that in MBP+PBR and ZPP+PBR groups (P<0.05). The cohesive failure was significantly more frequent in ZPP+PBR group than in ZPP, MBP and PBR groups (P<0.05).

Conclusion

Simultaneous application of zirconia primer and PBR is the most efficient technique for repair of all-ceramic zirconia restorations with composite resin.

Comparison of Bond Strength of Acrylic, Composite, and Nanocomposite Artificial Teeth to Heat-Cure Acrylic Denture Base Resin

Objectives:

The present study aimed to evaluate the bond strength of heat-cure denture base resin to newly designed Iranian artificial acrylic teeth.

Materials and Methods:

In this in-vitro experimental study, shear bond strengths of Ivoclar acrylic, Apple composite, and B-Star nanocomposite teeth to heat-cure acrylic denture base resin were compared. A total of 18 samples were selected from each group of teeth. The samples were attached to heat-cure resin according to ISO 10477 standard. For the assessment of bond strength, the samples were placed in a universal testing machine and were subjected to shear forces at a speed of 1 mm/minute to record the fracture load. Descriptive statistics, including frequency, mean, and standard deviation, were calculated using SPSS 20 software. Two-way analysis of variance was used to compare the shear bond strength of the groups with and without monomers and the studied artificial teeth.

Results:

The mean shear bond strengths of Ivoclar acrylic teeth were 392.22±23.76 MPa and 337.11±32.18 MPa with and without adding monomers to the tooth surface, respectively. The mean shear bond strengths were 250.44±29.84 MPa and 238.33±27.28 MPa (without monomers) and 438.33±24.16 MPa and 311.56±32.78 MPa (with monomers) for Apple composite and B-Star nanocomposite artificial teeth, respectively.

Conclusion:

The greatest shear bond strength was attributed to Ivoclar acrylic teeth followed by Apple composite and B-Star nanocomposite artificial teeth. Addition of monomers to the tooth surface significantly strengthened the shear bonding of acrylic base resin to the teeth.

Microshear Bond Strength of Scotchbond Universal Adhesive to Primary and Permanent Dentin: A Six-Month in Vitro Study

Objectives:

This study aimed to assess the microshear bond strength (MSBS) of Scotchbond Universal adhesive, used in self-etch and etch-and-rinse modes, to primary and permanent dentin at 24 hours and six months.

Materials and Methods:

A total of 88 composite micro-cylinders were divided into eight groups (n=11) as follows: (A) Etch-and-rinse, 24 hours, primary dentin; (B) Self-etch, 24 hours, primary dentin; (C) Etch-and-rinse, six months, primary dentin; (D) Self-etch, six months, primary dentin; (E) Etch-and-rinse, 24 hours, permanent dentin; (F) Self-etch, 24 hours, permanent dentin; (G) Etch-and-rinse, six months, permanent dentin; (H) Self-etch, six months, permanent dentin. The MSBS was measured by a testing machine at a crosshead speed of 0.5 mm/minute. Data were analyzed using three-way analysis of variance (ANOVA).

Results:

The mean MSBS was 12.3±2.3 MPa in A, 18.8±4.1 MPa in B, 11.9±3.7 MPa in C, 16±2.9 MPa in D, 19.1±2.7 MPa in E, 22.8±4.1 MPa in F, 16.2±2.6 MPa in G, and 17.2±4.4 MPa in H. In the self-etch mode, the MSBS was significantly higher than that in the etch-and-rinse mode (P<0.001). The MSBS in permanent teeth was significantly higher than primary teeth (P<0.001). At six months, the MSBS significantly decreased in all groups (P<0.001).

Conclusion:

The micro-shear bond strength of Scotchbond Universal adhesive decreases over time and depends on the type of tooth and the mode of application of the adhesive.

Shear Bond Strength of Self-Adhesive Flowable Composite, Conventional Flowable Composite and Resin-Modified Glass Ionomer Cement to Primary Dentin

Objectives:

This study aimed to compare the shear bond strength (SBS) of self-adhesive and conventional flowable composites and resin-modified glass-ionomer cement (RMGIC) to primary dentin.

