ORIGINAL RESEARCH. Sandhya CA Shyam Lohakare, Pushpa Vinay Hazarey ABSTRACT

Transcription

1 ORIGINAL RESEARCH Comparison of shear bond strength of no mix-composite resin, self cure resin reinforced glass ionomer cement and light cure resin reinforced glass ionomer cement: an in-vitro study Sandhya CA Shyam Lohakare, Pushpa Vinay Hazarey ABSTRACT Aims and Objectives: To compare the shear bond strength of no mix-composite resin, self cure resin reinforced glass ionomer cement and light cure resin reinforced glass ionomer cement by an in-vitro study. Materials and Method: The study sample consists of 90 young healthy premolar teeth extracted for orthodontic purpose. The sample was divided into three groups with 30 bicuspids in each group, which were embedded into acrylic blocks. Hounsfield tensometer machine was used to measure the shear bond strength under standard conditions. Results: The measured mean shear bond strength of brackets with no mix composite resin (medicept), self-cure resin reinforced glass inomer cement (GC Fuji Ortho), light cure resin reinforced glass inomer cement (GC Fuji Ortho LC), were 6.79 MPa, 6.75 MPa, 3.18 MPa respectively. Shear bond strength of composite resin and self-cure resin reinforced glass inomer cement was statistically insignificant but the difference between the shear bond strength of GC Fuji Ortho and GC Fuji Ortho LC was statistically significant. Conclusion: Shear strength of composite was more than the glass inomer cement. Introduction White introduced Glass ionomer cements as orthodontic bonding agents in Its use in orthodontics is encouraged because of easier bracket removal, a less affected enamel surface after debonding and protection of the enamel near the bracket base against demineralization due to its fluoride releasing effect. The fluoride release is high initially with glass ionomer cement, which is effective in preventing decalcification. 2 But it has weaker bond strength when compared to conventional composite resins. 3 It could therefore seen desirable to use a material that combines the high bond opposite resin and the fluoride releasing ability of the glass ionomer cement. 4 The great disadvantage in using composites as bonding material is the occurrence of decalcification or white spot lesions that often develop around brackets due to the accumulation of plaque. 5 Professional oral hygiene instructions during the course of treatment to be effective in reducing decalcification but it is not of full proof and needs patient cooperation. Consequently, certain methods of delivering fluoride to the most site of decalcification, which is independent of patient compliance, have been advocated. The purpose of this study was to compare the shear bond strength of no mix-composite resin, self cure resin reinforced glass ionomer cement and light cure resin reinforced glass ionomer cement by an in-vitro study. Materials and Method The present invitro study sample consists of 90 young healthy premolar teeth extracted for orthodontic treatment purpose at Government Dental College and Hospital, Nagpur. The teeth were collected and stored in distilled water so as to prevent them from becoming brittle. Inclusion criteria for the specimen selection for the present in vitro study includes, anatomically sound teeth, teeth having visibly perfect enamel on the buccal aspect, no history of any pre-treatment with chemical agents such as alcohol, H 2 O 2 or fluoride, teeth that Keywords: Shear bond strength; Housefield machine; Glass Inomer Cement. were non-carious and having no restoration, without enamel defects, and no history of previous orthodontic treatment and non hypoplastic or hyperplastic teeth. The root of all teeth were embedded in self-cure acrylic resin blocks which were colour coded for each group to permit subsequent identification. Polishing was done with a prophy brush and a slurry of pumice and water with a rotary slow handpiece (15000 RPM Made in japan) on the buccal surface of all the mounted bicuspids. After polishing teeth were rinsed with ample amount of water from a three way syringe. The materials used in this study were as follows: Brackets (stainless steel mesh backed beggs flat and curved Brackets) and adhesives (no mix composite resin - Medicept, self-cure resin rein reinforced glass ionomer cement for orthodontic bonding - GC Fuji Ortho, light cured resin reinforced glass ionomer cements for orthodontic bonding- GC Fuji Ortho LC). The tooth which showed any evidence of macroscopic damage to the enamel during extraction procedure were not considered for the study. The specimens were divided into three groups with 30 bicuspids in each. Group A consisted of 30 bicuspids used for the evaluation of the shear bond strength of brackets bonded with a no-mix composite resin (Medicept) (Figure1). Mounted teeth were dried with a hair dryer. The buccal surface of each tooth were etched for 60 seconds with 37% phosphoric acid, rinsed with copious amount of water and dried with a hair dryer. Brackets were then bonded with a no-mix composite to bench cure for 5 minutes and was then stored in distilled water for 24 hours. Group B consisted of 30 bicuspids used for the evaluation of the shear bond strength of brackets bonded with self-cure 12

