Patent Application
20210259933
The present disclosure relates to glass compositions for dentin-desensitizing compositions.
The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art.
Dentin sensitivity is dental pain that arises from exposed dentin surfaces in response to stimuli, such as thermal, evaporative, tactile, osmotic, chemical or electrical. Dentin sensitivity may be caused by gingival recession (receding gums) with exposure of root surfaces, loss of the cementum layer and smear layer, tooth wear, acid erosion, periodontal root planing, or dental bleaching.
Dentine contains many thousands of microscopic tubular structures that radiate outwards from the pulp. Changes in the flow of the plasma-like biological fluid present in the dentinal tubules can trigger mechanoreceptors present on nerves located at the pulpal aspect, thereby eliciting a pain response. This hydrodynamic flow can be increased by cold, air pressure, drying, sugar, sour (dehydrating chemicals), or forces acting onto the tooth. Hot or cold food or drinks, and physical pressure are typical triggers in those individuals with teeth sensitivity.
There is no universally accepted, gold-standard treatment which reliably relieves the pain of dental hypersensitivity in the long term. However, treatments can be divided into in-office (i.e. intended to be applied by a dentist or dental therapist), or treatments which can be carried out at home, available over-the-counter or by prescription.
The purported mechanism of action of these treatments is either occlusion of dentin tubules, or desensitization of nerve fibres/blocking the neural transmission.
The following introduction is intended to introduce the reader to this specification but not to define any invention. One or more inventions may reside in a combination or sub-combination of the apparatus elements or method steps described below or in other parts of this document. The inventors do not waive or disclaim their rights to any invention or inventions disclosed in this specification merely by not describing such other invention or inventions in the claims.
One example of a dentin-desensitizing composition known in the art is disclosed in PCT Publication No. WO2007144662A1. The disclosed toothpaste includes a bioactive glass comprising strontium. The disclosed bioactive glass occludes dentin tubules and induces precipitation and crystallization of a carbonated hydroxyapatite. The disclosed bioactive glass is designed to degrade at the same rate as the rate of the induced tissue ingrowth.
One example of a dentin-desensitizing composition known in the art is disclosed in U.S. Pat. No. 5,735,942. The disclosed toothpaste includes a mineral composition composed of CaO, Na2O, P2O5 and SiO2. The disclosed mineral composition chemically reacts with the surface of dentin and intimately bonds to tooth structure.
One or more described embodiments attempt to address or ameliorate one or more shortcomings involved with dentin-desensitizing compositions that include non-degradable particulate material that occludes dentin tubules. In some embodiments, the disclosed particulate material substantially degrades over a period between 12 and 24 hours under environmental conditions. In some embodiments, the disclosed particulate material provides a controlled release of fluoride over the same time period.
In some embodiments, the present disclosure provides a glass composition that includes from about 50 mol % to about 95 mol % of B2O3; from about 5 mol % to about 50 mol % of a glass component selected from the group consisting of: Li2O, Rb2O, K2O, Na2O, SrO, CaO, MgO, ZnO and any combination thereof; 0 mol % of CuO; less than 0.1 mol % of BaO; and less than 0.1 mol % of P2O5; where the glass composition comprises less than 30 mol % of Rb2O. The glass composition loses at least 5 mass % within 24 hours when exposed to a buffered saline solution, and the glass composition is a particulate material that comprises particles that are from about 1 to about 50 μm in size. The glass composition does not consist solely of B2O3 and Na2O.
In some examples of glass compositions according to the present disclosure, less than 20 mol %, such as less than 15 mol %, less than 10 mol %, or less than 5 mol % of the glass composition is CaO, MgO, and Na2O.
The glass composition may additionally include up to about 30 mol % of fluoride, wherein the fluoride is in the form of: CaF2, NaF, Na2PO3F, KF, or SnF2.
In other embodiments, the present disclosure provides a glass composition for desensitizing dentin, the glass composition includes from about 50 mol % to about 95 mol % of B2O3; from about 5 mol % to about 50 mol % of a glass component selected from the group consisting of: Li2O, Rb2O, K2O, Na2O, SrO, CaO, MgO, ZnO and any combination thereof; where the glass composition comprises less than 30 mol % of Rb2O. The glass composition loses at least 5 mass % within 24 hours when exposed to a buffered saline solution, and the glass composition is a particulate material that comprises particles that are from about 1 to about 50 μm in size.
In some examples of the glass compositions, less than 20 mol %, such as less than 15 mol %, less than 10 mol %, or less than 5 mol % of the glass composition is CaO, MgO, and Na2O.
The glass composition may additionally include up to about 30 mol % of fluoride, wherein the fluoride is in the form of: CaF2, NaF, Na2PO3F, KF, or SnF2.
In other embodiments, the present disclosure provides a glass composition that includes: fluoride, which is provided as from about 5 mol % to about 10 mol % of CaF2, SnF2, NaF, KF, or any combination thereof; and from about 90 mol % to about 95 mol % of a combination of B2O3, Na2O, MgO, and CaO, where the boron, the magnesium, the combination of Na and any K, and the combination of Ca and any Sn in the glass composition are present in elemental ratios of about 20: about 4: about 6: about 3, respectively.
One example of such a specific glass composition according to the present disclosure includes: about 50 mol % B2O3, about 15 mol % Na2O, about 20 mol % MgO, about 10 mol % CaO, and about 5 mol % CaF2.
Glass compositions according to the present disclosure may be formulated into a dentin-desensitizing composition, such as a toothpaste, a prophylaxis paste, a tooth varnish, a mouthwash, a dental gel, or a bonding agent. Dentin-desensitizing compositions according to the present disclosure are substantially water-free.
Glass compositions according to the present disclosure may be used for desensitizing dentin, such as in methods that include applying to an individual's dentin: a toothpaste, a prophylaxis paste, a tooth varnish, a mouthwash, a dental gel, or a bonding agent according to the present disclosure.
A glass composition according to the present disclosure may be prepared from a corresponding bulk glass. The chemical formulations are the same between the bulk glass and the particulate material. Another aspect of the present disclosure is a bulk glass having a chemical formulation as disclosed herein.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.