Materials and Methods:

In this in vitro, experimental study, the buccal surface of 48 primary canine and first molar teeth was longitudinally sectioned to expose dentin. The teeth were randomly divided into three groups (n=16) of 37.5% phosphoric acid+ OptiBond+ Premise Flow composite (group 1), Vertise Flow composite (group 2) and RMGIC (group 3). A plastic cylindrical mold was placed on the exposed dentin and filled with restorative materials. The samples were then immersed in distilled water at 37°C for 24 hours, subjected to 1000 thermal cycles between 5–55°C and underwent SBS test. The mode of failure was determined under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s test.

Results:

A significant difference was noted in SBS of the groups (P<0.05). The SBS of conventional flowable composite was significantly higher that of RMGIC and self-adhesive flowable composite (P<0.05). The difference in SBS of RMGIC and self-adhesive flowable composite was not significant (P>0.05). Failure at the dentin-restoration interface (adhesive failure) had the highest frequency in groups 1 and 2. The frequency of adhesive failure was 100% in group 3.

Conclusion:

Within the limitations of this study, the conventional flowable composite yielded the highest SBS to primary dentin. Self-adhesive flowable composite and RMGIC showed the lowest SBS with no significant difference with each other.

Effect of Storage Time of a Ceramic Primer on Microshear Bond Strength to Zirconia

OBJECTIVE

This study assessed the effect of shelf life of a ceramic primer containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) monomer on microshear bond strength of zirconia ceramic to composite resin.

MATERIALS AND METHODS

Sixty-four sintered zirconia samples (1.5×5×7 mm) were pretreated with Clearfil Ceramic Primer (CCP) at baseline and after one, two and six months of storage at 6°C. Composite cylinders were fabricated using Tygon tubes (1 mm height, 0.7 mm diameter) and placed on treated zirconia blocks, light-cured and subjected to microshear bond strength test. Mode of failure was determined under a stereomicroscope. Fourier-transform infrared spectroscopy (FTIR) was performed at each storage time point. Data were analyzed using one-way ANOVA and Tukey's test.

RESULTS

Significant differences were noted in microshear bond strength after six months of storage compared to baseline (P<0.05). Significant differences were noted in FTIR spectra at the four time points (P<0.05).

CONCLUSIONS

The effectiveness of one-component ceramic primer in bonding to zirconia was significantly affected by the storage of this material in a time-dependent manner. Visible new peaks and changes in FTIR spectra over time indicated alterations in the composition of ceramic primer affecting its shelf life.

Effect of Cyclic Loading on Shear Bond Strength of Orthodontic Brackets: An In Vitro Study

OBJECTIVES

In clinical conditions, orthodontic brackets are exposed to periodic stresses mainly induced by mastication and intraoral forces. The objective of the present study was to evaluate the effects of cyclic loading to simulate masticatory forces on shear bond strength (SBS) of metal brackets bonded to teeth using self-etch and total-etch bonding systems.

MATERIALS AND METHODS

Eighty-four caries- and crack-free bovine mandibular incisors were selected and randomly assigned to two groups based on the type of bonding system. After bonding, all samples were thermocycled (500 cycles) followed by cyclic loading of the half of the specimens in each group by applying 40 N load with 2 Hz frequency for 10,000 cycles. The SBS was measured using a universal testing machine. The adhesive remnant index (ARI) score was calculated subsequently. Data were analyzed using Kolmogorov-Smirnov test, two-way ANOVA and Mann-Whitney test.

RESULTS

The SBS was 10.09±3.78 MPa and 14.44±6.06 MPa for self-etch and total-etch bonding systems in cyclic loading group, respectively. The SBS was 9.43±5.3 MPa and 11.31±5.42 MPa in self-etch and total-etch groups without cyclic loading, respectively. Cyclic loading did not cause any significant difference in SBS (P>0.05). The ARI scores of the groups were significantly different (P<0.05).

CONCLUSIONS

The present results demonstrated that low masticatory forces at 10,000 cycles did not have a significant impact on bracket-adhesive SBS; however, they significantly changed the ARI score. Even though the total-etch bonding system yielded higher SBS than the self-etch system, the performance of both was clinically acceptable.

Comparison of the Dentin Bond Strength of Two Self-Etch Adhesives After Prolonged Air-Drying and Additional Light-Curing

OBJECTIVES

It has been reported that the water, solvents, or the primer incorporated into adhesive resins decrease the polymerization, compromise the mechanical properties, reduce the bond strength, and lead to a poor bonding performance of self-etch adhesives. This article evaluated the effect of air-drying and light-curing duration of self-etch adhesives on the micro-shear bond strength between composite resin and dentin.

