Influence of etching mode on bonding performance of self-adhesive flowable resin composites to bovine teeth

This study aimed to evaluate the bonding performance of self-adhesive flowable resin composites (SARs) to bovine teeth. Three SARs, one experimental, and two commercially available products, were used. The study parameters were shear bond strength (SBS), microleakage, and scanning electron microscopy (SEM) evaluation of bonding interfaces. The SBS of the materials was 14.1-15.1 MPa to enamel, 22.2-23.2 MPa to etched enamel, and 7.4-10.7 MPa to dentin. Specimens with pre-etching showed lower microleakage scores than those without pre-etching. SEM images of the interfaces of the materials showed excellent adaptation regardless of the substrate or etching mode. The study results indicate that enamel pre-etching can improve the bonding performance of SARs.

Scanning electron microscopy observation of dentin bond interfaces in different types of resin luting cements

This study aimed to observe and compare the resin luting cement (RLC)/dentin interfaces of different types of RLC systems with scanning electron microscopy (SEM). This study evaluated six self-adhesive resin luting cement systems (SARLCs), four systems combining a SARLC with a tooth primer (SARLCPs), and six conventional resin luting cement systems (CVRLCs). Cured resin composite rods were bonded to bovine dentin using RLCs in different etching modes. The morphological features at the interfaces were observed using SEM. Although all RLCs in etch-&-rinse (ER) mode showed a clear hybrid layer, most SARLCs had a thinner and more porous hybrid layer than the SARLCPs and CVRLCs. All SARLCPs with primer and CVRLCs showed a thin high-density layer below the primer layer in both etching modes. CVRLCs and SARLCPs with primer treatment systems may be more versatile and reliable when compared to simplified RLC systems.

Changes in enamel hardness, wear resistance, surface texture, and surface crystal structure with glass ionomer cement containing BioUnion fillers

This study investigated the potential of BioUnion filler containing glass ionomer cement (GIC) to enhance the properties of enamel surrounding restorations, with a specific focus on the effect on hardness. The hardness of the bovine enamel immersed in the cement was measured using Vickers hardness numbers. Following sliding and impact wear simulations, the enamel facets were examined using confocal-laser-scanning microscopy and scanning-electron microscopy. Surface properties were further analyzed using energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). A significant increase in Vickers hardness numbers was observed in the BioUnion filler GIC after 2 days. Furthermore, the mean depth of enamel facets treated with BioUnion filler GIC was significantly less than that of untreated facets. Characteristic XRD peaks indicating the presence of hydroxyapatite were also observed. Our findings imply that GIC with BioUnion fillers enhances the mechanical properties of the tooth surface adjacent to the cement.

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.

Influence of different curing modes on the bonding effectiveness of self-adhesive resin luting cements in combination with universal adhesives

OBJECTIVES

This study aimed to investigate the immediate dentin bond performance and bond durability of self-adhesive resin luting cements (RLCs) in combination with universal adhesives in different curing modes.

METHODS

Two self-adhesive RLCs were used with universal adhesives as primers. They were also used alone as self-adhesive RLCs. Two multiple-step RLC systems were used as comparison materials. To measure the shear bond strength (SBS) in different curing modes, 12 specimens were prepared for each group. Stainless-steel rods were bonded to bovine dentin, and the bonded specimens were assigned to the baseline group (stored for 24 h) and artificially aged group (thermal cycling [TC], 10,000 cycles). After each storage period, the SBS of the bonded specimens was measured. The Knoop hardness number (KHN) of the cured RLCs was measured with or without primer application in different curing modes at 24 h and after 10,000 TC. The representative RLC/dentin interfaces were observed using scanning electron microscopy (SEM).

RESULTS

Dentin SBS was significantly influenced by the RLC system but not by the curing mode. Self-adhesive RLCs alone showed significantly lower SBS values than self-adhesive RLCs with primer regardless of the curing mode or storage period. The storage period, curing mode, and RLC system significantly influenced the KHN.

SIGNIFICANCE

The use of universal adhesives as a primer may help enhance the immediate dentin bond performance and bond durability of self-adhesive RLCs.

Treatment of saliva contamination of resin core foundation before adhesive luting

This study aimed to evaluate the influence of surface pretreatment on the shear bond strength of resin luting cement to saliva-contaminated resin core foundation. The surface free energy (γS) of the adherent surfaces was examined. The two-way analysis of variance revealed that the surface pretreatment and storage conditions had a significant effect on the strength of the bond to resin core foundation. The γS values of the saliva-contaminated group were significantly lower than those of the other groups, and they tended to improve after surface pretreatment. The tendency of improvement in γS values differed depending on the type of pretreatment agents. Surface treatment with solutions containing functional monomers is effective in removing saliva contaminants from the resin core foundation surfaces and in creating an effective bonding surface for the resin luting cement.

Influence of surface roughness of universal shade resin composites on color adjustment potential

This study aimed to determine the influence of surface roughness of the color adjustment potential restoration of universal resin composites. A structural colored resin composite (Omnichroma, OC) and a pigment-employed universal shade resin composite (Beautifil Unishade, BU) were used. Each resin composite was placed in a cavity to determine its ability to match the color of artificial teeth. The surface of the resin composites was polished with #800- or #2000-grit SiC paper before performing color measurements. One-way analysis of variance and Tukey post hoc tests were performed (α=0.05). The color difference (ΔE*ab) ranged from 2.5-3.9 for OC and 1.8-8.7 for BU. OC has a more stable color adjustment than BU. The color adjustment potential of universal resin composites was affected by the surface roughness of the restorations.

Whitening efficacy and tooth sensitivity in a combined in-office and at-home whitening protocol: A randomized controlled clinical trial

OBJECTIVE

This controlled randomized clinical trial determined the whitening efficacy and the intensity and absolute risk of tooth sensitivity in dual whitening when prefilled at-home whitening trays were used between in-office whitening intervals.

