Objectives: To verify the influence of erosive challenge conditions (acid type, exposure time), type of brushing (manual, sonic) and type of substrate (human, bovine) on enamel surface loss. Protocols previously used in in situ long-term models were considered as references.
Methods: Acrylic blocks containing human and bovine enamel slabs (4x4x2mm) were prepared. Adhesive tapes were placed on their surfaces, exposing an enamel area of 1x4mm. Forty-eight selected blocks were randomly assigned into 6 groups (n=8). Testing groups (T1-T4) were submitted to cycles of demineralization (0.3% citric acid, pH2.6, 10ml/specimen, for 2[T1], 3[T2] or 5[T3] min) and remineralization (~2h), 4x/day, for 5 days. Brushing was performed in automated brushing machine (150g) 2x/day, with dentifrice (silica based, 1150ppm F as NaF, 5% KNO3)/de-ionized water slurry (1:3 w/w). The total exposure time to the slurry was 2min, with 15s of actual brushing action. T4 was similar to T2, except for brushing, which was performed manually with sonic toothbrush. Reference groups (R1-R2) simulated the daily protocols used in two previously performed in situ studies. After 5 days, surface loss of the exposed enamel area was analysed by optical profilometry considering the taped surfaces as references.
Results: Surface loss increased with acid-exposure time (p<0.05), with T1 showing surface loss values in between R1 and R2. Brushing with sonic brush resulted in higher surface loss values (p<0.05). Human and bovine enamel performed similarly, showing strong correlation (r-square: 0.83). R1 and R2 showed relatively higher surface loss than that previously observed in their respective in situ studies.
Conclusions: This study generated relevant information on the erosive challenge, brushing conditions and substrate type for the development of a clinically relevant in situ erosion-abrasion model.
(Supported by GlaxoSmithKline Consumer Healthcare, Weybridge, UK)
Keywords: Demineralization, Dentifrices, Enamel, Erosion and Fluoride