Chlorhexidine substantivity in root canal dentin

OBJECTIVE: The purpose of this investigation was to evaluate the substantivity of chlorhexidine (CHX) within a root canal system and to assess how long the CHX remains antimicrobially effective. STUDY DESIGN: Bovine roots were sectioned and standardized to 8 mm. Sections, which served as controls, were treated with 1% sodium hypochlorite and 1 mol/L EDTA, then obturated with gutta percha and AH26 sealer. Experimental sections were treated similarly except they were placed in 2% CHX for 10 minutes prior to obturation. Control specimens were divided into 4 control groups and stored in saline for 1 day, 3 weeks, 6 weeks, and 12 weeks. Experimental specimens were divided into 4 groups and stored in saline for 1 day, 3 weeks, 6 weeks, and 12 weeks. After their respective storage periods, all specimens were halved and canal wall dentin was ground out with Peeso reamers. Dentin specimens were agitated in 700 microl of saline for 5 hours to release CHX. After centrifugation the supernatants were analyzed with UV spectrophotometry at 253 nm. To determine whether the CHX from dentin samples remained antimicrobial, the extracts from experimental and control groups were mixed with cultures of Enterococcus faecalis. RESULTS: After 1 day of storage, the dentin extract contained approximately 0.0048% CHX. After 3, 6 and 12 weeks, dentin extracts contained approximately 0.0023%, 0.0016%, and 0.0010% CHX respectively. Extracts from the storage groups were found to be highly antimicrobial corresponding to the CHX concentration. CONCLUSION: The results of this study indicate that CHX is retained in root canal dentin in antimicrobially effective amounts for up to 12 weeks.     

离体牙储存方式对牙本质黏结剂微拉伸强度的影响

目的：对比研究不同的离体牙储存方法和时间对牙本质黏结剂Single Bond微拉伸强度的影响。方法：选用30颗因正畸拔除的第一前磨牙,随机分为5组。拔除后立即分别放人4℃的0．02％麝香草酚水溶液、10％甲醛溶液、1％氯胺溶液、蒸馏水中储存,以及用湿纱布包裹-20℃冰箱中储存。分别在储存的第10天、90天取出,在牙冠殆面表层牙本质上使用牙本质黏结剂Single Bond,复合树脂Z250黏结修复,测定牙本质黏结剂的微拉伸强度值。选用新鲜拔除的前磨牙作为对照组。用体视显微镜和扫描电子显微镜观察微拉伸强度测试样本的断裂类型。用SPSS11．5软件对牙本质黏结剂的微拉伸强度值做双因素方差分析。结果：不同的储存方法对牙本质黏结剂微拉伸强度有显著影响(P=0．01),与新鲜拔除的牙比较,蒸馏水中4℃储存(P=0．024)和0．02％麝香草酚水溶液4℃储存(P=0．008)的离体牙的微拉伸强度显著降低;不同的储存时间对牙本质黏结剂的微拉伸强度影响无统计学差异(P=0．279)。所有微拉伸强度测试样本的断裂均发生在黏结界面。结论：离体牙储存方法对牙本质黏结剂Single Bond的黏结强度有重要影响,建议使用离体牙评价牙本质黏结剂的黏结强度时,选用新鲜拔除的牙、-20℃冷冻的牙或1％氯胺溶液4℃储存的牙,以减小不必要的实验误差。     

黄芩对5种常见牙周细菌抑制作用的体外研究

目的：观察黄芩对5种常见牙周细菌的作用。方法：采用试管两倍稀释法测定黄芩甲醇提取物在体外厌氧环境对牙龈卟啉单胞菌、中间普氏菌、伴放线放线杆菌、具核梭杆菌、血链球菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。结果：黄芩对各实验菌株均有抑制作用，对牙周常见可疑致病菌牙龈卟啉单胞菌、中间普氏菌、伴放线放线杆菌、具核梭杆菌的MIC值为5g／L、MBC值为20g／L，对牙周有益菌血链球菌的MIC值为40g/L、MBC值为40g/L，结论：浓度为5g/L的黄芩在不破坏牙周局部生态平衡的情况下可有效抑制牙周可疑致病菌的生长。     

In vitro antibacterial effects of the dentin primer of Clearfil Protect Bond.

