Comparing Various Resin Luting Cement Systems in Different Etching Modes Through Bond Durability and Morphological Features

OBJECTIVES

This study aimed to investigate bond performance of various resin luting cement (RLC) systems on enamel and dentin in different etching modes and to compare the RLC-tooth interface morphology using scanning electron microscopy (SEM).

METHODS AND MATERIALS

The self-adhesive RLC systems used in combination with universal adhesives were as follows: Scotchbond Universal Adhesive Plus + RelyX Universal (3M Oral Care) and Clearfil Universal Bond Quick ER + SA Luting Multi (Kuraray Noritake Dental). These RLC systems were also used alone as self-adhesive RLC systems without universal adhesives (self-adhesive mode). The conventional RLC systems for comparison materials were as follows: BeautiBond Xtream + ResiCem EX (Shofu) and Tooth Primer + Panavia V5 (Kuraray Noritake Dental). Twelve specimens were prepared for each group to measure shear bond strength (SBS) in different etching modes. A stainless-steel rod was used as a substitute for indirect restorations. Bonded specimens were allocated to baseline (stored for 24 hours) and artificially aged (thermocycling [TC] for 10,000 cycles) groups. Representative treated tooth surfaces and RLC-tooth interfaces were observed using SEM.

RESULTS

Three-way analysis of variance (ANOVA) revealed that all the factors (etching mode, storage period, and RLC system) had a significant influence on the enamel SBS values (p<0.05). Enamel SBS was significantly higher in etch-&-rinse (ER) mode than in self-etch (SE) mode, regardless of RLC system or storage period. Three-way ANOVA showed that all the factors had a significant influence on the dentin SBS values (p<0.001). Most RLC systems showed significantly higher dentin SBS in SE mode than in ER mode, regardless of storage period. However, the combination with Scotchbond Universal Adhesive Plus and RelyX Universal showed no significant difference in SBS values between etching modes at the baseline and showed a significantly higher SBS value in ER mode than in SE mode after TC.

CONCLUSIONS

The self-adhesive RLC systems with universal adhesives tended to show higher enamel and dentin bond performance than the self-adhesive RLC systems alone. The morphology of treated tooth surfaces and resin cement-tooth interfaces were dependent on the RLC system and etching mode used. The RLC systems with primer application showed a thin, high-density layer above the intact dentin in both etching modes, suggesting chemical interaction.

Handling and Mechanical Properties of Low-viscosity Bulk-fill Resin Composites

This study aimed to evaluate the filler contents (FCs), flexural properties, depth of cure (DOC), wear resistance, and handling properties of different low-viscosity bulk-fill resin composites (LVBRCs) and to determine the correlations between the tested parameters. Six LVBRCs, Beautifil-Bulk (BBF), Bulk Base Hard (BBH), Bulk Base Medium (BBM), Filtek Bulk-Fill Flowable Restorative (FBF), G-ænial Bulk Injectable (GBI), and SDR flow+ Bulk-Fill Flowable (SDR) were used. The DOC and flexural property tests were conducted according to the ISO 4049 specifications. The flexural strength, elastic modulus, and resilience were determined in 12 specimens that were obtained from each of the 6 materials. Sliding-impact-wear testing was conducted by evaluating the wear facets of the specimens using a noncontact profilometer and by confocal laser scanning microscopy. The handling properties of the LVBRC was assessed via extrusion force and thread formation measurements. The DOC for the majority of the LVBRCs was approximately 4 mm. Although the FCs and mechanical properties were material dependent, some LVBRCs exhibited excellent flexural properties and wear resistance. The LVBRCs demonstrated a wide range of extrusion force and thread formation. Regarding the correlations between the tested parameters, extremely strong negative and positive correlations were observed for the DOC versus extrusion force, flexural strength versus elastic modulus, maximum depth versus volume loss, and maximum depth versus thread formation. In addition, strong correlations between FCs and DOC, resilience, wear resistance, and extrusion force were observed.

Effect of Layering Techniques on Polymerization Shrinkage Stress of High- and Low-viscosity Bulk-fill Resins

CLINICAL RELEVANCE

The use of layering techniques is still advisable with many bulk-fill resins and should be the default unless a particular resin is known to not need it.

SUMMARY

Objective: The purpose of this study was to investigate how layering techniques affect polymerization shrinkage stresses of high-and low-viscosity bulk-fill resins.Method: Six high-viscosity and six low-viscosity bulk-fill resins were evaluated. Aluminum blocks with a mesial-occlusal-distal (MOD) cavity were machined and randomly divided into groups for different filling techniques (bulk-fill vs horizontal layering vs oblique layering) and further subdivided according to type of resin (high- vs low-viscosity). The cuspal deflection resulting from the polymerization of bulk-fill resin bonded to a MOD cavity within an aluminum block was measured with a digimatic micrometer. Scanning electron microscopy analyses of tested resins were also conducted.Results: In the high-viscosity bulk-fill resins, cuspal deflection of the MOD cavity ranged from 11.2 to 18.2 μm with the bulk-filling technique, from 10.7 to 15.5 μm with the horizontal layering technique, and from 10.9 to 15.2 μm with the oblique layering technique. In the low-viscosity bulk-fill resins, cuspal deflection of the material ranged from 9.2 to 19.8 μm with the bulk-filling technique, from 8.2 to 15.7 μm with the horizontal layering technique, and from 8.4 to 16.4 μm with the oblique layering technique.Conclusion: Cuspal deflections for some high-and low-viscosity bulk-fill resins were significantly reduced by using layering techniques, but the resultant improvement of layering techniques was not applicable to all the bulk-fill resins used in this study.

Simulated Cuspal Deflection and Flexural Properties of Bulk-Fill and Conventional Flowable Resin Composites

CLINICAL RELEVANCE

Some bulk-fill flowable resin composites produce less cuspal deflection than a conventional incrementally filled flowable resin composites.

SUMMARY

Objective: This study investigated simulated cuspal deflection and flexural properties of bulk-fill and conventional flowable resin composites.Methods and Materials: Five bulk-fill and six conventional flowable resin composites were evaluated. Aluminium blocks with a mesio-occlusal-distal cavity were prepared and randomly divided into groups for each of the different measurement techniques and were further subdivided according to the type of flowable resin composite. The simulated cuspal deflection caused by the polymerization of resin composite within an aluminium block was measured using a highly accurate submicron digimatic micrometer or a confocal laser scanning microscope (CLSM). In addition, the flexural properties of tested resin composites were measured to investigate the relation between cuspal deflection and flexural properties, and the resin composites were observed using scanning electron microscopy.Results: Simulated cuspal deflection of some bulk-fill flowable resin composites was found to be significantly lower than or similar to those for conventional counterparts, regardless of the measurement method. There were statistically significant differences in flexural properties depending on the material, regardless of the type of flowable resin composite. Pearson correlation analysis did not reveal a statistically significant relationship between flexural properties and cuspal deflection.Conclusion: These results indicate that some bulk-fill flowable resin composites exhibit lower cuspal deflection with the bulk-filling technique than is shown by conventional flowable resin composites using the incremental filling technique. Simulated cuspal deflection can be measured using either a micrometer or CLSM, but this experiment failed to show a significant relationship between cuspal deflection and flexural properties of flowable resin composites.

The Effects of Aluminablasting on Bond Durability Between Universal Adhesives and Tooth Substrate

The aim of this study was to determine the effect of aluminablasting on the bond durability of universal adhesives and adherent surface characteristics. Adhese Universal (Ivoclar Vivadent), All-Bond Universal (Bisco), Bondmer Lightless (Tokuyama Dental), G-Premio Bond (GC), and Scotchbond Universal (3M ESPE) were used in self-etch mode. The prepared bovine enamel and dentin specimens were divided into two groups based on whether they received an aluminablasting prior to application of the universal adhesives. The resin composite bonded specimens were stored in distilled water at 37°C for 24 hours, following which the shear bond strength (SBS) of half of the specimens was measured (24-hour group). The other half was subjected to 30,000 thermal cycles between 5 and 55°C before SBS measurement (TC group). Surface roughness (Ra) and surface free energy (SFE) of the adherent surfaces were also measured, and scanning electron microscopy observation and scanning electron microscopy/energy-dispersive X-ray analysis were carried out. Most of the adhesives did not show any significant differences in enamel SBS values between the two pretreatment groups, regardless of the storage condition. However, the dentin SBS values were significantly lower in specimens that underwent aluminablasting compared with those that did not, irrespective of their storage conditions. Significantly higher Ra and SFE values were observed in the enamel and dentin of specimens that underwent aluminablasting. Although aluminablasting increased the Ra and SFE values of enamel and dentin, its effect on the SBS value was dependent on the tooth substrate. In addition to C, O, Na, Mg, P, and Ca, the element Al was detected in the enamel and dentin of samples that had undergone aluminablasting. These results suggest that although aluminablasting of the tooth surface is thought to be effective for modification of the adherent surface, it may not enhance enamel bond performance and may also adversely affect the dentin bond effectiveness of the universal adhesives.

