Selected physical properties of new resin-modified glass ionomer luting cements

Statement of problem

Two resin-modified glass ionomer (RMGI)-based luting agents have been recently marketed without independent reports of their physical properties.

Antibacterial and physical properties of EGCG-containing glass ionomer cements

Objectives

To evaluate the effect of the addition of epigallocatechin-3-gallate (EGCG) on the antibacterial and physical properties of glass ionomer cement (GIC).

Methods

A conventional GIC, Fuji IX, was used as a control. EGCG was incorporated into GIC at 0.1% (w/w) and used as the experimental group. Chlorhexidine (CHX) was added into GIC at 1% (w/w) as a positive control. The anti-biofilm effect of the materials was assessed by a colorimetric technique (MTT assay) and scanning electron microscopy (SEM). The leaching antibacterial activity of the materials on Streptococcus mutans was evaluated by an agar-diffusion test. The flexural strength of the materials was evaluated using a universal testing machine and the surface microhardness was measured using a microhardness tester. The fluoride-releasing property of the materials was tested by ion chromatography.

Results

The optical density (OD) values of the GIC-EGCG group were significantly decreased at 4 h compared with the GIC group, but only a slightly decreased tendency was observed at 24 h (P > 0.05). No inhibition zones were detected in the GIC group during the study period. Significant differences were found between each group (P < 0.05). Compared with the control group, there was a significant increase in the flexural strength and surface microhardness for the GIC-EGCG group (P < 0.05). The fluoride ion release was not influenced by EGCG-incorporation (P > 0.05).

Conclusions

These findings suggested that GIC-containing 0.1% (w/w) EGCG is a promising restorative material with improved mechanical properties and a tendency towards preferable antibacterial properties.

Clinical significance

Modification of the glass ionomer cements with EGCG to improve the antibacterial and physical properties showed some encouraging results. This suggested that the modification of GIC with EGCG might be an effective strategy to be used in the dental clinic. However, this was only an in vitro study and clinical trials would need to verify true outcomes.     

Incorporation of cellulose fiber in glass ionomer cement

This study investigated the effect of discontinuous cellulose microfibers with various loading fractions on selected physical properties of glass polyalkenoate (glass ionomer) cement (GIC). Fiber-reinforced GIC (Exp-GIC) was prepared by adding discontinuous cellulose microfiber (with an average length of 500 μm) at various mass ratios (1, 2, 3, 4, and 5 mass%) to the powder of conventional GIC (GC Fuji IX) using a high-speed mixing device. Fracture toughness, work of fracture, and compressive strength were determined for each experimental and control material. The specimens (n = 6) were wet stored (37°C for 1 d) before testing. A scanning electron microscope equipped with an energy dispersive spectroscope was used to examine the surface of fibers after treatment with cement liquid. Data were analyzed using ANOVA . The Exp-GIC (5 mass%) specimen had statistically significantly higher fracture toughness (0.9 MPa.m^1/2) than unreinforced material (0.4 MPa.m^1/2). On the other hand, Exp-GIC with 1 mass% displayed the highest compressive strength (116 MPa) among all tested groups. The use of discontinuous cellulose microfibers with conventional GIC matrix considerably increased the toughening performance compared with the particulate GICs used.     

Antibacterial and mechanical properties of arginine-containing glass ionomer cements

