Glass Ionomer Systems Research Articles

Clinical comparison of high-viscosity glass-hybrid systems with a sculptable bulk-fill composite resin in different cavity types.

This randomized, double-blind clinical investigation assessed the performance of two high-viscosity glass-ionomer systems and a bulk-fill composite in different cavity types. In 146 participants, 360 (class I, II, and V) cavities were restored using three different materials (Equia Forte HT, Chemfill Rock, and SonicFill 2) with equal allocation. Using modified World Dental Federation criteria, restorations were assessed after 1 week, 6 months, and 18 months by an experienced examiner. Statistical analysis was conducted using Fisher's exact and Wilcoxon signed rank tests (α = 0.05). After 18 months, 267 restorations were assessed in 116 participants. After 18 months, 5 Equia Forte HT restorations failed due to debonding and fracture. Only one loss was observed in the Chemfill Rock restorations. Equia Forte HT exhibited significantly lower retention than SonicFill 2 after 18 months (p = 0.019), irrespective of cavity type. At 1 week, 3 Class I restorations with SF showed postoperative sensitivity. The type of cavity did not affect the performance of the restorative materials used (p > 0.05). Equia Forte HT and Chemfill Rock presented similar clinical performance regardless of color match. Equia Forte HT showed a lower performance compared to SonicFill 2. Glass-hybrid materials presented a lower performance in terms of color match or retention when compared to a sculptable bulk-fill composite resin.

Polymer-induced liquid precursors: How are they being used and what is the effect on dentin remineralization? A scoping review

To identify the effectiveness of polymer-induced liquid precursors (PILP) on dentin remineralization and the assessment approaches used to evaluate remineralization. The analyses were done into six stages: (1) Identifying the research question; (2) Identifying the studies; (3) Selecting relevant studies; (4) Plotting the data; (5) Reporting results; and (6) Risk of bias. The searches were carried out in the following databases: PubMed, Web of Science, and Scopus. A total of 247 articles were identified in the electronic database search. After applying the eligibility criteria, only 12 articles were included for data extraction. The outcomes of dentin remineralization patterns were plotted in association to PILP agent type and application mode. The intrafibrillar mineralization occurred in 78% of studies where polyaspartic acid (pAsp) was used, and 50% when the polyacrylic acid (PAA) was used. All the studies where PILP was used in a restorative material (resin composite, glass ionomer, and adhesive system)—extra and intrafibrillar mineralization pattern was found. The association of PILP agents with other materials with potential for mineralization showed beneficial results in remineralization, since they provide a medium to high concentration of calcium and phosphate. The pAsp showed better results for interfibrillar remineralization when compared to PAA. The association with Ca/P release materials or solution Ca P are essentials for mineralization via PILP agent. Further studies are needed to assess the effectiveness of remineralization through PILP agents because the level of evidence of the studies was low.

What’s new for the clinician? - Excerpts from and summaries of recently published papers

Choosing an endodontic sealer clinical use is a decision that contributes to the long-term success of non-surgical root canal treatment. Sealers are used as a thin tacky paste which function as a lubricant and luting agent during obturation, allowing the core obturation material, such as gutta-percha points or other rigid materials, to slide in and become fixed in the canal. Sealers can fill voids, lateral canals, and accessory canals where core obturation materials cannot infiltrate. If the sealer does not perform its function, microleakage may cause root canal failure via clinically undetectable passage of bacteria, fluids, molecules or ions between the tooth and restorative material. It has been reported that extrusion of the sealer during root canal filling has cytotoxic effects on periapical tissues, causing periapical inflammation, necrosis and pain. Endodontic sealers are categorized by composition based on setting reaction and composition: zinc oxide eugenol, salicylate, fatty acid, glass ionomer, silicone, epoxy resin, tricalcium silicate, and methacrylate resin sealer systems. Aslan & Özkan (2021) reported on a trial that sought to evaluate the effect of two calcium silicate-based root canal sealers, Endoseal MTA and EndoSequence BC Sealer, on postoperative pain following single-visit root canal treatment on molar teeth compared to their epoxy/ amine resin-based counterpart AH Plus. The null hypotheses tested in this study were as follows:1. The type of sealer used would not change the incidence and the intensity of post-treatment endodontic pain2. The analgesic intake of patients following single-visit root canal treatment

Bonding ability of paste-paste glass ionomer systems to tooth structure: in vitro studies.

