341

Australian Dental Journal, October, 1979 Volume 24, No. 5

Endodontic treatment of primary teeth Kevin R. Allen, B.D.S., Cert.Ped.(lll.), F.I.C.D.

Senior Lecrurer in Children's Dentistry, The University of Adelaide

ABSTRACT- Endodontic treatment of primary teeth is undertaken by indirect pulp capping, direct pulp capping, formocresol pulpotomy and pulpectomy. The same treatment principles apply to both primary and permanent teeth with infected or necrotic pulps. The main differences are the use of formocresol for root canal medication and a resorbable zinc-oxide and eugenol paste for root canal obturation.

Although dental caries in children has been reduced by water fluoridation and an increased parental awareness of the causative factors, there are still many children with primary teeth which require pulp therapy. As the primary teeth are the best space maintainers, teeth with affected and infected pulps should be retained until exfoliation, whenever possible. The reparative potential of the pulp is much greater than formerly believed. Consequently, many teeth with affected pulps have been saved by vital pulp therapy using pulpotomy or direct and indirect pulp capping techniques.' The idea that a painful pulp is a dead pulp is a misconception because :(1) Clinical symptoms of pain are very poor indicators of pulpal status. Numerous histologic studies have shown little correlation between the clinical appearance of deep carious lesions, symptoms of pain and pulpal pathosis. (2) Failure to distinguish between dentinal pain and pulpal pain can contribute to an incorrect diagnosis. Dentinal pain is characterized by a sharp lancinating quality, evoked by mechanical and chemical agents such as sugars and acids. Pulpal pain is characterized by

a more continuous, dull throbbing ache which is increased by heat or lying down. (3) The idea that every pulp under a deep or superficial carious lesion is infected is vigorously denied. Thousands of histologic sections of pulps under deep, active (painful) carious lesions show that the pulp is not infected at all and only mildly inflamed.' The pulp of a tooth under a deep carious lesion with a distinct layer of tubular dentine still present between the pulp and the bacterial plaque is often inflamed and very painful but contains very few, or no histologically demonstrable bacteria. It is significant that the clinically acutely painful pulps are usually those affected and inflamed-but not yet infected. In contrast, the infected and necrotic pulp yields a history of lesser pain-chronic and in the past-but rarely severe or acute pain.* A diagnosis and treatment plan must be determined before treatment of the affected or infected pulp is commenced. Considerations in the diagnosis should include the child's medical and dental history, the use of any diagnostic aids and control of pain. Rubber dam should be used to give the operator a sterile field and the patient a sense of security.

Massler, M.-Preventive endodontics: Vital pulp therapy. Dent. Clin. North America, 6 6 3 4 7 2 (Nov.) 1967.

Massler, M., and Pawlack, J.-The affected and infected pulp. Oral Surg., 43: 6,929-947 (June) 1977.

348 Pulp treatment of primary teeth should be undertaken only if it in no way endangers the general health of the patient. It should not be carried out in children with cardiac abnormalities such as rheumatic heart or congenital heart defects. The failure of pulp therapy may produce a focus of microbial infection which may further affect the diseased condition. It should also be avoided on severely ill and debilitated ~ h i l d r e n . ~ The operator must be aware of the history of pain. Has there been an absence of pain or pain only for short periods, or has pain been present for a prolonged period of time? Has the pain been a chronic dull pain for several days or a severe throbbing pain? Has the pain occurred on reclining or during sleep? Has the pain occurred on percussion, during mastication or because of food impaction? Has the pain arisen due to hot or cold foods and liquids or sweet and sour foods? Wei3 has listed the subjective symptoms of pain as:A . Unfavourable 1. pain for prolonged periods of time; 2. severe throbbing pain; 3. pain due to sweet and sour foods; 4. pain on reclining or during sleep; 5. chronic dull pain for many days; 6 . sensitivity to percussion. B. Favourahle 1. absence of pain or pain for brief periods; 2. pain caused by cold liquid or cold foods only; _. 3. pain due to sweets and sour foods; 4. pain due to food impaction. A recent periapical radiograph must be checked for any periapical changes or evidence of calcified masses in the pulp. The value of the electric pulp test on primary teeth is questionable although it will give an indication of whether the pulp is vital. The test does not give reliable evidence of the degree of inflammation of the pulp. The reliability of the pulp test may also be questioned as once the test has been used an apprehensive child, may give a false response to both heat and the electric test.4 The comfort and lack of apprehension of a child must be paramount in any discussion of operative procedures. The use of local anaesthesia is indicated and relative analgesia is helpful for the apprehensive patient. In some instances it is possible to complete a vital pulpotomy using only relative analgesia without local anaesthesia. One of the main reasons for using rubber dam in restorative procedures for children is that it has a comforting effect so that many fall asleep during treatFull. C. A,, Johnson, R., Parkins. F. M., Walker, J. D., and Wei, S. H. Y.-Pedodontic diagnosis and treatment selfinstruction syllabus. Iowa City, The University of Iowa, 1972 (pp. 67-76). McDonald, R. E., and Avery, D. R.-Dentistry for the child and adolescent. Saint Louis, The C. V. Mosby Company, 3rd. ed, 1978 (pp. 149-171).

