Interfacial Characterization of a Conventional Glass-Ionomer Cement after Functioning for 1-year In Vivo

PURPOSE

To morphologically evaluate the interface between a conventional glass-ionomer cement (GIC) and dentin one day after placement, as well as the changes at the interface after one year of aging/functioning in monkey teeth.

MATERIALS AND METHODS

On the buccal surfaces of seven intact teeth in each of two monkeys, shallow class V cavities were prepared, which were then filled with Fuji IX GP (GC) to provide 1-year in vivo data. A year later, two more teeth in each monkey were similarly prepared and restored for the 1-day in vivo group. The following day, the restored teeth were extracted and the restoration interfaces observed using transmission electron microscopy (TEM). In addition, restorations were similarly placed in two extracted human teeth (control, 1-day in vitro group) and observed a day after placement using TEM.

RESULTS

The 1-day in vivo and in vitro results showed that the GIC appeared to bond to dentin through a demineralized zone similar to the hybrid layer produced by resinous adhesives. However, the interface between GIC and dentin after 1 year in vivo appeared to change over time: many needle-like crystals were detected within the remineralized layer and along the collagen fibrils. Slow diffusion of ions resulted in pores, which filled with mineral crystals and made the pores smaller.

CONCLUSION

The interface between GIC and dentin morphologically changes over time, and recrystallization or remineralization at the interface may occur (1 year in vivo).

Restorative Materials Exposed to Acid Challenge: Influence of Temperature on In Vitro Weight Loss

Consumption of acidic beverages and foods could provoke erosive damage, both for teeth and for restorative materials. Temperatures of consumption could influence the erosive effects of these products. The aim of this in vitro study is to assess the influence of an acidic challenge on the weight loss of different restorative materials. Resin composites and glass-ionomer cements (GIC) were tested. The medium of storage was Coca-Cola (Coca-Cola, Coca-Cola Company, Milano, Italy) at two different temperatures, 4 and 37 °C, respectively for Group A and Group B. For each group, nine specimens were prepared for each material tested. After 7 days, weight was assessed for each sample, and the percentage weight loss was calculated. For all the resin composites (Groups 1−13), no significant weight losses were noticed. (<1%). Conversely, GICs (Groups 14 and 15) showed significant weight loss during the acidic challenge, which was reduced in the case of these materials that included a protective layer applied above. Significant differences were registered with intra-group analysis; weight loss for specimens immersed in Coca Cola at 37 °C was significantly higher for almost all materials tested when compared to specimens exposed to a cooler medium. In conclusion, all the resin composites showed reliable behaviour when exposed to acidic erosion, whereas glass-ionomer cements generally tended to solubilize.

Effect of total-etch and self-etch adhesives on the bond strength of composite to glass-ionomer cement/resin-modified glass-ionomer cement in the sandwich technique - A systematic review

The success of the sandwich technique depends on the bond strength of composite to glass-ionomer cement (GIC)/resin-modified glass-ionomer cement (RMGIC). Currently used adhesives employ the total-etch and the self-etch techniques. The total-etch system is technique sensitive, whereas the self-etch system is popular for its ease of use. The aim of this systematic review is to compare the effect of total-etch and self-etch adhesives (SEAs) on the bond strength of composite to GIC/(RMGIC) in the sandwich technique. A literature search was conducted using electronic databases (PubMed, Web of Science, Ebscohost, and Scopus) limiting the year of publications from January 1, 2000, to September 30, 2018, to identify the relevant studies. All the cross-references of the selected studies were also screened. In vitro studies on extracted human teeth were selected. A total of 10 articles were included in this review. A conclusion was drawn that SEAs when used in the sandwich technique resulted in greater bond strength in comparison to total-etch adhesives. Moreover, increased bond strength was achieved when the primer was employed on unset GIC as compared to set GIC. Furthermore, the application of SEAs over uncured RMGIC (co-curing technique) resulted in better bond strengths as compared to their application over cured RMGIC.

Therapeutic properties of glass-ionomer cements: Their application to orthodontic treatment

Fluoride has been shown to be an effective agent in the prevention of caries during orthodontic treatment. Resin-modified glass-ionomer cements possess therapeutic anticariogenic properties acting as a fluoride reservoir and releasing fluoride into the environment, particularly at low pH where there is a threat of enamel demineralisation and white spot lesions (WSL's). Patient compliance to instructions in standard oral hygiene measures limits the success of caries prevention and the routine use of glass-ionomer cements can mitigate the lack of compliance, although RMGIC's are not a panacea against WSL's. The adhesion of GIC's to the enamel surface is a physicochemical bond rather than a mechanical bond which reduces the risk of iatrogenic damage to the enamel when bonding and debonding attachments. RMGIC's can be recommended as a bonding adhesive for all attachments but one needs to be selective when bonding molar attachments to avoid occlusal interferences as masticatory forces can be high in these areas.

