Generic tricalcium phosphate plugs: An adjunct in endodontics

0099-2399/91/1703-0131/$03.00/0 JOURNAL OF ENDODONTICS Copyright 9 1991 by The American Association of Endodontists

Printed in U.S.A.

VOL. 17, No. 3, MARCH 1991

CLINICAL AID Generic Tricalcium Phosphate Plugs: An Adjunct in Endodontics Henry Harbert, DMD

alternative to calcium hydroxide apexification (3, 4). It has also been shown to be effective for sealing furcation perforations because of its biocompatability and low inflammatory potential (5). There have been many studies supporting the use of b-TCP in dentistry (6, 7). However, b-TCP was expensive and has not been available since 1988. Shands (8) investigated the use of generic tricalcium phosphate(g-TCP) implanted in bone to see if an in situ depot of bone salts could contribute to osteogenesis. In one experiment the control sites with no implanted material healed faster than the g-TCP sites. In other experiments g-TCP increased the rate of osteogenesis in the ulna and decreased it in the spine. Haldeman and Moore (9) found implanted g-TCP either had no effect on osteogenesis or it appeared to favor osteogenesis. Although biocompatibility of g-TCP in bone seemed to be established, it appeared to have no therapeutic advantage. Because of the positive results claimed for b-TCP in endodontics and since g-TCP was biocompatible, inexpensive, and readily available, g-TCP was used as an endodontic plug. Two cases are presented to show g-TCP was a helpful adjunct as a plug in a large apex and a bifurcation perforation in mature pulpless permanent teeth. In both cases the medical history was noncontributory.

Unusual endodontic situations may necessitate an immediate plug inside the tooth in order to dry the canal system and provide resistance to condensation. Generic tricalcium phosphate is a powder that when hydrated handles like silver amalgam and is condensable into a hard plug deep inside the tooth. It is fast, relatively technique insensitive, comfortable postoperatively, biocompatible, inexpensive, and readily available. A practical technique is presented and two case reports illustrate its use as an apical plug and a furcation perforation plug.

The standard ways for achieving an apical stop are creating a shelf or a tapering funnel or a combination of the two (1). However, there are clinical situations for which standard diminishing taper techniques are not adequate. There may be the absence of a natural canal constriction at the apex, a restricted cervical access, the impracticality of tapering a narrow canal in a long thin root with more than one bend, immature root canal anatomy, or external resorption of the apex. Also, complications such as overzealous trephination, root perforations, and apicoectomy may be present. A variety of special techniques will always be an advantage in these nonstandard situations (1). The plug stop is one such aid that involves the extra step of packing a biocompatible material, such as calcium hydroxide, dentin chips, or tricalcium phosphate, to provide an immediate apical stop in cases where diminishing taper techniques are not feasible. Another occasionally serious problem is the ingress of fluids into the canal system during treatment. These fluids frustrate complete debridement and block the adhesion between dry dentin and sealer necessary for complete obturation. Beeler (2) demonstrated that an apical plug may also act as an immediate, total barrier to prevent the inflow of fluids. Hence, a strong, insoluble plug could halt fluid ingress in order to permit scrupulous debridement and dentin dessication prior to filling. fl-Tricalcium phosphate (b-TCP) has been used successfully as apical plug for immature pulpless permanent teeth. It provides an immediate apical barrier for condensation as an

M A T E R I A L S AND M E T H O D S Tricalcium phosphate (calcium phosphate, tribasic powder, USP/NF) (10) was ordered through a retail pharmacy from a wholesale pharmaceutical supplier (Professional Compounding Centers of America, Inc., Sugar Land, TX). One gram of the bulk powder was dispensed filling a 4-ml amber glass screw cap bottle (Professional Compounding Centers of America). Several loosely capped bottles were sterilized in a biologically monitored, dry heat oven at 350~ for 2 h (1). After cooling, the caps were tightened and the vials were stored in operatories for use. As routine canal preparation neared completion if the files or paper points showed exudate or hemorrhage of concern, gTCP was mixed immediately and packed into the canal. Half of the g-TCP powder in the bottle (1/2 g) was poured into a dappen dish, distilled water was added by drops and mixed with a stainless steel spatula. The consistency of the mixture was a stiff, crumbly, paste that handled like silver amalgam.

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It was carried with a Teflon sleeve alloy carrier to the orifice. With pluggers and files it was manipulated through the canal, packed very tightly at the apex, and then backpacked into the apical third of the canal. A new canal length was regained by chiseling with smaller files followed by larger files and using copious 2% sodium hypochlorite irrigation. Larger Hedstrom files, blunted at the tip to prevent diminishing the plug strength, were adjusted to the new length and used to peripherally file the walls to the wall-plug junction and test the stop for compression strength. The canals were flooded with 100% isopropyl alcohol, instrumented, and flooded again with alcohol. The canals were dried with compressed air and paper points, followed again by air. The remaining g-TCP plug depth ranged from 1 to 3 mm from the anatomical foramen, depending on the presumed configuration of the apex. Narrow diameter round apical foramina permitted a short l-mm plug and larger diameter, more irregular foramina required a longer plug. A gutta-percha cone with tug-back was formed, sealer was liberally added with a lentulo to coat the length of the canal, and the gutta-percha was packed using vertical and lateral condensation. CASE REPORTS Case 1 In January 1986, a 35-yr-old female presented with symptoms of increasingly severe, diffuse pain of the upper fight side of the face, swelling of the facial and palatal mucosa of

