Clinical Performance of Glass Ionomer Cement in Load-Bearing Restorations: A Systematic Review

Glass ionomer cement (GIC) is a self-adhesive dental restorative material composed of a polyacrylic acid liquid and fluoro-aluminosilicate glass powder. It is commonly used for cementation during dental restoration. This study aimed to systematically review the existing literature regarding the clinical performance of GIC in load-bearing dental restorations. A comprehensive literature search was conducted in EBSCO, PubMed, Embrace, and Cochrane databases. Only randomized controlled trials (RCTs) were included in the search, and a broad search technique was used, where inclusion and exclusion criteria were applied. After a thorough evaluation, 12 RCTs were extensively reviewed, and whether GIC is suitable for load-bearing restorations was determined. Significant variations in staining surface or margin, color match, translucency, esthetic anatomical form, retention, material fracture, marginal adaptation, surface luster, occlusal contour, wear, and approximal anatomical form indicated the unsuitability of GIC. By contrast, significance differences in patient view and periodontal response indicated that GIC is suitable. No significant differences in postoperative sensitivity, recurrence of caries, or tooth integrity were observed. Nevertheless, the results of the review demonstrated that the clinical performance of GIC is comparable to that of traditional restorative materials with regard to the parameters analyzed. GIC is a suitable restorative material for load-bearing restorations regarding surface margin, esthetic anatomical form, material retention and fracture, marginal adaptation, occlusal contour, wear, and approximal anatomical form. It reduces other parameters, such as postoperative sensitivity, recurrence of caries, and tooth integrity.

In vitro characterization of a novel resin-based restorative material containing alkaline fillers

OBJECTIVE

In this study, a comparative evaluation of the physicochemical properties of Cention N and other direct restorative materials was performed. Three restorative materials-a resin-modified glass ionomer (Fuji II LC), an alkasite-based resinous material (Cention N), and a resin composite (Tetric N Ceram)-were characterized in terms of degree of conversion, Knoop hardness number (KHN) ratio, flexural strength, elastic modulus, water sorption, water solubility, microshear bond strength to dentin, immediate microleakage, and radiopacity.

METHODOLOGY

The microshear bond strength to dentin and microleakage of Cention N were evaluated with and without the application of an adhesive system (Tetric N Bond Universal). A one-way ANOVA test was used to analyze the data in terms of degree of conversion, KHN ratio, water sorption, water solubility, microshear bond strength to dentin, and radiopacity. A two-way ANOVA test (carried out considering the material type and ethanol aging as factors) was used to analyze the data in terms of flexural strength and elastic modulus. The Kruskal-Wallis test was used to statistically analyze the data on microleakage. A significance level of α=0.05 was used for all tests.

RESULTS

Fuji II LC was found to have the highest degree of conversion, water sorption, and microleakage, as well as the lowest flexural strength. Cention N had the highest solubility; when used with an adhesive system, it achieved bond strength and microleakage similar to those of the Tetric N Ceram composite. Tetric N Ceram had the highest degree of conversion, KHN ratio, and radiopacity. Conclusion: The properties of Cention N validate its efficacy as an alternative direct restorative material when used in conjunction with an adhesive system.

Effect of ethanolic extract of propolis on antibacterial and microshear bond strength of glass-ionomer restorations to dentin

Objectives

This study was conducted to evaluate the effect of ethanolic extract of propolis on antibacterial and microshear bond strength of glass ionomer restorations to dentin.

Materials and methods

Conventional glass ionomer cement (Equia forte, GC Tokyo, Japan), resin-modified glass ionomer (Fuji II LC, GC Tokyo, Japan) and propolis powder (dried extract from honey bees) materials were used in this study. Both conventional glass ionomer and resin-modified glass ionomer were modified by two different concentrations of ethanolic extract of propolis (10 % and 25 % EEP). For antibacterial test, Streptococcus mutans strain was spread on agar petri dishes using a sterile swab. Discs of both glass ionomer restorative materials (without adding EEP, with 10 % EEP and with 25 % EEP) were fabricated within the agar plates. Antibacterial activity was evaluated by measuring the inhibition zones around each disc. For microshear bond strength test, 60 healthy human permanent molars were prepared by cutting occlusal surface and expose the dentin at the height of contour of all teeth then conditioned using poly acrylic acid conditioner, both glass ionomer restorative materials (without adding EEP, with 10 % EEP and with 25 % EEP) were mixed and applied on conditioned dentin surface by using tygon tube. Microshear bond strength was evaluated by the universal testing machine.

Results

Two-way ANOVA test revealed that both glass ionomer type and different concentrations of EEP had significant effect on the antibacterial test results and microshear bond strength values (p < 0,05). Glass ionomer restorative material with 25%EEP had the highest antibacterial values whereas glass ionomer restorative material without modifications (control groups) had the lowest values. Resin-modified glass ionomer without any modification (control group) had the highest bond strength while resin-modified glass ionomer with 25%EEP had the lowest bond strength.

Conclusions

Incorporation of ethanolic extract of propolis to glass ionomer restorative material increases the antibacterial effects of both conventional GIC and RMGI. Inspite of this advantage, it seems that it has deleterious effect on microshear bond strength to dentin.

Concept of a Novel Glass Ionomer Restorative Material with Improved Mechanical Properties

The objective of this study was to transfer the concept of ductile particle reinforcement to restorative dentistry and to introduce an innovative glass ionomer material that is based on the dispersion of PEG-PU micelles. It was hypothesized that reinforcing a conventional glass ionomer in this way increases the flexural strength and fracture toughness of the material. Flexural strength and fracture toughness tests were performed with the novel reinforced and a control glass ionomer material (DMG, Hamburg, Germany) to investigate the influence of the dispersed micelles on the mechanical performance. Transmission electron microscopy was used to identify the dispersed micelles. Fracture toughness and flexural strength were measured in a 3-point-bending setup using a universal testing machine. Before performing both tests, the specimens were stored in water at 37 °C for 23 h. The fracture toughness (MPa∙m0.5) of the novel glass ionomer material (median: 0.92, IQR: 0.89-0.94) was significantly higher than that of the control material (0.77, 0.75-0.86, p = 0.0078). Significant differences were also found in the flexural strength (MPa) between the reinforced (49.7, 45.2-57.8) and control material (41.8, 40.6-43.5, p = 0.0011). Reinforcing a conventional glass ionomer with PEG-PU micelles improved the mechanical properties and may expand clinical applicability of this material class in restorative dentistry.

Evaluation of the effect of nano-graphene oxide on shear bond strength of conventional and resin-modified glass ionomer cement

OBJECTIVES

Recently, nano-graphene oxide (nGO), a material with unique mechanical properties, has been introduced to improve the properties of glass ionomer cement (GIC). The purpose of this study was to investigate the effect of adding nGO on the shear bond strength (SBS) of conventional (CGIC) and resin-modified GIC (RMGIC).

METHODS

Sixty intact molars were mounted and their occlusal surface was cut at a depth of 1 mm below the dentinoenamel junction. 1 wt.% and 2 wt.% of nGO (US Research Nanomaterials, Inc.) were added to CGIC and RMGIC (GC Corporation). The samples were randomly divided into six groups (n = 10), including 1: CGIC,  2: CGIC + 1% GO, 3: CGIC + 2% GO, 4: RMGIC, 5: RMGIC + 1% GO, and 6: RMGIC + 2% GO. Plastic molds were placed on the surface of the dentin pretreated with 10% polyacrylic acid (GC Corporation) and filled with prepared cement according to the manufacturer's instruction. After 24 h of storage in an incubator, the SBS test was done by the universal testing machine. Data were analyzed using two-way analysis of variance and post hoc Tukey tests (p < .05).

RESULTS

In the group of CGIC, mean SBS was significantly lower than all other study groups (p < .001), and groups 5 (RMGIC + 1% GO) and 6 (RMGIC + 2% GO) showed significantly higher values compared to all other study groups (p < .001). However, the difference between groups 2 and 3, as well as the difference between groups 5 and 6, was not significant (p = .999 andp = .994, respectively). RMGI groups had significantly higher SBS than their corresponding CGIC groups.

CONCLUSIONS

The addition of 1% and 2% nGO significantly increased the SBS of CGIC and RMGIC to the dentin, which can be considered as a promising point for wider clinical application of this material.

Retrospective Clinical Evaluation of RMGIC/GIC Class V Restorations

The aim of this retrospective study was to evaluate the clinical performance of glass-ionomer cement (GIC) and resin-modified glass-ionomer cement (RMGIC) materials in Class V carious cervical lesions restored by dental students. Ninety-six (96) restorations performed with either GIC (Fuji IX) (n = 39) or RMGIC (Fuji II LC) (n = 57) were evaluated using the modified USPHS criteria by two independent investigators at two follow-up evaluations (two years apart). The Fisher statistical test was used to compare USPHS criteria and examine significant differences, with a significance level set at p < 0.05. The Kaplan-Meier algorithm was used to calculate the survival probability. The overall success rate of Class V restorations was 72.9% at the second follow-up evaluation, with restorations ranging in age from 2.5 to 3.5 years. The RMGIC (Fuji II LC) restorations exhibited a significantly higher overall success rate compared to the GIC (Fuji IX) restorations (p = 0.0104). Significant differences were observed in retention (p = 0.0034) and color match (p = 0.0023).

Phytic Acid: A Novel Dentine Conditioning Agent for Glass Ionomer Cement Restorations: An In Vitro Scanning Electron Microscopic Study

Background

Various dentin conditioners have been recommended to enhance the bond strength of glass ionomer cement (GIC) to dentin. The purpose of the in vitro study was to determine the efficacy of three dentin conditioners on the microshear bond strength of GIC and the failure patterns of the restoration, as well as the efficacy of removing the smear layer using a scanning electron microscope (SEM).

