Indian Patents. 263419:"A ROOT CANAL FILLING MATERIAL FORMULATION FOR PRIMARY TEETH"

Title of Invention	"A ROOT CANAL FILLING MATERIAL FORMULATION FOR PRIMARY TEETH"
Abstract	The present invention relates to a root canal filling material formulation for pnmary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source; a process for the preparation of the formulation and a method thereof.

Full Text	A ROOT CANAL FILLING MATERIAL FORMULATION FOR PRIMARY TEETH Field of the Present Invention The present invention relates to a root canal filling Material formulation for primary teeth; a method of root canal filling treatment for primary teeth in a subject in need thereof and a process for the preparation of the formulation. Background of the present Invention Endodontic treatment of primary teeth is a more challenging task as compared to their permanent counterparts1-4 because of the anatomical complexities of their root canal system5"8, proximity to the developing permanent tooth coupled with difficulty in behavior management of the child " . The major requirement for the success of root canal treatment of the primary teeth is that the root canal material should resorb at the same rate as that of their roots during physiologic resorption of primary teeth; the other factors being that it should be radio-opaque, non-toxic to the peri-apical tissue & tooth germ, easy to insert and non-shnnkable with a disinfecting property. ' Various root canal filling materials for primary teeth have been used from time to time; most commonly used and readily available are Zinc Oxide Eugenol (ZnOE) 5"8,14-20and Calcium hydroxide4',21-23. Zinc Oxide Eugenol has a slow rate of resorption2,4,,18 and has a tendency to get retained even after tooth exfoliation 2,18,19,24; in some cases un-resorbed material has been found to cause deflection of the succedaneous tooth 24,25. Zinc Oxide Eugenol has also been used in combination with different fixative agents viz. formaldehyde 26,27, formocresol 6,16,19, para-formaldehyde 26,28 and cresol26 which have their inherent cytotoxicity and other drawbacks29-32 " . Calcium hydroxide, despite its antiseptic and osteo-inductive properties33-35, has a tendency of getting depleted from the canals earlier than the physiologic resorption of the roots.4 Besides these materials, various iodoform based root canal filling materials are currently in use. Iodoform paste (after Walkhoff's paste)36 is commercially available as KRI (Paste-Pharmachemie AG, Switzerland) and contains iodoform, camphor, para-chlorophenol and menthol. Iodoform paste in combination with ZnO is available as Maisto's paste which in addition to the above-mentioned constituents contains Thymol and Lanolin . Iodoform paste in combination with Calcium hydroxide has also been used; it is commercially available as Vitapex (Neo Dental, Tokyo, Japan- In North America, DiaDent Group International Inc., Canada) and Metapex (ADT Dental Limited Co. Istanbul, Turkey) The above-mentioned iodoform containing products resorb if inadvertently get pushed beyond the apex, but rate of resorption of the material from within the canals is earlier than the physiologic root resorption.25 Another root canal filling material, a mixture of Iodoform, Calcium Hydroxide and Zinc Oxide is commercially available as Endoflas (Sanlor & Cia.S en C.S, Cali, Columbia). In addition it has eugenol (Tri-iodomethane, ZnO, Calcium Hydroxide, Barium Sulphate, Iodine, di-btiloorthocresol with liquid consisting of eugenol and paramonochlorophenol). It is reported to resorb when extruded beyond the apex but resist resorption intra-radicularly39. Eugenol, one of its constituents, is known to cause periapical irritation40. However, as such, there is questionable safety with the use of iodoform or its combinations because of allergic reaction to iodine in some individuals41 and its drawback of causing discoloration of the teeth42. Moreover, a few studies have even shown iodoform to be irritating to peri-apical tissues and causing cemental necrosis43. Bismuth iodoform paste has been reported to cause encephalopathy when used as wound dressing following head and neck surgery44. In order to overcome the disadvantages of Zinc oxide eugenol, Calcium hydroxide, Iodoform and their different formulations, Chawla et al.45 reported the use of a mixture of Zinc oxide powder and Calcium hydroxide as a root canal filling material in primary molars. This mixture was also reported to resorb earlier than the physiologic resorption of the roots of the primary teeth. One of the authors (HSC) thought that if fluoride is added in the mixture of Zinc oxide powder & Calcium hydroxide, it might form a mixture, which would resist resorption and may match with the physiologic resorption of the primary teeth. The present study was thus undertaken to evaluate the mixture of Zinc oxide powder, Calcium hydroxide and Sodium fluoride as a root canal filling material in primary mandibular molars. Objects of the Present Invention The object of the present invention relates to prepare a formulation for root canal filling material to be used in pulpectomy procedure for the primary teeth. Another object of the present invention relates to prepare a formulation for root canal filling material for primary teeth so that it would resorb along with the physiologic resorption of the primary (milk) teeth. Yet another object of the present invention relates method for root canal filling material. Still another object of the present invention relates to a process for preparing the root canal filling material formulation for primary teeth. Summary of the present Invention The present invention relates to a root canal filling material formulation for primary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source; a process for the preparation of the formulation and a method thereof. Statement of the present invention The present invention relates to a root canal filling Material formulation for primary teeth; a method of root canal filling treatment for primary teeth in a subject in need thereof and a process for the preparation of the formulation. Detailed description of the present Invention Accordingly, the present invention relates to a root canal filling material formulation for primary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source; a process for the preparation of the formulation and a method thereof. In an embodiment of the present invention, it relates to a formulation, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride. In another embodiment of the present invention, it relates to a formulation, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v. In yet another embodiment of the present invention, it relates to a formulation, wherein it is non-toxic. In still another embodiment of the present invention, it relates to a method of root canal filing treatment for primary molars in a subject in need thereof, said method comprising step of topical application of endodontically effective amount of a formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source to the subject. In still another embodiment of the present invention, it relates to a method of root canal filing treatment wherein the subject is animals and human beings. In still another embodiment of the present invention, it relates to the formulation resorbtion at the same rate as the root. In still another embodiment of the present invention, it relates to a formulation, wherein the fluoride source (sodium Fluoride) is of concentration range 2 to 15 % w/v. In still another embodiment of the present invention, it relates to a formulation, wherein the concentration of zinc oxide is about 52.43 % wt. In still another embodiment of the present invention, it relates to a formulation, wherein the concentration of calcium hydroxide is about 45.94% % wt. In still another embodiment of the present invention, it relates to a formulation, wherein the concentration of fluoride source in the formulation is about 2.62 % wt. In still another embodiment of the present invention, it relates to a formulation, wherein it is non-toxic. In still another embodiment of the present invention, it relates to a method of root canal filing treatment for primary molars in a subject in need thereof, said method comprising step of topical application of endodontically effective amount of a formulation comprising 70 mgm zinc oxide, 60mgm calcium hydroxide and 3.5mgm of sodium fluoride as fluoride source to the material. In still another embodiment of the present invention, it relates to a method of preparation of root canal filling material for primary teeth, wherein the subject is animals and human beings. In still another embodiment of the present invention, it relates to a method of root canal filling material for the primary (milk) teeth wherein the formulation resorbs at the same rate as its root during physiologic root resorption. In still another embodiment of the present invention, it relates to a process for the preparation of root canal filling material/formulation for primary molars, said process comprising step of mixing ZnO powder with Ca(OH)2 along with a fluoride source to obtain the formulation. In still another embodiment of the present invention, it relates to a process for the preparation, wherein said formulation comprising 52.43 % wt zinc oxide, 45.94 % wt calcium hydroxide and 2.62 % w/v fluoride source. In an embodiment of the present invention, it relates to a process for the preparation, wherein the fluoride source is selected from a group comprising sodium fluoride, calcium fluoride. In still another embodiment of the present invention, it relates to process for the preparation, wherein the fluoride source is of concentration range 2 to 15 % w/v. A mixture Calcium hydroxide, Zinc oxide made out by using different concentrations (2, 4,6, 8, 10 percent) of Sodium fluoride as a liquid. The 8 percent mixture, in the mid-tem evaluation is showing good results. Ca(OH)2 has alkaline pH (12), thus the mixture would be on the alkaline side, which in turn will help create a anti-bacterial action. This mixture when resorbs along with the physiological resorption of the tooth would leach out Fluoride—it is expected to get incorporated into the developing succedaneus tooth and make it caries resistant. To test this material, endodontic treatment was performed on twenty five pulpally involved mandibular primary molars in 4 to 9-year-old children; the root canals were obturated with a new root canal filling material consisting of a mixture of Calcium hydroxide, Zinc oxide and 10% Sodium fluoride solution using hand operated lentulo- spirals. All cases were evaluated clinically every 3 months and also radiographically every 6 months to assess the success and resorption of the root canal filling material from the root canals and the status of over pushed material if any, with the passage of time as the tooth resorbed. After six months, 2 teeth out of 25 had failed and one got exfoliated, while the remaining 22 were without any signs or symptoms. At the end of 2 years 14 children could be evaluated; out of these 12 had physiologically exfoliated. It was observed that the resorption of this root canal obturating mixture was quite similar to that of the physiologic root resorption of the primary teeth. In three cases, where there was an overpush of the mixture, a slow but gradual resorption was noted. The present investigation was carried out on 25 mandibular molars involving 4 to 9-year-old children. The cases were selected from amongst the patients attending the Out-Patient Department (OPD), Unit of Pedodontics and Preventive Dentistry, Oral Health Sciences Center, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The primary mandibular molars requiring endodontic treatment, depicting adequate bone support, root length, with no radigraphically discernable internal or pathological external resorbtion and without any sinus were included in the study; care was taken to select the sample from children with no history of systemic disease. Brief description of the accompanying drawings: Fig 1. shows pre- and post operative condition of the primary molar using the formulation of instant invention Fig 2. shows same rate of resorption for the formulation after 1 year and 10 months (followed till exfoliation) Fig 3. shows same rate of resorption