Influence of human dentine on the antibacterial activity of self-etching adhesive systems against cariogenic bacteria

OBJECTIVES: The incorporation of antibacterial agents into adhesive systems has been proposed to eliminate residual bacteria from dentine. This study used the agar diffusion method to evaluate the antibacterial activity of Clearfil Protect Bond (CPB), Clearfil SE Bond (CSEB), Clearfil Tri-S Bond (C3SB) and Xeno-III (XIII) self-etching adhesive systems, with or without light-activation, against cariogenic bacteria, and to assess the influence of human dentine on the antibacterial activity of these materials. METHODS: An aliquot of 10 microl per material (and individual components) were pipetted onto paper and dentine discs distributed in Petri dishes containing bacterial culture in BHI agar. Positive control was 0.2% chlorhexidine digluconate (CHX). RESULTS: After incubation, the adhesive components of CPB and CSEB, liquid A of XIII and C3SB did not present antibacterial activity when applied to paper discs. The non-light-activated CPB primer+adhesive promoted the greatest inhibition of Streptococcus mutans (p<0.05), whereas with light-activation, there was no significant difference between primer+adhesive and primer alone. For Lactobacillus acidophilus, CPB primer presented the greatest antibacterial activity in both light-activation conditions (p<0.05). Regarding the dentine discs, only CHX promoted an inhibitory effect, though less intense than on paper discs (p<0.05). CHX presented greater antibacterial activity against S. mutans than against L. acidophilus (p<0.05). CONCLUSIONS: Light-activation significantly reduced the antibacterial activity of the self-etching adhesive systems; MDPB incorporation contributed to the effect of adhesive systems against cariogenic bacteria; the components eluted from the adhesive systems were not capable to diffuse through 400 microm-thick dentine disc to exert their antibacterial activity against cariogenic bacteria.     

Penetration of bacteria in bovine root dentine in vitro

AIM: The aim of this study was to develop a test model to quantify the penetration of bacteria into dentinal tubules. METHODOLOGY: The model consisted of two compartments separated by a bovine dentine specimen with a thickness of 1.5-3.1 mm. The root cementum was removed from the root surface and the specimens were oriented in the model with the pulpal side facing the inoculated chamber of the test model. One compartment contained the test organism and the other was filled with sterile broth that was evaluated for growth of the test organism. The depth of bacterial penetration was measured in the dentine with or without a smear layer using both a histological and a quantitative recovering grinding technique, after 6 weeks of exposure to the microorganisms. RESULTS: E. faecalis penetrated dentine significantly deeper than A. israelii (P < 0.001). After removal of the smear layer with EDTA, E. faecalis penetrated significantly deeper than in dentine pretreated with saline only (P < 0.01) or with a combination of saline and sodium hypochlorite (P < 0.01). Microorganisms were found in 89% of the cultured specimens and in 80% of the specimens that were evaluated with light microscopy. Total penetration through the dentine specimen and infection of the broth in the test compartment of the model occurred in only two out of 72 specimens. CONCLUSION: Collection and immediate culturing of infected dentine dust and counting colony forming units (CFU) allowed an overview of the number of bacteria per sample and was more sensitive than microscopy. Removal of the smear layer enhanced bacterial penetration.     

Cultivatable bacteria in dentine after caries excavation using rose-bur or carisolv

To measure the amount of viable bacteria after excavation using conventional rose-bur or the chemo-mechanical Carisolv method, a total of 22 lesions were analyzed (one vital tooth per patient) in this open, controlled and randomized study. Two samples per lesion were taken under aseptic conditions using a rose-bur, one superficially in the caries lesion and one after completed excavation. In in vitro tests more material was collected from the hard caries free dentine as compared to the carious dentine. The samples were incubated on blood agar (aerobically and anaerobically), Rogosa (SL) agar and mitis salivarius (MS) agar. For blood agar (aerobic) both methods resulted in a significant decrease in CFU, for blood agar (anaerobic) and MS agar only the Carisolv method resulted in a significant decrease in CFU and for SL agar neither method resulted in a significant decrease in CFU. Comparing CFU before and after excavation, a considerable reduction of CFU was seen ranging from 10(1) to 10(4). Comparing the excavation methods, there were no significant differences, except in the case of blood agar (aerobic), which showed that Carisolv excavation was more effective in reducing CFU. This study indicated that bacterial sampling collected more material from hard dentine as compared from soft. Remaining bacteria after excavation were low in both groups. The Carisolv method seemed to remove bacteria at least up to and possibly beyond the extent of conventional drilling.     

Influence of fluoride-releasing restorative material on root dentine secondary caries in situ

The usefulness of fluoride-releasing restorations in secondary caries prevention may be questioned because of the presence of other common sources of fluoride and because of ageing of the restorations. This study tested the hypothesis that glass-ionomer cement restorations, either aged or unaged, do not prevent secondary root caries, when fluoride dentifrice is frequently used. Sixteen volunteers wore palatal appliances in two phases of 14 days, according to a 2 x 2 crossover design. In each phase the appliance was loaded with bovine root dentine slabs restored with either glass-ionomer or resin composite, either aged or unaged. Specimens were exposed to cariogenic challenge 4 times/day and to fluoridated dentifrice 3 times/day. The fluoride content in the biofilm (FB) formed on slabs and the mineral loss (DeltaZ) around the restorations were analysed. No differences were found between restorative materials regarding the FB and the DeltaZ, for either aged (p = 0.792 and p = 0.645, respectively) or unaged (p = 1.00 and p = 0.278, respectively) groups. Under the cariogenic and fluoride dentifrice exposure conditions of this study, the glass-ionomer restoration, either aged or unaged, did not provide additional protection against secondary root caries.     

Inhibition of root caries progression by an antibacterial adhesive

A dentin primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) has been shown to penetrate and kill the bacteria in artificially demineralized dentin. We hypothesized that an experimental adhesive system, which incorporates the MDPB-containing primer, would be effective in inhibiting the progression of root caries in vitro. Artificial caries lesions were prepared by either an acid-gel or a Streptococcus mutans culture technique on the roots of extracted human teeth. The progression of these lesions after the application of the experimental or proprietary adhesive system was examined. Further demineralization was completely prevented by the experimental adhesive system, while lesions managed with the proprietary materials showed limited ability to inhibit further demineralization. We conclude that the experimental adhesive system can inhibit the progression of root-surface caries in vitro, through a combination of its antimicrobial activity and sealing of the demineralized dentin.     

Cytotoxic effects of composite restorations employing self-etching primers or experimental antibacterial primers

OBJECTIVE: The aim of this study was to investigate the cytotoxic effects of composites which employ proprietary self-etching primers or experimental primers containing an antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on human pulpal cells by in vitro dentine barrier tests. METHODS: Experimental primers were prepared by the addition of MDPB to each of two control proprietary primers at 1, 2 and 5%. Direct and indirect composite specimens were placed using each primer on one side of a dentine disk assembled in a simple pulp chamber device. Human pulp cells were incubated on the other side of the disk. After 48 h of incubation, the uptake of [3H]-thymidine by the cells was compared with that for negative controls using wax. Tests were repeated four times for each material. The diffusion of monomers from each specimen was determined using the same device. RESULTS: The specimens with control primers showed 26-35% reduction in cell activity. There were no significant differences in cytotoxicity between the control and experimental primers-specimens (Kruskal-Wallis test, p > 0.05). 2-Hydroxyethyl methacrylate at more than 1 mg ml-1 diffused from all specimens and was considered to be the cause of cytotoxic effects. The concentrations of MDPB diffused from the experimental primers-specimens were less than the toxic level, even for 5% MDPB-containing specimens. CONCLUSIONS: The results demonstrate that composites employing proprietary self-etching primers produced cytotoxic effects on human pulpal cells in vitro, although the toxicity was not severe. Incorporation of MDPB into a proprietary primer of up to 5% had no significant influence on the cytotoxicity observed.     

In-vitro antibacterial susceptibility of bacteria taken from infected root dentine to a mixture of ciprofloxacin, metronidazole and minocycline

The aim of this study was to clarify the antibacterial effect of a mixture of ciprofloxacin, metronidazole and minocycline, with and without the addition of rifampicin, on bacteria taken from infected dentine of root canal walls. The efficacy was also determined against bacteria of carious dentine and infected pulps which may the precursory bacteria of infected root dentine. This efficacy was estimated in vitro by measuring bacterial recovery on BHI-blood agar Plates in the presence or absence of the drug combination. Bacteria ranging in number from 10² to 10⁶ occurred in samples of infected root dentine (27 cases). However, none was recovered from the samples in the presence of the drug combination at concentrations of 25 μg ml^-1 each. The respective drug alone (10, 25, 50 and 75 μg ml^-1) substantially decreased the bacterial recovery, but could not kill all the bacteria. Bacteria taken from carious dentine (25 cases) and infected pulps (12 cases) were also sensitive to the drug combination. These results may indicate that the bactericidal efficacy of the drug combination is sufficiently potent to eradicate bacteria from the infected dentine of root canals.     

A randomised,controlled clinical trial comparing chlorhexidine gel and low‐dose fluoride toothpaste to prevent early childhood caries

International Journal of Paediatric Dentistry 2013; 23: 216–224 Objectives. This randomised, controlled trial compared the effectiveness of 0.12% chlorhexidine (CHX) gel and 304% fluoride toothpaste to prevent early childhood caries (ECC) in a birth cohort by 24 months. Methods. The participants were randomised to receive either (i) twice daily toothbrushing with toothpaste and once daily 0.12% CHX gel (n = 110) or (ii) twice daily toothbrushing with toothpaste only (study controls) (n = 89). The primary outcome measured was caries incidence and the secondary outcome was percentage of children with mutans streptococci (MS). All mothers were contacted by telephone at 6, 12, and 18 months. At 24 months, all children were examined at a community dental clinic. Results. At 24 months, the caries prevalence was 5% (3/61) in the CHX and 7% (4/58) in the controls (P = 0.7). There were no differences in percentages of MS‐positive children between the CHX and control groups (54%vs 53%). Only 20% applied the CHX gel once daily and 80% less than once daily. Conclusions. Toothbrushing using 304% fluoride toothpaste with or without the application of chlorhexidine gel (0.12%) reduces ECC from 23% found in the general community to 5–7%. The lack of effect with chlorhexidine is likely to be due to low compliance.     

Penetration of an antibacterial dentine-bonding system into demineralized human root dentine in vitro

In this study, the penetration of three proprietary dentine-bonding agents (Prime & Bond 2.1, Single Bond, Liner Bond 2) and experimental dentine-bonding systems incorporating an antibacterial monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB), into artificial root caries lesions was evaluated, and the bactericidal activity of each material against Streptococcus mutans or Lactobacillus casei impregnated into demineralized dentine blocks was assessed. All of the commercial dentine-bonding agents were capable of penetrating into the artificial carious lesions to more than 150 microm. The depth of penetration of the experimental systems, which were based on Liner Bond 2, was not significantly different from that of their parent product. Liner Bond 2 primer exhibited the greatest bactericidal effects among the three proprietary dentine-bonding agents tested. Bactericidal activities of experimental primers containing MDPB were greater than those of any other products, and the application of 4% MDPB-containing primer resulted in complete killing of bacteria in demineralized dentine. The results indicate that the penetration of dentine-bonding agents into extensively demineralized root dentine is possible in vitro, and the experimental dentine-bonding systems containing the antibacterial monomer MDPB are capable of killing bacteria within demineralized dentine. This could be of benefit when managing root caries lesions.     

氯化钠溶液对人牙根面牙本质早期龋再矿化作用的影响

目的：探讨单纯用氯化钠（NaCl)溶液处理人牙根面牙本质早期龋后，提高根面早期龋再矿化作用的可行性，方法：在人牙根面上形成早期人工龋，将标本分组，分别用0．5mol/L,NaCl溶液和0．5mol/L EDTA二钠盐溶液浸泡后，用再矿化液处理，扫描电镜下观察比较早期龋矿化前牙根表面形态及矿化后牙根表面矿物盐沉积情况，显微X线照像及其图像分析比较矿化后矿物含量的不同。结果：人牙根面早期龋表面用NaCl溶液浸泡前后无明显改变，早期龋用EDTA二钠盐溶液浸泡后表面见大量牙本质小管开放，再矿化后，前者比后者表层明显增厚，表层阻射度明显增强。结论：用NaCl溶液处理人牙根面早期龋以后，再矿化效果明显增强，NaCl溶液对早期龋表面无不良影响。     

RECOLITE治疗老年人静止根面龋伴牙本质过敏症的临床研究

目的:观察RECOLITE(脱敏王)治疗老年人静止根面龋伴牙本质过敏症的疗效.方法:实验组使用RECOLITE,对照组使用0.48mol/L的氟化钠溶液.记录第3次治疗后的疗效及实验组3个月后的随访结果.结果:实验组:显效50颗(90.90%),有效3颗(5.45%),无效2颗(3.63%),总有效53颗(96.36%);对照组:显效23颗(40.90%),有效29颗(52.72%),无效3颗(5.45%),总有效52颗(94.90%).两组总有效率差异无显著性(P＞0.05),显效率差异显著(P＜0.05).3个月后实验组疗效:显效43颗(89.58%),有效3颗(6.25%),无效2颗(4.16%),总有效46颗(95.83%).结论:RECOLITE对老年人静止根面龋既有消毒作用又对其伴牙本质过敏症具有治疗作用.     

Removing dentine caries in deciduous teeth with Carisolv: a randomised, controlled, prospective study with six-month follow-up, comparing chemomechanical treatment with drilling

Dental fear is often associated with experience of pain, unpleasant sounds and uncomfortable vibrations caused by dental drills. Therefore patients welcome alternative, less painful excavating methods such as lasers, sandblasters and chemomechanical systems. The aim of this study was to compare a chemomechanical caries removal system (Carisolv) to traditional drilling with regard to patient acceptance and time consumption as well as the six-month success rate of fillings. Ninety-two primary teeth in 46 children were included in the study. From this study, the following conclusions can be drawn: patient acceptance of Carisolv-treatment compared to drilling is excellent, since 65% would choose Carisolv and no one drilling when treated next time. The dentists rated patients' degree of pain significantly lower in Carisolv situations than in drill situations. Time consumption is significantly higher when excavating with Carisolv (6.7 min.) than with drill (3.3 min.). The durability of fillings six months after treatment is equal in the two groups.     

In vitro analysis of inhibitory effects of the antibacterial monomer MDPB-containing restorations on the progression of secondary root caries

Objective

This study aimed to analyze in vitro inhibitory effects of restorative materials containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on the formation of artificial secondary root caries lesions.

Methods

Class V cavities (2 mm × 2 mm) were prepared in 75 human root fragments. Specimens were randomly divided into five groups (n = 15 fragments per group) and restored as follows: (I) MDPB-free adhesive system + MDPB-free composite (negative control); (II) resin modified glass ionomer (RM-GIC; positive control); (III) MDPB-free adhesive system + MDPB-containing composite (2.83% MDPB); (IV) MDPB-containing adhesive system + MDPB-free composite; (V) MDPB-containing adhesive system + MDPB-containing composite. Artificial secondary root caries lesions were produced by a biological artificial caries challenge. The restored specimens were immersed into a culture medium containing Streptococcus mutans and sucrose for 15 days. Histological slices (80 ± 20 μm) of the specimens were used for measuring the mean depths of the artificial lesions produced in both margins of the restorations using polarized light microscopy. Results were expressed in percentage related to the mean depth of the negative control, considered 100%. Data were compared by ANOVA followed by the Tukey's test (p ≤ 0.05).

Results

The depths of lesions adjacent to cavities filled with RM-GIC (GII; 85.17 ± 15.2%) were significantly (p < 0.01) shallower than those adjacent to restorations with MDPB-free composite (GI; 100.00 ± 10.04%), despite the presence of MDPB in the adhesive system (GIV; 101.95 ± 21.32%). The depths of lesions adjacent to cavities restored with MDPB-containing composite (GIII; 82.68 ± 12.81% and GV; 85.65 ± 15.42%), despite the adhesive system used, were similar to those of RM-GIC (GII). Mean lesions depths in these groups decreased from 13% (GV) to 17% (GIII) in relation to the negative control (GI).

Conclusions

MDPB-containing composite inhibits the progression of artificial secondary root caries lesions regardless of adhesive systems.     

Studies of dental root surface caries. 1: Comparison of natural and artificial root caries lesions

Qualitative polarized light microscopy and cross-sectional microhardness testing profiles were used to compare artificial root caries lesions with those naturally present in extracted human teeth. The artificial lesions were produced by immersion of roots with exposed windows in chemical buffers of acetate and lactate with no added enzymes or bacteria. The three buffer systems used produced lesions with the range of histological characteristics of natural lesions. These included a 'body' or 'surface' zone of the lesion when viewed in water, and a 'frontal' zone of reverse birefringence when viewed in quinoline. The 'frontal' zone was noted to first develop after three days of immersion in acetate buffer. Advanced natural lesions exhibited a wide, diffuse, advancing front, which was similar to that produced by 28-60 day lesions in acetate. Microhardness profiles of natural lesions could all be matched by one or more of the artificial lesions. The demineralizing process was seen to reduce mineral content across the lesion from 45 per cent in normal dentine to between 15 and 25 per cent.     

A split-mouth randomised controlled trial comparing the clinical effects of MVISTA with chorion membrane or connective tissue graft in multiple gingival recessions

ObjectivesModified form of VISTA (MVISTA), a novel surgical procedure, aims at comprehensive root coverage that maintains the inner continuity of the periosteum and papilla. This technique incorporates any regenerative graft material within the tunnel. The objective of study is to compare the MVISTA for treating multiple adjacent gingival recessions and chorion membranes or grafts of connective tissues.Materials and methodsThis is a split-mouth type randomized trial. In this trial total of 18 patients were considered. The patients in this trial had multiple adjacent, gingival recessions of Miller's Classes I/II, and they were randomized to either the MVISTA with chorion membrane (test) or connective tissue graft (CTG) (control) group. A baseline and one year after surgery were considered for recording to mean root coverage (MRC), complete root coverage (CRC), and clinical periodontal parameters. An intragroup comparison was made.ResultsThe intragroup comparison of recession depth baseline and 12 months after-surgery record found a significant difference between the two groups (P = 0.00). In the postoperative condition, the depth of recession reduction was higher in the test group than in the control group. However, from a statistical perspective, the difference was insignificant (P > 0.05). At the end of the year, it was found that the width of the keratinized tissue had increased significantly (P < 0.05). The MRC in the test group was significantly higher (91.33 %±8.17 %) than that in the control group (89.46 %±11.22 %) (P > 000). At the end of 1 year, the test group showed 66.67 % CRC compared to 44.44 % in the control group. The gingival phenotype displayed statistically significant improvement in the test group (p = 0.004). PD and CAL showed statistically nonsignificant outcomes (P > 0.05).ConclusionsAs far as multiple adjacent gingival recession treatment is concerned, MVISTA with chorion membrane treatment enhanced the gingival phenotype, restored complete root coverage (66.6%), and increased the width of keratinized tissue. CTG and CM demonstrated good root coverage results; the latter might be used as a substitute graft to treat multiple recessions.     

An in-vitro investigation of the antibacterial effect of nisin in root canals and canal wall radicular dentine