Effects of Finishing and Polishing Methods on the Surface Roughness and Surface Free Energy of Bulk-fill Resin Composites

The purpose of this study was to determine the influence of finishing and polishing methods on surface properties of bulk-fill resin composites through surface roughness (Ra) and surface free energy (SFE) measurements, and scanning electron microscopy (SEM) observations. Three bulk-fill resin composites, Tetric EvoCeram Bulk Fill (TB), Filtek Bulk Fill (FB), and Filtek Bulk Fill Flowable Restorative (FF), and two conventional resin composites, Clearfil AP-X (AP) and Estelite ∑ Quick (EQ) were used. Seventy cured specimens of each resin composite were prepared and divided into seven groups of 10 specimens. Ra, SFE measurements, and SEM observations were conducted after finishing and polishing procedures. Three groups of specimens were finished with a fine grit diamond bur (FDB), and three with a tungsten carbide bur (CBB). After finishing, one group from each type of finishing was polished with aluminum oxide flexible disks (SSD) and one group from each type of finishing was polished with diamond particles embedded in a silicone point (CMP). A baseline group of samples that were neither finished nor polished after removing the translucent strips from the surface was examined. Although the baseline group showed significantly lower Ra values than the other groups, most resin composites showed lower Ra values with CBB+SSD than with the other finishing and polishing groups. Among the tested resin composites, EQ showed significantly lower Ra values than the other resin composites, regardless of the finishing and polishing methods. On the other hand, AP showed significantly higher Ra values than the other resin composites in all finishing and polishing groups, apart from FB with FDB. For the finished specimens, most resin composites showed higher SFE values with CBB than with FDB. For the polished specimens, all the tested resin composites with CMP showed lower γ_S values than those with SSD, regardless of the finishing method. The baseline groups of TB and FB showed significantly lower SFE values than the other finished and polished groups. In the SEM observations, all the examined resin composites showed rougher surfaces after finishing with FDB than with CBB. However, when comparing the different polishing methods (CMP and SSD), surface smoothness appeared to be material dependent.

Influence of Application Time on Dentin Bond Performance in Different Etching Modes of Universal Adhesives

We attempted to determine the effect of universal adhesive application time on dentin bond performance in different etching modes based on shear bond strength (SBS) tests and surface free energy (SFE) measurements. The five universal adhesives used were Adhese Universal (AU), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Scotchbond Universal (SU), and Tokuyama Universal Bond (TU). Bovine dentin specimens were divided into four groups of 10 for each adhesive. SBS and SFE were determined after applying the following surface treatments: 1) self-etch (SE) mode with immediate air blowing after adhesive application (IA treatment), 2) SE mode with prolonged application time (PA treatment), 3) etch-and-rinse (ER) mode with IA treatment, and 4) ER mode with PA treatment. Bonded specimens were subjected to SBS testing. The SFE of adhesive-treated dentin surfaces was measured after rinsing with acetone and water. Three-way analysis of variance revealed that dentin SBS values (p<0.001) were significantly influenced by the factors of adhesive type and application duration, but the factor of pre-etching was not significant (p=0.985). The manufacturer's instructions require longer application times for AU and SU, which showed significantly lower SBS values in IA than in PA treatment in both etching modes. However, the difference in the other adhesives was not significant between the IA and PA treatments in either etching mode. The total SFE (γ_S) was dependent on the adhesive and etching mode. The γ_S value of the initial group (SiC paper ground group) at baseline was 69.5 (mN·m^-1) and that of the pre-etching group at baseline was 30.6 (mN·m^-1). For all the adhesives, γ_S in SE mode showed significantly higher values than in ER mode, regardless of the application time. In SE mode, almost all universal adhesives tested showed lower γ_S values in PA treatment than in IA treatment. For ER mode, all the adhesives showed significantly higher γ_S values than those of the pre-etching baseline, regardless of the application time. Most adhesives did not show any significant differences in γ_S values between IA and PA treatments, regardless of etching mode.

Enamel Etching for Universal Adhesives: Examination of Enamel Etching Protocols for Optimization of Bonding Effectiveness

OBJECTIVE

The purpose of this study was to evaluate whether different enamel etching methods with reduced etching times would improve the bonding effectiveness of universal adhesives.

METHODS AND MATERIALS

Three enamel etching methods, phosphoric acid ester monomer (PPM) etching, phosphoric acid (PPA) etching, and polyalkenoic acid (PLA) etching, and three universal adhesives, G-Premio Bond (GP), Prime&Bond elect (PE), and Scotchbond Universal Adhesive (SU), were evaluated. Initial bond strengths and fatigue strengths of universal adhesives to ground enamel and ground enamel etched for less than one, five, 10, and 15 seconds using different etching methods were determined. The bonded fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred with a staircase method. Atomic force micrograph (AFM) observations along with measurements of surface Ra roughness and modified surface area of enamel with different etching protocols were also conducted.

RESULTS

The bond fatigue durability of universal adhesives to enamel with PPA etching from less than one to 15 seconds and PLA etching for 15 seconds was significantly higher than that to ground enamel. The bond fatigue durability to enamel with PPM etching was not increased compared with ground enamel. The surface Ra roughness and surface area obtained with AFM of enamel increased after PPA and PLA etching, and those values were significantly higher than those of ground enamel. Furthermore, surface Ra roughness and surface area with PPA etching were significantly higher than those with PLA etching. However, surface Ra roughness and surface area of enamel with PPM etching were similar to those of ground enamel regardless of etching time.

CONCLUSION

PPA etching for less than one to 15 seconds and PLA etching for 15 seconds improve universal adhesive bonding, surface Ra roughness, and surface area of enamel. However, PPM etching is not effective, regardless of etching time, in improving bonds strengths, increasing surface roughness, and increasing surface area.

Effect of Active Application on Bond Durability of Universal Adhesives

The purpose of this study was to determine the effect of different adhesive application methods and etching modes on the dentin bond durability of universal adhesives under thermal cycling (TC). All-Bond Universal (Bisco), Adhese Universal (Ivoclar Vivadent), and Scotchbond Universal (3M ESPE) were used as adhesives. In total, 600 bovine teeth with exposed dentin were divided into 12 groups according to the type of adhesive and subjected to the following bonding procedures: 1) etch-and-rinse mode with active application; 2) etch-and-rinse mode with inactive application; 3) self-etch mode with active application; and 4) self-etch mode with inactive application. Bonded specimens were stored in distilled water at 37°C for 24 hours and then subjected to 5000, 10,000, 30,000, or 50,000 TC between 5°C and 55°C before shear bond strength (SBS) testing, creating a division into a total of five different storage conditions. Baseline specimens were stored in distilled water at 37°C for 24 hours. The SBS test was performed at a cross-head speed of 1.0 mm/min. Three-way analysis of variance revealed that all the factors of application mode, adhesive, and thermal cycle period significantly influenced the SBS values (p&lt;0.001), regardless of the etching mode. In the baseline groups, all of the tested adhesives with active application had higher SBS values than those with inactive application, regardless of etching mode. In the TC groups, significantly lower SBS values were observed at 50,000 TC with inactive application compared to those with active application, regardless of the etching mode. From the scanning electron microscopy observation of demineralized and deproteinized resin/dentin interfaces, dense resin tags longer than 50 μm were observed in the etch-and-rinse with active application group. On the other hand, the resin tags in self-etch mode were sparse, thin, and much shorter than those in etch-and-rinse mode. Comparing the penetration status of the resin tags with active and inactive application in self-etch mode, the resin tag penetration with inactive application was much lower than that with active application. Active application is effective in enhancing the dentin bond durability of universal adhesives. When using universal adhesives with different etching modes, practitioners should select the optimal etching mode and appropriate application method in accordance with the cavity conditions.

Effect of Reduced Universal Adhesive Application Time on Enamel Bond Fatigue and Surface Morphology

Objective:

The purpose of this study was to evaluate the effect of reduced application times of universal adhesives on enamel bond fatigue and surface morphology of the treated enamel with constant force atomic force microscopy (AFM).

Methods:

Four universal adhesives—Adhese Universal (AU), Clearfil Universal Bond Quick (CU), G-Premio Bond (GP), and Scotchbond Universal Adhesive (SU)—were evaluated in a laboratory for their ability to adhesively bond resin composite to enamel. Shear bond strengths were initially determined using 15 specimens per test group for each adhesive. Shear fatigue strengths were then determined using 20 specimens per test group for each the adhesives. The fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. AFM observations, surface Ra roughness measurements, and geometric surface area evaluations of enamel surface treated with the adhesive agents were also conducted.

Results:

A strong relationship was found between the initial shear bond strength and shear fatigue strength for enamel surface Ra roughness but not for geometric surface area. The initial shear bond strength and shear fatigue strength of CU and GP were not influenced by different application times, unlike those of AU and SU. While the surface area of enamel treated with the adhesive agents was not significantly influenced by different application times and type of adhesive, surface Ra roughness of the enamel in the AU and SU groups significantly increased with increasing application time, unlike CU and GP.