Australian Dental Journal, October, 1979 ment. After placement of rubber dam difficult patients frequently become co-operative patients; also the efficiency of the operator is increased and should a pulp become exposed, a pulpotomy can be performed immediately. The method of applying rubber dam as practised in the Pedodontic Clinic of The University of Adelaide is described in a previous paper by Allen.5

Treatment Pulp treatment of primary teeth will be discussed under four headings.

1. Indirect pulp capping The objectives of indirect pulp capping as listed by Wei3 are:(a) preserve the vitality of the pulp (b) prevent direct exposure of the pulp (c) promote secondary dentine formation by odontoblasts (d) promote remineralization of the demineralized layer. Indirect pulp capping is a two-appointment procedure. It should be completed on teeth with deep caries where there has been an absence of pain. At the first appointment the superficial necrotic layer of carious dentine along the dentino-enamel junction is removed. The affected. deeper, demineralized layer of dentine which is not infected is not removed. There has been controversy as to whether a base of calcium hydroxide or a zinc oxide and eugenol preparation should be the agent of ~ h o i c eThis . ~ is unimportant as the defense mechanism of living dentine against injury is by sclerosis of vital tubules under the lesion with partial remineralization of the demineralized dentine.6 I t is imperative that the cavity seal is maintained with a temporary or intermediate restorative material such as IRM,* a temporary filling made by mixing silver alloy filings with zinc phosphate cement or an amalgam restoration. If there has been gross destruction of the tooth a preformed or pinched stainless steel band is adapted and cemented to the tooth. At the second appointment in approximately three months, the intermediate restoration and sterilized carious dentine are removed. The demineralized dentine is removed until a hard cavity floor is achieved which may still exhibit staining. A regular cavity base is placed, * L. D. Caulk Co. Allen, K. R.-Restoration of the extensively carious primary molar. Austral. D. J., 16: I , 8-12 (Feb.) 1971. Eidelman, E., Finn, S. B., and Koulourides. T.-Remineralization of carious dentine treated with calcium hydroxide. J. Dent. Children, 32: 218-225 (4th Quarter) 1965.

Australian Dental Journal, October, 1979 followed by copal varnish and the final restoration of an amalgam or stainless steel crown. It has been shown that a 10 per cent stannous fluoride solution when applied to carious dentine promotes remineralization of the residual dentine. Furthermore, it has also been shown that stannous fluoride indirect pulp capping is superior to calcium hydroxide because the former increases the radiodensity and the hardness of the residual dentine.3 When using 10 per cent stannouSfluoride the solution is applied for five minutes to the demineralized dentine after removing the superficial necrotic layer of dentine and caries along the dentino-enamel junction. A temporary restoration, IRM or amalgam is placed. The second appointment is as described previously. The use of indirect pulp capping will maintain the vitality of many teeth, preventing unnecessary endodontics. 2. Direct pulp capping Because of the poor success rate when calcium hydroxide is used as a pulp capping agent and the high success rate of formocresol pulpotomy, it is rare for the direct pulp capping procedure to be used in the treatment of primary teeth. The only occasion when it should be considered is after a minimal mechanical exposure such as occurs when the patient bites the handpiece. Immediately after the exposure place a pellet of sterile cotton wool moistened with sterile normal saline or anaesthetic solution to prevent drying of the exposed pulp. Flow calcium hydroxide over the exposed pulp and if the cavity has been prepared, place a temporary dressing of zinc oxide, IRM, amalgam or composite restoration. A periapical radiograph is taken if a recent film is unavailable. After six to eight weeks the exposure site is inspected to determine the extent of dentinal bridging. If the healing is complete, the tooth is restored with amalgam or composite. If healing is incomplete, the site is flushed with sterile normal saline and again treated.'