for the formulation after 6 and 9 months Fig 4. shows same rate of resorption for the formulation after 9 months and 3 years - 2 months Fig 5. shows same rate of resorption for the formulation after 1 year 9 months (followed till exfoliation) Fig 6. shows same rate of resorption for the formulation (followed till exfoliation) Fig 7. shows same rate of resorption for the formulation after 1 year - 11 months (just before exfoliation) The root canal procedure involved primarily single-sitting pulpectomy, which was carried out by a single operator (S.S). The root canal treatment in each case was carried out under rubber dam, after administration of local anesthesia. The procedure involved cavity preparation, removal of all carious tooth structure, making a straight-line access and extirpation of pulpal debris from the root canals using files and copious irrigation with 2.5 percent sodium hypochlorite. A diagnostic radiograph was taken to ascertain the exact length of the root canal with snugly fitting files extending peri-apical to an average length of the root canal of that particular tooth. A good fit of the file into the canal is desirable to avoid error due to increase or decrease of the inserted file length during radiographic procedure. The radiographic procedure involved the removal of the rubber dam sheet from the frame and tying the free ends of the sheet together by slipping the rubber band over it. After establishing the working length, the canals were prepared with H files (30-35 size) using a pullback motion. Care was taken to do selective filing i.e. while filing the root canal; more pressure was maintained along the outer wall of the canal as the walls towards the inter-radicular areas are generally thin due to physiological resorption with an associated risk of perforation. The root canals were thoroughly irrigated with sodium hypochlorite and I.V. metronidazole solution (0.5 percent) was used as the last irrigating solution. The root canals were filled using the mixture made out of Calcium hydroxide paste, Zinc oxide powder with 10 percent Sodium fluoride solution as liquid. To standardize the quantity of each ingredient, 70 mg of zinc oxide powder was pre-weighed, placed in empty capsules and sterilized. A standard length of 7.5 cm of Calcium hydroxide paste (Reogan Rapid) was placed on the mixing pad and the ZnO powder, 70 mgm, from the pre-weighed capsule was emptied beside it. The two were mixed together along with drops of 10% sodium fluoride solution to achieve a desirable consistency. Hand lentulospiral with a clockwise rotatory motion was used to fill the material into the root canals. The lentulospiral was rotated in clockwise direction while inserting the material into the canal; and once the pre-determined length was obtained, agitating motion was done several times. Anticlockwise rotation was carried out while withdrawing the lentulospiral from the canals. The access cavity was sealed with a fast setting ZnOE paste followed by permanent filling; in some cases stainless steel crowns were given. The teeth were evaluated clinically regularly after 3 months and also radiographically every 6 months or till the exfoliation of the teeth. At each follow up visit, the teeth were assessed clinically for pain, tenderness on percussion, mobility and radiographically, for any sign of resorption of the over pushed material if any, and also from root canals as compared to the immediate postoperative radiographs. Single stage pulpectomy, using a mixture of Calcium hydroxide, Zinc oxide and 10% Sodium fluoride solution as a root canal obturation material was carried out in a total of 25 teeth, 7 first and 18 second primary molars, in 25 children aged 4 to 9 -years (Table 1). Table 1. Distribution of sample (Table Removed) Various concentrations of each of the three components of the formulation were used for filing treatment. The desired effect was obtained by using the three components in certain concentration ranges. These concentration ranges are 40 to 57% wt of zinc oxide, 40 to 50% wt of calcium hydroxide and 1 to 5% w/v of fluoride source. The patients experienced effectiveness of the filing within these concentration ranges. The teeth were followed at regularly at 3-months interval for a period of 24 months (Table 2). Table 2. Distribution of sample according to the follow up. (Please refer figures 1 to 7) (Table Removed) For the radiographic assessment, the mesial canals were considered as a single canal because of superimposition of the two canals seen on the intra-oral periapical radiographs. After a follow up period of 2 years, fourteen children involving 14 mandibular molars could be assessed; the roots of 12 primary molars had naturally resorbed and got exfoliated. Over a period of two years, the resorption of the material matched with the physiologic root resorption in all the 28 root canals, i.e. the root canal material from within the canal (intra-radicularly) resorbed along with the resorption of the roots. In three subjects where the material got over pushed, a slow but gradual resorption of the over-pushed material was observed, but even after a follow up period of more than 2 years, the over pushed material did not resorb completely in one instance. One tooth with the over pushed material beyond the apex got exfoliated physiologically along with the remaining extruded material. With predictable management and co-operation of children in clinics for dental treatment, using non-pharmacologic methods & nitrous oxide sedation and better understanding of the morphology of the root canals of primary teeth, more and more clinicians world over are recommending & performing pulpectomy procedures in these teeth. The primary goal of root canal treatment is to eliminate infection and retain the tooth in functional state until it is normally exfoliated. Pulpal management of infected primary teeth involves not only thorough debridement of the root canal system but also obturation by using a material which is bio-compatible and would resorb at the same pace as the roots of the involved tooth without endangering the succedaneous permanent tooth and its eruption. Till date, a number of investigators have tested different materials but none of these have been shown to possess requisite requirements of an ideal root canal filling material for primary teeth and having the major desirable property of its resorption matching with the physiologic root resorption of the primary teeth. Zinc oxide eugenol paste is the most frequently used root canal filling material for primary teeth. Clinical studies conducted on animals and humans have shown the success rate of ZnOE paste alone to range from 65-95 percent4'13. To improve its properties and success rate ZnoE in combinations with different compounds like formocresol6,16, formaldehyde26,27, para-formaldehyde26 and cresol26 have been tried; but the addition of these compounds neither increased the success rate nor made the material more resorbable as compared to ZnOE alone. Moreover, the use of phenolic compounds is not advocated due to their fixative nature, which has been proven to have cytotoxic, mutagenic and carcinogenic potential " . Calcium hydroxide, virtually an all purpose medicament in dentistry, ' has been widely used in permanent teeth for pulp capping and apexification; its use in primary teeth in pulpotomy has been curtailed due to the risk of internal resorption48'49. However, its use as a root canal filling material in primary teeth following pulpectomy has been reported by a few authors4,21,22 to have considerable success. A study conducted by Mam et al. has however observed the rate of calcium hydroxide resorption to be faster than the physiologic resorption of the roots and the material was seen to deplete from the canals much before their root resorption. Iodoform paste and its combinations with other compounds have been used by a number of authors with a success rate ranging from 70-90 percent3,10,11,13,50. Good clinical results utilizing Walkhoffs paste have been reported in several studies. High clinical and radiographic success has been reported using Vitapex , a commercial paste containing calcium hydroxide and iodoform that is available in pre-mixed syringes with disposables tips. The above-mentioned materials have the drawback of being resorbed earlier than the roots during physiologic resorption of primary teeth. Fuks et al. (2002)39 carried out a retrospective study , using Endoflas as a filling material, which is primarily a mixture of Calcium hydroxide, Zinc oxide, Iodoform and Eugenol. This material has been shown to have the resorption limited to excess extruded extra-radicularly without getting depleted intra-radicularly. The authors observed a lower success rate of 58% when there was over filling but 83% success in cases with flush and under filled root canals. The over-pushing of the root canal filling material is unavoidable in some cases in primary teeth is unavoidable because of the thin dentinal walls of the root canals toward the inter-radicular areas, which may give way during filing of root canals. However, the use of iodoform containing products in dentistry is questionable as such because of reported cases of iodine allergy41, discoloration of teeth42 & encephalopathy leading to coma44. Till the time the doubt regarding safety of Iodoform as root canal filling material is cleared it seems unlikely that the material shall become a material of mass usage for root canals of primary teeth. To overcome the draw backs of Calcium hydroxide (faster rate of resorption from within the canals) and ZnOE (slow rate of resorption), Chawla et al45 used a mixture of Calcium hydroxide and ZnO as a root canal filling material but this material also got depleted from the canals earlier as compared to the physiologic root resorption. In the present investigation, a mixture of Calcium hydroxide, Zinc oxide powder and Sodium fluoride (10%) was used, combing the advantages of both Calcium hydroxide and Zinc oxide. Calcium fluoride as a reaction product, gave radio-opacity to the root canal filling material, without the addition of any other radio-opaque material. The addition of fluoride was seen to give this material resorption rate, which matched with the resorption of the roots of the primary pulpectomised teeth. The probable reaction is as follows: Ca (OH)2 + ZnO + NaF (10%) to form: Sodium zincate = Na2Zn02 + CaF2 + H20 or = CaF2 + ZnF2 + H20 Fluorine is the most electronegative of all chemical elements. It has an atomic weight of 19.0 and an atomic number of 9. Combined chemically in the form of fluorides, chiefly as fluospar (CaF2), Fluoraptite (Ca (PO4)6F2) or cryolite (Na3AlF6). It is the seventeenth in order of abundance of elements in the earths crust The principal mineral of skeletal tissues is the particular crystallized form of calcium phosphate known as apatite: Ca10(Po4)6X2. When X is OH, the crystal is known as hydroxyapatite (HA) and impure HA is the main constituent of the mineralized tissues. An important property of apatite is that several different ions can occupy positions in the crystals with only minor changes in its dimension and without any significant change in its form; for example calcium ions can be replaced by strontium ions and phosphate by carbonate ions. Experiments with radioactive isotopes show that one ion may leave the crystal and be replaced by another Ca ion. Some ions are too large to enter the crystal and may become adsorbed onto the crystal surface or enter the hydration shell (the layer of adsorbed water that normally surrounds the crystal) Neuman and Newman (1958) proposed a three-stage mechanism to describe the entry of ions into the apatite crystal lattice. The first stage is that fluoride ions exchange with one of the ions or the polarized molecules present in the loosely integrated hydration cell. The second stage involves the exchange of fluoride in the hydration shell with an ion group at the surface of the apatite crystal. The ionic exchange would occur between fluoride ions and hydroxyl and bicarbonate groups and also with fluoride ions already present in the crystal. Finally, ions present in the crystal surface might slowly migrate into vacant space in the crystal interior during recrystallization. Pure HA interacts with concentrations of fluoride ions up to 100ppm