Glass compositions according to the present disclosure are at least a quaternary system. The glass compositions include from about 50 mol % to about 95 mol % of B2O3; and from about 5 mol % to about 50 mol % of one or more glass components selected from the group consisting of: Li2O, Rb2O, K2O, Na2O, SrO, CaO, MgO, and ZnO. The glass compositions include less than 30 mol % of Rb2O. Glass compositions according to the present disclosure degrade under physiological conditions, losing at least 5 mass % within 24 hours when exposed to a buffered saline solution.
The glass composition is a particulate material that includes particles that are from about 1 to about 50 μm in size. The glass composition includes at least some particles that are sized to occlude dentinal tubules, thereby desensitizing the dentin. In the context of the present disclosure, a particle sized to occlude a dentinal tubule should be understood to mean that the particle sits in or on top of the dentinal tubule, reducing the movement of the dentinal fluid.
In the context of the present disclosure, a glass composition that is “at least a quaternary system” should be understood to refer to glasses with four or more different elements. For example, a glass composition that is made up of only B2O3, Li2O and ZnO would be considered a quaternary system since the glass includes the elements boron, lithium, zinc, and oxygen. Similarly, a glass composition that is made up of only B2O3, CaO and CaF2 would be considered a quaternary system since the glass includes the elements boron, calcium, fluorine, and oxygen. In contrast, a glass composition that is made up of only B2O3 and Na2O would be considered a ternary system since the glass includes the elements boron, sodium, and oxygen.
It should be understood that “about 5 mol % to about 50 mol % of one or more glass components” refers to the total mol % of the glass components, and does not refer to the mol % percent of each individual component. For example, a glass composition according to the present disclosure could include 2.5 mol % of Li2O and 2.5 mol % of ZnO in order to provide the recited 5 mol % of the additional glass components.
It should be understood that “about X mol %” refers to any value that is within ±2% of the reported percentage. For example, “about 10 mol %” would refer to values from 8 mol % to 12 mol % since all those values would be within ±2% of the reported 10%; and “about 50 mol %” would refer to values from 48 mol % to 52 mol % since all those values would be within ±2% of the reported 50%.
It should be understood that “about X μm” in the context of particle size is determined based on accepted tolerances as per ASTM for a test sieve of the noted size. For example, the accepted tolerance for a 50 μm test sieve is 3 μm. Accordingly, “about 50 μm” refers to particles that are from 47 μm to 53 μm in size. In another example, the accepted tolerance for a 35 μm test sieve is 2.6 μm. Accordingly, “about 35 μm” refers to particles that are from 32.4 μm to 38.6 μm in size. The ASTM accepted tolerance for a 25 μm sieve is 2.2 μm. For test sieves without a standard, accepted tolerance (such as test sieves below 20 μm), the expression “about X μm” refers to ±15% for sizes from 5 to 15 μm, and ±50% for sizes less than 5 μm. For example “about 1 μm” refers to particles that are from 0.5 to 1.5 μm in size.
Glass Compositions
Glass compositions according to the present disclosure may include a source of fluoride, such as CaF2, NaF, Na2PO3F, KF, or SnF2. Including fluoride in the glass composition results in fluoride being released when the glass degrades. The released fluoride may form fluorapatite (Ca5(PO4)3F) in or around the dentinal tubules, which may form a protective precipitate and further decrease dentin sensitivity. In a glass composition that includes fluoride the source of fluoride may be up to 30 mol % of the glass composition. In some examples, the source of fluoride may be from about 1 mol % to about 10 mol %, for example from about 1 mol % to about 5 mol %, of the glass composition. In particular examples, the source of fluoride is about 15 mol % of the composition. Compositions that include CaF2 or SnF2 provide twice the amount of fluoride per mole of starting material compared to compositions that use NaF, Na2PO3F, or KF.
In some examples, the glass composition includes from about 1 mol % to about 10 mol % of fluoride. In some examples, the glass composition includes from about 1 mol % to about 5 mol % of fluoride.
In some examples, glass composition includes sufficient fluoride that 0.1 g of the particulate material releases the fluoride into 10 mL of a buffered saline solution at an average rate of about 1 ppm/hr to about 15 ppm/hr over 1, 2, 4, 8, 12, 18 or 24 hours.
In the context of the present disclosure, ppm is measured as mass/mass. In particular examples, the glass composition includes sufficient fluoride that about 4 to about 6 ppm of fluoride is released per hour over 1 hour.
In some examples of glass compositions according to the present disclosure, less than 20 mol %, such as less than 15 mol %, less than 10 mol %, or less than 5 mol % of the glass composition is CaO, MgO, and Na2O.
In an example of a glass composition according to the present disclosure, the glass composition does not include any CuO; and includes less than 0.1 mol % of BaO, and less than 0.1 mol % of P2O5. In particular examples, the glass composition does not include any CuO, BaO, or P2O5.
A glass composition according to the present disclosure may include from about 5 mol % to about 50 mol % of one or more glass components selected from the group consisting of: Li2O, Rb2O, K2O, Na2O, SrO, and ZnO; and wherein the glass composition comprises less than 0.1 mol % of CaO and less than 0.1 mol % of MgO.
A glass composition according to the present disclosure may include from about 5 mol % to about 50 mol % of one or more glass components selected from the group consisting of: Li2O, Rb2O, K2O, SrO, and ZnO; and wherein the glass composition comprises less than 0.1 mol % of CaO, less than 0.1 mol % of MgO, and less than 0.1 mol % of Na2O.
A glass composition according to the present disclosure may include from about 50 mol % to about 80 mol % of B2O3, such as about 50 mol % of B2O3.
A glass composition according to the present disclosure may include about 5 mol % to about 40 mol %, such as from about 20 mol % to about 40 mol %, of the one or more glass components selected from the group consisting of: Li2O, Rb2O, K2O, Na2O, SrO, CaO, MgO, and ZnO.
A glass composition according to the present disclosure may include B2O3, Li2O, and ZnO, and optionally Rb2O, Na2O, and/or a source of fluoride. In particular examples, the glass composition includes: from about 5 mol % to about 25 mol % Li2O, and from about 5 mol % to about 25 mol % Rb2O; or from about 5 mol % to about 25 mol % Li2O, and from about 5 mol % to about 15 mol % ZnO, and optionally from about 5 mol % to about 15 mol % of Na2O. The glass compositions may include about 50 mol % of B2O3, or about 70 mol % B2O3.