MATERIALS AND METHODS

An in-office whitening agent containing 35% hydrogen peroxide was used. A prefilled tray with a whitening agent containing 6% hydrogen peroxide was used for at-home whitening. Sixty-six subjects were randomly assigned to three groups. Group I: at-home whitening was performed 10 times between the in-office whitening treatments. Group II: at-home whitening was performed five times between the in-office whitening treatments. Group III: only in-office whitening was performed. The tooth color changes were evaluated using a spectrophotometer. A visual analog scale was used to express the pain intensity.

RESULTS

All the groups showed increased ΔE*ab, ΔE00 , and ΔWID with increased whitening sessions. Group I at the 3rd whitening session showed significantly higher ΔE*ab, ΔE00 , and ΔWID than group III. Tooth sensitivity showed higher values up to 24 h after whitening.

CONCLUSIONS

Although dual whitening with the prefilled tray and in-office whitening had higher whitening ability than in-office whitening alone, the intensity and absolute risk of tooth sensitivity was similar.

CLINICAL RELEVANCE

The dual whitening might produce faster and stronger whitening effects than in-office whitening alone.

Utility of biphasic calcium phosphate cement as a seal for root-end filling

The recently developed biphasic calcium phosphate cement (BCPC) consists of α-tricalcium phosphate-tetracalcium phosphate as the solid phase and calcium phosphate solution as the liquid phase. BCPC powder is composed of a single solid solution with a monomodal size distribution. Here, we used a bacterial leakage model to examine the utility of BCPC as a seal for root-end filling. We prepared large (median particle size=9.96 µm; BCPC-L) and small (median particle size=4.84 µm; BCPC-S) BCPC powders. In total, 45 single-rooted teeth were instrumented, resected at the root-end, and retrofilled with experimental materials. Mineral trioxide aggregate (MTA) was used as the control. After visual confirmation of BCPC powder size and retrofilling quality by microscopy, bacterial leakage tests were conducted using Enterococcus faecalis. The bacterial leakage tests did not reveal any significant differences between BCPC-S and MTA. Our findings suggest that BCPC-S is useful for root-end filling.

Bond durability of a two-step adhesive with a universal-adhesive-derived primer in different etching modes under different degradation conditions

This study investigated the enamel and dentin bond durability of a two-step adhesive system, using a universal adhesive-derived primer (G2-Bond Universal [GU]), and compared it with the two conventional, two-step, self-etch adhesive systems (Clearfil SE Bond 2 [CS] and OptiBond XTR [OX]) under thermal cycling (TC) and long-term water storage (WS). The shear bond strengths to bovine enamel and dentin were determined using the etch-and-rinse and self-etch modes. Twelve specimens per test group were prepared and further divided into the following subgroups: 1) subjected to TC, 2) long-term WS, and 3) WS for 24 h (baseline). The enamel and dentin bond durability of GU was superior to those of CS and OX in different etching modes and under different degradation conditions. The latest two-step adhesive system, which utilizes universal adhesives' benefits in its primer, might offer durable clinical bonding performances and can be widely used in a clinical setting.

Early Phase Enamel Bond Performance of a Two-step Adhesive Containing a Primer Derived from a Universal Adhesive

PURPOSE

To investigate the changes in the enamel bond performance of a two-step adhesive containing a primer derived from a universal adhesive in the early phase before 24 h and compare them to those of other adhesives. The Knoop hardness number (KHN) of the cured adhesive layers and resin composite was measured.

MATERIALS AND METHODS

A new two-step adhesive using universal adhesive technology, G2-Bond Universal, was tested. Two conventional two-step adhesives, Clearfil SE Bond 2 and OptiBond eXTRa, and an established universal adhesive, Scotchbond Universal Plus Adhesive, were used as comparison materials. Twelve specimens per group were used to measure the shear bond strength (SBS) to bovine enamel in different etching modes. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h before SBS testing. The KHN of the adhesive layer and resin composite was determined after the same storage periods as for SBS testing.

RESULTS

All adhesives exhibited increased SBS with prolonged storage periods, irrespective of the etching mode. The KHN of the adhesive layer and resin composite increased over time.

CONCLUSIONS

There were strong positive correlations between the SBS and KHN of the adhesive layer and resin composite. Phosphoric acid pre-etching of enamel effectively increases enamel bond performance. The two-step adhesive G2-Bond Universal demonstrated significantly higher bond strength in the early phase than the other adhesives in self-etch mode.

Effect of mold enclosure and chisel design on fatigue bond strength of dental adhesive systems

To examine the effect of mold enclosure and chisel design on macro shear fatigue bond strengths of dental adhesive systems. The fatigue bond strength testing was conducted with two commercially available dental adhesive systems, (1) OptiBond eXTRa and (2) Scotchbond Universal, for bonding a resin composite (Filtek Supreme Ultra) to both enamel and dentin using a mold enclosure and a non‐mold enclosure with a knife‐edge and two sized notched‐edge chisel assemblies for loading. As a loading reference for the fatigue testing, macro shear bond strengths of the adhesive systems to enamel and dentin were conducted using a mold enclosure and a knife‐edge chisel assembly. The shear bond strengths with the mold enclosure using knife‐edge chisel assembly did not exhibit a significant difference between the adhesive systems for either enamel or dentin. The fatigue bond strengths of bonded specimens demonstrated significant differences when comparing the mold enclosure and non‐mold enclosure, but not between knife‐edge and notched‐edge chisel assemblies. The fatigue bond strengths of dental adhesive systems demonstrated significantly higher values when using mold‐enclosed bonded specimens than a non‐mold enclosure, regardless of type of chisel assembly.

Influence of bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer

This study investigated the effect of the bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer. The bonding durability of a universal adhesive was compared with those of two conventional two-step adhesives by shear bond strength testing after thermal cycling. The primer was applied (with or without phosphoric acid pre-etching), and the specimens were divided into three groups based on the bonding agent application method used as follows: (i) strong air-flow application, (ii) gentle air-flow application, and (iii) gentle air-flow + second bonding application. The shear bond strength was determined after thermal cycling. All the factors (bonding agent application method, adhesive system, and storage condition) significantly influenced the dentin shear bond strength both with and without phosphoric acid pre-etching. The specimens exposed to gentle air-flow showed a higher shear bond strength than did those exposed to strong air-flow and gentle air-flow + second bonding. The bond durability of the tested adhesive systems was influenced by the bonding agent application method, and this trend was material dependent. The G2-Bond Universal exhibited the same or greater dentin bond durability to the other two-step adhesive systems.