This study investigated the effect of nonrinse conditioners (ie, Ketac Nano Primer [KNP] and GC Self Conditioner [SC]) used as substrate pretreatment and their respective paste-paste resin-modified glass-ionomer cement (RMGIC) (ie, Ketac Nano [KN] and Fuji Filling LC [FF]) on microtensile bond strength to dentin and marginal sealing when compared with traditional RMGIC (ie, Photac Fil [PF] and Fuji II LC [FII]) used in association with polyacrylic acid (ie, Ketac Cavity Conditioner [KC] and GC Cavity Conditioner [CC]). A total of 192 extracted human molars were allocated into eight groups: KNP-KN, KC-KN, KNP-PF, KC-PF, SC-FF, CC-FF, SC-FII, and CC-FII. For microtensile bond strength, the teeth were sectioned to expose occlusal dentin and restored according to the group. After 24 hours the teeth were cut to yield nine beams per tooth (±0.8 mm(2)). Testing was done using a universal testing machine followed by failure mode classification. For microleakage testing, standardized cavity preparations were made on the buccal cementoenamel junction and restored according to the group. The teeth were thermocycled (500 cycles, 8°C to 48°C), sealed, immersed in methylene blue for 24 hours, and then assessed for microleakage using a stereomicroscope. Microtensile bond strengths in megapascals (mean±SE) were KNP-KN: 14.9 ± 1.6, KC-KN: 17.2 ± 1.5, KNP-PF: 31.2 ± 1.6, KC-PF: 26.2 ± 1.2, SC-FF: 23.6 ± 1.5, SC-FII: 31.2 ± 1.5, and CC-FII: 21.9 ± 1.5. Cervical margins showed more microleakage compared with occlusal margins. Overall, the use of nonrinse conditioners in association with traditional RMGICs demonstrated superior microtensile bond strengths to dentin when compared with the paste-paste RMGICs. Meanwhile, the association between polyacrylic acid (CC) and a traditional RMGIC (FII) led to the least microleakage for cervical locations when compared with all other groups.

Preparation and evaluation of a novel star-shaped polyacid-constructed dental glass–ionomer system

ObjectiveThe objective of this study was to synthesize and characterize novel star-shaped poly(acrylic acid-co-itaconic acid)s via chain-transfer radical polymerization technique, use these polyacids to formulate the resin-modified glass–ionomer cements, and evaluate the mechanical strengths of the formed cements Materials and methodsThe star-shaped poly(acrylic acid-co-itaconic acid)s were synthesized via a chain-transfer radical polymerization reaction using a newly synthesized star-shaped chain-transfer agent. The effects of MW, GM-tethering ratio, P/L ratio and aging on the compressive properties of the formed experimental cements were studied. Compressive, diametral tensile as well as flexural strengths were evaluated and compared to those of Fuji II and Fuji II LC cements. ResultsThe star-shaped polyacids showed significantly lower viscosities in water as compared to their linear counterparts. The cements formulated with these novel polyacids showed significantly improved mechanical strengths i.e., 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS and 36% in FS, higher than commercial Fuji II LC. After aging in water for 30 days, the compressive strengths of the experimental cements were significantly changed with an increase of 29% in YS, 19% in modulus as well as 23% in CS and a decrease of 5% in toughness, indicating that aging in water enhances the salt-bridge formation and increases brittleness. ConclusionsA novel light-cured glass–ionomer cement system composed of the star-shaped poly(carboxylic acid)s has been developed via a cost-effective and time-efficient chain-transfer radical polymerization.

