Test Method for Temperature of Bleaching Gels, In Vitro

 

Aug 3, 2000
Clinical Science Department
Clinical Research Associates

I. Purpose of Test
II. Materials
III. Equipment Preparation
IV. Test Procedure
V. Analysis of Data

 

 

 

I. Purpose of Test

The purpose of this test is to measure the temperature of bleaching gel during in vitro simulation of the bleaching procedure.

 

II. Materials
bleach product(s) 250 ml beaker
curing light(s) 5 x 12 x 6 inch plastic basin
digital timer crushed ice
Tegam 871A digital thermometer calculator
Omega TT-K-30-50 FT thermocouple wire paper towels
Omega type K subminiature connector air / water syringe
Omega type K coiled extension cable circulating water bath
Unitek orthodontic bracket welder orange protective glasses
wire cutters cotton tipped applicators
wire strippers masking tape
razor blade or scalpel marking pen
scissors ruler
jeweler’s screw driver set extracted human lower central tooth
53/4 inch glass transfer pipet explorer
resin instrument light cured resin
banana plugs 2 x 2 gauze
1 MW resistor 16 gauge galvinized wire
soldering iron needle nose pliers
rosin core solder gloves
computer jeweler’s file
GMH Engineering Data Brick data acquisition system with host computer software & accessories perio probe
   

 

 

 

 

 

III. Equipment Preparation

A. Data Acquisition System

1. Connection Cable

a. Select a 5 wire sensor cable for channel 1 of the Data Brick.

b. Strip the cable for 2 inches & cut back the wire braid & metal foil shield.

c. Strip the green, white, & black wires for 1/4 inch.

d. Solder a 1 MW resistor between the white & black wires.

e. Connect banana plugs to the green & white wires.

f. Fold back the unused wires & tape them to the cable, out of the way.

2. Software Setup

a. The computer should be capable of operating in DOS & have an available COM port.

b. Create a directory called thebrick on the hard drive.

c. Within DOS, go to the thebrick directory, insert the floppy disk containing the Data Brick software, & type "a:\install" to install the program.

d. Within DOS, switch to the thebrick directory, & type "brick" to launch program.

e. Under Setup, set the following parameters to the indicated values:

Display: Color

Printer Type: (whatever you have connected)

Resolution: 90 ´ 90

Print Text As: Graphics

Brick Port: Com 1

Brick Baud: 57600

Printer Port: LPT1

Port Access: Direct

Backups: Keep

f. Under Brick, select Test Setup.

g. Create a new test file by typing in the file name "bleach_t", then selecting OK, then select Create New.

h. On the screen labeled Test Setup For: BLEACH_T.TST, type in the serial number of the Data Brick, & its name. Then select Edit to go to the Brick Setup screen.

i. Make sure that the Chn 1 Stat is selected to On.

j. Select the "1" under Chn to edit the channel 1 parameters to the following values:

Select Sensor: Default Analog Sensor

Serial Number: (blank)

Calibration Constant: (may be any number, depending on calibration)

Sensor Output Offset: 0 degrees C/volt

Sensor Output + & - Full Scale: 0 degrees C

Name: gel temp

Units: degrees C

Sample Rate: S1

Gain: 10

Channel Offset: Auto

Rest Offset: 0 Volts

Rest Value: 0 degrees C

Channel Range + Full Scale: (some value depending on calibration)

Channel Range - Full Scale: (some value depending on calibration)

Minimum Resolution: (some value depending on calibration)

k. Select OK to return to the Brick Setup screen.

l. Set the following parameters to the indicated values:

Data Acquisition Mode: Low Speed

Trigger Mode: Single Event

Trigger Type: Open=Triggered

Primary Sample Rate (P): 100 Samples/Second

Secondary 1 Sample Rate (S1): 10 Samples/Second

Secondary 2 Sample Rate (S2): 2 Samples/Second

Low Pass (Anti-Aliasing) Filter Corner Frequency: 1 Hz

Transducer Excitation: Off

Chn: 1 On, Rate: S1, Name: gel temp, Units: degrees C

(channels 2 - 8 are Off; counters A1 - B2 are Off)

Fill Memory: not selected

Maximum Trigger Events: ( 1- 1): 0

Data Set Size: 1 Samples

Memory Usage: 0.7%

Test Duration: 1800 Data Sets, 180 Seconds

Pre-Trigger: 0 Data Sets, 0 Seconds

m. Select Done to exit the Brick Setup screen & automatically save the setup.

n. On subsequent uses of this test method, it is necessary only to choose the "bleach_t.tst" test file to recall all these parameters.