OBJECTIVES: This study aimed to investigate the antibacterial effects of the dentin primer of a commercially available self-etching adhesive system, Clearfil Protect Bond, which contains antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB). METHODS: Inhibitory effects against Streptococcus mutans, Lactobacillus casei, or Actinomyces naeslundii were examined by an agar-disc diffusion method using the Clearfil Protect Bond primer containing 5% MDPB and an acidic adhesion-promoting monomer MDP, the primer only with MDP, and the primer with 1% cetylpyridinium chloride. The minimum inhibitory/bactericidal concentrations (MIC/MBC) of each primer for the three bacterial species were determined by serial microdilution assays. For testing the bactericidal effects seen in dentin, the primer was applied to demineralized dentin blocks in which S. mutans had been impregnated, and numbers of viable bacteria were counted. RESULTS: For all three bacteria, the sizes of the inhibition zones produced by Clearfil Protect Bond primer were significantly greater than for the other primers (p<0.05, ANOVA and Scheffe's F-test). The MIC/MBC values of Clearfil Protect Bond primer were less than those of the primer without MDPB, and comparable to those of the primer containing cetylpyridinium chloride. No bacterial recovery was obtained after application of Clearfil Protect Bond primer to the bacteria-impregnated dentin, although the primer without MDPB showed some bactericidal effect. SIGNIFICANCE: Clearfil Protect Bond primer has strong antibacterial activity based upon MDPB against S. mutans, L. casei and A. naeslundii, and the capability to disinfect cavities containing residual bacteria.     

Bactericidal effect of dentin primer containing antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human carious dentin

The aim of this study was to investigate the bactericidal effect of a dentin primer incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human dentinal carious lesions. To evaluate the antibacterial activity of MDPB against anaerobes, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against obligate anaerobes and facultative anaerobic strains of lactobacilli were determined. Bacteria were recovered from carious dentin samples obtained from the teeth of patients, and the bactericidal activities of the experimental primer containing 5% MDPB and three commercially available primers were compared by counting the number of viable cells after contact with diluted solutions of each primer for 30 s. MDPB showed strong antibacterial activity against anaerobes, the MIC and MBC values ranging from 3.9 to 31.3 micrograms/ mL-1 and 15.6-125 micrograms/ mL-1, respectively. Experimental primer containing MDPB was the most bactericidal among the materials tested (ANOVA, Fisher's PLSD test, P < 0.05) and was able to kill the bacteria completely even when diluted 40 times, while the three commercial products exhibited little activity at 40 times dilution. These results indicate that incorporation of MDPB into dentin primer could be beneficial for eliminating the residual bacteria in cavities.     

Chitosan: effect of a new chelating agent on the microhardness of root dentin

The effect of solutions of 0.2% chitosan, 15% EDTA and 10% citric acid on the microhardness of root dentin was evaluated comparatively in this study. Thirteen sound human maxillary central incisors were selected and decoronated at the cementoenamel junction. Ten roots were set into rapid polymerization acrylic resin and the root/resin block was fitted to the cutting machine to obtain slices from the cervical third. The first slice was discarded and the second slice was divided into four quadrants. Each quadrant was used to construct a sample, so that 4 specimens were obtained from each root slice, being one for each chelating solution to be tested: 15% EDTA, 10% citric acid, 0.2% chitosan and distilled water (control). The specimens were exposed to 50 μL of the solution for 5 min, and then washed in distilled water. A microhardness tester (Knoop hardness) with a 10 g load was used for 15 s. Data were analyzed statistically by one-way ANOVA and Tukey-Kramer test (α=0.05). The other 3 roots had the canals instrumented and irrigated at the end of the biomechanical preparation with the test solutions, and then examined by scanning electron microscopy (SEM) for qualitative analysis. All solutions reduced the microhardness of root dentin in a way that was statistically similar to each other (p>0.05) but significantly different from the control (p>0.05). The SEM micrographs showed that the three solutions removed smear layer from the middle third of the root canal. In conclusion, 0.2% chitosan, 15% EDTA and 10% citric acid showed similar effects in reducing dentin microhardness.     