A glass composition according to the present disclosure may include B2O3, and ZnO, and optionally Rb2O and/or a source of fluoride. In particular examples, the glass composition includes: from about 5 mol % to about 30 mol % ZnO. If present, the RbO2 may be included in an amount from about 5 mol % to about 30 mol %. The glass compositions may include about 50 mol % of B2O3.
A glass composition according to the present disclosure may include B2O3, and SrO, and optionally ZnO and/or a source of fluoride. In particular examples, the glass composition includes: from about 5 mol % to about 30 mol % SrO. If present, the ZnO may be included in an amount from about 5 mol % to about 30 mol %. The glass compositions may include about 50 mol % of B2O3.
As noted above, the present disclosure also provides a glass composition that includes: fluoride, which is provided as from about 5 mol % to about 10 mol % of CaF2, SnF2, NaF, KF, or any combination thereof; and from about 90 mol % to about 95 mol % of a combination of B2O3, Na2O, MgO, and CaO, where the boron, the magnesium, the combination of Na and any K, and the combination of Ca and any Sn in the glass composition are present in elemental ratios of about 20: about 4: about 6: about 3, respectively.
One specific example of such a glass composition includes: about 50 mol % B2O3, about 15 mol % Na2O, about 20 mol % MgO, about 10 mol % CaO, and about 5 mol % CaF2. This composition may be referred to herein as composition “PBF1”.
Another specific example of such a glass composition includes: about 48 mol % B2O3, about 9 mol % Na2O, about 19 mol % MgO, about 14 mol % CaO, and about 10 mol % NaF. This composition may be referred to herein as composition “PBF1-Na”.
Particle Size Distribution
A glass composition according to the present disclosure is a particulate material that includes particles that are from about 1 to about 50 μm in size. At least some of the particles are sized to sit in or on top of a dentinal tubule. Dentinal tubules have a natural variation in diameter and are primarily from about 0.5 to about 8 μm in size, for example, from about 0.5 to about 5 μm in size. Accordingly, glass compositions of the present disclosure may be used for desensitizing dentin, which may temporarily reduce pain associated with sensitive teeth.
In some examples, at least 75% of the particles making up the particulate material are smaller than 50 μm in size. In other examples, at least 85% or at least 95% of the particles are smaller than 50 μm in size. In some examples, at least 5% of the particles making up the particulate material are smaller than 7 μm in size.
In particular examples, the particulate material is made up of a plurality of particles where at least 5% of the particles are smaller than 35 μm in size, at least 5% of the particles are smaller than 15 μm in size, and at least 5% of the particles are smaller than 7 μm in size.
In particular examples, the particulate material is made up of a plurality of particles where at least 5% of the particles are from about 15 μm to about 35 μm in size, at least 5% of the particles are from about 6 μm to about 15 μm in size, and at least 5% of the particles are from about 3 μm to about 7 μm in size.
In some particular examples, the particulate material is made up of a plurality of particles where the particle size distribution is Dx10 of about 5 um, Dx50 of about 15 um, and Dx90 of about 30 um.
Degradation
Glass compositions according to the present disclosure degrade under physiological conditions, losing at least 5 mass % within 24 hours when exposed to a buffered saline solution. In some examples, the glass composition may lose at least 20 mass %, at least 40 mass %, at least 60 mass %, or at least 80 mass % within 24 hours when exposed to the buffered saline solution.
Dentin-Desensitizing Compositions
Glass compositions according to the present disclosure may be formulated in a dentin-desensitizing composition that includes a water-free, orally-compatible carrier. Dentin-desensitizing compositions according to the present disclosure are free of water since the glass composition degrades if exposed to water.
In the context of the present disclosure, “water-free” should be understood to mean that the dentin-desensitizing composition includes so little water that the glass composition remains capable of reducing dentin sensitivity over the expected lifespan of the product. The expected lifespan of the product refers to the longest expected time between when the dentin-desensitizing composition was produced and when the dentin-desensitizing composition was completely used up or disposed of.
The orally-compatible carrier used in the dentin-desensitizing composition may be a mouthwash, a carrier formulated to mix with additional components to form a mouthwash, or an orally-compatible viscous carrier, such as a toothpaste, a dental gel, a prophylaxis paste, a tooth varnish, a bonding agent, or a carrier that is formulated to mix with additional components to form a toothpaste. The orally-compatible viscous carrier may have a viscosity from about 100 cP at 30° C. to about 150,000 cp at 30° C.
The dentin-desensitizing composition may include a glass composition according to the present disclosure that includes fluoride, as discussed above, where the glass composition is present in a sufficient amount that the desensitizing composition includes about 100 ppm to about 5,000 ppm of the fluoride.
One example of a dentin-desensitizing composition according to the present disclosure is a toothpaste that includes a glass composition according to the present disclosure and: an abrasive; a detergent such as sodium lauryl sulfate; a fluoride source; an antibacterial agent; a flavorant; a remineralizer; a sugar alcohol such as glycerol, sorbitol, or xylitol; another dentin desensitizing agent; a hydrophilic polymer such as polyethylene glycol; or any combination thereof. The glass composition may be from about 0.5 to about 15 mass % of the toothpaste.
One particular example of a dentin-desensitizing composition according to the present disclosure is a toothpaste that includes a glass composition according to the present disclosure and: glycerin, silica, a polyethylene glycol (such as PEG 400), titanium dioxide, a carbomer, and a sweetener (such as potassium acesulfame or sodium saccharin).
Another particular example of a dentin-desensitizing composition according to the present disclosure is a toothpaste that includes a glass composition according to the present disclosure and: α-carbomer, DL-limonene, glycerin, mint flavor, a polyethylene glycol (such as PEG-8), silica, titanium dioxide, sodium lauryl sulphate, and a sweetener (such as potassium acesulfame or sodium saccharin).
