Clinical Research Associates
Swiss Master Light
This information supplements the February 2004 CRA Newsletter.
Index
1. Power
& Intensity Measurements
2. Width of
Cure Measurements
3. Speed of
Cure Measurements
4. Heating
of Tooth Measurements
5. Operation
Modes
1. Power & Intensity Measurements
Power & intensity were determined as follows (method
based on
1. The light guide was positioned over a Molectron PM3 laser power meter.
2. The light was activated for 10 seconds.
3. Maximum power (P) was recorded.
4. The diameter (d) of the aperture of the light guide was measured with digital calipers. Or, if there was no light guide, white mixing pad paper was held over the light & the effective diameter of the bright spot was measured.
5. The area (A) of the light was calculated from the diameter A = p(d/2)2.
6. Intensity (I) was calculated by dividing the power by the area of the light guide I = P/A.
The following graph shows the power measured for 9 curing lights using the Molectron PM3 detector & PM5200 power meter, with data logged by computer.
The following graph shows the calculated intensity for the same 9 lights. Light guide (or spot) area is shown in parentheses behind the light name.
2. Width of Cure Measurements
Width of cure was tested as follows:
1. Baseline hardness for each resin was determined as follows:
a. Resin was packed into a 2 mm deep X 5 mm diameter stainless steel mold.
b. The mold was backed by a 1 mm thick glass microscope slide, & the resin was covered by a strip of mylar plastic.
c. The aperture of a conventional halogen curing light (Optilux 401, 10 mm light guide) was centered 3 mm above the resin surface.
d. The light was activated for the time specified by the resin manufacturer (usually 40 seconds).
e. The mylar & glass slides were removed.
f. The hardness of the resin on the bottom surface (2 mm deep) was measured in the center of the sample & at two other locations 1 mm from the center with a Barcol hardness tester, model GYZJ 935.
g. The average hardness value was then calculated for the sample.
h. The hardness values of 3 separate samples were averaged & called the “baseline” hardness.
2. Resin was packed into a 2 mm deep X 20 mm diameter stainless steel mold.
3. 1 mm thick glass microscope slides were placed on each side of mold.
4. The aperture of the test light was centered 3 mm above the resin surface.
5. The light was activated for 10 seconds.
6. The glass slides were removed.
7. The hardness of the resin on the bottom surface (2 mm deep) was measured across two orthogonal diameters at 1 mm intervals with a Barcol hardness tester, model GYZJ 935.
8. If the hardness value was ³90% of the baseline hardness then the resin was considered cured.
9. Width of cure was recorded for each diameter, then the average calculated.
The following table shows the width of cure of two resins using the Swiss Master Light, a plasma arc light, & a fast halogen light:
WIDTH OF CURE DATA
|
|
Swiss Master Light 11 mm tip Fast cure mode 10 sec cure |
PowerPAC 7 mm tip 10 sec mode 10 sec cure |
Optilux 501 8 mm Turbo tip Boost mode 10 sec cure |
|
Heliomolar A4 Microfill resin Dark shade |
8.0 mm |
4.5 mm |
3.0 mm |
|
XRV Herculite Enamel A3 Hybrid resin Universal shade |
16.0 mm |
13.5 mm |
11.5 mm |
Results: All lights produced a respectable width of cure in a light shade hybrid resin. Only Swiss Master Light produced a respectable width of cure with the dark shade microfill resin.
3. Speed of Cure Measurements
Speed of cure was tested as follows:
1. Baseline hardness for each resin was determined as follows:
a. Resin was packed into a 2 mm deep X 5 mm diameter stainless steel mold.
b. The mold was backed by a 1 mm thick glass microscope slide, & the resin was covered by a strip of mylar plastic.
c. The aperture of a conventional halogen curing light (Optilux 401, 10 mm light guide) was centered 3 mm above the resin surface.
d. The light was activated for the time specified by the resin manufacturer (usually 40 seconds).
e. The mylar & glass slides were removed.
f. The hardness of the resin on the bottom surface (2 mm deep) was measured in the center of the sample & at two other locations 1 mm from the center with a Barcol hardness tester, model GYZJ 935.
g. The average hardness value was then calculated for the sample.
h. The hardness values of 3 separate samples were averaged & called the “baseline” hardness.
2. Resin was packed into a 2 mm deep X 5 mm diameter stainless steel mold.
3. The mold was backed by a 1 mm thick glass microscope slide, & the resin was covered by a strip of mylar plastic.
4. The aperture of the test light was centered 3 mm above the resin surface.
5. The light was activated for a recorded number of seconds.
6. The glass slide & mylar were removed.
7. The hardness of the resin on the bottom surface (2 mm deep) was measured in the center of the sample & at two other locations 1 mm from the center with a Barcol hardness tester, model GYZJ 935.
8. The average hardness value was then calculated for the sample
9. If the hardness value was ³90% of the baseline hardness, then the resin was considered cured.
10. If the hardness value was <90% of the baseline hardness, then the resin was considered uncured.
11. Additional samples were cured in 1 second intervals longer or shorter than the previous sample until the time required to transition from uncured to cured (or from cured to uncured) was identified & recorded as the minimum cure time.