ObjectiveThe study investigated the effect of incorporating l-arginine (Arg) in a glass ionomer cement (GIC) on its mechanical properties and antibacterial potential.MethodsPre-determined proportions (1%, 2%, and 4% by wt.) of Arg were incorporated in GIC powder; while GIC without Arg served as control. The flexural strength, nanohardness, surface roughness, elemental analysis using SEM-EDX (n = 6) and F/Arg/Ca/Al/Si release in deionized water for 21 days were assessed. The antibacterial potential was evaluated in a multi-species biofilm model with Streptococcus mutans, Streptococcus sanguinis, Streptococcus gordonii, and Lactobacillus acidophilus for 72 h. Real-time qPCR was used to analyse biofilm bacterial concentrations. Propidium monoazide modification of real-time qPCR was performed to quantify viable/dead bacteria. The pH, lactic acid, ADS activity, and H₂O₂ metabolism were measured. Confocal microscopy was used to investigate the biofilm bacterial live/dead cells, density, and thickness.ResultsThere was no difference in flexural strength among the different groups (p > 0.05). No significant difference in nanohardness and surface roughness was observed between 4% Arg + GIC and control (p > 0.05). The 4% Arg + GIC showed significantly higher F/Arg/Al/Si release than the other groups (p < 0.05), reduced total bacterial concentration and growth inhibition of viable S. mutans and S. sanguinis (p < 0.05). Lactic acid formation for 4% Arg + GIC was significantly higher than 1% Arg + GIC (p < 0.05). The spent media pH of 4% Arg + GIC was higher than the other groups (p < 0.05), with proportionately lower ammonia and higher H₂O₂ released (p < 0.05).SignificanceAddition of 4% l-arginine in GIC enhanced its antibacterial activity via a biofilm modulatory effect for microbial homeostasis, with no detrimental effect on its mechanical properties.     

Mineral loss on adjacent enamel glass ionomer cements restorations after cariogenic and erosive challenges

Objectives

the purpose of this study was to determine the mineral loss on surrounding enamel restored with glass ionomer cements (GIC) after erosive and cariogenic challenges.

Methods

Bovine enamel specimens were randomly assigned into six groups according to the restorative material: G1 – composite resin; G2 – high viscous GIC; G3 – resin-modified glass ionomer with nanoparticles; G4 – encapsulated resin-modified GIC; G5 – encapsulated high viscous GIC; G6 – resin-modified GIC. After restorative procedures, half of specimens in each group were submitted to caries challenge using a pH cycling model for 5 days, and the other half were submitted to erosive challenge in citric acid for 10 min. Before and after the challenges, surface Knoop microhardness assessments were performed and mineral changes were calculated for adjacent enamel at different distances from restorative margin.

Results

Data were compared for significant differences using two-way ANOVA and Student–Newman–Keuls tests (p < 0.05). Erosive challenge significantly reduced enamel surface hardness, but no significant difference was observed irrespectively restorative materials (p > 0.05). The cariogenic challenge promoted a higher surface hardness loss for the resin-modified GIC (G4) and only for the High viscous GIC (G2) an increase in surface hardness was observed. For enamel analyses, significant differences were observed with respect to the different materials (p < 0.001) and distances (p = 0.023). Specimens restored with the composite resin presented higher mineral loss and specimens restored with the conventional high viscous GIC and the encapsulated resin-modified GIC presented the lowest values for mineral loss.

Conclusion

The GICs exerts protective effect only for cariogenic challenge.     

Anti-biofilm activity of silver nanoparticle-containing glass ionomer cements

ObjectiveTo develop a silver nanoparticle (AgNP) formulation for incorporation into glass ionomer cements (GICs) which minimises biofilm growth on restoration surfaces.MethodsGICs, Fuji IX, Ketac Molar, and Riva Selfcure were modified with 6, 10 and 24 μg per GIC capsule of α-lipoic acid-capped AgNPs. Monoculture biofilms of Streptococcus mutans were cultured (72 h) on GIC specimens (n = 3) and biofilm accumulation was quantified using a viability stain with confocal laser scanning microscopy. Compression strength and flexural strength (CS & FS) were measured according to ISO 9917-1:2007 (n = 8, n = 25). GIC colour was measured at 0, 1, and 14 days following AgNP incorporation using a digital spectrophotometer. Silver release from AgNP-modified GIC specimens was monitored at 1, 3, 7 and 14 days using inductively coupled plasma-mass spectrometry.ResultsAgNP-modified Fuji IX demonstrated the greatest reduction in biofilm accumulation, with 10 μg Ag/capsule inhibiting biofilm formation by 99%. Ketac Molar and Riva Selfcure required 24 μg Ag/capsule to achieve 78% biofilm reduction. AgNP-modified GICs demonstrated significantly higher CS and FS than sintered silver-containing GICs, and possessed equivalent or higher strength values when compared to unmodified GICs. The colour shades of AgNP-modified GICs were more comparable to VITA shades of non-modified GICs than were sintered silver-containing GICs. The silver (≥99.6%) remained within the GIC for at least two weeks following incorporation.SignificanceAgNP-modified GICs exhibited significant antibiofilm activity and retained mechanical properties equivalent or superior to non-modified GICs. AgNP-modified GICs could reduce bacterial colonisation on and around restorations thereby reducing restoration failure caused by secondary caries.     

