Oval-shaped Root Canals Research Articles

Refinement influence in the cleaning efficacy of rotary nickel-titanium Mtwo instruments in oval-shaped canals by means of optical microscopy.

This study evaluated the cleaning efficacy of the rotary nickel-titanium Mtwo by means of optical microscopy in oval-shaped root canals and compared refinement influence using ultrasonic files or Hedströem files. Twenty mandibular incisors were accessed, included in epoxy resin blocks, and cut transversely at 3, 6, and 9 mm from the apex. Teeth were instrumented using rotary nickel-titanium Mtwo. Digital images of the root cross sections were obtained before and after instrumentation with a digital camera attached to an optical microscope. Subsequently, samples were randomly divided into two groups for refinement. Group I was refined using ultrasonic files #30 and group II with Hedströem files #30. Final digital images of cross sections after refinement were captured and analyzed. The boundaries for the uninstrumented perimeter were measured by the software ImageTool 3.0. The data obtained were statistically analyzed by analysis of variance (ANOVA) and t-test. Mtwo instrumentation produced 41.48% of the uninstrumented perimeter. The final refinement using Hedströem and ultrasonic files decreased the uninstrumented perimeter. Significant differences (t-test, P = 0.00) were found at the three thirds after the final refinement, except for the apical third that was enhanced by Hedströem file. However, there was no statistical difference between the two refinement techniques used (P > 0.05). Mtwo instrumentation was not capable of cleaning and shaping the entire perimeter of the root canals walls. The final refinement, either with ultrasonic files or with Hedströem files, resulted in significantly less uninstrumented perimeter.

Evaluation of the Efficacy of Self-Adjusting File Instrumenton Oval-shaped Root Canals

Purpose;Oval-shaped canals are a challenge when using rotary files because buccal and/or lingual recesses are commonly left uninstrumented. The aim of this study was to evaluate root canal preparation in flat- oval canals treated with ProTaper, Reciproc or self-adjusting file (SAF) instruments. Methodology; 60 mandibular premolars were divided into three groups. After biomechanical preparation, teeth were embedded in acrylic blocks. Roots were then sectioned 4, 8, and 12 mm from the apex using a precise saw, and the cut surfaces in the apical, middle, and coronal thirds were observed under a stereomicroscope at ×40 magnification. Results;The areas of prepared canal walls were significantly higher with the SAF than the ProTaper or Reciproc instruments (p<0.05). The SAF removed the dentin layer from all around the canal, whereas the others left substantial untouched areas. The area in the apical third of the teeth prepared with the Reciproc was significantly higher than with the other techniques, likely due to the high taper of the Reciproc file (p<0.01).Conclusions;In the coronal third, mean increases in the area of the canal were significantly higher with the SAF than with ProTaper or Reciproc. Using the SAF instrument, flat-oval canals were prepared homogenously and circumferentially.

Do oval posts improve fracture resistance of teeth with oval root canals?

To determine whether the use of oval posts increases fracture resistance of root canal treated teeth with oval-shaped canals. Extracted mandibular premolars with similar dimensions were decoronated. After root canal treatment, standardized post space preparations were performed to simulate the presence of oval-shaped root canal morphologies. Specimens were randomly assigned to 3 groups (n = 3 × 24). In group SFP (small fiber post), circular posts with a cervical diameter of 1.5 mm were used without additional form-congruent post space preparation. In group LFP (large fiber post), a circular post space preparation was performed to adapt posts with a cervical diameter of 1.9 mm. In group OFP (oval fiber post), oval posts with a long cervical diameter of 1.9 mm and short cervical diameter of 1.3 mm were utilized without additional post space preparation. Posts were cemented with dual-cure resin. All specimens were restored with standardized direct composite crowns. After thermo-mechanical loading in a computer-controlled masticator, all specimens underwent fracture resistance testing. Means and standard deviations were calculated. Data were analyzed using the Kruskal-Wallis test (α = 0.05). The highest mean fracture load was observed in group OFP (273N ± 51), the lowest in group LFP (258N ± 72). Kruskal-Wallis indicated no significant differences in fracture resistance among the three experimental groups. Within the limitations of this laboratory study, oval posts did not reveal increased fracture resistance of root canal-treated premolars with oval-shaped root canals compared with circular posts.

Micro–computed Tomography Study of Oval-shaped Canals Prepared with the Self-adjusting File, Reciproc, WaveOne, and ProTaper Universal Systems

IntroductionThe newly developed single-file systems claimed to be able to prepare the root canal space with only 1 instrument. The present study was designed to test the null hypothesis that there is no significant difference in the preparation of oval-shaped root canals using single- or multiple-file systems. MethodsSeventy-two single-rooted mandibular canines were matched based on similar morphologic dimensions of the root canal achieved in a micro–computed tomographic evaluation and assigned to 1 of 4 experimental groups (n = 18) according to the preparation technique (ie, Self-Adjusting File [ReDent-Nova, Ra’anana, Israel], WaveOne [Dentsply Maillefer, Ballaigues, Switzerland], Reciproc [VDW, Munich, Germany], and ProTaper Universal [Dentsply Maillefer] systems). Changes in the 2- and 3-dimensional geometric parameters were compared with preoperative values using analysis of variance and the post hoc Tukey test between groups and the paired sample t test within groups (α = 0.05). ResultsPreparation significantly increased the analyzed parameters; the outline of the canals was larger and showed a smooth taper in all groups. Untouched areas occurred mainly on the lingual side of the middle third of the canal. Overall, a comparison between groups revealed that SAF presented the lowest, whereas WaveOne and ProTaper Universal showed the highest mean increase in most of the analyzed parameters (P < .05). ConclusionsAll systems performed similarly in terms of the amount of touched dentin walls. Neither technique was capable of completely preparing the oval-shaped root canals.

A study to compare the efficiency of different instrumentation systems for cleaning oval-shaped root canals (An in vitro study)

Proper cleaning and shaping of the whole root canal space have been recognized as a real challenge, particularly in oval-shaped canals.This in vitro study was conducted to evaluate and compare the efficiency of different instrumentation systems in removing of dentin debris at three thirds of oval-shaped root canals and to compare the percentage of remaining dentin debris among the three thirds for each instrumentation system. Materials and methods: Fifty freshly extracted human mandibular molars with single straight oval-shaped distal root canals were randomly divided into five groups of ten teeth each. Group One: instrumentation with ProTaper Universal hand instruments, Group Two: instrumentation with ProTaper Universal rotary instruments, Group Three: instrumentation with Revo-Srotary instruments, Group Four: instrumentation withTwisted rotary files and Group Five: instrumentation with Self-Adjusting Files (SAF). Sodium hypochlorite (3%) was used as an irrigant for all groups. After canals preparation, the roots were split longitudinally and photographed with a professional digital camera. The images of root sections were then magnified to 100x and the percentage of remaining dentin debris calculated for the apical, middle and coronal thirds by dividing the pixels occupied by debris at each third by the total pixels representing the entire area of the canal using Adobe Photoshop CS6. Data were analyzed statistically by ANOVA and LSD at 1% and 5% significant levels. Results: Both ProTaper hand and ProTaper rotary files resulted in significantly cleaner canals than Revo-S and Twisted rotary files at the middle and coronal thirds. The Self-Adjusting Files produced significantly cleaner canals at the three thirds than all the other groups. The coronal and middle thirds showed a greater amount of remaining dentin debris than the apical third for all groups except a non-significant difference found between the apical and middle thirds in SAF group. Conclusion: The Self-Adjusting Files allowed more efficient cleaning of oval-shaped root canals than hand and rotary instruments.

Cleaning Efficiency of Anatomic Endodontic Technology, ProFile System and Manual Instrumentation in Ovalshaped Root Canals: An in vitro Study

