Resin-modified Glass Ionomer Materials Research Articles

Radiopacity evaluations of the novel calcium-silicate and glass-Ionomer-based materials

Aims: Radiopacity is a crucial property for a liner or base material, and these materials should provide an optimal contrast for detecting secondary caries in radiographic examinations. The purpose of this study was to assess the radiopacity characteristics of four calcium-silicate-based and two glass-ionomer-based materials used as a liner or base in direct or indirect vital pulp therapy.
 Methods: A total of 60 cylindrical-shaped and 1 mm thick specimens were prepared from a calcium-silicate (Biodentine, Septodont), a calcium-silicate (MTA, Angelus), a light-cured resin-modified calcium silicate (TheraCal LC, Bisco), a dual-cured resin-modified calcium silicate (TheraCal PT, Bisco), a glass hybrid glass-ionomer (Equia Forte HT, GC), and a resin-modified glass ionomer (Glass Liner, Wp Dental) material (n=10). Digital radiographic images of the specimens, a molar tooth section with 1 mm thickness, and an aluminum step wedge were obtained by a digital radiography system (Heliodent Plus, 
 Dentsply Sirona) with 60 kV voltage, 7 mA current, and 0.25 seconds exposure time. The mean gray values (MGV) of digital images were determined using the ImageJ software program (National Institute of Health, Bethesda, MD, USA). Kruskal-Wallis and Mann-Whitney tests (pBiodentine>Equia Forte HT>Theracal PT>Theracal LC>Glass Liner, respectively. All the tested liner or base materials exhibited significantly greater radiopacity values when compared to those of dentin (p

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

ObjectivesThis 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 methodsConventional 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. ResultsTwo-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. ConclusionsIncorporation 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.

CAD/CAM leucite-reinforced glass-ceramic for simulation of attrition in human enamel in vitro

ObjectiveInvestigate attrition simulation using CAD/CAM leucite-reinforced glass-ceramic antagonists on occlusal vs. buccal enamel. MethodsThree dental materials with known wear rates (resin-modified glass-ionomer, micro-filled, and fine particle composites) validated the wear simulator (CAD/CAM glass-ceramic antagonists, 200 cycles, 80 N load, deionised water irrigation, 0.7 mm sliding movement). Following this, human molars were sectioned into paired occlusal and buccal polished samples (n = 8/gp). Exposed 1.5 mm Ø enamel areas were subjected to attritional wear with and without pre-immersion in citric acid (5 min, 0.3%, pH 3.8). Profilometry measured step-height enamel wear and surface microhardness at different depths was calculated using Vickers indentation at 0.1 N and 0.5 N loads. ResultsDental material wear using the CAD/CAM antagonists showed consistency with previous data: mean (SD) resin-modified glass ionomer material loss of 177.77 (16.89) µm vs. 22.15 (1.30) µm fine particle hybrid composite resin wear vs. 13.63 (1.02) µm micro filled composite resin wear (P < 0.001). The coefficient of variation was less than 10%. Following validation, enamel sample wear was significantly increased when attrition was introduced (P < 0.001) independent of buccal vs. occlusal sample location (P < 0.05). Attrition resulted in occlusal wear of 26.1 ± 4.5 µm vs. buccal 26.3 ± 1.2 µm and attrition/erosion resulted in occlusal wear of 26.05 ± 4.46 µm vs. buccal 25.27 ± 1.16 µm. Whereas erosion-alone resulted in occlusal wear of 1.65 ± 0.13 µm and buccal 1.75 ± 0.03 µm. Microhardness testing at different loads revealed significantly greater hardness reductions in occlusal enamel vs. buccal enamel for 0.1 KgF indentations (P < 0.001) whereas in contrast 0.5 KgF indentations showed no differences. SignificanceWear simulation with CAD/CAM glass ceramic antagonists produced consistent wear in dental materials and human enamel, regardless of enamel surface origin. Lighter (0.1 KgF) hardness testing of occlusal vs. buccal origin revealed damage to the mechanical integrity of the superficial worn enamel.

