Showing papers in "Operative Dentistry in 2003"

Buonocore memorial lecture, adhesion to enamel and dentin: current status and future challenges

Abstract: Bonding to tooth tissue can be achieved through an "etch&rinse," "self-etch" or "glass-ionomer" approach. In this paper, the basic bonding mechanism to enamel and dentin of these three approaches is demonstrated by means of ultramorphological and chemical characterization of tooth-biomaterial interfacial interactions. Furthermore, bond-strength testing and measurement of marginal-sealing effectiveness (the two most commonly employed methodologies to determine "bonding effectiveness" in the laboratory) are evaluated upon their value and relevance in predicting clinical performance. A new dynamic methodology to test biomaterial-tooth bonds in a fatigue mode is introduced with a recently developed micro-rotary fatigue-testing device. Eventually, today's adhesives will be critically weighted upon their performance in diverse laboratory studies and clinical trials. Special attention has been given to the benefits/drawbacks of an etch&rinse versus a self-etch approach and the long-term performance of these adhesives. Correlating data gathered in the laboratory with clinical results clearly showed that laboratory research CAN predict clinical effectiveness. Although there is a tendency to simplify bonding procedures, the data presented confirm that conventional three-step etch&rinse adhesives still perform most favorably and are most reliable in the long-term. Nevertheless, a self-etch approach may have the best future perspective. Clinically, when adhesives no longer require an "etch&rinse" step, the application time, and probably more importantly, the technique-sensitivity are substantially reduced. Especially "mild," two-step self-etch adhesives that bond through a combined micromechanical and chemical interaction with tooth tissue closely approach conventional three-step systems in bonding performance.

Microtensile bond strengths of an etch&rinse and self-etch adhesive to enamel and dentin as a function of surface treatment

Abstract: In light of the current trend towards "minimal invasive" dentistry, diverse cavity preparation techniques have been introduced as an alternative or addition to common bur instrumentation. This study investigated whether diamond sonoabrasion (SonicSys Micro, Kavo), air abrasion (Prep Start, Danville) and Er:YAG laser irradiation (Fidelis) produce surfaces at enamel/dentin that are equally receptive to bonding as traditional mid-grit diamond-bur (Komet) and 600-grit SiC-paper prepared surfaces, of which the latter two served as controls. An etch&rinse adhesive (OptiBond FL, Kerr) applied with and without prior acid-etching and a self-etch adhesive (Clearfil SE, Kuraray) were employed to bond the restorative composite (Z100, 3M ESPE) to the diversely prepared enamel and dentin surfaces. The microtensile bond strength (microTBS) was determined after 24 hours of storage in water at 37 degrees C. The results indicated that the manner of preparation of enamel and dentin prior to bonding procedures significantly influenced the bonding effectiveness of both the etch&rinse and the self-etch adhesive. Using an etch&rinse adhesive, separate acid-etching of air-abraded and Er:YAG-irradiated enamel and dentin surfaces remains mandatory. Bonding to diamond-sonoabraded and air-abraded enamel and dentin was, in general, not different from bonding to conventional diamond-bur prepared surfaces, whereas, bonding to Er:YAG-irradiated enamel and dentin surfaces in general resulted in a significantly lower bonding effectiveness compared to bonding to diamond-bur prepared surfaces.

Clinical evaluation of in-office and at-home bleaching treatments.

Abstract: This three-month, single-blind clinical study compared two whitening treatments, at-home with 10% carbamide peroxide and in-office with 35% hydrogen peroxide, for the degree of color change of teeth, color relapse and tooth and gum sensitivity. The degree of color change and color relapse was evaluated by using a colorimeter, shade guide and color slide photography. Teeth and gum sensitivity were self-evaluated by the subjects, who recorded daily the tooth and gum sensitivity they experienced during the two weeks of treatment and one week post-treatment. A 14-day at-home treatment was compared with 60 minutes of in-office treatment (two appointments, each with three 10-minute applications). The at-home treatment produced significantly lighter teeth than the in-office treatment during all active-treatment periods and follow-up visits according to all three-color evaluation methods. Color relapse for both treatments stabilized by six weeks. At-home treatment resulted in statistically significant higher gum sensitivity than in-office treatment during the latter part of the first week. For tooth sensitivity there were no significant differences between the treatments. Eighty four percent of the subjects reported at-home treatment to be more effective and 16% found no difference between the treatments. There were no subjects who reported the in-office treatment to be superior in tooth whitening to the at-home treatment.

Incompatibility of self-etch adhesives with chemical/dual-cured composites: two-step vs one-step systems.

