Glass Ionomer Liner Research Articles

The effects of glass ionomer and flowable composite liners on the fracture resistance of open-sandwich class II restorations

This in vitro study aimed to investigate the effects of glass-ionomer and flowable composite liners on the fracture resistance of Class II amalgam and composite restorations. Group 1 cavities were restored with amalgam and Group 4 cavities with nanofill composite after the application of a dentin-bonding agent. For the remaining groups, light-cured-glass-ionomer liner was used in a gingival floor proximal box (Groups 2, 5) or flowable composite was used as a liner (Groups 3, 6), the remainder of the cavity was restored with amalgam (Groups 2, 3) or composite (Groups 5, 6). The restorations were loaded in compression to failure. The data was analyzed using Tukey's multiple comparison test. The fracture resistance was significantly higher (p<0.05) in Group 3 than in all other groups, except Group 2 (p>0.05). Flowable composite, glass-ionomer liners increased the fracture resistance of open-sandwich Class II amalgam restorations.

Cuspal Deflection in Premolar Teeth Restored Using Current Composite Resins With and Without Resin-modified Glass Ionomer Liner

To evaluate the effects of four different types of composite resins and a resin modified glass ionomer cement (RMGIC) liner on the cuspal deflection of large MOD cavities in vitro. One hundred twenty-eight extracted human upper premolar teeth were used. After the teeth were divided into eight groups (n=16), standardized large MOD cavities were prepared. The distance between cusp tips was measured before and after the cavity preparations with a digital micrometer. Then the teeth were restored with different resin composites (Filtek Supreme XT, Filtek P60, Filtek Z250, Filtek Silorane - 3M ESPE, St Paul, MN, USA) with and without a RMGIC liner (Vitrebond, 3M ESPE, St Paul, MN, USA). Cuspal deflection was measured 5 min, 24 h, and 48 h after the completion of restorations. The data were statistically analyzed with Friedman and Kruskal Wallis tests. A significant reduction in cuspal deflection was observed in Filtek Silorane restorations with and without RMGIC liner (p<0.05). In all restored teeth, the distance between cusps was reduced but they did not return to their original positions during the 48 h period. All teeth showed cuspal deflection, but placement of RMGIC liner reduced it. The use of silorane-based composites and the placement of RMGIC liner under the composite resin restorations resulted in significantly reduced cuspal deflection.

A comparative study of shear bond strength of two adhesive liners to nanocomposite

Aim: To compare the shear bond strength of resin-modified glass ionomer and nano-filled flowable composite liners to nanocomposite restorative material. Materials and Methods: In this in vitro study, 24 specimens were prepared in acrylic blocks for the study with 12 in each group. Group I consisted of resin-modified glass ionomer liner (GC Fuji II LC Improved) bonded to a cylinder of nanocomposite (Z350 Universal Restorative) whereas in Group II flowable composite liner (Filtek Z350 Flowable Restorative) was bonded to a cylinder of nanocomposite (Z350 Universal Restorative). Shear bond strength was determined using Instron Universal testing machine. Student's independent sample t test was used for analysis. Results: The mean shear bond strength value of Group I was greater than Group II and the difference was statistically significant (P = 0.001). Conclusion: Resin-modified glass ionomer appears to be a more compatible liner under nanocomposite restoration than flowable composite as it exhibited significantly higher shear bond strength.Clinical Relevance to Interdisciplinary DentistryResin-modified glass ionomer and flowable composites have been used as liners under resin composite restorations in both primary and permanent teeth to compensate for their polymerization shrinkage.Adequate bonding of liners to composites is as important as bonding to dentin for the success of this technique.Bonding of resin-modified glass ionomer liner to nanocomposite restorative material is better than flowable composite liner and hence should be preferred over flowable composite as a liner.