MATERIALS AND METHODS

A total of 120 extracted sound human third molars were randomly divided into twelve groups (n=10). The occlusal dentin in each tooth was exposed. Clearfil SE Bond (CSEB) and Clearfil S3 Bond (CS3B) were used according to the manufacturer's instructions, followed by air-drying for 3 and 10 seconds in different groups. The adhesives were light-cured for 10, 20 and 40 seconds in different subgroups. Next, the composite resin (Clearfil AP-X) was placed on the dentin surface and was polymerized for 40 seconds. The micro-shear bond strength values were determined using a universal testing machine, and the results were statistically analyzed by three-way ANOVA and Tukey's post-hoc test (α=0.05).

RESULTS

CSEB exhibited a significantly higher dentin bond strength than CS3B. Increasing the curing time of CSEB resulted in an increase in the bond strength, whereas an increase in the air-drying time did not affect the bond strength of the two adhesives.

CONCLUSIONS

Within the limitations of this study, an increase in the curing time improved the bond strength of CSEB, whereas the air-drying time did not affect the bond strength of the evaluated adhesives.

Effect of Self-Adhesive and Separate Etch Adhesive Dual Cure Resin Cements on the Bond Strength of Fiber Post to Dentin at Different Parts of the Root

OBJECTIVES

Bonding of fiber posts to intracanal dentin is challenging in the clinical setting. This study aimed to compare the effect of self-adhesive and separate etch adhesive dual cure resin cements on the bond strength of fiber post to dentin at different parts of the root.

MATERIALS AND METHODS

This in-vitro experimental study was conducted on 20 single-rooted premolars. The teeth were decoronated at 1mm coronal to the cementoenamel junction (CEJ), and the roots underwent root canal treatment. Post space was prepared in the roots. Afterwards, the samples were randomly divided into two groups. In group 1, the fiber posts were cemented using Rely X Unicem cement, while in group 2, the fiber posts were cemented using Duo-Link cement, according to the manufacturer's instructions. The intracanal post in each root was sectioned into three segments of coronal, middle, and apical, and each cross-section was subjected to push-out bond strength test at a crosshead speed of 1mm/minute until failure. Push-out bond strength data were analyzed using independent t-test and repeated measures ANOVA.

RESULTS

The bond strength at the middle and coronal segments in separate etch adhesive cement group was higher than that in self-adhesive cement group. However, the bond strength at the apical segment was higher in self-adhesive cement group compared to that in the other group. Overall, the bond strength in separate etch adhesive cement group was significantly higher than that in self-adhesive cement group (P<0.001).

CONCLUSIONS

Bond strength of fiber post to intracanal dentin is higher after the use of separate etch adhesive cement compared to self-adhesive cement.

Effect of Quaternary Ammonium Salt on Shear Bond Strength of Orthodontic Brackets to Enamel

OBJECTIVES

This study sought to assess the effect of quaternary ammonium salt (QAS) on shear bond strength of orthodontic brackets to enamel.

MATERIALS AND METHODS

In this in vitro experimental study, 0, 10, 20 and 30% concentrations of QAS were added to Transbond XT primer. Brackets were bonded to 60 premolar teeth using the afore-mentioned adhesive mixtures, and the shear bond strength of the four groups (n=15) was measured using a universal testing machine. After debonding, the adhesive remnant index (ARI) score was determined under a stereomicroscope. Data were analyzed using one-way ANOVA.

RESULTS

The mean and standard deviation of shear bond strength of the control and 10%, 20% and 30% groups were 23.54±6.31, 21.81±2.82, 20.83±8.35 and 22.91±5.66 MPa, respectively. No significant difference was noted in shear bond strength of the groups (P=0.83). Study groups were not different in terms of ARI scores (P=0.80).

CONCLUSIONS

The results showed that addition of QAS to Transbond XT primer had no adverse effect on shear bond strength of orthodontic brackets.

Comparison of Bond Strength of Metal and Ceramic Brackets Bonded with Conventional and High-Power LED Light Curing Units

OBJECTIVES

The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface.

MATERIALS AND METHODS

Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer's instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI).

RESULTS

The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P<0.001). The ARI score was not significantly influenced by the interaction between the type of LED unit and bracket.

CONCLUSIONS

The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.