Materials and Methods

Eighty healthy mandibular premolars were cleaned, isolated, and divided into four groups (n = 20). Flat coronal dentinal surfaces were accomplished by removing the occlusal surface of the crowns. Each group received the following treatment: group 1 with 10% polyacrylic acid; group 2 with 10% ethylenediaminetetraacetic acid (EDTA); group 3 with 1% phytic acid; and group 4 with no conditioning (control). High-strength Fuji IX GIC was applied to the dentin, and samples were thermocycled and de-bonded with a crosshead speed of 0.5 mm/min employing a shear force. A stereomicroscope and a SEM were used to examine the dentin surface at magnifications of 2000× and 5000×. One-way analysis of variance (ANOVA), Tukey's post hoc test, and Chi-squared test were used to assess data on microshear bond strength, smear layer removal, and failure modes.

Results

The bond strength of group 4 was statistically highly significant (P ≤ 0.001) compared to the other groups. However, the differences between groups 2 and 3 were insignificant. Mixed pattern of failure was the least in group 3 (IP6). In group 3, the SEM photomicrograph revealed open dentinal tubules with complete removal of the smear layer.

Conclusion

The results of the present study affirm that phytic acid enhances the bond strength of GIC restorations and removal of smear layer to a level comparable to EDTA as a dentin conditioner.

Microshear Bond Strength of Bioactive Materials to Dentin and Resin Composite

OBJECTIVES

 The aim of this study was to comparatively evaluate microshear bond strength (μSBS) of bioactive ionic resin composite and resin-modified glass ionomer liner (RMGI) to dentin and resin composite.

MATERIALS AND METHODS

 The enamel of 11 posterior molar teeth was removed to expose dentin and then placed in acrylic blocks. Each specimen received three microcylindrical Tygon tubes filled with bioactive ionic resin composite (Activa Bioactive base/liner (PULPDENT: , MA, USA)), RMGI (Riva light cure SDI LTD, Bayswater, Australia), and resin composite (Filtek Z350xt, MN, USA). Composite discs (n = 11) were fabricated from nanofilled resin composite (Filtek Z350xt) and then fixed in acrylic blocks. Each specimen received two microcylindrical Tygon tubes filled with Activa Bioactive base/liner and Riva RMGI. All specimens were mounted individually to universal testing machine for μSBS test. Failure modes were analyzed using stereomicroscope and scanning electron microscope.

RESULTS

 Filtek Z350xt nanofilled resin composite showed the highest μSBS values. No statistical significant difference was found between Activa Bioactive and Riva RMGI (p > 0.05).

CONCLUSION

 Bioactive ionic resin composite liner exhibited similar bond strength as RMGI to dentin and resin composite.

The effect of silver diamine fluoride on the bond strength of glass ionomer to the enamel of primary teeth

Background

Dental caries is a disease which is caused by the acidic by-products of the metabolic processes of dental plaque. Silver components are one of the clinical solutions to prevent caries. This study aimed to investigate the effect of silver diamine fluoride (SDF) application on the shear bond strength of glass ionomer to primary teeth enamel.

Materials and Methods

In this in vitro study, a total of 48 anterior sound primary teeth were randomly divided into four groups (n = 12). The control group (G1) consisted of healthy primary teeth, and the three experimental groups (G2-G4) were composed of demineralized primary teeth. The second group did not undergo SDF treatment, the third group underwent SDF treatment, and the fourth group underwent SDF treatment plus polishing. Glass ionomer cylinders were bonded to all specimens and subsequently tested by a universal testing machine to measure the glass ionomer shear bond strength. The type of fracture was examined by a stereomicroscope. Data analysis was carried out using the SPSS 22 statistical software. Data were analyzed by one-way analysis of variance and posthoc Tukey tests (α =0.05).

Results

The mean shear bond strength of the glass ionomer was significantly higher in the control group than in the other three groups (P < 0.05). The mean shear bond strength of glass ionomer was significantly higher in the SDF-treated group than in the non-SDF treated and SDF-treated and polished groups (P < 0.05).

Conclusion

Although the glass ionomer bond strength to sound enamel was higher than other groups by a significant margin, the application of SDF increases the shear bond strength of the glass ionomer to remineralized white spot enamel in primary teeth.

Evaluation of the clinical impact and In Vitro antibacterial activities of two bioactive restoratives against S. mutans ATCC 25175 in class II carious restorations

Background

Streptococcus mutans is a Gram-positive opportunistic bacterial pathogen and that causes dental caries and then restorative treatment remains the best clinical practice approach to repair and prevent dental caries.

Aims

This study compared the antimicrobial performance of resin modified glass ionomer cement (RM-GIC) and ACTIVA restoratives by evaluating the S. mutans count, pH levels, and plaque index (PI) scores before and on the 7^th day of restoration, and then determined the antimicrobial activities against S. mutans ATCC 25175 in both restoratives in vitro.

Materials and Methods

Seventy-eight eligible Saudi female participants, with class II carious lesions, were randomly distributed into RM-GIC and ACTIVA restorative groups. We evaluated the S. mutans count by the serial dilution technique and salivary pH by using a portable pH meter. The PI scores were determined by Silness-Löe method and the antibacterial activity by the agar well diffusion method. Statistical analysis of normality distribution was performed with the Kolmogorov-Smirnov and the difference between groups was an analysis by paired t-test. In addition, the independent sample was compared with the independent samples t-test.

Results

Both groups reduced the S. mutans count, pH acidity, and PI scores, and this reduction was statistically significant on the 7^th day of restoration (P < 0.05), preference for ACTIVA. The in vitro antibacterial activity against S. mutans ATCC 25175 showed a non-significant difference between both bioactive restorative materials (P < 0.05).

Conclusion

The novel application of ACTIVA restorative material is a promising option for patients at risk of caries.

Resin-modified glass ionomer enriched with BIOGLASS: Ion-release, bioactivity and antibacterial effect

Developing dental materials for the prevention of remineralization or demineralization is important for high-risk caries patients. This study aimed to evaluate the physicochemical and microbiological effects of adding 45S5 bioglass to resin-modified glass ionomer cement (RMGIC). Samples belonged to the following groups: GIC: conventional glass ionomer cement (Vitro Fil), RMGIC: resin-modified GIC (Vitro Fil LC), and RMGIC/45S5: RMGIC with 10% (wt %) of 45S5. Changes in pH and release of fluoride, calcium, and phosphorus ions under acidic (pH 4) and neutral (pH 7) pH conditions were evaluated. Antibacterial activity was verified based on colony-forming units. Material sorption and solubility were analyzed after bacterial exposure. After 28 days, the bioactivity of the materials was evaluated using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis of variance, post hoc Scheffe, and Tukey (α = 0.05) tests were employed for statistical analysis. RMGIC/45S5 showed higher alkalization activity, calcium release at pH 4 and 7, and sorption than GIC and RMGIC (p < .05). Release of phosphorus and fluoride at pH 4 and 7 was higher for GIC than that for RMGIC and RMGIC/45S5 (p < .05). RMGIC/45S5 showed higher values than RMGIC (p < .05). However, antibacterial activity did not differ among the groups. Precipitates of calcium and phosphorus were visualized in RMGIC/45S5 samples via SEM/EDS. These results indicate that the RMGIC/45S5 promotes alkalization and increases the release of calcium, phosphorus, and fluoride ions, resulting in precipitate deposition rich in calcium and phosphorus, thereby being a promising option to improve the bioactivity of RMGIC.

Shear Bond Strength and Fluoride Release of a Universal Adhesive: An In-Vitro Study on Primary Teeth

This investigation aimed to assess the shear bond strength and fluoride-releasing capabilities of Clearfil Universal Bond Quick (Kuraray Noritake Dental Inc., Tokyo, Japan). Forty-four extracted primary molars were divided into two groups, and the enamel substrate was prepared for evaluating shear bond strength. Scotchbond (3M ESPE) and Clearfil UBQ were used to bond composite-to-enamel substrates in each group (n = 22). Shear bond strength was measured using a universal testing device and compared. Sixteen discs (6 mm diameter and 3 mm thickness) were fabricated from each Clearfil UBQ, Fuji IX, and Fuji II LC. Over the course of 30 days, each materials' fluoride release was examined and compared using ion analysis. Results revealed that Clearfil UBQ had statistically similar shear bond strength to Scotchbond. Between the three materials, Clearfil UBQ had the lowest fluoride release at baseline (0.11 ± 0.25) and the lowest cumulative fluoride release (0.12-0.27 ppm) over 30 days. Fuji IX had the highest fluoride release at baseline (19.38 ± 2.50) and cumulatively (40.87 ± 4.03 ppm), followed by Fuji II LC. We conclude that Clearfil UBQ and Scotchbond showed comparable bond strengths to the enamel. Fluoride release was seen in Clearfil UBQ in the initial two days of the 30-day period. The amount of fluoride release was significantly less than with glass ionomer cements.

Long Process Incus necrosis in Revision Stapedotomy: Retrospective Clinical Study

OBJECTIVES

We describe our experience with long process incus (LPI) necrosis in revision stapedotomy and discuss the different management methods proposed in the literature to identify surgical techniques that can lead to satisfactory results over time.