This in vitro study is an attempt to compare the effectiveness in cleaning oval shaped root canals using Anatomic Endodontic Technology (AET®), ProFile system® and Manual Instrumentation with K-files. Sixty oval shaped single rooted maxillary and mandibular premolars with straight canals were divided in to three groups. The root canals were, confirmed as being oval shape by means of radiographs made in a buccolingual and mesiodistal direction. Automated canal preparation was performed using Anatomic Endodontic Technology (group 1) and the ProFile system® (group 2). Manual instrumentation (group 3) was performed with k-files. Irrigation was performed using alternatively 3% NaOCl and 17% EDTA, followed by rinsing with normal saline. The roots were split longitudinally into two halves and examined under a scanning electron microscope. The presence of debris and smear layer was recorded at distances 1, 5 and 10 mm from the working length using a three step scoring scale. Mean scores for debris and smear layer was calculated and statistically analyzed for between and within groups significance, using the Kruskal-Wallis nonparametric ANOVA test and Bonferroni's multiple comparison test. At 1, 5 and 10 mm levels the root canals prepared with AET had significantly less surface debris and smear layer on the canal walls as compared to canals prepared with ProFile system® or manual instrumentation. For all three groups significantly lower mean smear layer scores (p < 0.05) were recorded at 5 and 10 mm levels compared with the 1 mm level. Significantly lower mean debris scores (p < 0.05) were also recorded at 5 and 10 mm levels for the AET group whereas no significant differences were found between the three levels for the ProFile system® and manual instrumentation groups. Although better instrumentation scores were obtained in canals prepared with AET, complete cleanliness was not achieved with any of the techniques and instruments investigated.

Quantitative molecular and culture analyses of bacterial elimination in oval‐shaped root canals by a single‐file instrumentation technique

Bacterial reduction in oval-shaped root canals by a single-instrument technique was compared ex vivo with a conventional nickel-titanium rotary technique. Data obtained from two quantification methods, quantitative real-time polymerase chain reaction (qPCR) and culture, were also compared. Oval-shaped canals of extracted teeth contaminated with Enterococcus faecalis were instrumented using either a single Reciproc instrument or the BioRaCe instrument series. Bacteriological samples were taken before (S1) and after instrumentation (S2). Bacterial quantification was performed using qPCR and culture. Intragroup analysis showed that both protocols promoted a highly significant bacterial reduction (P < 0.001). Intergroup analysis (S2 samples) showed no significant differences between the two instrumentation systems (P > 0.05). As for the quantification methods, qPCR revealed significantly higher counts of E. faecalis in S1 than culture (P < 0.05), but no significant differences occurred for S2 (P > 0.05). The single-file technique was comparable with the conventional technique in oval-shaped canals provided the width of apical preparation, volume of irrigants and duration of irrigation are kept similar. No significant difference was observed for qPCR and culture in post-instrumentation samples, indicating that both methods can be reliably used for studies of antibacterial effectiveness.

Efficacy of irrigation systems on penetration of sodium hypochlorite to working length and to simulated uninstrumented areas in oval shaped root canals

To assess the ability of sodium hypochlorite (NaOCl) to penetrate simulated lateral canals and to reach working length (WL) when using the self-adjusting file (SAF). Seventy single-rooted teeth with oval-shaped canals were used. Upon access, presence of a single canal was confirmed by direct visualization under a dental-operating microscope. Canal length and patency were obtained using a size 10 K-file and root length standardized to 18 mm. Pre-enlargement was restricted to the coronal one-third. The apical size of each canal was gauged at WL and samples larger than size 30 were excluded. Canals were instrumented for 5 min using the SAF system while delivering a total of 20 mL of 5.25% NaOCl and 5 mL of 17% EDTA. Then, the apical diameters were standardized to size 35 using hand files. Four hundred and twenty simulated lateral canals were then created during the clearing process and roots coated with wax to create a closed system. All samples were then cleared and randomly assigned to four experimental groups: 1 (n = 15) positive pressure; 2 (n = 15) SAF without pecking motion; 3 (n = 15) SAF with pecking motion; 4 (n = 15) apical negative pressure (ANP) irrigation and (n = 10) control groups. Samples were scored on the basis of the ability of the contrast solution to reach WL and permeate into the simulated lateral canals to at least 50% of the total length. The Kruskal-Wallis test was used to analyse irrigant penetration and the Tukey test to determine statistical differences between groups (P < 0.05). All samples irrigated with ANP were associated with irrigant penetration to WL (Table 1). The differences between group 4 (ANP) and all other groups were significant in penetration to WL (P < 0.05). The pecking motion allowed for further penetration of the irrigant when using the SAF system but failed to irrigate at WL. None of the experimental groups demonstrated predictable irrigation of simulated lateral canals. In this laboratory model, ANP was the only delivery system capable of irrigating consistently to full WL. None of the systems tested produced complete irrigation in artificial lateral canals.

