The measurement and prevention of erosion and abrasion

OBJECTIVES: To develop a reproducible method to measure tooth wear and assess the protection given by dentine bonding agents in an erosive/abrasive wear regime. METHODS: Seal and Protect (Dentsply, UK) and Optibond Solo (Kerr, UK) were each applied to 20 extracted teeth and subjected to 3000 cycles in a reciprocating erosion/abrasion wear machine. A further 20 teeth, without protection, were subjected to the same wear regime and were either brushed in water or immersed in acid. Impressions were taken by a standardised technique and were scanned with a non-contacting laser profilometer. The amount of erosion was measured at the same co-ordinates before and after erosion using 2mm diameter metal discs as reference points. RESULTS: The amount of wear on Seal and Protect had a mean 24.8 microm (SD 57.4 microm) and for Solo it was 1.4 microm (24.5 microm), and this difference was statistically significant (p=0.02). There was no statistically significant difference in the wear measured on the teeth brushed in water or immersed in acid. The wear measured on the unprotected teeth was 243 microm (SD 120 microm) and was statistically significantly different to the protected surfaces (p=0.001). CONCLUSION: Both Seal and Protect and Solo protected the teeth in this wear regime and the technique could be used clinically for patients with uncontrolled dental erosion.     

The surface effects of erosion and abrasion on dentine with and without a protective layer

OBJECTIVE: The aim of this in situ study was to investigate with four imaging modalities whether covering dentine with adhesive resins could protect against erosion from acids. The objectives were to observe and quantify the effects of acids and the soft tissues, especially the tongue, on dentine and the bonding agents using four assessment techniques: qualitative assessment with SEM, surface roughness and thickness of resin with the TSM and volume loss with the laser profilometer. DESIGN: An in situ investigation using extracted dentine sections embedded in splints held on the palate of 10 volunteers. The dentine sections were protected by two resins and subjected to a tooth wear regime. RESULTS: Both Seal and Protect and Opitbond Solo protected the tooth surfaces from a tooth wear regime. There were no statistical differences between the control surfaces and those protected with dentine bonding agents for resin thickness, roughness and profilometry. The appearance of the slabs under both confocal and SEM showed that the material remained in place despite a vigorous wear regime and therefore protected the tooth surface. CONCLUSIONS: For patients with uncontrolled erosion or tooth wear, applying a dentine bonding agent to exposed dentine is a practical option to prevent further damage.     

The influence of fluoride varnish on the attrition of dentine

Previous investigations have shown the potential for fluoride to be protective in an abrasion/erosion laboratory model. The aim of this study was to investigate the effect of high concentrations of fluoride delivered in a varnish on attrition of dentine. Fifteen caries-free, intact lower third molar teeth were sectioned and the enamel removed by a water-cooled diamond disc. Polished dentine surfaces were divided into 8 areas, 4 of which were randomly covered with a high-concentration fluoride varnish for 24 h. The samples were subjected to 5,000 cycles of attrition bathed under artificial saliva. Microhardness testing adjacent to the wear scars showed no statistical difference between the fluoride-treated (71.42 KHN, SD 10.52) and control surfaces (72.66 KHN, SD 9.69). The volume of the wear scar was statistically greater for the fluoride-treated surface at 9.6 microm(3) (SD 4.92) and 8.13 microm(3) (SD 5.54) for the control areas (p = 0.029). The low pH of the fluoride varnish appears to have increased the amount of wear from attrition in this laboratory study.     

Investigation of erosion and abrasion on enamel and dentine: a model in situ using toothpastes of different abrasivity

