Methods: Caries-free extracted maxillary and mandibular molars were used obtained from the tooth bank at the Royal London Dental Hospital. In vitro occlusion of dentinal tubules was investigated using the dentine disc model [Mordan et al. 1997]. The teeth were sectioned mesio-distally into discs approximately 1 mm thick using an internal edge annular diamond blade (Microslice annular blade, Ultratec, USA) mounted on the Microslice 2 saw (Malvern Instruments Ltd., UK) and halved. The dentine discs were etched with 6% citric acid and rinsed with distilled water, prior to evaluation of both test and control toothpastes’ ability to block dentinal tubules by 1) Scanning Electron Microscopy (SEM) of the dentine surface 2) Measurement of fluid flow through dentine before and after 2 minute brushing of the test toothpaste.
Results: Following etching and subsequent brushing for 2 minutes of both test and control toothpastes all samples were prepared for SEM evaluation. Surface topography and characterisation of the test toothpaste samples indicated that hydroxyapatite particles covered the surface as well as partially occluding the dentinal tubules to a greater extent than the control product samples. Particle size analysis demonstrated that over 50% hydroxyapatite particles are capable of entering the dentinal tubules. Measurement of fluid flow through dentine sections for the hydroxyapatite samples (n=5) indicated a mean 41.7% (SD: 9.6) reduction in fluid flow compared to baseline values.
Conclusions: The results of the present in vitro study would suggest that a novel biomimetic hydroxyapatite may be an effective desensitising agent in reducing DH.