An in Vitro Comparative Study of the Effect of Different Surface Preparation Methods on Shear Bond Strength Between Ivoclar Sr Nexco Paste Indirect Composite Resin and Ivoclar Heliomolar Direct Composite Resin



Borujeni ESA¹ ; Kazemi SS¹ Show Affiliations
Source: Journal of Mazandaran University of Medical Sciences Published:2025

Abstract

Background and purpose: Due to the relatively high cost of cosmetic restorations with indirect composite resins, the time required for their complete replacement, and, in some cases, the need for significant tooth structure removal, repairing these restorations may sometimes be a more appropriate approach. This study aimed to investigate and compare the effects of different surface preparation methods on the shear bond strength between indirect and direct composite resins. Materials and methods: In this study, 102 indirect composite resin blocks of Ivoclar SR Nexco Paste were fabricated and assigned to three groups (n = 34) based on the preparation method. Group 1: roughening and etching with 37% phosphoric acid; Group 2: roughening and etching with 9.5% hydrofluoric acid; Group 3: air abrasion with 50-μm aluminum oxide particles. A total of 500 thermal cycles were performed before the repair process, and surface preparations were carried out. After applying the adhesive in all groups, the samples were repaired using the direct Ivoclar Heliomolar composite resin. The samples were then subjected to fracture by an Instron machine at a speed of 0.5 mm/min, and the shear bond strength was recorded. The data were then converted to MPa and evaluated using one-way ANOVA and the Tukey test. Results: The highest shear bond strength was recorded in Group 2 (mean± SD = 24.64± 2.28), and the lowest bond strength was recorded in Group 1 (mean± SD= 10.31± 1.67). Conclusion: In this study, preparation with hydrofluoric acid resulted in higher shear bond strength compared to phosphoric acid and air abrasion. © 2025, Mazandaran University of Medical Sciences. All rights reserved.