Physical chemical effects of zinc on in vitro enamel demineralization

Objectives

Zinc salts are formulated into oral health products as antibacterial agents, yet their interaction with enamel is not clearly understood. The aim was to investigate the effect of zinc concentration [Zn²⁺] on the in vitro demineralization of enamel during exposure to caries-simulating conditions. Furthermore, the possible mechanism of zinc's action for reducing demineralization was determined.

Methods

Enamel blocks and synthetic hydroxyapatite (HAp) were demineralized in a range of zinc-containing acidic solutions (0–3565 ppm [Zn²⁺]) at pH 4.0 and 37 °C. Inductively coupled-plasma optical emission spectroscopy (ICP-OES) was used to measure ion release into solution. Enamel blocks were analysed by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and HAp by X-ray diffraction (XRD) and neutron diffraction (ND).

Results

ICP-OES analysis of the acidic solutions showed a decrease in [Ca²⁺] and [PO₄³⁻] release with increasing [Zn²⁺]. FTIR revealed a α-hopeite (α-Zn₃(PO₄)₂.4H₂O)-like phase on the enamel surfaces at >107 ppm [Zn²⁺]. XRD and ND analysis confirmed a zinc-phosphate phase present alongside the HAp.

Conclusions

This study confirms that zinc reduces enamel demineralization. Under the conditions studied, zinc acts predominantly on enamel surfaces at PO₄³⁻ sites in the HAp lattice to possibly form an α-hopeite-like phase.

Clinical significance

These results have a significant implication on the understanding of the fundamental chemistry of zinc in toothpastes and demonstrate its therapeutic potential in preventing tooth mineral loss.     

Synchrotron X-ray diffraction to understand crystallographic texture of enamel affected by Hunter syndrome

ObjectiveTo determine whether Hunter syndrome (MPS II) affects the crystallographic texture (preferred orientation) of enamel.DesignSynchrotron X-ray diffraction, being a state of the art technique, has been used to determine the enamel crystallite orientation in enamel affected by Hunter syndrome (MPS II). The incisal, lingual and cervical regions of the MPS II affected tooth were observed and compared to healthy tooth.ResultsIt was observed that there is a loss of organization of crystallites in deciduous incisal enamel affected by Hunter syndrome (MPS II) as compared to healthy deciduous enamel tissue. Generally it was observed that, in contrast to the healthy enamel, the enamel affected by MPS II possessed a lower crystallographic preferred orientation, with a more uniform spatial distribution; however, the enamel at the incisal tip was relatively unaffected.ConclusionHunter syndrome affects the enamel texture in the lingual and cervical regions of the tooth.     

Effect of tricalcium silicate (Ca3SiO5) bioactive material on reducing enamel demineralization: An in vitro pH-cycling study

Objectives

The aim of this study was to investigate the effect of Ca₃SiO₅ on reducing enamel demineralization under pH-cycling conditions.

Methods

Forty bovine enamel samples were treated under four conditions: group 1, double distilled water (negative control); group 2, 1000 ppm F (as NaF, positive control); group 3, Ca₃SiO₅ slurry; and group 4, Ca₃SiO₅–F slurry (Ca₃SiO₅ with 1000 ppm F aq.). All the specimens were treated with treatment materials 4 times each day. Samples in groups 1 and 2 were soaked in test solutions for 2 min and samples in groups 3 and 4 were painted in treatment slurry for 2 min. At times between treatments, they were immersed in citric acid solution 3 times a day and 15 s each time. All the procedures were repeated for 7 days. Knoop microhardness, scanning electron microscopy (SEM), X-ray diffraction (XRD) and atom force microscopy (AFM) were used to examine samples.

Results

After treatment for 7 days, enamels in all the groups were significantly softened. The extents of microhardness reduction were 52.3%, 28.5%, 28.5% and 20.2% for groups 1, 2, 3 and 4, respectively. Samples in the negative control group showed a typical acid etched pattern while enamels in other groups were relatively compact. There was no significant difference between samples treated with Ca₃SiO₅ and F. The combination of Ca₃SiO₅ with F showed the best effect on reducing enamel demineralization.