Another example of a dentin-desensitizing composition according to the present disclosure is a carrier that includes a glass composition according to the present disclosure, where the carrier is formulated to be mixed with additional components to form a toothpaste.
Yet another example of a dentin-desensitizing composition according to the present disclosure is a carrier formulated to mix with additional components to form a mouthwash. Particular examples of the carrier include a glass composition according to the present disclosure and: a water-free alcohol, cetylpyridinium chloride, chlorhexidine, an essential oil, benzoic acid, a poloxamer, sodium benzoate, a flavor, a coloring, or any combination thereof. The additional component(s) that is/are mixed with the carrier to form the mouthwash may include: water, peroxide, cetylpyridinium chloride, chlorhexidine, an essential oil, alcohol, benzoic acid, a poloxamer, sodium benzoate, a flavouring, a colouring, or any combination thereof. The carrier and the additional components may be kept in separate compartments, and mixed together before the mixture is used as a mouthwash. The separate compartments may be in the form of a multi-chambered bottle, such as a bifurcated bottle.
Another example of a dentin-desensitizing composition according to the present disclosure is a prophylaxis paste (also referred to as a “prophy paste”) that includes a glass composition according to the present disclosure. Particular examples of contemplated prophy pastes include a glass composition according to the present disclosure and: pumice, glycerin, diatomite (preferably fine grit), sodium silicate, methyl salicylate, monosodium phosphate, sodium carboxymethylcellulose, a sweetener (such as potassium acesulfame or sodium saccharin), a flavouring, a colouring, or any combination thereof.
Methods
Glass compositions according to the present disclosure may be synthesized by: mixing appropriate molar amounts of the starting reagents; packing the precursor blend in a platinum crucible (Johnson Matthey, Noble Metals, Pa.); placing the packed crucible in a furnace (Carbolite, RHF 1600) at room temperature; heating the furnace (such as at a rate of 25° C./minute) to an initial dwelling temperature of 600° C.; holding the temperature for 60 minutes; ramping the temperature (such as at a rate of 20° C./minute) to a dwelling temperature of 1,100° C.; holding the temperature for 60 minutes; and quenching the glass melt between two stainless steel plates.
It should be understood that the specific ramp rate, times, and temperatures disclosed above could be modified, so long as the glass melts. Ramp rates from 10-20 degrees/min, and holding at the dwell temperature may remove at least some gas bubbles from the glass.
The resulting quenched glasses may be ground/milled separately within a planetary micro mill (Pulverisette 7, Fritsch, Germany) and sieved with ASTM E-11 compliant sieves (Cole Palmer, U.S.A) to obtain particles of <25 μm. Glasses may be stored under vacuum in glass scintillation vials.
Although the resulting glass composition includes oxides, the starting reagents may include oxides, carbonates, or both. For example, the starting reagent may include boron oxide, rubidium carbonate, lithium carbonate, and calcium fluoride. The rubidium carbonate and lithium carbonate decompose in the furnace to release CO2, generating their corresponding oxides.
Particle size is measured using a Malvern Mastersizer (MS) 3000 laser diffraction particle size analyzer. Glass powders are separately suspended in deionized water to obtain an obscuration value for the suspension between 5-8%. Suspensions are measured using both a blue (λ=470 nm) and red (λ=632.8 nm) laser and are measured 5 times (n=5).
Fluoride release is measured by placing 0.1 g of the glass composition in 10 ml of TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) in a 15 ml Falcon tube. The solution is agitated at 120 rpm and kept at a temperature of 37° C. for the desired release period, such as for 1, 3, 6, 12 or 24 h. On completion, the liquid portion is decanted and filtered using a 0.22 μm filter (Sarstedt syringe filter, Canada) into new clean 15 ml Falcon tubes, which were capped and then stored at 4° C. until the amount of fluoride is quantified. The concentration of the released fluoride is quantified using an Accumet®AB250 pH/ion selective electrode meter equipped with electrode fluoride combination (Accumet®). Standard solutions are prepared using a fluoride analytical standard specifically for ion selective electrodes (NaF, 0.1 M F, Sigma Aldrich, Canada) and calibration cures are retrieved before analysis. Liquid extracts derived from the extraction of each composition were prepared for ion analysis as per the electrode manufactures instructions. The ion concentrations are reported as the average of n=3±SD.
In the context of the present disclosure, mass loss of a glass composition is in relation to a solid glass cylinder that is 6 mm in length and 4 mm in diameter. The glass cylinder is prepared by producing molten glass, as described above, quenching the molten glass in a stainless steel mould (6 mm in length by 4 mm in diameter), set between two stainless steel plates. The excess glass on the cylinders is carefully etched off by a Speedy Sharp utensil and the remainder of the excess glass is removed (while placed back into the stainless steel moulds) using a grinding/polishing wheel with 240 sand paper and applying pressure to the moulds/glass on the wheel. Glass cylinders with uneven edges, air bubbles, or chips are excluded.
The mass loss for a given glass composition is measured using three cylinders. The length and diameter of each cylinder is measured and recorded 3 times (changing the position of measurement each time) and recorded as an average±SD. The mass of each cylinder is measured separately (Sartorius Cubis, Model MSU-224S 100 DI, Cole Palmer). The three cylinders are placed in separate 50 mL falcon tubes with 20 mL of TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) in each tube. The tubes are then placed in a shaking incubator (Thermos Scientific, MaxQ 4000) at 37° C. and agitated at 120 rpm for 24 hrs. After the 24 hours, the cylinders are filtered from the solution, rinsed with cold distilled H2O, and placed to dry overnight in a 37° C. oven. Once dry, the length, diameter and mass are measured.
Abrasiveness of a composition is determined by measuring the gloss and surface roughness of a resin composite or an enamel surface after brushing with the composition. ESPE Filtek Supreme Ultra Universal Restorative, shade A2B (3M, St. Paul, Minn., USA), is cured in a 12.7 mm diameter, 2 mm thick metal split-mold. Mylar sheets are placed above and below the mold and glass plates are used to press the composite flat and squeeze out any extra material. A broadband multiwave LED light curing unit (Valo Grand, Ultradent Products, South Jordan, Utah, USA) is placed directly on top of the specimens and cured for 20 s at the standard setting. Excess material is removed by hand before mounting the specimens for brushing.
