The Journal of Adhesive Dentistry, 01/2004

The aim of this study was to verify the influence of the storage time and the cutting speed during specimen preparation on the bond strength of a single-bottle adhesive to dentin. A flat dentin surface was exposed in 36 human third molars. The adhesive system (Single Bond) was applied according to the manufacturer's instructions, and composite resin crowns (Z250) were constructed incrementally. Specimens were stored for 10 min, 24 h, or 1 week in distilled water at 37°C before being longitudinally sectioned in both the "x" and "y" directions at different cutting speeds (0.5, 1.6, and 2.6 m/s) to obtain sticks with a cross-sectional area of approximately 0.8 mm2. The specimens were tested in a tensile load machine (0.5 mm/min) and the fracture mode analyzed. A two-way ANOVA with storage time (3 levels) and cutting speed (3 levels) as factors was used to compare the mean microtensile bond strengths. Highly significant main effects and interaction (p 0.0001) were detected. The highest mean bond strength was obtained with a storage time of 1 week and cutting speed of 2.6 m/s. The lowest mean was found when the specimens were prepared immediately after composite resin placement and sliced at 0.5 m/s. Both the storage time and the cutting speed may affect the bond strength results. Therefore, these variables must be controlled in microtensile bond strength tests. Keywords: microtensile test, cutting speed, resin-dentin bond strength

This study tested the hypothesis that the hydration condition of the tooth during bonding or storage may affect the bond strength of a single-step, self-etching adhesive to dentin. Twelve extracted human third molars were transversally sectioned to expose flat, mid-dentin surfaces. Six teeth were dehydrated in ascending ethanol concentrations for several days while 6 teeth were kept hydrated in distilled water. The teeth were bonded with the single-step, self-etching adhesive One-Up Bond F (Tokuyama, Japan) according to directions. Resin composite buildups were constructed incrementally with Z 250 (3M ESPE). The bonded hydrated and dehydrated teeth were then divided into 2 subgroups and stored either in distilled water or in a dry condition for 24 h before being prepared for the microtensile bond strength test. Bonded beams of approximately 0.8 mm2 were tested in tension at 0.5 mm/min in a testing machine. Separate dentin disks were bonded with the adhesive and prepared for transmission electron microscopy (TEM). Bond strengths of specimens stored in water were: 25.0 ± 10.6 and 18.9 ± 9.1 MPa for hydrated and dehydrated teeth, respectively. Bond strengths of specimens stored dry were significantly higher (p 0.001): 46.1 ± 21.4 and 40.9 ± 19.1, for hydrated and dehydrated teeth, respectively. Two-way ANOVA showed that previous hydration condition of the teeth had no effect on the bond strength, regardless of the storage condition (p > 0.05). However, storage of the bonded teeth in water caused significant reductions in the bond strength, regardless of the previous hydration condition of the teeth. TEM showed massive silver nitrate impregnation in the adhesive layer of water-stored specimens. Postbonding water exposure had a highly significant effect on bond strength of the single-step, self-etching adhesive. Keywords: dentin bonding, water trees, permeability

The aim of this in vitro study was to evaluate the microtensile bond strengths (MTBS) of two total-etch one-bottle adhesive systems to natural cervical lesions with 2 different etching times (15 s vs 30 s). Thirty-two human canines and premolars with saucer-shaped noncarious cervical defects were cleaned and randomly assigned to 4 groups. The adhesive systems - Single Bond (SB; 3M ESPE) or OptiBond Solo Plus (OP; Kerr) - were applied on cervical dentin after acid etching with the proprietary acid gel (35% or 37.5% phosphoric acid) for 15 s (manufacturer's instruction) or for 30 s. The respective hybrid composite was inserted in three increments and light cured. After 24 h water storage, the specimens were cut perpendicularly with a low-speed diamond saw (Isomet) to obtain slices with a cross section of ca 0.8 mm. After that, the slices were trimmed with a diamond bur to obtain a surface area of 0.7 ± 0.05 mm2 (n = 12). MTBS was measured in a Bencor device with an Instron machine at a crosshead speed of 0.5 mm/min. The data were subjected to two-way ANOVA and Tukey's LSD post-hoc test (p 0.05). MTBS are given in MPa (mean ± SD), where means with the same superscript letter are not statistically different at p 0.05: OP15 = 30.9 ± 8.8ab, SB15 = 25.6 ± 9.6bc, OP30 = 19.0 ± 4.8c, SB30 = 35.9 ± 11.0a. When data were pooled for "adhesive system", SB resulted in statistically higher bond strengths than OP (p 0.043). "Acid etching time" had no significant effect (p 0.766), but the interaction of the two main factors yielded significant differences (p 0.0001). Extending etching time to 30 s resulted in a more predictable bond to noncarious cervical sclerotic dentin with SB, but resulted in lower MTBS with OP. Composite bonding to cervical sclerotic noncarious dentin may depend on acid demineralization capacity and bonding system. Knowing the etching demineralization rates of the commercially available acid etching seems to be an important factor for selecting the best acid-etching time of cervical sclerotic dentin. Keywords: cervical sclerotic dentin, acid etching time, microtensile bond strength

