Use of NIR light and upconversion phosphors in light-curable polymers

Abstract

OBJECTIVE: Light-curable polymers are commonly used in restorative surgery, prosthodontics and surgical procedures. Despite the fact of wide application, there are clinical problems due to limitations of blue light penetration: application is restricted to defects exposed to the light source, layered filling of defect is required. METHODS: Combining photo-activation and up conversion allows efficient polymer hardening by deep penetrating near-infrared (NIR) light. The prerequisite 450 nm blue light to polymerize dental resins could be achieved by filler particles, which absorb the incident NIR irradiation and convert it into visible light. RESULTS: The on spot generated blue light results in uniform polymer hardening. Composite samples of 5mm thickness were cured two times faster than pure polymer cured by blue light (30 and 60 s, respectively). Overall degree of monomer conversion resulted in higher values of more than 40%. The enhanced transmission of NIR light was confirmed by optical analysis of dentin and enamel. The NIR transmittance surge in the 800-1200 nm window could improve sealing of complex and deep caries lesions. SIGNIFICANCE: We demonstrate faster curing and an improved degree of polymerization by using upconversion filler particles as multiple light emission centers. This study represents an alternative approach in curing dental resins by NIR source. AbstractObjective. Light-curable polymers are commonly used in restorative surgery, prosthodontics and surgical procedures. Despite the fact of wide application, there are clinical problems due to limitations of blue light penetration: application is restricted to defects exposed to the light source, layered filling of defect is required.Methods. Combining photo-activation and up-conversion allows efficient polymer hardening by deep penetrating NIR light. The prerequisite 450 nm blue light to polymerize dental resins could be achieved by filler particles, which absorb the incident NIR irradiation and convert it into visible light.Results. The on spot generated blue light results in uniform polymer hardening.Composite samples of 5 mm thickness were cured two times faster than pure polymer cured by blue light (30 and 60 sec, respectively). Overall degree of monomer conversion resulted in higher values of more than 40 %. The enhanced transmission of NIR light was confirmed by optical analysis of dentine and enamel. The NIR transmittance surge in the 800÷1200 nm window could improve sealing of complex and deep caries lesions.Significance. We demonstrate faster curing and an improved degree of polymerization by using upconversion filler particles as multiple light emission centers. This study represents an alternative approach in curing dental resins by NIR source.3

Rare-earth doped colour tuneable up-conversion ZBLAN phosphor for enhancing photocatalysis

“…In this sense, the observed high intense UV-blue up-conversion emissions are useful for an efficient conversion of highly tissue penetrating NIR into this UV-visible light, as a viable strategy to trigger photoactivatable metal complexes used in photodynamic cancer therapy or bio-fluorescence labelling, at wavelengths more suitable for in vivo applications [18,19]. Additionally, we have also obtained successful preliminary results using our up-conversion ZBLAN agent in NIR-driven photo-polymerization of light-curable polymers commonly used in restorative surgical procedures, prosthodontics [39] and also in NIR-curing of photo-sensible organic resins used in contemporary 3D-printing technology.…”

NaYF4:Yb3+–Er3+ nanocrystals/P(NIPAM-co-RhBHA) core–shell nanogels: Preparation, structure, multi stimuli-responsive behaviors and application as detector for Hg2+ ions

“…Therefore, developing new types of probes that need not excited by UV light has emerged as a tough challenge. In our opinion, the probes excited by near infrared ray (NIR) light may be a promising candidate [25][26][27].…”

Near‐Infrared Photoinduced Reactions Assisted by Upconverting Nanoparticles

“…For example, UV photoreactions are not suitable for deep‐tissue biomedical applications because short wavelength light is preferentially absorbed by tissue giving a limited penetration depth (Figure a) and the high energy associated with UV light may lead to damage of biological systems . In addition, UV light is not applicable for the photocuring of thick films (Figure b) . For this reason, UV curing of dental materials usually requires a layer‐by‐layer curing process .…”

“…The NIR range is defined as the “therapeutic window” because NIR light can penetrate deeper into tissue due to the greater optical transparency of tissue within this region (Figure a) . NIR photoreactions additionally showed potential for the photocuring of resins up to 13.7 cm thick or dental materials up to 10 mm thick (Figure c).…”