by exchanging with OH ions forming a fluorohydroxyapatite (FHA) or, it goes to completion, fluorapatite (FA) with no hydroxyl ions left but a fluoride content of 3.8%(38000ppm). Some fluoride is always present in the calcified tissues so its mineral is FHA. As HA is a complicated crystal (each unit containing 18 ions), when it crystallizes it tends to contain imperfections and occasional ions are absent forming vacancies or voids in the crystal. Studies by X-ray and neutron diffraction suggest that this is especially likely to occur in the hydroxyl groups, which form a column running trough the middle of each crystal. The orientation of the OHs is reversed at various places within the crystal, some OHs pointing downwards and other pointing upwards. Where this reversal occurs two adjacent OH ions cannot point in opposite direction because the H atom would be toe close together and would not fit into the lattice. A vacancy must therefore must occur between the two OH ions pointing in opposite direction and this vacancy introduces instability into the crystal that increase s its solubility. The dimension of fluoride and OH ions are similar, so that the fluoride ion can fill the vacancy and be also attached to the neighboring OH ions by hydrogen bonds, thus making the crystal more stable i.e. dissolve less readily. With concentration of fluoride higher than 100ppm, another reaction occurs with apatite resulting in the formation of CaF2. Caio(P04) (OH)2 + 20F = 10CaF2 +6(Po4)3+ + 2 (OH)" The concentration of fluoride applied topically in solution, gels or toothpastes are sufficiently high for CaF2 to form and its spherical crystals can be seen in SEMs of the enamel surface after treatment. The CaF2 gradually dissolves and acts as a reservoir of fluoride ions that can enter plaque and also diffuse into the enamel in concentration that lead to the filling of voids or to ionic exchange with hydroxyl ions. Calcium fluoride is soluble in KOH solution, so that estimation of the fluoride soluble in a KoH solution differentiates between CaF2 and F. Although CaF2 has a low solubility in water, its retention on the teeth after formation following topical application of fluoride is longer than would be predicted in view of fairly large throughput of water in the mouth as drinking fluid as saliva. CaF2 is less soluble in saliva than in water and it suggests that in mouth crystals of CaF2 become coated with some salivary constituent identified as protein phosphate or apatite derived from it which make them less soluble. The Halides, i.e., the Fluorides, the bromides, Chloride, and Iodides are halides because their electronic configuration is similar. Fluoride out of the lot is most ectro-negative and reactive and would quickly form Ca Fluoride which is a useful compound as it is expected to leach out F ions and exerts beneficial effects. Ca(OH)2 has alkaline pH (12), thus the mixture would be on the alkaline side which in turn will help create a anti-bacterial action. This mixture resorbs along with the physiological resorption of the tooth and on resorption would leach out Fluoride which is expected to get incorporated into the developing permanent tooth under lying the Primary tooth and make it caries resistant. When calcium hydroxide, zinc oxide powder are mixed with any of the compounds of the halogen family (NaF, NaBr, NaCl, Nal), there is generally a reaction which results in the formation of sodium zincate, calcium fluoride / bromide / chloride / iodide and water. The bonding in calcium fluoride is ionic; as the size of the halogen family increases there is a gradual shift in the type of bonding i.e. a shift from ionic bond to covalent bond. This is mainly because there is less polarization as the size of the halogen family member increases. Calcium hydroxide + Zinc oxide + NaF / NaBr / NaC / Nal = sodium zincate, calcium fluoride / bromide / chloride / iodide and water. Accept for Calcium fluoride, the others are not naturally occurring in the normal enamel structure; secondly, some people may be allergic to iodine as such—so it is not desirable. Moreover, we need F in the in the ionic to be helpful to the succedaneouus (developing permanent) tooth as F ions are expected to get incorporated into the hydroxyl-apatite structure of the maturing enamel Such root canal material, as the present formulation, for the primary teeth was needed because the existing materials would either resorb earlier man the tooth resorption (Ca(OH)2-based) or retain even after resorption of the tooth. The present formulation is biological and an inert material that also has the property of resorbing along with the physiologic resorption of the primary tooth. Various concentrations of each of the three components of the formulation were used for filing treatment. The desired effect was obtained by using the three components in certain concentration ranges. These concentration ranges are 40 to 57% wt of zinc oxide, 40 to 50% wt of calcium hydroxide and 1 to 5% w/v of fluoride source. The patients experienced effectiveness of the filing within these concentration ranges. The extrusion of the root canal material in the present study was seen in the peri-apical area and not in the inter-radicular area. This may be firstly due to 'selective filing' procedure carried out while preparing the canals and secondly the inclusion criteria of the teeth in the present study which were without presence of sinus and inter-radicular radiolucency. Taking into consideration that the walls of root canal toward the succedaneous tooth are thin & weak and are prone to perforation during instrumentation, so extrusion of the material sometime cannot be prevented. Since, in the present study, in all three cases of over filling, a slow but gradual resorption of the root canal filing material was noted and it was a continuously process, there seems little danger as to the over pushed material being retained after natural exfoliation of the primary tooth. References 1. Hobson P. 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Mani SA, Chawla HS, Tewari A, Goyal A. evaluation of calcium hydroxide and zinc oxide as a root canal filling material in primary teeth ASDC J Dent Child. 2000 Mar-Apr; 67(2): 142-7, 83 24. Sadrian R and Coll JA. Long terms follow up on the retention rate of zinc oxide eugenol filler after primary tooth pulpectomy Peditr Dent 1993; 15(4): 249-252. 25. Nukro C, GarciaGodoy F. Evaluation of calcium hydroxide/Iodoform paste (Vitapex) in root canal therapy for primary teeth. J Clin Pediatr Dent 1994; 23(4) 289-294. 26. Goodman J. Endodontic treatment for children. Brit Dent J 1985; 158:363-366. 27. Starkey PE pulpectomy and root canal filling in a primary molar: report of a case. J Dent Child 1973; 40:213-217. 28. Berk H and Krakow A. A Comparison of Pulpal pathosis in deciduous and permanent teeth. Oral Surg 1972; 34(6): 945-955. 29. Myers Dr, Pashley DH, Whitford GM, McKinney RV. Tissue changes induced by absorption of formocresol from pulpectomy sites in dogs. Pediatr Dent 1983; 5:6-8. 30. Myers Dr, Pashley DH, WhitfordGM, Sobel RE, Mckinney RV. The acute toxicity of high doses of systemically administered formocresol in dogs. Pediatr Dent 1981; 3:37-41. 31. Myers DR, Shoaf HK, Dirksen TR, Poshley DH, Whitford GM, Reynolds KE. Distribution of 14C-formaldehyde after pulpotomy with formocresol. J Am Dent Assoc. 1978; 96:805-813. , 32. Pruks RS, Olen GA, Sharma PS. Relationship between formocresol pulpotomies on primary teeth and enamel defects on their permanent successors. J Am Dent Dent Assoc. 1977; 94:698-700. 33. Hendry JA, Dummett CO and Burrel W. Comparison of calcium hydroxide and zinc oxide pulpectomies in primary teeth in dogs. Oral Surg 1982; 54:445-451. 34. Sjogren U, Figdor D, Sangberg L and Sundqvist G. The antibacterial effect of calcium hydroxide as a short-term intra canal dressing. Int Endod J 1991; 24:119-125. 35. Stevens RH, Grossman. Evaluation of anti microbial potential of calcium hydroxide as an intra canal medicament. Endod 1983; 9:372-374. 36. Walkhoff o; Mein system der medicin behandlung Schwererr Erkrankungen der zahnpulpen und des Periodontium Berlin. Meusser 1928. 37. Maisto OA Endodoncia Buenos Aires Editorial Mundi 1967 pp 203-204. 38. Fuks AB, Eielman E, Pauker N. Root canal filling with Endoflas in primary teeth: a retrospective study. J Clin Pediatr Dent 2002; 27(1): 41-46. 39. Erausquin J and Muruzabal M. Root canal fillings with zinc oxide eugenol in rat molars. Oral Surg Oral Med Oral Path 1967; 24:547-558. 40. Castagnola L and Orlay HG. Treatment of gangrene of the pulp by Walkhoff's method Brit Dent J1952; 93:93-102. 41. Erausquin J, Muruzabal M. Tissue reaction to root canal filling with absorbable pastes. Oral Surg Oral Med Oral Path. 1969; 28(4): 567-578. 42. Roy PM, Harr P, Cailleux A and Allain P. Dangers of Bismuth Iodoform Paraffin Paste Lancet 194; 344:1708. 43. Chawla HS, Mathur VP, Gauba K, Goyal A. A mixture of calcium hydroxide paste and zinc oxide as a root canal filling material for primary teeth- a preliminary study. J Indian Soc Pedo Prev Dent 2001;Septl9 (3): 107-109. 44. Foreman P C and Barnes I. A review of Calcium Hydroxide, Int Endodon J. 1990; 23:283-297. 45. Martin dm AND Crabb HSM. Calcium hydroxide in Root Canal Therapy: A review. Brit Dent J 1977; 142:277-283. 46. Doyle WA, Mc Donald RE and Mitchell DF. Formocresol versus Calcium hydroxide in pulpotomy. J Dent Child. 1962; 29:86. 47. Via WF Evaluation of deciduous molars treated by pulpotomy and calcium hydroxide. J Am Dent Assoc 1995; 5:34-43. 48. Mass E and Zilberman UL Endodontic treatment of infected primary teeth using Maisto's paste. J Dent Child 1989; 56:117-120. We Claim 1. A root canal filing formulation for primary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source. 2. A formulation as claimed in claim 1, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride. 3. A formulation as claimed in claim 2, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v. 4. A formulation as claimed in claim 1, wherein the concentration of zinc oxide is about 52.43 % wt; concentration of calcium hydroxide is about 45.94 %wt; and the concentration of fluoride source in the formulation is 2.62 % w/v. 5. A method of root canal filling treatment for primary molars in a subject in need thereof, said method comprising step of topical application of endodontically effective amount of a formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source to the subject. 6. A method of root canal filing treatment as claimed in claim 5, wherein the subject is animals and human beings. 7. A method of root canal filing treatment as claimed in claim 5, wherein the formulation resorbs at the same rate as the root. 8. A method of root canal treatment as claimed in claim 5, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride. 9. A method of root canal treatment as claimed in claim 5, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v. 10. A method of root canal treatment as claimed in claim 5, wherein the concentratior of zinc oxide is about 52.43 % wt; the concentration of calcium hydroxide is about 45.94 %wt; and the concentration of fluoride source in the formulation is 2.62 % wt. 11. A process for the preparation of root canal filling formulation for primary molars, said process comprising step of mixing ZnO powder with Ca (OH)2 along with a fluoride source to obtain the formulation. 12. A process for the preparation as claimed in claim 11, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride. 13. A process for the preparation as claimed in claim 11, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v. 14. A process for the preparation as claimed in claim 11, wherein the concentration of zinc oxide is about 52.43% wt; the concentration of calcium hydroxide is about 45.94%wt; and the concentration of fluoride source in the formulation is 2.62% wt. 15. A root canal filing formulation for primary teeth, substantially as herein described with reference to the accompanying drawings. 16. A method of root canal filling treatment for primary molars in a subject in need thereof, substantially as herein described with reference to the accompanying drawings. 17. A process for the preparation of root canal filling formulation for primary molars, substantially as herein described with reference to the accompanying drawings.