Conclusions:

The results of this study suggest that universal adhesives, used with reduced application times, have adequate Ra surface roughness to provide sufficient resistance to enamel bond fatigue at application times from &lt;1 second to 20 seconds, while the geometric surface area of adhesive-treated enamel did not show any significant changes at these different application times.

Influence of Thermal Stress on Simulated Localized and Generalized Wear of Nanofilled Resin Composites

Objective:

This study investigated the influence of thermal stress on the simulated localized and generalized wear of nanofilled resin composites.

Methods:

Six nanofilled resin composites were evaluated and then subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki (Alabama) wear simulation device after 24 hours of water storage (24-hour group) and 24 hours of water storage and 10,000 thermal cycles (TC group). Simulated localized wear was generated using a stainless-steel ball bearing, and simulated generalized wear was generated using a flat-ended stainless-steel cylinder. Wear testing was accomplished in a water slurry of polymethyl methacrylate beads. Simulated localized and generalized wear was determined using a noncontact profilometer (Proscan 2100) in conjunction with Proscan and AnSur 3D software.

Results:

Wear was significantly different (p&lt;0.05) among the resin composites for both simulated localized and generalized wear of either the 24-hour group or the TC group. The simulated localized wear of the TC group was significantly greater than that of the 24-hour group; however, the simulated generalized wear of most of the resin composites of the TC group was not significantly different from that of the 24-hour group.

Conclusion:

The simulated localized and generalized wear of nanofilled resin composites is material dependent. The simulated localized wear of nanofilled resin composites appears to be influenced by thermal stress, whereas this effect is not as apparent in simulated generalized wear testing.

Relationship Between Simulated Gap Wear and Generalized Wear of Resin Luting Cements

OBJECTIVE

The relationship between the simulated gap wear and generalized wear of resin luting cements was investigated.

METHODS

Five resin luting cements, G-Cem LinkForce (GL), Multilink Automix (MA), NX3 Nexus, Panavia V5 (PV), and RelyX Ultimate were evaluated and subsequently subjected to a wear challenge in a Leinfelder-Suzuki (Alabama) wear simulation device. Half of the specimens from each resin luting cement were photo-cured for 40 seconds and the other half were not photo-cured. The simulated gap and generalized wear were generated using a flat-ended stainless steel antagonist. Wear testing was performed in a water slurry of polymethyl methacrylate beads, and the simulated gap and generalized wear were determined using a noncontact profilometer (Proscan 2100) in conjunction with the Proscan and AnSur 3D software.

RESULTS

A strong relationship was found between the gap wear and generalized wear simulation models. The simulated gap wear and generalized wear of the resin luting cements followed similar trends in terms of both volume loss and mean depth of wear facets with each curing method. Unlike the simulated gap wear and generalized wear of GL and PV, those of MA, NX, and RU were influenced by the curing method.

CONCLUSION

The results of this study indicate that simulated gap wear of resin luting cements is very similar to simulated generalized wear. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing method.

Polymerization Behavior and Mechanical Properties of High-Viscosity Bulk Fill and Low Shrinkage Resin Composites

The present study determined the mechanical properties and volumetric polymerization shrinkage of different categories of resin composite. Three high viscosity bulk fill resin composites were tested: Tetric EvoCeram Bulk Fill (TB, Ivoclar Vivadent), Filtek Bulk Fill posterior restorative (FB, 3M ESPE), and Sonic Fill (SF, Kerr Corp). Two low-shrinkage resin composites, Kalore (KL, GC Corp) and Filtek LS Posterior (LS, 3M ESPE), were used. Three conventional resin composites, Herculite Ultra (HU, Kerr Corp), Estelite ∑ Quick (EQ, Tokuyama Dental), and Filtek Supreme Ultra (SU, 3M ESPE), were used as comparison materials. Following ISO Specification 4049, six specimens for each resin composite were used to determine flexural strength, elastic modulus, and resilience. Volumetric polymerization shrinkage was determined using a water-filled dilatometer. Data were evaluated using analysis of variance followed by Tukey's honestly significant difference test (α=0.05). The flexural strength of the resin composites ranged from 115.4 to 148.1 MPa, the elastic modulus ranged from 5.6 to 13.4 GPa, and the resilience ranged from 0.70 to 1.0 MJ/m3. There were significant differences in flexural properties between the materials but no clear outliers. Volumetric changes as a function of time over a duration of 180 seconds depended on the type of resin composite. However, for all the resin composites, apart from LS, volumetric shrinkage began soon after the start of light irradiation, and a rapid decrease in volume during light irradiation followed by a slower decrease was observed. The low shrinkage resin composites KL and LS showed significantly lower volumetric shrinkage than the other tested materials at the measuring point of 180 seconds. In contrast, the three bulk fill resin composites showed higher volumetric change than the other resin composites. The findings from this study provide clinicians with valuable information regarding the mechanical properties and polymerization kinetics of these categories of current resin composite.

Effect of Oxygen Inhibition Layer of Universal Adhesives on Enamel Bond Fatigue Durability and Interfacial Characteristics With Different Etching Modes

OBJECTIVE

The purpose of this study was to evaluate the effect of the oxygen inhibition layer of universal adhesive on enamel bond fatigue durability and interfacial characteristics with different etching modes.

METHODS

The three universal adhesives used were Scotchbond Universal Adhesive (3M ESPE, St Paul, MN, USA), Adhese Universal (Ivoclar Vivadent, Schaan, Lichtenstein), and G-Premio Bond (GC, Tokyo, Japan). The initial shear bond strength and shear fatigue strength to enamel was determined in the presence and absence of the oxygen inhibition layer, with and without phosphoric acid pre-etching. The water contact angle was also measured in all groups using the sessile drop method.

RESULTS

The enamel bonding specimens with an oxygen inhibition layer showed significantly higher (p<0.05) initial shear bond strengths and shear fatigue strengths than those without, regardless of the adhesive type and etching mode. Moreover, the water contact angles on the specimens with an oxygen inhibition layer were significantly lower (p<0.05) than on those without, regardless of etching mode.

CONCLUSION

The results of this study suggest that the oxygen inhibition layer of universal adhesives significantly increases the enamel bond fatigue durability and greatly changes interfacial characteristics, suggesting that the bond fatigue durability and interfacial characteristics of these adhesives strongly rely on its presence.

Influence of Different Curing Modes on Polymerization Behavior and Mechanical Properties of Dual-Cured Provisional Resins

This study determined the influence of curing mode on polymerization behavior and mechanical properties of dual-cured provisional resins. Three dual-cured bisacryl-based provisional resins were used: Tempsmart (TS; GC Corp), Luxatemp Automix Solar (LX; DMG Chemisch Pharmazeutishe Fabrik GmbH), and Integrity Multi·Cure (IG; Dentsply Caulk). A self-cured bisacryl-based provisional resin, Protemp Plus (PP; 3M ESPE) and a conventional poly(methyl methacrylate) (PMMA) provisional resin, Unifast III (UF; GC Corp) were used as controls. The inorganic filler content and coefficients of linear thermal expansion of the test materials were measured. Six specimens of each material were used to determine the flexural strength, elastic modulus, and resilience. The changes in ultrasound velocity during polymerization were measured. The average inorganic filler contents of the provisional resins, apart from UF, ranged from 24.4 to 39.3 wt%. The highest inorganic filler content was determined for LX, whereas TS showed the lowest value among the tested materials. The average coefficients of thermal expansion of the tested provisional resins ranged from 77.3 to 107.7 (×10^-6/°C). TS and IG showed significantly lower thermal expansions than the other tested provisional resins. The mean flexural strengths of the provisional resins ranged from 70.4 to 122.6 MPa, the mean elastic moduli ranged from 1.8 to 3.7 GPa, and the mean resilience of the provisional resins ranged from 1.1 to 2.3 MJ/mm³, respectively. Dual-cured provisional resins showed significantly higher flexural strengths than the PMMA resin. However, in all cases, the light-curing mode showed significantly higher flexural strengths than the self-curing mode. In the initial polymerization phase, dual-cured resins in the light-curing mode showed a rapid increase in the speed of sound (V) during light irradiation, followed by a slower increase. Conversely, the dual-cured resins in the self-curing mode showed a slower initial increase, followed by a rapid increase. Although no significant difference in V was observed between 10 and 15 minutes in the light-curing mode of all tested dual-cured resins, a significantly higher V value was obtained at 15 minutes than at 10 minutes in the self-curing modes for LX and IG. Regardless of the curing mode, tested dual-cured provisional resins showed superior mechanical properties than the conventional PMMA provisional resin. However, dual-cured provisional resin flexural properties and polymerization behavior were affected by the curing mode. This study indicated that the light-curing mode might be recommended for all dual-cured provisional resins because of the enhancement of their mechanical properties and reduction of chair time.

Interfacial Characteristics and Bond Durability of Universal Adhesive to Various Substrates

Objective: This study investigated the interfacial characteristics and bond durability of universal adhesives to various substrates.

