Role of Bioceramics
Even though this article focuses more on the restoration of endodontically treated teeth and not endodontic techniques, it is important to discuss the use of bioceramics in endodontics. Bioceramics have been around since the late 1960s, initially used in medicine for their ability to form hydroxyapatite. The introduction of bioceramics in endodontics came in 1990 with Torabinejad’s creation of mineral trioxide aggregate. The second generation of bioceramics is being used for root-end surgery, perforation repair, pulp capping, revascularization, and, more recently, as a root canal sealer and obturation material.
The goal of bioceramics is to take advantage of their bioactivity to elicit a biological response at the material–tissue interface, resulting in the development of a “biological bond” or a “monobloc” interface between sealer, obturation material, and the dentinal walls. The sealer material is bioactive during the hydration process (the moisture naturally in the root canal and dentinal tubules initiates and completes the setting reaction) and biostable upon setting. This, along with its hydrophilic nature and resistance to wash out, makes a bioceramic sealer the ideal filling material for root canals.
To Post or Not to Post?
After obturation, the next issue is when and how to restore the endodontically treated tooth to maximize both quality and efficiency for the patient. The most common practice by endodontists is to place a cotton pellet in the root canal chamber and a temporary restoration in the access cavity. However, whether or not the endodontic treatment is performed by a specialist or the restorative dentist, the authors recommend completion of immediate post space preparation for either immediate or delayed post and core placement or completion of just the foundational core build-up at the time of obturation.
Following endodontic treatment, the decision for post placement is based on the authors’ risk assessment criteria: location of the tooth, occlusal loads and habits, remaining tooth structure, age and gender of the patient, and whether the tooth is intended to support a single crown or is to be used as an abutment for a fixed or removable partial denture.
The first critical factor for the restoring clinician is determining the number of walls of tooth structure that remain to retain the foundation for the permanent restoration. It is also important to determine how many walls of tooth structure will remain after preparation for the final crown. When coronal tooth structure loss is minimal and the marginal ridges are intact, a bonded composite resin is suitable to seal the access cavity without further intervention. This is most likely the restoration for an anterior tooth, as the two main factors that differentiate anterior and posterior teeth are their dimensions and direction of forces.
As mentioned above, in addition to the quantity and quality of remaining tooth structure, directional forces based on tooth location and occlusal scheme as well as parafunctional habits should be taken into account while treatment planning. Lateral, horizontal, or oblique forces generated at various angles less than 90° are more destructive and can lead to greater failures when compared to vertical loads.23 With respect to the access cavity for molars, occlusion-related factors play a pivotal role in deciding the type of definitive restoration. It must be determined if a composite resin restoration will be sufficient to withstand the patient’s masticatory forces or whether the composite resin restoration should be used as the foundational crown build-up. In posterior teeth, long cuspal heights and group function may cause greater lateral forces compared to canine-protected occlusions.24 For anterior teeth, deep overbites, a horizontal envelope of function, and extreme parafunctional forces may heighten the possibility of fracture and subsequent tooth loss.
In a study of 220 endodontically treated molars that were not restored with crowns, the success rates were 96% at 1 year, 88% at 2 years, and 36% at 5 years.25 When maximum tooth structure was retained for the direct composite restoration, the survival rate was 78% at 5 years.25 In another study it was concluded that teeth with cuspal coverage had a six times greater survival rate than teeth without cuspal coverage.26 Deciding whether to place a crown or only use a direct composite restoration depends on additional factors previously mentioned, other than remaining tooth structure. Cusp preservation, however, does not always result in low fracture resistance in the long term for an endodontically treated tooth.
Recently, Murgueitio and Avila-Ortiz27 proposed a classification for endodontically treated anterior teeth that took into account the wall thickness and height of the abutment based on ferrule principles. Therapeutic guidelines were summarized based on the classification and the canal diameter of the teeth. This classification may serve to establish a comprehensive treatment plan and accurate prognosis for endodontically treated anterior teeth; this may be helpful for inter-clinician communication and standardized comparisons in clinical research.27
When two or more walls of a tooth are missing after caries excavation and endodontic treatment, a post is usually required for retention of the core foundation along with the final coronal restoration. This also helps to distribute occlusal stresses along the remaining tooth structure. The details of executing this clinical procedure have been the focus of controversy regarding the necessity of posts and the best types to use. It has been shown in the literature that posts do not strengthen a tooth.28 In fact, it is known that post space preparation weakens the radicular structure and may increase the risk of root fractures;28 therefore, post placement should always be balanced against tooth structure removal when selecting the most suitable build-up approach. It has been proven that the use of fiber posts does not improve the fracture resistance of endodontically treated teeth in which a ferrule has been preserved.28 Preservation of tooth structure is the most critical facet of successful management of structurally compromised, endodontically treated teeth. Posts should only be used when other options are not available to retain a core, such as teeth without any ferrule. In such cases, fiber posts may improve the retention and fatigue resistance of the restoration but may not necessarily improve the tooth’s fracture resistance.28
The authors have no relevant conflicts of interest to disclose.
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