Resin-modified glass ionomer containing calcium glycerophosphate: physico-mechanical properties and enamel demineralization

Effect of the association of microparticles and nano-sized β-calcium glycerophosphate in conventional toothpaste on enamel remineralization: In situ study

OBJECTIVES

This in situ study aimed to assess the remineralizing effect of a fluoride toothpaste supplemented with β-calcium glycerophosphate in both micro (β-CaGPm) and nano-sized forms (β-CaGPn).

METHODS

This blind and cross-over study was performed in 4 phases, each spanning 3 days. Twelve volunteers utilized palatal appliances containing four bovine enamel blocks with artificial caries lesions. Volunteers were randomly assigned to the following treatment groups: Placebo (no F-β-CaGPm-β-CaGPn); 1100 ppm F alone (1100F); 1100F plus 0.5% micrometric β-CaGP (1100F-0.5%β-CaGPm); and 1100F plus 0.25%nano-sized β-CaGP (1100F-0.25%β-CaGPn). Participants were instructed to brush their natural teeth with the palatal appliances in the mouth for 1 min (3 times/day), ensuring that the enamel blocks were exposed to the natural toothpaste slurries. Following each phase, evaluations were conducted to determine the percentage of surface hardness recovery (%SHR), integrated recovery of subsurface hardness (ΔIHR), profile subsurface lesion through polarized light microscopy (PLM), as well as fluoride (F), calcium (Ca), and phosphorus (P) concentrations within the enamel. Data were analyzed by ANOVA and Student-Newman-Keuls test (p < 0.001).

RESULTS

Treatment with 1100F-0.25%β-CaGPn resulted in %SHR ∼69 % and ∼40 % higher when compared to 1100F and 1100F-0.5%β-CaGPm (p < 0.001). The reduction in lesion body (ΔIHR; PLM) was ∼40 % higher with 1100F-0.25%β-CaGPn (p < 0.001) compared to 1100F. The addition of β-CaGPm and β-CaGPn did not influence enamel F concentration (p > 0.001). Treatment with 1100F-0.25%β-CaGPn led to an increase in the concentration of Ca and P in the enamel (p < 0.001).

CONCLUSION

The addition of 0.25%β-CaGPn into 1100F formulation increased the bioavailability of calcium and phosphate, promoting a higher remineralizing effect.

CLINICAL SIGNIFICANCE

Toothpaste containing 1100F-0.25%β-CaGPn showed a potential of higher remineralization to 1100 ppm F and 1100 ppm F micrometric β-CaGP could be a strategy for patients at caries activity.

Effect of enamel-surface modifications on shear bond strength using different adhesive materials

BACKGROUND

This study aimed to investigate the effect of enamel-surface modifications on the shear bond strength between ceramic brackets bonded using different adhesive materials and the enamel surface and to identify the most suitable clinical adhesive and bonding method. Whether the non-acid-etching treatment met the clinical bond strength was also determined.

METHODS

A total of 108 extracted premolars were divided into nine groups (n = 12) based on the different enamel-surface modification techniques (acid etching, deproteinization, and wetting). Group 1 was bonded with Transbond™ XT adhesive, whereas groups 2-9 were bonded with resin-modified glass ionomer cement (RMGIC). The treatment methods for each group were as follows: groups 1 and 2, acid etching; group 3, acid etching and wetting; group 4, acid etching and deproteinization; group 5, acid etching, deproteinization, and wetting; group 6, deproteinization; group 7, deproteinization and wetting; group 8, without treatment; and group 9, wetting. The samples' shear bond strength was measured using an universal testing machine. Adhesive remnant index (ARI) was examined using a stereomicroscope. The enamel-surface morphology was observed with a scanning electron microscope. One-way ANOVA with Tukey's post-hoc test and chi-square test were used for statistical analysis, and p < 0.05 and α = 0.05 were considered statistically significant.

RESULTS

The ARIs of groups 1-5 and 6-9 were statistically significant (p = 0.000). The enamel surface of groups 1-5 was demineralized, and only a tiny amount of protein remained in groups 7 and 8, whereas a thick layer of protein remained in groups 8 and 9.

CONCLUSIONS

RMGIC adhesive did not damage the enamel surface and achieved the required clinical bond strength. The enamel surface was better treated with 5.25% sodium hypochlorite preferably under non-acid-etching conditions.