Effect of Conventional and Resin-modified Glass-Ionomer Liner on Dentin Adhesive Interface of Class I Cavity Walls After Thermocycling

The aim of this in vitro study was to analyze the effect of glass-ionomer cement as a liner on the dentin/resin adhesive interface of lateral walls of occlusal restorations after thermocycling. Occlusal cavities were prepared in 60 human molars, divided into six groups: no liner (1 and 4); glass-ionomer cement (GIC, Ketac Molar Easymix, 3M ESPE) (2 and 5); and resin-modified glass-ionomer cement (RMGIC, Vitrebond, 3M ESPE) (3 and 6). Resin composite (Filtek Z250, 3M ESPE) was placed after application of an adhesive system (Adper Single Bond 2, 3M ESPE) that was mixed with a fluorescent reagent (Rhodamine B) to allow confocal microscopy analysis. Specimens of groups 4, 5 and 6 were thermocycled (5°C-55°C) with a dwell time of 30 seconds for 5000 cycles. After this period, teeth were sectioned in approximately 0.8-mm slices. One slice of each tooth was randomly selected for confocal microscopy analysis. The other slices were sectioned into 0.8 mm × 0.8 mm beams, which were submitted to microtensile testing (MPa). Data were analyzed using two-way ANOVA and Tukey test (p<0.05). There was no detectedstatistical difference on bond strength among groups (α<0.05). Confocal microscopy analysis showed a higher mean gap size in group 4 (12.5 μm) and a higher percentage of marginal gaps in the thermocycled groups. The RMGIC liner groups showed the lowest percentage of marginal gaps. Lining with RMGIC resulted in less gap formation at the dentin/resin adhesive interface after artificial aging. RMGIC or GIC liners did not alter the microtensile bond strength of adhesive system/resin composite to dentin on the lateral walls of Class I restorations.

Evaluation of microleakage in posterior nanocomposite restorations with adhesive liners.

Aims and Objectives:To compare the microleakage in class II nanocomposite restorations without liner, with resin-modified glass ionomer liner and flowable composite liner.Materials and Methods:Thirty-six sound premolars extracted for orthodontic reasons were selected and randomly assigned into three groups of 12 teeth each (Group I, II and III). Class II cavities of specified dimensions were prepared with margins located in the enamel. Cavities in group I were lined with resin modified glass ionomer (GC Fuji II LC-Improved), group II were lined with flowable composite (Filtex Z350 Flowable Restorative) and no liner was placed for cavities in group III. All the teeth were restored with nanocomposite (Z 350 Universal Restorative). The teeth were immersed in 0.5% methylene blue dye, sectioned mesiodistally and observed under stereomicroscope.Results:Group III showed maximum leakage compared to group I and II which was statistically significant. Microleakage was lesser in group lined with resin-modified glass ionomer as compared to flowable composite group but not statistically significant.Conclusions:Placement of liner beneath nanocomposite restoration results in significant reduction in microleakage. Both resin-modified and flowable composite liners under nanocomposite restorations result in comparable reduction of microleakage.

Spatially resolved assessments of composite shrinkage in MOD restorations using a digital-image-correlation technique

Objectives To analyze the influence of cavity geometry and lining materials in MOD composite restorations by characterizing the polymerization shrinkage and cusp deflection. Methods Eighty intact molars with similar sizes were collected and randomly divided into eight groups. MOD cavities with various widths and depths were prepared on these teeth: Group I, 2 ( W) × 2 ( D) mm; Group II, 4 ( W) × 2 ( D) mm; Groups III, IIIf, IIIg, 2 ( W) × 4 ( D) mm; and Groups IV, IVf, IVg, 4 ( W) × 4 ( D) mm. In Groups IIIf and IVf, flowable composite liner was placed prior to composite restoration, while glass-ionomer liner was used in Groups IIIg and IVg. Deformations of restorations resulted from composite shrinkage were recorded for 30 min following light irradiation using a digital-image-correlation (DIC) method to subpixel level. The displacements at the boundaries of the restorations were analyzed using one-way ANOVA and the post hoc test at a 5% significance level. The correlation between the geometric factors and the displacements was also analyzed. Results The inward displacements on free surfaces were greater than those on the bonded surfaces. Groups with flowable composite linings showed greater amount of displacements on free and bonded surfaces compared to the unlined and glass ionomer lining groups. The correlation analysis showed that the free surface shrinkage was related with the cavity width and C-factor, while cusp deflections were correlated with the cavity depth and the cusp compliance. Significance The DIC technique measures composite shrinkage on different boundaries of restorations to facilitate the investigation of polymerization kinetics. Using flowable composite lining and increased cusp depth may aggravate the cusp flexure.

