Resin-modified Glass Ionomer Cement Research Articles

Base Materials' Influence on Fracture Resistance of Molars with MOD Cavities.

The aim of this study was to compare fracture resistance of teeth presenting medium-sized mesial-occlusal-distal (MOD) cavities using different base materials. Thirty-six extracted molars were immersed for 48 h in saline solution (0.1% thymol at 4 °C) and divided into six groups. In group A, the molars were untouched, and in group B, cavities were prepared, but not filled. In group C, we used zinc polycarboxylate cement, in group D—conventional glass ionomer cement, in group E—resin modified glass ionomer cement, and in group F—flow composite. Fracture resistance was tested using a universal loading machine (Lloyd Instruments) with a maximum force of 5 kN and a crosshead speed of 1.0 mm/min; we used NEXYGEN Data Analysis Software and ANOVA Method (p < 0.05). The smallest load that determined the sample failure was 2780 N for Group A, 865 N for Group B, 1210 N for Group C, 1340 N for Group D, 1630 N for Group E and 1742 N for Group F. The highest loads were 3050 N (A), 1040 N (B), 1430 N (C), 1500 N (D), 1790 N (E), and 3320 N (F), the mean values being 2902 ± 114 N (A), 972 ± 65 N (B), 1339 ± 84 N (C), 1415 ± 67 N (D), 1712 ± 62 N (E), and 2334 ± 662 N (F). A p = 0.000195 shows a statistically significant difference between groups C, D, E and F. For medium sized mesial-occlusal-distal (MOD) cavities, the best base material regarding fracture resistance was flow composite, followed by glass ionomer modified with resin, conventional glass ionomer cement and zinc polycarboxylate cement. It can be concluded that light-cured base materials are a better option for the analyzed use case, one of the possible reasons being their compatibility with the final restoration material, also light-cured.

Comparison of the residual cement on custom computer-aided design and computer-aided manufacturing titanium and zirconia abutments: A preliminary cohort study

Statement of problemClinical studies comparing the occurrence and quality of residual cement between custom zirconia and custom titanium abutments with subgingival margins are scarce. PurposeThe purpose of this clinical study was to assess the difference in the amount of residual cement between custom zirconia and titanium abutments with a 1-mm subgingival margin. Material and methodsEighty participants were randomized to receive either a custom zirconia abutment with a bonded titanium insert or a custom titanium abutment with a 1-mm subgingival margin on a posterior bone-level implant. Monolithic lithium disilicate crowns with a screw-access hole were cemented to abutments randomly with either a resin-modified glass ionomer cement or a resin cement. After cementation, the crown-abutment assemblies were removed and photographed from the mesial, buccal, distal, and lingual of the specimen to record the residual cement. The length along the abutment margin of each aspect of the assembly was measured. The surface area of the residual cement (SA) and the surface area of the residual cement per unit length of margin (SA_P) were calculated. Results for the groups were compared with the Fisher exact test, the Friedman test, and the Mann-Whitney U test (α=.05). ResultsThe median (lower quartile, upper quartile) of SA and SA_P for the custom zirconia abutment with a bonded titanium insert was 1.9 (0.5, 3.9) mm2 and 0.086 (0.032, 0.02) mm2, respectively, and for the custom titanium abutment, the values were 2.9 (1.3, 5.1) mm2 and 0.138 (0.062, 0.239) mm2, respectively. No significant difference was found between the custom zirconia abutments with bonded titanium inserts and titanium abutments for SA (P=.075) and SA_P (P=.083) with the Mann-Whitney U test. No significant difference was found in residual cement between the 4 aspects of the abutment (SA: P=.852; SA_P: P=.954) with the Friedman test and between the 2 types of cement (SA: P=.447; SA_P: P=.878) with the Mann-Whitney U test. ConclusionsA similar amount of subgingival residual cement was recorded around the abutment-crown assembly, regardless of the abutment material or cement type used.