FIG 1. Emergency examination, tooth 7.

teeth 6 to 8, and sensitivity to percussion and palpation in that area. The periodontium probed within normal limits. The radiograph (Fig. 1) showed a radiolucency at the apex of tooth 7 and an endodontic access had been performed for tooth 7. There was a history of beginning root canal treatment 6 wk previously with several courses of penicillin, erythromycin, and codeine. Three times the tooth was treated and closed with subsequent pain and swelling, followed by emergency opening and leaving the canal open for relief. The patient was exhausted. At the consultation it was agreed endodontic therapy for tooth 7 should be completed immediately, followed by periapical surgery. Prescriptions for penicillin and Tylox were written and the patient was reappointed for treatment. Three days later her swelling had diminished somewhat and the pain had diminished 50%. The technical difficulties were a restricted lingual access, a curved canal, an apex previously trephined to a very large size, and copious periapical drainage into the canal. After preliminary cleaning and shaping of the canal, a tricalcium phosphate plug was packed at the apical foramen. The plug permitted complete cleaning and drying as well as a rigid apical stop against which to condense. Gutta-percha, sealer, and alloy were used to obturate (Fig. 2). The patient was monitored closely. The pain continued to abate rapidly, disappearing completely the next day. Because the swelling resolved over the next 3 days, surgery plans were cancelled and the patient placed on recall. The tooth remained symptom free and the periapical lesion healed as seen in the 4-yr postoperative recall radiograph (Fig. 3). If a periapical surgery had been necessary, the surgeon

FIG 2. Endodontic treatment completed after apical g-TCP plug.

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FIG 4. Emergency examination, tooth 19.

FIG 3. Four-year recall.

would have been assured that the original endodontic treatment was technically optimal. Case 2

A 27-yr-old female presented in March 1987 with symptoms of continuous spontaneous pain and pain to percussion from tooth 19. The pain had been mild for 2 wk and increased to severe in the third week. There was no swelling, and the periodontium probed normally. The radiograph showed radiolucent lesions in the bifurcation and at the mesial apex (Fig. 4). There was a history of root canal treatment followed by a stainless steel crown 9 yr previously and intermittent episodes of mild discomfort. The patient agreed to endodontic retreatment with the understanding that the chance of saving the tooth might be 50% or less. Upon opening the pulp chamber, the former paste filling was removed and two former perforations of the pulp chamber floor were located. With reference to the X-ray beam, the perforations were parallel and superimposed. G-TCP plugs were packed with alloy condensers into the perforations (2.5 and 2 mm in diameter) to stop the hemorrhage and permit good vision. The excess g-TCP was removed with an explorer and cotton pellets. Four canals were located and cleaned, and the chamber was closed with cotton and Cavit. The patient used three Tylenol #3 tablets in the first 18 h as the discomfort gradually diminished over 3 days. After the first treatment visit, the patient related a small swelling had appeared on the buccal attached gingiva of tooth 19, which drained spontaneously and appeared to be

clinically normal 1 wk later. At that time the cotton pulp chamber dressing was dry, not rancid, indicating the stainless steel crown margins and the TCP plugs were not grossly leaking. The canals were cleaned and filled with gutta-percha and sealer. Alloy, without cavity varnish, was condensed into the orifices, pulp chamber floor, and the endodontic access (Fig. 5). The g-TCP plugs permitted cleaning the canals without irritating the furcation, a dry filling procedure without hemorrhage or serous fluid weeping into the chamber, and a hard platform against which to condense alloy. The patient was placed on recall and advised of the need for a permanent cast crown. At the 2-yr recall, the radiograph showed the bone healed in the bifurcation and at the mesial and distal apices (Fig. 6). The patient remained symptom free except for a spontaneous, infrequent, mild awareness of tooth 19, not requiring aspirin for relief. Clinically, tooth 19 was not sensitive to vertical or lateral percussion but was sensitive to 45degree angle percussion on the mesiobuccal cusp, indicating possible traumatic occlusion. DISCUSSION g-TCP does not remain at the implant site to build new bone, but its components are slowly adsorbed into the general body pool over weeks and months (8, 9). In part, the method of removal depends on the size of the particles, b-TCP granules or blocks, being insoluble and much larger than g-TCP powder, are apparently removed only by phagocytosis (6, 7). No increase in serum Ca and P has been detected for b-TCP. Pathologic calicifications of necrotic tissue in situ have not been found, nor have renal or arthritic calcifications (7). Calcium phosphate implant materials in general lack toxicity, inflammatory or foreign body response, or a fibrous capsule response (6). Metsger et al. (7) stated b-TCP was stoichiometrically pure due to its naphthelene sublimation sintering manufacturing process. They cautioned that the chemical formula for g-TCP varied slightly, and it was impure because of its precipitation method of production (10). However, chemical dictionaries seldom mention b-TCP except as a "rare form" of TCP. Numerous articles have not distinguished between the two