METHODS

Twenty-two stapedotomy revisions, in 21 patients with the necrosis of the long process of the incus, are performed from 1997 to 2017. In cases of erosion or minimal necrosis of LPI, a new prosthesis of the same type or an angled prosthesis was applied higher on the residual incus stump. In cases of partial necrosis of LPI, a Donaldson type ventilation tube reshaped and placed on the residual incus stump to stabilize prosthesis, or glass ionomer bone cement was used. In cases of subtotal necrosis of LPI, a cup piston prosthesis in polycel was applied on incus residual stump. Pre- and postoperative (≥1 year) pure tone audiometry was performed for all cases. Air conduction threshold, bone conduction (BC) threshold, and air-bone gap (ABG) were documented according to the American Academy of Otolaryngology Head and Neck Surgery Committee of Hearing and Equilibrium guidelines.

RESULTS

At 1-year follow-up, postoperative ABG was reduced to ≤10 dB in 13 (59%) cases and ≤20 dB in 19 (86.4%) cases. The mean postoperative ABG significantly decreased in each group. There was no significant change in postoperative BC thresholds, and there were no cases with postoperative SNHL.

CONCLUSION

Excellent functional results can also be achieved in cases of long incus process necrosis. The choice of technique should be considered according to the degree of necrosis. Piston replacement with the same type or angled type prosthesis, in cases of erosion or minimal LPI necrosis, and modified Donaldson type ventilation tube, in cases of partial LPI necrosis, provided excellent hearing results.

Effect of ultrasonic vibration on the presence of voids in core build-up materials

The core build-up procedure is utilized to restore teeth with limited remaining coronal tooth structure. However, voids have been observed radiographically within composite resin- and glass ionomer-based core build-ups, potentially compromising the mechanical strength of a fully restored tooth and requiring build-up replacement before a final restoration can be delivered. The purpose of this in vitro study was to determine whether applying ultrasonic vibration during core build-up placement reduces the presence of radiographically detectable voids. A total of 120 acrylic resin mandibular premolar analogs were fabricated using a 3-dimensional printer and randomly allocated into 4 groups (n = 30). Dual-cured composite resin or glass ionomer core build-ups were placed with or without vibration. The final build-ups were assessed radiographically and rated by 3 independent calibrated clinicians based on a 4-category scale for the severity of voids. In an ordinal logistic regression model with the void severity rating as the outcome, a significant interaction was found for glass ionomer, composite resin, and the use of ultrasonic vibration (P = 0.03). Vibration was associated with worse void severity ratings in glass ionomer specimens (P < 0.01). No effect of vibration was found in the composite resin specimens. The Fleiss kappa score (κ = 0.36) indicated fair agreement in all severity ratings among the 3 raters. These results suggest that the application of ultrasonic vibration during core build-up placement may not be clinically advantageous for improving restorative outcomes.

Five-year randomized clinical trial to evaluate the clinical performance of high-viscosity glass ionomer restorative systems in small class II restorations

OBJECTIVE

Evaluate and compare the 5-year clinical performance of three high-viscosity glass ionomer restorative materials in small class II restorations.

MATERIALS AND METHODS

Forty patients, each with four class II restorations, were enrolled in this trial. A total of 160 restorations were placed, 25% for each material, as follows: three high-viscosity conventional glass ionomer restorative systems (Ketac Universal Aplicap, EQUIA Forte and Riva Self Cure HV) and a microhybrid resin composite system (Filtek Z250). Clinical evaluation was performed at baseline and after 1, 3, and 5 years by two independent examiners using FDI criteria. Epoxy resin replicas were observed under scanning electron microscope (SEM) to examine surface characteristics. Data were analyzed with Kruskal-Wallis, Mann-Whitney U, Friedman, and Wilcoxon signed-rank tests (p < 0.05).

RESULTS

The success rates were 100% for resin composite, 97.4% for Ketac Universal, and 94.9% for both EQUIA Forte and Riva HV restorations. Statistically significant differences were observed between all groups in terms of surface luster and color match criteria (p < 0.05). Statistically significant changes were found over time for all criteria except for fracture of material, postoperative hypersensitivity, recurrence of caries, tooth integrity, periodontal response, adjacent mucosa, and oral health criteria (p > 0.05). SEM evaluations were in accordance with the clinical findings.

CONCLUSIONS

Although drawbacks in surface luster and color match appeared over the 5-year evaluation period, the three high-viscosity glass ionomer restorative materials provided successful clinical performance in small to medium sized class II cavities compared to microhybrid resin composite.

CLINICAL SIGNIFICANCE

Glass ionomer restorations exhibited clinical performance similar to that of microhybrid resin composite restorations in small class II cavities subsequent to 5-year evaluation.

Electrochemical sensors for oral biofilm-biomaterials interface characterization: A review

Important processes related to the interaction of the oral microbiome with the tooth surface happen directly at the interface. For example, the chemical microenvironment that exists at the interface of microbial biofilms and the native tooth structure is directly involved in caries development. Consequentially, a critical understanding of this interface and its chemical microenvironment would provide novel avenues in caries prevention, including secondary caries that often occurs at the interface of the dental biofilm, tooth structure, and dental material. Electrochemical sensors are a unique quantitative tool and have the inherent advantages of miniaturization, stability, and selectivity. That makes the electrochemical sensors ideal tools for studying these critical biofilm microenvironments with high precision. This review highlights the development and applications of several novel electrochemical sensors such as pH, Ca2+ , and hydrogen peroxide sensors as scanning electrochemical microscope probes in addition to flexible pH wire sensors for real-time bacterial biofilm-dental surface and dental materials interface studies.

Effect of Surface Pre-Reacted Glass Ionomer Containing Dental Sealant on the Inhibition of Enamel Demineralization

The effect of a surface pre-reacted glass ionomer (S-PRG)-containing sealant on the demineralization inhibition and remineralization of intact enamel adjacent to the sealant material was investigated. BeautiSealant (BTS, S-PRG sealant, Shofu), Teeth Mate F-12.0 (TMF, fluoride-releasing sealant, Kuraray Noritake Dental), and an experimental silica-filler sealant were investigated. After pH cycling for 10 days, the enamel surface adjacent to the sealant material was observed using confocal laser microscopy and scanning electron microscopy. The polymerized sealant disks were immersed in a demineralized solution (pH: 4.3) to measure pH change. The enamel specimens with polymerized sealant disks were additionally immersed in demineralized solution, followed by energy-dispersive X-ray spectroscopy. The demineralized area of BTS was significantly smaller than that of TMF and SS (p < 0.05). The surfaces adjacent to the sealant of TMF and SS were demineralized, while the surface of BTS was comparatively intact. An increase in pH values were observed in the BTS and TMF groups. Enamel surfaces presented an inhibition of demineralization for BTS and TMF, but not for SS. Fluoride uptake from the polymerized sealant was greater for BTS than for TMF. The S-PRG-containing sealant showed a buffering ability, demineralization inhibition, promotion of remineralization, and it can be advised for clinical applications.

Evaluation of a Method to Determine Wear Resistance of Class I Tooth Restorations during Cyclic Loading

The aim of this study was the development of a test regime to determine the wear resistance and predict the clinical performance of conventional glass ionomer cement (GIC) restorations in Class I tooth cavities. Cavities were prepared in excised human teeth and restored using three conventional glass ionomer restorative materials: DeltaFil, Fuji IX GP and Ketac Universal. The restored teeth were mechanically and thermally stressed using a chewing simulator with a maximum number of 1,200,000 load cycles. Besides determining the number of cycles achieved, the abrasion volume after termination of the chewing simulation was calculated using µCT images. All teeth restored with DeltaFil reached 1,200,000 cycles without any restoration failure. Only 37.5% of the restorations each with Ketac Universal and Fuji IX GP were able to achieve the maximum cycle number. A significant lower abrasion volume for restorations with DeltaFil compared to Ketac Universal (p = 0.0099) and Fuji IX GP (p = 0.0005) was found. Laboratory chewing simulations are a useful tool to study basic wear mechanisms in a controlled setting with in-vivo related parameters. DeltaFil shows an improved wear resistance compared to other conventional GICs, indicating the high potential of this material for long-lasting Class I restorations.

The Measurement of Contact Angle, pH, and Conductivity of Artificial Saliva and Mouthwashes on Enamel, Glass-Ionomer, and Composite Dental Materials

The aim of this study was to tackle the topic of appropriate recommendations for artificial-saliva and mouthwash usage. The contact angle, pH, and conductivity of two artificial saliva solutions, four mouthwashes, and their mixtures on enamel, glass-ionomer, and composite dental materials were measured. The measurements were conducted with a MATLAB algorithm to minimize human error. The obtained values for the contact angle were in the range from 7.98° to 52.6°, and they showed completely nonlinear and nonuniform behavior for all investigated liquids and on all investigated substrates. Results reveal statistically significant differences among all tested liquids on all investigated substrates (p < 0.05). pH values ranged from 1.54 to 7.01. A wide range of conductivity values were observed, from 1205µS/cm in the saliva-stimulating solution to 6679 mS/cm in the artificial saliva. Spearman’s test showed a moderate positive correlation between the pH and conductivity of the tested fluids (R = 0.7108). A comparison of the data obtained using Image J software and the MATLAB algorithm showed consistency, not exceeding 5% error. When an experiment uses human material and bioactive materials THAT are used in biomedicine as substrates, an additional definition of protocols is highly recommended for future research on this topic.

Clinical effectiveness of resin-modified glass ionomer-based fluoride varnish for preventing occlusal caries lesions in partially erupted permanent molars: A randomised active-controlled trial

BACKGROUND

Deep pits and fissures in partially erupted permanent molars are vulnerable to dental caries.

AIM

To assess the clinical effectiveness of resin-modified glass ionomer-based fluoride varnish (RMGI-F varnish: Clinpro XT™ varnish) in preventing occlusal caries lesions in partially erupted permanent first molars.

