The Journal of Adhesive Dentistry, 02/2004

The purpose of this study was to investigate the dentin/adhesive interfacial characteristics of three current commercial adhesives with different relative hydrophilic/hydrophobic composition, using a nondestructive staining technique. Dentin surfaces of 18 unerupted human third molars were randomly selected for treatment with one of three commercial dentin bonding agents according to manufacturers' instructions for the "wet" bonding technique. The adhesives were ranked based on hydrophilic/hydrophobic component ratios (ie, ability to dissolve in water), highest to lowest, as follows: Uno (Pulpdent) > Prime&Bond NT (PBNT, Dentsply Caulk) > Single Bond (SB, 3M ESPE). Dentin/adhesive (d/a) interface sections were stained with Goldner's trichrome, a classical bone stain, and examined using light microscopy. The extent and degree to which the adhesive encapsulates the demineralized dentin matrix is reflected in the color differences in the stained sections. The depth of demineralization appeared comparable among these bonding systems, but adhesive infiltration varied from highest to lowest as follows: Uno > PBNT > SB. The differential staining technique provided a clear representation of the depth of dentin demineralization and extent/degree of adhesive encapsulation of the exposed collagen at the d/a interface. This technique provides a mechanism for readily identifying vulnerable sites at the d/a interface. The composition of the one-bottle adhesive systems has a substantial effect on the interfacial structure of the d/a bond. Keywords: collagen, encapsulation, dentin, adhesive

To compare the microtensile bond strength (MTBS) of two all-in-one adhesive systems and one experimental two-step self-etching adhesive system to two types of bur-cut dentin. Using one of the three adhesives, Xeno CF Bond (Xeno), Prompt L-Pop (PL), or the experimental two-step system ABF (ABF), resin composite was bonded to flat buccal and root dentin surfaces of eight extracted human premolars. These surfaces were produced using either regular-grit or superfine-grit diamond burs. After storage overnight in 37°C water, the bonded specimens were sectioned into six or seven slices approximately 0.7 mm thick perpendicular to the bonded surface. They were then subjected to microtensile testing. The surfaces of the fractured specimens were observed microscopically to determine the failure mode. In addition, to observe the effect of conditioning, the two types of bur-cut dentin surfaces were conditioned with the adhesives, rinsed with acetone, and observed with SEM. When Xeno and PL were bonded to dentin cut with a regular-grit diamond bur, MTBS values were lower than to superfine bur-cut dentin, and failures occurred adhesively at the interface, whereas the experimental two-step adhesive showed no significant difference in microtensile bond strength between two differently cut surfaces. The all-in-one adhesives tested here improved bond strengths when bonded to superfine bur-cut dentin as a substrate, whereas the experimental two-step adhesive system showed unchanged bonding to both regular and superfine bur-cut dentin surfaces. Keywords: all-in-one adhesive, two-step self-etching adhesive, bur-cut dentin, smear layer, microtensile bond strength

Incomplete infiltration of the demineralized collagen network may result in a weak zone within the hybrid layer and between the hybrid layer and dentin. The current study evaluates whether reducing the etching time to 5 s from the recommended 15 s or increasing it to 30 s has an effect on dentin bonding. 108 extracted molars were assigned to 3 bonding agent groups (n = 36): (a) Single Bond (SB), (b) One-Step (OS), and (c) Syntac Single Component (SSC). Each group was further divided into three subgroups (n = 12) of different etching times: 5, 15, and 30 s. All groups were bonded with Z100 composite resin according to the manufacturer's instructions. All specimens were thermocycled 300 times between ± 5°C and ± 55°C, and shear bond strength testing and mode of failure analysis were performed. The bond strength of SB (5 s: 15.5 MPa ± 4.4; 15 s: 16.5 MPa ± 3.1; 30 s: 16.8 MPa ± 3.2) and OS (5 s: 13.7 MPa ± 1.8; 15 s: 12.4 MPa ± 3.8; 30 s: 10.6 MPa ± 3.8) showed no significant differences (p 0.05) for the different etching times. For SSC, different etching times showed significant differences (5 s: 10.9 MPa ± 1.8; 15 s: 7.5 MPa ± 2.5; 30 s: 6.4 MPa ± 2.1). The mode of failure for SB and OS was adhesive or mixed adhesive/cohesive. For SSC, all failures were adhesive. Etching times of less than 15 s do not seem to adversely affect bonding to dentin. Keywords: etching time, dentin, shear bond strength, adhesion, single-component adhesive systems, dental materials

