MODIFIED GLASS IONOMER CEMENTS.

IN VITRO COMPARATIVE STUDY OF SORPTION, SOLUBILITY AND COMPRESSIVE STRENGTH OF THREE

MODIFIED GLASS IONOMER CEMENTS.

Dissertation submitted to

THE TAMILNADU DR.M.G.R MEDICAL UNIVERSITY

In partial fulfillment for the degree of MASTER OF DENTAL SURGERY

BRANCH VIII

PEDODONTICS AND PREVENTIVE DENTISTRY

THE TAMILNADU Dr.M.G.R MEDICAL UNIVERSITY CHENNAI – 600032

2017-2020

CERTIFICATE BY THE GUIDE

This is to certify that the dissertation entitled “

IN VITRO COMPARATIVE STUDY OF SORPTION, SOLUBILITY AND COMPRESSIVE STRENGTH OF THREE MODIFIED GLASS IONOMER CEMENTS”

is a bonafide research work done by DR.S.DHIVYA, in partial fulfillment of the requirements for the degree of MASTER OF DENTAL SURGERY in the speciality of PEDODONTICS AND PREVENTIVE DENTISTRY.

DATE:

PLACE:

GUIDE:

Dr.M.GAWTHAMAN, M.D.S, Professor,

Department of Pedodontics and Preventive Dentistry, VDCW.

ENDORSEMENT BY THE HEAD OF THE DEPARTMENT AND HEAD OF THE INSTITUTION

This is to certify that Dr.S.DHIVYA, Post Graduate Student (2017 – 2020) in the department of Pedodontics and Preventive Dentistry, Vivekanandha Dental College for Women, has done this dissertation titled IN VITRO COMPARATIVE STUDY OF SORPTION, SOLUBILITY AND COMPRESSIVE STRENGTH OF THREE MODIFIED GLASS IONOMER CEMENTS under our guidance and supervision in partial fulfillment of the regulations laid down by The Tamilnadu Dr.M.G.R Medical University, Chennai – 600 032 for Master of Dental Surgery (Branch VIII) PEDODONTICS AND PREVENTIVE DENTISTRY degree termination.

SIGNATURE AND SEAL OF THE SIGNATURE AND SEAL OF HOD THE PRINCIPAL

Dr. V. MAHESH MATHIAN, M.D.S.,

Dr.N.BALAN, M.D.S., PROFESSOR & HEAD PRINCIPAL.

DECLARATION BY THE CANDIDATE

TITLE OF DISSERTATION IN VITRO COMPARATIVE STUDY OF SORPTION, SOLUBILITY AND

COMPRESSIVE STRENGTH OF THREE MODIFIED GLASS IONOMER CEMENTS.

PLACE OF STUDY Vivekanandha Dental College for Women DURATION OF COURSE 3 Years

NAME OF THE GUIDE Dr. M.Gawthaman.M.D.S.

HEAD OF THE DEPARTMENT

Dr. V. Mahesh Mathian. M.D.S.

I hereby declare that no part of the dissertation will be utilized for gaining financial assistance for research or other promotions without obtaining prior permission of the Principal, Vivekanandha Dental College for Women, Tiruchengode.

In addition, I declare that no part of this work will be published either in print or electronic without the guide who has been actively involved in dissertation. The author has the right to reserve the publication of work solely with prior permission of the Principal, Vivekanandha Dental College for Women, Tiruchengode.

Dr.M.Gawthaman M.D.S., Dr.S.Dhivya

Signature of the Guide Signature of the Candidate

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This is to certify that this dissertation work titled

"IN VITRO COMPARATIVE STUDY OF SORPTION, SOLUBILITY AND COMPRESSIVE STRENGTH OF THREE MODIFIED GLASS IONOMER CEMENTS"

of the candidate

Dr.S.DHIVYA

with Registration Number

241725252

for the award of degree

MASTER OF DENTAL SURGERY

in the branch of

PEDODONTICS AND PREVENTIVE DENTISTRY

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ACKNOWLEDGEMENT

My sincere thanks and deep sense of gratitude to Dr. Capt. S. Gokulanathan, B.Sc, MDS, Dean and Dr. N. Balan, MDS, Principal, Vivekanandha Dental College for Women, for permitting me to pursue this work.

I owe an immense debt of gratitude to my guide and mentor Dr.M.Gawthaman, MDS, Professor, Department of Pedodontics and Preventive Dentistry, Vivekanandha Dental College for Women for being an epitome of strength and a great pillar of support throughout my dissertation. He is always approachable and his guidance has been crucial for the completion of my thesis.

I express my sincere gratitude to my head, Dr.V.Mahesh Mathian MDS, Professor and head of department. If not for constant support and encouragement, this thesis would have been incomplete and I thank my sir for helping me overcome the difficulties faced during the entire procedure involved in my dissertation.

I express my heartfelt gratitude to the faculty members of our department, Dr.S.Vinodh MDS, Reader , Dr.M.Manoharan MDS, Dr. Patil Disha MDS, Dr.M.Kamatchi MDS Senior Lecturers, Department of Pedodontics and Preventive Dentistry, Vivekanandha Dental College for Women, for their valuable guidance that enabled me to comprehend this dissertation and reach its successful culmination.

I sincerely acknowledge my seniors Preethi Archana.S, Ramyalakshmi.I.K and Niranjana.A, my batch mates Anjugam.p, Menaka.E.K. and my juniors GayatriKumary.T, Sharon Maria.E, YamunaDevi.E.S, Janani Priya.L, Ragini.K and Preethi.J for their support and encouragement.

Nothing can replace the love of my family members, who always been with me throughout the thick and thin of my PG life. A big thank to my appa (C.Senthamil Selvan B.E), amma (S.Jaya Lakshmi), sister (S.Nithya) and brother (S.Tamil Mani).

‘’Friend in need is a friend indeed^’’. I thank my friends for their never ending academic,moral and financial support in my life.

I thank my roommate (Dr.Krsishnaja) for constantly encouraging me to do this thesis work, without her my tears won^’t go away.

Everyone used to say, I gateher pose to many men flowers but the work done is by me, but this is not true without help from all them it is not possible.

Above all, I bow my head to God Almighty, for showering his blessings and making me what I am today.

.

