Indiana University-Purdue University Indianapolis (IUPUI) / The general aim of this study was to investigate the influence of the localized irradiance
beam profiles from multiple light-emitting-diode (LED) light-curing units (LCUs) on the
polymerization pattern within a resin-matrix composite (RMC). Irradiance beam profiles were
generated from one quartz-tungsten-halogen and various single and multiple emission peak LED
LCUs using a camera-based beam profiler system combined with LCU power measurements
obtained using an integrating sphere/spectrometer assembly. The influence of distance on
irradiance, radiant exposure (RE) and degree of conversion (DC) on the top and bottom surfaces
of a RMC increment, using various LCUs, at two clinically relevant distances was investigated.
Molar absorptivity of the photoinitiators present in the nano-hybrid RMC (Tetric EvoCeram
bleaching shade-XL) assessed was using UV-spectrophotometry. The correlation among
irradiance, RE and DC was explored. A mapping approach was used to investigate DC,
microhardness and cross-link density (CLD) within 5×5×2 mm specimens at various depths; top,
0.5, 0.7, 0.9, 1.1, 1.3,1.5 mm and bottom. The localized irradiance correlation with its
corresponding DC, microhardness and CLD was explored, and localized DC correlation with
microhardness was assessed. The DC was measured using micro-Raman spectroscopy, and CLD
was assessed by an ethanol-softening method (%KHN reduction) using an automated
microhardness tester.
Molar absorptivity of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide was 20-fold
higher than camphorquinone. Non-uniform LCU beam profiles caused localized polymerization
discrepancies that were significant at specific depths and points within the specimens with respect to DC, microhardness and CLD, which did not follow a specific pattern regardless of the LCU or
curing distance assessed.
A moderate correlation was displayed among irradiance, RE and DC. The localized
irradiance from the LCUs was weakly correlated with the corresponding DC, microhardness and
CLD on the top surface of a RMC at both curing distances. The localized microhardness was
moderately correlated with DC. In conclusion, polymerization within the RMC investigated was
non-uniform and did not reflect the LCU irradiance pattern at the area assessed. Also, a mapping
approach within the specimens provided a detailed polymerization pattern assessment occurring
within a RMC increment. Therefore, the LCUs explored may potentially increase the risk of
RMC fracture.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/12841 |
| Date | January 2017 |
| Creators | AlZain, Afnan Omar |
| Contributors | Platt, Jeffrey A., Chu, Tien-Min G., Bottino, Marco C., Hara, Anderson T., Goodpaster, John V., Roulet, Jean-Francois |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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