Be Smart and Active in Conservative Dentistry and Endodontics.

Numerous aspects of dentistry have been transformed by smart materials. In recent years, there have been advancements in dental materials that exhibit improved biological compatibility. These materials are specifically designed to interact effectively with the fluids found in the oral cavity, including saliva and gingival crevicular fluids. The search for the optimum restorative material results in the development of a more recent generation of dental materials known as smart materials. Smart materials react to stimuli, including stress, temperature, moisture, pH, electric field, and magnetic field, in a regulated way. Some of them are biomimetic and can imitate the dentin and enamel seen in natural teeth. These resources herald the start of a new era in dentistry known as "Smart Dentistry," and they project a promising future in terms of improved dependability and efficiency. These types of diverse materials can pick up and perform definite functionalities regarding adjustments in the nearby surroundings. Based on their capacity for recognition, analysis, and discrimination, these materials might be able to foresee problems in the near future. The superior biocompatibilities of smart materials, which have brought about a new generation of biosmart dentistry, are a crucial component of their utilization in numerous dental applications. We should use any material with intelligence as we progress in innovation and advanced technology. Additionally, we should purposefully incorporate intelligence into existing materials through design. Smart materials have proven advantageous in the field of dentistry, particularly in restorative applications. Various dental products, including smart composites, resin-modified glass ionomer materials, pit, and fissure sealants releasing amorphous calcium phosphate (ACP), smart ceramics, and compomers have all witnessed positive advancements due to the integration of smart materials.

Effect of Aging on Hardness of Glass Ionomer, Resin-Modified Glass Ionomer, Giomer and Compomer Dental Restorative Materials

Objective: To assess deionized water's aging effect on the hardness of four direct tooth colored dental filling materials i.e., Glass Ionomer Cement, Resin Modified Glass Ionomer, Giomer and Compomer.Study Design: An in vitro experimental study performed in triplicates.Place and Duration of Study: The study was carried out at PG Laboratory, Department of Science of Dental Materials, Army Medical College, Rawalpindi, Pakistan from February 2023 to August 2023.Methods: Three disc-shaped samples (n=3) of 10 mm diameter and 1 mm thickness of each restorative material were prepared using stainless steel molds per manufacturer's instructions. These disc-shaped samples were then suspended in a 15 mL conical centrifuge tube containing 10 mL deionized water, followed by incubation in a Forced Convection Laboratory Oven at 37 C where these were allowed to age over a period of 1-2 years. Vickers Hardness of each sample was then checked at two-time intervals, i.e., after 24 h setting and after 2.5 years of ageing through the Micro Vickers Hardness Tester calibrated at 1Kgf (9.80 N) with dwell time of 10 seconds and light intensity 10. Results: After one day (24 h) aging in deionized water, maximum mean Vickers hardness number (VHN) was exhibited by Compomer (539.83±58.08 VHN) and least by GIC (175.75±24.47 VHN). After aging the sample for 912 days, maximum mean VHN was observed for GIC (420.67±99.66 VHN) and least by Compomer (354.33±9.22 VHN). Conclusion: RMGIC sustains its hardness on aging, hardness of GIC increases while that of Giomer and Compomer decreases upon aging.&#x0D; How to cite this: Gul H, Nayyer M, Junaid Y, Pasha M, Ejaz T, Liaqat U, Hassan SH. Effect of Aging on Hardness of Glass Ionomer, ResinModified Glass Ionomer, Giomer and Compomer Dental Restorative Materials. Life and Science. 2023; 4(4): 438-444. doi: http://doi.org/10.37185/LnS.1.1.437

Newer Possibilities for Proximal Box Elevation – Tooth Substrate and Comparison with Conventional Materials: An Ex-vivo Study

