Principle & ProTec CEMNew Cements - Principle & ProTec CEM
Charateristics of New Cements - Feb. 1999
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Linear Expansion of Principle & ProTec CEM vs. Other Cements

Linear Expansion

Results:

This graph shows the percent linear expansion of Principle and ProTec CEM cements.  After 4 months, Principle has expanded about twice as much as ProTec CEM.   Both cements expand less than previously tested RRGI cements (Advance, Fuji Plus, Vitremer), but still more than resin, glass ionomer, and zinc phosphate (Panavia, Fuji I, and Flecks).  This amount of expansion, however, is not producing breakage of all-ceramic crowns.

Note:  Explanation of Linear vs. Volume Expansion

An isotropic, homogeneous material will expand equally in each dimension if it is unconstrained.  It is upon this basis that %Volume expansion and %Linear expansion are related.  Linear measurements are currently reported by cement manufacturer's and the research community.  The following equation shows how the two are related:
%vol = 3lin% - 0.03(lin%)2 + 0.00001(lin%)3 
A good approximation of volumetric expansion is three times the linear expansion.

Test Methods & Materials - Principle & ProTec CEM
New Cements - Feb. 1999

I. Test Question

What is the comparative expansion of Principle and ProTec CEM versus the control Vitremer Luting (3M) at various time intervals?

Time intervals include 1 hour, 24 hours, 3 days, 1 week, 1 month, 2 months, and if need continue monthly measurements until expansion stops.

II. Test Products
Brand Name Manufacturer Material Type
Principle Dentsply / Caulk Compomer
ProTec CEM Vivadent Hybrid Resin (RRGI cement)

Equipment Needed

Plastic plates (5x5x0.3 cm)
Parafilm (5x5 cm)
10-15 Teflon molds (outer dia: 25 mm, inner dia: 20 mm, thickness: 1 mm)
37°C incubator
37°C waterbath with shelf
0.85% NaCl solution
DI water (for waterbath)
C-clamps
Calipers
20 ml vials
Kimwipes
Dental tweezers
Straight edge
Scalpel
Sandpaper (600 grit)
Thermometer

III. Test Method

Prepare 10 chips for each material as follows:

  1. Pile 2 5x5 cm plastic plates on counter and cover with a 5x5 cm piece of Parafilm and center a 20x1 mm Teflon mold on the Parafilm.
  2. Place material to be tested in the mold. (Mix material following manufacturer instructions if the material needs to be mixed. See Appendix 3.)
  3. Carefully cover the material with another piece of Parafilm and 2 plastic plates.
  4. Gently apply pressure to the plastic plates to extrude excess material and air bubbles.
  5. For self cure material: Place the c-clamps on the sample and squeeze until excess material squeezes out of mold and store at 37°C for the allotted time for set.

    6. Note: To find set time: Test the hardness of the material at 5 minutes set increments using the Barkell Hardness Tester (BHN). Samples cannot be reused for testing after removal from the incubator. Samples are considered cured when the cements has a hardness of approximately 90 BHN.

  6. For light cure material: Place the c-clamps on the plates and squeeze until material squeezes out of the mold and light cure both sides 60 seconds using a curing light that is measured greater than 300 mW/cm2. Place sample in incubator for 15 minutes.
  7. Remove the sample from the 37° C storage and quickly remove clamp and outer plastic plates. Place remaining mold and sample immediately in a waterbath at 37°C.
  8. Do steps 11-15 (except 14) completely immersed in water.
  9. Remove the top plastic plate.
  10. Draw two cross lines (at 90°) through the center of the chip using a straight edge and scalpel.
  11. Remove the rest of the mold.
  12. Quickly sand the edge of the sample with 600 grit sandpaper at the marked lines to assure a consistent measuring surface and return the sample to the 37°C waterbath.
  13. Measure the diameters of the chip at each line twice with calipers to 0.01 mm as the initial measurements. Each line will be measured twice and averaged for the overall diameter (4 total measurements).
  14. Record each measurement accordingly.
  15. Submerge the chip in a vial previous filled with 0.85% NaCl solution and stored at 37°C. Cap bottle and place in 37°C incubator.
  16. After 1 hour, remove chip from the vial and place in shallow 37°C water and measure diameter twice at each line on the chip. Record each measurement (4 total measurements).
  17. Return chip to the same vial containing 0.85% NaCl and store in 37°C incubator to be measure as above at 24 hours, 3 days, 1 week, and 1 month.

IV. Reporting the Results

Use the following formula to calculate the linear expansion of the material:

% expansion = (Avg. of 4 measurements[after storage]/Avg. of 4 measurements[initial] - 1) * 100

Report the average of 10 samples for expansion at each interval.

Appendix

Procedures for each material was taken from manufacturer's directions.

Principle - Set time for test = >25 minutes

1. Fluff the powder, overfill the scoop & level powder with the collar at the top of the bottle.
2. Measure out 2 level spoonfuls and 2 drops of liquid. (4x to fill mold)
3. Mix powder into liquid rapidly for 30 seconds.

Taken from adhesive kit info:
Working time = 4 minutes

ProTec CEM - Set time for test = 25 minutes

1. Fluff the powder, overfill the scoop & level powder with the collar at the top of the bottle.
2. Measure out 1 level spoonfuls and 3 drops of liquid. (4x to fill mold)
3. Mix rapidly for 30 sec. (Mix initially only 1/2 of the powder with liquid. Then add the remainder and mix.)

Taken from adhesive kit info:
Working time = 3.0+/- 0.5 minutes

Vitremer Luting (Control) - Set time for test = 20 minutes

1. Fluff the powder, overfill the scoop & level powder with the collar at the top of the bottle.
2. Measure out 3 level spoonfuls and 3 drops of liquid. (3x to fill mold)
3. Mix rapidly for 30 seconds.

Taken from adhesive kit info:
Working time = 2.5 minutes

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