Clinical Research Associates
WHY RESIN CURING LIGHTS DO NOT INCREASE TOOTH LIGHTENING
The following information is a supplement to the August 2000 CRA Newsletter.
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Index
1. Temperatures reached using recommended lights & exposure times, in vitro
The following table lists the maximum bleaching gel temperatures recorded using the recommended lights & exposure times. Initial gel temperature was 28 - 30° C.
|
BLEACH
|
LIGHT
|
DISTANCE
|
TIME
|
MAX TEMP
|
|
PowerGel
|
Kreativ Kuring Light
|
3 mm
|
60 sec
|
47.9° C
|
|
Opalescence Xtra
|
PowerPAC
|
6 mm
|
5 sec
|
45.6° C
|
|
Opalescence Xtra
|
Optilux 500
|
6 mm
|
30 sec
|
42.9° C
|
|
Apollo Secret(original)
|
Apollo 95 E
|
6 mm
|
3 sec
|
40.4° C
|
|
Apollo Secret(new)
|
Apollo 95 E
|
6 mm
|
3 sec
|
37.5° C
|
|
QuickWhite
|
AccuCure 3000
|
6 mm
|
30 sec
|
35.6° C
|
|
Rembrandt Virtuoso Lightning
|
Virtuoso
|
6 mm
|
5 sec
|
35.2° C
|
|
QuasarBrite
|
PowerPAC
|
12 mm
|
10 sec
|
34.9° C
|
|
Opalescence Xtra
|
AccuCure 3000
|
6 mm
|
5 sec
|
33.2° C
|
|
QuasarBrite
|
AccuCure 3000
|
12 mm
|
30 sec
|
33.1° C
|
|
Hi Lite
|
Optilux 500
|
6 mm
|
300 secoscillating over
6 teeth
|
30.5° C
|
Summary of table: Maximum gel temperatures ranged from 30.5 - 47.9° C. The highest temperature was produced by the Kreativ Kuring Light exposing PowerGel for 60 seconds. The data indicate that higher intensity lights & longer exposure times both result in higher temperatures. Six of 11 treatments did not even raise the bleach gel to body temperature (37° C). When these data are compared to the decomposition rate graph in the Newsletter, there is only a gradual increase in the decomposition rate of H2O2 over the range of maximum temperatures achieved. This may explain why clinically, the use of curing lights did not increase the lightening of teeth over that of using the bleach alone. After examining these data, it was decided to test the gels using a high intensity light with a long exposure time to see what the maximum temperatures possible were.
Conclusions: When the currently recommended lights, distances, & exposure times are followed, gel temperatures remain relatively low (<50° C) & are not likely to damage healthy tissue nor significantly increase the amount of H2O2 broken down in the gel.
2. Temperatures reached using high intensity lights & long exposure times, in vitro
The following table lists the maximum bleaching gel temperatures recorded using a high intensity light & a 200 second exposure time. Initial gel temperature was 28 - 30° C.