Methods and Materials: Two universal adhesives were used: 1) Scotchbond Universal and 2) G-Premio Bond. The substrates used were bovine enamel and dentin with or without phosphoric acid etching, resin composite, lithium disilicate and leucite-reinforced glass ceramics, zirconia, and metal alloys. The surface free energy and the parameters of various substrates and of substrates treated by adhesive after light irradiation were determined by measuring the contact angles of three test liquids. Resin composite was bonded to the various substrates to determine shear bond strength after 24 hours water storage and 10,000 thermal cycles. A one-way analysis of variance (ANOVA) and the Tukey post hoc test were used for the surface free energy data, and a two-way ANOVA and the Tukey post hoc test were used for analysis of shear bond strength data (α=0.05).

Results: The interfacial characteristics of the various substrates show significant differences depending on the type of substrate, but the interfacial characteristics of substrate treated by adhesive after light irradiation did not show any significant differences regardless of the substrate used. The bond durability of two universal adhesives to various substrates differs depending on the type of substrate and the adhesive.

Conclusions: The results of this study suggest that universal adhesives modify the interfacial characteristics of a wide range of substrates and create a consistent surface, but the bond durability of universal adhesive to various substrates differs depending on the type of substrate and the adhesive.

Influence of Thermal Cycling on Flexural Properties and Simulated Wear of Computer-aided Design/Computer-aided Manufacturing Resin Composites

OBJECTIVE

The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites.

METHODS

The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software.

RESULTS

The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p<0.05), but there was no significant interaction (p>0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (p<0.05) depending on the material, and their values were influenced (p>0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (p<0.05) than those after 24 hours of water storage, unlike CS, KA, and VE.

CONCLUSION

The results of this study indicate that the flexural properties and simulated wear of CAD/CAM resin composites are different depending on the material. In addition, the flexural properties and simulated wear of CAD/CAM resin composites are influenced by thermal cycling.

Influence of Etching Mode on Enamel Bond Durability of Universal Adhesive Systems

The purpose of this study was to determine the enamel bond durability of three universal adhesives in different etching modes through fatigue testing. The three universal adhesives used were Scotchbond Universal, Prime&Bond Elect universal dental adhesive, and All-Bond Universal light-cured dental adhesive. A single-step self-etch adhesive, Clearfil S³ Bond Plus was used as a control. The shear bond strength (SBS) and shear fatigue strength (SFS) to human enamel were evaluated in total-etch mode and self-etch mode. A stainless steel metal ring with an internal diameter of 2.4 mm was used to bond the resin composite to the flat-ground (4000-grit) tooth surfaces for determination of both SBS and SFS. For each enamel surface treatment, 15 specimens were prepared for SBS and 30 specimens for SFS. The staircase method for fatigue testing was then used to determine the SFS of the resin composite bonded to the enamel using 10-Hz frequencies for 50,000 cycles or until failure occurred. Scanning electron microscopy was used to observe representative debonded specimen surfaces and the resin-enamel interfaces. A two-way analysis of variance and the Tukey post hoc test were used for analysis of the SBS data, whereas a modified t-test with Bonferroni correction was used for the SFS data. All adhesives in total-etch mode showed significantly higher SBS and SFS values than those in self-etch mode. Although All-Bond Universal in self-etch mode showed a significantly lower SBS value than the other adhesives, there was no significant difference in SFS values among the adhesives in this mode. All adhesives showed higher SFS:SBS ratios in total-etch mode than in self-etch mode. With regard to the adhesive systems used in this study, universal adhesives showed higher enamel bond strengths in total-etch mode. Although the influence of different etching modes on the enamel-bonding performance of universal adhesives was found to be dependent on the adhesive material, total-etch mode effectively increased the enamel bond strength and durability, as measured by fatigue testing.

Mechanical Properties and Sliding-impact Wear Resistance of Self-adhesive Resin Cements

The present study determined the mechanical properties and impact-sliding wear characteristics of self-adhesive resin cements. Five self-adhesive resin cements were used: G-CEM LinkAce, BeautiCem SA, Maxcem Elite, Clearfil SA Automix, and RelyX Unicem 2. Clearfil Esthetic Cement was employed as a control material. Six specimens for each resin cement were used to determine flexural strength, elastic modulus, and resilience according to ISO specification #4049. Ten specimens for each resin cement were used to determine the wear characteristics using an impact-sliding wear testing apparatus. Wear was generated using a stainless-steel ball bearing mounted inside a collet assembly. The maximum facet depth and volume loss were determined using a noncontact profilometer in combination with confocal laser scanning microscopy. Data were evaluated using analysis of variance followed by the Tukey honestly significantly different test (α=0.05). The flexural strength of the resin cements ranged from 68.4 to 144.2 MPa; the elastic modulus ranged from 4.4 to 10.6 GPa; and the resilience ranged from 4.5 to 12.0 MJ/m3. The results for the maximum facet depth ranged from 25.2 to 235.9 μm, and volume loss ranged from 0.0107 to 0.5258 mm3. The flexural properties and wear resistance were found to vary depending upon the self-adhesive resin cement tested. The self-adhesive cements tended to have lower mechanical properties than the conventional resin cement. All self-adhesive resin cements, apart from G-CEM LinkAce, demonstrated significantly poorer wear resistance than did the conventional resin cement.

The Effect of Phosphoric Acid Pre-etching Times on Bonding Performance and Surface Free Energy with Single-step Self-etch Adhesives

OBJECTIVE

The purpose of this study was to evaluate the effect of phosphoric acid pre-etching times on shear bond strength (SBS) and surface free energy (SFE) with single-step self-etch adhesives.

METHODS

The three single-step self-etch adhesives used were: 1) Scotchbond Universal Adhesive (3M ESPE), 2) Clearfil tri-S Bond (Kuraray Noritake Dental), and 3) G-Bond Plus (GC). Two no pre-etching groups, 1) untreated enamel and 2) enamel surfaces after ultrasonic cleaning with distilled water for 30 seconds to remove the smear layer, were prepared. There were four pre-etching groups: 1) enamel surfaces were pre-etched with phosphoric acid (Etchant, 3M ESPE) for 3 seconds, 2) enamel surfaces were pre-etched for 5 seconds, 3) enamel surfaces were pre-etched for 10 seconds, and 4) enamel surfaces were pre-etched for 15 seconds. Resin composite was bonded to the treated enamel surface to determine SBS. The SFEs of treated enamel surfaces were determined by measuring the contact angles of three test liquids. Scanning electron microscopy was used to examine the enamel surfaces and enamel-adhesive interface.

RESULTS

The specimens with phosphoric acid pre-etching showed significantly higher SBS and SFEs than the specimens without phosphoric acid pre-etching regardless of the adhesive system used. SBS and SFEs did not increase for phosphoric acid pre-etching times over 3 seconds. There were no significant differences in SBS and SFEs between the specimens with and without a smear layer.

CONCLUSION

The data suggest that phosphoric acid pre-etching of ground enamel improves the bonding performance of single-step self-etch adhesives, but these bonding properties do not increase for phosphoric acid pre-etching times over 3 seconds.

Simulated Wear of Self-Adhesive Resin Cements

One of the primary areas of concern with luting agents is marginal gap erosion and attrition. The purpose of this laboratory study was to evaluate bulk and marginal slit (gap) generalized wear of self-adhesive resin cements. Three self-adhesive resin cements were used in this study: G-CEM LinkAce (LA), Maxcem Elite (ME), and RelyX Unicem2 Automix (RU). A custom stainless-steel fixture with a cavity 4.5 mm in diameter and 4 mm deep was used for simulated generalized (bulk) wear. For simulated marginal gap wear, a two-piece stainless-steel custom fixture was designed with a slit (gap) 300 μm wide and 3 mm in length. For both wear models, 20 specimens each for each of the three adhesive cements were made for both light-cure and chemical-cure techniques. The cured cements were polished with a series of carbide papers to a 4000-grit surface and subjected to 100,000 cycles using the slit (gap) wear model and 400,000 cycles for generalized (bulk) wear in a Leinfelder-Suzuki (Alabama machine) wear simulator (maximum load of 78.5 N). Flat-ended stainless-steel antagonists were used in a water slurry of poly(methylmethacrylate) beads for simulation of generalized contact-free area wear with both wear models. Before and after the wear challenges, the specimens were profiled with a Proscan 2100 noncontact profilometer, and wear (volume loss [VL] and mean facet depth [FD]) was determined using AnSur 3D software. Two-way analysis of variance (ANOVA) and Tukey post hoc tests were used for data analysis for the two wear models. Scanning electron microscopy (SEM) was used to examine polished surfaces of the resin cements and the worn surfaces after the wear challenges. The two-way ANOVA of VL using the generalized (bulk) wear model showed a significant effect among the three resin cement materials for the factor of resin cement (p<0.001) and the interaction of the cement and cure method (p<0.001), but not for the cure method (p=0.465). The two-way ANOVA for FD also found a significant difference for the factor of resin cement (p<0.001) and the interaction of the resin cement and cure method (p<0.001), but not for the cure method (p=0.277). The simulated generalized (bulk) wear for the light-cure groups was as follows: VL (mm(3)): RU 0.631 (0.094), LA 0.692 (0.112), and ME 1.046 (0.141) and FD (μm): RU 43.6 (6.5), LA 47.0 (7.7), and ME 72.5 (9.9). The simulated generalized (bulk) wear for the chemical-cure groups was as follows: VL (mm(3)): LA 0.741 (0.105), RU 1.231 (0.234), and ME 1.305 (0.143) and FD (μm): LA 50.7 (7.2), RU 84.5 (16.1), and ME 91.7 (10.2). Simulated wear using the slit (gap) model for the light-cure groups was as follows: VL (mm(3)): RU 0.030 (0.006), LA 0.031 (0.006), and ME 0.041 (0.009) and FD (μm): RU 49.6 (5.7), LA 57.2 (8.4), and ME 70.9 (10.7). The wear values for the chemical-cure slit (gap) groups were as follows: VL (mm(3)): LA 0.031 (0.004), ME 0.038 (0.007), and RU 0.045 (0.009) and FD (μm): LA 53.9 (6.7), ME 63.5 (9.1), and RU 74.2 (12.9). Pearson correlation tests revealed a strong relationship between the two wear models for the light-cure groups and a good relationship for the chemical-cure groups. The observations using SEM showed differences in filler particle shape and size among the cements and the resultant effect of the wear challenges. The worn surfaces of each cement were essentially the same for both light-cure and chemical-cure methods. The bulk wear model and new slit (gap) model for evaluation of simulated generalized wear of luting agents demonstrated significant differences (p<0.05) in relative wear among three self-adhesive resin cements and between visible light- and chemical-cure techniques.