Dr. S. Dhivya Post Graduate Student

CONTENTS

S.NO CONTENTS PAGE NO

1 Introduction 1

2 Aim and objectives 7

3 Review of literature 8

4 Materials and methods 25

5 Results 39

6 Discussion 49

7 Conclusion 58

8 References 59

9 Annexure 69

LIST OF TABLES

S.NO TABLES PAGE NO

1 Mean values of sorption with standard deviation for all the three groups

40

2 Intergroup comparison between the groups for sorption 41

3 Mean values of solubility with standard deviation for all the three groups

43

4 Intergroup comparison between the groups for solubility 44

5 Mean values of compressive strength with standard deviation for all the three groups

46

6 The intergroup comparison between the groups for compressive strength

47

LIST OF FIGURES

S.NO FIGURES PAGE NO

1 Restorative materials used in this study 25

2 Artifical saliva 28

3 pH Strip 28

4 Metallic Split Mold 30

5 90 cylindrical samples 30

6 Capsule (Equiaforte) 31

7 Amalgamator 31

8 Placement of the materials by capsule applicator 31

9 Equiaforte samples 32

10 Dispersed P/L of Zirconomer Improved 32

11 Samples of Zirconomer Improved 32

12 Materials used for group C 33

13 Light curing of RMGIC in mold 33

14 Samples of RMGIC 33

15.a,b Samples in the thermocycling unit 34

16 Samples immersed in the artificial saliva 35

17 Precision weighing scale 36

18 Universal testing machine 38

19 Samples in the universal testing machine 38

LIST OF GRAPHS

S.NO GRAPHS PAGE NO

1 Mean values sorption of all the three groups in

artificial saliva. 42

2 Mean values solubility of all the three groups in

artificial saliva. 45

3 Mean values compressive strength of all the three

groups in artificial saliva. 48

LIST OF ABBREVIATIONS

Abbreviation Explanation

GI Glass ionomer

ASPA Alumina silicate polyacrylate

GIC Glass ionomer cement

RMGIC Resin modified glass ionomer cement

PAA Polyacrylic acid

HEMA Hexamethyl acrylate

UDMA Urethane dimethacrylate

SSF Spherical silica filler

TEM Transmission electron microscopy

SEM Scanning electron microscopy.

MPA Megapascal

FIG Figure

ADA American dental association

ANSI American national standards institute

BS British standard

ISO International organisation for standardization

1

INTRODUCTION

Dental caries has been affecting mankind from time immemorial. Since ancient times to 18th century, dental caries have been replaced or restored with wide variety of materials including stone chips, ivory, human teeth, turpentine resin, cork, gums and metal foils - tin and lead. Then, newer materials like gutta-percha, metals (gold leaf, amalgam, cast metals, alloys), cements, metal modified cements, unfilled resins, composites, ceramics and metal ceramics have been used for tooth restoration.

The success of any material is assessed by its longevity and biocompatibility in oral environment.

Dental professionals continue their voyage in pursuit of a ‘biomimetic’ ideal restorative dental material that may synergistically match enamel and dentin. It is of paramount importance by the dental professionals to preserve and conserve what nature has given. The restorative material that is serving this dual purpose of

‘restoring function’ and ‘maintaining aesthetics’ altogether in contemporary dentistry is GLASS IONOMER CEMENT. With the decline in popularity of amalgam in recent years, there is a need Glass ionomer (GI) cements. Since then, several modifications have been introduced with the purpose of enhancing their mechanical properties ⁽¹⁾.

In Laboratory of the Government Chemist, London, GIC were introduced by Wilson and Kent in 1972⁽²⁾. Synonoms of GIC: Glass Polyalkenoate Cement, Alimino Silicate PolyAcrylate (ASPA), Dentin Substitute, Man-Made Dentine, Artificial Dentin. ANSI/ADA Sp. No: 96.6⁽³⁾.

Compared to other restorative materials, need for placing bonding agents is not recommended for the restoration of cavities with GIC (Woods, 2014) ⁽⁴⁾.

2 Glass ionomer cements belong to the class of materials known as acid-base cements. GIC are basically water based materials and the three essential ingredients to glass-ionomer cement are polymeric water-soluble acid, basic (ion-leachable) glass, and water. These are commonly presented as an aqueous solution of polymeric acid and a finely divided glass powder, which are mixed by an appropriate method to form a viscous paste that sets rapidly by acid base reaction in the presence of water. They are based on the product of reaction of weak polymeric acids with powdered glasses of basic character. These materials are capable of forming chemical bonding with enamel and dentin, anticariogenicity, good biocompatibility and coefficient of thermal expansion close that of tooth structures. As a restorative material, the chemical bond to enamel and dentin facilitates ion exchange of fluoride with the hydroxyl ions in the apatite of the surrounding enamel. Setting occurs in concentrated solutions in water and the final structure contains a substantial amount of unreacted glass which acts as filler to reinforce the set cement⁽⁵⁾.

Glass-ionomers initially set within 2–3 min from mixing by an acid-base reaction. The first step is a reaction with hydrated protons from the polyacid at basic sites on the surface of the glass particles. This results in the movement of ions such as Na⁺ and Ca²⁺ (or Sr²⁺) from the glass into the polyacid solution, followed quickly by Al³⁺ ions. These ions then interact with the polyacid molecules to form ionic crosslinks, and the insolubilised polysalt that forms becomes the rigid framework for the set cement. When this setting reaction occurs, all of the water becomes incorporated into the cement, and no phase separation occurs. The second step is slow, and continues for approximately a day. After this initial hardening, there are further reactions, which take place slowly and are together known as maturation. They are associated with various changes in the physical properties of the resulting glass-

3 ionomer cement. Strength typically increases, as does translucency. In addition, the proportion of tightly-bound water within the structure increases. The physical properties of glass-ionomer cements are influenced by how the cement is prepared, including its powder:liquid ratio, the concentration of the polyacid, the particle size of the glass powder and the age of the specimens⁽⁶⁾.

Properties of glass ionomer cements, such as bonding to the dental substrate and fluoride release made them to use for clinical conditions. However, the remarkable uses of GIC are limited by their mechanical strength. To improve their mechanical properties, several modified glass ionomer cements have been developed, a fact that justifies the constant research effort that has been made to assess the alleged improvements.Various incarnations of glass-ionomers in form of Mircale Mix, Cermet, and RMGIC are the improvisation in this direction ⁽⁷⁾.

The compressive strength of a material is any important factor to be considered in relation to masticatory forces. It is the amount of stress required to distort the material in an arbitrary amount. Compressive strength may be considered to be a critical indicator of success because higher the compressive strength, maximum resistance to resist masticatory and parafunctional forces. One of the most commonly employed methods to better understand the physical properties of GICs is compressive strength testing because core build-ups usually replace a large amount of tooth structure and it must resist multidirectional masticatory forces⁽⁸⁾.

The polymers used in glass-ionomer cements are polyalkenoic acids, either homopolymer poly (acrylic acid) or the 2:1 copolymer of acrylic acid and maleic acid.

Poly (vinyl phosphonic acid) has been studied as a potential cement former, but its practical use is restricted to a single brand, where it is used in a mixture with poly

4 (acrylic acid) and effectively acts as a setting rate modifier. Cements prepared from homopolymers of acrylic acid show increase in compressive strength in the first 4–6 weeks. On the other hand, cements made from acrylic-maleic acid copolymers show an increase in compressive strength up to a point, but then there is a decline before an equilibrium value is reached. However, these alterations in measured compressive strength indicate that the material continues to undergo slow changes over time ⁽⁶⁾.