TiO2 nanotubes improve physico-mechanical properties of glass ionomer cement

ObjectivesThe aim of this study was to determine the physico-mechanical properties of a high viscosity glass ionomer cement (GIC) reinforced with TiO₂ nanotubes (TiO₂-nt).MethodsTiO₂-nt was incorporated into the GIC powder components (Ketac Molar EasyMix™) in concentrations of 0% (control group), 3%, 5%, 7% by weight. Compressive strength (n = 10/group), three point bending for flexural strength (n = 18/group), microshear bond strength to dentin and failure mode (n = 20/group), and surface roughness and weight loss before and after brushing simulation (30,000 cycles) (n = 8/group) were evaluated. Data were submitted to Shapiro-Wilk, ANOVA, Tukey and Chi-square tests (α ≤ 0.05).ResultsAddition of 5% of TiO₂-nt into GIC presented the highest values for compressive strength and differed from the control, 3% and 7% groups (p = 0.023). There were no significant differences in flexural strength (p = 0.107) and surface roughness before and after the dental brushing (p = 0.287) among the groups. GIC added with 5% TiO₂-nt showed the lowest weight loss values (p = 0.01), whereas the control, 3% or 5% TiO₂-nt groups presented similar microshear bond strength values (p ≥ 0.05). The 5% TiO₂-nt group featured higher microshear bond strength than the 7% TiO₂-nt group (p = 0.034). Cohesive in material was the most representative failure mode for all groups.SignificanceThe incorporation of TiO₂-nt did not affect GIC’s adhesiveness to dentin, but improved its compressive strength at 5%. Furthermore, TiO₂-nt decreased the percentage of weight loss after GIC’s surface wear.     

Effects of aging and cyclic loading on the mechanical properties of glass ionomer cements

The purpose of this study was to examine the effect of cyclic loading on the flexural strength and fracture toughness of a conventional glass ionomer cement (GIC), a metal containing GIC, hybrid GICs, and, for comparison, a composite. Two sets of specimens were evaluated: a set of controls (at 37 degrees C and 95% humidity) and a set aged for 9 months at 37 degrees C in water. The specimens were tested in static loading in air and water, and cyclic loaded in water. Cyclic loading and aging decreased the flexure strength of all materials significantly. However, wet static fracture toughness did not change on aging, and occasionally increased. Cyclic fracture toughness was lower with all materials except a hybrid glass ionomer without aging. Deterioration in properties was related to relative amount of glass ionomer vs. the resin component. Both flexural strength and fracture toughness of these materials were significantly affected by testing environment, aging and cyclic loading. The lower the resin component of the material, the lower the mechanical properties. The influence of these parameters should be given importance in considering their clinically durability in the oral environment.     

Mechanical,antibacterial and bond strength properties of nano-titanium-enriched glass ionomer cement

The use of nanoparticles (NPs) has become a significant area of research in Dentistry.

Objective

The aim of this study was to investigate the physical, antibacterial activity and bond strength properties of conventional base, core build and restorative of glass ionomer cement (GIC) compared to GIC supplemented with titanium dioxide (TiO₂) nanopowder at 3% and 5% (w/w).

Material and Methods

Vickers microhardness was estimated with diamond indenter. Compressive and flexural strengths were analyzed in a universal testing machine. Specimens were bonded to enamel and dentine, and tested for shear bond strength in a universal testing machine. Specimens were incubated with S. mutans suspension for evaluating antibacterial activity. Surface analysis of restorative conventional and modified GIC was performed with SEM and EDS. The analyses were carried out with Kolmogorov-Smirnov, ANOVA (post-hoc), Tukey test, Kruskal-Wallis, and Mann Whitney.