DESIGN

In this randomised active-controlled superiority trial with a single-blind parallel design, 74 children with 182 partially erupted first permanent molars were allocated into two groups: Group 1: RMGI-F varnish; and Group 2: GI sealant (active control), with an application of 0.1% sodium fluoride varnish for all other teeth. The primary outcome was ICDAS score ≥1 at 12 months of follow-up. Data were analysed using adjusted Chi-square test and GEE regression for binary outcomes.

RESULTS

Group 1 (15.7%) and Group 2 (13.8%) did not differ significantly in ICDAS ≥1 scores at 12 months of follow-up (adjusted χ²  = 0.373, p = .541). There was no significant difference in retention between Group 1 (48.3%) and Group 2 (20.7%) at 12 months of follow-up (adjusted χ²  = 0.1, p = .752). Mean application time per tooth (16 ± 5.9 vs 20.2 ± 5.4 min) was significantly different (t = 5.26, p = .014).

CONCLUSIONS

RMGI-F varnish was not superior to GI sealant in preventing occlusal caries lesions in partially erupted molars.

Effect of Different Concentrations of Silver Nanoparticles on the Quality of the Chemical Bond of Glass Ionomer Cement Dentine in Primary Teeth

Background: The nanotechnologies have been applied for dental restorative materials manufacturing such as glass ionomer cement, composites, tooth regeneration, and endodontic sealers. The study aimed to investigate the chemical bond of conventional glass ionomer cement and to evaluate the addition of different concentrations of silver nanoparticles (AgNPs) on the quality of the chemical bond of glass ionomer cement to primary dentin.

Methods: Silver nanoparticle (AgNP) powder was added in concentrations of 0.2, 0.4, and 0.6% to the conventional powder of GIC Fuji II. Then, the powder was added to the liquid and mixed with the recommended powder/liquid ratio of 3.6:1 g. The Fourier-transform infrared spectra (FTIR) of teeth with 0.2%, 0.4%, and 0.6% w/w of silver nanoparticles in GIC fills and the control tooth were obtained. The conventional glass ionomer was used as a control group. The control and the plain silver tooth were subjected to FTIR analysis using an ATR–FTIR spectrophotometer (ThermoFisher Scientific, Waltham, MA, United States) with zinc selenide (ZnSe) ATR crystal (attenuated total reflection) and OPUS v7.5 software. All spectra were recorded in the range of 500–3,500 cm⁻¹ in the transmission mode with an ATR module.

Results: The AgNPs added at 0.2, 0.4, and 0.6% concentration to GIC provided some information in the context of bond interaction with the dentin. Various bond peaks were seen for calcium, carbonate, phosphate, and amide. In our study, only the amide and phosphate were generated. The amide peaks were almost similar to the control, 0.2%, 0.4%, and 0.6%, with the peaks in the range of 1250–1650 cm⁻¹. There was a clear shift in the phosphate peak from the control, 0.2, and 0.4%, which was about 1050 cm⁻¹, whereas for 0.6%, there was a clear shift from 1050 cm⁻¹ to 880 cm⁻¹.

Conclusion: GIC supplemented with AgNPs showed that a concentration above 0.4% of AgNPs altered the bond quality in dentin interaction. In conclusion, adding AgNPs at a minimal level improves the mechanical properties and maintains the same bond quality as GIC.

In vitro biocompatibility testing of different base materials used for elevation of proximal subgingival margins using human gingival epithelial cells

PURPOSE

To analyze the biological effects of four base materials used for elevation of proximal subgingival margins on gingival epithelial cells.

METHODS

Twenty-eight specimens for each of the four base materials (total 112 specimens) were used: resin-modified glass ionomer (RMGI), glass hybrid (HV-GIC), flowable bulk fill resin composite (Bulk Flow) and bioactive ionic resin (Activa). Proximal enamel and root dentin were used as controls. Gingival epithelial cell viability was calculated after direct incubation on all four types of material for either 24 h or 72 h using both the methyl tetrazolium and trypan blue dye exclusion assays. Data were analyzed statistically using one-way analysis of variance, Tukey post hoc test and independent sample t-test (P < 0.05).

RESULTS

Cell viability values in both assays showed significant differences among the study groups. Bulk Flow showed the highest values, followed in order by Activa and the control groups. Both HV-GIC and RMGI had the lowest values. Cell viability in all of the study groups was higher after incubation for 72 h than after 24 h.

CONCLUSION

In terms of biocompatibility with epithelial tissues, bulk fill resin composite appears to be most suitable, followed by bioactive composite, for subgingival placement than glass ionomer-based materials, especially that containing 2-hydroxy-ethyl methacrylate.

Influence of Conventional Polymer, Hybrid Polymer and Zinc Phosphate Luting Agents on the Bond Strength of Customized Zirconia Post in Premolars-An In-Vitro Evaluation

The aim was to identify the influence of conventional polymeric resin based cement (RC), hybrid polymer modified glass ionomer (RMGIC) and Zinc phosphate cement (ZPC) on the pull out strength of the customized zirconia post in premolars. Access cavity and root canals were performed in sixty premolar teeth with the standardized crown down technique (ProTaper Universal, Dentsply). Post space impressions were scanned, and the pre-sintered Zenostar Zr Translucent blanks (Weiland Dental, Pforzheim) were milled with the Opera-system to form the post. All prepared specimens were divided equally in three groups based on the cement type employed for luting as follows: group A: ZPC; group B (GC Fuji PLUS Capsule): RMGIC; group C (and RC (3M RelyX ARC). Ten specimens in each group were thermocycled (TC) at 5 and 55 °C in distilled water baths (40,000 cycles). Pull out bond strength was assessed using a universal testing machine at 0.5 mm/min. The means and standard deviations were compared using ANOVA and Tukey Kramer multiple comparisons tests. A significant difference among the cement groups as well as between TC and non-thermocycled (NTC) groups (p < 0.05) was observed. The highest tensile stress was demonstrated among group C (Resin, 69.89 ± 4.81 (NTC), 64.06 ± 4.36 (TC)) with the least in group A, (zinc phosphate, 43.66 ± 5.02 (NTC), 37.70 ± 5.10 (TC)) for both groups. Group A presented with 100% adhesive bond failures, followed by 80% in group C and 70% in group B, respectively. A similar outcome was observed in the TC group for the cement; however, unlike the NTC group, the TC group showed more cohesive failures compared to the NTC mixed failure. Dual cure polymer based cement demonstrated higher bond strength and efficient adhesive bonding of the customized Zr post with root dentine compared to zinc phosphate (non-polymeric) and RMGIC (hybrid polymer). Thermocycling compromised Zr post adhesive bonding to root dentin.

Long-Term Water Balance Evaluation in Glass Ionomer Restorative Materials

The complex role of water in glass ionomer cement (polyalkenoate) dental restorative materials has been studied, but much of the present understanding concerning water balance within these materials is based on very early studies and short-term experiments. This study evaluated the nature of the water species of six conventional and four resin modified glass ionomer restorative materials over 3 years using thermogravimetric analysis techniques. Materials were prepared, placed in crucibles, and stored in physiologic phosphate buffered saline and evaluated at 24 h, 1 week, and then at 1, 3, 6, 9, 12, 18, 24, 30 and 36 months. All materials demonstrated a significant increase in unbound water percentage content but except for the resin modified materials, the enthalpy required to remove the unbound water species did not significantly change over 36 months. Also, bound water content percentage and removal enthalpy was established at 24 h, as no significant increase was noted in both bound water content and removal enthalpy over the course of this evaluation. This study suggests that unbound water species may increase with time and is loosely held except for the resin modified materials. Protective coatings placement and re-evaluation are prudent to prevent unbound water loss.

Structural, Physical, and Mechanical Analysis of ZnO and TiO2 Nanoparticle-Reinforced Self-Adhesive Coating Restorative Material

This study aimed to modify an EQUIA coat (EC; GC, Japan) by incorporating 1 and 2 wt.% of zinc oxide (ZnO; EC-Z1 and EC-Z2) and titanium dioxide (TiO₂; EC-T1 and EC-T2) nanoparticles, whereby structural and phase analyses were assessed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Thermogravimetric analysis/differential scanning calorimetry, micro-hardness, and water absorption analyses were conducted, and the microstructure was studied by scanning electron microscopy/energy-dispersive spectroscopy. FTIR spectra showed a reduction in peak heights of amide (1521 cm^-1) and carbonyl (1716 cm^-1) groups. XRD showed peaks of ZnO (2θ ~ 31.3°, 34.0°, 35.8°, 47.1°, 56.2°, 62.5°, 67.6°, and 68.7°) and TiO₂ (2θ ~ 25.3°, 37.8°, 47.9, 54.5°, 62.8°, 69.5°, and 75.1°) corresponding to a hexagonal phase with a wurtzite structure and an anatase phase, respectively. Thermal stability was improved in newly modified materials in comparison to the control group. The sequence of obtained glass transitions was EC-T2 (111 °C), EC-T1 (102 °C), EC-Z2 (98 °C), EC-Z1 (92 °C), and EC-C (90 °C). EC-T2 and EC-T1 showed the highest (43.76 ± 2.78) and lowest (29.58 ± 3.2) micro-hardness values. EC showed the maximum water absorption (1.6%) at day 7 followed by EC-T1 (0.82%) and EC-Z1 (0.61%). These results suggest that EC with ZnO and TiO₂ nanoparticles has the potential to be used clinically as a coating material.

Glass Hybrid Versus Nanocomposite for Restoration of Sclerotic Non-carious Cervical Lesions: 18-Month Results of a Randomized Controlled Trial

PURPOSE

To compare the clinical performance and treatment times between glass hybrid (GH; EQUIA Forte Fil/EQUIA Forte Coat, GC) and adhesive/nanofilled resin composite restorations (RC; OptiBond FL, Kerr/Filtek Supreme XTE, 3M Oral Care) of sclerotic non-carious cervical lesions (sNCCL).