Abstract: This study tested the null hypothesis that there no difference between two-step and one-step self-etch adhesives in their compatibility with these composites. The microtensile bond strengths (microTBS) of two two-step systems (Clearfil SE Bond, Kuraray and Tyrian SPE/One-Step Plus, BISCO) were compared with two one-step systems (Xeno III, Dentsply DeTrey and Brush&Bond, Parkell) for their coupling to a dual-cured composite. Silver tracer penetration of the four adhesives bonded to a light-cured or a chemical-cured composite was examined using TEM. Significant differences in microTBSs between composite curing modes were seen only in the one-step adhesives. For one-step self-etch adhesives bonded to the chemical-cured composite, TEM revealed signs of frank composite uncoupling along the adhesive-composite interface, which may be attributed to the adverse chemical interaction between the acidic adhesive and the composite. In addition, "water trees" that represent channels of increased permeability with the polymerized adhesive layer were also observed in the one-step adhesives. Both features were absent along the resin-dentin interfaces when chemical-cured composites were coupled to the two-step self-etch adhesives.

Effectiveness of composite cure associated with different curing modes of LED lights.

Abstract: This study compared the effectiveness of cure of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M-ESPE; GC e-Light [EL], GC) to conventional (Max [MX], Dentsply-Caulk [control]), high intensity (Elipar TriLight [TL], 3M-ESPE) and very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen lights. The 10 light-curing regimens investigated were: FL1 400 mW/cm2 [40 seconds], FL2 0-400 mW/cm2 [12 seconds] --> 400 mW/cm2 [28 seconds], EL1 750 mW/cm2 [10 pulses x 2 seconds], EL2 350 mW/cm2 [40 seconds], EL3 600 mW/cm2 [20 seconds], EL4 0-600 mW/cm2 [20 seconds] --> 600 mW/cm2 [20 seconds], TL1 800 mW/cm2 [40 seconds], TL2 100-800 mW/cm2 [15 seconds] --> 800 mW/cm2 [25 seconds], AS1 1200 mW/cm2 [10 seconds], MX 400 mW/cm2 [40 seconds]. Effectiveness of cure with the different modes was determined by measuring the top and bottom surface hardness (KHN) of 2-mm thick composite (Z100, [3M-ESPE]) specimens using a digital microhardness tester (n=5, load=500 g; dwell time=15 seconds). Results were analyzed using one-way ANOVA/Scheffe's post-hoc test and Independent Samples t-test (p<0.05). At the top surface, the mean KHN observed with LED lights ranged from 55.42 +/- 1.47 to 68.54 +/- 1.46, while that of halogen lights was 62.64 +/- 1.87 to 73.14 +/- 0.97. At the bottom surface, the mean KHN observed with LED and halogen lights ranged from 46.90 +/- 1.73 to 66.46 +/- 1.18 and 62.26 +/- 1.93 to 70.50 +/- 0.87, respectively. Significant differences in top and bottom KHN values were observed between different curing regimens for the same light, and between LED and halogen lights. Although curing with most modes of EL resulted in significantly lower top and bottom KHN values than the control, no significant difference was observed for the different modes of FL. Hence, the effectiveness of composite cure with LED LCUs is product dependent.

Mechanical properties of luting cements after water storage.

Abstract: This study determined the effect of water storage on flexural strength (FS) and compressive strength (CS) of 12 luting cements from different material classes. In addition, the influence of the curing method on the mechanical properties was investigated. The materials examined were two zinc phosphate cements (Harvard cement and Fleck's zinc cement), two glass ionomer cements (Fuji I and Ketac-Cem), three resin-modified glass ionomer cements (Fuji Plus, Fuji Cem and RelyX Luting), four resin cements (RelyX ARC, Panavia F, Variolink II and Compolute) and one self-adhesive universal resin cement (RelyX Unicem). The samples were prepared and tested according to ISO specifications. Specimens for FS and CS were loaded to fracture at a constant crosshead speed of 1 mm/minute. The mechanical properties were measured after the materials were stored in distilled water at a temperature of 37.0 +/- 1.0 degrees C for 24 hours and 150 days after mixing. In a one-way ANOVA, multiple mean value comparisons using Duncan's multiple comparison tests were performed. Resin cements had the highest flexural and compressive strengths, followed by self-adhesive universal resin cement. These materials were statistically stronger than resin-modified glass ionomer cements, glass ionomer cements and zinc phosphate cements.

Marginal adaptation, retention and fracture resistance of adhesive composite restorations on devital teeth with and without posts.

Abstract: This in vitro study generated data on the quality of marginal adaptation, fracture resistance and retention of several indirect adhesive composite configurations on root-treated premolars before and after a long-term fatigue test and compared these results to a control group of adhesive onlays on "vital" teeth. Six root-treated extracted human premolars per group, with four different restorative configurations with and without adhesive fiber posts, were evaluated. Another group of six premolars, "revitalized" by using diluted horse serum to simulate pulpal fluid and restored with adhesive composite onlays, served as the control. Marginal adaptation before and after long-term occlusal loading (1,200,000 occlusal loading cycles at max 49 N) was assessed by using the replica technique and quantitative evaluation in SEM at 200x magnification. The number of lost restorations was recorded after loading. Fracture resistance and fracture patterns were evaluated by using a universal-testing machine on the fatigued samples. No significant differences (p > 0.05) between groups were detected before and after loading for the percentage of "continuous margin" at the total marginal length. Loading had a significant (p 0.05) for fracture resistance was detected and no lost restorations were observed. The results suggest that for both the less decayed and the more significantly decayed devital teeth, the minimally invasive adhesive restorative approach is promising.