Full Text

A ROOT CANAL FILLING MATERIAL FORMULATION FOR PRIMARY
TEETH
Field of the Present Invention
The present invention relates to a root canal filling Material formulation for primary
teeth; a method of root canal filling treatment for primary teeth in a subject in need
thereof and a process for the preparation of the formulation.
Background of the present Invention
Endodontic treatment of primary teeth is a more challenging task as compared to their
permanent counterparts1-4 because of the anatomical complexities of their root canal
system5"8, proximity to the developing permanent tooth coupled with difficulty in
behavior management of the child " . The major requirement for the success of root
canal treatment of the primary teeth is that the root canal material should resorb at the
same rate as that of their roots during physiologic resorption of primary teeth; the other
factors being that it should be radio-opaque, non-toxic to the peri-apical tissue & tooth
germ, easy to insert and non-shnnkable with a disinfecting property. '
Various root canal filling materials for primary teeth have been used from time to time;
most commonly used and readily available are Zinc Oxide Eugenol (ZnOE) 5"8,14-20and
Calcium hydroxide4',21-23. Zinc Oxide Eugenol has a slow rate of resorption2,4,,18 and has a
tendency to get retained even after tooth exfoliation 2,18,19,24; in some cases un-resorbed
material has been found to cause deflection of the succedaneous tooth 24,25. Zinc Oxide
Eugenol has also been used in combination with different fixative agents viz.
formaldehyde 26,27, formocresol 6,16,19, para-formaldehyde 26,28 and cresol26 which have

