Our tooth anatomy contains many complex working parts, and endodontists often have to handle cases where the shapes, morphologies, and sections of the teeth are at different lengths and levels. Because of how much variety there is in root canal anatomy, endodontists have developed classification systems, patient teeth reviews, and reports on dental anomalies to better understand how to restore compromised endodontically treated teeth. Endodontic treatment aims to achieve this by the wide use of fiber posts to rebuild the tooth from the coronal and middle portions of the crown.
Fiber posts have resulted in a new interest in the tooth’s anatomy for dentists, and for endodontists working with fiber post techniques, understanding the portions of the canal affected is critical. Beyond this, by assessing the post-space availability, the anatomical variations, and the overall condition of the tooth, and by looking at these factors, we can determine what combination of fiber posts is best suited for certain techniques and treatments.
The Ins and Outs of Fiber Post Cores and Root Canal Shapes
In dentistry, dentists work with classifications of root canals according to their shape and define these root canal shapes through the basic concepts of anatomic endodontic technology. Through these observations, we can define root canals by these shapes:
- Tubular Canals: Tubular canals are pipe-like shaped and typically pose deeper root canal space than most teeth. Tubular-shaped canals are often found within the maxillary incisors, mandibular canines, maxillary first premolars, and maxillary first molars. Tubular is a parent classification for oval, rounded, and triangular canal shapes.
- Oval Canals: Oval or rounded canals tend to pose a smaller but circular shape to the canal opening, and depending on the areas looked at, mandibular canines, maxillary incisors, and mandibular first premolars are most commonly where these types of canals would be found.
- Triangular Canals: Although considered rarer within the mouth, the most common place where triangle-shaped canals are found is within the maxillary canines, and thus need extra consideration when committing to fiber posts.
- Straight Canals: Straight canals often lack the fiber post space necessary when compared to ovals and triangular but accommodate the tooth structure for the mandibular first premolars, often requiring a lateral approach during endodontic treatment.
- Semilunar Canals: Considered a rarer shape among root canal formations, semilunar canals are curved in their shape but are typically found in areas where normally triangular canals are found, such as the maxillary canines.
- Infinity or “8”-shaped canals: In these cases, the root canal formation presents buccolingual variations, extending the space available along the outer edges of the tooth. Some examples of this type of shape are found in the mandibular incisors, mandibular canines, and the maxillary first and second premolars.
All of these root variations need to be accommodated when working with fiber post techniques for endodontic treatment. As a crucial part of achieving successful, nonsurgical endodontic treatment, there are many techniques that can be used to adapt to the root canal shape, the tooth’s current condition, and other health factors.
Fiber Posts: The Three Techniques to Rule Them All
When going over fiber post techniques, it’s important to understand the basics behind how fiber posts operate and work. Fiber posts are anisotropic, meaning they have a similar elasticity to the tooth’s dentin. These posts are able to flex slightly within the tooth, reducing overall damage to the inner tooth’s canal and roots. They can appear in tooth-colored versions, the posts can be retreated, and are rarely suspectable to corrosion. When viewed along the surface, they are invisible under crowns, veneers, and other restorations.
In terms of using the fiber post technique, however, not all fiber posts will work the same, despite how similar they are in terms of their mechanical properties. Therefore, different techniques can be used to accommodate the varieties in both root canal shapes and fiber post variations. These techniques include:
The Simple Canal Technique: The simple fiber post technique works with canal shapes that are more conservative in shape. More specifically, it works with canal shapes that are less than 25% larger than the fiber post, meaning shapes such as oval, tubular, and triangle are recommended. To perform the technique, endodontists are encouraged to use the bottom-up approach, where the canal is prepared with matching post-size drills. Once the space is available for bonding, the fiber posted is shortened to the height of the core to avoid uneven setting and curing. But overall, this technique is referred to as simple due to its straightforward instructions and ease of handling with defined root canal shapes.
Anatomical Post and Core Technique: Through the anatomical post and core technique, endodontists are encouraged to use build-up core material against overly large oval canal spaces that are larger than 25% of the fiber post. This technique is meant to compensate for any remaining deficiencies present within the materials used, and through building down the core materials, a moderate flare can create an isolated space for the fiber post and further restorative techniques.
Post and Accessory Post Technique: The post and accessory technique work with additional posts to help facilitate a wider canal opening, which can be used for straight, semilunar, and infinity-shaped canal spaces. The additional posts included with this technique are cut and pre-bonded together, and the area created within the space is light-cured to achieve better compressive strength for future restorations and endodontic treatments.
Overall, these techniques work with different methods to minimize the risk of shrinkage, reduce thickness variances in cement, reduce the need for drilling, and increase the rate of fracture resistance for endodontically affected teeth. Fiber post techniques have many benefits, as they work to reduce the risk of endodontic failures due to the higher amount of stress distribution it provides. No matter the method used, understanding these techniques can help reinforce structurally unstable teeth and provide room for improvements in endodontic treatments. Most of all, it can reduce the return rate of endodontic failures and promote better tooth conservation and better patient health.