Background: Adhesive bonding in deep sub-gingival areas is a challenge due moist environment leading to poor marginal seal and microleakage in deep class II cavities. The deep margin elevation technique is advocated in such areas.&#x0D; Aim: The aim of this study is to evaluate enamel, a natural substrate as an alternative material for deep margin elevation, and compare it with the resin-modified glass ionomer and composite material by evaluating microleakage at the tooth-restoration interface in Class II cavities.&#x0D; Materials and Methods: For this study 21 patients having at least one tooth indicated for extraction and 7 patients having at least two teeth indicated for extraction were included.Class II cavities were prepared on the 28 teeth with proximal margins 1mm below the CEJ and were divided into 4 groups(n=7) Group 1: flowable composite was used for deep margin elevation(DME) up till 2mm above CEJ, Group 2: RMGIC was used for DMEup till 2 mm above CEJ, Group 3: enamel slab luted with RMGIC (for DME)up till 2mm above CEJ,enamel slab obtained from other seven teeth of same patient also indicated for extraction, Group 4(control): no intermediate material was used for margin elevation. Then the remaining part of the cavities were restored using the FILTEK P60. The prepared teeth were extracted after one week. The class II cavities were evaluated for microleakage using dye penetration method.&#x0D; Results: RMGIC and enamel slab showed significantly less microleakage as compared to flowable composite and the control group. However there was insignificant difference between RMGIC and Enamel slab group. The control group exhibited highest microleakage as compared to all the other groups.&#x0D; Conclusion: RMGIC and enamel slab exhibit least microleakage when used as materials for deep-margin elevation.

Smart composites — The new era in smart dentistry

The current dental materials were improvised to make them smarter. The use of these smart materials such as, smart ceramics, smart composites, amorphous calcium phosphate releasing pit and fissure sealants, compomers, resin-modified glass ionomer, etc. and other materials such as smart impression material, orthodontic shape memory alloys, smart suture, smart burs, etc. Has revolutionized dentistry. The quest for an ideal restorative material leads to the discovery of a newer generation of materials in dentistry which is called as smart materials. These materials are called smart as they can be altered in a controlled fashion by stimulus such as stress, temperature, pH, moisture, electric or magnetic field. These smart materials hold future in terms of improved efficiency and mark the beginning of a new generation or era in Smart dentistry. The objective of this review article is to review about smart materials and its classification, dental composite resin and its historical background, smart composites, smart monochromatic composite.

18 - Evaluation of the mechanical properties of three resin-modified glass-ionomer materials

18 - Evaluation of the mechanical properties of three resin-modified glass-ionomer materials

Clinical bracket failure rates between different bonding techniques: a systematic review and meta-analysis.

Bracket failure increases the treatment time of orthodontic therapy and burdens patients with unnecessary costs, increased chair time, and possible new appointments. To compare the bond failures of different orthodontic materials based on the results of available clinical studies. A systematic search of clinical trials was performed in the Cochrane, Embase, and Pubmed databases with no limitations. The list of investigated techniques contained conventional acid-etch primer (CM-AEP), self-etch primer (SEP), self-cure resin (SCR), and simple or resin-modified glass ionomer (RM-GIC) materials and procedures. Clinical studies reporting the failure rate of bonded brackets after using direct adhesive techniques on buccal sites of healthy teeth were included. Bracket failure rates from eligible studies were extracted by two authors independently. Risk ratios (RRs) were pooled using the random-effects model with DerSimonian-Laird estimation. Thirty-four publications, involving 1221 patients, were included. Our meta-analysis revealed no significant difference in the risk of bracket failures between SEP and CM-AEP. After 6, 12, and 18 months of bonding, the values of RR were 1.04 [95% confidence interval (CI), 0.67-1.61], 1.37 (95% CI, 0.98-1.92), and 0.93 (95% CI, 0.72-1.20), respectively. At 18 months, bracket failure was 4.9 and 5.2% for SEP and CM-AEP, respectively. Heterogeneity was good or moderate (I2 < 42.2%). The results of RM-GIC at 12 months indicated a 57% lower risk of bracket failure using SCR as compared with RM-GIC (RR: 0.38; 95% CI, 0.24-0.61). At 18 months, bracket failures for SCR and RM-GIC were 15.8 and 36.6%, respectively (RR: 0.44; 95% CI, 0.37-0.52, I2 = 78.9%), demonstrating three to six times higher failure rate than in the case of etching primer applications. A major limitation of the present work is that the included clinical trials, with no exceptions, showed variable levels of risk of bias. Another possible problem affecting the outcome is the difference between the clustering effects of the split mouth and the parallel group bracket allocation methods. The results revealed no significant difference between SEP and CM-AEP up to 18 months after application. RM-GIC had much worse failure rates than acid-etching methods; additionally, the superiority of SCR over RM-GIC was evident, indicating strong clinical relevance. Prospero with CRD42020163362.

