Abstract
Objective: of this study was to characterize and correlate the absorption spectra of three photoinitiators [camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO)], using second or third-generation light curing units (LCU), and to evaluate the degree of conversion and the physical properties of an experimental resin adhesive. Material and methods: Second-generation (Radii-cal® and Emitter D®) and third-generation (Valo® Cordless and Bluephase N®) LCU were assessed regarding spectrum and irradiance rate of emitted light. Also, the photoinitiators (CQ, TPO and BAPO) were characterized by a light absorption spectrum assessed by UV-Vis spectroscopy, degree of conversion and yellowing effect. Statistical analyzes considered two-way ANOVA and post-hoc Tukey test. Results: BAPO presented higher reactivity compared to TPO. Regarding degree of conversion of the photoinitiators activated by different light-curing units, the Emitter D® device promoted a high degree of conversion. BAPO presented the highest yellowing effect values. Conclusions: The emission and absorption characteristics of the photoinitiators were different. The polymerization reaction activated by the second-generation light-curing unit was reduced when using an experimental resin with photoinitiator TPO, and the third-generation light-curing unit showed a higher polymerization potential regardless of the photoinitiator. Keywords Light-curing of dental adhesives; Photoinitiators dental; Curing lights dental.
Highlights
The evolution of conservative restorative dentistry has progressed significantly since the introduction of resin-based composites (RBC) and dental adhesives
One of the most common photoinitiators used in dental adhesives is camphorquinone (CQ) [6], several other photoinitiators have been developed to reduce the impact of color instability, such as diphenyl(2,4,6trimethylbenzoyl) phosphine oxide (TPO) [8], and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) [8]
The 3rd generation light curing units (LCU) presented a broad light spectrum and higher values compared than the 2nd generation
Summary
The evolution of conservative restorative dentistry has progressed significantly since the introduction of resin-based composites (RBC) and dental adhesives Restorative procedures using these approaches have been widely used [1], offering tooth restoration that minimizes the wear of tooth structures [2]. One of the most common photoinitiators used in dental adhesives is camphorquinone (CQ) [6], several other photoinitiators have been developed to reduce the impact of color instability, such as diphenyl(2,4,6trimethylbenzoyl) phosphine oxide (TPO) [8], and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) [8] These substances have been shown to have an adequate degree of C=C conversion [9] of RBCs. These substances have been shown to have an adequate degree of C=C conversion [9] of RBCs It is uncertain what mechanical properties of these photoinitiators [10,11] are satisfactory in relation to different light sources. The greater results of dental adhesives must consider the light-curing process as critical toward achieving a satisfactory degree of conversion, to the extent that it will be able to improve the properties of these adhesive materials
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