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.     

In vitro infection and disinfection of dentinal tubules

An in vitro model for dentinal tubule infection of root canals was developed. Cylindrical dentin specimens, 4 mm high with a diameter of 6 mm and a canal 2.3 mm wide, were prepared from freshly extracted bovine incisors. The cementum was removed from all dentin blocks. The tubules were opened by four-minute treatments with 17% EDTA and 5.25% NaOCl before being infected with Enterococcus faecalis ATCC 29212 in yeast extract-glucose broth. Bacteria rapidly invaded the tubules. After three weeks of incubation, a heavy infection was found 400 micron from the canal lumen, and the front of the infection reached 1000 micron in some blocks. Camphorated paramonochlorophenol (CMCP) and a calcium hydroxide compound, Calasept, were tested for their disinfecting efficacy toward E. faecalis-infected dentin. Liquid CMCP rapidly and completely disinfected the dentinal tubules, whereas CMCP in gaseous form disinfected tubules less rapidly. Calasept failed to eliminate, even superficially, E. faecalis in the tubules. The method used in bacteriological sampling allowed for sequential removal of 100-micron-thick zones of dentin from the central canal toward the periphery. Control specimens were uniformly infected and yielded growth in bur samples up to some 500 microns from the surface. The model proved quite sensitive and seems suitable for in vitro testing of root canal medicaments.     

A new noninvasive model to study the effectiveness of dentin disinfection by using confocal laser scanning microscopy

Introduction

The present study was designed to develop a standardized model for quantification of the effectiveness of dentin disinfection by different antibacterial solutions including a new root canal irrigant, Qmix.

Methods

Dentinal tubules from the root canal side in semicylindrical dentin specimens were infected with Enterococcus faecalis by centrifugation of the bacterial suspension into the tubules. Scanning electron microscopy (SEM) was used to verify the presence of bacteria in dentin. The outer side of dentin pieces was closed, and the specimens were subjected to 1-minute and 3-minute exposure to sterile water, 1%, 2%, 6% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and Qmix. Confocal laser scanning microscopy (CLSM) and viability staining were used to quantitatively analyze the proportions of dead and live bacteria inside dentin.

Results

A heavy invasion by E. faecalis was detected by both SEM and CLSM throughout the dentinal tubules. The amount of dead cells in dentin increased with increasing NaOCl concentration and time of exposure (P < .05). Qmix was equally effective in killing bacteria in dentin as 6% NaOCl; more than 40% and 60% of the bacteria were killed by both at 1 minute and 3 minutes, respectively. One percent and 2% NaOCl and 2% CHX killed 20%–30% and 30%–40% bacteria after 1 and 3 minutes of exposure, respectively, with no statistically significant differences among the 3 agents (P > .05). In the control group, which was treated with sterile water, only 4%–6% of the bacteria were dead.

Conclusions

Centrifugation helped to create a heavy, evenly distributed infection deep into the dentinal tubules. The new model made it possible to compare the effectiveness of several disinfecting solutions in killing bacteria inside dentin by a noninvasive CLSM method.     

In vitro disinfection of dentinal tubules by various endodontics irrigants

Effectiveness of endodontic irrigants within dentinal tubules of human teeth was evaluated. Mid-sections of single-rooted teeth were prepared into dentin wedges. The pulpal sides of the sections were exposed to Micrococcus luteus or Bacillus megaterium that grew into the tubules. Irrigants used in the study included: 0.525% NaOCl, 0.12% chlorhexidine, RC Prep, 0.5% betadine iodine, and sterile H2O (as a control). Pulpal surfaces were exposed to an irrigant and then rinsed in sterile water. The samples were then cracked, exposing a fresh surface. Culture of the exposed dentin surfaces showed that selected irrigants reached to the far ends of the dentinal tubules in a concentration sufficient to kill 100% of the M. luteus. However B. megaterium was neither killed nor apparently inhibited by any irrigant. We conclude that endodontic irrigants permeate throughout dentinal tubules, but their effectiveness is dependent on the type of bacteria found within the tubules.     

Effectiveness of three root canal medicaments to eliminate Actinomyces israelii from infected dentinal tubules in vitro.