To evaluate bonding penetration into different enamel substrates. Ten extracted human molars were mesiodistally sectioned. Buccal and lingual enamel surfaces were divided into four equal areas using sticky wax. The central two areas of each tooth (n = 20) were demineralized for 12 weeks using an acidic gel (pH 4.8). The lateral areas served as controls. After demineralization, ten specimens were remineralized in a saliva substitute for three weeks. An amine fluoride solution (Elmex Fluid) was applied on one half of each specimen before acid etching. After etching for 120 s, an enamel-bonding agent (Heliobond) containing 0.1% rhodamine was applied onto test and control areas, and was light cured for 60 s. Subsequently, the specimens were sectioned and tag length was determined using a confocal laser scanning microscope (CLSM). Results were statistically compared with ANOVA followed by Scheffe's and Bonferroni/Dunn post hoc tests. With a mean penetration depth of 68 ± 22 µm, tags in demineralized enamel were significantly longer than in other groups (p = 0.01). Penetration decreased significantly in remineralized areas or when fluoride was used (p = 0.01), but was still significantly deeper than in control sites (p = 0.01). Penetration of an unfilled resin into enamel was considerably influenced by the degree of dental hard tissue mineralization. Penetration was increased in demineralized enamel; however, remineralized enamel also allowed good penetration of the bonding agent. Keywords: dental material, enamel-bonding agent, penetration, enamel, confocal scanning laser microscopy, in vitro

To determine the bond strengths promoted by an adhesive system to human, bovine, and porcine enamel and dentin, and compare their etched micromorphology by scanning electron microscopy. Thirty sound freshly extracted teeth were used in this study: ten human third molars, ten bovine incisors, and ten porcine molars. The crowns of human (H), bovine (B), and porcine (P) teeth were ground with 600-grit SiC paper to expose either enamel (E) or mid-depth dentin (D) surfaces. After application of the adhesive resin, composite crowns approximately 8 mm high were built up with TPH Spectrum composite. After 24 h of water storage, specimens were serially sectioned in the buccal-lingual direction to obtain 0.8 mm slabs, which were trimmed to an hourglass shape of approximately 0.8 mm2 at the bonded interface. Specimens were tested in tension in a universal testing machine (0.5 mm/min). Results were statistically analyzed with ANOVA and Tukey's test at the 95% confidence level. Tukey's test showed significant differences between bond strengths obtained on enamel and dentin (p 0.05). However, there were no statistically significant differences in µTBS between human, bovine, and porcine teeth. SEM observations revealed a similar dentinal morphology for the three species. However, porcine enamel specimens presented a very different distribution of enamel prisms. Bovine teeth proved to be possible substitutes for human teeth in either dentin or enamel bond testing. However, even though porcine teeth provided enamel and dentin bond strengths similar to human and bovine teeth, enamel morphology presented a very different configuration. Keywords: enamel, dentin, porcine, bovine, bond strength

The aim of this study was to evaluate the effect of three different adhesive systems on microleakage of Class V restorations after the use of sodium hypochlorite. One-hundred eighty bovine incisors were selected and randomly divided into 9 groups (n = 20): G1: Single Bond (SB); G2: 10% NaOCl solution (NS) + SB; G3: 10% NaOCl gel (NG) + SB; G4: Prime & Bond NT (PB); G5: NS + PB; G6: NG + PB; G7: Gluma One Bond (GOB); G8: NS + GOB; G9: NG + GOB. Standardized Class V cavities were prepared. All teeth were etched with 37% phosphoric acid for 15 s. In groups 2, 5, and 8, a 10% NaOCl solution was applied for 60 s to the dentin, and in groups 3, 6, and 9, a 10% NaOCl gel was applied to dentin for 60 s. All cavities were restored with composite resin Definite. The specimens were thermocycled for 1000 cycles (5°C to 55°C) and then immersed in 2% buffered solution of methylene blue for 4 h. The specimens were sectioned and analyzed according to a ranking score (0 to 4). Kruskal-Wallis and Mann-Whitney non-parametric tests (p = 0.05) were used for statistical analysis. The NaOCl treatment significantly increased microleakage at the dentin margin (p = 0.0129) as shown by the following sums of ranks: G1 = 1008.0a; G4 = 1301.5ab; G3 = 1687.0ab; G7 = 1744.0bc; G2 = 1802.0c; G9 = 1880.0c; G5 = 1889.0c; G8 = 1950.0c; G6 = 1963.0c (different superscripts indicate significant differences). For enamel, there were no statistically significant differences among the groups (p > 0.05). Depending on the adhesive system used, the application of NaOCl increased microleakage along dentin margins. Keywords: sodium hypochlorite, microleakage, dentin