Effect of low-elastic modulus liner and base as stress-absorbing layer in composite resin restorations

Objectives The aim of this study was to evaluate the effectiveness of liner and base materials to reduce the stress resulting from polymerization shrinkage. The null hypothesis tested was that the presence of low-viscosity liner and base materials under the composite resin restoration reduces the polymerization shrinkage stress. Methods A quasi-three-dimensional photoelastic model of a second premolar with a class I preparation was restored using four experimental groups ( n = 7): RC, resin composite (Filtek Z250); FLRC, flowable liner (Filtek Flow) + resin composite restoration; VLRC, resin-modified glass-ionomer liner + resin composite restoration; and VBRC, resin-modified glass-ionomer base + resin composite restoration. The maximum shear stresses ( τ max) were calculated along the adhesive interface in 13 predefined and standardized point locations. Data were submitted to one-way ANOVA, followed by a Tukey's post hoc test ( p < 0.05). Results A significant difference was found among the experimental groups ( p = 0.001); therefore, the null hypothesis was rejected. The mean maximum shear stress was: 38.0 kPa for RC, 52.1 kPa for FLRC, 72.8 kPa for VLRC, and 90.2 kPa for VBRC. The polymerization shrinkage stress level from least to greatest was: RC < FLRC < VLRC < VBRC. The overall stress distribution in class I restoration indicated that stresses were primarily accumulated at the cavosurface and internal line angles. Significance Using a flowable composite or resin-modified glass-ionomer as liner or base material under composite resin restoration increases the polymerization shrinkage stresses at the adhesive interface leading to a possible adhesive failure.

Clinical and microbiological performance of resin-modified glass-ionomer liners after incomplete dentine caries removal

The aims of this study were to evaluate clinically and microbiologically the effects of two resin-modified glass-ionomer cements (RMGICs) used as liners after incomplete dentine caries removal and to identify Streptococcus mutans and Streptococcus sobrinus strains isolated from dentine samples, before and after indirect pulp treatment. Twenty-seven primary molars with deep carious lesions, but without signs and symptoms of irreversible pulpitis, were submitted to indirect pulp treatment. Treatment consisted of incomplete excavation of the carious dentine, application of one of the RMGICs (Vitrebond or Fuji Lining LC) or calcium hydroxide cement (Dycal), and sealing for 3 months. Clinical evaluation (consistency, color, and wetness of dentine) and carious dentine collects were performed before temporary sealing and after the experimental period. Microbiological samples were cultivated in specific media for subsequent counting of mutans streptococci (MS) and lactobacilli (LB). MS colonies were selected for identification of S. mutans and S. sobrinus by polymerase chain reaction. After 3 months, the remaining dentine was hard and dry, and there was a significant decrease in the number of MS and LB, in all groups, although complete elimination was not achieved in 33% and 26% of the teeth for MS and LB, respectively. From 243 MS colonies selected, 216 (88.9%) were identified as S. mutans and only 2 (0.8%) as S. sobrinus. The use of resin-modified glass-ionomer liners after incomplete caries removal, as well as a calcium hydroxide cement, promoted significant reduction of the viable residual cariogenic bacteria in addition to favorable clinical changes in the remaining carious dentine.

Effects of Total and Selective Bonding on Marginal Adaptation and Microleakage of Class I Resin Composite Restorations In Vitro

This study assessed the marginal integrity and microleakage of standardized Class I resin composite restorations when placed with either "total" or "selective bonding" techniques. Sixty standardized Class I cavities comprising the main fissure system were prepared (9 mm length and 7 mm width). Cavity depth was set at 2.5 mm. In cavities where a glass ionomer liner was placed, the cavity was deepened by an additional 0.5 mm. In "total bonding" specimens, enamel and dentin were conditioned using a four-step adhesive system (Syntac Classic). In teeth with "selective bonding," a chemical curing conventional glass ionomer cement (GIC; Ketac Fil) and light-curing resin-modified glass ionomer liner (RMGI; Vitrebond) or three-step adhesive bonding liner (Syntac) were applied. The cavity margins of the latter specimens were finished with water-spray, acid-etched and a bonding agent was applied. All restorations were placed in two oblique increments. Totally bonded ceramic inlays (Cerec) served as the control. All specimens were subjected to thermo-mechanical loading (1.2 Mio cycles) and marginal quality and microleakage were assessed. The highest percentage of margins rated as "perfect" was found in selective bonding samples with glass ionomer liners and totally bonded inlay restorations. All the other groups showed significantly decreased marginal quality (p < 0.05). The same results were found for the microleakage assessment. The authors of the current study concluded that the application of a GIC liner significantly improved the overall marginal adaptation of direct Class I restorations. The use of an adhesive bonding agent for cavity sealing as currently used is not recommended.