Survival analysis of crown margin repair: A retrospective study in a dental school setting

BackgroundRepairing crowns with defective margins is minimally invasive and cost-effective compared with replacement. The authors’ objectives were to examine the survival trajectory of crown margin repairs and to determine the factors associated with survival. MethodsRecords of adult patients from January 2008 through August 2019 were reviewed for crown margin repairs completed at University of Iowa College of Dentistry. A total of 1,002 crown margin repairs were found. Each repair was followed through the end of study in 2019 or until an event (for example, additional repair, endodontic treatment, crown replacement, or extraction). A Cox proportional hazards model was used to study the relationship between selected covariates and time to event. ResultsDuring the follow-up period, 32.8% of the repairs needed reintervention. In the final model, repair material was the only significant covariate. No difference was found between the survival of repairs done with resin-modified glass ionomer and amalgam. However, the repairs done with resin-based composite and conventional glass ionomer were more likely (1.5 times: 95% CI, 1.02 to 2.10 times; and 2 times: 95% CI, 1.40 to 2.73 times, respectively) to need reintervention than were those done with amalgam. ConclusionsMedian survival time of crown margin repairs was 5.1 years (95% CI, 4.48 to 5.72 years). Median survival times for amalgam, resin-modified glass ionomer, resin-based composite, and glass ionomer repair materials were 5.7 years (95% CI, 4.80 to 6.25 years), 5.3 years (95% CI, 4.73 to 6.34 years), 3.2 years (95% CI, 2.51 to 6.19 years), and 3.0 years (95% CI, 2.53 to 3.62 years), respectively. Practical ImplicationsWhen considering crown margin repairs, resin-modified glass ionomer or amalgam is preferable to resin-based composite or glass ionomer.

Demineralization Inhibition by Two Calcium-releasing Restorative Materials.

To compare the ability of two calcium-releasing restorative materials to inhibit root dentin demineralization in an artificial caries model. Preparations were made at the cementum-enamel junction of extracted human molars (40, n=10/material) and restored with two calcium-releasing materials (Experimental composite, Pulpdent Corporation and Cention N, Ivoclar Vivadent), a resin composite (Filtek Supreme Ultra, 3M Oral Care), and a resin-modified glass ionomer (RMGI) (Fuji II LC, GC). All materials (other than the RMGI) were used with an adhesive (Scotchbond Universal Adhesive, 3M Oral Care) in the self-etch mode, which was light cured for 10 seconds. All restorative materials were light cured in 2-mm increments for 20 seconds and then finished with a polishing disc. Teeth were incubated (37°C) for 24 hours in water. An acid-resistant varnish was painted onto the teeth around the restoration, leaving a 2-mm border of uncovered tooth. A demineralization solution composed of 0.1 M lactic acid, 3 mM Ca3(PO4)2, 0.1% thymol, and NaOH (to adjust pH=4.5), and a remineralization solution composed of 1.5 mM Ca, 0.9 mM P, and 20 mM Tris(hydroxymethyl)-aminomethane (pH=7.0) were prepared. Specimens were placed in the demineralization solution for 4 hours, followed by the remineralization solution for 20 hours and cycled daily for 30 days. The specimens were embedded, sectioned into 100-μm sections, and the interface between the restorative material and root dentin was viewed with polarized light microscopy. A line was drawn parallel with the zone of demineralization for each tooth. The area of "inhibition" (defined as the area external to the line) or "wall lesion" (defined as the area internal to the line) was measured with image evaluation software. Areas of inhibition were measured as positive values, and areas of wall lesions were measured as negative areas. A one-way analysis of variance (ANOVA) found significant differences between materials for "inhibition/wall lesion" areas in root dentin (p<0.001). Tukey post hoc analysis ranked materials (μm2, mean ±SD): Fuji II LC (5412±2754) > Cention N (2768±1576) and experimental composite (1484±1585) > Filtek Supreme Ultra (-1119±1029). The experimental composite and Cention N materials (used with an adhesive) showed net areas of inhibition greater than a reference resin composite, albeit at a lower level than a reference RMGI material (used with no adhesive).

