Fig. 7.1
Experimental setup: Dentin discs are placed pulpal side down in a split chamber device. Hydrostatic pressure is applied to the dentin disc via the bottom inlet port by increasing the pressure inside the pressure vessel containing the fluid reservoir
The bottom portion of the split chamber device which contains the dentin section is closed except for a single port connected to a fluid reservoir, containing usually Earles’ solution, and the top portion of the chamber is open. Hydrostatic pressure is applied to the dentin disc via the bottom inlet port by increasing the pressure inside the pressure vessel to 1 psi. After the stabilization period, the flow rate through both the control and experimental sections is independently measured using a bubble flow meter.
7.4 Clinical Trials
Many clinical trials were conducted to evaluate different treatments for dentin hypersensitivity; however, the methods used and results reported were sometimes contradictory. In addition, the variability of the study methods makes the comparison between different products difficult. It is widely recognized that there is a need to rationalize testing methods and to establish a bench mark for future testing and evaluation of methods for treating dentin hypersensitivity (Holland et al. 1997).
In 1994, a committee was set up comprising academics, clinical specialists, and industrial representatives who had interest in the subject of dentin hypersensitivity and its clinical testing. The committee reported guidelines for conducting clinical trials and set many recommendations for proper testing for DH (Holland et al. 1997). Below is a summary of these recommendations:
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Clinical measurement, data collection, and documentation should be in accordance with FDA and European guidelines for Good Clinical Practice.
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A double-blind, randomized, parallel group design is recommended although the crossover design may be used for the preliminary screening of agents.
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A proper diagnosis of the condition is necessary for subject selection. As DH has many differential diagnoses, it is essential to rule out the various conditions which can be confused with DH (refer to Chap. 4).
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The facial surfaces of permanent incisors, canines, and premolars are the mostly recommended teeth and surfaces for clinical testing.
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Tactile, cold, and evaporative stimuli are the recommended tests for diagnosing DH as these tests are physiologic and controllable.
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At least two hydrodynamic stimuli should be employed starting with the least painful stimulus. It is also very important to leave enough time between applications to minimize the interaction between stimuli.
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Calibration is mandatory for multiple evaluators. Alternatively, each subject should be followed by the same evaluator, or the same stimulus should be applied to all subjects by the same evaluator.
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Controversy exists on the use of controls in the clinical trials. Despite their essentialism in clinical trials, there has not been a consensus on the type of controls to be used. The type and aim of the study should dictate the type of control to be used.
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A run-in/washout period is recommended before the testing starts in order to standardize the subjects and eliminate any already existing effects.
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Eight-week median duration for the clinical trials was reported. However, the duration should vary depending on pilot testing.
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Assessment of the response or treatment results can be stimulus based, which involves measurement of pain threshold, or response-based which involves measuring severity of pain evoked.
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The main objective should be to produce a clinically significant reduction in symptoms rather than a small but statistically significant reduction.
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