Bond strength of adhesive systems to dentin and enamel—Human vs. bovine primary teeth in vitro

Micro-shear Bond Strength of an Alternative Self-etch Application of "No Wait" Universal Adhesive to Caries-affected and Sound Dentin in Permanent and Primary Teeth

OBJECTIVE

This study aimed to compare the micro-shear bond strength (μSBS) of caries-affected dentin (CAD) and sound dentin (SoD) in primary and permanent teeth using an alternative self-etch application of "no wait" universal adhesive.

METHODS AND MATERIALS

Flat midcoronal dentin surfaces from 72 permanent third molars and 72 second primary molars were distributed randomly into 12 groups according to the substrate SoD and artificially-created CAD (pH cycling for 14 days) and the adhesive system (GLUMA Bond5, a two-step etch & rinse adhesive, GLUMA Bond, a one-step self-etch adhesive, and Tokuyama Universal Bond, a one-step self-etch adhesive) (n=12). Bonded dentin resin discs were put through micro-shear bond strength testing after 10,000 thermocycles. The results were evaluated using two-way ANOVA and the Bonferroni test with a significance level of α = 0.05.

RESULTS

When compared to SoD, the etch & rinse system's test results on artificially created CAD showed a statistically significant poorer bonding performance in both permanent and primary teeth in all groups (p<0.05). While the bond strengths of permanent teeth using total-etch adhesive on sound dentin were statistically significantly higher than those using Tokuyama Universal Bond adhesive (p<0.05), there was no significant difference in sound dentin in primary teeth (p>0.05).

CONCLUSIONS

The etch & rinse system performed the poorest of all adhesive systems on CAD. The Tokuyama Universal Bond's adhesive strength was similar in SoD and CAD on primary teeth. The use of Tokuyama Universal Adhesives can speed up restorative treatment in pediatric dentistry.

[Histological characteristics of bovine dentin using Masson's Trichrome staining]

Objectives

Identify the histological characteristics of bovine dentin using histological technique by decalcification with Masson's Trichrome staining.

Materials and Methods

This was an observational and descriptive study using units of analysis. Bovine teeth were used, which were subjected to a decalcification technique and Masson's trichrome staining. Microscopic observation and registration of the structures was carried out.

Results

In the microscopic observation of the teeth subjected to decalcification, dentin, predentin and the structural organization of the tubular and peritubular dentin were observed. The odontoblasts arranged in a palisade with the odontoblastic process included within the dentinal tubule and the periprocedural space. The presence of interglobular dentin is not observed in areas of coronary dentin. The histomorphological pattern corresponding to dentin-predentin-pulp is arranged in a similar way to human teeth.

Conclusions

Bovine dentin constitutes an ideal substrate for in vitro research work with dental biomaterials, since it presents histological characteristics similar to bovine teeth; the absence of interglobular dentin would not represent a significant difference according to what was observed in this study.

Effect of root perforation repair with mineral aggregate-based cements on the retention of customized fiberglass posts

The purpose of this study was to investigate whether the root perforation repair with mineral aggregate-based cements affects the retention of customized fiberglass posts to bovine intraradicular dentin. Sixty-four bovine mandibular incisors had their root canals endodontically treated and prepared for fiberglass posts luting. Teeth were randomly distributed into four groups (n = 16), according to the cement used for the perforations repair (MTA HP; calcium aluminate cement-CAC; and CAC + calcium carbonate nanoparticles-nano-CaCO₃) and control group (no perforation). The groups were redistributed according to the fiberglass posts luting protocol (n = 8): total-etching (TE) (MTA HP/TE; CAC/TE; CAC + CaCO₃/TE and control/TE) and self-etching (SE) (MTA HP/SE; CAC/SE; CAC + CaCO₃/SE and control/SE). Roots were sectioned into 1.3 mm-thick dentin slices obtaining samples that were submitted to the push-out test in Universal Testing Machine (Instron, Model 4444-0.5 mm/min). The fractured samples were analyzed under stereomicroscope and Scanning Electron Microscope (SEM). CAC/TE and CAC/SE groups had significant difference between the cervical and middle thirds (p < 0.05). When the root thirds were not considered, CAC/SE had the lowest bond strength and differed statistically from CAC/TE and CAC + CaCO₃/TE groups, which had the highest mean bond strength values (p < 0.05). The root perforations repair did not affect the bond strength of resin cement/customized fiberglass posts to bovine dentin. The increase in bond strength is luting protocol dependent.

Etching Patterns of Self-Etching Primers in Relation to Shear Bond Strength on Unground Enamel Samples

It was the intention of the study to evaluate the etching effects of several self-etching primers on unground enamel and their relevance for shear bond strength testing. Seven self-etching primers (Clearfil SE, Futurabond NR, M-Bond, One Coat, Optibond, Transbond SEP+, Xeno III) and a conventional 35% phosphoric gel acid were applied to bovine incisors according to the manufacturer's instructions. All specimens were analyzed by electron microscopy. A visual four-step grading was used for the characterization of the macroscopic (5000×) and microscopic (20,000×) etching patterns. In addition, shear bond strength for all the products was tested with an Instron 3344 after 1000 thermocycles between 5 °C and 55 °C. Statistical analysis was carried out using Kruskal-Wallis with Dunn's post-test and Pearson's correlation coefficient. Very strong etching patterns with well-defined prisms were found for the conventional etching, Transbond SEP+, and to a lesser degree, for Xeno III. Clearfil SE and Futurabond NR revealed moderate etching patterns, and M-Bond, One Coat, and Optibond revealed very weak etching patterns. The bond strength correlated well with the etching patterns. The highest shear strength was obtained with conventional etching and Transbond SEP+, followed by Clearfil SE. Moderate shear bond strengths were found for Xeno III, Futurabond NR, One Coat, and M-Bond, and the lowest were found with Optibond.