Two important physical properties that influence the clinical durability of a restorative material are water sorption and solubility of the material. Since glass ionomer was hydrophilic, the early contamination of glass ionomer resulted in the binding of water molecules by polyacrylic acid (PAA) and ion leachable glass. In this way, the chemical setting was disrupted and the decrease in hardness occurred as a result of the absorption of water as the initial phase of degradation. Moreover, the presence of excess water during the growth of the hydrated silicate phase might have resulted also in a weaker material ⁽⁹⁾.

Cement solubility and water sorption are important in clinical selection, because they show different behaviour when exposed in water and oral fluids for long periods. The water sorption properties and the solubility of the cement change the mechanical characteristics of the material by directly interfering in the half-life of the restorations⁽¹⁰⁾.

Water sorption can increase the volume of the material and it can act as a plasticizer and cause deterioration of the matrix structure of the material. There is always an interface between the teeth and restoration margins (about 40 microns) and so the use of cement with low solubility is very more important. Water sorption changes the mechanical properties through two effects: lamination and degradation.

5 The solubility of the restorative material causes loss of material mass, adversely affecting its mechanical properties, as well as causing tooth/restoration interface failure, increasing the risk of marginal microleakage and leading to restoration failure⁽¹¹⁾.

Resin-Modified Glass-Ionomers were introduced to the dental profession in 1991. They contain the same essential components as conventional glass-ionomers (basic glass powder, water, polyacid), but also include a monomer component and associated initiator system. The monomer is typically 2-hydroxyethyl methacrylate, HEMA, and the initiator is camphorquinone. Resin modified glass-ionomers set by the twin processes of neutralization (acid-base reaction) and addition polymerization, and the resulting material has a complicated structure based on the combined products of these two reactions. Moreover, competition between these two network-forming reactions means that there is a sensitive balance between them. This mixture of setting reactions may jeopardize the reliability of the set material, and as a consequence, close adherence to the manufacturer’s recommendations on the duration of the irradiation step is essential in order to produce material optimal properties ⁽¹²⁾.

A yet new material- Zirconomer improved reinforces structural integrity of restoration and imparts higher mechanical properties befitted for utilization in posterior teeth. This is a high strength restorative material, reinforced with zirconia nano fillers known as zirconomer improved and has been a recent substitute to glass ionomer cement in dentistry. Zirconia (ZrO2) is a white crystalline oxide of zirconium. It is a polycrystalline ceramic without a glassy phase and exists in several forms. The name “zirconium” comes from the Arabic word “Zargon” which means

“golden in color” ⁽¹³⁾.

6 The recent development in the glass ionomer cement restoration is the introduction of bulk fill glass hybrid restorative system (Equiaforte) which represents the latest innovation in glass ionomer and resin technologies working in synergy. It is a combination of a self-adhesive, chemically cured, highly filled GIC and a self- adhesive, filled resin surface sealant.

Since the comparison of the physical and mechanical properties of glass ionomer cement would help the clinician to choose the appropriate and best material available for the restoration of weakened tooth structure, the present study has been conducted to comparatively evaluate the physical properties like sorption, solubility and mechanical properties like compressive strength of three different types of glass ionomer cement namely resin modified glass ionomer cement, Zirconomer improved and glass hybrid restorative system (Equiaforte) in artificial saliva.

7

AIM AND OBJECTIVES

Aim of the study

The aim of this study was to evaluate and compare the sorption, solubility and compressive strength of three modified glass ionomer cements – Glass Hybrid Restorative System (Equiaforte), Zirconomer Improved and resin modified glass ionomer cement (RMGIC) in artificial saliva.

Objectives of the study

1. To evaluate the sorption and solubility of Glass Hybrid Restorative System (Equiaforte) in artificial saliva by using weighing method.

2. To evaluate the sorption and solubility of zirconomer improved in artificial saliva by using weighing method.

3. To evaluate the sorption and solubility of resin modified glass ionomer cement (RMGIC) in artificial saliva by using weighing method.

4. To evaluate the compressive strength of Glass Hybrid Restorative System (Equiaforte) in artificial saliva by using universal testing machine.

5. To evaluate the compressive strength of zirconomer improved in artificial saliva by using universal testing machine.

6. To evaluate the compressive strength of resin modified glass ionomer cement (RMGIC) in artificial saliva by using universal testing machine.

8 REVIEW OF LITERATURE

Williams et al (1989) conducted study on increase in compressive strength of glass ionomer restorative materials with respect to time: a guide to their suitability for use in posterior primary dentition and observed compressive strength at 30 min, 60 min and 24 hours. They found at 30 min the ranking order were as follows (from lowest to highest strength) Ceramfil β < ASPA; Fuji II; KetacFil; KetacSilver <

ChemFil IK ChemFil II Express, after 60 min Ceramfil β showed a considerable increase in strength but the ranking order had changed considerably after 24hours.The lowest were now Fuji II < ASPA, then KetacSilver, Ceramfilβ < KetacFil < ChemFil II, ChemFil II Express. ChemFil II and ChemFil II Express remained the strongest materials tested ⁽¹⁴⁾.

Yap et al (1997) determined the water sorption and solubility of several resin modified polyalkenoate cements. The materials evaluated include were as follows Variglass used as a restoration, base and liner; Fuji II LC; Fuji Liner; Vitrebond;

Vitremer and Photac-Bond. Z100, a composite resin, was used as control. Results showed that the composite resin control had significantly less water sorption than any of the resin-modified polyalkenoate cements evaluated. The degree of water sorption was product dependent and appeared to be influenced by the resin (HEMA) content.

Some of the resin modified polyalkenoate cements retained water in their set structure and hence solubility could not be assessed ⁽¹⁵⁾.

Cattani-Lorente MA et al (1999) in his study determined the Compressive, diametral compressive and flexural strengths of resin-modified composite resin Dyract (Detrey Dentsply) and the resin-modified glass ionomer cement Fuji II LC

9 (GC) using specimens aged up to three months and the effect of water sorption of those materials. After 24 hours Dyract exhibited very little expansion then fuji II LC.

Those differences are related to their chemical composition. Fuji II LC was hydrophilic, as it contains polyHEMA. In the presence of water, Fuji II LC behaves like a hydrogel, but the network resulting from the copolymerization of acidic and UDMA monomers was less hydrophilic, and the effect of water on Dyract was retarded⁽¹⁶⁾.

Akashi et al (1999) compared the relationship between the characteristics and mechanical strength of resin modified glass ionomer cements after long-term water storage. Water absorption was analyzed using a gravimetric analysis for 12 months, while the diffusion coefficients were obtained using Fick's law of diffusion. Water solubility was determined based on the weight of the residue in the immersed water.

The compressive and diametral tensile strength was measured at 1, 2, 6, and 12 months. Fuji II exhibited highest compressive strength and vitrebond showed largest solubility than other cements. Diametral tensile strength of fuji II and vitrebond decreased after 12 months ⁽¹⁷⁾.