Effect of Addition of Curcumin Nanoparticles on Antimicrobial Property and Shear Bond Strength of Orthodontic Composite to Bovine Enamel

OBJECTIVES

This study sought to assess the effect of curcumin nanoparticles (curcNPs) on antimicrobial property and shear bond strength (SBS) of orthodontic composite to bovine enamel.

MATERIALS AND METHODS

In this in vitro, experimental study, 1%, 5% and 10% curcNPs were added to Transbond XT composite. Stainless steel brackets were bonded to 48 sound bovine incisors in four groups (n=12) using composite containing 0% (control), 1%, 5% and 10% curcNPs. The bracket-tooth SBS was measured by a universal testing machine. The adhesive remnant index (ARI) score was calculated after debonding using a stereomicroscope. Also, 180 discs were fabricated of the four composites; 108 were subjected to eluted component test, 36 were used for disc diffusion test and 36 were used for biofilm test to assess their antimicrobial activity against Streptococcus mutans, Streptococcus sanguinis and Lactobacillus acidophilus.

RESULTS

The highest and lowest SBS belonged to control and 10% curcNP groups, respectively. The difference in SBS was significant among the four groups (P=0.008). The SBS of control group was significantly higher than that of 10% curcNPs (P=0.006). The four groups were not significantly different in terms of ARI score (P>0.05). Growth inhibition zones were not seen in any group. In biofilm test, the colony counts of all bacteria significantly decreased by an increase in percentage of curcNPs. Colony count significantly decreased only at 30 days.

CONCLUSIONS

At 1% concentration, curcNPs have significant antimicrobial activity against cariogenic bacteria with no adverse effect on SBS. However, insolubility of curcNPs remains a major drawback.

In-Vitro Evaluation of the Effect of Herbal Antioxidants on Shear Bond Strength of Composite Resin to Bleached Enamel

OBJECTIVES

A reduction in bond strength of composite to bleached enamel has been reported immediately after bleaching treatment. Application of some antioxidant agents may decrease the adverse effects of whitening agents on bond strength and enhance composite bond to enamel. This study aimed to assess the effect of green tea, sodium ascorbate, sage and grape seed extract on bond strength of composite to bleached enamel.

MATERIALS AND METHODS

In this in-vitro study, 90 human enamel surfaces were randomly divided into six groups as follows (n=15): G1, no bleaching; G2, bleaching with 40% hydrogen peroxide (HP); G3, HP+1000 μmol epigallocatechin gallate (EGCG) for 10 minutes; G4, HP+10% sodium ascorbate for 10 minutes; G5, HP+10% sage for 10 minutes and G6, HP+5% grape seed extract for 10 minutes. The specimens were bonded to composite in all groups. The shear bond strength of specimens was measured in Megapascals (MPa). Data were analyzed using one-way ANOVA and Tukey's HSD test (α=0.05).

RESULTS

The highest and the lowest mean shear bond strength values were observed in group 1 (22.61±3.29MPa) and group 2 (5.87±1.80MPa), respectively. The reduction in bond strength in group 2 was greater than that in other groups (P<0.001). No significant difference was found among groups 1, 3, 4, 5 and 6 (P>0.05).

CONCLUSIONS

All the herbal antioxidants used in this study equally compensated for the reduced bond strength of composite to bleached enamel.

Shear Bond Strength of Orthodontic Brackets to Tooth Enamel After Treatment With Different Tooth Bleaching Methods

Background:

Bleaching treatments decrease shear bond strength between orthodontic brackets and teeth; although definite results have not been reported in this regard.

Objectives:

This study determined the effects of different bleaching protocols on the shear bond strength of orthodontic brackets to teeth.

Materials and Methods:

This experimental study was performed in Iran. Forty-eight extracted human premolars were randomly assigned into four groups. In the control group, no bleaching treatment was performed. In groups 2 - 4, the bleaching procedures were performed using carbamide peroxide 45%, carbamide peroxide 20% and diode laser, respectively. Two weeks later, brackets were bonded to teeth and thermocycled. The shear bond strengths of the brackets to the teeth were measured. Data was analyzed by one-way ANOVA and Dunnett post-hoc test.

Results:

Shear bond strength of the brackets to the teeth were 10.54 ± 1.51, 6.37 ± 0.92, 7.67 ± 1.01 and 7.49 ± 1.19 MPa, in groups 1 - 4, respectively. Significant differences were found between control group and all other groups (P < 0.001); and also between groups 2 and 3 (P < 0.05). No significant differences were found between the other groups.

