5. Shear Bond Testing Protocol for Buildup Resins

 
(This is the Notched Shear Bond Test Method developed by Ultradent Products Inc.)
I. Preparation   
    Human Molars stored in refridgerated non-fluoridated tap water that are less than 6 months old have been used in this test.  They have had no contact with disinfecting chemicals.
     A. Prepare Teeth
   

1.

 Record number of the tooth to be used in bonding which identifies date of extraction, patient age and gender, and other information regarding the tooth.
2. Grind proximal surfaces of the molar about 1mm deep using a 320 grit wet sandpaper (3M Silicon Carbide 051144-02015) mounted on a model trimmer (Handler Model #31).  See Figure 1.
     

Figure 1.

 
    3. Section the tooth in half using a Slow Speed Diamond Saw (Beuhler Isomet cat#11-1180-170 with diamond cut-off wheel Norton 1A1R 4 x .012 x 1/2 ME104180).  See Figure 2.
     

Figure 2.

 
     B. Embed Teeth
    1. Place mylar tape (Manco High Performance) on the bottom of embedding mold (Ultradent Delron Mold, 15 samples at a time).
    2. Dry ground surface of the tooth and place it face down on the mylar tape.  Repeat until embedding mold is full. (This must be done quickly to avoid dehydration of the tooth.)  See Figure 3.
     

Figure 3.

 
    3. Mix monomer and polymer components of methyl methacrylate in a 1 to 3 ratio and place into embedding mold over the teeth.  See Figure 4.
     

Figure 4.

 
    4.

Wait for approximated 5 minutes until resin starts to exotherm and place in a cold water bath.
    5. After 5 more minutes remove tape from mold and let mold sit in water for another 15 minutes.
    6. Remove the individual embedded teeth out of the mold.  A light tap from a hammer may be necessary to break embedded teeth out the mold.
     C. Grind Teeth
    1. Using the rotating jig (Ultradent) with its stage mounted on a model trimmer grind the bottom end of the embedded sample on wet 24 grit wet Carbodent wheel (Handler MFG 122121-6 10 x 1/4x 1).  See Figure 5.
     

Figure 5.

 
    2.

Repeat step 1 above with the top end or tooth end of the embedded sample.
    3. Grind the tooth end of the sample again using 320 grit wet sandpaper while rotating the wheel.  This should be done the day of bonding and teeth should be stored in room temperature water until bonded to.
II. Construction
    1.

Rinse tooth to remove any foreign material.
    2. Make positive there is adequite dentin bonding site.
    3. Etch or prime with recommended etchant or primer for the recommended etch time (15 seconds with most adhesives with 32-37% phosphoric acid).  See Figure 6.
     

Figure 6.

 
    4.

Rinse tooth for 5 seconds with air water syringe.
    5. Apply and thin adhesive per manufacturer’s instructions. See Figure 7.
     

Figure 7.

 
    6.   Place the tooth in bonding jig (Ultradent) and turn the screws down such that 1/2 of the leaf spring is compressed and there is no arching of the plastic insert as it sits on the tooth. (Make sure that sample will be bonded only to sound dentin.)  See Figure 8.
     

Figure 8.

 
    7. Cure the adhesive for the manufacturer’s recommended time using Optilux 500 (Demeteron Kerr 11mm tip).  See figure 9.
     

Figure 9.

 
    8.

Place mixed buildup resin in centrix syringe and inject into mold.
    9. Cure per manufacturers' instructions.
     

Figure 10.

 
    10.

Place in incubator (37°C) for 10 minutes & remove.
    11. Place the large end of condensor (1.6mm on the composite stub, loosed the nuts on the bonding jig and gently remove the sample from the jig.  This requires little force, if it requires a lot of force to remove, a new plastic insert is needed for bonding jig. 
See Figure 11.
     

Figure 11.

 
    12.

Clean excess uncured adhesive off with a Kim Wipe being careful not to bump the stub.
    13. Using a razor blade and stereo microscope to remove samll ring of flash around the stub.
III. Debonding
    1.

Remove debris from sample with an air water syringe.
    2. Mount sample in holder such that the force breaks sample in the apical to occlusal direction.
    3. Using force transducer (MTS 810)  measure the force to debond the sample at 1mm/min rate.  Make sure the notched blade is placed directly over the resin stub flush against the tooth.  See Figure 12.
      Figure 12.

 
    4. Record force value and label sample number on analog recorder.
IV.  Data Analysis
    1.

Inspect sample for failure mode under 50x stereo microscope.  If mixed mode failure, assign percentage of sample to each type of mode.
    2. Calculate shear bond strength by dividing the force by the area of the bonding interface.
    3. Perform statistical analysis to differentiate products using General Linear Model (GLM) and Tukey’s multiple comparison.
       

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