Clinical performance of a new glass ionomer based restoration system: A retrospective cohort study

Objectives This retrospective clinical study evaluated the suitability of a glass ionomer system as a permanent restoration material in posterior cavities. Methods 26 Class I (1-surface (S1)) and 125 Class II (84 2-surface (S2), 41 3- and 4-surface (S3+)) restorations were placed in permanent molars ( n = 94) and premolars ( n = 57) in 43 patients in 6 dental practices. Restorations were evaluated at 4.5× magnification using modified USPHS criteria. Statistical analysis was performed using the Pearson's Chi-square-test ( p ≤ 0.05). Results The median age of the restorations was 24 months. No failures were observed. The original volume of the restoration was retained in 88.5% of the S1, in 64.2% of the S2 and in 53.7% of the S3+ restorations. A distinct volume loss in S1 restorations was evident in 3.8%. A visible and perceptible roughness was shown in 11.5% of the S1, in 14.3% of the S2 and in 24.4% of the S3+ restorations. Marginal disintegrities occurred in none of the S1, in 1.2% of the S2 and in 7.3% of the S3+ restorations. A distinct marginal discoloration was found less than 1%. Conclusions Within the limitations of this study it can be concluded that EQUIA can be used as a permanent restoration material for any sized Class I and in smaller Class II cavities. However, results of ongoing prospective studies shall provide a more exact indication definition in Class II situations. Significance Modern glass ionomer systems may not only serve as long-term temporaries, but also as permanent restorations in posterior teeth.

Correlation between microtensile bond strength data and clinical outcome of Class V restorations

Objective To determine if the results of resin–dentin microtensile bond strength (μTBS) is correlated with the outcome parameters of clinical studies on non-retentive Class V restorations. Methods Resin–dentin μTBS data were obtained from one test center; the in vitro tests were all performed by the same operator. The μTBS testing was performed 8 h after bonding and after 6 months of storing the specimens in water. Pre-test failures (PTFs) of specimens were included in the analysis, attributing them a value of 1 MPa. Prospective clinical studies on cervical restorations (Class V) with an observation period of at least 18 months were searched in the literature. The clinical outcome variables were retention loss, marginal discoloration and marginal integrity. Furthermore, an index was formulated to be better able to compare the laboratory and clinical results. Estimates of adhesive effects in a linear mixed model were used to summarize the clinical performance of each adhesive between 12 and 36 months. Spearman correlations between these clinical performances and the μTBS values were calculated subsequently. Results Thirty-six clinical studies with 15 adhesive/restorative systems for which μTBS data were also available were included in the statistical analysis. In general 3-step and 2-step etch-and-rinse systems showed higher bond strength values than the 2-step/3-step self-etching systems, which, however, produced higher values than the 1-step self-etching and the resin modified glass ionomer systems. Prolonged water storage of specimens resulted in a significant decrease of the mean bond strength values in 5 adhesive systems (Wilcoxon, p < 0.05). There was a significant correlation between μTBS values both after 8 h and 6 months of storage and marginal discoloration ( r = 0.54 and r = 0.67, respectively). However, the same correlation was not found between μTBS values and the retention rate, clinical index or marginal integrity. Significance As μTBS data of adhesive systems, especially after water storage for 6 months, showed a good correlation with marginal discoloration in short-term clinical Class V restorations, longitudinal clinical trials should explore whether early marginal staining is predictive for future retention loss in non-carious cervical restorations.

Glass Ionomer Derivates Have Better Retention Rates in Cervical Restorations Compared to Self-Etching Adhesive Systems

