根管超声冲洗效果的扫描电镜研究

目的用扫描电镜的方法评价根管超声冲洗的效果。方法选择直单根管前磨牙20颗，随机分为超声冲洗组（U组）和注射器冲洗组（S组）。用逐步后退法预备根管后，2组选用不同方法，均用40ml2．5g／L NaOCI最后冲洗根管。样本去冠后沿牙长轴纵向劈开，扫描电镜观察，记录电镜照片上牙本小管开口的数目并对均数进行统计学分析。结果U组牙本质小管开口数明显多于S组（P〈0．05）；2组相应部位比较，颈1／3处牙本质小管开口数之间的差异无统计学意义（P〉0．05），U组在根中1／3和根尖1／3的牙本质小管开口数数明显多于S组（P〈0．05）。结论用2．5g／L NaOCl超声根管冲洗效果优于用注射器冲洗。     

复方冰硼冲洗液用于根管冲洗的清洁性实验研究

目的：评价复方冰硼冲洗液用于根管冲洗的清洁性。方法：收集40个新鲜拔除的单根管前磨牙,随机分为4组,每组10个。采用不锈钢K锉和逐步深入预备技术预备根管,分别使用4组冲洗液进行根管冲洗。Ⅰ组为5mL复方冰硼冲洗液;Ⅱ组为2.5mL 5.25%次氯酸钠溶液（NaOCl）＋2.5mL 17%乙二胺四乙酸溶液（EDTA）;Ⅲ组为2.5mL 3%双氧水＋2.5mL 0.9%生理盐水;Ⅳ组为5mL 0.9%生理盐水。最后用3mL生理盐水冲洗根管。采用数码照相机照相和扫描电镜观察,分别比较根尖1/3区和根中1/3区根管内的碎屑百分数和牙本质小管开口数。结果：在根尖1/3区,Ⅳ组碎屑百分数明显高于其他3组,Ⅳ组牙本质小管开口数明显少于其他3组（P〈0.05）。在根中1/3区,Ⅳ组的碎屑百分数明显高于Ⅱ组,Ⅰ、Ⅱ组牙本质小管开口数明显多于Ⅲ、Ⅳ组（P〈0.05）。结论：Ⅰ、Ⅱ、Ⅲ组的根管冲洗效果好于Ⅳ组,冲洗液的化学特性非常重要。冲洗液的清洁性排序为：NaOCl组、复方冰硼冲洗液组、双氧水组、生理盐水组。复方冰硼冲洗液被认为是可能用于根管冲洗的中药冲洗液。     

Effect of endodontic irrigation on bonding of resin cement to radicular dentin

The influence of endodontic irrigation on shear bond strengths of resin cement to radicular dentin was investigated. Human radicular dentin blocks were divided into four groups and subjected to one of four endodontic irrigations: ethylenediaminetetraacetic acid (EDTA) group, 17% EDTA for 60 s; EDTA/sodium hypochlorite (NaOCl) group, 17% EDTA for 60 s followed by 10 ml of 5% NaOCl for 15 s; NaOCl group, 10 ml of 5% NaOCl for 15 s; and control group, no treatment. Morphological changes of dentin surface after endodontic irrigation were observed by scanning electron microscopy (SEM). A resin block was bonded to the radicular dentin after irrigation using resin cement with either wet-bonding (Uni-Etch/One-Step; Bisco) or self-etching (Tyrian SPE/One-Step Plus; Bisco) adhesives. Shear bond strengths were measured and the penetration of resin tags into dentinal tubules at resin-dentin interface was observed by SEM. With the wet-bonding system, the shear bond strengths for the EDTA/NaOCl group, in which dentinal tubules openings and uniform resin tag penetration into dentinal tubules were observed, were significantly higher than the EDTA and control groups. With the self-etching system, the shear bond strengths were significantly lower in the EDTA group compared with the NaOCl and control groups. The effects of endodontic irrigation on the bonding of resin cement to radicular dentin depended on the dentin bonding system used.     