349

(b) the patient is in poor health and his resistance to infection is low: e.g., in cases of diabetes, leukaemia, rheumatic fever, haemophilia; (c) retention of the tooth is not in harmony with the occlusion or growth of the jaws; (d) an acceptable cavity cannot be prepared; (e) the crown of the tooth cannot be restored; (f) evidence of periodontal or bone involvement; (g) internal resorption; (h) prolonged pain; (i) a purulent or necrotic pulp; 6) calcified structures in the pulp. In addition, consideration is given to the following factors:(a) the very young or handicapped child who may be unable to give the necessary co-operation ; (b) the time required to complete the operationthis would apply to treatment under general anaesthesia and handicapped children; (c) the cost of the treatment. Parents should be informed of the fee as well as the success rate, which is approximately 97 per cent; (d) if other teeth have been extracted, the desirability of extracting this tooth and inserting a space maintainer. There are two different formocresol techniques. A five-minute one-appointment procedure, or a seven-day two-appointment procedure. The five minute technique has been described previou~ly.~ In the two-appointment procedure after removal of the pulp from thepulpchamberacottonpellet moistened with formocresol is sealed in contact with the pulp stumps for approximately seven days. At the second appointment, the cotton pellet is removed and the pulp stumps covered with a layer 1-2 mm thick of 50j50 mix consisting of one drop of formocresol and one drop of eugenol mixed with zinc oxide to a thick paste. A layer of thick zinc phosphate cement is placed over the SOj50 layer and the tooth restored with amalgam or a stainless steel crown.

3. Formocresol pulpotomy Formocresol vital pulpotomies of primary teeth is the 4. Pulpectomy Although the two-appointment formocresol treatment of choice when the pulp has a carious or a large mechanical exposure. The contraindications to pulpotomy has been used in treating many teeth with treatment which have been listed by Brauer" and FinnQ necrotic or degenerating pulps, the success rate is not as satisfactory as treatment with pulpectomy. When a are :primary tooth has exhibited spontaneous pain the root (a) the tooth is mobile and about to be exfoliated; canals are cleansed and a pulpectomy completed. Alternatively, the tooth is extracted and a spacemaintainer placed, if necessary. ' Bonus, H. W.. and Anderson, A. W.-Clinical andlaboratory Full root therapy using forms of resorbable paste is handbook for pediatric dentistry. Chicago, Department of increasingly used in incisor and canine teeth in the Pediatric Dentistry, The University of Illinois, 2nd revision. March, 1977 (pp. V1, 1-10). primary dentition. Dissatisfaction with pulp capping Brauer, J. C.-Dentistry for children. New York, McGrawand some pulpotomy procedures in posterior teeth has Hill Book Co., 5th edn, 1964 (pp. 463-478). also led many practitioners to attempt obturation of root Finn, S. B.-Clinical Pedodontics. Philadelphia, W. B. canal systems in these teeth.9 Saunders Co.. 4th edn. 1973 (pp. 201-218).

350

Australian Dental Journal, October, 1979

Before commencing a pulpectomy it is essential that the practitioner is aware of the three-dimensional anatomy of the root canal systems of primary teeth. Barker and his colleaguesln have described in detail these root canal systems. Other factors which need to be assessed are the age of the patient, the development of the tooth and the amount of root resorption. The anterior primary teeth usually have a simple one canal root system. As resorption occurs more on the lingual aspect of the root, the anatomical root apex may vary considerably from the radiographic apex. The root canal should be obturated to the anatomical apex, which is a matter of clinical judgement depending on the amount of resorption. In 75 per cent of specimens the palatal and distobuccal roots of the maxillary primary first molars are fused completely or incompletely by a thin dentino-cementa1 lamina and this contains a complicated meshwork of canal divisions connecting palatal and distobuccal canals. Although 58 per cent of maxillary second molars have a similar tendency to incomplete separation of palatal and distobuccal roots, three separate roots are frequently encountered. In young specimens of mandibular primary first molars with incompletely formed apices, the roots may possess single and very wide root canals. Partitioning results in a meshwork of transverse communications with maturity. Eventually, each of the two roots may possess two partially or completely separate canals so that four canals may be encountered. The primary mandibular second molar exhibits greater root divergence than the first molar. Root canals may be single and very broad in young teeth, but two canals with transverse communication may eventually separate off in each root. O Radiographs show the anatomy of teeth in a mesiodistal plane but not in a buccolingual plane. The majority of variations of root canal systems in primary molars occurs in the buccolingual plane. Radiographs are therefore a poor tool for viewing the anatomy of root canal systems. Periapical radiographs are a valuable aid in diagnosis and also provide a record of the condition of the tooth and surrounding structures. Contraindications for pulpectomy of primary teeth are : (a) pathologic root resorption; (b) the tooth is unrestorable; (c) the tooth exhibits internal resorption, which is always larger than the area viewed on the radiograph; (d) perforation of the pulpal floor which has occurred due to instrumentation or caries; (e) mobility if due to the tooth exfoliating ~

