Dental treatments

Abstract

Dental methods and materials are disclosed for treating diseased or traumatized teeth and peridontal tissues. Physiologically compatible and soluble calcium phosphate compounds are prepared into a porous aggregate paste or powder and positioned adjacent to calcified tissue in contact with a blood supply. Such a technique permits improved methods for pulp capping procedures, root canal procedures, tooth replanting procedures and for corrective peridontal procedures.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to dental procedures for treating various trauma and disease conditions. More particularly this invention relates to materials and treatment procedures for enabling the growth of certain tissues to provide repairs of improved efficacy, predictability and longevity.

With many types of dental treatments or procedures, it is desirable that the human body regenerate tissues in order to restore health and function to diseased or traumatized teeth, peridontal tissues, or supportive bone. This is true for example, with pulp capping procedures, root canal procedures, corrective peridontal procedures and tooth replanting procedures.

Pulp capping treatment is used where there has been an exposure or opening into the pulp chamber of the tooth because the pulp has been insulted by disease or injury. An exposed pulp will become hyperemic, infected and devital if left untreated. The pulp capping procedure involves the placing of a material in the opening. This material should reduce the inflammation and allow the pulp to heal. Additionally, it should cause a dentinal bridge to be laid down spanning the opening into the pulp chamber via odontoblastic cells of the pulp.

Many different agents have been used as pulp capping materials with various degrees of success. Such agents include charcoal, ivory chips, sulfa drugs, a variety of antibiotics, anti-inflammatory corticoides, zinc-oxide-eugenol, calcium hydroxide and formocresol. At the present time, zinc oxide-eugenol and calcium hydroxide are the two materials most commonly employed in pulp capping treatment of adult teeth.

Although calcium hydroxide can cause formation of a calcified bridge, such a calcium hydroxide induced bridge is usually not continuously connected from one side of the defect to the other. Usually an opening or hole remains in the calcium hydroxide induced bridge forming an avenue which may leak and may permit the passage of saliva and bacteria into the pulp chamber causing infection and inflammation of the pulp. It is known also, that a calcified bridge induced by calcium hydroxide often breaks down eventually, resulting in pulpal necrosis.

Thus a need exists for a material and procedure which will consistently permit the formation of a healthy system of odontoblasts to form and maintain a permanent and continuous, protective, dentinal layer or bridge impervious to noxious stimuli.

If focal disease within a tooth pulp is not treated soon enough, the pulp will become totally diseased and necrotic. Necrosis of the diseased pulp will cause the emission of toxic products through the apex of the tooth root, producing inflammation of peridontal tissues, and frequent abcess formation. Such a condition will often initiate resorption of the root with destruction of the apex. In devital teeth which have undergone a significant degree of root resorption, the resultant open apex makes filling and sealing of the root canal with a dense material virtually impossible unless retrograde surgical procedures are employed. A similar, open apex, condition exists in young devital teeth which have not yet developed closed apices.

If an open apex tooth is cleaned out with files and an attempt is made to fill it, there is nothing against which to pack the filling material. Therefore the root canal may not be hermetically sealed by merely packing in a filling material. A non-sealed root canal will leak and allow the exchange of tissue fluids, metabolic breakdown products and probably initiate a chronic inflammatory condition. After two to four years many open apex root canals, treated but not properly sealed, break down with the periapical tissues becoming reinfected, possibly with the formation of another abcess.

The purpose of this type of root canal procedure, is to provide a wall at the apex against which a dense filling material may be packed thus preventing leakage or the ingrowth of undesirable cell structures into the root canal.

There presently are three basic techniques used in the endodontic treatment of nonvital teeth with open apices. The first is to gain access to the tooth apex surgically and mechanically close the apical opening through the insertion of a retrograde filling material, generally amalgam. The second is to introduce a filling material into the root canal by way of an occlusal access opening and obturate or fill the root canal. This filling material is generally gutta-percha. The third technique is to induce apical closure by placing a medicated dressing within the root canal. This dressing is conventionally a mixture containing calcium hydroxide.

The third technique does produce some continued apical development and restriction. However, a substantial number of cases have been observed which do not respond to such treatment. Even after continuous treatment of 2 years and longer, there are cases which have not responded favorably. When apical closure is not obtained, endodontic failure often occurs due to the recurrence of an acute inflammatory condition. This condition historically dictates surgical intervention for the placement of a retrograde filling or the extraction of the tooth.

There is therefore a need for a technique and material which can reliably provide the physiological closure of an open apex tooth against which a filling material may be packed to obtain a permanent and complete seal.

The peridontal ligament and periapical bone, supporting the involved tooth, is often lost in the immediate area of the apex. Conventionally, no separate definitive treatment is administered to allow for specific regeneration of these tissues. Healing or regeneration normally proceeds in these areas after the infective process has been eliminated. However, peridontal ligament fibers which are regenerated do not reorient themselves in the same fashion found prior to their destruction.