MATERIALS AND METHODS

This is an 18-month interim analysis of a 36-month cluster-randomized trial (ClinicalTrials.gov Identifier: NCT02631161). Eighty-eight patients (50-70 years) with 175 sNCCLs were randomized to receive GH or RC restorations. Restorations were placed without mechanical cavity preparation, and treatment time was recorded. After 18 months, restorations were evaluated using FDI criteria. Factors associated with restoration survival were evaluated using multi-level Cox-regression analysis. Generalized linear mixed modelling was used to analyze factors associated with treatment time.

RESULTS

After a mean of 18 months (min/max: 8/25), 78 patients (160 restorations) were assessed. Fifteen restorations (18%) failed in GH, and 11 (12%) in the RC, without a significant difference in survival (p = 0.904/Cox). Retention loss was the most common reason for failure in both groups. Restorations placed in older patients showed lower risk of failure [OR (95% CI): 0.90 (0.81-0.99) per year], while mandibular teeth showed higher risks [2.89 (1.00-8.31)]. Treatment time was significantly shorter for GH (mean ± SD: 8.6 ± 4.3 min) than RC (11.7 ± 5.7 min; p < 0.001).

CONCLUSIONS

GH may be a suitable alternative to RC for restoring sNCCLs, without any significant difference in survival between the two materials at this interim analysis. In addition, placing GH restorations required less chairtime than did placing RC restorations.

Experimental Bioactive Glass-Containing Composites and Commercial Restorative Materials: Anti-Demineralizing Protection of Dentin

The purpose of this in vitro study was to investigate whether different types of experimental and commercial restorative dental materials can protect dentin against acid-induced softening. Experimental composites were prepared with a photocurable mixture of methacrylates and two types of bioactive glass (45S5 and a customized low-Na F-containing formulation). Human dentin samples were prepared from mid-coronal tooth slices and immersed in lactic acid solution (pH = 4.0) at 5 mm from set specimens of restorative material. After 4, 8, 12, 16, 20, 24, 28, and 32 days, surface microhardness of dentin samples and pH of the immersion solution were measured, followed by replenishing of the immersion medium. Microstructural analysis was performed using scanning electron microscopy. The protective effect of restorative materials was determined as dentin microhardness remaining statistically similar to initial values for a certain number of acid additions. Scanning electron microscopy showed a gradual widening of dentinal tubules and proved less discriminatory than microhardness measurements. To produce a protective effect on dentin, 20 wt% of low-Na F-containing bioactive glass was needed, whereas 10 wt% of bioactive glass 45S5 was sufficient to protect dentin against acid-induced demineralization. The anti-demineralizing protective effect of experimental and commercial restoratives on dentin was of shorter duration than measured for enamel in a previous study using the same experimental approach.

Effect of fluoride varnish on glass ionomer microhardness changes in endogenous acid erosion challenge

OBJECTIVE

This study aimed to assess the effect of fluoride varnish on glass ionomer microhardness changes after endogenous acid erosion challenge.

METHODOLOGY

In this study, 40 conventional glass ionomer (CGI; Fuji IX) and 40 resin-modified glass ionomer (RMGI; Fuji IILC) discs were fabricated and divided into 4 subgroups (n = 10) for immersion in synthetic gastric acid or saliva for 27 h with/without fluoride varnish application. The surface microhardness was measured at baseline and after immersion, and the change in microhardness was calculated. Data were analyzed using analysis of variance and T-test.

RESULTS

A reduction in microhardness was noted in all subgroups following immersion. The lowest change in microhardness of both CGI and RMGI occurred in artificial saliva. In CGI groups, the highest reduction in microhardness occurred in synthetic gastric acid with fluoride varnish application, and the reduction was significantly different from that of the CGI group with fluoride varnish application (p value = .01). In RMGI groups, the highest reduction in microhardness was noted in synthetic gastric acid without fluoride varnish application, and the reduction was significantly different from that of the other groups (p value < .05).

CONCLUSIONS

Exposure to synthetic gastric acid caused a significant reduction in microhardness of RMGI. Varnish application significantly decreased the acid susceptibility of RMGI, but not that of CGI.

Effect of Nano-Filled Protective Coating and Different pH Enviroment on Wear Resistance of New Glass Hybrid Restorative Material

The purpose of the study was to determine the wear rate of Equia Forte HT Fil with Equia Forte Coat or without coating and compare it with Fuji IX GP high-viscosity glass ionomer cement (GIC) in conditions with acid load or at neutral pH. The samples were stored for 7 days: (1) in artificial saliva, (2) in artificial saliva and cyclically exposed to low pH, and (3) in distilled water and cyclically exposed to low pH. Wear was determined by measuring the difference in mass before and after brushing in an abrasion testing device. The wear of Fuji IX GP was significantly higher than that of Equia Forte HT Fil with or without coating (p = 0.000). The difference between Equia Forte HT Fil with and without Coat was not statistically significant (p < 0.803). The differences in wear resistance between samples stored in saliva and in distilled water were not significant (p = 0.588). Periodic exposure to the low pH solution significantly affected the wear resistance of all materials (p = 0.000). Equia Forte HT Fil was more resistant to wear than Fuji IX GP in all storage conditions. A resinous coat did not significantly increase wear resistance.

Evaluation of Er:YAG and Er,Cr:YSGG laser irradiation for the debonding of prefabricated zirconia crowns

BACKGROUND

Reduced tooth structure in the pediatric and adolescent population is frequently restored with prefabricated zirconia crowns. On permanent teeth, these restorations may need to be removed and replaced with permanent restorations.

OBJECTIVES

To explore and compare the use of 2 high-powered erbium lasers for removing prefabricated zirconia crowns from molar teeth as a non-invasive alternative to rotary instruments.

MATERIAL AND METHODS

Twenty-five permanent molars were prepared to dentin and prefabricated all-ceramic zirconia crowns were fitted and cemented with resin modified glass ionomer (RMGI) cement. The teeth were randomly assigned into one of the 2 retrieval treatment groups: the erbium-doped yttrium, aluminum and garnet (Er:YAG) laser group (G1; n = 12) or the erbium, chromium-doped yttrium, scandium, gallium and garnet laser (Er,Cr:YSGG) laser group (G2; n = 13). The laser operating parameters for the Er:YAG laser were 300 mJ, 15 Hz, 4.5 W, and 50-microsecond pulse duration (SSP mode); for the Er,Cr:YSGG laser, they were 4.5 W, 15 Hz, 20 water/20 air, and 5 W, 15 Hz, 50 water/50 air, and 60-microsecond pulse duration (H mode). The experiment was repeated twice. The surface area and the volume of teeth and crowns were measured and the cement space was calculated. The retrieval time and temperature changes were tested and recorded. The data were analyzed with the t-test. The surfaces of the dentin and the crown from each group were further examined using scanning electron microscopy (SEM).

RESULTS

The average time for crown removal using the Er:YAG laser was 1 min 32.7 s; for the Er,Cr:YSGG laser it was 3 min 13.9 s (p < 0.0001). The mean temperature changes were 1.41 ±1.36°C for the Er:YAG laser and 2.2 ±0.99°C for the Er,Cr:YSGG laser (p = 0.0321). The SEM examination showed no damage or major structural changes caused by treatment with either erbium-family laser.

CONCLUSIONS

Both lasers are effective, non-invasive tools to remove prefabricated zirconia crowns cemented with resin cement and should be considered as viable alternatives to rotary instrumentation.

Antibacterial activity of a glass ionomer containing silver nanoparticles against Streptococcus mutans and Streptococcus sanguinis

Aim

Nano-sized metal particles exhibit special biological, chemical, and physical properties. The aim of this study was to evaluate the effect of incorporating silver nanoparticles into a resin-modified glass ionomer (GI) on its antimicrobial property.

Materials and Methods

Antibacterial action of GI samples containing 0, 40, 80 ppm silver nanoparticles against standard strains of Streptococcus sanguinis and Streptococcus mutans were assessed by agar diffusion and direct contact tests. Data were analyzed using analysis of variance and Duncan test (P < 0.05).

Results

Agar diffusion test showed no bacterial inhibition zone, but direct contact test exhibited significant antimicrobial activity against S. sanguinis and S. mutans in resin containing 80 ppm of nanosilver.

Conclusion

Incorporation of a certain amount of silver nanoparticles into GI can increase its antimicrobial activity compared to the original material.

An in vitro evaluation of the compressive strength and shear bond strength of resin-modified glass-ionomer cement containing purified powder of Salvia officinalis

BACKGROUND

In this study, the effect of adding purified powder of Salvia officinalis on the mechanical properties and bonding ability of resin-modified glass ionomer (RMGI) cement is investigated.

MATERIALS AND METHODS

In this in vitro study Purified powder of S. officinalis with particles smaller than 50 μ, in weight percentages of 0.5%, 0.75%, 1%, and 1.25%, was added to RMGI powder (GC Fuji II LC, GC USA). Fifty samples in five groups of control and percentages that considered, from the powder of GI combined with liquid, according to the manufacturer instructions and prepared samples with 4 mm × 6 mm dimensions and placing in distilled water in an incubator with temperature 37°C for 24 h. Fifty sound extracted upper premolars were collected and divided into five groups. The dentinal cross-sections on the occlusal surfaces of teeth were prepared and assessed under a stereomicroscope with ×16. Then, samples with 2 × 4 dimensions from RMGI was prepared on dentin surface and keeping in moisture environment in an incubator with temperature 37°C for 24 h. Compressive strength and shear bond strength test done with a universal testing machine at the rate of 0.5 mm/min. For the assessment of mode of failure, stereomicroscope with a digital camera and ×20 was used, and photographs from bonding surface were taken. After collecting data, the ANOVA test was used for comparing shear bond strength between groups and Kruskal-Wallis test was used for comparing compressive strength. The Chi-square test was used for comparing the mode of failure between groups. The significance level for all tests was considered 5%.