Cellulitis with no radiographic evidence of periapical patholosis, as well as acute exacerbations of chronic periapical patholosis which show radiographic radiolucency or a fistula, are not contraindications for pulpectomy in primary teeth. These teeth can be treated by incision of any fluctuant local swelling, a full course of antibiotic cover and routine treatment by pulpectomy. In the majority of'cases the tooth is sealed with a temporary dressing after the initial treatment, but where there is profuse swelling and exudate the tooth may be left open for 24 hours. If the infection cannot be controlled by these means, the tooth should be extracted and a decision made on the necessity of placing a spacemain tainer. The technique for pulpectomy of primary teeth is similar to permanent teeth. The major differences are that between the first and second appointments formocresol is used for medication of the canals, and obturation of the canals is with a resorbable paste of zinc-oxide and eugenol. As it is impossible to cleanse completely the root canal systems of primary molars mechanically or chemically, the objective is to remove pulpal debris down to a level the body can tolerate. At the first appointment after administering local anaesthesia the tooth is isolated with rubber dam. The pulp chamber is opened so that all the root canals are exposed; there may be as many as six canals. The pulp is removed using a barbed broach or a file. The root length is estimated from the periapical radiograph and the plastic stops on the files and reamers are adjusted. The distal root of the mandibular primary molar may be 2-3 mm shorter than the mesial root as the tooth bud of the first premolar is situated more under the distal root. Files are placed in the root canals and a radiograph is taken to determine the root length. The canals are enlarged with small files and during instrumentation are irrigated with chlorhexidine gluconate solution,t EDTAS followed by chlorhexidine gluconate solution, or rc-prefi and sodium hypochlorite. The canals are dried with paper points and demethylchlortetracycline hydrochloride pasten introduced into the canals with a lentulo spiral. A cotton wool pellet is placed in the pulp chamber and sealed with cavit or IRM. A cotton pellet moistened with formocresol may be placed in the pulp chamber instead of using demethylchlortetracycline hydrochloride paste. Careful filing of the root canal should be practised to prevent pushing the file through the apex which could result in trauma to the permanent tooth bud. At the second appointment the temporary filling is removed and the canals are cleansed as previously described. The paste is removed with small files having rubber stops adjusted to the corrected length of the ~~t Snvlon. Imperial Chemlcal Industries of Australia and New Zealand ~~

I"

Barker, B. C. W., Parsons, K. C., Williams, G. L.. and Mills, P. R.- Anatomy of root canals. IV. Deciduous teeth. Austral. D. J., 20: 2, 101-106 (Apr.) 1975.

Limited. t: Ethylenediemine tetra-acetic acid, Orapharm (Vic.) Pty. Lid. p Medical Products Laboratories. 7 Lederle Pharmaceuticals

Australian Dental Journal, October, 1979 canals. The canals are dried and filled with zinc oxide and eugenol paste without the inclusion of the accelerator zinc acetate. The zinc oxide paste is introduced into the canals by a lentulo spiral, a pressure syringe or mixing into a thick paste and packing with root canal pluggers. A zinc phosphate cement base is placed and the tooth restored with amalgam or a stainless steel crown. Local anaesthesia is not required for the second appointment except for a soft tissue anaesthesia before applying the rubber dam clamp. The reaction of the patient will determine whether the canals have been filled to the anatomic apex. Subsequently, a periapicai radiograph is taken to confirm that the canals have been adequately filled. Radiographic checks should be made regularly at intervals of 1-2 years. As there is a difference between the resorption rate of the zinc oxide paste and the tooth root, small areas of zinc oxide paste may remain as the root is resorbed. Primary teeth successfully treated with a pulpectomy remain as functional units in the dental arch until the time of exfoliation.

35 1 Summary Endodontic treatment of primary teeth has been discussed under four headings :(1) Indirect pulp capping. (2) Direct pulp capping. (3) Formocresol pulpotomy (4) Pulpectomy. Although the child may have a local swelling, a cellulitis, or a fistula due to pulpal necrosis, it is not a contraindication to pulpectomy in primary teeth. The same principles of technique apply to the treatment of both primary teeth and permanent teeth with infected or necrotic pulps. The main differences are the use of formocresol for medication of the root canals and a resorbable paste of zinc-oxide and eugenol for root canal obturation. Department of Dental Health, The University of Adelaide, Box 498, G.P.O., Adelaide, S.A., 5001.

Endodontic treatment of primary teeth.

341 Australian Dental Journal, October, 1979 Volume 24, No. 5 Endodontic treatment of primary teeth Kevin R. Allen, B.D.S., Cert.Ped.(lll.), F.I.C.D...
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