Conclusions

Ca₃SiO₅ is an effective material against enamel demineralization alone but in combination with F a better anti-demineralization effect may be obtained.     

The application of synchrotron radiation induced X-ray emission in the measurement of zinc and lead in Wistar rat ameloblasts

The development of analytical techniques for the measurement of trace elements in cellular compartments of developing teeth remains an important methodological issue in dental research. Recent advances in third generation synchrotron facilities have provided high brilliance X-ray sources that can be effectively used to study trace element distributions in small spatial regions with low detection limits. The present study describes for the first time the application of synchrotron radiation induced X-ray emission (SRIXE) in measuring the distribution of zinc and lead in the ameloblasts of developing Wistar rat teeth. Wistar rats were fed a standard rat diet, containing the normal dietary requirements of zinc, ad libitum and exposed to 100 ppm of lead in drinking water. Resin embedded sections of first mandibular molars were analysed using a 13.3 keV incident monochromatic X-ray beam focussed to a 0.2 μm spot. Characteristic X-rays arising from the entire thickness of the sample were measured using an energy dispersive detector for quantitative analysis of elemental concentrations. The results showed that intranuclear concentrations of zinc were greater than levels in the cytoplasm. Furthermore, nuclear and cytoplasmic concentrations of zinc in the maturation stage (742 ± 27 and 424 ± 25 ppm, respectively) were significantly higher than the zinc levels observed in the nucleus and cytoplasm of presecretory stage ameloblasts (132 ± 10 and 109 ± 10 ppm, respectively) (p < 0.05). A clear lead signal above the background was not detected in the ameloblasts and lead concentrations could only be reliably measured in the developing enamel. Overall, SRIXE was an effective method of studying the spatial distribution of zinc in the cells of developing teeth and offered a unique combination of sub-micron spatial resolution and parts-per-million detection limits (0.8-1 and 0.6-1 ppm for zinc and lead, respectively).     

Validation of enamel erosion in vitro

Objectives

Many tools are available to quantify dental erosion, but each technique has its own inherent disadvantages. This study aims to validate the use of quantitative light-induced fluorescence (QLF) and non-contacting surface profilometry compared to the gold standard transverse microradiography (TMR) for the quantification of enamel erosion in vitro.

Methods

This was an in vitro laboratory based study. 60 bovine incisors were divided into 6 groups of 10. Each tooth's labial surface was completely varnished except for a window of enamel approximately 3 mm × 5 mm. Each was baseline imaged with QLF and non-contacting surface profilometry before being subjected to an erosive solution (pH 3.4) for up to 36 h. The lesions were imaged using non-contacting surface profilometry and QLF, sectioned and analysed with TMR. Correlation coefficients were calculated to assess the validity of the methods of measurement as compared to TMR.

Results

A range of lesion severities resulted. Mineral loss measured as ΔQ (QLF) and step height (profilometry), was recorded and confirmed by TMR. A correlation was found between ΔZ (TMR) and profilometry lesion depth of r = 0.648 (p < 0.001). A poorer correlation was found between ΔZ and ΔQ: r = 0.217 (p = 0.096).

Conclusions

Profilometry lesion depth and ΔZ correlated significantly. Both methods allow for quantification of erosive crater depth. QLF correlated poorly with ΔZ, but is useful for measuring subsurface loss of mineralisation. TMR is valuable but is destructive and can only be used in vitro. Currently only QLF can be used in vivo. Advances in these technologies may allow the development of non-destructive in vivo measurements of mineral loss, combining the positive features of each measurement method.     

Effect of fluoride varnish supplemented with sodium trimetaphosphate on enamel erosion and abrasion: An in situ/ex vivo study

Objective

To evaluate the effect of fluoride (F) varnishes supplemented or not with sodium trimetaphosphate (TMP) on enamel erosive wear followed or not by abrasion in situ.