A clinical evaluation of two in-office bleaching products.

Abstract: This half-mouth design, two-week treatment phase, combined with an 11-week evaluation double-blinded randomized clinical trial was conducted to compare two in-office bleaching products, StarBrite (35% hydrogen peroxide) with Opalescence Xtra Boost (38% hydrogen peroxide), for degree of color change of teeth, any relapse effect (darkening) associated with discontinued use and gingival irritation and tooth sensitivity associated with use. The degree of color change and relapse was evaluated by using a colorimeter, shade guide and color slide photographs. Participants self-evaluated their gingival irritation and tooth sensitivity. They recorded daily the level of gingival irritation and tooth sensitivity experienced during the first three weeks of the study. The results of this study showed no statistical difference between products during active treatment periods and any follow-up visits using the three-color evaluation methods. Color relapse began after the bleaching treatments were finished and continued until the fifth week, after which no further significant changes appeared. Also, there was no statistical difference in gingival irritation and tooth sensitivity between the products.

Bonding of photo and dual-cure adhesives to root canal dentin

Abstract: This study evaluated the regional tensile bond strength of a dual-cure resin composite core material to root canal dentin using photo and dual-cure adhesives and different modes of polymerization. Nineteen extracted premolars were decoronated and their root canals prepared to a depth of 8 mm and a width of 1.4 mm using Para Post drills. For the microtensile bond strength (microTBS) test, 15 roots were randomly divided into five groups and their canal walls treated with a dual-cure self-etching primer (Clearfil Liner Bond 2V Primer, Kuraray Medical Co, Japan). Adhesive resin (Clearfil Liner Bond 2V Bond A) was applied to two of the groups and light cured for 20 seconds. A dual-cure adhesive resin (Clearfil Liner Bond 2V Bond A+B, Kuraray Medical Co, Japan) was applied to the remaining three groups, one of which was light cured. The post spaces of all the groups were filled with a dual-cure resin composite (DC Core) and three were light cured for 60 seconds from a coronal direction. Chemical-cure resin composite was placed on the outer surfaces of the roots, which were then stored in water for 24 hours. They were serially sliced perpendicular to the bonded interface into eight 0.6 mm-thick slabs, then transversely sectioned into beams approximately 8 x 0.6 x 0.6 mm for the microTBS test. All of the failure modes were observed under SEM and analyzed using the Kruskal-Wallis Rank test. For Knoop hardness testing, four specimens were prepared in a similar manner, two were light-cured and the other two chemically-cured. The specimens were longitudinally sectioned into two pieces, and three indentations were made at 100 microm intervals from a coronal to an apical direction in the eight halves. Data were divided into two groups (coronal/apical halves of post space) and analyzed using two-way ANOVA and Scheffe's test (p 0.05). Light exposure of both the adhesive resin and resin composite resulted in significantly higher microTBS than chemical-cure alone (p<0.05). Light exposure also significantly increased Knoop hardness at both the coronal and apical regions (p<0.05). When the bonding resin and dual-cure resin composite were chemically-cured, failures occurred cohesively within the resin. Photo-initiated polymerization of the adhesive resin and dual-cure resin composite was necessary to achieve good bonding to root canal dentin, which was not dependent upon region.

Effects of regional enamel and prism orientation on resin bonding.

Abstract: Human enamel, with its prismatic, rod-like apatitic morphology, is an anisotropic material. Because of this structural anisotropy, variation in enamel bonding sites might influence the bonding ability of current adhesive systems. This study investigated the effects of regional enamel and the direction of enamel sectioning on the bonding ability of two commercially available resin adhesives: a self-etching primer system (Clearfil SE Bond) and a one-bottle adhesive system intended for use with a total-etch wet bonding technique (Single Bond). Two regions of enamel, cuspal and mid-coronal enamel, were chosen, then sectioned in three different directions, horizontally, axially and tangentially. Slices of the sectioned enamel were then bonded with each adhesive system and submitted to a micro-shear bond test. The results of a micro-shear bond testing showed that the bonding of a one-bottle adhesive system (Single Bond) to enamel was high at the surface perpendicular to the enamel prisms (40 MPa to 51 MPa) and low at the surface parallel to the enamel prisms (24 MPa to 27 MPa). In the case of a self-etching primer system (Clearfil SE Bond), 35 MPa to 45 MPa bond strengths were obtained from all surfaces. The bond strengths of the two adhesive systems were significantly influenced by the anisotropic structure of enamel (p < 0.05). However, the effect of a self-etching primer system was less influenced by the orientation of the prismatic structure of enamel than that of a one-bottle adhesive system (p < 0.05). SEM and CLSM microphotographs showed that the self-etching primer effectively modified the smear layer without being excessively destructive to the enamel.