Effect of Phosphoric Acid Pre-etching on Fatigue Limits of Self-etching Adhesives

The purpose of this study was to use shear bond strength (SBS) and shear fatigue limit (SFL) testing to determine the effect of phosphoric acid pre-etching of enamel and dentin prior to application of self-etch adhesives for bonding resin composite to these substrates. Three self-etch adhesives—1) G- ænial Bond (GC Corporation, Tokyo, Japan); 2) OptiBond XTR (Kerr Corp, Orange, CA, USA); and 3) Scotchbond Universal (3M ESPE Dental Products, St Paul, MN, USA)—were used to bond Z100 Restorative resin composite to enamel and dentin surfaces. A stainless-steel metal ring with an inner diameter of 2.4 mm was used to bond the resin composite to flat-ground (4000 grit) tooth surfaces for determination of both SBS and SFL. Fifteen specimens each were used to determine initial SBS to human enamel/dentin, with and without pre-etching with a 35% phosphoric acid (Ultra-Etch, Ultradent Products Inc, South Jordan, UT, USA) for 15 seconds prior to the application of the adhesives. A staircase method of fatigue testing (25 specimens for each test) was then used to determine the SFL of resin composite bonded to enamel/dentin using a frequency of 10 Hz for 50,000 cycles or until failure occurred. A two-way analysis of variance and Tukey post hoc test were used for analysis of SBS data, and a modified t-test with Bonferroni correction was used for the SFL data. Scanning electron microscopy was used to examine the area of the bonded restorative/tooth interface. For all three adhesive systems, phosphoric acid pre-etching of enamel demonstrated significantly higher (p&lt;0.05) SBS and SFL with pre-etching than it did without pre-etching. The SBS and SFL of dentin bonds decreased with phosphoric acid pre-etching. The SBS and SFL of bonds using phosphoric acid prior to application of self-etching adhesives clearly demonstrated different tendencies between enamel and dentin. The effect of using phosphoric acid, prior to the application of the self-etching adhesives, on SBS and SFL was dependent on the adhesive material and tooth substrate and should be carefully considered in clinical situations.

Localized and Generalized Simulated Wear of Resin Composites

A laboratory study was conducted to examine the wear of resin composite materials using both a localized and generalized wear simulation model. Twenty specimens each of seven resin composites (Esthet•X HD [HD], Filtek Supreme Ultra [SU], Herculite Ultra [HU], SonicFill [SF], Tetric EvoCeram Bulk Fill [TB], Venus Diamond [VD], and Z100 Restorative [Z]) were subjected to a wear challenge of 400,000 cycles for both localized and generalized wear in a Leinfelder-Suzuki wear simulator (Alabama machine). The materials were placed in custom cylinder-shaped stainless steel fixtures. A stainless steel ball bearing (r=2.387 mm) was used as the antagonist for localized wear, and a stainless steel, cylindrical antagonist with a flat tip was used for generalized wear. A water slurry of polymethylmethacrylate (PMMA) beads was used as the abrasive media. A noncontact profilometer (Proscan 2100) with Proscan software was used to digitize the surface contours of the pretest and posttest specimens. AnSur 3D software was used for wear assessment. For localized testing, maximum facet depth (μm) and volume loss (mm3) were used to compare the materials. The mean depth of the facet surface (μm) and volume loss (mm3) were used for comparison of the generalized wear specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean depth of the facet for generalized wear. The results for localized wear simulation were as follows [mean (standard deviation)]: maximum facet depth (μm)—Z, 59.5 (14.7); HU, 99.3 (16.3); SU, 102.8 (13.8); HD, 110.2 (13.3); VD, 114.0 (10.3); TB, 125.5 (12.1); SF, 195.9 (16.9); volume loss (mm3)— Z, 0.013 (0.002); SU, 0.026 (0.006); HU, 0.043 (0.008); VD, 0.057 (0.009); HD, 0.058 (0.014); TB, 0.061 (0.010); SF, 0.135 (0.024). Generalized wear simulation results were as follows: mean depth of facet (μm)—Z, 9.3 (3.4); SU, 12.8 (3.1); HU, 15.6 (3.2); TB, 19.2 (4.8); HD, 26.8 (6.5); VD, 29.1 (5.5); SF, 35.6 (8.4); volume loss (mm3)—Z, 0.132 (0.049); SU, 0.0179 (0.042); HU, 0.224 (0.044); TB, 0.274 (0.065); HD, 0.386 (0.101); VD, 0.417 (0.076); SF, 0.505 (0.105). The ANOVA showed a significant difference among materials (p&lt;0.001) for facet depth and volume loss for both localized and generalized wear. The post hoc test revealed differences (p&lt;0.05) in localized and generalized wear values among the seven resin composites examined in this study. The findings provide valuable information regarding the relative wear characteristics of the materials in this study.

Mechanical Properties and Simulated Wear of Provisional Resin Materials

The purpose of this study was to determine flexural properties and erosive wear behavior of provisional resin materials. Three bis-acryl base provisional resins-1) Protemp Plus (PP), 2) Integrity (IG), 3) Luxatemp Automix Plus (LX)-and a conventional poly(methylmethacrylate) (PMMA) resin, UniFast III (UF), were evaluated. A resin composite, Z100 Restorative (Z1), was included as a benchmark material. Six specimens for each of the four materials were used to determine flexural strength and elastic modulus according to ISO Standard 4049. Twelve specimens for each material were used to examine wear using a generalized wear simulation model. The test materials were each subjected to wear challenges of 25,000, 50,000, 100,000, and 200,000 cycles in a Leinfelder-Suzuki (Alabama) wear simulator. The materials were placed in custom cylinder-shaped stainless-steel fixtures, and wear was generated using a cylindrical-shaped flat-ended stainless-steel antagonist in a slurry of nonplasticized PMMA beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The laboratory data were evaluated using two-way analysis of variance (ANOVA; factors: 1) material and 2) cycles) followed by Tukey HSD post hoc test (α=0.05). The flexural strength ranged from 68.2 to 150.6 MPa, and the elastic modulus ranged from 2.0 to 15.9 GPa. All of the bis-acryl provisional resins (PP, IG, and LX) demonstrated significantly higher values than the PMMA resin (UF) in flexural strength and elastic modulus (p<0.05). However, there was no significant difference (p>0.05) in flexural properties among three bis-acryl base provisional resins (PP, IG, and LX). Z1 demonstrated significantly (p<0.05) higher flexural strength and elastic modulus than the other materials tested. The results for mean facet wear depth (μm) and standard deviations (SD) for 200,000 cycles were as follows: PP, 22.4 (5.0); IG, 51.0 (6.5); LX, 63.7 (4.5); UF, 70.5 (8.0); and Z1, 7.6 (1.2). Volume loss (mm(3)) and SDs for 200,000 cycles were as follows: PP, 0.311 (0.049); IG, 0.737 (0.074); LX, 0.919 (0.053); UF, 1.046 (0.127); and Z1, 0.111 (0.017). The two-way ANOVA showed a significant difference among materials (p<0.001) and number of cycles for both facet depth and volume loss. The post hoc test revealed differences (p<0.05) in wear values among the tested materials examined in this study. The findings provide valuable information regarding the flexural properties and the relative wear behavior of the provisional resins examined in this study.

Wear rates of resin composites

SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [μm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (μm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

Spark erosion as a metal–resin bonding system

PURPOSE

Resin to metal bond strength of two commercial and one experimental metal-resin bonding system for crown and bridge veneer composites was evaluated.