Thus, functional forces and stresses, placed upon endodontically treated teeth, are not properly transmitted to the supporting bone. This lack of proper force transmission, allows a chronic inflammatory process to persist in the immediate area of the tooth root apex. Bone is never fully regenerated under such circumstances. In fully 92 per cent of all endodontically treated teeth, a chronic inflammatory process or condition exists in the immediate area of the root apex.

There is therefor a need for a treatment and material which would allow for the re-establishment of a peridontal ligament with normally oriented fibers, thus allowing for the transmission of forces to the supporting bone, with possible elimination of the chronic inflammatory condition and establishment of a more normal bone level or pattern about the root apex.

In still another dental procedure, a dentist is occasionally called upon to replant a tooth which has been accidentally avulsed from the mouth, for example, through an athletic inuury. Even when such a tooth is replaced within the first few minutes, resorption of the root usually begins which results in eventual loss of the tooth. There is therefore a need for a material and a technique to enable a dentist to replant avulsed teeth with the elimination of subsequent root resorption.

SUMMARY OF THE INVENTION

Most broadly defined, the method of the present invention comprises the positioning of one or a plurality of physiologically soluble and compatible calcium phosphate compounds in various forms adjacent to various radicular and periapical calcified tissues and in contact with a blood supply, sufficient to permit formation of a blood clot in the calcium phosphate compounds. The invention contemplates the positioning of the calcium phosphate compounds at both the interior and the exterior of a tooth as described more particularly in the following discussion. The method of the present invention enables the growth of the appropriate tissue elements; fibroblasts, odontoblasts, cementoblasts, and osteoblasts, at the appropriate sites, where needed, in or around a treated tooth.

It is therefore an object of the invention to enable the regeneration of tissues in a manner which provides a substantially permanent repair of a tooth and its supporting structure permitting normal function.

It is another object of the invention to provide an improved pulp capping technique.

Still another object of the invention is to provide an improved root canal technique.

Yet another object of the invention is to provide an improved technique for replanting teeth.

Further objects and features of the invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings illustrating several embodiments of the invention.

DETAILED DESCRIPTION

The following particular dental procedures are described as examples of techniques embodying the present invention. The material used in the following techniques are physiologically soluble and physiologically compatible calcium phosphate compounds. The most effective materials are high purity forms of .alpha.Ca.sub.3 (PO.sub.4).sub.2 and .beta.Ca.sub.3 (PO.sub.4).sub.2, commonly known as whitlockite and CaHPO.sub.4, commonly known as Brushite and mixtures thereof. However, other calcium phosphate compounds are contemplated. We have found that CaH.sub.4 (PO.sub.4).sub.2 does not work because it does not meet the above definition.

In the family of calcium phosphate compounds defined as above, the invention contemplates the use of those compounds which have minimal or no harmful effects on the human body and additionally have a strong tendency to go into solution as calcium and phosphorous in body fluids to be either retained in or eliminated from one body.

Although these materials may be used in the form of small crystals or ground into a suitable powder, it has been found particularly desirable to sinter particles of the desired material into porous blocks and then grind the blocks into a granular material. This sintering and subsequent grinding improves the porosity of the granular material. Sterile water, normal physiological saline solution, methyl cellulose or other suitable vehicle, is then mixed in sufficient quantity with the finer forms of granular powder to form a putty-like mixture. This putty-like paste form of the preferred materials, is advantageous for use in performing procedures of the present invention. It is very plastic and consequently, is easy to use. The smaller the particles are ground from the sintered block the more plastic and consequently the more advantageous the material becomes. It is also particularly desirable that the powder be ground into particles so small that the surface forces become an important factor in determining its properties, approaching colloidal properties.

PULP CAPPING TECHNIQUE

In performing the pulp capping procedure according to the present invention, the tooth is prepared by removing decay and diseased tooth structures until sound hard dentin and viable pulp tissue is present. In this manner, the diseased tissue is cleaned out with, for example, a dental bur or excavator and occasional irrigation using substantially conventional dental skills and techniques. The cavity formed in this manner must extend into communication with a blood supply. There must therefore be bleeding from a portion of the pulp.

The size of the pulpal opening and the amount of diseased pulp tissue removed is, of course, dependent upon the extent to which the diseased pulpal condition has progressed. The size may vary from a minor insult upon the pulp to a pulpotomy which is the removal of all the coronal pulp down to the orifice of the root canals leaving only the pulp tissue in the root canal.

A layer of the dry granular powder or putty-like material, described above, is then laid upon the bleeding pulp as a pulp capping agent. This layer may be 1mm to 2mm thick. Upon this layer, a dental base material is placed. Carboxylate cement or zinc ozide eugenol preparations have been used. The dental base, or cement layer keeps the pulp cap in place, provides some insulation and presents forces from being exerted directly upon the pulp cap and the pulp tissues while placing an amalgam or other restoration upon the tooth.