Microhardness evaluation around composite restorations using fluoride-containing adhesive systems

The purpose of this study was to evaluate the microhardness of dental enamel around composite restorations bonded with fluoride-containing adhesive systems (FCAS), after thermo- and pH-cycling protocols. Standardized cylindrical cavities were prepared on enamel surfaces of 175 dental fragments, which were randomly assigned into seven experimental groups (n=25). Four groups used FCAS: Optibond Solo (OS); Prime&Bond 2.1 (PB); Syntac Sprint (SS) and Tenure Quick (TC). Other groups consisted of "Sandwich" technique restoration (STR) (glass ionomer liner + hydrophobic adhesive resin /restorative composite) or used Single Bond with (SB) or without (SBWC) cycling protocols. Adhesive systems were applied according to manufacturers' instructions and cavities were restored with a microfilled composite (Durafill VS). After finishing and polishing, all groups were submitted to 1,000 thermal cycles (5 ºC and 55 ºC) and to demineralization (pH 4.3) and remineralization (pH 7.0) cycling protocols, except for SBWC group. The Knoop microhardness of enamel surfaces were measured around restorations. Indentations were recorded at 150, 300 and 450-mm from the cavity wall. Data were analyzed by two-way ANOVA and Duncan's Test (a=0.05%). Means ± SD of enamel microhardness for the groups were (Kg/mm²): SBWC: 314.50 ± 55.93ª ; SB: 256.78 ± 62.66b; STR: 253.90 ± 83.6b; TQ: 243.93 ± 68.3b; OS: 227.97 ± 67.1c; PB: 213.30 ± 91.3d; SS: 208.73 ± 86.6d. Means ± SD of microhardness for the distances 150, 300, 450mm from the cavity wall were, respectively: 234.46 ± 77.81ª; 240.24 ± 85.12ª; 262.06 ± 79.46b. SBWC group, which was not submitted to thermo- and pH-cycling protocols, showed the highest enamel microhardness mean value and the FCAS resulted in lower microhardness values. At 450 mm from the cavity wall, the enamel microhardness increased significantly.

Effect of a resin-modified glass ionomer liner on volumetric polymerization shrinkage of various composites

Objective. The aim of this study was to evaluate the volumetric polymerization shrinkage of a selection of composite resins alone, and in contact with a resin-modified glass ionomer (RMGI) liner. Methods. Volumetric polymerization shrinkage was measured for five different composite resins by means of the Watts and Cash deflecting disk method. Shrinkage measurements were determined for 300 s for each composite alone, and when placed over pre-cured RMGI liner. Each sample was placed within a brass ring fixed to a glass microscope slide. A linear vertical displacement transducer (LVDT) was brought into contact with a flexible glass coverslip placed over the composite sample. On curing, the contraction of the setting composite sample caused distortion of the coverslip, the resulting deflection being recorded via the LVDT by means of data-logging software. All RMGI samples were prepared at 85% relative humidity (RH) and 35°C. In all cases the composite was light-cured at ambient RH and 35°C. Results. Analysis of the data demonstrated statistically significantly less shrinkage for each composite when cured in contact with the set RMGI liner than when cured alone, at p<0.001. Significance. Use of an RMGI liner was found to significantly reduce volumetric polymerization contraction for all the light-curing composite resin restorative materials tested.