MATERIALS AND METHODS

All specimens were prepared and tested according to ISO 10477 Amendment 1. A high precious alloy (HPA), a Co/Cr-alloy (Co/Cr) and pure titanium (Ti) were wet-ground to a final surface finish of 800 grit and air-dried. Twenty specimens of each metal were treated with Rocatec (RO), 20 with a Silano-Pen (SP), and 20 with the experimental spark-erosion (SE) bonding system. A light-curing opaque and a crown and bridge veneer composite were applied to each metal specimen. Ten specimens of each metal and bonding system were stored in water for 24h at 37 degrees C, 10 were thermocycled (TC) 5000 times in a water-bath between +5 and +55 degrees C prior to measuring shear bond strength (SBS). Scanning electron microscopy (SEM) was used to examine the treated metal surfaces.

RESULTS

After 24h SE generated significantly higher SBS values on Ti than RO (p<0.05). SP revealed the highest SBS for Co/Cr. After TC significant decreases occurred for RO on HPA, for SP on Co/Cr and Ti, and for SP on Ti. SE revealed the highest mean bond values for all metals. These results and SEM proved that no sandblasting is required for SE to obtain good bond strength.

SIGNIFICANCE

The experimental spark-erosion bonding system is an easy and very effective method for surface-treating alloys to obtain high SBS values for crown and bridge veneer composites.

The effects of thermocycling on the flexural strength and flexural modulus of modern resin-based filling materials

OBJECTIVE

Evaluation of flexural strengths and flexural moduli of hybrids, packables, ormocers, compomers and flowables prior to, and after, thermocycling.

MATERIALS AND METHODS

Twenty specimens, size (25 +/- 2) mm x (2 +/- 0.1) mm x (2+/-0.1) mm, of Herculite (HE), Point 4 (P4), TetricCeram (TC), Miris (MI), TetricCeram HB, (HB), Solitaire 2 (SO), Surefil A (SU), Definte (DE), Admira (AD), Dyract AP (DY), Compoglass (CO) and TetricFlow (TF) were made according to ISO 4049. A three-point-bending test was carried out for the first 10 specimens after 24 h water storage at 37 degrees C and for the second 10 specimens after 30-day water storage at 37 degrees C, followed by 5000 thermocycles between +5 and +55 degrees C. For each test series flexural strengths and flexural moduli were calculated. Statistical significance was p < 0.05.

RESULTS

Flexural strengths of DY and CO missed the 80 MPa limit of ISO 4049 for occlusal fillings prior to and after thermocycling. AD missed it after thermocycling. HE, P4, TC, MI, HB, SO, SU, DE and TF did not significantly differ prior to and after thermocycling. Flexural strength of SO and AD significantly decreased after thermocycling. No change of the flexural moduli could be observed for any of the test materials. Only SU exceeded 10,000 MPa prior to and after thermocycling.

SIGNIFICANCE

Only DY and CO missed the flexural strength limit of ISO 4049 for occlusal fillings. Only SU exceeded a flexural modulus of 10,000 MPa prior to and after thermocycling.

Effect of exponential polymerization on color stability of resin-based filling materials

PURPOSE

To investigate the influence of a halogen light curing device used with constant or exponential polymerization mode on the color stability of contemporary resin-based filling materials.

MATERIALS AND METHODS

Eight samples of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) each were light-cured with constant power or with soft-start mode (Translux Energy) for 20, 40 or 60s. The CIE-Lab-values (L(*), a(*), b(*)) were measured prior to and after performing dry aging, water aging or a Suntest (EN ISO 7491) and Delta L-, Delta a-, Delta b-, and Delta E-values were calculated.

RESULTS

Statistical analysis (GLM and repetition of measures) showed significant changes (p<0.05) of the color values for each material's curing mode and time after each of the aging processes. Four-way ANOVA revealed significant differences (p<0.05) between Delta L-, Delta a-, Delta b-, and Delta E of the materials in dependence on the curing time and mode and aging condition. Exponentially-cured DU was the most color-unstable material after aging in water followed by the 20s exponentially cured DE and CH samples. After the Suntest, DY showed significant bleaching (negative Delta b) and the largest Delta E for all curing times and modes followed by the DE samples. DU and CH were the most color-stable materials in this test.

SIGNIFICANCE

The extent of discoloration depends on the (a) curing time, (b) curing mode, (c) aging condition, and (d) material. For the constant curing mode, 40s curing time for the exponential 60s seems to be appropriate.

Comparison of total nucleated cell measurements of UC blood samples using two hematology analyzers

BACKGROUND

The total nucleated cell (TNC) content of umbilical cord blood (UCB) units currently serves as the most important measure for determining suitability for transplantation. Hence it is important that TNC measurements are performed in an accurate manner. TNC content is evaluated routinely by hematology analyzers (HA) as WBC counts. The objective of the study was to compare TNC content utilizing two different HA, one utilizing an impedance channel and optical channel, and the other using only an optical channel.

METHODS

The HA utilized in this study used two different modes of operation for lysis, regular mode (RM) and extended lysis mode (ELM). Cell-Dyn 3200 (CD3.2) utilizes optical technology for WBC measurements, involving WBC optical count (WOC) and nuclear optical count (NOC), whereas the Cell-Dyn 3700 (CD3.7) utilizes both the impedance (WIC) and optical technology (WOC) for WBC measurements. TNC content was determined with 17 identical samples using CD3.2 in one laboratory and CD3.7 in the other laboratory. Cord blood samples processed to concentrate nucleated cells by either of the laboratories were sent by overnight courier and assays were performed on the same day by both laboratories.

RESULTS

For CD3.7, the WOC values were consistently lower than the WIC using the regular mode, but showed no significant differences (P>0.05). The WIC and WOC values were comparable on using the ELM and RM. For CD3.2, WOC values using RM and NOC values using ELM showed no significant differences (P>0.05), even though the WOC measurement was lower than the NOC values for most samples. The best comparison of TNC measurement between the two HA could be achieved by comparing CD3.7-WIC with CD3.2-NOC values. The results were equivalent (P>0.05) and 12 of 17 samples had equal to or less than 10% difference (mean 9.5%).

DISCUSSION

TNC measurements of UCB samples were essentially identical using the WIC channel of the Cell-Dyn 3700 and the NOC channel of the Cell-Dyn 3200.

Localized wear of compomer restorative materials

PURPOSE

To determine and compare the localized wear of six compomer restorative materials.

MATERIALS AND METHODS

Ten specimens of Dyract, Dyract AP, F2000, Compoglass F, Elan and Hytac were prepared in a custom fixture and polished. A pretest surface profile was generated using an MTS 3-D surface profilometer and the specimens were subjected to 400,000 cycles in a Leinfelder wear machine equipped with a conical stylus tip to simulate localized wear. A post-test profile was generated and the before and after profiles were fitted and analyzed using AnSur 3-D software. The total volume loss and depth of the wear facet on each specimen was calculated and statistical analysis was accomplished (ANOVA and Tukey's test).

RESULTS

Volume loss (mm3) was as follows: F2000, 0.027 +/- 0.002; Hytac, 0.007 +/- 0.023; Elan, 0.054 +/- 0.013; Compoglass F, 0.135 +/- 0.006; Dyract AP, 0.135 +/- 0.023; Dyract, 0.185 +/- 0.032. Maximum depth of the wear facets (microm) was as follows: F2000, 112.2 +/- 10.2; Hytac, 132.8 +/- 9.3; Elan, 144.3 +/- 23. 1; Compoglass F, 168.3 +/- 13.0; Dyract AP, 194.0 +/- 19.7; Dyract, 220.6 +/- 15.8. There was not a difference (P > 0.05) in volumetric loss between F2000 and Hytac or between Hytac and Elan. The volume loss and maximum depth of the wear facets of F2000, Hytac and Elan was significantly less (P< 0.05) than Compoglass F, Dyract AP and Dyract The results of this study indicate that there are significant differences in the in vitro wear rates of compomer materials.

Laboratory evaluation of a metal-priming agent for adhesive bonding

OBJECTIVE

The purpose of this laboratory study was to determine the bond strength of a base metal alloy to a high-noble alloy and amalgam when a new chemical adhesion promoter was used in conjunction with a resin cement.

METHOD AND MATERIALS

Specimens of high-noble alloy and amalgam were prepared in epoxy-filled rings. Base metal cylinders were cast. The ends of the cylinders and the metal bonding substrates were wet ground and air abraded with aluminum oxide. The base metal cylinders were cemented with Panavia 21 resin cement after application of 1 of the following to the high-noble and amalgam metal surfaces: (1) Alloy Primer, (2) ED Primer, (3) Alloy Primer and ED Primer, or (4) tin plating. Bond values were determined after 24 hours' storage and after 3 months' storage and thermocycling.

RESULTS

At both 24 hours and 3 months, tin plating yielded the highest bond strengths to a high-noble alloy, but the value for the Alloy Primer groups was not significantly lower. There was no statistically significant difference between the 24-hour and 3-month values within the 4 treatment regimens.

