Restoration timing and survival of endodontically treated teeth
Timing of a crown placement after root canal therapy (RCT) can significantly affect the survival rate of endodontically treated teeth (ETT).
That key finding is part of an 8-year retrospective study published in the November issue of Journal of Endodontics.
Researchers designed the study with a 2-fold purpose: to investigate the effects of factors associated with various coronal restorative methods after RCT on the survival of ETT and to measure the effect of time lapse between endodontic intervention and crown placement to form a tooth loss hazard model.
Researchers used 882 samples from 880 patients from Case Western Reserve University who had a mean age of 46 years. Undergraduate clinicians at the School of Dental Medicine at Case Western Reserve University placed all definitive restorations. Elapsed time from the endodontic treatment to the placement of the restoration was noted for all ETT. American Dental Association Code on Dental Procedures and Nomenclature (ADA CDT) dental procedure codes for extraction in computerized records were considered a failure. Survival was defined as the presence of ETT in the oral cavity by the end of the study (January 1, 2016). ETT with no extraction ADA CDT codes were considered to have survived.
From 882 examined teeth, 441 teeth (50%) received a full-coverage crown after RCT, 198 teeth (23%) received composite/amalgam buildup restorations, and 243 (27%) never received a final restoration after RCT. A total of 105 teeth (11.9%) were extracted, and 777 teeth survived until the end of the study. Extracted teeth included 23% with no restoration, 11.6% with a buildup restoration, and 5.7% with crown coverage. Eight teeth were extracted for reasons related to endodontics. Most extractions were carried out owing to crown failures.
The 8-year survival rate of ETT regardless of restoration type after RCT was 79%. The 8-year survival rate after RCT was 84% with full-coverage crowns. ETT that received core buildup restorations without placement of a full-coverage crown had an 8-year survival rate of 71%. Teeth that did not receive a permanent restoration after RCT had an 8-year survival rate of 58%. Researchers also found that ETT that received composite/amalgam buildup restorations were 2.29 times more likely to be extracted. ETT that did not receive any follow-up permanent restoration were 4 times more likely to be extracted compared with ETTs that received full-coverage crowns.
Researchers noted the survival rates of ETT that received a crown within 4 months and after 4 months of RCT were 85% and 68%, respectively. ETT that received a crown 4 months after RCT were extracted at 3 times the rate of teeth that received a crown within 4 months after RCT. The tooth loss hazard ratio showed a dramatic increase after 4 months, stayed constant up to 18 months, and then experienced another sharp increase.
“The delay in the crown placement in the present study might be due to the study being conducted in a school setting,” researchers noted. “Also, socioeconomic status of patients might affect the timing of crown placement, which should be considered in future studies.”
Read the original article.
Consulting Editor: Susan Wood, DDS
Diplomate, American Board of Endodontics
Outcome of revascularization procedure in necrotic immature teeth
The outcome of revascularization in which healing of periapical periodontitis and maturation of roots occurs is high. The outcome analysis should include both the radiographic healing of apical periodontitis and the radiographic signs of further root development.
Those 2 findings are part of a study published in the December issue of Journal of Endodontics.
Researchers set out to measure the outcomes of consecutive revascularization procedures in necrotic immature teeth treated by faculty and residents in the Department of Endodontics in the School of Dental Medicine at the University of Pennsylvania from 2009 through 2012.
Researchers used 28 teeth from 23 patients for the study. The protocol for revascularization involved 3 visits. Visit 1 consisted of using local anesthetic, rubber dam isolation, access preparation, irrigation with 3% sodium hydrochlorite, minimal or no instrumentation, and placement of triple antibiotic paste as an interappointment dressing. An open apex was clinically verified with a size 100 K file. The access opening was temporarily sealed for an average of 37 days with a temporary restoration material. Visit 2 involved 3% mepivacaine without a vasoconstrictor as a local anesthetic, removal of the temporary restoration under rubber dam isolation, triple antibiotic paste flushed out with 3% sodium hydrochlorite, and a final rinse with 17% ethylenediaminetetraacetic acid. A blood clot was induced with a size 10 K file to lacerate the apical tissues. After the clot was formed, the clinician placed either EndoSequence Bioceramic Putty or mineral trioxide aggregate below the cementoenamel junction and either above the blood clot directly or using a matrix barrier, based on the clinician’s judgment. The access opening was again sealed with a temporary restoration material. At visit 3 the use of Bioceramic Putty or mineral trioxide aggregate was confirmed before placing the permanent composite resin.
Most of the follow-up periods ranged from 7 to 31 months. Each case was assigned to 1 of 3 categories at follow-up: complete healing, indicated by the absence of clinical signs and symptoms, total resolution of periadicular radiolucency, and an increase in the root dentin thickness and length and apical closure; incomplete healing, indicated by the periapical lesion completely healed without any signs of root maturation or thickening, the periapical lesion either reduced in size or unchanged with or without radiographic signs of increasing root dentin thickness and length, or apical closure; failure, the indication of persistent clinical signs and symptoms, increased size of the periadicular lesion or both.
A total of 21 cases (75%) healed completely, 3 cases (10.7%) failed and needed further treatment, and 4 cases (14%) exhibited incomplete healing. Of the 20 cases that were associated with a history of trauma, 15 (80%) exhibited complete healing.
Caries occurred in 5 cases (18%), and an anatomic anomaly occurred in 3 cases (11%), with a complete healing of 60% in cases of caries and 67% in the 3 cases associated with a fractured talon cusp.
Researchers noted 3 key limitations of the study, including the lack of randomized clinical outcome studies to validate its long-term efficacy; the lack of a standardized treatment protocol, which hindered proper comparison between studies to gain more information about the prognostic factors affecting the outcome; and the lack of a clear definition of success and failure as an outcome in revascularization studies.