Siloranes-Suitability of a Novel Adhesive for Orthodontic Bracket Bonding

Recently, an epoxy-based resin-Filtek Silorane-has been proposed for restorative fillings. It was the aim of the investigation to evaluate the suitability of this novel resin for orthodontic bracket bonding on unground enamel. Shear bond strength was measured for two adhesives-Filtek Silorane, Transbond XT-in combination with steel, ceramic and polymer brackets. For Filtek Silorane etching was performed with the Silorane self-etching primer, as well as phosphoric acid. The Transbond XT samples were etched with phosphoric acid only and served as the control group. All samples were thermo-cycled (1000×, 5-55 °C). Shear testing was carried out with an Instron 3344. In addition, ARI scores were evaluated. The Shear bond strength showed a weak adhesion of Filtek Silorane to unprepared enamel, either with the self-etching primer or the conventional etching (0.87-4.28 MPa). The Shear bond strength of the control group was significantly higher (7.6-16.5 MPa). The ARI scores showed a clear failure at the enamel-adhesive interface for all Filtek Silorane samples. For the combination of Transbond XT and different brackets the failure was found at the adhesive-bracket interface. The novel epoxy-based resin Filtek Silorane is not appropriate for bracket bonding to unprepared enamel.

Is buffalo enamel a suitable substrate for bond strength tests?

Aim

The aim of this study was to compare the bonding strength of dental materials in buffalo (Bubalus bubalis var. kerebau), bovine, and human enamel and the susceptibility of these substrates in acid etching.

Materials and methods

A total of 20 human third molars, 20 bovine incisors, and 20 buffalo incisors were used in a mechanical assay of microshear. The substrates were demineralized via conditioning with 37% phosphoric acid, and the ultra-morphological pattern of each substrate was analyzed by scanning electron microscopy.

Results

The results showed that there was no significant difference in adhesive bonding strength values between buffalo and human enamel (P≥0.05), with a fracture pattern of mixed type for all experimental groups.

Conclusion

The results indicate that buffalo enamel is similar to human dental substrate in tests of adhesive bonding strength and also show a similar behavior in the acid conditioning of the enamel.

Comparison of an Er: YAG laser osteotome versus a conventional drill for the use in osteo- odonto-keratoprosthesis (OOKP)

OBJECTIVES

The osteo-odonto-kerato-prosthesis (OOKP) procedure is a complex, multi-stage, multidisciplinary surgical intervention for the treatment of severe corneal blindness. One step of the OOKP consists of creating a precise hole into a tooth in which an optic cylinder is subsequently inserted; its shape must ensure a perfect watertight fit. The Er: YAG laser (L) used in this study is part of CARLO®, the first laser osteotome that enables surgical planning based on computed tomography data, robot guidance, and a precise execution of laser cuts in teeth and bone tissue, using laser photoablation rather than conventional mechanical methods. The purpose of this study was to assess whether the Er: YAG laser is non-inferior compared to a conventional drill.

METHODS

Thirty-two bovine incisors were grounded to a thickness of 1.5 mm. In 16 teeth, a 3.5 mm hole was drilled progressively into each tooth, using dental burs (B) of increasing diameter that were attached to a fixed drill machine. In the other 16 teeth, a hole was created using an Er: YAG laser at a wavelength of 2.94 µm (Part of CARLO®). In seven teeth of each group, the cylinder was inserted and fixated with polymethylmethacrylate (PMMA) bone cement. In the remaining seven teeth of each group, the cylinder was inserted without fixation material (press-fit). After bonding and drying, all specimens were stored in water until force measurements were recorded using a uniaxial traction machine. The force required to move the optical cylinder out of the hole in the tooth was measured using an Instron 3344 testing system. Scanning electron microscope (SEM) and light microscope (LM) visualization of the holes created with the laser and the drill were performed in two teeth (SEM)/four teeth (LM) per method.

RESULTS

Significant differences (P < 0.001) were found for the following parameters: B PMMA versus B press-fit; B PMMA versus L press-fit; L PMMA versus B press-fit; L PMMA-L press-fit. This shows that PMMA bone cement fixation is superior to press-fit. No significant differences were found between B PMMA-L PMMA (P = 0.93) and B press-fit-L press-fit (P = 0.83). The SEM pictures showed a smoother surface using L.

CONCLUSIONS

The laser cut holes were as strong as bur-drilled holes, although SEM pictures showed a smoother surface of the laser cut holes. Hence, laser osteotomes open the possibility to custom fit the hole exactly to the width of the cylinder, which represents a potential advantage of the laser over the conventional bur. Lasers Surg. Med. 51:531-537, 2019. © 2019 Wiley Periodicals, Inc.

Influence of self-etch all-in-one adhesives on fissure sealant shear bond strength under contaminated enamel conditions

AIM

To determine the influence of two all-in-one self-etching adhesive systems on shear bond strength of a fissure sealant applied under different enamel surface conditions.

METHODS

A total of 180 bovine enamel specimens were randomly distributed to nine experimental groups, defined by the combination of the sealant application technique (using phosphoric acid, or a self-etching water-based adhesive or a self-etching ethanol and water-based adhesive) and enamel surface conditions (dry enamel, saliva or water contaminated enamel). The specimens were submitted to thermocycling prior to the shear bond strength test.

RESULTS

High shear bond strength mean values were obtained with the classic technique for dry enamel (31.47 MPa), statistically similar values were obtained when the sealant was combined with a self-etching water-based adhesive, in dry enamel (32.36 MPa), and when the sealant was combined with a self-etching water-based adhesive in water contaminated enamel (32.62 MPa). Under enamel salivary contamination, the best results were achieved using a water-based adhesive (24.78 MPa).

