Endodontics: A year in review
As we turn the page on the year 2012 and look toward the future, the field of endodontics continues to strive for innovations to provide the best possible patient care. Current advances in endodontics include improved techniques that connect innovative science and materials with biological understanding. Technology continues to allow us to improve our ability to detect and treat each tooth's unique pulpal anatomy.
Digital imaging is an area of technology that has greatly enhanced our ability to view dental and surrounding anatomy. The advent of 2-D digital imaging has allowed us to attain accurate and clear instantaneous images. However, the latest development of CBCT provides 3-D images that can be constructed by computer software to view tooth anatomy at any angle or direction. This provides a new level of information that improves our ability to diagnose and treat. This technological advancement provides a more detailed and clear perspective of the tooth as a whole and can be used to view slices of the tooth to detect canal location, curvatures and other anatomical variations (Fig. 1). As we continue to use this technology our understanding of its clinical applications and indications will improve. Although CBCT can reveal much that is not possible with 2-D images, our prudent discretion regarding when it is appropriate to expose our patients to higher levels of radiation must be of paramount consideration.
With the advent of more advanced imaging comes the realization of how much pulpal anatomy exists beyond the main canals that we are accustomed to treating. Root-canal anatomy is complex and our ability to cleanse and seal this anatomy continues to present a challenge (Fig. 2). Irrigation is a critical aspect of root-canal treatment. As studies have demonstrated that rotary instruments contact only about 35 percent of canal-wall surface area, we must depend on the chemical debridement of debris and bacteria by our irrigation solutions. The ability to flow solutions along the entire canal in order to come in contact with the complete canal anatomy is a goal we are striving to achieve.
In 2012, the literature in support of ultrasonic irrigation shows great improvement over conventional irrigation methods. Ultrasonic irrigation can be described as active or passive. Active ultrasonic irrigation flows the irrigant solution into the chamber with the activated ultrasonic tip in place. Passive ultrasonic irrigation (PUI) is described as placing irrigant solution into the canals first, then introducing the activated ultrasonic tip into the solution already in the canals. PUI has been shown as a significant improvement compared with needle irrigation alone. PUI is able to remove dentinal debris from canals up to 3 mm beyond where the ultrasonic tip is placed down the canal. Malki et al. indicated that the flow of the irrigant was unaffected by curvatures in the canal. We should continue to strive to find improved methods for irrigation, as we must depend on the power of the solutions to debride much of the complex apical canal anatomy that our instruments are unable to address.
Vital pulp therapy has been a hot topic within the field of endodontics. Whereas the procedures of direct pulp capping and partial pulpotomies were met with little success in the past, the future shows promise. Bioactive hydrophilic materials with hard-tissue inductive and conductive properties such as MTA (mineral trioxide aggregate) have improved our ability to maintain healthy vital pulp tissue once the pulp chamber has been encroached upon.[4,5] Studies have supported the ability of viable cell growth of young pulpal cells and cementum onto the surface of MTA.[6,7] Owing to the innate ability of vital pulp tissue to elaborate dentine and complete natural dentinal wall formation and root-end closure, maintaining this tissue is critical. Therefore, having a biocompatible material to cap vital pulp tissue allows the clinician to remove inflamed pulp tissue present due to decay and allows the remaining tissue to return to health. This will allow natural root formation to be completed. This treatment option provides a significant benefit over performing full root-canal treatment on immature roots.
Regenerative endodontics is a very exciting area of endodontic treatment today. First introduced as a protocol in 2004, the concept of revascularizing a previously necrotic canal has become reality. The indication for this procedure is an immature permanent root that has become necrotic prior to completion of root formation. The protocol calls for access to the canal, debridement of the canal space by irrigation only and then placement of an antibiotic paste for two weeks. The second treatment visit involves further irrigation of the canal space followed by instigation of bleeding from the periapical area into the canal. Once a blood clot has been achieved in the area of the cemento-enamel junction, an MTA plug is placed over the blood clot and the chamber is then sealed with restorative material. The regenerative capability is achieved by the presence of a stem-cell source from the apical papilla. Stem cells from the apical papilla are able to migrate into the blood clot. The clot serves as a scaffold to support the stem-cell growth into vital tissue. This procedure is able to reprogram the root to continue formation until the root end is closed. The advantage of this procedure versus conventional apexification or apical closure procedures is the natural thickening of the dentinal walls, providing the tooth with greater support and fracture resistance. This treatment protocol is continuing to evolve, with a recent publication this year by Drs. Garcia-Godoy and Murray.
Rotary NiTi files are an engineering wonder that continue to evolve and impress. The latest buzz in file systems comes in the form of the concept of reciprocation. The method of canal instrumentation in a reciprocating motion is a decades-old technique that has been performed with stainless-steel hand files in back-and-forth 45-degree motions. The newer NiTi files that employ reciprocation (WaveOne, DENTSPLY Tulsa Dental; Reciproc, VDW) are driven in a specifically designed motor and handpiece to rotate the file in different directions during instrumentation. The system employs one file for the entire canal preparation. The reciprocating motion is thought to minimize the risk of file separation.
The concept of canal shaping using reciprocating motion differs from full-rotation rotary instruments. Rotation of the rotary NiTi files is done in full 360-degree revolutions. Currently available files have a variety of flute designs, cross-sectional shapes and features. The newest design for full-rotation NiTi files forms the cutting edges by twisting the metal, as opposed to the features being cut into the metal (Twisted Files, Axis SybronEndo). The advantage of twisting versus cutting the metal is maintaining the grain structure of the metal. This mode of manufacturing maximizes the inherent properties such as an increased resistance to cyclic fatigue compared with other files. Hashem et al. demonstrated that the performance of this file design maintained the original canal curvatures, allowed better centering ability within curved canals and minimized transportation and unnecessary dentine removal compared with other file systems currently on the market.
The main point of emphasis that highlights the clinical differences between the conventional full rotation and reciprocating motion is the removal of dentinal and pulpal debris during instrumentation. Whereas full rotary instruments channel the debris coronally and out of the canal, constant reciprocation within the canal with a single file can potentially pack debris apically. The apical extrusion of dentinal and pulpal debris can result in periapical irritation. This effect may be minimized by the more experienced clinician diligently adhering to the proper technique.
Sadly, in 2012, the field of endodontics lost a pioneer, innovator and teacher in Dr. Franklin S. Weine. He made significant contributions to endodontic literature and textbooks and served as a revered educator, clinician and mentor to many. I am fortunate to have personally known Weine in his later years. The logic of his thinking and brilliance of his mind were to be admired. As a lifelong Chicagoan, his memory will be honored by the dedication of a new surgical suite in his name at the University of Illinois at Chicago College of Dentistry.
A complete list of references is available from the publisher.