Still, they concluded, “outcome analysis should include both the radiographic healing of apical periodontitis and the radiographic signs of further root development and that they should not be analyzed as separate entities.” Researchers noted that their study was the first to create outcome criteria that would address both factors.
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Activation and tissue dissolving activity of irrigants from artificial grooves in root canals of maxillary central incisors
Activation increases the tissue dissolving activity of irrigants from artificial grooves in root canals of maxillary central incisors.
That key finding is from a study published online December 3 in International Endodontic Journal.
The purpose of the ex vivo study was to measure porcine palatal mucosa dissolution from artificial grooves in prepared root canals by a final rinse with sodium hypochlorite (NaOCL), with ethylenediaminetetraacetic acid (EDTA) as an intermediate solution, with or without sonic or ultrasonic activation.
Researchers chemomechanically prepared the root canals of 83 human maxillary central incisors split the teeth. They created a standardized longitudinal intracanal groove in 1 of the root halves. They collected 83 porcine palatal mucosa samples and adapted them to fit into the grooves and weighed them. The baseline weight of the fragments was between 3 and 6 milligrams.
They randomly divided reassembled specimens into 4 experimental groups based on the final rinse: no activation, sonic activation using the Endoactivator, passive ultrasonic activation, and the use of Eddy tips with a 2.5% NaOCL with an EDTA intermediate rinse. A control group was irrigated with distilled water without activation.
Researchers delivered the solutions by using a syringe and needle 2 millimeters from working length. Total irrigation time was 150 seconds, including 60 seconds of activation in the specific groups. Root canal preparation and irrigation assays were carried out at 36 ± 2°C by an experienced endodontist. A blinded assessor then dried the canals, disassembled the roots, and rinsed, blotted dry, and weighed the palatal mucosa samples.
Weight loss occurred in all experimental groups. Irrigant activation resulted in greater weight loss compared with the nonactivated group. Researchers noted that sonic and ultrasonic activation likely enhanced the solution’s replenishment, considering also the risk of stagnation of the solutions through the canal. The large volume of NaOCL used in the study and overall study setup likely allowed the rinse out of the EDTA and EDTA/NaOCL mixtures, which have a limited tissue dissolution capacity.
“The addition of EDTA on the free available chlorine from NaOCL, and therefore its tissue-dissolution ability,” researchers concluded, “is dependent on time.”
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Effect of fiber posts on the fracture resistance of maxillary central incisors with Class III restorations
The placement of a fiber post does not affect the fracture resistance of endodontically treated maxillary central incisors with 2 Class III restorations.
That conclusion is from a study published online November 16 in The Journal of Prosthetic Dentistry.
Researchers of the in vitro study set out to measure the effect of fiber posts on the fracture resistance of endodontically treated maxillary incisors with Class III restorations. Researchers used 40 maxillary central incisors with similar root forms and labiopalatal and mesiodistal dimensions. Specimens were assigned to 4 equally sized groups: a control group of endodontically treated central incisors without posts (GHT), endodontically treated central incisors with 2 Class III cavities filled with composite resin and no post, endodontically treated central incisors with 2 Class III cavities filled with composite resin after placement of a carbon fiber post (GCF), and endodontically treated central incisors with 2 Class III cavities filled with composite resin after placement of glass fiber posts (GGF).
After the researchers removed the gutta-percha, they prepared post spaces with a corresponding low-speed drill to achieve a post space of 12 millimeters. They irrigated post spaces with 3% sodium hypochlorite, rinsed them with 70% ethanol, and dried them with absorbent paper points. They preconditioned post spaces by using a self-etching primer, irrigated them with water, and air dried them. They placed resin cement into the post spaces using a periodontal probe and onto both types of posts using disposable microbrushes.
Researchers placed each post into the post space by using finger pressure for 10 seconds. They cemented each post by using a custom-made device with a force of 20 newtons for 3 minutes. After conditioning the dentin with a self-etching primer, researchers filled both Class III cavities with light-polymerizing composite resin. They applied a compressive load at a 45-degree angle to the long axis of the tooth on the palatal surface using a universal testing machine to measure failure load.
They determined the mode of failure by means of visual inspection. They observed 2 types of root fractures, including specimens that presented cervical one-third fracture classified as favorable, and specimens that presented middle and apical one-third classified as unfavorable. Researchers found that the control group showed a significantly higher resistance to fracture than the other groups. The other groups showed no significant differences.
Researchers also found that the control group GHT without Class III restorations showed significantly high resistance to fracture. Substance loss, they found, decreased the fracture resistance of endodontically treated teeth (ETT). The amount of substance loss after endodontic treatment is a crucial factor for the prognosis of ETT. Fracture strength for the GCF and GGF groups showed that the presence of prefabricated fiber posts did not improve the fracture resistance of ETT.
The authors reported limitations of their in vitro study, noting that transferring the results directly to a clinical situation would be difficult because simulating all conditions of the oral environment is not possible. They also noted that specimens were stored in water at room temperature without thermal cycling and that only a single load was examined from a single direction.
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What is Specialty Scan?
This is one in a series of quarterly newsletters updating dentists on selected specialties in dentistry. Information presented is aggregated and summarized from previously published materials, each item attributed to its publication of origin. This issue of JADA Specialty Scan focuses on endodontics, the fourth in the series on this topic for 2016. Other specialty scan issues are devoted to oral pathology, oral and maxillofacial radiology, orthodontics, periodontics and prosthodontics. The ADA has engaged the specialty organizations in these areas as well as its own Science Institute and Division of Legal Affairs to assist with these newsletters. We welcome your feedback on this and all specialty scan issues.
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