The persistence of anaerobic bacteria in the root canal system often leads to treatment failure. One possible reason for this may be the retention of micro-organisms in the dentinal tubules of root canal walls. This study was performed to compare the effectiveness of two root canal medicaments and a chlorhexidine solution in disinfecting Actinomyces israelii-infected root canal walls and dentinal tubules in vitro. Dentinal tubules of root canal walls of human teeth were experimentally infected with A. israelii. The root canals were exposed to either iodine potassium iodide, calcium hydroxide or 2% chlorhexidine for periods of 3, 7 and 60 days. At the end of the medication periods samples were removed at different depths and tested for A. israelii viability. Chlorhexidine was the only disinfectant that was able to eliminate A. israelii from all the samples after 3, 7 as well as 60 days while 25% of the specimens treated with iodine potassium iodide and 50% of the specimens treated with calcium hydroxide still had viable A. israelii after treatment. It is clear from this study that 2% chlorhexidine is superior to iodine potassium iodide and calcium hydroxide in its ability to remove A. israelii from infected dentinal tubules. However, in vivo trials need to be undertaken before its clinical use can be recommended.     

Nd:YAG激光照射根管后的形态学观察

目的：了解感染根管管壁牙本质的病变特点，根管预备及Nd：YAG激光照射对感染根管的作用。方法：选用单根患牙60颗，随机分为5组：对照组（治疗前感染根管）、根管预备组（用手用器械根管预备）、3个激光组（在常规根管预备后，采用3种不同能量参数照射1min），做扫描电镜观察。结果：对照组：感染根管牙本质小管形态不规则，排列紊乱。根管预备组：能去除病变的牙本质层，形成玷污层。50mj 10Hz激光组不能封闭牙本质小管。100mj 10Hz、150mj 10Hz激光照射1min根管壁呈熔融状态，去除了玷污层，牙本质小管封闭和半封闭。结论：激光剂量在100mj 10Hz或在此以上时，能有效清洁根管壁玷污层和封闭牙本质小管。     

Effect of maleic acid on the bond strength of fibre posts to root dentine

The aim of this study was to evaluate the effect of maleic acid (MA) on both the bond strength of fibre post to root dentine and smear layer removal after post space preparation. Sixty, single‐canal premolars were endodontically treated and randomly assigned to four groups: group 1 [0.9% saline solution (control]); group 2 [2.5% sodium hypochlorite (NaOCl)]; group 3 [17% ethylenediaminetetraacetic acid (EDTA) followed by 2.5% NaOCl]; and group 4 (7% MA followed by 2.5% NaOCl). Self‐adhesive resin cement was used to test the adhesion of a glass‐fibre post to the root dentine through a micropush‐out test. Scanning electron microscopy was performed to examine and score the treated specimens for smear layer removal, and stereomicroscopy was applied to investigate the failure modes of fibre posts. Maleic acid exhibited the highest mean bond‐strength values in the apical regions among all the groups. Most failure modes (31.9%) were adhesive‐type failures between the dentine and luting materials. Maleic acid performed statistically significantly better than the other groups regarding smear layer removal, especially in the apical region. Maleic acid is an effective irrigant that can remove the smear layer, open dentinal tubules, and act as a high‐efficiency final irrigant in activation protocols.     

Recovery of Enterococcus faecalis after single- or multiple-visit root canal treatments carried out in infected teeth ex vivo

AIM: To assess the presence of Enterococcus faecalis after root canal treatment in single or multiple visits in an ex vivo model. METHODOLOGY: Forty-five premolar teeth were infected ex vivo with E. faecalis for 60 days. The canals were then prepared using a crowndown technique with System GT and Gates-Glidden burs and irrigated with 2% chlorhexidine gel. The specimens were divided into five groups (G1, G2, G3, G4 and G5) according to the time elapsed between chemical-mechanical preparation and root canal filling, the irrigant solution used and the use or nonuse of a calcium hydroxide intra-canal medicament. The teeth were then root-filled and incubated for 60 days at 37 degrees C. Dentine chips were removed from the canal walls with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing Brain-Heart Infusion broth. These samples were placed onto agar plates and colony forming units were counted after 24 h at 37 degrees C. Data were ranked and analysed using the Kruskal-Wallis statistical test. RESULTS: Enterococcus faecalis was recovered from 20% (three of 15 specimens) of G1 (chlorhexidine irrigation and immediate root filling in a single visit), 25% (four of 15 specimens) of G2 (chlorhexidine irrigation and filling after 14 days use of a calcium hydroxide dressing in multiple visits), 40% (two of five specimens) of G3 (chlorhexidine irrigation and filling after 7 days), 60% (three of five specimens) of G4 (saline irrigation and filling after 7 days) and from 100% (five of five specimens) of G5 (saline irrigation and immediate filling without sealer). CONCLUSIONS: Neither single- nor multiple-visit root canal treatment ex vivo, eliminated E. faecalis completely from dentinal tubules. Up to 60 days after root filling, E. faecalis remained viable inside dentinal tubules. When no sealer was used, E. faecalis presented a higher growth rate.     