MEDLINE search and search of abstracts of IADR/AADR and ConsEuro conferences published between January 1998 and May 2004 revealed 85 prospective clinical trials on the clinical effectiveness of 57 different adhesive systems (or restoratives) in Class V restorations; 35 of these trials were published in peer-reviewed journals and 50 as conference abstracts. No further selection was made. All studies had to include information on the retention rates. Five types of adhesives were differentiated: 3 and 2 step etch-and-etch adhesives, 2 and 1 step self-etch adhesives, and glass ionomer derivates. No minimal or maximal exposure limit was set. The main outcome was the annual retention loss in relation to one of the 5 adhesive systems used in non-carious Class V restorations. The observation period of the studies varied between 0.5 years and 6 years. Restorations with glass ionomer derivates showed the highest success rate in regard to retention with a mean annual loss of retention of 1.9% (range 0%-7.6%). Three-step etch-and-rinse adhesive systems and 2-step self-etch adhesive systems showed a clinically reliable and predictably good clinical performance with a mean annual retention loss of 4.8% (range 0%-16%) and 4.7%(range 0%-19%) respectively, whereas the mean annual retention loss of 2-step etch-and-rinse adhesive systems was 6.2% (range 0%-19.5%) and that of 1-step self-etching adhesives 8.1% (range 0%-48%). However, due to the great variability a statistically significant difference was found only for glass ionomer versus 2-step etch-and-rinse and glass ionomer versus 1-step self-etch adhesive systems when the Kruskall-Wallis and Dwass-Steel-Chritchlow-Fligner test for multiple comparisons was applied. The percentage of adhesive systems--according to the adhesive category--which would get the full ADA acceptance was as follows: glass ionomer derivates 96%, 3-step etch-and-rinse 81%, 2-step self-etch 71%, 1-step self-etch 68%, 2-step etch-and-rinse 51%. The authors concluded that although there is a tendency towards adhesives with simplified application procedures, simplification appears to induce loss of effectiveness.

Randomised trial of resin-based restorations in Class I and Class II beveled preparations in primary molars: 48-Month results

This randomised clinical trial evaluated the survival rate of resin-based restorations in Class I and Class II beveled preparations in primary molars, over 48 months. Forty-eight children received 141 restorations in beveled cavosurface margin preparations in primary molars randomly assigned by a lottery method: 46 received treatment with Vitremer Tri-Cure Glass Ionomer System (33 Class I and 13 Class II restorations); 51 received treatment with Freedom (36 Class I and 15 Class II restorations); 44 received treatment with TPH Spectrum (30 Class I and 14 Class II restorations). Two calibrated examiners (weight kappa> or =0.85) evaluated the restorations using the modified USPHS criteria and visible plaque index score at baseline and after 12, 24, 36 and 48 months. Cox regression with survival analysis and logistic regression evaluated the clinical performance of restorations. After 48 months, 11 teeth had exfoliated, 16 restorations were dropouts, 83 restorations were clinically successful of which 26 had used Vitremer, 32 had used Freedom and 25 had used TPH Spectrum. Thirty-one restorations failed because of secondary caries, fractures and loss of retention. The cumulative survival was 73.9%, 83.4% and 79.6%, respectively for Vitremer, Freedom and THP Spectrum with no differences among materials (Log Rank Mantel-Cox, p>0.05). However, the Class II cavity preparation reduced the survival of the restorations (OR=5.1) for all materials evaluated (p>0.05). The life expectancy of Vitremer, Freedom and THP Spectrum in Class I and Class II restorations could be comparable after 48 months.

A randomized trial of resin-based restorations in class I and class II beveled preparations in primary molars: 24-month results

The authors conducted a randomized clinical trial to evaluate the survival rate of esthetic restorations in Class I and Class II beveled preparations in primary molars 24 months after placement. The null hypothesis was that there is no difference among survival rates of the restorative materials used. Forty-eight children (mean age, 5 years 9 months) received 141 restorations in beveled cavosurface margins in primary molars randomly assigned by lottery method: 46 received treatment with Vitremer Tri-Cure Glass Ionomer System (3M ESPE Dental Products, St. Paul, Minn.) (33 Class I and 13 Class II restorations), 51 received treatment with Freedom (SDI, Bayswater, Victoria, Australia) (36 Class I and 15 Class II restorations); 44 received treatment with TPH Spectrum (Dentsply, Petropolis, Rio de Janeiro, Brazil) (30 Class I and 14 Class II restorations). Two examiners whose technique had been calibrated (weight kappa > 0.85) evaluated the restorations using modified U.S. Public Health Service criteria and Visible Plaque Index score at baseline and at 12, 18 and 24 months. After two years, the authors censored data for 17 restorations, considered 101 restorations to be clinically successful and deemed 23 restorations failed because of loss of marginal integrity, anatomical form discrepancies and secondary caries. For Class I and Class II restorations, the cumulative survival rates were higher than 80 percent and 55 percent, respectively, for all materials (life table, Gehan-Wilcoxon Test, P > .05; P > .05). At the 24-month clinical recall, the authors found no differences among materials in Class I (P > .05) or Class II beveled preparations (P > .05) in primary molars, but all materials showed higher survival rates in Class I than in Class II restorations.

