Hypersensitive dentin: testing of procedures for mechanical and chemical obliteration of dentinal tubuli

Crystal growth in dentinal tubules with bio-calcium carbonate-silica sourced from equisetum grass

BACKGROUND/PURPOSE

One effective way to deal with dentin hypersensitivity is to develop materials to seal the tubules. The porous bio-calcium carbonate-silica (BCCS) contained well-dispersed CaCO₃ would form calcium phosphates to seal the dentinal tubules when mixed with an acidic solution. The acidic hydrothermal treatment and calcination to isolate the BCCS from the agricultural waste like equisetum grass was used, which would be more environmentally friendly than chemically synthesized mesoporous biomaterials. The aim of this study was to develop mesoporous materials from natural resources to occlude the dentinal tubules which could be more environmentally-friendly.

METHODS

Dentin disc samples were prepared and treated with different methods as follows: (1) BCCS mixed with H₃PO₄; (2) BCCS mixed with KH₂PO₄; (3) Seal & Protect® was used as a comparison group. Sealing efficacy was evaluated by measuring the depths and percentages of precipitate occlusion in dentinal tubules with SEM.

RESULTS

The N₂ adsorption-desorption isotherm of the BCCS demonstrated a pore size of around 15.0 nm and a surface area of 61 m²g-1. From the results of occlusion percentage and depth, the BCCS treated with H₃PO₄ or KH₂PO₄ demonstrated promising sealing efficacy than the commercial product.

CONCLUSION

This synthetic process used the agricultural waste equisetum grass to produce bio-calcium carbonate-silica would be environmentally friendly, which has great potential in treating exposed dentin related diseases.

Novel calcium encapsulated mesocellular siliceous foams for crystal growth in dentinal tubules

OBJECTIVES

The aim of this study was to investigate the novel mesocellular siliceous foams (MCF) containing CaCO₃ nanoparticles (denoted as CMCF) combined with phosphoric acid could occlude dentinal tubules through the formation of biomimetic crystal barrier.

METHODS

Ultrastructures of MCF and CMCF were examined by transmission electron microscopy (TEM). Elemental components were analyzed with energy dispersive X-ray spectrometry (EDX). CMCF was mixed with distilled water, 10%, 20% and 30% phosphoric acid then applied on dentine discs. Crystals were characterized by X-ray powder diffractometry (XRD). The sealing efficacy of the dentinal tubules was examined by scanning electron microscopy.

RESULTS

TEM images showed MCF presented a pore size of approximately 30.0 nm and CMCF contained abundant nano-CaCO₃. Sealing efficacy showed that CMCF, when reacted with 30% phosphoric acid, would form crystals in the dentinal tubules to a depth of 83.2 ± 17.6 μm at an occlusion percentage of 75.6 ± 12.8% on average; both occlusion percentage and depth were higher than those obtained with 10% or 20% phosphoric acid (p < 0.05). The results of XRD and EDS indicated that the crystal growth in the dentinal tubules could be transformed into the biomimetic crystals.

CONCLUSION

This study showed that the CMCF with 30% phosphoric acid could effectively occlude the dentinal tubules through the formation of biomimetic crystal barrier.

CLINICAL SIGNIFICANCE

The novel CMCF combined with phosphoric acid may have potential for the treatment of dentine hypersensitivity.

Synthesis of nanobioglass and formation of apatite rods to occlude exposed dentine tubules and eliminate hypersensitivity

The occlusion of patent dentine tubules may reduce or eliminate hypersensitivity by restricting dentinal fluid movement. The efficacy of a novel sol-gel nanobioglass and a melt-derived bioglass to occlude tubules and promote apatite formation was tested by mechanically brushing a slurry of bioglass powder and human saliva onto dentine possessing exposed tubules. Scanning electron microscopy, focused ion beam and energy-dispersive X-ray spectroscopy were used to characterize the powders and assess tubule occlusion. Melt-derived bioglass possessed an irregular particle morphology and had a mean size of 3.30 +/- 0.42 microm. The sol-gel bioglass particles were spherical, with a mean size of 0.65 +/- 0.19 microm. Dentine treated with melt-derived bioglass exhibited a tightly adherent continuous apatite layer. Treatment with nanobioglass resulted in particle deposition within tubules and formation of apatite rods which were tightly adherent to tubule walls and continuous to a measured depth of 270 microm.

