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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 13  |  Issue : 5  |  Page : 272-275  

A new zinc reinforced glass ionomer cement: A boon in dentistry


1 Consultant Endodontist, Patna, Bihar, India
2 Department of Public Health Dentistry, Sarjug Dental College and Hospital, Darbhanga, Bihar, India
3 Dentist, Primary Health Centre, Dhanarua, Patna, Bihar, India
4 Consultant Endodontist, Suryapeth, Telangana, India
5 Department of Prothodontics and Implantology, Rama Dental College and Hospital, Kanpur, Uttar Pradesh, India
6 Department of Dentistry, Anugrah Narayan Magadh Medical College and Hospital, Gaya, Bihar, India

Date of Submission03-Nov-2020
Date of Decision28-Nov-2020
Date of Acceptance28-Nov-2020
Date of Web Publication05-Jun-2021

Correspondence Address:
Manoj Kumar
Department of Prothodontics and Implantology, Rama Dental College and Hospital, Kanpur, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpbs.JPBS_730_20

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   Abstract 


Background: Conventional glass ionomer cement (CGIC) has many beneficial properties, but it has poor physical and mechanical properties. Therefore, new glass ionomer cement (GIC) is manufactured by adding zinc to improve the mechanical properties of GIC ChemFil Rock. This material possesses better flexural tensile strength and compressive strength in comparison to conventional to CGIC. Objectives: The aim of this study was to compare four properties of ZRGI like fracture toughness, surface micro-hardness, abrasive wear, and roughness to other GIC material, which are commercially available as: resin-coated glass ionomer (EQUIA FIL). Materials and Methods: The study was done in dual phase. In phase-1, micro-hardness surface roughness, abrasion of four GIC and a composite resin as control was analyzed and in phase-2, fracture toughness of four GIC was done at 24 h interval so that all cement achieve its peak strength. Results: Micro-hardness value of ChemFil Rock was lowest among different GIC groups. All four GIC group exhibit similar abrasion capacities, while composite were more wear-resistant significantly. Roughness change was highest on ChemFil Rock compared to other GIC. EQUIA FIL has the highest fracture toughness, followed by ChemFil Rock. Conclusion: We can conclude that incorporating zinc in the matrix of chemfil rock increases fracture toughness and good abrasive wear, but it does not improve micro-hardness or surface roughness.

Keywords: Composite resin, glass ionomer cement, micro-hardness, surface roughness


How to cite this article:
Kumar A, Raj A, Singh DK, Donthagani S, Kumar M, Ramesh K. A new zinc reinforced glass ionomer cement: A boon in dentistry. J Pharm Bioall Sci 2021;13, Suppl S1:272-5

How to cite this URL:
Kumar A, Raj A, Singh DK, Donthagani S, Kumar M, Ramesh K. A new zinc reinforced glass ionomer cement: A boon in dentistry. J Pharm Bioall Sci [serial online] 2021 [cited 2021 Oct 27];13, Suppl S1:272-5. Available from: https://www.jpbsonline.org/text.asp?2021/13/5/272/317655




   Introduction Top


Glass ionomer cement Conventional glass ionomer cement was introduced by Wilson and Kent (1969)[1] which is composed of powder and liquid calcium fluoroaluminate glass powder and an aqueous solution of the acrylic acid polymer[2] and commercially, it is available as conventional glass ionomer cements (CGIC) and resin-modified glass ionomer cement (RMGIC).[3]

Although CGIC has many beneficial properties, it has poor physical and mechanical properties such as rough surface texture, susceptibility to dehydration, moisture contamination, and high opacity during initial setting, along with low fracture toughness and flexural strength.[4],[5] Therefore, it cannot be used in stress-bearing areas like class-1 and class-2 restorations.[2],[6],[7] and are mostly used in class 3rd and 5th restorations (low stress-bearing area).[8]

To predict the life of a restorative material, micro-hardness is considered as important as an important property.[9] Hardness means when force is applied, there is a resistance to permanent alteration on the surface of solid material and which can bears wear and the ability to withstand fracture of restorative material.[10]

Literature shows CGIC possess higher micro-hardness in comparison to RMGIC[2],[11] considering this “High strength” GICs have been manufactured by reinforcing materials such as resins, metals, or modifying glass. Therefore, new GIC is manufactured by adding zinc to improve mechanical properties of GIC (ChemFil Rock, Dentsply, York PA, USA). This material possess better flexural tensile strength and compressive strength in comparison to conventional to CGIC.[12] This material is considered 25% stronger than other glass ionomer material. However, more investigation and study is required as limited data available in the literature.