A novel light-cured glass-ionomer system for improved dental restoratives

A novel light-cured glass-ionomer cement (LCGIC) system based on the 4-arm star-shape poly(acrylic acid) (AA) tethered with glycidyl methacrylate has been developed. The 4-arm poly(AA) polymer was synthesized using atom-transfer radical polymerization. The purified polymer was used to formulate with water and Fuji II LC filler to form LCGICs. Compressive strength (CS) was used as a screening tool for evaluation. The effects of grafting ratio, polymer/water (P/W) ratio, filler powder/polymer liquid (P/L) ratio and aging on strengths were investigated. All the specimens were conditioned in distilled water at 37 degrees C for 24 h prior to testing. The results show that the 4-arm poly(AA) polymer exhibited a lower viscosity as compared to its linear counterpart that was synthesized via conventional free-radical polymerization. This novel LCGIC system was 13% in CS, 86% in diametral tensile strength (DTS) and 123% in flexural strength higher but 93.6% in shrinkage lower than Fuji II LC. Increasing P/W ratio significantly increased both CS and DTS. Upon increasing grafting ratio, the CS was increased from 35% to 50% but not from 50% to 70%. Likewise, when P/L ratio was increased, the CS was increased from 2.2 to 2.7 but not from 2.7 to 3.0. During aging, the ultimate CS (MPa) was significantly increased from 209.2 at 1 h to 329.7 at 1 week. It appears that this novel LCGIC system will be a better dental restorative because it demonstrated improved mechanical strengths as well as little shrinkage and may eliminate cytotoxicity in current LCGICs caused by leached HEMA.

A novel comonomer-free light-cured glass-ionomer cement for reduced cytotoxicity and enhanced mechanical strength

Objective The objective of this study was to develop a novel comonomer-free light-cured glass-ionomer system based on the 4-arm star-shape poly(acrylic acid). The mechanical strengths and in vitro cytotoxicity of the formed system were evaluated and compared with those of several representative commercial glass-ionomer cements. Materials and methods The 4-arm poly(acrylic acid) was synthesized using ATRP and tethered with glycidyl methacrylate (GM). The GM-tethered polymer was formulated with water, photo-initiators, and Fuji II LC filler. Fuji II, Fuji II LC and Vitremer were used for comparison. Compressive strength (CS) and MTT assay were used as tools to evaluate the mechanical strengths and in vitro cytotoxicity of the cements, respectively. Results The experimental cement exhibited significantly high compressive, diametral tensile and flexural strengths as compared to commercial glass-ionomer cements, Fuji II, Fuji II LC and Vitremer. The effects of polymer/water (P/W) ratio, GM-grafting ratio, glass powder/polymer liquid (P/L) ratio and aging in water on strengths were significant. Similar to conventional glass-ionomer cement Fuji II, the eluates from the experimental cement showed little in vitro cytotoxicity to Balb/c mouse fibroblast cells, as compared to Fuji II LC and Vitremer that contain HEMA as a comonomer. Conclusions It appears that this novel comonomer-free light-cured glass-ionomer cement will be a promising dental restorative because it demonstrated significantly improved mechanical strengths and almost no in vitro cytotoxicity as compared to current commercial light-cured glass-ionomer cements.

