Yasar Meric Tunca

Bacterial reduction by extensive versus conservative root canal instrumentation in vitro

Objective. This study aimed to test the hypothesis that aggressive dentin removal through greater-tapered instrumentation reduces the intracanal bacteria more effectively than conservative dimension instrumentation. Material and methods. Twenty extracted human lower premolar teeth were used. After extirpation of the pulps, the teeth were autoclaved and immersed in a broth inoculated with Enterococcus faecalis and incubated for 7 days to allow infection of the dentinal tubules. The teeth were divided into 2 experimental groups, each comprising 10 teeth. The teeth were instrumented either with ProTaper or with Hero Shaper nickel-titanium rotary instrumentation techniques. It was calculated that ProTaper theoretically has the potential to remove at least twice the dentin volume compared with Hero Shaper. The apical preparation was standardized to file size 30. Saline solution was used for irrigation. Bacteriological samples were taken before and after instrumentation and plated onto tryptic soy agar, and the reduction in numbers was calculated. Results. Both instrumentation techniques significantly reduced the number of bacteria in the root canal (p<0.05). Reduction in absolute bacterial numbers was up to 98%. There was no statistically significant difference between the two techniques. Conclusions. Preparation with an instrumentation technique removing substantial amounts of dentin did not reduce the intracanal bacteria more effectively than a more conservative instrumentation technique.

Structural effects of sodium hypochlorite solution on RaCe rotary nickel-titanium instruments: an atomic force microscopy study

OBJECTIVE The aim of this study was to investigate the effect of sodium hypochlorite immersion on the surface characteristics of RaCe rotary nickel-titanium instruments using atomic force microscopy (AFM). STUDY DESIGN Four new RaCe instruments were used in this study (two 30.06 and two 30.02). One 30.06 and one 30.02 instrument were immersed in sodium hypochlorite solution for 5 min. Surface topography of the instruments was evaluated using the AFM. The instruments were analyzed on 11 points along a 3-mm section. Root mean square (RMS) values were used to compare the topographic deviations. The data were analyzed using Student t test. RESULTS Mean RMS values for NaOCl measurements were higher than the measurements on new files, and the difference was statistically significant (P < .01). CONCLUSION The AFM results show that NaOCl causes deterioration on the surface of RaCe instruments and should be used with care during clinical use because of the risk of unexpected failure.

Comparison of shaping ability of RaCe and Hero Shaper instruments in simulated curved canals

OBJECTIVE This study compared the shaping ability of Hero Shaper and RaCe instruments in simulated curved canals. STUDY DESIGN Forty simulated canals in resin blocks were divided into 2 experimental groups, each comprising 20 resin blocks, and prepared with Hero Shaper and RaCe using the crown-down technique. Preoperative and postoperative photographs, recorded using a digital camera, were superimposed and aberrations were recorded. Material removal was measured at 10 points beginning 1 mm from the end point of the canal. Mean total widths, outer and inner width measurements, were determined on each central canal path and differences were statistically analyzed using Student t test. RESULTS The Hero Shaper and RaCe instruments removed almost the same amount of material from the inner side of the simulated canals. On the outer canal wall, the RaCe instruments removed significantly more material from the first 3 mm (P < .05). However, Hero Shaper removed more material from the middle and coronal aspects of the canal and the differences were statistically significant (P < .01). CONCLUSION RaCe instruments removed more resin from the outside of the curvature at the apical thirds, while Hero Shaper removed more material from the middle and coronal thirds on the outer canal wall. Hero Shaper instruments showed better centering ability and fewer aberrations. No instrument fractures but some deformations were observed for both systems.

Comparison of cyclic fatigue resistance of used and new RaCe instruments

OBJECTIVE The aim of this study was to evaluate cyclic fatigue resistance of used and new RaCe rotary nickel-titanium instruments. STUDY DESIGN Forty RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) instruments of sizes 30/.06, 30/.02, 25/.04, and 25/.02 were selected and divided into 2 groups: group A = 20 new instruments; group B = 20 used instruments. In group B, each instrument was used for shaping 5 curved molar root canals. Cyclic fatigue testing of new and used instruments was performed using a device that allowed the instruments to rotate freely inside a stainless steel artificial canal. Data were analyzed using t test to determine any statistical significance between used and new instruments of the same file size. RESULTS For all sizes, new instruments were more resistant to failure then the used ones (P < .05). A reduction in lifespan was observed ranging from 18% (30/.06) to 51% (25/.02). CONCLUSION The results showed that clinical use significantly reduced cyclic fatigue resistance of RaCe rotary instruments compared with new ones.