CONCLUSIONS

In saliva contaminated enamel, the combination of a sealant with a water-based self-etching adhesive can maintain high and satisfactory values of bond strength.

Evaluation of a Fluorescence-aided Identification Technique (FIT) for removal of composite bonded trauma splints

BACKGROUND/AIM

Accurate removal of composite bonded titanium trauma splints (TTS) can be challenging. The aim of this study was to evaluate a Fluorescence-aided Identification Technique (FIT) compared with a conventional light source (CT) for removal of trauma splints regarding loss of tooth substance, residual composite, and time taken.

MATERIALS AND METHODS

Twenty maxillary models with six bovine teeth (13 - 23) were fabricated. An optical three-dimensional impression was taken and a TTS was applied from 12 to 22 with two bonding sites on every tooth under standardized conditions using an etch-and-rinse adhesive and resin composite. Two operators removed 10 splints each (5x FIT and 5x CT). For FIT, a 405 nm light-emitting headlamp was used. Time was recorded. A post-operative scan was superimposed on the pre-operative scan using OraCheck software. A qualitative and quantitative analysis of tooth defects and composite remnants was performed by two operators and statistically analyzed.

RESULTS

Compared with the CT, FIT led to significantly fewer and smaller enamel defects (mean volume: -0.04 mm³ vs -0.33 mm³ ) (P < 0.001), significantly less composite remained (mean volume: 0.02 mm³ vs 0.28 mm³ ) (P < 0.001), and the removal procedure with FIT was significantly quicker (mean: 162 seconds vs 268 seconds) (P < 0.001), CONCLUSIONS: FIT facilitated the removal of composite used to bond trauma splints leading to less time-consuming as well as less invasive treatment. It left fewer composite residues on enamel surfaces.

Effects of regional enamel and prism orientations on bovine enamel bond strength and cohesive strength

This study investigated the regional microtensile bond strength (MTBS) and cohesive strength of bovine enamel. The crowns of bovine incisors were sectioned, either horizontally along incisal and cervical thirds to produce horizontal and tangential segments, or longitudinally along the midline to produce longitudinal segments. Half of the horizontal and longitudinal segments were prepared using a 45° bevel. Then, the differently sectioned enamel surfaces were treated with one- or two-step self-etch adhesives (Clearfil SE Bond or Clearfil S3 Bond) and a composite resin (Clearfil Majesty) was placed. Resin-bonded enamel samples were cut into beams for use in the MTBS tests. Labial horizontal and longitudinal segments of pure enamel beams were prepared for cohesive strength tests. Enamel microstructures were analyzed by scanning electron microscopy. Three-way anova followed by Tukey's post-hoc HSD multiple comparisons procedure showed that a 45° bevel cut did not statistically significantly improve enamel MTBS, which varied with the different regions. The longitudinally sectioned resin-bonded enamel samples had the lowest MTBS, and the horizontal enamel cohesive strength was weaker than that of the longitudinal enamel. The scanning electron microscopy fractographs indicated that rows of parallel prisms were detached from the fractured surfaces. In conclusion, the regional enamel MTBS and the cohesive strength are strongly related to the enamel microstructures and prism orientations.

Er:YAG pre-treatment for bonding of orthodontic bracket: 1 year of in vitro treatment

Objective

The aim of this study was to evaluate in vitro bond strength of metal brackets bonded with: total etch, total etch with erbium: yttrium aluminum garnet laser (Er:YAG) and self-etching adhesive systems, submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment.

Materials and methods

For the study, 80 bovine incisors were randomly divided into 3 experimental groups (n=16 each): XT- acid etching + Transbond XT, XT/Er:YAG- Transbond XT associated with Er:YAG laser irradiation (λ=2.94 μm, 60 mJ, 10 Hz) and SEP- Transbond Plus Self Etching Primer. Samples were submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment. Afterward, the shear bond strength test was performed in a universal test machine at a speed of 0.5mm/min. Samples were evaluated under a stereomicroscope and by scanning electron microscopy for analysis of enamel surface and adhesive remnant index. Data were analyzed using Kruskal–Wallis and Mann–Whitney (with Bonferroni correction) statistical tests.

Results

Statistically significant difference was observed between the groups studied (p<0.05). Groups XT and SEP showed the highest bond strength values, without statistical difference between them, while group XT/Er:YAG showed reduction in bond strength values. Higher frequency of adhesive failures between enamel and adhesive system was verified for groups XT and XT/Er:YAG.

Conclusion

The conventional (XT) and self-etching (SEP) adhesive systems showed mean bond strength values, similar between them, whereas the previous application of Er:YAG laser promoted the lowest bond strength values.

Timing considerations on the shear bond strength of orthodontic brackets after topical fluoride varnish applications

Objectives:

To assess the best temporal association between the application of a fluoride varnish on enamel and bonding procedures.

Materials and Methods:

Eighty mandibular bovine incisors were used. Teeth were divided into 4 groups (20 per group); Groups 1–3 were treated with fluoride varnish (Fluor Protector, Ivoclar Vivadent, Schaan, Liechtenstein), and Group 4 served as control with no pretreatment. Tooth were stored in deionized water (37°C) and subjected to thermal cycling for 400 (Group 1), 800 (Group 2), and 2500 (Group 3) cycles corresponding, respectively, to 15, 30, and 90 days in order to simulate the three different timing of bracket bonding. Shear bond strength (SBS) was measured using an Instron Universal Testing machine. Tooth surfaces were examined under a stereomicroscope at 10× magnification to assess the amount of adhesive remnant index (ARI). One-way analysis of variance (ANOVA) and Tukey's honestly significant difference post-hoc test were used for the comparison of SBS values between groups (P < 0.05). The Chi-square test was used to examine differences among ARI scores. (P < 0.05).

