In vitro dentin permeability after application of Gluma® desensitizer as aqueous solution or aqueous fumed silica dispersion

Abstract

Objectives: To assess and to compare the effects of Gluma® Desensitizer (GDL) with an experimental glutaraldehyde and HEMA containing fumed silica dispersion (GDG) on dentin permeability using a chemiluminous tracer penetration test.

Material and methods: Twenty disc-shaped dentin specimens were dissected from extracted human third molars. The dentin specimens were mounted in a split chamber device for determination of permeability under liquid pressure using a photochemical method. Ten specimens were randomly selected and allocated to the evaluation groups Gluma® Desensitizer as aqueous solution and glutaraldehyde/HEMA as fumed silica dispersion, respectively. Dentin disc permeability was determined at two pressure levels after removal of smear with EDTA, after albumin soaking, and after application of the desensitizing agents. Two desensitizer-treated and rinsed specimens of each group were examined by scanning electron microscopy (SEM) for surface remnants.

Results: Comparatively large standard deviations of the mean EDTA reference and albumin soaked samples permeability values reflected the differences of the dentin substrates. The mean chemiluminescence values of specimen treated with GDL and GDG, respectively, were significantly reduced after topical application of the desensitizing agents on albumin-soaked dentin. The effects of GDL and GDG on permeability were not significantly different. Treated specimens showed no surface remnants after rinsing.

Conclusions: The experimental desensitizer gel formulation reduced dentin permeability as effectively as the original Gluma® Desensitizer solution.

Figure 1

Measuring device for determination of dentin permeability. The activator solution (trigger) is enclosed in the chamber on the pulpal side of the specimen. Upon start of measurement, the trigger is pressurized to 2.5 and 13 kPa respectively, while the luminol remains at atmospheric pressure. The trigger penetrates through the dentin specimen, and a photochemical reaction is generated upon contact with the luminol. Light emission is detected with a photodetector through a window of the chamber on the occlusal side and outputted as DC signal

Figure 3

Permeability of dentin discs (n=10), expressed as integrated output of chemiluminescence (mV•s) under 2.5 kPa pressure at different treatment and evaluation stages. EDTA: samples cleaned for smear on both saw-cut surfaces; Albumin: dentin discs soaked with albumin; Gluma: albumin-soaked specimens topically treated with GDL or GDG; Gluma re-application: specimens of Gluma groups after second application of GDL or GDG. The box-plots show the medians, interquartile distances, the whiskers give the extreme values. The square signatures illustrate the mean values. White and grey boxes refer to groups that received GDL and GDG treatments, respectively. The EDTA and albumin groups’ output signals were not significantly different. The boxes connected with brackets for "Albumin" and the three Gluma groups were significantly different. No significant differences were found between neighboring GDL and GDG boxes. Significant differences by non-parametric tests: (p<0.05)

Figure 4

As Figure 2, however permeability of dentin discs (n=10) determined under 13 kPa pressure at the different treatment and evaluation stages

Figure 5

Representative scanning electron microscope micrographs (3,000x) of GDL and GDG treated dentin disc surfaces and of samples fractured perpendicular through the desensitizer-treated surfaces after rinsing with water. The morphologies of the treated surfaces are similar; no remnants of the thickening agent of GDG on free surface or inside tubules. In two of the longitudinally exposed tubules of GDG transverse septa are displayed (arrows)