Shear bond strength of brackets to demineralize enamel after different pretreatment methods

Objective: To compare the influence of demineralized and variously pretreated demineralized enamel on the shear bond strength of orthodontic brackets. Materials and Methods: Sixty bovine enamel specimens were allocated to five groups (n  =  12). Specimens of group 1 were not demineralized and were not pretreated, but served as controls. The other specimens were demineralized to form artificial carious lesions. Samples from group 2 were only demineralized and were kept untreated in artificial saliva. The other samples were pretreated with highly concentrated fluoride preparations (group 3: Elmex Gelee, 1.23% F; group 4: Clinpro White Varnish, 2.23% F) or with an infiltrating resin (group 5: Icon). After respective pretreatments, brackets were adhesively fixed on all specimens with an adhesive system after etching with 35% phosphoric acid and application of a primer and bracket resin cement (Transbond XT). Bracket shear bond strength was evaluated with a universal testing machine. Statistical analysis was performed by one-way analysis of variance followed by a post-hoc Scheffé test. Results: Shear bond strength in control group 1 was statistically significantly greater compared with that in all other groups. Application of the infiltrating resin Icon (group 5) as pretreatment resulted in statistically significantly greater bond strength as compared with pretreatments with fluoride compounds (groups 3 and 4) and treatment provided without pretreatment (group 2). Groups 2, 3, and 4 did not significantly differ from each other. Conclusion: Pretreatment with the infiltrating resin is a beneficial approach to increasing the shear bond strength of brackets to demineralized enamel

Impact of storage conditions on profilometry of eroded dental hard tissue

The aim of the present study was to analyze in how far drying of eroded dentin and enamel surfaces influence the results of profilometrical determinations with a stylus profilometer. Each five dentin and enamel samples were eroded with HCl (pH 2.6, 2min). Surface profiles of the samples were recorded with a stylus profilometer in three series. In series 1, the samples were measured while stored in water and in series 2, under ambient conditions (21°C, 35% humidity). In series 3, samples were completely desiccated and then rewetted. Profilometry was conducted at various time intervals for a period of up to 181min (series 1 and 2) and 72h (series 3). Only the dentin samples were affected by the storage conditions. Stable profilometrical readings for the eroded dentin samples were only feasible when the specimens were stored in water during the complete period of the experiment, including the profilometrical measurement. Thus, for erosion experiments using profilometrical analysis with a stylus profilometer, it is advised to store and measure dentin samples under wet condition

Deposition of fluoride on enamel surfaces released from varnishes is limited to vicinity of fluoridation site

The aim of the in-situ study was to determine fluoride uptake in non-fluoridated, demineralized enamel after application of fluoride varnishes on enamel samples located at various distances from the non-fluoridated samples. All enamel samples used were demineralized with acidic hydroxyethylcellulose before the experiment. Intra-oral appliances were worn by ten volunteers in three series: (1, Mirafluorid, 0.15% F; 2, Duraphat, 2.3% F and 3, unfluoridated controls) of 6days each. Each two enamel samples were prepared from 30 bovine incisors. One sample was used for the determination of baseline fluoride content (BFC); the other was treated according to the respective series and fixed in the intra-oral appliance for 6days. Additionally, from 120 incisors, each four enamel samples were prepared (one for BFC). Three samples (a-c) were placed into each appliance at different sites: (a) directly neighboured to the fluoridated specimen (=next), (b) at 1-cm distance (=1cm) and (c) in the opposite buccal aspect of the appliance (=opposite). At these sites, new unfluoridated samples were placed at days 1, 3 and 5, which were left in place for 1day. The volunteers brushed their teeth and the samples with fluoridated toothpaste twice per day. Both the KOH-soluble and structurally bound fluoride were determined in all samples to determine fluoride uptake and were statistically analyzed. One day, after fluoridation with Duraphat, KOH-soluble fluoride uptake in specimen a (=next) was significantly higher compared to the corresponding samples of both the control and Mirafluorid series, which in turn were not significantly different from each other. At all other sites and time points, fluoride uptake in the enamel samples were not different from controls for both fluoride varnishes. Within the first day after application, intra-oral-fluoride release from the tested fluoride varnish Duraphat leads to KOH-soluble fluoride uptake only in enamel samples located in close vicinity to the fluoridation sit

The role of fluoride and casein phosphopeptide/amorphous calcium phosphate in the prevention of erosive/abrasive wear in an in vitro model using hydrochloric acid