Xie D et al (2000) calculated the flexural strength (FS), compressive strength (CS), diametral tensile strength (DTS), Knoop hardness (KHN) and wear resistance of ten commercial glass-ionomer cements they were as follows ketac bond, alpha silver, alpha fil, Ketac – Silver, Ketac –Fil, Ketac Molar, Fuji II, Vitremer, Fuji II LC, Photac Fil. The fracture surfaces of these cements were analysed using scanning electron microscopic techniques to ascertain relationships between the mechanical properties and microstructures of these cements. The resin-modified GICs exhibited much higher FS and DTS, not generally higher CS, often lower Knoop hardness and

10 generally lower wear resistance, compared to the conventional GICs. Vitremer (3M) had the highest values of FS and DTS; Fuji II LC (GC International) and Ketac-Molar (ESPE) had the highest CS; Ketac-Fil (ESPE) had the highest KHN. Ketac-Bond (ESPE) had the lowest FS; a-Silver (DMG-Hamburg) had the lowest CS. Four GICs namely a-Fil (DMG-Hamburg), a-Silver, Ketac-Bond and Fuji II) had the lowest values of DTS, which were not significantly different from each other; a-Silver and Ketac-Silver had the lowest values of KHN. The highest wear resistance was exhibited by a-Silver and Ketac-Fil; F2LC had the lowest wear resistance ⁽¹⁸⁾.

Xu X et al (2003) determine the compressive strength, fluoride releases and recharge profiles of 15 commercial fluoride-releasing restorative materials. The materials include glass ionomers (Fuji IX, Ketac Molar, Ketac Silver, and Miracle Mix), resin-modified glass ionomers (Fuji II LC Improved, Photac-Fil, and Vitremer), compomers (Compoglass, Dyract AP, F2000, and Hytac) and composite resins (Ariston pHc, Solitaire, Surefil and Tetric Ceram). To determine the cumulative fluoride release from different materials five equation were used. The equation[F]c=[F]I(1-e^-bt)+β best describes the cumulative fluoride release for most glass ionomers, resin-modified glass ionomers, and some high fluoride-releasing compomers and composites, whereas [F]c=[F]I/(t1/2+t)+αt best describes the cumulative fluoride release for most compomers and composite resins. Solitaire exhibited higher compressive strength and Compoglass and Ariston have sustained fluoride release at a higher level (10– 20mg/cm2/day) ⁽¹⁹⁾.

Toledano M et al (2003) conducted study to elucidated the water sorption and solubility of different resin based restorative dental materials. Results showed that Compoglass and Compoglass F had the lowest values of water sorption and solubility,

11 while Vitremer and Fuji II LC displayed the highest values. Solubility values of Prodigy, Z100, Dyract and Dyract AP did not show significant differences among them, while their water sorption values attained some differences and were lower for Prodigy followed by Dyract and Z100 ⁽²⁰⁾.

Aratani M et al (2005) calculated the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC.

For each material, P/L ratio and storage time, 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. They concluded that Compressive strength of resin-modified glass ionomer cements Fuji II LC and Vitremer was reduced when powder/ liquid ratio was reduced from 1:1 to 1:2 and 1:3. Storage in water for 24 hours, 7 days and 28 days had little influence on compressive strength of Fuji II LC and Vitermer. Only Fuji II LC at 1:3 P/L ratio was affected with an increase in strength after 28 days of storage ⁽²¹⁾.

Tjandrawinata R et al (2005) evaluated the effects of 10 wt% spherical silica filler(SSF) addition on 24-h compressive strength, modulus of elasticity, water uptake, and immediate setting shrinkage of conventional glass-ionomer (Fuji II and Experimental) and resin modified glass-ionomer (Fuji II LC EM) cements. The glass- ionomer cement powders were modified by being mixed with 10 wt% SSF with an

12 average particle diameter of 0.3mm.The materials were mixed to consistencies similar to the flow of Fuji II mixed with a powder-liquid ratio of 2.7:1 (w/w). The 24-h compressive strength, modulus of elasticity, water uptake, and immediate setting shrinkage were observed and the results compared with the original materials mixed with similar flow. The addition of SSF increased the compressive strength value to 1.1 times, while the increase of moduli of elasticity was 1.10 to 1.35 times. In general, the addition of SSF decreased the 24-h water uptake to 80–90% and reduced the immediate setting shrinkage to 70–79% of the original materials. The addition of 10 wt% SSF improved the characteristics of conventional and resin-modified glass- ionomer cement ⁽²²⁾.

Morter E et al (2005) determined the water sorption characteristics and solubility behaviour of Filtek P60, Solitaire 2, Admira, Compoglass F and Fuji II LC (resin modified glass ionomer cement). A constant mass (m1) was measured after polymerization of each material. After immersion in distilled water for 7 days m2 was measured. Then disks were again desiccated and weighed every day for 35days (mass m3). Resin modified glass ionomer cement showed highest water sorption and solubility and admira least ⁽²³⁾.

Wang XY et al (2006) analysed the effect of early water exposure on the shear strength of a spectrum of glass ionomer restoratives. The materials evaluated include conventional auto-cured (Fuji II [FT], GC), resin-modified light-cured (Fuji II LC [FL]) and, recently introduced, high strength auto-cured (Fuji IX GP Fast [FN], GC; Ketac Molar Quick [KQ], 3M-ESPE; Ketac Molar [KM], 3M-ESPE) cements.

Sixteen specimens (8.7-mm in diameter and 1-mm thick) of each material were prepared in metal washers and randomly divided into 2 groups. They found that early

13 access to water did not negatively influence the strength of glass ionomer restoratives.

Contrary to the instructions issued by most manufacturers, there was no need for placement of a resin coating over high strength auto-cured cements, unless they require protection from dehydration. Although the strength of resin-modified light- cured and modern conventional auto-cured materials were not affected by early water contact, resin coating was still advocated until the effects of early water contact on aesthetic properties were determined⁽²⁴⁾.

Mallmann A et al (2007) examined the compressive strength of two glass ionomer cements, a conventional one (Vitro Fil - DFL) and a resin-modified material (Vitro Fil LC- DFL), using two test specimen dimensions: One with 6 mm in height and 4 mm in diameter and the other with 12 mm in height and 6 mm in diameter.

Mean compressive strength values (MPa) were: 54.00 ± 6.6 and 105.10 ± 17.3 for the 12 mm x 6 mm sample using Vitro Fil and Vitro Fil LC, respectively, and 46.00 ± 3.8 and 91.10 ± 8.2 for the 6 mm x 4 mm sample using Vitro Fil and Vitro Fil LC, respectively. The value exhibited by resin-modified glass ionomer cement was higher for both specimens. For both glass ionomer materials, the 12 mm x 6 mm matrix led to higher compressive strength results than the 6 mm x 4 mm matrix. ⁽⁷⁾.

Keyf F et al (2007) investigated the water sorption and solubility of provisional, permanent luting cements and restorative cements. According to adhesive potantial, permanent luting cements can be divided low (zinc phosphate, silicate cements), medium (polycarboxilate cement), high (glass ionomer cements and filled or unfilled resins) luting materials. Provisional luting materials are of two main types:

calcium hyroxide and zinc oxide cements (with eugenol or alternative substances).