In vitro antibacterial effect of different irrigating solutions on Enterococcus faecalis

Was evaluated the minimum inhibitory concentration (MIC) and the antibacterial effect (AE) of 2.5% NaOCl, 0.2% chlorhexidine gluconate (CHX) and 17% EDTA on Enterococcus faecalis. The antibacterial capacity was assessed by difusion in agar. The AE was evaluated on contaminated root dentin, employing apical and middle portions of human roots, sterilized and contaminated with Enterococcus faecalis, immersed in the irrigation solutions and incubated at 37 degrees C. Viable cells were counted at 0, 4, 8 and 24 hours. MIC: NaOCl and CHX: 0.2%, EDTA below 5%. Diffusion in agar: NaOCl 2.5% = 21 mm. CHX 0.2% = 14 mm. EDTA 17% = 20 mm. Effect on root dentin: NaOCl 2.5%: Enterococcus faecalis was totally inhibited for 24 hours in the apical area, and for 8 hours in the middle area. CHX 0.2% elicited a reduction of more than 5 log CFU and EDTA 17% induced a reduction of more than 3 log CFU at all the time points examined in the apical and middle areas.     

牙本质无机物在牙本质粘接过程中的作用

目的探讨牙本质无机物在牙本质粘接过程中的作用。方法采用几种不同的牙本质处理方法，测试分析了牙本质与４ＭＥＴＡ／ＭＭＡＴＢＢ树脂之间的抗张粘接强度（ｔｅｎｓｉｌｅｂｏｎｄｉｎｇｓｔｒｅｎｇｔｈ，ＴＢＳ）。结果选用１０％柠檬酸和３％三氯化铁组成的酸盐体系预处理液（ａｃｉｄｓａｌｔｐｒｅｔｒｅａｔｉｎｇｓｏｌｕｔｉｏｎｓｙｓｔｅｍ，ＡＰＳＳ）去除牙本质污染层，再用次氯酸钠溶解牙本质胶原。暴露牙本质无机物时，牙本质的抗张粘接强度为５９３ＭＰａ，明显高于用蒸馏水冲洗的对照组（３７１ＭＰａ）（Ｐ＜００５）。结论说明牙本质无机物在牙本质粘接过程中确实具有一定的作用     

Effect of gamma radiation on dentin bond strength and morphology.

Sterilization by gamma radiation is a method often used for bone and extracted teeth banking. The bond strength of human dentin submitted to gamma rays has not been reported. Therefore, the aim of this study was to assess the effect of gamma radiation on dentin shear bond strength and morphology. The roots were removed from extracted human bicuspids and their crowns divided into two groups: an untreated control and crowns submitted to gamma radiation sterilization. The crowns were mounted in epoxy resin and the buccal enamel removed exposing the subjacent dentin. SBMPPlus adhesive system was applied to a 3-mm diameter area after 15 s of 35% phosphoric acid etching. The samples were mounted in composite resin cylinders and stored in distilled water at 37 degrees C for 24 h until the shear test. Dental fragments from both groups were prepared for SEM analysis. There was no statistically significant difference between the results of the shear test for the two groups according to the Tukey test (p > 0.05). Scanning electron micrographs also did not show alterations. These results indicate that gamma radiation neither affected the shear bond strength of SBMPPlus nor altered the dentin surface morphology.     

