The effect of mixing time on the handling and compressive strength of an encapsulated glass-ionomer cement

Comparison between the effect of adding microhydroxyapatite and chitosan on surface roughness and Microhardness of resin modified and conventional glass ionomer cements

Background

This study aimed to compare the effect of chitosan (CH) and hydroxyapatite (HP) on the surface roughness and microhardness of a conventional glass ionomer cement (CGIC) and a resin modified glass ionomer cement (RMGIC).

Material and Methods

60 disk-shaped specimens (2mm x 6mm) were prepared in 6 groups; group I: CGIC, group II: RMGIC, group III: CGIC + 15% volume CH solution in liquid, group IV: CGIC +10% weight micro-HP in powder, group V: RMGIC + 15% volume CH, group VI: RMGIC + 10% weight micro-HP. After storage in deionized water at room temperature for 24 hours, the surface roughness and microhardness of the specimens were measured using a surface profilometer and Vickers microhardness (VHN) tester, respectively. Data were analyzed using two-way ANOVA, Tukey HSD test and paired t-test (P<0.05).

Results

The microhardness values of RMGIC and CGIC decreased significantly with the addition of micro-HP (P<0.001). None of the CH-containing GICs showed significant changes in microhardness (P = 0.552). The VHN values of CGIC were higher than RMGIC, regardless of the added substance (P<0.001). The surface roughness (Ra) values (μm) of both RMGIC and CGIC decreased significantly with the addition of CH (P = 0.004). The incorporation of micro-HP into GICs did not have a significant effect on surface roughness values (P = 0.700). The RMGIC showed less Ra values compared to the CGIC regardless of the added substance (P<0.001). The lowest and highest Ra values were observed in RMGIC + CH and CGIC + micro-HP groups, respectively.

Conclusions

The addition of CH to GIC and RMGIC reduced the surface roughness and did not have an adverse effect on the microhardness. Mixing GIC and RMGIC with micro-HP resulted in microhardness reduction and did not affect the surface roughness.

Key words:Glass ionomer, hydroxyapatite, chitosan, hardness, surface roughness

A Review of Dental Cements

This review provides an in-depth comparison of advantages and disadvantages of different types of dental cements as they are used for cementing base metal alloy crowns in dogs.

The Repair of Furcal Perforations in Different Diameters with Biodentine, MTA, and IRM Repair Materials: A Laboratory Study Using an E. Faecalis Leakage Model

The aim of this study is to evaluate the microleakage of repair materials MTA, IRM, and Biodentine applied on furcal perforations with different diameters. One hundred and forty extracted human teeth were used in this study. The teeth were divided into 2 main groups (60 teeth in each) which were then divided into 3 subgroups (n = 20). The remaining 20 teeth were divided into 2 groups (10 in each) to serve as controls. The furcal areas of the teeth were perforated with #2 cylindrical burs in Group 1 whereas perforations were made using #4 cylindrical burs in Group 2. Each subgroup of both Groups 1 and 2 received ProRoot MTA (ProRoot, USA), Biodentine (Septodont), or IRM (Dentsply, USA) to repair the perforations. An experimental set-up was established to contaminate repaired perforations with E. Faecalis (ATCC29212). The turbidity of bacteria was observed on the 7th, 15th, 30th, and 45th days. The data was analysed by chi-square test (p > 0.05). The number of bacteria in the group perforated by bur #2 and closed by MTA was found to be lower than the other groups on the 7th day (p < 0.05). There was no statistical difference in the bacterial counts of other groups on the 15th, 30th, and 45th days (p > 0.05). ProRoot MTA was found to be more successful in the prevention of bacterial leakage compared to IRM and Biodentine in smaller perforations during the 1st week.

Glass Polyalkenoate Cements Designed for Cranioplasty Applications: An Evaluation of Their Physical and Mechanical Properties

Glass polyalkenoate cements (GPCs) have potential for skeletal cementation. Unfortunately, commercial GPCs all contain, and subsequently release, aluminum ions, which have been implicated in degenerative brain disease. The purpose of this research was to create a series of aluminum-free GPCs constructed from silicate (SiO₂), calcium (CaO), zinc (ZnO) and sodium (Na₂O)-containing glasses mixed with poly-acrylic acid (PAA) and to evaluate the potential of these cements for cranioplasty applications. Three glasses were formulated based on the SiO₂-CaO-ZnO-Na₂O parent glass (KBT01) with 0.03 mol % (KBT02) and 0.06 mol % (KBT03) germanium (GeO₂) substituted for ZnO. Each glass was then mixed with 50 wt % of a patented SiO₂-CaO-ZnO-strontium (SrO) glass composition and the resultant mixtures were subsequently reacted with aqueous PAA (50 wt % addition) to produce three GPCs. The incorporation of Ge in the glass phase was found to result in decreased working (142 s to 112 s) and setting (807 s to 448 s) times for the cements manufactured from them, likely due to the increase in crosslink formation between the Ge-containing glasses and the PAA. Compressive (σc) and biaxial flexural (σf) strengths of the cements were examined at 1, 7 and 30 days post mixing and were found to increase with both maturation and Ge content. The bonding strength of a titanium cylinder (Ti) attached to bone by the cements increased from 0.2 MPa, when placed, to 0.6 MPa, after 14 days maturation. The results of this research indicate that Germano-Silicate based GPCs have suitable handling and mechanical properties for cranioplasty fixation.