Radiopacity of resin-modified glass ionomer liners and 2 bases

Statement of problem. Lining and base materials for restorations have traditionally been autopolymerized and include conventional glass ionomer cements. Light-cured resin-modified glass ionomer cements have recently become available, but a lack of information exists regarding their radiopacity. Purpose of study. In this study the radiopacity of glass ionomer cements was assessed with a standard method that related densitometric measurements to an equivalent thickness of aluminum. Material and methods. Radiographs were made of specimens with seven materials commonly used as liners and bases: two reinforced zinc oxide–eugenol cements (Kalzinol and Intermediate Restorative Material, De Trey Dentsply), a zinc phosphate cement (SS White, S.S. White Manufacturing), three resin-modified glass ionomer liners (Vitrebond [3M Dental Products], Fuji Lining LC [GC Dental], and Photac-Bond [ESPE Dental Medizin GmbH]), and a conventional glass ionomer liner/base (Ketac-Bond, ESPE Dental-Medizin GmbH), with dentin as a control. The radiopacity of all materials was compared with dentin. Results. Kalzinol had the greatest radiopacity of the materials tested. The glass ionomer cements were substantially less radiopaque than other materials. The conventional glass ionomer cement, Ketac-Bond, was more radiopaque than the three resin-modified glass ionomer cements. Of the three resin-modified glass ionomer materials, Vitrebond was the most radiopaque and Fuji Lining LC was the least radiopaque. Conclusion. Future resin-modified glass ionomer materials are recommended to be formulated to increase radiopacity for improved clinical detection. (J Prosthet Dent 1997;77:239-42.)

In vitro evaluation of antibacterial effects of photo-cured glass ionomer liners and dentin bonding agents during setting

Two dentin bonding agents (Optibond and Syntac), an enamel bonding agent (Heliobond), and two photo-cured glass ionomer cements (Vitremer and Variglass VLC) and their inhibitory effects on bacterial growth during setting were examined. Cultures of eight bacterial species were used to test these materials, except for Vitremer glass ionomer cement, which was tested against only five species. The photo-cured glass ionomer cements and the Syntac dentin bonding system with glutaraldehyde demonstrated a significant inhibitory effect on the growth of several bacteria. Meanwhile, Variglass VLC glass ionomer cement did not exhibit this effect on Lactobacillus casei and Streptococcus sobrinus. Optibond light-cured dentin bonding agent, with fluoride and fillers in its composition, and Heliobond (negative control group) did not demonstrate any inhibitory effect.

The effect of glass ionomer liners in lowering pulp temperatures during composite placement, in vitro

New restorative systems allow for more esthetic restorations, but may cause adverse pulp tissue reactions due to either physical or chemical effects. This study evaluated the effect of glass ionomer liners in limiting temperature rise during composite placement with visible light-cure lamps. Neither chemical or light-cured glass ionomer liners limited the amount of pulp chamber temperature rise. Exposure time of the lightcure lamps played the greatest role in pulpal temperature rise regardless of glass ionomer liner or composite. Visible lightcure lamps varied in the amount of heat emitted.

In vitro characterization of visible light-cured glass ionomer liners

The purpose of this study was to characterize the in vitro performance of three visible light-cured glass ionomer liners. The liners containing 2-HEMA showed significantly higher compressive strength, diametral tensile strength and Vickers hardness than the liner without 2-HEMA. Statistically significant differences were found in the optical properties of the materials tested. The liners containing 2-HEMA manifested higher shear strength at liner/composite than at dentin/liner interfaces. The acid-base reaction was significantly delayed after light exposure in all the liners tested. The liner without 2-HEMA presented the greatest maximum gap at the liner/dentin interface. Significant correlations were detected between the optical properties of the liners and the top-bottom differences in the extent of conversion, as well as between the maximum marginal gap at the dentin/liner interface and the bond strength with dentin and composite. These correlations suggest the following areas for further developments: incorporation of low molecular weight polyalkenoic acids or accelerating agents to increase the initial carboxylate yield, increase in total transmittance and reduction in diffuse reflectance to improve the in-depth conversion, and reinforcement of the dentin liner interface to prevent gap formation.

