Written by Eudes Gondim, Jr, DDS, MS, PhD, and Frank C. Setzer, DDS, MS, PhD Saturday, 28 February 2009 19:00
Within the past 35 years, dental implants gradually developed to a point where they are considered a reliable and affordable treatment for missing or severely compromised teeth. For many years, the only available option for a single-unit restoration was to save a compromised tooth by endodontic therapy and prosthodontic restoration, which in some cases truly turned out to be “Herodontics.” One of the major contemporary issues confronting the dentist is the treatment planning decision between extracting a tooth with subsequent placement of an implant versus preserving it by conventional or surgical endodontic treatment.
Defining the criteria for a clinically guarded prognosis is controversial and subject to differences in interpretation.1 A patient’s best interests must always be the major factor in making clinical decisions and treatment plans. When endodontic procedures are ethically or technically judged to be unsuitable, implants represent a potential benefit for patients. However, a tooth should not be needlessly extracted because of technical limitations or an operator’s abilities. Even in the absence of important clinical resources (including time), a dentist who is serious and ethical should always do what is best for the patient. After a critical review of outcome assessment studies, every clinician will fully understand the need for both treatment alternatives.
FACTORS IN ENDODONTIC SUCCESS
Many different factors may affect the clinical outcome of an endodontic treatment. A higher success rate represents a better prognosis. A practitioner who has obtained a consistently elevated level of success in the performance of endodontic therapy will regard the preservation of the natural tooth as the preferred clinical alternative. The application of aseptic techniques, as exemplified by the routine use of rubber dam and the incorporation of recent technical advances in endodontic therapy (ie, Ni-Ti rotary instruments, electronic apex locators, the surgical operating microscope, microsurgical instruments, ultrasonic generators and tips, obturation devices, and regenerative materials) will improve the safety and efficiency of endodontic treatment greatly.2
Among all innovations, the use of the dental microscope can be highlighted as a powerful tool that increases the visualization capability for conventional or surgical endodontic procedures alike.3 Magnification and illumination enable the clinician to identify difficulties before problems occur and therefore will also improve every subsequent step of the technical procedure.
Conventional root canal treatment does not always result in clinical success. Some irritants may remain in the root canal system after cleaning and shaping, such as in missed canals or other areas with inadequate irrigation and instrumentation. Apical periodontitis can persist, or newly develop in the presence of bacterial, chemical, and/or mechanical irritants; consequently increasing the potential of failure. This can be a result of coronal leakage, fractures, perforations, missed or blocked canals, short fillings, canal transportation, etc. In these cases, periradicular surgery or conventional retreatment techniques must be considered.
Irrigation and access are 2 of the most important, demanding, and critical aspects of endodontic therapy. In contemporary endodontics, improved techniques are available for irrigation. The recently developed apical negative-pressure system4 may take our irrigation techniques one-step-ahead and help to (dis) solve parts of the problem: better and more efficient irrigation results in cleaner canals with less bacterial biofilm.5
Despite the use of micro-ultrasonic techniques, the endodontic access is still a challenge. The visualization and preparation of particular root canals can be very difficult; especially in teeth that have been heavily restored, calcified, malpositioned, severely decayed, or may have sustained extensive damage from aggressive access attempts during previous treatment. In these situations, the original anatomy of the tooth has changed, and the knowledge of anatomical landmarks and root canal configurations can provide greater certainty about the total number of canals.6
Enhanced visualization with a microscope also provides the clinician with a better 3-D idea of the tooth contours, the location of the pulp chamber, and the correct angle of the canals. When searching for canals, one must remember that secondary dentin is generally colorless or opaque, while the pulp chamber floor is darker and grayer. Diamond or zirconium-nitrate coated ultrasonic tips have been in use to locate hidden or calcified canals for about 15 years. The sleek design of these ultrasonic instruments allows for unobstructed views of the working space, as they are operated without a bulky handpiece. In addition, ultrasonic technology provides back-and-forth brush-stroking motion in the tip, which is safer than plunging the bur inside the chamber in a vertical motion. It is a fast and safe technique, allowing the clinician to search and respect the important landmarks that serve as a guide into the canal orifices.
This article presents several clinical situations where differently designed ultrasonic tips and magnification were fundamental in achieving a high quality and predictable endodontic result.
IMPORTANCE OF THE ACCESS CAVITY
The access cavity is the key to success in 2 important ways. First, it provides access to the canals, allowing a straight-line path to facilitate easier preparation of curved canals by reducing the severity of the curvature. Nevertheless, the canals should be shaped without sacrificing more remaining tooth structure than necessary. Second, it allows access to the foramen after negotiating the coronal two thirds using hand instruments, irrigants, Gates Glidden drills, Ni-Ti shaping files and, if necessary, ultrasonic tips. Small files are used to negotiate the canal, confirm a smooth glide path to the terminus, and to establish patency.7
The design and features of ultrasonic access tips is very important. Each type was developed for a specific purpose. Some are used for cutting, digging, and modeling; and others are used for refining, opening spaces inside the canal, and removing instruments/blockages while establishing access to the foramen.
