Effect of Age On Root Canal Configurations
Studies of patients ≤20 to ≥40 years of age have shown that both pulp chamber size and root canal diameter decrease as people age. Such changes may also result from carious lesions, deep restorations and periodontal disease. Although many studies appear to support these conclusions, their applicability is limited due to studies’ restriction to a single type of tooth, a single root, a specific extra canal in a specific root or a specific root canal configuration. Additionally, small sample size has been a problem with these studies.
Martins et al from the University of Lisbon, Portugal, used cone beam computed tomography (CBCT) to analyze the prevalence of root canal systems in a large population of various ages (mean age, 51 years). They evaluated CBCT examinations performed over a 5-year period in 670 patients (243 males, 421 females).
All teeth were included in their study except for third molars, teeth with previous endodontic treatment, and teeth with immature apices or root resorption, for a total of 12,325 teeth. Root canal systems were classified by Vertucci type. Patients were divided into 4 groups by age: ≤20 years; 21 to 40 years; 41 to 60 years; and ≥61 years.
Information for only 151 teeth was available for the patient group that was ≤20 years old; because of the scarcity of data, that group was not included in the statistical analysis.
The second maxillary molar showed the greatest variation of all the maxillary teeth, with a progressive decrease in Vertucci type I configuration (single canal from crown to apex) and a corresponding increase in Vertucci type II configuration (2 canals near the crown reuniting into 1 canal near the apex).
The distal root of the mandibular first molar showed a decrease in Vertucci type I prevalence in patients ≥61 years old. Several other mandibular teeth showed a similar pattern of decrease in Vertucci type I configurations, but the differences were not as substantial. The root canal configurations of most anterior teeth did not vary greatly by age.
This study demonstrated a tendency for a greater prevalence of Vertucci type I configuration in younger people than in older people. The older population also showed a large increase in the number of root canals, primarily in the maxillary and mandibular second molars and in the distal root of mandibular first molars. These considerations must be taken into account when planning endodontic treatment for older patients.
Martins JNR, Ordinola-Zapata R, Marques D, et al. Differences in root canal system configuration in human permanent teeth within different age groups. Int Endod J 2018;doi:10.1111/iej.12896.
Successful Endodontic Treatment in Cracked Teeth
The American Association of Endodontists classifies tooth cracks or fractures into 5 subgroups: craze lines, fractured cusps, cracked tooth, split tooth and vertical root fracture. Cracked teeth were defined as “greenstick” fractures with a history of cold sensitivity and acute pain upon chewing.
The proper treatment of cracked teeth requires a determination of tooth restorability and pulpal status. In teeth with irreversible pulpitis or necrosis, root canal treatment should be undertaken only if the teeth are restorable. Teeth with deep pockets associated with the crack but no other signs of periodontal bone loss are rarely restorable. Whether cracked teeth with necrotic pulps should be treated or extracted remains an open question.
Because long-term studies of treatment outcomes for cracked teeth receiving orthograde root canal treatment in the United States do not exist, Krell and Caplan from the University of Iowa analyzed the 1-year outcomes for such teeth treated by 1 private practice endodontist over a 25-year period. Teeth were filled using the lateral condensation technique and Roth’s 801 sealer. All patients received recall cards 1 year after treatment, at which time they were evaluated for the presence or absence of symptoms, radiographic resolution of previous lesions and the presence of a crown. If no signs or symptoms were seen and any previous pathosis seen on radiographs had resolved with the development of no new pathosis, the treatment was deemed a success.
All teeth included in the analysis had cracks confirmed by direct visualization. Cusp fractures, split teeth and teeth with vertical root fractures were excluded from the analysis. Of the 2086 patients seen with at least 1 cracked tooth, 1406 underwent root canal therapy; 363 patients who returned for follow-up at 1 year were included in the analysis. Success at 1 year was seen in 296 teeth (82%). The 3 variables that best predicted failure were:
- teeth with marginal ridge cracks
- teeth with mesial or distal probing pocket depths of ≥5 mm
- periapical diagnosis of chronic apical periodontitis (CAP), suppurative apical periodontitis (SAP) or acute apical abscess (AAA)
Based on these results, the authors created a novel prognostic index (Figure 1) for successful orthograde root canal therapy in cracked teeth, rated from most likely to least likely to succeed:
- Iowa stage I: no probing pocket depths ≥5 mm; no crack across the distal marginal ridge
- Iowa stage II: no probing pocket depths ≥5 mm; crack present across the distal marginal ridge; no periapical diagnosis of CAP or SAP or AAA
- Iowa stage III: no probing pocket depths ≥5 mm; crack present across the distal marginal ridge; a periapical diagnosis of CAP or SAP or AAA
- Iowa stage IV: ≥1 mesial or distal probing pocket depth ≥5 mm
Of course, standard treatment methods and technology have evolved over the 25 years covered by this study; for example, the endodontist incorporated nickel–titanium instrumentation 10 years after beginning private practice. Overall, the results of this study suggested that root canal treatment in cracked teeth may have a higher rate of success than had been previously reported.
Krell KV, Caplan DJ. 12-month success of cracked teeth treated with orthograde root canal treatment. J Endod 2018;doi:10.1016/joen.2017.12.025.
Supine vs Upright Position for Inferior Alveolar Nerve Block
Pivotal for successful treatment, profound anesthesia prior to endodontic therapy is not always easy to achieve, especially in the lower molar area. To improve the likelihood of success, various approaches have been proposed, such as using solutions with or without vasoconstrictors, increased volume or increased concentration of the anesthetic solution, buffered anesthetic solutions, and Gow-Gates and Akinosi-Vazarani injection techniques. Studies have suggested that having the patient maintain an upright or semi-upright position after administering the inferior alveolar nerve block (IANB) increases its success, because the anesthetic solution diffuses down along the ramus and is therefore more likely to hit the target.