The aim of this study was to evaluate the marginal integrity of four self-etching adhesives (Prompt L-Pop III, Resulcin Aqua Prime & MonoBond N, AC Bond, AC Bond + Desensitizer) and three total-etch adhesives (OptiBond FL, Excite, Gluma Comfort Bond) in two different application protocols. Standardized MOD cavities (n = 40) were prepared in 280 extracted human teeth (one cervical margin in cementum, one in enamel). In one application protocol, the adhesive was applied prior to placement of the Tofflemire matrix (n = 20); in the other, the metal matrix was placed first (n = 20). Light curing was carried out from the occlusal aspect. After thermocycling (5000 times, 5°C and 55°C), specimens were immersed in 2% methylene blue for 10 s. Then the median percentages of dye-penetrated margins (surface analysis) were determined separately for the cervical cementum, cervical enamel, and lateral enamel margins of the proximal boxes. At the cervical cementum margins, statistically significantly worse results were obtained for all adhesives when the matrix system was placed prior to application of the adhesive. In the cervical enamel margins, OptiBond FL, Gluma Comfort Bond, and Prompt L-Pop III performed significantly better when the adhesive was applied prior to the matrix. On lateral enamel margins, only OptiBond FL and Resulcin Aqua Prime showed significantly less dye penetration if the matrix was placed first. Most of the total-etch materials produced marginal integrity significantly superior to that of the majority of the self-etching materials. Due to a significant influence of the application protocol on marginal integrity, it is strongly recommended to apply the adhesive system before placement of the matrix. Keywords: self-etching adhesives, Class II cavities, in vitro study, marginal integrity, dye penetration

To evaluate the effects of removing dentin collagen exposed by acid etching on the microleakage of bonded restorations with and without flowable composite application and submitted to thermocycling and long-term water storage. Standardized Class V cavities were prepared in 180 bovine incisors. They were randomly assigned to three groups according to the adhesive technique used. Conventional group (C): Single Bond was applied according to the manufacturer's instructions and Z250 composite was placed. Hypochlorite group (H): After acid etching a 10% NaOCl aqueous solution was applied for 1 min, then Single Bond and Z250 were applied. Hypochlorite and Flowable group (HF): Similar to group H, but following adhesive application, a thin layer of Natural Flow flowable composite was applied before the Z250. Each group was divided into three subgroups (0, 6, 12), which remained immersed in distilled water for 24 h or 6 or 12 months and underwent 500, 1500 or 2500 thermal cycles, respectively. At the end of each storage time, the specimes were stained with silver nitrate, decalcified, immersed in methyl salicylate for clearing and observed under a stereomicroscope to determine microleakage (scores 0 to 4). The data were analyzed using the Kruskal-Wallis and the Multiple Comparison Tests (α = 0.05). After 12 months, every group showed significant increases in microleakage. There was no significant difference between Groups H and HF for the three different periods of time, but they showed statistically less microleakage than Group C. The removal of dentinal collagen reduced the marginal microleakage when compared to the conventional technique. The use of the flowable composite did not produce significant effects. No technique was completely effective in preventing microleakage. Keywords: adhesion, microleakage, dentin, deproteinization, sodium hypochlorite