OBJECTIVE: To investigate the effect of various fluoride compounds and casein phosphopeptide/amorphous calcium phosphate (CPP-ACP) on the reduction of erosive/abrasive tooth wear. METHODS: Forty enamel samples were prepared from bovine lower incisors, stratified and allocated to 4 groups (1-4). Samples in group 1 remained untreated and served as negative controls. The test samples were treated for 2 min/day as follows: group 2 amine/sodium fluoride gel (pH 4.8; 12,500 ppm), group 3 sodium fluoride gel (pH 7.1; 12,500 ppm) and group 4 CPP-ACP-containing mousse. De- and remineralization cycling was performed for 20 days with 6 erosive attacks for 20 s with HCl (pH 3.0) per day. Samples were stored in artificial saliva between cycles and overnight. Toothbrushing (15 s; 60 strokes/min; load 2.5 N) with a toothpaste slurry was performed each day before the first and 1 h after the last erosive exposure. Tooth wear was measured by comparing baseline surface profiles with the corresponding posttreatment profiles. RESULTS: Tooth wear was significantly reduced in groups 2 and 3 compared with group 1, while the enamel loss of group 4 was not significantly lower compared to the negative control group 1. Between the fluoride groups 2 and 3, no significant difference in tooth wear was recorded. CONCLUSION: Erosive/abrasive tooth wear under the conditions used could be reduced significantly by the daily application of fluoride gels, irrespective of the fluoride compound, while the application of CPP-ACP-containing mousse was less effective

Effects of various fluoride solutions on enamel erosion in vitro

The objective of this in vitro study was to investigate the effect of different fluoride solutions on enamel erosion. Human enamel specimens were pretreated with 1 of 10 different fluoride solutions (n = 20): TiF(4), NaF, AmF, ZnF(2), or SnF(2), each at native pH (pH range: 1.2-7.8) or buffered pH (pH = 4). The control group samples received no fluoride pretreatment. All samples were then eroded by citric acid (pH 2.6) for 6 x 1 min daily over 5 days. Between the erosive cycles, the samples were stored in artificial saliva. Erosion effects were investigated by surface profilometry (n = 10), scanning electron microscopy (n = 4), and energy-dispersive X-ray spectroscopy (n = 6) after fluoride pretreatment and after erosion. To test the effects of pH only, additional experiments were carried out with fluoride-free solutions at similar pH to that of fluoride solutions. In general, AmF solution was more effective in protecting enamel erosion compared to all other fluoride agents. However, the application of native TiF(4), native and buffered SnF(2), and native and buffered AmF solutions also resulted in significantly less enamel loss compared to the control group. A Ti-rich coating was formed after application of native TiF(4), but partially dissolved due to erosive attack. Samples pretreated with SnF(2) showed a significant increase in surface tin content. Surface fluoride concentration was significantly increased by native TiF(4), native and buffered AmF, buffered ZnF(2), and buffered NaF application. Under the current experimental setting, the fluoride agents at lower pH had better protective potential. Highly concentrated TiF(4), AmF, and SnF(2) solution was effective in inhibiting erosion of enamel

Impact of laminar flow velocity of different acids on enamel calcium loss

Objective: The aim of the study was to evaluate the impact of flow velocity under laminar flow conditions of different acidic solutions on enamel erosion. Material and methods: A total of 240 bovine enamel specimens were prepared and allocated to 30 groups (n = 8 each). Samples of 18 groups were superfused in a flow chamber system with laminar flow behavior using 1ml of citric acid or hydrochloric acid (HCl) of pH 2.0, 2.6 or 3.0. Flow rates in the sample chamber were adjusted to 10, 60 or 100μl/min. To simulate turbulent flow behavior, samples of six groups were immersed in 1ml of the respective solution, which was vortexed (15min, 600rpm). For simulating non-agitated conditions, specimens of the remaining six groups were immersed in 1ml of the respective solution without stirring. Calcium in the solutions, released from the enamel samples, was determined using Arsenazo III method. Results: For acidic solutions of pH 2.6 and 3.0, erosive potential of citric acid was equivalent to that of HCl at a flow of 100μl/min. The same observation was made for the samples subjected to turbulent conditions at pH 3. At all other conditions, citric acid induced a significantly higher calcium loss than HCl. Conclusion: It is concluded that under slow laminar flow conditions, flow rate variations lead to higher erosive impact of citric acid compared to hydrochloric acid at pH 2.0, but not at pH ≥ 2.6 and increasing laminar flow or turbulent conditions. Clinical relevance: Erosive enamel dissolution under laminar flow conditions is a complex issue influenced by flow rate and acidic substrat