their inherent cytotoxicity and other drawbacks29-32 " . Calcium hydroxide, despite its antiseptic and osteo-inductive properties33-35, has a tendency of getting depleted from the canals earlier than the physiologic resorption of the roots.4
Besides these materials, various iodoform based root canal filling materials are currently in use. Iodoform paste (after Walkhoff's paste)36 is commercially available as KRI (Paste-Pharmachemie AG, Switzerland) and contains iodoform, camphor, para-chlorophenol and menthol. Iodoform paste in combination with ZnO is available as Maisto's paste which in addition to the above-mentioned constituents contains Thymol and Lanolin . Iodoform paste in combination with Calcium hydroxide has also been used; it is commercially available as Vitapex (Neo Dental, Tokyo, Japan- In North
America, DiaDent Group International Inc., Canada) and Metapex (ADT Dental Limited Co. Istanbul, Turkey)
The above-mentioned iodoform containing products resorb if inadvertently get pushed beyond the apex, but rate of resorption of the material from within the canals is earlier than the physiologic root resorption.25 Another root canal filling material, a mixture of Iodoform, Calcium Hydroxide and Zinc Oxide is commercially available as Endoflas (Sanlor & Cia.S en C.S, Cali, Columbia). In addition it has eugenol (Tri-iodomethane, ZnO, Calcium Hydroxide, Barium Sulphate, Iodine, di-btiloorthocresol with liquid consisting of eugenol and paramonochlorophenol). It is reported to resorb when extruded beyond the apex but resist resorption intra-radicularly39. Eugenol, one of its constituents, is known to cause periapical irritation40.
However, as such, there is questionable safety with the use of iodoform or its combinations because of allergic reaction to iodine in some individuals41 and its drawback of causing discoloration of the teeth42. Moreover, a few studies have even shown iodoform to be irritating to peri-apical tissues and causing cemental necrosis43. Bismuth iodoform paste has been reported to cause encephalopathy when used as wound dressing following head and neck surgery44.
In order to overcome the disadvantages of Zinc oxide eugenol, Calcium hydroxide, Iodoform and their different formulations, Chawla et al.45 reported the use of a mixture of Zinc oxide powder and Calcium hydroxide as a root canal filling material in primary molars. This mixture was also reported to resorb earlier than the physiologic resorption of the roots of the primary teeth. One of the authors (HSC) thought that if fluoride is added in the mixture of Zinc oxide powder & Calcium hydroxide, it might form a mixture, which would resist resorption and may match with the physiologic resorption of the primary teeth. The present study was thus undertaken to evaluate the mixture of Zinc oxide powder, Calcium hydroxide and Sodium fluoride as a root canal filling material in primary mandibular molars.
Objects of the Present Invention
The object of the present invention relates to prepare a formulation for root canal filling material to be used in pulpectomy procedure for the primary teeth.
Another object of the present invention relates to prepare a formulation for root canal
filling material for primary teeth so that it would resorb along with the physiologic
resorption of the primary (milk) teeth.
Yet another object of the present invention relates method for root canal filling material.
Still another object of the present invention relates to a process for preparing the root
canal filling material formulation for primary teeth.
Summary of the present Invention
The present invention relates to a root canal filling material formulation for primary teeth,
said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide
and 1 to 5% w/v of fluoride source; a process for the preparation of the formulation and a
method thereof.
Statement of the present invention
The present invention relates to a root canal filling Material formulation for primary
teeth; a method of root canal filling treatment for primary teeth in a subject in need
thereof and a process for the preparation of the formulation.
Detailed description of the present Invention
Accordingly, the present invention relates to a root canal filling material formulation for
primary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt
calcium hydroxide and 1 to 5% w/v of fluoride source; a process for the preparation of
the formulation and a method thereof.
In an embodiment of the present invention, it relates to a formulation, wherein the
fluoride source is selected from a group comprising sodium fluoride and calcium
fluoride.
In another embodiment of the present invention, it relates to a formulation, wherein the
fluoride source is solution of sodium fluoride or calcium fluoride of concentration
ranging between 2 to 15% w/v.
In yet another embodiment of the present invention, it relates to a formulation, wherein it
is non-toxic.
In still another embodiment of the present invention, it relates to a method of root canal
filing treatment for primary molars in a subject in need thereof, said method comprising
step of topical application of endodontically effective amount of a formulation
comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of
fluoride source to the subject.
In still another embodiment of the present invention, it relates to a method of root canal
filing treatment wherein the subject is animals and human beings.
In still another embodiment of the present invention, it relates to the formulation
resorbtion at the same rate as the root.
In still another embodiment of the present invention, it relates to a formulation, wherein
the fluoride source (sodium Fluoride) is of concentration range 2 to 15 % w/v.
In still another embodiment of the present invention, it relates to a formulation, wherein
the concentration of zinc oxide is about 52.43 % wt.
In still another embodiment of the present invention, it relates to a formulation, wherein
the concentration of calcium hydroxide is about 45.94% % wt.
In still another embodiment of the present invention, it relates to a formulation, wherein
the concentration of fluoride source in the formulation is about 2.62 % wt.
In still another embodiment of the present invention, it relates to a formulation, wherein it
is non-toxic.
In still another embodiment of the present invention, it relates to a method of root canal
filing treatment for primary molars in a subject in need thereof, said method comprising
step of topical application of endodontically effective amount of a formulation
comprising 70 mgm zinc oxide, 60mgm calcium hydroxide and 3.5mgm of sodium
fluoride as fluoride source to the material.
In still another embodiment of the present invention, it relates to a method of preparation
of root canal filling material for primary teeth, wherein the subject is animals and human
beings.
In still another embodiment of the present invention, it relates to a method of root canal
filling material for the primary (milk) teeth wherein the formulation resorbs at the same
rate as its root during physiologic root resorption.
In still another embodiment of the present invention, it relates to a process for the
preparation of root canal filling material/formulation for primary molars, said process
comprising step of mixing ZnO powder with Ca(OH)2 along with a fluoride source to
obtain the formulation.
In still another embodiment of the present invention, it relates to a process for the
preparation, wherein said formulation comprising 52.43 % wt zinc oxide, 45.94 % wt
calcium hydroxide and 2.62 % w/v fluoride source.
In an embodiment of the present invention, it relates to a process for the preparation,
wherein the fluoride source is selected from a group comprising sodium fluoride, calcium
fluoride.
In still another embodiment of the present invention, it relates to process for the
preparation, wherein the fluoride source is of concentration range 2 to 15 % w/v.
A mixture Calcium hydroxide, Zinc oxide made out by using different concentrations (2,
4,6, 8, 10 percent) of Sodium fluoride as a liquid. The 8 percent mixture, in the mid-tem
evaluation is showing good results.
Ca(OH)2 has alkaline pH (12), thus the mixture would be on the alkaline side, which in
turn will help create a anti-bacterial action.
This mixture when resorbs along with the physiological resorption of the tooth would
leach out Fluoride—it is expected to get incorporated into the developing succedaneus
tooth and make it caries resistant.
To test this material, endodontic treatment was performed on twenty five pulpally
involved mandibular primary molars in 4 to 9-year-old children; the root canals were
obturated with a new root canal filling material consisting of a mixture of Calcium
hydroxide, Zinc oxide and 10% Sodium fluoride solution using hand operated lentulo-
spirals. All cases were evaluated clinically every 3 months and also radiographically
every 6 months to assess the success and resorption of the root canal filling material from
the root canals and the status of over pushed material if any, with the passage of time as
the tooth resorbed. After six months, 2 teeth out of 25 had failed and one got exfoliated,
while the remaining 22 were without any signs or symptoms. At the end of 2 years 14
children could be evaluated; out of these 12 had physiologically exfoliated. It was
observed that the resorption of this root canal obturating mixture was quite similar to that
of the physiologic root resorption of the primary teeth. In three cases, where there was an
overpush of the mixture, a slow but gradual resorption was noted.
The present investigation was carried out on 25 mandibular molars involving 4 to 9-year-old children. The cases were selected from amongst the patients attending the Out-Patient Department (OPD), Unit of Pedodontics and Preventive Dentistry, Oral Health Sciences Center, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The primary mandibular molars requiring endodontic treatment, depicting adequate bone support, root length, with no radigraphically discernable internal or pathological external resorbtion and without any sinus were included in the study; care was taken to select the sample from children with no history of systemic disease.
Brief description of the accompanying drawings:
Fig 1. shows pre- and post operative condition of the primary molar using the formulation of instant invention
Fig 2. shows same rate of resorption for the formulation after 1 year and 10 months (followed till exfoliation)
Fig 3. shows same rate of resorption for the formulation after 6 and 9 months Fig 4. shows same rate of resorption for the formulation after 9 months and 3 years - 2 months
