The Journal of Adhesive Dentistry, 03/2003

The effect of carbamide peroxide concentration and length of exposure on fracture toughness (KIC) of existing composite-dentin interfaces was assessed using the notchless triangular prism (NTP) specimen KIC test. Freshly extracted human molars and premolars were wet ground on 600-grit SiC to obtain 4 x 4 x 4 x 4 mm triangular prisms, exposing buccal or lingual dentin. Dentin surfaces were bonded using a resin composite (Z-250, 3M) and SingleBond dentin bonding system (3M) to obtain 180 8-mm-long dentin-composite NTP specimens. The bonding system was applied using the "wet-bonding" technique. The bonded specimens were randomly assigned to 20 groups. The effect of exposure to three control solutions (tap water, Carbopol, and Carbopol-urea) and to four concentrations (11%, 13%, 16%, 21%) of carbamide peroxide (Perfecta, Premier) was assessed. Testing was conducted after 1, 2, and 3 weeks representing a cumulative exposure of 14, 42, and 70 h. The maximum force recorded before fracture was used to calculate KIC. The data were statistically analysed using two-factor ANOVA followed by one-way ANOVA and Bonferroni multiple means comparisons. Selected fractured surfaces were characterized using SEM. Data analysis revealed that cumulative exposure to bleaching agent for 70 h significantly (p 0.01) decreased the interfacial KIC, regardless of concentration. For the 16% and 21% concentrations, a significant reduction was observed after 42 h. The results suggest that bleaching could adversely affect the interfacial fracture toughness of dentin-resin composite adhesive interfaces.

To determine the effects of different surface moisture on the bond strength of an ethanol/water-based (Single Bond [SB]), an acetone-based (One-Step [OS]), and a water-based (Syntac Single Component [SC]) adhesive system to dentin. On 90 human third molars, a flat superficial dentin surface was exposed by abrasion with 600-grit SiC paper. The adhesives were applied to a delimited area of 52 mm2 according to the manufacturers' instructions on either dry (oil-free air/30 s) or rewetted surfaces (1.5, 2.5, 3.5, 4.0 or 4.5 µl of distilled water), and composite crowns were constructed incrementally. After storage in distilled water at 37°C for 24 h, the teeth were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks with a cross-sectional area of 0.8 mm2. The specimens were tested in tension at 0.5 mm/min and the fracture mode analyzed. Resultant bond strength was expressed as an index that includes bond strength values of the different fracture patterns and the specimens that failed during preparation for the microtensile testing. The data was analyzed by two-way ANOVA, Tukey's multiple comparison, and regression analysis. Highly significant main effects and interaction (p 0.0001) were detected. A quadratic relationship between the bond strength index and the surface moisture was identified (R2 = 0.95, p 0.001). SB showed a maximum bond strength (42.2 ± 6.7 MPa) that was statistically similar (p = 0.4996) to the maximum bond strength of OS (40.1 ± 4.6 MPa), although obtained at a different degree of moisture (ca 1.5 µl for SB and 3.5 µl for OS). SC showed its maximum bond strength (27.7 ± 3.9 MPa) with 1.5 µl moisture. SB presented its highest bond strength at 1.5 µl of water, which was significantly higher than the bond strength obtained at any other degree of moisture (p 0.05). OS achieved its maximum bond strength at 3.5 µl of water; however, that value was not statistically different (p > 0.05) from the values obtained with 1.5 µl to 4.0 µl of water. Similarly, highest bond strengths obtained with SC were not different (p > 0.05) within the range of 0 µl to 3.5 µl of water. All adhesive systems tested had a different moisture spectrum in which higher bond strengths were obtained. SB and SC performed better on a drier substrate, while OS showed better performance on wetter substrates. OS and SC had a broader range of moisture within which maximal bond strength could be achieved.

This study determined which light source was best at photopolymerizing five representative brands of resin composite. The hypothesis was that there would be no difference in the hardness of the composites when irradiated by any of the lights. Six curing light/tip combinations were used to photopolymerize five resin composites. In accordance with the manufacturer's instructions, the PAC light was used for 3 s and the high intensity QTH light was used for 5 s. The other QTH and LED lights were used for 40 s. To represent the clinical environment, the samples were irradiated at a distance of 2 and 9 mm away from the tip of the light guide. The Knoop hardness was measured at the top and bottom of the composites after 15 min and again at 24 h. The hardness data were compared using a general linear model analysis with Sidak's adjustment for multiple comparisons with p 0.01 as the level of significance. The 6 curing light/tip combinations had different effects on the hardness of the 5 composites (p 0.01). The two LED lights could not cure the neutral shade of Pyramid Enamel in 40 s. As the distance increased from 2 to 9 mm, the decrease in hardness was not similar amongst the different light/tips and composite combinations (p 0.0012). The curing light/tip combination which delivered the greatest total energy produced the hardest specimens. 1) The 6 curing light/tip combinations had different effects on the hardness of the 5 composites (p 0.01). 2) Neither of the two LED lights used was able to adequately polymerize the five resin composites tested. 3) The QTH light, which delivered the greatest total energy, always produced the hardest resin composite. 4) When the distance of the composites from the light guides was increased, the effect on their hardness was not the same for all light/tip combinations. It is therefore not possible to predict the performance of a curing light at 9 mm based upon power density measurements or hardness data recorded when the tip of the light guide is 2 mm away.