Results:

One-way ANOVA and Tukey post-hoc test showed that the SBS of different groups were significantly different and was impacted by different timing of bonding (P < 0.05). The main differences were between the control group (17.02 ± 6.38 MPa) and Group 1 (6.93 ± 4.3 MPa). The ARI scores showed that there were no significant differences between the four tested groups.

Conclusions:

The SBS of the brackets bonded 15 days after the application of the fluoride was set back to an optimal value.

Influence of Different Etching Modes on Bond Strength to Enamel using Universal Adhesive Systems

INTRODUCTION

The adhesive systems and the techniques currently used are designed to provide a more effective adhesion with reduction of the protocol application. The objective of this study was to evaluate the bond strength of universal adhesive systems on enamel in different etching modes (self-etch and total etch).

MATERIALS AND METHODS

The mesial and distal halves of 52 bovine incisors, healthy, freshly extracted, were used and divided into seven experimental groups (n = 13). The enamel was treated in accordance with the following experimental conditions: FUE-Universal System - Futurabond U (VOCO) with etching; FUWE - Futurabond U (VOCO) without etching; SB-Total Etch System - Single Bond 2 (3M); SBUE-Universal System - Single Bond Universal (3M ESPE) with etching; SBUWE - Single Bond Universal (3M ESPE) without etching; CLE-Self-etch System - Clearfil SE Bond (Kuraray) was applied with etching; CLWE - Clearfil SE Bond (Kuraray) without etching. The specimens were made using the composite spectrum TPH (Dentsply) and stored in distilled water (37 ± 1°C) for 1 month. The microshear test was performed using the universal testing machine EMIC DL 2000 with the crosshead speed of 0.5 mm/minute. The bond strength values were analyzed using statistical tests (Kruskal-Wallis test and Mann-Whitney test) with Bonferroni correction.

RESULTS

There was no statistically significant difference between groups (p < 0.05), where FUE (36.83 ± 4.9 MPa) showed the highest bond strength values and SBUWE (18.40 ± 2.2 MPa) showed the lowest bond strength values. The analysis of adhesive interface revealed that most failures occurred between the interface composite resin and adhesive.

CONCLUSION

The universal adhesive system used in dental enamel varies according to the trademark, and the previous enamel etching for universal systems and the self-etch both induced greater bond strength values.

CLINICAL SIGNIFICANCE

Selective enamel etching prior to the application of a universal adhesive system is a relevant strategy for better performance bonding.

Comparative Analysis of Root Dentin Morphology and Structure of Human Versus Bovine Primary Teeth

This study evaluated the structural and morphological differences between human and bovine primary root canals. Primary human maxillary central incisors (H) (n=9) and primary bovine incisors (B) (n=9) were selected. The roots were sectioned in the vestibular-lingual direction, planed and delimited in cervical, middle, and apical thirds. Tubule density (number of tubules per mm2) and diameter were analyzed by scanning electron microscopy (1,000 and 5,000×) using Image J 1.47 software. Data were submitted to two-way repeated measures ANOVA and Tukey tests (α=0.05). The highest tubule density was observed for B (28.527±1.717 mm2) compared with H (15.931±0.170 mm2) (p<0.01). Regarding root thirds, the cervical third presented a greater tubule density (26.417±11.654 mm2) than the apical third (17.999±5.873 mm2). The diameter of the dentin tubules was not different for cervical (3.50±0.08 µm), middle (3.45±0.30 µm) and apical thirds (3.42±0.33 µm) and substrate (H-3.29±0.14 µm; B-3.63±0.06 µm). It could be concluded that: (1) the radicular dentin structure of human and bovine primary teeth and root thirds differ in terms of the tubule density; (2) the radicular dentin morphology of human and bovine primary teeth and root thirds are similar in terms of the diameter of the dentin tubules.

Effects of six different preventive treatments on the shear bond strength of orthodontic brackets: in vitro study

Objective: The aim of this study is to evaluate the effect of six different prophylactic agents on shear bond strength (SBS) of orthodontic brackets. Materials and methods: One hundred twenty-six freshly extracted mandibular bovine incisors were used. Teeth were randomly divided into 7 equal groups (18 per group) as follows: group-1 served as control with no pre-treatment; group-2 enamel treated with fluoride varnish (Fluor Protector, Ivoclar Vivadent); group-3 containing casein-phosphopeptide-amorphous calcium-phosphate (CPP-ACP) paste (GC Tooth Mousse, RECALDENT™); group-4 with ozone (HealOzone, Kavo); group-5 with glycine powder (Perio Flow, EMS); group-6 with hydroxyapatite powder 99.5% (Coswell S.p.A.); group-7 with a toothpaste made of hydroxyapatite nanocrystals (BioRepair® Plus, Coswell S.p.A). Brackets were all bonded using the same technique with transbond XT (3 M Unitek, Monrovia, CA). All the bonded specimens were stored for 24 h in deionized water (37 °C) and subjected to thermal cycling for 1000 cycles. The SBS was measured with an Instron Universal Testing machine and the adhesive remnant was assessed with the adhesive remnant index (ARI) using a stereomicroscope at 10× magnification. Results: Statistical differences (ANOVA) were found among the seven investigated groups (F = 12.226, p < 0.001). SBS of groups 2, 5 and 6 were significantly lower than the control group (p < 0.05). ARI scores (chi-square test) were correlated with the differences of SBS values. Conclusion: CPP-ACP paste, ozone or BioRepair® did not compromise on bracket bond strength. Fluoride, glycine or hydroxyapatite significantly decreased the SBS; only the fluoride group showed significant clinically low (<6 MPa) SBS values.