XP-endo Finisher锉对根管内壁玷污层清除效果的体外研究

目的 评估XP-endo Finisher（XPF）锉与被动超声冲洗（PUI）对根管内壁玷污层的清除效果。方法 选择60颗离体单直根管下颌前磨牙,距根尖16 mm处截冠,采用S3镍钛锉预备到3S,根据终末处理方式不同将样本随机分成6组。A组：3 mL 3%次氯酸钠溶液联合XPF处理1 min;B组：3 mL 3%次氯酸钠溶液联合XPF处理1 min,再用4 mL 17%乙二胺四乙酸（EDTA）溶液冲洗1 min;C组：3 mL 3%次氯酸钠溶液联合PUI处理1 min;D组：3 mL 3%次氯酸钠溶液联合PUI处理1 min,再用4 mL 17%EDTA溶液冲洗1 min;E组：3 mL 3%次氯酸钠溶液30号侧方冲洗针冲洗1 min;F组：3 mL 3%次氯酸钠溶液30号侧方冲洗针冲洗1 min,再用4 mL 17%EDTA溶液冲洗1 min。采用扫描电子显微镜观察玷污层形态,并比较根尖1/3区、根中1/3区牙本质小管开口数。结果 A、C、E组实验样本整个根管壁都有玷污层覆盖,A组与C组牙本质小管开口数明显高于E组（P<0.05）,而A组与C组的差异无统计学意义（P>0.05）;F组根中区、B组和D组根尖区有少量玷污层覆盖,牙本质小管开放或半开放;F组根尖区可见玷污层,牙本质小管封闭或半封闭;B和D组根中区根管壁玷污层均被有效去除;在根尖1/3区和根中1/3区,B组与D组牙本质小管开口数高于其他4组（P<0.05）,而B组和D组间的差异无统计学意义（P>0.05）。结论 XPF锉对根管内壁玷污层的清洁效果与PUI无明显差异,可用于根管预备后提高根管清洁效果。     

三种超声仪根管冲洗效果的比较

目的:比较Odontoson-M,P-MAX和Spartan3种超声仪根管冲洗的效果。方法:选择完整离体单直根管前磨牙,采用不锈钢K锉和逐步深入技术根管预备后超声冲洗。冲洗后纵向劈开标本,采用数码照相机照相和扫描电镜观察,分别计算比较根管内碎屑百分数及牙本质小管开口数。结果:以5g/L次氯酸钠为冲洗液时,Odontoson-M超声仪在根管中1/3区的碎屑百分数明显低于其他2种超声仪(P<0.05),管壁牙本质小管的开口数明显多于其他2种超声仪(P<0.05)。结论:在实验条件下,Odontoson-M超声仪根管冲洗效果可能好于其他2种超声仪。     

不同浓度次氯酸钠根管超声冲洗的实验研究

目的：比较不同浓度次氯酸钠溶液的根管冲洗效果。方法：选择根尖发育完成的单、直根管前磨牙50颗,随机分为5组,每组10颗。不锈钢K锉和逐步深入技术根管预备后,分别使用蒸馏水,0．5％、1％、2％或5．25％次氯酸钠进行根管超声冲洗。采用数码照相机照相和扫描电镜观察,分别比较根尖1／3区和根中1／3区根管内的碎屑百分数和牙本质小管开口数。结果：蒸馏水组在根尖和根中1／3区的碎屑百分数明显高于其他4组,牙本质小管开口数明显少于其他4组;去除蒸馏水组后,0．5％次氯酸钠组在根中1／3区的碎屑百分数明显高于其他3组,牙本质小管开口数明显少于其他3组。结论：4种不同浓度次氯酸钠溶液的根管冲洗效果均好于蒸馏水;0．5％次氯酸钠根管冲洗的效果比其他3种较高浓度的次氯酸钠差。     

In vitro evaluation of endodontic debris removal as obtained by rotary instrumentation coupled with ultrasonic irrigation

The cleaning capacity of rotary Ni-Ti instrumentation using Profile GT files, coupled with irrigation energised by ultrasound, was evaluated. Thirty-six human mandibular incisors were instrumented in vitro using the crown-down technique with the Profile GT system to 1 mm from the anatomical apex to a size 30.04 taper file. The instrumented teeth were then divided randomly into four groups where various final irrigations were used: Group I: 100 ml of 1% NaOCl with a Luer-Lok syringe (control group); Group II, Group III and Group IV: final irrigation with 100 ml of 1% NaOCl energised by ultrasound for 1, 3 and 5 min, respectively. After biomechanical preparation, the apical thirds of the roots were submitted to histological processing and examination. The specimens were analysed at 40x magnification and the images submitted to morphometric analysis with an integration grid. anova showed a statistically significant difference (P < 0.01) between the irrigation techniques. Group I (Luer-Lok syringe) showed the highest percentage of debris (35.81 +/- 4.49) and was statistically different from the other groups energised by ultrasound: Group II (27.28 +/- 4.49), Group III (24.39 +/- 5.72) and Group IV (18.46 +/- 5.25). It was concluded that rotary instrumentation using Ni-Ti files associated with final irrigation of 1% NaOCl energised by ultrasound leads to better debris removal from the apical third of mesio-distally flattened root canal.     