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FIG 5. Treatment completed over g-TCP plugs in bifurcation perforations.

merly named Peri-OSS, Miter Inc., Columbus, OH) was $226 for 2 g or $3204 per ounce. g-TCP is very stable in oxygen, but it slowly breaks down with humidity (10). If stored in a tight container, its shelf life may be 5 to 10 yr. In pharmacy g-TCP is used as an excipient for tablet manufacturing because of its compactability in either the hydrated or dry form. In a bench test g-TCP was condensed, as it would be handled clinically, into a metal ring and measured with a Shimadzu type M microhardness tester. g-TCP set to its full clinical hardness 30 s after it was condensed. The Vickers microhardness was 193 kg per m m 2 at a test load of 15 g. Radiographically, condensed g-TCP is indistinguishable from dentin. Undoubtedly, the packing of plug material in these two cases resulted in g-TCP overfills into acutely infected periodontium. There was no increase in pain resulting after the plugging in case 1 or 2. In both cases the presenting emergency pain resolved quickly. For asymptomatic cases the mild inflammatory potential of g-TCP translates clinically to no additional postoperative pain or a mild sensation of pressure after plug placement. This is corroborated for plugs in general by several clinical reports of no pain after placement of plugs

(2). Cleaning the plug material out of the canal prior to filling is a dilemma. If the plug material is durable enough to remain in the apex while the canal is recleaned, then it is difficult to remove from the body of the canal. If the nearly insoluble gTCP slowly dissolves out of the canal over time, then voids could open up to weaken obturation. On the other hand, a material like Ca(OH)2 is easily cleaned from the canal with water but the Ca(OH)2 apical plug is also weakened and washes out. As a disadvantage, g-TCP packs tightly in canal fins and isthmuses and is not readily removed by sodium hypochlorite or water. With effort it can be removed from smooth dentin walls with K and H files. Ultrasonic cleaning may be helpful, g-TCP also clings to glass and stainless steel clogging the interiors of the stainless steel alloy carrier. A noncorrodible Teflon alloy carrier sleeve is easier to clean. FIG 6. Two-year recall. Dr. Harbert is an endodontist in private practice in Everett, WA.

and have frequently rated calcium phosphates as a group as highly biocompatible. Furthermore, there has not been a test directly measuring for biological response differences between the two. The claims for b-TCP (6, 7) may have originated from its original use as a bone substitute and graft extender. It was to provide an osteoconductive scaffold for bone regrowth, resorb entirely by phagocytosis at a rate coincident to bone ingrowth, have a uniform pore size compatible for bone growth, and integrate to bear stress as the bone eventually completely remodeled itself (6). In contrast, g-TCP fulfilled different requirements for the endodontic plugs described here. The endodontic criteria were biocompatibility, ability to compact into a hard barrier that is temporarily insoluble, clinical practicality, ready availability, and low cost. Himel et al. (5) stated the cost of the implant material was an important consideration. The cost of g-TCP was $1 per ounce. The average quantity used per endodontic appointment was 1/2 g (1 ounce avoirdupois = 28.35 g) for $0.02 per visit. Calcium hydroxide was $7 per ounce. The cost of bTCP (Synthograft; Johnson & Johnson, Skilman, N J, for-

References 1. Cohen S, Burns RC, Pathways of the pulp. 4th ed. St. Louis: CV Mosby Co., 1987:94, 160-1,183. 2. Beeler WJ. Permeability of the apical root foramen of human teeth: the effect of apical barriers [Thesis]. Eugene, OR: University of Oregon, 1987. 3. Coviello J, Brilliant JD. A preliminary clinical study on the use of tricalcium phosphate as an apical barrier. J Endodon 1979;5:6-13. 4. Koenigs JF, Heller AL, Brilliant JD, Melfi RC, Driskell TD. Induced apical closure of permanent teeth in adult primates using a resorbable form of tricalcium phosphate ceramic. J. Endodon 1975;1:102-6. 5. Himel VT, Brady J, Weir J. Evaluation of repair of mechanical perforations of the pulp chamber floor using biodegradable tricalcium phosphate or calcium hydroxide. J Endodon 1985;11:161-5. 6. Jarcho M. Calcium phosphate ceramics as hard tissue prosthetics. Clin Orthop 1981 ;157:259-78. 7. Metsger SD, Driskell TD, Paulsrud JR. Tricalcium phosphate ceramic-a resorbable bone implant: Review and current status. J Am Dent Assoc 1982;105:1035-8. 8. Shands AR. Studies in bone formation: The effect of local presence of calcium salts on osteogenesis. J Bone Joint Surg 1937;19:1065-76. 9. Haldeman KO, Moore JM. Influence of a local excess of calcium and phosphorus on the healing of fractures. Arch Surg 1934;29:385-96. 10. United States Pharmacopeia. 21st rev. National Formulary, 16th rev. 1985;1539-40.