According to our best current opinion, the pulp capping agent operates in the following manner. Blood from the bleeding pulp seeps into the calcium phosphate compound and forms a blood clot having fibrin fibrils. Endothelial cells are then laid down to form a vascular blood supply within the porous aggregate of the capping agent. Undifferentiated mesenchymal cells then migrate out of the walls of the blood vessels into the matrix of the pulp capping agent. These cells differentiate into fibroblasts or odontoblasts which begin laying down colagen, which in turn subsequently mineralizes. Calcifications are observed around and entrapping the particles of pulp capping agent.

Simultaneously, with this intramatrical proliferation of tissue, the pulp capping agent, according to the present invention, is slowly being resorbed. As time progresses, the calcifications become thicker and eventually replace the pulp capping agent and form a continuous and protective bridge. Eventually, after sufficient maturation, the cells adjacent to the pulpal aspect of the bridge appear to be true odontoblasts which lay down what appears to be secondary dentin.

It was observed that with treatment according to the present invention, the odontoblasts of the pulp tends to remain in close association with the tissue of the dentinal bridge. With the conventional pulp capping techniques, the pulp often retreats from the bridge as from a foreign body and local foci of necrosis are often seen as well as internal resorption of the root canal walls.

PULP CAPPING EXPERIMENTS

Twenty-eitht teeth of four cynalmolgus monkeys were used in this experiment. Radiographs were taken before and after each pulp-capping procedure. Molars and pre-molars were selected as teeth of choice because of their larger pulp chambers. Upper right first molars and upper right pre-molars were used as control teeth utilizing calcium hydroxide. .beta.-phase tricalcium phosphate was used in the remaining molar and pre-molar teeth as the pulp capping agent.

The animals were anesthetized with Sernylan and Pentobarbitol. Atropine was used to decrease saliva flow. The teeth were isolated under rubber dam and disinfection was attempted using Betadine solution for five minutes. The occlusal portion of the vital tooth was opened with a high speed No. 4 round bur. This same bur was used to remove the roof of the pulp chamber. The vital pulp tissue of the chamber was removed with a small spoon excavator hoping to reduce injury to the remaining vital pulp tissue in the root canals. After the pulpotomy was completed, hemorrhage was controlled with a sterile cotton pellet. Pressure was applied until a blood clot formed on the canal tissue stumps. Excess blood and clot were rinsed from the chamber with physiological saline.

Calcium hydroxide powder plus physiological saline was mixed into a paste and used as the control pulp-capping material. .beta.-phase tricalcium phosphate powder and physiological saline was mixed into a similar type paste. Calcium hydroxide paste was used in seven teeth and .beta.-phase tricalcium phosphate paste was used in twenty-one teeth. Pulpal hemorrhage was controlled by pressure application of sterile cotton pellets followed by the application of the pulp capping materials on the exposure site. Due to evaporation of the saline solution, it was difficult to place the same amount of paste over each exposure site.

After the calcium hydroxide or tricalcium phosphate paste was placed as the pulp-capping agent, a mix of fast setting zinc oxide eugenol was used to form a protective base before the placement of the final amalgam restoration. Care was taken to attempt to place the zinc oxide eugenol base without pushing the pulp-capping materials into the remaining pulpal tissues.

The monkeys were anesthetized with Sernylan and sacrificed by profusion with 10 per cent formalin to allow 2, 3, 5, 8, 16 and 24 weeks studies to be considered. After death the mandible and maxilla were removed, stripped of soft tissue and sectioned so one tooth remained in each section. After fixing the block section in 10 per cent formalin for two weeks, the sections were demineralized in 5 per cent formic acid. The specimens were then imbedded in paraplast and cut serially at 6-10 microns. Each section was cut longitudinally in a mesio-distal plane. Every fifth section was stained routinely with hematoxylin and eosin stain and examined microscopically. In areas of importance to the study, every section was stained.

Before the pulp-capping procedures were started or before the animal was sacrificed, a clinical evaluation of the tissue was completed. No fistulas were found before or after the procedures. The gingival tissue was classified from as mild to severe inflammation which is common among the monkey population due to the large amount of calculus present. Radiographs were taken before the pulp-capping procedures, immediately following the procedure and at time of animal sacrifice. No abcess formations were evident on the radiographs. Due to the small pulp canals it was very difficult to conclude that the radiographs showed evidence of a protective bridge; either with calcium phosphate or calcium hydroxide. The following results are histological evidence of the specimens.

2 week post-op experimental

Three specimens were used. The specimens showed evidence of a calcified matrix formation. There was no evidence of a calcified bridge. There was a characteristic "compartmenization" that is evident from the two-week through the twenty-four week studies. These compartments appear to be areas of connective tissue surrounding the calcium phosphate particles with evidence of large amounts of blood supply. The compartments give the appearance of a "basket-weave" with the connective tissue and calcium phosphate particles weaving through out the coronal portion of the canal. The inflammation index was low, the odontoblasts are viable, and blood supply was evident in great quantity. There was evidence of a thickened pre-dentin layer. The periapical tissue was healthy and without inflammation.