Fig 5. shows same rate of resorption for the formulation after 1 year 9 months (followed till exfoliation)
Fig 6. shows same rate of resorption for the formulation (followed till exfoliation) Fig 7. shows same rate of resorption for the formulation after 1 year - 11 months (just before exfoliation)
The root canal procedure involved primarily single-sitting pulpectomy, which was carried out by a single operator (S.S). The root canal treatment in each case was carried out under rubber dam, after administration of local anesthesia. The procedure involved cavity preparation, removal of all carious tooth structure, making a straight-line access and extirpation of pulpal debris from the root canals using files and copious irrigation with 2.5 percent sodium hypochlorite. A diagnostic radiograph was taken to ascertain the exact length of the root canal with snugly fitting files extending peri-apical to an average length of the root canal of that particular tooth. A good fit of the file into the canal is desirable to avoid error due to increase or decrease of the inserted file length during radiographic procedure.
The radiographic procedure involved the removal of the rubber dam sheet from the frame and tying the free ends of the sheet together by slipping the rubber band over it. After establishing the working length, the canals were prepared with H files (30-35 size) using a pullback motion. Care was taken to do selective filing i.e. while filing the root canal; more pressure was maintained along the outer wall of the canal as the walls towards the inter-radicular areas are generally thin due to physiological resorption with an associated risk of perforation. The root canals were thoroughly irrigated with sodium hypochlorite and I.V. metronidazole solution (0.5 percent) was used as the last irrigating solution. The root canals were filled using the mixture made out of Calcium hydroxide paste, Zinc oxide powder with 10 percent Sodium fluoride solution as liquid. To standardize the quantity of each ingredient, 70 mg of zinc oxide powder was pre-weighed, placed in empty capsules and sterilized. A standard length of 7.5 cm of Calcium hydroxide paste (Reogan Rapid) was placed on the mixing pad and the ZnO powder, 70 mgm, from the pre-weighed capsule was emptied beside it. The two were mixed together along with drops of 10% sodium fluoride solution to achieve a desirable consistency. Hand lentulospiral with a clockwise rotatory motion was used to fill the material into the root canals. The lentulospiral was rotated in clockwise direction while inserting the material into the canal; and once the pre-determined length was obtained, agitating motion was done several times. Anticlockwise rotation was carried out while withdrawing the lentulospiral from the canals. The access cavity was sealed with a fast setting ZnOE paste followed by permanent filling; in some cases stainless steel crowns were given. The teeth were evaluated clinically regularly after 3 months and also radiographically every 6 months or till the exfoliation of the teeth. At each follow up visit, the teeth were assessed clinically for pain, tenderness on percussion, mobility and radiographically, for any sign of resorption of the over pushed material if any, and also from root canals as compared to the immediate postoperative radiographs.
Single stage pulpectomy, using a mixture of Calcium hydroxide, Zinc oxide and 10% Sodium fluoride solution as a root canal obturation material was carried out in a total of 25 teeth, 7 first and 18 second primary molars, in 25 children aged 4 to 9 -years (Table 1).
Table 1. Distribution of sample
(Table Removed)
Various concentrations of each of the three components of the formulation were used for
filing treatment. The desired effect was obtained by using the three components in certain
concentration ranges. These concentration ranges are 40 to 57% wt of zinc oxide, 40 to
50% wt of calcium hydroxide and 1 to 5% w/v of fluoride source. The patients
experienced effectiveness of the filing within these concentration ranges.
The teeth were followed at regularly at 3-months interval for a period of 24 months
(Table 2).
Table 2. Distribution of sample according to the follow up. (Please refer figures 1 to
7)
(Table Removed)
For the radiographic assessment, the mesial canals were considered as a single canal
because of superimposition of the two canals seen on the intra-oral periapical
radiographs.
After a follow up period of 2 years, fourteen children involving 14 mandibular molars could be assessed; the roots of 12 primary molars had naturally resorbed and got exfoliated.
Over a period of two years, the resorption of the material matched with the physiologic root resorption in all the 28 root canals, i.e. the root canal material from within the canal (intra-radicularly) resorbed along with the resorption of the roots. In three subjects where the material got over pushed, a slow but gradual resorption of the over-pushed material was observed, but even after a follow up period of more than 2 years, the over pushed material did not resorb completely in one instance. One tooth with the over pushed material beyond the apex got exfoliated physiologically along with the remaining extruded material.
With predictable management and co-operation of children in clinics for dental treatment, using non-pharmacologic methods & nitrous oxide sedation and better understanding of the morphology of the root canals of primary teeth, more and more clinicians world over are recommending & performing pulpectomy procedures in these teeth. The primary goal of root canal treatment is to eliminate infection and retain the tooth in functional state until it is normally exfoliated.
Pulpal management of infected primary teeth involves not only thorough debridement of the root canal system but also obturation by using a material which is bio-compatible and would resorb at the same pace as the roots of the involved tooth without endangering the succedaneous permanent tooth and its eruption. Till date, a number of investigators have tested different materials but none of these have been shown to possess requisite requirements of an ideal root canal filling material for primary teeth and having the major desirable property of its resorption matching with the physiologic root resorption of the primary teeth. Zinc oxide eugenol paste is the most frequently used root canal filling material for primary teeth.
Clinical studies conducted on animals and humans have shown the success rate of ZnOE paste alone to range from 65-95 percent4'13. To improve its properties and success rate ZnoE in combinations with different compounds like formocresol6,16, formaldehyde26,27, para-formaldehyde26 and cresol26 have been tried; but the addition of these compounds neither increased the success rate nor made the material more resorbable as compared to
ZnOE alone. Moreover, the use of phenolic compounds is not advocated due to their fixative nature, which has been proven to have cytotoxic, mutagenic and carcinogenic potential " . Calcium hydroxide, virtually an all purpose medicament in dentistry, ' has been widely used in permanent teeth for pulp capping and apexification; its use in primary teeth in pulpotomy has been curtailed due to the risk of internal resorption48'49. However, its use as a root canal filling material in primary teeth following pulpectomy has been reported by a few authors4,21,22 to have considerable success. A study conducted by Mam et al. has however observed the rate of calcium hydroxide resorption to be faster than the physiologic resorption of the roots and the material was seen to deplete from the canals much before their root resorption.
Iodoform paste and its combinations with other compounds have been used by a number of authors with a success rate ranging from 70-90 percent3,10,11,13,50. Good clinical results utilizing Walkhoffs paste have been reported in several studies. High clinical and radiographic success has been reported using Vitapex , a commercial paste containing calcium hydroxide and iodoform that is available in pre-mixed syringes with disposables tips. The above-mentioned materials have the drawback of being resorbed earlier than the roots during physiologic resorption of primary teeth. Fuks et al. (2002)39 carried out a retrospective study , using Endoflas as a filling material, which is primarily a mixture of Calcium hydroxide, Zinc oxide, Iodoform and Eugenol. This material has been shown to have the resorption limited to excess extruded extra-radicularly without getting depleted intra-radicularly. The authors observed a lower success rate of 58% when there was over filling but 83% success in cases with flush and under filled root canals. The over-pushing of the root canal filling material is unavoidable in some cases in primary teeth is unavoidable because of the thin dentinal walls of the root canals toward the inter-radicular areas, which may give way during filing of root canals. However, the use of iodoform containing products in dentistry is questionable as such because of reported cases of iodine allergy41, discoloration of teeth42 & encephalopathy leading to coma44. Till the time the doubt regarding safety of Iodoform as root canal filling material is cleared it seems unlikely that the material shall become a material of mass usage for root canals of primary teeth.
To overcome the draw backs of Calcium hydroxide (faster rate of resorption from within the canals) and ZnOE (slow rate of resorption), Chawla et al45 used a mixture of Calcium hydroxide and ZnO as a root canal filling material but this material also got depleted from the canals earlier as compared to the physiologic root resorption. In the present investigation, a mixture of Calcium hydroxide, Zinc oxide powder and Sodium fluoride (10%) was used, combing the advantages of both Calcium hydroxide and Zinc oxide. Calcium fluoride as a reaction product, gave radio-opacity to the root canal filling material, without the addition of any other radio-opaque material. The addition of fluoride was seen to give this material resorption rate, which matched with the resorption of the roots of the primary pulpectomised teeth. The probable reaction is as follows: Ca (OH)2 + ZnO + NaF (10%) to form: Sodium zincate
= Na2Zn02 + CaF2 + H20 or = CaF2 + ZnF2 + H20 Fluorine is the most electronegative of all chemical elements. It has an atomic weight of 19.0 and an atomic number of 9. Combined chemically in the form of fluorides, chiefly as fluospar (CaF2), Fluoraptite (Ca (PO4)6F2) or cryolite (Na3AlF6). It is the seventeenth in order of abundance of elements in the earths crust