12. Two additional cure time determinations (series of samples) were made for each resin.
13. The three minimum cure times were averaged & rounded up to the next whole second & recorded as the speed of cure.
The following table shows the speed of cure of two resins using the Swiss Master Light, a plasma arc light, & a fast halogen light:
SPEED OF CURE DATA
|
|
Swiss Master Light 11 mm tip Fast cure mode |
PowerPAC 7 mm tip 10 sec mode |
Optilux 501 8 mm Turbo tip Boost mode |
|
Heliomolar A3 Microfill resin Universal shade |
5 sec |
3 sec |
4 sec |
|
Heliomolar A4 Microfill resin Dark shade |
11 sec |
6 sec |
14 sec |
|
XRV Herculite Enamel A3 Hybrid resin Universal shade |
4 sec |
3 sec |
4 sec |
|
XRV Herculite Cervical YB Hybrid resin Dark shade |
7 sec |
5 sec |
8 sec |
Results: Overall, the Swiss Master Light cured resins slightly faster than the Optilux 501 fast halogen light, & slightly slower than the PowerPAC plasma arc light. Note that the metal molds used in this test limit the light to a 5 mm aperture. This diameter favors the lights with the small light guides & may have been a disadvantage for the Swiss Master Light, where much of its energy was outside the 5 mm diameter area.
4. Heating of Tooth Measurements
The high power & intensity of the Swiss Master Light raised concerns of excessive heating of oral tissues. To test for potentially dangerous temperature increases, an in vitro test simulating the curing of a liner in a deep Class II preparation within 0.5 mm of the pulp was performed as follows:
1. An extracted human molar was prepared with a thermocouple in a pulp horn.
a. A Class II MOD prep was cut into a maxillary first molar using a #57 12-fluted carbide bur. The occlusal floor was cut to within 0.5 mm of the pulp horn, as verified by radiographs.
b. A 0.5 mm thick layer of Vitrebond (3M) was placed on the occlusal floor & light cured (thickness verified with radiographs).
c. Approximately 5 mm of the root tips were removed with the carbide bur & endodontic files used to remove as much pulp tissue as possible.
d. The root canal below the highest pulp horn was enlarged with files or burs.
e. A type K miniature thermocouple was lightly coated with a flowable resin, inserted up the root & into the pulp horn, & light cured in place by curing through the tooth. Placement was verified with radiographs.
2. A pliable wire was inserted 5 mm into another root canal & bent to shape to act as a hanger to position the tooth vertically.
3. The tooth was positioned in a circulating water bath up to the CEJ.
4. The water bath temperature was adjusted until pulp temperature was 37° C ±0.2° C.
5. The test light was positioned over the center of the occlusal surface, 1 mm above the highest cusp.
6. The light was activated & the following temperatures & times recorded:
a. The maximum temperature reached using the light manufacturer’s recommended (or standard, or default) cure time.
b. The maximum temperature reached using longer cure times than recommended by the light manufacturer.
c. The time required to cause a pulp temperature increase of 5.5° C (shown to cause irreversible damage to pulp).
6. Following light exposure, the tooth was allowed to cool back to 37° C.
7. The test was repeated at least 2 additional times.
8. The average temperature increases & times were calculated from the 3 tests.
The following table shows the heat data, listed from lowest to highest temperature reached:
|
CURING LIGHT |
LIGHT ACTIVATION TIME (seconds) |
PULP TEMPERATURE INCREASE |
|
Mini L.E.D. (LED) 7.5 mm tip; Fast Curing mode |
10 sec |
1.3° C |
|
Optilux 501 (Fast Halogen) 8 mm Turbo tip; Boost mode |
10 sec |
2.4° C |
|
Ultra-Lume LED 5 (LED) Clear oval lens |
20 sec |
2.8° C |
|
Swiss Master Light 11 mm tip; Fast Cure mode |
4 sec |
2.9° C |
|
Swiss Master Light 11 mm tip; Fast Cure mode |
6 sec |
3.3° C |
|
Optilux 401 (Conventional Halogen) 11 mm tip |
60 sec |
4.9° C |
|
Swiss Master Light 11 mm tip; Fast Cure mode |
13.9 sec |
5.5° C |
|
Rembrandt Virtuoso Sapphire 9 mm tip; Standard mode |
7.9 sec |
5.5° C |
|
PowerPAC (Plasma Arc) 7 mm tip; 10 second mode |
5.5 sec |
5.5° C |
Results: The Swiss Master Light caused an average pulp temperature increase of 3.3° C when activated for 6 seconds in the Fast Cure Mode. This temperature increase is significant for so short a cure time. Caution should be exercised when using this light, particularly when working close to the pulp or in small (thin) teeth. Allow the tooth to cool between repeated exposures & do not leave the light on one tooth during lengthy exposures in Bleach mode.
The Swiss Master Light did not cause the extreme heating typical of plasma arc lights, despite its high power & intensity. It is theorized that the wide spread of the energy due to the wide diameter light guide helps prevent intense localized heating.
5. Operation Modes
The output power profiles of the Swiss Master Light in each of its operation modes was recorded as follows:
1. A calibrated research radiometer & digital data acquisition system were configured.
a. Input optics: INS250 integrating sphere; F flat response filter; SEE015 detector (International Light).
b. Radiometer: IL1500 Research Radiometer, Range A (readout in watts) (International Light).
c. Output: 1000 mV.
d. Data acquisition: LabPC+ (National Instruments) with custom program recording power every 0.25 seconds.
2. The light guide was positioned over the input port of the integrating sphere.
3. The desired mode of operation of the light was selected.
4. The data acquisition system was started.
5. The light was activated three successive times.
6. The mode was changed & the three activations repeated until all modes had been recorded.
7. Power data were graphed & analyzed for power output level, time, profile characteristics, & consistency.
Mode profiles are shown in the following graph:
Results: The Fast
Cure & Bleaching modes have the same high output, just different time
options. The two Ramp modes are more
accurately described as “step” modes.
The user programmable Variable modes allow the user to select the
desired time & power.