RGUHS Nat. J. Pub. Heal. Sci Vol No: 17 Issue No: 2 pISSN:
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1Dentizz Dental Care, No.10, Serpentine Street, Richmond Town, Bangalore, Karnataka, India
2Department of Prosthodontics and Crown & Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Bangalore, Karnataka, India
3Department of Prosthodontics and Crown & Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Bangalore, Karnataka, India
4Department of Prosthodontics and Crown & Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Bangalore, Karnataka, India
5Dr. Saadath Afzaa SA, Senior Lecturer, Department of Prosthodontics including Crown and Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Hebbal, Bangalore, Karnataka, India.
6Department of Prosthodontics and Crown & Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Bangalore, Karnataka, India
*Corresponding Author:
Dr. Saadath Afzaa SA, Senior Lecturer, Department of Prosthodontics including Crown and Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, Hebbal, Bangalore, Karnataka, India., Email: afzaasa@gmail.com
Abstract
Objective: To evaluate and compare the compressive strength and diametral tensile strength of Calcium Aluminate Glass Ionomer cement (Ceramir) with three other commercially available glass ionomers namely, Fuji 1, Meron Plus, and Shofu HY Bond.
Methodology: For the study, a total of 160 samples were used. Four different glass ionomers were grouped as Group I, II, III & IV. Each group was tested for compressive and diametral tensile strengths before and after storage in artificial saliva for 24 hours. All the samples were tested using Universal testing machine. The load at the fracture point of specimens was noted and the strength value was determined.
Results: The values recorded for compressive strength were: Group IV > Group II > Group I > Group III among the control groups and Group IV > Group II, Group III > Group I among storage groups. The values recorded for diametral tensile strength were: Group IV > Group I > Group III > Group II among the control groups, and Group IV > Group I > Group II > Group III among storage groups. The study also showed a significant increase in compressive and diametral tensile strength values of individual cements after storage in artificial saliva for 24 hours, except for Meron plus which showed a reduced diametral strength after storage.
Conclusion: Within the limitations of the study, it can be concluded that Ceramir demonstrated intermediate compressive and diametral strength values, whereas Shofu HY Bond glass ionomer showed the highest compressive and diametral tensile strength values among all the cements tested.
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Introduction
Dental luting agents help retain restorations in the oral environment in a stable, long-lasting state. To do so, it requires favorable strength and toughness to prevent the dislodgement of a prosthesis due to cohesive failures.1-3 Several modifications in the composition of luting agents have been carried out to improve the physical and mechanical properties. High tensile, shear, and compressive strength are essential to resist the stresses at the restoration-tooth interface.2
The common tests performed to determine the mecha-nical properties of luting agents are, compressive strength and diametral tensile strength.4 High compressive strength is important to tolerate masticatory stresses.5 Many clinical failures, however, are attributed to tensile stress. Since the tensile strength of brittle materials like Glass Ionomer Cements (GICs) is impossible to test directly, diametral tensile strength was adopted by the British Standards Institution as a substitute.4
Although luting cements are partly exposed to saliva, factors such as pH and buffering capacity can affect the setting and maturation. These changes, in turn, influence the cement’s integrity in transferring stresses from crowns or fixed partial dentures. Therefore, simulating the role of saliva is a critical requirement when testing the mechanical properties of luting cements to assess their clinical performance.6,7
To date, Glass ionomer cement (GIC) is the most widely used material in a dental practice. Despite its advantages, GIC has few drawbacks, including moisture sensitivity and desiccation during the initial setting stages, as well as relatively poor physical properties.1
The physical properties of glass ionomer cement can be controlled through carefully selected variations in its chemical composition.8
A relatively newer cement which is a hybrid combination of Calcium Aluminate and Glass Ionomer Cement (CERAMIR) has been developed as a luting cement intended for permanent cementation. The composition of this cement is water-based and has been demonstrated to be bioactive. The term ‘bioactivity’ refers to the ability of a material to form hydroxyapatite (HA) when immersed in vitro in a physiological phosphate-buffered saline solution.9
An independent study of basic comparative data is essential to characterize newer materials in relation to traditional cements. Strength parameters play a significant role in the selection of luting agents.7,10,11 Therefore, the purpose of this study was to determine whether the modified Calcium Aluminate GIC exhibits mechanical properties equal to or superior to those of other commonly used luting GICs in dental practice.