Influence of olive oil emulsions on dentin demineralization in vitro

The effect of two different concentrations of olive oil emulsions on development of artificial caries-like dentin lesions under severe demineralizing conditions was investigated. Bovine dentin samples (n = 180) were ground flat, polished, divided into four groups, and subjected to three demineralization cycles per day. Samples were stored in one of the following solutions for 5 min prior to demineralization in a buffer solution (pH 5): Group 1: 50% oil emulsion (olive oil and distilled water); group 2: 5% oil emulsion; group 3: distilled water; and group 4: 1,500 ppm sodium fluoride. Daily up to 9 days, lesion depth (ld) and mineral loss (deltaZ) were determined by means of microradiography and analyzed by ANOVA and Tukey's studentized range test (p < or = 0.05). Lesion depth increased with time for all groups. Mineral loss increased in groups 1-3. A small but significant decrease in mineral loss was observed following treatment with lipid emulsions as compared to treatment with distilled water, but fluoride treatment was considerably more effective. Mean mineral loss (means +/- SD in vol% x microm) averaged over the study period was 4,368 +/- 1,599, 4,536 +/- 1,823, 4,849 +/- 1,798, and 789 +/- 177 for group 1, 2, 3, and 4, respectively. Ratio (deltaZ/ld) remained constant around 30 vol% for groups 1-3, but decreased for group 4. In conclusion, externally provided lipids have the potential to reduce dentin demineralization in vitro.     

Water movement in the hybrid layer after different dentin treatments.

The aim of this study was to examine the morphology of the hybrid layer (HL) of bonded water-stored specimens after different chemical pre-treatments of dentin. MATERIALS AND METHODS: Twenty-seven recently extracted human molars were selected. Fifty-four dentin disks in middle/deep dentin were obtained with a slow speed saw with a diamond-impregnated disk under water lubrication. Smear layers were created with 180 grit silicon carbide under running water for 1 min. Different pre-treatments of dentin were: Group (1) no treatment; Group (2) 35% H3PO4 etch for 15 s followed by 10% glutaraldehyde for 120 s; Group (3) 37% H3PO4 etch for 15 s followed by 5% NaOCl for 120 s. Three dentin bonding agents (DBAs), Prime and Bond NT (P and B), AdmiraBond (AB), and Clearfil SE Bond (SEB) were applied in association with a resin composite following the manufacturers' directions. Each specimen was then longitudinally sectioned and polished with wet SiC papers (up to #4000 grit). Impressions of the polished dentin were immediately taken with a silicone impression material. Bonded specimens were then stored for 3 or 12 h in deionized water. Further impressions of stored specimens were taken after air-drying of specimens for 10 s. Positive replicas were obtained using a polyether impression material. All the replicas and the original specimens were inspected by SEM. RESULTS: A line of droplets (0.5-4 microm in diameter) was observed along the region of the adhesive-HL junction in all replicas of specimens stored in water, except in group 3, when P and B and AB were used. When SEB was used in each group the droplet were found in all groups except the zone of droplets was thinner. No differences in droplets dimensions were seen between 3 or 12 h water storage, or between the different dentin treatments. CONCLUSIONS: The replica procedure used in this study was able to detect water trapped in the adhesive-HL region that was released during the setting of the impression material. The droplets observed in this region support the hypothesis that there can be bidirectional water movement within the adhesive-HL complex.     

臭氧水溶液对牙本质微硬度影响的实验研究

目的:评价臭氧水溶液对根管内壁牙本质微硬度的影响。方法:选取40颗因正畸拔牙的离体前磨牙随机分为5组,A组:2.15 mg/L臭氧水溶液组;B组:1%次氯酸钠组;C组:3%过氧化氢组;D组:15%EDTA组;E组:蒸馏水组(阴性对照组)。将牙冠于牙颈部截断后将牙冠沿牙体长轴纵向劈开暴露牙本质,以5组不同根管冲洗液分别处理5 min、15 min后用微硬度测试仪测定牙本质的微硬度。结果:1%次氯酸钠,3%过氧化氢,15%EDTA均降低了牙本质的微硬度,尤以15%EDTA为甚,而2.15 mg/L臭氧水溶液对牙本质微硬度无明显影响。结论:2.15 mg/L臭氧水溶液作为根管冲洗液对牙本质微硬度没有影响。     