AIM: To determine whether nisin, a bacteriocin, would be effective at killing Enterococcus faecalis and Streptococcus gordonii cells in solution and within the root canal system. METHODOLOGY: Bacterial isolates of E. faecalis and S. gordonii were grown from glycerol stocks in closed tubes containing BHY broth at 37 degrees C. The minimum bactericidal concentration (MBC) of nisin for both bacterial species was determined by a microdilution method. Extracted human teeth were decoronated to produce roots of equal length with a single canal and divided into six groups of 10 roots. The canals were prepared to a master apical size 30 file using 0.04 taper Ni-Ti rotary instruments. Bacterial samples of each species were inoculated into three groups of prepared roots and incubated in closed tubes at 37 degrees C for 21 days. The root canals in each group were then medicated with water (control), calcium hydroxide powder mixed with sterile water [Ca(OH)2], or nisin and incubated for a further 7 days. Rotary Ni-Ti files were used to take radicular dentine samples from the walls of each canal which were then incubated in BHY broth for 24 h. Optical density (OD600) readings were taken as a measure of bacterial growth. RESULTS: The MBC of nisin for E. faecalis and S. gordonii was 70 and 20 mg mL(-1) respectively. Calcium hydroxide and nisin medication eradicated infection within the root canal while cells remained viable in the control group. Mean optical density (OD600) readings from canal wall dentine shavings infected with E. faecalis were 1.32 +/- 0.98, 0.73 +/- 0.27 and 0.69 +/- 0.38 for the control, Ca(OH)2 and nisin samples respectively. Corresponding mean readings for S. gordonii were 1.19 +/- 0.18, 0.73 +/- 0.15 and 0.60 +/- 0.29. The Ca(OH)2 and nisin group readings were significantly (P < 0.01) lower than the control for each species as tested by Student's t-test and Mann-Whitney U statistical analysis. Values for Ca(OH)2 and nisin were not significantly (P > 0.01) different. CONCLUSION: Nisin was effective at eradicating E. faecalis and S. gordonii cells in pure culture and was comparable with Ca(OH)2 in the elimination of these species from within the root canal system.     

The association of selected bacteria with the lesions of root surface caries

Plaque from the root surfaces of 165 subjects (mean age 65.5 years, 22-26 teeth/subject) was analysed for specific bacteria. Five subject groups were defined: A (DMFS 16.4), B (DMFS 55.9), C1 (DMFS 55.6), C2 (DMFS 57.0) and C3 (DMFS 48.1). Groups C1 and C2 had unrestored root surface lesions; Group A, B and C3 were free of unrestored root caries and differed in their coronal caries experience. Streptococcus mutans was isolated more frequently from the root lesions in Groups C1 and C2 than from intact root surfaces in Group A. Streptococcus oralis, Streptococcus mitis 1 and Streptococcus sanguis were isolated more frequently from Group A. The percentage contribution that S. mutans made to plaque from lesions in Groups C1 and C2 was higher than that from plaque in Group A and Actinomyces viscosus serovar 2 contributed more to plaque in Group C1 than in samples from Group A. The percentage counts of Lactobacillus in plaque from lesions in Groups C1 and C2 were higher than those from intact roots in Groups A, B, and C3. Subjects were also grouped on the presence of Lactobacillus and S. mutans in plaque samples. Samples with both organisms (n = 17) showed significantly higher isolation frequencies of specific strains of S. mitis 1 and also A. viscosus serovar 2 compared with samples of plaque containing S. mutans or Lactobacillus. Actinomyces naeslundii serovar 1 was not isolated from samples containing both S. mutans and Lactobacillus. The results confirm an association of S. mutans and Lactobacillus with root surface lesions and suggest a relationship between lesions and A. viscosus serovar 2.     

The permeability of natural dentine caries before and after restoration: An in vitro study

OBJECTIVES: The objectives of this experiment were to determine in vitro the permeability of teeth exhibiting a range of natural dentine caries and the effects of caries excavation and subsequent restoration on the dentine permeability of extracted teeth. METHODS: Forty-five human permanent molars with obvious occlusal caries were selected and coronal dentine permeability was measured before (baseline) and after caries excavation, as well as after acid etching the prepared cavity and finally, after restoration. RESULTS: The small permeability values for all teeth made statistical testing between the different stages of specimen preparation both meaningless and inappropriate. An alternative means of examining the data was to calculate the percentage of teeth which had exhibited permeability values greater than zero at each of the four specimen preparation stages. The percentage of teeth with permeability greater than zero remained unchanged before and after cavity preparation (23%). Removal of the smear layer, however, increased substantially the percentage of teeth demonstrating permeability greater than zero, to 72%. None of the restored teeth demonstrated measurable permeability. CONCLUSION: The teeth chosen exhibited a range of dentine caries and, surprisingly, demonstrated either low or no measurable permeability. This experiment highlighted the need for more investigation into the quality of carious-affected dentine and the properties of the smear layer produced from such dentine.