Shear bond strengths of one-bottle adhesives to moist enamel

Effect of Extra Hydrophobic Resin Layer on Bonding of Universal Adhesive Systems to Enamel

OBJECTIVE

The objective of this study was to compare the effect of solvent in universal adhesives (UA) and the application of an extra layer of hydrophobic bonding resin on enamel shear bond strengths (SBS).

METHODS AND MATERIALS

Crowns of 224 bovine mandibular incisors were embedded in acrylic resin, wet-polished up to 600-grit silicon carbide paper and assigned to 3 UAs with different solvents (n=32): ethanol-based UA (ADU, AdheSE Universal, Ivoclar Vivadent); isopropanol-based UA (PBU, Prime&Bond Universal, Dentsply Sirona); and acetone-based UA (OPT, OptiBond Universal, Kerr Co). The same UAs were also applied with an extra layer of a hydrophobic bonding resin (HLB, Heliobond, Ivoclar Vivadent): ADU + HLB; PBU + HLB; and OPT + HLB. HLB alone was used as control. Enamel was etched with 37.5% H3PO4 (Kerr Gel Etchant, Kerr Co) for 15 seconds, rinsed with water, and air dried. UAs were applied according to the respective manufacturer's instructions. After adhesive application, composite cylinders (Filtek Z250, 3M Oral Care) were built up and light-cured (40 seconds/increment, 40 J/cm2) keeping the light tip in contact with the mold. Specimens were stored in water for 24 hours (24H) or for 6 months (6M). A knife-edged metallic rod (Ø=2.8-mm semicircular notch) loaded the composite cylinders until fracture. Mode of failure was analyzed with optical microscopy (40×). Statistics included twoway analysis of variance (ANOVA; adhesive strategy and water storage) and Tukey honestly significant difference (HSD) post hoc test (α=95%).

RESULTS

Mean enamel SBS ranged from 3.6 (±2.2) MPa (HLB/6M) to 24.7 (±7.1) MPa (ADU + HLB/6M). ANOVA revealed significant differences for adhesive strategy (p≤0.001) but no significant differences for water storage (p>0.05). All UAs resulted in similar mean enamel SBS with or without an extra layer of HLB at 24H. After 6M, only ADU resulted in higher enamel SBS when an extra layer of HLB was applied. All UAs resulted in higher mean enamel SBS than HLB (control). Most failures were adhesive exception for PBU/HLB/6M, which had mostly mixed failures.

CONCLUSIONS

UAs resulted in statistically higher enamel SBS than the nonsolvated hydrophobic bonding resin (control), regardless of the solvent in their composition. Application of an extra layer of hydrophobic bonding resin over UAs did not improve mean enamel SBS for isopropanol- and acetone-based UAs but did improve mean enamel SBS for the ethanol-based UA after 6M. Resin composite bonding to enamel using a hydrophobic bonding resin alone is not recommended.

Tooth surface treatment strategies for adhesive cementation

PURPOSE

The aim of this study was to evaluate the effect of tooth surface pre-treatment steps on shear bond strength, which is essential for understanding the adhesive cementation process.

MATERIALS AND METHODS

Shear bond strengths of different cements with various tooth surface treatments (none, etching, priming, or etching and priming) on enamel and dentin of human teeth were measured using the Swiss shear test design. Three adhesives (Permaflo DC, Panavia F 2.0, and Panavia V5) and one self-adhesive cement (Panavia SA plus) were included in this study. The interface of the cement and the tooth surface with the different pre-treatments was analyzed using SEM. pH values of the cements and primers were measured.

RESULTS

The highest bond strength values for all cements were achieved with etching and primer on enamel (25.6 ± 5.3 - 32.3 ± 10.4 MPa). On dentin, etching and priming produced the highest bond strength values for all cements (8.6 ± 2.9 - 11.7 ± 3.5 MPa) except for Panavia V5, which achieved significantly higher bond strengths when pre-treated with primer only (15.3 ± 4.1 MPa). Shear bond strength values were correlated with the micro-retentive surface topography of enamel and the tag length on dentin except for Panavia V5, which revealed the highest bond strength with primer application only without etching, resulting in short but sturdy tags.