Immediate bond performance of resin composite luting systems to saliva-contaminated enamel and dentin in different curing modes

The purpose of this study was to evaluate the immediate shear bond strength of resin composite luting systems to tooth with or without saliva contamination in different curing modes. The Knoop hardness number of the resin composite luting agents was measured. Four combinations of resin composite luting systems were used. The shear bond strength to bovine teeth was measured with and without saliva contamination in different curing modes at different storage periods. The Knoop hardness number of the resin composite luting agents was also evaluated. Significantly lower enamel and dentin shear bond strengths and Knoop hardness number values were observed in all resin composite luting systems at 5 min versus 24 h, regardless of the curing mode or saliva contamination. The influence of the curing mode of the resin composite luting systems on shear bond strengths and Knoop hardness number was dependent on material. For the saliva contamination conditions, only G-CEM ONE EM did not show any significant difference in shear bond strength among the groups with and without saliva contamination, regardless of curing mode, storage period, or tooth substrate. All the resin composite luting systems showed lower shear bond strengths and Knoop hardness number values immediately after setting.

Evaluation of the effect of a glass ionomer cement containing fluoro-zinc-silicate glass on dentin remineralization using the ultrasonic pulse-echo method

The purpose of this study was to investigate the protective effect of a glass ionomer cement (GIC) consisting of fluoro-zinc-silicate glass on the demineralization of bovine dentin using the ultrasonic pulse-echo method. The findings were compared with those obtained using a conventional GIC. Slabs of dentin from bovine teeth were sliced, shaped into a rectangular form, and immersed in 0.5 M ethylenediaminetetraacetic acid solution at 25ºC for 6 days, followed by storage in distilled water for 3 days. After demineralization, they were immersed in artificial saliva with and without the GIC specimens. The propagation times of the longitudinal ultrasonic waves in the samples were measured. The ultrasonic velocities of the fluoro-zinc-silicate glass-containing GICs were significantly increased 2-3 days after the start of the experiment and showed an upward trend thereafter. These findings indicate that the GICs containing fluoro-zinc-silicate glass might exhibit the potential to promote remineralization in the dentin.

Influence of masticating cycles and chewing patterns on inadvertent enamel wear caused by zirconia brackets

Little information is available about enamel wear caused by zirconia brackets, an inadvertent side effect of orthodontic treatment. The purpose of this study was to examine potential enamel damage induced by contact with zirconia brackets. Sliding and impact wear simulations were performed using bovine enamel specimens positioned at a 25° slant to a zirconium ball to determine wear behaviour. Different chewing patterns, tapping and grinding, were simulated. Specimens were profiled using confocal laser scanning microscopy, and the mean maximum depth and surface roughness were measured. Scanning electron microscopy was also performed. The mean maximum depth of wear values differed according to the number of mastication cycles, with a higher number of cycles producing higher depths of wear. The facet wear depth was significantly greater with the tapping pattern than with the grinding pattern. Scanning electron microscopic observation of the wear facets revealed that surface textures at the edges were rougher than those at the centre of all facets. The results of this study indicated that enamel wear was induced by contact with zirconia brackets during the early period of mastication, and that the patterns and number of cycles of mastication affected the wear progression of enamel.

Effect of ion-releasing filler-containing gel application on dentin remineralization using optical coherent tomography

PURPOSE

To examine the effects of an ion-releasing filler-containing gel on the remineralization of dentin using optical coherence tomography (OCT).

METHODS

Dentin slabs of bovine teeth were sliced and shaped into a rectangular form. Specimens were treated with undersaturated 0.1 M lactic acid buffer solution (pH 4.75) for 10 minutes and then placed in artificial saliva (pH 7.0). This procedure was repeated three times a day for 28 days. The dentin remineralization effects of a fluoride/S-PRG filler-containing gel (PRG) and a 38% SDF solution (SDF) on dentin slabs of bovine teeth were compared. After treatment, the dentin slabs were immersed in a 0.1 M lactic acid buffer solution and then placed in artificial saliva. This procedure was repeated three times a day for 28 days. OCT imaging was conducted on the selected location of the dentin surface. The peak intensity and width at 1/e² were recorded in each of the six areas on the sample and averaged. Each group had a sample size of 10. Knoop hardness number (KHN) measurements and scanning electron microscopy (SEM) observations were also conducted. The data for each group were subjected to a one-way repeated-measures ANOVA and Tukey tests (α= 0.05). The samples were also observed using SEM.

RESULTS

The peak signal intensities of SDF and PRG decreased on day 7 and then slightly increased during the experimental period for the one-off application groups and then decreased for frequent-time application groups. Although the width at 1/e² in the untreated specimens decreased over the test period, SDF and PRG for the one-off application groups exhibited an increase in widths on day 7 followed by a slight decrease, whereas it increased for the frequent-time application groups. The average KHN of the dentin samples exhibited the same tendency as the width at 1/e². Closure of the dentin tubules and crystal precipitation were detected on the surface of both SDF and PRG groups.

CLINICAL SIGNIFICANCE

S-PRG filler-containing gel might have the ability to prevent dentin demineralization and could be useful for the prevention of hard-to-access lesions. This material achieved remineralization of the demineralized root dentin and had the same remineralization ability as SDF in vitro.

Ultrasonic measurement of dentin remineralization effects of dentifrices and silver diamine fluoride

OBJECTIVE

This study investigated the dentin remineralization effect of the application of a functionalized tri-calcium phosphate (fTCP) dentifrice and a silver diamine fluoride (SDF) solution.