Reversal of dentin bonding to bleached teeth.

Abstract: Many studies have shown a considerable reduction in enamel bond strength of resin composite restorations when the bonding procedure is carried out immediately after bleaching. These studies claim that a certain waiting period is needed prior to restoration to reach the original bond strength values prior to bleaching. This study determined the effect of anti-oxidant applications on the bond strength values of resin composites to bleached dentin. Ninety human teeth extracted for orthodontic purposes were used in this study. The labial surface of each tooth was ground and flattened until dentin appeared. The polished surfaces were subjected to nine different treatments: 1) bleaching with gel (35% Rembrandt Virtuoso); 2) bleaching with gel + 10% sodium ascorbate (SA); 3) bleaching with gel + 10% butylhydroxyanisole (BHA); 4) bleaching with sol (35% hydrogen peroxide); 5) bleaching with sol + 10% sodium ascorbate; 6) bleaching with sol + 10% BHA; 7) bleaching with gel + immersed in artificial saliva for seven days; 8) bleaching with sol + immersed in artificial saliva for seven days; 9) no treatment. After bonding application, the resin composite in standard dimensions was applied to all specimens. The teeth were stored in distilled water at 37 degrees C for 24 hours and a universal testing machine determined their resistance to shear bond strength. The data was evaluated using ANOVA and Duncan tests. Bond strength in the bleached dentin group significantly decreased compared to the control group. On the other hand, the antioxidant treatment had a reversal effect on the bond strength to dentin. After the bleaching treatment, the 10% sodium ascorbate application was effective in reversing bond strength. In the samples where antioxidant was applied after the bleaching process, bonding strength in dentin tissue was at the same level as those teeth kept in artificial saliva for seven days.

The effect of organic solvents on one-bottle adhesives' bond strength to enamel and dentin.

Abstract: This study evaluated the microtensile bond strength (pTBS) of ethanol/water- and acetone-based, one-bottle adhesive systems to enamel (E) and dentin (D) in the presence (P) or absence (A) of their respective solvents. Thirty-two freshly extracted third molars were flattened with 600-grit SiC paper and restored with Single Bond (SB) or PrimeB G7-23.6 +/- 11.3ab; G6-12.8 +/- 2.1bc; G8-6.2 +/- 3.1c. SEM examination indicated that the dentin group failure modes were significantly different from the enamel groups. The results suggest that the presence of organic solvents does not influence microTBS to enamel. However, microTBS to dentin was significantly affected by the absence of solvents in the adhesive system.

Adhesive permeability affects composite coupling to dentin treated with a self-etch adhesive.

Abstract: Dentin bonded with one-step self-etch adhesives does not couple well to chemically-cured composites despite the presence of ternary catalysts in some systems. To determine whether additional factors are responsible for the poor coupling of dentin bonded with these adhesives, the authors used a one-step self-adhesive in which the ternary catalyst is incorporated separately in the brush applicator for activating the adhesive. The activated adhesive was bonded to dentin or prepolymerized composites. For microtensile bond strength evaluation, a dual-cured hybrid composite was used for coupling to the bonded substrates and activated using: (1) the light-cured mode (LC), (2) delayed light-activation (DL) and (3) the chemical-cured mode (CC). In addition, the composite polymerized in the CC mode was coupled to the two substrates bonded with (4) additional experimental adhesive versions without the ternary catalyst and (5) without the ternary catalyst and tertiary amine. Silver tracer penetration into bonded interfaces was examined using TEM by replacing the dual-cured composite with a light-cured or a chemically-cured microfilled composite. In the CC mode, the composites coupled poorly to both substrates bonded with the unactivated adhesive (5). The use of activated adhesives allowed for good coupling of the composites polymerized in all curing modes to bonded composite, but only in the LC mode to bonded dentin. Water-filled channels in the form of water trees and water blisters were present in the adhesive layer under all composite-curing modes in bonded dentin. These features were completely absent in the bonded composites, showing that the source of the water was from dentin. Water blisters were also observed along the adhesive-composite interfaces in bonded dentin when the coupling composites were polymerized using the CC or DL modes.

The effect of a "resin coating" on the interfacial adaptation of composite inlays.