Comparisons among different restorative cements indicated that the water sorption

14 and solubility of these materials were different. It was found that zinc phosphate and zinc polycarboxylate cements were the most stable materials for solubility and sorption ⁽²⁵⁾.

Mese A et al (2008) measured the solubility, sorption, and dimensional change of eight luting cements (six resin-based and two resin modified glass ionomer cements) in two different solutions: 50 percentage ethanol:water and distilled water.

GC Fuji Plus and RelyX Luting showed the highest values of sorption and solubility both in water and ethanol:water. The percentage changes in volume for Maxcem, Nexus 2, Panavia F, RelyX Veneer, and VariolinkII were considerably smaller than for GC Fuji Plus (RMGIC), RelyX Luting2 (RMGIC), and set in both water and ethanol:water and after desiccation. Stability occurred within 2 weeks for all the eight materials when in water, while GC Fuji Plus, Maxcem, Panavia F and seT (resin luting cement) took 3 to 4 weeks to stabilize in ethanol: water ⁽²⁶⁾.

Xie et al (2008) formulated bioactive cement with light-curable star-shape polyacrylic acid, Fuji II LC filler, water and bioactive glass S53P4, and evaluated the mechanical strengths and in vitro bioactivity of the formed cement under simulated physiological conditions. The results showed that the system not only provided strengths comparable to original commercial Fuji II LC cement but also allowed the cement to help mineralize the dentin in the presence of stimulated body fluid. It appears that this bioactive glass ionomer cement system has direct therapeutic impact on dental restorations that require root surface fillings ⁽²⁷⁾.

Nilufer et al (2009) conducted an in vitro study to determine the solubility levels of three different resin modified glass ionomer cements namely, Advance, Vitremer and Protec-Cem. Ten specimens for each group, 15±1 mm hole and 1mm

15 thickness were prepared. They showed that the solubility of three tested materials can be classified respectively from higher to lower as: Protec-Cem>Vitremer>Advance

(28).

Al- shekhli AR et al (2010) evaluated and compared water solubility values of luting resin cement with other three conventional luting cements. Four commercial dental luting cement materials were selected: GIC cement, Zinc polycarboxylate cement, Zinc Phosphate cement and Resin cement. Ten disc specimens were prepared for each cement material using a stainless steel mold with 10 mm in inner diameter and 2 mm in thickness. Water solubility of different cement materials were calculated by weighing the samples before and after water immersion (15 days) and desiccation.

It was revealed that resin cement has the highest resistance to solubility in comparison with other conventional luting cements ⁽²⁹⁾.

Gemalmaz D et al (2012) assessed the disintegration of zinc phosphate, glass ionomer, resin modified glass ionomer cement and resin cement. An intraoral sample holder was made having four holes of 1.4mm diameter and 2mm depth. The holder was soldered onto the buccal surface of an orthodontic band, which was cemented to the first upper molar in 12 patients, average age 26 years. The holes were filled with zinc phosphate, glass ionomer, resin-modified-glass ionomer, and resin cement. At baseline, and 6, 12, and 18 months impression taken from which epoxy replicas were made, which were scanned with an optical scanner. The lowest cement loss was recorded for Calibra after 6 months (<0.005mm³), whereas phosphate cement after 18 months recorded the greatest loss (0.31mm³). Of all luting agents, phosphate cement showed the highest mean loss of substance at all observation times. Increasing the

16 observation time resulted in a marked increase in loss from the surface of phosphate cement ⁽³⁰⁾.

Qahtani M et al (2012) conducted study to determine the effects of immersion in artificial saliva and distilled water on the water sorption and solubility properties of different tooth-colored restoratives. Ten disks/ material of (Z250, Z250XT, Z350XT, P90, SDR, F2000, N100) were fabricated. The specimens were placed in a desiccator at 37ºC for 22 h and then transferred to another desiccator at 22ºC ± 1ºC for 2 h, weighed to a precision accuracy of ± 0.0001 g. This cycle was repeated to obtain constant mass (m1), and then the specimens were divided into two groups (5/each), immersed in distilled water or artificial saliva at 37ºC for 7 days.

After storage, the specimens were re-weighed to obtain m2, and then reconditioned in the desiccator to obtain m3. Resin-modified glass ionomer (N100) showed the highest and non-acceptable mean values for water sorption in both media, followed by marginal values for compomer (F2000), and flowable composite (SDR). Silorane- based low-shrink composite (P90) had the lowest mean value for water sorption in artificial saliva and no sorption in distilled water. Resin-modified glass ionomer (N100) showed the highest solubility and non-acceptable mean values in both media.

Microhybrid composite (Z250) showed no solubility in both media ⁽³¹⁾.

Dinakaran S et al (2014) evaluated and compared the solubility and sorption values of compomer, conventional glass-ionomer (fuji II) and resin modified glass ionomer cements (fuji II LC improved) in various beverages such as tea, coffee, coca- cola and lime with saline as control. Twenty five circular discs per restorative material were prepared. Five specimens of each material were kept immersed in the test media and saline for seven days. Water sorption and solubility were calculated using ISO

17 guidelines. Among the media tested lime influenced both sorption and solubility values more than the other media. Fuji II was revealed to have more sorption and solubility values than the other two materials ⁽¹¹⁾.

Xie D et al (2014) conducted study to develop a novel high performance dental glass-ionomer cement (GIC) restorative and evaluate the mechanical strengths of the formed cements. Polyacrylic acids were synthesized via an advanced atom- transfer radical polymerization technique. The purified polymers were then used to formulate the light-cured GIC with Fuji II LC glass powders. Specimens were fabricated in molds at 23^oC and conditioned in distilled water at 37^oC for 24 h prior to testing. Fuji II LC cement was used as control and prepared per manufacturer’s instruction. Mechanical strengths including compressive strength, diametral tensile strength, flexural strength, hardness, fracture toughness and wear resistance of the cements were evaluated. The experimental cement showed significantly higher mechanical properties, i.e., 53% in compressive strength, 50% in compressive modulus, 125% in diametral tensile strength, 95% in flexural strength, 21% in fracture toughness and 96% in hardness, higher than Fuji II LC. The experimental cement was only 5.4% of the abrasive and 6.4% of the attritional wear depths of Fuji II LC. It appears that novel experimental glass ionomer cement was a clinically attractive dental restorative and may be potentially used for high-wear and high stress-bearing site restorations ⁽³²⁾.