MATERIAL AND METHODS

The materials used were: a fluoride-containing dentifrice with fTCP (fTCP＋), a fluoride-containing dentifrice without fTCP (fTCP-) and a 38% SDF solution. Following treatment, the dentin slabs were immersed in a 0.1-M lactic acid buffer solution and then placed in artificial saliva. This procedure was repeated three times daily for 28 days. The propagation time of longitudinal ultrasonic velocities (UV) and the Knoop hardness (KH) of the samples were measured. The samples were also observed using scanning electron microscopy.

RESULTS

The SDF and fTCP＋ groups showed higher UV than the fTCP - group regardless of the application method. The F-SDF group at 28 days showed significantly higher UV (4121 ± 102 m/s) than the F-fTCP + group (3731 ± 65 m/s) (p < .05). The F-SDF group at 28 days showed significantly higher KH (47.4 ± 2.2) than the F-fTCP＋ group (43.3 ± 1.0) and the F-fTCP - group (42.9 ± 2.1) (p < .05). Closure of the dentinal tubules and crystal precipitation was detected on the surface of the fTCP＋ group to a greater extent than the fTCP - group.

CONCLUSIONS

The fTCP-containing dentifrice and SDF solution effectively enhanced bovine dentin remineralization.

Influence of Different Application Methods on the Bonding Effectiveness of Universal Adhesives to Dentin in the Early Phase

PURPOSE

To investigate the changes in the dentin bond strengths of universal adhesives during the early phase and evaluate the effect of a double-layer adhesive application on the performance of the dentin bond.

MATERIALS AND METHODS

Three universal adhesives and a two-step self-etch adhesive were employed to ascertain the shear bond strengths (SBS) of specimens to bovine dentin with the use of the etch-and-rinse or self-etch mode. The specimens were further divided into two groups based on adhesive application in a single or a double layer. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h prior to SBS measurement and the adhesives' Knoop hardness number (KHN).

RESULTS

All the adhesives showed increased SBS with prolonged storage periods regardless of the adhesive layer (single or double) or etching mode. Most universal adhesives in the double adhesive layer groups showed significantly higher SBS than single adhesive layer groups for the same storage period. All the adhesives also showed increased KHN with increased storage period.

CONCLUSION

The SBS and KHN values of the adhesives increased with increasing storage duration over a 24-h period. Double adhesive layer application mediated increased dentin bond strength in the early phase.

Bonding ability of resin cements to different types of CAD/CAM composite blocks

This study investigated the bonding performance of two different types of resin cements to computer-aided design/computer-aided manufacturing (CAD/CAM) composite blocks based on the shear bond strength (SBS) test. A silane-containing self-adhesive resin cement (Panavia SA Cement Universal) and resin luting cement (Block HC Cem) with a primer, were used. Specimens were fabricated from three different types of CAD/CAM composite blocks, and their surfaces were blasted with alumina. Resin cements were bonded to the specimens, and their SBSs were measured after 15 min, 24 h, and after being subjected to thermal cycling for 10,000 and 30,000 cycles. Three-way ANOVA for bond strength revealed that CAD/CAM composite block, resin cement and storage time significantly influenced the SBS values, and the three-way interactions between the evaluated factors, and all the interactions were significant. It was concluded that the bonding performance of resin cements to CAD/CAM composite blocks were material and storage period dependent.

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.

Flexural Properties and Polished Surface Characteristics of a Structural Colored Resin Composite

OBJECTIVE

The aim of this study was to determine the flexural properties and surface characteristics of a structural colored resin composite after different finishing and polishing methods, in comparison to those of conventional resin composites.

METHODS AND MATERIALS

A structural color resin composite, Omnichroma (OM, Tokuyama Corp, Chiyoda City, Tokyo, Japan), and two comparison resin composites, Filtek Supreme Ultra (FS, 3M, St Paul, MN, USA) and Tetric EvoCeram (TE, Ivoclar Vivadent, Schaan, Liechtenstein), were used. The flexural properties of the resin composites were determined in accordance with the ISO 4049 specifications. For surface properties, 70 polymerized specimens of each resin composite were prepared and divided into seven groups of 10. Surface roughness (Sa), gloss (GU), and surface free energy (SFE) were investigated after the following finishing and polishing methods. Three groups of specimens were finished with a superfine-grit diamond bur (SFD), and three with a tungsten carbide bur (TCB). After finishing, one of the two remaining groups was polished with a one-step silicone point (CMP), and the other with an aluminum oxide flexible disk (SSD). A group ground with SiC 320-grit was set as a baseline.

RESULTS

The average flexural strength ranged from 116.6 to 142.3 MPa in the following order with significant differences between each value: FS > TE > OM. The average E ranged from 6.8 to 13.2 GPa in the following order with significant differences between each value: FS > TE > OM. The average R ranged from 0.77 to 1.01 MJ/mm3 in the following order: OM > FS > TE. The Sa values of the OM groups polished with CMP and SSD were found to be significantly lower than those of the other resin composites, regardless of the finishing method. The GU values appeared to be dependent on the material and the finishing method used. The OM specimens polished with SSD showed significantly higher GU values than those polished with CMP. Most of the resin composites polished with SSD demonstrated significantly higher γS values compared to the other groups. Extremely strong negative correlations between Sa and GU in the combined data from the three resin composites and each resin composite and between Sa and γS in the OM specimens were observed; GU showed a strong positive correlation with γS in the same material.

CONCLUSION

These findings indicate that both flexural and surface properties are material dependent. Furthermore, the different finishing and polishing methods used in this study were observed to affect the Sa, GU, and SFE of the resin composites.

Influence of light irradiation for in-office tooth whitening: A randomized clinical study

PURPOSE

To evaluate the influence of light irradiation on the clinical efficiency of an in-office whitening agent.

METHODS

The in-office whitening agent (Opalescence Boost 35%) was used in this study. Two whitening regimens were evaluated on maxillary anterior teeth: (1) with light irradiation; and (2) without light irradiation. The ΔE*, changes of L*, a*, b*, and the best shade match on the central incisor before, immediately after, and 6 months after whitening procedures were evaluated using a dental spectrophotometer.