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。     

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.     

Effectiveness of three endodontic irrigants at various tubular depths in human dentin

Bacteria from infected root canals can invade dentinal tubules, thus dentin disinfection is an important aspect of endodontic therapy. This study compares three endodontic irrigants for efficiency in killing bacteria established within human dentinal tubules. Root canals in extracted teeth were prepared and sterilized. Broth cultures of Enterococcus faecalis were allowed to grow within the canals to penetrate dentinal tubules. The infected canals were exposed individually to each of the irrigants for 1 min. Irrigants were 0.525% sodium hypochlorite, Tubulicid (0.2% EDTA), and 0.12% chlorhexidine (Peridex). Sterile water was the control. Viable bacteria were analyzed by drilling incrementally into dentin from the cementum toward the canal. Smaller diameter drills were used for each depth. Shavings were cultured at three depths, for each of three root levels: coronal, midroot, and apical. Although considerable variation occurred between roots, sodium hypochlorite seemed to be superior. Tubulicid and Peridex were better than water. More bacteria remained viable at greater distances from the pulp. These observations apparently apply to all levels in the canal.     

Evaluation of the interaction between sodium hypochlorite and chlorhexidine gluconate and its effect on root dentin

The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) forms a precipitate. The aim of this study was to evaluate the effect of irrigating root canals with a combination of NaOCl and CHX on root dentin and dentinal tubules by using the environmental scanning electron microscope (ESEM) and a computer program (Photoshop CS2). Forty-four extracted single-rooted human teeth were instrumented and irrigated with both NaOCl and CHX to produce a precipitate. Root canal surfaces were analyzed with the ESEM. The amount of remaining debris and number of patent tubules were determined. There were no significant differences in remaining debris between the negative control group and the experimental groups. There were significantly fewer patent tubules in the experimental groups when compared with the negative control group. The NaOCl/CHX precipitate tends to occlude the dentinal tubules. Until this precipitate is studied further, caution should be exercised when irrigating with NaOCl and CHX.     

Effectiveness of oxidative potential water as a root canal irrigant

AIM: The aim of this study was to evaluate the effectiveness of oxidative potential water (OPW) as an irrigant, based on its ability to remove the smear layer and/or debris from instrumented root canals. METHODOLOGY: One hundred and twenty root canals from extracted human maxillary incisors were instrumented using a conventional step-back technique with irrigation from sodium hypochlorite (NaOCl) or oxidative potential water (OPW). After instrumentation, the canals were irrigated by syringe or ultrasound using 15% EDTA or OPW as an irrigant. The volume of each irrigant used for syringe irrigation was 10, 20, and 30 mL, respectively, whilst the duration for ultrasonic irrigation was 1, 3, and 5 min, respectively. After irrigation, each root was split longitudinally in two with cutting pliers, and the specimens were prepared for SEM observation. The presence of debris and smear layer on each canal wall was assessed using a three-point scale for each parameter. RESULTS: Smear layer was effectively removed with EDTA both introduced via syringe and via ultrasonic irrigation. A similar effect was observed with OPW via syringe irrigation following instrumentation with 5% NaOCl. The canal walls in any of these cases showed open and patent dentinal tubules following smear layer removal. Some specimens irrigated with EDTA exhibited the effect of demineralization on the dentine resulting in funnelling of tubule orifices. Syringe irrigation was more effective in smear layer removal, except for ultrasonic irrigation with 15% EDTA, whilst ultrasonic irrigation was more effective in debris removal including the use of OPW as irrigant following instrumentation with 5% NaOCl. Neither syringe nor ultrasonic irrigation with OPW following instrumentation with OPW removed smear layer or debris effectively. CONCLUSIONS: The most effective irrigation technique for smear removal was 15% EDTA irrigation by means of syringe following instrumentation with 5% NaOCl solution. However, the most effective irrigation technique for debris removal was ultrasonic irrigation regardless of irrigant used. OPW irrigation by means of syringe following instrumentation with 5% NaOCl showed a similar effect to that of 15% EDTA irrigation for removal of smear layer and debris.     