CONCLUSION

Treatment of amalgam or high-noble alloy with either tin plating or Alloy Primer before bonding with Panavia 21 resin cement yielded equivalent bond strengths to a base metal alloy. ED Primer was not an effective metal primer. There was no advantage to combining Alloy Primer and ED Primer.

Approaches for intraoral repair of ceramic restorations

Ceramic-based restorations are an important part of a dentist's armamentarium for durability and esthetics. Because of the brittle nature of ceramic materials, these restorations have the potential to fracture. Repairing ceramic-based restorations can increase the clinical longevity of failed restorations and offer the dentist and patient a cost-effective alternative to replacement. Newer porcelain repair systems show excellent adhesion durability of resin-based composites to the fractured ceramic and exposed metal surfaces. This article reviews the basic principles of ceramic repair and details the use of five intraoral porcelain repair systems.

Comparison of composite resin-to-porcelain bond strength with three adhesives

Three resin-based adhesives were evaluated for suitability for porcelain repair with composite resin, as measured by shear bond strength of attachment. Photo Bond and SE Bond were associated with significantly greater shear bond strengths than their respective controls at both time periods investigated. Single Bond did not have shear bond strengths greater than its control and its values were significantly lower than those obtained with the other resins.

Physical properties of three packable resin-composite restorative materials

This study evaluated selected physical properties of three packable resin composites (Alert, SureFil and Solitaire) and compared them to two conventional hybrid materials (Prodigy and Z-100). The specific properties investigated were diametral tensile strength, transverse strength, elastic modulus and fracture toughness. Following photopolymerization, specimens for each composite material were stored in deionized water at 37 degrees C for 35 days. A one-way ANOVA and Tukey's post-hoc test were employed for each property to determine whether significant differences occurred with respect to specific restorative materials. All materials had statistically similar diametral tensile strengths. Alert had the highest mean fracture toughness and elastic modulus but had a low mean transverse-strength value. SureFil exhibited good mean physical property values compared to both the conventional and packable materials. Solitaire had low mean fracture toughness, transverse strength and elastic modulus values, which could cause concern regarding use in posterior restorations. The packable resin composites tested had a wide range of mean values for the physical properties investigated. Generally, Alert and SureFil were superior to Solitaire and comparable to the hybrid materials Prodigy and Z-100, but clear discrimination among performance of these materials requires clinical testing.

Effect of air abrasion and acid etching on sealant retention: an in vitro study

PURPOSE

This in-vitro study evaluated shear bond strength and analyzed, via scanning electron microscopy, enamel prepared for pit and fissure sealant placement. Various surface pretreatment methods were conducted prior to short-term (72-hour) and long-term (120-day) analysis.

METHOD

Six treatment groups of 14 teeth, having 28 bonding surfaces (buccal and lingual) were treated. Cylinders of Delton pit and fissure sealant were placed on the prepared buccal and lingual surfaces and light-cured for 60 seconds. One-half of each group's specimens were stored in distilled water for 72 hours and the other half were stored in water distilled for 120 days followed by thermocycling. All specimens were subjected to shear bond strength analysis as determined on an Instron testing machine.

RESULTS

All acid treated groups were equivalent and greater than air abrasion alone after 72 hours of water storage. Scanning electron microscopy of air-abraded and combination treated enamel surfaces revealed a more detailed retentive pattern in the combination treatment than in either treatment alone.

CONCLUSION

Based on in-vitro shear bond strength values, air abrasion with 50 micron alumina is an effective pre-etch treatment for sealant placement and in concert with phosphoric acid treatment significantly enhanced the long-term bond of a sealant to enamel. The clinical relevance of this has not been established.

Bond strength of composite to enamel and dentin using Prime & Bond 2.1

A laboratory study was conducted to determine the bond strength of composite to enamel and dentin using a one-component dental adhesive system (Prime & Bond 2.1) with three application regimens ranging from four to seven procedural steps. In addition, the effect of acid conditioning of dentin on bond strength was evaluated. Enamel bond strengths ranged from 29.2 to 29.8 MPa, and dentin bond strengths ranged from 18.6 to 21.3 MPa. Enamel bond strengths were significantly higher (P = 0.000) than dentin values. There was no significant difference (P > 0.05) among the bond strengths in either the enamel or dentin groups using the three application regimens. Nor did acid conditioning of dentin increase bond strengths (P = 0.683).

Dental adhesives in contemporary restorative dentistry

Significant progress has been made in the area of adhesives in restorative dentistry. With respect to composite restoratives, bond strengths greater than the targeted 17 MPa are now routinely achieved by modern dentin bonding systems in laboratory tests. Each adhesive system must be handled according to the manufacturer's instructions and with careful attention to the details of application for maximal success. Clinical documentation of the success of the modern systems is limited. This especially true for the multipurpose applications often advocated by the product instructions or clinicians lecturing from personal anecdotal experience. The confirmation of laboratory results with controlled clinical trials often occurs late or not at all. A thorough understanding of the in vivo performance is needed to gain the knowledge necessary to further the technologic advances in this area.

Three-year clinical evaluation of the Clearfil Liner Bond system

Modern dental adhesive systems have improved the bond of restorative materials to mineralized tooth structures. The purpose of this study was to evaluate the clinical performance of composite restorations placed in abrasion and erosion lesions using the Clearfil Liner Bond dental adhesive system. Following ADA clinical guidelines for dentin and enamel adhesive materials, 62 facial class 5 smooth surface erosion or abrasion lesions with no undercuts and involving primarily root surfaces were restored in 25 adult male and female patients. The teeth were restored without preparations using Clearfil Liner Bond and Clearfil Photo Anterior composite resin. The clinical performance of the restorations was assessed by two examiners at baseline, 6 months, 1, 2, and 3 years using the following evaluative parameters: color match, marginal discoloration, and marginal integrity according to modified Ryge criteria; the presence or absence of recurrent decay; pre- and postoperative sensitivity; and restoration failure due to loss of retention or other causes. At the end of 3 years, four of the 55 restorations remaining in the study failed due to lack of retention (92.7% retention rate). The evaluations of the other clinical parameters demonstrated excellent performance by this system.

Recombinational construction in Escherichia coli of infectious adenoviral genomes

A two-step gene replacement procedure was developed that generates infectious adenoviral genomes through homologous recombination in Escherichia coli. As a prerequisite, a human adenovirus serotype 5 (Ad5)-derived genome was first introduced as a PacI restriction fragment into an incP-derived replicon which, in contrast to ColE1-derivatives (e.g., pBR322 or pUC plasmids), is functional in a polA mutant of E. coli. Any modification can be introduced at will following two consecutive homologous recombinations between the incP/Ad5 replicon and the ColE1 plasmid. The overall procedure requires only the in vitro engineering of the ColE1-derivative by flanking the desired modification with small stretches of identical sequences. In the first step, a cointegrate between the tetracycline-resistant incP/Ad5 replicon and the kanamycin-resistant ColE1-derivative is selected by growing the polA host in the presence of both antibiotics. Resolution of this cointegrate is further selected in sucrose growth conditions due to the loss of a conditional suicide marker (the sacB gene of Bacillus subtilis) present in the ColE1 plasmid, leading to unmodified and modified incP/Ad5 replicons that can be differentiated upon restriction analysis. Consecutive rounds of this two-step cloning procedure allowed the introduction of multiple independent modifications within the virus genome, with no requirement for an intermediate virus. The potential of this procedure is demonstrated by the recovery of several E1E3E4-deleted adenoviruses following transfection of the corresponding E. coli-derived genomes in IGRP2 cells.

Characterization of human apolipoprotein A-I expressed in Escherichia coli

Human apolipoprotein A-I (apoA-I), with an additional N-terminal extension (Met-Arg-Gly-Ser-(His)6-Met) (His-apoA-I), has been produced in Escherichia coli with a final yield after purification of 10 mg protein/1 of culture medium. We have characterized the conformation and structural properties of His-apoA-I in lipid-free form, and in reconstituted lipoproteins containing two apoA-I per particle (Lp2A-I) by both immunochemical and physicochemical techniques. The lipid-free forms of the two proteins present very similar secondary structure and stability, and have also very similar kinetics of association with dimyristoyl phosphatidylcholine. His-apoA-I and native apoA-I can be complexed with 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) to form similar, stable, either discoidal or spherical (sonicated) Lp2A-I particles. Lipid-bound native apoA-I and His-apoA-I showed very similar alpha-helical content (69% and 66%, respectively in discoidal Lp2A-I and 54% and 51%, respectively in spherical Lp2A-I). The conformation of His-apoA-I in lipid-free form and in discoidal or spherical Lp2A-I has also been shown to be similar to native apoA-I by immunochemical measurements using 13 monoclonal antibodies recognizing distinct apoA-I epitopes. In the free protein and in reconstituted Lp2A-I, the N-terminal has no effect on the affinity of any of the monoclonal antibodies and minimal effect on immunoreactivity values. Small differences in the exposure of some apoA-I epitopes are evident on discoidal particles, while no difference is apparent in the expression of any epitope of apoA-I on spherical Lp2A-I. The presence of the N-terminal extension also has no effect on the reaction of LCAT with the discoidal Lp2A-I or on the ability of complexes to promote cholesterol efflux from fibroblasts in culture. In conclusion, we show that His-apoA-I expressed in E. coli exhibits similar physicochemical properties to native apoA-I and is also identical to the native protein in its ability to interact with phospholipids and to promote cholesterol esterification and cellular cholesterol efflux.

