Measurement of eroded dentine tubule patency and roughness following novel dab-on or brushing abrasion.

OBJECTIVES: To investigate the effect of dab-on or brushing of stannous-fluoride SnF2 or sodium-fluoride NaF dentifrice on eroded dentine tubule patency, surface and inter-tubular dentine roughness, using Confocal-Laser-Scanning-Microscopy (CLSM), Atomic-Force-Microscopy (AFM), Energy-Dispersive-X-ray-Spectroscopy (EDX), Scanning-Electron-Microscopy (SEM) and Contact-Profilometry (CP). METHODS: 75-polished human dentine samples were prepared and eroded in agitated 6% citric acid to expose patent tubules and 'initiate' DH. Samples were randomly allocated into 5 intervention groups; artificial saliva control (1); electric tooth-brushing with NaF (2) or SnF2 (3), and dab-on application of NaF (4) or SnF2 (5). Samples underwent three cycles of intervention followed by further acid challenge. Patent tubules, likely to cause DH clinically, were measured using validated biocomputational methods with CLSM images of dentine surfaces taken baseline and post-intervention. Randomised samples (n = 15, 20 %) were investigated using AFM, EDX and SEM to study surface and sub-surface tubular occlusion. Dentine surface and inter-tubular roughness were measured using CP and AFM respectively. RESULTS: At baseline, mean tubule patency in all samples was 216 (SD 58) with no significant inter-group differences. Post-intervention, the mean patency was 220 (40) and 208 (35) in groups 1 and 2 respectively (p ≥ 0.06), but decreased to 62 (41), 62 (21) and 63 (19) in groups 3, 4 and 5 respectively (p < 0.0001). Patency was confirmed using AFM, SEM and EDX. SnF2 interventions created greater sub-surface occlusion (p < 0.01), and increased CP surface roughness (p = 0.015). Significant negative correlation (-0.6) existed between CP surface roughness and tubule patency (p = 0.009). CONCLUSIONS: Dab-on with NaF and SnF2 or brushing with SnF2 reduces DH in eroded dentine with ongoing acid challenges. Contacting surface roughness measures indicate risk of DH. CLINICAL SIGNIFICANCE: Dab-on is a convenient supplementary method of dentifrice application to reduce DH; it beneficially avoids brushing post-erosion or overzealous brushing, enables re-establishment of an appropriate brushing regime post-DH and supports oral health. Significant modes of action of SnF2 in reducing DH are revealed. Finally, CP roughness measures provide indication of dentine lesions that may cause DH clinically.

Novel Confocal-Laser-Scanning-Microscopy and conventional measures investigating eroded dentine following dentifrice dab-on and brushing abrasion.

OBJECTIVES: To validate novel non-contacting Confocal-Laser-Scanning-Microscopy (CLSM) methodology with conventional Contacting Profilometry (CP) measures investigating brushing or dab-on of stannous-fluoride dentifrice on early aggressive dentine erosion. METHODS: 75 polished human dentine samples were prepared and eroded in agitated 6% citric acid then randomly allocated into 5 intervention groups; artificial saliva control (1); controlled use of a pressure sensitive counter-rotating oscillatory powered toothbrush with sodium-fluoride NaF (2) or stannous-fluoride SnF2 (3), and dab-on application of NaF (4) or SnF2 (5). Samples underwent three cycles of intervention and 2-min agitated 6 % citric acid challenges. CLSM images were taken and 3D reconstructions produced of step height using a developed software algorithm. In addition, 20 % samples were randomised and profiled using CP to measure step height and surface roughness. Vickers's diamond micro-hardness testing was carried out on all samples. RESULTS: Comparing CLSM and CP; Pearson correlation was 0.77 and Intra-class correlation 0.81 (p = 0.01). There were no significant statistical differences in step height between groups using both CLSM and CP. From baseline, SnF2 brushing (3) increased micro-hardness more than control (1) (p = 0.03), NaF (4) and SnF2 dab-on (5) (p ≤ 0.001), and increased surface roughness more than control (p = 0.02), NaF brushing (2) and NaF dab-on (4) (p ≤ 0.017). Dab-on of SnF2 (5) produced rougher surfaces than control (1) (p = 0.014) and reduced hardness compared with NaF brushing (p = 0.04). CONCLUSIONS: Good agreement and correlation exists between CLSM and CP measures in dentine. There were no significant differences in surface loss after interventions between groups. Compared with control, SnF2 application increased dentine surface roughness and SnF2 controlled powered brushing application increased dentine hardness, likely caused by exposure of uneroded dentine. CLINICAL SIGNIFICANCE: Isosurfaces produced using CLSM can be used to represent dentine step height loss. They show good correlation and agreement with conventional CP measures, following early aggressive erosion-abrasion cycles of dentine. The CLSM and computer algorithm therefore provides an accurate, standalone and non-contacting three-dimensional measurement of early dentine wear. Stannous-fluoride brushing, and dab-on application offer no benefits following early aggressive erosion in dentine. To reduce dentine wear, limiting erosive challenges and avoiding brushing post-erosion is advised.