Two-year randomized clinical trial of different restorative techniques in non-carious cervical lesions and MMP activity in gingival crevicular fluid

To evaluate different restorative techniques for non-carious cervical lesions (NCCLs) and the activity of matrix metalloproteinases (MMPs) in gingival crevicular fluid. Two hundred restorations were performed in 50 patients using resin composite restorative system without (I) and with selective enamel conditioning (II) and resin-modified glass-ionomer cement without (III) and with EDTA pretreatment (IV). Gingival crevicular fluid samples were collected in 15 patients. Restorations were evaluated using USPHS criteria at baseline and after 2years. Percentages of MMP activity were assessed by zymography as a surrogate outcome. Equality tests of two proportions, logistic regression analysis, survival analysis, ANOVA repeated measures, and Fisher tests were used. No differences in clinical performance were found among groups. Group I had lower retention at 2years than at baseline. Decreased alpha scores for marginal integrity and marginal discoloration were observed for all groups after 2years. MMP-2 decreased after 1year, and its activity increased back to the initial level after 2years, mainly for groups I, II, and III. MMP-9 increased after 1year, and it was reduced to the initial level after 2years, mainly for group I. All restorative techniques performed similarly in NCCLs after 2years with initial marginal defect alterations. MMP-2 reestablished its initial levels after 2years, and MMP-9 had few alterations over time in crevicular fluid. Clinical relevance The different restorative techniques are equally successful in NCCLs after 2years of clinical functioning and have similar effects on MMPs present in crevicular fluid.

Evaluation of enamel roughness after the removal of brackets bonded with different materials: In vivo study

The aims of this in vivo study were to evaluate the effect of bonding with resin-modified glass ionomer cement (RMGIC) and to assess enamel surface roughness before and after the removal of brackets bonded with composite or RMGIC from the maxillary central incisors. Fifteen orthodontic patients were selected for the study. For each patient, the teeth were rinsed and dried, and brackets were bonded with composite (Transbond XT) and RMGIC (Vitremer Core Buildup/Restorative). At the conclusion of orthodontic treatment, their brackets were removed. Dental replicas were made of epoxy resin in initial conditions (before bonded) and after polishing with an aluminum oxide disc system. Adhesive remnant index (ARI) and surface roughness was measured on the dental replicas and data were evaluated statistically by Mann-Whitney and paired t-test, respectively. No bracket debonding occurred during patients' treatment periods. It was verified that the ARI values of the two maxillary central incisors were similar (p = 0.665). For both bonding materials, the ARI value of 3 was predominant. After polishing, surface roughness was similar in the composite and RMGIC groups (0.245 μm and 0.248 μm, respectively; p = 0.07). In both groups, enamel surface roughness values were significantly lower after polishing compared with the initial condition (p < 0.001). RMGIC promoted efficiency in cementing brackets without fail during treatment; the choice of composite or RMGIC materials was not a factor that influenced the roughness of the enamel surface, however, polishing led to smoother surfaces than those found at the beginning of the treatment.

In Vitro Analysis of Microbiologic Sealing of Two Different Fixed Implant-Supported Prosthesis Designs Cemented By Four Different Dental Cements.

Despite the high success rate of implant-supported fixed restorations in dentistry, there is a lack of evidence on the marginal seal for dental cement. Thus, this study aimed to evaluate the marginal seal of implant-supported crowns and partial dentures cemented using four different dental cements. The study evaluated the marginal seal of implant-supported crowns and partial dentures cemented using zinc phosphate, resin-modified glass-ionomer, self-adhesive resin, and noneugenol, acrylic-urethane polymer-based temporary dental cements. After cementation and thermal cycling procedures, the samples were incubated in Escherichia coli suspension for 5 days at 37°C under an aerobic environment. After debonding the restorations under sterile conditions, sterile cotton swabs were used to obtain microbial samples from the inner surface of each restoration and abutment surface. To analyze the contamination, each sample was immersed in a brain-heart infusion culture medium and incubated at 37°C for 24 hours, and then, the colony-forming units were counted and recorded. Regarding the number of colonies for Escherichia coli, the results revealed no substantial difference between the crowns and the fixed partial restorations (P = .25). However, the differences in the level of contamination between the cement groups were significant (P ≤ .001). The self-adhesive resin cement samples showed the lowest level of contamination, followed by the zinc phosphate and resin-modified glass-ionomer cements. The difference in the level of contamination between these groups was not significant. The temporary cement group exhibited significantly higher numbers of bacterial colonies in comparison to the other cement groups. Self-adhesive resin cement has better biologic properties for retaining implant-supported restorations than other types of dental cement.

