Concept of experimental preparation for treating dentin hypersensitivity open medicine normal blood sugar levels australia

Dentinal hypersensitivity (DH) is a diagnostic and therapeutic problem now appearing more frequently in modern dentistry. The reasons for this ailment have not been explained until now. Dentin hypersensitiveness seems to be connected with irritation of nerve endings at a dentin/ pulp boundary in response to thermal, chemical, mechanical, dehydrative and osmotic stimuli. As a result, an acute pain of various intensities arises which can not be explained by other teeth diseases [ 1]. Indicating the type of treatment is problematic in dentistry since establishing reasons behind DH is difficult.

DH may arise from teeth having dentinal tubules that are exposed at the surface and patent to the pulp. There are other theories of DH but the most widely accepted is the hydrodynamic one, proposed c.a. 100 years ago by Gysi, described in detail and modified by Brannstorn in the 1960s [ 2, 3].

The theory assumes that irritation of nerve fibers neighboring to odontoblasts and in initial sections of dentinal tubules is caused by a sudden bulk flow of tubular fluid in the presence of an irritating stimulus. As shown by scanning electron miscroscopy (SEM) investigations, hypersensitive teeth have 8-fold number of dentinal tubules with twofold diameter compared to the “normal” tooth, which causes greater flow of tubular fluid and intensification of symptoms [ 2].

Sensitivity to a thermal stimulus is the most distinct symptom of DH. The intensity of the pain felt depends on the psychic condition of the patient, their subjective reaction to the pain, and even on the season in the year. Pain occurs most frequently during brushing, consumption of either cold or hot drinks, and inhalation of cold air. The ailment may concern a single tooth or a number of teeth. Dentinal hypersensitivity happens mainly in adults, and most frequently in the cuspids, premolars, incisors and molars [ 4]. The factors and methods known to abolish DH may be divided into three following basic groups.

Physical factors act on the basis of destroying nerve conduction in some area of the dentin. Methods of treatment include application of laser radiation, where a high energy laser beam is used to partially melt and thus block dentin tubules. This reduces sensitivity to nerve impulses and decreases nerve conduction speed [ 5, 6].

Physicochemical methods are based on introduction of some chemicals into dentinal tubules and application of an electric current. That can be ionophoresis with use of 1-2% NaF and a direct current of 1-5mA. The electric current enhances uptake of fluoride ions by a dentin which results in obliteration of dentinal tubules. When supplied electrophoretically into tubules, the fluoride ions penetrate deeper and are less susceptible to be washed out than those applied in a classic way [ 7].

Chemical factors – chemicals include various inorganic and organic compounds, such as fluorine compounds (sodium fluoride, sodium fluorosilicate, tin fluoride, amine hydrofluorides), calcium compounds (calcium phosphate), oxalates (ferric oxalate and aluminum oxalate), strontium compounds (strontium chloride), protein precipitating agents (glutaraldehyde), adhesive and non-adhesive resins, potassium compounds (potassium nitrate), etc. The mode of therapeutic action of some chemicals is given in Table 1 [ 3, 4].

Analyses: 1H NMR spectra were recorded using UNITY/ INOVA 300MHz NMR spectrometer (Varian). The samples were tested as solutions in deuteriated acetone containing tetramethylsilane (TMS) as a chemical shift internal standard. Infra-red spectra were recorded using FT-IR Nicolet 6700 spectrophotometer. DSC analysis was performed using METTLER-TOLEDO (DSC822 e) instrument.

Chemicals: Bis-GMA resin was synthesized as previously reported [ 9]. PMDA (pyromellitic anhydride; 1,2,4,5-benzenetetracarboxylic anhydride, Aldrich) was recrystallized from acetic anhydride. HEMA (2-hydroxyethyl methacrylate, Sigma) and acetone (POCh) were dried over anhydrous magnesium sulphate. TEGDMA (triethylene glycol dimethacrylate, Fluka), HMDI (hexamethylene diisocyanate, Fluka), DBTDL (dibutyltin dilaurate, Fluka), HA (hydroxyapatite nanopowder, Aldrich), triclosan (irgasan; 5-chloro-2-(2,4-dichlorophenoxy)phenol, Sigma Aldrich), KF (potassium fluoride, UCB), DMAEMA (N, N-dimethylaminoethyl methacrylate, Merck), CQ (camphorquinone, Aldrich) as well as other auxiliary reagents and solvents were used as supplied.

Syntheses: Methacrylate resin: The modified patented recipe was applied. Thus, 6g of bis-GMA resin, 4g of TEGDMA and catalytic amount of DBTDL (0.05% by weight) were homogenized manually by stirring with a glass rod with gentle heating. After that, 0.3g of HMDI was added dropwise whilst the mixture was magnetically stirred at 40°C for 4hrs. The product was left to stand overnight in a thermostat at 40°C. According to stoichiometry and our previous findings [ 9] the resin should contain ca. 20% by weight of bis-GMA/HMDI adduct as well as TEGDMA and unreacted bis-GMA.

The composition of SealProtect as revealed by NMR analysis, indicates that desensitizing formulation of prolonged action basically consist of two groups of ingredients: those responsible for formation of stable polymeric layer (methacrylates, adhesive monomer, photoinitiating system) and those responsible for desensitization (triclosan, cetylamine hydrofluoride, silica nanofiller). Additionally, a volatile solvent (to be evaporated after application) facilitates penetration of the composition into a tooth structure.

The formulation investigated in this work complies with such an idea. The basic differences to SealProtect are another methacrylate resin, new adhesive monomer PMMAn, incorporation of hydroxyapatite instead of silica, and potassium fluoride as a source of potassium and fluoride ions. Moreover, addition of HEMA – hydrophilic monomer of low viscosity, enabled reduction of acetone solvent content considerably. The proposed percentages of particular species are collected in Table 4.