Abstract: The relatively low bond strengths of resin cements to dentin may result in poor interfacial adaptation of composite inlays. This study determined whether the interfacial adaptation of composite inlays could be improved by applying an adhesive system and a low viscosity microfilled resin to the prepared cavity walls before making an impression. Ten MOD cavities were prepared on extracted human premolars with gingival margins located above and below the cemento-enamel junction. A "resin coat" consisting of a self-etching primer system (Clearfil SE Bond) and a low viscosity microfilled resin (Protect Liner F) was applied to the cavities of half of the prepared teeth, while the remaining teeth served as non-coated control specimens. All the teeth were restored with composite inlays (Estenia) fabricated by the indirect method and cemented with a dual-cured resin cement (Panavia F). After finishing the margins with superfine burs, the bonded inlays were thermocycled between 4 degrees C and 55 degrees C for 400 cycles. Specimens were sectioned with a diamond saw and the tooth-restoration interfaces were observed with a confocal laser scanning microscope. The data were analyzed with two-way ANOVA and Fisher's PLSD test (p < 0.05). The percentage length of gap formation at the dentin-restoration interface of the "resin coated" teeth (7.1 +/- 3.5) was significantly less than that of the non-coated teeth (85.7 +/- 6.7) (p < 0.05). The concept of coating the prepared cavity with an adhesive system and a low viscosity microfilled resin resulted in observing fewer gaps at the internal dentin-restoration interface compared with the non-coated specimens.

Effects of in-office bleaching products on surface finish of tooth-colored restorations.

Abstract: A number of "high power" in-office bleaching products have recently been re-introduced into the market. The use of such strong oxidizing agents has raised questions as to possible adverse effects on tooth structure and restorative materials. This study evaluated the effects of 35% carbamide peroxide (Opalescence Quick) and 35% hydrogen peroxide (Opalescence Xtra) on the surface finish of four tooth-colored restorative materials (Spectrum TPH, Dyract AP, Reactmer and Fuji II LC). Twenty-seven matrix-finished specimens of each material were fabricated, stored in distilled water at 37 degrees C for seven days and randomly divided into three groups. Specimens in Group 1 were stored in distilled water at 37 degrees C (control). Specimens in Groups 2 and 3 were treated with 35% carbamide peroxide and 35% hydrogen peroxide, respectively. A total of three 30-minute bleaching sessions were conducted at one-week intervals. Storage medium during the hiatus period was distilled water at 37 degrees C. Surface roughness measurements were carried out using profilometry after each bleaching session. Data was analyzed using ANOVA/Scheffe's test at a 0.05 significance level. No significant difference in surface roughness was observed between the bleached and the control groups for all materials. In-office bleaching products are not detrimental to the surface finish of composites, compomers, giomers and resin-modified glass ionomer cements.

Fluoride release and uptake capacities of fluoride-releasing restorative materials.

Abstract: Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount fluoride release of these materials is still uncertain. This study investigated the fluoride release and uptake characteristics of four flowable resin composites (Heliomolar Flow, Tetric Flow, Wave, Perma Flo), one flowable compomer (Dyract flow), one conventional glass ionomer cement mixed with two different powder/liquid ratios (ChemFlex Syringeable and ChemFlex Condensable), one packable resin composite (SureFil), one ion-releasing composite (Ariston pHc) and one resin-modified glass ionomer cement (Vitremer). Seven discs (6-mm diameter and 1.5-mm height) were prepared for each material. Each disc was immersed in 3.5 ml of deionized water within a plastic vial and stored at 37 degrees C. The deionized water was changed every 24 hours and the release of fluoride was measured for 30 days. At the end of this period, the samples were recharged with 2 ml of 1.23% acidulated phosphate fluoride (APF) gel for four minutes. Then, all samples were reassessed for an additional 10 days. The fluoride release of all samples was measured with a specific fluoride electrode and an ionanalyzer. Statistical analyses were conducted using two-way repeated measure ANOVA and Duncan's multiple range tests. For all tested materials, the greatest fluoride release was observed after the first day of the study (p 0.05). Ariston pHc released the highest amount of fluoride, followed by ChemFlex Syringeable, Vitremer and ChemFlex Condensable. There were statistically significant differences among these materials (p<0.05). Fluoride release of all materials were significantly increased after the first day following refluoridation and Ariston pHc released the greatest among all materials (p<0.01). At the end of two days of refluoridation, the fluoride release rate for each material dropped quickly and stabilized within three days.

Technique sensitivity in bonding to vital, acid-etched dentin

Abstract: Just as vital dentin is moist after removing the smear layer, avoiding collapse of the collagen matrix after acid-etching requires in vivo validation. This study hypothesizes that there is no difference between moist bonding performed in vitro or in vivo, and that excessive drying or wetting of vital acid-etched dentin produces inferior results. Resin-dentin interfaces bonded with a moist bonding technique (control), either in vitro or in vivo with Excite DSC (Vivadent), were examined with and without tracer penetration using transmission electron microscopy. Specimens bonded in vivo under excessively dry and wet conditions were also examined. The patterns of silver deposition were similar within the adhesive and hybrid layers created in vitro or in vivo. No hybrid layer was observed in vivo after excessive drying. Excessive wetting in vivo resulted in more extensive nanoleakage and water tree formation along resin-dentin interfaces.