Results

Conventional GIC and GIC modified with TiO₂ nanopowder for the base/liner cement and core build showed no differences for mechanical, antibacterial, and shear bond properties (p>0.05). In contrast, the supplementation of TiO₂ NPs to restorative GIC significantly improved Vickers microhardness (p<0.05), flexural and compressive strength (p<0.05), and antibacterial activity (p<0.001), without interfering with adhesion to enamel and dentin.

Conclusion

GIC supplemented with TiO₂ NPs (FX-II) is a promising material for restoration because of its potential antibacterial activity and durable restoration to withstand the mastication force.     

Antibacterial properties of copper iodide-doped glass ionomer-based materials and effect of copper iodide nanoparticles on collagen degradation

Objectives

This study investigated the antibacterial properties and micro-hardness of polyacrylic acid (PAA)-coated copper iodide (CuI) nanoparticles incorporated into glass ionomer-based materials, and the effect of PAA-CuI on collagen degradation.

Materials and methods

PAA-CuI nanoparticles were incorporated into glass ionomer (GI), Ionofil Molar AC, and resin-modified glass ionomer (RMGI), Vitrebond, at 0.263 wt%. The antibacterial properties against Streptococcus mutans (n = 6/group) and surface micro-hardness (n = 5/group) were evaluated. Twenty dentin beams were completely demineralized in 10 wt% phosphoric acid and equally divided in two groups (n = 10/group) for incubation in simulated body fluid (SBF) or SBF containing 1 mg/ml PAA-CuI. The amount of dry mass loss and hydroxyproline (HYP) released were quantified. Kruskal-Wallis, Student’s t test, two-way ANOVA, and Mann-Whitney were used to analyze the antibacterial, micro-hardness, dry mass, and HYP release data, respectively (p < 0.05).

Results

Addition of PAA-CuI nanoparticles into the glass ionomer matrix yielded significant reduction (99.999 %) in the concentration of bacteria relative to the control groups. While micro-hardness values of PAA-CuI-doped GI were no different from its control, PAA-CuI-doped RMGI demonstrated significantly higher values than its control. A significant decrease in dry mass weight was shown only for the control beams (10.53 %, p = 0.04). Significantly less HYP was released from beams incubated in PAA-CuI relative to the control beams (p < 0.001).

Conclusions

PAA-CuI nanoparticles are an effective additive to glass ionomer-based materials as they greatly enhance their antibacterial properties and reduce collagen degradation without an adverse effect on their mechanical properties.

Clinical relevance

The use of copper-doped glass ionomer-based materials under composite restorations may contribute to an increased longevity of adhesive restorations, because of their enhanced antibacterial properties and reduced collagen degradation.

     

Effect of eluates from zirconia-modified glass ionomer cements on DNA double-stranded breaks in human gingival fibroblast cells

Objective

To formulate novel glass ionomer cements (GICs) containing zirconia (nanoparticles (NPs) and micro-particles (MPs)) and investigate the genotoxic effect of their eluates on DNA double-strand breaks of human gingival fibroblasts (HGFs) in vitro using a γ-H2AX fluorescent assay.

Evaluation of a conventional glass ionomer cement with new zinc formulation: effect of coating, aging and storage agents

Objective

The study focused on a recently launched conventional glass ionomer cement (GIC) with a particular chemical formulation of both, filler and acrylic liquid, by analysing its mechanical behaviour in comparison to three conventional GICs. Furthermore, the effect of resin coating and storage conditions was evaluated.

Materials and methods

Three commercially available GICs were chosen: Riva Self Cure (SDI), Fuji IX Fast (GC) and Fuji IX GP Extra/Equia (GC). Additionally a newly developed zinc-containing GIC—ChemFil Rock (Dentsply)—was tested. Mechanical properties were determined at macro- [flexural strength (FS) and modulus of elasticity (E _flexural)] and micro-scale [Vickers hardness (VH) and indentation modulus (E)] after storing coated and uncoated specimens in artificial saliva and distilled water for 7 and 30 days.