RESULTS

The ΔE and shade had no significant differences with or without light irradiation. In addition, the ΔE, changes of L*, a*, b*, and shade did not change over 6 months after bleaching at a level detectable to the naked eye. The results suggested that the in-office whitening agent using 35% hydrogen peroxide without photocatalysts can improve tooth color with or without light irradiation for 6 months after whitening.

CLINICAL SIGNIFICANCE

In office whitening using 35% hydrogen peroxide without photocatalysts should be considered as a good treatment option for vital teeth whitening.

Handling properties and surface characteristics of universal resin composites

OBJECTIVE

This study investigated the handling and surface characteristics of universal resin composites and determined the interrelations among the composites' handling, mechanical, and physical properties.

METHODS

Five recently introduced universal resin composites were tested. Twelve specimens per material were used to measure the stiffness and stickiness (handling properties) of the resin composite pastes. Additionally, surface properties (Knoop hardness number [KHN], surface roughness [Sa], surface gloss [SG], water contact angle [CA], and surface free energy [SFE]) of cured resin composites were determined in 12 specimens per material immediately after preparation (baseline) and after subjection to thermal cycles (TCs).

RESULTS

Handling and surface properties of the resin composites were material dependent. All the resin composites showed significantly lower KHN in the post-TC subgroups than that in the baseline subgroups. However, the influence of TC on the other surface properties was dependent on the material used. Some resin composites did not indicate any significant differences in Sa, SG, or CA between the baseline and post-TC groups.

SIGNIFICANCE

Although the resin composites in the baseline groups presented with different handling and surface properties, the surface properties of most of the composites were significantly affected by TC. Extremely strong positive or negative correlations were observed between stiffness and stickiness, KHN and Sa, KHN and SG, Sa and SG, and CA and SFE. Most correlations between the handling and surface properties were weak. Therefore, the selection of resin composites in clinical situations should be based on comprehensive consideration of their properties.

Prevention of acidic attack on tooth enamel surfaces using polishing paste containing ion-releasing filler

The purpose of this study was to investigate the ability of polishing paste containing surface pre-reacted glass-ionomer (S-PRG) filler to prevent acidic attack on tooth enamel surfaces. Resin composites were filled in the standardized cavities and finished with silicon carbide paper. These specimens were divided into three groups: the unpolished "control" group, the "PRG" group polished with S-PRG paste, and the "DDP" group polished with diamond-containing polishing paste. Following polishing, the specimens were immersed in a lactic acid buffer solution for 28 days. Optical coherence tomography (OCT) signals were measured to obtain the signal intensity and width at 1/e² at selected locations on the enamel surface adjacent to the restoration. Although signal intensity significantly increased in all groups, widths at 1/e² did not change significantly in the PRG group. For both the control and DDP groups, signal intensity and width at 1/e² increased and decreased over time, respectively.

Bonding and wear properties of self-adhesive flowable restorative materials

The purpose of this study was to evaluate the bonding and wear properties of self-adhesive flowable restorative materials. Five self-adhesive flowable restorative materials were used. The study parameters were: (i) shear bond strengths; (ii) microleakage; (iii) occlusal wear; and (iv) qualitative evaluation of the bonding interface. The range of shear bond strengths of the materials was as follows: 7.4-12.2 MPa to ground enamel, 22.5-32.5 MPa to etched enamel, and 1.3-4.2 MPa to dentin. The microleakage scores of the materials did not show any statistically significant differences regardless of the presence or absence of etching. The wear facets on the materials showed 0.099-0.447 mm³ of volume loss and 148.6-365.3 µm maximum depth, with statistically significant differences between materials. Scanning electron microscopic images of the interfaces of the materials showed good adaptation regardless of substrate. The bonding and wear properties of self-adhesive flowable restorative materials were still limited and showed lower values than previously reported results for nanofilled composites with an adhesive system. Selective enamel etching can improve the bonding performance of these materials.

Evaluation of Color-matching Ability of a Structural Colored Resin Composite

PURPOSE

The present study evaluated the color-matching ability of a structural colored resin composite to compare it with resin composites employing pigments.

METHODS AND MATERIALS

A structural colored resin composite (Omnichroma [OMC]), a supranano-filled resin composite (Estelite ∑ Quick [ELQ]), and a nano-filled resin composite (Filtek Supreme Ultra [FSU]) were used. Each resin composite was packed into a Teflon mold and pressed down with a clear strip under a glass slide. The specimens were light irradiated through the slide with a light-emitting diode curing unit. The thickness of the specimens (n=6) was measured with a digital caliper before being transferred to distilled water and stored at 37°C for 24 hours. The measurements of the optical characteristics of the specimens on a black-and-white background were performed using a spectrophotometer. D65 (CIE D65) was used as a light source for the spectrophotometer. Measurements were repeated three times for each specimen under each color-measurement condition, and average values for three same-shade specimens were calculated. One-way analysis of variance and Tukey post hoc tests were used (α=0.05). To determine its ability to match the color of artificial teeth, each shade of resin composite was placed in a cavity before performing color measurements. Using a spectrophotometer (CMS-35F S/C) with a flexible sensor, L*, a*, and b* values were obtained.

RESULTS

The spectral reflectance curve of OMC showed that it reflected light wavelengths from 430-700 nm regardless of the background color and thickness of the specimens. The percentage of reflectance of ELQ decreased near wavelengths of 550-580 nm. Regarding the influence of background color on CIE L*, a*, b* values, the L* level showed significantly higher values for all tested materials with white backgrounds, and OMC was most affected by the difference in background color. However, a* values of ELQ and FSU were significantly higher with a black background than with a white background, and OMC showed a significantly higher value with a white background than with a black background. The b* values were higher with a white background than with a black background and were significantly higher for all three products, and these tendencies were much greater for ELQ and FSU.

CONCLUSIONS

The ability of OMC to match the color of artificial teeth showed acceptable color compatibility, regardless of the shade of the artificial teeth and the depth of the cavity. However, ELQ and FSU showed reduced color compatibility, especially for a cavity depth of 3.0 mm. Excellent color matching ability was confirmed for the structural colored resin composite OMC, resulting in reduced color differences and therefore improving the esthetic appearance of the restoration, simplifying shade matching, and compensating for any color mismatch.

