An evaluation of microbial leakage after using MTAD as a final irrigation

Cleaning the root canal is not possible without using proper irrigation. The aim of this in vitro study was to evaluate the effect of MTAD as a final irrigant on bacterial leakage of the root canal, and its interaction with two conventional root canal sealers. We used 132 extracted human maxillary anterior teeth. The teeth were randomly divided into three experimental groups (n=40) and two groups (n=6) of positive and negative control. In group 1, the smear layer was not removed and irrigation was performed using 5.25% NaOCl. In group 2, the smear layer was removed using EDTA, and in group 3, the smear layer was removed using MTAD according to the clinical protocol of use. The teeth in each group were obturated with gutta-percha and AH-Plus or Rickert sealer. The coronal portion of each root was placed in contact with inoculum of Streptococcus mutans in Brain Heart Infusion (BHI) culture media. Each root tip was placed in one bottle containing sterile BHI. Mean duration of bacterial penetration in groups 2 and 3 was significantly greater than in group 1, but there was no significant difference between groups 2 and 3. According to our findings, it takes longer for bacteria to penetrate when either EDTA or MTAD is used for smear layer removal. The root canals obturated with AH Plus showed significantly longer duration of resistance to bacterial penetration than canals obturated with Rickert.     

Effects of metal combinations on cytotoxicity evaluation using a dynamic extraction method

The effects of metal combinations on cytotoxicity were examined following dynamic extraction by freely gyrating two spherical metals in a glass vessel. The cell viabilities of an Au alloy, a Ag-Pd-Au alloy and Ti were little affected by combinations among three metals. Cell viability ranged between 60 and 80% when precious alloys were in combination with Co-Cr or Ni-Cr alloys. Ti showed a clear difference in cell viability either in combination with Co-Cr or Ni-Cr alloys. The cell viability of the Ti/Co-Cr alloy combination was the same as that of precious alloys/Co-Cr or Ni-Cr alloy combinations. However, in an analogy with Co-Cr alloy/Ni-Cr alloy combination, the Ti/Ni-Cr alloy combination depressed the cell viability below 20%. This suggested that when new metals are to be used in combination with dissimilar metals, the cytotoxicity of the metals could be evaluated in extraction conditions using the mutual dynamic contact of dissimilar metals.     

MTT法评价牙科激光立体成形钛锆合金的细胞毒性

目的：评测口腔修复体用激光立体成形钛锆合金的细胞毒性。方法：采用激光立体成形的方法制备出钛锆合金的试件,根据国家标准制备试件的浸提液;通过体外细胞培养,四唑盐（MTT）比色方法评价材料的细胞毒性。结果：激光立体成形钛锆合金的细胞毒性为0～1级,阴性对照组、浸提液各浓度组细胞增殖曲线几乎重叠,并呈线性增加趋势。结论：激光立体成形的牙科钛锆合金材料具有较好的生物相容性。     

BioPure MTAD对AH Plus根尖封闭性能的影响

目的:评价BioPure MTAD作为根管冲洗液对根管充填糊剂AH Plus根尖封闭性能的影响.方法:选取人单根管牙44颗,随机分为A、B、C、D、E、F等6组,分别选用蒸馏水、1.3%NaClO、5.25%NaClO+17%EDTA、1.3%NaClO+BioPure MTAD和1.3%NaClO+3%EDTA等几组冲洗液进行根管冲洗.预备后进行根管充填,将所有实验样本染色,采用透明牙技术测量根尖微渗漏长度.采用SPSS12.0软件包对结果进行方差分析.结果:C组(1.3%NaClO)、D组(5.25%NaClO+17%EDTA)、E组(1.3%NaClO+BioPure MTAD)、F组(1.3%NaClO+3%EDTA)根尖微渗漏长度分别为(1.81±0.73)am、(0.53±0.49)mm、(0.40±0.44)mm和(0.39±0.55)mm,C组微渗漏长度显著大于其他3个实验组(P＜0.05);而D、E、F组根尖微渗漏情况无统计学差异(P＞0.05).结论:与临床常用根管冲洗液组合相比,BioPure MTAD冲洗根管对根管充填糊剂AH PluS的根尖封闭性能无明显不良影响.     