B. Tooth

1. Support Wire

a. Using pliers, bend a piece of galvanized wire into a wide, flat "U" shape which snugly fits into the water bath.

b. Bend each side over so that they will support the wire on the sides of the bath, with the wire extending across the bath about 12 mm below the water level.

c. Shape the extended ends into a "T" shape that will lay flat on the sides of the bath & prevent the wire from rotating.

Figure 1: Shaped support wire

2. Test Tooth

a. Position the tooth over the middle of the wire with about one quarter of its root below the wire. The facial surface should be vertical.

b. Mold light cured resin around the root & wire, then cure to secure tooth in place.

3. Thermocouple Guide

b. Position a pipet so that the tip is pointed at the center of the facial surface of the tooth, about 5 mm away.

c. Mold strands of light cured resin around the pipet & support wire. Cure resin to secure pipet in place.

Figure 2: Tooth & guide pipet mounted on support wire (also showing placement of thermocouple)

C. Thermometer

1. Thermocouple

a. Cut a 24 inch length of thermocouple wire.

b. Separate one end for 1/2 inch & cut away the clear outer sheath with scissors.

c. Strip the separated ends for 1/4 inch.

d. Open the subminiature connector with a jeweler’s screwdriver.

e. Connect the stripped ends under the screw terminals: yellow wire to +, brown wire to -.

f. Close the connector, making sure the wires are not pinched & no bare wires are exposed.

g. Strip, but do not separate the other end for 1/16 inch. Use a razor blade to carefully remove the clear outer sheathing & the yellow & brown insulation without damaging the wires.

h. Position the two exposed wires between the electrodes of the spot welder.

i. Activate the spot welder to join the wires. Repeated attempts may be necessary. The goal is to get as small a joint as possible.

Figure 3: Close up view of welded thermocouple.

j. File down the tip as necessary to remove any sharp edges.

Figure 4: Finished thermocouple.

 

3. Calibration

a. Connect thermal probe.

i. Connect the thermocouple to the thermometer TC1 jack.

ii. Set thermometer to ° C & TC1.

iii. Turn on thermometer.

b. Prepare ice water bath.

i. Place beaker into plastic basin.

ii. Fill beaker & basin with crushed ice.

iii. Fill beaker with cold water, partially fill basin with water.

iv. Allow system to come to equilibrium at 0° C, approximately 10 minutes.

v. Insert thermocouple into beaker. Thermometer should read 00.0° C.

Figure 5: Ice bath at 0.0° C.

c. Connect Data Brick.

i. Connect sensor cable to output jacks of thermometer: white wire to +mV output, green wire to -mV output.

ii. Plug in Data Brick.

iii. Plug I/O serial cable of Data Brick into COM1 port on computer.

iv. Launch the Brick software.

v. Under Brick select Test Setup.

vi. Select bleach_t.tst test file & press OK.

vii. Select Edit.

viii. Select Chn 1.

ix. Set Calibration Constant to: 1 degrees C/volt, & press OK.

x. Select Done, Done.

xi. Select Brick, Brick.

xii. Select Calibrate, Clear Auto Offset, wait for it to clear, then select Done.

xiii. Select Acquire Data, Now, wait for it to clear memory, then press OK.

d. Make temperature measurements.

i. Press trigger to begin data collection (green light should extinguish).

ii. Wait approximately 30 seconds with probe in water bath at 0.0° C.

iii. Remove thermocouple to another temperature (example: ~ 36° C under tongue), & wait 30 seconds after it has stabilized, & record temperature.

iv. Remove probe to a third temperature (example: room temperature at ~20° C or warm water bath at ~ 60° C), & wait 30 seconds after it has stabilized, & record temperature.

v. Put thermocouple back into 0.0° C water bath for remainder of time.

vi. When yellow light on Data Brick turns on, the data acquisition is complete.

vii. Select Upload Data, & type in a filename & press OK. Then enter any comments (such as the sequence of temperatures) & select OK.

viii. Select Post Process Data & select the filename just created, then press OK.

ix. Select Done.

x. Select Brick, ASCII Export.

xi. Select the filename of the calibration file, select Speadsheet import (*.CSV), & press Export. This will create an ASCII file of the data with the CSV extension.

xii. Exit the Brick software.

e. Calculate calibration constant.

i. Start MicroSoft Excel.

ii. Import the calibration file (with .csv extension).

iii. Calculate the average value for each of the stable temperature regions. It may help to graph the data to visualize the stable temperature regions.

Example: initial 0.0° C ice water = 0.00147 volts

body temp of 36.0° C = 0.03629 volts

warm bath at 57.3° C = 0.05758 volts

final 0.0° C ice water = 0.00033 volts

iv. Calculate the calibration constant for the elevated temperatures by dividing the temperature by the voltage.

Example: 36.0° C / 0.03629 volts = 992.0088

57.3° C / 0.05758 volts = 995.1372

v. Verify that the calibration constants are similar, then average them.