In vitro and in vivo analyses of the effects of desensitizing agents on dentin permeability and dentinal tubule occlusion

This study was done to assess the influence of the topical application of two different desensitizing agents on dentin permeability and dentinal tubule occlusion. Twenty-one rats provided 84 teeth: 36 for the in vitro and 48 for the in vivo investigation. The following agents were tested: Group 1, 2% potassium nitrate plus 2% sodium fluoride gel; Group 2, 5% sodium fluoride varnish; Group 3, 3% hydroxyethylcellulose gel (control). Cervical cavities were prepared and EDTA was applied to expose the dentinal tubules. After each treatment, Evans blue dye was applied to the teeth. Dentin permeability, scanning electron microscope (SEM) sections, and energy dispersive X-ray (EDX) were analyzed. One-way ANOVA was used to compare the data. There were significant differences (P < 0.05) among groups for dentin permeability, number of tubules/mm(2), tubule area and tubular diameter. Groups 1 and 2 (both in vitro and in vivo) showed open and partially occluded tubules. Group 3 had the most open tubules. EDX revealed similar composition for both experimental conditions. Within the limits of the study, 2% nitrate potassium plus 2% sodium fluoride gel and 5% fluoride varnish decreased the dentin permeability, resulting in partial tubular occlusion.

In-office treatment of dentinal hypersensitivity

Dentinal hypersensitivity is a common dental complaint, especially in periodontal patients. It is believed to be mediated by a hydrodynamic mechanism in which various stimuli result in increased fluid flow in dentinal tubules, thereby generating action potentials in associated nerve fibers. Although it is often perceived as mild discomfort by the patient, it can be severe. A variety of interventions has been used, although few have been subjected to rigorous study. This article surveys those in-office treatments that are available, and suggests directions for research so that clinicians may treat patients based on best evidence. Until such evidence is available, it seems prudent to employ therapies that are least likely to cause harm and are reversible.

Clinical evaluation of ferric oxalate in relieving dentine hypersensitivity

Previous in vitro permeability and scanning electron microscopic (SEM) studies have demonstrated the effectiveness of the oxalate ion in dentine permeability reduction and effective tubule occlusion. The aim of this randomized double-blind, split mouth 4-week clinical study, therefore was to determine whether a 1-min application of ferric oxalate (Sensodyne Sealant) on exposed root dentine was effective in reducing dentine hypersensitivity (DH). Thirteen subjects [8F:5M, mean age 46.2 (s.d. 4.15) years] completed the study. The subjective response was evaluated by tactile, thermal and evaporative methods of assessment. Data were collected at baseline and post-application at +5 min and 4 weeks. Analysis was based on paired t-test (P=0.05) and Wilcoxon-Mann-Whitney tests. No statistically significant differences were noted between ferric oxalate and placebo preparations at +5 min and 4 weeks for any of the test stimuli. There was, however, a clear trend towards immediate reduction (+5 min) in DH reverting back to baseline values at 4 weeks with the exception of the Biomat Thermal Probe mean values, which maintained the reductions in DH compared with placebo. The results of the present study demonstrated that a 1-min application of ferric oxalate is both rapid and effective in reducing DH although its long-term effectiveness still needs to be determined.

