Revisiting Pulse-delay Photocuring Technique for Polymerization of Dental Composites
Objectives: To clarify effects of parameters (irradiance and radiant exposure of initial pulse) associated with the pulse-delay photocuring technique (PPT) on the degree of monomer conversion (DC), polymerization stress (PS), and temperature change (TC) for resin-based dental composites. Methods: Model dental composites comprising a 7:3 mixture of Bis-GMA and TEGDMA resin, conventional visible-light initiator system, and silanized micro-sized glass fillers were prepared. Two filler contents were used, 30 % (low-fill) and 75 % (high-fill) by mass, for the study. A cantilever-based instrument (NIST SRI 6005) integrated with a programmatically controlled LED, a NIR spectrometer, and a miniature thermocouple was used to measure the DC, PS, and TC simultaneously in real time. The measured photopolymerization properties were compared with the standard photocuring technique (SPT) while the parameters of PPT were varied at equivalent radiant exposures. Results: For the low-fill composite, the PPT achieves lower DC (up to 3%) in comparison to the SPT. For the high-fill composite, the PPT achieves similar DC in comparison to the SPT. For both the composites, the PS with the PPT was found to be lower (up to 33%) when compared with the SPT at similar DC. This reduction in PS is due to the lower thermal shrinkage and not due to stress relaxation. The TC with the PPT was found to be lower (up to 61%) than the SPT. Conclusions: The results show that changes in TC (by changing the parameters of the PPT) influences the DC (via effecting the mobility of the reactants) and PS (via thermal contraction). The PS reduction that can be achieved with the PPT, without comprising the DC, depended on its parameters as well as the composition of the composites (i.e., resin viscosity and filler contents).
Division:IADR/AADR/CADR General Session
Meeting:2020 IADR/AADR/CADR General Session (Washington, D.C., USA) Location:Washington, D.C., USA
Year: 2020 Final Presentation ID:0742 Abstract Category|Abstract Category(s):Dental Materials 2:Polymer-based Materials
Authors
Palagummi, Sri Vikram
( National Institute of Standards and Technology
, Gaithersburg
, Maryland
, United States
)
Hong, Taeseung
( National Institute of Standards and Technology
, Gaithersburg
, Maryland
, United States
)
Chiang, Martin
( National Institute of Standards and Technology
, Gaithersburg
, Maryland
, United States
)
Support Funding Agency/Grant Number: Interagency Agreement between the National Institute of Dental and Craniofacial Research and the National Institute of Standards and Technology, NIH/NIDCR [ADE12017-0000].
Financial Interest Disclosure: NONE
SESSION INFORMATION
Poster Session
Polymer-based Materials: General Properties
TABLES
Values of the photopolymerization properties (degree of monomer conversion - DC, polymerization stress - PS, and peak temperature change - PTC) when a composite of 7:3 mixture of Bis-GMA : TEGDMA resin with low-fill (30 % by mass) content is cured under different photocuring conditions.
Photocuring condition
DC (%) α,β
PS (MPa) α,β
PTC α,β
0.1 W/cm2 × 270 s
63.41 ± 0.16 a,b
1.57 ± 0.09 a
15.25 ± 0.84 a
0.1 W/cm2 × 5 s, 0.45 W/cm2 × 60 s γ,δ
62.83 ± 0.72 a,c
1.23 ± 0.05 b
14.21 ± 2.87 a
0.1 W/cm2 × 2 s, 0.45 W/cm2 × 59.8 s γ
61.82 ± 0.38 c
1.47 ± 0.05 a
13.45 ± 1.75 a
0.45 W/cm2 × 60 s δ
64.98 ± 0.57 d
2.13 ± 0.11 d
29.75 ± 1.70 b
0.45 W/cm2 × 5 s, 0.45 W/cm2 × 55 s γ
63.10 ± 0.43 a,c
1.61 ± 0.06 a,c
28.84 ± 2.44 b
0.45 W/cm2 × 8 s, 0.45 W/cm2 × 52 s γ
62.98 ± 0.67 a,c
1.76 ± 0.07 a,e
26.91 ± 3.82 b
0.45 W/cm2 × 10 s, 0.45 W/cm2 × 50 s γ
64.79 ± 0.66 b,d
2.03 ± 0.01 c,d
27.77 ± 3.81 b
4 W/cm2 × 6.6 s
71.71 ± 0.59 f
3.82 ± 0.17 g
60.06 ± 3.13 c
4 W/cm2 × 0.2 s, 4 W/cm2 × 6.4 s γ
64.70 ± 0.47 b,d
1.82 ± 0.11 c,e
29.72 ± 2.64 b
4 W/cm2 × 0.8 s, 4 W/cm2 × 5.8 s γ
61.99 ± 0.81 a,c
1.18 ± 0.17 b
23.34 ± 1.75 d
4 W/cm2 × 1.6 s, 4 W/cm2 × 5 s γ
62.19 ± 0.80 a,c
1.41 ± 0.08 a,b
42.91 ± 3.58 e
4 W/cm2 × 2.4 s, 4 W/cm2 × 4.2 s γ
67.51 ± 0.97 e
2.79 ± 0.07 f
49.57 ± 11.13 e
α Values represent mean ± standard deviation.
β Same letter superscripts in each column represent statistical similarity (ANOVA, Holm-Sidak method, p > 0.05).
γ Pulse-delay photocuring technique with a delay time of 120s between the two pulses of photocuring.
δ This photocuring condition was used in Lu et al. ("Impact of curing protocol on conversion and shrinkage stress." Journal of Dental Research 84, no. 9 (2005): 822-826) and is replicated in this study for comparison.
Values of the photopolymerization properties (degree of monomer conversion - DC, polymerization stress - PS, and peak temperature change - PTC) when a composite of 7:3 mixture of Bis-GMA : TEGDMA resin with high-fill (75 % by mass) content is cured under different photocuring conditions.
Photocuring condition
DC (%) α,β
PS (MPa) α,β
PTC α,β
0.5 W/cm2 × 40 s
62.45 ± 1.15 a
2.62 ± 0.13 a
10.97 ± 1.36 a
0.5 W/cm2 × 1.6 s, 0.5 W/cm2 × 38.4 s γ
60.40 ± 0.13 b
2.11 ± 0.04 c
10.38 ± 1.27 a
0.5 W/cm2 × 3.2 s, 0.5 W/cm2 × 36.8 s γ
62.13 ± 0.62 a
2.13 ± 0.05 c
11.64 ± 1.49 a
0.5 W/cm2 × 6.4 s, 0.5 W/cm2 × 33.6 s γ
61.69 ± 1.28 a
2.20 ± 0.25 c
11.09 ± 2.05 a
4 W/cm2 × 5 s
62.55 ± 0.74 a
3.01 ± 0.11 b
25.75 ± 3.96 b
4 W/cm2 × 0.2 s, 4 W/cm2 × 4.8 s γ
61.75 ± 1.27 a
2.02 ± 0.09 c
12.27 ± 2.19 a
4 W/cm2 × 0.4 s, 4 W/cm2 × 4.6 s γ
61.91 ± 1.43 a
2.11 ± 0.10 c
11.69 ± 0.87 a
4 W/cm2 × 0.8 s, 4 W/cm2 × 4.2 s γ
60.11 ± 0.49 b
1.96 ± 0.11 c
13.10 ± 2.64 a
α Values represent mean ± standard deviation.
β Same letter superscripts in each column represent statistical similarity (ANOVA, Holm-Sidak method, p > 0.05).
γ Pulse-delay photocuring technique with a delay time of 120s between the two pulses of photocuring.