Evaluation of mandibular block using a standardized method

The purpose of this prospective randomized study was to investigate the manifestations and efficiency of mandibular block (MB) using a standardized method. In this study, 123 patients requiring MB were randomly assigned to receive MB using a repeated measures design. Mandibular block was administered in each patient by using 2.1 mL of 2% lidocaine with 1:100 000 epinephrine for the inferior alveolar nerve, lingual nerve, and/or buccal nerve. Clinical parameters including the electric pulp test and test for soft tissue sensation using a sharp dental explorer were assessed on both the operated side and contralateral side before and 5, 10, and 15 minutes after injection, and at the end of surgical procedure. Results of the test of the contralateral tooth served as the control group. No response to the electric pulp test at a maximum output (80 readings) was used as the criterion for pulpal anesthesia. Results obtained with electric pulp test and sharp explorer test were not significantly different during various intervals on the contralateral side, indicating the reliability of this standardized method for assessing MB. The MB technique achieved a high rate of subjective numbness (100%) according to the perception of the patients of overall numbness and lip numbness. Overall anesthetic success rates of pulpal anesthesia were 5.7% for the central incisor, 38.2% for the canine, 55.3% for the first premolar, and 90.2% for the first molar. No significant difference was found in the efficiency of anesthesia related to sex or age of the patients. A slower onset of pulpal anesthesia after MB was found for the anterior teeth than for the posterior teeth. This study suggests that the use of a standardized method might produce a clearer and more comprehensive evaluation of the efficiency and manifestations of MB.     

MTT法评价镓合金的细胞毒性

目的研究新型不含汞的牙体充填材料镓合金的细胞毒性。方法采用一种能快速评定细胞增殖率和细胞毒性的比色分析方法——MTT比色法,检测镓合金和高铜银汞合金对小鼠成纤维细胞L929细胞相对增殖率的影响,评价其细胞毒性。结果参照上海市医用生物材料生物性能测试标准,镓合金表现出较高的细胞相对增殖率,2d时为93.0%±4.9%,4d时为102.0%±3.5%,7d时为107.2%±4.2%,其细胞毒性为0级,即无明显细胞毒性;高铜银汞合金表现为中度细胞毒性。结论镓合金无明显的细胞毒性。     

In Vitro Evaluation of the Antibacterial Activities of MTAD in Combination with Nisin against Enterococcus faecalis

Introduction

MTAD is a common intracanal irrigant. Although MTAD inhibits Enterococcus faecalis in root canals, its bactericidal effect against E. faecalis remains to be improved. Nisin, an antibacterial peptide, possesses a strong bactericidal effect. The study evaluated the synergetic action between MTAD and nisin against E. faecalis.

Methods

The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were used to measure the antibacterial activities of MTAD, MTAN (substitution of doxycycline with nisin), and MTADN (nisin in combination with doxycycline), respectively. The synergetic effect between nisin and doxycycline was evaluated by fractional inhibitory concentration (FIC) and time-killing curves. Furthermore, morphologic changes in E. faecalis were observed by scanning electron microscopy after E. faecalis was treated with MTAD, MTAN, or MTADN for 24 hours.

Results

The MBC of MTADN against E. faecalis was lower than that of MTAD and MTAN. The combination of nisin and doxycycline had a significantly synergetic antibacterial effect on E. faecalis. Among the 3 antimicrobial treatments, MTADN caused the most severe damage to E. faecalis.

Conclusions

The combination of nisin and doxycycline has a synergetic antibacterial effect on E. faecalis, and MTAD in conjunction with nisin inhibits E. faecalis better than MTAD alone.     

不同含锶量的掺锶羟磷灰石陶瓷细胞毒性评价

目的　研究不同含锶量的掺锶羟磷灰石陶瓷的细胞毒性。方法　通过溶液反应方法制备含不同浓度锶元素的羟磷灰石陶瓷 ,采用细胞相对增殖率法和细胞形态直接观察法测定细胞与材料作用后的生长情况。结果　不同含锶量的陶瓷材料其细胞相对增殖率均在 94 %～ 10 2 %之间 ,细胞毒性级为 0级或 1级 ;随着材料中掺锶量的增加其细胞毒性存在略微增大的趋势。结论　锶元素的掺入对羟磷灰石材料的细胞毒性没有明显的影响     