Flexural properties and wear behavior of computer-aided design/computer-aided manufacturing resin blocks

This study investigates the flexural properties, Knoop hardness number (KHN), and wear behavior of computer-aided design and computer-aided manufacturing (CAD/CAM) resin blocks and compares these values with those of conventional resin composites for direct restoration (RCDs). Four CAD/CAM resin blocks and two RCDs are compared. Ten specimens per material are used to obtain the flexural properties according to ISO 6872 specifications, and five specimens per material are used for KHN measurement. For sliding impact wear testing, twelve specimens are prepared. Confocal laser scanning microscopy (LSM) is used to determine maximum facet depth and volume loss. Polished material surfaces and worn surfaces after wear testing are observed using scanning electron microscopy and LSM. While measured flexural properties and KHN are found to be material-dependent, CAD/CAM resin blocks exhibit higher wear resistance than RCDs. CAD/CAM resin blocks polymerized at high-pressure and high-temperature are found to exhibit wear behaviors far superior to those of RCDs.

Bond durability of universal adhesives to intact enamel surface in different etching modes

This study aimed at determining the enamel bond durability of universal adhesives to intact enamel (IE) and ground enamel (GE) in different etching modes under thermal cycling (TC) and fatigue stresses. Two universal adhesives and a two-step self-etch adhesive were used. Enamel specimens were divided into four groups by treatment: (i) GE in etch-and-rinse, (ii) IE in etch-and-rinse, (iii) GE in self-etch, and (iv) IE in self-etch. Bonded specimens were subjected to TC, and then shear bond strengths (SBS) were conducted. SBS tests were also conducted after storage in 37°C water for 24 h (baseline). For shear fatigue strength (SFS) testing, bonded specimens were subjected to fatigue stress at a frequency of 10 Hz for 50,000 cycles. At baseline, all adhesives showed significantly higher SBS values with GE than IE in self-etch mode in contrast to in etch-and-rinse mode. After TC, the universal adhesives with IE showed lower SBS values than the baseline, regardless of the etching mode. Universal adhesives showed significantly lower SFS values with IE in etch-and-rinse, but not in self-etch mode. Phosphoric acid pre-etching or grinding of the aprismatic enamel may be helpful in establishing reliable initial and long-term bonds to enamel when using universal adhesives in self-etch mode.

Influence of a Primer Resembling Universal Adhesive on the Bonding Effectiveness of an Experimental Two-step Self-etch Adhesive

Purpose: To investigate the effect of application of a primer resembling a universal adhesive with or without light irradiation followed by a hydrophobic bonding agent on bonding effectiveness, based on shear bond strength (SBS) and shear fatigue strength (SFS) tests. Materials and Methods: An experimental two-step self-etch adhesive (BZF) that comprises a primer resembling a universal adhesive (BZP) and a hydrophobic bonding agent (BZB) were used. The two-step self-etch adhesive, Clearfil SE Bond 2 (SE), served as a comparison. Three experiments were conducted. Experiment 1: (1) BZP alone without light irradiation (BZP w/o); (2) BZP alone with light irradiation (BZP w/); (3) BZP without light irradiation followed by BZB (BZPB w/o); (4) BZP with light irradiation followed by BZB (BZPB w/). Experiment 2: (1) BZPB w/o, (2) SE primer + BZ bonding agent (SEP + BZB), and (3) SE primer + SE bonding agent (SEPB). The bonded specimens of experiment 1 and 2 were subjected to SBS tests. Experiment 3: Bonded specimens following the same experimental protocol as experiment 2 were subjected to SFS tests. Results: BZPB showed significantly higher mean enamel and dentin SBS than did BZP. BZPB showed significantly higher SBS without light irradiation than with light irradiation to both substrates. The group of BZPB without light irradiation showed significantly higher SBS than the group of BZPB with light irradiation to both substrates. For experiments 2 and 3, although no significant differences were found in SBS among groups for enamel, SEP + BZB showed a significantly lower SBS and SFS than other groups for dentin. Conclusions: BZF showed bonding performance equivalent to that of the gold standard Clearfil SE Bond 2.

Influence of one-step professional mechanical tooth cleaning pastes on surface roughness and morphological features of tooth substrates and restoratives

PURPOSE

This study investigated the influence of professional mechanical tooth cleaning (PMTC) pastes on the surface texture of different subject materials.

METHODS

Two one-step PMTC pastes, Clinpro Cleaning Paste for PMTC (CP) and PRG Pro-Care Gel (PG), and multiple-step PMTC pastes, Merssage Regular (MR), Merssagge Fine (MF), and Merssage Plus (MP), were used. For comparison, PMTC was performed using distilled water without paste (DW). The subjected materials used were bovine enamel (ENA) and dentin (DEN), a resin composite (FSU), and lithium disilicate (IEC). The prepared specimens were polished using a #2000-grit silicon carbide paper. PMTC was performed using a brush at 1,000 rpm for 15 s.

RESULTS

The surface roughness (Ra) values of the specimens before and after PMTC were measured by laser scanning microscopy. The Knoop hardness number (KHN) of the subjected material was obtained. The types of PMTC pastes and subject materials had a significant influence on the Ra values and KHN. For the majority of subject materials, the descending order of Ra values after PMTC was MR > MF > CP > PG > MP > DW. The descending order of KHN of the materials was IEC > ENA > FSU > DEN.

CONCLUSION

Although one-step PMTC pastes appeared to be effective, it is important to consider the subject material during PMTC.

Ultrasonic measurement of remaining dentin thickness using a pencil-type transducer

PURPOSE

To evaluate the ability of a pencil-type transducer connected to a pulser-receiver to measure remaining dentin thickness (RDT).

METHODS

A total of 24 freshly extracted bovine incisors were used to prepare dentin disks with certain thicknesses (0.5, 1.0, 1.5 and 2.0 mm). The thicknesses of the specimens were measured with an ultrasonic technique using a pencil-type transducer, and the data obtained were compared with the direct measurement obtained using a micrometer. The Bland-Altman comparison method and paired t-test were performed at a 0.05 significance level.

