Abstract:
Disclosed is dental root canal filling (intracanal medicament) compositions that are effective against resistant root canal infections caused by  Enterococcus faecalis  and Vancomycin-resistant Enterococci.

Description:
This application is the U.S. national phase of International Patent Application No. PCT/IN2012/000619, filed Sep. 17, 2012, which claims the benefit of Indian Patent Application No. 2619/MUM/2011, filed Sep. 15, 2011. 
     FIELD OF THE INVENTION 
     The present invention relates, in general, to the field of endodontic materials suitable for root canal filling and, in particular, to a dental root canal filling composition that are effective against most infection causing root canal based micro organisms including resistant root canal infections caused by  Enterococcus faecalis  and Vancomycin-resistant Enterococci. 
     BACKGROUND OF THE INVENTION 
       Enterococcus faecalis  has often been isolated from asymptomatic and persistant root canal infections, chronic apical periodontitis and failed endodontic cases. It can survive in dentinal tubules for up to 10 days without nutrient supply. Serine protease and Ace aid in the adhesion of  Enterococcus faecalis  with dentin. 
     Calcium hydroxide has widely been accepted and used as a dental intracanal medicament because of its antimicrobial properties and its action on gram negative bacteria. It releases hydroxyl ions that are responsible for the creation of high alkalinity which has a destructive effect on bacterial cytoplasmic membrane and protein structure. The cytoplasmic membrane in most organisms is similar, irrespective of morphologic, tinctorial and respiratory characteristics of the organism. This means that calcium hydroxide will have similar effects on aerobic, anaerobic, gram positive and gram negative organisms. A pH of 10.5-11 delays the growth of  Enterococcus faecalis , while a pH of 11 or more is known to eliminate  Enterococcus faecalis . However,  Enterococcus faecalis  contains a proton pump that carries protons to the interior of the cell, acidifying its cytoplasm in situations of increased alkalinity in its environment. Thus,  Enterococcus faecalis  has been found to be resistant to most intracanal medicaments containing calcium hydroxide. 
     Linezolid is a synthetic antibiotic of the oxazolidinone group. It has been shown to be effective only on gram positive organisms. It inhibits protein synthesis in micro-organisms by disrupting the translation of messenger RNA (mRNA) into proteins in the ribosome. Linezolid acts during the initiation of protein synthesis by binding to the 23S portion of the 50S subunit (the centre of peptidyl transferase activity), preventing the formation of 70S ribosome complex that is responsible for the formation of the ‘initiation complex’ (composed of 30S and 50S subunits of the ribosomes, tRNA and mRNA). 
     Linezolid has been medically used for the treatment of skin and soft tissue infections, diabetic foot infections, pneumonia, infective endocarditis, tuberculosis, neutropenia, endophthalmos, meningitis, bone and joint infections including chronic osteomylitis. It has also shown to be effective against certain organisms which are also found inside root canals of teeth like:  Staphylococccus aureus, Streptococcus agalactiae, Streptococcus pneumonia, Streptococcus pyogens, Streptococcus viridans  group,  Listeria monocytogenes  and  Corynebacterium . Linezolid is also effective against organisms responsible for resistant root canal infections like  Enterococcus faecalis, Vancomycin -resistant  Enterococcus faecalis  and Vancomycin-resistant Enterococci. 
     The present inventors have meticulously carried out earnest work and devised a dental root canal filling composition that is very effective resistant root canal infections caused by  Enterococcus faecalis  and Vancomycin-resistant Enterococci. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to provide dental root canal filling compositions for use during an endodontic procedure. The dental root canal filling compositions according to the present invention comprises an antibiotic agent linezolid, calcium hydroxide and other pharmaceutically acceptable excipients. 
     The dental root canal filling compositions according to the present invention are effective against resistant root canal infections caused by  Enterococcus faecalis  and Vancomycin-resistant Enterococci. 
     These and other additional features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described with respect to particular embodiments but the invention is not limited thereto only by the claims. Where an indefinite or definite article is used when referring to a singular noun e.g. “a” or “an”, “the”, this includes a plural of that noun unless something else is specifically stated. 
     In the embodiments of the present invention, the dental root canal filling composition comprises of 2 to 10% by weight of linezolid, 30 to 60% by weight of calcium hydroxide, 2 to 20% by weight of a tackifier selected from the group consisting of polyethylene glycol, polyvinyl pyrrolidone, polyvinyl methylether, carbopol or a combination thereof, and 30 to 65% by weight of liquid paraffin. 
     In some embodiments of the present invention, the dental root canal composition further comprises a radio-opaque material selected from but not limited to barium sulphate, bismuth subnitrate, bismuth trioxide, bismuth carbonate and zirconium oxide. In some preferred embodiments, amount of the radio-opaque material is preferably 5 to 20 parts by weight based on 100 parts by weight of the filling composition. 
     In some embodiments of the present invention, the dental root canal composition further comprises a disinfectant in amount of 0.5 to 5 parts by weight based on 100 parts by weight of the filling composition. In some preferred embodiments, the disinfectant is selected from iodoform and iodine. 
     The following examples illustrate the present invention and are not to be construed as limiting the spirit and scope of the invention. 
     EXAMPLE 1 
     A dental root canal filling composition was formed having the following components and concentrations range: 2-10% by weight of linezolid, 30-60% by weight of calcium hydroxide, 2-20% by weight of polyethylene glycol, 5-20 parts by weight of barium sulphate based on 100 parts by weight of the filling composition, 0.5-5 parts by weight of iodoform based on 100 parts by weight of the filling composition, and 30-65% by weight of liquid paraffin. 
     EXAMPLE 2 
     A dental root canal filling composition was formed having the following components and concentrations range: 2-10% by weight of linezolid, 30-60% by weight of calcium hydroxide, 2-20% by weight of polyethylene glycol, 5-20 parts by weight of barium sulphate based on 100 parts by weight of the filling composition, 0.5-5 parts by weight of iodine based on 100 parts by weight of the filling composition, and 30-65% by weight of liquid paraffin. 
     EXAMPLE 3 
     A dental root canal filling composition was formed having same components and concentrations as in Examples 1-2 except that polyvinyl pyrrolidone was used instead of polyethylene glycol. 
     EXAMPLE 4 
     A dental root canal filling composition was formed having same components and concentrations as in Examples 1-2 except that polyvinyl methylether was used instead of polyethylene glycol. 
     EXAMPLE 5 
     A dental root canal filling composition was formed having same components and concentrations as in Examples 1-2 except that carbopol was used instead of polyethylene glycol. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrated and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.