Physical Properties of Newly Developed Resin Modified Glass Ionomer Cement with Synthesised Coumarin Derivatives

The aim of this study was to determine the effects of two types of coumarin derivatives, namely, 3-acetylcoumarin (AC) and coumarin thiosemicarbazone (CT) on surface characteristics such as the roughness, hardness, and morphology of resin-modified glass-ionomer cement (RMGIC). The release of coumarin from the fabricated RMGIC was also investigated. AC and CT at 1.0% (w/w) concentration were added into 0.3 g of RMGIC powder and mixed with 0.1 g of polyacrylic acid. The fabricated RMGIC-AC and RMGIC-CT were evaluated for surface characteristics such as roughness, hardness and topography. The coumarin release of AC and CT from RMGIC was also determined. The RMGIC-CT demonstrated a decreased roughness value among the materials. The surface roughness exhibited by the RMGIC was statistically higher (p &lt; 0.05) than that of fabricated materials. The RMGIC-AC was observed to have the highest hardness value compared to the RMGIC-CT and RMGIC, and this value was significantly higher (p &lt; 0.05). The surface morphologies of the RMGIC-AC and RMGIC-CT showed a number of pores and irregular surfaces. Meanwhile, the surface roughness value of the RMGIC was statistically higher (p &lt; 0.05) than both RMGIC-AC and RMGIC-CT. In conclusion, the large-sized AC particles significantly increased the surface hardness of the fabricated RMGIC. Conversely, the particle size of both coumarins were not influenced the surface roughness value and the coumarin release profile of fabricated RMGICs.

Characteristics of experimental resin-modified glass-ionomer cements, containing alternate monomers to HEMA

ObjectiveResin-modified glass ionomer cements (RMGICs) present several advantages (e.g. fluoride release), but their reported cytotoxicity has been associated with hydroxyethyl methacrylate (HEMA) monomer release. Therefore, different monomers were tested for use in RMGICs in order to improve their biocompatibility and reduce monomer release. MethodsEight experimental liquid compositions were prepared replacing different percentages of HEMA (conventional monomer used in commercial RMGICs) with hydroxypropyl-methacrylate (HPM) and/or tetrahydrofurfuryl-methacrylate (THFM), which are known to have better biocompatibility. Moreover, two commercial materials (Fuji-Plus and RelyX) and two compositions, based on these (home), were included as controls. Monomer release of all materials (commercial, home and experimental) were tested using high-performance liquid chromatography (HPLC) methods after immersing discs in deionized-water (DW) or ethanol:DW. Cytotoxicity of the materials extracts was tested on normal human oral fibroblast line (NHOF-1) using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. ResultsThree experimental materials containing THFM (F3, R3 and R4) showed less or similar monomer release compared to corresponding commercial products. Furthermore, two experimental materials (F3 and F4) showed similar effects on NHOF-1 cells compared to the negative control medium. SignificanceThe lower monomer release and higher cell viability of some experimental THFM compositions are encouraging. THFM partially replacing HEMA is potentially a suitable alternative for producing biocompatible RMGICs.

Evaluation of the Water Sorption and Solubility Behavior of Different Polymeric Luting Materials.

