The inability of Streptococcus mutans and Lactobacillus acidophilus to form a biofilm in vitro on dentine pretreated with ozone

Ozone therapy in dentistry: An overview of the biological mechanisms involved (Review)

At low medically-relevant concentrations, ozone serves as an oxidant with a wide spectrum of antimicrobial activity and the ability to promote healing and reduce inflammation. Despite providing therapeutic benefits in a range of diseases, certain adverse effects and contraindications of ozone treatment must be considered. These are primarily related to toxicity from inhalation and systemic types of administration and can be avoided by following relevant guidelines and recommendations. Ozone therapy has been implemented in a number of fields of dentistry and the most commonly used formulations for the oral cavity are gaseous ozone, ozonized water and ozonized oil. The biological mechanisms underlying the molecular effects of ozone have been increasingly reported, but currently remain largely unknown. The aim of the present review was to provide an overview of the mechanisms involved in ozone interaction with dental tissues. The present review focused on relevant evidence regarding the effect of ozone on dental tissues, including periodontal structures, dental cells, enamel and dentine, considering in vitro studies in addition to animal and human studies. A variety of biological mechanisms acting through multiple biochemical target pathways were reported to be responsible for the therapeutic effects of ozone. The main beneficial effects of ozone occurred in the following domains: antimicrobial activity, remineralization and microstructural changes of hard dental tissues, immunomodulation and biostimulation of dental and periodontal cells. Additional research could provide further insights into the use of ozone, increase its use for broader clinical applications and assist in the selection of targeted protocols.

Effect of 20-ppm ozone and 1% chlorhexidine gels on plaque index and Streptococcus mutans counts in the dental plaque in 6-12-year-old children: A randomized, double-blind clinical trial

Background

One of the methods to control dental caries is to use ozone. Since it is difficult for children to use mouthwashes, the present study aimed to evaluate 20-ppm zone and 1% chlorhexidine (CHX) gels' effects on the plaque index and Streptococcus mutans counts in 6-12-year-old children.

Methods

In the present double-blind clinical trial, 165 children, 6-12 years of age, referring to the Department of Pediatric Dentistry, Tabriz Faculty of Dentistry, were selected based on inclusion and exclusion criteria and randomly assigned to three groups: ozone gel, CHX gel, and control. The subjects were instructed to place an adequate amount of the gels on all the surfaces of their teeth with one clean finger. The patients and evaluators were blinded to the study groups. The plaque index and S. mutans counts in plaque samples were determined before intervention and three weeks after intervention on the buccal surface of the most posterior maxillary tooth (left or right). S. mutans counts were determined by culture. STATA software version 14 was used for statistical analyses using Wilcoxon, Kruskal-Wallis, and post hoc Dum tests. Statistical significance was defined at P<0.05.

Results

The 20-ppm ozone and 1% CHX gels significantly decreased dental plaque compared to the control group (P<0.05), and their effects were similar (P>0.05). These gels significantly decreased the colonies and bacterial counts of S. mutans (P<0.05).

Conclusion

The performance of 20-ppm ozone gel in decreasing the dental plaque and S. mutans counts was similar to 1% CHX gel.

Ozone therapy in management and prevention of dental caries- A Review

Dental caries is the irreversible microbial disease of teeth causing demineralization of inorganic and destruction of organic. It is of serious concern as it can lead to pain due to various pulpal and periapical pathologies. It is a tedious job to prevent this dental caries which is very common dental problem with each and everyone. With new concepts emerging in prevention and management of caries, Ozone therapy is tool to prevent and manage dental caries. The use of ozone (O3) gas as a therapy is skeptical due to unstable structure. The main beneficial effect of ozone is its antibacterial effect against various bacteria. These antibacterial effects are even attributed to the prevention and management of caries. This therapy is of controversy as some prove this to be less or no effective or some prove to be more effective. This article reviews various benefits of ozone therapy in prevention and management of caries and also discussion on controversies to it.

Comparative Evaluation of the Remineralization Potential of Fluoride-containing Toothpaste, Honey Ginger Paste and Ozone. An In Vitro Study

Introduction

A drop in pH of the oral cavity results in demineralization, which, if continued, leads to loss of minerals from tooth structure, resulting in dental caries. A goal of modern dentistry is to manage noncavitated caries lesions noninvasively through remineralization in an attempt to prevent disease progression.