Conclusions:

The bleaching procedures using 20% carbamide peroxide and 45% carbamide peroxide and diode laser significantly decreased shear bond strength of brackets to the teeth. 45% carbamide peroxide had a more significant effect on bond strength compared to 20% carbamide peroxide. The difference in bond strength was not significant between laser group and either carbamide peroxide groups.

Shear Bond Strength of a Resin Cement to Different Alloys Subjected to Various Surface Treatments

OBJECTIVES

Micromechanical retention of resin cements to alloys is an important factor affecting the longevity of metal base restorations. This study aimed to compare the bond strength and etching pattern of a newly introduced experimental etchant gel namely Nano Met Etch with those of conventional surface treatment techniques for nickel-chrome (Ni-Cr) and high noble alloys.

MATERIALS AND METHODS

A total of 120 discs (8×10×15 mm) were cast with Ni-Cr (n=20), high noble BegoStar (n=50) and gold coin alloys (n=50). Their Surfaces were ground with abrasive papers. Ni-Cr specimens received sandblasting and etching. High noble alloy specimens (BegoStar and gold coin) received sandblasting, sandblasting-alloy primer, etching, etch-alloy primer and alloy primer alone. Cylindrical specimens of Panavia were bonded to surfaces using Tygon tubes. Specimens were subjected to micro-shear bond strength testing after storing at 37°C for 24 hours.

RESULTS

In gold coin group, the highest bond strength was achieved after sandblasting (25.82±1.37MPa, P<0.001) and etching+alloy primer (26.60 ± 5.47 MPa, P<0.01). The lowest bond strength belonged to sandblasting+alloy primer (17.79±2.96MPa, P<0.01). In BegoStar group, the highest bond strength was obtained in the sandblasted group (38.40±3.29MPa, P<0.001) while the lowest bond strength was detected in the sandblast+ alloy primer group (15.38±2.92MPa, P<0.001). For the Ni-Cr alloy, bond strength in the etched group (20.79±2.01MPa) was higher than that in the sandblasted group (18.25±1.82MPa) (P<0.01).

CONCLUSIONS

For the Ni-Cr alloy, etching was more efficient than sandblasting but for the high noble alloys, higher Au content increased the efficacy of etching.

Comparison of Shear Bond Strength of Composite to Stainless Steel Crowns Using Two Mechanical Surface Treatments and Two Bonding Systems

OBJECTIVES

This study aimed to compare the shear bond strength (SBS) of composite to stainless steel crowns (SSC) using two mechanical surface treatments (MSTs) and two bonding systems.

MATERIALS AND METHODS

Eighty-four SSCs were divided into six groups of 14; Group1: No MST+Scotchbond Universal adhesive (N+U), Group 2: Surface roughening by a diamond bur+Scotchbond Universal adhesive (R+U), Group 3: Sandblasting+Scotchbond Universal adhesive (S+U), Group 4: No MST+Alloy Primer+Clearfil SE Primer and Bond (N+A), Group 5: Surface roughening by a diamond bur+Alloy Primer+Clearfil SE Primer and Bond (R+A), Group 6: Sandblasting+Alloy Primer+Clearfil SE Primer and Bond (S+A). After MST and bonding procedure, composite cylinders were bonded to the lingual surface of SSCs, then the SBS of composite to SSCs was measured using a universal testing machine following thermocycling.

RESULTS

The SBS of groups R+U and S+U was significantly higher than that of group N+U. No significant difference was noted in SBS of groups R+U and S+U. The SBS of group S+A was significantly higher than that of groups N+A and R+A. No significant difference was noted in the SBS of groups N+A and R+A (P>0.05).

CONCLUSIONS

In Scotchbond Universal adhesive groups, sandblasting and surface roughening by diamond bur significantly increased the SBS of composite to SSCs compared to no MST. In Alloy Primer groups, sandblasting significantly increased the SBS of composite to SSC compared to surface roughening with diamond bur and no MST.

Effect of an Extra Hydrophobic Resin Layer on Repair Shear Bond Strength of a Silorane-Based Composite Resin

OBJECTIVES

Composite repair is a minimally invasive and conservative approach. This study aimed to evaluate the effect of an additional hydrophobic resin layer on the repair shear bond strength of a silorane-based composite repaired with silorane or methacrylate-based composite.