Shear bond strength of an orthodontic self-etching adhesive after intracoronary bleaching

OBJECTIVES

To evaluate the effects of intracoronary bleaching on the bond strength of orthodontic brackets using self-etching and total-etch adhesive systems.

MATERIAL AND METHODS

In 60 bovine incisors, a coronal lingual access was made to clean the pulp chamber and standardise the thickness of the dentine. The sample was randomly divided into four groups (each n = 15): (CT), control group, without bleaching and bonded with the total-etch system (Transbond(™) XT-3M); (CTSE), without bleaching treatment and bonded with the self-etching system (Transbond(™) Plus Self-Etching Primer-3M); (BT), treated with 35% hydrogen peroxide for internal bleaching and bonded with the total-etch adhesive system; and (BTSE), treated with 35% hydrogen peroxide and bonded with the self-etching adhesive system. Shear bond strength was measured using a universal testing machine (EMIC). The adhesive remnant index (ARI) score was verified. The data were analysed using a two-way anova and Tukey test (p < 0.05).

RESULTS

Significant differences were found, and the self-etching adhesive groups presented the highest bond strength values (CTSE=11.55 ± 2.85 MPa; BTSE=14.14 ± 2.23 MPa). The ARI scores revealed significant differences among the groups; the greater amount of remaining adhesive was observed in the CTSE group, and the lowest scores were observed in the BT group.

CONCLUSIONS

The use of the self-etching adhesive system, even after intracoronal bleaching, presented satisfactory adhesive strength for the bonding of brackets.

Comparison of microtensile bond strength of a resin composite to enamel conditioned by acid etching and Er,Cr:YSGG laser in human primary teeth

AIM

This study was designed to compare the bond strength of composite resin restorations on the buccal surface of primary human canine after conditioning by conventional acid etching and Er,Cr:YSGG laser.

METHODS

Twenty sound primary canines were cut buccolingually into two halves and each half was randomly placed in Er,Cr:YSGG laser or acid etch group. The samples in the acid etch group were etched with 37% phosphoric acid for 30 s. The samples in the laser group were prepared by Er,Cr:YSGG laser. The G6-Tips and 600 µm diameter were used with a 1.5 W of power output, pulse duration of 140 µs and repetition rate of 20 Hz. The bonding agent was applied on the buccal surface of each sample and layers of resin composite were placed. The samples' bond strengths were evaluated by a microtensile test instrument.

RESULTS

The mean of microtensile bond strength was 18.55±6.41 in the laser group and 24.62±5.56 in acid etch group. Microtensile bond strength achieved by laser conditioning was significantly lower than microtensile bond strength achieved by the conventional acid etching. Statistics To compare the results between the acid etch and laser group, the paired t test was performed (p value<0.001).

CONCLUSION

Conditioning enamel in primary teeth by Er,Cr:YSGG laser, cannot be used as an alternative method for acid etching and cannot substitute this conventional method.

Effect of Two Microshear Test Devices on Bond Strength and Fracture Pattern in Primary Teeth

This in vitro study evaluated the influence of two devices for application of shear load in microshear tests on bond strength and fracture pattern of primary enamel and dentin. Eighty primary molars were selected and flat enamel (40 teeth sectioned mesio-distally) and dentin (40 teeth sectioned transversally) surfaces were obtained. Both surfaces were polished to standardize the smear layer. Two-step etch-and-rinse adhesive systems (Adper Single Bond and XP Bond) were used. Polyethylene tubes was placed over the bonded surfaces and filled with composite resin. The microshear testing was performed after storage in water (24 h/37 °C) using two devices for application of microshear loads: a notched rod (Bisco Shear Bond Tester) or a knife edge (Kratos Industrial Equipment). Failure modes were evaluated using a stereomicroscope. Bond strength data were subjected to ANOVA and chi-square test to compare the failure mode distributions (α=0.05). No significant differences were observed between the groups for dentin and enamel bond strength or fracture patterns (p>0.05). The predominant failure mode was adhesive/mixed. In conclusion, the devices for application of shear loads did not influence the bond strength values, regardless of adhesive system and substrate.

Bond strength to radicular dentin and sealing ability of AH Plus in combination with a bonding agent

OBJECTIVE

To evaluate the sealing ability and bond strength of AH Plus sealer associated with the hybridization protocol of radicular dentin with Scotchbond Multi Purpose (SB).

MATERIALS AND METHODS

Ninety palatal roots of maxillary molars were selected and divided into three groups (n = 30) according to filling protocol (G1, AH Plus/Resilon; G2, SB/AH Plus/Resilon; and G3, AH Plus/Gutta-Percha). In groups in which AH Plus + resin cones were used, dentin was hybridized before applying sealing material. For the bond strength test, 60 roots of bovine teeth were selected. Six holes were made in each root, two in the cervical, middle and apical third of the root. The roles were filled with AH Plus sealer with or without an adhesive system and submitted to push out test and the fracture mode was examined using a stereomicroscope (×32).

RESULTS

Statistical analysis showed that ScotchBond Multi Purpose (SB) + Resilon cone + AH Plus group promoted higher sealing ability than the gutta-percha + AH Plus group (p < 0.05). Bond strength was lower with SB application than without it (p < 0.05). A reverse correlation was found between bond strength and sealing ability. The fracture mode methodology revealed 22.77% of adhesive, 11.67% of cohesive and 65.55% of mixture fractures for SBMP/AH Plus protocol, whereas the AH Plus protocol indicated 86.11% of cohesive and 13.89% of mixed fractures.

CONCLUSION

It was concluded that the use of the adhesive system Scotchbond Multi Purpose improved coronal sealing ability of AH Plus, but bond strength of sealer was reduced when adhesive was applied.