Materials and methods

A total of 40 extracted premolar teeth were selected for the study. The specimens were divided into four groups, group I, the control group; group II, remineralizing agent as fluoride toothpaste; group III, the treatment material as ginger and honey paste; and group IV, the treatment material as ozone oil. An initial reading of surface roughness and hardness was recorded for the group (control group). Repeated treatment has continued lasting 21 days. This saliva was changed each day. Following the lesion formation procedure, the surface microhardness was measured for all specimens. The parameters were 200 gm force for 15 seconds with a Vickers indenter and the roughness of the demineralized area of each specimen was obtained by using the surface roughness tester.

Results

Surface roughness was checked by using a surface roughness tester. Before starting the pH cycle, the baseline value for the control group was calculated. The baseline value for the control group was calculated. The surface roughness average value for 10 samples is 0.555 µm and the average surface microhardness is 304 HV; the average surface roughness value for fluoride is 0.244 µm and the microhardness is 256 HV, 0.241 µm, and 271 HV value for honey-ginger paste. For ozone surface roughness average value is 0.238 µm and the surface microhardness average mean value is 253 HV.

Conclusion

The future of dentistry will rely on the regeneration of tooth structure. There is no significant difference seen between each treatment group. Considering the adverse effect of fluoride, we can consider honey-ginger and ozone as good remineralizing agents for fluoride.

How to cite this article

Kade KK, Chaudhary S, Shah R, et al. Comparative Evaluation of the Remineralization Potential of Fluoride-containing Toothpaste, Honey Ginger Paste and Ozone. An In Vitro Study. Int J Clin Pediatr Dent 2022;15(5):541-548.

The effect of dietary fiber on gut barrier function, gut microbiota, short-chain fatty acids, inflammation and clinical outcomes in critically ill patients: A systematic review and meta-analysis

BACKGROUND

Although some studies have explored the relationships between dietary fiber (DF) supplement and gut barrier function, changes of gut microbiota and other clinical outcomes in critically ill patients, the results from different studies were not consistent.

OBJECTIVE

The purpose of this study was to explore the effect of dietary fiber on gut barrier function, gut microbiota, short-chain fatty acids (SCFAs), inflammation and clinical outcomes in critically ill patients.

METHODS

A search was performed through PubMed, Embase, the Cochrane Central Register of Clinical Trials, Web of Science and EBSCO-host that includes Health Sciences Research from inception to July 12, 2021. Data were pooled using fixed effects model for low heterogeneity and random effects model for high heterogeneity. Data were expressed as mean difference (MD) or odds ratio (OR) with confidence interval.

RESULTS

A total of 21 studies involving 2084 critically ill patients were included. The results showed that there was a significant reduction in intestinal permeability demonstrated by lactulose/rhamnose ratio (MD:-0.04; 95%CI:-0.08, -0.00; P = 0.03) on day 8 in DF supplement group. Three studies reported the relative abundance (RA) of gut microbiota and the results showed the RA of some SCFAs producers increased higher in DF supplement group. There was a significant decrease in C-reactive protein on day 14 (MD:-36.66; 95%CI:-44.40, -28.93; P<0.001) and the duration of hospital stay (MD:-3.16; 95%CI:-5.82, -0.49; P<0.05) after DF supplement. There were no significant differences on SCFAs levels, the duration of mechanical ventilation and mortality between the two groups. However, in subgroup analysis, the results indicated there was a significant reduction on the duration of mechanical ventilation in fiber combined probiotic group (MD:-13; 95%CI:-19.69, -6.31; P<0.001). Besides, significant decreases in the duration of hospital stay and risk of mortality were seen in the subgroups with fiber supplementary dose ≥20 g/d (MD:-5.62; 95%CI: -8.04, -3.21; P<0.0001; OR: 0.18, 95%CI: 0.06, 0.57, P = 0.004), as well as in medical ICU (MD:-4.77; 95%CI: -7.48, -2.07; P<0.01; OR: 0.13; 95%CI: 0.03, 0.65; P<0.05).

CONCLUSIONS

Dietary fiber may improve the gut barrier function, modulate the intestinal microbiota, decrease systemic inflammatory response and may advance the clinical outcomes in critically ill patients. This article is protected by copyright. All rights reserved.