The principal mineral of skeletal tissues is the particular crystallized form of calcium phosphate known as apatite: Ca10(Po4)6X2. When X is OH, the crystal is known as hydroxyapatite (HA) and impure HA is the main constituent of the mineralized tissues. An important property of apatite is that several different ions can occupy positions in the crystals with only minor changes in its dimension and without any significant change in its form; for example calcium ions can be replaced by strontium ions and phosphate by carbonate ions. Experiments with radioactive isotopes show that one ion may leave the crystal and be replaced by another Ca ion. Some ions are too large to enter the crystal and may become adsorbed onto the crystal surface or enter the hydration shell (the layer of adsorbed water that normally surrounds the crystal)
Neuman and Newman (1958) proposed a three-stage mechanism to describe the entry of ions into the apatite crystal lattice. The first stage is that fluoride ions exchange with one of the ions or the polarized molecules present in the loosely integrated hydration cell. The second stage involves the exchange of fluoride in the hydration shell with an ion group at
the surface of the apatite crystal. The ionic exchange would occur between fluoride ions and hydroxyl and bicarbonate groups and also with fluoride ions already present in the crystal. Finally, ions present in the crystal surface might slowly migrate into vacant space in the crystal interior during recrystallization.
Pure HA interacts with concentrations of fluoride ions up to 100ppm by exchanging with OH ions forming a fluorohydroxyapatite (FHA) or, it goes to completion, fluorapatite (FA) with no hydroxyl ions left but a fluoride content of 3.8%(38000ppm). Some fluoride is always present in the calcified tissues so its mineral is FHA.
As HA is a complicated crystal (each unit containing 18 ions), when it crystallizes it tends to contain imperfections and occasional ions are absent forming vacancies or voids in the crystal. Studies by X-ray and neutron diffraction suggest that this is especially likely to occur in the hydroxyl groups, which form a column running trough the middle of each crystal. The orientation of the OHs is reversed at various places within the crystal, some OHs pointing downwards and other pointing upwards. Where this reversal occurs two adjacent OH ions cannot point in opposite direction because the H atom would be toe close together and would not fit into the lattice. A vacancy must therefore must occur between the two OH ions pointing in opposite direction and this vacancy introduces instability into the crystal that increase s its solubility. The dimension of fluoride and OH ions are similar, so that the fluoride ion can fill the vacancy and be also attached to the neighboring OH ions by hydrogen bonds, thus making the crystal more stable i.e. dissolve less readily.
With concentration of fluoride higher than 100ppm, another reaction occurs with apatite resulting in the formation of CaF2.
Caio(P04) (OH)2 + 20F = 10CaF2 +6(Po4)3+ + 2 (OH)" The concentration of fluoride applied topically in solution, gels or toothpastes are sufficiently high for CaF2 to form and its spherical crystals can be seen in SEMs of the enamel surface after treatment. The CaF2 gradually dissolves and acts as a reservoir of fluoride ions that can enter plaque and also diffuse into the enamel in concentration that lead to the filling of voids or to ionic exchange with hydroxyl ions. Calcium fluoride is soluble in KOH solution, so that estimation of the fluoride soluble in a KoH solution differentiates between CaF2 and F.
Although CaF2 has a low solubility in water, its retention on the teeth after formation
following topical application of fluoride is longer than would be predicted in view of
fairly large throughput of water in the mouth as drinking fluid as saliva. CaF2 is less
soluble in saliva than in water and it suggests that in mouth crystals of CaF2 become
coated with some salivary constituent identified as protein phosphate or apatite derived
from it which make them less soluble.
The Halides, i.e., the Fluorides, the bromides, Chloride, and Iodides are halides because
their electronic configuration is similar. Fluoride out of the lot is most ectro-negative and
reactive and would quickly form Ca Fluoride which is a useful compound as it is
expected to leach out F ions and exerts beneficial effects.
Ca(OH)2 has alkaline pH (12), thus the mixture would be on the alkaline side which in
turn will help create a anti-bacterial action.
This mixture resorbs along with the physiological resorption of the tooth and on
resorption would leach out Fluoride which is expected to get incorporated into the
developing permanent tooth under lying the Primary tooth and make it caries resistant.
When calcium hydroxide, zinc oxide powder are mixed with any of the compounds of the
halogen family (NaF, NaBr, NaCl, Nal), there is generally a reaction which results in the
formation of sodium zincate, calcium fluoride / bromide / chloride / iodide and water.
The bonding in calcium fluoride is ionic; as the size of the halogen family increases there
is a gradual shift in the type of bonding i.e. a shift from ionic bond to covalent bond.
This is mainly because there is less polarization as the size of the halogen family member
increases.
Calcium hydroxide + Zinc oxide + NaF / NaBr / NaC / Nal = sodium zincate, calcium
fluoride / bromide / chloride / iodide and water.
Accept for Calcium fluoride, the others are not naturally occurring in the normal enamel
structure; secondly, some people may be allergic to iodine as such—so it is not desirable.
Moreover, we need F in the in the ionic to be helpful to the succedaneouus (developing
permanent) tooth as F ions are expected to get incorporated into the hydroxyl-apatite
structure of the maturing enamel
Such root canal material, as the present formulation, for the primary teeth was needed because the existing materials would either resorb earlier man the tooth resorption (Ca(OH)2-based) or retain even after resorption of the tooth.
The present formulation is biological and an inert material that also has the property of resorbing along with the physiologic resorption of the primary tooth. Various concentrations of each of the three components of the formulation were used for filing treatment. The desired effect was obtained by using the three components in certain concentration ranges. These concentration ranges are 40 to 57% wt of zinc oxide, 40 to 50% wt of calcium hydroxide and 1 to 5% w/v of fluoride source. The patients experienced effectiveness of the filing within these concentration ranges. The extrusion of the root canal material in the present study was seen in the peri-apical area and not in the inter-radicular area. This may be firstly due to 'selective filing' procedure carried out while preparing the canals and secondly the inclusion criteria of the teeth in the present study which were without presence of sinus and inter-radicular radiolucency. Taking into consideration that the walls of root canal toward the succedaneous tooth are thin & weak and are prone to perforation during instrumentation, so extrusion of the material sometime cannot be prevented. Since, in the present study, in all three cases of over filling, a slow but gradual resorption of the root canal filing material was noted and it was a continuously process, there seems little danger as to the over pushed material being retained after natural exfoliation of the primary tooth. References
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We Claim
1. A root canal filing formulation for primary teeth, said formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source.
2. A formulation as claimed in claim 1, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride.
3. A formulation as claimed in claim 2, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v.
4. A formulation as claimed in claim 1, wherein the concentration of zinc oxide is about 52.43 % wt; concentration of calcium hydroxide is about 45.94 %wt; and the concentration of fluoride source in the formulation is 2.62 % w/v.
5. A method of root canal filling treatment for primary molars in a subject in need thereof, said method comprising step of topical application of endodontically effective amount of a formulation comprising 40 to 57% wt zinc oxide, 40 to 50% wt calcium hydroxide and 1 to 5% w/v of fluoride source to the subject.
6. A method of root canal filing treatment as claimed in claim 5, wherein the subject is animals and human beings.
7. A method of root canal filing treatment as claimed in claim 5, wherein the formulation resorbs at the same rate as the root.
8. A method of root canal treatment as claimed in claim 5, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride.
9. A method of root canal treatment as claimed in claim 5, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v.
10. A method of root canal treatment as claimed in claim 5, wherein the concentratior of zinc oxide is about 52.43 % wt; the concentration of calcium hydroxide is about 45.94 %wt; and the concentration of fluoride source in the formulation is 2.62 % wt.
11. A process for the preparation of root canal filling formulation for primary molars, said process comprising step of mixing ZnO powder with Ca (OH)2 along with a fluoride source to obtain the formulation.
12. A process for the preparation as claimed in claim 11, wherein the fluoride source is selected from a group comprising sodium fluoride and calcium fluoride.
13. A process for the preparation as claimed in claim 11, wherein the fluoride source is solution of sodium fluoride or calcium fluoride of concentration ranging between 2 to 15% w/v.
14. A process for the preparation as claimed in claim 11, wherein the concentration of zinc oxide is about 52.43% wt; the concentration of calcium hydroxide is about 45.94%wt; and the concentration of fluoride source in the formulation is 2.62% wt.
15. A root canal filing formulation for primary teeth, substantially as herein described with reference to the accompanying drawings.
16. A method of root canal filling treatment for primary molars in a subject in need thereof, substantially as herein described with reference to the accompanying drawings.
17. A process for the preparation of root canal filling formulation for primary molars, substantially as herein described with reference to the accompanying drawings.