Influence of moisture conditions on dentin bond strength of single-step self-etch adhesive systems

This study was conducted to clarify the influence of dentin surface moisture on bond strength of single-step self-etch adhesive systems. The adhesive systems used were Adper Prompt L-Pop (AP), Clearfil tri-S Bond (CT), Fluoro Bond Shake One (FB), G-Bond (GB), and One-Up Bond F Plus (OF). Bovine mandibular incisors were wet-ground with #600 SiC to expose the labial dentin. After rinsing with tap water, the dentin surface was dried with air for 10 sec (Dry condition) or blotted (Wet condition). Adhesives were applied according to each manufacturer's instructions, followed by resin composite polymerization. Ten samples per test group were stored in distilled water at 37 degrees C for 24 h, then shear tested at a crosshead speed of 1.0 mm/min. The data were analyzed by Student's t test and Tukey HSD test at a probability level of 0.05. The mean bond strengths for Dry condition ranged from 13.9 MPa to 18.2 MPa, and those for Wet condition ranged from 7.1 MPa to 18.4 MPa. Significantly lower bond strengths were obtained for the Wet condition for GB, FB, and OF. Failure after the test was commonly due to adhesive breakdown associated with partial cohesive failure in the dentin. These data suggest that air-drying of the dentin surface is appropriate for the adhesive systems tested.     

In vitro evaporative vs. convective water flux across human dentin before and after conditioning and placement of glass-ionomer cements

PURPOSE: To assess the convective and evaporative fluid movement across glass-ionomer treated dentin. METHODS: Crown segments made from extracted human teeth, were divided into two groups of 14 teeth each. Each segment was cemented onto a plexiglass slab penetrated by a stainless steel tube, permitting filling of the pulp chamber with water. This set-up was attached to a device that measured fluid movement through the dentin in the crown segment. The experimental design involved repeated measurements of convective and evaporative fluid movements in each of the following conditions: smear layer-covered dentin, conditioned dentin, dentin after placement of one of two glass-ionomers (Fuji IX or Ketac-Molar), with and without a protective coating. The same water fluxes were remeasured after storage of the samples for 24 hours in distilled water. RESULTS: Statistical analysis of the results using ANOVA indicated a significant difference between the two measured water fluxes (P < 0.001). There was also a significant difference between the two materials (P < 0.001), with Ketac-Molar allowing higher permeability than Fuji IX. Conditioning the dentin surface with polyacrylic acid increased the convective water flux (P < 0.05) but did not change the evaporative water flux. Placement of the glass-ionomer material did not change the rate of spontaneous evaporation of water from the dentin, but the application of a coating agent reduced the evaporative water loss. These values were not significantly different when the specimens were stored for 24 hours.     

Effects of potassium oxalate on dentin hypersensitivity in vivo

This study compared 30% dipotassium oxalate (DO) and 3% monohydrogen-monopotassium oxalate (MO) on the reduction of dentin hypersensitivity in vivo. Four treatments were utilized: (1) distilled water followed by 30% DO; (2) distilled water followed by 3% MO; (3) 30% DO followed by 3% MO and (4) distilled water only. Treatments were randomly assigned so that each of the 17 participants received all four treatments, one per tooth tested. Response to cold at baseline and immediately, 1 week, 2 weeks, and 4 weeks posttreatment was measured. Testing began with water at 20 degrees C and decreased at 5 degrees C intervals until a positive response was obtained or until 0 degrees C was reached. No differences were found for time when compared across treatments. When treatments were compared across time, significant reductions occurred in immediate and 4 week posttreatment measurements for treatment 2. In addition, highly significant reductions occurred in 1 week and 2 week posttreatment measurements for treatment 3. Results suggest a decrease in dentin hypersensitivity following the application of 3% MO alone, and 30% DO followed by 3% MO.     