Results

ChemFil Rock revealed the highest FS, but the lowest VH and E. The micro-mechanical properties of the analysed GICs did neither benefit from the new zinc formulation nor from resin coating. A resin coating is nevertheless a valuable support for GIC fillings, since it offers the absence of visible surface defects like crazing and voids, and thus, it led to significant improvements in flexural strength. This statement is also valid for ChemFil Rock, contrary to manufacture recommendation. The impact of storage agent and storage duration on the measured properties was low.

Conclusions

The new development (ChemFil Rock) might represent a promising approach regarding longevity of GIC fillings in molar regions, due to the high flexural strength and the absence of visible surface defects like crazing and voids.

Clinical relevance

All GICs should receive surface protection in order to perform their maximum in stability.     

Hertzian load-bearing capacity of a ceramic-reinforced glass ionomer cement stored wet and dry

ObjectiveTo investigate the development of the load-bearing capacity of a ceramic-reinforced glass ionomer cement (GIC), stored dry or wet, using Hertzian indentation.MethodsGIC discs 2 mm thick and 10 mm in diameter were made (Amalgomer CR, Advanced Healthcare, Tonbridge, Kent, UK), randomly divided into 8 groups and stored at 37 °C in air or artificial saliva (AS) for 1, 7, 30 and 90 days. Discs were tested by loading centrally using a 20 mm diameter hard steel ball while resting freely on a filled-nylon substrate (E: 10 GPa), at 23 °C in air. The failure load at the first bottom-initiated radial crack was detected acoustically.ResultsAll the failure loads of air-stored specimens were higher than those of AS-stored specimens. The failure load was relatively stable for air-stored specimens but showed a significant decreasing tendency for AS-stored specimens.SignificanceZirconia-reinforced GIC is sensitive to moisture. Artificial saliva storage has a detrimental effect on the failure load of ceramic-reinforced GIC that may indicate long-term deterioration in service.     

Antibacterial and mechanical properties of propolis added to glass ionomer cement

Objective:To investigate whether adding ethanolic extracts of propolis (EEP) might influence the antibacterial and mechanical (shear-peel band strength [SPBS]) properties of conventional glass ionomer cement (GIC) used in orthodontic band cementation.Materials and Methods:The cement was divided into four groups: one using the original composition and three with 10%, 25%, and 50% EEP added to the liquid and then manipulated. An antimicrobial assay, broth-dilution method was used to determine the antibacterial capacity of the GIC containing EEP. Eighty teeth were used for the mechanical assay, and an Instron testing machine was used to evaluate the SPBS. Kolmogorov-Smirnov and Kruskal-Wallis tests were used for statistical analyses.Results:GIC with the addition of 25% and 50% EEP activated inhibition of Streptococcus mutans (ATCC 25175) growth, but this effect did not occur in the group to which 10% EEP was added or in the control GIC group. There was no significant difference between the groups in terms of SPBS (P > .05).Conclusions:The addition of EEP may increase antibacterial properties without negatively modifying the mechanical properties of conventional GIC.     

Crown retention with three resin-modified glass ionomer luting agents

BackgroundThe author used a standardized technique to investigate the retentive properties of three resin-modified glass ionomer (RMGI) cements in the cementation of precious gold copings.MethodsThe author machined premolars on a jeweler's lathe to a taper of 16 ± 0.5 degrees. The occlusal table measured 4 millimeters. The author fabricated wax patterns with a uniform 360-degree internal fitting surface of 2.7 mm. Each group consisted of 10 samples. The author invested the wax patterns and cast them in gold. He cemented the copings as follows: group 1, RelyX Luting Plus (3M ESPE, St. Paul, Minn.); group 2, Fuji Plus Resin-Reinforced, Multipurpose Cement (GC America, Alsip, Ill.) and group 3, UltraCem Resin-Reinforced Glass Ionomer Cement (Ultradent Products, South Jordan, Utah). The author performed the cementation under controlled pressure. After 24 hours, he applied a tensile force until catastrophic failure (expressed as kilogram force at failure) occurred. The author used analysis of variance for statistical analysis (P < .05).ResultsA statistically significant difference was demonstrated between UltraCem and the other two cements tested (P < .05), whereas no statistical difference could be demonstrated between RelyX and Fuji Plus (P > .05).ConclusionsBy using an established standardized ex vivo crown retention test, the author found that the three RMGI cements he tested generated retention values that were clinically desirable when compared with those of other commercially available cements that have been used successfully for many years. UltraCem scored the highest values, followed by Fuji Plus and RelyX, respectively.Clinical ImplicationsCementation of precious alloy crowns and bridges by using RMGI cements tested in this study generated retentive values that mostly exceeded those of conventional luting agents.     