BACKGROUND: Studies in vitro suggest that abrasion and erosion may act synergistically to produce wear of enamel and dentine. Methods in situ are recently available to study separately erosion and abrasion of dental tissues. The aim of this study was to combine two in situ protocols to study the interplay between erosion and abrasion of enamel and dentine. METHOD: The study was a single-blind, randomised, five-treatment cross-over design involving 15 healthy volunteers. During each 10-day study period, subjects wore from 0900 to 1700 h an upper removable acrylic appliance holding one polished enamel and one polished dentine specimen. The specimen treatment regimens were: 1. Drinking water and brushing with toothpaste A. 2. Drinking water and brushing with toothpaste B. 3. Drinking orange juice. 4. Drinking orange juice and brushing with toothpaste A. 5. Drinking orange juice and brushing with toothpaste B. Drinking and brushing times were around 0900, 1100, 1300 and 1500 h. Drinks were consumed as 250 ml over 10 min and brushing ex vivo for 1 min to each specimen. Measurement of tissue loss was made on days 5 and 10 of each period using a profilometer. RESULTS: All treatments produced increasing tissue loss over time, which was considerably greater for dentine than enamel. For enamel, the data at days 5 and 10 showed a significant effect for erosion (i.e. orange juice was significantly more erosive than water), but no significant effect for abrasion (i.e. no significant difference between the two toothpaste treatments). The combined orange juice and toothpaste effects were directional for synergy but did not reach significance. For dentine at day 10, many specimens exceeded the 50 microm set limit of the profilometer and only day 5 data were considered. There were significant effects for erosion (orange juice produced significantly more erosion than water) and for abrasion (paste A was significantly more abrasive to dentine than paste B). The synergy effect could not be examined for dentine due to the truncation effect as the set limit of the profilometer was exceeded. CONCLUSIONS: Erosion increases the susceptibility of enamel to toothpaste abrasion. Dentine is considerably more susceptible than enamel to erosion and abrasion alone or combined. Dentine loss appears to correlate with toothpaste abrasivity (RDA value).     

Clinical measurement of palatal tooth wear following coating by a resin sealing system

This study investigated the hypothesis that coating eroded teeth with a resin-based dentin bonding agent gave protection from tooth wear. Nineteen adults with palatal tooth wear exposing dentin were recruited, following referral by their general dental practitioner. Alternate teeth were coated with the resin adhesive, while the uncoated teeth acted as controls. Accurate impressions of the eroded teeth, onto which were cemented machined stainless steel discs to act as reference areas, were scanned with a non-contacting laser profilometer at 3, 6, 12 and 24 months. The mean thickness of resin at baseline application was 0.15 mm and, from 0 to 6 months, the rate of wear of the control teeth was higher than those covered with Seal & Protect. There was a statistically significant difference in "wear" measured between resin covered and control teeth at three months. The Inter Class Correlations (repeated measurements) for the step heights obtained for the original and repeat impressions was excellent at 0.99. This study shows that coating eroded teeth with a resin-based adhesive has the potential to prevent further tooth wear.     

In vitro evaluation of different remineralization periods in improving the resistance of previously eroded bovine dentine against tooth-brushing abrasion.

One dentine specimen was prepared from each of 90 bovine incisors. The samples were then evenly distributed among nine groups (A-I) and submitted to 10 alternating de- and re-mineralization cycles, including abrasion by tooth brushing. Each cycle started with a demineralization using the erosive soft drink Sprite Light for 1 min, followed by storing the samples in pooled human saliva for a total of 240 min. The specimens were removed from the saliva at different intervals (group A, 0 min; B, 15 min; C, 30 min; D, 45 min; E, 60 min; F, 90 min; G, 120 min) and brushed in an automatic brushing machine. Groups H (erosion, but no brushing) and I (no erosion, but brushing), which were also stored in saliva for 240 min, served as controls. After these cycles, loss of dentine was determined by profilometry, producing the following values (mean+/-S.D.), which were analysed statistically (P< or = 0.05): group A (5.03+/-1.49 microm), B (4.44+/-1.09 microm), C (4.91+/-0.95 microm), D (5.47+/-1.52 microm), E (5.29+/-1.45 microm), F (4.76+/-0.74 microm), G (5.16+/-0.71 microm), H (2.61+/-1.31), I (1.11+/-0.39). Groups A-G had no significant differences, but they showed a significantly greater loss of dentine than groups H and I. It is concluded that the abrasion resistance of eroded bovine dentine is still decreased after a remineralization period of 120 min.     

Fluoride release and anti-erosive effects of dentifrices containing PVM/MA copolymers

Objective

To evaluate fluoride release from dentine discs and study the effects of dentine tubule occlusion and erosion prevention of dentifrices containing fluoride and PVM/MA copolymers in a cycling erosive challenge model.