Materials & Methods
Materials
The study utilized a total of 160 samples, with 40 samples from each of the four cement groups, namely:
Group I- Ceramir Crown and Bridge (Doxa Dental)
Group II- Fuji I (GC)
Group III- Meron Plus (Voco)
Group IV- HY-Bond Glass Ionomer CX (Shofu)
In each group, 20 samples were used for compressive strength determination before and after storage in artificial saliva, while the remaining 20 samples were used to measure diametral tensile strength under the same conditions.
Grouping of Samples
1. Group I: Ceramir
A1- Control group for compressive strength - 10 samples
A2- Compressive strength after storage in artificial saliva for 24 hours - 10 samples
A3- Control group for diametral tensile strength - 10 samples
A4- Diametral tensile strength after storage in artificial saliva for 24 hours - 10 samples
2. Group II: Fuji 1
B1- Control group for compressive strength - 10 samples
B2- Compressive strength after storage in artificial saliva for 24 hours - 10 samples
B3- Control group for diametral tensile strength - 10 samples
B4- Diametral tensile strength after storage in artificial saliva for 24 hours - 10 samples
3. Group III: Meron Plus
C1- Control group for compressive strength - 10 samples
C2- Compressive strength after storage in artificial saliva for 24 hours - 10 samples
C3- Control group for diametral tensile strength - 10 samples47
C4- Diametral tensile strength after storing in artificial saliva for 24 hours - 10 samples
4. Group IV: Shofu Glass Ionomer
D1- Control group for compressive strength - 10 samples
D2- Compressive strength after storage in artificial saliva for 24 hours - 10 samples
D3- Control group for diametral tensile strength - 10 samples
D4- Diametral tensile strength after storage in artificial saliva for 24 hours - 10 samples
Methods
A single silicon mould was made using dimethylpolysiloxane to prepare the specimens for testing both parameters. A cylindrical indentation of 3 mm x 6 mm (3 mm diameter & 6 mm in height) was made for compressive strength testing and a circular indentation of 6 mm x 3 mm (6 mm in diameter & 3 mm in height) was made for testing the diametral tensile strength using the silicon mould.
Specimen Preparation for Compressive Strength and Diametral Tensile Strength
For the fabrication of specimens to test, the cement from each group was manipulated according to the manufacturer’s instructions manually and was then filled into the customized cylindrical mould space of 3 mm diameter & 6 mm height, as per ISO 9917 for compressive strength testing, while a disc-shaped mould space of 6 mm diameter & 3 mm height was used to test the diametral tensile strength.
The samples were allowed to set based on the respective recommended setting times. After the initial set of the luting cement, specimens were carefully removed from the mould and deflashed with sandpaper to remove any irregularities.12
Measurement of Compressive Strength
The samples were measured for height and diameter using a digital caliper and tested using the Universal testing machine at a crosshead speed of 1 mm/min. The force was applied along the vertical axis of the cylindrical specimens and the peak force required to fracture the samples was recorded. The same procedure was used to test all the samples (Figure 1, Figure 2).
Compressive strength was calculated using the following equation:
CS= 4F/ πd2
F = Maximum load at fracture (N); d = Diameter of the
specimen (mm); π = constant
Measurement of Diametral Tensile Strength
The samples prepared were measured using a digital caliper and were tested using the Universal testing machine at a crosshead speed of 1 mm/min. The force was applied along the diametric axis of the disc-shaped specimens, and the load at which the samples were fractured was recorded. All specimens were tested using the same procedure (Figure 3, Figure 4).
Diametral tensile strength was calculated using the following equation:
DS = 2F/πdh
F = Maximum load at fracture; d = Diameter of the specimen; h = Height of the specimen; π = constant
Effect of Storage in Artificial Saliva
Half the samples were stored in artificial saliva for 24 hours and then measured for compressive strength and diametral tensile strength at room temperature.