2 week post-op control

Two specimens were used. One specimen showed complete necrosis through out the pulp chamber and canals. The other specimen showed evidence that a calcified matrix was starting to develop. Inflammation was evident in the coronal portion of the pulp canals. Inflammation was not present in the periapical tissues. The odontoblasts appear normal with no thickening of the predentin layer.

3 week post-op experimental

Three specimens were used. Each specimen showed similar results compared to the two-week specimen except that there was evidence of a more developed matrix forming over the exposed pulp. A low index of inflammation was present in the coronal portion of the pulp but not evident in the apical portion of the pulp. There was evidence of a thickened pre-dentin layer continuous with the calcifying matrix. Vascular supply was evident through out the pulpal tissue. The odontoblasts were healthy and appeared to be functioning.

3 week post-op control

One specimen was used. There was evidence of a calcified matrix band starting to form. It was more mature than the two-week specimen. Inflammation was present in the coronal portion of the pulp canal but was not seen in the periapical tissue. Particles of calcium hydroxide powder was evident apical to the area where the calcified matrix was forming. The odontoblasts and pre-dentin layer appear normal and functioning.

5 week post-op experimental

Four specimens were used. There was evidence of a calcified matrix formation. The matrix appears well defined with thicker walls surrounding the remaining calcium phosphate than was evident in the three-week study. The characteristic "compartmenization" is every evident. It appears that the calcium phosphate crystals are being phagocytized or go into solution within the matrix compartment. All four specimens showed viable odontoblasts with thickening pre-dentin layer continuous with the calcified matrix. Some areas of the predentin contain cells which appear to be entrapped odontoblasts. These odontoblasts appear healthy and viable. The thickened pre-dentin layer and calcified matrix form a continuous cap over the exposed pulp. Histological serial sections show the calcified matrix to be a complete layer from one side to the other side of the canal. Blood vessels are numerous through out the compartmentized matrix, Periapical and apical pulp tissue appear to be void of inflammation.

5 week post-op control

One specimen was used. The specimen showed a well developed bridge was formed. Histological serial examination did show the bridge was not complete from wall to wall of the canal. The pre-dentin layer was thickened and continuous with the calcified bridge. Odontoblasts adjacent to the coronal portion of the bridge are few in number. There is evidence of a "void" area beginning adjacent to the thickened pre-dentin layer and inferior to the calcified bridge. Apical odontablasts appear to be viable with a small amount of pre-dentin thickening. Blood vessels appear to be few in number.

8 week post-op experimental

Three specimens were used. The calcified matrix is more mature with evidence of less calcium phosphate particles in the individual compartments. Viable cells, perhaps fibroblasts or ostoid-producing cells are evident within areas of the matrix. The odontoblastic layer is very healthy from the matrix to the apex. The pre-dentin layer is thickened only at the coronal portion where it unites with the calcified matrix. The pulpal tissue is very healthy, noninflammatory and is supplied by many blood vessels. Histological serial sections show the calcified matrix is complete in two specimens from side to side of the canal. The other specimen is almost complete from side to side of the canal. Periapical tissue is healthy and shows no inflammation.

8 week post-op control

One specimen was used. There was evidence of a calcified bridge. Histological serial sections, however, showed that the bridge was not complete from side to side of the canal as tissue was evident in some sections. Odontoblasts from the bridge apically to the apex showed areas of vacoules believed to be death of these cells. There was no evidence of thickening of the predentin layer below the bridge. The pulp tissue showed a fatty degeneration center with areas of scattered necrosis. An abcess was forming under one area of the bridge in several histological sections. Very few blood vessels were evident. The periapical tissues had a low index of inflammation.

16 week post-op experimental

Three specimens were used. One specimen showed complete necrosis through out the chamber and canal but the periapical tissue had a low index of inflammation. The other two specimens showed the characteristic compartmenization of the calcified matrix. Most of the calcium phosphate particles have resorbed within the compartments allowing for thicker, more mature matrix walls. The pre-dentin is thickened and continuous with the calcified matrix forming a complete histological serial bridge from wall to wall of the canals. Viable cells are evident within the matrix proper. The pulpal and periapical tissues are healthy and without inflammation. The odontoblasts are viable and uniform in position. Many blood vessels are evident through out the pulpal tissue as well as within the compartmenized matrix.

16 week post-op control

One specimen was used. A calcified bridge was formed which was complete in histological serial section from wall to wall of the canal. The pupal and periapical tissue appeared healthy with no evidence of inflammation. The pre-dentin area showed slight thickening. The odontoblasts appear healthy and uniform in position. Normal amount of blood vessels are observed through out the pulpal tissue.