To explore the effect of patient position on IANB success, Crowley et al from The Ohio State University recruited 110 healthy adults (55 women, 55 men; age range, 20–36 years) for a crossover-design study. Participants received 2 IANB injections of 2% lidocaine with 1:100,000 epinephrine at least 2 weeks apart, 1 while seated upright and the other while in a supine position. Researchers randomly decided whether the patient was to be seated upright or in a supine position during the first injection, making each participant his or her own control.
A total of 3.2 mL of the anesthetic solution was injected by a computer-controlled local anesthetic device over a period of 1 minute and 52 seconds.
All patients were repeatedly asked whether they felt profound lip numbness after the injections; if numbness was not achieved within 15 minutes, the block was considered unsuccessful. After each injection, the first and second molars, premolars, central and lateral incisors, and a contralateral canine (as a control) were stimulated with an electric pulp tester (EPT) in 4-minute cycles for 60 minutes. Success was defined as the patient maxing out on the EPT without feeling the stimuli for 2 consecutive times and sustaining the numbness for 60 minutes.
The authors found no statistical difference between the 2 positions in achieving profound anesthesia for the molars and incisors, but the supine position significantly improved success for both premolars. There were wide differences in the success rates for the anesthesia: The second molars had a 65% to 73% success rate, but the central incisors had only an 8% to 11% success rate. Most importantly, neither position for IANB administration consistently provided complete pulpal anesthesia.
This study found that the patient’s position is not critical to achieving profound IANB. It remains important to assess the patient’s level of anesthesia prior to initiating therapy and, if numbness has not been achieved, then supplementary injections such as periodontal ligament or long buccal should be tried.
Crowley C, Drum M, Reader A, et al. Anesthetic efficacy of supine and upright positions for the inferior alveolar nerve block: a prospective, randomized study. J Endod 2017;doi:10.1016/j.joen.2017.09.014.
Is a Glide Path Necessary for the New Reciprocating NiTi Files?
It has been well established that nickel-titanium (NiTi) alloy files are able to maintain the original canal shape during the instrumentation procedure. However, they do come with one important disadvantage: a higher risk of file separation or breakage compared with stainless steel hand files. If a file breaks inside a canal, it is usually very difficult, if not impossible, to retrieve it, and it is not possible to further instrument and irrigate beyond it. The likelihood of a successful therapy can thereby be greatly diminished.
NiTi files principally break for 2 reasons:
- Cyclic fatigue occurs when the file has been bent too many times; repeated tension and compression stresses cause fatigue crack propagation, and the file simply breaks.
- Torsional failure occurs when the tip of the file engages inside the canal such that it does not rotate anymore, but the motor continues to rotate the rest of the file. If the torque control of the motor does not sense this, the file will break, leaving the tip firmly engaged inside the canal.
Many manufacturers of NiTi files have, with some success, actively developed new file designs and heat treatments of the NiTi alloy to improve cyclic fatigue and flexibility of the NiTi files, thereby reducing the risk of file breakage when they are used inside the canals. These improvements, however, have come at some cost to the torsional strength.
Over the years, research has discovered that one way to reduce the risk of torsional failure is to establish a “glide path” down to the apical area of the tooth prior to using the motor-driven shaping NiTi files. Creating a glide path of sufficient size before introducing the initial rotary NiTi file into the canal has been shown to significantly reduce the risk of file breakage. It is not clear, however, whether the new and improved NiTi files, particularly those that reciprocate within the canals rather than rotate 360°, need a glide path prepared as do the older NiTi files.
Kwak et al from Pusan National University, South Korea, investigated the effect of glide paths on new reciprocating NiTi files by establishing glide paths in 15 resin endodontic training blocks using rotating files specifically designed to create such a path (ProGlider, Dentsply/Maillefer; Figure 1, see above). An additional 15 blocks did not have glide paths.
To compare the newer file design and heat-treated alloy, the authors measured 2 types of WaveOne files (Dentsply/Maillefer): the older version WaveOne and the newer version, WaveOne Gold (Figure 1). The blocks were instrumented with the files while the authors carefully monitored the torque applied to each file. They found that WaveOne Gold had significantly reduced torque created if a glide path had been established; the older version generated a higher maximum torque than did WaveOne Gold regardless of the establishment of a glide path (Tables 1 and 2, see below).
Based on this study, it is clear that, in order to reduce the risk of file breakage due to torsional failure, dentists should create a sufficient glide path in the apical area of the canal prior to using these new, highly flexible NiTi files.
Kwak SW, Ha J-H, Cheung GS-P, et al. Effect of the glide path establishment on the torque generation to the files during instrumentation: an in vitro measurement. J Endod 2017;doi:10.1016/j.joen.2017.09.016.
Combating Misinformation in Mass Media
Have you heard about the newest documentary sensationalism? Netflix, hopefully by now, has removed its controversial documentary, “Root Cause”, a video which has caused quite the stir in the dental community and the public at large as a result of its claims to link RCT treatment to cancer.
But remember… correlation and causation are two different animals.
Our faculty wanted to address this in the hopes that you’d be able to better field questions from patients, concerned over information they’ve received and don’t know enough about.
A good article can be found here in Today’s RDH website
Read more in another article HERE from the Canadian Dental Association and Canadian Association of Endodontics
Knowledge is power! Arm yourselves for when patients come with fear. And arm yourselves with compassion.