Mechanical and antimicrobial property of different surface treated glass ionomer cements under desiccated condition

BACKGROUND

The purpose of this in vitro study was to evaluate the effect of five different surface treatments on the mechanical property and antimicrobial effect of three desiccated glass ionomer cements.

MATERIALS AND METHODS

In this in vitro experimental study, 300 rectangular blocks of three different restorative materials were fabricated using an aluminum mold, Group I (n = 100) Micron bioactive, Group II (n = 100) GC Fuji IX GP Extra, and Group III (n = 100) bioglass R. These blocks were stored in 100% humidity for 24 h and then placed in air to desiccate for another 24 h. These groups were further divided into two major groups (n = 50) for both mechanical (Flexural) and antimicrobial testing. The blocks of mechanical and antimicrobial groups were further divided into five subgroups (n = 10) based on the medias used for surface treatment (senquelNaF, MI varnish, chlorhex plus, kedodent mouthwash, and 100% humidity [control]). Flexural strength (FS) was measured using the universal testing machine. Fracture strength of groups was compared using the one-way analysis of variance and Tukey's post hoc test with P ≤ 0.05 considered statistically significant. Antimicrobial effect was carried out by covering the specimens in a suspension of Streptococcus mutans followed by incubation for 24 h. The blocks were later washed, vortex mixed, serially diluted, and plated. Ccolony-forming unit/ml was calculated after 3 days of incubation. Data were then analyzed using the Kruskal-Wallis and Mann-Whitney U nonparametric test, with P ≤ 0.05 considered statistically significant.

RESULTS

Micron bioactive with the surface treatment of MI varnish significantly exhibited highest FS. Surface treatment of desiccated restorative materials with chlorhex plus exhibited no growth of S. mutans. GC Fuji IX GP Extra with surface treatment of MI varnish exhibited highest reduction in S. mutans growth compared to other experimental group.

CONCLUSION

Surface treatment of restorative material with MI varnish improved their mechanical and antimicrobial property while among three restorative materials Micron bioactive showed better mechanical property, whereas GC Fuji IX GP Extra exhibited better antimicrobial property.

Meta-Analysis of In-Vitro Bonding of Glass-Ionomer Restorative Materials to Primary Teeth

Restoration of primary teeth is among the main clinical applications of glass-ionomer cements (GIC). The aim of the study was to review and summarize existing evidence of in vitro bond strength of glass-ionomer (GI) restoratives to enamel and dentin of primary teeth. A literature search was performed in PubMed/Medline, Scopus, Web of Science, Cochrane, and Google Scholar databases to identify studies published until April 2021. The search strategy was: (“glass”) and (“ionomer”) and (“primary” or “deciduous”) and (“bond” or “tensile” or “shear”). Two researchers independently retrieved articles that reported on the bond strength of GIC to primary dentin and/or enamel. The meta-analysis was performed to compare the bond strength values of conventional (C) GIC and resin-modified (RM) GIC to different substrates. From 831 potentially eligible articles, 30 were selected for the full-text examination, and 7 were included in the analysis. Studies were rated at high (3), medium (3), and low (1) risk of bias. RM-GIC showed higher bond strength to primary enamel and dentin compared to the C-GIC. Meta-analysis of in vitro studies, evaluating bonding properties of GI restoratives to primary teeth, suggests the superior performance of RM-GIC. However, there is a lack of studies that examine the properties of novel GI formulations.

Translucency parameter of conventional restorative glass-ionomer cements

OBJECTIVE

To evaluate the translucency parameter (TP) and contrast ratio (CR) of different conventional restorative glass-ionomer cements (GICs).

MATERIALS AND METHODS

Eighteen brands of GICs were evaluated. Five disks of each material were made following ISO 9917-1. The luminous reflectance and Central Bureau of the International Commission on Illumination parameters of disks were evaluated using a colorimeter, against backings of white and black, to obtain the translucent parameter and contrast ratio of different brands of glass-ionomer cements. The correlation between translucency parameter and contrast ratio was assessed with the Pearson correlation test. The translucent and contrast ratio parameters values were submitted to the one-way ANOVA and Tukey test for multiple comparisons (p < 0.05).

RESULTS

There was a strong inverse relationship between CR and TP (r²  = 0.94, p < 0.001). The contrast ratio decreased as translucency increased. There were significant differences in TP and CR among brands (p < 0.001).