|
BLEACH
|
LIGHT
|
DISTANCE
|
TIME WHEN REACHED MAXIMUM
TEMPERATURE
|
MAX TEMP
|
|
Opalescence Xtra
|
PowerPAC
|
6 mm
|
190 sec
|
107° C
|
|
QuickWhite
|
PowerPAC
|
6 mm
|
188 sec
|
63.5° C
|
|
PowerGel
|
PowerPAC
|
6 mm
|
96 sec
|
62.5° C
|
|
Rembrandt Virtuoso Lightning
|
PowerPAC
|
6 mm
|
200 sec
|
62.5° C
|
|
Apollo Secret(new)
|
PowerPAC
|
6 mm
|
200 sec
|
55.5° C
|
|
QuasarBrite
|
PowerPAC
|
6 mm
|
200 sec
|
55.0° C
|
|
Hi Lite
|
PowerPAC
|
6 mm
|
70 sec
|
54.0° C
|
Summary of table & observations: Maximum gel temperatures ranged from 54 - 107° C. The highest temperature was produced in Opalescence Xtra. QuickWhite, Rembrandt Virtuoso Lightning, Apollo Secret, & QuasarBrite all steadily increased in temperature over the 200 second exposure (although QuickWhite may have been leveling off). Opalescence Xtra peaked after 190 seconds & then started to gradually drop in temperature (exposure time was extended to 250 seconds, due to this behavior). Hi Lite & PowerGel reached their maximum temperatures after 70 & 96 seconds, respectively. PowerGel then remained constant for the remainder of the exposure time, while Hi Lite began to gradually decrease. The behavior of the temperature roughly correlated to physical changes seen in the gels themselves. Those that peaked, then dropped in temperature had become dried out, dull, or white. The other gels, too, had slight physical changes which seems to have effected how quickly their temperatures rose. If these data are compared to the decomposition rate graph in the Newsletter, it can be seen that even when using a high intensity light with a long exposure the increase in rate is only minimal for current bleach gels. For example: the hottest gel (Opalescence Xtra) has a relatively low rate increase, even for temperatures as high as 100° C. This suggests that with current lights & bleach formulations, it may not be possible to achieve high enough temperatures to significantly effect the clinical outcome of the bleach procedure. The unanesthetized patient will probably not tolerate high temperatures on their teeth, which was tested next.
Conclusions: When using a high intensity light & long exposure times, temperatures ranged from 54 - 107° C, which may cause pain & damage healthy tissue, but still doesn’t significantly raise the decomposition rate for most gel formulations.
3. Temperatures reached & endurance times, in vivo
Three patients volunteered to be exposed to bleach gels & curing lights for as long as they could tolerate it. Tooth numbers 7, 10, 22 - 27 were treated. Patients were instructed to indicate when they wanted the light removed. In addition, the researcher, who could monitor the gel temperature throughout the procedure, could chose to remove the light. Initial gel temperatures on the teeth ranged from 25 - 30° C. The lights were set at the bleach manufacturer’s recommended distance from the tooth.
Patient A
|
BLEACH |
LIGHT
(Intensity) |
TOOTH # |
STOP TIME DUE TO SENSATION |
MAX TEMP |
MAX TIME WITHOUT SENSATION |
COMMENTS |
|
Apollo Secret |
Apollo Elite
(2300 mW/cm2) |
25 |
24 sec |
62.7° C |
soft tissue got hot |
|
|
Rembrandt Virtuoso Lightning |
Virtuoso
(1700 mW/cm2) |
26 |
35 sec |
48.3° C |
soft tissue hurt, then tooth hurt |
|
|
Opalescence Xtra |
PowerPAC
(2000 mW/cm2) |
24 |
55 sec |
74.1° C |
very hot, gingiva got warm, felt the exhale |
|
|
Apollo Secret |
Apollo Elite
(2300 mW/cm2) |
22 |
70.6° C |