To evaluate the influence of occlusal load cycling on cervical microleakage of proximal slot restorations located in dentin, using two self-etching and two one-bottle dentin adhesive systems. 240 proximal slot cavities were prepared in 120 bovine teeth and divided into two groups, one with load cycling and one without. The groups were then subdivided into four subgroups according to the adhesive system used (Experimental EXL 547 Self-etching 3M, Clearfil SE Bond, Single Bond, and Optibond Solo Plus) and restored following the manufacturers' instructions. The teeth were then submitted to mechanical load cycling with a force of 80 N and a frequency of 5 Hz, simultaneously over both restorations of each tooth, for a total of 50,000 cycles per specimen. All specimens were subsequently immersed in a 2% methylene blue solution (pH 7.0), and sectioned to examine the extent of dye penetration under a stereomicroscope (40X). There was no statistically significant difference (p = 0.00002) between the loaded and unloaded teeth. However, a statistically significant difference was observed between the adhesive systems used. The experimental self-etching EXL 547 presented the lowest mean microleakage, but was only statistically significantly different from the Single Bond loaded and unloaded groups and the Clearfil SE Bond unloaded group. The application of 50,000 loading cycles did not affect the microleakage of the two self-etching and the two one-bottle adhesive systems evaluated. In vitro mechanical load cycling is an important factor to consider when evaluating the performance of adhesive systems under simulated masticatory conditions.

To evaluate in Class II restorations the marginal adaptation of ten packable composite resins in combination with the proprietary adhesive system. Standard Class II cavities were prepared in 100 extracted molars. The sample was randomly divided into ten groups. In each group, one specific packable composite was tested in association with its own adhesive: Groups: 1) Scotchbond1/FiltekP60; 2) Etch&Prime3.0/Definit; 3) Prime & Bond 2.1/SureFil; 4) Excite/Tetric Condensable; 5) Gluma/Solitaire; 6) Kerr Bonding/Prodigy Condensable; 7) One-step/Pyramid; 8) Tenure/Virtuoso; 9) Syntac/Cavex Packable; 10) Excite/Tetric flow/Tetric Ceram. The restored teeth were sectioned at three levels in the mesiodistal direction and processed for the microleakage test. On each section, the degree of dye penetration along the margins of the restoration was assessed, and the differences in the leakage given by the ten materials at either the occlusal or the cervical margin were evaluated for statistical significance. A statistical analysis was also conducted to assess the significance of the differences between the scores recorded at the occlusal margin and those measured at the cervical margin of the restoration. In general, the scores recorded at the cervical margin were significantly higher than those measured at the occlusal margin (p 0.05). When all of the groups were compared for microleakage at the occlusal margin, the only significant difference revealed by the statistical analysis was that the specimens treated with Etch″ 3.0 and Definit (group 2) exhibited a marginal adaptation significantly worse than that seen in groups 1, 3, 4, 6, 8, 10. The application of a thin layer of a flowable composite at the cervical margin as a liner underneath the packable composite enhanced the marginal adaptation of the restoration. The use of a self-etching primer to condition the dental substrate resulted at the occlusal margin in greater microleakage than when phosphoric acid was applied.

The incorporation of composite denture teeth as pontics in resin-bonded fixed partial dentures has been deemed to be short-lived. This study investigated whether pre- or posttreatments could improve the bonding of denture tooth pontics. A model fixed partial denture was fabricated that included composite denture teeth (Endura) bonded with 1 of 2 resin systems (C&B-Metabond or Aeliteflo). The bonding surface of the pontic was pretreated with one of three methods (air-particle abrasion [AA], AA plus silanization, or cavity preparation plus AA). The bonding areas between pontic and abutments were posttreated with 1 of 2 methods (reinforcement with fiber or metal post). Five bonded specimens for each treatment group were subjected to 20,000 thermocycles (4°C to 60°C; dwell time 60 s) before retentive forces (N) were determined. All data were analyzed with two-way ANOVA and Bonferroni's test (p = 0.05). All specimens that underwent the pre- and posttreatment outperformed untreated specimens. For the specimens bonded with C&B-Metabond and posttreated with a polyethylene fiber (Ribbond) or a metal post (DC Post), the mean retentive forces were 316 N and 301 N for mandibular specimens, and 354 N and 380 N for maxillary specimens, respectively. These values were significantly higher than those obtained with other pretreatment methods (p = 0.0003). For mandibular specimens bonded with Aeliteflo, specimens posttreated with Ribbond exhibited significantly higher retentive forces (332 N) compared to other specimens (p = 0.0001). Within the limitations of this study, the bond strength of a resin-bonded fixed partial denture incorporating a composite denture tooth as the pontic was improved by reinforcement with either a polyethylene fiber or a metal post.

Amelogenesis imperfecta is an inherited disorder that presents a major challenge to the dentist for prosthetic treatment of missing and/or malformed tooth structures. This clinical report presents the use and short-term clinical performance of adhesively-inserted full-ceramic restorations in the restoration of a case of amelogenesis imperfecta.

A clinical case is presented in which a new type of fiber post was used in combination with the proprietary dual-curing resin cement to bond in a wide, nonrounded root canal. The anatomic post was inserted and the relining resin photopolymerized. The anatomic post was then removed and a luting procedure was performed, as for any other translucent post. The clinical procedure was simple, and a superior fit to the root canal walls was achieved, thus reducing the amount of cement needed. The luting procedure described can be proposed as a clinical technique for routine use when the prepared root canal is too wide or not perfectly round.