CONLUSIONS

GICs exhibit different translucency and contrast ratio behavior. Some brands of GICs presented very low TP and this condition would be unacceptable for areas with esthetic demands. In addition, TP and CR showed a strong linear relationship.

CLINICAL SIGNIFICANCE

The results found in this study demonstrated that the knowledge of the translucency and CR of different conventional restorative GICs is important in order to guide clinicians in the selection of restorative GICs for anterior teeth.

Biocompatibility of Ionomeric Cements Modified by Red Propolis: A Morphological and Immunohistochemical Analysis

PURPOSE

To evaluate the biocompatibility in rat subcutaneous tissue of conventional orthodontic cements, Riva (R) and Meron (M), modified by the addition of ethanolic extract of red propolis (EERP), at different concentrations and time intervals.

MATERIALS AND METHODS

One hundred eight male adult Wistar rats were used, distributed in nine groups of cements with added EERP at the concentrations used (C-control, MC, M10, M25, M50, RC, R10, R25, and R50). The rats were sacrificed after 3 time intervals (7, 15, and 30 days). Histological and immunohistochemical analyses were performed. The findings were statistically analyzed using the Kruskal-Wallis test followed by Dunn's test (p < 0.05).

RESULTS

The highest concentrations led to a higher level of inflammation at the initial times (p < 0.05), but without differences after 30 days. In terms of collagen, there was less collagenization at the initial times in comparison with the control group C. However, over time, the addition of propolis resulted in healing compatible with that of group C. The level of CD68 immunostaining was statistically significantly higher in the groups with the highest concentrations (R50 and M50) (p = 0.001).

CONCLUSION

Orthodontic cements with the addition of EERP were found to be biocompatible in rat subcutaneous tissue. Riva cement with the addition of 50% EERP showed the highest tissue inflammation, but with satisfactory tissue repair.

Enhancing the Mechanical Properties of Glass-Ionomer Dental Cements: A Review

This paper reviews the strategies that have been reported in the literature to attempt to reinforce glass-ionomer dental cements, both conventional and resin-modified. These cements are widely used in current clinical practice, but their use is limited to regions where loading is not high. Reinforcement might extend these applications, particularly to the posterior dentition. A variety of strategies have been identified, including the use of fibres, nanoparticles, and larger particle additives. One problem revealed by the literature survey is the limited extent to which researchers have used International Standard test methods. This makes comparison of results very difficult. However, it does seem possible to draw conclusions from this substantial body of work and these are (1) that powders with conventional particle sizes do not reinforce glass-ionomer cements, (2) certain fibres and certain nanoparticles give distinct improvements in strength, and (3) in the case of the nanoparticles these improvements are associated with differences in the morphology of the cement matrix, in particular, a reduction in the porosity. Despite these improvements, none of the developments has yet been translated into clinical use.

Assessment of the Impact of the Addition of Nanoparticles on the Properties of Glass-Ionomer Cements

The aim of the study was to evaluate the effects of incorporation of Al2O3, ZrO2 and TiO2 nanoparticles into glass-ionomer cements (GICs). Two different GICs were used in the study. Four groups were prepared for each material: the control group (without nanoparticles) and three groups modified by the incorporation of nanoparticles at 2, 5 or 10 wt %, respectively. Cements were mixed and placed in moulds (4 mm × 6 mm); after setting, the samples were stored in saline (one day and one week). Compressive strengths were measured and the morphology of the fractured surfaces was analyzed by scanning electron microscopy. The elements released into the storage solutions were determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES). Addition of nanoparticles was found to alter the appearance of cements as examined by scanning electron microscopy. Compressive strength increased with the addition of ZrO2 and especially TiO2 nanoparticles, whereas the addition of Al2O3 nanoparticles generally weakened the cements. The ion release profile of the modified cements was the same in all cases. The addition of Al2O3, ZrO2 and TiO2 nanoparticles into GICs is beneficial, since it leads to reduction of the microscopic voids in the set cement. Of these, the use of ZrO2 and TiO2 nanoparticles also led to increased compressive strength. Nanoparticles did not release detectable levels of ions (Al, Zr or Ti), which makes them suitable for clinical use.

Clinical Performance of Non-Carious Cervical Restorations Restored with the "Sandwich Technique" and Composite Resin: A Systematic Review and Meta-analysis

PURPOSE

To compare the retention rates of non-carious cervical restorations (NCCLs) constructed using the sandwich technique (a lining of glass-ionomer cement [GIC] or resin-modified glass-ionomer cement [RMGIC] and composite resin [CR]) with CR-only restorations.