Methods

Human dentine discs, 15 in each group, were eroded by 1.0% citric acid and treated by ProNamel^® (PRN, 1450 ppm fluoride), Colgate^® Total Sensitive (CTS, 1100 ppm fluoride), a prototype dentifrice containing 5000 ppm fluoride and 2% PVM/MA copolymers (PVD) and distilled water (control). Fluoride release from each dentine disc was evaluated every 2 h in a 12-h period. For cycling erosive challenges, dentine discs were treated by dentifrice slurries twice daily, followed by immersion in saliva and erosive challenges by orange juice. Dentine discs were stored in saliva between treatment cycles and the cycling erosive challenges were repeated for 15 days. On days 5, 10, and 15, size of dentine tubule openings and level of dentine tubule occlusion were evaluated with a 3D scanning microscope.

Results

PVD released more fluorides than other dentifrices in a 12-h period (p < 0.05). CTS released more fluorides than PRN at 2, 4, 6, and 8 h following a single application (p < 0.05). The size of the dentine tubules was smaller and the number of occluded dentine tubules was greater in the CTS and PVD groups than those in the control and PRN groups on day 15 of the erosive challenges.

Conclusion

Bioadhesive PVM/MA copolymers facilitate fluoride retention and release from dentine discs, and promote dentine tubule occlusion and erosion prevention when combined with hydrated silica particles.     

Influence of buffering effects of dentifrices and fluoride gels on abrasion on eroded dentine

OBJECTIVE: Evaluation of abrasion resistance of eroded and non-eroded dentine brushed with experimental dentifrices and gels of varying buffering capacities. DESIGN: One hundred and twenty human dentine specimens were distributed among six groups (A-F) according to the different buffering capacities of experimental toothpastes and gels. The dentifrices (pH: 4.5) and gels (pH: 4.5) differed in fluoride content, RDA-value and buffer capacity (given as mg KOH needed for neutralisation): (A) 0.125%F, RDA: 77, 6mg KOH; (B) 0.125%F, RDA: 125, 24mg KOH; (C) 0.125%F, RDA: 129, 12mg KOH; (D) 0%F, RDA: 81, 1.55mg KOH; (E) 1.25%F, RDA: 21, 8.5mg KOH; (F) 0.125%F, RDA: 7, 3.11mg KOH. Ten specimens were cycled through three alternating demineralisations (1% citric acid, 5min) and remineralisations (artificial saliva, 1min) including brushing abrasion in an automatic brushing machine (2 x 2000 strokes). Ten samples of each group were not eroded, but only brushed. RESULTS: After three cycles, loss of dentine was determined by profilometry (mean +/- S.D. [microm]). Eroded samples: (A) 37.12+/-4.95; (B) 48.67+/-4.77; (C) 39.88+/-3.76; (D) 32.92+/-2.67; (E) 3.65+/-1.35; (F) 6.47+/-1.31. Uneroded samples: (A) 30.78+/-6.47; (B) 37.84+/-7.75; (C) 30.07+/-3.05; (D) 26.93+/-2.30; (E) 1.76+/-0.94; (F) 0.51+/-0.18. Analysis of variance revealed significantly higher abrasion values for the eroded compared to the non-eroded samples (P相似文献   

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.     

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

Objectives

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro.

Methods

Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm × 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n = 10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle = artificial saliva (2 h, pH 7.0) + erosion (0.3% citric acid, pH 3.2, 5 min) + fluoride/control (5 min) + attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in μm was measured using optical profilometry.

Results

When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences.

Conclusions

The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.     

The protective nature of pellicle towards toothpaste abrasion on enamel and dentine

OBJECTIVES: To determine the protective nature of pellicle towards toothpaste abrasion. METHODS: The enamel region of human enamel-dentine blocks was indented with a Knoop diamond and the profile across the enamel-dentine junction was measured. Blocks were either exposed to deionised water or placed onto intra-oral appliances and worn in the mouth to produce in situ pellicles. This was followed by a 10-day period of tooth brushing experiments. Each day, specimens were brushed with a slurry of either Toothpaste A (RDA=90) or Toothpaste B (RDA=204) for 25 cycles (10s) on a brushing machine. This was repeated three times per day for a total of 750 brushing cycles. Between brushing cycles specimens were returned to water or in situ. The geometry of the Knoop indents and the enamel-dentine profile were re-measured and the enamel and dentine wear calculated. Specimens were also prepared for TEM analyses. RESULTS: The mean enamel wear (microm) for Toothpastes A and B (water) was 0.23 and 0.06, and for Toothpastes A and B (in situ) was 0.03 and 0.08, respectively. The mean dentine wear (microm) for Toothpastes A and B (water) was 5.08 and 6.03, and for Toothpastes A and B (in situ) was 1.94 and 1.70, respectively. For Toothpaste A, the presence of in situ pellicle significantly (p<0.05) reduced enamel and dentine wear compared to water and for Toothpaste B, dentine wear was significantly reduced compared to water. After tooth brushing, residues of the in situ pellicle layer could be detected on enamel and dentine surfaces by TEM analysis. CONCLUSIONS: The study has demonstrated for the first time that the presence of pellicle can significantly reduce toothpaste abrasion.     