Influence of curing tip distance on resin composite Knoop hardness number, using three different light curing units.

Abstract: This in vitro study evaluated the influence of curing tip distance on the Knoop Hardness Number (KHN) of a resin composite when using three different light curing units: (1) a halogen light (XL 1500 curing unit-3M), (2) a "softstart-polymerization" (Elipar Trilight curing in an exponential mode-ESPE) and (3) a PAC (Apolo 95E curing unit-DMD). The resin composite, Filtek Z250 (3M), was cured by these curing units at three light-tip distances from the resin composite: 0 mm, 6 mm and 12 mm. The resin composite specimens were flattened to their middle portion and submitted to 18 KHN measurements perspecimen. The results showed that for the Elipar Trilight unit, the hardness of the resin composite decreased as the light tip distance increased. The XL 1500 unit presented a significant decrease in hardness as the depth of cure of the resin composite increased. Apolo 95E caused a decrease in the resin composite hardness values when the depth of cure and light tip distance increased.

Wear and microhardness of different resin composite materials.

Abstract: This study determined the three-body abrasive wear resistance of two packable composites (P-60; Solitaire 2), an ion-releasing composite (Ariston AT), a hybrid composite (Tetric Ceram) and an ormocer (Admira). The study also looked at the correlation between wear resistance and hardness of the composites. Three-body wear testing was performed using an ACTA wear machine with 15 N contact force using millet seed as the third body. Wear depth (microm) was measured by profilometry after 200,000 cycles. The hardness test was performed using a digital microhardness tester (load: 500 g; dwell time: 15 seconds). The data were analyzed by using Kruskal Wallis (p AristonAT = Tetric Ceram = Solitaire 2 = Admira). The results of this study indicate that there are significant differences in the wear resistance of the resin composites. The correlation between hardness and wear was significant with a correlation coefficient of r:-0.91. A significant negative correlation exists between hardness and three-body wear of resin composites.

The durability of a fluoride-releasing resin adhesive system to dentin.

Abstract: The durability of a fluoride-free (SE Bond) and a fluoride-containing (KBF) self-etching primer/ adhesive system were compared by measuring the microtensile bond strengths (microTBS) of these adhesive systems to human dentin in vitro. After bonding, the restored teeth were serially sectioned into multiple slabs that were trimmed to a 1 mm2 cross-sectional area at the bonded interface. For the three and six month specimens, half were fully covered with nail varnish (SE+, KBF+), while the other half were incubated at 37 degrees C in water without any protective varnish (SE-, KBF-). The microTBS of the one-day specimens were 44.6 +/- 11.2 MPa for SE Bond and 39.8 +/- 8.0 MPa for KBF (p > 0.05). When unprotected specimens were incubated in water for three and six months, the microTBS fell to 26.3 +/- 8.8 MPa and 23.6 +/- 10.7 MPa for SE-, respectively, but did not change in the specimens protected with nail varnish (SE+, 41.9 +/- 12.8 MPa and 41.8 +/- 9.8 MPa, respectively). In contrast, in specimens bonded with a fluoride-containing resin, KBF, the bond strengths of the unprotected specimens did not change over three and six months KBF-. Values were 32.4 +/- 6.1 MPa and 36.8 +/- 2.3 MPa, respectively. Similarly, varnish-protected KBF+ specimens did not change over three and six months (39.3 +/- 13.6 MPa and 40.9 +/- 14.7 MPa, respectively). The results indicate that decreases in bond strength over six months' storage are water-dependent but can be prevented by using fluoride-containing resins.

Effect of resin viscosity and enamel beveling on the clinical performance of Class V composite restorations: three-year results.

Abstract: This study evaluated the effect of the elastic modulus and margin configuration on the clinical performance of resin-based composite restorations in Class V non-carious defects. One hundred and five cervical non-carious defects on buccal surfaces of canines and premolars were included in this study. Defects were randomly divided into three Groups and restored according to the following techniques: Group 1--no enamel bevel was placed and the defect was restored with a microfilled resin-based composite (Durafill VS); Group 2--the enamel margin was beveled and the defect restored as in Group 1; Group 3-the enamel margin was beveled and the defect was restored with a flowable resin-based composite (Natural Flow). Each group comprised 35 lesions. A total-etch, one-bottle adhesive (One-Step) was used in all groups. Retention rate, pre- and post-operative sensitivity, marginal discoloration and secondary caries were determined over a three-year period and the data were analyzed statistically. At six months post-insertion, the restorations placed with beveled enamel margins resulted in 100% retention regardless of the composite used compared to a 66% retention of the non-beveled margins. At two and three years, no significant difference in retention rate was found among the three groups. Post-operative sensitivity, marginal discoloration and secondary caries were not affected by enamel beveling and restorative material. Beveled enamel margins resulted in significantly better clinical retention in the first six months only. Enamel beveling and composite viscosity appeared to not significantly affect the clinical performance of Class V non-retentive composite restorations after three years.

