Cementation of a gold post and core of tooth #7

Today I observed a cementation of a gold post and core of tooth #7, a shoulder preparation, fabrication of a temporary pre-fabricated crown, final impression technique of the prepped tooth, and then observed the temporary cementation of the #7 pre-fab crown.  

Patient presented with a past root canal treatment done on #7, but had recently fallen, hitting her front teeth, especially # 7 and #8.  She was seen by an Oral Surgeon to make sure that there was no bone or facial fracture and was given a splint to keep her anterior teeth intact. 

I learned that there are different treatment options for this patient.  She could have extracted #7 and placed an implant, or extracted #7 and make a 3 unit bridge from #6 to #8, or do ortho to recline #7 and then prep it to make a PFM crown or an all ceramic crown.  Since the patient fell and could have fractured her root or crown of #7, ortho tx to move tooth would cause more fractures, so the prognosis would be poor; therefore, ortho treatment before crown prep would not be a treatment option.  

The observation first began by opening up the access of #7 by removing the temp filling with a bur. Then the gold post and core of #7 was inserted. The post was refined with a bur, then it was checked with occlude spray to observe for pressure/tight areas. Once the post and core fit adequately, then it was permanently cemented which took 12 minutes to cement.  Then a shoulder prep was done with a bur, made the margins clear and checked to see if the prep was tapered and not labially reduced, in another words made the prep slightly more lingual on the facial side.  Then I observed the selection process of a pre-fab #7 crown.  Once the pre-fab crown was chosen, the margins were reduced to make it fit the prepped tooth.  A mixture of monomer and acrylic was made and poured into the pre-fab crown, and then the crown was placed into the prepared tooth to get the internal fit of the pre-fab crown.  Then, the excess was removed around the margins.   

After that, I observed the final impression of #7 prepped tooth.   Since the patient has existing porcelain veneers on her anterior teeth, it’s a good technique to put Vaseline on the veneers and to block out the embrasures with wax, so that when the impression is taken and then removed, there is no chance of her other porcelain veneers coming out.  I learned how to analyze an impression to see if the margins came out or not.  I observed the selection of the final shade of the porcelain crown which was B1. A Polaroid film was taken, so that the lab could match the correct shade. Then, the pre-fab temp crown was refined with a mixture of monomer and acrylic and the excess was removed with a bur.  Finally, once the fit was adequate, then the pre-fab temp crown was cemented with temporary cement.  I also observed the bite registration technique; the registration of the anterior incisors where taken so that the lab has the patient’s occlusion which helps with the fabrication of the porcelain crown.  Then the lower anterior incisal impression was taken with alginate, so that the lab could pour up a lower anterior cast as a guide to make the porcelain crown and check the occlusion. 

In conclusion, today’s observation was a great learning experience.  I learned that we should never put Vaseline on the prepped tooth to get the internal fit of the pre-fab crown because it could contaminate the cements.  Also, I learned that it’s more efficient to fabricate the temp crown before taking the final impression of the prepped tooth. 

G.Y., New York University College of Dentistry, Observation 1

Categorised in: Dental Student Experiences

This post was written by Interns