Powdered compositions based on polyhydroxyalkanoates and uses thereof in dental prophylaxes

Abstract

Powdered composition comprising: (a) 100 parts by weight of at least one polyhydroxyalkanoate (PHA) in the form of particles having an average diameter (d50) from 1 μm to 100 μm, preferably from 5 μm to 60 μm; (b) from 0.1 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, of at least one silicate or silica. The powdered composition, having a relatively low abrasivity index and high flowability, can be used in air-polishing without causing excessive abrasion of the enamel and of the root cementum and without causing sticking in the device. Furthermore, the presence of PHA, being a polymer characterized by high biodegradability, makes the powdered composition particularly suitable for use in the oral cavity.

Claims

1. A powdered composition, comprising: (a) 100 parts by weight of at least one polyhydroxyalkanoate (PHA) in a form of particles having an average diameter (d50) greater than or equal to 1 micron (μm) and less than or equal to 100 μm: and (b) greater than or equal to 0.1 parts by weight and less than or equal to 10 parts by weight of at least one silicate or at least one silica.

2. The powdered composition of claim 1, wherein the at least one PHA is in the fou ii of particles having substantially spherical shape and a polydispersity index (span) greater than or equal to 1.0 and less than or equal to 2, where the span is a ratio (d90-d10)/d50, where d90 is a diameter value below which 90% by weight of a population of the particles is found, where d10 is the diameter value below which 10% by weight of the population of the particles is found, and where d50 is the diameter value below which 50% by weight of the particle population of the particles is found (median value).

3. The powdered composition of claim 1, wherein the at least one PHA is selected from: polyhydroxybutyrate (PHIS), polyhydroxybutyrate-hydroxyvalerate copolymer, or a mixture thereof.

4. The powdered composition of claim 1, wherein the at least one silica is selected from: pyrogenic silica or colloidal silica.

5. The powdered composition of claim 1, wherein the at least one silicate is selected from: phyllosilicatesor or hydroxysilicates.

6. The powdered composition of claim 1, wherein the at least one silicate or the at least one silica is in a form of particles having an average diameter (d50) greater than or equal to 1 in and less than or equal to 50 μm.

7. The powdered composition of claim 1, wherein the at least one silica comprises hydrophobic silica.

8. The powdered composition of claim 1, further comprising an additional component selected from: calcium phosphate, calcium carbonate, calcium bicarbonate, fluorinated salts, or mixtures thereof.

9. The powdered composition of claim 8, wherein the additional component is present in an amount greater than or equal to 5 parts by weight and less than or equal to 90 parts by weight.

10. The powdered composition of claim 1, further comprising: greater than or equal to 0.1 parts by weight and less than or equal to 10 parts by weight of at least one sulfate of metal selected from: alkali metals, alkaline earth metals, or aluminum.

11. The powdered composition of claim 1, having a flow index, determined by the “flow through an orifice” method described in chapter 2.9.36 of the European Pharmacopoeia (IX Edition of 1 Jan. 2017), less than or equal to 20.

12. The powdered composition of claim 1, further comprising: greater than or equal to 0.1 parts by weight and less than or equal to 5 parts by weight of at least one flavoring.

13. The powdered composition of claim 1, further comprising: an additional abrasive component selected from: sodium bicarbonate, glycine, or erythritol, in an amount greater than or equal to 1 part by weight and less than or equal to 50 parts by weight.

14. The powdered composition of claim 1, further comprising: at least one adjuvant additive selected from: hemostatic agents, antimicrobial agents, bleaching agents, soothing agents, gum revitalizers, or dyes.

15. The powdered composition of claim 1, wherein the at least one PHA in the form of particles is obtained from aqueous suspension of the at least one PHA using an atomization (spray drying) process.

16. A method of dental prophylaxis, the method comprising: air-polishing teeth using the powdered composition of claim 1.

17. The method of claim 16, wherein the teeth are human teeth.

18. The method of claim 16, wherein the teeth are other than human teeth.

19. A powdered composition, comprising: (a) 100 parts by weight of at least one polyhydroxyalkanoate (PHA) in a form of particles having an average diameter (d50) greater than or equal to 5 microns (μm) and less than or equal to 60 μm; and (b) greater than or equal to 0.1 parts by weight and less than or equal to 10 parts by weight of at least one silicate or at least one silica.

20. A powdered composition, comprising: (a) 100 parts by weight of at least one polyhydroxyalkanoate (PEIA) in a form of particles having an average diameter (d50) greater than or equal to 1 micron (μm) and less than or equal to 100 μm; and (b) greater than or equal to 0.5 parts by weight and less than or equal to 5 parts by weight of at least one silicate or at least one silica.

