Dental composite biodeterioration in the presence of oral Streptococci and extracellular metabolic products

OBJECTIVE

Secondary caries is a primary cause of early restoration failure. While primary dental caries has been extensively researched, our knowledge about the impact of secondary caries on dental restorations is relatively limited. In this study, we examined how different clinically relevant microbially-influenced environments impact the degradation of nano-filled (FIL) and micro-hybrid (AEL) dental composites.

METHODS

Material strength of two commercial dental composites was measured following incubation in aqueous media containing: i) cariogenic (Streptococcus mutans) and non-cariogenic bacteria (Streptococcus sanguinis) grown on sucrose or glucose, ii) abiotic mixtures of artificial saliva and sucrose and glucose fermentation products (volatile fatty acids and ethanol) in proportions known to be produced by these microorganisms, and iii) abiotic mixtures of artificial saliva and esterase, a common oral extracellular enzyme.

RESULTS

Nano-filled FIL composite strength decreased in all three types of incubations, while micro-hybrid AEL composite strength only decreased significantly in biotic incubations. The strength of both composites was statistically significantly decreased in all biotic incubations containing both cariogenic and non-cariogenic bacteria beyond that induced by either abiotic mixtures of fermentation products or esterase alone. Finally, there were no statistically significant differences in composite strength decrease among the tested biotic conditions.

CONCLUSIONS

The results show that conditions created during the growth of both cariogenic and non-cariogenic oral Streptococci substantially reduce commercial composite strength, and this effect warrants further study to identify the mechanism(s).

CLINICAL SIGNIFICANCE

Dental biofilms of oral Streptococci bacteria significantly affect the mechanical strength of dental restorations.

Effect of lactoferrin on enamel characteristics of primary and permanent teeth: an in-vitro study

BACKGROUND

Lactoferrin, a glycoprotein naturally found in breast milk, is known for its bactericidal and antiviral properties, as well as its capacity to modulate the immune system; therefore, pediatricians routinely recommend it as dietary support. The objective of this study was to determine how lactoferrin oral suspension could affect the enamel surface characteristics of primary and permanent teeth.

METHODS

This research was conducted on 40 unidentified extracted teeth, including primary and permanent teeth. Experimental teeth were free of cracks or enamel defects, as confirmed by careful examination using a dental operating microscope. The crowns were bisected into 80 specimens and assorted into two groups based on the type of dentition. Group DM included 40 specimens of second deciduous molars, while Group PM contained 40 samples of first premolars. Each of the DM and PM specimens was subsequently split based on the type of dispersion medium into two subgroups: a control subgroup (artificial saliva) and a test subgroup (lactoferrin suspension). The specimens were immersed in lactoferrin suspension for two minutes, then kept in artificial saliva for the rest of the 24 h for 30 successive days. This is a pioneering study about the effect of orally supplemented lactoferrin on teeth; therefore, we examined enamel hardness, ultra-morphology, and mineral contents.

RESULTS

Our findings indicated a highly significant decrease (p < 0.01) in the microhardness of the lactoferrin subgroup in Group DM (second deciduous molars) and a significant reduction (p < 0.05) in the microhardness of the lactoferrin subgroup in Group PM (premolars). Calcium weight% was not statistically different (p > 0.05) compared with a significant decline (p < 0.05) in phosphorus weight% in lactoferrin subgroups in both DM and PM groups. The enamel surface of lactoferrin subgroups in both DM and PM groups was demineralized and porous, with the enamel of deciduous teeth being more affected by lactoferrin than permanent teeth.

CONCLUSION

Lactoferrin suspension decreased the microhardness of enamel and both calcium and phosphorus weight percentages. Both dentitions exhibited erosions in the enamel surface, with primary teeth being more affected than the permanent teeth.

Berberine-fluconazole microparticle-based combination therapy to treat candidiasis infections

AIM

This study aims to incorporate alginate microparticles containing berberine and fluconazole into two different types of pharmaceutical formulations, to subsequently evaluate the antifungal activity against Candida albicans.

METHODS AND RESULTS

Alginate microparticles containing BBR (berberine) and FLU (fluconazole) were produced by the spray-drying technique, characterized and incorporated in two pharmaceutical formulations, a vaginal cream and artificial saliva. Broth microdilution, checkerboard, time-kill curve, and scanning electron microscopy were carried out to determine the antifungal effects of BBR and FLU against C. albicans. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of free BBR were 125 μg ml-1. Synergism between BBR and FLU was demonstrated by a fractional inhibitory concentration index (FICI) = 0.0762. The time-kill curve for the combination BBR + FLU showed a more pronounced decrease in fungal growth in comparison to free drugs, and an antibiofilm effect of BBR occurred in the formation and preformed biofilm.

CONCLUSION

Alginate microparticles containing BBR and FLU were obtained and incorporated in a vaginal cream and artificial saliva. Both formulations showed good stability, antifungal effects, and organoleptic characteristics, which suggest that BBR-FLU microparticles in formulations have potential as antifungal therapy.

Effect of three different remineralising agents on prevention against acidic erosion of primary teeth: an in vitro study

PURPOSE

This study aimed to evaluate and compare the protective effect of fluoride varnish (Enamelast™, Ultradent Inc., Cologne, Germany), casein phosphopeptide-amorphous calcium phosphate fluoride/CPP-ACPF (MI Paste Plus, GC Corp., Tokyo, Japan) and self-assembling P11-4 peptide (Curodont™ Protect, Credentis AG, Windisch, Switzerland), against acidic erosion of primary teeth.

METHODS

Forty primary anterior teeth were randomly assigned to four groups (n = 10): group 1: control, group 2: fluoride varnish, group 3: CPP-ACPF and group 4: self-assembling P11-4 peptide. After applying remineralising agents, except for the control group, all specimens underwent an erosive challenge of carbonated soft drink and artificial saliva for 15 cycles of 6 s each at 6-h intervals for a day. Groups were compared in terms of surface microhardness, roughness readings, and surface scanning with an extra-oral scanner (D800; 3Shape A/S) before and after the erosive process.

RESULTS

All experimental groups showed superior results than the control group regarding microhardness, surface roughness, and substance loss. The fluoride varnish group showed significantly favourable results in microhardness change. There was no significant difference between the experimental groups regarding surface roughness and enamel loss measurements.

CONCLUSION

5% NaF fluoride varnish, CPP-ACPF and self-assembling P11-4 peptide protect the enamel of primary teeth against erosion compared to artificial saliva alone.

Solutions containing a statherin-derived peptide reduce enamel erosion in vitro

The effect of solutions containing a statherin-derived peptide (Stn15pSpS) on the protection against enamel erosion in vitro was evaluated. Bovine enamel specimens were divided into 4 groups (n = 15/group): 1) Deionized water (negative control), 2) Elmex Erosion Protection™ (positive control), 3) 1.88 × 10-5 M Stn15pSpS and 4) 3.76 × 10-5 M Stn15pSpS. The solutions were applied on the specimens for 1 min. Stimulated saliva was collected from 3 donors and used to form a 2-h acquired pellicle on the specimens. Then, the specimens were submitted to an erosive pH-cycling protocol 4 times/day, for 7 days (0.01 M HCl pH 2.0/45 s, artificial saliva/2 h, and artificial saliva overnight). The solutions were applied again during pH cycling, 2 times/day for 1 min after the first and last erosive challenges. Enamel loss (µm) was assessed by contact profilometry. Data were analyzed by Kruskal-Wallis and Dunn's test (p < 0.05). The best protection against erosion was conferred by Elmex Erosion Protection that significantly differed from all the other treatments, followed by the solutions containing Stn15pSpS, regardless of the concentration. However, 3.76 × 10-5 M Stn15pSpS did not differ from the negative control. The solution containing the lower concentration of Stn15pSpS protected against erosion in vitro, which should be confirmed using protocols that more closely resemble the clinical condition.

Effect of different surface treatments on the microhardness and colour change of artificial enamel lesions

BACKGROUND

To investigate the effect of three different surface treatments on the microhardness and colour change of artificial enamel lesions.

MATERIALS AND METHODS

One hundred bovine teeth were randomly assigned into four groups. Artificial enamel lesions were created using demineralizing solution for all groups except the sound enamel group. Different surface treatments were then performed G1: resin-infiltrant; G2: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP); G3: artificial saliva; G4: Sound Enamel. Each group was subdivided into three subgroups, where each subgroup was subjected to a different testing method. Subgroup 1: surface microhardness; subgroup 2: cross-sectional microhardness; subgroup 3: colour measurement. Statistical analysis was performed by ANOVA, followed by Tukey's post hoc test.

RESULTS

Sound enamel group recorded the highest surface and cross-sectional microhardness results. No significant difference was found between the resin-infiltrant group and CPP-ACP regarding surface and cross-sectional microhardness at different lesion depths. Resin-infiltrant group showed the least colour change (∆E) results compared to the other groups.

CONCLUSION

Resin-infiltrant can effectively enhance surface microhardness and enamel resistance to demineralization, additionally, reduces the staining susceptibility of white spot lesions (WSLs) after treatment. CPP-ACP application for 4 weeks seems to improve surface microhardness; however, has a limited effect in resisting staining of WSLs after treatment. © 2022 Australian Dental Association.

Synthesis, characterization, and evaluation of the antifungal properties of tissue conditioner incorporated with essential oils-loaded chitosan nanoparticles

Purpose

This study aims to investigate new tissue conditioner (TC) formulations involving chitosan nanoparticles (CSNPs) and essential oils (EO) for their antifungal potential, release kinetics, and hardness.

Materials and methods

CSNPs were synthesized, and the separate solutions of CSNP were prepared with two types of EO, i.e., Oregano oil and Lemongrass. The EO was loaded separately in two concentrations (200 μL and 250 μL). The blank and EO-loaded CSNPs were screened against Candida albicans (C. albicans), and their minimum inhibitory concentration was established. GC Reline^™ (GC corporation, USA) TC was considered a control group, whereby the four experimental groups were prepared by mixing CSNPs/EO solutions with TC powder. The antifungal effectiveness (C. albicans) and release kinetics behavior (1–6 h, 24 h, 48 h, and 72 h) was investigated. The Shore A hardness of control and experimental groups was evaluated in dry and wet modes (deionized water and artificial saliva). For statistical analysis, SPSS version 22 was used to do a one-way ANOVA post-hoc Tukey’s test.

Results

Compared to the control group, TCs containing blank CSNPs and CSNPs loaded with EO showed 3 and 5 log reductions in C. albicans growth, respectively. A significantly high antifungal effect was observed with TC containing lemongrass essential oil (200 μL). The continuous release of EO was detected for the first 6 hours, whereas completely stopped after 48 hours. Mean hardness values were highest for dry samples and lowest for samples stored in artificial saliva. The statistically significant difference within and between the study groups was observed in mean and cumulative essential oils release and hardness values of TCs over observed time intervals irrespective of storage media.

Conclusion

TCs containing essential-oil-loaded CSNPs seem a promising alternative treatment of denture-induced stomatitis, however, a further biological analysis should be taken.

Effect of experimental and commercial artificial saliva formulations on the activity and viability of microcosm biofilm and on enamel demineralization for irradiated patients with head and neck cancer (HNC)

The effect of different artificial saliva formulations on biofilm activity and viability, and on enamel demineralization for head and neck cancer (HNC) patients was evaluated. Irradiated enamel samples were treated (1 min) with BioXtra® or with experimental formulations containing carboxymethylcellulose plus inorganic constituents alone (AS) or containing 0.1 mg mL^-1 CaneCPI-5 (AS + Cane), 1.0 mg mL^-1 hemoglobin (AS + Hb) or combination of both (AS + Cane + Hb). Phosphate-buffered-saline and chlorhexidine (0.12%) were negative and positive control, respectively. Biofilm was produced from the saliva of five male HNC patients, under 0.2% sucrose exposure for 5 days, and daily treated with the formulations (1 min). No significant effects were observed for the different experimental treatments. BioXtra^® significantly reduced lactobacilli, demonstrating antibacterial potential for this group. Chlorhexidine was an effective treatment to significantly reduce all parameters, being an important antimicrobial and anticaries agent. Future in vitro studies must be performed using a new approach for the design of the experimental formulations.

Analysis of permeability and biological properties of dentin treated with experimental bioactive glasses

OBJECTIVES

To evaluate obliterating capability and biological performance of desensitizing agents.

METHODS

50 dentin blocks were distributed according to the desensitizing agent used (n = 10): Control (Artificial saliva); Ultra EZ (Ultradent); Desensibilize Nano P (FGM); T5-OH Bioactive Glass (Experimental solution); F18 Bioactive Glass (Experimental solution). Desensitizing treatments were performed for 15 days. In addition, specimens were subjected to acid challenge to simulate oral environment demineralizing conditions. Samples were subjected to permeability analysis before and after desensitizing procedures and acid challenge. Cytotoxicity analysis was performed by using Alamar Blue assay and complemented by total protein quantification by Pierce Bicinchoninic Acid assay at 15 min, 24-h and 48-h time points. Scanning electron microscopy and energy dispersion X-ray spectroscopy were performed for qualitative analysis. Data of dentin permeability was analyzed by two-way repeated measures ANOVA and Tukey's test. For cytotoxicity, Kruskal-Wallis and Newman-Keuls tests.

RESULTS

for dentin permeability there was no significant difference among desensitizing agents after treatment, but control group presented highest values (0.131 ± 0.076 Lp). After acid challenge, control group maintained highest values (0.044 ± 0.014 Lp) with significant difference to other groups, except for Desensibilize Nano P (0.037 ± 0.019 Lp). For cytotoxicity, there were no significant differences among groups.

CONCLUSION

Bioglass-based desensitizers caused similar effects to commercially available products, regarding permeability and dentin biological properties.

CLINICAL SIGNIFICANCE

There is no gold standard protocol for dentin sensitivity. The study of novel desensitizing agents that can obliterate dentinal tubules in a faster-acting and long-lasting way may help meet this clinical need.

Antimicrobial and Physicochemical Properties of Artificial Saliva Formulations Supplemented with Core-Shell Magnetic Nanoparticles

Saliva plays a crucial role in oral cavity. In addition to its buffering and moisturizing properties, saliva fulfills many biofunctional requirements, including antibacterial activity that is essential to assure proper oral microbiota growth. Due to numerous extra- and intra-systemic factors, there are many disorders of its secretion, leading to oral dryness. Saliva substitutes used in such situations must meet many demands. This study was design to evaluate the effect of core-shell magnetic nanoparticles (MNPs) adding (gold-coated and aminosilane-coated nanoparticles NPs) on antimicrobial (microorganism adhesion, biofilm formation), rheological (viscosity, viscoelasticity) and physicochemical (pH, surface tension, conductivity) properties of three commercially available saliva formulations. Upon the addition of NPs (20 µg/mL), antibacterial activity of artificial saliva was found to increase against tested microorganisms by 20% to 50%. NPs, especially gold-coated ones, decrease the adhesion of Gram-positive and fungal cells by 65% and Gram-negative bacteria cells by 45%. Moreover, the addition of NPs strengthened the antimicrobial properties of tested artificial saliva, without influencing their rheological and physicochemical properties, which stay within the range characterizing the natural saliva collected from healthy subjects.

Ions release Evaluation and Changes in Mini-implant Orthodontic Surface

AIM

To evaluate, in vitro, the mini-implant surface changes and the release of ions after immersion in artificial saliva during follow-up of 60 and 120 days.

MATERIALS AND METHODS

As for the surface features, examined in a scanning electron microscope (SEM), before and after immersion in artificial saliva, there was a rough and uneven surface, suggestive of corrosion areas for the two trademarks evaluated after 120 days of immersion. The extracts generated in artificial saliva analysis were submitted to energy dispersive spectroscopy to identify the solid corrosion products produced on the surfaces of miniscrews.

RESULTS

Both SIN miniscrews and Neodent brands were observed to release minimal quantities of silver ions, chromium, iron, nickel, titanium, and vanadium. Regarding titanium, this index varied from 88.84% in the control group of Neodent brand, and 91.29% in the control group of SIN brand. For the aluminum content, the quantities ranged from 4.91% in group immersed for 60 days in Neodent brand to 8.71% for the SIN control group. Considering vanadium, the index ranged from 2.65% in the group immersed for 120 days to 4.53% in the control group, both for Neodent brand. Statistically significant differences in iron ion were observed between the control group and the miniscrews brand SIN after 60 and 120 days and for Neodent after 60 days of immersion. The titanium ions suffered statistically significant decrease for both brands after 120 days of storage when compared with the control group.

CONCLUSION

The studied miniscrews showed results consistent with the biosafety of alloys for use, in vivo.

CLINICAL SIGNIFICANCE

The knowledge of the physical/chemical state of corrosion products released in the oral cavity is very important for the toxicological assessment of metal alloys used in dental miniscrews.

Corrosion of dental alloys in artificial saliva with Streptococcus mutans

A comparative study of the corrosion resistance of CoCr and NiCr alloys in artificial saliva (AS) containing tryptic soy broth (Solution 1) and Streptococcus mutans (S. mutans) species (Solution 2) was performed by electrochemical methods, including open circuit potential measurements, impedance spectroscopy, and potentiodynamic polarization. The adherence of S. mutans to the NiCr and CoCr alloy surfaces immersed in Solution 2 for 24 h was verified by scanning electron microscopy, while the results of electrochemical impedance spectroscopy confirmed the importance of biofilm formation for the corrosion process. The R(QR) equivalent circuit was successfully used to fit the data obtained for the AS mixture without S. mutans, while the R(Q(R(QR))) circuit was found to be more suitable for describing the biofilm properties after treatment with the AS containing S. mutans species. In addition, a negative shift of the open circuit potential with immersion time was observed for all samples regardless of the solution type. Both alloys exhibited higher charge transfer resistance after treatment with Solution 2, and lower corrosion current densities were detected for all samples in the presence of S. mutans. The obtained results suggest that the biofilm formation observed after 24 h of exposure to S. mutans bacteria might enhance the corrosion resistance of the studied samples by creating physical barriers that prevented oxygen interactions with the metal surfaces.

The influence of pH and chemical composition of beverages on color stability of a nanofilled composite resin

Due to increasing consumer knowledge about the health benefits associated with anthocyanin-rich foods and beverages-such as acai and blueberry juices-the growing consumption of these products should be a source of concern for dentists. Since anthocyanins are colorants that can discolor teeth and restorations, the aim of this study was to investigate the staining effects of 2 anthocyanin-rich beverages on a nanofilled composite resin. Specimens were prepared, separated into 3 groups, and immersed in either artificial saliva or 1 of the 2 staining solutions (blueberry or acai juice) at 37°C for 7 days. The color stability of the resin was significantly affected by both the storage times (P < 0.001) and the solutions (P < 0.001). The blueberry juice, which had the lowest pH level, had the greatest effect on color stability and changes in lightness of the composite resin (ΔE* = 14.71; ΔL* = -8.25; P < 0.001), followed by acai juice (ΔE* = 10.21; ΔL* = -8.77; P < 0.001) and artificial saliva (ΔE* = 1.36; ΔL* = -0.44; P < 0.001). In the present study, a nanofilled composite resin did not exhibit color stability when exposed to acai and blueberry beverages.

COMPARISON OF CHILDREN'S FOLLOW-ON INSTANT POWDERED COW'S MILK FORMULA, BUFFALO MILK FORMULA AND CHICKEN-BASED FORMULA ON ENAMEL MICROHARDNESS OF BOVINE TEETH IN VITRO

Dental caries are a major public health problem worldwide. The aim of this study was to compare the effects of children's follow-on instant powdered cow's milk formula, buffalo milk formula and a chicken-based formula on microhardness of bovine enamel with artificial caries-like lesions. Forty bovine teeth were each placed in acrylic blocks and the enamel surfaces were polished to create flat 5 x 5 millimeter surfaces. The teeth surfaces were then demineralized using 0.1M lactic acid (pH 4.5) to achieve an enamel microhardness of 35-65 Vickers Hardness Numbers (VHN). All specimens were then randomly allocated into one of 4 groups (n=10/group). For remineralization, each group was soaked in a different kind of milk formula for 2 hours at 37°C except group 1 which was a negative control (artificial saliva) group. Group 2 was soaked in Murrah™ buffalo milk formula (a positive control ), group 3 in S-26-Promil-Gold™ (cow's milk formula) and group 4 in a chicken-based formula (Siriraj Hospital, Mahidol University). The microhardness of the specimens was then measured again. Data were analyzed using a one-way ANOVA and paired t-test with a 95% confidence interval. After exposure to the formula, the mean VHN for each study group was significantly higher (paired t-test, p < 0.05) except for group 1 (p = 0.345). The mean VHN for the the Murrah™ buffalo milk formula, the chicken-based formula and the S-26-Promil-Gold™ formula group were not significantly different from each other (one-way ANOVA, p > 0.05). In conclusion, S-26-Promil-Gold™ follow-on cow milk formula, Murrah™ buffalo milk formula and the chicken-based formula all increased bovine enamel microhardness after soaking for 2 hours.

Physicochemical properties and biological activities of Thai plant mucilages for artificial saliva preparation

CONTEXT

Plant mucilages can be found in various parts of several Thai plants, which can be used as thickening, moisturizing, and lubricating agents in artificial saliva formulations.

OBJECTIVE

The objective of this study was to evaluate the physicochemical properties, biological activity, and cytotoxicity of Thai plant mucilages.

MATERIALS AND METHODS

The mucilages from Thai plants were extracted by various processes (temperature and pH variation, microwave oven, steam, and Tris-HCl buffer extraction). The viscosity and the rheology were evaluated using viscometer. Antioxidative activities including DPPH radical scavenging and metal chelating activities were investigated. The mucilages were determined for cytotoxicity on normal human gingival fibroblasts and anti-adherent activity of Streptococcus mutans.

RESULTS

Mucilages from Ocimum citriodorum Vis. (Lamiaceae), Artocarpus heterophyllus Lam. (Moraceae), Abelmoschus esculentus (Linn.) Moench. (Malvaceae), and Basella alba Linn. (Basellaceae) exhibited pseudoplastic non-Newtonian rheology. The highest DPPH radical-scavenging and metal-chelating activities were observed in the mucilages from B. alba (microwave, 3 min) and A. esculentus (microwave, 1 min) with the SC50 and MC50 values (50% of scavenging activity and 50% of metal chelating activity, respectively) of 0.71 ± 0.32 and 1.11 ± 0.52 mg/ml, respectively. Most mucilages exhibited no cytotoxicity to normal human gingival fibroblasts. The mucilage from A. esculentus (microwave, 5 min) gave the shortest wetting time of 2.75 ± 0.51 min. The highest S. mutans adhesion inhibition was observed in A. esculentus (pH 11) of 5.39 ± 9.70%.

DISCUSSION AND CONCLUSION

This study has indicated the suitable physicochemical and biological properties and the potential application of mucilages from Thai plants for artificial saliva preparation.

Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching

OBJECTIVES

To evaluate 1) the influence of five bleaching agents (with additional light activation) on enamel and dentin surface microhardness and chemical composition and 2) the remineralizing potential of artificial saliva and amorphous calcium phosphate (ACP).

METHODS AND MATERIALS

The study was conducted on 125 human third molars dissected into quarters for separate enamel and dentin measurements. The bleaching process was performed with 38% and 25% hydrogen peroxide (HP) and 30%, 16%, and 10% carbamide peroxide (CP) gels two times for 15 minutes each time. All bleaching gels were tested alone and in combination with ZOOM2, light-emitting diode (LED), organic LED, and femtosecond laser. A total of 25 bleaching combinations (n=10) were evaluated. Microhardness was measured by a Vickers diamond. Chemical analysis was performed using energy-dispersive X-ray spectroscopy.

RESULTS

Bleaching agents used in the absence of light activation caused a significant reduction in enamel and dentin surface microhardness (p<0.001), ranging from 8% for 16% CP to 40% for 25% HP. The effects of different light activations were negligible. After two-week treatment with ACP and artificial saliva, maximum deviation from baseline microhardness was just 3%. Such treatment increased the concentrations of calcium, phosphorus, and fluorine.

CONCLUSIONS

An increase in peroxide concentration and gel acidity negatively affected microhardness and concentrations of calcium and phosphorus in enamel and dentin. ACP and artificial saliva stimulated the remineralization of hard tissues.

The effect of saliva substitutes on enamel erosion in vitro

OBJECTIVES

To investigate the effect of saliva substitutes on enamel erosion in vitro.

METHODS

A total of 204 bovine enamel samples were embedded in acrylic resin and allocated to 17 groups (n=12). The specimens were eroded in an artificial mouth (3 days; 6×30 s/days, flow rate: 2 ml/min) using citric acid (pH: 2.5). Immediately after the erosive attacks, saliva substitutes (12 sprays, 3 gels) were applied. Between the erosive cycles the specimens were rinsed with artificial saliva (flowrate: 0.5 ml/min). A SnCl2/AmF/NaF-containing mouthrinse was used as positive control, water spray served as negative control. Enamel loss was measured profilometrically and the data were analyzed using one-way ANOVA followed by Scheffé's post hoc tests (p<0.05).

RESULTS

Four saliva substitutes increased enamel erosion, probably due to the low pH or the content of citric acid. Several saliva substitutes were able to reduce enamel erosion significantly by 60-90% (in the range of the positive control). The protective potential of these products was in the range of the positive control (reduction of enamel loss to 30% of negative control). The erosion-protective potential of these high-viscous products is probably related to their film-forming properties, leading to a mechanical protection of the surface.

CONCLUSION

Saliva substitutes containing a very low pH exhibit a distinct erosive potential, while most high-viscous products present an erosion-protective effect. It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

CLINICAL SIGNIFICANCE

It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

Influence of self-made saliva substitutes on tribological characteristics of human enamel

This paper describes the results of tests on the influence of human saliva and its substitutes on tribological characteristics of friction pairs. Each pair consists of enamel and one of the following materials: ceramics, the Meridian B2 dental composite, the GK dental amalgam, and Ti-6Al-4V titanium alloy. The saliva substitutes used were prepared using pyrophosphates, xanthan gum, and mucins dissolved in a saline buffer. The results of the tribological tests show that the values of the parameters under investigation (coefficient of friction and linear wear) were different from each other. Some similarity was observed between the evaluated level of wear characteristics after the friction process in the environment of human saliva and that in the environment of one of the mucins tested. Microscopic observations of the surfaces of the enamel samples after friction revealed varied forms of tribological wear.

Friction coefficients and wear rates of different orthodontic archwires in artificial saliva

The aim of this paper is to analyze the influence of the nature of the orthodontic archwires on the friction coefficient and wear rate against materials used commonly as brackets (Ti-6Al-4V and 316L Stainless Steel). The materials selected as orthodontic archwires were ASI304 stainless steel, NiTi, Ti, TiMo and NiTiCu. The array archwire's materials selected presented very similar roughness but different hardness. Materials were chosen from lower and higher hardness degrees than that of the brackets. Wear tests were carried out at in artificial saliva at 37 °C. Results show a linear relationship between the hardness of the materials and the friction coefficients. The material that showed lower wear rate was the ASI304 stainless steel. To prevent wear, the wire and the brackets have high hardness values and in the same order of magnitude.

Amounts of Sr and Ca eluted from deciduous enamel to artificial saliva related to dental caries

This study was performed to elucidate the relationship between dental caries and the levels of Sr and Ca eluted from enamel, and to examine whether these elements are useful as factors to assess caries risk. The available 103 (Sr) and 108 (Ca) samples were obtained among 111 collected deciduous teeth. The healthy regions of enamel were decalcified in artificial saliva at pH 6.2 and 5.5. The eluted levels of these elements from enamel were determined using atomic absorption spectrophotometry. Sr and Ca levels were not affected by the sex nor tooth type. Sr levels of the caries-experienced tooth (CE) group were 2.6-fold (pH 6.2) and 2.2-fold (pH 5.5) higher than those of the sound tooth (ST) group, respectively. Furthermore, the Sr levels were significantly higher in the teeth with treated than in those with untreated caries. Only at pH 6.2 was a significant difference found in Ca levels between the ST and CE groups. In the ST group, at pH 5.5, both the Sr and Ca levels significantly increased when the children had six or more carious teeth. The Sr and Ca elution levels were significantly inhibited in the teeth receiving fluoride application every 3 or 4 months compared to those that were not. These findings indicate that Sr can be an indicator of the acid resistance of teeth, and a useful factor to assess future caries risk.

Effect of various forms of calcium in dental products on human enamel microhardness in vitro

The aim of this in vitro study was to compare the remineralization potential of dental products containing calcium on human enamel softened by soft drinks. Fifty sound human premolar teeth were randomly divided into 5 treatment groups (n=10): artificial saliva, 1,000 ppm fluoride toothpaste, CPP-ACP paste, CPP-ACP with 900 ppm fluoride paste and tricalcium phosphate with 950 ppm fluoride paste. All specimens were immersed in cola soft drink and artificial saliva for 10 cycles of 5 seconds each; this procedure was repeated twice at six-hour intervals. All specimens were remineralized by treatment with the dental products mentioned above for 5 minutes and kept in artificial saliva at 37 degrees C for 6 hours. The surface microhardness of the enamel was measured with a Vickers hardness tester (100 grams, 15 seconds) at baseline, after erosion and after remineralization. Comparison of the mean microhardness numbers within groups was made by one-way repeated measures ANOVA and between groups with the one-way ANOVA with a level of significance of p<0.05. The mean surface microhardness in all groups decreased significantly after being eroded by the soft drink and increased after treatment. After remineralization treament, the mean surface microhardness of the artificial saliva group was significantly less than the other groups. The CPP-ACP paste, CPP-ACP with 900 ppm fluoride paste and tricalcium phosphate with 950 ppm fluoride paste treatments all increased the hardness of the teeth in vitro.

The effect of casein phosphopeptide-amorphous calcium phosphate on enamel surface rehardening. An in vitro study

AIM

Casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) has been shown to remineralise enamel subsurface lesions. The aim of this study was to determine the effect of a paste containing 10% CPP-ACP (Toothmousse; GC) on enamel surface microhardness in vitro.

MATERIALS AND METHODS

Thirty enamel blocks (3x2 mm) were prepared for the study group from the buccal surface of extracted teeth. The microhardness of the enamel surface was determined for the specimens initially before artificial demineralisation. After demineralization the specimens were incubated in 10% CPP-ACP for 5 min. Artificial saliva was used as a remineralising solution for the control group.

RESULTS

The mean baseline surface microhardness analyses of enamel blocks were 318.61±25.75 and 262.49±26.82. The data show that after demineralisation the mean microhardness decline in the experimental groups (247.05± 38.31 and 186.92± 63.77). The results showed that 10% CPP-ACP (281.79±26.32) was comparable to the control (252.27± 31.05) for remineralisation of enamel subsurface lesions in vitro. The highest surface microhardness recovery (%SMHR) was found for control, but the differences of % SMHR between 10% CPP-ACP and control was not statistically significant (p=0.805).

CONCLUSION

From the results it can be concluded that CPP-ACP may have positive effects on enamel remineralisation.

Effect of bamboo salt-NaF dentifrice on enamel remineralization

PURPOSE

To evaluate the laboratory remineralization effects of a dentifrice with bamboo salt and NaF on artificial caries-like enamel lesions, at both the surface and deep areas.

METHODS

Early dental caries lesions were formed by treating bovine enamel samples for 48 hours at 37 degrees C with a demineralization solution (pH 5.0) containing 0.1 M lactic acid, 0.2% Carbopol 907, and 50% saturated calcium phosphate tribasic. pH cycling was then performed by immersing the samples in dentifrice slurry for 2 minutes every 8 hours per day, and in demineralization solution for 4 hours and mixed saliva for the remaining time period. The mixed saliva consisted of 50% human saliva and 50% artificial saliva. The surface hardness and the level of mineral surface alterations were analyzed using a hardness tester and transversal microradiography, among negative control (fluoride free), positive control (sodium fluoride 1100 ppm, Crest Cavity Protection), and test dentifrice (3.0% bamboo salt with sodium fluoride 1,000 ppm) groups.

RESULTS

Test and positive control groups significantly increased the level of the surface hardness and decreased mineral loss of the artificial caries-like enamel lesions compared to the negative control (P<0.05). The test dentifrice also significantly decreased the lesion depth compared to the other two groups (P<0.05).

Occlusion of dentin tubules with antibacterial ammonium hexafluorosilicate solution for the prevention of dentin caries

PURPOSE

To evaluate the degree of penetration of an ammonium hexafluorosilicate [SiF: (NH4)2SiF6] solution containing various antibacterial agents into dentin and the depth of dentin tubule occlusion by the precipitate.

METHODS

Various antibacterial SiF solutions were prepared with the addition to chlorhexidine (CHX), cetylpyridinium chloride (CPC), isopropyl methylphenol (IPMP), or epigallocatechin gallate (EGCG), respectively. Two types of dentin disks were prepared from extracted teeth. One was a dentin surface covered with a smear layer, and the other treated with EDTA for 2 minutes to remove the smear layer and open dentin tubules. Then, the disks were treated with SiF solution with or without antibacterial agents for 3 minutes. The dentin surface and a longitudinally divided surface were observed with scanning electron microscopy (SEM) immediately after SiF treatment and after immersion in synthetic saliva for 7 days.

RESULTS

SEM photographs demonstrated that dentin tubules after treatment with SiF were occluded homogeneously and similar to those on conventional SiF treatment regardless of the addition of an antibacterial agent. However, the depth of occlusion became significantly shallower when SiF was applied to dentin specimens covered with a smear layer.

Corrosion behaviour of β-Ti20Mo alloy in artificial saliva

To evaluate the potential of β-Ti20Mo alloy as a dental material, we tested its corrosion behaviour in artificial saliva in comparison to that of cp-Ti. Open-circuit potential (E(OC)), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used as electrochemical methods to characterize the corrosion behaviour of Ti20Mo alloy and cp-Ti, respectively. Corrosion current and passive current densities obtained from the polarization curves showed low values indicating a typical passive behaviour for Ti20Mo alloy. The EIS technique enabled us to study the nature of the passive film formed on the binary Ti20Mo alloy at various imposed potentials. The Bode phase spectra obtained for Ti20Mo alloy in artificial saliva exhibited two-time constants at higher potential (0.5 V, 1.0 V), indicating a two-layer structure. According to our experimental measurements, Ti20Mo alloy appears to possess superior corrosion resistance to that of cp-Ti in artificial saliva.

Total bacterial counts on oral mucosa after using a commercial saliva substitute in patients undergoing hematopoietic cell transplantation

PURPOSE

The commercial saliva substitute Oralbalance has been reported to alleviate symptoms of postradiotherapy xerostomia in head and neck cancer patients. Oralbalance may also be effective for xerostomia in patients undergoing hematopoietic cell transplantation (HCT) with high-dose chemotherapy and total-body irradiation. However, HCT patients are in a severely compromised condition, and saliva substitute must not promote infection. We reported previously that Oralbalance has antimicrobial effects against microbial species detected during HCT in vitro. This study was performed to determine the in vivo effects of Oralbalance on oral mucosal total bacterial counts in patients undergoing HCT.

METHODS

A total of 18 neutropenic patients undergoing HCT were enrolled in this study. Before and after 1 week of Oralbalance use, bacterial samples were obtained from patients by wiping an area of varphi1 cm on the buccal mucosa with sterilized cotton swabs. Total bacterial counts of the obtained samples were examined by quantitative polymerase chain reaction amplification of the bacterial 16S ribosomal RNA gene. As controls, bacterial samples were also obtained from ten healthy subjects, and total bacterial counts were examined.

RESULTS

No significant increase in bacterial count was observed with use of Oralbalance. None of the patients showed bacterial counts above the range found in healthy controls after using Oralbalance.

CONCLUSIONS

In neutropenic patients undergoing HCT, Oralbalance did not increase the total counts of oral mucosal bacteria beyond the range found in healthy controls. Oral care using Oralbalance may alleviate the symptoms induced by hyposalivation without promoting infection.

In-vitro-Studie zur Untersuchung eines neuen Speichelersatzmittels (Saliva natura®) auf Schmelz und Dentin

BACKGROUND

Hyposalivation is an important chronic side effect of radiotherapy in the head and neck area, and patients often alleviate their symptoms using saliva substitutes. The aim of this study was to evaluate the effects of two commercially available saliva substitutes (Saliva natura and Glandosane) on the mineral loss of bovine enamel and dentin in vitro. An aqueous remineralization solution served as control.

METHODS

Each 45 bovine enamel and dentin specimens were prepared. Prior to (control of sound dentin) and after (control of demineralized dentin) demineralization (37 degrees C; enamel: pH 4.95; 14 d; dentin: pH 5.0; 7 d) one third of each specimens surface was covered with nail varnish. Subsequently, the specimens (n = 15) were exposed to Glandosane and Saliva natura as well as a remineralization solution for 14 days (37 degrees C). Specimens were examined using transversal microradiography.

RESULTS

Compared to Saliva natura and the reminerlization solution, Glandosane induced both significantly increased mineral losses as well as lesion depths of the enamel specimens (p < 0.05; ANOVA, Bonferroni). After exposure of the dentin specimens to Saliva natura a significantly increased mineral loss could be observed (p < 0.001), whereas no differences in mineral loss could be observed for the enamel specimens (p = 0.078; t-test).

CONCLUSIONS

Within the limitations of an in vitro study it can be concluded that Glandosane revealed a demineralizing potential on bovine enamel as well as on dentin and should not be recommended for dentate patients. Since Saliva natura has a demineralizing effect on dentin, a further improvement regarding the remineralizing capacity would be desirable.

Potential of fluoridated carbamide peroxide gels to support post-bleaching enamel re-hardening

OBJECTIVE

Aim of the in vitro study was to evaluate the time period needed to re-establish enamel surface microhardness after bleaching with fluoridated (0.5% F(-) as NaF) and unfluoridated carbamide peroxide (CP) bleaching gels under a daily de- and remineralization protocol.

MATERIALS AND METHODS

Ninety enamel specimens were prepared from bovine incisors and prepared for Knoop microhardness determination. The samples were divided into five groups and bleached for 7 days (8h per day) with experimentally designed neutral and acidic 10% CP gels: A (0.5% F(-), pH 7.0), B (0.5% F(-), pH 5.5), C (no F(-), pH 7.0) and D (no F(-), pH 5.5). Group E served as control and was not bleached. After each 8-h bleaching period the samples were subjected to a de- and remineralization protocol. In the following 5 days, the specimens were not bleached, but stored in artificial saliva for 8h instead; the daily de- and remineralization cycles were maintained during this period. Knoop microhardness determinations were conducted at baseline, after each bleaching interval and after completion of each daily de- and remineralization cycle. A repeated measures two-way ANOVA statistical analysis and a comparison of confidence intervals was conducted to check for hardness recovery during the post-bleaching period.

RESULTS

After completion of bleaching therapy on day 7 a statistically significant hardness loss was observed for all bleaching groups in the range of about 7-15% hardness reduction as compared to baseline. The fluoridated gels proved significantly less hardness loss than the unfluoridated gels. In the following period, from days 8 to 12 recovery of hardness to baseline data was observed in the fluoridated groups (A and B) after the first de-/remineralization cycle on day 8 (group A) and after the second 8-h remineralization period on day 9 (group B), respectively. Hardness of the specimens treated with the unfluoridated bleaching gel C returned to baseline values after day 10. The samples of group D did not show recover of hardness data during the 5-day post-bleaching period.

CONCLUSION

Fluoridated 10% carbamide peroxide bleaching gels support re-hardening of bleached enamel with a shorter period needed for hardness recover as compared to unfluoridated gels.

Linseed based saliva substitutes and their effect on mineral dissolution of predemineralized bovine dentin in vitro

OBJECTIVES

Polymers used in saliva substitutes might inhibit remineralization. The present study evaluated the effects of various calcium, phosphate, and fluoride concentrations of linseed based solutions on the mineral loss of predemineralized bovine dentin in vitro.

METHODS

Dentin specimens were prepared, embedded and polished. The specimens were demineralized (pH 5.6; 6 d; 37 degrees C) and half of each sample was covered with nail varnish. Subsequently, the specimens (n=10) were exposed to 14 linseed based solutions (calcium 0-1.1 mM; phosphate 0-7.7 mM, fluoride 0-0.03 mM) at pH 5.5 and 6.5 as well as to Salinum for 14 days (37 degrees C). The differences in mineral loss (DeltaDeltaZ) between the values prior to and after storage in the solutions were evaluated from microradiographs of thin sections.

RESULTS

After the exposure to the various solutions decreased mineral contents compared to those after demineralization could be observed (p<0.05; paired t-test) whereas for the specimens stored in solution with the highest calcium and phosphate concentration no significant change in mineral loss could be evaluated (p>0.05). Salinum induced a significantly greater mineral loss compared to the equivalent saturated solution (p<0.05; ANOVA, Bonferroni). The general linear model revealed a significant dependency for DeltaDeltaZ on 'phosphate' (p=0.000) and 'fluoride' (p=0.001), but not on 'calcium' (p=0.397) and 'pH' (p=0.368).

CONCLUSIONS

The addition of calcium, phosphates, and fluorides seems to have a positive effect on the remineralizing qualities of linseed based saliva substitutes.

Influence of rotating-oscillating, sonic and ultrasonic action of power toothbrushes on abrasion of sound and eroded dentine

OBJECTIVE

This in vitro study aimed to evaluate the susceptibility of sound and eroded dentine to brushing abrasion performed by different rotating-oscillating, sonic and ultrasonic toothbrushes.

METHODS

Toothbrushing abrasion (20 cycles, each 30 s) was applied to bovine dentine samples (each subgroup n = 10) exhibiting both a demineralized (each cycle: 1% citric acid, pH: 2.3, 60 s; 30 min remineralization in artificial saliva) and a sound surface area. Toothbrushing was performed in an automatic brushing machine with the rotating-oscillating, sonic and ultrasonic toothbrushes either (a) activated, supplemented by 20 strokes/min of the brushing machine, (b) inactivated, supplemented by 20 strokes/min of the brushing machine or (c) inactivated, supplemented by 80 strokes/min of the brushing machine. A manual toothbrush was applied with 20, 80 or 100 linear strokes/min. Specimens of the control group were not brushed after erosion. After each cycle, the samples were stored in artificial saliva for 4 h. After 20 cycles, loss of sound and softened dentine was determined by profilometry. Mann-Whitney-Wilcoxon test and Bonferroni corrections were applied to the data (p < 0.05).

RESULTS

For all groups, demineralized dentin areas exhibited significantly higher abrasion values than the respective sound dentine surfaces. However, mean dentine loss of both softened and sound dentine was higher after use of the rotating-oscillating, sonic and ultrasonic brushes with the activated regime [(a) eroded dentine: 9.94-16.45 microm; sound dentine: 3.31-5.47 microm] than after brushing with the inactivated regimes [(b) eroded dentine: 5.10-5.62 microm; sound dentine: 1.16-1.81 microm; (c) eroded dentin: 7.64-8.89 microm; sound dentine: 1.38-1.69 microm].

CONCLUSION

The results indicate that rotating-oscillating, sonic or ultrasonic action of the power toothbrushes leads to an increased loss of demineralized and sound dentine.

Effect on enamel microhardness of two consumer-available bleaching solutions when compared with a dentist-prescribed, home-applied bleaching solution and a control

BACKGROUND

There exists limited data in the literature regarding the efficacy and safety of consumer-available, paint-on bleaching solutions.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of two consumer-available, paint-on bleaching products on enamel microhardness against a control and a dentist-prescribed, home-applied (DPHA) bleaching product.

MATERIALS AND METHODS

Eighty enamel slabs were obtained from extracted human teeth and randomly divided into four treatment groups: (1) control; (2) Opalescence (Ultradent Products, Inc., South Jordan, UT, USA); (3) Crest Night Effects (Procter & Gamble, Cincinnati, OH, USA); and (4) Colgate Simply White Night (Colgate-Palmolive Co., Piscataway, NJ, USA). Opalescence is a carbamide peroxide DPHA product, whereas Crest Night Effects and Colgate Simply White Night are consumer-available products. The specimens in groups 2 to 4 underwent 2 weeks of treatment for 8 h/d. Specimens were maintained in artificial saliva at 37 degrees C between treatments. Subsequently, one-half of the specimens in groups 2 to 4 (n=10) underwent an additional seven treatments for 8 h/d, while the other half were stored in artificial saliva, receiving no further treatment. Microhardness was measured as Knoop hardness numbers (KHNs) at baseline and after 1, 7, 14, and 21 treatment days. The results were analyzed for statistical significance both intra- and intergroups using analysis of variance (p=.05).

RESULTS

A statistically significant reduction in mean KHN was observed compared with baseline at 1, 7, 14, and 21 treatment days for group 4 and at 7 treatment days for group 3. When compared with the control or DPHA product, group 4 was the only treatment that resulted in significantly lower mean KHNs at 7, 14, and 21 treatment days.

CONCLUSION

When evaluating enamel microhardness, consumer available, paint-on bleaching solutions may adversely affect enamel microhardness compared to a control and 10% carbamide peroxide DPHA bleaching solution.

CLINICAL SIGNIFICANCE

With numerous consumer-available bleaching products on the market, it is crucial to be judicious in their selection and use. The results of this in vitro study showed that the consumer-available, paint-on bleaching solutions adversely affected enamel microhardness at some time during the study. Consumers should be made aware of this effect on enamel.

Flexural Strength and Modulus Properties of Carbamide Peroxide?Treated Bovine Dentin

BACKGROUND

The effects of carbamide peroxide bleach on tooth structure are uncertain.

PURPOSE

The purpose of this study was to investigate the effects of direct or indirect carbamide peroxide application on dentin flexural strength and modulus in vitro.

MATERIALS AND METHODS

Dentin bars were machined from bovine incisors and treated with 10% carbamide peroxide for 6 h/d for 14 days. Four groups were created, with eight bars in each group: group 1-direct bleach application only; group 2-indirect bleach application only; group 3-direct bleach application followed by a 2-week storage in artificial saliva; group 4-direct bleach application followed by a 2-week storage in artificial saliva and daily topical fluoride treatments. The specimens' flexural strength and modulus were tested after 24 hours, and the results were compared with water controls using independent t-tests (p < .05).

RESULTS

Flexural strength results (in megapascals) for bleached versus control dentin (1=205+/-26 vs 215+/-14, 2=257+/-25 vs 261+/-14, 3=180+/-22 vs 193+/-36, 4=157+/-18 vs 184+/-11) were significantly lower in group 4 (p=.005). Modulus results (in gigapascals) for bleached versus control dentin (1=10.7+/-1.4 vs 12.2+/-0.6, 2=14.2+/-1.7 vs 14.4+/-1.6, 3=10.0+/-2.0 vs 10.9+/-1.3, 4=9.0+/-1.2 vs 11.1+/-1.0) were significantly lower in groups 1 and 4 (p=.013 and p=.003, respectively). There were no significant differences in strength and modulus results between the bleached and control dentin in groups 2 and 3. A direct application of carbamide peroxide to bovine dentin significantly decreased some dentin mechanical properties in vitro. An indirect application of carbamide peroxide to dentin did not significantly decrease dentin strength and stiffness.

CLINICAL SIGNIFICANCE

This in vitro study suggests that a bleaching treatment, when applied to the enamel of intact teeth, does not significantly affect the mechanical properties of the underlying dentin. However, when applied directly to dentin in clinical situations such as root exposure or occlusal attrition, the bleaching treatment may result in altered mechanical properties of dentin. The clinical consequences of this observation are, however, unknown.

Effect of 10% sodium ascorbate on the shear bond strength of composite resin to bleached bovine enamel

The purpose of this study was to comparatively investigate the effect of antioxidant treatment and delayed bonding after bleaching with three different concentrations of carbamide peroxide (CP) on the shear bond strength of composite resin to enamel. One hundred flat buccal enamel surfaces obtained from bovine incisors were divided into three bleaching groups of 10, 16 and 22% CP (n = 30) and a control group. Each bleaching group was then divided into three subgroups (n = 10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with antioxidant agent, 10% sodium ascorbate, while Group 3 specimens were immersed in artificial saliva for 1 week after bleaching. Specimens in the control group were not bleached. After the specimens were bonded with Clearfil SE Bond and Clearfil AP-X, they were thermocycled and tested in shear until failure. Fracture analysis of the bonded enamel surface was performed using scanning electron microscope. The shear bond strength data was subjected to one-way analysis of variance followed by Duncan's multiple range test at a significance level of P < 0.05. Shear bond strength of composite resin to enamel that was bonded immediately after bleaching with 10, 16 and 22% CP was significantly lower than that of unbleached enamel (P < 0.05). For all three bleaching groups, when the antioxidant-treated and delayed bonding (1 week) subgroups were compared with the control group, no statistically significant differences in shear bond strength were noted (P < 0.05).

In vitro evaluation of toothbrushing abrasion of differently bleached bovine enamel

PURPOSE

To evaluate in vitro, the effect of different external bleaching agents on the susceptibility of enamel against toothbrushing abrasion.

METHODS

96 bovine enamel specimens were embedded in acrylic resin, polished and covered with tape except for a 1.4 x 10 mm window. The samples were divided into eight groups (A-H), 12 specimens each (A-G) were treated with seven different home-bleaching (A: Whitestrips, B: Rapid White, C: Opalescence 10%, D: Opalescence PF 15%) and in-office-bleaching agents (E: Opalescence Extra, F: Opalescence Quick, G: Opalescence Extra Boost) according to manufacturers' instructions. Before and after each individual bleaching treatment the samples were brushed 40 times in an automatic brushing machine using a slurry containing artificial saliva and fluoridated toothpaste. The control group (Group H) was not bleached, but also brushed. After each cycle the specimens were stored in artificial saliva for 24 hours.

RESULTS

After 20 cycles loss of enamel was determined by profilometry, resulting in the following values (mean +/- standard deviation) which were statistically analyzed: Group A: (0.169 microm +/- 0.035), Group B (11.108 microm +/- 0.655), Group C (0.207 microm +/- 0.042), Group D (0.154 microm +/- 0.028), Group E (0.081 microm +/- 0.015), Group F (0.084 microm +/- 0.018), Group G (0.087 microm +/- 0.014), Group H (0.076 microm +/- 0.012). Group B differed significantly from the other groups (r = 0.001). Samples of Groups C, D and A showed a significant difference compared to the control H (r = 0.001). Statistical analysis revealed no significant difference between enamel loss of Groups E, F, G and the Control H. It could be proven that toothbrushing abrasion of bleached enamel may be increased depending on the bleaching agent and application form used. Nevertheless, with the exception of bleaching treatment with Rapid White, toothbrushing abrasion of bleached enamel seems to be clinically less relevant.

Potential remineralization of demineralized enamel after application of fluoride varnish

PURPOSE

To evaluate remineralization effects of a topical fluoride varnish applied over a caries-like lesion compared to around a caries-like lesion.

METHODS

Caries-like lesions were created on 30 molar surfaces. Sections were cut through each lesion, photographed under polarized light microscopy, and quantitated with a computerized imaging system. The sections were repositioned with only the lesion exposed. Half were painted with a 5% NaF varnish, including the surface of lesion. The remaining half were painted excluding the surface of the lesion. The sections were placed in artificial saliva for 30 days, re-photographed and re-quantitated.

RESULTS

Using a student t-test for analysis, the results demonstrated the mean (+/- S.E.) percent remineralization of lesion size to be 10.8 (4.8) for lesions completely covered by the fluoridated varnish and 9.5 (2.9) for lesions that had the fluoridated varnish surrounding the lesion. Both application techniques indicated remineralization effects, yet there was no significant difference between the two application techniques evaluated in this study (P < 0.05). The data from this in vitro study indicated that there was no significant difference in methods of application for fluoridated varnish. Both application techniques demonstrated effective remineralization.

The effect of artificial saliva on the rheological properties of tooth whitening systems

This work was undertaken to explore the effect of saliva addition on the rheological properties of two contrasting tooth bleaching systems, one of which was a paste (Colgate Platinum) and the other a gel (Zaris, 3M ESPE). Using a dynamic stress rheometer with cone and plate geometry, it was shown that addition of artificial saliva reduced the apparent viscosity of each material. However, in some cases this was accompanied by an increase in elasticity. It is suggested that saliva may not have a deleterious effect on the ability of the materials to remain in the bleaching tray.

Toothbrush Abrasion of Surface Softened Enamel Studied with Tapping Mode AFM and AFM Nanoindentation

The aim of the present in vitro study was to investigate the toothbrush abrasion of surface softened enamel using tapping mode atomic force microscopy (TM-AFM) and AFM nanoindentation. TM-AFM investigations showed that the typical prismatic pattern as observed after demineralisation was retained after toothbrushing. The exposure to artificial saliva resulted in the deposition of a 'sausage-shape' material with random orientation. Brushing of these samples did not lead to a complete removal of this deposited material. Enamel mineral loss increased with increasing demineralisation time and increased further, although only to a small extent, due to subsequent toothbrushing. Exposure to artificial saliva did not alter the amount of enamel mineral lost due to the brushing treatment. AFM nanoindentation investigations showed that the three different demineralisation treatments caused three statistically different reductions in both surface hardness and reduced elastic modulus values, with the shortest exposure time having the least effect on the nanomechanical properties of the enamel samples. Toothbrushing did result only in a small increase in hardness and reduced elastic modulus. The present study has shown that toothbrushing of surface softened enamel leads to minor changes in the surface morphology and nanomechanical properties. The amount of enamel lost due to toothbrushing was independent of the demineralisation time and was lower compared to the mineral loss caused by the demineralisation treatments. Furthermore, the exposure to artificial saliva offers minimal protective effect to the softened enamel surface against toothbrushing.

The influence of antimicrobial peptides and mucolytics on the integrity of biofilms consisting of bacteria and yeasts as affecting voice prosthetic air flow resistances

The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses afterm biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance.

Effects of carbohydrate polymers applicable in saliva substitutes on the anti-Candida activity of a histatin-derived peptide

The effects of polymers applicable in saliva substitutes on the anti-Candida activity of the cationic antimicrobial peptide dhvar1 were investigated. Dhvar1 is a derivative of the 14 C-terminal amino acids of histatin 5. The effects of the following polymers were tested: uncharged hydroxyethylcellulose (HEC), negatively charged xanthan (XG) and three types of negatively charged carboxymethylcellulose (CMC) of identical mass but different degrees of carboxylic acid-group substitution (DS). The effects were tested at pH 4.0, 7.0 and 8.5 in a killing assay. HEC had no effect at any pH tested; XG and the three types of CMC caused a decrease in activity at increasing concentrations. Within the CMC group, inhibition increased slightly with increasing DS. These results suggest that the reduction in activity associated with these polymers is the result of electrostatic interaction between the positively charged peptides and the negatively charged polymers. In the absence of polymers, no effect of pH was found on the activity of dhvar1. In the presence of the charged polymers XG and CMC, lowering the pH from 7.0 to 4.0 resulted in a decrease of dhvar1 activity. It was concluded that, with respect to the retention of activity, HEC is the most appropriate polymer for use in combination with dhvar1. However, for use in saliva substitutes XG seems more suitable because of its rheological properties. If XG or CMC are to be used, their reductive effect on the anti-Candida activity of dhvar1 should be compensated for by increasing the peptide dose.

The effect of commercially available saliva substitutes on predemineralized bovine dentin in vitro

OBJECTIVE

The objective of this study was to evaluate the effects of various saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac; Oralbalance) on the lesion depth and the mineral content of predemineralized bovine dentin in vitro.

MATERIALS AND METHODS

Ninety-six dentin samples were prepared from 24 freshly extracted bovine incisors. The samples were predemineralized (pH 5.5; 10 days), and subsequently exposed to the various artificial salivas. A carbonate-reduced mineral water (Hirschquelle) as well as the mouthwash solutions Meridol and biotène served as controls. Lesion depth and mineral loss were evaluated from microradiographs of thin sections (110 microm) by a dedicated software package (TMR 1.24).

RESULTS

After storage in Glandosane and biotène, the results indicated a significant mineral loss and an increase in lesion depth (P < 0.01; Wilcoxon). In contrast, specimens stored in Oralube showed a decrease in lesion depth and an increase in mineral content (P < 0.05; Wilcoxon).

CONCLUSIONS

Thus, the use of neither Glandosane nor biotène can be recommended in dentate patients with severe xerostomia.

Effects of two 10% peroxide carbamide bleaching agents on dentin microhardness at different time intervals

OBJECTIVE

The purpose of this in vitro study was to evaluate the microhardness of human dentin exposed to two 10% carbamide peroxide agents at different bleaching times.

METHOD AND MATERIALS

Opalescence 10% and Rembrandt 10% were tested. A placebo agent was used as a control group. The bleaching and placebo agents were applied to the surface of human dentin fragments for 8 hours and then stored in individual receptacles with artificial saliva for the remaining 16 hours each day. Microhardness testing was performed at baseline, after 8 hours, 7, 14, 21, 28, 35, and 42 days of treatment, and 7 and 14 days posttreatment.

RESULTS

Analysis of Variance and the Tukey test revealed significant differences in microhardness values for dentin treated with the agents within each time interval. There was a decrease in the microhardness values of dentin for both bleaching agents after 8 hours of treatment. Fourteen days after the completion of treatment, the microhardness values for dentinal surfaces treated with either Opalescence or Rembrandt reached the baseline values; the dentinal surfaces treated with a placebo exhibited an increase in microhardness values posttreatment.

CONCLUSION

Ten percent carbamide peroxide bleaching agents decreased dentinal microhardness over time, but after 14 days in artificial saliva storage at the completion of treatment, the baseline microhardness values were recovered.

Clinical applications of antimicrobial host proteins lactoperoxidase, lysozyme and lactoferrin in xerostomia: efficacy and safety

Innate human salivary defence proteins, lysozyme, lactoferrin and peroxidase, are known to exert a wide antimicrobial activity against a number of bacterial, viral and fungal pathogens in vitro. Therefore, these proteins, alone or in combinations, have been incorporated as preservatives in foods and pharmaceuticals as well as in oral health care products to restore salivas' own antimicrobial capacity in patients with dry mouth. These antimicrobials used in oral health care products, such as dentifrices, mouth-rinses, moisturizing gels and chewing gums, have been purified from bovine colostrum. In this review I critically evaluate the clinical efficacy and safety of this kind of preventive approach against various oral diseases and symptoms.

Effect of a bicarbonate-containing dentifrice on pH changes in a gel-stabilized plaque after exposure to sucrose

Because many factors influence the acid-forming ability of dental plaque in the mouth, a model system was used in which reproducible Stephan curves could be generated after exposure of a gel-stabilized plaque to sucrose. Simulation of the use of a high-bicarbonate dentifrice at a time when plaque pH had fallen to about 4.5 caused a rapid return of the pH toward neutrality, whereas simulation of the use of a low-bicarbonate dentifrice had much less effect.

Effect of salivary components on volatile partitioning from solutions

Partition of fourteen volatile compounds, representing the diverse physicochemical properties of aroma compounds, was measured by static equilibrium headspace in solutions containing the components of artificial saliva, either singly or in mixtures. Comparison of a bovine salivary mucin and pig gastric mucin showed no significant difference in partition behavior of the volatiles, so gastric mucin was used. Mucin viscosity changed with pH, but binding of volatile compounds did not show a marked dependence on pH. All combinations of the salivary components were tested for their effect on partition. Three types of behavior were noted. Partition of some compounds was unaffected by mucin, and with other compounds mucin decreased partition, whereas another group showed a decrease with mucin that was affected by the presence of salivary salts and sugar. When volatiles or sugar were added to a mucin solution, the final headspace concentration depended on the order of addition, indicating some competition for binding. These solute-mucin effects are discussed in relation to mucin structure and behavior in solution.

Oral mucous membrane flora in patients using saliva substitutes

Salivary substitutes are sometimes valuable for elderly people and radiotherapy patients, and may be used indefinitely. It is possible that this change in the ecology may effect the oral flora.

OBJECTIVE

To analyse the presence of micro-organisms on oral mucous membranes during use of saliva substitutes.

DESIGN

Cross-over single-blind study.

SETTING

Clinic for Maxillofacial Surgery, Malmö University Hospital and Department of Oral Microbiology, Malmö University.

SUBJECTS

19 patients with low salivary secretion who had been radiated for cancer in the head and neck region.

INTERVENTION

Two saliva substitutes: linseed extract and a carboxymethyl cellulose preparation (Salinum and MAS-84) were used for 3 week periods.

MEASUREMENTS

Microbial samples taken, processed and analysed.

RESULTS

No differences were observed when comparing baseline values with the results after the saliva substitutes and no significant differences between the use of different agents.

CONCLUSION

The study suggests that use of linseed extract and carboxymethyl cellulose preparation during periods of weeks does not influence flora commonly related to caries, periodontitis or infections in the oral mucous membranes.

Use of transverse microradiography to quantify mineral loss by erosion in bovine enamel

The aim of the present study was to develop transverse microradiography (TMR) in order to quantitatively assess the influence of artificial saliva and orange juice on the erosion of bovine enamel. Bovine incisors were sectioned sagittally into two equal halves. Each half was coated with acid-resistant nail varnish except for a rectangular enamel window on the labial surface of the tooth. While both halves of each tooth were immersed in pure orange juice 6 times daily for a period of 5 min at each occasion making a total of 30 min per day, one half was stored in artificial saliva and the other half in deionized distilled water between exposures to orange juice and for the remaining 12 h overnight, for 24 days making a total of 12 h of exposure to orange juice. Sections bearing intact and eroded enamel surfaces were cut from each specimen and ground to 80 microm thickness, and TMR of the sections was made. Mineral loss was quantified from the microradiographs using two-step image analysis. Mineral loss was significantly greater in those specimens cycled in orange juice and de-ionized distilled water. TMR was used successfully to quantify the mineral loss by erosion in vitro, and it is envisaged that it will be useful for specimens used in intra-oral appliances during in situ trials. Artificial saliva saturated with respect to calcium and phosphate salts can possibly remineralize an erosive lesion and may reduce the degree of erosion.

Effect of dentin desensitizers and dentin bonding agents on dentin permeability

PURPOSE

To determine the effect of dentin desensitizing agents (oxalates and glutaraldehyde) and dentin bonding agents, with and without resin-based composite (RBC) on dentin permeability and morphology of the dentin surface. The influence of saliva and toothbrushing on these agents was also evaluated.

MATERIALS AND METHODS

Radicular dentin discs +/-1 mm thick were obtained from extracted human teeth. The thickness of the discs was standardized by grinding them with 600 grit silicon carbide powder. Both pulpal and periodontal surfaces of the discs were treated with 6% citric acid for 2 min prior to the baseline measurement of dentin permeability. Permeability was measured for the discs, using a split-chamber apparatus, at four different time points: at baseline, after treatment with each desensitizing modality, after 24 hrs of saliva immersion and after simulated toothbrushing equivalent to 3 weeks of normal brushing. The treatment modalities were: Sensodyne Dentin Desensitizer, Gluma Dentin Desensitizer, All-Bond DS (primers without etching), Etch+Primers (All-Bond 2 system), Etch+Primers+Adhesive and Etch+Primers+Adhesive+RBC (AElite Flo). Radicular dentin discs were prepared separately for scanning electron microscopy (SEM). One group was left untreated as the control group. Discs in the other groups were treated with the modalities listed above. One disc from each group was viewed under the SEM after treatment with the desensitizing modality. The second disc in each group was viewed after 24 hrs of saliva immersion following desensitizing treatment and the third disc after 3 weeks of simulated toothbrushing following desensitizing treatment and saliva immersion.

RESULTS

The greatest reduction in permeability was caused by All-Bond DS followed by Sensodyne Dentin Desensitizer and Etch+Primers+Adhesive+RBC. Gluma Dentin Desensitizer, Etch+Primers, and Etch+Primers+Adhesive did not reduce permeability by a significant amount. Saliva immersion increased permeability significantly only for the Gluma and Etch+Primers+Adhesive groups. There was a trend towards increase in permeability after toothbrushing; however, this increase was not statistically significant for any group (P > 0.05). Thus, placement of primers without etching (All-Bond DS) reduced permeability more than any other treatment modality. These data indicate that etching a sensitive dentin area may be appropriate only if RBC is to be placed in the area. Exposure to saliva and toothbrushing countered the decrease in permeability caused by dedicated desensitizers and dentin bonding agents. The SEM micrographs revealed that in most cases, form corroborated function and the morphology of the dentin surface corresponded to the dentin permeability values.

Techniques for the production of dental eroded lesions in vitro

This project firstly demonstrated an in vitro technique for the production of eroded lesions which simulates the in vivo conditions, and secondly evaluated the influence of salivary parameters on the degree of erosion in vitro. Teeth were sectioned sagitally into three equal portions. The portions were randomly assigned to one of three experimental groups (A, B and C). Lesions were produced by cycling the teeth between orange juice and either artificial saliva (A) or water (B) for a total period of 12 h, or by a single 12 h immersion in orange juice (C). Sections were prepared from each specimen and mineral loss was quantified using transverse microradiography. Mineral loss was significantly lower in group A compared with B and C. Greatest mineral loss was observed in B though not significant when compared with C. The present technique mimics the in vivo conditions with the saliva reducing the degree of erosion and possibly remineralizing the lesions.