Results
Compressive Strength Test
The statistical results of the compressive strength test are presented in Tables 1 & 2 and Graph 1.
Table 1: Difference in the compressive strength values of Groups I, II, III & IV using One-way ANOVA test
Discussion
To define the word cement broadly, it refers to any mate-rial with adhesive and cohesive properties that enable it to bind mineral fragments into a compact mass.13 Glass ionomer cement, introduced in clinical use in the early 1970s, is known to be a successor to both silicate and polycarboxylate cements. It is primarily composed of aluminum fluorosilicate glass particles and a liquid containing itaconic, maleic, and tricarboxylic acids, and it sets through an acid-base reaction. The cement bonds to the tooth structure through ionic interactions, with positive ions in the tooth structure and negative ions in the cement. It also exhibits long-term fluoride ion release. However, its brittleness, moisture sensitivity, susceptibility to desiccation during initial setting phase limits its use.14,15
Luting agents mainly fail due to microfracture than dissolution, eventually leading to dislodgement of the prosthesis. It has been mentioned in literature that high mechanical strength is the foremost factor for the adhesion of glass ionomer cement to the metal surface.3,6
Aluminate glass ionomer cement developed by Hermansson in the year 1987 has gained popularity in the field of adhesive dentistry. This material is more biocompatible than amalgam. The luting variant of this cement is a hybrid composition combining both calcium aluminate and glass ionomer chemistry bearing the brand name CERAMIR (Crown & Bridge, Doxa Dental). The glass ionomer component adheres to the tooth structure whereas the calcium aluminate component in the cement adds up to the strength and retention over time by fixing the GIC structure and hinders the ionomer glass from continuously leaking over time.16,17 The physical properties of this material which have been previously studied by many researchers proved to have unsatisfactory results. Thus, this study entails the understanding of the physical behavior of calcium aluminate glass ionomer cement by comparing the compressive strength and diametral tensile strength properties of this cement with three other commercially available glass ionomer luting cements having varied compositions.9,18
The quality of compressive strength is a critical indi-cator of the success of a dental cement as this quality is attributed to withstand high masticatory stresses.7,17,19 Thus any dental cement is expected to have adequate strength under compressive load for the clinical success of the prosthesis.
Although compressive strength proves to be a suitable test for brittle materials, tensile and shear strength also play a vital role at the atomic level. Besides it has also been suggested that materials behave differently under different test configurations and it is advisable not to have conclusions based on a single test. Thus, diametral tensile strength was also used in this study to determine the mechanical behavior.6,20 Since the dental cements are brittle and do not have any plastic deformation before fracturing, the British Standard Institution has adopted the diametral tensile strength as a useful parameter.4
Role of Saliva: The pH of saliva, buffering capacity, and water content (primarily) affects the setting and maturation of dental cements.17,21
In the current study, the compressive strength of calcium aluminate glass ionomer cement- was found to be similar to the other commercially available glass ionomer cement namely, Meron Plus GIC (Resin-modified), which is in agreement with the previous literature published.13,22,23 However, the compressive strength of Calcium Aluminate GIC was found to be lesser than Fuji 1 GIC (conventional) and Shofu HY bond Glass ionomer cement had the highest value among all the four types of glass ionomers. This result could be due to variations in filler content in the composition of different cements. The experimental design, sample size or sample conditioning methods also influence the reduced strength of the dental cement.15,24
The study analyzed the diametral tensile strength of calcium aluminate glass ionomer cement- with other three types of commercially available glass ionomers. It was found that the diametral tensile strength was higher than Fuji 1 glass ionomer (conventional), and this significant increase in value could be due to the aluminum ion concentration in calcium aluminate when compared to the conventional type.15,25 The strength value of calcium aluminate GIC was found to be equivalent to Meron plus glass ionomer (resin-modified). However, Shofu HY bond glass ionomer showed the greatest value among all the four types of glass ionomers. This could be due to variations in the manufacturer’s recommended powder-liquid ratio for different brands of glass ionomers as strength favorably depends on the powder/liquid ratio of the dental cement.3,26,27
The strength value for both compressive and diametral tensile strength of stored samples significantly increased after storage for Calcium Aluminate GIC (Ceramir), Fuji 1 (conventional), and Shofu HY bond glass ionomer cements. This could be due to the following reason-the glass ionomer cement acquires its early strength by chemical composition, the microstructure of the glass concentration, molecular weight of polycarboxylic acid, and powder liquid ratio.18,27,28
Although there was an increase in compressive strength after storage, there was a significant decrease in diametral tensile strength seen in Meron Plus (resin-modified) glass ionomer cement after storing it in artificial saliva. This could be due to the diffusion of water through polymeric materials forming micro-voids, which results in the disintegration of the cement matrix affecting the diametral tensile strength of the dental cement.19,29
In compression, calcium aluminate (Ceramir) showed the least value and Shofu HY bond showed the highest value among all four groups. However, Fuji 1 was equivalent to Meron Plus GIC and their values were intermediate between calcium aluminate GIC and Shofu HY bond GIC.