RESULTS

According to the statistical analysis, compressive strength (P = 0.486) and shear bond strength (P = 0.076) were not significantly different between the five groups. The distribution of mode of failure was not significantly different between groups (P = 0.663).

CONCLUSION

The addition of purified powder of S. officinalis to RMGI powder does not affect compressive strength and shear bond strength of RMGI cement.

Shear bond strength of glass ionomer and resin-based cements to different types of zirconia

OBJECTIVE

To investigate the shear bond strength (SBS) of a glass ionomer (GI) cement, an 10-methacryloyloxy-decyl dihydrogen phosphate (MDP)-based adhesive resin cement (MDP-based AC), an MDP-based self-adhesive resin cement (MDP-based SAC), an MDP-free self-adhesive resin cement (MDP-free SAC), and a resin-modified GI (RMGI) cement to a 3 mol% yttria-stabilized (3Y-TZP) and a 5 mol% yttria partially stabilized zirconia (5Y-PSZ).

MATERIALS AND METHODS

Fifty blocks were produced using 3Y-TZP and 5Y-PSZ, assigned to subgroups based on the five cements investigated (n = 10) and luted to cylindrical specimens of the same substrate. Each specimen was loaded in a SBS apparatus to failure. Mean SBS (MPa) values and standard deviations were calculated. Data were analyzed using a two-way analysis of variance and Tukey tests (α = .05). Failed specimens were subjected to fractographic analysis.

RESULTS

MDP-based AC and MDP-based SAC cements displayed the highest SBS values with both the substrates; GI cement showed the lowest. RMGI and MDP-free SAC cements performed better with 3Y-TZP than with 5Y-PSZ. Fractographic analysis revealed only adhesive and mixed failures.

CONCLUSIONS

MDP-based AC and MDP-based SAC cements are suitable for both 3Y-TZP and 5Y-PSZ. MDP-free SAC and RMGI cements are adequate choices for 3Y-TZP, but seem less effective with 5Y-PSZ.

CLINICAL SIGNIFICANCE

MDP-based SACs appear to be as reliable as MDP-based ACs for both 3Y-TZP and 5Y-PSZ cementation. Specifically, for 5Y-PSZ cementation, resin-based MDP-free SACs do not seem to guarantee predictable results in terms of SBS.

Comparative Evaluation of Antimicrobial Efficacy and Fluoride Release of Seven Different Glass-Ionomer-Based Restorative Materials

PURPOSE

The aim of this study was to evaluate one high-viscosity glass-ionomer cement (EQUIA/GC), two resin-modified glass ionomers (Fuji II LC/GC, Photac Fil Quick Aplicap/3M Oral Care), two traditional glass ionomers (Ketac Molar Easymix/3M, Fuji II/GC), and two compomers (Freedom/SDI, Dyract XP/Dentsply Sirona) through a comparison of fluoride release and antimicrobial effects.

MATERIALS AND METHODS

A total of 210 samples were prepared, as 10 for each of the 7 materials for fluoride release and 20 for each material for the antimicrobial effect tests. To measure fluoride release, 5 ml distilled water and 5 ml TISAB II were added to the samples, which were then incubated at 37˚C. The fluoride levels of the material were measured using the selective ion electrode on days 1, 3, 7, 14 and 28. To compare the antimicrobial effects, 20 samples were divided in two groups and implanted in culture media containing Streptococcus mutans and Lactobacillus acidophylus. Measurements were taken on days 2, 4 and 6. The diameter of the inhibition zone was recorded in millimetre (mm).

RESULTS

All the materials released fluoride and the difference between them was determined to be statistically significant (p < 0.01). The antimicrobial effect values of the materials against S. mutans and L. acidophylus were evaluated and statistically significant difference was determined between the materials on all the measurement days.

CONCLUSIONS

All the materials were observed to release fluoride. With the exception of the compomers, all the other materials showed an antimicrobial effect against S. mutans and L. acidophylus. Key words: fluoride, glass ionomer, antimicrobial, S. mutans, L. acidophylus.

Fluoride release and fluoride-recharging ability of three different sealants

BACKGROUND

We aimed to determine the fluoride release and fluoride-recharging ability of a sealant containing surface pre-reacted glass (S-PRG) ionomer filler particles (BeautiSealant) with a fluoride-releasing resin sealant (Helioseal F), and a glass-ionomer sealant (Fuji VII).

METHODOLOGY

Forty-eight disc-shaped specimens of each material were immersed in deionized water to determine the fluoride release utilizing a fluoride ion-selective electrode. After 21 days, 8 specimens were soaked in 0.22% Sodium Fluoride solution for 2 min; 8 specimens were coated with 1.23% Acidulated Phosphate Fluoride (APF) gel for 4 min, and the fluoride-recharging ability was evaluated for 40 days. Data were analyzed using one way-ANOVA and Bonferroni post hoc tests.

RESULTS

Total fluoride release over the 21-day period was: Fuji VII > BeautiSealant > Helioseal F, (P = 0.000). After refluoridation of the specimens with 0.22% Sodium Fluoride solution, the cumulative fluoride release during the 40-day period for each material was: BeautiSealant > Fuji VII > Helioseal (P = 0.000). After exposure to 1.23% APF gel, the cumulative fluoride release during the 40-day period for each material was: BeautiSealant > Fuji VII > Helioseal F (P = 0.000).

CONCLUSION

Glass ionomer-based sealants (Fuji VII) exhibited higher initial fluoride release whilst the surface pre-reacted glass-ionomer filler containing sealant (BeautiSealant) demonstrated superior fluoride recharging properties.

Histologic Evaluation of Artificial Floors Under MTA and Nano-Filled Resin-Modified Glass Ionomer Used to Repair Furcation Perforations in Dogs

Objective

This study aimed to compare the tissue reaction of two repair materials for furcation perforations, nano-filled resin modified glass ionomer (Nano-FRMGI) and mineral trioxide aggregate (MTA), used with or without an artificial floor.

Methods

A total of 96 teeth in 6 dogs were used for this study. After access cavities, root canals were prepared and obturated with gutta percha using cold lateral condensation technique. Perforations were then created on the floors of the pulp chambers. The perforations divided into four groups n=24/group that were sealed with MTA alone, MTA with calcium sulphate artificial floor (CSAF), FRMGI alone and Nano-FRMGI with CSAF. All access cavities were filled with composite resin. Two dogs were sacrificed at 1, 3, and 6 month. The experimental tooth along with the surrounding alveolar bone were cut in block sections and histologically evaluated for tissue response. Data were analyzed by Chi-square (P≤0.05).

Results

MTA and MTA with CSAF showed more bone and cementum apposition when compared to Nano-FRMGI at 6-month interval. MTA and MTA with CSAF showed less bone resorption, epithelium proliferation and inflammation compared to Nano-FRMGI at 6-month interval.

Conclusion

MTA with CSAF or MTA-alone show better outcomes in the repair of pulp chamber floor perforation.

In Vitro Wear Resistance of Self-Adhesive Restorative Materials

PURPOSE

To investigate simulated localized and generalized wear of self-adhesive restorative materials.

MATERIALS AND METHODS

Three commercially available restorative materials and one experimental material with self-adhesive properties were evaluated. The experimental material was tested in both light-cured and self-cured conditions. Activa (A), Fuji II LC (F), and Equia Forte (E) and the experimental material ASAR-MP4 (S) were investigated. Two kinds of wear were simulated in an Alabama wear machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The wear challenge was carried out in an aqueous slurry of polymethyl methacrylate beads. Material volume loss was measured on polyvinyl siloxane replicates of each worn surface using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software.

RESULTS

There were significant differences (p < 0.05) among the materials for both generalized and localized wear. The experimental material in both curing modes exhibited significantly less localized wear than F and A and significantly less generalized wear than F and E.

CONCLUSION

Self-adhesive materials offer unique handling properties for direct placement of posterior restorations in permanent teeth. The experimental material ASAR-MP4 generated similar wear values to the other self-adhesive materials tested.

In vitro evaluation of apical microleakage in retrofillings with different resection angles

The aim of this study was to evaluate the effect of flowable composite or glass ionomer liners on the shrinkage stress of a restorative composite resin. Fifteen previously sandblasted metal boxes were attached to a universal mechanical testing machine (INSTRON 1011, Instron Corporation). Five of these boxes were filled with Filtek Z350 XT (FXT) Universal Restorative A2 (3M ESPE) (Group 1 or Control). Two further groups of 5 boxes were prepared by interposing a layer of Vitrebond Light Cure Glass Ionomer 3M ESPE (VGI) (Group 2 or G.I.) or Filtek Z350 XT Flowable Restorative A2 3M ESPE (FFR) (Group 3 or Flowable) between the box and the composite resin, completing with the same volume of composite as in Group 1. Upon activating lightcuring, the filled boxes mounted on the testing machine were videoed for 60 seconds (40 s photoactivation and 20 s postcuring), timed with a digital chronometer. Force values were recorded in newtons and converted into stress according to contact surface. Stress values were recorded every 10 s. Results were analyzed using repeated measures ANOVA. Mean and standard deviation in kPa (stress) recorded for each group were: Control group: 126.2 (30.8); G.I.: 48.4 (18); Flowable: 27.9 (19.5). Statistical analysis showed significant differences between the control group and the rest (p<0.01), with no significant difference between groups with glass ionomer liners and flowable resin liners (G.I. and Flowable). Under the experimental conditions of this study, it can be concluded that polymerization shrinkage stress can be reduced by the presence of a liner between the preparation and the restorative material.