The effect of oxalic acid incorporation on the setting time and strength of a glass-ionomer cement

Oxalic acid and its metal oxalate salts have been used extensively in dentistry in a range of applications: as desensitisers, in cavity preparation, and as bonding agents. This study investigated the influence of oxalic acid upon the working time, initial setting time, 24-h hardness and compressive strength of a glass-ionomer cement. Conventional glass-ionomer liquids were prepared from polyacrylic acid, tartaric acid, water, and oxalic acid at concentrations of 0–7% w/w. Liquids were dosed into capsules with a commercial glass-ionomer powder, activated and mixed. The resultant pastes were assessed for working time, initial setting time, 24-h hardness and 24-h compressive strength. Liquids containing 0.5–1% oxalic acid lengthened the working time and initial setting time. At concentrations greater than 2%, both working and initial setting times decreased with increasing oxalic acid. Surface hardness values using liquids with 3% and 7% oxalic acid were less hard than the control. Compressive strength was unchanged over the concentrations tested. Oxalic acid may be a useful reaction modifier in glass-ionomer systems. It accelerated the setting reaction without affecting strength, but was limited to low concentrations because of its relatively poor solubility in water.

The effect of mixing time on the handling and compressive strength of an encapsulated glass-ionomer cement

The effects of varying mixing times on the properties of glass-ionomer cements have been poorly investigated, and many clinicians are uninformed about the potential changes in handling achieved by this. This study aims to explore the effects of mixing time variation. An experimental glass-ionomer system was dosed into a capsule, activated, and triturated for varying lengths of time, from 2 to 14 s. Measurements were made of working time, initial setting time, compressive strength and compressive modulus, and a subjective assessment of handling conducted. The working time and initial setting time decreased as mixing time increased, while compressive strength and compressive modulus increased to a maximum at 12 s mixing time. The material essentially pre-gelled after 14 s of mixing, which resulted in breaking of the gel matrix and poorer properties. Clinicians should feel confident, within limits, of varying mixing times of glass ionomer cements to improve properties or to slow the reaction.

Setting shrinkage strains of chemical-cured glass ionomer-based dental restorative materials

Shrinkage strains are exhibited by the current formulations of chemical-cured dental restorative systems. In resin-modified glass ionomer systems, these have been linked to filler contents, types and quantity of monomer. Post-gelation rigid contraction that follows onset of cure leading to marginal defects is a clinically significant factor, although flow is noted to compensate for shrinkage effects during pre-gelation phase. The bonded-disk technique was employed to study the shrinkage strains of chemical-cured and light-activated glass polyalkenoate-based cements at two clinical temperatures of 37EC and 60EC over a period of 2 hours. Magnitudes of shrinkage strains obtained were subjected to one-way ANOVA and Schefe's 0.5 significant level statistical analysis. The time-dependent shrinkage strain data characteristic of the materials indicated a linear initial rigid and rapid contraction, which is appropriately represented by the Kohlrausch-Williams-Watts stretched exponential decay curve. The kinetics of shrinkage was expressed by the overall time constant and the initial contraction strains at 30 s, following the onset of cure. Data obtained after 15 minutes up to 2 hours indicated high contraction strains at 60EC compared to that at the intra-oral temperature, 37EC. There is a relatively slow development of contraction strains in glass ionomer-based systems compared to resin-based ones. This is, however, a positive quality for the glassy materials in their use as marginal seals. Nevertheless, contraction strains in dental restorative systems with their destructive shrinkage stresses remain unresolved. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 2 No. 3 (2000) pp. 103-112

