The Journal of Adhesive Dentistry, 03/2002

To compare the bonding potential to human dentin of adhesive/composite combinations including five 2-step and two 3-step total-etch (TE) bonding systems, two systems with self-conditioning (SC) primers, and one SC all-in-one adhesive by use of the microtensile bond test. Hybrid resin composites were bonded to the occlusal dentin of 50 extracted human molars. After water storage (37°C, 24 h), 3 1-mm-thick slabs were cut from the middle of the teeth perpendicular to their long axis. Microtensile bond strength was determined and debonded surfaces were examined under the SEM for mode of failure. Statistics: GLM multivariate procedure for repeated measurements, Student-Newman-Keuls test (SPSS version 10.0; p = 0.05). Mean bond strengths of the simplified (2-step) TE systems (OptiBond Solo, Gluma One Bond, Solobond M, Prime&Bond NT, One Coat Bond; 19.9 MPa to 39.9 MPa) were not significantly lower than that of the traditional 3-step TE systems (EBS Multi: 26.0 MPa; OptiBond FL: 32.7 MPa), and not related to phosphoric acid concentration. Dentin treatment with SC primers (Clearfil Liner Bond 2: 22.0 MPa; Clearfil Liner Bond 2V: 22.4 MPa) was as effective as etching with phosphoric acid. The SC all-in-one adhesive (Etch″ 3.0: 10.1 MPa) produced significantly lower bond strength than all other systems evaluated. The use of adhesive/composite combinations including simplified bonding systems does not necessarily result in reduced bond strength to dentin. SC primers offer a promising alternative to phosphoric acid etching as far as bonding to dentin is concerned. In contrast, the SC all-in-one adhesive evaluated needs to be improved.

The purpose of this study was to analyze a resin cement/dentin interface by comparing the diffusion of a resin cement into dentin surfaces pretreated with a self-etching primer with or without pretreatment by conventional acid etching. Dentin surfaces of 8 unerupted human third molars were treated with a self-etch primer (Panavia 21) with or without conventional phosphoric acid pretreatment. Panavia 21 resin cement was applied according to manufacturer's instructions. Dentin/resin cement interface sections from each tooth were examined with scanning electron microscopy and micro-Raman spectroscopy. When the self-etch primer was used following conventional acid pretreatment, the resin cement did not penetrate to the depth of the zone of demineralized dentin, leaving a substantial area of exposed dentin matrix at the dentin/cement interface. In contrast, there was substantial resin cement diffusion throughout the demineralized dentin when the self-etch primer was used without acid etching pretreatment. The in vitro evaluation of resin cement penetration throughout the zone of demineralized dentin is an important step in identifying sites of exposed dentin matrix that may promote postoperative sensitivity and may leave the dentin/resin cement interface vulnerable to premature degradation under clinical conditions. In this study, the self-etch primer used alone produced substantial resin cement penetration and left no exposed dentin matrix at the dentin/resin cement interface.

To evaluate the tensile bond strength of two self-etching adhesive systems and one one-bottle system applied on dentin surfaces after different smear layer treatments. The crowns of 36 extracted third molars were transversally sectioned with a diamond saw to expose dentin. Flat dentin surfaces were abraded wet with 600-grit SiC paper and randomly assigned to 12 groups, according to three adhesive systems - Prime & Bond NT (PB), Clearfil Mega Bond (CMB) and Etch & Prime 3.0 (EP) - and four dentin surface treatments: direct application over smear layer (no treatment), sandblasting with 50 µm Al2O3 for 10 s, etching with 36% phosphoric acid for 15 s, or conditioning with 0.5 M EDTA for 2 min. Composite "crowns" (6.0 mm high) were incrementally built on the bonded surfaces and teeth were stored in distilled water at 37°C. Teeth were vertically, serially sectioned in both x and y directions to obtain bonded specimens of approximately 0.8 mm2 cross-sectional area. Each specimen was tested in tension in a universal testing machine at 0.5 mm/min. Overall microtensile bond strength (MPa) was 40.43 ± 7.63 for PB, 27.03 ± 8.40 for CMB, and 14.73 ± 3.91 for EP. Mean bond strength for PB was significantly higher than self-etching systems. No significant differences were observed among smear layer treatments within the same dentin adhesive. Bond strength values were significantly different according to the adhesive system used. Different smear layer treatments prior to bonding did not affect tensile bond strength within the same bonding agent.