Remineralising Effectiveness of Two Fluoride Varnishes Containing Additives: An In Vitro Study

PURPOSE

To assess the remineralising efficacy of fluoride varnish containing additives and conventional sodium fluoride varnish.

MATERIALS AND METHODS

72 extracted upper central incisors specimens were randomly allocated to four groups after demineralisation: control; 5% sodium fluoride varnish (FV) (Fluoritop-SR); resin modified glass ionomer-based calcium phosphate containing fluoride varnish (CV) (Clinpro XT); fluoride varnish with xylitol coated calcium phosphate (cXp) (Embrace). Change in surface morphology, calcium phosphorous ratio and fluoride content of enamel were evaluated using scanning electron microscope and energy dispersive X-ray analysis (SEM-EDAX). Change in surface roughness was evaluated using profilometer analysis. All readings were taken at baseline, after demineralisation, at 2 weeks and 4 weeks of remineralisation.

RESULTS

At 4 weeks of remineralisation surface roughness values were ranked as follows: control > FV = cXp > CV. Calcium phosphorus ratios were in the order: CV > FV = cXp > control and fluoride content (for treatment groups): CV = cXp > FV. Scanning electron microscopy images showed mineral deposition on the surfaces of the treatment groups with different deposition pattern of minerals.

CONCLUSION

Fluoride varnishes with or without additives are effective in remineralisation of early enamel lesions. Glass ionomer-based fluoride varnish results in better remineralisation than xylitol coated calcium phosphate containing fluoride varnish and 5% sodium fluoride varnish.

Evaluation of Preventive Antibacterial Properties of a Glass-Ionomer Cement Containing Purified Powder of Salvia officinalis: An In vitro Study

Background

In this study, the anti-Streptococcus mutans and anti-Lactobacillus casei properties of a restorative glass-ionomer cement (GIC) modified with extract powder of Salvia officinalis as a safe and effective herbal extract at weight concentration levels of 0.5%, 0.75%, 1%, and 1.25% are investigated.

Methods

The S. officinalis extract powder is provided by doing a multistep laboratory procedure and is filtered to obtain particles smaller than 50 μ. The GIC powder is modified by adding extract powder in weight concentrations of 0.5% (Group II), 0.75% (Group III), 1% (Group IV), and 1.25% (Group V) to form experimental groups, each of 1 g. Five disk-shaped samples, 1 cm in diameter and 2 mm height, of each group (including control group [Group I]) are prepared for each bacterial category of S. mutans and L. casei. The twenty-five samples for each category are tested in vitro against strains of S. mutans and L. casei. Following Agar diffusion tests, the inhibition zone diameters are recorded. The data are tested for normality by means of Kolmogorov-Smirnov procedure. The Kruskal-Wallis and Mann-Whitney tests are used to perform a one-way ANOVA and to do pair-wise comparisons, respectively, at 5% significance level.

Results

The mean diameter of the inhibition zones are significantly different among the test groups and also the test groups and the control group except for the group with 0.5% in L. casei category which shows no significant difference with the control group.

Conclusions

The present study revealed direct inhibitory activities of S. officinalis-containing GIC against S. mutans and L. casei in a dose-response manner.

Sealants revisited: An efficacy battle between the two major types of sealants - A randomized controlled clinical trial

BACKGROUND

The aim of this study is comparing the retention and caries preventive effect of the glass-ionomer fissure sealant and resin-based fissure sealant.

MATERIALS AND METHODS

A randomized-controlled split-mouth study was conducted to compare the retention and the caries preventive effect of light-cured resin-based sealant (3M ESPE) and glass ionomer sealant (Fuji VII). The sealants were applied to either the right or the left lower mandibular molars (7-9 yrs of age) in 120 school children, based on the randomization process. They were recalled for assessment of clinical retention at intervals of 3, 6, and 12 months. The caries-preventive effect between the two materials was tested statistically by the McNemar's test for matched pairs, and the differences observed with regard to the retention of the materials was tested by Chi-square tests. The level of significance was set to be at P < 0.05.

RESULTS

At the end of 12^th month, sealant retention is found to be higher in the resin-based sealant group compared to the glass ionomer group. In the glass ionomer sealants placed, 101 (91%) were caries-free and 10 (9%) had caries. In the resin-based sealant, 105 (94.60%) had sound teeth and 6 (5.4%) had dental caries (P = 0.34).

CONCLUSION

The glass ionomer sealant was less retentive when compared to resin sealants. The caries incidence between the glass ionomer and resin-based sealants was not statistically significant.

Comparison of bond strength of a composite resin with two different adhesive systems and a resin modified glass ionomer to calcium enriched mixture

Context:

It is necessary to have a proper bond between pulp-capping agent and composite materials to maintain effective coronal seal.

Aims:

This study aims to compare the shear bond strength of a composite resin with two different adhesive systems and a resin-modified glass ionomer (RMGI) to calcium-enriched mixture (CEM).

Methods:

In this study, 30 acrylic blocks (with a central hole 4 mm diameter and 2 mm height) were prepared and filled with CEM. The blocks were divided into three groups: single bond2 (SB) with Filtek Z250, single bond universal (SBU) with Filtek Z250, and RMGI. The restorative materials were placed on the CEM, and shear bond strength was measured. Data were analyzed using one-way ANOVA and games Howell tests. P < 0.05 was considered statistically significant.

Result:

Bond strength of both composite groups to CEM showed significantly higher values than RMGI-CEM group (both P < 0.001). The type of the adhesive system( total etch or universal) had no significant effect on the bond strength of composite to CEM (P > 0.05). All the failures in composite groups were as cohesive in CEM and in RMGI group was as adhesive.

Conclusions:

Shear bond strength of composite resin to CEM cement was higher than RMGI irrespective of the type of the adhesive system. The universal bonding system is recommended for bonding of composite to CEM for ease of use.

Comparative evaluation of fluoride release and recharge potential of novel and traditional fluoride-releasing restorative materials: An in vitro study

Aim

The aim of this study was to evaluate and compare the fluoride ion release and uptake of glass ionomer cement GP IX Extra (GE), EQUIA^® Forte Fil (EF), Beautifil Bulk (BB), Dyract^® XP (DXP), Tetric N-Ceram^® (TNC) in vitro.

Materials and Methods

The restorative materials were divided into five groups (n = 12), namely G1 - GE, G2 - EF, G3 - BB, G4 - DXP, G5 - TNC. Fluoride release was checked using fluoride ion-selective electrode (Orion 9609BNWP, Ionplus Sure-Flow Fluoride, Thermo Scientific, USA) at time intervals of 1 day and thereafter at 3, 7, 14, 21, and 28 days. Following this, fluoride recharge was done with 1.23% acidulated phosphate fluoride gel (12,300 ppm, Pascal International Inc., 2929 Northup Way, Bellevue, USA) after 28 days and each sample was re-checked for fluoride release at the same time intervals.

Statistical Analysis

One-way ANOVA with post hoc Games-Howell test for intergroup and repeated measures ANOVA with post hoc Bonferroni test for intragroup analysis. P < 0.05 was considered statistically significant.

Results

On intergroup analysis, Group 2 showed high values of fluoride release and recharge at all-time intervals which were significantly higher (P < 0.001) than Groups 1, 3, 4 and 5. Intragroup analysis showed significantly higher (P < 0.001) fluoride release and recharge at the end of day 1 which decreased progressively with time for all the tested materials.

Conclusion

EF showed the highest fluoride release and recharge potential across all time intervals compared to other tested restorative materials and the greatest fluoride release was seen on day 1.

Rheological Characterization as an Alternative Method to Indentation for Determining the Setting Time of Restorative and Endodontic Cements

This study explored an alternative approach using rheology to assess setting time. The following cements were tested: ProRoot^® MTA (Dentsply, Tulsa, OK, USA), Biodentine^® (Septodont, Saint Maur des Fosses, France), Fuji VII^®, FujiVII^® EP, and Fuji IX^® (from GC Corporation, Tokyo, Japan), RealSeal SE™ Sealer (SybronEndo, Amersfoort, The Netherlands), AH 26^® and AH Plus (both from Dentsply DeTrey, Konstanz, Germany). Freshly mixed cements were placed into a strain-controlled rheometer (1 rad·s^-1 with an applied strain of 0.01%). From measurements of elastic modulus over time, the time taken to reach 90% of the plateau elastic modulus (designated as the setting time) was determined for each cement. In increasing order, the setting times were as follows: Fuji VII EP 3.3 min, Fuji VII 3.6 min, Fuji IX 3.7 min, ProRoot MTA 5.1 min, Biodentine 15.9 min, RealSeal 22.2 min, AH Plus 5933 min, and AH 26 5067 min. However, ProRoot MTA did not yield reliable results. The time to reach the 90% plateau elastic modulus correlates well with the setting time of glass ionomer cements and Biodentine. Using this approach gives much longer setting times for endodontic sealers than previously recognized.

In vitro evaluation of a silica whitening toothpaste containing blue covarine on the colour of teeth containing anterior restoration materials

OBJECTIVES

To investigate the effects of a silica-based whitening toothpaste containing blue covarine on the colour of restorations in extracted human teeth.

METHODS

Human extracted teeth were mounted in acrylic resin. A cavity was cut into the enamel surface and the specimen restored with either glass ionomer or composite dental materials. Following 4 weeks storage in water, specimens were treated with either water, red wine or a toothpaste containing blue covarine (n=10) for 24h followed by brushing with a silica-based toothpaste. Specimens were imaged with a digital imaging system at baseline, after 24h treatment and after brushing with a silica-based toothpaste. CIELAB colour parameters were determined for the restoration and the whole specimen and overall mean colour changes calculated (ΔE). Baseline and post-brushing images were compared subjectively for overall stain and staining around the restoration margin.

RESULTS

Red wine produced the largest ΔE values for whole specimens and for all restoration materials and the largest subjective stain scores for whole specimens and restoration margins. The red wine stain was not completely removed by brushing with a silica-based toothpaste. Comparisons of the red wine group with either the blue covarine toothpaste group or the water group were of statistical significance for all parameters (ANOVA, Tukey-Kramer, p<0.05). Following brushing with the silica-based toothpaste, specimens from the blue covarine toothpaste group were not significantly different (p>0.05) to the water group, for all restoration material types.

CONCLUSIONS

Exaggerated treatment with a blue covarine containing toothpaste does not significantly affect the colour of the restoration or the restoration margin of the dental materials tested versus a water alone treatment.

CLINICAL SIGNIFICANCE

The silica-based blue covarine containing toothpaste does not permanently stain the restorative materials tested or their margins.

Shear Bond Strength and Remineralisation Effect of a Casein Phosphopeptide-Amorphous Calcium Phosphate-Modified Glass Ionomer Cement on Artificial "Caries-Affected" Dentine

This study investigated the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified glass ionomer cement (GIC) on shear bond strength (SBS) and remineralisation of artificial “caries-affected” dentine. Human dentine slices were demineralised and allocated to three groups: group 1, conventional GIC; group 2, CPP-ACP-modified GIC; and group 3, resin-modified GIC. The SBS was measured using a universal testing machine (n = 16 per group). Remaining samples (n = 8 per group) were subjected to pH-cycling for 28 days. After pH-cycling, lesion depth and micro-mechanical properties at the sample-bonding interface were investigated using micro-computed tomography (micro-CT) and nano-indentation, respectively. The SBS for groups 1 to 3 were 4.6 ± 1.5 MPa, 4.2 ± 1.1 MPa, and 5.9 ± 1.9 MPa, respectively (p = 0.007; group 1, group 2 < group 3). Lesion depths determined by micro-CT for groups 1 to 3 were 186 ± 8 µm, 149 ± 14 µm, and 178 ± 8 µm, respectively (p < 0.001; group 2 < group 1, group 3). The mean (±SD, standard deviation) nano-hardness values for groups 1 to 3 were 0.85 ± 0.22 GPa, 1.14 ± 0.21 GPa, and 0.81 ± 0.09 GPa, respectively (p = 0.003; group 1, group 3 < group 2). The mean (±SD) elastic moduli for groups 1 to 3 were 1.70 ± 0.33 GPa, 2.35 ± 0.44 GPa, and 1.59 ± 0.13 GPa, respectively (p < 0.001; group 1, group 3 < group 2). The results suggest that the incorporation of CPP-ACP into GIC does not adversely affect the adhesion to artificial caries-affected dentine. Furthermore, CPP-ACP-modified GIC is superior to conventional GIC in promoting dentine remineralisation.

Effect of Silver Diamine Fluoride and Potassium Iodide Treatment on Secondary Caries Prevention and Tooth Discolouration in Cervical Glass Ionomer Cement Restoration

This study investigated the effect of silver diamine fluoride (SDF) and potassium iodide (KI) treatment on secondary caries prevention and tooth discolouration in glass ionomer cement (GIC) restoration. Cervical GIC restorations were done on 30 premolars with: Group 1, SDF + KI; Group 2, SDF (positive control); Group 3, no treatment (negative control). After cariogenic biofilm challenge, the demineralisation of dentine adjacent to the restoration was evaluated using micro-computed tomography (micro-CT) and Fourier transform infrared (FTIR) spectroscopy. The colour of dentine adjacent to the restoration was assessed using CIELAB system at different time points. Total colour change (∆E) was calculated and was visible if ∆E > 3.7. Micro-CT showed the outer lesion depths for Groups 1, 2 and 3 were 91 ± 7 µm, 80 ± 7 µm and 119 ± 8 µm, respectively (p < 0.001; Group 2 < Group 1 < Group 3). FTIR found that there was a significant difference in amide I-to-hydrogen phosphate ratio among the three groups (p < 0.001; Group 2 < Group 1 < Group 3). ∆E of Groups 1, 2 and 3 after biofilm challenge were 22.5 ± 4.9, 70.2 ± 8.3 and 2.9 ± 0.9, respectively (p < 0.001; Group 3 < Group 1 < Group 2). SDF + KI treatment reduced secondary caries formation on GIC restoration, but it was not as effective as SDF treatment alone. Moreover, a perceptible staining on the restoration margin was observed, but the intensity of discolouration was less than that with solely SDF treatment.

Incorporation of CPP-ACP into Luting and Lining GIC: Influence on Wear Rate (in the Presence of Artificial Saliva) and Compressive Strength

The improvement of mechanical and antibacterial properties of glass ionomer cements (GICs) is an important goal in dental research. In this way, modification of GIC with caries preventive and remineralizing materials such as casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is a new strategy to enhance its anticariogenic properties and the remineralization of teeth. However, one main concern is that adding CPP-ACP may have negative effects on the mechanical properties of GIC. This study investigated the influence of adding CPP-ACP on the wear rate (in the presence of artificial saliva) and compressive strength of luting and lining glass ionomer cement. CPP-ACP was incorporated into a luting and lining glass ionomer cement at different percentages (1, 1.56, and 2%). Wear rate and compressive strength were measured for each group using Pin-on-Disk tribometer device (in artificial saliva condition) and universal testing machine, respectively. The wear test was carried out in the presence of artificial saliva for better simulation of the oral environment. Our results demonstrated that increasing the percentage of CPP-ACP from 0 up to 1.56% (w/w), caused a decrease of 19% in the wear rate. However, at 2% (w/w) CPP-ACP, the wear rate increased. Compressive strength was improved by 31% when the CPP-ACP concentration was increased to 1.56% (w/w), but decreased when the concentration was raised to 2% (w/w). In conclusion, adding 1.56% CPP-ACP into luting and lining glass ionomer cement appears to provide an acceptable combination of two important mechanical properties, compressive strength and wear rate.

Do Dental Resin Composites Accumulate More Oral Biofilms and Plaque than Amalgam and Glass Ionomer Materials?

A long-time drawback of dental composites is that they accumulate more biofilms and plaques than amalgam and glass ionomer restorative materials. It would be highly desirable to develop a new composite with reduced biofilm growth, while avoiding the non-esthetics of amalgam and low strength of glass ionomer. The objectives of this study were to: (1) develop a protein-repellent composite with reduced biofilms matching amalgam and glass ionomer for the first time; and (2) investigate their protein adsorption, biofilms, and mechanical properties. Five materials were tested: A new composite containing 3% of protein-repellent 2-methacryloyloxyethyl phosphorylcholine (MPC); the composite with 0% MPC as control; commercial composite control; dental amalgam; resin-modified glass ionomer (RMGI). A dental plaque microcosm biofilm model with human saliva as inoculum was used to investigate metabolic activity, colony-forming units (CFU), and lactic acid production. Composite with 3% MPC had flexural strength similar to those with 0% MPC and commercial composite control (p > 0.1), and much greater than RMGI (p < 0.05). Composite with 3% MPC had protein adsorption that was only 1/10 that of control composites (p < 0.05). Composite with 3% MPC had biofilm CFU and lactic acid much lower than control composites (p < 0.05). Biofilm growth, metabolic activity and lactic acid on the new composite with 3% MPC were reduced to the low level of amalgam and RMGI (p > 0.1). In conclusion, a new protein-repellent dental resin composite reduced oral biofilm growth and acid production to the low levels of non-esthetic amalgam and RMGI for the first time. The long-held conclusion that dental composites accumulate more biofilms than amalgam and glass ionomer is no longer true. The novel composite is promising to finally overcome the major biofilm-accumulation drawback of dental composites in order to reduce biofilm acids and secondary caries.

Effects of thermal fatigue on shear punch strength of tooth-colored restoratives

Aims:

This study investigated the effect of thermal fatigue on the shear strength of a range of tooth-colored restorative materials including giomers, zirconia-reinforced glass ionomer cement (GIC), nano-particle resin-modified GIC, highly viscous GICs, and composite resin.

Materials and Methods:

Twenty specimens of each material were fabricated in standardized washers (17 mm outer diameter, 9 mm internal diameter, 1 mm thick). The specimens were cured, stored in 100% humidity at 37.5°C for 24 h, and randomly divided into two groups of 10. Group A specimens were nonthermocycled (NT) and stored in distilled water at 37°C for 168 h. Group B specimens were thermocycled (TC) for 10,000 cycles (168 h) with baths X, Y, and Z adjusted to 35°C, 15°C, and 45°C, respectively. Each cycle had dwell times of 28 s in X, and 2s in Y/Z in the order XYXZ. Specimens then underwent shear punch testing at a crosshead speed of 0.5 mm/min with a 2 kN load cell. Statistical analysis of shear strength was done using t-test and two-way ANOVA/Scheffe's post hoc test at significance level P < 0.05.

Results:

The effect of thermal fatigue on shear strength was material dependent. Except for the “sculptable” giomer (Beautifil II) and a highly viscous GIC (Fuji IX GP Fast), no significant differences in shear strength were generally observed between the NT and TC groups. For both groups, the composite resin (Filtek Z250XT) had the highest shear strength while the zirconia-reinforced (zirconomer) and a highly viscous GIC (Ketac Molar Quick) had the lowest.

Conclusions:

The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The “sculptable” composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the “flowable” injectable hybrid giomer was intermediate between the composite and GICs.