60 sec |
soft tissue got hot |
|
|
QuasarBrite |
PowerPAC
(2000 mW/cm2) |
10 |
43.2° C |
120 sec |
warm tooth, felt discomfort at 80 sec |
|
|
QuasarBrite |
AccuCure Elite
(700 mW/cm2) |
27 |
36.7° C |
120 sec |
||
|
QuickWhite |
AccuCure Elite
(525 mW/cm2) |
7 |
38.2° C |
120 sec |
||
|
Opalescence Xtra |
Optilux 401
(600 mW/cm2) |
23 |
43.9° C |
120 sec |
Patient B
|
BLEACH
|
LIGHT(Intensity)
|
TOOTH#
|
STOP TIME DUE TO SENSATION
|
MAX TEMP
|
MAX TIME WITHOUT SENSATION
|
COMMENTS
|
|
Apollo Secret
|
Apollo Elite
(2300 mW/cm2) |
25
|
7 sec
|
56.6° C
|
hot tooth, dull ache
|
|
|
QuasarBrite
|
PowerPAC
(2000 mW/cm2) |
10
|
31 sec
|
? ° C
|
||
|
QuasarBrite
|
AccuCure Elite
(700 mW/cm2) |
24
|
38 sec
|
38.9° C
|
subtle ache
|
|
|
Rembrandt Virtuoso Lightning
|
Virtuoso
(1700 mW/cm2) |
23
|
38 sec
|
54.4° C
|
hot tooth, light ache, felt
warmth
|
|
|
Opalescence Xtra
|
PowerPAC
(2000 mW/cm2) |
27
|
39 sec
|
79.8° C
|
sudden sharp pain
|
|
|
Opalescence Xtra
|
Optilux 401
(600 mW/cm2) |
26
|
52.2° C
|
120 sec
|
||
|
QuickWhite
|
AccuCure Elite
(525 mW/cm2) |
7
|
bleach wicked onto gingiva,
aborting test after 48 sec
|
Patient C
|
BLEACH
|
LIGHT(Intensity)
|
TOOTH#
|
STOP TIME DUE TO SENSATION
|
MAX TEMP
|
MAX TIME WITHOUT SENSATION
|
COMMENTS
|
|
Rembrandt Virtuoso Lightning
|
Apollo Elite
(2300 mW/cm2) |
25
|
» 70° C
|
60 sec
|
inside of mouth getting
warm, tooth felt a sensation
|
|
|
Rembrandt Virtuoso Lightning
|
PowerPAC
(2000 mW/cm2) |
23
|
» 80° C
|
95 sec
|
burning papilla, had to
stop, inside of mouth warm
|
|
|
Rembrandt Virtuoso Lightning
|
Virtuoso
(1700 mW/cm2) |
24
|
62.4° C
|
120 sec
|
tooth is warm
|
|
|
Rembrandt Virtuoso Lightning
|
AccuCure Elite
(700 mW/cm2) |
26
|
35.0° C
|
120 sec
|
||
|
Rembrandt Virtuoso Lightning
|
Optilux 401
(600 mW/cm2) |
23
|
39.0° C
|
120 sec
|
Observations & Summary of Tables:
1. There was a difference among patients, as indicated by the toleration times.
2. There appeared to be some psychological factors involved.
a. Patients became accustomed to the test & stopped responding to the first "sensation" felt.
b. Some patients suppressed the first pains, waiting for a truly hurtful one.
c. As the operators watched the clock & the temperature of the tooth, they became worried for the safety of the patient & stopped the test before the patient responded.
3. Tooth number (size) appeared to make a difference, larger teeth tolerated the heat longer.
4. Heating of soft tissue became mixed up with heating of tooth itself. Both are clinical.
5. An overall pattern emerged: The higher the intensity of the light, the higher the temperature, & the shorter the toleration time.
6. The data indicate that curing light (& hence intensity) is the single greatest factor.
Toleration times for each light are listed below, including the intensity (I). Times marked with * indicate that the operator stopped the test before the patient complained.
)
|
LIGHT
|
I
|
TIME (seconds
|
|
Apollo Elite
|
2300
|
7, 15, 24, 60*, 60* |
|
PowerPac
|
2000
|
20, 31, 39, 55, 95, 120*(1/2 inch away) |
|
Virtuoso
|
1700
|
24, 35, 38, 120* |
|
AccuCure Elite(250 mW
mode)
|
700
|
38, 45*, 120*, 120*(1/2 inch away) |
|
Optilux 401
|
600
|
80*, 120*, 120*, 120* |
|
AccuCure Elite (200 mW
mode)
|
525
|
48+*, 120* |
7. Temperature data is listed below, by light, in the same order as above. Again, I is the intensity of the light, & * indicates that the operator stopped the test.