A scanning electron microscopic study of dentinal erosion by final irrigation with EDTA and NaOCl solutions

AIM: The purpose of this in vitro study was to examine dentinal erosion caused by final irrigation with EDTA and NaOCl. METHODOLOGY: Twenty-five single-rooted human teeth were instrumented with rotary nickel-titanium Series 29 Profile Instruments. The teeth were divided into five groups and subjected to final irrigation as follows: group A, irrigated with 6% NaOCl (3 mL) for 2 min; group B, 15% EDTA (3 mL) for 1 min; group C, 15% EDTA (3 mL) for 1 min, followed by 6% NaOCl (3 mL) for 2 min; group D, 15% EDTA (3 mL) for 3 min and group E, 15% EDTA (3 mL) for 3 min, followed by 6% NaOCl (3 mL) for 2 min. Photomicrographs of dentinal walls were produced using a scanning electron microscope (3000 x) at 1, 3 and 6 mm from the apex. The amount of debris and dentinal tubule diameter were evaluated, and values were statistically analysed using one-way ANOVA and Fisher's PLSD test. RESULTS: When the root canal was irrigated with 15% EDTA alone, the dentine had a smooth and plane appearance, and dentinal tubule orifices were regular and separated. When the root canal was irrigated with EDTA followed by NaOCL the dentine was eroded and the dentinal tubule orifices were irregular and rough. Dentinal tubule diameter increased to 3.43 +/- 0.23 microm in group C and to 3.93 +/- 0.44 microm in group E. Significant differences were observed between groups B and C, and between groups D and E (P < 0.05). However, more debris was removed by irrigation with EDTA followed by NaOCl than with EDTA alone (P < 0.05). CONCLUSIONS: Final irrigation with 6% NaOCl accelerates dentinal erosion following treatment with 15% EDTA.     

Effect of three different time periods of irrigation with EDTA-T, EDTA, and citric acid on smear layer removal

OBJECTIVE: An in vitro study was conducted to evaluate the effect of EDTA-T, 17% EDTA, and 10% citric acid on the removal of smear layer from root canal dentin after final irrigation for 3, 10, and 15 min. STUDY DESIGN: Root canals of 90 extracted human canines were divided into 9 groups of 10 teeth; each group received a final irrigation with one of the irrigants for the established time intervals. After irrigation, the teeth were split and prepared for SEM analysis to determine the number of open dentinal tubules. RESULTS: There were statistically significant better results (P <.05) when irrigation with 10% citric acid for 3 min was compared to 10 and 15 min, and when irrigation with EDTA for 3 min was compared to 15 min. In all cases, irrigation for 3 min presented the greatest number of open dentinal tubules. There were no significant differences (P>.05) for the 3 time intervals of irrigation for EDTA-T, although there were a greater number of open tubules at 3 min. CONCLUSION: These 3 irrigants were effective at the shortest time tested and did not demonstrate an improved effect with an increase in time.     

二氧化氯作为根管超声冲洗剂的清洁效果

目的 评价二氧化氯用作根管超声冲洗剂的清洁效果.方法 选择30颗离体单根管前磨牙,截去牙冠后随机平分成A、B、C三组,用手持不锈钢器械逐步后退法进行根管预备,超声波冲洗,冲洗剂分别为蒸馏水、1.0%次氯酸钠和0.1%二氧化氯溶液.完成根管预备后纵行劈开牙根,扫描电镜观察,在根管颈1/3、中1/3、尖1/3各部位随机拍照,在电镜照片上评定根管壁上碎屑和玷污层记分,计数牙本质小管开放数目,并进行统计学分析.结果 A、B、C各组碎屑记分差异无统计学意义(P＞0.05);B、C两组的玷污层明显少于A组,差异有统计学意义(P＜0.01);牙本质小管开放数也明显多于A组,差异有统计学意义(P＜0.01),但B、C两组之间差异无统计学意义(P＞0.05).结论 0.1%二氧化氯溶液用作根管超声冲洗剂,具有良好的清洁作用,对碎屑和玷污层的去除能力不亚于1.0%次氯酸钠,明显优于蒸馏水.     