Functionalized epigallocatechin gallate copolymer inhibit dentin matrices degradation: Mechanical,solubilized telopeptide and proteomic assays

Objectives

We investigated the biostability of dentin organic matrices treated with epigallocatechin gallate (EGCG) in comparison to chlorhexidine (CHX), both extracted from functionalized copolymers.

In vitro evaluation of antimicrobial property of silver nanoparticles and chlorhexidine against five different oral pathogenic bacteria

Introduction

Numerous antimicrobial agents are used to eliminate oral biofilm. However due to emergence of multi drug resistant microorganisms, the quest to find out biologically safe and naturally available antimicrobial agents continues.

对氨基苯甲酸对乳杆菌生长影响的体外实验

目的:探讨对氨基苯甲酸菌株(PABA)对牙本质龋、根面龋致病菌之一的乳杆菌生长的影响。方法:10倍系列稀释法配制浓度为10-3~10-10gPL的PABA液,将其分别加入改良的Carlsson培养基中,再将乳杆菌ATCC4356放入该培养基厌氧培养48 h(80%N2、10%H2、10%CO2),用紫外可见分光光度仪测定细菌浓度OD值(K=540 nm);并在琼脂平板培养观察细菌生长的情况,进行菌落计数。结果:PABA也有促进乳杆菌生长的能力,当PABA的浓度从 10-10~10-4gPL增加时,其促进乳杆菌生长的能力增强(P<0.05),且当浓度为10-5gPL时,促进乳杆菌生长的能力达最强,随着PABA的浓度增加到10-4gPL时,此促进作用开始下降,PABA的浓度再增加至10-3gPL时,对乳杆菌的生长无明显的促进作用。结论:PABA的浓度为10-5gPL时,促进乳杆菌生长的能力达最强,高于或低于此浓度,这种促生长的作用均下降。     

Shear bond strength after dentin bleaching with 10% carbamide peroxide agents

This in vitro study evaluated the shear bond strength (SBS) of dentin treated with two 10% carbamide peroxide bleaching agents 15 days after bleaching and storage in artificial saliva. Dentin fragments were randomly divided into 3 groups (n = 20) for the treatment with the two different bleaching agents (Rembrandt 10% or Opalescence 10%) or with a placebo agent, applied to the tooth surface for 8 hours a day. During the remaining time, the specimens were stored in artificial saliva. After 42 days, the fragments were stored in artificial saliva for 14 days. Another group (n = 20) was exposed to distilled and deionized water for 56 days. An adhesive system and microhybrid composite resin were used to prepare specimens for the SBS test. SBS tests were performed and the fractured surfaces were visually examined using a stereoscope at 30 x magnification. The analysis of variance (ANOVA) and SIDAK tests showed higher SBS values for dentin treated with Opalescence 10% than for dentin treated with Rembrandt 10% or placebo. Groups treated with Rembrandt 10%, Opalescence 10% or placebo did not differ from the group treated with distilled and deionized water. Ten percent carbamide peroxide agents or a placebo agent caused no differences in SBS of dentin after 15 days of storage in artificial saliva.     

The antimicrobial effect of biopure MTAD on eight strains of Enterococcus faecalis: an in vitro investigation

The purpose of this investigation was to determine the antimicrobial effect of MTAD as a final irrigant on eight strains of Enterococcus faecalis (E. faecalis) and to measure the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC) of MTAD. The roots of 240 extracted human teeth were instrumented using 1.3% NaOCl and 17% EDTA. The roots were divided into eight groups and contaminated with one of eight strains of E. faecalis. After irrigating with 1.3% NaOCl, the root canal and the external surfaces were exposed to MTAD for 5 minutes. Roots or dentin shavings were cultured to determine the growth of E. faecalis. The results showed that this treatment regimen was effective in completely eliminating growth in seven of eight strains of E. faecalis. The MIC/MLC tests showed that MTAD inhibited most strains of E. faecalis growth when diluted 1:8192 times and killed most strains of E. faecalis when diluted 1:512 times.