Methods

Ten volunteers were selected and randomly divided into four groups, according to the varnishes tested: placebo (no F or TMP), 5% NaF (positive control), 2.5% NaF and 2.5% NaF/5% TMP. Enamel blocks (n = 4) were mounted in palatal devices and received an application of each test varnish, following a double-blind, crossover protocol. After 6 h, varnishes were completely removed and the blocks were subjected to erosive challenges by ex vivo immersion in citric acid (5 min, 4×/dia, 5 days). Following, half of the blocks were subjected to abrasion by brushing with a placebo dentifrice slurry for 15 s. Enamel wear (μm), surface hardness (SH_f) and cross-sectional hardness (ΔKHN) were assessed after each experimental period. Results were analyzed by ANOVA, Student–Newman–Keuls's test and Pearson correlation coefficient (p < 0.05).

Results

The fluoride varnish supplemented with TMP promoted significantly lower wear and ΔKHN when compared to the other groups after erosive challenges, followed or not by abrasion (p < 0.05). As for (SH_f) the fluoride varnish supplemented with TMP promoted similar results to the 5% NaF product, being significantly higher than the remaining groups after erosive and erosive + abrasive challenges (p < 0.05).

Conclusion

TMP significantly enhanced the effects of F on enamel wear after erosive challenges, followed or not by abrasion.     

Effect of rinsing with water immediately after neutral gel and foam fluoride topical application on enamel remineralization: An in situ study

Objective

The aim of this study was to evaluate, in situ, the effect of rinsing with water immediately after neutral fluoride foam application (Foam) or fluoride gel application (Gel).

Design

Ten volunteers wore acrylic palatal appliances containing 4 enamel blocks selected by surface hardness with artificial caries. Five experimental regimes of 3 days each were set according to treatment: placebo; Gel and Foam followed by no rinsing or consuming of liquids or solids for the next 30 min; Gel and Foam followed by immediately washing with water jet. After each phase, surface hardness was again measured for analysis of mineral gain, evaluated through percentage of surface hardness recovery (%SHR) and integrated loss of subsurface hardness (ΔKHN). The concentration of loosely bound fluoride (CaF2) and firmly bound fluoride (FA-like) formed and retained were also determined.

Results

Fluoride treatments produced greater remineralization (%SHR and ΔKHN) compared to placebo group (p < 0.05). There was no difference in the ability to promote remineralization and in the concentration of fluoride formed and retained, in each analysis, between Gel and Foam (p > 0.05).

Conclusion

The data suggest that rinsing with water immediately after topical application does not seem to have an influence on the ability of fluoride to promote remineralization.     

Mapping the spatial and temporal progression of human dental enamel biomineralization using synchrotron X-ray diffraction

Objective

The complex biological, physicochemical process of human dental enamel formation begins in utero and for most teeth takes several years to complete. Lost enamel tissue cannot regenerate, therefore a better understanding of the spatial and temporal progression of mineralization of this tissue is needed in order to design improved in vivo mineral growth processes for regenerative dentistry and allow the possibility to grow a synthetic whole or partial tooth.

Method

Human dental enamel samples across a range of developmental stages available through archaeological collections have been used to explore the spatial and temporal progression of enamel biomineralization. Position sensitive synchrotron X-ray diffraction was used to quantify spatial and temporal variations in crystallite organization, lattice parameters and crystallite thickness at three different stages in enamel maturation. In addition X-ray microtomography was used to study mineral content distributions.

Results

An inverse correlation was found between the spatial variation in mineral content and the distribution of crystallite organization and thickness as a function of time during enamel maturation. Combined X-ray microtomography and synchrotron X-ray diffraction results show that as enamel matures the mineral content increases and the mineral density distribution becomes more homogeneous. Starting concurrently but proceeding at a slower rate, the enamel crystallites become more oriented and larger; and the crystallite organization becomes spatially more complex and heterogeneous.

Conclusion

During the mineralization of human dental enamel, the rate of mineral formation and mineral organization are not identical. Whilst the processes start simultaneously, full mineral content is achieved earlier, and crystallite organization is slower and continues for longer. These findings provide detailed insights into mineral development in human dental enamel which can inform synthetic biomimetic approaches for the benefit of clinical dentistry.     

Combined effect of amoxicillin and sodium fluoride on the structure of developing mouse enamel in vitro

Objective

Excess fluoride intake during tooth development is known to cause dental fluorosis. It has also been suggested that amoxicillin use in early childhood is associated with enamel hypomineralization. The aim was to investigate separate and combined effects of sodium fluoride (NaF) and amoxicillin on enamel formation in vitro.

Design

Mandibular molar tooth germs of E18 mouse embryos were cultured for 10 days in a medium containing NaF (10, 12 or 15 μM) and/or amoxicillin (0.5, 1, 2 or 3.6 mg/mL) or sodium clavulanate (0.07 mg/mL) alone or in combination with 0.5 mg/mL of amoxicillin. Morphological changes were studied from the whole tooth photographs and histological tissue sections with light microscope.

Results

Only with the highest concentrations of NaF or amoxicillin alone the extent of enamel in the first molars measured as the vertical enamel height/crown height ratio was reduced (p < 0.01, p < 0.001, respectively). At lower concentrations, combination of NaF (12 μM) and amoxicillin (2 mg/mL) significantly reduced enamel extent compared with the controls (p < 0.001). Histologically, the ameloblasts were still columnar but poorly organized and the nascent enamel was often non-homogeneous. Enamel formation was not seen in any second molars exposed to 12 μM NaF and 2 mg/mL of amoxicillin (or higher concentrations) compared with the presence of enamel in half of the controls (p < 0.001).

Conclusions

Amoxicillin and NaF dose dependently affect developing enamel of mouse molars in vitro and the effects are potentiative. The clinical significance of the results remains to be studied.     

Sodium fluoride mouthrinse used twice daily increased incipient caries lesion remineralization in an in situ model

Objectives

To investigate the remineralizing effects of fluoride mouthrinses used at different times and frequency in addition to fluoride toothpaste.

Methods

A randomized crossover single blinded study comprised 4 experimental phases of 21 days each. Twelve orthodontic volunteers were fixed with an orthodontic bracket containing an artificial carious enamel slab, which was from the same tooth in all 4 phases, and were randomly assigned to the following groups: (1) brushing with F toothpaste 2× per day (F- brush), (2) F- brush + rinsing with 0.05% NaF (F- rinse) after lunch, (3) F- brush + F-rinse before bedtime, and (4) F- brush + F- rinse 2× per day. Mean mineral gain after each phase was determined from mineral density profiles obtained using Micro-CT.

Results

The mean mineral gain in all treatments with F- brush and F-rinse were significantly greater than those in F- brush (p < 0.05). Moreover F- rinse 2× per day increased lesion remineralization more than F- rinse once a day.

Conclusions

The twice-daily use of 0.05% NaF mouthrinse combined with twice-daily regular use of fluoride toothpaste resulted in the greatest remineralization of incipient caries. These data indicate that rinsing frequency is a factor affecting the effectiveness of fluoride mouthrinse.

Clinical significance

The rinsing frequency of NaF mouthrinse, when used with fluoride toothpaste, also affects the remineralization. This finding, if confirmed by a clinical study, would lead to a new recommendation for fluoride mouthrinse used in high caries risk patients who could benefit from using it twice a day.     

Effects of fluoride concentration on enamel demineralization kinetics in vitro

Objectives

The aim of the present study was to measure the effects of fluoride concentration on the real-time in vitro demineralization of enamel during exposure to caries-simulating conditions using Scanning Microradiography (SMR).

Methods

Enamel blocks obtained from non-carious human molars were fixed in SMR environmental cells, through which acidic solutions (0.1 M acetic acid, pH 4.0) were circulated for periods of 48 h. SMR was used to quantitatively measure continuous mineral mass loss. Subsequently, the effects of sequentially increasing fluoride concentration (0.1–4500 mg/L [F⁻]) in the acidic solutions were measured on the rate of enamel demineralization.

Results

The data shows a log-linear relationship between [F⁻] and reduction in demineralization up to 135 mg/L [F⁻]. Above 135 mg/L, no further significant decrease in demineralization occurred.

Conclusion

The optimum range of local fluoride concentration for reducing enamel demineralization was in the range 0.1–135 mg/L [F⁻] under the conditions studied.