Samples are stored at 37° C. in the dark for a minimum of 24 h before use. The surface of the enamel specimens are prepared by polishing with varying levels of grit to produce a flat and smooth surface. Low grit sandpaper is used to create the initial flat surface (P800C, Klingspor, Haiger, Germany) and then increasing amounts of grit are used, followed by polishing. The final polishing steps are carried out on cloth pads with 3 μm and then 0.3 μm alumina oxide powder slurries (Buehler Ltd., Lake Bluff, Ill., USA). Each polishing step is carried out for approximately 1 min with pressure applied by hand.
A custom-built brushing machine (Ultradent, South Jordan, Utah, USA) simulates toothbrushing of 10 samples simultaneously. It is equipped with toothbrushes (GUM brand 459PC, Sunstar, Guelph, Ontario, Canada) with constant loads of 176 g applied during brushing. The toothbrushes are replaced after 10,000 brushing cycles. The samples are covered with a minimum of 3 mm of a 5:8 weight ratio toothpaste slurry with distilled water during brushing. Samples are rotated to a different position every 2,500 brush cycles (ensuring that the sample was brushed with the same toothpaste each time it was moved). 20,000 brush cycles represent approximately 2 years of brushing. The repetitions and position of the toothpastes in the machine are randomized with a random number generator (for each substrate material), while manually assuring there was a minimum of two repeats of the same toothpaste during a single run to ensure rotation of toothbrushes.
A glossmeter (Novo-Curve G, Rhopoint Instruments, Hastings, UK) is used to measure the gloss of the composite and enamel surfaces. The gloss is measured in three random points to create an average for the surface. The glossmeter calibration is verified each day using a traceable calibration tile with high and low reflectivity. The gloss is measured at 0, 5,000, 10,000, 15,000 and 20,000 brush cycles and new toothpaste slurry is used after measuring the gloss.
The average roughness of the surfaces is also measured before brushing and after 20,000 brushing cycles. An atomic force microscope (nGauge, ICSPI Corporation, Rev. 1.0, Waterloo, Ontario, Canada) is used to measure the average roughness at 3 different positions to form an average of the surface. A 25×25 μm area is scanned at a rate of 1200 μs/pixel. The data is analyzed using Gwyddion (http://gwyddion.net) software.
The glass compositions shown in Table 1 were all synthesized by: weighing determined amounts of the analytical grade reagents (boron oxide, rubidium carbonate, lithium carbonate, and calcium fluoride) (Sigma Aldrich, Canada). The individual formulations were mixed for 60 mins to ensure homogeneity. Each precursor blend was placed and packed in 50 mL platinum crucibles (Johnson Matthey, Noble Metals, Pa.). The pack crucible was then placed in a furnace (Carbolite, RHF 1600) at room temperature. The furnace was heated (25° C./minute) to an initial dwelling temperature of 600° C. and held for 60 minutes. The temperature was then ramped (20° C./minute) to a final dwelling temperature of 1,100° C. and held for 60 minutes. On removal, each glass melt was quenched between two stainless steel plates. The resulting quenched glasses were ground/milled separately within a planetary micro mill (Pulverisette 7, Fritsch, Germany) and sieved with ASTM E-11 compliant sieves (Cole Palmer, U.S.A) to obtain particles of <25 μm.
The particle size distribution for the exemplary glasses of Table 1 is shown in Table 2.
It should be understood that where “Dx(#)” refers to # % of particles that are smaller in size than the noted value. For example, BCF100 has a Dx(10) of 5.16 microns, which means that 10% of the particles are less than 5.16 microns in size.
The particles of the exemplary glasses of Table 1 were evaluated for fluoride release in a buffered saline solution over 12 and 24 hours using the method discuss above. The ppm values of released fluoride are shown in Table 3.
BCF201 was formulated into two toothpastes to test the abrasive effects of the glass particles, and compared to the abrasive effects of Sensodyne™ Whitening Repair and Protect™ toothpaste (“Sensodyne”), and Colgate™ Optic White™ toothpaste (“Colgate Optic”). The exemplary glass was formulated with: (a) Colgate™ Enamel Health Sensitivity Relief™ (Colgate-Palmolive, Toronto, ON, Canada) (“Colgate EN”), or (b) Gel 7 HT (Germiphene, Brantford, ON, Canada) (“Gel”), a neutral pH fluoride gel dentifrice that does not contain any abrasive materials.
The results of the abrasive tests are illustrated the following tables, and in
Additional exemplary glass compositions according to the present disclosure are shown in Table 8, along with glass compositions that are not examples of the present disclosure, which shows the mole percentages of different components.
The exemplary glass compositions, and additional compositions, shown in Table 8 were selected based on a design of mixtures (Design Expert 8.0.4, Stat-Ease Inc.) to evaluate the effect of various ranges of components on the glass composition.
The glass compositions were synthesized as described above. Briefly, sufficient amounts of analytical grade reagents (Sigma Aldrich, Canada) needed to form each of the above compositions were weighed. The individual formulations were mixed for 60 mins to ensure homogeneity. Each precursor blend was placed and packed in 50 mL platinum crucibles (Johnson Matthey, Noble Metals, Pa.). The pack crucible was then placed in a furnace (Carbolite, RHF 1600) at room temperature. The furnace was heated (25° C./minute) to an initial dwelling temperature of 600° C. and held for 60 minutes. The temperature was then ramped (20° C./minute) to a final dwelling temperature of 1,100° C. and held for 60 minutes. On removal, each glass melt was quenched between two stainless steel plates.
The following compositions are specific examples of compositions that formed glasses under the above-described quench conditions, such conditions represent one option for standard quench conditions that would be suitable for a production-scale process.
The resulting quenched glasses for the exemplary compositions listed in Table 9 had the following bulk properties:
The resulting quenched glasses for the exemplary compositions listed in Table 9 were ground/milled separately within a planetary micro mill (Pulverisette 7, Fritsch, Germany) and sieved with ASTM E-11 compliant sieves (Cole Palmer, U.S.A) to obtain particles of <25 μm.