RESULTS

The agreement between different measurement methods was analyzed to evaluate the inter-methodology variation. The Bland-Altman comparison method revealed a mean difference of 0.0098 ± 0.724 mm between the ultrasonic technique and the direct measurement, with the 95% Bland-Altman limits of agreement ranging from 0.1322 to 0.1517 mm.

CLINICAL SIGNIFICANCE

Ultrasonic measurement using the pencil-type transducer may be a promising method to evaluate remaining dentin thickness.

Comparison of different etch-and-rinse adhesive systems based on shear fatigue dentin bond strength and morphological features the interface

OBJECTIVES

The aim of this study was to investigate dentin bonding durability of different etch-and-rinse (ER) adhesive systems under fatigue stress and to compare morphological features of resin/dentin interfaces using SEM.

METHODS

Two three-step ER adhesives, a two-step ER adhesive, and a universal adhesive in ER mode were evaluated. Before application of either primer or adhesive, phosphoric acid etching of human dentin was completed. Fifteen bonded specimens for each adhesive system were stored in distilled water at 37 °C for 24 h, then subjected to a shear bond strength (SBS) test. Bonding durability was assessed from the perspective of biomechanical stress. 25 bonded specimens for each adhesive system were subjected to shear fatigue strength (SFS) testing with a repeated subcritical load at a frequency of 20 Hz for 50,000 cycles or until failure.

RESULTS

Mean SBS and SFS values ranged from 33.3 to 41.2 MPa, and from 18.3 to 20.3 MPa, respectively. Three-step adhesives showed higher SBS and SFS values than the other adhesive systems. Under SEM, resin tags in different adhesive systems showed similar features, but morphology below the hybrid layer was material dependent. The universal adhesive in ER mode showed an obvious thin, high-density reaction layer below the hybrid layer.

SIGNIFICANCE

Three-step adhesives showed higher dentin bond durability than the other ER adhesives; no significant differences in SFS were found between the universal adhesive in ER mode and the three-step ER adhesives. The results of this in vitro study indicate that some ER adhesives might establish chemical bonding with intact dentin below the hybrid layer in addition to micromechanical retention.

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.

Influence of surface treatment on bonding of resin luting cement to CAD/CAM composite blocks

The aim of this study was to determine the influence of different surface treatments of CAD/CAM composite blocks on bonding effectiveness of resin cements, based on the shear bond strength test and the surface science examination. Specimens were fabricated from two types of CAD/CAM composite blocks (Cerasmart and VITA Enamic), and the specimen surfaces were alumina sandblasted. Specimen surfaces were treated with i) silane, ii) primer, and iii) silane+primer, then two types of cements (Block HC Cem and Super Bond) were bonded. After 24 h storage, bond strengths were measured. Surface free energy measurements were performed of the treated CAD/CAM composite blocks surfaces. The groups ii) and iii) showed significantly higher bond strengths than the group i), apart from VITA Enamic with Block HC Cem. Although the total surface free energy showed different trends in different surface treatments, a similar trend was found in both CAD/CAM composite blocks.

Minimally invasive technique for non-vital tooth bleaching using traditional Japanese paper

The purpose of this case report is to describe a minimally invasive technique for non-vital tooth bleaching using traditional Japanese paper, known as washi. Non-vital tooth bleaching with a mixture of sodium perborate and 30% hydrogen peroxide rolled in Japanese paper for a traumatically injured tooth, and in-office vital-tooth bleaching for the upper front six teeth and first premolars, were performed. Five-year follow-up showed satisfactory stability in the bleaching effects and did not show any problems in the traumatically injured tooth. The use of Japanese paper for non-vital tooth bleaching may minimize damage to discolored non-vital teeth.

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.

Effect of double-layer application on the early enamel bond strength of universal adhesives

OBJECTIVES

The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes.

METHOD

Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37 °C for 5 min or 1, 6, 12, or 24 h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods.

RESULTS

All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period.

CONCLUSION

Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding.

CLINICAL RELEVANCE

Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling.

Comparison of occlusal wear between bulk-fill and conventional flowable resin composites

PURPOSE

To investigate the occlusal wear of bulk-fill and conventional flowable resin composites.

METHODS

Four bulk-fill flowable resin composites: (1) Filtek Bulk Fill Flowable Restorative (FB); (2) G-ænial Bulk Injectable (GB); (3) SDR Flow+ (SD); and (4) Tetric EvoFlow Bulk Fill (TB), and four conventional flowable resin composites: (1) Clearfil Majesty IC (CM); (2) Filtek Supreme Ultra Flow (FF); (3) G-ænial Universal Flow (GF); and (4) Herculite XRV Ultra Flow (HF) were evaluated. Localized wear was simulated using 400,000 cycles in a Leinfelder-Suzuki (Alabama) device with a stainless-steel ball bearing antagonist. Volume loss and maximum depth of wear facets were measured using a Proscan 2100 noncontact profilometer in conjunction with analyzing software. Scanning electron microscopy observations were also conducted on the wear specimens.

RESULTS

Simulated occlusal wear was significantly different (P< 0.05) among the materials tested. FF, GB and GF showed significantly less wear than the other tested resin composites. The rank order of volume loss and maximum depth was GF-GB-FF-FB-CM-HF-TB-SD.

CLINICAL SIGNIFICANCE

Bulk-fill flowable resin composites showed a much wider range of wear properties than conventional flowable resin composites. Some composites of each type may be suitable for use in occlusal contact areas of posterior restorations, but care must be taken when selecting such a resin.

In Vitro Wear Resistance of Self-Adhesive Restorative Materials

PURPOSE

To investigate simulated localized and generalized wear of self-adhesive restorative materials.

MATERIALS AND METHODS

Three commercially available restorative materials and one experimental material with self-adhesive properties were evaluated. The experimental material was tested in both light-cured and self-cured conditions. Activa (A), Fuji II LC (F), and Equia Forte (E) and the experimental material ASAR-MP4 (S) were investigated. Two kinds of wear were simulated in an Alabama wear machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The wear challenge was carried out in an aqueous slurry of polymethyl methacrylate beads. Material volume loss was measured on polyvinyl siloxane replicates of each worn surface using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software.