Effect of brushing on surface roughness, fluoride release, and biofilm formation with different tooth-colored materials

Background/purposeTooth brushing, material mechanical ageing procedure, is the most effective way in removing biofilm. The purpose of this study was to investigate the surface roughness, fluoride-release, and S. mutans biofilm formation on various tooth-colored restorative materials before and after brushing. Materials and methodsDiscs of materials, a nanocomposite (Filtek Z350XT; CO), a giomer (Beautifil II; GIOMER), a resin-modified glass-ionomer material (Fuji II LC; RMGI), and a conventional glass-ionomer material (Fuji IX GP Extra; GI), were prepared, polished with abrasive discs (SofLex), and divided into brushed and not brushed groups. The surface roughness of specimens was observed using a contact profilometer, fluoride-release was measured using a fluoride-specific ion electrode, and S. mutans biofilm formation, biovolume and live/dead cells, was observed under a confocal laser scanning microscope. ResultsHigher roughness was observed on GI and RMGI than on CO and GIOMER. Brushing had no effect on the roughness. The fluoride-release of GI and RMGI was higher than that of GIOMER. The fluoride-release decreased after brushing in all materials. The biovolume of S. mutans was not significantly different between GIOMER, RMGI and GI, while CO showed the highest. Brushing resulted in a higher biovolume for all materials, except CO, which showed no change. After brushing, all the tested materials demonstrated identical biovolumes. There were no significant differences in live/dead cells among all groups. ConclusionBrushing demonstrated a negative effect on the fluoride-release and biovolume of S. mutans biofilms for all tested materials except nanocomposites.

Surface Analysis and Spectrophotometric Evaluation of Different Esthetic Restorative Materials Frequently Exposed to a Desensitizing Agent.

Background Patients with tooth sensitivity are frequently exposed to desensitizing agents on a regular basis. These agents might have an impact on the surface properties and color of existing oral restorations. Accordingly, this study aimed to investigate the color stability, surface microhardness, and surface roughness of resin-modified glass ionomer (RMGIC), amalgomer CR, nanohybrid, and bulk-fill resin composites restorative materials after frequent exposure to a desensitizing agent. Materials and Methods. One hundred and twenty specimens were prepared; 10 specimens for each restorative material were equally subdivided into control and desensitizing-agent-exposed groups in each test. Surface microhardness and surface roughness were evaluated using the Vickers microhardness tester and surface profilometer, respectively. The color change was measured by using a spectrophotometer using the CIE L∗a∗b∗ formula. Surface topography was analyzed using a scanning electron microscope (SEM). The collected data were analyzed with Student's t-test, one-way ANOVA, and Tukey post hoc tests for pairwise comparison at a level of significance of 0.05. Result The frequent use of a desensitizing agent significantly decreased surface hardness of RMGIC, amalgomer, and bulk-fill composite materials. However, nanohybrid composite exhibited a significant surface hardness increase. The surface roughness of RMGIC, amalgomer, and nanohybrid composite increased significantly. Meanwhile, the bulk-fill resin composite showed a nonsignificant decrease. Both RMGIC and amalgomer exhibited significantly higher values of color change in comparison to those of nanohybrid and bulk-fill composites. Conclusion The bulk-fill composite seems to be more resistant to discoloration and surface topographical changes than other tested materials on frequent exposure to the desensitizing agent. However, this exposure may pose a negative impact on its surface hardness. Bulk-fill resin composite may be the most suitable esthetic restorative in patients who frequently use desensitizing agents.