A novel dual-action antimicrobial peptide for caries management

OBJECTIVES

To develop a novel dual-action peptide with antimicrobial and mineralising properties.

METHODS

A novel peptide, namely GA-KR12, was synthesised through grafting gallic acid to KR12. The secondary structure of GA-KR12 was evaluated by circular dichroism spectroscopy. The stability was evaluated by high-performance liquid chromatography. The cytotoxicity was evaluated by a mitochondrial dehydrogenase activity assay. The antimicrobial properties against common cariogenic species were evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC). The morphology of cariogenic species was analysed by transmission electron microscope (TEM). To assess the mineralising effect of GA-KR12 on enamel, the lesion depths, mineral loss, surface morphology, calcium-to-phosphorus ratio and crystal characteristics were determined using micro-computed tomography, scanning electron microscopy (SEM) and energy dispersive spectroscopy X-ray diffraction, respectively.

RESULTS

GA-KR12 did not exhibit cytotoxicity against HGF. Around 82% of the GA-KR12 remained in human saliva at 37°C for 1 h. The MIC and MBC/MFC against the tested species were 10-320 μM and 20-1,280 μM, respectively. GA-KR12 induced remarkable morphological defects in the tested species. The enamel treated with GA-KR12 had smaller lesion depths (p < 0.001), less mineral loss (p < 0.001) and higher calcium-to-phosphorus molar ratios (p < 0.001) than those in the enamel treated with water. SEM showed a well-organised prism pattern in enamel treated with GA-KR12. X-ray diffraction revealed that the hydroxyapatite on the enamel treated with GA-KR12 was better crystalised.

CONCLUSIONS

This study developed a biocompatible and stable peptide which inhibited the growth of cariogenic species and mineralised the enamel caries.

CLINICAL SIGNIFICANCE

The novel dual-action peptide, GA-KR12, is potential applicable in the management of caries.

Treatment of symptomatic, deep, almost cariously exposed lesions using ozone

The aim of this controlled randomized crossover study was to assess post-treatment pain and the need for root canal treatment after the use of a traditional caries removal method followed by restoration, or after an ozone method of more conservatively managing the deep caries and a restoration. 84 participants (42 males and 42 females, mean age ± SD = 23.9 ± 2.0 years) were randomly allocated to receive either a traditional (n = 42, 21 males and 21 females) or ozone (n = 42, 21 males and 21 females) method. The ozone method only differed from the traditional method by leaving the deep leathery caries on the pulpal floor and then treating this with 20 s of ozone from the healozone X4 (Curozone, Germany). All caries was removed in the traditional group. A conventional glass ionomer cement (Riva Self Cure High Viscosity, SDI, Australia) was placed followed by a bonded composite resin restoration (Filtek Z250 Universal Restorative, 3 M ESPE, USA) in each cavity. The visual analogue scale was used to assess pain scores before treatment and after 24 h. The participants were then followed up for 2 years to assess the need for root canal treatment. Statistical significance levels were set at α ≤ .05. Both groups were associated with significant reduction of pain scores 24 h after treatment (p < .0001). The ozone treatment was associated with less pain 24 h after treatment (p < .0001) and less need for root canal treatment (p = .014), after 2 years follow up, than the conventional treatment. In conclusion, treatment of symptomatic, deep carious lesions by ozone following partial removal of caries was accompanied with less pain and occurrence of RCT after treatment compared to traditional complete caries removal.

Effect of Prebiotics-Enhanced Probiotics on the Growth of Streptococcus mutans

Streptococcus mutans predominantly creates an acidic environment in an oral cavity. This results in dental demineralization and carious lesions. The probiotics are beneficial microorganisms that modulate the bacterial balance in the digestive system. Prebiotics are defined as nondigestible oligosaccharides that are utilized for the selective stimulation of the beneficial microorganisms. The objective of this study was to evaluate the efficacy of the prebiotics, galactooligosaccharides (GOS) and fructooligosaccharides (FOS), for enhancing the probiotic Lactobacillus acidophilus ATCC 4356, for inhibiting Streptococcus mutans (A32-2) for the prevention of dental caries. The growth rate of the S. mutans significantly decreased when cocultured with L. acidophilus in the GOS-supplemented medium at 3%, 4%, and 5%. In the FOS-supplemented medium, the growth rate of S. mutans significantly decreased in all concentrations when cocultured with L. acidophilus. There was no significant difference in the growth rate of L. acidophilus in all concentrations of either GOS or FOS. It can be concluded that the growth rate of S. mutans was significantly retarded when cocultured with L. acidophilus and the proper concentration of prebiotics. These prebiotics have potential for a clinical application to activate the function of the naturally intraoral L. acidophilus to inhibit S. mutans.