Effect of MTAD on the bond strength to enamel and dentin

The purpose of this study was to compare the effect of MTAD (a mixture of a tetracycline isomer [doxycycline], an acid [citric acid], and a detergent [Tween 80]) and phosphoric acid on the bond strength to enamel and dentin using a conventional OptiBond Solo Plus dentin adhesive system. One hundred flat surfaces (50 enamel/50 dentin) were prepared for bonding. Specimens were embedded in acrylic with the flat surface exposed. One of the following surface treatments was applied before bonding composite with Optibond Solo Plus (Kerr Corp): 1 min NaOCl/1 min EDTA; 1 min NaOCl/1 min MTAD; 30 s etch with H3PO4 (positive control), 2 min saline (negative control), or 20 min NaOCl/5 min MTAD (clinical protocol for MTAD). Shear bond strength was tested 30 min after bonding. Data were analyzed using a one-way ANOVA followed by the Student-Newman-Keuls multiple comparison method. Surface pretreatment with acid etch resulted in the greatest enamel bond strengths (p < 0.05). All surface pretreatments were superior to saline for dentinal bonding (p < 0.05). On the basis of our findings, it appears that teeth endodontically treated with the MTAD protocol for clinical use (20 min 1.3% NaOCl/5 min MTAD) may not need any additional dentin conditioning before the application of the dental adhesive.     

5种着色氧化锆陶瓷的细胞毒性评价

目的：对掺杂5种微量着色剂的氧化锆陶瓷的生物安全性进行初步评价.方法：采用四氮唑盐比色法（MTT）细胞毒性评价方法,用5种着色氧化锆陶瓷材料的浸提液体外培养L929小鼠成纤维细胞2 d、4 d、7 d,于倒置相差显微镜下观察细胞形态;用MTT检测各实验组和对照组的吸光度值（OD值）,计算各组细胞的相对增殖率,并按照6级毒性分类法对各实验组进行评级.结果：培养期细胞贴壁生长,细胞形态正常.随着培养天数增加细胞大量增殖,各实验组的毒性评级为0-1级.结论：添加5种微量着色剂的氧化锆陶瓷无细胞毒性,具备体内应用的生物安全基础.     

根管冲洗剂次氯酸钠和氯亚明的细胞毒性

目的:评价次氯酸钠(NaOCl)和氯亚明溶液在相同有效氯浓度下的细胞毒性.方法: 按有效氯浓度为0.500 0%、0.250 0%、0.200 0%、0.150 0%、0.125 0%、0.062 5%分别配制NaOCl溶液和氯亚明溶液,使其与L929细胞接触2 h、30 min、10 min,用MTT法检测各组的细胞存活率.结果: 在所设定的浓度范围内,除高低两端组(0.500 0%-2 h及0.062 5%-30 min)外,细胞在其余各组NaOCl溶液中的存活率均大于氯亚明,差异有统计学意义(P<0.05).结论: 在0.250 0%以下的有效氯浓度范围,NaOCl溶液的细胞毒性小于氯亚明溶液.     

The effect of MTAD on the coronal leakage of obturated root canals

The purpose of this study was to evaluate the effect of smear-layer removal using MTAD on coronal leakage of obturated root canals using a dye-leakage test. Fifty, extracted, single-rooted, human teeth were cleaned and shaped and divided into 5 equal groups of 10 each. The smear layer in groups 1 to 3 was left intact. The smear layer in groups 4 and 5 was removed using 17% EDTA or MTAD, respectively. After obturation of root canals, the access opening to each canal was filled with India ink for 48 h. The depth of coronal-dye penetration was measured using the Sigmascan software. ANOVA showed statistically significant differences among the groups (p < 0.05). Samples treated with MTAD yielded significantly less leakage than samples treated with sodium hypochlorite. The amount of dye penetration was not statistically different between teeth treated with MTAD or EDTA (p = 0.062).     