The role of erosion, abrasion and attrition in tooth wear

There is increasing clinical awareness of erosion of enamel and dentine by dietary acids and the consequent increased susceptibility to physical wear. Enamel erosion is characterized by acid-mediated surface softening that, if unchecked, will progress to irreversible loss of surface tissue, potentially exposing the underlying dentine. In comparison, dentine erosion is less well understood as the composition and microstructure are more heterogeneous. Factors which affect the erosive potential of a solution include pH, titratable acidity, common ion concentrations, and frequency and method of exposure. Abrasion and attrition are sources of physical wear and are commonly associated with tooth brushing and tooth-to-tooth contact, respectively. A combination of erosion and abrasion or attrition exacerbates wear; however, further research is required to understand the role of fluoride in protecting mineralized tissues from such processes. Abrasive wear may be seen in a wide range of patients, whereas attritive loss is usually seen in individuals with bruxism. Wear processes are implicated in the development of dentine hypersensitivity. Saliva confers the major protective function against wear due to its role in pellicle formation, buffering, acid clearance, and hard tissue remineralization. This review focuses on the physiochemical factors impacting tooth wear.     

Development of a method in situ to study toothpaste abrasion of dentine. Comparison of 2 products

BACKGROUND/AIMS: The abrasivity of toothpastes is usually determined using in vitro methods; as such, the clinical significance of the findings is uncertain. The aim of the present study was to develop and evaluate a method in situ to study abrasion of dentine by two toothpastes of different Relative Dentine Abrasivity (RDA). METHOD: The study was a single blind, randomised, 2 way cross over design involving 10 healthy dentate volunteers. Subjects wore an maxillary removable acrylic appliance containing two flat human dentine specimens, taped to expose a window of tissue, from 9 am to 4 pm during the two 10 working day study periods. No food or drink was consumed when the appliance was in place. On five occasions each day, the appliances were removed and the dentine windows brushed ex vivo with the allocated paste for 60 s each. Dentine abrasion at days 5 and 10 was measured using a profilometer. RESULTS: Both toothpastes produced measurable abrasion in all subjects and the depth increased in most subjects between 5 and 10 days. There was significant subject and specimen variation both within and between toothpastes. There was significantly increased abrasion by the toothpaste with the higher RDA value and in mean terms the ratio of abrasion between the two pastes was similar to the ratio of the RDA values. CONCLUSION: The method in situ, already used to study dental hard tissue erosion, appears ideally suitable to study dental abrasion alone and the interaction between aetiological factors involved in tooth wear.     

Is bovine dentine an appropriate substitute for human dentine in erosion/abrasion tests?

Summary  The study aimed to compare the dentine wear of primary and permanent human and bovine teeth because of erosion/abrasion and evaluate if bovine dentine is an appropriate substitute for human dentine in further erosion/abrasions tests. Dentine samples from deciduous molars and human third molars as well as from calves' and cattle's lower incisors were prepared and baseline surface profiles were recorded. Each day all samples were demineralized in 1% citric acid, tooth brushed with 100 brushing strokes with toothpaste slurry and stored in artificial saliva for the rest of the day. This cycle was run for 20 days. Afterwards, new surface profiles were recorded and dentine wear was calculated by a customized computer program. Dentine wear because of erosion/abrasion was not statistically, significantly different for human third molars and cattle's lower incisors ( P  = 0·7002). The dentine wear because of erosion/abrasion of deciduous molars and calves' lower incisors was significantly different ( P  < 0·0000). No statistically significant difference in the dentine wear of human third molars and cattle's lower incisors was observed, so that the use of cattle's lower incisors as substitute for adult human teeth for further investigations in erosion/abrasion studies could be accepted.     