Considering the paucity the aim of this study was to compare four properties of ZRGI like fracture toughness, surface micro-hardness, abrasive wear, and roughness to other GIC material which are commercially available as: resin-coated glass ionomer (EQUIA FIL) Two high strength packable GIC (Fuji IX GP Extra and ketac molar) and premise resin-matrix composite (kerr) was kept as control group.


   Materials and Methods Top


The study was done in dual phase. In phase-1, micro-hardness surface roughness, abrasion of four GIC and a composite resin as a control was analyzed and in phase-2 fracture toughness of four GIC was done at 24 h interval, so that all cement achieve its peak strength and A-2 shade of all material was kept standard to avoid bias.

Phase-1: Analysis of micro-hardness, surface wears, and abrasive wear

A total of 50 specimen were fabricated, which were filled with specimens of chemfil rock (group 1) Fuji IX GP Extra (group 2), ketac molar quick Aplicap (group 3), and EQUIA FIL (group 4), and premise (group 5 as control group). A circular metal molds were selected in size of 5 mm in width and 2 mm in height. All materials were mixed according to manual instructions and the material was pour into mold and surface was covered with Mylar strip and pressure was applied manually with finger to make a flat surface. All materials were kept isolated and allowed to set as every material has different setting time. While EQUIA FIL (group 4) material was light cure for 20 s as mentioned in instructions manual similarly, control material was also injected in the same way and was covered with Mylar strip, and finger pressure was applied to flatten the surface and further it was light cure for 40 s. All specimens were kept at 37°C for 20 min after which all specimens were embedded in acrylic resin. A block mold was prepared by resin of dimension 12 mm length x 12 mm width x 8.5 mm height.

Ninety specimens were randomly divided into three testing groups so that all three materials of each group contain 30 specimens. All specimens were scanned by 3d optical profilometer (proscan 2000, Taunton England). For scanning, two areas were selected one 0.5 mm × 0.5 mm center portion for roughness test with 0.1 * 0.1 step size and 3 mm × 3 mm, i.e., whole specimen for determining surface wear. The scan was performed at 100 Hz frequency with sensor speed at 100%, which was set as baseline for calculating surface roughness and surface loss changes.

Micro-hardness test

It was determined by using Knoop hardness tester. Testing machine was set, and specimen were positioned, A diamond indenter with 30 s dwell time and 25 g load.[2],[11],[13] For analyzing micro-hardness, three points were tested on the surface of each specimen.

Abrasion wear and surface Roughness testing

For each specimen, new toothbrush was used. All specimens were stabilized on custom-made toothbrushing machine. Tooth brushing was done with a force of 1.96 N with 175 cycle/minute speed with 20000 double stroke.[7],[14] For abrasive slurry, dentifrice was used, and specimen were brushed with 90 g of slurry and rinse gently with tap water and air dried.

After abrasion surface measurement was done, rescanning of all specimens was done using Proscan profilometer. All specimens were placed on the custom jig so that all specimen were positioned at the identical position, pre- and post-treatment images were recorded. Surface loss and roughness was analyzed by image subtraction

Phase-2nd fracture toughness test

Stainless steel mold (25 mm × 2.5 mm × 5 mm) size was selected into with each material was poured. All specimen were maintained at 100% humidity for 1 h and then immersed in distilled water for 24 h at 37°C before testing. All values entered into software (leftworks 4.0, MIS System, USA) for calculating fracture toughness, 3 point bending test device with crosshead speed of 0.2 mm/min was set.

The following equation used to calculate fracture toughness:

KIc = f(/)(F/√w).

where:

  • KIc-Fracture toughness (MPa m½)
  • F-Force at the beginning of crack propagation (N) a Crack length (mm)
  • H-Specimen thickness
  • W-Specimen width (mm)


f (a/w)-Fracture geometry factor; which can be calculated by:

6α½ [1.99 – α (1−α) (2.15 − 3.93α + 2.7α2)]/[(1 + 2α) (1 − α)3/2],

A material with a higher KIc value is more resistant to crack propagation than a material with a lower value.