The aim of this study was to assess the microleakage of a pit-and-fissure sealant after classical enamel preparations (prophylaxis followed by acid etching alone and mechanical widening with bur) and after air abrasion. Ninety noncarious freshly extracted third molars were randomly assigned to three groups of 30. In each group, the mesial halves of the fissures were treated with air abrasion and conditioned with acid etching for 15 s. In group 1, the distal halves were treated with acid etching alone. In group 2, the distal halves of the fissures were widened mechanically with a bur and etched for 15 s. In group 3, the distal halves were prepared with air abrasion alone. Then the sealant (Clinpro) was applied on the occlusal fissures of all teeth, according to the manufacturer's recommendations. The teeth were thermocycled and the samples placed in a 1% methylene blue dye solution. The teeth showing microleakage and the means of infiltration were assessed with an image analysis system. The microleakage of sealants prepared with air abrasion alone displayed significantly greater microleakage (80%) (p 0.0001) than the ones placed after prophylaxis and etching (13.33%), bur and etching (20%), or air abrasion and etching (22.2%). The samples prepared with air abrasion alone also showed the highest mean microleakage (1.14 ± 1.4 mm) when compared to samples receiving prophylaxis and acid etching (0.12 ± 0.41), bur and acid etching (0.08 ± 0.26), or air abrasion and acid etching (0.09 ± 0.4) (p 0.05). No significant difference was noted between the three types of enamel preparation when etching was performed. Air-abrasion treatment does not eliminate the need for etching the enamel surface before applying the sealant. Keywords: microleakage, air-abrasion, etching, sealant

The aim of this study was to evaluate the marginal adaptation of high-viscosity resin composite restoratives bonded to dentin in a cylindrical cavity model. The buccal enamel of 64 human premolars was removed and cylindrical cavities 3 mm in diameter and 1.3 mm in depth were prepared on each dentin surface. The cavities were divided into 8 groups of 8 cavities each and restored according to the manufacturers' instructions with the following adhesive/composite systems: Bond 1/Alert, Stae/Glacier, OptiBond Solo/Prodigy Condensable, One-Step/Pyramid, Solidbond/Solitaire, Prime&Bond NT/Surefil, One Coat Bond/Synergy, and Scotchbond 1/Z250. The composite surfaces were pressed against mylar strips, covered with cover slips, and photopolymerized in a single increment for 40 s. The restorations were polished with wet SiC papers of 320 to 1000 grit size to expose dentin margins. The marginal adaptation was evaluated immediately after photopolymerization and again after 1 week of storage in water at 37 ± 1°C. Evaluation was performed under a metallographic microscope at 200X magnification by recording the frequency of gap-free restorations (GF), the percentage length of the debonded margins relative to the cavity periphery (DM), the width of the maximum marginal gap (MG), and the marginal index (MI = MG x DM / 100). The results were statistically analyzed with one-way ANOVA and the Mann-Whitney U-test at α = 0.05. No incidence of gaps was found in 62.5% of One Coat Bond/Synergy and 37.5% of OptiBond Solo/Prodigy Condensable restorations. All the other restorative systems exhibited restorations with gaps. One Coat Bond/Synergy, Scotchbond 1/Z250, and OptiBond Solo/Prodigy Condensable were the groups with the lowest DM values, while Stae/Glacier showed the highest DM values. One Coat Bond/Synergy and OptiBond Solo/Prodigy Condensable revealed the lowest MI values and Stae/Glacier the highest. No statistically significant differences were recorded between immediate evaluation and evaluation after 1 week of water storage. The results showed that all the adhesive/composite systems examined failed to achieve gap-free margins with dentin. The restorative systems One Coat Bond/Synergy, Optibond Solo/Prodigy Condensable, and Scotchbond 1/Z250 presented the best marginal adaptation of all the systems tested. No improvement was recorded on the quality of marginal adaptation following 1 week of water storage. Keywords: high-viscosity resin composites, marginal adaptation, dentin bonding