Maintaining Apical Patency Does Not Increase Postoperative Pain in Molars with Necrotic Pulp and Apical Periodontitis: A Randomized Controlled Trial

Introduction: This prospective, single‐center, single‐blind, randomized controlled trial aimed to evaluate whether maintaining apical patency (AP) during endodontic treatment increases postoperative pain in molar teeth with necrotic pulp and apical periodontitis. Methods: Three hundred twenty qualified patients between 21 and 45 years of age were randomized into 1 of 2 groups (the AP group and the nonapical patency [NAP] group) using a series of random numbers in a 1:1 ratio. Qualified patients were selected from patients who had necrotic pulp and apical periodontitis in the maxillary or mandibular molar teeth. The primary outcome was to assess postoperative pain severity, and the secondary outcome was to evaluate analgesic consumption during the 7‐day follow‐up period using the visual analog scale (VAS). The VAS consisted of a 100‐mm line. Pain severity was evaluated as no pain (0–4 mm), mild pain (5–44 mm), moderate pain (45–74 mm), and severe pain (75–100 mm). The Student t test was used to identify statistically significant differences between the study groups (P < .05). Results: The mean VAS scores were significantly lower in the AP group in the first 5 postoperative days (P < .05); after which, it was nonsignificant. In the NAP group, the postoperative pain increased between 12 and 24 hours, whereas the postoperative pain decreased in the AP group during that period. At 12 and 24 hours, the mean VAS scores for the AP group were 42.90 and 37.78 mm, respectively. The mean VAS scores for the NAP group were 64.46 and 65.74 mm, respectively. None of the patients had severe postoperative pain during the follow‐up period. No significant difference was found in analgesic consumption (P > .05) between the groups. Conclusions: The maintenance of AP in molar teeth with necrotic pulp and apical periodontitis was associated with less postoperative pain when compared with NAP.

Does Maintaining Apical Patency during Instrumentation Increase Postoperative Pain or Flare-up Rate after Nonsurgical Root Canal Treatment? A Systematic Review of Randomized Controlled Trials

Introduction: The concept of maintaining apical patency (AP) is a controversial issue in endodontics. The primary objectives of this systematic review of randomized controlled trials (RCTs) were to determine the influence of maintaining AP during instrumentation on postoperative pain severity and the prevalence of flare‐ups. A second objective was to assess the effect of maintaining AP on the use of analgesics. Methods: RCTs and controlled clinical trials were searched for in MEDLINE (Ovid), Embase (Ovid), and the Cochrane Library. Four reviewers independently screened all identified articles for eligibility. The included studies were assessed for bias using the Cochrane Risk of Bias Tool. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the quality of the body of evidence. Because of the considerable heterogeneity of the studies, a meta‐analysis was not possible. Therefore, the results were analyzed narratively. Results: Five RCTs that included a total of 848 patients were found eligible and included in the review. An assessment of the risk of bias in the included studies provided results that classified the studies as showing a low risk (n = 1), high risk (n = 1), or unclear risk (n = 3) of bias. The available evidence indicated that maintaining AP (1) did not increase postoperative pain in teeth with nonvital pulp, (2) did not increase postoperative pain in teeth with vital pulp, and (3) did not cause (0%) flare‐ups. The available evidence also indicated that maintaining AP did not increase analgesic use. The available evidence indicated that maintaining AP did not increase postoperative pain when a single‐visit or 2‐visit root canal treatment approach was used. Conclusions: In light of the current evidence, maintaining AP does not increase postoperative pain in teeth with vital/nonvital pulp when compared with nonapical patency (low to moderate quality evidence). Furthermore, maintaining AP did not cause flare‐ups (low evidence) and did not increase analgesic use (moderate evidence). HIGHLIGHTSMaintaining apical patency does not increase postoperative pain compared with nonapical patency.Maintaining apical patency does not cause a flare‐up.Further studies should focus on the long‐term effects of maintaining apical patency on the healing rates of periapical lesions.