Development of glass-ionomer cement systems

In the 1960s the idea of positive physico-chemical adhesion with tooth substance resulted in the invention of polyacrylic acid-based cements, first the zinc polycarboxylate and, subsequently, the glass-ionomer cements. These materials were shown to undergo specific adhesion with hydroxyapatite and proved to have properties satisfactory for a variety of clinical applications. The key properties of the glass-ionomer cements—fluoride release over a prolonged period and specific adhesion to enamel and dentine coupled with aesthetic qualities—are related to their characteristics as aqueous polyelectrolyte systems. In order to improve toughness, speed of setting and resistance to dehydration, hybrid materials in which some of the water content of the glass-ionomer system was replaced by water-soluble polymers or monomer systems capable of ambient polymerization were formulated in the late 1980s. These materials, which have been termed resin-modified glass-ionomer cements, involve, ideally, the formation of an interpenetrating polymer network combining the acid–base cross-linking reaction of the metal ion–polyacid with the cross-linking polymerization of the monomer system or additive action of the polymers. In the predominantly resin materials there is little polyelectrolyte character and it is controversial whether such materials should be categorized as glass-ionomer cement systems. The specific advantages of these materials over traditional glass-ionomer systems and over composite restorative systems remain to be fully documented. Studies of adsoption to hydroxyapatite of typical monomers using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF SIMS) indicate that resistance to water displacement decreases as hydrophobicity increases.

Microhardness of N-Vinylpyrrolidone Modified Glass-Ionomer Cements

ABSTRACT The water soluble N-vinylpyrrolidone (NVP) monomer was used to prepare poly(N-vinylpyrrolidone-co-itaconic acid-co-acrylic acid) glass-ionomer copolymers, using a free-radical polymerization process. NVP modified terpolymer was mixed with glass powders from four commercial glass ionomer systems. Microhardness from the set cement was measured and compared to several commercial glass-ionomer systems. The Knoop hardness number (KHN) values were recorded on polished specimens conditioned for 48 hours and 7 days. One-way analysis of variance and Tukey-Kramer tests were used to determine the significant differences among the materials tested in each group. Among the four commercial cements, Ketac-Molar (KM) showed the highest value and α-Silver (AS) snowed the lowest value in KHN. Fuji II (F2) and α-Fil (AF) showed much the same values in KHN. At the same P/L ratio, NVP modified glass-ionomers showed higher KHN values than the AS, similar to the AF and F2, and lower than the KM. The effect of P/L ratios was evident and highest KHN values for each group were basically presented by the one with a higher P/L ratio. Higher P/W ratio did not improve the KHN for the AS and KM group, but improved the F2 group.

The Short-term Fluoride Release of a Hand-mixed vs. Capsulated System of a Restorative Glass-ionomer Cement

The present study investigated whether variability in fluoride release was reduced by use of a capsulated system as compared with a hand-mixed system based on the same qualitative and quantitative glass-ionomer formulation. Five operators independently prepared five disks of each type of glass-ionomer restorative filling material. The amount of fluoride released in water by each specimen after 1, 2, 3, 7, and 14 days was determined. The variance and the mean value of the fluoride release at a given time were independent of the operator, regardless of the glass-ionomer system considered. However, the variance and the mean value of the fluoride release at a given time were considerably greater for the capsulated system than for the hand-mixed system. A regression analysis further showed that the cumulative amount of fluoride released, [F], as a function of the time t conformed to [F] = a[1 - exp (-bt)] + ct0.5 for each glass-ionomer specimen, suggesting the simultaneous occurrence of two processes. Whereas the parameter b was the same for the hand-mixed and capsulated system and was independent of both a and c, the latter parameters were positively correlated. Moreover, the values for a and c were significantly greater for the capsulated system. On the basis of these results, it is concluded that the mixing process drastically influences the short-term as well as the long-term fluoride release.

Glass Ionomers and Esthetic Dentistry: What the New Properties Mean to Dentistry

Ingenuity in research and development of glass ionomer systems has slowly but surely improved their handling properties and appearance. The author reviews the latest developments in relation to esthetic dentistry.

Bonding agents and adhesives.

Development of molecules which will adhere to tooth structure is a high-priority area of dental research. Although enamel and dentin present formidable obstacles to adhesive mechanisms, there is substantial progress in the formulation of agents which are already altering certain procedures, such as the conservative restoration of the erosion lesion. These materials are evaluated with particular attention to dentin bond agents and the glass-ionomer system. The latter is of particular interest due to its proved biocompatibility, fluoride leach, and bonding capability. The exact status of dentin bond agents based on phosphonates remains controversial, and the possible reasons for the divergent data are discussed.