Bonding of brackets using a caries-protective adhesive patch

OBJECTIVES: The purpose of this study was to assess the shear bond strength (SBS) of metal brackets when placed with a caries protective adhesive patch. METHODS: Forty stainless steel brackets (Ormco) were bonded to 40 bovine enamel samples according to the following conditioning/bonding procedures using a resin-based orthodontic luting material (Heliosit Orthodontic, N=10 per group): (A) 35% phosphoric acid (30s), rinse and dry; (B) as in A but additional placement of a prototype adhesive patch (Ivoclar Vivadent) using a bonding agent (Heliobond); (C) application of a two-step self-etch adhesive (AdheSE); (D) as in C but additional patch placement. Samples were stored at 37 degrees C for 24h. SBS was measured with a universal testing machine with a crosshead speed of 0.5mm/min and the adhesive remnant index (ARI) was determined under a stereomicroscope (16x). RESULTS: Mean SBS (standard deviation) values were as follows: (A) 16.6 (6.4)MPa; (B) 12.2 (5.8); (C) 12.9 (5.0); and (D) 10.5 (4.7). Analysis of variance followed by Bonferroni correction revealed no statistically significant differences. In 2 (B) and 4 (D) specimens, complete retention of the adhesive patch was observed. CONCLUSIONS: All treatment groups showed adequate bond strength values. The adhesive patch could therefore be applied in combination with orthodontic brackets and seal the enamel adjacent to the bracket

In vitro tooth cleaning efficacy of electric toothbrushes around brackets

This in vitro study assessed the cleaning efficacy of different electric toothbrushes around upper incisor brackets. Standard and Mini Diamond™ brackets were fixed on black-stained teeth. The teeth were coated with white titanium oxide and brushed in a machine twice for 1 minute each. Twelve different brush heads with either a wiping or an oscillating-rotating action were tested. After brushing, the teeth were scanned, the black surfaces were assessed planimetrically and a modified plaque index for orthodontic patients (PIOP) was introduced. Tooth areas, which were black again after brushing indicated tooth surface contact of the filaments and were expressed as a percentage of total area. The remaining white areas around the brackets indicated 'plaque-retentive' niches. Analysis of variance was used for individual comparison of the brush types. Bonferroni/Dunn adjustment was applied for multiple testing. The Sonicare® toothbrush handle with the brush head 'Compact ProResults' (81.7 per cent) and the brush head 'Standard ProResults' (80.8 per cent), as well as the sonic Waterpik® toothbrush SR 800E with the standard brush head (78.2 per cent), showed statistically significantly better cleaning efficacy than all others. The poorest cleaning efficacy was observed for the oscillating-rotating Braun Oral-B Professional Care with the brush head 'Ortho' (less than 50 per cent). The planimetric findings were in correspondence with the results of the PIOP assessment. Cleaning efficacy of electric toothbrushes around brackets on upper incisors was different between the tested brushes. The PIOP was practicable, effective, and easy to use, although it has to be verified in a clinical stud

Comparison of residual salivary fluoride retention using amine fluoride toothpastes in caries-free and caries-prone children.

This was to compare the salivary fluoride levels following tooth brushing with amine fluoride toothpastes containing three different concentrations of F (250 ppm F, 500 ppm F and 1250 ppm F) and to evaluate the effect of rinsing with water on the oral fluoride levels up to 90 min.A double blind randomised six-arm crossover study was conducted with 32 child participants. Patients were divided into two groups depending on their caries experience with caries-free group (n = 17, mean age = 72.9 months) and caries-prone group (n = 15, mean age = 69.6 months, mean dmfs = 12.3). Each participant brushed their teeth with a smear of dentifrice containing (250 ppm, 500 ppm and 1250 ppm F toothpastes) for 60 s. After spitting out the dentifrice/saliva slurry, participants either rinsed with water or did not rinse at all. Samples of whole mixed unstimulated saliva were collected at 0 (baseline), 1, 15, 30, 45, 60 and 90 mins post-brushing/rinsing.After completing the study on residual fluoride concentration it was found that caries was not a significant variable (p = 0.567) while every other variable was (all p values 1000 ppm F concentration in children with an increased caries risk in addition to spitting excess toothpaste with no rinsing following brushing