Penetration depth of a dye marker into dentine using a novel hydrodynamic system (RinsEndo)

AIM: To investigate the efficiency of a hydrodynamic irrigation system compared with conventional cleansing techniques in root canals. METHODOLOGY: Forty-five freshly extracted single-rooted teeth were de-coronated and their root canals were enlarged to size 30 at the apex. The teeth were randomly divided into three groups (n = 15) for the final rinsing sequence using 2% NaOCl plus acid fuchsin: group I: static application of irrigant, 3 min; group II: flushing with a syringe; 5-mL NaOCl, 1 min; group III: RinsEndo-system; 5-mL NaOCl, 50 s. Apical extrusion was documented photographically. The roots were sectioned at 2, 4, 6 and 8 mm from their apices and the penetration depths of dye into dentine measured, using a stereomicroscope. Wilcoxon's test and Pearson's chi-squared test were employed to prove statistic relevance. RESULTS: Greater dye penetration depth into the dentinal tubules was achieved when employing hydrodynamic rinsing procedures. Using this technique, 23% of the specimens were penetrated for more than 50% of their dentine thickness, whereas the results for flushing with a syringe were 12% (static application, 7%). No penetration of dentine occurred in 63% of specimens with static application, 39% flushing with a syringe and 15% using the hydrodynamic system (P < 0.05 Pearson's chi-squared test). Apical extrusion occurred more frequently after hydrodynamic rinsing (extruded specimens: RinsEndo = 80%; static application/flushing with a syringe = 13%; P < 0.05 Pearson's chi-squared test). CONCLUSIONS: Hydrodynamic rinsing demonstrated an improvement over conventional methods in terms of dentine penetration of a dye marker. A higher risk of apical extrusion with the RinsEndo-system was evident.     

5种冲洗剂组合对前牙直根管清洁效果的比较

目的：比较5种冲洗剂组合对前牙直根管的清洁效果。方法：25颗离体直根管前牙,随机分为5组,不锈钢K锉常规法预备根管．应用5种冲洗剂组合进行冲洗。第1组：根管器械预备期间和预备结束后依次用1％NaOCl和3％H2O2冲洗;第2组：根管器械预备期间用1％NaOCl冲洗,预备结束后用17％EDTA冲洗;第3组：根管器械预备期间和预备结束后依次用1％NaOCl和17％EDTA冲洗：第4组：根管器械预备期间依次用17％EDTA和1％NaOCl冲洗,器械预备结束后用17％EDTA冲洗;第5组：根管器械预备期间依次用17％EDTA、1％Triton X-100(表面活性剂)和1％NaOCl冲洗．器械预备结束后用17％EDTA冲洗。每组冲洗剂剂量和冲洗时间均为22ml和7min。将牙纵劈后进行扫描电镜观察。结果：第1组,根管壁上见典型玷污层结构和大量杂质和残屑。第2组在根管冠、中1／3能部分去除玷污层．根尖1／3残留大量玷污层。第3组虽然能有效去除玷污层．但会引起牙本质小管中度腐蚀。第5组在根管冠、中1／3能部分去除玷污层,但根管壁上黏着大量杂质和残屑．此外还存在重度腐蚀现象。第4组根管清洁效果最好,且对牙本质小管无腐蚀性。结论：在严格控制冲洗时间和顺序的情况下,联合应用17％EDTA和1％NaOCl能有效去除玷污层．且不会腐蚀牙本质小管。     

Sodium hypochlorite penetration into dentinal tubules after manual dynamic agitation and ultrasonic activation: a histochemical evaluation