CONCLUSION

The highest bond strength can be achieved for Panavia F 2.0, Permaflo DC, and Panavia SA plus when the tooth substrate is previously etched and the respective primer is applied. The new cement Panavia V5 displayed low technique-sensitivity and attained significantly higher adhesion of all tested cements to dentin when only primer was applied.

Cross-Compatibility of Methacrylate-Based Resin Composites and Etch-and-Rinse One-Bottle Adhesives

Cross-compatibility between different combinations of methacrylate-based resin composites and etch-and-rinse one-bottle adhesives was evidenced for products from different manufacturers. This represents a desirable property of adhesives as it allows the flexibility to select different composite systems based on the specific restorative needs.

Influence of human and bovine substrate on the microleakage of two adhesive systems

The aim of this study was to evaluate in vitro the marginal sealing of two adhesive systems and to analyze the influence of human and bovine substrates on marginal microleakage in enamel. Rectangular-shaped class V cavities (4 mm wide x 2 mm high x 2 mm deep) were made as follows: 8 cavities were prepared on the buccal and lingual surfaces of the human teeth with margins located on enamel and 16 cavities were prepared on the buccal surfaces of the bovine teeth. The cavities were randomly assigned to 4 groups of 8 cavities according to the adhesive system and substrate: G1--Prime & Bond 2.1 (Dentsply)/human substrate; G2--Adhese (Ivoclar/Vivadent)/human substrate; G3--Prime & Bond 2.1 (Dentsply)/bovine substrate; G4--Adhese (Ivoclar/Vivadent)/bovine substrate. The cavities were filled with microhybrid composite resin (Fillmagic) and after polishing/finishing procedures, the teeth were subjected to a thermocycling regimen of 500 cycles with 1-min immersions in water at 55 degrees+/-2 degrees C and 5 degrees+/-2 degrees C. Next, the teeth were coated with two layers of nail polish to within 1 mm of the margin, submerged in a 50% silver nitrate solution for 2 h, rinsed thoroughly in running tap and immersed in developing solution for 8 h. The restorations were bisected resulting in 16 specimens. Microleakage was observed under a stereomicroscope at x25 and recorded using four-point (0-3) scoring system. The data were analyzed statistically by the Mann Whitney U-test at 5% significance level. Leakage was present in all specimens and there was statistically significant difference between the adhesive systems. Adhese self-etching system showed significantly more leakage in both substrates (human--p= 0.0001 and bovine--p=0.0031). There was no statistically significant difference between human and bovine substrates for either of the adhesive systems based on different bonding mechanisms (Prime & Bond 2.1--p= 0.6923 and Adhese--p= 0.6109). Neither of the adhesive systems was capable to completely prevent microleakage and the self-etching system was more susceptible to microleakage.

Shear bond strength of acetone-based one-bottle adhesive systems

The aim of this study was to assess the shear bond strength of four acetone-based one-bottle adhesive systems to enamel and dentin, and compare to that of an ethanol-based system used as control. Fifty human molars were bisected mesiodistally and the buccal and lingual surfaces were embedded in acrylic resin using PVC cylinders. The buccal surfaces were ground to obtain flat dentin surfaces, while the lingual surfaces were ground to obtain flat enamel surfaces. All specimens were polished up to 600-grit sandpapers and randomly assigned to 5 groups (n=20; 10 dentin specimens and 10 enamel specimens), according to the adhesive system used: One-Step (Bisco); Gluma One Bond (Heraeus Kulzer); Solobond M (Voco); TenureQuik w/F (Den-Mat) and OptiBond Solo Plus (Kerr) (control). Each adhesive system was applied according to the manufacturers' instructions. The respective proprietary hybrid composite was applied in a gelatin capsule (d=4.3mm) and light-cured for 40 s. The specimens were tested in shear strength with an Instron machine at a crosshead speed of 5 mm/min. Bond strengths means were analyzed statistically by one-way ANOVA and Duncan's post-hoc (p£0.05). Shear bond strength means (MPa) (±SD) to enamel and dentin were: Enamel: One-Step=11.3(±4.9); Gluma One Bond=16.3(±10.1); Solobond M=18.9(±4.5); TenureQuik w/F=18.7(±4.5) and OptiBond Solo Plus=16.4(±3.9); Dentin: One-Step=6.4(±2.8); Gluma One Bond=3.0(±3.4); Solobond M=10.6(±4.9); TenureQuik w/F=7.8(±3.9) and OptiBond Solo Plus=15.1(±8.9). In enamel, the adhesive systems had statistically similar bond strengths to each other (p>0.05). However, the ethanol-based system (OptiBond Solo Plus) showed significantly higher bond strength to dentin than the acetone-based systems (p£0.0001). In conclusion, the solvent type (acetone or ethanol) had no influence on enamel bond strength, but had great influence on dentin bonding, which should be taken into account when choosing the adhesive system.