This study compares the percentage decrease in power output of light-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing devices at different distances between the light guide tip and a radiometer. Three LED curing devices (Elipar FreeLight/3M ESPE, Luxomax/Akeda, e-Light/GC) were compared to two QTH curing devices (Elipar TriLight/3M ESPE, Optilux 501 conventional and Turbo light guides/Kerr-Demetron). Power density was measured with a Fieldmaster GS/Coherent unit (Sensor LM-3 HTD) at increasing distances from the light guide tip (0 to 20 mm at 1-mm increments, n=6). The mean decrease in power density available for curing at a distance of 10 mm between the light guide tip and the radiometer was 68% for the FreeLight, 83% for the e-Light, 42% for the Luxomax, 38% for the TriLight, 33% for the Optilux with the standard light guide, and 44% for the Optilux with the turbo light guide. The power density of the Luxomax was only 40% of that of the other LED curing devices at 0 mm distance. The blue LED curing devices Elipar FreeLight and GC e-Light showed a significantly higher percentage decrease in power output at a distance of 10 mm from the light guide tip to the radiometer compared to the QTH curing devices. Therefore, although blue LED curing devices might have the same curing potential compared to a QTH device when placed in direct contact to a resin composite, blue LED curing devices may not provide a sufficient cure when placed at a clinically relevant distance of 10 mm to the resin composite surface.

This study examined the effect of powdered and powder-free latex glove contamination on bond strength. Sixty caries-free human third molars were mounted in acrylic, sectioned with a diamond saw to expose a flat occlusal dentin surface, and finished with 400- and 600-grit silicon carbide paper. Teeth were assigned to one of 5 groups: 1) no latex glove contamination (control); 2) powdered latex glove contamination before etching; 3) powder-free latex glove contamination before etching; 4) powdered latex glove contamination after dentin bonding agent application but prior to resin composite placement; 5) powder-free latex glove contamination after dentin bonding agent application but prior to resin composite placement. Excite dentin bonding agent was used per manufacturer's instructions. Z-250 resin composite was applied in 2- x 2-mm increments using a split Teflon mold, each light cured for 20 s. Bonded samples were thermocycled 500 cycles between 5°C and 55°C water baths. Specimens were stored in 37°C distilled water. One-week shear bond strength values were determined using a Tinius Olsen testing machine at a crosshead speed of 0.5 mm/min. Results were analyzed with one-way ANOVA (α = 0.05). No significant difference (p = 0.47) in bond strength was found between the experimental groups and the control. Groups 1, 2, 3, and 5 exhibited predominantly mixed failures while the majority of samples in Group 4 showed adhesive failures. Under the conditions of this study, contamination of dentin by powdered or powder-free latex gloves did not significantly affect bond strength. Future research should be directed toward evaluating the effects of dentin contamination on bond strength of other bonding agents and include ultrastuctural examination in determining what role, if any, powder plays as a contaminant.