The Self-Adjusting File Optimizes Debridement Quality in Oval-shaped Root Canals

Introduction Oval-shaped canals represent a challenge for rotary nickel-titanium (NiTi) files because buccal and/or lingual recesses are commonly left uninstrumented. The aim of the present study was to evaluate the debridement quality of the Self-Adjusting File (SAF) system in oval canals and compare it with the debridement achieved by a commonly used NiTi rotary system. Methods A careful specimen selection resulted in two equal groups each consisting of 12 extracted mandibular canines with oval canals that had vital pulps before extraction. All canals had a buccolingual diameter that was at least 2.5 times larger than that of the mesiodistal one as defined from radiographs. One group was subjected to the SAF protocol, whereas the other group underwent conventional protocol; the ProTaper system up to the F2 instrument was used with syringe and open end needle irrigation. Sodium hypochlorite (5.25%) was used as an irrigant for both groups. The roots were then histologically processed and 0.6-μm-thick cross-sections were obtained every 0.5 mm from the 1- to 5-mm apical levels. Morphometric evaluation was performed on cross-sections to determine the amount of remaining pulp tissue as a percent of the root canal area. Results The group-by-location interaction was not significant ( P > .05), which means that the group comparisons were not dependent on the cross-sectional level. There was significantly greater residual pulp tissue left after ProTaper system instrumentation versus SAF instrumentation (21.4% vs 9.3%, P < .05). Conclusions The SAF protocol was significantly more efficient for debridement of oval root canals than the rotary ProTaper protocol.

Micro–computed Tomography Evaluation of the Preparation of Long Oval Root Canals in Mandibular Molars with the Self-adjusting File

Introduction The aim of this study was to assess the shaping potential of a novel nickel-titanium instrument, the self-adjusting file (SAF), in long oval root canals in distal roots in mandibular molars. Methods Twenty mandibular molars with long oval distal root canals were selected and scanned preoperatively and postoperatively by using micro–computed tomography at an original resolution of 20 μm. Canals were shaped with the SAF, three-dimensionally reconstructed, and evaluated for volume, surface area, canal transportation, and prepared surface. Data were statistically contrasted by using paired t tests and regression analysis. Results Preoperatively, canal volume was 7.73 ± 2.13 mm 3, and canal area was 42.83 ± 8.14 mm 2. Volumes and surface areas increased significantly ( P < .001) by 4.84 ± 1.73 mm 3 and 3.34 ± 1.73 mm 2, respectively, and no gross preparation errors were detected. Unprepared canal surface varied between individual canals, and mean unprepared surface was 23.5% ± 8.9%. Prepared areas were significantly larger compared with rotary canal preparation done in a previous study. Canal transportation scores were higher in the coronal root canal third (106 ± 50 μm) compared with the apical third (81 ± 49 μm). Conclusions In vitro, preparation of long oval-shaped root canals in mandibular molars with the SAF was effective and safe. Moreover, shapes generated with the SAF were more complete compared with rotary canal preparation.

Disinfecting Oval-shaped Root Canals: Effectiveness of Different Supplementary Approaches

Introduction This study compared the ability of different approaches to supplement the antibacterial effects of chemomechanical preparation in oval-shaped root canals. Methods Long oval canals from extracted teeth infected with Enterococcus faecalis (ATCC 29212) were chemomechanically prepared up to a 40/04 rotary BioRaCe instrument using 2.5% NaOCl irrigation and then subjected to two supplementary protocols. In the passive ultrasonic irrigation (PUI)/chlorhexidine (CHX) group, canals were subjected to PUI for the activation of NaOCl followed by a final rinse with 0.2% CHX digluconate solution. In the Hedström group, canals received additional Hedström filing directed towards the buccal and lingual canal recesses. Bacteriological samples were taken before and after preparation, after PUI or Hedström instrumentation, and after CHX final rinsing. Results Chemomechanical preparation and the supplementary steps promoted a highly significant bacterial reduction ( P < .001). Quantitative (reduction in levels) and qualitative (frequency of negative cultures) analyses showed that PUI alone or Hedström filing did not significantly increase bacterial reduction ( P > .05). Further rinsing with CHX also failed to significantly increase bacterial elimination when compared with post-PUI samples. However, the cumulative antibacterial effects of PUI and CHX final rinse were effective in significantly reducing bacterial counts to levels below those achieved after preparation ( P = .03). This combined PUI/CHX approach also resulted in a significant increase in the incidence of negative cultures ( P = .04). Conclusions Findings suggest that there may be a benefit of using the PUI for the activation of NaOCl followed by a final rinse with CHX as supplementary steps in the treatment of infected oval-shaped root canals.