24 week post-op experimental

Three specimens were used. All three teeth showed the same results. Proceeding from the coronal to the apical portion of the canal; the most coronal portion of the pulpcap showed very little evidence of remaining calcium phosphate. The characteristic compartmenization was much smaller with well defined calcified matrix walls. Viable cells were evident within the walls of the calcified matrix. Blood vessels were evident through out the matrix and compartments. Directly under the calcified matrix compartments was an area of scattered solid calcifications mixed with many blood vessels. Proceeding apically was an area of complete calcification which made a bridge that histologically in serial sections showed to be a complete bridge from wall to wall of the canals. This bridge showed evidence of a few viable cells. Under the calcified bridge was found an area of thickened pre-dentin that was continuous with the thickened pre-dentin area from the sides of the canal walls. The pre-dentin thickened portion was complete through out from side to side of the canals. Directly under the pre-dentin layer was found odontoblasts that were lined up in direct apposition to the pre-dentin layer adjacent to the calcified bridge. The odontoblasts are viable and functional as evidence by the pre-dentin thickness. A few small calcified bodies are evident in apposition to the coronal odontoblasts. The pulpal tissue is very healthy, numerous with blood vessels and shows no signs of inflammation. The periapical tissues are also healthy and highly vascular.

24 week post-op control

One specimen was used. The specimen showed complete necrosis of the pulp chamber and pulp canal. There was evidence of periapical inflammation and possible periapical abcess formation. It was not possible to tell if a bridge had once been formed.

From these experiments it appears that the .beta. phase tricalcium phosphate was more predictable in forming a dentinal bridge. Success was observed in the teeth pulp capped with tricalcium phosphate. While only one of the twenty-one teeth treated with .beta. phase tricalcium phosphate was considered a failure, three of the seven teeth treated with calcium hydroxide had totally failed and another was failing.

Calcium hydroxide also seems to cause or allow internal resorption of the dentin to take place. No such internal resorption has been seen with the teeth treated with tricalcium phosphate. In fact, no adverse affects have been seen.

The pulp capping technique described above has been performed on approximately 30 human teeth. To date, the teeth are vital, asymptomatic, and are in function.

ROOT CANAL TECHNIQUE

As briefly described above, the root canal procedure is used for the apexification of young devital teeth or the apexification of devital, mature teeth that have undergone apical root resorption. An advantage of the procedure now described is that the root canal procedure may be accomplished without surgery.

An acess opening is made through the crown portion of the tooth on the lingual or occlusal aspect. The access opening must be large enough and contoured properly so that when the dentist instruments to the apex with files, no interference is met. The instruments must be positioned so that the entire interior portion of the root canal down to the open apex is biomechanically cleansed and shaped. This is done according to standard dental practice through a combination of filing and intermittent irrigation using a material which will dissolve necrotic debris and remove break down products. Once the walls are relatively smooth and the interior of the tooth free of necrotic dentin and pulp, resolution of the abcess will usually proceed.

In cleaning the interior of the tooth roots, progressively larger, endodontic files are used. The largest file, for example, might have a diameter of 0.8 millimeters. A physiologically compatible and soluble calcium phosphate compound preferably prepared as described above is then packed into the apical 3 or 4 millimeters of the root canal. Preferably, the calcium phosphate compound is "pushed" so that it is slightly extruded out of the open apex, and allows blood to infiltrate the calcium phosphate.

As an alternative to extruding the calcium phosphate compound by "packing," the compound may be positioned exteriorly of the root by injecting some of the material out of the bottom of the tooth root prior to packing the interior of the apex.

A relatively soft temporary filling material, such as gutta-percha is then used to fill the remainder of the canal. A relatively hard protective and restorative cover, such as amalgam, is then placed at the access opening.

Over the next five or six months the human body will begin first, to resolve the abcess formed at the exterior of the tooth root. Additionally, the fresh blood supply will initially allow a blood clot to form in the calcium phosphate compound. This will result in the formation of a vascular supply which will supply cells which mature and lay down a colagen-like matrix in the manner similar to that described above with the pulp capping technique. Eventually, an osteodentin barrier will be formed across the apex in a manner, it is believed, similar to that described above with the pulp capping procedure.

After an approximate five or six month period it is desirable to remove the temporary filling and reinstrument the interior of the tooth down to the hard, newly formed ostenodentin plug at the apex. The interior of the tooth is cleaned and repacked with a dense, filling material.

This second cleaning and repacking, after five to six months, is done in order to assure that the soft tissue matrix within the osteodentin plug at the apex will be removed, thus eliminating the possibility of tissue differentiation into a cell type which could cause internal resorption of the tooth. The root canal is now filled and sealed, and then provided with a hard surface restoration such as amalgam.

With other root canal procedures involving peridontal damage, some sort of cushioning ligament is formed during "normal" healing of the abcessed region between the tooth and the bone. However, the observed cushioning ligament after such normal healing is merely a dense, basket-like, fibrous network with no particular alignment of its fibers.