[The need for specific toothpaste in patients receiving occlusal splint therapy]

The aim of the study is to determine the optimal properties of toothpaste for patients receiving occlusal splint therapy. The study comprised 50 people with full dentition (21 male and 29 female) divided into two groups. The main group included 25 individuals receiving occlusal splint therapy while 25 people who did not use splints were recruited as controls. Each group was further divided into two subgroups according to toothpaste used for regular oral hygiene. Examinations were performed after 14, 30 and 90 days using hygienic indices of NCI-C and Turesky and PMA gingival index. The combined effect of toothpaste was estimated by the change in the volume and acidity of saliva. The results suggest a better level of hygiene in the group I, which used toothpaste with sodium bicarbonate and silica.

[Comparative effectiveness of therapeutic toothpastes with fluoride and hydroxyapatite]

The purpose of the study was to assess the impact of toothpastes containing hydroxyapatite and fluoride on enamel caries resistance and remineralization rate. Study groups comprised 160 patients divided in 2 groups of 80 patients: 40 - at the age of 15-17 and 40 at the age of 18-25 who have been using toothpastes with hydroxyapatite and fluoride during 1 year. The plaque determination was carried out with the use of OHI-S and Turesky indexes. Litmus test pieces were used to determine oral fluid pH. The clinical determination of enamel remineralization rate, dynamics of acid resistance of enamel were carried out. Oral hygiene at baseline examination was poor in both groups. After oral hygiene training, there was a tendency towards indexes decrease more pronounced in the 18-25 age group regardless of the composition of the toothpastes used. Mean baseline oral fluid pH in the observation group was 6.5±0.4, in the comparison group - 6.8±0.4. By the end of the trial there was a tendency towards the increase of the oral fluid pH, which were 7.3±0.3 and 7.7±0.3, respectively. The enamel acid resistance of the patients of the observation group was significantly higher (p>0.05) compared with the group of patients using fluoride toothpaste, as well as the proportion of patients in whom the enamel recovery occurred within 24 hours (47.5% vs. 22.5%, respectively).

Inactivation of Pseudomonas aeruginosa biofilms formed under high shear stress on various hydrophilic and hydrophobic surfaces by a continuous flow of ozonated water

The inactivation of Pseudomonas aeruginosa biofilms grown on glass under high shear stress and exposed to a range of dissolved ozone concentrations (2, 5 and 7 ppm) at 10 and 20 min was investigated. The regression equation, log reduction (biofilm) = 0.64 + 0.59×(C - 2) + 0.33×(T - 10), described the dependence of biofilm inactivation on the dissolved ozone concentration (C, ppm) and contact time (T, min). The predicted D-values were 11.1, 5.7 and 2.2 min at 2, 5 and 7 ppm, respectively. Inactivation of biofilms grown on various surfaces was tested at a single dissolved ozone concentration of 5 ppm and a single exposure time of 20 min. Biofilms grown on plastic materials showed inactivation results similar to that of biofilms on glass, while biofilms grown on ceramics were statistically significantly more difficult to inactivate, suggesting the importance of utilizing non-porous materials in industrial and clinical settings.

[Efficiency of paste and suspension with nano-hydroxyapatite on the sensitivity of teeth with gingival recession]

The purpose of our study was to assess the efficiency of toothpaste 'Intensive strengthening of supersensitive teeth with nano-GAP' INNOVA and the suspension 'Liquid Enamel' INNOVA on the sensitivity of teeth with gingival recession. We examined 40 people aged 20-25 years. Each group consisted of 20 people: 10 women, 10 men. The first group (observations) used the paste and the suspension for 14 days, and the second group (comparisons) cleaned teeth only with a brush without a paste. Schiff aerial test was performed to assess the rate of hypersensitivity. As a result of the study, it was found that the combination of paste and liquid suspension with nano-hydroxyapatite for 14 days effectively reduced the hypersensitivity of the teeth with gingival recession that was shown by a statistically significant decrease in the Schiff index in the observation group. Thus, this combination is the method of choice in the treatment of hyperesthesia and can be used as an alternative substitute therapy.

