Assessment of the Effect of Acid and Base Cycling on Mechanical Properties of Various Esthetic Restorative Materials
Horieh Moosavi
Department of Operative Dentistry, Dental Materials Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
Fatemeh Rezaei
I. M. Sechenova Medical Institute, Moscow, Russia.
Zahra Rezaei
Laboratory of Sciences Students, Bojnord University of Medical Sciences, Mashhad, Iran.
Zahra Soroush *
Department of Prosthodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
*Author to whom correspondence should be addressed.
Abstract
Objective: The purpose of this study is the evaluation of the effect of pH cycling, including both acidic and alkaline environments, on the mechanical properties of tooth-colored restorative materials.
Methods and Materials: 20 rectangular bar specimens of one bulk-fill restorative composite, two conventional nanohybrid restorative composites, and one restorative resin-modified glass ionomer were produced according to ISO 4049. Half of the materials were stored in an acid and base cycling defined as two-day storage in acidic (pH =4) and alkaline (pH=8) solutions. The rest of the materials were incubated in distilled water as a control group. The storage lasted for 48 days. Finally, flexural strength, elastic modulus, and microhardness of the specimens in each group determined. Data analyzed with Kruskal-Wallis, Dunn, MANOVA, Tukey HSD and T-test.
Results: The pH cycling model had a significant influence on all mechanical properties of the bulk-fill restorative composite and resin-modified glass ionomer than those stored in water (P <0.05). One of the conventional nanohybrid restorative composites showed a significant reduction in elastic modulus and microhardness while the other one showed a significant reduction only in flexural strength.
Conclusion: pH cycling negatively affects the mechanical properties of resin composites, and the materials’ composition is an important factor in the degradation of the resin-based materials examined.
Keywords: Resin composite, bulk-fill, mechanical properties, dental materials, acid-base