MATERIALS AND METHODS

The search was performed in various databases, including the Cochrane Library, PubMed, Scopus, and Web of Science. Gray literature was inspected, as were ongoing and unpublished abstracts from the IADR (1990-2017). Study quality was evaluated using the Cochrane Collaboration bias risk tool. Data from primary and secondary outcomes were meta-analyzed at 1-, 2- and 3-year follow-ups using the random effects model. The quality of the body of evidence was assessed using the GRADE approach.

RESULTS

Initially, a total of 3645 articles were selected. After selection by titles, abstracts, and full texts, 6 articles were retrieved, but three were follow-ups of the same RCT. Therefore, a total of four studies remained for analysis. All studies were at unclear risk for bias. Among all outcomes, only loss of retention was lower for the sandwich technique at the 3-year follow-up (risk ratio [RR]: 7.5; 95% CI: 2.1 to 27.2; p = 0.002).

CONCLUSIONS

Based on the limited number of available studies, higher retention rates in NCCL restorations were observed with the sandwich technique compared to CR-only restorations at the 3-year follow-up. Secondary outcomes were not influenced by the restorative technique. Except for retention rates, which were of moderate quality, the evidence quality of all secondary outcomes was low.

Effects of Ions-Releasing Restorative Materials on the Dentine Bonding Longevity of Modern Universal Adhesives after Load-Cycle and Prolonged Artificial Saliva Aging

This study aimed at evaluating the microtensile bond strength (MTBS) and fractographic features of dentine-bonded specimens created using universal adhesives applied in etch-and-rinse (ER) or self-etching (SE) mode in combination with modern ion-releasing resin-modified glass-ionomer cement (RMGIC)-based materials after load cycling and artificial saliva aging. Two universal adhesives (FTB: Futurabond M+, VOCO, Germany; SCU: Scotchbond Universal, 3M Oral Care, USA) were used. Composite build-ups were made with conventional nano-filled composite (AURA, SDI, Australia), conventional resin-modified glass ionomer cement (Ionolux VOCO, Germany), or a (RMGIC)-based composite (ACTIVA, Pulpdent, USA). The specimens were divided in three groups and immersed in deionized water for 24 h, load-cycled (350,000 cycles; 3 Hz; 70 N), or load-cycled and cut into matchsticks and finally immersed for 8 months in artificial saliva (AS). The specimens were cut into matchsticks and tested for microtensile bond strength. The results were analyzed statistically using three-way ANOVA and Fisher's LSD post hoc test (p < 0.05). Fractographic analysis was performed through stereomicroscope and FE-SEM. FTB showed no significant drop in bond strength after aging. Unlike the conventional composite, the two RMGIC-based materials caused no bond strength reduction in SCU after load-cycle aging and after prolonged aging (8 months). The SEM fractographic analysis showed severe degradation, especially with composite applied on dentine bonded with SCU in ER mode; such degradation was less evident with the two GIC-based materials. The dentine-bond longevity may be influenced by the composition rather than the mode of application (ER vs. SE) of the universal adhesives. Moreover, the choice of the restorative material may play an important role on the longevity of the finalrestoration. Indeed, bioactive GIC-based materials may contribute to maintain the bonding performance of simplified universal adhesives over time, especially when these bonding systems are applied in ER mode.

Surface Conditioning Prior to the Application of Glass-Ionomer Cement: A Systematic Review and Meta-analysis

PURPOSE

To systematically review the literature to determine whether the laboratory and clinical performance of glass-ionomer cement (GIC) is influenced by surface conditioning with polyacrylic acid (PAA).

MATERIALS AND METHODS

This systematic review was conducted according to PRISMA and registered in PROSPERO (CRD42016039305). A comprehensive literature search was conducted in seven electronic databases considering clinical and laboratory studies published up to July 2018, with no limit on year of publication. Two reviewers independently selected papers, extracted data, and assessed the risk of bias. Of 141 eligible studies, 23 were fully analyzed. A total of 15 studies (12 laboratory and three clinical trials) were included in the systematic review and three laboratory studies concerning the microtensile bond strength (μTBS) were included in the meta-analysis.

RESULTS

The meta-analysis showed that pretreating the surface with PAA before using GIC significantly improved the μTBS (OR = 3.17; 95% CI: 0.51-5.83; p = 0.02). In the longitudinal clinical trials, no significant difference was observed between applying PAA or not into the cavities before using GIC. Risk of bias was considered high in all study designs.

