179 Transmission from Light-Cure Units and Bulk-Fill Composite Cure-Depths

Thursday, March 20, 2014: 10:45 a.m. - 12:15 p.m.
Location: 208A (Charlotte Convention Center)
Presentation Type: Oral Session
D.C. WATTS, University of Manchester, UK, Manchester, England, A. SADEGHYAR, Medical University of Vienna, Vienna, Austria, and A. SCHEDLE, Medical University of Vienna, Bernhard Gottlieb University Clinic of Dentistry, Vienna, Austria

Objectives: Depth-of-Cure (DoC) is a key parameter of bulk-fill composites: potentially a function of: (i) composite formulation; (ii) cavity mold material /dimensions; (iii) irradiation source & protocol – irradiance x time; (iv) the selected cure-dependent property. As part of a comprehensive investigation, we focus here on DoCs from hardness-depth profiles for bulk-fill composites, in relation to their light absorption coefficients, with a single light-cure-unit (LCU).

Methods: Six bulk-fill composites were examined and assigned the codes: SDR-BF, TEC-BF, V-BF, XB-BF, F-BF, SF-BF. Two standard composites were studied for comparison: TEC and CX. Six specimens of each material were prepared in circular cavities (diameter 5 mm) in a series of white Acetal molds of increasing cavity depth (d), from 1-6 mm. Materials were directly irradiated with an Elipar S10 LCU, of irradiance 1200 mW/cm2 (MARC-RC, BlueLight Analytics, Inc), for manufacturer-recommended time-periods. After light-cure, the specimens were allowed to dark post-cure for 24 h at 37 oC. Vickers hardness (Hv) of each specimen was then measured 10 x on both top and bottom surfaces, (300 g load, 15 s). Light transmission through specimens was subsequently measured via MARC-RC.

Results: Maximum Hv varied within the range 40-80, depending on filler loading. Top-surface Hv was approximately invariant with mold depth (d).  Bottom-surface Hv decreased gradually with increasing d, for BF materials, and DoC could be assigned - corresponding to 80 % of maximal Hv - which ranged from 3.3 to 5.5 mm. When light absorption coefficients (a) were derived (Watts: J Dent 1994, 22: 112-7) from the BF transmission data, excluding XB-BF, a negative linear regression was found (r = - 0.900) of DoC on a.

Conclusion: Measurement of 24 h bottom-hardness versus (Acetal) mold depth is a viable method of deriving Depth-of-Cure data, which for five BF composites varied approximately according to the light-absorption coefficient.

Keywords: Composites, Dental materials, Hardness, Light-Curing and Polymerization
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 10/07/2013 by D.C. WATTS