Ozone Gas Effect on Mineral Content of Dentin exposed to Streptococcus mutans Biofilm: An Energy-dispersive X-ray Evaluation

AIM

This study aims to assess the effect of ozone gas on dentin exposed to Streptococcus mutans biofilm by evaluation of mineral content [log calcium-to-phosphorus (Ca/P)] using energy-dispersive X-ray (EDX) spectroscopy.

MATERIALS AND METHODS

Five human third molars were sectioned into four slices of dentin and distributed in four groups: I - control (no treatment); II - ozone therapy; III - biofilm development; IV - ozone therapy followed by biofilm development. Mineral content (log Ca/P) was evaluated by EDX. Data were analyzed by analysis of variance and Tukey's test (p < 0.05).

RESULTS

Results showed that the mineral content of control group (I) was similar to ozone group (II), and was statistically higher than biofilm (III) and ozone + biofilm (IV). The lowest log Ca/P was determined in biofilm group (III).

CONCLUSION

It can be concluded that ozone gas did not grant preventive effects of demineralization by S. mutans biofilm on dentin surface.

CLINICAL SIGNIFICANCE

Ozone gas therapy may be an alternative noninvasive treatment aiming to reduce the levels of caries-associated microorganisms. This therapy may, thereby, be an alternative and/or complementary treatment strategy in preventive dentistry.

Effect of long term application of toothpaste Apadent Total Care Medical nano-hydroxyapatite

The aim of the study was to evaluate the efficacy of toothpaste «Apadent Total Care» containing nanocalciumhydroxyapatite and its influence on caries resistance of tooth enamel and teeth sensitivity. The study involved 30 people: 15 patients aged 17-25 years and 15 aged 35-44 years. Study participants used «Apadent Total Care» toothpaste with nanocalciumhydroxyapatite. To evaluate the effectiveness of toothpastes clinical assessment of enamel remineralization rate was carried out, as well as the dynamics of enamel acid resistance and teeth sensitivity (Shiff index). Clinical evaluation of tooth enamel before the procedure and after 3 months of use of toothpaste with nanohydroxyapatite showed the improvement of all indices. Time for complete remineralisation of enamel in both groups did not exceed 3 days. Acid resistance of tooth enamel increased by 1.65 in group I and 1,75 in group II. The Schiff index after 3 months of using «Apadent» toothpaste also decreased in both groups.

Co-operative effect of exogenous dextranase and sodium fluoride on multispecies biofilms

Background/purpose

The co-operative effect of exogenous dextranase (Dex) and sodium fluoride (NaF) on Streptococcus mutans monospecies biofilms is impressive. Here we investigated the effects of the combination on a mature cariogenic multispecies biofilm and analyzed the potential mechanism.

Materials and methods

A multispecies biofilm of S. mutans, Lactobacillus acidophilus, and Actinomyces viscosus was established in vitro. Dex and NaF were added separately or together. The effects of the agents on the biomass were measured. The exopolysaccharide production was determined with the scintillation counting method. The viability and morphology were evaluated using colony forming unit and confocal laser scanning microscopy, respectively.

Results

In general, biofilms treated with Dex and a little concentration of NaF exhibited a lower biomass, exopolysaccharide production, and viability compared with the control group (P < 0.05). Confocal laser scanning microscopy using a vital fluorescence technique showed the combination treated biofilms appeared to be loose relatively and single cells could be observed. Furthermore, the thickness and viability were also lower than either of the separate agent groups (P < 0.05).

Conclusion

Overall, these findings reveal that a combination of 1 U/mL Dex and 80 μg/mL NaF is a promising candidate for disrupting complex cariogenic multispecies biofilms. This feature may be in that Dex loses the structure of biofilms, thereby facilitating NaF penetration and enhancing its antibacterial effects.

Ozone therapy in the management and prevention of caries

The purpose of this article was to assess the effectiveness of ozone therapy in the management and prevention of caries, reviewing clinical and in vitro studies. Ozone has proven to be effective against gram-negative and gram-positive bacteria, viruses, and fungi. In dentistry, most of the published articles are based on ozone's antimicrobial effects and the treatment of caries. Most of the clinical studies reported ozone to be a promising alternative to conventional methods for caries management. However, a few studies have shown ozone to be insufficient for preventing caries and reducing microorganisms in open occlusal carious lesions. Ozone might be a useful tool to reduce and control oral infectious microorganisms in dental plaque and dental cavity. However, the results of in vitro studies are controversial; while some researchers reported that ozone therapy had a minimal or no effect on the viability of microorganisms, others suggested ozone to be highly effective in killing both gram-positive and gram-negative oral microorganisms. Therefore, more evidence is required before ozone can be accepted as an alternative to present methods for the management and prevention of caries.

Antibacterial effects of silver diamine fluoride on multi-species cariogenic biofilm on caries

Backgrounds

Silver diamine fluoride (SDF) has clinical success in arresting dentin caries, this study aimed to investigate its mechanism of action.

Methods

Using a computer-controlled artificial mouth, we studied the effect of 38% SDF on cariogenic biofilms and dentin carious lesions. We used five common cariogenic bacteria (Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus rhamnosus and Actinomyces naeslundii) to form a cariogenic biofilm that generated carious lesions with a depth of approximately 70 um on human dentin blocks. We applied 38% SDF to the lesions in the test group and water to those in the control group. The blocks were incubated in the artificial mouth for 21 days before evaluation. Microbial kinetics, architecture, viability and distribution were evaluated every 7 days using colony forming unit (CFU), scanning electron microscopy and confocal laser scanning microscopy. The physical properties of the carious lesions were evaluated with microhardness testing, energy dispersive spectroscopy (EDS) and Fourier transform infra-red spectroscopy (FTIR).

Results

The CFU results revealed fewer colony forming units in the test group compared with the control group (p < 0.01). Scanning electron microscopy and confocal microscopy showed less bacterial growth in the test group, and confluent cariogenic biofilm in the control group (p < 0.01). The microhardness and weight percentages of calcium and phosphorus in the test group from the outermost 50mum were higher than in the control group (p < 0.05). EDS showed that calcium and phosphous were higher in outer 50 mum in test groups than in the control FTIR revealed less exposed collagen I in the test lesions compared with the control group (p < 0.01).

Conclusions

38% SDF inhibits multi-species cariogenic biofilm formation on dentin carious lesions and reduces the demineralization process.

Ozone action on Streptococcus mutans and Lactobacillus fermentum: A pilot study

AIM: To study the effectiveness of ozone in the elimination of cariogenic bacteria, followed with fluoride supplements.

METHODS: Sixty extracted teeth free of caries were used, and five groups were constituted. In Group I, the teeth were immersed in artificial saliva. In Group II, the teeth were inoculated with Streptococcus mutans (S. mutans) and immersed in artificial saliva. In Group III the teeth were inoculated with Lactobaccilus fermentum (L. fermentum) and immersed in artificial saliva. In Group IV the teeth were inoculated with S. mutans and L. fermentum and immersed in artificial saliva and the teeth in Group V were inoculated with S. mutans and L. fermentum, and were subjected to the application of ozone and to the action of a fluoride mineralizing gel. DIAGNOdent was used to evaluate the caries of the teeth 3 wk after inoculation of bacteria and after that the teeth of Group V were subjected to the application of ozone during 60 s, by HealOzone. After the application of ozone, products of the remineralization kit supplied by the manufacturer were applied daily, during 30 d. At the end samples were collected for analysis and evaluation of bacterial activity by polymerase chain reaction.

RESULTS: Regarding the value of caries, obtained via DIAGNOdent, in the initial measurement the groups are homogeneous (P = 0.730). There was an increase in DIAGNOdent values, presenting statistical significant difference regarding the initial measurement in all groups (P ˂ 0.001), except in group I - only artificial saliva - which shows that the artificial carie model was effective. Comparing the initial and final measurements for each of the 60 teeth, it can be observed that in 9 teeth (15.0%) there was a decrease in values between the two measurements, one (1.7%) retained the same values in the two measurements and in the remaining 50 cases (83.3%) there was increase in values between the initial and final measurements. It should also be noted that in the teeth inoculated with S. mutans + L. fermentum, there was an increase of the values in 100% of cases, and in all groups except the group with artificial saliva, there is a more frequent increase in the values. In group V, subject to the application of ozone, bacterial DNA was not detected, in group IV, bacterial DNA was detected.

CONCLUSION: Ozone was effective in the elimination of the study bacteria.

Effect of different disinfectant methods on the initial microtensile bond strength of a self-etch adhesive to dentin

The aim of this in vitro study was to evaluate the effect of different disinfection methods on the initial microtensile bond strength of a two-step, self-etch adhesive to dentin. Twenty mandibular molars were sectioned parallel to the occlusal plane to expose the mid-coronal dentin. All of the teeth were divided into four groups (n = 5 per group): (1) in group OZ, the dentin surfaces were exposed to ozone gas from the Ozonytron X delivery system (OzonyTron X-Bioozonix, Munich, Germany), (2) in group ND, the dentin surfaces were irradiated with an Nd:YAG laser (Pulsmaster 600 IQ, American Dental Technologies, U.S.), (3) in group CHX, the dentin surfaces were treated with a 2% chlorhexidine solution, and (4) in the control group, no treatment was applied. In all of the groups, the teeth were restored with Clearfil SE Bond (Kuraray, Tokyo, Japan) and Clearfil Majesty Posterior (Kuraray, Tokyo, Japan), according to the manufacturer's instructions. The teeth were sectioned perpendicular to the bonded surface (surface area of approximately 1 mm(2)). Thus, six to seven specimens were obtained from each tooth, and a total of 34 specimens were analyzed in each group. The specimens were attached to the microtensile test machine (Micro Tensile Tester, T-61010 K, Bisco, U.S.). The data was analyzed using the one-way analysis of variance (ANOVA) and Tukey test (p < 0.05). Fracture modes of each specimen were determined using a stereomicroscope (SZ-PT Olympus, Tokyo, Japan) and a scanning electron microscope (SEM). The lowest bond strength occurred in the OZ group. Significant differences were determined only between group OZ and the other groups (group ND, group CHX, and control group) (p < 0.05). In conclusion, although ozone decreased the microtensile bond strength of the self-etch adhesive system to dentin, the Nd:YAG laser and 2% chlorhexidine did not change the microtensile bond strength so in context of the present study it would appear that the Nd:YAG laser and 2% chlorhexidine may be used as pre-restorative sterilization procedures on the dentin prior to the application of a two-step, self-etch adhesive.

Antibacterial effect of ozone on cariogenic bacterial species

OBJECTIVE

The aim was to evaluate the antibacterial effect of ozone on cariogenic bacterial species with and without the presence of saliva and a possible effect on the salivary proteins.

METHODS

Suspensions of Actinomyces naeslundii (ACTCC 12104(T)), Lactobacilli casei (N CTC 151) and Streptococcus mutans (NCTC 10449), in salt buffer or in saliva, were exposed to ozone gas delivered by the ozone generator Healozone 2130C. Aliquots of the suspensions were taken after 10, 30 and 60s ozone exposures and cultivated on agar plates. Initial number of bacteria per ml was 8.0 x 10(7) (SD 2.2 x 10(7)) (A. naeslundii), 1.0 x 10(8) (SD 3.1 x 10(6)) (L. casei) and 1.0 x 10(8) (SD 7.0 x 10(5)) (S. mutans), respectively. The proteins were separated by SDS electrophoresis and visualized by silver staining.

RESULTS

In salt buffer 92%, 73% and 64% of the initial numbers of A. naeslundii, S. mutans and L. casei, respectively, were killed already after 10s ozone exposure, while approximately 99.9% of the bacteria were dead after a 60s exposure. After 10 and 30s, but not after 60s exposure to ozone, S. mutans and L. casei were less efficiently killed in saliva compared to the salt buffer. Various saliva proteins were degraded by ozone after a 60s exposure.

CONCLUSIONS

The cariogenic species S. mutans, L. casei and A. naeslundii were almost eliminated following 60s of ozone treatment. This killing was reduced in the presence of saliva although increasing the ozone application time to 60s overcame these reductants in saliva. Detection of altered salivary proteins indicates that saliva components constitute additional targets for ozone.