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。     

Interaction between Octenidine-based Solution and Sodium Hypochlorite: A Mass Spectroscopy,Proton Nuclear Magnetic Resonance,and Scanning Electron Microscopy–based Observational Study

Introduction

Octenisept (OCT; Schülke & Mayr, Nordersdedt, Germany), an antimicrobial, antibiofilm agent and a promising root canal irrigant, can be potentially combined with sodium hypochlorite (NaOCl) during endodontic treatment. The aim of this study was first to identify the precipitate formed on the interaction between OCT and NaOCl and secondly to compare its effect on dentinal tubules with that of precipitate formed on combining chlorhexidine (CHX) and NaOCl.

The influence of volume, type of irrigant and flushing method on removing artificially placed dentine debris from the apical root canal during passive ultrasonic irrigation

AIM: To determine the influence of volume, irrigant and method of flushing on the removal of artificially-placed dentine debris from the apical part of root canals during passive ultrasonic irrigation. METHODOLOGY: Access cavities were prepared in 15 canine teeth and their root canals instrumented to size 20, 0.10 taper. Each root was split longitudinally, forming two halves. A groove was cut in the canal wall 2-6 mm from the apex in each half which was then filled with dentine debris prior to the roots being reassembled. All canals were ultrasonically irrigated, using a size 15, 0.02 taper smooth wire to a length of 21 mm that was placed in the canal to the apical foramen. In group 1 the canal was flushed with a continuous flow of 50 mL 2% sodium hypochlorite (NaOCl). In group 2 the continuous flow was not used but the canal was flushed with 12 mL 2% NaOCl, at a rate of 2 mL 30 s-1 using a syringe. Group 3 was treated in the same way as group 2 but the canal was flushed with 6 mL 2% NaOCl, at a rate of 2 mL min-1. Group 4 was treated in the same way as group 1 but water was used as the irrigant. Before and after irrigation, images of the grooves were captured and stored. The quantity of dentine debris in the groove was evaluated. The differences in debris scores between the experimental groups were analysed with the Kruskal-Wallis test and the Mann-Whitney U-test. The level of significance was set at P=0.05. RESULTS: The difference between all groups was statistically significant (K-W test P<0.001).Groups 1, 2 and 3 differed significantly from group 4 (P<0.001); there was no significant difference between groups 1, 2 and 3 (P=0.550). CONCLUSIONS: Syringe delivery of 2% NaOCl (6 and 12 mL) was as effective as a continuous flow of 2% NaOCl (50 mL). Water was not effective in removing dentine debris from grooves in the apical portion of root canals.     

In vitro and in vivo research of atmosphere pressure nonequilibrium plasmas on root canal disinfection: implication for alternative strategy for irrigation

Objective

To investigate an intracanal disinfection methodology of APNPs (atmosphere pressure nonequilibrium plasmas) or modified APNPs in root canal treatment and evaluate the antimicrobial efficiency against in vitro infected dentinal tubules and in vivo experimental apical periodontitis.

Materials and methods

Dentine specimens were centrifugated with Enterococcus faecalis to generate 1-day-old and 3-week-old biofilms, and were treated with 2% chlorhexidine (Chx), APNP or modified APNP for 3 and 10 min (n=4). LIVE/DEAD staining was employed to analyze the ratio of deactivated bacteria. Experimental apical periodontitis in beagles was induced. Root canal therapy with APNPs or modified APNPs was performed and the antimicrobial effect was evaluated by histological and radiographical analyses.

Results

APNP deactivated 1-day-old and 3-week-old E. feacalis in dentinal tubules as much as 2% Chx irrigating. Modified APNP significantly deactivated more E. faecalis biofilms in dentinal tubules for 3-min and 10-min treatments, without thermal damage or dentinal destruction being observed. In beagles’ apical periodontitis, significantly increased BV/TV and decreased lesion volume of apical bone were found in modified APNP group than 2% Chx irrigation group according to μCT. Fewer inflammatory cells and bacterial residual in dentine were observed in modified APNP-treated apical tissue by histology staining compared with those in the 2% Chx irrigation group.

Conclusion

The antimicrobial effect of APNP jet irradiation was comparable to that of 2% Chx irrigation. No structural damage in dentine or tissue necrosis at the periapical region was induced upon treatment. The modified APNP demonstrated an increased antimicrobial efficacy compared with 2% Chx irrigation both in vitro and in vivo.