With a normal natural tooth, the fibers of the peridontal ligament begin near the crown portion of the tooth in a nearly vertical orientation. As one descends along the root of the tooth the fibers are found to be more and more oblique until finally at the apex of the tooth the fibers are generally horizontally aligned. With this orientation the peridontal ligament is able to effectively withstand the type of forces encountered at the various positions on the tooth. For example, the peridontal ligament near the upper root portion of the tooth adjacent the crown, generally must withstand lateral and shear forces, while the ligament at the base of the tooth must withstand compressive forces.

However, with the ligament formed during normal healing without treatment according to the present invention, the ligament often has no particular orientation at the root apex and therefore does not provide for proper distribution of forces. The remarkable result observed with the present invention is that the peridontal ligament is formed with naturally oriented fibers. Since peridontal ligament tissue is laid down by fibroblasts, it appears that the use of the described calcium phosphate compounds causes or enables the growth of fibroblasts which have more naturally functioning characteristics.

Cementum and bone are also formed. Therefore cementoblasts and osteoblasts are also caused or enabled to be formed naturally by the proper use of a calcium phosphate compound. In this manner the treated tooth is held in a firm, solid foundation, permitting normal function.

ROOT CANAL EXPERIMENTS

Four female cynalmolgus monkeys, ranging approximately from four to six years of age were used as the experimental animals.

Twenty-Four root canals were used for study purposes. Maxillary and mandibular cuspids and central incisors were selected because their apices are widely spaced or separated by a suture line. Each apex could be studied individually, without danger of introducing additive or crossover effects from any other tooth used as either a control or experimental tooth in the same animal.

Radiographs were taken at the following times:

1. prior to treatment;

2. with the endodontic file through the apex,

3. to determine the level of the gutta-percha just prior to obturation, and

4. just after the animals death.

Anesthesia was induced with intravenous Sernylan and Pentobarbitol Sodium. Atropine was employed to control salivation. Radiographs were taken of the teeth to be used in the study, and the teeth isolated, individually, under the rubber dam. Tooth surface disinfection was accomplished with betadine. An access opening was made through the lingual side of the crown and the pulp extripated with barbed broaches. All canals were prepared through the apex with 4 millimeters, up to the size No. 80 file, as determined from a working length radiograph. The root canals were irrigated frequently during instrumentation with 5 per cent sodium hypochlorite. Upon completion of biomechanical preparation, each canal was flushed with normal saline and dried with absorbent paper points.

In twenty experimental teeth, a specially prepared form of tricalcium phosphate was introduced into the canal and forced gently through the apex, thus an attempt was made to fill any defect created by the endodontic file with tricalcium phosphate. The tricalcium phosphate was then removed from all but the apical 3 to 5 millimeters of the root canal. A gutta-percha cone was tried and adjusted for tug-back to the level of the tricalcium phosphate within the canal. Using Diaket as a sealer, the canals were obturated with the fit gutta-percha cone, using the lateral condensation technique. Lingual access was sealed with a silver amalgam filling.

In each of the four monkeys one tooth was selected to act as a control. In the control teeth NO tricalcium phosphate was used. After biomechanical preparation had been completed a gutta-percha cone was adjusted for tug-back at a level about four millimeters short of the radiographic apex. Diaket sealer and lateral condensation of the guttapercha were used to obturate the canals. Lingual access was sealed with a silver amalgam filling.

At intervals of 2, 5, 16 and 24 weeks the animals were anesthetized as before and sacrificed by perfusion with 10 per cent formalin through the left ventrical. After 10 minutes of perfusion, the mandible and maxilla were removed, stripped of soft tissue and sectioned so one tooth remained in each block section. Individual segments, appropriately labeled, were fixed an additional 7 days in 5 per cent buffered formalin solution. After fixation was complete the individually labeled specimens were rinsed in tap water, and spaced in five per cent formic acid for demineralization. The acid was changed every day for approximately twenty-one days, at which time chemical tests indicated that decalcification was complete. Upon completion of the demineralization process all specimens were embedded in paraplast and oriented, in the final paraplast block, to yield labiolingual sections parallel to the long axis of the tooth when sectioned on the micratome.

Six to eight micron, longitudinal sections, were obtained in serial sections from all teeth. Every fifth section was stained with hemotoxylin and eosin and examined under the light microscope. Each specimen was evaluated for:

1. the degree of inflammation present in the periapical tissues.

2. cementum, dentin, and bone resorption or deposition, and

3. replacement of the tricalcium phosphate material by osteoid, osteo-dentin or osteocementum in the apical portion of the root canal and surrounding bone.

In animal sacrifice between two weeks and six months, the degree of inflammation about the apex was found to be very low. A blood clot had formed in the tricalcium phosphate and vascularization did occur. Absorption of the tricalcium phosphate had taken place with a consequent deposition of a dentin type material within the root of the tooth.

After the six month period, the dentin type material filled about 90% of the total circumference of the root canal leaving only a very small opening. Peridontal ligament had not only formed but it had reassumed its normal form and orientation and presumably its function. Bone morphology appeared normal with no active resorption of bone or tooth seen at any place in the teeth where tricalcium phosphate had been used. There was therefore a very high predictability of apical closure when tricalcium phosphate was used according to the present invention.

In all of the control teeth, in which no materials were used, there was some ingrowth of bone into the root canal observed but there was no significant deposition of cementum of dentin on the walls of the root canal. There was in fact, no apical closure and a moderate to severe inflammatory response observed in 50% of the cases.

In prior studies using clacium hydroxide the degree of sucess approached 70%. However, after a period of 1 to 4 years in perhaps 15 to 20% of the cases a breakdown is observed in the periapical area resulting from leakage with eventual reinfection of the root canal and surrounding periapical structures.

Although approximately 20 children and four or five adults have been treated with the root canal procedure of the present invention, insubstantial time has passed for an analysis of results.

However, internal-external root resorption observed in humans has been treated by similar procedures involving cleansing of the root canal and packing it with tricalcium phosphate with a sufficient force to attempt to extrude the tricalcium phosphate into the area of external resorption. Observation of these cases show that the external resorption appears to have stopped and a filling in of hard material seems to be taking place.

TOOTH REPLANTING

It is known that approximately one quarter of all teeth which have been traumatized, but not avulsed, subsequently undergo external resorption. It is also observed that, unless teeth, which have been completely dislodged, are replanted within approximately ten minutes, the root is similarly resorbed and the tooth is eventually lost.

Six such avulsed teeth in humans were replanted. Subsequently, root canal procedures as described above were performed with tricalcium phosphate being injected into the periapical regions. It has been observed after six months that there is no evidence of external resorption. Preferably however, a dry tricalcium phosphate powder would be dusted onto the exterior root surfaces using, for example, a particulate atomizer or sprayer prior to replanting of the tooth.

It is of course known that bone, cementum and dentin are formed from cells termed osteoblasts, cementoblasts and dentinoblasts respectively. It is known that these same calcified materials are resorbed by cells termed osteoclasts, cementoclasts, and dentinoclasts. It also known that these "blasts" and "clasts" all originate from cells known as osteosites, cementosites and dentinosites.

It is therefore theorized by the inventors that the physiologically compatible and soluble calcium phosphate compounds described above appear to provide an environment conducive to the growth of blasts and will stimulate the metamorphosis of clasts into sites to permit the further differentiation into the necessary blasts.

It is to be understood that while the detailed drawings and specific examples given, describe preferred embodiments of the invention they are for the purposes of examples only, that the method of the invention is not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims.

Claims

We claim:

1. A method for enabling the naturally functioning growth of at least one of the following: fibroblasts, odontoblasts, cementoblasts and osteoblasts, said method comprising positioning a porous mass of a physiologically soluble and compatible calcium phosphate compound adjacent the calcified tissues of a tooth and in contact with a blood supply sufficient to permit the formation of a blood clot in said calcium phosphate compound.

2. A method according to claim 1 wherein said calcium phosphate compound comprises CaHPO.sub.4.

3. A method according to claim 1 wherein said calcium phosphate compound comprises .alpha. phase Ca.sub.3 (PO.sub.4).sub.2.

4. A method according to claim 1 wherein said calcium phosphate compound comprises .beta. phase Ca.sub.3 (PO.sub.4).sub.2.

5. A method according to claim 1 wherein said calcium phosphate compound comprises a mixture of at least two of the following compounds: .alpha. phase Ca.sub.3 (PO.sub.4).sub.2 ; .beta. phase Ca.sub.3 (PO.sub.4).sub.2 ; and CaHPO.sub.4.

6. A method according to claim 1 for enabling the regeneration of calcified and peridontal tissue said method more particularly comprising the steps of:

a. preparing a diseased site by excising diseased tissue of at least one of the above types and forming a cavity so as to communicate with a blood supply;

b. at least partially filling the interior of said cavity with said physiologically soluble and compatible calcium phosphate compound in a configuration in contact with said blood supply; and

c. closing the cavity by filling it and rebuilding its outer functional surface.

7. A method according to claim 6 wherein said calcium phosphate compound comprises CaHPO.sub.4.

8. A method according to claim 6 wherein said calcium phosphate compound comprises .alpha. phase Ca.sub.3 (PO.sub.4).sub.2.

9. A method according to claim 6 wherein said calcium phosphate compound comprises .beta. phase Ca.sub.3 (PO.sub.4).sub.2.

10. A method according to claim 6 wherein said calcium phosphate compound comprises a mixture of at least two of the following compounds: .alpha. phase Ca.sub.3 (PO.sub.4).sub.2 ; .beta. phase Ca.sub.3 (PO.sub.4).sub.2 ; and CaHPO.sub.4.