The particle size distribution for the exemplary glasses listed in Table 9 is shown in Table 11. BCF315, BCF326 degraded in the deionized water too quickly to obtain accurate particle size measurements.
The particles of the exemplary glasses listed in Table 9 were evaluated for mass loss and fluoride release in a buffered saline solution at 1, 4 and 24 hours. Samples were prepared in 15 mL conical test tubes (n=3), which were weighed and recorded. 0.1 grams of each glass powder (<25 microns) were separately weighed out and placed in 10 mL TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) in the weighed 15 mL Falcon tubes. The tubes were sealed with parafilm before being placed in a shaking incubator at 37° C. and agitated at 120 rpm for four separate time points: 5 mins, 30 mins, 1 hr, 3 hrs, 24 hours and 48 hours. After the specified time points elapsed, the tubes were removed from the incubator and the solutions were immediately centrifuged (Eppendorf, Centrifuge 5702) at 3.0 RCF/4.4 RPM for 15 minutes. The supernatant was decanted into fresh 15 mL Falcon tubes. Additionally, samples of the 48-hour incubated powders were re-suspended in 10 mL of fresh TRIS buffered saline by vortex mixing, and allowed to incubate for an additional 8 hours (for a total of 56 hours of incubation). The re-incubated powders were processed in an identical manner as the other samples. The pellets were dried in an oven at 50° C. in their respective Falcon tubes.
The release of fluoride ions was measured using an Accumet AB250 pH/ion selective meter equipped with an Fluoride electrode (Fisher Scientific). To calibrate the probe, 6 standard solutions were prepared using a fluoride analytical standard specifically for ion selective electrodes (NaF, 0.1 F, Sigma Aldrich, Canada). The fluoride concentrations of the standards were synthesized as follows: 1000 ppm, 100 ppm, 10 ppm, 1 ppm, 0.1 ppm and 0.01 respectively, using TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) as the solvent. TISAB concentrate (4.5 mL) was added to each standard before calibration (as per manufacturer's instructions). Once the probe was calibrated, the slope of the standard was checked to ensure it was within range from the instructions of use. TISAB concentrate (1.0 mL) was added to the decanted supernatants and were then measured for its fluoride concentrations using the calibrated probe. The ion concentrations are reported as the average±SD.
The mass losses and ppm values of released fluoride are shown in Table 12. BCF314 degraded completely in the buffered saline solution before the 1 hour time point, and additionally did not include any source of fluoride.
The compositions listed in Table 8 reflect a design space. The results of the tested compositions provided the following equations, which may allow for the relative comparison of different compositions and/or which may be useful to identify trends associated with different components of the compositions. While experimental and modeling error prevents absolute prediction of glass properties, the equations may be used to guide and refine glass composition design. When used together, these models may help suggest which factors may be traded off in the tailoring of multi-component compositions within the tested composition space. In the following equations, the values for the listed components are in percentages (not fractions or decimals). For example, 50 mol % of B2O3 would be “50” (and not “0.5”).
Glass is generally expected to form under the tested quench conditions if the following formula is less than or equal to 1.60:
(2.01*ey+0.99)/(1+ey)
where y=−0.086622*[B2O3]+0.14169*[Li2O]−0.565849*[ZnO]+0.192175*[Na2O]−0.461537*[CaF2]+0.036636*[KF]+0.00365*[NaF]+0.191201*[SnF2]+0.192612*[RbO2]+0.199999*[SrO]+0.01393*[B2O3]*[ZnO]+0.012239*[B2O3]*[CaF2]−0.012412*[Li2O]*[CaF2]−0.013904*[Li2O]*[RbO2]−0.010857*[ZnO]*[CaF2]−0.013296*[ZnO]*[RbO2]−0.010699*[ZnO]*[SrO]+0.010128*[CaF2]*[KF]−0.012103*[CaF2]*[SrO].
The density of a glass may be generally predicted using the following formula:
The glass transition temperature (Tg) may be generally predicted using the following formula:
The equation related to percent of mass loss after 1 hour under the tested conditions is:
(100*ey)/(1+ey)
where y=0.088098*[B2O3]+0.062481*[Li2O]−0.262486*[ZnO]+0.055442*[Na2O]−0.165517*[CaF2]+0.089171*[KF]+0.075875*[NaF]+0.10439*[SnF2]+0.109897*[RbO2]−0.089987*[SrO]. The above equation is highly predictive for identifying glass compositions which demonstrate complete dissolution within 1 hour under the tested conditions, and may be useful for identifying other glasses which degrade under this time frame. Further, although the equation does not provide accurate mass loss estimates for slower degrading compositions, the equation may be useful to predict the relative changes in degradation which could be expected to occur with changes of the composition. Such relative changes may be used as a guide in glass composition design.
The equation related to release of fluoride (in ppm) after 1 hour under the tested conditions is:
(2750*ey)/(1+ey)
where y=−0.05785*[B2O3]−0.158337*[Li2O]−0.170872*[ZnO]−0.184773*[Na2O]+0.05638*[CaF2]+0.101381*[KF]+0.053886*[NaF]−0.307462*[SnF2]−0.183034*[RbO2]−0.184126*[SrO]. Although the above equation does not provide an accurate estimate of the amount of fluoride released for all glass compositions, the model may still be useful to predict the relative changes in fluoride release which could be expected to occur with changes of the composition.
PBF1 was synthesized by: weighing 11.60 g of B2O3, 5.30 g of Na2CO3, 2.69 g of MgO, 3.33 g of CaCO3, and 0.7 g of CaF2 (Sigma Aldrich, Canada). The starting materials were mixed for 60 mins to ensure homogeneity. The blend was placed and packed in 50 mL platinum crucibles (Johnson Matthey, Noble Metals, Pennsylvania). The pack crucible was then placed in a furnace (Carbolite, RHF 1600) at room temperature. The furnace was heated (25° C./minute) to an initial dwelling temperature of 600° C. and held for 60 minutes. The temperature was then ramped (20° C./minute) to a final dwelling temperature of 1,200° C. and held for 60 minutes. On removal, the glass melt was quenched between two stainless steel plates. The resulting quenched glasses were ground/milled separately within a planetary micro mill (Pulverisette 7, Fritsch, Germany) and sieved with ASTM E-11 compliant sieves (Cole Palmer, U.S.A) to obtain particles of <25 μm.