MATERIALS AND METHODS

Sixty bar-shaped composite blocks were fabricated and stored in saline for 72 hours. The surface of the samples were roughened by diamond burs and etched with phosphoric acid; then, they were randomly divided into three groups according to the repairing process: Group 1: Silorane composite-silorane bonding agent-silorane composite; group 2: Silorane composite-silorane bonding agent-hydrophobic resin-silorane composite, and group 3: Silorane composite-silorane bonding agent-hydrophobic resin methacrylate-based composite. Repairing composite blocks measured 2.5×2.5×5mm. After repairing, the samples were stored in saline for 24 hours and thermocycled for 1500 cycles. The repair bond strength was measured at a strain rate of 1mm/min. Twenty additional cylindrical composite blocks (diameter: 2.5mm, height: 6mm) were also fabricated for measuring the cohesive strength of silorane-based composite. The data were analyzed using One-way ANOVA and the post hoc Tukey's test (α=0.05).

RESULTS

Cohesive bond strength of silorane composite was significantly higher than the repair bond strengths in other groups (P<0.001). The repair bond strength of group 3 was significantly higher than that of group 1 (P=0.001).

CONCLUSION

Application of an additional hydrophobic resin layer for repair of silorane-based composite with a methacrylate-based composite enhanced the repair shear bond strength.

Effect of Intermediate Agents and Preheated Composites on Repair Bond Strength of Silorane-Based Composites

OBJECTIVES

Repairing composite restorations is a challenging procedure especially when two different types of composites are used. This study aimed to compare the repair strength of silorane-based composite (SC) (Filtek P90) with that of preheated SC, methacrylate composite (MC)(Z250), flowable MC (Filtek Supreme Plus) and different adhesive/composite combinations.

MATERIALS AND METHODS

Eighty-four SC specimens were fabricated and randomly divided into seven groups (G). In the control group (G7), SC was bonded immediately to SC. The other specimens were water-aged for two months and were then roughened, etched and repaired with the following materials: G1) Silorane Adhesive Bond (SAB)/SC; G2) Preheated SC; G3) SAB/MC; G4) Adper Single Bond (SB)/MC; G5) Flowable MC/MC; G6) Preheated MC. After water storage and thermocycling, the repaired specimens were subjected to shear bond strength testing. The data were analyzed using ANOVA and Tukey's test.

RESULTS

Preheated SC and MC, flowable MC and SAB/SC resulted in bond strength comparable to that of the control group. Preheated SC showed significantly higher bond strength when compared to SAB/MC (P=0.04) and SB/MC (P<0.001). Bond strength of SB/MC was significantly lower than that of the other groups (P<0.05), except for SAB/SC and SAB/MC.

CONCLUSION

All repairing materials except for SB/MC resulted in bond strength values comparable to that of the control group. Repair with preheated SC yielded the highest bond strength.

Effect of Four Methods of Surface Treatment on Shear Bond Strength of Orthodontic Brackets to Zirconium

OBJECTIVES

Providing reliable attachment between bracket base and zirconia surface is a prerequisite for exertion of orthodontic force. The purpose of the present study was to evaluate the effect of four zirconium surface treatment methods on shear bond strength (SBS) of orthodontic brackets.

MATERIALS AND METHODS

One block of zirconium was trimmed into four zirconium surfaces, which served as our four study groups and each had 18 metal brackets bonded to them. Once the glazed layer was removed, the first group was etched with 9.6% hydrofluoric acid (HF), and the remaining three groups were prepared by means of sandblasting and 1W, and 2W Er: YAG laser, respectively. After application of silane, central incisor brackets were bonded to the zirconium surfaces. The SBS values were measured by a Dartec testing machine with a crosshead speed of 1 mm/min. Data were analyzed using one-way ANOVA and Tukey's HSD for multiple comparisons.

RESULTS

The highest SBS was achieved in the sandblasted group (7.81±1.02 MPa) followed in a descending order by 2W laser group (6.95±0.87 MPa), 1W laser group (6.87±0.92 MPa) and HF acid etched group (5.84±0.78 MPa). The differences between the study groups were statistically significant except between the laser groups (P<0.05).

CONCLUSION

In terms of higher bond strength and safety, sandblasting and Er: YAG laser irradiation with power output of 1W and 2W can be considered more appropriate alternatives to HF acid etching for zirconium surface treatment prior to bracket bonding.