CONCLUSION

Surface preconditioning with PAA has a positive effect on the bond strength of GIC. However, this finding was not confirmed in longitudinal clinical trials.

Effect of two prophylaxis methods on marginal gap of Cl Vresin-modified glass-ionomer restorations

Background. This study evaluated the effect of two prophylaxis techniques on the marginal gap of CI V resin-modified glass-ionomer restorations.

Methods. Standard Cl V cavities were prepared on the buccal surfaces of 48 sound bovine mandibular incisors in this in vitro study. After restoration of the cavities with GC Fuji II LC resin-modified glass-ionomer, the samples were randomly assigned to 3 groups of 16. In group 1, the prophylactic procedures were carried out with rubber cup and pumice powder and in group 2 with air-powder polishing device (APD). In group 3 (control), the samples did not undergo any prophylactic procedures. Then the marginal gaps were measured. Two-way ANOVA was used to compare marginal gaps at the occlusal and gingival margins between the groups. Post hoc Tukey test was used for two-by-two comparisons. Statistical significance was set at P < 0.05.

Results. There were significant differences in the means of marginal gaps in terms of prophylactic techniques (P < 0.001), with significantly larger marginal gaps in the APD group compared to the pumice and rubber cup group, which in turn exhibited significantly larger marginal gaps compared to the control group (P < 0.0005). In addition, the means of marginal gaps were significant in terms of the margin type (P < 0.001), with significantly larger gaps at gingival margins compared to the occlusal margins (P < 0.0005).

Conclusion. The prophylactic techniques used in this study had a negative effect on the marginal gaps of Cl V resin-modified glass-ionomer restorations.

Caries-preventive Effect of Supervised Toothbrushing and Sealants

To investigate the effectiveness of 3 caries-preventive measures on high- and low-caries risk occlusal surfaces of first permanent molars over 3 y. This cluster-randomized controlled clinical trial covered 242 schoolchildren, 6 to 7 y old, from low socioeconomic areas. At baseline, caries risk was assessed at the tooth surface level, through a combination of ICDAS II (International Caries Detection and Assessment System) and fissure depth codes. High-caries risk occlusal surfaces were treated according to daily supervised toothbrushing (STB) at school and 2 sealants: composite resin (CR) and atraumatic restorative treatment-high-viscosity glass-ionomer cement (ART-GIC). Low-caries risk occlusal surfaces received STB or no intervention. Evaluations were performed after 0.5, 1, 2, and 3 y. A cavitated dentine carious lesion was considered a failure. Data were analyzed according to the proportional hazard rate regression model with frailty correction, Wald test, analysis of variance, and t test, according to the jackknife procedure for calculating standard errors. The cumulative survival rates of cavitated dentine carious lesion-free, high-caries risk occlusal surfaces were 95.6%, 91.4%, and 90.2% for STB, CR, and ART-GIC, respectively, over 3 y, which were not statistically significantly different. For low-caries risk occlusal surfaces, no statistically significant difference was observed between the cumulative survival rate of the STB group (94.8%) and the no-intervention group (92.1%) over 3 y. There was neither a difference among STB, CR, and ART-GIC on school premises in preventing cavitated dentine carious lesions in high-caries risk occlusal surfaces of first permanent molars nor a difference between STB and no intervention for low-caries risk occlusal surfaces of first permanent molars over 3 y.

Effect of G-Coat Plus on the mechanical properties of glass-ionomer cements

BACKGROUND

Although various mechanical properties of tooth-coloured materials have been described, little data have been published on the effect of ageing and G-Coat Plus on the hardness and strength of the glass-ionomer cements (GICs).

METHODS

Specimens were prepared from one polyacid-modified resin composite (PAMRC; Freedom, SDI), one resin-modified glass-ionomer cement; (RM-GIC; Fuji II LC, GC), and one conventional glass-ionomer cement; (GIC; Fuji IX, GC). GIC and RM-GIC were tested both with and without applying G-Coat Plus (GC). Specimens were conditioned in 37 °C distilled water for either 24 hours, four and eight weeks. Half the specimens were subjected to a shear punch test using a universal testing machine; the remaining half was subjected to Vickers Hardness test.

RESULTS

Data analysis showed that the hardness and shear punch values were material dependent. The hardness and shear punch of the PAMRC was the highest and GIC the lowest. Applying the G-Coat Plus was associated with a significant decrease in the hardness of the materials but increase in the shear punch strength after four and eight weeks.

CONCLUSIONS

The mechanical properties of the restorative materials were affected by applying G-Coat Plus and distilled water immersion over time. The PAMRC was significantly stronger and harder than the RM-GIC or GIC.