TY - JOUR
T1 - Influence of photoactivation protocol and light guide distance on conversion and microleakage of composite restorations
AU - Froes-Salgado, N. R.G.
AU - Pfeifer, C. S.C.
AU - Francci, C. E.
AU - Kawano, Y.
PY - 2009/7
Y1 - 2009/7
N2 - Purpose: To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. Methods and Materials: Three photoactivation protocols (600mW/cm 2 × 40 seconds; 400 mW/cm2 × 60 seconds or 200 mW/cm2 × 20 seconds, followed by 500 mW/cm2 × 40 seconds) and three distances from the light source (0, 3 or 7 mm) were tested. Cylindrical specimens (5 mm diameter; 2 nun tall; n=3) were prepared for the DC test (FT-Raman). Class V cavities were made in 90 bovine incisors to conduct the microleakage test. The specimens were conditioned for 15 seconds with phosphoric acid (37%), followed by application of the adhesive system Prime&Bond NT (Dentsply/Caulk). The preparations were restored in bulk. The specimens were stored for 24 hours in distilled water (37°C) before being submitted to the silver-nitrate microleakage protocol. The restorations were sectioned and analyzed under 25x magnification. Results: Statistical analyses (two-way ANOVAs and Tukey test, α=0.05) found significance only for the factor distance (p=0.015) at the top of the composite for the DC test. Conversion was statistically lower for the 7 mm groups compared to the 0 and 3 mm groups, which were equivalent to each other. At the bottom of the specimens, none of the factors or interactions was significant (p<0.05). The Kruskal-Wallis test showed that, in general, the soft-start method led to lower microleakage scores when compared to the continuous modes, mainly when associated with a distancing of 7 mm (p<0.01). With the exception of specimens irradiated with 400mW/cm2 that did not demonstrate variations on scores for the distances tested, higher microleakage was observed for shorter distances from the light source. Conclusions: Soft-start methods may reduce microleakage when the light guide distancing provides a low level of irradiance, which also causes a discrete reduction in the DC.
AB - Purpose: To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. Methods and Materials: Three photoactivation protocols (600mW/cm 2 × 40 seconds; 400 mW/cm2 × 60 seconds or 200 mW/cm2 × 20 seconds, followed by 500 mW/cm2 × 40 seconds) and three distances from the light source (0, 3 or 7 mm) were tested. Cylindrical specimens (5 mm diameter; 2 nun tall; n=3) were prepared for the DC test (FT-Raman). Class V cavities were made in 90 bovine incisors to conduct the microleakage test. The specimens were conditioned for 15 seconds with phosphoric acid (37%), followed by application of the adhesive system Prime&Bond NT (Dentsply/Caulk). The preparations were restored in bulk. The specimens were stored for 24 hours in distilled water (37°C) before being submitted to the silver-nitrate microleakage protocol. The restorations were sectioned and analyzed under 25x magnification. Results: Statistical analyses (two-way ANOVAs and Tukey test, α=0.05) found significance only for the factor distance (p=0.015) at the top of the composite for the DC test. Conversion was statistically lower for the 7 mm groups compared to the 0 and 3 mm groups, which were equivalent to each other. At the bottom of the specimens, none of the factors or interactions was significant (p<0.05). The Kruskal-Wallis test showed that, in general, the soft-start method led to lower microleakage scores when compared to the continuous modes, mainly when associated with a distancing of 7 mm (p<0.01). With the exception of specimens irradiated with 400mW/cm2 that did not demonstrate variations on scores for the distances tested, higher microleakage was observed for shorter distances from the light source. Conclusions: Soft-start methods may reduce microleakage when the light guide distancing provides a low level of irradiance, which also causes a discrete reduction in the DC.
UR - http://www.scopus.com/inward/record.url?scp=68149108541&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=68149108541&partnerID=8YFLogxK
U2 - 10.2341/08-104
DO - 10.2341/08-104
M3 - Article
C2 - 19678445
AN - SCOPUS:68149108541
SN - 0361-7734
VL - 34
SP - 408
EP - 414
JO - Operative dentistry
JF - Operative dentistry
IS - 4
ER -