Suboptimal Debridement Quality Produced by the Single-file F2 Protaper Technique in Oval-shaped Canals

Introduction The aim of this study was to determine whether the debridement quality of the single-file F2 ProTaper instrumentation technique is comparable to a full conventional ProTaper sequence in both round and oval-shaped root canals. Methods Fifty-four recently extracted vital lower incisors were instrumented with either a full range of ProTaper Universal instruments in rotary motion (group 1) or with the single-file F2 ProTaper technique in reciprocating motion (group 2). Teeth were previously classified as round or oval-shaped by means of bidirectional radiographs, resulting in 24 round canals, 24 oval canals, and 12 controls. After instrumentation, the roots were demineralized, and the apical 3 mm was multi-sliced and processed for histologic examination. The percentage of residual pulp tissue (PRPT) was calculated with the aid of image analysis software. Univariate analysis of variance was used to verify the variables influencing PRPT. Results Both canal shape and technique significantly influenced PRPT ( P < .05). Oval-shaped canals displayed much more PRPT than round canals in both techniques ( P < .05). The difference in PRPT between the techniques depended on the root canal shape, since a significant interaction between canal shape and technique was observed ( P < .05). Group 1 displayed considerably less PRPT in oval canals than group 2 ( P < .05), whereas in round canals no significant difference was found between the 2 techniques ( P > .05). Conclusions The single-file F2 ProTaper technique displayed similar PRPT to the full range of ProTaper instruments in round canals. However, the debridement quality of the single-file F2 ProTaper technique was suboptimal in oval canals.

Ability of Chemomechanical Preparation with Either Rotary Instruments or Self-adjusting File to Disinfect Oval-shaped Root Canals

Introduction Oval-shaped root canals might represent a great challenge for proper disinfection. This study compared the capability of a newly developed instrument, the self-adjusting file (SAF), and rotary nickel-titanium (NiTi) instrumentation to eliminate Enterococcus faecalis populations from long oval root canals of extracted human teeth. As a secondary purpose, the ability of a modification in sampling technique to recover bacteria lodged in recesses of oval canals was evaluated. Methods Long oval canals from mandibular incisors and maxillary second premolars were infected with E. faecalis (ATCC 29212) for 30 days and then randomly distributed into 2 experimental groups. In group 1, canals were prepared up to a 40/04 rotary BioRaCe instrument by using irrigation with NaviTip needles; in group 2, canals were prepared by using the SAF system with continuous irrigation. NaOCl and ethylenediaminetetraacetic acid were used as irrigants. Bacteriologic samples were taken before (S1) and after preparation (S2a and S2b). Results Reduction in the bacterial populations was highly significant in both groups ( P < .001). Preparation of long oval canals with the SAF was significantly more effective than rotary NiTi instrumentation in reducing intracanal E. faecalis counts ( P = .01). Frequency of positive cultures in S2 samples was 11 of 20 (55%) for rotary instrumentation and 4 of 20 (20%) for SAF instrumentation ( P = .048). S2b samples (modified method) yielded more positive samples than S2a (12/40 vs 5/40), but this difference reached no statistical significance ( P > .05). Conclusions The SAF system was significantly more effective than rotary NiTi instrumentation used with syringe/needle irrigation in disinfecting long oval root canals in vitro. A modified sampling technique might be necessary for oval canals.