Effect of Saliva pH on Shear Bond Strength of Orthodontic Brackets

OBJECTIVES

The purpose of this study was to evaluate the effect of salivary pH on the shear bond strength (SBS) of orthodontic brackets to tooth surface.

MATERIALS AND METHODS

Eighty intact premolars were randomly divided into four groups of 20. After bonding a bracket on each tooth, the groups one to four were stored in artificial saliva at a pH of 3.8, 4.8, 5.8, and 6.8, respectively for two months. The artificial saliva solutions were refreshed weekly. Each tooth was then embedded in an acrylic block so that the crown was exposed and its buccal surface was parallel to the direction of the force during SBS testing. All brackets were debonded using Dartec universal testing machine, and the mean values of SBS in different groups were compared using one-way analysis of variance (ANOVA).

RESULTS

The mean SBS value in group one (pH 3.8) was significantly lower than that in other groups (P<0.05). The differences between other groups were not significant (P>0.05).

CONCLUSION

Decreased salivary pH due to poor oral hygiene and/or frequent consumption of acidic beverages may be responsible for orthodontic bracket bond failure.

Comparison of the Shear Bond Strength of Resin Modified Glass Ionomer to Enamel in Bur-Prepared or Lased Teeth (Er:YAG)

OBJECTIVE

The purpose of this study was to evaluate the effect of Er:YAG laser on the shear bond strength of resin modified glass ionomer (RMGI) to enamel.

MATERIALS AND METHODS

Twenty extracted caries-free human premolars were selected. The teeth were embedded in acrylic resin. The buccal surfaces of each sample were ground to plane enamel with carbonated disc. The teeth were randomly divided in two groups. In the first group, the surfaces were treated by Er:YAG laser (350mJ/10Hz). The second group was prepared by carbide bur. Fuji IX RMGI was adhered to surfaces of the samples in both groups in rod shape. The shear bond strength of samples was measured by a universal testing machine. The results of the two groups were analyzed by T- test.

RESULTS

The means and standard deviations of shear bond strength of the laser-treated group and the bur-treated group were 6.75 ± 1.99 and 4.41 ± 1.62 Mpa, respectively. There is significant difference in the shear bond strength of RMGI between the two groups (P-value=0.01).

CONCLUSION

The laser group showed better results. Er:YAG laser can be an alternative technology in restorative dentistry.

Effect of multiple adhesive coating on microshear bond strength to primary tooth dentin

OBJECTIVE

Multiple adhesive coating is a controversial topic, especially in primary dentition that should be clarified. We evaluated the effect of multiple consecutive adhesive resin coatings on the microshear bond strength (μSBS) of composite resin to primary tooth dentin utilizing a filled (Adper Single Bond Plus) and an unfilled (Adper Single Bond) adhesive resin.

MATERIALS AND METHODS

Thirty extracted primary canines were randomly allocated into two groups based on the adhesive used. Dentin occlusal surfaces were exposed and further polished on 400, 600 and 800-grit silicon-carbide paper. The surfaces were divided into two halves in the labial-lingual orientation. After etching, the adhesives were used either in double coats, or four coats on the halves of the same tooth followed by air evaporation for each layer and finally light curing. Cylinders of composite were bonded to the dentin surfaces. After 24 h shear bond testing was evaluated by Bisco tensile tester. ANOVA, Student t test and paired t test were used for statistical analysis.

RESULTS

The mean (standard deviation) for double coats or four coats in single bond were 31.99 (2.94) and 30.25 (2.69), while they were 29.18 (3.35) and 31.26 (2.07) in single bond plus, respectively. No significant differences were found between the double coated specimens and those receiving four coatings with both adhesives (p>0.05). Micro SBS values of Single Bond double coated specimens were significantly higher than Single Bond Plus (p=0.02). In four-coated specimens, there were no significant differences between Single Bond and Single Bond Plus (p=0.26).

CONCLUSION

Applying four coats of adhesive did not improve the μSBS to primary tooth dentin.

Assessment of Bond Strength between Metal Brackets and Non-Glazed Ceramic in Different Surface Treatment Methods

OBJECTIVE

The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods.

MATERIALS AND METHODS

Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only. In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C.

RESULTS

The difference of tensile bond strength between groups I and III was not significant (P=0.999). However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001). The adhesive remnant index scores between the three groups had statistically significant differences (P<0.001).

CONCLUSION

With the application of scotch bond multi-purpose plus adhesive, we can use phosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramic restorations.