Clinical significance

Relatively low [F⁻] can exhibit near-optimum protection. Increasing the fluoride concentrations above 135 mg/L may not necessarily give an increased cariostatic benefit. Improving the means of delivery of relatively low fluoride concentrations to the oral fluids through slow releasing mechanisms, such as the oral fluoride reservoirs, is the more appropriate way forward for sustaining long-term clinical efficacy.     

The effect of acidic beverages on the ultrastructure of the acquired pellicle—An in situ study

Aim

The aim of the present in situ study was to investigate ultrastructural alterations as well as protective properties of the pellicle layer during consumption of acidic beverages.

Methods

Bovine enamel slabs were fixed on buccal and palatal aspects of individual splints and exposed in the oral cavities of three subjects for 120 min. In the following, the subjects drank orange juice, coke light or sprite light. Half of the specimens were removed afterwards, the others were exposed to the oral fluids for another 120 min. Erosive alterations of the bovine enamel slabs were measured by determination of the Knoop-micro-hardness. In addition, the ultrastructure of the pellicle was evaluated by transmission electron microscopy (TEM).

Results

Determination of Knoop-micro-hardness yielded only little reduction of the relative Knoop-hardness in situ during consumption of sprite light (−0.053 ± 0.019) and coke light (−0.075 ± 0.04). With orange juice nearly no change of the hardness was recorded. TEM-pictures showed that the globular outer layers of the pellicle were removed to a different extent according to the localisation of the specimens in the oral cavity, whereas the basal pellicle was not affected by the acidic beverages. On the specimens carried for another 120 min after the erosive attack, lacunae filled with organic structures were observed underneath the basal side of the pellicle.

Conclusion

During fast consumption of acidic beverages in situ, the erosive effects on pellicle coated bovine enamel are moderate and juices seem to be less harmful as compared with low pH soft drinks. Pellicle proteins in eroded lacunae may impact the remineralisation process.     

Effect of experimental mouthrinses containing the combination of NaF and TiF4 on enamel erosive wear in vitro

Objective

This study analysed the anti-erosive effect of experimental solutions containing TiF₄ and NaF.

Methods

Bovine enamel samples (n = 15) were treated with: (1) commercial solution with SnCl₂/NaF (Erosion Protection^®); (2) experimental solution with 0.0815% TiF₄; (3) 0.105% NaF; (4) 0.042% NaF + 0.049% TiF₄; (5) 0.063% NaF + 0.036% TiF₄ or (6) control. The samples were submitted to pH cycles and daily fluoride applications for seven days. The enamel wear was measured using a contact profilometer and analysed by ANOVA (p < 0.05).

Results

The best anti-erosive effect was found for experimental solution with 0.0815% TiF₄ (99% reduction in enamel wear), followed by SnCl₂/NaF (78%) and 0.049% TiF₄ + 0.042% NaF solution (41%).

Conclusions

The experimental solution containing a specific combination of TiF₄ + NaF has the ability to partially reduce enamel erosion.     

X-ray microtomographic study of mineral concentration distribution in deciduous enamel

OBJECTIVE: To determine the mineral concentration distribution in deciduous enamel by quantitative X-ray microtomography (XMT). DESIGN: Tooth rods ( approximately 2 mm x 2 mm) were removed from the mid-buccal region of 11 deciduous molars. Three XMT slices were taken at 1.5, 2.0 and 2.5 mm from the amelocemental junction. The distribution and variation in mineral concentration of enamel were studied from the XMT images. RESULTS: The mean mineral concentration for all the teeth was 2.81 (S.D. = 0.065) g cm(-3). There was no notable difference in the mean mineral concentration values between the three XMT slices of each tooth. However, there was up to 8% variation between different teeth (2.69-2.92 g cm(-3)). Gradients of increasing mineral concentration from the amelodentinal junction (ADJ) to the external surface were found, ranging from 0.08 to 0.60 mg cm(-3) microm(-1) with a mean of 0.366 mg cm(-3) microm(-1). The mineral concentration gradients in the occlusal slices were steeper than those in the cervical slices. The difference in mineral concentration between the inner and outer enamel ranged from 1.5 to 8.7%. CONCLUSION: In view of the large variation in both the means and the gradients of mineral concentration in deciduous molars, the mineral distribution of each experimental tooth should be measured as baseline data in studies of caries progression.     

