Reduction of polymerization contraction stress for dental composites by two-step light-activation

Lim, Bum-Soon; Ferracane, Jack L.; Sakaguchi, Ronald L.; Condon, John R.

doi:10.1016/s0109-5641(01)00066-5

Cited by 254 publications

(225 citation statements)

References 26 publications

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“…Therefore, "soft-start" polymerization modes, such as the two-step mode and the ramping mode have been developed. These curing modes could significantly reduce shrinkage stress during polymerization [84,85]. However, "soft-start" polymerization has not displayed any consistent effect on marginal integrity [86][87][88].…”

Section: The Effect Of Light Curing Modesmentioning

confidence: 99%

Challenges to the clinical placement and evaluation of adhesively-bonded, cervical composite restorations

Kubo

Yokota

et al. 2013

Dental Materials

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Objectives: The incidence of non-carious cervical lesions (NCCLs) has been increasing.The clinical performance of resin composites in NCCLS was previously unsatisfactory due to their non-retentive forms and margins lying on dentin. In order to address this problem, a lot of effort has been put into developing new dentin adhesives and restorative techniques. This article discusses these challenges and the criteria used for evaluating clinical performance as they relate to clinical studies, especially long-term clinical trials. Polymerization contraction, thermal changes and occlusal forces generate debonding stresses at adhesive interfaces.Methods: In laboratory studies, we have investigated how these stresses can be relieved by various restorative techniques and how bond strength and durability can be enhanced. Lesion forms, restorative techniques, adhesives (adhesive strategies, bond strengths, bond durability, and the relationship between enamel and dentin bond strengths) were found to have a complex relationship with microleakage. With regard to some restorative techniques, only several short-term clinical studies were available.

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Section: The Effect Of Light Curing Modesmentioning

confidence: 99%

Challenges to the clinical placement and evaluation of adhesively-bonded, cervical composite restorations

Kubo

Yokota

et al. 2013

Dental Materials

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“…In addition, the stress development is affected by the reaction kinetics as a higher polymerization rate is accompanied by high polymerization stress [15,16]. The material plastic deformation is time dependent phenomenon in which the material needs time to flow to accommodate the contraction stresses before the development of the modulus of elasticity [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Polymerization shrinkage kinetics and shrinkage-stress in dental resin-composites

2016

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Shrinkage-strainShrinkage-stress Strain rate Modulus of elasticity Bulk-fill a b s t r a c tObjectives. To investigate a set of resin-composites and the effect of their composition on polymerization shrinkage strain and strain kinetics, shrinkage stress and the apparent elastic modulus.Methods. Eighteen commercially available resin-composites were investigated. Three specimens (n = 3) were made per material and light-cured with an LED unit (1200 mW/cm 2 ) for 20 s. The bonded-disk method was used to measure the shrinkage strain and Bioman shrinkage stress instrument was used to measure shrinkage stress. The shrinkage strain kinetics at 23 • C was monitored for 60 min. Maximum strain and stress was evaluated at 60 min. The shrinkage strain rate was calculated using numerical differentiation. Significance. The nature of the monomer system determines the amount of the bulk contraction that occurs during polymerization and the resultant stress. Higher values of shrinkage strain and stress were demonstrated by the investigated flowable materials. The bulk-fill materials showed comparable result when compared to the traditional resin-composites.

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“…13 Among the photoactivation protocols suggested, those using an initial pulse with radiant exposure up to 1 J/cm 2 seem to be the most efficient in reducing shrinkage stress. [13][14][15][16] Several authors have tested initial irradiances between 100 and 650 mW/cm 2 when evaluating the influence of pulse-delay curing on shrinkage stress and other properties of composites. 5,[13][14]17 Previous studies have reported a decrease in microleakage 5 and shrinkage stress [13][14] without compromising the degree of conversion.…”

Section: Introductionmentioning

confidence: 99%

“…19 Indeed, a previous study verified that higher polymerization stress reduction (between 12% and 27% when compared to the high irradiance continuous mode) was obtained with irradiances as low as 60 mW/cm 2 and exposure times of 5 seconds for the initial pulse. 15 Another important parameter is delay time between irradiances. During the dark period, polymerization reaction still occurs, but at a reduced rate.…”

Section: Introductionmentioning

confidence: 99%

“…During the dark period, polymerization reaction still occurs, but at a reduced rate. 15 Therefore, longer delay periods between pulses would increase the possibility for viscous flow and chain relaxation. Significant reductions in shrinkage stress and microleakage have been reported for pulse-delay methods, with dark periods varying from 1 to 5 minutes.…”

Section: Introductionmentioning

confidence: 99%

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Pulse-delay Curing: Influence of Initial Irradiance and Delay Time on Shrinkage Stress and Microhardness of Restorative Composites

Pfeifer

Braga

Ferracane

2006

Operative Dentistry

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©Operative Dentistry, 2006, 31-5, 610-615 CSC Pfeifer • RR Braga • JL Ferracane Clinical RelevanceNew photoactivation protocols need to be tested before being recommended for clinical use. This study suggests that pulse-delay curing may be an efficient way to reduce polymerization shrinkage stress without compromising degree of conversion or polymer network structure. SUMMARYObjectives: Evaluate the influence of pulse-delay curing on shrinkage stress and microhardness of 2 restorative composites (Herculite XRV and Tetric Ceram). Methods: Two pulse irradiances (500 and 100 mW/cm 2 ) were applied for 1 or 5 seconds, respectively (radiant exposure = 0.5 J/cm 2 ). In both cases, photoactivation was completed applying 500 mW/cm 2 for 39 seconds after a delay time of 0, 1 or 3 minutes. Shrinkage stress was monitored for 10 minutes in specimens 5-mm in diameter by 1-mm in height. Knoop hardness (KHN) was used to estimate the degree of conversion 10 minutes after photoactivation and after 48 hours of storage in distilled water (37°C) in specimens with similar geometry and dimensions. Additional KHN readings after 48 hours of storage in ethanol (37°C) were used to estimate polymer structure. The results were evaluated using ANOVA/Tukey test and Student t-test (α α=0.05). Results: For Tetric Ceram, 3-minute delay led to stress reduction compared to continuous curing at 500 mW/cm 2 (4.7±0.6 MPa and 7.0±1.3 MPa, respectively). At 100 mW/cm 2 , 1 minute delay was enough to cause significant stress reduction (5.2±0.5 MPa). For Herculite, the pulse with 3 minute delay led to stress reduction compared to no delay for both irradiances (100 mW/cm 2 : 6.3±0.5 MPa and 7.8±0.8 MPa, respectively; 500 mW/cm 2 : 6.4±0.3 MPa and 7.8±0.7 MPa, respectively). At 10 minutes, only small differences in microhardness were observed for both materials. No differences were found after water and ethanol storage (p>0.05). Conclusions: The composites behaved differently when subjected to pulse curing. Stress reduction was influenced by delay time but not by pulse irradiance. KHN results suggest that similar degrees of conversion and polymer structure were achieved with the photoactivation methods tested.

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Reduction of polymerization contraction stress for dental composites by two-step light-activation

Cited by 254 publications

References 26 publications

Challenges to the clinical placement and evaluation of adhesively-bonded, cervical composite restorations

Challenges to the clinical placement and evaluation of adhesively-bonded, cervical composite restorations

Polymerization shrinkage kinetics and shrinkage-stress in dental resin-composites

Pulse-delay Curing: Influence of Initial Irradiance and Delay Time on Shrinkage Stress and Microhardness of Restorative Composites

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