Comparative glass compositions (referred to as Comparative Examples (CE) 1 and 2) were synthesized similarly, using: 5.80 g B2O3, 23.66 g P2O5, 5.30 g Na2CO3, 1.34 g MgO, 6.67 g CaCO3, and 0.70 g CaF2 to result in: CE1 with about 25 mol % B2O3, about 25 mol % P2O5, about 15 mol % Na2O, about 10 mol % MgO, about 20 mol % CaO, and about 5 mol % CaF2; and 5.80 g B2O3, 23.66 g P2O5, 7.07 Na2CO3, 1.34 g MgO, 5.00 g CaCO3, and 0.70 g CaF2to result in CE2 with about 25 mol % B2O3, about 25 mol % P2O5, about 20 mol % Na2O, about 10 mol % MgO, about 15 mol % CaO, and about 5 mol % CaF2.
The density of the glass powders were measured using an AccuPyc 1340 helium pycnometer (Micromeritics, USA) equipped with a 1 cm3 insert. Prior to use, a standard with a volume of 0.718512 cm3 was used to calibrate the pycnometer. For glass analysis, the insert was packed with about 0.5 to 0.7 grams of glass powder. Three samples of each of the glasses were run and each measurement is the mean of 10 readings.
The density of PBF1 was measured as 2.5951±0.0072 g/cm3. The density of CE1 was measured as 2.7079±0.0021 g/cm3. The density of CE2 was measured as 2.6749±0.0013 g/cm3.
The release of fluoride and the loss of mass was measured for PBF1, CE1 and CE2. Samples were prepared in 15 mL conical test tubes (n=3), which were weighed and recorded. 0.1 grams of each glass powder (<25 microns) were separately weighed out and placed in 10 mL TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) in the weighed 15 mL Falcon tubes. The tubes were sealed with parafilm before being placed in a shaking incubator at 37° C. and agitated at 120 rpm for four separate time points: 5 mins, 30 mins, 1 hr, 3 hrs, 24 hours and 48 hours. After the specified time points elapsed, the tubes were removed from the incubator and the solutions were immediately centrifuged (Eppendorf, Centrifuge 5702) at 3.0 RCF/4.4 RPM for 15 minutes. The supernatant was decanted into fresh 15 mL Falcon tubes. Additionally, samples of the 48-hour incubated powders were re-suspended in 10 mL of fresh TRIS buffered saline by vortex mixing, and allowed to incubate for an additional 8 hours (for a total of 56 hours of incubation). The re-incubated powders were processed in an identical manner as the other samples. The pellets were dried in an oven at 50° C. in their respective Falcon tubes.
The release of fluoride ions was measured using an Accumet AB250 pH/ion selective meter equipped with an Fluoride electrode (Fisher Scientific). To calibrate the probe, 6 standard solutions were prepared using a fluoride analytical standard specifically for ion selective electrodes (NaF, 0.1 F, Sigma Aldrich, Canada). The sodium fluoride concentrations of the standards were synthesized as follows: 1000 ppm, 100 ppm, 10 ppm, 1 ppm, 0.01 ppm and 0.001 respectively, using TRIS buffered saline (BioUltra, Sigma Aldrich, Canada) as the solvent. TISAB concentrate (4.5 mL) was added to each standard before calibration (as per manufacturer's instructions). Once the probe was calibrated, the slope of the standard was checked to ensure it was within range from the instructions of use. TISAB concentrate (1.0 mL) was added to the decanted supernatants and were then measured for its fluoride concentrations using the calibrated probe. The ion concentrations are reported as the average±SD.
The amount of fluoride ion released by PBF1 was measured as: 89±2 ppm at 5 mins; 94±3 ppm at 30 mins; 105±5 ppm at 1 hour; and 94±7 ppm at 3 hours. There was no measurable fluoride ion released by CE1 or CE2.
The loss of mass was calculated by comparing the mass of the dried samples after their exposure to the TRIS buffered saline to the initial mass of the samples. The mass loss for PBF1 was: 42.0±2.1% after 5 minutes; 47.3±2.7% after 30 minutes; 51.5±4.3% after 1 hour; 41.7±5.7% after 3 hours; 70.1±6.8% after 24 hours; and 100% after 48 hours.
The particle size of seven different samples of PBF1 was measured using a Malvern Mastersizer 3000 model laser diffraction particle size analyzer. Glass particles were separately suspended in distilled water to obtain an obscuration value between 2-5%. Prior to analysis, the glass powder was stored in a vacuum desiccator and was removed for analysis for 3×5 runs lasting approximately 20 secs/run. Suspensions were measured using both a blue (λ=470 nm) and red (λ=632.8 nm) laser (n=5).
Apatite formation in simulated body fluid was confirmed for PBF1, but was not evident with CE1 or CE2. Simulated Body Fluid was synthesized as per the methods and instructions published by Kokubo and Takadama (Kokubo, T. and Takadama, H. Biomaterials (2006) 27:15, pp 2907-2915).
1 L batches of SBF were prepared in 1000 mL Nalgene bottle (FEP bottle). The prepared SBF was stored at room temperature for 24 hrs immediately after synthesis to ensure stability before experimental use. The SBF was preserved in a Nalgene bottle with the lid on tightly and kept at 6° C. if not needed immediately (for up to 30 days for experimental use).
As per the TCO4 method (published in Maçon, A. L. B., Kim, T. B., Valliant, E. M. et al. J Mater Sci: Mater Med (2015) 26:115) 0.75 g of glass powder of each glass composition (n=3) was immersed in 50 mL of SBF, as synthesized per above, in polyethylene containers. Containers were then placed in an incubating orbital shaker at 37° C. and agitated at 120 rpm for 3 time points: 30 mins, 3 hrs and 12 hrs. After the time points elapsed, each specimen was vacuum filtered with Whatman 42 or 5 grade filter paper (particle retention of 2.5 μm) to collect the solid material from the solution. The solids were immediately washed with distilled water and acetone to stop any further reaction.