Effects of air-polishing devices with different abrasives on bovine primary and second teeth and deciduous human teeth

OBJECTIVE

The present study investigates the effect of air polishing using different combinations of devices and abrasive powders on bovine secondary and primary dentition and on human deciduous teeth.

MATERIALS AND METHODS

Lower incisors of freshly slaughtered calves and cows were partially embedded in polyurethane and polished flat. Human deciduous incisors and second molars were subjected to the same procedure. These various tooth types (bovine secondary, bovine primary, human deciduous) were then randomly assigned to 22 groups containing 10 teeth each. The specimens in each group were treated by a specific combination of an air-polishing device (n=2; PROPHYflex 3®, Air-Flow® Handy 2+) and an abrasive (n=3; Air-Flow® Pulver Classic, ClinPro™ Prophy Powder, PROPHYpearls®) applied from a distance of 5±0.5 mm at maximum setting for 60 s. Additional groups of specimens were polished with CCS® 40 or Cleanic® pastes applied with a rotating brush at low speed. A Perthometer PCV profilometer was used to analyze the degrees of surface roughness and enamel reduction in each group.

RESULTS

PROPHYpearls® created significantly (p<0.05; t-test) more surface roughness and enamel reduction than both Air-Flow® and ClinPro™. There was no significant difference between the latter two abrasives. Any surface changes created by blasting or polishing were significantly (p<0.05; t-test) smaller on the bovine secondary teeth than on bovine primary or human deciduous teeth, with no significant difference between the latter two. The degrees of surface roughness induced by air polishing surpassed the effect of CCS® 40 paste but resembled the effect of Cleanic® paste.

CONCLUSION

Both Air-Flow® Handy 2+ and PROPHYflex 3® are appropriate devices to remove plaque and discoloration from the surface of deciduous teeth. PROPHYpearls® powder is excessively aggressive.

Osteo-odonto-keratoprosthesis (OOKP) and the testing of three different adhesives for bonding bovine teeth with optical poly-(methyl methacrylate) (PMMA) cylinder

AIM

Preparation of the lamina during osteo-odonto-keratoprosthesis (OOKP) design is complex, and its longevity and watertightness important. To date, only acrylic bone cements have been used for bonding the optical cylinder to the tooth dentine. Our aim was to evaluate different dental adhesives for OOKP preparation.

METHODS

Specimens of bovine teeth were produced by preparing 1.5-mm thick dentine slices with holes having a diameter of 3.5 mm. Each group (n=10 per group) was luted with either classic poly-(methyl methacrylate) (PMMA) bone cement, universal resin cement or glass ionomer cement. All specimens underwent force measurement using a uniaxial traction machine.

RESULTS

The highest mean force required to break the bond was measured for PMMA bone cement (128.2 N) followed by universal resin cement (127.9 N), with no statistically significant difference. Glass ionomer cement showed significantly lower force resistance (78.1 N).

CONCLUSIONS

Excellent bonding strength combined with easy application was found for universal resin cement, and thus, it is a potential alternative to acrylic bone cement in OOKP preparation.

Shear bond strength of two adhesive materials to eroded enamel

AIM

To evaluate the bond strength of one etch-and-rinse adhesive system and one resin-modified glass ionomer cement to sound and eroded enamel.

MATERIALS AND METHODS

Forty-eight bovine incisors were embedded in acrylic resin and ground to obtain flat buccal enamel surfaces. Half of the specimens were submitted to erosion challenge with pH-cycling model (3x/cola drink for 7 days) to induce eroded enamel. After that, all specimens were randomly assigned according to adhesive material: etch-andrinse adhesive system (Adper Single Bond 2 - 3M ESPE, USA) or resin-modified glass ionomer cement (Vitro Fil LC - DFL, Brazil). The shear bond testing was performed after 24 hours water storage (0.5 mm/min). Shear bond strength means were analyzed by two-way ANOVA and Tukey post hoc tests (p < 0.05).

RESULTS

Adper Single Bond 2 showed the highest bond strength value to eroded enamel (p < 0.05), whereas no difference was observed in sound enamel compared with Vitro Fil LC (p > 0.05).

CONCLUSION

Bond strength of etch-and-rinse adhesive system increases in eroded enamel, while no difference is verified to resin-modified glass ionomer cement.

CLINICAL SIGNIFICANCE

Adhesive materials may be used in eroded enamel without jeopardizing the bonding quality; however it is preferable to use etch-and-rinse adhesive system.

Shear bond strength and fracture analysis of human vs. bovine teeth

Purpose

To evaluate if bovine enamel and dentin are appropriate substitutes for the respective human hard tooth tissues to test shear bond strength (SBS) and fracture analysis.

Materials and Methods

80 sound and caries-free human erupted third molars and 80 freshly extracted bovine permanent central incisors (10 specimens for each group) were used to investigate enamel and dentine adhesion of one 2-step self-etch (SE) and one 3-step etch and rinse (E&R) product. To test SBS the buccal or labial areas were ground plane to obtain appropriate enamel or dentine areas. SE and E&R were applied and SBS was measured prior to and after 500 thermocycles between +5 and +55°C. Fracture analysis was performed for all debonded areas.

Results

ANOVA revealed significant differences of enamel and dentin SBS prior to and after thermocycling for both of the adhesives. SBS- of E&R-bonded human enamel increased after thermocycling but SE-bonded did not. Bovine enamel SE-bonded showed higher SBS after TC but E&R-bonded had lower SBS. No differences were found for human dentin SE- or E&R-bonded prior to or after thermocycling but bovine dentin SE-bonded increased whereas bovine dentine E&R-bonded decreased. Considering the totalized and adhesive failures, fracture analysis did not show significances between the adhesives or the respective tooth tissues prior to or after thermocycling.

