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.