The effectiveness of cure of LED and halogen curing lights at varying cavity depths.

Abstract: This study compared the effectiveness of cure of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M-ESPE and GC e-Light [EL], GC) to conventional (Max [MX] (control), Dentsply-Caulk), high intensity (Elipar TriLight [TL], 3M-ESPE) and very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen lights at varying cavity depths Ten light curing regimens were investigated They include: FL1-400 mW/cm2 [40 seconds], FL2-0-400 mW/cm2 [12 seconds] --> 400 mW/cm2 [28 seconds], EL1-750 mW/cm2 [10 pulses x 2 seconds], EL2-350 mW/cm2 [40 seconds], EL3-600 mW/cm2 [20 seconds], EL4-0-600 mW/cm2 [20 seconds] --> 600 mW/cm2 [20 seconds], TL1-800 mW/cm2 [40 seconds], TL2-100-800 mW/cm2 [15 seconds] --> 800 mW/cm2 [25 seconds], AS1-1200 mW/cm2 [10 seconds], MX-400 mW/cm2 [40 seconds] The effectiveness of cure of the different modes was determined by measuring the top and bottom surface hardness (KHN) of 2-mm, 3-mm and 4-mm thick composite (Z100, [3M-ESPE]) specimens using a digital microhardness tester (n = 5, load = 500 g; dwell time = 15 seconds) Results were analyzed using ANOVA/Scheffe's post-hoc test and Independent Samples t-Test (p < 005) For all lights, effectiveness of cure was found to decrease with increased cavity depths The mean hardness ratio for all curing lights at a depth of 2 mm was found to be greater than 080 (the accepted minimum standard) At 3 mm, all halogen lights produced a hardness ratio greater than 080 but some LED light regimens did not; and at a depth of 4 mm, the mean hardness ratio observed with all curing lights was less than 080 Significant differences in top and bottom KHN values were observed among different curing regimens for the same light and between LED and halogen lights While curing with most modes of EL resulted in significantly lower top and bottom KHN values than the control (MX) at all depths, the standard mode of FL resulted in significantly higher top and bottom KHN at a depth of 3 mm and 4 mm The depth of composite cure with LED LCUs was, therefore, product and mode dependent

Thermal emission by different light-curing units.

Abstract: This study quantified and compared the thermal emission of different light curing units (LCU) Three LED (Elipar Freelight [3M]; GC e-light [GC]; Coolblu [Dentalsystemscom]) and three halogen (Max [Dentsply-Caulk]; Elipar Trilight [3M]; Astralis 10 [Ivoclar-Vivadent]) lights were selected for the study Thermal emission of the LCUs, when used in various curing modes, was assessed using a K-type thermocouple and a digital thermometer at distances of 3 mm and 6 mm compared to the conventional halogen LCU (Max) The temperature profiles and mean maximum temperature change (n = 7) generated by each LCU were obtained Data was subjected to ANOVA/Scheffe's post-hoc test and Independent Samples t-test at significance level 005 At 3 mm, temperature rise observed with LED lights ranged from 41 degrees C to 129 degrees C, while halogen lights ranged from 174 degrees C to 464 degrees C At 6 mm, temperature rise ranged from 24 degrees C to 75 degrees C and 127 degrees C to 255 degrees C for LED and halogen lights, respectively Thermal emission of LED lights was significantly lower than halogen lights Significant differences in temperature rise were observed between different curing modes for the same light and between different LED/halogen lights

Shear bond strength of current adhesive systems to enamel, dentin and dentin-enamel junction region.

Abstract: This study investigated the bonding of current resin adhesives to the region approximating the dentin-enamel junction (DEJ), where the etch pattern to enamel or dentin may be different. Three kinds of tooth substrates were chosen for testing: enamel, dentin and the DEJ region. A self-etching primer system (Clearfil SE Bond) and two total-etch wet bonding systems (Single Bond and One-Step) were used. Each tooth region was bonded with one of the adhesive systems, and a resin composite and was subjected to a micro-shear bond test. In addition, morphological observations were performed on debonded specimens and etched surfaces using confocal laser scanning microscopy (CLSM). CLSM observations showed that the DEJ region was etched more deeply by phosphoric acid gel than enamel or dentin, suggesting that the action of acid etch seemed to be more intense on the DEJ. However, no statistically significant differences of shear bond strength values were observed between the DEJ region and enamel or dentin, or the adhesive systems used (p>0.05). Bonding to the DEJ is potentially as good as that to enamel or dentin.