The aim of this study was to compare the effects of Manual Dynamic Agitation and Passive Ultrasonic Irrigation on sodium hypochlorite (NaOCl) penetration into dentinal tubules using its bleaching ability. Thirty-four single-rooted teeth with round-shaped root canals were distributed in two homogeneous groups and one control group, characterized by different NaOCl activation systems: Manual Dynamic Agitation and Passive Ultrasonic Irrigation. After instrumentation, all root canals were stained with 10% copper sulphate solution followed by 1% rubeanic acid alcohol solution under vacuum. Final irrigation was performed with 5 mL of 5.25% NaOCl solution for 1 min and activated with Manual Dynamic Agitation or Passive Ultrasonic Irrigation for another 1 min depending on the treatment group. The teeth were transversely sectioned at the middle portion of the apical, middle, and coronal thirds and observed under light microscope. NaOCl solution penetration was evaluated by measuring the percentage of bleached circumference of the root canal relative to the stained circumference, bleached areas, mean, and maximum penetration depth. No differences in the evaluated parameters were observed between groups (p?>?0.05). Within groups, an increase of values was recorded from apical to coronal direction as for percentage of staining, percentage of bleaching and bleached area. NaOCl penetration into dentinal tubules did not significantly vary among the three levels. No significant differences in penetration of sodium hypochlorite into dentinal tubules when activated by means of Manual Dynamic Agitation or Passive Ultrasonic Irrigation were observed in the apical, middle, and coronal thirds of teeth with single straight round root canals.     

Efficacy of various concentrations of NaOCl and instrumentation techniques in reducing Enterococcus faecalis within root canals and dentinal tubules

AIM: To evaluate the efficacy of 0.5%, 2.5% and 5.25% sodium hypochlorite (NaOCl) as intracanal irrigants associated with hand and rotary instrumentation techniques against Enterococcus faecalis within root canals and dentinal tubules. METHODOLOGY: A total of 180 extracted human premolar teeth were infected for 21 days with E. faecalis. The specimens were divided into 12 groups, as follows: group 1: 5.25% NaOCl + Hybrid technique (Valdrighi et al. 1998); group 2: 5.25% NaOCl + nickel-titanium (NiTi) rotary technique 4 mm shorter than the apex (by FOP-UNICAMP); group 3: 5, 25% NaOCl + NiTi rotary technique (Hero 642); group 4: 2.5% NaOCl +Hybrid technique; group 5: 2.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 6: 2.5% NaOCl + NiTi rotary technique (Hero 642); group 7: 0.5% NaOCl + Hybrid technique; group 8: 0.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 9: 0.5% NaOCl + NiTi rotary technique (Hero 642); group 10: sterile saline solution + Hybrid technique; group 11: sterile saline solution + NiTi rotary technique 4 mm shorter than the apex; group 12: sterile saline solution + NiTi rotary technique (Hero 642). Canals were sampled before and after preparation. After serial dilution, samples were plated onto brain heart infusion (BHI) agar, and the colony forming units (CFU) that were grown were counted. The teeth were sectioned into three thirds and dentine chips were removed from the canals with conical burs. The samples obtained with each bur were immediately collected into test tubes containing BHI broth, and were incubated at 37 degrees C and plated onto BHI agar. The CFU were counted and analysed. RESULTS: At all depths and thirds of the root canals and for all techniques used, 5.25% NaOCl was shown to be the most effective irrigant solution tested when dentinal tubules were analysed, followed by 2.5% NaOCl. No differences among concentrations in cleaning the canals were found. CONCLUSIONS: Especially at higher concentrations, NaOCl, was able to disinfect the dentinal tubules, independent of the canal preparation technique used.     

The effect of dentinal tubule orientation on the removal of smear layer by root canal Irrigants

Summary. Fifteen anterior teeth and 15 artificial canals obtained from five molar teeth were used in this study. The artificial and natural canals were instrumented with K-files and then divided into three groups. The first group was irrigated with 20 ml saline, the second with 20 ml EDTA, and the third with 10ml EDTA followed by 10ml NaOCl solution. Following this experimental procedure, all canals were split and examined in a scanning electron microscope. The results showed that the smear layers in both artificial and natural canals were similar in appearance and responded similarly to all irrigation solutions. In addition, in the artificial canals, it was observed that the dentinal tubule orientation had no detectabie effect on formation and removal of smear layers.     