Effect of casein phosphopeptide amorphous calcium fluoride phosphate and calcium glycerophosphate on incisors with molar-incisor hypomineralization: A cross-over, randomized clinical trial

BACKGROUND: Within the scope of minimally invasive dentistry, the use of different biocompatible remineralization agents on incisors affected by molar-incisor hypomineralization (MIH) gains importance. OBJECTIVE: To evaluate the effect of casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) and calcium glycerophosphate (CaGP) in mineral density (MD) of white/creamy and yellow/brown demarcated opacities on incisors affected by MIH by means laser fluorescence (LF). METHODS: As a cross-over, randomized trial, twenty-two children with 167 incisors affected by MIH were recruited and randomly assigned to one of the two different agents and crossed over to other agents with two weeks washout in between. Incisors were examined by using LF at all before and after three months periods. RESULTS: The results of the paired t-tests for determining the period effect between the baseline findings showed significant difference in white/creamy and yellow/brown demarcated opacities of LF values for both groups (p < 0.05). The difference between both groups according to after categorization of 20% increasing in MD in the percent of change before and after application on LF values; was not found statistically significant in white/creamy (p = 0.970) and yellow/brown (p = 0.948) opacities. CONCLUSIONS: The primary outcome was CPP-ACFP and CaGP had a positive effect in decreasing hypomineralization on MIH-affected enamel for three months period.

Effect of the incorporation of hydroxyapatite on the diametral tensile strength of conventional and hybrid glass ionomer cements

The objective was to evaluate the effect of the incorporation of calcium hydroxyapatite particles (HAp) in the diametral tensile strength of a conventional type II glass ionomer (GC Gold Label 2) and a resin-modified glass ionomer cement (GC Gold Label 2 LC R). Two experimental HAp (E1HAp or E2HAp) were synthesized and characterized using X-ray diffraction and Confocal Raman spectroscopy. Both HAp were added into the powder of a conventional or resin-modified glass ionomer cement at 5 or 10 wt.%. A commercial HAp (CHAp) was used as reference material. For each glass ionomer cement, a group without the incorporation of HAp was used as a control. A universal testing machine was used for the mechanical test. The results were analyzed through a two-way ANOVA test followed by a complementary Tukey test. For all analyzes, the level of significance was set at α = 0.05. The average particle size for E1Hap was 15 µm, E2HAp was 35 μm and for CHAp was 1 µm. For conventional GIC, the addition of 10% E1HAp and 5% CHAp significantly increased the diametral tensile strength values (p ≤ 0.005). On the other hand, for the resin-modified GIC, except for the 5% E2HAp group, all experimental groups significantly reduced the values of diametral tensile strength (p ≤ 0.007). The addition of HAp improved the mechanical properties only for the conventional glass ionomer cement.

Evaluation of Surface Roughness of Composite, Compomer and Carbomer After Curing Through Mylar Strip and Glycerin: A Comparative Study

Aim:

To compare the effect of mylar strip and glycerin topical application on the surface roughness of composite, compomer, and carbomer during polymerization.

Materials and Method:

Each of 45 disc-shaped specimens of Z250, Dyract, Carbomer, were prepared according to manufacturer’s instructions and molded in silicone rubber molds by one operator (5 mm diameter × 2 mm thickness; n = 135). Each restorative group was divided into 3 groups as oxygen group (control), mylar strip, and glycerin group (n = 15). In the control group, specimens were light cured in the open air for 40 s, whereas in the test groups they were covered either with a mylar strip or a drop of glycerin solution and cured for 40 s. Glycerin was rinsed off before polishing. Sof-Lex discs were used for polishing before the surface roughness measurements by a profilometer. The obtained data were statistically analyzed using two-way analysis of variance at a confidence level of 95% ( P < .05).

Results:

The mean surface roughness values of composite, compomer, and carbomer polymerized in air, through mylar strip and glycerin showed no statistically significant difference ( P > .05).

Conclusion:

Mylar strip and glycerin application did not affect the surface roughness of the composite, compomer, and carbomer. Polishing may mask the effect of different curing conditions.

Effect of the restorative technique on load-bearing capacity, cusp deflection, and stress distribution of endodontically-treated premolars with MOD restoration

Objectives

To evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity.

Materials and Methods

Forty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with α = 5%. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations.

Results

MP showed the highest cusp (p = 0.027) deflection (24.28 ± 5.09 µm/µm), followed by FGP (20.61 ± 5.05 µm/µm), CR (17.72 ± 6.32 µm/µm), and GIC (17.62 ± 7.00 µm/µm). For load-bearing, CR (38.89 ± 3.24 N) showed the highest, followed by GIC (37.51 ± 6.69 N), FGP (29.80 ± 10.03 N), and MP (18.41 ± 4.15 N) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post.

Conclusions

There is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.