Fluoride release from dual-cured glass-ionomer liners: An in vitro study

The purpose of this study was to investigate the release of fluoride from commercially available dual-cured glass-ionomer liners and to compare it with the conventional glass-ionomer cement. The dual cured glass-ionomers used were XR-ionomer (XR), Zionomer (Zio), Vitrebond (VB) and Fuji Lining LC(Fuji) and the conventional glass-ionomer was GC Lining cement (GC). Eight discs measuring 10·0 mm × 2·0 mm of each material were prepared. Four discs of each were suspended individually in 10 ml deionized water or artificial saliva. The specimens were kept in a shaking water bath at 37°C. At fixed intervals the collecting media were changed and the fluoride released determined electrometrically. TISAB III was used as a buffer. Results showed that the dual-cured glass-ionomer liners release variable amounts of fluoride. The total fluoride released by the various materials was observed in the following order; XR>GC > VB > Fuji > Zio. The release pattern was similar to that of the conventional glass-ionomer cement and appeared to be diffusion controlled. More fluoride was released into artificial saliva.

A new light-activated adhesive cavity liner: an in vitro bond strength and microleakage study

A new formulation of a light-activated calcium hydroxide-based cavity liner was developed for this study. Its shear bond strength and marginal microleakage in a Class V cavity preparation were compared to those of commercially available light-activated liners and conventional glass ionomer liners: GC Lining Cement (GC), Ketac-Bond (ESPE), Time Line (Caulk), Vitrabond (3M), XR lonomer (Kerr), and Zionomer (DenMat). The new formulation had significantly higher shear bond strength to dentin that the commercially available materials. Its microleakage along gingival (cemento-dentin) walls was statistically equivalent to one of the other materials and significantly better than all the others.

Effect of glass ionomer liners on bonding strength of laminate veneers

This study compared shear bond strengths of porcelain laminate veneers, fabricated on refractory dies, which were lengthened incisally by 0.5 mm. Specimens were divided into four separate groups. In group A, the teeth were reduced 0.5 mm and the bonding was to enamel. The teeth of the remaining groups were reduced 1.0 mm and the bonding was to dentin. For two of the groups glass ionomer liners were applied before etching. Bonding to enamel was best, with cohesive fractures in porcelain. In the other groups, failure was adhesive in nature, occurring at the resin-tooth interface.

Effects of ultrasonic instrumentation on microleakage in composite restorations with glass ionomer liners.

The aim of this study was to determine the effect of ultrasonic instrumentation on composite resin restorations lined with glass ionomer cement by measuring the extent of dye penetration at the restoration/tooth interface. Preparations, 2.0 mm in diameter and 2.5 mm in depth, were made with a 331 bur in 96 human molar teeth without a bevel. The teeth were restored with glass ionomer cement liners (Shofu) and one of two types of composite resin (Silux and P-30). Half of the samples were ultrasonically instrumented for 10 s. The teeth were immersed in 0.5% methylene blue dye solution and vertically sectioned. Microleakage was scored visually using a scale of 0 to 4. Statistical comparisons were made with chi 2 analysis and the Mann-Whitney U-test at the P less than 0.05 level. Microleakage was significantly different between both resin types (P less than 0.001), and between the lined and unlined resins (P less than 0.001) that were instrumented, particularly in the P-30 restorations. Although P-30 restorations exhibited much less microleakage than Silux, the use of a glass ionomer liner did not reliably reduce microleakage in either type of material after instrumentation with an ultrasonic device.

Adhesion to Dentin and Physical Properties of a Light-cured Glass-ionomer Liner/Base

The objective of this study was to determine the adhesion to dentin and the physical properties of Vitrabond Light Cure Glass Ionomer Liner/Base and to compare these values with those of a conventional material, 3M Glass Ionomer Liner (3MGI). Shear bond strengths to bovine dentin after 24 h in distilled water were determined to be 12 +/- 3 MPa for Vitrabond Liner/Base, while for 3MGI, bond strengths were 4 +/- 2 MPa. The failure mode was cohesive in dentin or the ionomer. Immediate adhesion of the light-cured material was also significantly higher than that of the conventional glass-ionomer liner. Thermal cycling experiments showed that the bond of Vitrabond Liner/Base to dentin was a stable one. Adhesion studies carried out on human dentin showed high adhesion values as well. Compressive and diametral tensile strengths for Vitrabond Liner/Base were determined immediately after light curing and also after storage in water for 24 h, one week, one month, and seven months. There was no significant difference in the values of compressive and diametral tensile strengths obtained immediately after curing and after extended storage in water at 37 degrees C.