By Michael Miller, DDS
After prepping a lower molar tooth for a crown, the tooth required endo. However, the lab had already fabricated the PBM. The endodontist sent the case back with a temp filling in it. I will use Core Paste as my permanent fill, but how do I technically get the new crown and the permanent filling to fit each other?
Step 1: Remove the provisional restoration and make sure the crown fits. Do any occlusal and/or contact adjustments at this time.
Step 2: If the endo access is merely through the occlusal of your crown prep, you can just restore the access prep and leave the build-up slightly undercontoured. Otherwise, lubricate the inside of the crown plus the cervical third of the external surface with Vaseline or, even better, MQ Lubricant (an old but very effective silicone-type product available through most dental dealers). Wipe out excess with cotton pellet or small section of a 2x2 so only a very thin layer remains. Use a strong air blast if necessary to further thin the lubricant.
Step 3: Fill access prep with build-up material. Try not to overfill. Slight underfill is better.
Step 4: Seat lubricated crown and have patient bite into full occlusion. Make sure crown is seated completely. Have the patient open slightly, insert cotton roll on occlusal surface of crown, and then have the patient resume applying pressure. Set a timer for the set time of the material, usually 5 to 10 minutes.
Step 5: Remove the crown with finger pressure. If the crown won’t budge, wipe off any lubricant from the external surface, soften a Richwil crown remover, and place it over the crown using cotton pliers as a placement instrument. Use your fingers to adapt the still softened Richwil over the facial, occlusal, and lingual surfaces of the crown, and then cool it with an air-water spray to get it hard.
Step 6: Grab the Richwil with a curved hemostat and move the crown slightly back and forth in a buccolingual direction. If you properly lubricated the crown, it should come off.
Step 7: Trim any excess build-up material with a diamond or disc.
Step 8: Clean the prep and crown.
Step 9: Cement crown.
What is your current cement of choice for cementing metal posts and also for fiber posts? I am somewhat concerned when using a dual-cure cement that it may not fully set in the depth of the canal because it’s hard to get light to it. I also hear some of these dual-cure cements don’t particularly have a strong chemical cure component.
Duolink from Bisco scores high marks due to its strong self-cure mechanism, automix option, and low cost. It’s also easy to use, has no tricky steps, and works with a variety of adhesives.
Do you recommend hydrogen peroxide before cementation of veneers to prevent the black discoloration? I recently used it and everything looked fine when I cemented them. The patient left the office that day and everything looked great. The next day, she called and said there was a white spot on one of her veneers. Do you think it could be caused by the hydrogen peroxide? Also, what are your feelings about the white residue that can form inside the veneer after etching the porcelain with HF acid? Should that be removed before cementation? If so, how? Does the veneer need to be re-etched again if the white residue is removed? Do you think this could have caused my white spot? However, the spot didn’t appear until the next day.
There is no reason to use peroxide to prevent any discoloration, assuming your preparation is cleaned properly and there is no contamination during bonding. For the proper methods to clean preparations, see our publication, The Techniques, Vol. 1, p.15. For the proper materials, see the 2006 Annual Edition, Vol. 20, pgs. 89-94.
It is, however, highly unlikely that conventional hydrogen peroxide could have caused the white spot on the veneer, assuming you thoroughly rinsed the preparation after applying the peroxide. It is difficult to speculate on the cause of the post-cementation white spot. Even if you are 100 percent sure it wasn’t there before you bonded the veneer, there are some instances where a white spot or other unwanted characterization in the veneer does not become apparent until the veneer is bonded.
Regardless of the reason for the spot, if it is obvious and bothers the patient, you may have to remake it (not a good option) or prepare a small area in the veneer to remove the white spot and take an impression. The lab can then make a small “porcelain piece” from the same ceramic used for the veneer. You would then bond this “piece” to fill the defect. In most cases, this will be invisible and the patient will accept this minor remediation.
Concerning the white residue inside the veneer after etching with HF, it appears to be some type of precipitate. We suggest scrubbing the inside of the veneer with soap and water using a toothbrush - this should remove most of the precipitate - then bond as usual. Do not re-etch. It is highly unlikely this precipitate could have caused the white spot, but anything is possible.
When you light cure DC bonding agents, will the self-cure mode be blocked?
It depends on the product. Our tests show Matrixx Cabrio CQ with catalyst has higher bond strengths in the dual-cure or self-cure mode when it is not light cured before placing the dual-cure or self-cure composite. On the other hand, Prime & Bond NT Dual Cure has higher bond strengths when it is light cured before placing the restorative material. For the full report, see Dental Adhesives in the 2006 Annual Edition.
I have been using Excite with Variolink II to cement posterior indirect onlays and inlays made from Empress. I love the conservative nature of this procedure versus doing a full crown. However, many patients experience post-op sensitivity following delivery of the final onlay. There is usually no sensitivity during the temp phase. I use rubber dam isolation, take care not to overdesiccate the dentin, etch enamel 15s and dentin 10s. Then I brush on-off Excite, evaporate solvent, light cure, place silane primer on restoration followed by Excite on restoration, place Variolink in cavity prep, seat, and cure.
I use Clearfil Protect Bond for my direct restorations with minimal to no post-op sensitivity. I know that its thickness is too thick to use for indirects. I feel that my technique when using Excite is right on the money and that it may be the semipermeable membrane effect that I am experiencing. Can you make any recommendations for a different bonding agent, preferably one that has a low film thickness and would not have a semipermeable membrane effect?
Excite is not one of our recommended adhesives. To overcome the semipermeable membrane effect, you need to use a multi-component adhesive such as OptiBond FL, Scotchbond Multi-Purpose Plus, or All-Bond 2. With these three adhesives, you do not cure the bonding resin until after seating the restoration, so film thickness is not an issue. Please check out the new simplified techniques in the 2006 Annual Edition.
Dr. Michael Miller is the publisher of REALITY and REALITY Now, the information source for esthetic dentistry. He is an international lecturer and a fellow of the American Academy of Cosmetic Dentistry, as well as a founding member. He maintains a private practice in Houston. For more information on REALITY and to receive a complimentary issue of his monthly update, REALITY Now, call (800) 544-4999 or visit www.realityesthetics.com.