Undetected Excess Cement at Marginal Areas of Zirconia Crown Copings: In Vitro Analysis of Two Luting Agents and Their Influence on Retention.

To evaluate the amount of residual cement (ECL) around the margins of zirconia crown copings after careful luting and cleaning procedures and to investigate these factors in relation to two tested luting materials. An experimental model of a maxillary arch was selected for this in vitro study. The maxillary first molar was prepared to receive an all-ceramic, single, full-crown restoration with a finish line located 1 mm below the artificial gingiva. After scanning of the prepared tooth, 20 paired zirconia coping-abutment assemblies were CAD/CAM fabricated. A slot in the model allowed for insertion and removal of the assemblies for each new test. Specimens were divided into two groups according to the cementation procedure: half (n = 10) were luted using a resin-modified glass-ionomer (RMGI) (Ketac-Cem Plus) (GI group), and the other half with a dual-curing self-adhesive resin agent (RelyX Unicem 2) (UN group). The substructures were loaded with cement, and a customized preseating device was adopted for preliminary reduction of excess. The zirconia copings were finally seated on their respective abutments located on the simulation model. A blinded investigator attempted to remove all excess cement with clinically available instruments. The amount of excess cement left in situ after cleaning procedures was weighed in grams. Dislodging forces of luted coping-abutment assemblies were obtained by using pull-off tests in a universal testing machine (crosshead speed of 0.5 mm/minute) after 24 hours of water storage. Means and standard deviations were calculated for ECL and for retention force values, and Mann-Whitney and ANOVA tests were carried out to detect significant differences (α = .05) among groups. Cement remnants were found in all specimens despite the cleaning procedures, with a typical distribution in interproximal areas. Mean ECL values for the GI and UN groups were 0.0079 ± 0.0060 and 0.0107 ± 0.0081, respectively. No statistically significant differences were found between tested cements (P = .3284). Removal stress values (MPa) were significantly higher (P = .0313) for the UN group (12.4 ± 6.5) than for the GI group (6.57 ± 4.69). Similar amounts of undetected cement remnants were discovered around the esthetic margins of zirconia crown copings regardless of cement type. The luting procedure using the self-adhesive resin cement provided significantly higher early retention values than the RMGI material.

Linear Coefficient of Thermal Expansion Evaluation of Glass Ionomer and Resin-Modified Glass Ionomer Restorative Materials.

The purpose of this evaluation was to evaluate the linear coefficient of thermal expansion (LCTE) of 12 conventional glass ionomer (GIC) and four resin-modified glass ionomer (RMGI) restorative materials. GIC and RMGI specimens (2 mm × 5 mm × 5 mm) were fabricated (n=12) following manufacturer instructions and were placed in 0.2M phosphate-buffered saline and stored at 37°C and 98% humidity for one week. Specimens had LCTE determined with a thermomechanical analysis (TMA) unit using a 15°C-50°C heating cycle as well as a 50°C-15°C cooling cycle at a 5°C/min rate, using a 3-mm ball-point probe under 0.02 N probe pressure with all specimens kept saturated with PBS using a specially designed quartz container. Each specimen was tested three times, with the mean representing the specimen LCTE. Mean results between specimen heating and cooling were compared with paired Wilcoxon sign rank test, while results between materials were compared with Kruskal-Wallis/Dunn's ( α=0.05). GIC LCTE ranged from approximately 5°C to 20°C ppm °K-1, while the RMGI LCTE ranged from approximately 25°C to 47°C ppm °K-1. With some exception, the LCTE during cooling displayed a greater trend. Under moisture conditions similar to the oral cavity, GIC materials overall had LCTE values closer to that reported for tooth structure. RMGI materials displayed higher values, which was thought to be related to the amount of resin in the matrix. A generally greater LCTE trend with cooling for all materials was noted, but the small magnitude of the difference is presently thought to be of minor clinical significance.

