Once the post and core has been inserted in the root canal, what is left over the gum is the head of the post. A tooth stump is built around the post to assist restoration with a crown. A tooth stump is made of different materials – amalgam (the hardest tooth stumps), photopolymer, glass ionomer cement. The material is applied using special tools, layer by layer, or in one dose, and various types of ring-like molds can be used (transparent or opaque), depending on the kind (photopolymerizable or self-hardening). Once the tooth stump is made, it is molded in the required form and it is proceeded to fabrication of the crown. This is the cheapest, easiest and fastest way to construct a tooth stump, but there is one significant drawback.
This type of construction has a weak spot, which is the relationship between the metal post and the material used for the part of the tooth stump above the gum.
This disadvantage is avoided by making a post and a tooth stump as one whole. The root post and the tooth stump are molded together in the dental lab – so-called pinlay.
The method of making pinlay is as follows. First, a canal is drilled for a post at the root of the tooth. Then, an appropriate impression, with a plastic prototype of the post, is taken. The impression is sent to the dental laboratory, where a dental technician molds a gypsum model. Using the molded gypsum model, the dental technician makes a wax post and a tooth stump and then casts them out of metal. Then, the cast structure, which is called pinlay, is send back to the dental practice, where it is glued in the root canal of the tooth using a special cement.
Using the finished pinlay, an impression for a crown is taken. In rare cases fine grinding is necessary to correct any imperfections.
An advantage of this method is the better retention and maximal recovery of the function of the tooth. An accurate and precise way of working of the dentist and the dental technician are required.
The disadvantage is the higher price of the pinlay and a longer time for construction (it takes two visits to the dentist).
The construction of the tooth stump is followed by construction of a crown.