Influence of enamel wetness on composite restorations using various dentine bonding agents: part II-effects on shear bond strength

OBJECTIVES

To investigate the bond strength and fracture characteristics of various dentine bonding agents (DBAs) on wet or dry enamel.

METHODS

Forty molar halves with enamel flattened were divided into 5 groups. Groups 1-4, teeth were acid-etched and treated separately with either an ethanol-based adhesive (Single Bond) or an acetone-based adhesive (Prime & Bond NT) on dry or wet enamel. Group 5 was treated with a self-etching adhesive (Clearfil SE Bond). The treated enamel surfaces were bonded with Z 250 composite with metal rings. The composite-ring assemblies were subjected to shear bond test until failure. Failure patterns on the debonded surfaces were inspected under a scanning electron microscope. The bonded enamel thickness was measured on sectioned specimens to investigate their statistical evidence. Results of open margin and enamel microcrack ratios from Part I of this study were compared with these fracture characteristics. Data was analyzed statistically.

RESULTS

There was no difference in the bond strength between paired groups using the same DBA on wet or dry enamel. The teeth restored with self-etching adhesive exhibited lower bond strength and higher adhesive-enamel failure rate than the other groups. No correlation between enamel thickness, microcrack, bond strength, and failure patterns was revealed.

CONCLUSION

The self-etching adhesive had a lower enamel bond strength than the other bonding systems. The difference in the failure patterns of groups with ethanol- and acetone-based DBAs on wet or dry enamel was indistinct. The frequently observed enamel microcrack cannot be directly correlated with the bond strength of bonding systems.

Shear bond strength of adhesive systems to enamel and dentin. Thermocycling influence

OBJECTIVES

The purpose of the this study was to evaluate the influence of thermocycling on shear bond strength on bovine enamel and dentin surfaces of different adhesive systems.

METHODS

Thirty sound bovine incisors were sectioned in mesiodistal and inciso-cervical direction obtaining 60 incisal surfaces (enamel) and 60 cervical surfaces (dentin). Specimens were randomly assigned to 3 groups of equal size (n=40), according to the adhesive system used: I-Single Bond; II-Prime & Bond NT/NRC; III-One Coat Bond. After 24-h storage in distilled water at 37 degrees C, each main group was divided into two subgroups: A-specimens tested after 24 h storage in distilled water at 37 degrees C; B-specimens submitted to thermocycling (500 cycles). Shear bond strength tests were performed. Data were submitted to ANOVA and Tukey test.

RESULTS

Means (MPa) of different groups were: I-AE-16.96, AD-17.46; BE-21.60, BD-12.79; II-AE-17.20, AD-11.93; BE-20.67, BD-13.94; III-AE-25.66, AD-17.53; BE-24.20, BD-19.38.

SIGNIFICANCE

Thermocycling did not influence significantly the shear bond strength of the tested adhesive systems; enamel was the dental substrate that showed larger adhesive strength; One Coat Bond system showed the best adhesive strength averages regardless of substrate or thermocycling.

Tensile bond strengths of fourth- and fifth-generation dentin adhesives with packable resin composites

PURPOSE

Placement of packable composites would be simplified if a single-bottle dentin bonding agent, rather than the more complex, multiple-bottle dentin bonding agents, involving multiple steps, could be used successfully with adequate bond strength. This study was designed to compare the tensile bond strengths to extracted human dentin of four single-bottle (fifth-generation) and four multiple-bottle (fourth-generation) dentin bonding agents with four packable composites.

MATERIALS AND METHODS

Packable composites (P60, 3M Dental Products Division; ALERT, Jeneric-Pentron; Pyramid Dentin, Bisco; and Clearfil AP-X, Kuraray America) were tested for in vitro tensile bond strength to human dentin with their single-bottle and their multiple-bottle dentin bonding agents. Bond strengths were measured using a truncated cone tensile test, with a bonding diameter of 3 mm, after storage of specimens in water at 37 degrees C and 100% relative humidity for 24 hours, and using a testing machine at a crosshead speed of 0.5 mm per minute.