A study in vitro of the combined effects of soft drinks and tooth brushing with fluoride toothpaste on the wear of dentine

The aim of this study was to measure loss of dentine produced by soft drinks alone and combined with tooth brushing with and without toothpastes. Groups of flat human dentine specimens were exposed for 10 min and then 30 min to orange juice (OJ), carbonated cola (CC) or modified blackcurrant (MB) drinks alone or after the exposures brushed with a fluoride toothpaste for 10 s. Further groups were exposed to OJ as before but brushed with water or non-fluoride toothpaste or placed in slurries of fluoride paste. Five cycles of each regimen were carried out. Tissue loss was determined by profilometry. Water immersion/brushing and brushing controls were included. OJ and CC produced similar erosion and significantly more than MB. Compared with drinks alone, dentine loss was reduced by fluoride toothpaste brushing but increased by water and non-fluoride toothpaste brushing. Fluoride toothpaste slurry had no significant effect on soft drink erosion. Very little abrasion with brushing alone was recorded over the time frame of these experiments. It is concluded that fluoride toothpaste could provide protection, albeit small, against erosion. The data again support the concept of brushing before meals.     

Assessing the tooth-restoration interface wear resistance of two cementation techniques: effect of a surface sealant

This study compared (1) the tooth-restoration interface width of conventional and "resin coating" cementation techniques, (2) the toothbrushing wear resistance of the two interfaces and (3) this study evaluated the influence of a restoration surface sealing on toothbrush wear resistance on both cementation technique interfaces. Mid-coronal buccal surfaces of 40 bovine teeth were ground to obtain a flat enamel surface. For each specimen, a 3 mm x 4 mm x 3 mm dimension rectangular cavity was prepared. The teeth were divided into four groups. Two groups (RC) received a "resin coating" (ED Primer + Tetric Flow) prior to cementation. The remaining two groups (NC) served as non-coated groups. All teeth were restored with composite inlays (Z250) fabricated by the indirect method and were cemented with dual cure resin cement (Panavia F). After finishing the margins, one group from each of the cementation techniques (RC+S and NC+S) had the tooth-restoration interface protected with a restoration surface sealant (Biscover). The specimens were subjected to 100,000 brushing abrasion cycles. The tooth-restoration width was obtained using a Hommel Tester T 1000-basic profilometer and Turbo Datawin NT 1.34 Software (microm). The interface wear (vertical loss/microm and area/microm2) was calculated with Image Tool 3.0 Software. Data were analyzed with Student t-test, one-way analysis of variance and Tukey test (alpha=0.05). Mean interface width for the NC group was 67 microm and 72 microm for the RC group. The student t-test showed no significant differences between groups (p=0.53). ANOVA showed significant differences (p<0.01) in vertical loss among groups (NC: 49.30 microm; NC+S: 7.90 microm; RC: 27.15 microm; RC+S: 4.74 microm). Also, ANOVA showed significant differences (p<0.01) in worn areas among groups (NC: 2,008 microm2; NC+S: 128 microm2; RC: 1,580 microm2 and RC+S: 88 microm2). No differences were found in tooth-restoration interface width and worn area between conventional and "resin coating" techniques. "Resin coating" interface presented reduced vertical loss. Restoration surface sealing provided reduced wear in tooth-restoration interface for both techniques.     

The effect of repeated fluoride recharge and storage media on bond durability of fluoride rechargeable Giomer bonding agent

Background:  For a restorative material or adhesive to exhibit caries inhibitive potential through fluoride release, it must be capable of fluoride recharge. The aim of this study was to evaluate the effect of repeated fluoride recharge and different storage media on dentine bond strength durability. Methods:  Two self‐etch adhesive systems (two‐step) were evaluated: fluoride‐rechargeable Giomer FL‐Bond II and non‐fluoride‐containing UniFil Bond. For each adhesive 32 human dentine specimens were prepared for shear bond strength testing. The specimens were randomly allocated to one of four storage groups: Group 1 – 24‐hour water ageing; Group 2 – four‐month water ageing; Group 3 – four‐month water ageing with weekly fluoride recharge (5000 ppm for 10 minutes); and Group 4 – four‐month acid ageing with weekly fluoride recharge. Results:  Weekly fluoride recharge over four months ageing did not significantly (p > 0.05) reduce the dentine shear bond strength of FL‐Bond II or UniFil Bond. Storage media did not significantly (p > 0.05) affect bond durability. Conclusions:  The adhesion between fluoride rechargeable FL‐Bond II and dentine maintained durability despite regular fluoride recharge over the four months ageing. Clinicians prescribing the fluoride recharge regime used in the present study to reduce recurrent caries incidence associated with Giomer FL‐Bond II restorations can do so without compromising dentine bond strengths.     