The aim of this study was to evaluate: 1) the effect of five dentin desensitizing agents (DDAs) on permeability using hydraulic conductance, and 2) morphological tubule changes with scanning electron microscopy (SEM). The agents tested were Seal & Protect, Gluma Desensitizer, HurriSeal, D/Sense 2, and Super Seal. Thirty extracted human molars were sectioned into 1-mm mid-coronal dentin disks. Dentin permeability was measured at baseline and after treatment using bovine serum and phosphate-buffered saline at 10 psi. Treatments were applied to the occlusal surfaces of dentin according to the manufacturer's instructions. Representatives from each group were selected for SEM observation. Kruskal-Wallis ANOVA and Tukey's post-hoc comparisons were used to evaluate differences between groups. Mean percent reduction in dentin permeability for each group: SuperSeal = 97.5 ± 4.0, HurriSeal = 54.2 ± 35.3, D/Sense 2 = 46.6 ± 20.4, Gluma Desensitizer = 39.6 ± 26.7, and Seal & Protect = 33.8±19.4. The data provided strong evidence of differences in permeability reduction among the agents (p < 0.01). Pairwise comparisons of means demonstrated that the effects of SuperSeal differed significantly from the reductions achieved using Seal & Protect, Gluma Desensitizer, and D/Sense 2. Differences in the degree and content of dentinal tubule occlusion were seen among all DDAs under SEM. Of the materials included in this in vitro study, SuperSeal may be the most beneficial when treating dentin sensitivity. The wide range of results may reflect the various approaches and chemistries used to occlude tubules.

An in vitro dye-penetration study was performed on 2 different self-etching adhesives (Prompt L-Pop II, 3M-Espe; NRC, Prime&Bond NT Quix, Dentsply/DeTrey) in comparison to conventional conditioning of the cavity with phosphoric acid (Conditioner 36, P&B NT Quix, Dentsply/DeTrey). Standardized mod cavities (one cervical margin in cementum, one in enamel) were prepared in 80 extracted human teeth (n = 20/group). Prompt L-Pop II was employed in two different sequences: A: placing the matrix band first, then applying the adhesive, B: first applying the adhesive, then placing the matrix band. The adhesive was cured in both cases. Conditioning and application of P&B NT Quix was carried out after placement of the matrix band in both procedures. The compomer Dyract AP was used as a restorative material in all cavities. After thermocycling, the median percentages of dye-penetrated (2% methylene blue) margins were determined separately for the cementum and enamel margins of the approximal boxes and for the lateral enamel margins of the boxes. The results showed that when using Prompt L-Pop II in Class II cavities, the adhesive should be applied before placing the matrix band (p < 0.0001). When the matrix band was placed first, P&B NT Quix showed superior results at a statistically significant level (p < 0.0001) in comparison to Prompt L-Pop II. There was no significant difference in the use of P&B NT Quix in combination with NRC or phosphoric acid in these Class II cavities. It is strongly recommended that Prompt L-Pop be applied prior to placement of the matrix band. Prime & Bond NT Quix seems to provide clinically relevant marginal seal in Class II cavities, regardless of whether NRC or phosphoric acid is used for conditioning.

The aim of this in vitro study was to determine the influence of deviations from the manufacturer's instructions for use of six adhesive systems on the bond strength of resin composite to enamel and dentin. Detailed questionnaires completed by 355 dentists in a survey of the use of adhesive systems in Denmark were analyzed, and the types of deviations from the manufacturer's recommended clinical procedures were categorized for the six most commonly used adhesive systems (Scotchbond Multi-Purpose, Scotchbond 1, Prime&Bond 2.1, Syntac, Gluma Classic, and Gluma CPS). Plane tooth surfaces were treated with one of the six adhesive systems either according to the manufacturer's instructions or with the deviations identified (eg, shortened application times, omission of second layers). Resin composite, which varied with the adhesive system, was then bonded to the treated surfaces. After storage in water at 37°C for 7 days, the bonded specimens were tested to failure to determine shear bond strength (n = 6). Certain deviations from the manufacturer's protocols significantly reduced bond strength to dentin for three (Scotchbond Multi-Purpose, Scotchbond 1, and Prime&Bond 2.1) of the six adhesive systems, while no negative effects were found on bond strength to enamel for any of the six systems. The adhesive systems varied regarding sensitivity to deviations from the instructions for use. Bonding to dentin was more technique-sensitive than bonding to enamel. For the most reliable result, the clinical procedure recommended by the manufacturer should be followed meticulously.