2 Comparison of shear bond strength... an in-vitro Study Figure 1. Medicept n-mix Composin resin kit, Figure 2. GC Fuji Ortho self cure reinforced glass inomer cement kit, Figure 3. fuji Ortho Light cure kit with dentin conditioner, Figure 4. Hounsfield tensometer machine, Figure 5. Closeup view of Hounsfield tensometer machine showing measuring scale and grapgh, Figure 6. Closeup view of Hounsfield tensometer machine showing wire hardness engaged in the bracket slot. Group Group A Group B Group C Table 1. Group definition Material mix composite resin (Medicept) Self cure resin reinforced glass ionomer cement (GC Fuji Ortho) Table 2. Shear bond strength of a no-mix, composite resin (medicept). Light cure resin reinforced glass ionomer cement (GC Fuji Ortho LC) Table 3. Shear bond strength of a Solf cure, resin reinforced glass lonomer cement (GC Fuji Ortho) 13

3 Lohakare et al / Table 4. Shear bond strength of a light cured, resin reinforced glass lonomer cement (Fuji Ortho LC) resin reinforced glass ionomer cement (GC Fuji Ortho) (Figure2). Teeth were kept moist. GC Fuji Ortho powder and liquid were dispensed on a mixing pad and mixed according to the manufacturer s recommendations. Small amount of material was placed over the mesh pad of brackets and positioned on the buccal enamel surface of tooth with a firm pressure. Brackets were placed with each mix using a reverse action and the excess removed from the margins with a straight probe. Immediately after this tooth was cured, the mounted teeth were stored in distilled water for 24 hours. Group C consisted of 30 bicuspids used for the evaluation of the shear bond strength of brackets bonded with Light cure resin reinforced glass ionomer cement (GC Fuji Ortho LC) (Figure3). Teeth were kept moist. GC Fuji Ortho LC powder and liquid were dispensed on a mixing pad and mixed according to the manufacturer s recommendations. Small amount of Material was placed over the mesh pad of brackets and positioned on the buccal tooth enamel surface with a firm pressure. Brackets were placed with each mix using a reverse action and the excess removed from the margins with a straight probe and Light cured for 60 sec. Immediately after this tooth was cured, the mounted teeth were stored in distilled water for 24 hours. The same operator performed a standard technique for bonding of all the brackets. Shear bond strength measurement: Hounsfield tensometer machine was used to measure shear force (Figure 4,5). The brackets were placed under a continual load rate of 5mm per minute until a breaking Point (debonding points) was reached. A special harness was fabricated which consist of an oval loop of round stainless steel, 22 gauge wire measuring 4mm x 6mm in diameter. The harness was fixed in the crosshead grip and loop was engaged in the bracket slot (Figure 6). A shear was performed on each sample with the pull of cross head parallel to the bracket enamel interface. The point of breakage for each sample was recorded in kilograms. The diameter of the mesh pad of the bracket was measured with a Vernier caliper and the surface area was area was calculated in square mm. The surface area of the mesh pad was 3mm x 3mm = 9mm2. SPSS V.16 was used for the statistical analysis to compare the mean and difference between the groups. Material N n SD A -mix Composite resin (medicept) B Self cure, resin Reinforced glass Ionomer cement (GC Fuji Ortho) C Light cured, Resin reinforced Glass ionomer Cement (Fuji Ortho LC) Table 5. bond strength and standard deviation for each group Comparison of Groups t Tabulated Value Significance A vs B Insignificant B vs C Highly Significant A vs C Highly Significant Table 6. Calculated t value for testing the significance of difference between shear bond strength of various materials at 1% level of significance. 14