Conclusion

Although SBS was different on human and bovine teeth, no differences were found for fracture analysis. This indicates that solely conducted SBS on bovine substrate are not sufficient to judge the perfomance of adhesives, thus bovine teeth are questionnable as a substrate for shear bond testing.

A novel dentin bonding system containing poly(methacrylic acid) grafted nanoclay: synthesis, characterization and properties

OBJECTIVES

Developing a novel dentin bonding system containing poly(methacrylic acid)-grafted-nanoclay (PMAA-g-nanoclay) as reinforcing filler, with high stability of nanoparticle dispersion and improved bond strength and mechanical properties were the main objectives of this study.

MATERIALS AND METHODS

Poly(methacrylic acid) (PMAA) was grafted onto the pristine sodium montmorrillonite (Na-MMT) nanoclay surface and characterized using FTIR, TGA, and X-ray diffraction (XRD). The PMAA-g-nanoclay was incorporated into an experimental dentin bonding system as filler in different concentrations and stability of nanoclay dispersion in the dilute adhesive, morphology of nanoclay layers in the photocured adhesive matrix, shear bond strength to caries-free extracted human premolar teeth, and mode of failure were studied. The mechanical properties including diametral tensile strength (DTS), flexural strength (FS), and flexural modulus (FM) were also investigated. The measured FM was also compared to theoretical prediction models.

RESULTS

The grafting of PMAA onto the nanoclay surface was confirmed and the results revealed a partially exfoliated structure for PMAA-g-nanoclay. The dispersion stability of the modified nanoparticles in the dilute adhesive increased more than 45 times in comparison with the pristine nanoclay. The incorporation of 0.5wt.% PMAA-g-nanoclay to the adhesive resulted in a significant increase in microshear bond strength, DTS, and FS. Higher PMAA-g-nanoclay contents resulted in increased flexural modulus. The experimental flexural modulus was in good agreement with the Halpin-Tsai theoretical model.

SIGNIFICANCE

Incorporation of PMAA-g-nanoclay particles as novel functional fillers into dental adhesive could result in the development of bonding systems with improved physical, mechanical, and adhesion properties.

Influence of caries infiltrant contamination on shear bond strength of different adhesives to dentin

OBJECTIVES

To analyze whether the contamination with a caries infiltrant system impairs the adhesive performance of etch-and-rinse and self-etching adhesives on dentin.

MATERIALS AND METHODS

Dentin contamination with the caries infiltrant system (Icon, DMG) was simulated by applying either hydrochloric acid (15 % HCl, Icon Etch, 15 s), the resin infiltrant (Icon infiltrant, 4 min), or both prior to the application of the respective adhesives (each group n = 10). In the control groups, the etch-and-rinse adhesive (Optibond FL, Kerr) and the self-etching adhesive (iBOND Self Etch, Hereaus) were applied without former contamination with the infiltrant system. Additionally, the adhesive performance of the resin infiltrant alone was tested. Shear bond strength of a nano-hybrid composite was analyzed after thermocycling (5,000×, 5-55°C) of the specimens and analyzed by ANOVA/Scheffé post hoc tests (p < 0.05) and Weibull statistics. Failure mode was inspected under a stereomicroscope at × 25 magnification.

RESULTS

Contamination with the resin infiltrant alone did not impair shear bond strength, while contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant reduced shear bond strength (MPa) of the adhesives (Optibond FL: 20.5 ± 3.6, iBOND Self Etch: 17.9 ± 2.6) significantly. Hydrochloric acid contamination increased the number of adhesive failures. The adhesive performance of the caries infiltrant system alone was insufficient.

CONCLUSION

The contamination with the caries infiltrant system impaired the shear bond strength of conventional dental adhesives.

CLINICAL RELEVANCE

Contamination of the caries infiltrant system on dentin should be avoided due to the detrimental effect of hydrochloric acid etching.

Bovine teeth as substitute for human teeth in dental research: a review of literature

The aim of this paper was to review in vitro and in situ studies that directly compared the use of bovine teeth as a substitute for human teeth in dental experiments. A PubMed search was conducted for papers published from 1953 to December 30, 2010 using the following keywords: "human bovine enamel" or "human bovine dentin" or "human bovine teeth". The abstracts of the studies resulting from the keyword search were read, and all papers that compared human and bovine teeth were fully read. Only original articles written in English and directly comparing human and bovine substrates were included in the review. The search was supplemented by manual searches of the reference lists from each identified paper. Out of 76 studies initially selected, 68 fulfilled the selection criteria for inclusion. The studies covered seven categories: dental morphology, chemical composition, physical properties, dental caries, dental erosion/abrasion, bonding/adhesive strength, and marginal microleakage. Inconsistent data exist regarding whether bovine teeth can be considered an appropriate substitute for human teeth in dental research. Morphological, chemical compostion and physical property differences between the two substrates must be considered when interpreting results obtained from any experiment using bovine tooth substrate.

The use of easily debondable orthodontic adhesives with ceramic brackets

We experimentally produced an easily debondable orthodontic adhesive (EDA) containing heat-expandable microcapsules. The purpose of this in vitro study was to evaluate the best debondable condition when EDA was used for ceramic brackets. Shear bond strengths were measured before and after heating and were compared statistically. Temperatures of the bracket base and pulp wall were also examined during heating. Bond strengths of EDA containing 30 wt% and 40 wt% heat-expandable microcapsules were 13.4 and 12.9 MPa, respectively and decreased significantly to 3.8 and 3.7 MPa, respectively, after heating. The temperature of the pulp wall increased 1.8-3.6°C after heating, less than that required to induce pulp damage. Based on the results, we conclude that heating for 8 s during debonding of ceramic brackets bonded using EDA containing 40 wt% heat-expandable microcapsules is the most effective and safest method for the enamel and pulp.