Scanning electron microscopy (SEM) investigation of selected desensitizing agents in the dentine disc model

Dentine sensitivity is a painful clinical conditions that can affect up to 35% of the population at any one time. Both professionally available (in-office) or commercially available (over-the-counter) products have been used to treat dentine sensitivity. The aim of the present study was to investigate whether selected in-office desensitizing agents occluded dentine tubules in the dentine disc model. Both surface effects and tubule penetration of the five selected test products were examined by scanning electron microscopy. The results of the present study appeared to demonstrate that all of the applied desensitizing agents produced some occlusion of the tubules although the level of coverage and occlusion varied between the products. Of all the agents tested, ferric oxalate, the active ingredient of Sensodyne Sealant, produced crystal-like structures which occluded a higher proportion of the tubules across the dentine disc surface. ALL-BOND 2 and One-Step (both light-cured primer systems) produced similar crystal-like structures and, although coverage was not uniform across the disc surface, there was some reduction in tubule diameter. These three products, however, appeared to be more effective than either Butler Protect (potassium oxalate) or Oxa-gel (potassium oxalate in a gel) where there was a marked decrease in both the level of coverage and tubule occlusion. Both quantitative and functional studies are required in order to determine the effects of these agents on dentine permeability (fluid flow) as well as clinical studies to determine their effectiveness over time in reducing pain arising from dentine sensitivity.

Fluoride use in periodontal therapy: a review of the literature

Although the relationship between fluoride and dental caries has been widely studied and definitively determined, the relationship between fluoride and periodontal health and disease is not clear. Conflicting studies in the literature either suggest routine fluoride usage as an adjunct to conventional periodontal therapy or argue against topical fluoride use on periodontally involved teeth. This review summarizes the literature that addresses the utility of fluoride in patients with periodontal disease and aims to advance a rational criterion for the use of fluorides in the management of periodontal diseases.

The Dentin Disc surface: a plausible model for dentin physiology and dentin sensitivity evaluation

Dentin sensitivity (DS) is a painful clinical condition which may affect 8-35% of the population. Various treatment modalities have claimed success in relieving DS, although at present there does not appear to be a universally accepted desensitizing agent. Current opinion based on Brännström's Hydrodynamic Theory would suggest that following exposure of the dentin surface (through attrition, abrasion, or erosion), the presence of open dentinal tubules, patent to the pulp, may be a prerequisite for DS. The concept of tubule occlusion as a method of dentin desensitization, therefore, is a logical conclusion from the hydrodynamic theory. The fact that many of the agents used clinically to desensitize dentin are also effective in reducing dentin permeability tends to support the hydrodynamic theory. This paper reviews the in vitro evaluation of desensitizing agents, the techniques used to characterize their effects on the prepared dentin surface, and the ability of these agents to reduce permeability through tubule occlusion, and presents recent findings from ongoing research based on the Pashley Dentin Disc model. It can be concluded that the use of this model to determine surface characteristics, and reductions in dentin permeability through tubule narrowing or occlusion, provides a useful screening method for evaluating potential desensitizing agents. Interpreting changes observed in vitro is difficult, and extrapolation to the clinical situation must be tempered with caution.

Comparison of two desensitizing agents for the treatment of cervical dentine sensitivity

Numerous desensitizing agents have been utilized in an effort to alleviate the discomfort associated with cervical dentine sensitivity (CDS). Recently several new tubule-occluding and sealant systems have been marketed for treatment. The aim of this study was to compare two desensitizing agents (ALL-BOND 2 and Butler Protect) in a 3-month clinical study. Ten subjects (6F; 4M mean age 45.1 years (SD 8.81) who had provided voluntary written informed consent participated in a single-blind 3-month clinical study. Subjects were evaluated for tactile (Yeaple probe) and air sensitivity (dental air syringe) together with subjective perception of pain (VAS scores) at 0.5 min, 1, 2 and 3 months. There was an overall trend in reduction of CDS over the study period in all group with no significant differences detected between groups. The results suggested that while subjects reported overall reductions in sensitivity levels, this may not necessarily be substantiated when assessed objectively. Furthermore, there appeared to be a strong placebo effect in this study.