Mensudar et al (2015) investigated the effect of GCoat plus (nanofilled self- adhesive light cured resin) on both conventional and RMGIC by evaluating the mechanical properties (compressive strength, flexural strength, surface hardness) on three different types of GIC (Type II, Type XI, and Fuji LC). Two conventional GIC

18 (Type II and Type IX) and one RMGIC were used in this study (Group I – III) respectively. The three groups were subdivided into Subgroup A and B. Each group contained 30 samples, thus a total of 216 samples were prepared. Among the 72 samples in each group, 12 samples were used to evaluate compressive strength, 12 samples for flexural strength, and the remaining 12 samples were used for surface hardness. The samples were then tested to investigate the effect of surface coating by evaluating their mechanical properties. Comparison of subgroups in Type II, Type XI and Fuji LC indicate that the mean values of the two groups, namely no coat and G coat, are different in all three types of GIC in their mechanical property. Comparison among the groups was made; the samples coated with G-coat plus showed a higher value for all types of cements ⁽³³⁾.

Rodrigues DS et al (2015) determined the influence of porosity, microstructure, and chemical composition on the wear and compressive strength of nano-hybrid resin composite, resin-modified glass ionomer and conventional glass ionomer. Porosity and topography of the materials were evaluated by optical and scanning electron microscopy. Roughness was evaluated by profilometer. Then, compressive tests were performed at 1 mm/min. Wear tests were carried out at 20 N, 2.5 mm of displacement, at 1 Hz for 90 min in artificial saliva solution. Resin composite revealed a lower porosity (1.21 ± 0.20 %) than glass-ionomer restoratives (5.69–7.54 %) as well as lower values of roughness. Also, resin composite showed significantly higher values of mechanical strength (334 ± 15.9 MPa) compared to conventional (78.78 ± 13.30 MPa) or modified glass ionomer (169.50 ± 20.98 MPa).

For maximal depth of wear, resin composite also showed significantly lower values than glass ionomer. Mechanical properties were superior for composite than glass ionomers ⁽³⁴⁾.

19 Vemina et al (2016) compare the diametral tensile strength and compressive strength of the zirconomer, conventional glass ionomers and amalgam using universal testing machine. The result showed that glass ionomer exhibited lower compressive and diametral strength than amalgam and zirconomer ⁽³⁵⁾.

Karkera et al (2016) conducted a study on comparison of the solubility of conventional luting cements with that of the polyacid modified composite luting cement and resin-modified glass ionomer cement. For each of these groups of cements, three resin holders were prepared containing two circular cavities of 5 mm diameter and 2 mm depth. All the cements to be studied were mixed in 30 seconds and then placed in the prepared cavities in the resin cement holder for 30 seconds. He revealed that polyacid modified resin cement had lowest solubility to water at the given time intervals of immersion than polycarboxylate, zinc phosphate, and GIC.

RMGIC showed the highest mean loss of substance at all immersion times in water from 2 to 8 minutes. The solubility of cements decreased by 38% for GIC, 33% for ZnPO4, 50% for polyacid modified resin composite, 29% for polycarboxylate, and 17% for RMGIC ⁽³⁶⁾.

Glamoc AG et al (2017) evaluated and compared the water sorption of three luting cements in three different solutions: distilled water and artificial saliva with different pH values (7.4 and 3.0). Materials used were as follows: Resin-modified glass-ionomer cement (GC fuji plus) and two resin cements (Multilink Automix and Variolink II). Before and after immersion in artificial saliva, water sorptions of the cements were calculated by weighing the specimens and desiccation weight was also measured. They concluded resin modified glass-ionomer cement (Fuji Plus) showed

20 the significantly highest water sorption values in all three examined solutions when compared with other cements ⁽³⁷⁾.

Kim HJ et al (2017) analyzed the influence of curing mode (dual- or self- cure) on the surface energy and sorption/solubility of four self-adhesive resin cements and one conventional resin cement. The degree of conversion and surface energy parameters including degree of hydrophilicity were determined using Fourier transform infrared spectroscopy and contact angle measurements. Sorption and solubility were assessed by mass gain or loss after storage in distilled water or lactic acid for 60days. For all materials, the dual-curing consistently produced significantly higher percentage degree of conversion values than the self-curing. Significant negative linear regressions were established between the percentage degree of conversion and in both curing modes. Overall, the self adhesive showed higher sorption and solubility values, in particular when immersed in lactic acid, than the conventional resin cement. Linear regressions revealed that percentage degree of conversion and were negatively and positively correlated with the sorption and solubility values, respectively. Dual-curing of self adhesive resin cements seems to lower the sorption and/or solubility in comparison with self-curing by increased percentage degree conversion and occasionally decreased hydrophilicity ⁽³⁸⁾.

Wajong et al (2017) conducted a study on the effects of shelf life on the compressive strength of resin modified glass ionomer cement. The compressive strength was measured by using universal testing machine after the specimen were prepared with diameter of 4mm and 6mm height and then they were immersed into aqua des and incubated at a temperature of 37⁰ c for 24 hours. He revealed that there

21 was decrease in the compressive strength value along with the duration of storage time ⁽³⁹⁾.

Shetty et al (2017) conducted a study to determine the compressive strength of restorative materials Ketac Molar, Zirconomer, and Zirconomer Improved. For compressive strength examination, 30 cylindrical specimens were fabricated measuring 3 mm in diameter and 6 mm in height and grouped into three study groups (n = 10): Group I (KetacTM Molar, 3M, ESPE), Group II (Zirconomer, Shofu Inc., Japan), and Group III (Zirconomer Improved, Shofu Inc., Japan). The results shown that highest compressive strength was for Zirconomer followed by Zirconomer Improved and Ketac Molar ⁽⁴⁰⁾.

Neshander et al (2018) analyzed the solubility of zinc phosphate, glass ionomer and resin modified glass ionomer cement in artificial saliva. In this study, specimen were prepared in twenty disks of sixe 8 x 3 mm. Using an electronic analytical scale with accuracy up to 0.1 mg W1 was measured. Artificial saliva was prepared and buffered pH was evaluated with strip and for conformation pH meter was used. For 96 hours, the specimens were immersed in 50 ml of artificial saliva neutral pH 6.8 at 37°C and weighed W2. After that specimen were dried in hot air oven and weighed on the electronic weight analyzer with readability up to 0.1 mg (W3). He found that the zinc phosphate cements exhibit the highest value of solubility followed by glass ionomer and resin modified glass ionomer shows the lowest value of solubility among three materials⁽⁴¹⁾.

Farias JF et al (2018) examined the water sorption and solubility of glass ionomer cements indicated for atraumatic restorative treatment considering the time and the pH of the storage solution. The materials used in this study were as follows:

22 Ketac Molar Easymix, Maxxion R, Vitro Molar, Vitremer and Vitro Fil LC. Total of 75 specimen were fabricated with 15 each in 5 groups. After that weighed on a precision analytic balance and then heated at 37 degree Celsius, again weighed. Then out of 15 specimen in each group, 5 specimen were immersed in deionized water, artificial saliva and neutral artificial saliva respectively and weighed 24 hours, 7, 14 and 21 days. Then it was stored in plastic recipients and dessicated, followed by this weighed again. He found that the highest water sorption rate, for all the materials, occurred in the first twenty-four hours after immersion, with a stabilization tendency for some materials in 7 and 14 days and disintegration rate were not influenced by the various storage solutions ⁽⁴²⁾.