In vitro antimicrobial efficacy of MTAD and sodium hypochlorite

The purpose of this study was to compare the ability of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) with that of sodium hypochlorite (NaOCI) to disinfect human root canals that had been contaminated with whole saliva. One hundred and thirty-two root canals of extracted human teeth were cleaned and shaped using the passive step-back technique and rotary NiTi files. The smear layer was removed, and the teeth were autoclaved. Six autoclaved samples were transferred to sterile broth without contamination with saliva to serve as negative controls. Whole saliva was used to contaminate the root canals of the rest of the samples for 48 h. Six of these contaminated samples were irrigated with Brain Heart Infusion (BHI) broth and served as positive controls. The rest of the contaminated specimens were then divided into two experimental groups of 60 teeth each. In one group, the canals were irrigated with 1 ml MTAD, and the samples were immersed in 2 ml of the same solution for 5 min. In the second group, the specimens were similarly treated with 5.25% NaOCl. All samples were washed in BHI broth and then placed in another tube containing BHI broth and incubated for 96 h. Disinfection of the samples was determined based on presence or absence of turbidity in the broth 96 h later. Twenty-three of 60 teeth treated with NaOCl remained infected. Only one of 60 teeth treated with MTAD remained infected. Statistical analysis of the data using the Chi-square test showed a significant difference between the two groups (p < 0.0001).     

Biopure MTAD去除根管壁玷污层效能的体外实验研究

目的采用离体牙评价Biopure MTAD作为根管冲洗液去除根管壁玷污层的能力。方法将40颗人单根牙随机分为5组进行根管预备。各组根管预备过程中和预备完成时的冲洗液分别为：A组蒸馏水,B组5.25% NaClO和17% EDTA,C组1.3% NaClO,D组1.3% NaClO和Biopure MTAD,E组1.3% NaClO和3% EDTA。预备完后将样本纵向剖开,在扫描电镜下观察,评价根管壁玷污层和腐蚀情况。结果A组和C组实验样本整个根管壁都有玷污层覆盖。B、D、E组牙根冠和中1/3区根管壁玷污层均被有效去除,3组间无统计学差异（P＞0.05）;D组根尖1/3区根管壁基本无玷污层,与B、E组相比有统计学差异（P＜0.05）。B组根冠和根中1/3的根管壁的腐蚀度较大,与D、E组相比有统计学差异（P＜0.05）;根尖1/3区各组根管壁的腐蚀度无统计学差异（P＞0.05）。结论Biopure MTAD与1.3%的NaClO联合使用能更有效去除根管壁玷污层且对根管壁表面的结构无明显破坏。     

The antimicrobial effect of MTAD: an in vitro investigation

Pulp and periradicular diseases are of microbial origin. To effectively clean the root canal system a disinfecting agent must be able to penetrate into difficult-to-reach areas and kill microorganisms with minimal damage to the host tissues. The purpose of this investigation was to test the ability of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) to kill Enterococcus faecalis and compare its efficacy to that of sodium hypochlorite (NaOCl) and ethylene diamine tetraacetic acid (EDTA). The zones of inhibition and minimum inhibitory concentrations were measured for these solutions. Measurement of zones of inhibition and determination of the minimum inhibitory concentrations showed that MTAD is as effective as 5.25% NaOCl and significantly more effective than EDTA (p < 0.0001). Furthermore, MTAD is significantly more effective in killing E. faecalis than NaOCl when the solutions are diluted (p < 0.0001). Measurement of the minimum inhibitory concentrations demonstrated that although MTAD is still effective in killing E. faecalis at 200x dilution, NaOCl ceases to exert its antibacterial activity beyond 32x dilution. EDTA did not exhibit any antibacterial activity. Based on the results of this study, it seems that MTAD is an effective solution in eradicating E. faecalis.     

4种铸造合金对人牙龈成纤维细胞的毒性研究

目的:检测镍铬合金、钛合金、钴铬合金、金合金4种铸造合金的细胞毒性.方法:用MTT法测定人牙龈成纤维细胞在不同合金浸提液中培养2、4、7 d的吸光度(A值),计算细胞相对增殖率(RGR),判断细胞毒性的级别.用流式细胞仪测定不同合金浸提液中培养的人牙龈成纤维细胞不同增殖周期时相的DNA百分含量,计算细胞的增殖指数百分比.结果:各组细胞不同时间点相埘增殖率均在96%～106%之间,细胞毒性分级为1级或0级.4种合金对细胞增殖指数由小到大的顺序为镍铬合金、钛合金、钴铬合金、金合金.结论:2种方法检测结果相同,常用的4种铸造合金的细胞毒性试验均在临床应用的允许范围内,可以保证铸造修复体对人体具有肯定生物相容性和安全性.