Effect of surface treatments on the mechanical properties and antimicrobial activity of desiccated glass ionomers

ObjectivesThe purpose of this study was to evaluate the effect of various surface treatments on the mechanical properties and antibacterial activity of desiccated glass-ionomer (GI) and resin-modified glass-ionomer (RMGI) materials. MethodsOne hundred GI and RMGI specimens were fabricated in a mold, stored in 100% humidity for 24h, placed in air to desiccate for 24h, and then stored for one week in one of the five media [casein phosphopeptide–amorphous calcium phosphate (CPP–ACP), chlorhexidine (CHX), sodium fluoride (NaF), cetylpyridinium chloride (CPC), or 100% humidity (control)]. Fifty GI and RMGI specimens were tested in flexure to determine flexural strength and modulus, with the fragments used for Knoop hardness testing. The remaining 50 GI and RMGI specimens were covered with a suspension of Streptococcus mutans and incubated for 24h. The bacterial suspension was removed and the specimens were washed. Sterile saline was added, vortex mixed, serially diluted, and plated. CFU/mLs were calculated after 3days of incubation. ResultsCompared to the 100% humidity control group, surface treatment of the desiccated GI and RMGI materials had a variable effect on the mechanical properties. In general, NaF provided the greatest improvement in flexural strength and modulus. Surface treatment of the desiccated GI or RMGI specimens with CHX or CPC resulted in no growth of the S. mutans. NaF resulted in significantly lower CFU/mL than CPP–ACP, which was significantly lower than the control group. SignificanceSurface treatment with 5% NaF provides improved antimicrobial and strength properties of desiccated GI or RMGI materials.

Microleakage of Lithium Disilicate Crown Margins Finished on Direct Restorative Materials.

For some esthetic clinical situations, it is necessary to finish crown margins on direct restorative materials to preserve tissue integrity, bonding integrity, and biological width. The purpose of this research was to investigate microleakage at the interface between bonded lithium disilicate crowns and various direct restorative materials in a class III and class V position. Class III or class V restorations were prepared on one side of extracted incisors with either Tetric EvoCeram, Tetric Evoceram Bulk, Fuji II LC, or Tetric Evoflow. The teeth were prepared for and received a lithium disilicate crown. After load fatiguing, the specimens were thermo-cycled with a fuchsin dye and sectioned. The depth and area of dye penetration were measured with a dimensional grid in micrometers using stereomicroscopy and reported as mean dye depth and area (μm) ± SD. The comparison of multiple categorical independent variables with ratio scale dependent variables was evaluated with an analysis of variance and Tukey's post hoc analysis. A statistically significant higher dye penetration was noted for all treatment groups compared with the positive control (side opposite the restoration after sagittal sectioning was used as positive control) regardless of material or placement area (p<0.05). In comparing treatment groups, the Tetric EvoFlow experienced a statistically higher dye penetration than did the other treatment groups regardless of material or placement area (p<0.05). There was no statistically significant difference between the Tetric EvoCeram, Tetric Evoceram Bulk, and Fuji II LC materials regardless of placement area (p>0.05). Within the limitations of this study, it can be concluded that flowable composite materials as finish lines that interact with resin cements could lead to exacerbated interfacial degradation. Finishing lithium disilicate all-ceramic crowns on flowable resin composite materials in the esthetic zone should be used with caution. If necessary, finishing lithium disilicate all-ceramic crowns on nanofilled resin composite or resin-modified glass ionomer materials seems to provide the least dye penetration depth and area.