RESULTS

Means and standard deviations (n = 10) of tensile bond strengths (MPa) for the single-bottle system were P60, 21.3 MPa (6.7); ALERT, 26.6 MPa (4.2); Pyramid Dentin, 14.8 MPa (4.4); and Clearfil AP-X, 18.6 MPa (3.7). For the multiple-bottle system they were P60, 20.0 MPa (8.6); ALERT, 20.6 MPa (6.2); Pyramid Dentin, 16.0 MPa (3.4); and Clearfil AP-X, 17.8 MPa (6.0). Two-way analysis of variance showed significant differences among composites but no significant differences between single-bottle and multiple-bottle bonding agents. The Tukey-Kramer interval (p < .05) for comparisons of bond strengths among composites was 4.8 MPa.

CONCLUSIONS

For single-bottle agents, bond strengths were ranked as ALERT > P60, P60 = Clearfil, P60 > Pyramid, and Clearfil = Pyramid. For multiple-bottle agents, there were no significant differences in bond strengths among the composites.

CLINICAL SIGNIFICANCE

Single-bottle bonding agents provide similar in vitro bond strengths for use with packable composites as do the same manufacturers' multiple-bottle bonding agents.

Porcelain veneer restorations: a clinician's opinion about a disturbing trend

The conservative nature of the porcelain veneer technique introduced in 1982 is becoming less evident today. Even though dentin bonding materials are improving and emerging clinical research is encouraging, intact enamel provides the most reliable substrate for etched porcelain veneer restorations. Preparations can be designed with supragingival finish lines and, with the CLE, can be virtually invisible. Recent trends indicate that some practitioners dismiss the importance of enamel. An alarming number of patients are presenting with partial or complete debonding of porcelain veneer restorations placed for elective esthetics. When such failures do occur, the need for corrective measures is no longer discretionary. For many clinical conditions, porcelain veneer restorations offer dentists and their patients an outstanding, conservative alternative to traditional crowns. Veneers should always be minimally invasive. Dentists should not yield co pressures generated by well-meaning dental technicians and colleagues who disregard the importance of enamel bonding. They should also consider treatment options that preserve natural tooth structure, promote a healthy dentition, and reduce the need for future re-treatment. Sometimes the appropriate option is no treatment. Few dentists would want to have their own teeth aggressively prepared if a more conservative approach were feasible. Their patients certainly deserve the same consideration.

Tensile bond strength of adhesive systems--effects of primer and thermocycling

The objective of this study was to evaluate the effects of primer and thermocycling on the bond strength of multi-purpose adhesive systems applied to enamel, under tensile stress. The following bonding systems were applied, according to the manufacturers' instructions, on unground enamel buccal surfaces of 96 premolars, with or without the application of primer: Scotchbond MP, OptiBond FL, Amalgambond Plus and OptiBond (dual-cure). A composite resin (Z100, 3M) was applied and light-cured in a cast metal hollow cone, which was previously fixed to the enamel surfaces. Half of the sample was subjected to 3,000 thermocycles (5-37 degrees C; 37-55 degrees C, dwell time of 60 s), and the other half was stored in water at 37 degrees C for the same period. The data were treated by means of ANOVA and no significant effects were detected, which indicates that tensile bond strength was not affected by the adhesive systems, application of primer or thermocycling.

Ceramic restorations for posterior teeth: guidelines for the clinician

Metal-free ceramic restorations are increasingly popular for restoring posterior teeth. These restorations are generated through a variety of techniques (e.g., CAD-CAM, copy-milling, heat-pressing, and firing). When appropriately indicated and made, ceramic inlays or onlays can be reliable and provide a highly serviceable restoration. The aim of this article is to review and present updated information regarding indications, restorative technique, and maintenance for this class of restorations, with emphasis to fired ceramic inlays or onlays. The information presented is based on 15 years of controlled clinical experience with this category of restorations. Clinical cases that represent some applications also are presented.

CLINICAL SIGNIFICANCE

The fired ceramic inlay/onlay technique is presented as a viable option for the esthetic and adhesive restoration of posterior teeth.