Enamel wetness effects on bond strength using different adhesive systems

OBJECTIVE

To evaluate, through the application of different dentin bonding systems, the influence of wetness on shear bond strength in enamel.

METHODS

This study evaluated three etch-and-rinse adhesive systems (Scotchbond MP [used with and without primer]; Singlebond; and Prime&Bond 2.1) and two self-etching adhesive systems (Clearfil SE Bond; and Xeno IV). Flat bovine enamel surfaces were either air-dried for 30 seconds or blotted with absorbent paper after acid-etching for the conventional bonding agents or before the application of self-etching bonding agents. The resin composite EsthetX was bonded to flat surfaces that had been treated with one of the adhesives, following the manufacturer's instructions. After being stored in water at 37°C for one week, bonded specimens were broken in shear. Data were evaluated with two-way analysis of variance (ANOVA) and Student-Newman-Keuls tests (α=0.05). For comparing each condition individually, regardless of the adhesive or wetness condition, a one-way ANOVA and a Student-Newman-Keuls test (α=0.05) were applied.

RESULTS

The two-way ANOVA showed significant differences among adhesive systems. An interaction effect was also observed (p<0.05), but wetness did not influence shear bond strength (p=0.98). The one-way ANOVA showed that the all-in-one adhesive was the only material influenced by the presence of water at the enamel's surface.

CONCLUSION

The all-in-one adhesive behaved differently depending on whether the enamel surface was dry or wet.

Bonding efficiency of contemporary adhesives to the dentinoenamel junction zone

The aim of this study was to investigate the bonding of dental adhesives to the dentinoenamel junction (DEJ) zone. Bonding of four adhesives [two etch-and-rinse adhesives (ERAs) and two self-etching adhesives (SEAs)] to enamel, dentin, and the DEJ zone was evaluated using a micro-shear test. Based on the measured bond strengths of dentin/enamel and on the area percentages of dentin in the DEJ zone, predicted bond strengths for the DEJ zone were calculated and compared with those measured. The DEJ zone was analyzed, using scanning electron microscopy, after conditioning, resin infiltration, and debonding. Regardless of the adhesive, bond strengths were significantly influenced by substrates, exhibiting the following order of bond strength (strongest to weakest): dentin >DEJ zone > enamel. The predicted values of the DEJ zone for the ERA groups were significantly higher than the measured values. Analysis of the ERA specimens using scanning electron microscopy showed distinct etching textures of enamel and dentin, which outlined the DEJ and increased the adhesive thickness at the enamel side of the DEJ. Those characteristics could not be detected in the SEA groups. The DEJ zone displayed bond properties that were stronger than enamel but weaker than dentin and therefore may be considered as transitional bond properties. Enamel/dentin within the DEJ zone might bond more weakly to ERAs than its counterpart of the bulk tissue. The presence of the DEJ in the bond area might compromise the bonding efficiency of ERAs.

A comparative evaluation of casein phosphopeptide-amorphous calcium phosphate and fluoride on the shear bond strength of orthodontic brackets

The purpose of the study was to evaluate and compare the effects of topical application of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride on the shear bond strength (SBS) of orthodontic brackets bonded to human premolar teeth. Eighty extracted human premolar teeth were cleansed of soft tissue, then polished with non-fluoridated pumice, and immersed in water for 1-3 months until testing. The teeth were randomly divided into four groups: group 1, control, without pre-treatment of the enamel; group 2, the enamel was treated with 5 per cent sodium fluoride varnish for 4 minutes; group 3, the enamel was treated with CPP-ACP for 3 minutes; and group 4, the enamel was treated with 5 per cent sodium fluoride and CPP-ACP. All bonded specimens were immersed in distilled water at room temperature for 24 hours and subsequently tested for SBS in a universal testing machine. After debonding, the bracket bases and the enamel surfaces were examined by eye to assess any adhesive remaining, in accordance with the Adhesive Remnant Index (ARI). Descriptive statistics were calculated for each group. Analysis of variance and Tukey honestly significant difference (HSD) test were performed to compare the SBS of the groups. The chi-square test was used to evaluate differences in ARI scores between the groups. The SBS in group 2 was significantly lower than groups 1, 3, and 4 (P < 0.001). ARI scores were not significantly different between the four groups (P > 0.05). CPP-ACP, either alone or combined with fluoride, may safely be used as a prophylactic agent before bracket bonding.

Shear bond strength of fluoride-releasing orthodontic bonding and composite materials

Several fluoride-releasing bonding materials are available for orthodontic bracket placement. These are supposed to prevent white spot lesions during therapy. The objectives of this in vitro study were to evaluate the shear bond strength (SBS) and failure mode of a recently introduced fluoride-releasing adhesive, as well as the comparison with established orthodontic adhesives. Sixty bovine mandibular incisors were randomly allocated to three groups (n = 20): stainless steel brackets were bonded with Transbond Plus Color Change Adhesive, Transbond XT, or Light Bond. A universal testing machine was used to determine the SBS at a crosshead speed of 1 mm/minute. After debonding, the adhesive remnant index (ARI) was used to assess the adhesive remaining on the brackets. One-way analysis of variance comparing the three experimental groups showed no differences between the bonding systems for mean SBS (P = 0.27). ARI scores showed more residual adhesive on the teeth bonded with the Transbond systems (P < 0.01). As the fluoride-releasing bonding system provided sufficient mean bond strength in vitro (19.9 MPa), it may be used as an additional prophylactic measure in orthodontic therapy. However, the clinical effectiveness of its fluoride release may be questionable, as the amount of fluoride required from a bonding material to be caries preventive is still unknown.