Energy dependent polymerization of resin-based composite.
OBJECTIVE
This study explores the relationship between the extent of polymerization and the radiant energy (dose) applied during the photopolymerization of resin-based composites.


METHODS
FTIR was used to measure the 5-min and 24-h conversion of four resin-based composites prepared in a thin film and polymerized under conditions of decreasing intensity and a constant exposure time (30s) using a tungsten halogen curing light. The measured conversion was obtained over a wide range of applied radiant energy. Additionally, samples for two of the materials were polymerized at various intensities and exposure times such that the dose remained constant. This process was performed at four dose levels representing approximately 75% of the conversion range.


RESULTS
The curing profiles (percent conversion versus applied radiant energy) depict a gradual decrease in conversion with decreasing energy followed by a rapid descent. Though there are differences in the maximum conversion attained between the materials, when conversion is represented as a fractional conversion relative to the maximum 24-h value, their 5-min and 24-h curing profiles appear quite similar. Additionally, very similar conversion was measured when the films were exposed using equivalent doses providing evidence for a reciprocal relationship between irradiance (power density) and exposure time. For the 24-h measurements, statistical equivalence (Fishers protected LSD at the 0.05 level) was noted for most of the combinations of exposure time and power density within a given dose. Generally, the exceptions occurred with the shortest exposure times.


CONCLUSIONS
A reciprocal relationship between exposure time and power density adds significance to the study of conversion as a function of the total applied dose. This relationship establishes the curing profile as a universal correlation between exposure time and power density.
Halvorson
Rolf H
RH
3M Dental Products, St. Paul, MN, USA. rhhalvorson@mmm.com
Erickson
Robert L
RL
Davidson
Carel L
CL
D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects; D000538:Aluminum Silicates / Q000737:chemistry / Q000528:radiation effects; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D004735:Energy Transfer; D006801:Humans; D008027:Light; D008029:Lighting / Q000295:instrumentation; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared; D013223:Statistics as Topic; D013499:Surface Properties; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry / Q000528:radiation effects
D000180:Acrylic Resins; D000538:Aluminum Silicates; C029012:Composite Dental Resin; D003188:Composite Resins; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D019279:Resin Cements; C083568:Z100 composite resin; C065770:Herculite XR; C074741:Silux Plus; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide