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Effect of shade and thickness on the microhardness of resin-based composite specimens at different points considering curing light beam's inhomogeneity

Authors
 Lan Wang  ;  Hyemin Ku  ;  Dohyun Kim  ;  Sung-Ho Park 
Citation
 BMC ORAL HEALTH, Vol.24(1) : 865, 2024-07 
Journal Title
BMC ORAL HEALTH
Issue Date
2024-07
MeSH
Color* ; Composite Resins* / chemistry ; Composite Resins* / radiation effects ; Curing Lights, Dental* ; Dental Enamel / radiation effects ; Dental Materials / chemistry ; Dental Materials / radiation effects ; Dentin / radiation effects ; Hardness* ; Humans ; Light ; Light-Curing of Dental Adhesives / methods ; Materials Testing* ; Polymerization ; Surface Properties
Keywords
Beam inhomogeneity ; Light curing unit ; Microhardness ; Resin-based composite ; Thickness and shade
Abstract
Background: Recent studies have reported the inhomogeneity in the light emitted by dental light-curing units (LCUs). It is essential to understand how this uneven light distribution affects the physical properties of resin-based composites (RBCs) at various points across their surfaces. This study aimed to evaluate the effect of LCU beam’s inhomogeneity on the microhardness of RBCs with different shades and thicknesses. Methods: Four body (A1B, A2B, A3B, and A4B), one dentin (A3D), and one enamel shade (A3E) of RBC (Filtek Z350 XT) were examined. The specimens were fabricated in four thicknesses (1, 2, 3, and 4 mm) and subjected to a 40-second light-curing. Vickers microhardness testing was performed at the center point, and 3 mm left and right from the center at the bottom surface of each sample. The LCU beam profile was characterized using a beam profiler, while irradiance after specimen passage was measured using a spectrometer. One-way analysis of variance (ANOVA) and Tukey’s post-hoc tests were used to analyze the effects of shades and thicknesses on irradiance and microhardness, respectively. One-way repeated-measures ANOVA was used to compare the microhardness across different points. Pearson’s correlation analysis examined the relationship between irradiance and microhardness. Results: The beam profile of LCU revealed inhomogeneous light distribution. Light irradiance was decreased with both the increase in thickness and darker shade of the specimens (p < 0.05). Microhardness was found to decline with an increase in sample thickness (p < 0.05), and was consistently higher at the center point compared to the periphery, particularly in thicker (3 and 4 mm) and darker shades (A3B, A4B, and A3D). A positive correlation was found between the irradiance and microhardness across all evaluated points (p < 0.05). Conclusions: Inhomogeneous light emission from LCU significantly influences the microhardness of RBC samples, depending on the thicknesses and shades. The findings underline the importance of considering LCU beam inhomogeneity in clinical settings to ensure optimal polymerization of RBC.
Files in This Item:
T202404971.pdf Download
DOI
39080607
Appears in Collections:
2. College of Dentistry (치과대학) > Dept. of Conservative Dentistry (보존과학교실) > 1. Journal Papers
Yonsei Authors
Kim, Dohyun(김도현) ORCID logo https://orcid.org/0000-0002-0772-6985
Park, Sung Ho(박성호) ORCID logo https://orcid.org/0000-0003-2171-235X
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/200416
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