Documents:

32-DEL-2005-32-DEL-2005-32-DEL-2005-Claims-(03-06-2013).pdf

32-DEL-2005-32-DEL-2005-32-DEL-2005-Correspondence-Others-(03-06-2013).pdf

32-DEL-2005-32-DEL-2005-32-DEL-2005-GPA-(03-06-2013).pdf

32-del-2005-abstract.pdf

32-del-2005-Claims-(27-06-2014).pdf

32-del-2005-claims.pdf

32-del-2005-Correspondence Others-(27-06-2014).pdf

32-del-2005-Correspondence-Others-(06-03-2014).pdf

32-del-2005-correspondence-others.pdf

32-del-2005-description (complete).pdf

32-del-2005-drawings.pdf

32-del-2005-form-1.pdf

32-del-2005-form-18.pdf

32-del-2005-form-2.pdf

32-del-2005-form-26.pdf

32-del-2005-form-3.pdf

32-del-2005-form-5.pdf

32-del-2005-petition-138.pdf

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Patent Number

263419

Indian Patent Application Number

32/DEL/2005

PG Journal Number

44/2014

Publication Date

31-Oct-2014

Grant Date

28-Oct-2014

Date of Filing

06-Jan-2005

Name of Patentee

POSTGRADUATE INSTITUTE OF MEDICAL EDUCATION OF MEDICAL EDUCATION AND RESEARCH

Applicant Address

ORAL HEALTH SCIENCES CENTRE POSTGRADUATE INSTITUTE POSTGRADUATE INSTITUTE OF MEDICAL EDUCATION AND RESEARCH, CHANDIGARH 160 012, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHAWLA, HARPINDER SINGH	ORAL HEALTH SCIENCES CENTRE POSTGRADUATE INSTITUTE POSTGRADUATE INSTITUTE OF MEDICAL EDUCATION AND RESEARCH, CHANDIGARH 160 012, INDIA.

PCT International Classification Number

A61C 5/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA