If a developing permanent tooth is too badly damaged or inflamed for any of the pulp tissues inside it to remain alive and uninfected, the dentist can attempt procedures to build a calcium plug at the end of the existing root, in order to fully enclose and seal it against future bacterial invasion. This procedure for doing this is known as apexification. If the procedure is not successful, the incompletely developed root will have a wide open “blunderbuss apex”. In such cases, placement of a rubbery gutta percha root canal filling will be difficult or impossible to achieve.
Apexification involves locally anesthetizing the tooth so that it can be operated on comfortably. A rubber dam is used to isolate the tooth from mouth moisture and oral bacteria. Using sterile instrumentation, the pulpal tissues are completely removed from the crown and root canal to the existing apex of the incompletely formed tooth. This complete removal of the pulpal tissues is known as pulpectomy.
Care is taken not to file on the already thin walls of the developing tooth. A plug of medical grade calcium hydroxide is generally placed in the tooth near the apex to stimulate closure of the open root tip by living cells occupying an expanse of tissue around the developing root tip known as Hertwig’s epithelial root sheath. Calcium hydroxide is used because of its anti-microbial effects and its ability to induce calcium deposition at the root tip. Current studies are underway to investigate the use of Mineral Trioxide Aggregate (MTA), a medical grade Portland cement, as an alternative to calcium hydroxide for apexification procedures.
Once the medicated plug is placed near the developing root apex, a temporary filling is placed in the crown of the tooth to prevent bacteria from getting inside the tooth during root completion. The filling can be made to look remarkably esthetic.
When the apexification process is complete (several months later), the temporary filling is removed and conventional endodontic (root canal) treatment is performed to seal the tooth against future bacterial invasion. Depending on how much damage was done to the tooth’s crown, a permanent filling, onlay or crown will typically be placed as the final restoration.
It is important to realize that teeth which require apexification will have very thin dentin walls at their apex, which is structurally weaker than a fully developed root. This is because the cells that make and deposit dentin die when the rest of the pulp tissues die. The resulting thin walls make the tooth more vulnerable to future fractures.
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