Despite the improvements of resin-modified glass-ionomer cements, the dentin bond strength of these materials remains inferior to that provided by "bonding system/composite" combinations and limits the clinical use of RMGIC. The objective of this in vitro study was to investigate the effect of new self-etching bonding systems on the adhesion to dentin of Fuji II LC. Seven recent self-etching systems were studied (Clearfil SE Bond = CSE, Optibond Solo Plus Self-Etching Primer = OSP, One Up Bond F = OUP, Mac Bond II = MB2, Xeno III = XB3, ADPER Prompt-L-Pop = ADP, Unifil Bond = UB) and compared with Cavity Conditioner (C). After the bonding procedure, a resin-modified glass-ionomer cylinder (Fuji II LC) was bonded to the surface using a Teflon mold (diameter: 3 mm; height: 5 mm). The different specimens were tested in a shear bond mode (0.5 mm/min). Statistical analyses were performed with one-way ANOVA and Fischer PLSD test (p 0.05). The one-way ANOVA revealed a significant influence of the surface treatment parameter (p 0.0001). The lowest shear bond strength values were obtained with Cavity Conditioner. The highest values were obtained with MB2. The multiple comparisons revealed that ADP = OBP = XB3 = OUB = UB = CSE and that UB = CSE = MB2. The application of the 7 self-etching adhesives tested in this study improves the dentin shear bond strengths of Fuji II LC. This increase depended on the adhesive system and ranged from 50% for ADP up to 130% for MB2. Keywords: resin-modified glass-ionomer cements, self-etching adhesives, shear bond strength

To study the dentin disinfecting capacity of glutaraldehyde-containing bonding agents. Uniformly sized bovine dentin blocks infected with Enterococcus faecalis ATCC 29212 were treated according to manufacturer's instructions with a three-step bonding system (Syntac Classic), its single components, or Gluma Primer. Bacterial growth from dentinal filings obtained immediately after application of the bonding agents was assessed at different dentin depths. Minimal inhibitory concentration and minimal bactericidal concentration of glutaraldehyde against E. faecalis were determined. Both Gluma Primer and Syntac Adhesive disinfected dentin, while the other components failed to do so. This was explained by the high antibacterial efficacy of glutaraldehyde even at low concentrations. Applied in consecutive order, the Syntac bonding system disinfected dentin blocks equally well with or without previous application of Gluma Primer. Under the conditions of the current study, bonding agents containing glutaraldehyde appear to be good dentin disinfectants compatible with bonding systems. However, their effect on pulp tissue awaits further clarification. Keywords: dentin disinfection, glutaraldehyde, bonding, adhesive

The aim of this in vivo study was to evaluate the clinical performance of porcelain veneers after 5 and 10 years of clinical service. A single operator placed porcelain laminates on 87 maxillary anterior teeth in 25 patients. All restorations were recalled at 5 years and 93% of the restorations at 10 years. Clinical performance was assessed in terms of esthetics, marginal integrity, retention, clinical microleakage, caries recurrence, fracture, vitality, and patient satisfaction. Failures were recorded either as "clinically unacceptable but repairable" or as "clinically unacceptable with replacement needed". Porcelain veneers maintained their esthetic appearance after 10 years of clinical service. None of the veneers were lost. The percentage of restorations that remained "clinically acceptable" (without need for intervention) significantly decreased from an average of 92% (95 CI: 90% to 94%) at 5 years to 64% (95 CI: 51% to 77%) at 10 years. Fractures of porcelain (11%) and large marginal defects (20%) were the main reason for failure. Marginal defects were especially noticed at locations where the veneer ended in an existing composite filling. At such vulnerable locations, severe marginal discoloration (19%) and caries recurrence (10%) were frequently observed. Most of the restorations that present one or more "clinically unacceptable" problems (28%) were repairable. Only 4% of the restorations needed to be replaced at the 10-year recall. It was concluded that labial porcelain veneers represent a reliable, effective procedure for conservative treatment of unesthetic anterior teeth. Occlusion, preparation design, presence of composite fillings, and the adhesive used to bond veneers to tooth substrate are covariables that contribute to the clinical outcome of these restorations in the long term. Keywords: porcelain veneers, adhesion, clinical trial