The aim of this in vitro study was to compare the microtensile bond strength (MTBS) between root canal and pulp chamber dentin with two bonding strategies (self-etching primer and total-etch technique). The pulp chamber of four human canines was accessed and the pulp chamber and root canal prepared with spiral drills. The teeth were cut into halves parallel to the long axis of the tooth and randomly assigned to two groups: Clearfil SE Bond + AP-X(SE) (Kuraray) and SingleBond + Filtek Z250(SB) (3M ESPE). After 24 h in water storage, the specimens were cut perpendicular to the root into 1.0-mm slices with a low-speed diamond saw. Specimens were trimmed to obtain hourglass shapes with a bond area of 1.0 mm2 (n = 12). Three specimens were obtained from the cervical root canal dentin (R) and from the coronal pulp chamber dentin (C). The MTBS was measured in a Bencor device with an Instron machine at a crosshead speed of 0.5 mm/min. The data was analyzed with two-way ANOVA and Tukey LSD post hoc (p 0.05). MTBS in MPa (mean ± SD) were: SB.C = 25.3 (± 6.5)a; SB.R = 16.9 (± 6.0)b; SE.C = 16.9 (± 3.4)b; SE.R = 16.8 (± 5.3)b. Means with the same letter are not statistically different at p 0.05. When data were pooled for "dentin region", coronal pulp chamber dentin resulted in statistically higher bond strengths than root canal dentin (p 0.013). Bonding to pulp chamber dentin seems to be more predictable than to root canal dentin. In the former region, the total-etch technique may result in a higher bond strength. Keywords: microtensile bond strength, root canal, dentin bonding, one-bottle bonding system, acid etching, self-etching primer

To evaluate the efficacy of two adhesive systems in reducing microleakage when applied with three different adhesive placement techniques. Sixty freshly extracted caries-free human premolars and molars were used. MO/DO Class II standardized preparations were performed with the gingival margin placed 1 mm above the CEJ. Teeth were randomly divided into 2 groups (group I: Prime& Bond NT, Dentsply/Caulk; group II: Single Bond, 3M Espe). Each group was divided into 3 subgroups: (A) application of 2 coats and one cure: IA-IIA; (B) 2 coats and 2 cures of each adhesive system: IB-IIB; and (C) one coat of each adhesive along with the manufacturers' B1 flowable resin (0.5-mm thick layer) cured together at once: IC-IIC. Each coat was cured for 20 s at 800 mW/cm2 using a quartz-tungsten halogen light (Elipar Trilight, 3M ESPE). Teeth were then restored using 2-mm increments of an A2 microhybrid composite (Esthet-X, Dentsply/Caulk). All teeth were stored in distilled water at 37°C for 24 h, thermocycled (500x, 5° to 55°C, 30 s dwell) and then placed in a 0.5% methylene blue dye solution for 24 h at 37°C. Samples were sectioned longitudinally and evaluated for microleakage at the gingival margin under a stereomicroscope at 20X magnification. Dye penetration was scored using an ordinal scoring system, where 0: no penetration; 1: enamel penetration; 2: gingival dentin penetration; 3: axial dentin penetration. Kruskal-Wallis and Mann-Whitney tests were used. A Mann-Whitney U-Test revealed no statistically significant difference between subgroups. Although not statistically significant, P&B NT (two coats and one cure) revealed the lowest microleakage scores. In the experimental model adopted for this study, microleakage was not affected either by the adhesive or its placement technique. Keywords: adhesive system, Class II restoration, composite resin, microleakage