Clinical relevance

The modified APNPs can be used as an alternative intracanal disinfection strategy.

     

Quantitative analysis of the effect of irrigant solution sequences on dentin erosion

Objective

The purpose of the study was to examine the level of erosion on root canal wall dentin caused by immersion in different irrigant solutions in alternative sequences.

Methods

Dentin specimens from teeth with one root canal were instrumented and randomly divided into five groups. Each group was subjected to 17% EDTA, 17% ethyleneglycoltetraacetic acid (EGTA), or 10% citric acid (CA) and 5.25% sodium hypochlorite (NaOCl) varying the time of irrigant exposure and the order of the irrigants. The specimens were examined by scanning electron microscopy (SEM), and randomized digital images of the dentin surface were taken. The area of tubule openings was measured by a semiautomatic method.

Results

No erosion was detected when demineralizing agents were used as a final rinse after NaOCl. However, the erosion of peritubular and intertubular dentin was detected when EDTA, EGTA, or CA were used first followed by 5.25% NaOCl (P < .05), and an increase over 100% in the area of dentin tubule openings was measured (P < .01).

Conclusions

NaOCl used as a final irrigant solution after demineralization agents causes marked erosion of root canal dentin.     

Effect of medications for root canal treatment on bonding to root canal dentin

Use of resin-based restorative materials recently has become widely accepted for treatment of endodontically treated teeth. However, some solutions routinely used during endodontic treatment procedures may have an effect on bond strengths of adhesive materials to root canal dentin. The purpose of this in vitro study was to evaluate the effect of various medications on microtensile bond strength to root canal dentin. Fourteen extracted human single-rooted teeth were used. The crowns and the pulp tissues were removed. The root canals were then instrumented and widened to the same size. The teeth were randomly divided into seven groups of two teeth each. The root canal dentin walls of the roots were treated with 5% sodium hypochloride (NaOCI), 3% hydrogen peroxide (H2O2), the combination of H2O2 and NaOCl, or 0.2% chlorhexidine gluconate for 60 s; or calcium hydroxide or formocresol for 24 h. The teeth in control group were irrigated with water. The root canals were obturated using C&B Metabond. After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut, and approximately 12 samples were obtained from each group. Microtensile bond strengths to root canal dentin were then measured by using an Instron machine. The data were recorded and expressed as MPa. The results indicated that NaOCI, H2O2, or a combination of NaOCl and H2O2 treatment decreased bond strength to root canal dentin significantly (p < 0.05). The teeth treated with chlorhexidine solution showed the highest bond strength values (p < 0.05). In conclusion, chlorhexidine is an appropriate irrigant solution for root canal treatment before adhesive post core applications.     

An in vitro evaluation of the antimicrobial efficacy of irrigants on biofilms of root canal isolates

AIM: The bactericidal effect of four antimicrobial agents was investigated against single-species biofilms derived from a range of root canal isolates. METHODOLOGY: Single-species biofilms of Prevotella intermedia, Peptostreptococcus micros, Streptococcus intermedius, Fusobacterium nucleatum and Enterococcus faecalis were generated on membrane filter discs and subjected to 15 min or 1 h incubation with 5 p.p.m. colloidal silver, 2.25% sodium hypochlorite (NaOCl), 0.2% chlorhexidine, 10% iodine or phosphate buffered saline (PBS) as a control. The antimicrobial activity of the agents was neutralized and the bacterial cells were harvested from the discs by vortexing, serially diluted in reduced transport fluid, plated on fastidious anaerobe agar containing 5% horse blood, incubated anaerobically and colony-forming units calculated. RESULTS: Iodine and NaOCl were more effective than chlorhexidine except against P. micros and P. intermedia where they were all 100% effective. Iodine and NaOCl elicited a 100% kill after 1 h incubation for all strains used. However, after 15 min, they showed differing bactericidal effects depending on the strain. None of the agents were effective against F. nucleatum after 15 min but NaOCl, iodine and chlorhexidine were all effective after 1 h. Colloidal silver was generally ineffective. CONCLUSIONS: The effectiveness of a particular agent was dependent on the nature of the organism in the biofilm and on the contact time. NaOCl was generally the most effective agent tested, followed by iodine. However the clinical efficacy of these agents must be considered in light of the complex root canal anatomy and polymicrobial nature of root canal infections.