Survival rate of approximal-ART restorations using a two-layer technique for glass ionomer insertion

Objective

Good survival rates (SR) have been reported for occlusal-atraumatic restorative treatment (ART) restorations but not for approximal-ART restorations. The high-viscosity consistency of the glass ionomer cement (GIC) may lead to its incorrect adaptation into the cavity and thus to failure of the restoration. Because the use of a flowable GIC layer seemed to improve its adaptation in approximal restorations in vitro, we evaluated whether the use of an intermediate flowable GIC layer would improve the SR of approximal-ART restorations.

Methods

A total of 208 children (6–7 years old) with at least one occluso-proximal carious lesion in a primary molar were selected and randomly allocated to two groups: G1, conventional technique, one-layer GIC (powder/liquid ratio 1:1); and G2, two-layer technique, consisting of a first layer of GIC with a flowable consistency (powder/liquid ratio 1:2) and a second layer of a regular consistency. Restorations were made by final-year students and evaluated after 1, 6, 12 and 18 months. Restoration survival was evaluated using Kaplan–Meier survival and logrank test. Poisson regression analyses (α?=?5) were used to verify the influence of factors such as insertion technique, restoration surface and operators.

Results

The overall SR of the restorations after 18 months was 68 %. There was no difference in SR between the techniques, neither did the other factors influence the SR.

Conclusions

Over 18 months, the use of an intermediate flowable GIC layer in approximal-ART restorations does not improve the restoration survival.

Clinical relevance

This study suggests that the two-layer technique is not the answer for increasing approximal-ART restoration longevity.     

Mechanical behavior of a bi-layer glass ionomer

Objective

A high-viscosity consistency of the glass-ionomer cement (GIC) may lead to poor adaptation into the cavity. The use of a flowable GIC layer seemed to improve its adaptation in approximal restorations in vitro. In this study we assessed the flexural strength of a two-layered GIC, using a flowable GIC as a liner (two-layer technique). Additionally, finite element analysis on standardized bar-shaped models and on a representative tooth model was performed to rationalize the obtained results.

Methods

The flexural strength and Young's modulus were calculated from the results of a three-point-bending test. Bar-shaped specimens were prepared either with a conventional GIC, with a flowable GIC (powder/liquid ratio 1:2), or with two-layers (either with the flowable layer down or on the top of the specimen). Three dimensional FEA models of the bar-shaped specimens and a model of tooth 46 provided information on the stress distribution of each component of the specimen and on the restoration.

Results

The apparent flexural strength and Young's modulus of both two-layered groups were significantly lower than that of the conventional group. FEA showed that the layers of the two-layer specimens with the flowable GIC down separated from each other under load. The tooth model showed better stress distribution for the two-layer restorations.

Significance

The two-layer GIC showed inferior flexural strength, which might be explained by the detachment of the layers under load. Nevertheless the tooth model showed that the two-layer GIC provides a lower stress concentration on the occlusal surface of the material.     