Statistical analysis

To compare groups for difference in Knoop hardness, surface roughness, abrasives wear, and fracture toughness Wilcoxon rank-sum test was used. 5% significance level was set.


   Results Top


Knoop micro-hardness value

The Knoop micro-hardness value of all materials is summarized in [Table 1]. Statistically significant differences were found among material groups was (P < 0.005). Fuji IX (group 2), Ketac Molar (group 3) mean hardness value was significantly higher than that of EQUIA Fil (group 4), while the mean value of ChemFil Rock (group 1) was lower than that of group 2 and 3. Premise (control group) showed significantly lower mean hardness values when compared to the other groups.
Table 1: Knoop hardness number test

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Among all materials, Fuji IX, i.e., group 2 showed the highest values (65.85 KHN), while Premise had the lowest values (44.43 KHN) among the tested materials.

Abrasion caused by toothbrush

[Table 2] depicts the mean values and the standard deviations of tooth abrasion caused by tooth brush. Although no significant differences were found in any glass ionomer groups. i.e. chemfil rock (group 1) Fuji IX GP Extra (group 2), ketac molar quick Aplicap (group 3), and EQUIA FIL (group 4), and premise (group 5). No significant difference was found between any cement group, they were significantly different from group 5 (control group).
Table 2: Abrasion test caused by toothbrush

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Surface roughness

[Table 3] depicts comparison of roughness measurements (Ra) of each material before and after toothbrushing. The mean average change in roughness values of group 1, 2, 3, 4, and 5 was 0.68 μm, 0.9 μm, 0.51 μm, 0.13 μm, and 0.57 μm, respectively. Significantly change values were observed higher for group 1 when compared to group 2.3 and 4. While the control group showed the intermediate change in the values, which were not significantly different from any of cement group.
Table 3: Surface roughness (Ra)

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Fracture toughness results

[Table 4] depicts fracture toughness mean and standard deviation value. All four cement group: group 1, 2, 3, and 4 shows crack which originated at apex till the load point.
Table 4: The fracture toughness

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   Discussion Top


GIC is one of the most widely used materials in clinical practice as it can chemically adhere to tooth structure, fluoride release, and biocompatible. Every material has its pros and cons. The main drawback of GIC is that poor physical properties like low wear resistance, sensitive to moisture during initial setting, and fracture toughness.[6]

To overcome this drawback, GIC has been amalgamated with many materials like silver amalgam alloy particle, which improves its physical property but wear resistance and esthetic was not improved significantly. Recently, chemFil rock by dentsply is a new GIC in which zinc is incorporated, which is the claim to increase its mechanical property. Zinc enhances setting reaction, which leads to higher strength with working time same as CGIC.[7]

Control group (premise) was included because various GIC group might not show the obvious difference. Al-Angari et al.[8] found no significant difference between Fuji IX and ketac molar hardness, which was similar to our study. Similarly, Zoergiebel and Ilie and Bonifácio et al. also found the same result.[9],[10] Micro-hardness of premise was lower as compared to other GIC group. Kim et al. and Blackham et al. also reported that premise has the least micro-hardness.[11],[15]

While ChemFil Rock has low hardness, it might be due to its filler size and morphology or it has been assumed that zinc might not has dispersed into glass particles. All four GIC group exhibit similar abrasion capacities while composite was more wear-resistant significantly. Studies have been done, which shows GIC exhibits more abrasion compared to composite. This is due to the matrix of GIC is weaker than the matrix of composite.[13]

Roughening of restoration margin around tooth accumulate dental plaque which leads to secondary caries.[12] Therefore, it is necessary to polish dental restoration carefully. In our study, we found ChemFil Rock cement got greater roughness compared to other GIC; it might be due to differences in composition. The conclusion has been made that it might be due to filler size and shape of particles in matrix.

Fracture toughness of the test was assessed after 24 h. So, that material achieves its peak strength. EQUIA FIL(group-4) have the highest fracture toughness followed by ChemFil Rock (group-1) it might be due to the formation of zinc polycarboxylate during its setting reaction and another reason might be due to the small particle size as compared to another Conventional GIC.[14]

ChemFil Rock GIC cement has showed significant results and can be used clinically as it has intermediate fracture toughness and good abrasive wear.


   Conclusion Top


A novel approach was made to compare different cement group to evaluate their micro-hardness, Toothbrush Abrasion, surface roughness, and fracture toughness; we can conclude that incorporating zinc in the matrix of chemfil rock increases fracture toughness and good abrasive wear, but it does not improve micro-hardness, or surface roughness.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Bonifácio CC, Kleverlaan CJ, Raggio DP, Werner A, de Carvalho RC, van Amerongen WE. Physical-mechanical properties of glass ionomer cements indicated for atraumatic restorative treatment. Aust Dent J 2009;54:233-7.  Back to cited text no. 1
    
2.
Raggio DP, Bonifácio CC, Bönecker M, Imparato JC, Gee AJ, Amerongen WE. Effect of insertion method on knoop hardness of high viscous glass ionomer cements. Braz Dent J 2010;21:439-45.  Back to cited text no. 2
    
3.
Yu H, Wegehaupt FJ, Wiegand A, Roos M, Attin T, Buchalla W. Erosion and abrasion of tooth-colored restorative materials and human enamel. J Dent 2009;37:913-22.  Back to cited text no. 3
    
4.
Carvalho FG, Sampaio CS, Fucio SB, Carlo HL, Correr-Sobrinho L, Puppin-Rontani RM. Effect of chemical and mechanical degradation on surface roughness of three glass ionomers and a nanofilled resin composite. Oper Dent 2012;37:509-17.  Back to cited text no. 4
    
5.
McKinney JE, Antonucci JM, Rupp NW. Wear and micro-hardness of a silver-sintered glass-ionomer cement. J Dent Res 1988;67:831-5.  Back to cited text no. 5
    
6.
Dowling AH, Fleming GJ. The impact of montmorillonite clay addition on the in vitro wear resistance of a glass-ionomer restorative. J Dent 2007;35:309-17.  Back to cited text no. 6
    
7.
DENTSPLY. Wissenschaftliches Kompendium ChemFil Rock. Available from: http://www.dentsply.de. [Last accessed on 14 Feb 2011].  Back to cited text no. 7
    
8.
Al-Angari SS, Hara AT, Chu TM, Platt J, Eckert G, Cook NB. Physicomechanical properties of a zinc-reinforced glass ionomer restorative material. J Oral Sci 2014;56:11-6.  Back to cited text no. 8
    
9.
Zoergiebel J, Ilie N. Evaluation of a conventional glass ionomer cement with new zinc formulation: Effect of coating, aging and storage agents. Clin Oral Investig 2013;17:619-26.  Back to cited text no. 9
    
10.
Bonifácio CC, Kleverlaan CJ, Raggio DP, Werner A, de Carvalho RC, van Amerongen WE. Physical- mechanical properties of glass ionomer cements indicated for atraumatic restorative treatment. Aust Dent J 2009;54:233-37.  Back to cited text no. 10
    
11.
Kim KH, Ong JL, Okuno O. The effect of filler loading and morphology on the mechanical properties of contempo-rary composites. J Prosthet Dent 2002;87:642-49.  Back to cited text no. 11
    
12.
Tanoue N, Matsumura H, Atsuta M. Wear and surface roughness of current prosthetic composites after toothbrush/dentifrice abrasion. J Prosthet Dent 2000;84:93-97.  Back to cited text no. 12
    
13.
Davidson CL. Advances in glass-ionomer cements. J Appl Oral Sci 2006;14 Suppl: 3-9.  Back to cited text no. 13
    
14.
Xie D, Brantley WA, Culbertson BM, Wang G. Mechanical properties and microstructures of glass-ionomer cements. Dent Mater 2000;16:129-38.  Back to cited text no. 14
    
15.
Blackham JT, Vandewalle KS, Lien W. Properties of hybrid resin composite systems containing prepolymerized filler particles. Oper Dent 2009;34:697-702.  Back to cited text no. 15
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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