Effect of a 10% carbamide peroxide on wear resistance of enamel and dentine: In situ study

Objectives

This triple-blind, 2 × 2 crossover in situ study, was undertaken to verify whether the wear resistance of enamel and root dentine would be affected by bleaching with a 10% carbamide peroxide agent and a placebo agent.

Methods

Thirty slabs of each substrate (2 mm × 3 mm × 2 mm) were selected for each phase, after flattening and polishing procedures and microhardness test. After a 7-day lead-in period, one specimen of each substrate was randomly bonded on the facial surface of each one of 30 subject's upper second premolars. The volunteers received instructions on how to perform toothbrushing and application of gel in the tray. Fifteen volunteers bleached their maxillary arch with a 10% carbamide peroxide bleaching agent for a 2-week period, while the remainders used a placebo agent. After a 1-week washout period, a new set of enamel and root dentine slabs were bonded to the premolars and volunteers were crossed over to the alternate agent for 14 days. The resistance of enamel and root dentine to wear following bleaching, toothbrushing and intraoral exposure was measured with a profilometer, using reference areas.

Results

For enamel, ANOVA did not demonstrate significant difference between wear provided by placebo and bleaching agent (p = 0.3713), but higher wear depth was observed for bleached root dentine (p = 0.0346).

Conclusions

While overnight bleaching caused no alteration in wear resistance of enamel, root dentine showed increased tissue loss.     

红色荧光定量分析法评价釉质早期龋的临床研究

目的采用定量光导荧光（QLF）技术的红色荧光分析法检测釉质早期龋,并监测含氟牙膏促进早期龋再矿化的效果,评价该技术诊断早期龋的能力。方法选择有上颌前牙光滑面釉质早期龋的96名小学生为研究对象,指导其在6个月的时间内使用含氟牙膏（氟离子质量分数为0.145%）刷牙。分析基线和6个月后的上颌前牙光滑面荧光图像,获得红色荧光变量（包括荧光面积Ar、平均荧光量△R、荧光总量R）,将其与绿色荧光变量（包括荧光面积Aw、平均荧光损失量△F、荧光损失总量△Q）进行比较,并通过配对t检验评价使用含氟牙膏后龋损的变化情况。结果红色荧光变量Ar、△R、lgR与对应的绿色荧光变量Aw、△F、lg△Q的Pearson相关系数分别为0.89、0.54、0.72（P<0.05）,具有高度相关性。使用含氟牙膏6个月后,红色和绿色荧光变量均较基线明显降低,其差异有统计学意义（P<0.05）。结论采用QLF技术的红色荧光分析法能够评价釉质早期龋的严重程度,并纵向监测病变,适用于评价龋损防治措施的效果。     

Colour and surface analysis of carbamide peroxide bleaching effects on the dental restorative materials in situ

Objectives

The aim of this in vivo study was to evaluate the effects of a home-bleaching agent on the color and surface properties of four tooth-colored restorative materials.

Methods

Two composite resins (a nano-hybrid and a packable), a polyacid-modified composite and a conventional glass-ionomer were tested. Specimens were inserted into custom-fabricated trays, and underwent a routine home-bleaching treatment. CIE Lab* color coordinates of the specimens were obtained using a spectrophotometer. Ultra-structural effects were investigated by SEM and ATR–FTIR. The color data were analyzed with ANOVA and Tukey's post hoc analysis.

Results

Significant color changes were found among all the materials after bleaching. However, the color differences decreased and fell into the clinically acceptable range (except for the compomer) after withdrawal of the bleaching treatment. Surface dissolution was detected in the polyacid-modified composite and glass-ionomer cement. ATR–FTIR analyses found chemical composition alterations in the polyacid-modified composite.