Comparison of the abrasive effects of children's toothpaste on glass ionomer cement

ObjectivesTo evaluate the effect of two different children's toothpaste on the surface properties of conventional glass ionomer cement (GIC), which is used in Atraumatic Restorative Treatment (ART) method.MethodsThere were 3 groups and 10 glass ionomer cements in each group. The distribution was as follows: Group 1, Splat; Group 2, R.O.C.S.; Group 3, Control. A test aparatus made of steel with a screw design that allows the replacement of electric toothbrushes was designed to provide 2 N force. Brushing was carried out for each samples for duration of 2 min, twice a day, for seven days. One-way ANOVA for intergroup comparison and paired sample T tests for intragroup comparisons were used in statistical analysis, the significance level was p < 0.05.ResultsAccording to the results, no statistically significant difference was found between the baseline and 7th day roughness values within and between groups (p > 0.05). Although not statistically significant, as a percental increase in roughness was found in each group compared to the initial values. This amount of increase was found in Group 2, Group 1 and Group 3 as a descending order. The results were supported by scanning electron microscopy analysis.ConclusionAs a result of this study, child pastes that do not cause a statistically significant increase in roughness were found to be safe for daily use. When considering long-lasting restorations, low relative dentin abrasivity (RDA) value child pastes can be recommended as they will encourage brushing with both taste and smell compared to brushing with water.     

纳米羟磷灰石对玻璃离子黏固剂的性能影响

目的探讨添加纳米羟磷灰石（ nano- HAP）的玻璃离子黏固剂（ GIC）的力学性能、充填后的材料- 牙本质界面渗漏状况和矿化性能。方法将nano- HAP按8%的质量分数比均匀混入GIC粉末形成复合材料（ 实验组材料）,单纯GIC为对照组材料。采用两种材料分别制备20个柱状样本,测定其三点弯曲强度和压缩强度。选用120颗完整的离体牙,在颊面制备Ⅴ类洞,分别采用两种材料充填后放入质量分数1%若丹明- B- 异硫氰酸盐溶液中染色24 h,在激光共聚焦显微镜下观察充填界面的渗漏现象。在健康犬磨牙上制备Ⅴ类洞,分别用两种材料充填,8周后拔除充填牙,在偏振光显微镜下观察材料内部和充填界面的矿化情况。结果添加nano- HAP的GIC复合材料的三点弯曲强度、压缩强度与单纯GIC相比有所提高（ P<0.001,P<0.05）;添加nano- HAP的GIC复合材料和单纯GIC充填离体牙标本后均出现纳渗漏和微渗漏,但前者出现微渗漏概率较后者低（ P=0.004）;复合材料充填界面有新形成的羟磷灰石晶体,并沉积形成矿化带,单纯GIC充填界面没有羟磷灰石晶体形成。结论添加nano- HAP的GIC充填牙齿后能形成较紧密的材料- 牙本质界面,并有矿化潜能,可作为窝洞衬里或预防性充填材料应用。     

Resin-modified and conventional glass ionomer restorations in primary teeth: 8-year results

OBJECTIVES: To compare the longevity and cariostatic effects of resin-modified (RMGIC) and conventional glass ionomer (GIC) restorations in primary teeth in the Danish Public Dental Health Service. METHODS: The sample consisted of 543 RMGIC and 451 GIC restorations in all cavity types in the primary teeth of 640 children, aged 3.0-17.5 years. The restorations were in contact with 480 unrestored surfaces. The restorations and the adjacent surfaces were followed until exfoliation/extraction of the teeth, repair/replacement of restorations or operative treatment of adjacent surfaces. Survival analyses supplied with multivariate analyses were performed to assess the influence of different factors on the longevity of restorations, occurrence of prevalent failures, and caries treatment of adjacent surfaces. RESULTS: After 8 years, 2% of the restorations were still in function and 37% of the RMGIC and 44% of the GIC restorations had been repaired or replaced. Fracture and loss of retention predominated as the reasons for failure of restorations in both materials. The 50% survival time for restorations was 55 months for RMGIC and 48 months for GIC (p = 0.01). Progression of caries lesions required operative treatment on 20% of the surfaces in contact with RMGIC and on 14% of surfaces adjacent to GIC restorations. The 75% survival time was 35 months for surfaces in contact with both materials (p = 0.37). CONCLUSIONS: RMGIC and GIC showed similar cariostatic effects on restored teeth and adjacent tooth surfaces, but RMGIC should be preferred for class II restorations in the primary dentition, and class III/V restorations should be made in GIC due to enhanced longevity.