The effect of air abrasion with two new bonding agents on composite repair.

Abstract: This study evaluated the shear bond strength of repairs made with a composite (Herculite/Kerr) when two different surface treatment methods and two new generation bond materials were used. The bonding surfaces were prepared by sanding with 500-grit aluminum oxide sandpaper or air abrading with 25-micron aluminum oxide. Treated resin surfaces were acid etched, washed for one minute and air dried. Before adding the composite Herculite, either Optibond Solo (Kerr), Solobond M (Voco) bonding agent or no bonding agent (control group) was applied. The specimens were evaluated for shear bond strength after thermocycling. Fracture surfaces of some samples were also evaluated with SEM. Light microscope and SEM examination of fractured repair surfaces indicated mostly cohesive failure within the air-abraded group. The results showed that surface treatment with air abrasion plus Optibond Solo application had the highest shear bond strength.

Polymerization shrinkage and microleakage in Class II cavities of various resin composites.

Abstract: This study investigated the polymerization shrinkage of restorative materials and microleakage in the proximal box of Class II restorations. Twenty caries free extracted human molars were prepared on the mesial and distal, making 40 slot cavities. Groups (n=10) were classified as: Group 1: Single bond/Filtek Z-250; Group 2: Single Bond/Filtek Flow/Filtek Z-250; Group 3: Admira Bond/Admira; Group 4: Ariston Liner/Ariston. Dentin bonding systems and resin composites were applied according to the manufacturer's instructions. The specimens were stored in distilled water for one week at 37 degrees C, thermocycled (5 degrees-55 degrees C x 2000), stained with 50% aqueous silver nitrate, immersed in a diluted developer solution (24 hours), rinsed and sectioned in two pieces with a low speed saw (Isomet). Dye penetration (Score 0-4) was determined separately at the occlusal enamel margin and cementoenamel junction. The volumetric polymerization shrinkage of materials was determined with the apparatus of Watts and Cash (Watts Cash, 1991) for 300 seconds. Polymerization shrinkage results were as follows: Filtek Flow (3.5% +/- 0.1) > Admira (2.1% +/- 0.1) = Ariston AT (2.3% +/- 0.1) > Filtek Z-250 (1.8% +/- 0.1) (One-way Anova, post hoc Bonferroni test at p = 0.05 level). No statistical difference was found at the enamel margins for any of the materials (Score 0-1). At the cemento-enamel junction, all test groups showed significantly higher microleakage when compared to the enamel margins (Kruskal-Wallis test, Mann-Whitney U). Dye penetration results at dentin were as follows: Filtek Flow + Filtek Z-250 = Admira < Ariston AT = Filtek Z-250. microleakage than the ion-releasing and hybrid composites lined only with bonding agent at the cementoenamel junction in Class II cavities.

Cytotoxicity evaluation of single component dentin bonding agents.

Abstract: This study evaluated the cytotoxicity of four single component dentin bonding agents: Syntac Single Component, Prime & Bond 2.1, Single Bond and One Up Bond F. The test materials were applied on dentin discs of dentin barrier models in the same way as in the clinical procedures recommended by each manufacturer. Cell viability of L 929 after exposure with the bonding agents was determined by MTT assay. The results revealed that cell survival of the first three bonding agents was 60%, while the fourth was an impressive 93%. This study showed that a total-etching bonding system is more cytotoxic than a self-etching bonding system.

Composite cure and shrinkage associated with high intensity curing light.

Abstract: This study investigated the effectiveness of cure and post-gel shrinkage of three visible light-cured composite resins (In Ten-S [IT], Ivoclar Vivadent; Z100 [ZO], 3M-ESPE; Tetric Ceram [TC], Ivoclar Vivadent) when polymerized with a very high intensity (1296 +/- 2 mW/cm2) halogen light (Astralis 10, Ivoclar Vivadent) for 10 seconds. Irradiation with a conventional (494 +/- 3 mW/cm2) halogen light (Spectrum, Dentsply) for 40 seconds was used for comparison. The effectiveness of cure was assessed by computing the hardness gradient between the top and bottom surfaces of 2-mm composite specimens after curing. A strain-monitoring device was used to measure the linear polymerization shrinkage associated with the various composites and curing lights. A sample size of five was used for both experiments. Data was analyzed using ANOVA/Scheffe's post-hoc and Independent Samples t-tests at significance level 0.05. Results showed that the effect of the curing method on the effectiveness of cure and shrinkage was material-dependent. Polymerization of IT and TC with Spectrum for 40 seconds resulted in significantly more effective cure than polymerization with Astralis for 10 seconds. Polymerization of ZO with Spectrum for 40 seconds resulted in significantly more shrinkage than polymerization with Astralis for 10 seconds. In view of the substantial time saving, using high intensity lights may be a viable method to polymerize composites.