Sajjad A et al (2019) conducted a study on Characterization and enhancement of physico-mechanical properties of glass ionomer cement by incorporating a novel nano zirconia silica hydroxyapatite composite synthesized via sol-gel. By means of using transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and dot mapping, in this study they created a new nano zirconia–silica–hydroxyapatite.

They determine compressive strength, flexural strength and surface roughness and effectiveness of addition of nanoZrO2–SiO2–HA to the conventional GIC.

Conformation was done by characterization studies that all particles were in the nanoscale range with spherical zirconia and silica particles embedded in the voids between rod-shaped HA crystallites. Dispersion of nano paticles was uniform throughout the sample with high density patterns visible for zirconia, calcium and phosphorus. The incorporation of 5% nanoZrO2–SiO2–HA has resulted in considerable improvement in the compressive and flexural strengths of cGIC. The GIC 5% nanoZrO2–SiO2–HA showed an increase in compressive (144.12 ± 13.88

23 MPa) and flexural strength (18.12 ± 2.33 MPa) over cGIC. It also described surface roughness profile (0.15 ± 0.029 μm) similar to that of cGIC (0.15 ± 0.019 μm).

Therefore, in stress bearing areas these nano restorative materials can be used as a promising material ⁽⁴³⁾.

Giliiard et al (2019) surveyed the influence of mixing methods on the compressive strength and fluoride release of conventional and resin modified glass ionomer cements. In this study, they used hand and mechanical mixing of two conventional glass ionomer cements, two resin modified glass ionomer cements and one ready to use glass ionomer cement. To determine the compressive strength, the specimen were manipulated with the standard height of 6mm and 4mm diameter and subjected to universal testing machine. Then the fluoride release was monitored by means of electrode connected to a digital ion analyzer. It was revealed that ionoseal exhibit highest compressive strength and fluoride release for conventional glass ionomer was more ⁽⁴⁴⁾.

Maryam et al (2019) compared the compressive, diametral tensile, and flexural strengths of EQUIA Forte Fil with Fuji IX GP and ChemFil Rock in addition to this fluoride-releasing properties and surface hardness of the GICs were also assessed. The specimens were tested after 24 hours and 7 days of immersion in distilled water at 37 degree C and measured using mechanical machine. EQUIA Forte Fil glass ionomer cements exhibited significantly greater (P<.05) flexural strength and surface hardness than Fuji IX GIC specimens. However, no significant difference (P>.05) was observed between the compressive and diametral tensile strength of EQUIA Forte Fil and Fuji IX GIC specimens. ChemFil Rock showed higher flexural

24 strength than EQUIA Forte Fil (P>.05) but significantly lower compressive strength and microhardness (P<.05) ⁽⁴⁵⁾.

Kutuk et al (2019) determined the compressive strength and resistance the glass hybrid restorative system with microhybrid composite in 48 mandibular molars were used for a fracture resistance test and divided into four groups: Group1 – sound teeth; Group2 - extended size Class 2 cavities prepared on the mesial surfaces of teeth; Group3, -extended size Class2 cavities restored with a composite; and Group 4- extende size Class2 cavities restored with GH. Specimens were subjected to loading until a fracture occurred and concluded that composite reported higher compressive strength than glass hybrid restorative system ⁽⁴⁶⁾.

Salinovic I et al (2019) analyzed the compressive strength of Ketac Universal Applicap, Equia and Equiaforte. In that study they used silicone molds with standard dimensions of specimen measuring 6mm height and 4mm in diameter and he found that ketac universal exhibited higher strength than other cements ⁽⁴⁷⁾.

Poornima et al (2019) performed a study to compare the compressive strength and surface microhardness of EQUIA Forte, light cure, and conventional glass ionomer cement Fifty four pellets of G - Coat (GC) Gold Label 2, GC Gold Label light cured universal restorative material, and EQUIA Forte were divided into three groups (18) each and were preserved at 37°C for 1 h and then soaked in 20 ml of deionized water, artificial saliva, and lactic acid six each, respectively, over 30 days.

Samples were subjected to surface microhardness and compressive strength test on the 1st day, 7th day, and 30th day. Results showed that the compressive strength and microhardness of EQUIA Forte from day 1 to 30 when placed in artificial saliva were significantly high compared to other groups ⁽⁴⁸⁾.

25

MATERIALS AND METHODS

After obtaining approval from institutional ethics committee, Vivekanandha Dental College for Women with the registration no: VDCW/ IEC/71/2017. The present study was conducted in Vivekanandha Dental College for Women, Tiruchengode, Namakkal district in collaboration with Department of Biotechnology, Vivekanandha Educational Institution for Women, Tiruchengode and Department of Plastic Engineering, Central Institute of Plastics Engineering and Technology (CIPET), Chennai.

Following materials were selected for this study: (fig no: 1)

Group A: Hybrid ionomer restorative system - Equiaforte (GC Corporation, Tokyo, Japan).

Group B: Zirconomer improved(Shofu Inc., Japan).

Group C: Resin modified glass ionomer cement - Fuji II Lc Improved (GC Corporation, Tokyo, Japan).

Fig: no: 1 Restorative materials used in this study

26 Information about the materials used in the study:

Group A: Hybrid ionomer restorative system – Equiaforte.

Composition:

Fluoroaluminosilicate glass, high molecular weight polyacrylic acid, surface‑treated glass

Indications:

1. Class I restorations.

2. Stress bearing class II restorations.

3. Non stress bearing class II restorations.

4. Intermediate restorations.

5. Class V and root surface restorations.

6. Core build up.

Group B: Zirconomer Improved.

It contains zirconium oxide, glass powder, tartaric acid (1 - 10%), polyacrylic acid (20 - 50%), and deionized water as its liquid. Zirconium oxide, the main oxide, the main powder component of Zirconomer, results from Baddeleyite (ZrO2) that contains high levels of zirconia ranging from 96.5 to 98.5% [18].

Zirconomer Improved developed as a reliable and durable self-adhesive tooth coloured zirconia reinforced posterior bulk fill restorative comprises of nano-sized zirconia fillers to enhance aesthetic properties and superior handling characteristics.

27 Indications:

1. Class I and II restorations in primary teeth.

2. Class I and II restorations in required permanent teeth.

3. For atraumatic restorative technique.

4. As long term for temporary replacement of cusps.

5. Structural base in sandwich restoration.

6. Core build-up.

7. Repair of crown margins.

Features of Zirconomer Improved: a) Superior Mechanical Properties with remarkable edge strength, excellent marginal adaptation, and Excellent resistance to abrasion and erosion, b) Self-adhesive with tooth-like co-efficient of thermal expansion, c) Sustained fluoride protection, especially in cases with high caries risk, c) Excellent mixing and handling qualities, d) Higher translucency for a closer match to natural tooth, and e) durability like silver amalgam without mercury toxicity.

Group C: Resin modified glass ionomer cement.

