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Influence of inhomogeneity of the polymerization light beam on the microhardness of resin cement under a CAD-CAM block

Authors
 Yu-Ra Go  ;  Kwang-Man Kim  ;  Sung-Ho Park 
Citation
 JOURNAL OF PROSTHETIC DENTISTRY, Vol.127(5) : 802.e1-802.e10, 2022-05 
Journal Title
JOURNAL OF PROSTHETIC DENTISTRY
ISSN
 0022-3913 
Issue Date
2022-05
MeSH
Ceramics ; Computer-Aided Design* ; Dental Porcelain ; Materials Testing ; Polymerization ; Resin Cements* / therapeutic use ; Surface Properties
Abstract
Statement of problem: The beam profile of a light polymerization unit shows an inhomogeneous distribution. Therefore, the light passing through indirect restorations may be inhomogeneous and affect the polymerization of the resin cement.

Purpose: The purpose of this in vitro study was to investigate the effects of the inhomogeneous distribution of irradiance passing through a computer-aided design and computer-aided manufacturing (CAD-CAM) block on the microhardness of resin cement.

Material and methods: IPS e.max CAD (A3 LT, A3 HT), Celtra Duo (A3 LT), LAVA Ultimate (A3 LT), and Vita Enamic (A3 T) blocks were tested and cut into 1.0-, 1.5-, 2.0-, and 4.0-mm thicknesses (N=100). The resin cements were Variolink N base (light-polymerized) and RelyX U200 (dual-polymerized). The light transmission, irradiance, and beam profile of each block were measured. For microhardness measurement, 5 points (-4 mm, -2 mm, 0 mm, +2 mm, and +4 mm) that coincided with the distance from the center to the periphery of the tip were marked on the specimen's surface. At each point, microhardness was measured 24 hours after polymerization. Repeated measured 1-way ANOVA with the LSD test was performed to analyze the effect of measuring points on the microhardness (α=.05).

Results: The microhardness of the resin cements decreased with an increase of the CAD-CAM block thickness (P<.05). Resin cements under a 1-mm CAD-CAM block showed relatively uniform microhardness, whereas those under 2-mm and 4-mm blocks showed inhomogeneous microhardness (P<.05).

Conclusions: Inhomogeneous light transmission from a light polymerization unit through CAD-CAM blocks resulted in the nonuniform microhardness of resin cement.
Full Text
https://www.sciencedirect.com/science/article/pii/S0022391322000877?via%3Dihub
DOI
10.1016/j.prosdent.2022.02.004
Appears in Collections:
2. College of Dentistry (치과대학) > Dept. of Conservative Dentistry (보존과학교실) > 1. Journal Papers
2. College of Dentistry (치과대학) > Dept. of Dental Biomaterials and Bioengineering (치과생체재료공학교실) > 1. Journal Papers
Yonsei Authors
Kim, Kwang Mahn(김광만) ORCID logo https://orcid.org/0000-0002-5235-0294
Park, Sung Ho(박성호) ORCID logo https://orcid.org/0000-0003-2171-235X
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/189439
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