Bond strength of an adhesive polymerized under nitrogen

PURPOSE

To evaluate the use of nitrogen, in conjunction with visible light polymerization, for improving composite-to-dentin bond strengths.

MATERIALS AND METHODS

Composite cylinders were bonded to dentin with Scotchbond Multi-Purpose. Immediate (Groups 1-4) and 24-hour (Groups 5-8) strengths were determined for the following two adhesive application and two polymerization techniques: Groups 1 & 5: gentle air thinning of adhesive and polymerization with conventional visible light curing (VLC) unit; Groups 2 and 6: aggressive air thinning of adhesive and conventional VLC; Groups 3 and 7: gentle air thinning of adhesive and polymerization in nitrogen environment with modified VLC unit; and Groups 4 and 8: aggressive air thinning of adhesive and polymerization in nitrogen environment with modified VLC unit.

RESULTS

The immediate bond strengths (MPa) were: Group 1: 15.1 +/- 1.8, Group 2: 6.1 +/- 2.1, Group 3: 17.8 +/- 3.1, Group 4: 15.8 +/- 2.0. The 24-hour strengths were: Group 5: 26.7 +/- 4.4, Group 6: 13.5 +/- 7.5, Group 7: 24.1 +/- 5.7, Group 8: 26.4 +/- 4.3. Visible light polymerization of a thinned layer of adhesive resin in a nitrogen environment produced significantly higher immediate and 24-hour bond strengths than when compared to visible light polymerization in ambient air.

Modulation of colonic aberrant crypt foci and proliferative indexes in colon and prostate glands of rats by vitamin E

The effect of a high vitamin E diet on the early stages of colon carcinogenesis and on the proliferative indexes in the colon and in the prostate glands was investigated in rats. F344 male rats were injected with azoxymethane (AOM, 15 mg/kg sc). One week later, animals were randomly allocated into two dietary groups (n = 8 rats/group): normal vitamin E (50 IU/kg diet) and high vitamin E (200 IU/kg diet). The basal diet was the AIN-76 diet modified to contain high corn oil (23% wt/wt). After eight weeks of feeding, concentrations of vitamin E in plasma, liver, and prostate were analyzed. Enumeration of aberrant crypt foci (ACF) in colons and proliferative indexes of colons and prostate glands were determined. The total number of ACF and the average number of aberrant crypts (AC) per focus were similar in both dietary groups. ACF were classified as small (1-3 crypts/focus), medium (4-6 crypts/focus), or large (> or = 7 crypts/focus). Only the ACF in the small category showed a significant treatment effect, with values being lower in the high vitamin E group than in the control group (p < or = 0.05). No significant difference was observed in colonic proliferative indexes assessed by enumeration of metaphase cells, S phase cells, or cells exhibiting proliferative cell nuclear antigen (PCNA). The PCNA labeling index in the prostate glands and the activity of prostatic acid phosphatase in plasma were higher in high vitamin E-fed rats (p < or = 0.05) than in control animals. The present study demonstrates that additional vitamin E does not inhibit the induction and growth of ACF; also it enhances the proliferative status of the prostate glands.

4-year clinical study of castable ceramic crowns

PURPOSE

To evaluate the 4-year clinical performance of castable glass ceramic crowns used to restore teeth in the posterior segments.

MATERIALS AND METHODS

101 castable ceramic (Dicor) full++ crown restorations were placed in 61 molar and 40 premolar teeth using a bonded resin cement.

RESULTS

After 4 years of clinical performance, 15 of the original 101 restorations were known to have failed with 13 of those failures affecting molar restorations. All serviceable restorations were rated as excellent for color match, margin adaptation, proximal contact and gingival health. Cavosurface margin discoloration received a 93.5% alfa response. The results of this study show that Dicor crowns meet the esthetic and biological requirements for posterior restorations. The incidence of fracture of molar restorations in this study indicated that when used for restoring molars, careful case selection and caution must be employed.

Identification of specific amphipathic alpha-helical sequence of human apolipoprotein A-IV involved in lecithin:cholesterol acyltransferase activation

To investigate the structure-function relationship of human apolipoprotein A-IV (apoA-IV), several deletion mutants of this protein were constructed by sequentially removing pairs of 22-residue repeats, potentially having an amphipathic alpha-helical conformation. The mutants, produced as recombinant poly-histidine-tagged apolipoproteins (t-apo) in Escherichia coli, assembled with phosphatidylcholine (i.e. dimyristoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine, or egg lecithin) as did native apoA-IV. Lecithin:cholesterol acyltransferase (LCAT) cofactor function, measured as cholesterol esterification occurring when t-apo-phosphatidylcholine-cholesterol complexes were incubated with purified enzyme, decreased significantly when pairs of repeats between residues 117 and 248 were deleted and most markedly when residues 117-160 were deleted. LCAT cofactor activity decreased by 90 and 75%, respectively, when egg lecithin or palmitoyloleoylphosphatidylcholine was used to form the particles with the delta aa 117-160 mutant. Thus, on the basis of deletion scanning of t-apo, residues 117-160 seem to be involved in the LCAT cofactor function of apoA-IV.

Purification and characterization of recombinant human apolipoprotein A-II expressed in Escherichia coli

We have expressed recombinant human apolipoprotein A-II (apoA-II) in Escherichia coli, as a fusion protein with Schistosoma japonicum glutathione-S-transferase (GST). The GST-AII fusion protein was recovered by affinity chromatography using glutathione as a ligand. After thrombin cleavage and removal of the GST carrier, recombinant apoA-II was obtained in a highly purified form and was exclusively composed of dimeric apoA-II. Kinetics of association to dimyristoylglycerophosphocholine (Myr2GroPCho) vesicles showed that recombinant apoA-II exhibited the same pattern of association as human plasma apoA-II. Electron microscopic analysis of the complexes showed a typical pattern of rouleaux, characteristic of stacked discs, with a diameter similar to that determined by gradient-gel electrophoresis. Circular dichroism measurements showed that the alpha-helical content of both plasma and recombinant apoA-II increased similarly when the proteins associated with Myr2GroPCho vesicles, at the expense of a random-coil structure. Lipid-bound apoA-II consisted of 70-72% alpha helices, suggesting the presence of three 18-residue alpha helices/apoA-II monomer. Cross-linking experiments indicated that Myr2GroPCho complexes contained two molecules dimeric apoA-II/vesicle. Recombinant apoA-II was as efficient as plasma apoA-II in associating with HDL subclasses, and in displacing apoA-I from dipalmitoylglycerophosphocholine/cholesterol/apoA-I complexes, most likely due to its highly ordered secondary structure when associated with Myr2GroPCho vesicles. These findings demonstrate that recombinant apoA-II exhibits the same structural and functional properties as human plasma apoA-II. Thus, the expression system utilized is appropriate to produce mutagenized forms to further structure/function analysis.

Bond strength of a resin cement to a cured composite inlay material

Although resin cements have been effectively bonded to mineralized tooth structures, bonding to a cured composite material has remained a challenge. This study evaluated the shear bond strength of a resin cement bonded to a cured composite inlay material by use of a variety of composite surface treatments: (1) hydrofluoric acid/60 seconds, (2) ammonium bifluoride/60 seconds, (3) resin adhesive, (4) microabrasion with 50 microns aluminum oxide, and (5) microabrasion with 50 microns aluminum oxide and application of a resin adhesive. The resin cement was also bonded to human enamel that was etched with phosphoric acid. Scanning electron microscopy examinations were completed to evaluate the effects of the composite surface treatments. The results indicated that microabrasion of a cured composite enhances bonding of a resin cement. The bond strength of a resin cement to a composite surface that was air abraded with aluminum oxide, with or without the application of a resin adhesive, was higher than surface treatments with hydrofluoric acid or ammonium bifluoride. Scanning electron microscopy indicated that an irregular surface on the composite was created with aluminum oxide air abrasion.

Clinical evaluation of castable ceramic veneers

Laboratory fabricated veneering of discolored or malformed anterior teeth is becoming a widely used technique. Etched Dicor and Dicor Plus ceramic veneers cemented with Dicor Light Activated Cement with Fluoride is one technique available to the practitioner. The purpose of this study was to evaluate the clinical effectiveness of castable ceramic veneers and the cementation system. Forty-three Dicor and 18 Dicor Plus veneers were placed in 12 patients. An intraenamel preparation was completed with a bullet-nosed diamond bur in an ultra-speed handpiece with air-water spray, and a polyvinylsiloxane impression was made. All veneers were fabricated on dies by the same laboratory technician and placed by one practitioner. The restorations were examined by two evaluators at baseline, 3 months, and 1 year, using modified Ryge criteria.