Composition:

Powder: aluminosilicate glass, pigments.

Liquid: polyacrylic acids, distilled water, HEMA(17%), dimethacrylate monomer, camporoquinone.

Indications:

1. Class III and V cavities.

2. Pediatric restoration.

3. Cervical erosion.

28 4. Base or liner.

5. Core build up.

Gupta et al (2011): Composition of artificial saliva (fig no: 2)

▪ 0.4gm sodium chloride

▪ 1.21gm potassium chloride

▪ 0.78gm sodium dihydrogen phosphate dehydrate

▪ 0.005gm hydrated sodium sulphide

▪ 1gm urea and

▪ 1000ml of distilled water.

To this mixture 10 N sodium hydroxide was added until the pH value was measured to be as 6.75 ± 0.15⁽⁴⁹⁾.

Fig: No: 2 Artificial Saliva Fig: No: 3 pH Strip

29

Study design:

Preparation of cylindrical specimen:

Metallic split mold (fig no:4) was manipulated with diameter 4mm and height of 6mm according to ISO specification number 9917 – 1: 2007.

Total cylindrical specimen - 90

Group A - Hybrid ionomer restorative system (30)

Sorption and Solubility (group A₁) - 15

compressive strength (Group A₂) - 15

Group B - Zirconomer Improved (30)

Sorption and Solubility (group B₁) - 15

compressive strength (Group B₂) - 15

Group C - RMGIC ( 30)

Sorption and Solubility (group C₁) - 15

compressive strength (Group C₂) - 15

30 Fig. No: 4 Metallic Split Mold

Total of 90 cylindrical samples (fig no: 5) measuring 4mm diameter and 6mm height were fabricated in metallic split mold.

Fig: No:5 90 Cylindrical Samples

Prior to the placement of any material in the metallic mold, petroleum jelly was applied on the inner side of the mold. Then for group A (equiaforte), one end of the capsule (fig no: 6) which is to be placed on the applicator was pressed against the firm surface to loosen the powder, following this the capsule was positioned in the amalgamator (fig no: 7) for mixing with dwell time of 10sec. Immediately capsule was placed into a capsule applier and the lever was clicked until the mold was completely filled by the material.

Group A – Equiaforte Group B – Zirconomer Improved Group C -RMGIC

31 Fig: No: 6 Capsule (Equiaforte)

Fig: No: 7 Amalgamator

Fig: No: 8 Placement of material by capsule applicator

32 Fig No: 9 Equiaforte samples

For group B (Zirconomer Improved), for easy retrieval of material from the mold petroleum jelly was applied on the inner surface. Powder and liquid ratio for each sample in this group was 3.6 / 1.0 (2 Scoops: 1 Drop), dispensed on the mixing pad with working time: 1min 30 sec (from start of mixing) and then it was placed on the mold by means of plastic instrument incrementally and condensed. (fig no:10,11)

Fig No: 10 and 11 Dispersed P/L and samples of Zirconomer Improved

For group c (RMGIC) also petroleum jelly was applied on the inner surface of mold. Then powder and liquid was dispensed on the mixing pad with the ratio of 3.2g:

1.0 with working time of 3min and 45 sec, and then by means of plastic instrument it was placedon the mold and light cured.

Group A – Equiaforte

Group B – Zirconomer Improved

33 Fig No: 12 Materials used for group C

Fig No: 13 and 14 Light curing of RMGIC in mold and samples of RMGIC Following the placement material in the mold for each group, back and forth of the mold was covered with mylar strip and pressed against glass slab to remove the excess the material. Finally each cylindrical specimen was smoothed by carbide paper and then it was left undisturbed.

After this all the 90 samples were subjected to thermo cycling test (fig no: 15) comprising 500 cycles between 5°C and 55°C with the dwell time 15 secs.

Group C -RMGIC

34 Fig no : 15(a)Thermocycle Unit

Fig no: 15 (b): samples in thermocycle unit

35 Determination of sorption and solubility:⁽⁵⁰⁾

15 of each material with total of 45 specimens were weighed with precision weighing scale. The initial weight was termed as W1 (μg).

Immediately after weighing the samples, they were soaked in artificial saliva (fig no: 16) at pH 7 and placed in incubator at 37°C for 28 days.

Fig No: 16 Samples immersed in artificial saliva

After removing samples from artificial saliva which was stored in incubator with the help of distilled water washed then dried with an absorbent paper, waved in air for 15 seconds and weighed. This weight was termed as W2 (μg).

Then for determination of solubility specimen were then dehydrated in an hot air oven at 37°C for 24 hours and weighed again; this weight was termed as W3 (μg).

By taking the means of two measurements at right angles to each other made to an accuracy of ±0.01 mm using digital vernier caliper, diameter and thickness of each specimen was measured. The volume (V) of each specimen was calculated as follows in cubic millimeters using the mean thickness and diameter:

V = π× r² × h

where r is the mean sample radius (diameter/2) in millimeters and h is the mean sample thickness in millimeters.

36 The loss of material (solubility) was obtained from the difference between the initial and final drying mass of each sample (W1 – W3). The water sorption was obtained from the difference between initial weighing and the wet weighing (W2 – W1).

The values of water sorption (Wsp) and solubility (Wsol), for each sample were calculated using the following equations:

Wsp = (W2 – W1)/V Wsol = (W1 – W3)/V Wsp: sorption of test material (µg/mm³) Wsol: solubility of test material (µg/mm³)

W1: weight prior to immersion in artificial saliva.

W2: weight after immersion in artificial saliva.

W3: dehydrated weight.

V is the volume of test material in mm3.

Fig no: 17 Precision weighing scale

37 Determination of compressive strength:⁽⁵⁰⁾

After subjecting the specimen to thermocyclying, 45 samples were selected for compressive strength determination with 15 of each material. Following this, all samples were soaked in artificial saliva at 37°C at pH 7 for 23 ± 0.5 hours. Then each specimen was placed with the flat ends between the plates of the universal testing machine and a compressive load was applied along the long axis at a crosshead speed of 1mm/minute. (Fig no: 18, 19)

The compressive strength was calculated, in MPa, using the following formula:

C = (4p)/ (πd²)

Where p was the maximum force applied, in Newton; d is the average measured diameter of specimen, in mm and π which has a numerical constant of 3.14.

38 Fig no: 18 Universal Testing Machine

Fig no: 19 Samples in universal testing machine

39 RESULTS

STATISTICAL ANALYSIS:

The data obtained in this study were calculated using the SPSS version 22 with P value < 0.05 was considered statistically significant.

The statistical normal distribution suitability of sorption, solubility and compressive strength values was tested using the Kolmogorov‑Smirnov method.

Since the obtained values show normal distribution differences between the groups data were analyzed using the one way analysis of variance (ANOVA). Descriptive statistics were used to determine mean, standard deviation, minimum and maximum values between groups. The difference between groups was found to be significant (p<0.05). For pairwise evaluation between the groups post hoc dunnet t3 test was used