Figure 1a. CPR tips 1 to 5 are diamond coated with built-in water ports.
Figure 1b. Spartan Ultrasonic Unit.
Figure 2. (Case 1, tooth No. 14): Ultrasonic tip CPR-1 deroofing dentin, flaring and locating the MB2 orifice.
Figure 3. (Case 1): The MB2 canal was uncovered and instrumentation was initiated.
Figure 4. (Case 1): MB and MB2 canals are prepared and the orifices are clean.
|Figure 5a and 5b. (Case 2, tooth No. 3): CPR-2 tip was used to precisely dig the groove between the palatal and MB canals (8x).|
Figure 6. (Case 3, tooth No. 14): CPR-3 ultrasonic tip deroofing dentin and flaring the palatal canal.
Figure 7. (Case 3): The use of ultrasonic tips showed the absence of the MB2 canal.
Figure 8. (Case 3): Final radiograph.
Figure 9. (Case 4, tooth No. 30): CPR-2 exploring the groove and searching for the middle-mesial canal.
|Figure 10. (Case 4): Despite the access made right through a prosthetic crown the absence of the middle-mesial canal and the presence of MB and ML orifices (8x) is clear.||
Figure 11a. Preoperative radiograph shows very calcified canals.
Figure 11b. Difficult to clinically identify the canals.
Figure 11c. Clinical picture after the locating of MB and DB canals.
In case numbers 1 to 5 (Figures 2 to 11) the access was prepared using a No. 4 round bur to gain access to the pulp chamber. In addition, a tapered diamond bur was used to make the access walls regular and to allow an ideal line angle extension for the files. CPR-1 tips were used for deroofing the pulp chamber and to refine the access (Figures 2 and 11). A CPR-2 (or BUC-1) was used to precisely carve the groove between the palatal and MB1 canal, until the MB2 canal orifice was located (Figures 4 and 5). In some cases, a CPR-2 can be used to vibrate on and remove calcifications in the pulp chamber and a BUC-2 to grind the floor until dark colored dentin is encountered (Figures 5 and 7). In case No. 3, no MB2 canal was apparent. Differently colored dentin areas can be seen clearly (Figures 6 and 7). In very difficult cases (Figure 11), when the canal orifices are not visible and one can hardly identify the different dentin colors even under high magnification, the use of ultrasonic tips is mandatory and only option to locate the canals safely. CPR-5 and -6 can be applied to dig deeper and follow calcified canals until patency is achieved. This procedure can be carried out in the coronal aspect, as well as in the middle and apical areas, of the canal. However, extreme care must be taken. The dentin must show texture and color indications of the previous root canal area.
Figure 12a. Preoperative radiograph shows a separated instrument in the MB canal and periapical area.
Figure 12b. A photo of the fragment in the canal (8x).
Figure 12c. Postoperative radiograph 5 years after the instrument retrieval.
For the removal of posts, broken instruments (Figures 12 to 13), or other intracanal obstructions; the use of ultrasonic tips inside the canal is also a very good alternative. Again, one must use great caution when working around a canal curvature even with fine tips.
Figure 13a. Preoperative radiograph shows a separated McSpadden condenser in the canal and periapical area of a tooth No. 8.
|Figures 13b and 13c. Retrieving procedure using a 23-gauge tip (Obtura Spartan) (8x).|
Figure 13d. The fragment.
Figure 13e. A check radiograph. The instrument was removed with ultrasonic vibration.
In order to achieve endodontic success, the objectives of root canal therapy are to properly clean, shape, and pack the root canal system under all circumstances. A detailed knowledge of root canal anatomy and the use of new technologies are demanded, whether dealing with usual or unusual cases. The access preparation to the canals has a great impact on all of the subsequent steps of treatment. This underlines the importance in utilizing a dental microscope and ultrasonic instrumentation as an integral part of modern endodontics. Excellence in all endodontic treatment is the name of the game!
- Iqbal MK, Kim S. A review of factors influencing treatment planning decisions of single-tooth implants versus preserving natural teeth with nonsurgical endodontic therapy. J Endod. 2008;34:519-529.
- Pettiette MT, Delano EO, Trope M. Evaluation of success rate of endodontic treatment performed by students with stainless-steel K-files and nickel-titanium hand files. J Endod. 2001;27:124-127.
- Gondim E Jr, et al. Surgical operating microscope: the new frontier of XXI century clinical dentistry. Revista da Federacion Odontologica Latinoamericana. 1997;3:147-152.
- Schoeffel GJ. The EndoVac method of endodontic irrigation, part 2: efficacy. Dent Today. Jan 2008;27:82-87.
- Zehnder M. Root canal irrigants. J Endod. 2006;32:389-398.
- Krasner P, Rankow HJ. Anatomy of the pulp-chamber floor. J Endod. 2004;30:5-16.
- Ruddle C. Endodontic access preparation: an opening for success. Dent Today. Feb 2007;26:114-119.
Disclosure: Dr. Gondim reports no conflict of interest.
Disclosure: Dr. Setzer reports no conflict of interest.
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