Clinical implication
The strength parameter is a notable factor in the selection of a luting agent. From the study conducted, it can be analyzed that, the relatively new dental cement-calcium aluminate glass ionomer stands even-handed with the properties tested with the rest of the chosen commercially available brands.
Limitation of the study
Laboratory tests might not have reached the level of clinical simulation but they serve as an indisputable parameter of analyses. ISO protocol was followed for preparation of samples. However, there may still be variations between the materials compared, the environmental conditions, and the design of the study. The following limitations can be considered.
1. The study considered static loading, whereas in the mouth, a prosthesis combined with the luting cement is subjected to dynamic nature of forces.
2. The storage media (artificial saliva) may not exactly replicate the oral environment.
3. Alterations in the viscosity of different specimens of different brands tested may differ even though the manipulation of the cement was done following the manufacturer’s recommended ratios.
4. Factors like homogeneity and internal porosity were not considered.
5. Effect of aging at different time intervals and temperature variations were not contemplated.
Conclusion
Glass ionomer cements used in the present study revealed major differences in their mechanical behavior. Within the limitations of the current study, we can draw the following conclusions:
1. Calcium aluminate glass ionomer cement (Ceramir) showed a compressive strength value between Meron Plus and Fuji 1 glass ionomer cement before storage and the least compressive strength after storage in artificial saliva when compared to the other three glass ionomer cements.
2. Calcium aluminate glass ionomer cement showed diametral tensile strength values between Fuji 1 and Meron Plus glass ionomer cement before and after storage in artificial saliva.
3. Shofu HY Bond glass ionomer exhibited superior compressive and diametral tensile strength values as compared to the other three commercially available glass ionomers.
4. The strength values of the three cements - Ceramir, Fuji 1, and Shofu HY Bond showed a significant increase in strength after storage in the artificial saliva in both compression and diametric tension, suggestive of their favorably superior clinical performance in the oral cavity when in contact with saliva.
5. Meron Plus glass ionomer cement (Resin-modified) showed reduced diametral tensile strength, and higher compressive strength after storage in artificial saliva.
Conflict of Interest
Nil
Supporting File
Figure 1: Test specimen under the loading for compressive strength using UTM" width="200px" src="https://hm-journals.s3.ap-south-1.amazonaws.com/home/journals/5GnVB3qhmyqt18G9fAsEmZgqDcpOGyBcJu4W5q4X.png">
Figure 2: Schematic illustration of compressive strength" width="200px" src="https://hm-journals.s3.ap-south-1.amazonaws.com/home/journals/Hqq3FyqdUYhtAew58wJQKbtysUr0PskIBjbHFPSj.png">
Figure 3: test specimen under the loading for diametral tensile strength using UTM" width="200px" src="https://hm-journals.s3.ap-south-1.amazonaws.com/home/journals/3BOb7sKN9f45ikv9qtooUGqI2zAHXsS4lXNrY3g8.png">
Figure 4: schematic illustration of diametral tensile strength" width="200px" src="https://hm-journals.s3.ap-south-1.amazonaws.com/home/journals/5cspPX2smWisU8cvak2bs6znLqCiEug7Kvva772n.png">
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