1161 Shade Dependent Change in Dental Composite Light Transmittance During Curing

Friday, March 21, 2014: 3:30 p.m. - 4:45 p.m.
Location: Exhibit Hall AB (Charlotte Convention Center)
Presentation Type: Poster Session
Track: Clinician Track
C.K. CHRISTOFERSON1, C.S. PFEIFER2, C. FELIX3, and J.L. FERRACANE1, 1Oregon Health & Science University, Portland, OR, 2School of Dentistry, Oregon Health and Science University, Portland, OR, 3BlueLight analytics inc, Halifax, NS, Canada

Objective: During curing, the resin in dental composites changes refractive index, typically allowing more light transmittance as cure proceeds.  This study evaluated the effect of shade on the change in transmittance of light through various thicknesses of one dental composite during curing.

Materials and Methods: Twelve shades of Venus Diamond (Heraeus) were light cured in 1, 2, and 3 mm thick Delrin disks (6 mm diameter; n=3) with the bottom surface placed atop a MARC Resin Calibrator (Blue Light Analytics).  Irradiance at the bottom during light curing (1500 mW/cm2; Valo, Ultradent) was measured continuously for 10 seconds; then specimens were re-irradiated 3X-10s while continuously recording irradiance.  Groups were compared with 2-way ANOVA/Tukey's (α=0.05).

Results: Total light energy reaching the bottom vs. top was 13, 9 and 5% at 1, 2 and 3 mm, resp.  For combined shades, increases in bottom irradiance during the 10s initial cure varied significantly with depth: 49mW/cm2@1mm > 32mW/cm2@2mm > 16mW/cm2@3mm (Figure 1), providing evidence for improved refractive index match of the resin and filler during curing.  Shades visually perceived as lighter (Figure 2) generally showed greater increase in bottom irradiance than darker shades at all depths (Figure 1). Additional changes in irradiance during subsequent exposures were reduced (<0, ~5%, ~10-20% for 1, 2, 3 mm, resp.).  This was likely due to the small additional changes in degree of conversion, which were accentuated somewhat at greater depths due a lower initial bottom cure for these specimens. 

Conclusions: All shades and all thicknesses (up to 3 mm) of one specific composite experienced some increase in light transmittance during curing, but the amount was shade dependent, with darker shades and greater depths of material showing less improvement.  This study confirms that for one specific resin composite formulation, some increase in translucency with cure occurs independent of shade.

 

Student Presenter This abstract is based on research that was funded entirely or partially by an outside source: This work was supported in part by Blue Light Analytics, Inc.

Keywords: Color, Composites, Curing lights, Dental materials and Polymers
Presenting author's disclosure statement:

I have a significant financial interest/arrangement or affiliation with an organization/institution whose products or services are being discussed in this session. I understand that I must disclose this information to the participants who attend my presentation. No
I have read the IADR policy on licensing.
Signed on 10/08/2013 by C.K. CHRISTOPHERSON