Example: 993.573

vi. Return to the Brick software & enter this calibration constant into the Channel 1 Setup.

f. Verify calibration.

i. Repeat the calibration test with the new calibration constant (sections 3.C.xi. - 3.D.ix).

ii. Select Plot, select the filename, & press OK, OK.

iii. Select Config, Cursor, Ok, to turn on the green cursor line.

iv. Click & drag the cursor over the graph. Verify that the stable temperature regions at the various temperatures match the temperature readout recorded from the thermometer itself.

D. Curing Light

1. Review the bleach instructions to find the recommended distance that the light is to be held from the tooth (1/4 inch or 6 mm is typical).

2. Using the ruler, make a mark on the handle of a cotton tipped applicator at the specified distance from the end.

3. Cut the handle about 3/8 inch beyond the mark.

4. Tape the cut piece to the light guide with the mark flush to the end, it then becomes a spacer which will maintain the light at the correct distance from the tooth.

Figure 6: Light guide with spacer in place.

E. Record Form

1. Prepare a record form with spaces for the following information to be recorded:

date

bleach product

curing light

distance between light & tooth

bleach thickness

recommended light irradiation time, with number of passes & applications

maximum temperature reached

comments on bleach appearance (color, surface, porosity or bubbles, etc.)

intensity of curing light(s)

filename where temperature information is stored

F. Water bath

1. Place support wire with tooth & pipet across the sides of the water bath so that the tooth is suspended in the bath.

2. Tape down the sides of the support wire, stabilizing the fixture in the bath.

3. Fill water bath with distilled or deionized water until it reaches 1 mm below the DEJ of the tooth.

4. Plug in bath & turn it on.

5. Set temperature of bath to 37° C.

6. Insert thermocouple into back of pipet & push it through until the bead is positioned on the center of the facial surface of the tooth.

7. Place the following items in the area of the water bath:

2 x 2 gauze

Kimwipes

paper towels

air/water syringe

bleach product(s)

curing light(s)

gloves

thermometer

Data brick data acquisition system with computer & thermometer

timer

perio probe

G. Bleach

1. Mix each bleach according to the manufacturer’s directions just prior to beginning test.

2. If a bleach specifies mixing immediately before application to teeth, then do not mix it until ready to apply.

 

IV. Test Procedure

A. Prepare for Treatment

1. Turn on thermometer, Data Brick, & computer.

2. Launch Brick software & load the bleach_t.tst test file.

3. Prepare the data acquisition system by selecting Acquire Data Now, OK, so it is only waiting for the trigger signal.

B. Perform Bleach Procedure

1. Apply a small amount of bleach to the facial surface of the tooth. Use perio probe to check that it matches the manufacturer’s specified thickness.

2. Verify that the thermocouple is seated within the bleach & touching the tooth surface.

3. Press the trigger of the Data Brick to begin data acquisition. Wait a few seconds to get the baseline temperature recorded prior to activating light.

4. Position curing light directly over bleach, held off at the correct distance by the spacer.

5. Activate curing light.

6. Keep track of elapsed time with digital timer or using audible signals from the light.

7. During treatment, record observations about bleach & the time & temperature at which they occured. It is helpful to have a second person to act as scribe.

8. Shut off curing light when time has elepsed. (Note: Time may be the manufacturer’s recommended time, or some other time determined by the researcher.)

9. Let the system sit at least 20 more seconds to record the cool down period.

10. Rinse tooth clean with air / water spray. Use 2 ´ 2 gauze or Kimwipes to help remove bleach, if necessary.

C. Record Data

1. Record any other observations about the bleach.

2. Make sure all the fields on the record sheet are properly filled in, especially the maximum temperature & time.

3. Wait for yellow light to turn on, indicating end of data acquisition.

4. Select Upload Data.

5. Type in a filename for this test & light / bleach treatment. Press OK.

6. Enter comments- usually the light & bleach used, press OK.

7. Select Post Process Data. Select the filename & press OK.

 

V. Analysis of Data

A. Determine Maximum Temperature

1. Plot each file in the Brick software.

2. Use the cursor to find the maximum temperature. The peak is usually a well defined point just prior to a precipitous drop in temperature when the light was turned off.

3. Record the maximum temperature.

4. Check the duration of the exposure. Where the temperature first rises sharply is when the light was activated. Where the temperature drops precipitously is when it was deactivated.

5. Export the Data Brick files to .csv format for reading in a spreadsheet program.

B. Expression of Results

1. Make a table showing each unique treatment tested (bleach / light combination).

2. Next to each treatment, show the exposure times & maximum temperatures for each test.

3. Order the data by each variable to look for patterns in the data.

4. Perform a statistical analysis to determine which treatments are statistically different, & which variables are significant.

 

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