|
LIGHT
|
I
|
MAX TEMP (° C)
|
|
Apollo Elite
|
2300
|
57, 63, 71*, 70* |
|
PowerPac
|
2000
|
50, 80, 74, 80, 43*(1/2 inch away) |
|
Virtuoso
|
1700
|
48, 54, 62* |
|
AccuCure Elite (250 mW
mode)
|
700
|
39, 62*, 37*(1/2 inch away) |
|
Optilux 401
|
600
|
52*, 39*, 44* |
|
AccuCure Elite (200 mW
mode)
|
525
|
39*, 38* |
8. No single maximum toleration time or temperature is apparent for any given light. However, it does appear that the Optilux 401 & AccuCure 3000 laser (in a lower power mode) can be tolerated for long periods of time, perhaps indefinitely.
10. A clinical maximum temperature can be estimated by matching up the light(s) with each bleach that recommends them, & looking across the temperatures measured in the clinical & laboratory tests. These temperatures then represent a realistic upper limit for each bleach gel & light combination. This can then be used to determine how high the decomposition rate could go, looking at the graph in the Newsletter.
|
BLEACH
|
TEMP(° C)
|
LIGHT(S)
|
|
Apollo Secret
|
70
|
Plasma arc |
|
*HiLite
|
60
|
Halogen / plasma arc |
|
Opalescence Xtra
|
80
|
Plasma arc |
|
PowerGel
|
60
|
Plasma arc / high intensity halogen |
|
QuasarBrite
|
50
|
Plasma arc / laser |
|
QuickWhite
|
60
|
Plasma arc / laser |
|
Rembrandt Virtuoso Lightning
|
60
|
Plasma arc |
*HiLite is the only bleach among these that does not currently recommend or show a high intensity light being used with it. In lab tests using plasma arc lights, the highest temperature recorded was 57° C, which is not that much higher than the 50° C reached with standard halogen lights.
Conclusions: No single maximum temperature or toleration time is apparent for any given gel & curing light combination due to such uncontrollable factors as patient sensitivity & tooth mass. When combined, however, the clinical & laboratory data suggest an upper limit to the temperature possible & tolerable for any given bleach gel. When these upper limit temperatures are compared to the decomposition rate graph in the Newsletter, it can be seen that with current lights & bleaches it may not be possible to get enough extra breakdown of H2O2 to make a clinical difference in the bleaching outcome, over the use of the gel alone.
4. H2O2 Assay results: lighted versus non-lighted bleaching gels, in vivo
A split-arch study design was used to determine if use of resin curing lights resulted in increased tooth lightening. A rubber dam was inserted between the upper or lower centrals to prevent light from illuminating the bleach on the other side of the arch. The bleach gel was applied in an identical manner & for identical time to both sides of the arch. One side was also illuminated with the resin curing light in the specified manner, while the other side received no light treatment. Following the treatment, & later after rehydration of the teeth, shades were taken to determine the amount of lightening that occured on each side of the arch.
Throughout the treatment, which usually involved several applications, the bleach gel was assayed for percent H2O2. Three different samples of gel were assayed for each application: 1) Gel removed from the application syringe or mixing container (called the "mix" or "control"), it was not placed on the teeth nor exposed to resin curing light; 2) Gel removed from the teeth that was exposed to the resin curing light; & 3) Gel removed from the teeth that was not exposed to resin curing light.
The assumption is that the gel exposed to the light & consequent heat will experience more breakdown of the H2O2 molecules. If this is occuring to a significant degree, then the assay should show less percent H2O2 for the light treated bleaching gel.
SEE CHART FOR EACH BLEACH PRODUCT
Conclusions: In all cases, the percent H2O2 assayed was similar for the mixed gel, the gel which was treated with light, & the gel that received no light. This indicates that the light does not cause clinically significant additional breakdown of the H2O2 molecules, & helps explain why the use of resin curing lights did not result in increased tooth lightening.
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