Quantifying light energy delivered to a Class I restoration

To measure the amount of light energy that dental students actually deliver to a Class I preparation in a dental mannequin.

Approval for the study was obtained from the Dalhousie University Health Sciences Research Ethics Board. Each of 20 third-year dental students light-cured a Class I preparation in tooth 27 in a mannequin head. A photodetector located at the bottom of the cavity preparation measured how much light would be received by a restoration. Each student cured the simulated restoration for 20 seconds using a quartz-tungsten-halogen curing light (Optilux 401). The irradiance received (mW/cm2) was recorded in real time, and the energy per unit area (J/cm2) delivered to the detector by each student was calculated. The students were then given detailed instructions on how to effectively use the curing light, and the experiment was repeated.

When the curing light was fixed directly over the tooth, the greatest amount of light energy delivered to the detector in 20 seconds was 13.9 +/- 0.4 J/cm2. Before instruction, the students delivered between 2.0 and 12.0 J/cm2 (mean +/- standard deviation [SD]: 7.9 +/- 2.7 J/cm2). After receiving detailed instructions, the same students delivered between 7.7 and 13.4 J/cm2 (mean +/- SD: 10.0 +/- 1.4 J/cm2). A paired student"s t test showed that instruction resulted in a significant improvement (p < 0.001).

Although instruction yielded improvements, the mean energy delivered was much less (7.9 J/cm2 before instruction and 10.0 J/cm2 after instruction) than the expected 13.9 J/cm2. To maximize the energy delivered, the operator should wear eye protection, should watch what he or she is doing and should hold the light both close to and perpendicular to the restoration.