Resistência à tração diametral de cimentos de ionômero de vidro submetidos à aplicação de ondas de ultrassom

INTRODUÇÃO: O cimento de ionômero de vidro é um material odontológico que apresenta limitações de uso devido às suas propriedades mecânicas, como baixa resistência ao desgaste, microdureza, compressão e tração diametral. Com base nisso, este estudo investigou o efeito da excitação ultrassônica sobre o CIV, em diferentes tempos de aplicação, por meio da resistência à tração diametral. MATERIAL E MÉTODO: Os materiais utilizados foram o Ketac Molar Easymix (KME) e o Ketac Cem Easymix (KCE). Foram confeccionados 10 corpos de prova para cada condição estudada: grupo controle, e os grupos que receberam aplicação de ultrassom por 15s, 30s e 45s, para ambos materiais. A excitação ultrassônica foi aplicada durante a reação de presa inicial do CIV, logo após sua inserção na matriz de silicone. Os valores de resistência à tração diametral foram analisados pelo teste Shapiro Wilk e Anova (α = 0.05). RESULTADO: A aplicação de excitação ultrassônica não apresentou efeito estatisticamente significante na resistência à tração diametral dos materiais testados, independente do tempo de aplicação (p > 0,05). O KME apresentou resistência estatisticamente maior que o KCE (p = 0,023). CONCLUSÃO: A utilização das ondas ultrassônicas não influenciou na resistência à tração diametral dos CIV testados independentemente do seu tempo de aplicação.

Are encapsulated anterior glass-ionomer restoratives better than their hand-mixed equivalents?

OBJECTIVES

The performance of encapsulated anterior GI restoratives were compared with their hand-mixed equivalents for the range of powder to liquid mixing ratios routinely encountered clinically. The clinically induced variability of powder to liquid mixing variations of an anhydrous GI restorative formulation was also compared with conventional GI restorative formulations that contained a polyalkenoic acidic liquid.

METHODS

Mean compressive fracture strengths, mean elastic moduli and mean total volumetric wear were determined for the encapsulated anterior GI restoratives mechanically mixed in a Capmix or Rotomix machine and the hand-mixed GI restoratives prepared with powder contents reduced from that recommended by the manufacturer (100%) in 10% increments to 50% for a constant weight of liquid. Multiple comparisons of the group means were made using a one-way analysis of variance (ANOVA) and Tukey's multiple range tests employed at P<0.05.

RESULTS

For the encapsulated GI restoratives, the mean compressive fracture strength, mean elastic modulus and in-vitro wear resistance were significantly increased compared with their hand-mixed equivalents prepared with powder contents below that recommended by the manufacturers. The conventional GI restoratives resulted in a linear deterioration (R2>0.95) of the mean compressive fracture strength and mean elastic modulus with powder content compared with the bi-modal deterioration for the anhydrous GI restorative.

CONCLUSIONS

Encapsulated anterior GI restoratives outperform their hand-mixed equivalents for the range of powder to liquid mixing ratios routinely encountered clinically such that they are advocated for use in clinical practice. Anhydrous GI restorative formulations are more susceptible to clinically induced variability on mixing compared with conventional GI restorative formulations that contained a polyalkenoic acidic liquid.

Is encapsulation of posterior glass-ionomer restoratives the solution to clinically induced variability introduced on mixing?

OBJECTIVES

Three GI restorative systems were evaluated to determine if encapsulated GI restoratives performed more favorably than the hand-mixed equivalents prepared with powder contents progressively decreased from that recommended by manufacturers in 10% increments for a constant weight of liquid which are routinely employed in clinical practice.

METHODS

Mean compressive fracture strengths, associated Weibull moduli and mean elastic moduli were determined for series of 30 nominally identical cylindrical specimens for three hand-mixed GI restoratives prepared with 100-50% of the recommended powder content for a constant weight of liquid and the equivalent encapsulated GI restoratives mechanically mixed in the Capmix or Rotomix machines.

RESULTS

Decreasing the powder content of the three hand-mixed GI restoratives for a constant weight of liquid from that recommended by the manufacturers resulted in a progressive deterioration of the mean compressive fracture strengths and the mean elastic modulus. The elastic modulus was more sensitive than the compressive fracture strength to highlighting the impact of mixing ratio variations in the GI restoratives. There were no significant differences between mean compressive fracture strengths of mechanically mixed encapsulated GI restoratives, however, variations in mean elastic modulus were dependent upon the mixing time employed.

CONCLUSIONS

The employment of an intrinsic material property was more sensitive than a non-intrinsic material property to highlight the impact of mixing ratio variations in hand-mixed restoratives and the effect that the method of mechanical mixing has on encapsulated GI restoratives. Encapsulated GI restoratives are a potential solution to the operator induced variability associated with hand-mixed GI restoratives.

Dental cements for definitive luting: a review and practical clinical considerations

Dental cement used to attach an indirect restoration to a prepared tooth is called a luting agent. A clinically relevant discussion of conventional and contemporary definitive luting agents is presented in this article. Physical properties are listed in table form to assist in comparison and decision-making. Additional subtopics include luting agent requirements, classifications, retention and bonding, cement considerations for implant-supported teeth, and fatigue failure.