Sealer penetration and apical microleakage in smear-free dentin after a final rinse with either 70% isopropyl alcohol or Peridex

Tensioactive agents may alter dentinal wettability allowing increased sealer penetration into dentinal tubules. This may improve the apical seal and better entomb remaining bacteria. The purpose of this study was to determine if a final rinse with either 70% isopropyl alcohol or Peridex in instrumented, smear-free canals would affect apical microleakage or Roth's 801 sealer penetration into dentinal tubules. Sixty root segments were instrumented followed by smear layer removal. The segments were randomly divided into three groups receiving a final rinse with 6% sodium hypochlorite (NaOCl), 70% isopropyl alcohol or Peridex. Obturation was completed using lateral compaction and Roth's 801 sealer pigmented with carbon black. Microleakage was measured by fluid filtration. Sealer penetration was measured using light microscopy. No significant differences were found between groups for microleakage or sealer penetration. Although a final rinse with either 70% isopropyl alcohol or Peridex did not increase sealer penetration, neither significantly affected apical microleakage compared to NaOCl.     

Effectiveness of 1 mol L-1 citric acid and 15% EDTA irrigation on smear layer removal

AIM: The aim of this study was to evaluate in vitro the cleansing and smear layer removal capability of alternate canal irrigation with citric acid and NaOCl. METHODOLOGY: Eighty-one teeth were divided into three groups on the basis of the type of instrumentation, namely, manual stainless steel, Ni-Ti mechanized ProFile .04 taper or MACXim. The groups were further divided on the basis of irrigation protocol: 5% NaOCl alone, NaOCl alternated with 1 mol L-1 citric acid solution or a combination of 15% EDTA and Cetrimide solution. After longitudinal sectioning, dentinal walls were microphotographed with scanning electron microscopy at x300 and x1000 magnifications. Qualitative and quantitative cleansing level evaluations were performed using computerized image analysis software. Data were statistically evaluated using Kruskal-Wallis analysis and t-test. RESULTS: Qualitative evaluation at x300 and x1000 showed no statistically significant differences in cleansing ability between citric acid, EDTA and NaOCl groups. Quantitative evaluation of smear layer removal, measured as open tubules/total dentinal surface ratio, showed that 1 mol L-1 citric acid solution was comparable to EDTA (11.97% vs. 10.36%) (NS); in samples treated with ProFile .04 taper instruments citric acid was most effective (16.17%), whilst in the group treated with manual instrumentation EDTA and Cetrimide were the most effective (11.94%). Specimens irrigated with 5% NaOCl demonstrated significantly more cleansing than those obtained in the other two groups (P < 0.001). CONCLUSIONS: 1 mol L-1 citric acid solution was as effective in removing smear layer as EDTA, but was superior in specimens treated with ProFile .04 taper instruments.     

An SEM study of posts cemented with an unfilled resin

Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structured was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.     

Efficacy of several concentrations of sodium hypochlorite for root canal irrigation.

Sodium hypochlorite (NaOCl) has been recommended for irrigation during root canal preparation. This investigation used scanning electron microscopy to examine instrumented and uninstrumented surfaces in the middle third of root canals following the use of several concentrations of NaOCl (5.25%, 2.5%, 1.0%, and 0.5%). NaOCl was delivered with either an endodontic irrigation needle or an ultrasonic device. All of the concentrations of NaOCl with either delivery system were very effective in flushing out loose debris from the root canals. A smear layer with some exposed dentinal tubules was seen on all instrumented surfaces regardless of concentration of NaOCl or irrigation device. NaOCl in concentrations of 5.25%, 2.5%, and 1% completely removed pulpal remnants and predentin from the uninstrumented surfaces. Although 0.5% NaOCl removed the majority of pulpal remnants and predentin from the uninstrumented surfaces, it left some fibrils on the surface.     

The risk of intentional dissolution of the smear layer after mechanical preparation of root canals

The root canals of 27 caries-free human cuspids were divided into 3 groups of 9 teeth each. Group I was mechanically prepared with reamers and files. Alternate irrigation with 5.25% NaOCl and 3% hydrogen peroxide was used between each instrument. The group II root canals were prepared with the use of alternate irrigation with the same concentrations of NaOCl and hydrogen peroxide and finally flushed with 17% EDTA and NaOCl solution. Group III was prepared mechanically with the use of sterile distilled water as an irrigant followed by a final flush with 17% EDTA solution. The root canals of all specimens were obturated with gutta-percha points and Tubliseal by means of the lateral condensation technique. After the root canals were obturated, samples of each of the three groups were immersed in separate flasks containing Streptococcus mutans, Staphylococcus epidermidis, and Corynebacterium hofmannii. All the microorganisms tested invaded the coronal dentin--where the access cavity had been sealed with Fynal--and/or the main foramen.