Preparation of Oval-shaped Root Canals in Mandibular Molars Using Nickel-Titanium Rotary Instruments: A Micro-computed Tomography Study

IntroductionThis study evaluated the prepared surface areas of oval-shaped canals in distal roots of mandibular molars using four different instrumentation techniques. MethodsTeeth were prescanned and reconstructed using micro–computed tomography (MCT) scans at low resolution (68 μm). Forty-eight molars with ribbon-shaped/oval distal root canals were selected and randomly assigned to four groups. Distal canals (n = 12 each) were prepared by circumferential filing using Hedström files to apical size #40 (group H/CF); with ProTaper nickel-titanium rotaries to finishing file 4 (F4) considering the distal canal as 1 canal (group PT/1); ProTaper to F4 considering buccal and oral aspects of the distal canal as 2 individual canals (group PT/2); ProTaper to F4 in a circumferential filing motion (PT/CF). Before and after shaping, teeth were evaluated using MCT at 34-μm resolution. The percentage of prepared surface was assessed for the full canal length and the apical 4 mm. Statistical analysis was performed using analysis of variance and Bonferroni/Dunn multiple comparisons. ResultsPreoperatively, canal anatomy was statistically similar among the groups (p = 0.56). Mean (± standard deviation) untreated areas ranged from 59.6% (±14.9, group PT/2) to 79.9% (±10.3, PT/1) for the total canal length and 65.2% to 74.7% for the apical canal portion, respectively. Canals in group PT/1 had greater untreated surface areas (p < 0.01) than groups PT/2 and PT/CF. Among all groups, amounts of treated surface areas were statistically similar in the apical 4 mm. ConclusionsPreparations of oval-shaped root canals in mandibular molars left a variable portion of surface area unprepared regardless of the instrumentation technique used. However, considering oval canals as two separate entities during preparation appeared to be beneficial in increasing overall prepared surface.

Comparison of Three Techniques for Preparing Oval-shaped Root Canals

Introduction This study compared three techniques for preparing oval-shaped root canals: Anatomic Endodontic Technology (AET), hand instruments (Hedström files; Dentsply Maillefer, Ballaigues, Switzerland), and rotary nickel-titanium (EndoWave; Morita, Osaka, Japan) instruments with regard to cleaning ability and final canal shape. Methods Three groups each of 13 extracted human mandibular premolars with oval-shaped canals were used. After canal preparation, teeth were sectioned at three levels (coronal, middle, and apical), photographed to assess cross-sectional canal shape, and processed for histologic evaluation of canal wall planing and the presence of debris. Results None of the techniques resulted in completely prepared and cleaned canals. No significant difference was found among the three techniques with regard to untouched surface, cross-sectional area, remaining fins, and canal shape at the three levels. Rotary NiTi instruments resulted in significantly less debris in the apical third compared with AET and hand instrumentation. Conclusions AET did not perform better than rotary NiTi or hand instruments in oval-shaped canals.

A comparison of techniques for obturating oval-shaped root canals

This study compared the effectiveness of three obturation techniques for oval-shaped canals. Roots of 42 extracted teeth with oval canals were randomly divided into three groups: (1) ProTaper canal preparation and single cone obturation with matching gutta-percha point; (2) ProTaper preparation plus thermoplastic obturation (Thermafil); (3) Profile .06 taper and matching master cone with lateral condensation. Cross-sectional area of the canal space occupied by sealer cement and gutta-percha was measured in the coronal, middle, and apical thirds using an image analysis software. The percentage of the cross-sectional shape occupied by sealer cement was calculated. The Thermafil group was significantly lower than the single cone group or the lateral condensation group in the middle third (p<0.01) and lower than the single cone group in the coronal third (p<0.05). There were no significant differences between the single cone obturation group and the lateral condensation group in each level.

Limited Ability of Three Commonly Used Thermoplasticized Gutta-Percha Techniques in Filling Oval-shaped Canals

The present study was designed to compare the percentage of gutta-percha–filled area (PGFA) achieved in oval-shaped canals after filling by 3 thermoplasticized techniques. Eighty-seven oval-shaped root canals were prepared and root-filled as follows: lateral condensation (n = 20), thermomechanical compaction (n = 20), wave of condensation (n = 20), and Thermafil system (n = 20). A cross section of each tooth was made 5 mm from the apex, and the samples were prepared for microscopic analysis. Digital image measurements of the cross-sectioned area of the canal and the gutta-percha were performed, and the PGFA was calculated. Nonparametric statistical analysis was performed with the Kruskal-Wallis H test and post hoc Dunn test. Overall, PGFAs were variable among the experimental groups, ranging from 37.1%–98.5%, and the pooled data from all techniques had a general mean of 69.6% ± 18%. Thermafil system, wave of condensation, and thermomechanical compaction produced significantly higher PGFAs than lateral condensation (P < .05); however, no significant differences among these techniques were detected (P > .05). Therefore, a limited ability to fill oval-shaped canals was achieved in the 3 thermoplasticized techniques tested.

The effect of the canal‐filled area on the bacterial leakage of oval‐shaped canals

To compare the sealing ability and the canal-filled area (gutta-percha + sealer) of three current filling techniques in oval-shaped canals. A total of 50 oval-shaped root canals were prepared and root filled as follows: G1: lateral condensation (n = 10), G2: System B (n = 10) and G3: Thermafil system (n = 10). All teeth were mounted in a two-chamber apparatus and the coronal access was exposed to human saliva. The appearance of turbidity in the BHI broth over a 15-week period was observed. A cross section of each tooth was made 5 mm from the apex and the samples were prepared for microscopic analysis. Digital image measurements of the cross-sectional area and the area filled by gutta-percha and sealer were performed. Log-rank and Fisher's exact tests were used to analyse the leakage data. Student's t-test was used to analyse the filled-area data. Overall, 30% of the specimens of G1 and G2 and 20% of G3 demonstrated leakage after 15 weeks and no significant difference was found amongst the groups (P > 0.05). The percentage of canal-filled area was 68, 70 and 78%, respectively (P > 0.05). The correlation analysis revealed no significant relation between the pattern of bacterial leakage and canal-filled area (P = 0.128). No significant difference in apical sealing and canal-filled area in oval-shaped canals was seen between the three filling techniques. No significant correlation was found between the quality of the apical seal and the filled-area of the root canal space.

Retreatment efficacy of hand versus automated instrumentation in oval‐shaped root canals: an ex vivo study

To compare the efficacy of hand versus automated instrumentation when retreating oval-shaped root canals. Sixty human premolars with single oval canals were instrumented and filled with gutta-percha and sealer and divided into three groups (n = 20)--group 1: ProFile .04 taper rotary instruments; group 2: Anatomic Endodontic Technology (AET), and group 3: manual instrumentation with Hedström files. The teeth were split longitudinally and gutta-percha/sealer remnants in the coronal, middle and apical thirds were assessed with light microscopy. The mean percentage of gutta-percha/sealer remnants for each group was calculated and statistically analysed for significance using an ANOVA repeated measures (P < 0.001) and Tukey's multiple comparison test. The time required for retreatment was analysed using a one-way ANOVA and Tukey's test (P < 0.001). Overall, 10-18% of the canal walls were covered with gutta-percha/sealer remnants after preparation using any technique. Statistical analysis demonstrated that the mean values for remnants of filling material in the ProFile group were significantly higher than for the other groups (P < 0.001), except in the apical third where no significant difference occurred. In all groups, the mean values in the middle third were higher than the coronal and apical thirds. The retreatment time for ProFile and AET was significantly shorter compared to manual instrumentation with Hedström files (P < 0.001). Under the experimental conditions, AET instruments and manual instrumentation with Hedström files resulted in cleaner canals. However, completely clean root canal walls were not produced with any of the techniques investigated.

Cross-sectional analysis of root canals prepared with NiTi rotary instruments and stainless steel reciprocating files

To determine whether the shaping of oval-shaped root canals using 2 different preparation techniques resulted in significant morphologic differences. Forty lower premolars with oval-shaped root canals were divided into group A, instrumented with the Anatomic Endodontic Technology (AET) system, and group B, treated with ProTaper instruments. A modified Bramante technique was used to analyze changes in root canal diameters (DeltaD), changes in surface area (DeltaA), and the change in buccolingual and mesiodistal ratio (DeltaR). The data were subjected to a Student t test at a significance level of P < 0.05. Statistically significant differences were found between the 2 groups at coronal and middle levels. There was no statistically significant difference at the apical level. The 2 techniques produced a significant difference in the ultimate shape of the coronal and middle portions of oval-shaped root canals, with the AET system removing more tooth structure at these levels. However, no differences were observed at the apical third.