11. A method according to claim 1 wherein said calcium phosphate compound is prepared by sintering together particles of said compound into a unitary body; then grinding said body into a grated particulate; then adding a vehicle to said powder in sufficient quantity to form a putty-like mixture for filling into said cavity.

12. A method according to claim 11 wherein said powder consists substantially of particles which are ground sufficiently small that the putty-like mixture exhibits colloidal properties.

13. A method according to claim 1 for performing a pulp capping procedure which enables the formation of a dentinal bridge in a tooth, said method comprising:

a. preparing said tooth by removing diseased tissue thereby creating a cavity communicating from the tooth surface to the pulpal tissue, and in fluid communication with the blood supply of remaining healthy tooth pulp;

b. at least partially filling the interior of said cavity with a physiologically soluble and compatible calcium phosphate compound in a configuration having at least a portion thereof in contact with said blood supply; and

c. forming a protective, relatively hard cover sealing the surface opening of said cavity.

14. A method according to claim 13 wherein said calcium phosphate compound comprises CaHPO.sub.4.

15. A method according to claim 13 wherein said calcium phosphate compound comprises .alpha. phase Ca.sub.3 (PO.sub.4).sub.2.

16. A method according to claim 13 wherein said calcium phosphate compound comprises .beta. phase Ca.sub.3 (PO.sub.4).sub.2.

17. A method according to claim 13 wherein said calcium phosphate compound comprises a mixture of at least two of the following compounds: .alpha. phase Ca.sub.3 (PO.sub.4).sub.2 ; .beta. phase Ca.sub.3 (PO.sub.4).sub.2 ; and CaHPO.sub.4.

18. A method for enabling the naturally functioning growth of at least one of the following: fibroblasts, odontoblasts, cementoblasts and osteoblasts, said method comprising positioning a physiologically soluble and compatible calcium phosphate compound adjacent the calcified tissues of a tooth and in contact with a blood supply sufficient to permit the formation of a blood clot in said calcium phosphate compound said method more particularly comprising a root canal procedure for the apexification of an open apex tooth root said procedure comprising:

a. forming an access opening into a tooth pulp chamber through the crown portion of a tooth;

b. cleansing and shaping said pulp chamber including the root canal portion and extending it to communication with a fresh blood supply;

c. filling an extreme apical part of said root canal portion with said physiologically soluble and compatible calcium phosphate compound; and

d. filling the remainder of the chamber with a filling material and forming a relatively hard protective cover at said access opening.

19. A procedure according to claim 18 wherein said procedure further comprises the steps of:

a. initially filling said pulp chamber with a relatively soft, temporary filling material;

b. after approximately a five month period, removing said protective cover and said temporary filling material, biomechanically cleansing the internal portion of the root canal; and

c. filling said chamber with a dense permanent filling material and forming a relatively hard protective cover at said access opening.

20. A method according to claim 19 wherein said calcium phosphate compound comprises CaHPO.sub.4.

21. A method according to claim 19 wherein said calcium phosphate compound comprises .alpha. phase Ca.sub.3 (PO.sub.4).sub.2.

22. A method according to claim 19 wherein said calcium phosphate compound comprises .beta. phase Ca.sub.3 (PO.sub.4).sub.2.

23. A method according to claim 19 wherein said calcium phosphate compound comprises a mixture of at least two of the following compounds: .alpha. phase Ca.sub.3 (PO.sub.4).sub.2 ; .beta. phase Ca.sub.3 (PO.sub.4).sub.2 ; and CaHPO.sub.4.

24. A procedure according to claim 19 wherein said calcium phosphate compound is also forcibly extruded out through the open tooth apex when being filled into said root canal.

25. A method for enabling the naturally functioning growth of at least one of the following: fibroblasts, odontoblasts, cementoblasts and osteoblasts, said method comprising positioning a physiologically soluble and compatible calcium phosphate compound adjacent the calcified tissues of a tooth and in contact with a blood supply sufficient to permit the formation of a blood clot in said calcium phosphate compound said method more particularly comprising a procedure for replanting an avulsed tooth, said procedure comprising:

a. coating said calcium phosphate compound onto the exterior surface of the root portion of said tooth; and

b. replanting said tooth in its natural socket.

26. A method according to claim 25 wherein said calcium phosphate compound comprises CaHPO.sub.4.

27. A method according to claim 25 wherein said calcium phosphate compound comprises .alpha. phase Ca.sub.3 (PO.sub.4).sub.2.

28. A method according to claim 25 wherein said calcium phosphate compound comprises .beta. phase Ca.sub.3 (PO.sub.4).sub.2.

29. A method according to claim 25 wherein said calcium phosphate compound comprises a mixture of at least two of the following compounds: .alpha. phase Ca.sub.3 (PO.sub.4).sub.2 ; .beta. phase Ca.sub.3 (PO.sub.4).sub.2 ; and CaHPO.sub.4.