The filtered specimens were dried in a vacuum desiccator for further analysis. Imaging of each specimen was performed using a Hitachi S-4700 FEG (Hitachi, Chula Vista, Calif.) scanning electron microscope operating at 3 KV and 15 mA under magnification of 1000× and 10000×. Samples were mounted on stubs using double sided carbon tape and sputter coated with gold-palladium for 70 s (Leica EM ACE200, Wetzlar, Germany). The scanning electron microscope images of PBF1 at 30 minutes, 3 hours and 12 hours are shown in
PBF1 was also assessed for dentin tubule occlusion by developing an application protocol and statistical analysis of SEM images graded by two assessors according to a categorical occlusion scale. Sections of human dentin (about 1 to 1.5 mm thick) were prepared from the crowns of caries-free, unrestored molars, perpendicular to the long axis of the roots, using a diamond disc saw. Each section was etched for 2 minutes with 10% citric acid, followed by water rinsing for 60 seconds, sonication for 2 minutes and a further water rinse for 60 seconds. Each section was placed into a 25 mm diameter mould and covered with 3 mm-deep acrylic resin. Once the resin hardened, the dentin face was polished sequentially with 800, and 2500-grit paper to a mirror finish. Following a deionised water rinse, the surface was etched, sonicated and rinsed once more. Sample integrity, tubule density and patency were once again checked under a light microscope, and then with SEM.
A single dentin sample was assigned to each treatment group. The dentin sample was treated with (i) an unformulated mixture of exemplary glass particles, (ii) a test toothpaste that included a mixture of exemplary glass particles, or (iii) a control toothpaste without any additional glass particles. The unformulated mixture was applied using a non-powder nitrile gloved finger for 10 seconds. The test and control toothpastes were applied to the sample with an electric toothbrush for 10 second. The toothpaste was left for 30 seconds before being rinsed until all visible paste was removed. This was repeated for a total of 4 applications of the toothpaste.
Dentin samples were dried in an oven for 1 hour at 37° C., sputter coated with gold, and visualized using a Phenom ProX Scanning Electron Microscope. Five images at ×3000 magnification were taken of different portions of each sample, in which the tubules were perpendicular to the surface. Each ×3000 micrograph was examined by two single-blinded assessors for the extend of dentin tubule occlusion based on a five-point categorical scale. The grading classification was defined as:
Mean scores for each image were derived from the scores of the two assessors. Standard deviations were calculated, though no formal statistical comparisons were made due to the fact that only one dentin sample was used per treatment group.
Seven different treatment groups were tested, as outlined in Table 14.
As discussed above, each sample treatment group was tested on a dentin sample and five SEM micrographs of each sample were taken at ×3000. Each micrograph was categorically assessed by two assessors. The average score for each micrograph, and the five micrographs per sample, were combined to obtain a group mean score and standard deviation (see Table 15).
The mean baseline score of 4.90 for treatment group 1 illustrates that virtually all dentin tubules were un-occluded. The mean score of 1.50 for the unformulated PBF1 rubbed directly into the dentin sample illustrates a nearly complete tubule blockage. The treatment groups 5, 6 and 7 (control groups lacking PBF1 or any other glass composition according to the present disclosure) had mean occlusion scores from 3.2 to 3.6. The treatment groups 3 and 4 (commercial toothpaste formulated with 5% or 15% PBF1 w/w) had lower mean occlusion scores, indicating a greater degree of tubule occlusion. The degree of occlusion for the commercially available toothpaste Sensodyne™ Complete Protection increased from about 30% occlusion (score 3.6) to about 50% occlusion (score 2.5) when 15% w/w/ of PBF1 was added.
PBF1 was further assessed for dentin tubule occlusion using a 5% w/w PBF1 sodium lauryl sulfate (SLS) paste. In this assessment, the PBF1-toothpaste and control toothpaste were applied to three different dentin samples for each treatment group. The samples were each brushed once for two minutes with the treatment toothpaste. Specifically, each dentin sample was brushed with 0.25 g of a treatment toothpaste for 120 seconds and subsequently rinsed with DI water for 30 seconds. The 5% PBF1-SLS paste resulted in a mean occlusion score of 2.7±0.84. The SLS paste without the PBF1 resulted in a mean occlusion score of 3.80±1.03. A control test using Sensodyne™ Repair & Protect resulted in a mean occlusion score of 3.90±0.66.
PBF1-Na was prepared following the protocols discussed above. Briefly, the glass was synthesized by: weighing 11.05 g of B2O3, 3.36 g of Na2CO3, 2.56 g of MgO, 4.77 g of CaCO3, and 1.33 g of NaF (Sigma Aldrich, Canada). The starting materials were mixed for 60 mins to ensure homogeneity. The blend was placed and packed in 50 mL platinum crucibles (Johnson Matthey, Noble Metals, Pa.). The pack crucible was then placed in a furnace (Carbolite, RHF 1400) at room temperature. The furnace was heated (25° C./minute) to an initial dwelling temperature of 600° C. and held for 60 minutes. The temperature was then ramped (20° C./minute) to a final dwelling temperature of 1,200° C. and held for 60 minutes. On removal, the glass melt was quenched between two stainless steel plates. The resulting quenched glasses were ground/milled separately within a planetary micro mill (Pulverisette 6, Fritsch, Germany) and sieved with ASTM E-11 compliant sieves (Cole Palmer, U.S.A) to obtain particles of <25 μm.
The particle size of ten different samples of PBF1-Na was measured as discussed above.
The density, % crystallinity, and glass transition temperatures for the ten different samples were also measured as discussed above.
The mass loss and fluoride release after 24 hours for the ten different samples were also measured as discussed above.
In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the examples. However, it will be apparent to one skilled in the art that these specific details are not required. Accordingly, what has been described is merely illustrative of the application of the described examples and numerous modifications and variations are possible in light of the above teachings.
Since the above description provides examples, it will be appreciated that modifications and variations can be effected to the particular examples by those of skill in the art. Accordingly, the scope of the claims should not be limited by the particular examples set forth herein, but should be construed in a manner consistent with the specification as a whole.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2019/051237 | 9/4/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62847807 | May 2019 | US | |
| 62727377 | Sep 2018 | US |