Objective: The study evaluated the water sorption (WSP) and water solubility (WSL) characteristics of different luting agents over a 180-day water storage period. Materials and Methods: Nine luting materials, i.e., conventional resin cement: Panavia F (PF), Rely X ARC (RA), self-adhesive resin cement: Rely X Unicem (RU), Breez (BZ), Maxcem Elite (MX), BisCem (BC) and resin-modified glass ionomer cement: FujiCem (FC), FujiPlus (FP) Rely X luting plus (RL) were assessed and fifty-two-disc specimens of each material were fabricated. All specimens were desiccated until a constant weight (W0) was reached. Thirteen specimens for each luting material were then randomly assigned to one of the four water immersion periods (7, 30, 90, and 180 days). After each period, the specimens were removed from the water and weighed to get W1. The samples were again desiccated for a second time and W2 was measured. Both WSP and WSL were determined by the following equations: WSP (%) = (W1 − W2) × 100/W0 and WSL (%) = (W0 − W2) × 100/W0. Assessments were performed following ISO standards. ANOVA was used to assess the effect of luting agent and time period on water sorption and solubility. Pair-wise comparisons were adjusted using Tukey’s multiple comparison procedure. A significance level of 0.05 was used for all statistical tests. Results: The highest mean WSP and WSL (WSP/WSL) were demonstrated by resin-modified glass-ionomers (RL 18.32/3.25, FC 17.08/4.83, and FP 14.14/1.99), while resin luting agents showed lower WSP and WSL results (PF 1.6/0.67 and RA 1.76/0.46), respectively. The self-adhesive agents exhibited a wide range of WSP and WSL values (RU 1.86/0.13, BZ 4.66/0.93, and MX 3.68/1.11). Self-adhesive cement showed lower WSP and WSL compared with the resin-modified glass-ionomers (p < 0.05). All the materials reached equilibrium after 90-days. Conclusions: Resin-based luting materials have the lowest sorption and solubility. Rely X Unicem self-adhesive luting materials were comparable to resin luting materials for WSL and WSP. Resin-modified glass-ionomer showed the highest water sorption and solubility compared with both resin and self-adhesive materials.

Biocompatible orthodontic cement with antibacterial capability and protein repellency

BackgroundWhite spot lesions (WSLs) often occur in orthodontic treatments. The objectives of this study were to develop a novel orthodontic cement using particles of nano silver (NAg), N-acetylcysteine (NAC) and 2-methacryloyloxyethyl phosphorylcholine (MPC), and to investigate the effects on bonding strength, biofilms and biocompatibility.MethodsA commercial resin-modified glass ionomer cement (RMGIC) was modified by adding NAg, NAC and MPC. The unmodified RMGIC served as the control. Enamel bond strength and cytotoxicity of the cements were investigated. The protein repellent behavior of cements was also evaluated. The metabolic assay, lactic acid production assay and colony-forming unit assay of biofilms were used to determine the antibacterial capability of cements.ResultsThe new bioactive cement with NAg, NAC and MPC had clinically acceptable bond strength and biocompatibility. Compared to commercial control, the new cement suppressed metabolic activity and lactic acid production of biofilms by 59.03% and 70.02% respectively (p < 0.05), reduced biofilm CFU by 2 logs (p < 0.05) and reduced protein adsorption by 76.87% (p < 0.05).ConclusionsThe new cement with NAg, NAC and MPC had strong antibacterial capability, protein-repellent ability and acceptable biocompatibility. The new cement is promising to protect enamel from demineralization during orthodontic treatments.

Monomer Conversion, Dimensional Stability, Biaxial Flexural Strength, Ion Release, and Cytotoxicity of Resin-Modified Glass Ionomer Cements Containing Methacrylate-Functionalized Polyacids and Spherical Pre-Reacted Glass Fillers.

The aim of this study was to prepare RMGICs for pulp protection that contain polyacids functionalized with methacrylate groups (CMs) to enable light-activated polymerization without the need for toxic 2-hydroxyethyl methacrylate (HEMA) monomers. The effects of using CM liquids with 0 or 5 wt% HEMA on the physical/mechanical properties and cytotoxicity of the experimental RMGICs were assessed. Spherical pre-reacted glass fillers (SPG) were used as the powder phase. The experimental RMGICs were prepared by mixing SPG with CM liquid (0 wt% HEMA, F1) or CMH liquid (5 wt% HEMA, F2). Commercial materials (Vitrebond, VB; TheraCal LC, TC) were used for the comparisons. The degree of monomer conversion and fluoride release of both F1 and F2 were significantly lower than those of VB. F1 showed comparable biaxial flexural strength with VB but higher strength than TC. The dimensional stability (mass/volume changes) of the experimental materials was comparable with that of the commercial materials. F1 and F2 exhibited higher Sr/Ca ion release and relative cell viability than VB. The use of CMH liquid reduced the strength but enhanced the fluoride release of the experimental RMGICs. In conclusion, the experimental RMGICs showed comparable strength but lower cytotoxicity compared to the commercial RMGICs. These novel materials could be used as alternative materials for pulp protection.

An in-vitro comparative evaluation of microleakage between giomer, compomer, composite and resin-modified GIC

Introduction: The marginal ingress of oral fluids and bacteria between the tooth – restoration interface is termed as microleakage or marginal leakage. The ability to maintain an unfailing margin improves the durability of a restoration to a large extend. Aim: Aim of this study was to evaluate microleakage of a Giomer, Hybrid composite, Compomer and Resin Modified Glass Ionomer Cement (RMGIC) along the enamel and cemental margins of class V cavities. Materials and Methods: This in-vitro study was performed on 80 human maxillary and mandibular premolars which were extracted for orthodontic reasons. Class V cavities were prepared on the buccal surfaces of teeth centered on the Cemento Enamel Junction (CEJ). Teeth were divided into four groups of 20 each and restored with RMGIC, Giomer, Compomer and Hybrid composite and were subjected to thermocycling. Teeth were then immersed in 0.5% Methylene blue dye for 24 hours. They were sectioned longitudinally from the middle of cavity into mesial and distal parts. The sections were observed under stereomicroscope(SM) to evaluate microleakage at both enamel and cemental margins. Depth of dye penetration was measured using a scoring system. Statistical Analysis: The data was analysed using the one-way ANOVA (Analysis of variance) test. The result is considered statistically significant if the ‘p’ value obtained is Results: The microleakage values of Giomer, Compomer and Hybrid Composite do not differ significantly from each other at the enamel margins while the microleakage of RMGIC is significantly higher than the other three materials (p Conclusion: At the enamel margins, giomer, compomer and hybrid composite showed comparable microleakage values which were significantly lower than RMGIC. At the cemental margins, compomer and hybrid composite showed significantly lower microleakage values compared to giomer and RMGIC. All materials exhibited greater microleakage at the cemental margins than at the enamel margins.

Comparative Evaluation of Tensile and Compressive Strength Of Cention N And Resin Modified Glass Ionomer Cements

Comparative Evaluation of Tensile and Compressive Strength Of Cention N And Resin Modified Glass Ionomer Cements

Clinical behavior of bioactive glass ionomer (45S5) in moderate caries injuries: Study protocol of a clinical trial

Bioactive materials that are capable of releasing remineralizing ions may be an interesting alternative treatment to prevent the development of carious lesions. The purpose of this study is to evaluate the effectiveness of the association of 45S5 with resin-modified glass ionomer cement (GIC-MR) for conservation and prevention of the progression of initial carious lesions in permanent molars. A total of 36 patients, aged 8 to 14 years, with at least two permanent molars homologous with ICDAS (International Caries Detection and Assessment System) 3 or 4 will be selected to participate in a clinical study of the split-mouth type. The DLF-T (Decayed, Lost and Filled Teeth index), ICDAS, BOP (Bleeding on probing), and VPI (Visible Plaque Index) will be analyzed. A complementary radiographic exam will be performed to assess the dentin underlying lesion. The selected teeth will be randomly assigned into two groups: GIC-MR and GIC-MR + 45S5. Parameters such as retention, the clinical performance of materials, and caries evolution will be evaluated into the two studied groups. Two calibrated evaluators will perform clinical, radiographic, and microscopic evaluations at one, six, 12, and 24 months of follow-up. The results obtained will be evaluated using a Chi-square test. The intention-to-treat protocol will be followed. The results of this study will help to assess the behavior of a bioactive glass ionomer in lesions with enamel microcavities. Innovative research projects, such as the one described here, are needed to determine whether new materials can be used as a treatment alternative.

Atraumatic restorative treatment

Dental caries is a sugar-dependent disease that damages tooth structure and, due to loss of mineral components, may eventually lead to cavitation. Dental caries is the most prevalent disease worldwide and is considered the most important burden of oral health. To overcome the limitations of conventional restorative treatment, the Atraumatic Restorative Treatment (ART) was developed, mainly for treating caries in children living in under-served areas of the world where resources and facilities such as electricity and trained manpower are limited. ART is a minimally invasive approach which involves removal of decayed tissue using hand instruments only, without use of anaesthesia and electrically driven equipment, and restoration of the dental cavity with an adhesive material (glass ionomer cement (GIC), composite resins, resin-modified glass-ionomer cement (RM-GICs) and compomers). The ART approach so far has mainly used high-viscosity glass-ionomer as the sealant and restorative material.

Evaluation of Shear Peel Bond Strength of Different Adhesive Cements Used for Fixed Space Maintainer Cementation: An In Vitro Study.

Aim and objectiveThis study aims to compare the retentive strength of different adhesive cements used for band cementation of fixed space maintainer by comparing the shear peel bond strength and mode of failure for each adhesive material using three different adhesive cements.Materials and methodsEighty intact extracted teeth were used to assess the shear peel bond strength. Preformed bands were adapted to each tooth. Three cements compared in this in vitro study are glass ionomer cement [Ketac Cem radiopaque (3M ESPE)], resin-modified glass ionomer cement [RelyX luting 2(3M ESPE)], and self-adhesive resin cement [RelyX U200 (3M ESPE)]. The teeth were randomly divided to four groups of 20 samples each. All samples were stored at 37°C for 24 hours before testing. All specimens were tested in a tensile mode using a universal testing machine to determine shear peel bond. After debonding procedure, each specimen was visually assessed at the site of cement.ResultsThe results of our study showed that the greatest resistance to decementation was shown by self-adhesive resin cement (256.85 N) followed by resin-modified GIC (165.40 N) and GIC (127.40 N) (p < 0.001). Self-adhesive resin cement has the greatest shear peel bond strength (2.36 MPa) followed by resin-modified GIC (1.53 MPa), conventional GIC (1.22 MPa), and bands without cementation (0.29 MPa) (p < 0.001). In terms of adhesive remnant index (ARI) scores, it was seen that the decementation of bands of both conventional GIC and self-adhesive resin cements occurred at the band/enamel interface. However, resin-modified GIC showed varied results in the ARI scores.ConclusionThe findings of our study suggest that self-adhesive resin cements can be used for cementation of bands of fixed space maintainers. However, further research with short-term and long-term data is required to evaluate the ability of these cements for its application in vivo.How to cite this articleKaur J, Singh A, Sadana G, et al. Evaluation of Shear Peel Bond Strength of Different Adhesive Cements Used for Fixed Space Maintainer Cementation: An In Vitro Study. Int J Clin Pediatr Dent 2021;14(2):175–179.

Evaluation of Adhesive Bond Strength, and the Sustained Release of Fluoride by Chitosan-infused Resin-modified Glass Ionomer Cement: An In Vitro Study

Aim and objectiveTo evaluate the adhesive bond strength, and sustained release of fluoride in chitosan (CH)-infused RMGIC.Materials and methodsTwenty caries-free human permanent premolar teeth, extracted for orthodontic purposes, were cleaned and stored in thymol solution. The crown of each tooth was cut into two halves and RMGIC (n = 10) and CH-infused RMGIC (n = 10) was placed between the two halves of the crown. The tooth was then stored in 10 mL of artificial saliva for a period of 30 days. The fluoride levels of the saliva were checked on the 15th- and the 30th-day using ion chromatography. The adhesive bond strength was checked on the 30th day using a universal testing machine.ResultsThis study has shown that the bond strength of RMGIC was not affected by the inclusion of CH in it. Whereas, the sustained fluoride release of CH-modified RMGIC indicated that the fluoride release of CH-RMGIC was 8.47% >RMGIC at the end of 15 days, and, 39.68% >RMGIC at the end of 30 days.ConclusionThe inclusion of CH in RMGIC does not alter its bond strength, while it does cause a greater release of fluoride.Clinical significanceIn progression with these results, the inclusion of CH in RMGIC could provide desirable properties like mechanical reinforcement effects and catalytic effects on the fluoride release and growth factors.How to cite this articlePatel A, Dhupar JKMS, Jajoo SS, et al. Evaluation of Adhesive Bond Strength, and the Sustained Release of Fluoride by Chitosan-infused Resin-modified Glass Ionomer Cement: An In Vitro Study. Int J Clin Pediatr Dent 2021;14(2):254–257.

The Effect of Dentin Bonding and Material Thickness on the Flexural Properties of a Lithium-Disilicate Glass-Ceramic.

Thanks to adhesive techniques and strengthened glass ceramics, ultrathin bonded occlusal veneers have been recently introduced. However, since a universally accepted thickness limit for ultrathin ceramics has yet to be established, their resistance to fracture needs to be better investigated. The purpose of this in vitro study was to evaluate the effect of dentin bonding on the flexural properties (ie, fracture load and flexural strength) of a lithium-disilicate (LD) glass ceramic when used in thicknesses equal to or less than the manufacturer's recommendations for occlusal restorations. A total of 96 dentin slices (2.0 mm thick and 15 mm long) were obtained by sectioning bovine teeth along their long axes. LD slices of different thicknesses (1.5 mm/1.3 mm/1.0 mm/0.8 mm/0.6 mm) and 15 mm in length were cut from CAD/CAM LD blocks (IPS e.max CAD-C16). In each of 5 experimental groups, 16 dentin slices were adhesively luted to 16 LD slices (n = 16) of the same thickness, in order to create 16 bi-layered dentin-LD bonded assemblies. In the control group, the 16 remaining dentin slices were conventionally cemented to 1.5-mm-thick LD slices (n = 16) using a resin-modified glass-ionomer cement (FujiCEM 2). All dentin-LD assemblies were cut perpendicularly to their joint interface, in order to obtain 1-mm-wide, 15-mm-long bi-layered prismatic beams, having the following final thicknesses: for the 5 experimental groups, 2 mm (dentin layer) + 1.5 mm/ 1.3 mm/1.0 mm/0.8 mm/0.6 mm (LD layer); for the control group, 2 mm (dentin layer) + 1.5 mm (LD layer). All prismatic beams were subjected to a three-point bending test (14-mm span, load applied on the LD side). Fracture loads (N) and flexural strengths (MPa) were recorded. Data were analyzed using one-way ANOVA on ranks tests (α = 0.05). The correlations between the recorded flexural strengths and the dentin:LD thickness ratio and between the flexural strength and the luting strategy were also investigated. The failure modes were observed and classified. No statistically significant differences were recorded between the conventionally luted control group (LD thickness 1.5 mm; fracture load 35.26 N; flexural strength 60.44 MPa) and the thinnest adhesively luted experimental group (LD thickness 0.6 mm; fracture load 28.97 N; flexural strength 90.01 MPa) in terms of fracture load and flexural strength. A fracture involving both the dentin and the LD of the bi-layered prismatic beam, but without any debonding between the LD and the dentin substrates of the broken specimen, was the most common failure mode observed on the adhesively luted samples. Compared to conventional cementation, when LD is bonded to dentin, the flexural properties of the whole system are improved, and the two different substrates seem to behave like a single unit. Once adhesively luted, 0.6-mm-thick LD has the same fracture load and flexural strength as that of the conventionally luted 1.5-mm-thick LD.

Sealing of cavitated occlusal carious lesions in the dentine of deciduous molars: a two-year randomised controlled clinical trial.

This two-arm, parallel-group, tooth-randomised, controlled noninferiority clinical trial aimed to compare survival rates between the sealing and restoring of cavitated occlusal carious lesions in dentine [International Caries Detection and Assessment System (ICDAS) 5] of deciduous molars using resin-modified glass-ionomer cement (RMGIC) and to assess caries progression radiographically. A total of 68 molars with ICDAS 5 occlusal lesions were randomly allocated into two groups, a sealing group (n = 31), in which RMGIC was placed directly over the carious lesion, and a restoration group (n = 37), in which a restoration with the same material was placed after selective caries removal. During the baseline and follow-up visits, dental caries was registered and caries activity was assessed according to a visuotactile criterion. At baseline, patient caries status (dmf-t) and cavity depth and extent (mesiodistal and buccolingual) were measured before RMGIC placement. An independent and blinded examiner evaluated the treated teeth using the USPHS criteria after one and two years. Standardised interproximal radiographs were taken for caries progression assessments. During the follow-up period, no lesion progression was observed radiographically. After one year (n = 60; 27 sealed and 33 restored) and two years (n = 48; 23 sealed and 25 restored) of follow-up, the treatment success rates were 78.8% and 76.0% in the restoration group and 59.3% and 47.8% in the sealing group, respectively. Multivariate Cox regression showed that lesions smaller than 2mm in the mesiodistal extent were less prone to fail after one year (p = 0.03). However, survival curves (log-rank test) were statistically significantly different only after two years (p < 0.001). Sealing ICDAS 5 occlusal lesions of deciduous molars using RMGIC achieved lower survival rates than restorations. Both sealing and restoration effectively arrested caries progression for two years. Clinical relevance Sealing dentine carious lesions can be effective for treating lesions involving the inner and outer half of the dentine. Ultraconservative treatments can arrest carious lesions presenting obvious cavitation in primary molars. ReBEC Register no. RBR-225n35.

Rheological Properties, Surface Microhardness, and Dentin Shear Bond Strength of Resin-Modified Glass Ionomer Cements Containing Methacrylate-Functionalized Polyacids and Spherical Pre-Reacted Glass Fillers.

The aim of this study was to prepare experimental resin-modified glass ionomer cements (RMGICs) containing low levels of hydroxyethyl methacrylate (HEMA) for pulp protection. Liquid and powder phases of the experimental RMGICs were polyacid functionalized with methacrylate groups and spherical pre-reacted glass fillers (SPG). Two types of liquid phase containing 0 wt. % HEMA (CM liquid) or 5 wt. % HEMA (CMH liquid) were formulated. The experimental RMGICs were prepared by mixing SPG fillers with CM liquid (F1) or CMH liquid (F2). Rheological properties were examined using a strain-controlled rheometer (n = 5). The Vickers microhardness (n = 5) and dentin shear bond strength (SBS) (n = 10) of the materials were tested. Commercial pulp protection materials (Vitrebond and TheraCal LC) were used as comparisons. The viscosity and surface microhardness of F1 (22 m Pa·s, 18 VHN) and F2 (18 m Pa·s, 16 VHN) were significantly higher than those of Vitrebond (6 mPa·s, 6 VHN) and TheraCal (0.1 mPa·s, 7 VHN). The SBS of F1 (10.7 MPa) and F2 (11.9 MPa) was comparable to that of Vitrebond (15.4 MPa) but higher than that of TheraCal LC (5.6 MPa). The addition of 5 wt. % HEMA showed no significant effect on viscosity, surface microhardness, or SBS of the experimental RMGICs. The experimental materials showed higher viscosity and microhardness but similar SBS when compared with the commercial RMGIC.

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.