RESULTS

There were significant differences (p < 0.05) among the materials for both generalized and localized wear. The experimental material in both curing modes exhibited significantly less localized wear than F and A and significantly less generalized wear than F and E.

CONCLUSION

Self-adhesive materials offer unique handling properties for direct placement of posterior restorations in permanent teeth. The experimental material ASAR-MP4 generated similar wear values to the other self-adhesive materials tested.

Enamel and Dentin Bond Durability of Self-Adhesive Restorative Materials

PURPOSE

To use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the durability of adhesion of self-adhesive restorative materials compared to composite resin bonded with a universal adhesive.

MATERIALS AND METHODS

A universal adhesive, Prime & Bond Active, was used in self-etch mode to bond Z-100 composite resin to enamel and dentin. Three commercially available restorative materials and one experimental material with self-adhesive properties, Activa (A), Fuji II LC(F), and Equia Forte (E) and ASAR-MP4 (S) were also bonded to enamel and dentin. The SBS and SFS were determined for all materials. A staircase method was used to determine the SFS with 10 Hz frequency for 50,000 cycles or until failure occurred.

RESULTS

On enamel, S generated similar values to the adhesive/composite materials and higher values than F, E, and A. On dentin, the composite/universal adhesive showed significantly higher SBS and SFS than the self-adhesive materials. S, F, and E generated higher values than A on dentin.

CONCLUSION

SBS and SFS values to enamel were similar for all materials tested except Activa which generated lower enamel values. On dentin surfaces, the self-adhesive materials generated similar SBS and SFS, with the exception of Activa. Those values were lower than that generated with composite resin and a universal adhesive.

Laboratory evaluation of dentin tubule occlusion after use of dentifrices containing stannous fluoride

The purpose of this study was to examine the effect of desensitizing dentifrices containing stannous fluoride (SnF₂) on dentinal tubule occlusion. Two experimental dentifrices with the same ingredients but different SnF₂ concentrations (Group II, 0.4% w/w; Group III, 0.454% w/w) were used; distilled water was used in the control group (Group I). Third molars were collected from Japanese and American dental patients. The crowns were removed and sectioned to obtain dentin discs, which were further cut into quarters. Thirty-six specimens each from Japanese and American patients were divided into three sets (n = 12 each) and assigned to each of the three treatment groups. The specimens were brushed for 10 s twice per day for 4 days. After treatment, the discs were observed by scanning electron microscopy, and the extent of dentinal tubule occlusion in the images was expressed on a five-point categorical scale. Group II and III specimens from Japanese and American patients showed greater dentinal tube occlusion than those from Group I, but the differences were not statistically significant. The present results suggest that both SnF₂ concentrations mitigate dentin hypersensitivity, regardless of patient ethnicity.

Comparison of dentin bond durability of a universal adhesive and two etch-and-rinse adhesive systems

OBJECTIVE

This study aimed to compare dentin bond durability under different degradation conditions between two etch-and-rinse (ER) systems and a universal adhesive in ER mode.

METHOD

This study used a universal adhesive [Scotchbond Universal (SU)], a three-step ER adhesive [Scotchbond Multi-Purpose Plus (SM)], and a two-step ER adhesive [Single Bond Plus (SB)]. A phosphoric acid-etching agent was applied to bovine dentin prior to the application of either a primer or the adhesive. After acid etching, bonding procedures were conducted. The specimens were divided into three group classes: (1) subjected to 10,000, 30,000, or 50,000 thermal cycles (TC); (2) stored in distilled water at 37 °C for 6 months or 1 year (WS); and (3) stored in distilled water for 24 h (baseline). Shear bond strength (SBS) tests were conducted.

RESULTS

SB showed a higher baseline SBS than the other adhesives. Defining the baseline SBS value for each adhesive system as 100%, TC groups ranged from 56.1 to 70.3% for SM, from 98.4 to 103.7% for SB, and from 120.3 to 126.7% for SU. WS groups ranged from 66.2 to 71.4% for SM, from 98.1 to 103.3% for SB, and from 102.5 to 118.1% for SU.

CONCLUSIONS

Although SB showed relatively stable dentin bond performance under all degradation conditions, SM showed decreased dentin SBS with prolonged degradation. SU did not show any significant decrease in SBS from the baseline under any degradation condition.

CLINICAL RELEVANCE

The universal adhesive showed comparable adhesive performance with the two-step ER adhesive.

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.

SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives

OBJECTIVE

The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse (ER) and self-etch (SE) adhesive systems.

METHODS

Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy.

RESULTS

The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1-2μm, with a high-density zone (reaction layer [RL]) below the HL.

CONCLUSION

The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin-dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL.

SIGNIFICANCE

The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.

Etch-and-rinse vs self-etch mode for dentin bonding effectiveness of universal adhesives

In this study, dentin bond fatigue resistance and interfacial science characteristics of universal adhesives through etch-and-rinse and self-etch modes were investigated. Resin composite was bonded to human dentin with four universal adhesives, namely, Adhese Universal, All-Bond Universal, G-Premio Bond, and Scotchbond Universal Adhesive. The initial bond strengths, bond fatigue strengths, and interfacial science characteristics of the universal adhesives with dentin through etch-and-rinse and self-etch modes were determined. Bond fatigue resistance (initial bond strength and bond fatigue strength) of universal adhesives in etch-and-rinse mode showed no significant difference in contrast to that in self-etch mode and was material-dependent regardless of the etching mode. Although phosphoric acid conditioning of dentin did not have a strong impact on the bond fatigue resistance, surface free energy and parameters of dentin were significantly decreased by etching and by application of universal adhesives regardless of etching mode. Changes in γ_S and γ_S^h for when universal adhesive was applied to etched and ground dentin were significantly different depending on the adhesive. The results suggest that bonding performance of universal adhesives was effective in both etching modes; however, bonding mechanisms may be different for each.