4 Comparison of shear bond strength... an in-vitro Study Comparison of Groups t Tabulated Value Significance A vs B Insignificant B vs C Highly significant A vs C Highly significant Table 7. Calculated t value for testing the significance of difference between shear bond strength of various materials at 5% level of significance. Results Sample specimen for this in-vitro study comprised of 90 young healthy premolars, divided into three groups of 30 each for evaluation of shear bond strength of a no mix composite resin and a self cured resin reinforced glass ionomer cement and light cure resin reinforced glass inomer cement (Table1). The measured mean shear bond strength of brackets with no mix composite resin, self-cure resin reinforced glass inomer cement, light cure resin reinforced glass inomer cement were 6.79 MPa, 6.75 MPa, 3.18 MPa respectively (Table 2, 3, 4, 5). Statistical analysis revealed that the bond strength of a no mix composite resin (medicept) was significantly greater as compared to the bond strength of a light cured resin reinforced glass ionomer cement and shear bond strength of a no-mix composite resin was significantly insignificant as compared to the bond strength of self-cure resin reinforced glass ionomer cement. strength of brackets bonded with a self cure resin reinforced glass ionomer cement was significantly stronger, in comparison to the bond strength of the brackets bonded with a light cured resin reinforced glass ionomer cement at 1% and 5% level of significance. The difference between their bond strength was statistically highly significant. strength of brackets bonded with a no- mix composite resin was statistically highly significant in comparison to the bond strength of brackets bonded bonded with a light cured resin forced glass ionomer cement it the level of 1% and 5% level of significance ( Table 6,7). Discussion Shear bond strength of self-cure, resin reinforced glass ionomer cement is more than light cured resin reinforced glass ionomer cement which is similar to the previous observations. 6 Mahindra and Hazarey did an in-vitro study and reported significantly greater bond strength for the two composite resins, right on no mix system (0.56 kg/mm2) and Alpha dent (0.61 kg/mm2) compared to two GIC s, chemfil (0.44 kg/mm2) and Aqua Cem (0.26kg/mm2) used in their study. They found no significant difference in the bond strength of chemfil using conditioning with H2O2 ( kg/mm2) as compared to without conditioning (0.452 kg/mm2). They concluded simple prophylaxis of enamel surface achieved best results of GIC. 7 Blight S J and Lynch E compared in-vitro bond strength of two resin reinforced glass ionomer cements in comparison to composite resin 8 similar to the present study methods. The development of adhesives, which will successfully bond orthodontic attachments directly to enamel, has been greatly influenced by the research work directed improving the adhesives proving properties of materials used in conservative dentistry. Buonocore 9 was the first to demonstrate bonding of acrylic restorative material was substantially increased by conditioning the enamel with 85% phosphoric acids for 30 seconds. He suggested that the acid etching could due to an increase in surface area bring about increased adhesion. He also thought that treatment could increase the wettability of the adherent surface, allowing for a more intimate contact with the adhesive. 9 It was noticed that the cement adhered significantly better to the bracket base than to the tooth surface. The most advantage of glass ionomer cement over composite resin is the property of the glass ionomers to act as reservoir for fluoride ions. The shear bond strength of no-mix composite resin is MPa. The shear bond strength of a self-cure, resin reinforced glass ionomer cement is MPa. The shear bond strength of a light cured resin reinforced glass ionomer cement is MPa. The bond strength of no mix composite resin is more than the self-cure resin reinforced glass ionomer cement. The difference is statistically insignificant. The bond strength of self-cure resin reinforced glass ionomer cement is more than the light cured resin reinforced glass ionomer cement. The difference is statistically highly significant. The bond strength of no mix composite resin is more than the light cured, resin, reinforced glass ionomer cement. The difference is statistically highly significant. Finally this study reveals that the new self-cure, resin reinforced glass ionomer cement possesses the following advantages over the composite resin for bonding orthodontic brackets, i.e., it saves a significant amount of chair time, eliminates the need for working in a dry field, eliminates the need for etching and priming enamel surfaces, fluoride release prefects teeth against decalcification, the enamel surface remains clean after debonding, repairs are quick and easy with increased patient and operator comfort. Conclusion In conclusion, on the basis of this in-vitro evaluation, eventhough self cure resin reinforced glass ionomer cement may well become the method of choice of bonding orthodontic brackets than the light cured resin reinforced glass ionomer cement the shear bond strength of composite was more than the glass inomer cement. Authors Affiliations 1. Sandhya CA Shyam Lohakare MDS, Professor, Department of Orthodontics, VSPM Dental College and Research Centre, Digdoh, Hingna, Nagpur, Maharashtra, India, 2. Pushpa Vinay Hazarey MDS, Professor and Head, Department of Orthodontics, SPDC, Sawangi, Wardha, Maharashtra, India. 15

5 Lohakare et al References 1.Mitra S. Adhesion to dentin and physical properties of a light-cured glass-ionomer liner/base. Journal of Dental Research. 1991;70(1): Ashcraft DB, Staley RN, Jakobsen JR. Fluoride release and shear bond strengths of three light-cured glass ionomer cements. American journal of orthodontics and dentofacial orthopedics. 1997;111(3): Cook P, Youngson C. An in vitro study of the bond strength of a glass ionomer cement in the direct bonding of orthodontic brackets. Journal of Orthodontics. 1988;15(4): Bishara SE, Fehr DE, Jakobsen JR. A comparative study of the debonding strengths of different ceramic brackets, enamel conditioners, and adhesives. American Journal of Orthodontics and Dentofacial Orthopedics. 1993;104(2): Blight S, Lynch E. strengths of ceramic brackets using different bonding techniques. Journal of Orthodontics. 1995;22(1): Buonocore M. Principles of adhesive retention and adhesive restorative materials. Journal of the American Dental Association (1939). 1963;67: Meyer J, Cattani-Lorente M, Dupuis V. Compomers: between glass-ionomer cements and composites. Biomaterials. 1998;19(6): Cacciafesta V, Sfondrini MF, Tagliani P, Klersy C. In-vitro fluoride release rates from 9 orthodontic bonding adhesives. American Journal of Orthodontics and Dentofacial Orthopedics. 2007;132(5): Klockowski R, Davis EL, Joynt RB, Wiezkowski Jr G, MacDonald A. strength and durability of glass ionomer cements used as bonding agents in the placement orthodontic brackets. American Journal of Orthodontics and Dentofacial Orthopedics. 1989;96(1):60-4. How to cite this artice Lohakare SCAS, Hazarey PV. Comparison of shear bond strength of no mix-composite resin, self cure resin reinforced glass ionomer cement and light cure resin reinforced glass ionomer cement -an in vitro study.int. J. Dent.Clinics. 2013;5(4): Address for Correspondence Dr. Sandhya S. Lohakare MDS, Professor, Department of Orthodontics, VSPM Dental College and Research Centre, Digdoh, Hingna, Nagpur (MS), India lohkare_sandhya@yahoo.com Source of Support: Nil Conflict of Interest: ne Declared 16