Dentine desensitization induced by prophylactic and air-polishing procedures: An in vitro dentine permeability and confocal microscopy study
Introduction
Non-surgical periodontal therapy performed with sonic and manual instruments aims to remove plaque and calculus from the root surfaces to improve gingival health.1, 2, 3 Nevertheless, the cementum in the cervical region and along the root is very thin, ranging from 20 to 50 μm even when intact and histologically normal, which can be easily removed during non-surgical periodontal therapy increasing the risk for root dentine hypersensitivity (RDH).1, 4
The clinical symptoms of dentine hypersensitivity (DH) are principally caused by exposure of dentinal tubules as a result of enamel loss and/or gingival root surface exposure due to attrition, abrasion, erosion, abfraction or gingival recession.5, 6, 7 It has been defined as a short sharp pain in response to thermal, evaporative, tactile, osmotic or chemical stimuli which may not be ascribed to any other form of dental defect or pathology.5, 6
Based on Brännström's hydrodynamic theory,8 dentine hypersensitivity is caused by movement of fluids within open dentine tubules. It is assumed that when a stimulus is applied on the exposed dentine surface it causes movement of tubular fluid, which in turn activates mechanoreceptor nerves, eliciting pain and discomfort.9, 10 Therefore, the occlusion of the tubules may reduce the fluid movement inside the dentinal tubules and the clinical symptoms of DH.11 However, it is important to consider that if the occlusion of tubules is only superficial, daily tooth brushing, saliva or consumption of acidic beverages may easily open the dentinal tubules leading to short-term desensitizing effects.12, 13, 14 In this regard, various desensitizing agents may be effective in occluding the dentinal tubules and reducing dentine permeability, unfortunately, little information is available on the effects of prophylactic measures on the DH.
Air-polishing devices such as Air-flow® (EMS, Nyon, Switzerland) or Prophyflex (KaVo, Germany) or Aquacut (Velopex, Horesham, UK) have become established for prophylactic treatments, enamel cleaning prior to pit and fissure sealing or orthodontic bracket bonding.15, 16, 17 Moreover, these systems might also be used in the treatment of root surfaces during non-surgical periodontal therapy as a valid alternative to hand, sonic and ultrasonic scalers because these latter instruments are considered technically demanding and considered unpleasant by patients. Some authors have also affirmed that repeated use of these instruments may lead to hypersensitivity, weakening of the respective roots or even root fracture.18, 19
The purpose of this study was to evaluate the changes in hydraulic conductance (i.e., dentinal permeability) after application of prophy-pastes or air-polishing powders during prophylactic procedures on exposed dentine immediately, after artificial saliva immersion and following final exposure to citric acid. A confocal scanning laser microscope (CLSM) was used to evaluate the percentage of occluded tubules (OCT%) and the changes in dentine morphology induced by experimental treatments. The null hypotheses tested in this study were that all the tested materials are able to reduce the dentine permeability at the same level and that citric acidic attack will induce no statistically significant change in dentine permeability reduction.
Section snippets
Specimen preparation for dentine permeability
Human third molars (age 20–40) extracted for surgical reasons were collected and stored in deionized water (pH 7.4) at 4 °C prior to the experiments. All experiments were conducted within 1 month of extraction. Local protocols, reviewed and approved by the Ethics Committee of the Academic Health Science Centre at King's College London were followed, including informed consent for tissue use in research. Dentine crown segments were obtained by first removing the roots 1.5 mm beneath the
Dentine permeability after prophylactic procedures
The dentine permeability results are expressed as means (%) and standard deviations in Table 3. All the products statistically reduced the maximum fluid flow of PA-etched dentine. Although artificial saliva induce no statistical differences in dentine permeability, several changes were observed after citric acid challenge (Table 3).
The treatment of dentine with 35%-PA increased the permeability to a maximum level which was arbitrarily considered equal to 100%.
The air-polishing procedures
Discussion
The aim of this study was the evaluation of the dentine permeability after prophylactic treatments performed with different prophy-pastes or prophy-powders using the Velopex air-polishing system on exposed dentine immediately, after artificial saliva immersion and after a citric acid challenge.
The in vitro evaluation of the efficacy of desensitizing agents, in agreement with the scientific literature,7, 10, 14, 20, 21, 22 may be performed using a fluid filtration system for hydraulic
Acknowledgments
This study was supported by a grant from the OSSPRAY Ltd. Company, London, UK.
The authors also acknowledge support from the Department of Health via the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy's & St Thomas’ NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust.
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