Finalreport

Effects of Desensitizing Agents on Dentinal Tubule Occlusion

Heinrich-Heine University University clinic Düsseldorf

Dental School Dept of Operative and Preventive Dentistry

Mooren Str. 5 40225 Düsseldorf, Germany

Düsseldorf, 20.02.2008 (Dr. Mozhgan Bizhang)

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Effects of Desensitizing Agents on Dentinal Tubule Occlusion

Introduction Hypersensitive Dentine is a common chronic condition which affects a high

proportion of the adult population (8-35%) [1,2]. Dentine hypersensitivity can be

defined as a pain arising from exposed dentine typically in response to chemical,

thermal, tactile or osmotic stimuli, which cannot be explained as arising from any

other from of dental defect or pathology [3]. Although dentine hypersensitivity is

commonly encountered in dental clinics, no consistent treatment regimen has been

established.

The major problem regarding the development of dentin desensitizing agents is that

the mechanism of dentin sensitivity is not yet clearly understood [4]. The most widely

accepted hypothesis about how the stimuli influence nerve fibres is Brainstorm’s

hydrodynamic theory. This theory states that fluid within the dentinal tubules moves

in either an inward or outward direction when stimuli are applied. This stimulates the

nerve endings at the pulp/dentin interface, resulting in generation of pain impulses [5].

Various techniques and agents have been reported to be effective, e.g., potassium

oxalate [5], sodium fluoride [6,7], and strontium chloride [8], as well as resin liner [9]. One

of the aims of these treatments is to block the dentinal tubules in order to reduce the

flow of tubular fluid. If the hydrodynamic theory [10] of pain transmission is valid,

occlusion of patent dentinal tubules would be an effective means of treating dentin

hypersensitivity, since this treatment would reduce the fluid flow in the dentinal

tubules. Indeed, significant differences in the openings of dentinal tubules have been

reported between hypersensitive and naturally desensitized areas [11-13].

Currently, other methods of treatment have emerged such as oxlate solution, which

have been shown significant effectiveness in reducing dentin permeability and pain.

These agents precipitate calcium oxlate crystals that occlude patent exposed dentinal

tubules[5,14]. These crystals reduce dentine hypersensitivity.

The Aim of this study was to evaluate the ability of potassium oxalate on dentine

tubule occlusion and morphological tubule changes using scanning electron

microscopy.

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Material and Methods Dentine discs from eight unerupted, caries-free, surgically extracted human third

molars were used for the study. The discs were prepared from the buccal surface (3

specimens from the lower and 3 specimens from the upper jaw) of the crown using a

trephine bur of 6 mm diameter. Each specimen was ground (2500-grit) flat on a

polishing machine (Exakt Appartebau, Norderstedt, Germany) to remove the enamel

and expose the underlying dentine in the cervical area.

The dentine discs were stored in distilled water containing 0.1% thymol. The removal

of enamel was confirmed by inspection of the specimens under a dissecting

microscope (8 x magnifications).

Specimens were treated with 0.5 mol/ L EDTA for 20 seconds to enlarge the dentinal

tubules. This process simulated the state of dentinal tubules in subjects with

hypersensitivity dentine. The specimens were then washed with distilled water and

used immediately for the experiments. Thereafter, impressions of the samples were

taken (Provil NOVO, Heraeus Kulzer, Hanau, Germany). The impressions were cast

with Epoxy resin (Araldite, Heidelberg, Germany).

Using an Applicator (99.9 g) Remesense (3% potassium oxalate, Remedent

Company, Deurle, Belgium) was applied on the specimens for 10 min as per the

manufacturers´ instructions. The specimens were then washed with distilled water

again. The casts were sputter coated (Cressington 108 auto, Cressington Scientific

Instruments Ltd, UK) after EDTA-treatment and the specimens after Remesense-

treatment. The dentine surface areas of casts with EDTA-treatment were evaluated

with a scanning electron microscope (SEM) (Hitachi S-3000N, Hitachi, Japan) under

one magnification (x1000) and the specimens with Remesense-Treatment under

three magnifications (x1000, x1800, and x4000).

Specimens were fractured with a sharp blade placed perpendicular to the buccal

surface. The occlusion of the dentinal tubules was evaluated by observing the

morphological changes of the precipitate in the dentinal tubules with a scanning

electron microscope (SEM) under three magnifications (x1000, x2500, and x4000).

Results A scanning electron micrograph of dentine with the EDTA treatment demonstrated

the typical appearance of opened dentine tubules. Those surfaces, from six different

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dentine specimens (Diameter about 1-3 µm) were uniformly distributed over the

surfaces (Fig.1-6). The intertubular matrix and the walls of the tubules were free of

any debris or other irregular deposits. Treatment of EDTA surfaces with Remesense

(3% potasium Oxalate) from six different dentine specimens resulted in crystal

formation on the surface and a thin layer of the product could be seen over the

dentine, occluding the entrance of dentinal tubules (Fig.7-12). After splitting from six

different dentine specimens, the crystal formation could be seen extending into the

tubules (Fig.13-18).

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Fig.2: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

Fig. 1: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

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Fig.4: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

Fig.3: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

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Fig.6: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

Fig.5: SEM photomicrographs of a dentine surface with EDTA treatment, there are many tubule openings at the surface. (1000 x)

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Fig.7: SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

Fig.8 SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

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Fig.9: SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

Fig.10: SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

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Fig.11: SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

Fig.12: SEM photomicrographs of a dentine surface after Remesense treatment, there are many crystal-like inclusions at the surface. (1000 x)

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Fig.13: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

Fig.14: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

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Fig.15: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

Fig.16: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

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Fig.18: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

Fig.17: SEM photomicrograph of dentine after treatment with Remesense, There is a tin layer of the product on the dentine surface and the tubules are plugged below the surface, deeper into the dentine tubules. (1000 x)

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Discussion Dentine hypersensitivity is an exaggerated response to a sensory stimulus that

usually causes no response in a normal healthy tooth and is associated with dentine

exposure to the oral environment. Several different empirical treatments have been

used in the past to decrease or eliminate dentine hypersensitivity. However none of

them worked predictably.

Treatment with Remesense (3% potassium oxalate) has potential value as a

treatment for dentine hypersensitivity due to the fact that SEM photomicrographs of a

dentine surface after Remesense treatment show many crystal-like inclusions at the

surface of the dentine tubules. Furthermore those photographs show that the tubules

are stuffed below the surface with crystals proving that the product penetrates deep

into the dentine tubules. The general remark that one could make is that the depth of

the precipitate in the dentine tubules, measured from the dentinal surface, is

important from the point of sustenance of treatment, since daily brushing could easily

remove the precipitate if it was not deep enough or if it was precipitated only on the

dentinal surface. A deeper precipitate provides a greater surface area for mechanical

locking between the precipitate and dentinal tubules, which then makes the

precipitate difficult to remove from the dentinal tubules.

Conclusion Within the limitation of this in-vitro study, it was found that 3% potassium oxalate is

an effective treatment for dentine hypersensitivity. The result of this study confirmed

the results of the other studies with oxalate solution for the treatment of dentine

hypersensitivity[5,14].

.

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