Dental Materials: What Goes Where? Class V Restorations.

A large number of Class V restorations are placed per annum to restore cervical lesions. This paper evaluates the pathogenesis of these lesions, with particular reference to the role of occlusal factors, and reviews the literature in order to provide advice on the material(s) which are most likely to produce optimal longevity of a Class V restoration. CPD/CLINICAL RELEVANCE: Resin-modified glass ionomer materials appear to provide optimal survival for a Class V restoration, but a (flowable) comDosite miaht Droduce a better aesthetic result.

Setting Reaction of Dental Resin-Modified Glass Ionomer Restoratives as a Function of Curing Depth and Postirradiation Time

Specular reflectance Fourier transform infrared (SR-FTIR) spectroscopy was used to study the setting reaction of dental resin-modified glass ionomer (RMGI) restoratives as a function of curing depth and postirradiation time. Two light-cure and one tri-cure RMGI materials were selected and used according to the manufacturers’ instructions. Samples were prepared by filling the mixed materials into custom-made molds and then light-irradiating using a dental curing light. The degree of conversion and the extent of acid-base reaction of the materials at different depths (0, 1, 2, and 4 mm) and postirradiation times (10 min, 1 day, and 7 days) were determined using SR-FTIR spectroscopy in conjunction with the Kramers-Kronig (K-K) transformation. The setting reaction was also investigated using microhardness measurements. The results showed that the depth of cure increased over time by the continuous acid-base reaction rather than photopolymerization or chemical polymerization. Microhardness tests seemed less suitable for studying the setting reaction as a function of postirradiation time, probably due to softening from the humidity. Analysis using specular reflectance in conjunction with the K-K algorithm was an easy and effective method for monitoring the setting reaction of dental RMGI materials.

Influence of Photoactivation Source on Restorative Materials and Enamel Demineralization

The objective of this study was to evaluate the influence of the photoactivation source on the polymerization depth of restorative materials and its effects on resistance to enamel demineralization. Argon-ion laser (AL) irradiation itself provides a reduced depth of caries lesions in sound enamel. Eighteen human teeth were sectioned into 36 blocks and distributed into two groups according to the respective restorative material: resin-modified glass ionomer material (RMGI) (Vitremer-3M ESPE; A3; n=18) and composite resin (CR) (Z350-3M ESPE; n=18). Each group was subdivided into three subgroups and activated by a quartz-tungsten-halogen (QTH) lamp, an AL, or a light-emitting diode (LED) (n=6). Knoop microhardness (KHN) analysis of the materials was evaluated at two different depths: 0 and 1.6 mm from the enamel surface. The blocks were thermocycled and submitted to five demineralization-remineralization cycles at 37°C. The KHN values of the enamel surface (0 mm) were evaluated. The specimens were longitudinally sectioned, and the restorative material was evaluated at a depth of 1.6 mm. Data were evaluated by two way analysis of variance (ANOVA) and Tukey tests (p<0.05). The evaluation of subsuperficial enamel demineralization by KHN analysis was conducted by seven indentations located at 100 μm from the restored cavity. Data were evaluated by three way ANOVA and Tukey tests (p<0.05). Comparing the two restorative materials, the KHN values at the surface (0 mm) were greater for CR, whereas at 1.6 mm, they were greater for RMGI. In addition, there was less development of enamel demineralization around RMGI restorations than CR restorations. Moreover, there were statistically significant differences on subsuperficial enamel demineralization between the two restorative materials and between the three photoactivation methods (p<0.05); RMGI presented the highest KHN values, and QTH and AL presented the lowest. The photoactivation source did not influence superficial enamel demineralization, but LED activation positively influenced the subsuperficial microhardness of enamel.