Description

EXAMPLE 1

(1) A powdered composition was prepared as outlined in Table 1:

(2) TABLE-US-00001 TABLE 1 parts by Component % (w/w) weight polyhydroxybutyrate 60 100 (PHB) hydroxyapatite 38 63.3 natural orange 1.5 2.5 flavouring hydrophobic pyrogenic 0.5 0.8 silica

(3) The PHB was in the powder form obtained through spray drying an aqueous suspension of PHB.

(4) Through a laser diffraction particle size analyzer (Mastersizer 3000 by Malvern), equipped with a wet dispersion unit, the particle size of the PHB was determined after spray-drying. For that purpose, increasing quantities of the powdered PHB were dispersed in water, until a laser obscuration value of about 10% was reached. The average particle diameter, expressed as d50, was equal to 30 μm, while the polydispersity index (span) was equal to 1.90.

(5) The pyrogenic silica was made hydrophobic through treatment with 1,1,1-trimethyl-N-(trimethylsilyl) silanamine, and had a surface area (BET) equal to 230-290 m.sup.2/g.

(6) Flow Index.

(7) The flow index of the above powdered composition was evaluated.

(8) The flow index was determined through the “flow through an orifice” method described in chapter 2.9.36 of the European Pharmacopoeia (IX Edition of 1 Jan. 2017), using the “Powder Flowability Test Model BEP2” instrument.

(9) In particular, 50 g of powdered composition were placed in a hollow cylinder closed, in the lower portion, by a disc provided with an orifice of a known diameter. A collecting beaker was placed below the cylinder in proximity to the orifice. The test is positive when the powdered composition flow from the orifice leaving it clearly visible to an observer located above the cylinder. The test was sequentially repeated with discs provided with an orifice of a gradually smaller diameter. The value of the flow index coincides with the diameter (expressed in mm) of the smallest orifice with which the test result was positive.

(10) For the above composition a flow index of 18 was determined.

(11) Transport Speed.

(12) For the above powdered composition, the transport speed in an air-polishing device (“Combi touch” apparatus made by Mectron SpA) was evaluated. The powdered composition was made to flow through the device, in the absence of water, for about 1 minute. The jet of powder and air was conveyed into a collecting beaker full of water, in order to collect all of the powdered composition that flows through the device.

(13) Thus a transport speed of 2.30 g/min was measured.

(14) Abrasivity Index.

(15) For the above powdered composition the abrasivity index of the dentin was evaluated.

(16) The test was performed in vitro on recently extracted bovine teeth. After extraction the teeth were washed by rinsing with deionized water. Subsequently the surface of the tooth root was smoothed through treatment with abrasive paper. The teeth thus treated were fixed to a support and covered with a film only leaving a strip 2 mm wide uncovered at the tooth root. At this point the zone without film was treated with the air-polishing technique using the above powdered composition in an air-polishing device (“Combi touch” device made by Mectron SpA). The air-polishing treatment was performed for 10 seconds at a jet pressure of 4 bar and at a distance of 4 mm from the tooth root to the device.

(17) After the air-polishing treatment was completed, the abrasivity index was evaluated, i.e. the loss of dentin through a Hirox 3D digital microscope.

(18) The evaluation was performed by marking out 5 depth profiles perpendicular to the plane on which the 2 mm wide strip lies and calculating the average of the 5 depth measurements of the defects created following the air-polishing treatment. The average value of the depth measurements was expressed in μm and corresponds to the abrasivity index of the powdered composition used for performing the air-polishing treatment.

(19) For the above composition of Example 1 an abrasivity index of 1.5 μm was determined.

(20) From the results obtained it is therefore possible to state that the powdered composition according to the present invention has a sufficient abrasivity index for the removal of plaque but however relatively low, therefore it does not cause any excessive abrasion of the enamel or the root cementum. Furthermore, the presence of PHA, being a polymer characterized by high biodegradability and biocompatibility, makes the powdered composition particularly suitable for use in the oral cavity. Furthermore, the flow index and transport speed measurements demonstrate that the composition can be effectively used in an air-polishing device, without causing any sticking or flow irregularities.

EXAMPLE 2

(21) A powdered composition as reported in Table 2 was prepared:

(22) TABLE-US-00002 TABLE 2 parts by Component % (w/w) weight polyhydroxybutyrate 81.5 100 (PHB) sodium bicarbonate 15 18.4 natural orange 2.5 3.1 flavouring hydrophobic pyrogenic 1 1.2 silica

(23) The PHB, hydrophobic pyrogenic silica and sodium bicarbonate were the same ones used in Example 1. The average particle diameter (d50) was equal to 40 μm and the polydispersity index (span) was equal to 2.00.