An experiment on the attrition of acid demineralized dentine in vitro

Background: A laboratory investigation was designed to test the hypothesis that acids increase the rate of wear caused by attrition on dentine. Methods: Dentine sections from 10 teeth were polished, cleaned in an ultrasonic bath and divided into 8 equally sized areas. The occlusal tip of a tooth, placed vertically in a wear machine and loaded at 150 N, was moved against each dentine section for 5000 return strokes with artificial saliva acting as a lubricant. Each dentine section was divided into 8 sections and half randomly immersed in a 1% citric acid solution (pH 2.3) for 20 minutes. The wear regime produced 8 wear scars in total per dentine sample. The volume of each wear scar was measured using a contacting digitizing profilometer. Results: A total of 80 wear scars were produced with 40 treated with acid and 40 acting as controls. The mean for wear volume of the dentine scars with acid was 4.84 μm³ (1.38) and for the non‐acid surface 2.95 μm³ (0.86). This difference was statistically significant (p < 0.05). Conclusions: These results support the hypothesis that acids increase the rate of wear caused by attrition on dentine.     

Brushing abrasion of eroded bovine enamel pretreated with topical fluorides

Topical fluorides have been proposed for the prevention of erosive dental wear. This study evaluated the in vitro effect of a single professional application of 4% titanium tetrafluoride (TiF4), 1% amine fluoride (AmF) and 0.1% difluorosilane varnish (FV) in preventing wear due to combined erosion and brushing abrasion. One hundred and eight bovine enamel samples were used. Control groups were not pretreated with any product (C), pretreated with a fluoride-free varnish (FV-bl) or pretreated with fluoride varnish and subsequently submitted to varnish removal (FV-r). Wear was modeled by submitting the fluoride-treated and control groups to 3 cycles of the following regimens: erosion/remineralization (er/remin), abrasion/remineralization (abr/remin) or erosion/abrasion/remineralization (er/abr/remin). Erosion was simulated by immersion of the samples for 10 min in citric acid 50 mM (pH 3). Abrasion was carried out for 1 min (200 strokes, load 150 g) in a wear device. Remineralization (2 h artificial saliva) took place between the cycles. Two-way ANOVA showed that there was a significant interaction (p相似文献   

Effect of different concentrations of fluoride in dentifrices on dentin erosion subjected or not to abrasion in situ/ex vivo

This in situ/ex vivo study assessed the effect of different concentrations of fluoride in dentifrices on dentin subjected to erosion or to erosion plus abrasion. Ten volunteers took part in this crossover and double-blind study performed in 3 phases (7 days). They wore acrylic palatal appliances containing 4 bovine dentin blocks divided in two rows: erosion and erosion plus abrasion. The blocks were subjected to erosion by immersion ex vivo in a cola drink (60 s, pH 2.6) 4 times daily. During this step, the volunteers brushed their teeth with one of three dentifrices D (5,000 ppm F, NaF, silica); C (1,100 ppm F, NaF, silica) and placebo (22 ppm F, silica). Then, the respective dentifrice slurry (1:3) was dripped on dentin surfaces. While no further treatment was performed in one row, the other row was brushed using an electric toothbrush for 30 s ex vivo. The appliances were replaced in the mouth and the volunteers rinsed with water. Dentin loss was determined by profilometry and analyzed by 2-way ANOVA/Bonferroni test (a = 0.05). Dentin loss after erosive-abrasive wear was significantly greater than after erosion alone. Wear was significantly higher for the placebo than for the D and C dentifrices, which were not significantly different from each other. It can be concluded that the presence of fluoride concentrations around 1,100 ppm in dentifrices is important to reduce dentin wear by erosion and erosion + abrasion, but the protective effect does not increase with fluoride concentration.