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.

Tooth wear: diet analysis and advice

Diet analysis and advice for patients with tooth wear is potentially the most logical intervention to arrest attrition, erosion and abrasion. It is saliva that protects the teeth against corrosion by the acids which soften enamel and make it susceptible to wear. Thus the lifestyles and diet of patients at risk need to be analysed for sources of acid and reasons for lost salivary protection. Medical conditions which put patients at risk of tooth wear are principally: asthma, bulimia nervosa, caffeine addiction, diabetes mellitus, exercise dehydration, functional depression, gastroesophageal reflux in alcoholism, hypertension and syndromes with salivary hypofunction. The sources of acid are various, but loss of salivary protection is the common theme. In healthy young Australians, soft drinks are the main source of acid, and exercise dehydration the main reason for loss of salivary protection. In the medically compromised, diet acids and gastroesophageal reflux are the sources, but medications are the main reasons for lost salivary protection. Diet advice for patients with tooth wear must: promote a healthy lifestyle and diet strategy that conserves the teeth by natural means of salivary stimulation; and address the specific needs of the patients' oral and medical conditions. Individualised, patient-empowering erosion WATCH strategies; on Water, Acid, Taste, Calcium and Health, are urgently required to combat the emerging epidemic of tooth wear currently being experienced in westernised societies.

Erosion and attrition of human enamel in vitro part II: influence of time and loading

OBJECTIVES

To determine the influence of load and time on enamel wear by attrition under neutral and acid environments in vitro.

METHODS

Groups of 10 enamel cusp and smooth surface specimens obtained from unerupted third molars were opposed in a wear machine under loads of 200, 400 and 600 g in citric acid at pH 3.2 and in physiological saline at 35 degrees C for 30 min (2280 wear cycles). The experiment was repeated with a load of 600 g for 10 and 20 min accompanied by 10 taped specimens to measure erosion only. Erosion and attrition of smooth surface specimens was determined by profilometry.

RESULTS

At a load of 600 g attrition in saline increased with time from 7.9 microm (SD 3.7 microm) at 10 min, 10.2 microm (SD 4.8 microm) at 20-25.5 microm (SD 9.1 microm) after 30 min and combined attrition/erosion in citric acid from 1.5 microm (SD 0.4 microm) to 2.5 microm (SD 0.9 microm) to 6.0 microm (SD 3.7 microm). At a fixed time of 30 min, attrition in saline was 5.2 microm (SD 3.6 microm) at 200 g and 8.1 microm (SD 1.5 microm) at 400 g and combined attrition/erosion in citric acid 2.8 microm (SD 1.2 microm) and 3.6 microm (SD 0.7 microm). Comparison between both environments revealed significant differences at fixed load at all time points (p < 0.01) and at fixed time between 400 and 600 g (p < 0.01).

CONCLUSIONS

Load and time significantly influence enamel wear both in acid and neutral conditions but the effects were not linear.

Erosion and attrition of human enamel in vitro part I: interaction effects

OBJECTIVE

The aim of the study in vitro was to measure the interplay of attrition and erosion of human enamel under several different pH conditions.

MATERIALS AND METHODS

Cusp and smooth surface enamel specimens were prepared from unerupted human third molar teeth. Cusp and smooth surface specimens opposed each other in a wear machine under a load of 600 g. The machine simulated tooth grinding for 30 min (2280 wear cycles). Six groups of 10 specimens were worn in the following environmental conditions: saline, citric acid at pH values of 3.2, 5.5 or 7.0 and two cycling groups (pH 3.2/saline or saline/pH 3.2). Additionally, 10 smooth surface specimens were exposed to the same fluids without attrition. Tissue loss on smooth surface specimens was determined by profilometry. The worn specimen surfaces were studied by SEM.

RESULTS

Attrition depth in saline and pH 7.0 citric acid was 25.5 microm. At pH 3.2 and 5.5 attrition depths were 6.0 and 4.3 microm, respectively. Cycling in saline/citric acid and vice versa produced attrition depths of 9.2 and 7.9 microm, respectively. In the erosion only specimens lesion depths were 3.0, 1.2 and 0 microm at pH 3.2, 5.5 and 7.0 and saline, respectively. Attrition specimens at pH 7.0 and in saline showed very rough surfaces. At low pH enamel surfaces appeared flat and smooth.

CONCLUSIONS

Enamel wear in neutral conditions is significantly higher than in acidic conditions (p < 0.05), apparently due to a smoothing effect of erosion on contacting surfaces.