Significance

A 15% carbamide peroxide home-bleaching gel did not cause color changes in the composites and glass-ionomer cement. However, significant color and chemical composition alterations were found in the polyacid-modified composite.     

Efficacy of enzymatic toothpastes for immobilisation of protective enzymes in the in situ pellicle

Aim

Different enzyme-containing toothpastes are available on the market. The aim of the present in situ study was to investigate their efficacy for immobilisation of protective enzymes in the pellicle layer.

Methods

Pellicle formation took place in situ on bovine enamel slabs fixed to individual upper jaw splints carried by 6 subjects. After pellicle formation for 1 min, brushing was performed for 3 min with the commercially available toothpastes Enzycal, biotène and BioXtra, respectively. Before as well as 0, 20 and 40 min after brushing, samples were removed from the splints and tested for lysozyme, peroxidase and glucoseoxidase activity. The assays for the respective enzyme activities were based on fluorogenic substrates. Separate experiments were conducted for the different enzymes and toothpastes.

Results

Brushing with the toothpastes caused an extensive increase of glucoseoxidase activity in the pellicle, but it was of low tenacity whereas peroxidase activity was enhanced considerably. However, targeted accumulation of lysozyme in the pellicle was not very pronounced. Brushing without toothpaste had no effect on enzyme activities in the acquired pellicle.

Conclusion

Targeted immobilisation of enzymes in the in situ pellicle can be achieved with toothpastes.     

Clinical study investigating abrasive effects of three toothpastes and water in an in situ model

Objectives

This in situ study compared the abrasive effect of repeated brushings (over 10 days) of a low relative abrasive dentine (RDA) toothpaste with moderate and high relative abrasive dentine (RDA) toothpastes, on human dentine in situ.

Materials and methods

The study design was single centre, single blind, randomized, split mouth, two period, four-treatment cross-over, in situ study in 20 healthy subjects. Subjects wore bi-lateral lower buccal appliances each fitted with four dentine sections with treatment applied with a power toothbrush, during each 10 day study period. Samples were measured at baseline, day 5 and day 10 by contact profilometry, and baseline and day 10 with non-contact profilometry.

Results

Nineteen subjects were included in the efficacy analysis. Results as measured by contact and non-contact profilometry from brushing with the moderate RDA paste and high RDA paste showed significantly (p < 0.0001) more abrasion to dentine than brushing with the low RDA paste or water after 10 days. Dentine loss following tooth brushing with the low RDA paste was not significantly different from brushing with water, after 10 days.

Conclusions

The methodology successfully showed clear differentiation between the amount of dentine lost following toothbrushing with the low RDA paste compared to the moderate or high RDA pastes. Dentine loss following brushing with the low RDA paste showed a comparable degree of abrasion to brushing with water.     

Efficacy of enzymatic mouth rinses for immobilisation of protective enzymes in the in situ pellicle

Aim

Mouth rinses containing enzymes are designed for patients suffering from xerostomia. The objective of the present in situ study was to investigate the efficacy of these rinses for targeted accumulation and immobilisation of protective enzymes in the acquired pellicle.

Methods

A number of six healthy subjects carried bovine enamel slabs fixed on individual upper jaw splints for pellicle formation in situ. After 1 min, they rinsed with biotène or BioXtra for 10 min, respectively. Enzyme activities of lysozyme, peroxidase and glucoseoxidase in the in situ pellicle and in the saliva were assayed before as well as 0, 20 and 40 min after the rinses. The assays for the respective enzyme activities were based on fluorogenic substrates. Separate experiments were performed for the different enzymes and mouth rinses, respectively. Statistical evaluation was carried out with the Kruskal-Wallis test.

Results

None of the investigated rinses had any significant impact on the activities of lysozyme, peroxidase and glucoseoxidase detectable in the in situ pellicle or in the saliva (Kruskal-Wallis test, p > 0.05). Despite the fact that both products should contain lactoperoxidase activity according to manufacturers’ instructions, no peroxidase activity was measurable in the pure mouth rinses.

Conclusion

With the tested enzymatic mouth rinses targeted accumulation and immobilisation of protective enzymes in the in situ pellicle did not seem possible.