To determine the depth of cure of 5 blue LED curing devices compared to that obtained with 3 QTH curing devices. The LED curing devices tested were 1) e-Light: 40 s; 2) Elipar FreeLight: 40 s; 3) Elipar FreeLight 2: 20 s and 40 s; 4) Ultra-Lume LED 2: 20 s and 40 s; 5) LEDemetron 1: 20 s and 40 s. The QTH curing devices tested were 1) Optilux 501: standard light guide 20 s and 40 s, turbo light guide 20 s; 2) Elipar TriLight: 40 s; 3) Astralis 10: 20 s. Surface hardness was measured (Zwick Z2.5/TS1S) 10 min after exposure on the top and bottom surface of resin samples (Tetric Ceram A3, 1 to 5 mm; 0.5 mm increment, diameter 5 mm, n = 9) which were cured at a distance of 7 mm from the bottom of the sample to the light-guide tip to simulate a Class II curing situation. A reference sample was cured under direct contact with the light guide. The reference sample with the greatest top surface hardness of all devices measured served as the overall control. A bottom/top surface hardness ratio of >= 80% of the reference sample cured at zero distance was defined as clinically acceptable for safe curing. A descriptive statistical analysis was carried out. With QTH lamps, the mean maximum resin composite sample thickness which cured sufficiently (relative surface ratio >= 80%) was: 3 mm for Optilux 501, standard light guide, 40 s; 2.5 mm for Trilight, 40 s; and 1.5 mm for Astralis 10, 20 s. The first-generation LED curing devices FreeLight and GC e-Light, both applied for 40 s, and the Optilux 501 operated for 20 s with the standard and the turbo light guide could not sufficiently cure a 1-mm-thick sample at a distance of 7 mm. The new FreeLight 2 and the Ultra-Lume LED 2 cured resin samples up to 2.5 mm thick in 40 s with a relative surface ratio >= 80%, while no sufficient depth of cure was found after 20 s exposure time for the FreeLight 2. However, a 1.5-mm depth of cure with the Ultra-Lume LED 2 and the LEDemetron 1 with the 13/11 mm light guide was obtained after 20 s. The LEDemetron 1 equipped with a 13/8 mm light guide reached a depth of cure of 2.0 mm. No significant difference was found between the Elipar FreeLight 2, Ultra-Lume LED 2, and LEDemetron 1 in their overall curing potential (linear statistical model, 5% level, Bonferroni-correction) given 40 s or 20 s of exposure time. Application of the first-generation LED curing devices FreeLight and e-Light did not ensure clinically sufficient depths of cure, while the new high-power LED curing devices FreeLight 2, Ultra-Lume LED 2, and LEDemetron 1 showed a curing potential equal to the Optilux 501, given 40 s of exposure time. Keywords: blue LED curing devices, QTH curing devices, depth of cure, clinically relevant distance, posterior teeth

The purpose of this in vivo study was to evaluate the marginal integrity of composite resin buildups after full crown preparation, and to identify possible changes during the provisional phase of the manufacturing process of the final restorations. Two test groups were determined for the use of an autocuring (Clearfil New Bond, Kuraray) and a light-curing (Optibond FL, Kerr) dentin adhesive. After rubber-dam application, both dentin adhesives were used with the total-etch technique. Then, an autocuring composite resin was applied for the core buildup. Impressions of the built-up teeth were taken directly after preparation and before cementation of the final restorations. During the provisional phase, which lasted from 7 to 28 days, the prepared teeth were restored with cemented provisional crowns. Replicas of the built-up teeth were manufactured and examined with a scanning electron microscope. For the autocuring dentin adhesive, only one buildup showed a gap 10 µm wide and 100 µm long. For the light-curing dentin adhesive, two samples revealed gaps that were 10 µm wide and had lengths of 100 µm and 75 µm, respectively. No change could be perceived when comparing the state of the composite/tooth interface after preparation and before final cementation. The results show that when using an autocuring composite resin in combination with dentin adhesives, nearly gap-free margins of composite buildups can be achieved and therefore might serve as a sound basis for the final restoration. Keywords: composite resin buildup, marginal fit, clinical study

The aim of this study was to evaluate the clinical performance of two polyacid-modified resin composites (Dyract AP and F2000) in posterior teeth after 1 year of clinical service. Seventy-two Class I restorations were performed in 33 patients (average age 25 years) by one operator. Eighty-two per cent of the restorations were located in molars. Before the proceedings, patients were informed about the aim of the study and they gave written consent to participate. At least one restoration of each material was placed in each individual. The materials were applied according manufacturer's instructions. Following finishing and polishing, one examiner performed the clinical baseline examination using the adapted USPHS system. To be included in the clinical trial, a restoration had to be rated "Alpha". After one year, 25 patients were recalled and 56 restorations were evaluated using the adapted USPHS system. All restorations were classified as clinically satisfactory (Alpha or Bravo). However, there was a decrease in restoration quality compared to baseline. Statistical analysis (X2 and Fisher's exact test) demonstrated differences only in relation to superficial roughness, with exhibiting F2000 more surface roughness than Dyract AP (p 0.01). Based on the methodology employed, all restorations were satisfactory after one year and the two materials performed similarly, except for the surface roughness criteria. Keywords: compomer, clinical trial, Dyract AP, F2000